Insulin resistance increases cardiovascular disease

Insulin resistance (IR), resistance of the insulin receptor due to overstimulation, elicits a rise of insulin levels to overcome the reduced receptor sensitivity. The resulting elevated insulin levels damage tissues throughout the body, and are a major contributing cause of cardiovascular disease. This is well known to many practitioners, so it was disturbing to read an article in the New York Times describing endocrinologists who are baffled by the fact that medications for type 2 diabetes that increase insulin levels worsen the risk for cardiovascular disease. The wealth of scientific evidence has been accumulating for a long time.

Insulin resistance and coronary artery disease

Insulin resistance and CADA study published in 1996 in the journal Diabetologia described the strong connection between CAD (coronary artery disease) and insulin resistance with its consequent hyperinsulinemia.

“The purpose of the present study was to quantitate insulin-mediated glucose disposal in normal glucose tolerant patients with angiographically documented coronary artery disease (CAD) and to define the pathways responsible for the insulin resistance.”

Of particular interest is that all the study subjects, both those with CAD and controls, had a normal oral glucose tolerance test. HOWEVER…

Fasting plasma insulin concentration and area under the plasma insulin curve following glucose ingestion were increased in CAD vs control subjects. Insulin-mediated whole body glucose disposal was significantly decreased in CAD subjects and this was entirely due to diminished non-oxidative glucose disposal. The magnitude of insulin resistance was positively correlated with the severity of CAD.”

It is hard to over emphasize the importance to clinicians of being vigilant in recognizing insulin resistance in the presence of normal glucose levels.

“In the CAD subjects basal and insulin-mediated rates of glucose and lipid oxidation were normal and insulin caused a normal suppression of hepatic glucose production. In conclusion, subjects with angiographically documented CAD are characterized by moderate-severe insulin resistance and hyperinsulinaemia and should be included in the metabolic and cardiovascular cluster of disorders that comprise the insulin resistance syndrome or ’syndrome X’.

Hypertension, Dyslipidemia, and Atherosclerotic Cardiovascular Disease

In 1991 a paper published in Diabetes Care described how insulin resistance promotes multiple factors that cause atherosclerosis.

“Diabetes mellitus is commonly associated with systolic/diastolic hypertension, and a wealth of epidemiological data suggest that this association is independent of age and obesity. Much evidence indicates that the link between diabetes and essential hypertension is hyperinsulinemia. Thus, when hypertensive patients, whether obese or of normal body weight, are compared with age- and weight-matched normotensive control subjects, a heightened plasma insulin response to a glucose challenge is consistently found.”

Moreover…

“…insulin resistance…correlates directly with the severity of hypertension. The reasons for the association of insulin resistance and essential hypertension can be sought in at least four general types of mechanisms: Na+ retention, sympathetic nervous system overactivity, disturbed membrane ion transport, and proliferation of vascular smooth muscle cells.”

It is also well-known that IR with its hyperinsulinemia cause elevated lipid levels.

Insulin resistance and hyperinsulinemia are also associated with an atherogenic plasma lipid profile. Elevated plasma insulin concentrations enhance very-low-density lipoprotein (VLDL) synthesis, leading to hypertriglyceridemia. Progressive elimination of lipid and apolipoproteins from the VLDL particle leads to an increased formation of intermediate-density and low-density lipoproteins, both of which are atherogenic.”

And elevated insulin directly fosters atherosclerosis:

“Last, insulin, independent of its effects on blood pressure and plasma lipids, is known to be atherogenic. The hormone enhances cholesterol transport into arteriolar smooth muscle cells and increases endogenous lipid synthesis by these cells. Insulin also stimulates the proliferation of arteriolar smooth muscle cells, augments collagen synthesis in the vascular wall, increases the formation of and decreases the regression of lipid plaques, and stimulates the production of various growth factors. In summary, insulin resistance appears to be a syndrome that is associated with a clustering of metabolic disorders, including non-insulin-dependent diabetes mellitus, obesity, hypertension, lipid abnormalities, and atherosclerotic cardiovascular disease.”

 

Controlling insulin resistance more important than glucose or LDLA more recent study in Diabetes Care presents striking data demonstrating the massive impact reduction in heart attacks that would occur by preventing insulin resistance. In setting out to determine what portion of coronary artery disease is caused by IR, the authors used data from the National Health and Nutrition Examination Survey 1998–2004 to simulate a population representative of young adults in the U.S. They applied the Archimedes model was to estimate the proportion of heart attacks that would be prevented by maintaining insulin resistance at healthy levels. Their data painted a dramatic picture:

“In young adults, preventing insulin resistance would prevent ∼42% of myocardial infarctions. The next most important determinant of CAD is systolic hypertension, prevention of which would reduce myocardial infarctions by ∼36%. Following systolic blood pressure, the most important determinants are HDL cholesterol (31%), BMI (21%), LDL cholesterol (16%), triglycerides (10%), fasting plasma glucose and smoking (both ∼9%), and family history (4%).”

Preventing insulin resistance beat the pants off controlling LDL cholesterol and smoking! Interestingly, they found that the effects were especially important for women:

“The effects of insulin resistance are also affected by sex. Today’s young men face a higher rate of myocardial infarctions than today’s young women: 55 vs. 32%. However, insulin resistance plays a larger relative role in women than in men, with normalization of insulin resistance reducing the myocardial infarction rate ∼57% for women (from 32 to 14%), compared with ∼29% (from 55 to 39%) for men.”

Preventing insulin resistance carries more weight than controlling glucose

In their conclusion the authors make points that are crucial for clinicians to bear in mind:

“Of the risk factors that we believe are sufficiently well studied to permit quantitative analysis, insulin resistance is the most important single risk factor for CAD. Our results indicate that insulin resistance is responsible for approximately 42% of myocardial infarctions. Its effect on CAD is indirect, mediated through its effects on other variables such as SBP, HDL cholesterol, triglycerides, glucose, and apoB.”

Effect of insulin resistance on myocardial infarction

In comparing their results with other research, the authors highlight the critical error made by depending on medications that increase insulin to control glucose:

“Our results are not directly comparable with those of clinical trials, where the effects of glucose lowering on CAD were either much smaller or null. The reason is that in the clinical trials, the focus was on lowering blood glucose—not preventing or curing insulin resistance. The drugs used in the trials either lowered glucose without affecting insulin resistance (e.g., sulfonylureas and insulin) or lowered insulin resistance to some extent but did not eliminate it (e.g., metformin and rosiglitazone). Furthermore, we normalized insulin resistance over the entire lifetimes of the subjects, whereas the treatments in the trials were given only after individuals had developed diabetes and were given only for the limited durations of the studies. Thus, the results of the trials do not represent the full eff

ect of normalizing insulin resistance and are actually consistent with our results.”

Note the implication that cardiovascular damage by IR occurs long before losing glucose control and crossing the border into diabetes territory.

Insulin resistance without diabetes causes cardiovascular disease

Investigators publishing in PLoS One make the same point about cardiovascular damage caused by IR well before diabetes sets in.

“To enable a comparison between cardiovascular disease risks for glucose, insulin and HOMA-IR, we calculated pooled relative risks per increase of one standard deviation…We included 65 studies (involving 516,325 participants) in this meta-analysis. In a random-effect meta-analysis the pooled relative risk of CHD (95% CI; I2) comparing high to low concentrations was 1.52 (1.31, 1.76; 62.4%) for glucose, 1.12 (0.92, 1.37; 41.0%) for insulin and 1.64 (1.35, 2.00; 0%) for HOMA-IR. The pooled relative risk of CHD per one standard deviation increase was 1.21 (1.13, 1.30; 64.9%) for glucose, 1.04 (0.96, 1.12; 43.0%) for insulin and 1.46 (1.26, 1.69; 0.0%) for HOMA-IR.”

They concluded that insulin resistance (HOMA-IR) was the leading culprit:

“The relative risk of cardiovascular disease was higher for an increase of one standard deviation in HOMA-IR compared to an increase of one standard deviation in fasting glucose or fasting insulin concentration.”

The authors also demonstrate that IR is a much better biomarker than fasting insulin:

 “The present meta-analyses showed that fasting glucose, fasting insulin and HOMA-IR were all associated with incident cardiovascular disease in individuals without diabetes. In a standardized meta-analysis we found that coronary heart disease risk increased with 46% for an increase of one standard deviation in HOMA-IR concentration compared to an increase of 21% for fasting glucose concentration and an increase of 4% for fasting insulin concentration.”

Insulin resistance causes fat expansion and vascular endothelial damage

An excellent paper published in Arteriosclerosis, Thrombosis, and Vascular Biology details how IR causes cardiovascular disease beyond abnormal glucose, lipids, hypertension, and its proinflammatory effects.

“…insulin’s action directly on vascular endothelium, atherosclerotic plaque macrophages, and in the heart, kidney, and retina has now been described, and impaired insulin signaling in these locations can alter progression of cardiovascular disease in the metabolic syndrome and affect development of microvascular complications.”

The authors describe how IR causes vascular inflammation and atherosclerosis:

“Insulin action directly on vascular endothelial cells affects endothelial function beyond regulating blood flow or capillary recruitment. Conditional knockout of the insulin receptor in endothelial cells causes a 2- to 3-fold increase in the atherosclerotic lesion size in apolipoprotein E–null mice…the increased atherogenesis in this model can be attributed to insulin action directly on endothelial cells rather than effects mediated through systemic parameters. The accelerated atherosclerosis in mice with endothelial cell insulin receptor knockout is preceded by a dramatic increase in leukocyte rolling and adhesion to endothelium and an increase in expression of vascular cell adhesion molecule-1…insulin signaling independent of NO is responsible for this effect.”

They state that IR promotes the necrotic core at the heart of vulnerable plaque:

Insulin resistance in macrophages, however, promotes formation of a necrotic core in atherosclerotic plaques by enhancing macrophage apoptosis. This is an important event in advanced atherosclerosis because exposure of the necrotic core to circulating blood in the event of plaque rupture can precipitate thrombosis, leading to unstable angina pectoris, transitory cerebral ischemia, stroke, or myocardial infarction.”

Regarding cardiomyocyte function…

“…it is likely that the changes in metabolic substrate inflexibility and increased mitochondrial production of oxidants caused by cardiomyocyte insulin resistance can contribute to development of heart failure in the metabolic syndrome.”

The authors conclude with important clinical points:

“Research on insulin receptor signaling using tissue–specific gene manipulation in mice as well as other methods has provided important insights into insulin action and revealed insulin effects in tissues that a decade or 2 ago were considered nonresponsive to insulin….insulin sensitizers would theoretically have better profiles of action if they improved insulin resistance in tissues regulating glucose and lipid metabolism, as well as in the endothelium and other vascular tissues where impaired insulin signaling is proatherosclerotic independent of metabolic effects. Second, insulin analogues should be carefully evaluated for deleterious effects on insulin signaling pathways which are not affected by insulin resistance, such as those pathways which promote dyslipidemia or increase vascular expression of endothelin-1.”

Insulin resistance promotes advanced plaque progression

A paper published in Cell Metabolism details additional mechanisms by which IR promotes atherosclerosis. The authors note that…

“…the pathophysiological processes involved in the initiation and progression of early lesions are quite different from those that cause the formation of clinically dangerous plaques,…advanced plaque progression is influenced primarily by processes that promote plaque necrosis and thinning of a collagenous “scar” overlying the lesion called the fibrous cap… and distinguishing the effects of insulin resistance and hyperglycemia on these processes is critically important.”

They echo other investigators who point out the crucial fact that insulin resistance does damage before glucose control is lost:

“There is ample clinical evidence that insulin resistance increases the risk for coronary artery disease (CAD) even in the absence of hyperglycemia. Insulin resistance syndromes can promote both atherogenesis and advanced plaque progression, and the mechanisms likely involve both systemic factors that promote these processes, particularly dyslipidemia but also hypertension and a proinflammatory state, as well as the effect of perturbed insulin signaling at the level of the intimal cells that participate in atherosclerosis, including endothelial cells, vascular smooth muscle cells, and macrophages.”

They highlight the critical clinical implication that insulin resistance also entails overstimulation of various tissues by insulin elevated in compensation for receptor resistance or by insulin-elevating medications:

“…“insulin resistance” can mean either defective insulin receptor signaling or, ironically, overstimulation of insulin receptor pathways caused by hyperinsulinemia.”

They also note the difference between ‘ordinary’ atherosclerosis and the lesions, vulnerable plaque, that actually cause heart attacks and ischemic strokes.

“Most importantly, the primary objective of this study was to address an entirely different question, namely, the effect of myeloid IR deficiency on advanced lesional macrophage apoptosis and plaque necrosis. Recall that most atherosclerotic lesions in humans do not cause acute coronary artery disease, because they undergo outward remodeling of the arterial wall, which preserves lumen patency, and do not undergo plaque rupture or erosion and thus do not trigger acute lumenal thrombosis. The small percentage of lesions that do cause acute vascular disease are distinguished by the presence of large areas of necrosis and thin fibrous caps, which promote plaque disruption, acute lumenal thrombosis, and tissue infarction. This concept is particularly important for the topic of this review, because advanced atherosclerotic lesions in diabetic subjects are characterized by large necrotic cores when compared with similarly sized lesions from nondiabetic individuals”

In their conclusion the authors state the role of insulin resistance over hyperglycemia:

“These studies have provided evidence that insulin resistance in macrophages and endothelial cells may play important roles in both atherogenesis and clinically relevant advanced plaque progression. Hyperglycemia, on the other hand, appears to primarily promote early stages of lesion formation…”

Insulin resistance inhibits nitric oxide synthase

An interesting paper published in the Italian journal Panminerva Medica further elucidates key mechanisms, including the damage by IR to nitric oxide regulation done by increasing asymmetric dimethylarginine, which inhibits nitric oxide synthase. The author includes this under the rubric ‘insulin resistance syndrome’.

“…the more insulin resistant an individual, the more insulin they must secrete in order to prevent the development of type 2 diabetes. However, the combination of insulin resistance and compensatory hyperinsulinemia increases the likelihood that an individual will be hypertensive, and have a dyslipidemia characterized by a high plasma triglyceride (TG) and low high-density lipoprotein cholesterol (HDL-C) concentration….Several other clinical syndromes are now known to be associated with insulin resistance and compensatory hyperinsulinemia. For example, polycystic ovary syndrome appears to be secondary to insulin resistance and compensatory hyperinsulinemia. More recently, studies have shown that the prevalence of insulin resistance/hyperinsulinemia is increased in patients with nonalcoholic fatty liver disease, and there are reports that certain forms of cancer are more likely to occur in insulin resistant/hyperinsulinemic persons. Finally, there is substantial evidence of an association between insulin resistance/hyperinsulinemia, and sleep disordered breathing. Given the rapid increase in the number of clinical syndromes and abnormalities associated with insulin resistance/hyperinsulinemia, it seems reasonable to suggest that the cluster of these changes related to the defect in insulin action be subsumed under the term of the insulin resistance syndrome.”

Specifically in regard to cardiovascular disease…

“…in addition to a high TG and a low HDL-C, the atherogenic lipoprotein profile in insulin resistant/hyperinsulinemic individuals also includes the appearance of smaller and denser low density lipoprotein particles, and the enhanced postprandial accumulation of remnant lipoproteins; changes identified as increasing risk of CVD. Elevated plasma concentrations of plasminogen activator inhibitor-1 (PAI-1) have been shown to be associated with increased CVD, and there is evidence of a significant relationship between PAI-1 and fibrinogen levels and both insulin resistance and hyperinsulinemia. Evidence is also accumulating that sympathetic nervous system (SNS) activity is increased in insulin resistant, hyperinsulinemic individuals, and, along with the salt sensitivity associated with insulin resistance/hyperinsulinemia, increases the likelihood that these individuals will develop essential hypertension.”

Moreover…

“The first step in the process of atherogenesis is the binding of mononuclear cells to the endothelium, and mononuclear cells isolated from insulin resistant/hyperinsulinemic individuals adhere with greater avidity. This process is modulated by adhesion molecules produced by endothelial cells, and there is a significant relationship between degree of insulin resistance and the plasma concentration of the several of these adhesion molecules. Further evidence of the relationship between insulin resistance and endothelial dysfunction is the finding that asymmetric dimethylarginine, an endogenous inhibitor of the enzyme nitric oxide synthase, is increased in insulin resistant/hyperinsulinemic individuals. Finally, plasma concentrations of several inflammatory markers are elevated in insulin resistant subjects.”

 

A paper published in Diabetes Metabolism Research and Reviews draws this point further.

“In recent years, it has become clear that insulin resistance and endothelial dysfunction play a central role in the pathogenesis of atherosclerosis. Much evidence supports the presence of insulin resistance as the fundamental pathophysiologic disturbance responsible for the cluster of metabolic and cardiovascular disorders, known collectively as the metabolic syndrome. Endothelial dysfunction is an important component of the metabolic or insulin resistance syndrome and this is demonstrated by inadequate vasodilation and/or paradoxical vasoconstriction in coronary and peripheral arteries in response to stimuli that release nitric oxide (NO). Deficiency of endothelial-derived NO is believed to be the primary defect that links insulin resistance and endothelial dysfunction. NO deficiency results from decreased synthesis and/or release, in combination with exaggerated consumption in tissues by high levels of reactive oxygen (ROS) and nitrogen (RNS) species, which are produced by cellular disturbances in glucose and lipid metabolism.”

And a vicious cycle ensues…

“Endothelial dysfunction contributes to impaired insulin action, by altering the transcapillary passage of insulin to target tissues. Reduced expansion of the capillary network, with attenuation of microcirculatory blood flow to metabolically active tissues, contributes to the impairment of insulin-stimulated glucose and lipid metabolism. This establishes a reverberating negative feedback cycle in which progressive endothelial dysfunction and disturbances in glucose and lipid metabolism develop secondary to the insulin resistance. Vascular damage, which results from lipid deposition and oxidative stress to the vessel wall, triggers an inflammatory reaction, and the release of chemoattractants and cytokines worsens the insulin resistance and endothelial dysfunction.”

In their conclusion the authors state:

“…endothelial dysfunction and insulin resistance commonly occur together and can be detected early in the pathogenesis of atherosclerosis. Insulin resistance can be inferred by the presence of a cluster of metabolic and cardiovascular abnormalities known collectively as the metabolic syndrome or by direct measurement of impaired insulin-stimulated glucose and lipid metabolism . Endothelial dysfunction can be documented by the demonstration of inadequate vasodilation and/or paradoxical vasoconstriction in coronary and peripheral arteries. Lack of endothelial-derived NO may provide the link between insulin resistance and endothelial dysfunction.”

Plea to clinicians

Many resources are available for practitioners to apply a functional medicine model of objectively targeted treatment to resuscitate insulin receptor function and address lifestyle issues, especially diet, for the management of type 2 diabetes that minimizes the use of agents that lower glucose by increasing insulin, and therefore insulin resistance. It is my sincere wish that not only endocrinologists, but all clinicians, recall the mechanisms by which medications that promote insulin resistance increase cardiovascular disease, and act accordingly to protect their patients.

Insulin resistance is a huge topic, and there are numerous posts here pertaining to IR an conditions as diverse as Alzheimer’s disease and breast cancer that can be viewed by using the search box. They include the earlier post on the correlation of IR with blood vessel damage leading to heart attack and stroke.

Subclinical hypothyroidism worsens cardiometabolic profile

Subclinical hypothyroidism and cardiometabolic biomarkersSubclinical hypothyroidism (SCH), poor thyroid effect throughout the body in the presence of ‘normal’ thyroid serum tests, is a widespread yet under-appreciated clinical challenge. A recent study published in the Journal of the Endocrine Society documents adverse cardiometabolic biomarkers in the presence of subclinical hypothyroidism. Additionally, practitioners must bear in mind that more than adequate iodine intake can worsen the condition.

Clarifying the definition of normal thyroid function

The authors note that uncertainty around the definition of normal thyroid function can go beyond contention involving different opinions on laboratory reference ranges by examining the effect of suboptimal thyroid function on the entire organism.

“As thyroid function has multisystemic effects, its derangement could affect a broad range of cardiometabolic pathways potentially related to clinical manifestations. However, the definition of normal thyroid function has been intensely debated, with some experts advocating for lowering the upper limit of normal for thyroid stimulating hormone (TSH) and others for maintaining the current standard. In this regard, thyroid-related risk for incident type 2 diabetes (T2D) and cardiovascular disease (CVD) may impact the definition of TSH normality.”

They note some of the mechanisms by which SCH can adversely affect cardiovascular and metabolic function:

“The potential relationship of thyroid hypofunction with T2D and CVD may be mediated by abnormalities in lipids, lipoprotein subclasses, endothelial function, coagulation, inflammatory pathways, and insulin resistance.”

This hardly exhausts the list of adverse physiological effects since every part of the body, including the brain, requires the stimulus of thyroid hormone to produce energy and function. The public health implications are enormous.

“Detailed assessment of thyroid function effects on these mediators/markers may have high population health implications, especially along the milder hypofunction spectrum within euthyroidism and SCH. Understanding the role of thyroid function in cardiometabolic pathways may guide the clinically relevant definition of thyroid function and unveil potential targets for controlling related morbidity.”

Subclinical hypothyroidism increases cardiometabolic risk

Thus the authors set out to…

“…examine thyroid function across the spectrum of euthyroid to HT in relationship to cardiometabolic pathways represented by lipids, lipoproteins, inflammation, coagulation, glycemic, and insulin resistance biomarkers.”

They examined data for 28,024 apparently healthy middle-aged and older women, and indeed found that cardiometabolic health worsens on a gradient from normal thyroid (euthyroid) function, through subclinical hypothyroidism, to full-blown hypothyroid:

Going from euthyroid to HT, the lipoprotein subclass profiles were indicative of insulin resistance: larger very-low-density lipoprotein size (nm); higher low-density lipoprotein (LDL) particle concentration (nmol/L), and smaller LDL size. There was worsening lipoprotein insulin resistance score from euthyroid to SCH and HT. Of the other biomarkers, SCH and HT were associated with higher high-sensitivity C-reactive protein and hemoglobin A1c. For increasing TSH quintiles, results were overall similar.”

TSH, total and LDL cholesterol not so useful

They note that it was other biomarkers that revealed the actual progressive risk:

“In this population of apparently healthy middle-aged and older women, individuals with SCH and HT had differences in the lipid and lipoprotein subclass profile that indicated worsening insulin resistance and higher cardiometabolic risk compared with euthyroid individuals, despite having similar LDL cholesterol and total cholesterol. Of the other biomarkers, only hs-CRP and HbA1c were associated with SCH and HT. For TSH quintiles mostly within the normal range, lipid and lipoprotein results for TSH quintiles were generally similar but null for other biomarkers. Hence, progressive thyroid hypofunction was associated with insulin-resistant and proatherogenic lipids and lipoproteins profile in a graded manner, with potential clinical consequences.”

Mechanisms

Besides thyroid as a driver of metabolic activity, insulin resistance appears to play a key role. They point out that insulin resistance appears to affect lipoprotein metabolism before glucose metabolism, an observation important for clinicians to bear in mind.

Thyroid hormones act as modulators of cholesterol synthesis and degradation through key enzymes. One of the main mechanisms is the stimulus of thyroid hormones over sterol regulatory element–binding protein 2, which in turn induces LDL receptor gene expression. However, it was shown that the association of HT and higher LDL cholesterol levels is present only in insulin-resistant subjects. Indeed, the lack of LDL cholesterol differences could be explained by our insulin-sensitive study population (low HbA1c levels). HT has also been associated with lower catabolism of lipid-rich lipoproteins by lipoprotein lipase, hepatic lipase, and decreased activity of cholesterol ester transfer proteinthat mediates exchanges of cholesteryl esters of HDL particles with triglyceride-rich LDL and VLDL particles. These mechanisms might explain the relationship of thyroid hypofunction with atherogenic and insulin-resistant lipid and lipoprotein abnormalities. Finally, the milder differences noted in HbA1c compared with LPIR across thyroid categories may be explained by the earlier effects of insulin resistance on lipoprotein metabolism than on glucose metabolism.”

Practitioners should be attentive to the authors’ conclusion:

“In this large population of apparently healthy women, individuals with SCH had differences in their biomarker profile that indicated worsening lipoprotein insulin resistance and higher cardiometabolic risk compared with euthyroid individuals, despite having similar LDL cholesterol and total cholesterol levels. These findings suggest that cardiometabolic risk may increase early in the progression toward SCH and overt HT.

Iodine supplementation reminder

More than adequate iodine increases autoimmune thyroiditisClinicians who may be tempted to reflexively offer iodine supplementation for thyroid disorders including subclinical hypothyroidism should remember the body of evidence showing this can fire up autoimmune thyroiditis. One example by way of a reminder is a study published in the European Journal of Endocrinology showing that more thanequate iodine intake may increase subclinical hypothyroidism and autoimmune thyroiditis. The authors describe their intent:

“With the introduction of iodized salt worldwide, more and more people are exposed to more than adequate iodine intake levels with median urinary iodine excretion (MUI 200–300 μg/l) or excessive iodine intake levels (MUI >300 μg/l). The objective of this study was to explore the associations between more than adequate iodine intake levels and the development of thyroid diseases (e.g. thyroid dysfunction, thyroid autoimmunity, and thyroid structure) in two Chinese populations.”

They examined thyroid hormones, thyroid autoantibodies in serum, iodine levels in urine were measured. and B-mode ultrasonography of the thyroid for 3813 individuals, in two areas with differing levels of iodine exposure. The levels of iodine intake were: Rongxing, MUI 261 μg/l; and Chengshan, MUI 145 μg/l. (MUI =median urinary iodine excretion.) They found a blatant difference in thyroid biomarkers:

“The prevalence of subclinical hypothyroidism was significantly higher for subjects who live in Rongxing than those who live in Chengshan. The prevalence of positive anti-thyroid peroxidase antibody (TPOAb) and positive anti-thyroglobulin antibody (TgAb) was significantly higher for subjects in Rongxing than those in Chengshan. The increase in thyroid antibodies was most pronounced in the high concentrations of TPOAb (TPOAb: ≥500 IU/ml) and low concentrations of TgAb (TgAb: 40–99 IU/ml) in Rongxing.”

Their results suggest there is a discrete window for thyroid intake:

“Compared with the adequate iodine intake level recommended by WHO/UNICEF/ICCIDD MUI (100–200 μg/l), our data indicated that MUI 200–300 μg/l might be related to potentially increased risk of developing subclinical hypothyroidism or autoimmune thyroiditis. This result differs from the WHO’s suggestion that MUI >300 μg/l may increase the risk of developing autoimmune thyroid diseases.”

Practitioners should be cautious with dosing of supplemental iodine in keeping with the authors’ conclusion:

“In conclusion, compared with the population with MUI 145 μg/l in Chengshan, the population with MUI 261 μg/l in Rongxing had a higher risk to develop autoimmune thyroiditis and subclinical hypothyroidism. Thus, more than adequate iodine intake might not be recommended for the general population in terms of keeping a normal function of thyroid.”

Readers may wish to also see the earlier post Hypothyroidism can be provoked by small amounts of supplemental iodine.

Prediabetes, chronic inflammation and hemoglobin A1c

PrediabetesPrediabetes, blood glucose is slightly higher than normal but not enough to qualify for diabetes, is associated with an increased systemic burden of inflammation and elevated risk for cardiovascular, cancer, dementia and other diseases. The first study described in this post, published in the European Journal of Nutrition, highlights the link between prediabetes, chronic inflammation and mortality from a range of diseases tied to HgbA1c (hemoglobin A1c, glycosylated hemoglobin), the key biomarker for glucose regulation. The authors state:

Chronic inflammation is associated with increased risk of cancer, cardiovascular disease (CVD), and diabetes. The role of pro-inflammatory diet in the risk of cancer mortality and CVD mortality in prediabetics is unclear. We examined the relationship between diet-associated inflammation, as measured by dietary inflammatory index (DII) score, and mortality, with special focus on prediabetics.”

Pro-inflammatory diet plus prediabetes (increased HgbA1c)

Of great significance is the effect they reveal when a pro-inflammatory diet, measured by the dietary inflammatory index (DII) score, is consumed when there is elevated HgbA1c. They categorized 13,280 subjects between the ages 20 of and 90 years according to whether or not they were prediabetic, which they defined as a HgbA1c percentage of 5.7–6.4. Their data highlighted this connection between all-cause mortality, a pro-inflammatory diet and prediabetes:

“The prevalence of prediabetes was 20.19 %. After controlling for age, sex, race, HgbA1c, current smoking, physical activity, BMI, and systolic blood pressure, DII scores in tertile III (vs tertile I) was significantly associated with mortality from all causes (HR 1.39, 95 % CI 1.13, 1.72), CVD (HR 1.44, 95 % CI 1.02, 2.04), all cancers (HR 2.02, 95 % CI 1.27, 3.21), and digestive-tract cancer (HR 2.89, 95 % CI 1.08, 7.71). Findings for lung cancer (HR 2.01, 95 % CI 0.93, 4.34) suggested a likely effect.”

The authors conclude:

“A pro-inflammatory diet, as indicated by higher DII scores, is associated with an increased risk of all-cause, CVD, all-cancer, and digestive-tract cancer mortality among prediabetic subjects.”

 Prediabetes and cardiovascular risk

Research published in The BMJ (British Medical Journal) focusses on the substantial impact of prediabetes on the risk of heart attack and ischemic stroke. The authors set out to…

“…evaluate associations between different definitions of prediabetes and the risk of cardiovascular disease and all cause mortality…”

…by analyzing 53 prospective cohort studies with 1,611,339 individuals that passed the screening tests for validity. In this study they applied several definitions of prediabetes:

“Prediabetes was defined as impaired fasting glucose according to the criteria of the American Diabetes Association (IFG-ADA; fasting glucose 5.6-6.9 mmol/L = 101-124 mg/dL), the WHO expert group (IFG-WHO; fasting glucose 6.1-6.9 mmol/L = 110-124 mg/dL), impaired glucose tolerance (2 hour plasma glucose concentration 7.8-11.0 mmol/L = 141-198 mg/dL during an oral glucose tolerance test), or raised haemoglobin A1c (HbA1c) of 39-47 mmol/mol [5.7-6.4%] according to ADA criteria or 42-47 mmol/mol [6.0-6.4%] according to the National Institute for Health and Care Excellence (NICE) guideline.”

Their data show that prediabetes with a ‘mildly’ elevated HgbA1c was clearly associated with increased cardiovascular risk:

“Compared with normoglycaemia, prediabetes (impaired glucose tolerance or impaired fasting glucose according to IFG-ADA or IFG-WHO criteria) was associated with an increased risk of composite cardiovascular disease (relative risk 1.13, 1.26, and 1.30 for IFG-ADA, IFG-WHO, and impaired glucose tolerance, respectively), coronary heart disease (1.10, 1.18, and 1.20, respectively), stroke (1.06, 1.17, and 1.20, respectively), and all cause mortality (1.13, 1.13 and 1.32, respectively). Increases in HBA1c to 39-47 mmol/mol [5.7-6.4%] or 42-47 mmol/mol [6.0-6.4%] were both associated with an increased risk of composite cardiovascular disease (1.21 and 1.25, respectively) and coronary heart disease (1.15 and 1.28, respectively), but not with an increased risk of stroke and all cause mortality.”

Interestingly, risk of stroke does not emerge from these data, suggesting other factors promoting vascular inflammation. The authors conclude:

“…we found that prediabetes defined as impaired fasting glucose or impaired glucose tolerance is associated with an increased risk of composite cardiovascular events, coronary heart disease, stroke, and all cause mortality. There was an increased risk in people with fasting plasma glucose as low as 5.6 mmol/L [100 mg/dL]. Additionally, the risk of composite cardiovascular events and coronary heart disease increased in people with raised HbA1c. These results support the lower cut-off point for impaired fasting glucose according to ADA criteria as well as the incorporation of HbA1c in defining prediabetes.”

HgbA1c and risk of all-cause and cause-specific mortality without diabetes

Similar results were obtained in a study published in Scientific Reports. Here the authors concluded:

“We found evidence of a non-linear association between HbA1c and mortality from all causes, CVD and cancer in this meta-analysis. The dose-response curves were relatively flat for HbA1c less than around 5.7%, and rose steeply thereafter. This fact reveals a clear threshold effect for the association of HbA1clevels with mortality. In addition, from the perspective of mortality benefit and health care burden, it suggests that the most appropriate HbA1c level of initiating intervention is approximately 5.7%…higher HbA1c level is associated with increased mortality from all causes, CVD, and cancer among subjects without known diabetes. However, this association is influenced by those with undiagnosed diabetes or prediabetes .Because of limited studies, the results in relation to cancer mortality should be treated with caution, and more studies are therefore warranted to investigate whether higher HbA1c level is associated with increased cancer mortality.”

 

Magnesium mediates insulin resistance, diabetes risk

Magnesium, insulin resistance and diabetesMagnesium is required for hundreds crucial functions, not least of which are its calming, parasympathetic nervous system supporting and anti-inflammatory effects. Patients in our practice are also informed that a good magnesium level is necessary for insulin receptor function, further evidence for which has just been published in the journal Diabetologia. The results of this study demonstrate a causal role for low magnesium in diabetes and prediabetes, especially through insulin receptor resistance.

Magnesium and diabetes

An association with diabetes has long been observed, but questions have remained regarding whether this is a cause or an effect. For this reason the authors investigated its role in prediabetes.

“Previous studies have found an association between serum magnesium and incident diabetes; however, this association may be due to reverse causation, whereby diabetes may induce urinary magnesium loss. In contrast, in prediabetes (defined as impaired fasting glucose), serum glucose levels are below the threshold for urinary magnesium wasting and, hence, unlikely to influence serum magnesium levels. Thus, to study the directionality of the association between serum magnesium levels and diabetes, we investigated its association with prediabetes. We also investigated whether magnesium-regulating genes influence diabetes risk through serum magnesium levels. Additionally, we quantified the effect of insulin resistance in the association between serum magnesium levels and diabetes risk.”

 Prediabetes and insulin resistance

They examined data from 8555 subjects for an association with prediabetes/diabetes, and further sought to determine if genes influence diabetes risk through serum magnesium levels. They also aimed to determine how much of the effect is mediated through insulin resistance  by HOMA-IR). Their data show a robust role in regulating insulin receptor function and effect on diabetes risk.

A 0.1 mmol/l decrease in serum magnesium level was associated with an increase in diabetes risk (HR 1.18 [95% CI 1.04, 1.33]), confirming findings from previous studies. Of interest, a similar association was found between serum magnesium levels and prediabetes risk (HR 1.12 [95% CI 1.01, 1.25]). Genetic variation…significantly influenced diabetes risk and for CNNM2, FXYD2, SLC41A2 and TRPM6 this risk was completely mediated by serum magnesium levels.”

Condensing these results they state:

“In this large population-based cohort, we found that over a median follow-up of almost 6 years, low serum magnesium levels are associated with an increased risk of prediabetes, with comparable risk estimates to that of diabetes. Furthermore, we found that common genetic variants in magnesium-regulating genes influence diabetes risk and that this risk is mediated through serum magnesium levels.”

In the clinic

Practitioners are aware of two well-known facts: serum magnesium is a poor, insensitive biomarker for sufficiency; and clinical insufficiency is extremely common. (Even RBC membrane levels are not as dependable as the EXA test—see under ‘Useful Links’.) Thus when serum magnesium is suboptimal it should be diligently attended to by the clinician.

The authors conclude:

“…we found that low serum magnesium levels are associated with an increased risk of prediabetes, with similar effect estimates as compared with diabetes. The effect of serum magnesium on prediabetes and diabetes risk is partly mediated through insulin resistance. Furthermore, common genetic variation in magnesium regulating genes TRPM6, CLDN19, SLC41A2, CNNM2 and FXYD2 significantly modify the risk of diabetes through serum magnesium levels. Both findings support a potential causal role of magnesium in the development of diabetes...”

HgbA1c (hemoglobin A1c) predicts prediabetes better than glucose

HgbA1c predicts prediabetesHgbA1c (hemoglobin A1c) is hemoglobin that has been ruined by glycation (bonding with sugar). It has long been recognized as a biomarker for average glucose over an approximately three month time span as well as a metric for the degree of damaging glycation occurring throughout the body. Now further evidence for its superior value as a predictor for prediabetes is presented in a study just published in The Lancet Diabetes & Endocrinology.The authors…

“…compared the risk of future outcomes across different prediabetes definitions based on fasting glucose concentration, HbA1c, and 2 h glucose concentration during over two decades of follow-up in the community-based Atherosclerosis Risk in Communities (ARIC) study. We aimed to analyse the associations of definitions with outcomes to provide a comparison of different definitions.”

HgbA1c compared to fasting and 2 hour glucose

They compared several prediabetes definitions in their ability to predict major long-term health problems. They analyzed data from over seven thousand subjects drawn from four communities across the USA who participated in the Atherosclerosis Risk in Communities (ARIC) study. HgbA1c was pitted against fasting and 2 hour postprandial glucose:

“Fasting glucose concentration and HbA1c were measured at visit 2 and fasting glucose concentration and 2 h glucose concentration were measured at visit 4. We compared prediabetes definitions based on fasting glucose concentration (American Diabetes Association [ADA] fasting glucose concentration cutoff 5·6–6·9 mmol/L and WHO fasting glucose concentration cutoff 6·1–6·9 mmol/L), HbA1c (ADA HbA1ccutoff 5·7–6·4% [39–46 mmol/mol] and International Expert Committee [IEC] HbA1c cutoff 6·0–6·4% [42–46 mmol/mol]), and 2 h glucose concentration (ADA and WHO 2 h glucose concentration cutoff 7·8–11·0 mmol/L).”

HgbA1c better identifies those at risk for diabetes and serious complications

Chronic kidney disease, cardiovascular disease and death were more accurately predicted by HgbA1c than by fasting glucose:

“After demographic adjustment, HbA1c-based definitions of prediabetes had higher hazard ratios and better risk discrimination for chronic kidney disease, cardiovascular disease, peripheral arterial disease, and all-cause mortality than did fasting glucose concentration-based definitions (all p<0·05). The C-statistic for incident chronic kidney disease was 0·636 for ADA fasting glucose concentration clinical categories and 0·640 for ADA HbA1c clinical categories. The C-statistics were 0·662 for ADA fasting glucose clinical concentration categories and 0·672 for ADA HbA1c clinical categories for atherosclerotic cardiovascular disease, 0·701 for ADA fasting glucose concentration clinical categories and 0·722 for ADA HbA1c clinical categories for peripheral arterial disease, and 0·683 for ADA fasting glucose concentration clinical categories and 0·688 for ADA HbA1c clinical categories for all-cause mortality. Prediabetes defined using the ADA HbA1c cutoff showed a significant overall improvement in the net reclassification index for cardiovascular outcomes and death compared with prediabetes defined with glucose-based definitions.”

Clinical Significance

HgbA1c study reviewed in Medscape Family Medicine

Medscape Family Medicine remarks:

“The researchers found that using an HbA1c-based definition, those identified as having prediabetes were 50% more likely to develop kidney disease, twice as likely to develop CVD, and 60% more likely to die from any cause compared with those with normal HbA1c.”

The authors, quoted in Medscape Family Medicine, comment on the practical significance of their findings:

“When someone is told they have prediabetes, we hope it will cause them to make changes to their habits in order to prevent the development of diabetes and its complications,” added the study’s senior author, Elizabeth Selvin, PhD, MPH, a professor in the Bloomberg School’s department of epidemiology.

“Being identified as having prediabetes can also make it easier to receive weight-loss and nutritional counseling as well as reimbursement for these services. Intensive lifestyle changes and weight loss can reduce the risk of diabetes, so it is critically important we identify those persons who are at high risk.

At the same time, we also don’t want to overdiagnose people. Using the hemoglobin A1c test allows us to more accurately identify those persons at highest risk,” she added.

This is important information for physicians and it is also important information for professional organizations. Coming to a global consensus on how to define and diagnose prediabetes would really help move the field forward — and help patients all over the world,” she concluded.”

The authors conclude:

“Our results suggest that prediabetes definitions using HbA1c were more specific and provided modest improvements in risk discrimination for clinical complications. The definition of prediabetes using the ADA fasting glucose concentration cutoff was more sensitive overall.”

Autoimmune diabetes (type 1): half develops after age 30

EASD abstract on autoimmune diabetesAutoimmune diabetes (type 1), earlier thought to occur almost exclusively in the pediatric population, is dramatically increasing among adults. Data recently presented at the 2016 Annual Meeting of the European Association for the Study of Diabetes (EASD) and reported in Medscape confirms that it now occurs as frequently in adults over 30 as it does in children.

Onset of type 1 diabetes is just as likely to occur in people older than 30 years of age as in those younger, new research shows.”

This is a manifestation of the giant increase in autoimmune and autoinflammatory conditions present but too often overlooked in clinical practice.

Autoimmune diabetes lurks in the general population

MedscapePractitioners active in case management of autoimmune conditions are already aware of this, but to many it may come as a surprise.

“Obtained using genetic data from the UK Biobank, the startling results refute the long-held belief that type 1 diabetes is primarily a “juvenile” condition…Clinically, the findings are particularly relevant for primary care, where people who develop autoimmune-mediated diabetes in adulthood are often misdiagnosed as having type 2 and prescribed metformin instead of insulin.”

Dr Nicholas JM Thomas, of the Institute of Biomedical and Clinical Science, University of Exeter Medical School, United Kingdom, who presented the data, is quoted in Medscape:

“I think it’s an eye-opener and obviously has implications for how we diagnose and manage people and also the education people receive. We very much focus on childhood and adolescence and perhaps people diagnosed later don’t get the same education.”

Autoimmune diabetes can be mixed with type 2 (metabolic)

2016-10-23_17-29-31Experienced clinicians will recognize that HgbA1c going up in a lean adult almost always implies an autoimmune component. Harder to recognize is a person for whom both are occurring: there is insulin resistance with compensatory elevated insulin forcing the storage of calories as fat resulting in overweight or obesity but combined with further carbohydrate intolerance due to an autoinflammatory attack on beta cells, insulin, the GAD enzyme, or other factors that further damage blood glucose regulation. It can develop rapidly or slowly as LADA (latent autoimmune diabetes of adults).  I am seeing this in practice and I’m sure others paying attention are too.

Medscape further quotes Dr. Thomas:

“He advised that clinicians should at least be aware that adults can develop autoimmune diabetes, as either classic type 1 or the slower-onset phenomenon known as “latent autoimmune diabetes of adulthood (LADA).”

“It’s knowing this does happen, and therefore just keeping an open mind when you spot someone who’s not behaving like type 1 or not responding as you would anticipate when you go through the usual treatment guidelines for type 2,” he said, citing the example of British Prime Minister Theresa May, who was diagnosed with type 1 diabetes at age 56 and who “progressed very rapidly.”

He reiterated that type 1 diabetes is evenly distributed within the first 6 decades of life, but after age 30, the increase in type 2 diabetes makes the type 1 cases harder to recognize and treat correctly.

Diagnosis

Antibody measurements, particularly to the islet cells, insulin and glutamic acid decarboxylase 65 are a mainstay even though subject to the vulnerabilities of antibody expression. And there is a new approach:

“Dr Thomas and colleagues used a “robust, novel, genetic approach” using a risk score comprising 30 single nucleotide polymorphisms associated with type 1 diabetes (T1D-GRS).”

Firstly the clinician should be alert to impaired blood glucose control in adult patients who are not overweight or for whom the correct diet (LCHF) and targeted therapies are not yielding the result they should. This is a tipoff that the case has to be managed as autoimmune diabetes or LADA with the underlying causes for loss of immune tolerance investigated and targeted for therapy.

The session comoderator Catharine Owen, MD, associate professor of diabetes at the Oxford Center for Diabetes, Endocrinology, and Metabolism, United Kingdom, is also quoted in Medscape:

“I think it’s absolutely crucial for people to be aware that type 1 diabetes can present at any age. Physicians shouldn’t be complacent when people aren’t responding to oral agents, or they’re not bringing A1c down to target when they should.”

Insulin in the brain affects cognition, appetite and weight

Nature Reviews EndocrinologyInsulin has long been known as crucial for muscle, liver and adipose tissue metabolism. It’s effect in the brain on cognition, behavior and physiology is a more recent focus described in an excellent paper published recently in Nature Reviews Endocrinology.

The brain is sensitive to insulin

Since glucose uptake into the brain occurs independently it took a while to recognize the function of the receptors that are found there. The first clue came with the brain-specific knockout mouse model of the insulin receptor.

“Such knockout mice became obese due to increased food intake and developed whole-body insulin resistance with increased plasma levels of insulin and dyslipidaemia.”

Insulin-sensitive brain areasThen investigations comparing infusion of insulin versus saline on human brain activity has widespread effects.

“…these studies provided strong evidence that systemic insulin administration modulates cortical brain activity in humans…not only homeostatic areas (as shown in animal studies) but also higher functional areas involved in sensory and cognitive processes.”

And intranasal administration was shown to affect basal and evoked brain activity. How does it naturally get there?

Whole body insulin resistance affects the brain

“…various studies in animals clearly demonstrated that insulin was transported across the blood–brain barrier by a saturable transport system…”

And it humans it gets from the CSF (cerebrospinal fluid) through the BBB (blood brain barrier).

“Concentrations of insulin in the CSF increase when the hormone is administered into the bloodstream, again indicating transport across the blood–CSF barrier.”

Importantly, insulin resistance in the rest of the body affects the brain, and this has been associated with Alzheimer’s disease.

Insulin transport into CSF is attenuated in individuals with reduced whole-body insulin sensitivity, which suggests that insulin resistance at the blood–CSF barrier could impair transport of the hormone into the brain. Accordingly, insulin concentrations in CSF are lower in individuals with obesity, who are generally more insulin resistant, than in people without obesity. Furthermore, insulin concentrations within brain tissue and CSF are reduced in older individuals…In Alzheimer disease, a condition often associated with insulin resistance, insulin levels in the CSF have been reported to be reduced.”

 

Fasting insulin reliably shows insulin resistance

International Journal of ObesityInsulin resistance requires elevated levels of insulin to promote cellular uptake of glucose from the bloodstream. Higher levels of insulin do harm throughout the brain and body long before blood glucose levels go up (either fasting or during a glucose tolerance test) as the compensatory system fails. How should clinicians detect early stages of insulin resistance that occur before elevations in blood glucose or HgbA1c? Research published in the International Journal of Obesity offers evidence that fasting plasma insulin reliable detects insulin resistance, at least in cases of obesity. The authors state:

Insulin resistance is the major contributor to cardiometabolic complications of obesity. We aimed to (1) establish cutoff points for insulin resistance from euglycemic hyperinsulinemic clamps (EHCs), (2) identify insulin-resistant obese subjects and (3) predict insulin resistance from routinely measured variables.”

Using reference ranges for hepatic and peripheral insulin sensitivity calculated from healthy non-obese men, they examined data for data from both non-obese and obese men who using two-step EHCs using (insulin infusion dose 20 and 60 mUm−2min−1, respectively). Reference ranges for hepatic and peripheral insulin sensitivity were calculated from healthy non-obese men. Based on these reference values, obese men with preserved insulin sensitivity or insulin resistance were identified. They succeeded in showing that the obese subjects with insulin resistance could be discriminated from those with normal insulin sensitivity by the fasting insulin level:

“Cutoff points for insulin-mediated suppression of endogenous glucose production (EGP) and insulin-stimulated glucose disappearance rate (Rd) were 46.5% and 37.3μmolkg1min1, respectively. Most obese men (78%) had EGP suppression within the reference range, whereas only 12% of obese men had Rd within the reference range. Obese men with Rd <37.3μmolkg−1min−1 did not differ from insulin-sensitive obese men in age, body mass index (BMI), body composition, fasting glucose or cholesterol, but did have higher fasting insulin (110±49 vs 63±29pmol) and homeostasis model assessment of insulin resistance (HOMA-IR) (4.5±2.2 vs 2.7±1.4). Insulin-resistant obese men could be identified with good sensitivity (80%) and specificity (75%) from fasting insulin >74pmoll−1.”

Body mass index (BMI), body composition, fasting glucose and cholesterol were not good predictors of insulin resistance but the fasting plasma insulin level was. [I’m surprised that they didn’t include triglycerides levels which are particularly sensitive to insulin levels.] Note: fasting insulin >74pmoll−1 = >10.7 μU/ml.

There are a number of benign and wholesome agents along with lifestyle adjustments that can be employed to ameliorate insulin resistance. This study shows that 10.7 μU/ml can be used as a clinical decision level for more aggressive targeting of IR. Moreover, it stands to reason that this biomarker can be used for slim but ‘metabolically obese’ patients. The authors conclude:

“Most obese men have hepatic insulin sensitivity within the range of non-obese controls, but below-normal peripheral insulin sensitivity, that is, insulin resistance. Fasting insulin (>74pmoll−1 with current insulin immunoassay) may be used for identification of insulin-resistant (or metabolically unhealthy) obese men in research and clinical settings.”

Skipping breakfast worsens blood glucose and insulin later

Diabetes CareBreakfast is a cornerstone of healthy metabolism. A study just published in the journal Diabetes Care now shows that skipping breakfast damages the blood glucose and insulin response to meals later in the day. The authors note:

Skipping breakfast has been consistently associated with high HbA1c and postprandial hyperglycemia (PPHG) in patients with type 2 diabetes. Our aim was to explore the effect of skipping breakfast on glycemia after a subsequent isocaloric (700 kcal) lunch and dinner. “

They compared postprandial plasma glucose, insulin, C-peptide, free fatty acids (FFA), glucagon, and intact glucagon-like peptide-1 (iGLP-1) for subjects randomly assigned to one day with breakfast, lunch, and dinner (YesB) and another with lunch and dinner but no breakfast (NoB). Their data show that skipping the morning meal messed up metabolism for the rest of the day:

“Compared with YesB, lunch area under the curves for 0–180 min (AUC0–180) for plasma glucose, FFA, and glucagon were 36.8, 41.1, and 14.8% higher, respectively, whereas the AUC0-180 for insulin and iGLP-1 were 17% and 19% lower, respectively, on the NoB day (P < 0.0001). Similarly, dinner AUC0-180 for glucose, FFA, and glucagon were 26.6, 29.6, and 11.5% higher, respectively, and AUC0-180 for insulin and iGLP-1 were 7.9% and 16.5% lower on the NoB day compared with the YesB day (P < 0.0001). Furthermore, insulin peak was delayed 30 min after lunch and dinner on the NoB day compared with the YesB day. “

In other words, it worsened hyperglycemia and insulin resistance after both lunch and dinner. The authors conclude:

“Skipping breakfast increases PPHG after lunch and dinner in association with lower iGLP-1 and impaired insulin response. This study shows a long-term influence of breakfast on glucose regulation that persists throughout the day. Breakfast consumption could be a successful strategy for reduction of PPHG in type 2 diabetes.”

It’s also clearly important for prevention of type 2 diabetes and all the depredations of insulin resistance and dysregulated blood sugar.

Insulin resistance indicated by neutrophil-lymphocyte ratio

BMC Endocrine DisordersInsulin resistance (IR) is central to type 2 diabetes and a contributing cause to cardiovascular and neurodegenerative disorders, chronic kidney disease (CKD), a number of cancers and more. A study recently published in BMC Endocrine Disorders the ratio between neutrophils and lymphocytes (neutrophil-lymphocyte ratio, NLR) is a valuable and inexpensive predictive marker for insulin resistance. The authors note:

“Insulin resistance (IR) is a reduction in reaction or sensitivity to insulin and is considered to be the common cause of impaired glucose tolerance, diabetes, obesity, dyslipidemia, and hypertensive diseases….several studies have confirmed the relationship between systemic inflammation and insulin resistance, in which an altered immune system plays a decisive role in the pathogenesis of DM. The immune response to various physiological challenges is characterized by increased neutrophil and decreased lymphocyte counts, and NLR is often recognized as an inflammatory marker to assess the severity of the disease.”

Furthermore…

“Scholars have rarely investigated the relationship between IR and NLR. This study aims to evaluate the relationship between IR and NLR, and determine whether or not NLR is a reliable marker for IR.”

Mean neutrophil-lymphocyte ratio (NLR) values of the groups. Group 1 is diabetic w/o IR, Group 2 is diabetic with IR.

Mean neutrophil-lymphocyte ratio (NLR) values of the groups. Group 1 is diabetic w/o IR, Group 2 is diabetic with IR.

So they investigated the neutrophil-lymphocyte ratio in 413 patients with T2DM, 310 of whom had a HOMA-IR value (fasting plasma glucose (mmol/L) multiplied by fasting serum insulin (mIU/L) divided by 22.5) of > 2.0, indicating insulin resistance. They were compared to a control group of 130 healthy subjects and found a strong association:

“The NLR values of the diabetic patients were significantly higher than those of the healthy control, and the NLR values of the patients with a HOMA-IR value of > 2.0 are notably greater than those of the patients with a HOMA-IR value of ≤ 2.0. Pearson correlation analysis showed a significant positive correlation of NLR with HOMA-IR. Logistic regression analysis showed that the risk predictors of IR include NLR, TG and HbA1c. NLR levels correlated positively with IR. The IR odds ratio increased by a factor of 7.231 (95%) for every one unit increase in NLR.”

 Diabetes, cancer and cardiovascular diseases

In relation to their confirmation of NLR as a predictor for insulin resistance the authors observe…

“Many epidemiological studies have determined that DM is associated with chronic inflammation, which may contribute to the acceleration of diabetic microangiopathy and the development of macroangiopathy; IR is a characterized of T2DM, whereas the exact molecular action leading to IR is not yet understood, several studies have associated IR with inflammation, experimental studies have demonstrated a link between chronic inflammation and insulin resistance through mechanisms involving obesity and atherosclerosis. NLR has been recently defined as a novel potential inflammation marker in cancer and cardiovascular diseases. NLR can easily be calculated using the neutrophil-lymphocyte ratio in peripheral blood count. Calculating NLR is simpler and cheaper than measuring other inflammatory cytokines, such as IL-6, IL-1β, and TNF-α.”

Diabetes and chronic inflammation

These findings highlight the relationship between chronic inflammation, insulin resistance and type 2 diabetes.

“he pathological activation of innate immunity leads to inflammation of the islet cells, resulting in a decrease in pancreatic beta-cell mass and impaired insulin secretion. Patients with T2DM are in a state of low-degree chronic inflammation that induces hypersecretion of inflammatory factors, such as CRP, IL-6, TNF-α, and MCP-1, which results in a constantly elevated neutrophilic granulocyte count. One mechanism by which increased levels of neutrophils could mediate IR may be through augmented inflammation. The increase in NLR appears to underlie the elevated levels of pro-inflammation, as evident from the persistent neutrophil activation and enhanced release of neutrophil proteases with T2DM.”

 NLR tracks HgbA1c and triglycerides

Glycation of hemoglobin (HgbA1c) and triglycerides (TG) both go up as insulin resistance progresses along with the neutrophil-lymphocyte ratio.

“A logistic regression analysis of the following risk factors was conducted: NLR, TG and HbA1c. In our study, in conjunction with the rising of the level of HbAlc, the degree of IR increased significantly. HbA1c showed an association with early-phase insulin secretion assessed by insulinogenic index. Heianza et al. reported that elevated HbA1c levels of above 41 mmol/mol (>5.9%) were associated with a substantial reduction in insulin secretion and insulin sensitivity as well as an association with β-cell dysfunction in Japanese individuals without a history of treatment of diabetes. Increased accumulation of TG has been observed in human muscle tissue of obese and type 2 diabetic subjects, and associated with IR, which is in agreement with the present study. IR reduces the inhibition effect of lipolysis in adipose tissue, resulting in the increase of the free fatty acid (FFA) level in plasma.”

NLR is a superior biomarker

Although susceptible to modification by dehydration, elevated PSA or catecholamine release induced by exercise, the NLR is more sensitive than the neutrophil count alone or CRP levels.

“NLR represents a combination of two markers where neutrophils represent the active nonspecific inflammatory mediator initiating the first line of defense, whereas lymphocytes represent the regulatory or protective component of inflammation. NLR is superior to other leukocyte parameters (e.g., neutrophil, lymphocyte, and total leukocyte counts) because of its better stability compared with the other parameters that can be altered by various physiological, pathological, and physical factors. Thus, as a simple clinical indicator of IR, NLR is more sensitive compared with the neutrophilic granulocyte count and CRP levels, which are widely used as markers of IR.”

Clinical bottom line

Practitioners should not fail to make use of this significant, inexpensive biomarker that is under our noses every day. The authors sum it up:

“…in the present study, NLR serves an important function in predicting the risk of IR. IR in diabetic patients is related to chronic inflammation, and NLR may be helpful in assessing the prognoses of these patients…We recommend that the NLR values of diabetic patients be calculated as NLR is a cheap, predictive, and prognostic marker for IR. High NLR values were independently related to IR.”