There is an evidence-based middle ground between the dogmas of those who assert that cholesterol is the main cause of cardiovascular disease and those who insist that its contribution is trivial. An interesting paper just published in the Journal of Clinical Lipidology illustrates an important mechanism by which cholesterol crystals trigger an inflammatory response.
“The response to arterial wall injury is an inflammatory process, which over time becomes integral to the development of atherosclerosis and subsequent plaque instability…In this review, a model of plaque rupture is hypothesized with two stages of inflammatory activity.”
In the first stage buildup of cholesterol crystals inside the “foam” cells that accumulate cholesterol induces their death (“apoptosis”); these dead cells elicit an inflammatory response that gathers more lipids into a vulnerable plaque. In stage two further expansion of crystals leads to intimal (blood vessel wall) injury…
“…which can manifest as a clinical syndrome with a systemic inflammation response…We recently demonstrated that when cholesterol crystallizes from a liquid to a solid state, it undergoes volume expansion, which can tear the plaque cap. This observation of cholesterol crystals perforating the cap and intimal surface was made in the plaques of patients who died with acute coronary syndrome.”
The authors refer to their previous work showing that alcohol, aspirin and statins can dissolve cholesterol crystals. Their conclusion:
“…we propose that cholesterol crystallization could help explain in part both local and systemic inflammation associated with atherosclerosis.”
Of course there are a number of other pathways to inflammation in cardiovascular disease (please see related posts) but this is one of the reasons why I prefer that patients who have both high cholesterol and evidence of inflammation have the benefit of the natural statin derived from red rice yeast with the necessary supportive and protective cofactors including coenzyme Q10. This paper published recently in the American Journal of Cardiology provides evidence that red rice yeast is as effective and better tolerated than the commonly prescribed drug pravastatin:
“The present trial evaluated the tolerability of red yeast rice versus pravastatin in patients unable to tolerate other statins because of myalgia.”
The authors enrolled adults who had to discontinue statins due to muscle pain. Their findings are reassuring for those who prefer a natural alternative to pharma statins:
“The low-density lipoprotein cholesterol level decreased 30% in the red yeast rice group and 27% in the pravastatin group. In conclusion, red yeast rice was tolerated as well as pravastatin and achieved a comparable reduction of low-density lipoprotein cholesterol in a population previously intolerant to statins.”
This is a serious issue. Statin-associated myalgia or the diagnosis rhabdomyolysis does not do justice to the devastating side effects I recently observed in a patient who had a bad reaction to lovastatin.
But how do we know when to intervene since high cholesterol alone is not a reliable risk factor and CRP (c-reactive protein) may not be elevated if the inflammation it is supposed to report is also preventing the liver from making it? One very helpful test for discriminating whether high cholesterol is contributing to vascular disease is the lipoprotein-associated phospholipase A2 (Lp-PLA2, PLAC) test, described here in an earlier post, that is associated specifically with inflammation in plaques. Another relies on the fact that it is cholesterol that has been damaged by oxidation that participates in the vascular lesion. To gauge this we can measure lipid peroxides. As this paper published in the journal Atherosclerosis documents, atherosclerosis is strongly associated with the presence of oxidized LDL:
“We investigated the relation between serum lipids including oxidized LDL and the severity of coronary atherosclerosis. Serum lipids and oxidized LDL was measured in 62 men (33–66 years), who underwent diagnostic coronary angiography and sonography to measure the carotid intima-media thickness…Regression analysis indicated that the carotid intima-media thickness and…the ox-LDL:LDL ratio…were the only factors associated independently with the severity of coronary atherosclerosis.”
We have also a fascinating study just published in the German medical journal Seminars in Thrombosis & Hemostasis that shows how oxidized LDL taken up by platelets induces inflammation in the blood vessel:
“Platelets are involved in the initiation of atherosclerosis by adherence to inflamed endothelium…In this study we investigated the functional consequences of oxidized low-density lipoprotein (oxLDL) uptake on platelet function and interaction with the endothelium.”
The authors were actually able to visualize the intracellular vesicles (microscopic sacs) containing the oxidized LDL using immunoflorescence microscopy. They made a fascinating observation: the platelets containing oxLDL provoked more cellular stickiness than regular LDL, oxLDL in the bloodstream or platelets without oxLDL.
“Furthermore, oxLDL-laden platelets induced foam cell development from CD34+ progenitor cells. On endothelial regeneration, oxLDL-laden platelets had the opposite effect: The number of CD34+ progenitor cells (colony-forming units) able to transform into endothelial cells was significantly reduced in the presence of oxLDL-platelets, whereas native LDL had no effect.”
This is a striking insight: it was only the oxidized LDL that prevented the endothelial cells (lining the blood vessel wall) from repairing, not the ‘native’ LDL.
Doctors and patients alike need to bear in mind the summary of their findings:
“Our results demonstrate that activated platelets internalize oxLDL and that oxLDL-laden platelets activate endothelium, inhibit endothelial regeneration, and promote foam cell development. Platelet oxLDL contributes significantly to vascular inflammation and is able to promote atherosclerosis.”
But, you may ask, since diabetes and pre-diabetes (metabolic syndrome) are so strongly associated with cardiovascular disease shouldn’t there be some kind of connection here? This study published in the journal Lipids shows the evidence that there is.
“Oxidized low-density lipoprotein (ox-LDL) plays a key role in the progression of atherosclerosis and diabetes complications. The aim of this study was first, to evaluate the association between ox-LDL and diabetes duration, and second, to examine serum level of ox-LDL in patients with prolonged diabetes and a desirable LDL-cholesterol level.”
It’s important to appreciate that the study group had ‘regular’ LDL in the desirable range, so a typical blood test would appear to be fine. Their very interesting observation is that the longer the person had diabetes (= the longer the risk factor for cardiovascular disease was building up) the more oxLDL they had in proportion to regular LDL:
“The ox-LDL-to-LDL ratio was dramatically higher in patients with diabetes duration >5 years in comparison to newly diagnosed patients and healthy participants. Ox-LDL was significantly associated with diabetes duration.”
Their final comments must be borne in mind by anyone caring for patients with both diabetes and a significant burden of insulin resistance:
“In conclusion, this study showed that the serum ox-LDL level increases with the length of diabetes, even though the patients’ LDL-cholesterol level is maintained at a desirable level. Our findings highlight that possibly more attention should be focused on markers of oxidative stress in the management of lipids in diabetic patients.”
Can we reliably measure oxidized LDL as implied by the lab test mentioned above? This study published in the journal Blood Pressure assure us that we can:
“Cardiovascular diseases are accompanied by the presence of active oxygen species and organic free radical generation. The aim of this study was to examine the possibility of using malondialdehyde (MDA)-modified low-density lipoprotein (LDL) analyses as a diagnostic and prognostic biomarker.”
MDA-modified LDL is the same as oxLDL. What conclusion did they draw from their data?
“MDA-modified LDL estimation has a diagnostic accuracy and may be used as an independent biochemical marker for atherosclerosis.”
Truthfully, the functional approach to cardiovascular disease encompasses a number of other important aspects, but I’m wondering if you’ve gotten this far. As a reward for your diligence I’ll conclude this limited post with a few interesting items of satisfying practical significance. First we have a paper just published in The Journal of Steroid Biochemistry & Molecular Biology that reassures us of the benefit of vitamin D in the prevention and treatment of cardiovascular disease.
“Cardiovascular disease (CVD) is the leading cause of morbidity and mortality in patients with type 2 diabetes mellitus (T2DM). In type 2 diabetics, the prevalence of vitamin D deficiency is 20% higher than in non-diabetics, and low vitamin D levels nearly double the relative risk of developing CVD compared to diabetic patients with normal vitamin D levels.”
The authors endeavored to uncover the mechanism behind vitamin D’s benefit:
“We found that 1,25-dihydroxy vitamin D3 [1,25(OH)2D3] suppressed foam cell formation by reducing acetylated low density lipoprotein (AcLDL) and oxidized low density lipoprotein (oxLDL) cholesterol uptake in diabetics only. …In addition, 1,25(OH)2D3…improved insulin signaling, downregulated SR-A1 expression, and prevented oxLDL- and AcLDL-derived cholesterol uptake.”
You can remember their conclusion when getting your vitamin D level checked:
“The results of this research reveal novel insights into the mechanisms linking vitamin D signaling to foam cell formation in diabetics and suggest a potential new therapeutic target to reduce cardiovascular risk in this population.”
Throw some nuts in there too. A nice original study was published not long ago in The Anatolian Journal of Cardiology evaluated the benefit of hazelnuts (filberts) on atherosclerosis. The authors observed a number of interesting effects:
“Lag time for oxidation and α-tocopherol content of LDL were found to be increased while ox-LDL levels decreased during the study period. Total cholesterol, LDL-cholesterol, apolipoprotein (apo) B and apo B/apo AI ratio were found to be significantly lower while apo AI was higher. In respect to LDL subfraction, ratio of large/small LDL was significantly increased at the end of the study.”
They summed up their ‘take home’ message on hazelnuts (which earlier posts suggest applies to most if not all nuts) accordingly:
“Hazelnut-enriched diet may play important role in decrease in atherogenic tendency of LDL by lowering the susceptibility of LDL to oxidation and plasma ox-LDL levels, and increasing the ratio of large/small LDL beyond its beneficial effect on lipid and lipoprotein levels.”
Helicobacter pylori infection is, as you likely know, extremely common—according to WHO the most common infection in the world. It is a causative agent in almost all gastric ulcers. We see it here all the time. Finding out if you have it and getting it treated is another important therapeutic point for cardiovascular disease as this paper just published in the journal Digestive Diseases and Sciences reminds us. The authors investigated the impact of H. pylori infection on coronary atherosclerosis by examining the effects of infection on levels of serum lipid, high-sensitivity C-reactive protein (hsCRP) and oxidized low-density protein (oxLDL). What did their data show?
“The levels of total cholesterol, LDL, apolipoprotein B, serum hsCRP, oxLDL were significantly elevated and the severity of coronary atherosclerosis was significantly increased in H. pylori…group.”
Their conclusion echoes the findings of other investigators:
“More serious coronary atherosclerosis was observed in CHD patients with H. pylori…infection. H. pylori…infection might be involved in coronary atherosclerosis by modifying serum lipids, enhancing LDL oxidation, and activating the inflammatory responses.”
Remember, the most reliable ways to diagnose H. pylori infection are by stool antigens, a provoked breath test, or PCR (DNA amplification). H. pylori antibodies are not dependable.
Although it’s a major topic that deserves more space, mention at least much be made of the autoimmune aspect of cardiovascular disease as described in this recent paper published in the journal Angiology:
“Atherosclerosis is now recognized as a chronic inflammatory disease and is characterized by features of inflammation at all stages of its development. It also appears to display elements of autoimmunity, and several autoantibodies including those directed against oxidized low-density lipoprotein (ox-LDL) and heat shock proteins (Hsps) have been identified in atherosclerosis.”
The authors then describe their investigation of immune complexes, antibodies and receptor signaling in this process. Certain cases demand a thorough evaluation of the autoimmune component of their CVD.
It would also not be appropriate to close without at least alluding to the influence of hormones on cardiovascular disease, a topic that has many aspects treated in other posts. This paper recently published in the journal Endocrinology makes a very important but little known point for men (for whom most everyone knows that too little testosterone or excess conversion to estrogen is a big risk factor for CVD). Testosterone is normally converted into its dihydrotestosterone form (DHT) which does a lot of the heavy lifting because it’s ten times stronger than the original. Men with prostate disease are commonly prescribed medications (including saw palmetto) that block the conversion of testosterone to DHT, but without first measuring the levels of the bioactive forms of these hormones. These medications don’t always help because not everyone with a prostate condition has too much DHT. Moreover, DHT is important for protection against cardiovascular disease. The authors…
“…investigated the effect of…dihydrotestosterone (DHT) on the rabbit atherogenesis in relation to…oxidized-low-density lipoprotein receptor-1 (LOX-1) and its downstream molecules.”
What did they find?
“…DHT significantly reduced HCD-induced [high cholesterol diet-induced] foam cell formation…DHT inhibited the formation of foam cells induced by oxidized low-density lipoprotein. Moreover, the expression of LOX-1 and inflammatory cytokines in the cultured macrophages was significantly suppressed by DHT.”
Inappropriately blocking the conversion of testosterone to DHT can thus open a door to cardiovascular disease. So remember, both gentlemen and ladies: no hormone interventions without measuring the free-fraction bioactive levels before and after!