Fish oil may be an antidote for the cardiovascular risk of smoking

Activation of group IVC phospholipase A(2) by polycyclic aromatic hydrocarbons induces apoptosis of human coronary artery endothelial cells

Exposure to environmental pollutants, such as polycyclic aromatic hydrocarbons (PAHs) found in coal tar mixtures and tobacco sources, is considered a significant risk factor for the development of heart disease in humans. The goal of this study was to determine the influence of PAHs present at a Superfund site on human coronary artery endothelial cell (HCAEC) phospholipase A(2) (PLA(2)) activity and apoptosis. Extremely high levels of 12 out of 15 EPA high-priority PAHs were present in both the streambed and floodplain sediments at a site where an urban creek and its adjacent floodplain were extensively contaminated by PAHs and other coal tar compounds. Nine of the 12 compounds and a coal tar mixture (SRM 1597A) activated group IVC PLA(2) in HCAECs, and activation of this enzyme was associated with histone fragmentation and poly (ADP) ribose polymerase (PARP) cleavage. Genetic silencing of group IVC PLA(2) inhibited both (3)H-fatty acid release and histone fragmentation by PAHs and SRM 1597A, indicating that individual PAHs and a coal tar mixture induce apoptosis of HCAECs via a mechanism that involves group IVC PLA(2). Western blot analysis of aortas isolated from feral mice (Peromyscus leucopus) inhabiting the Superfund site showed increased PARP and caspase-3 cleavage when compared to reference mice. These data suggest that PAHs induce apoptosis of HCAECs via activation of group IVC PLA(2).

Iatrogenic lipodystrophy in HIV patients – the need for very-low-fat diets

In HIV patients, chronic treatment with protease inhibitors often precipitates a peripheral lipodystrophy associated with insulin resistance syndrome and premature coronary disease. In vitro studies demonstrate that these drugs can compromise the ability of adipocytes to store triglycerides; in vivo, peripheral subcutaneous adipocytes appear to be most affected, such that body fat often redistributes to visceral or truncal adipose stores. Dysfunction of peripheral subcutaneous adipocytes - ordinarily quite efficient for storing fat - can be expected to give rise to an excessive flux of free fatty acids (FFAs) following fatty meals; chronic overexposure of tissues to FFAs is a likely explanation for the insulin resistance syndrome associated with lipodystrophy. These considerations suggest that a very-low-fat diet - less than 15% fat calories - may ameliorate the cardiovascular risk associated with lipodystrophy; such diets are known to have a favorable effect on the insulin sensitivity of healthy subjects. Very-low-fat whole-food vegan diets are particularly recommendable in this context, as they may help to shrink visceral fat depots while markedly reducing LDL cholesterol. Appropriate adjunctive measures may include aerobic exercise training - beneficial both for insulin sensitivity and weight control - as well as administration of statins or policosanol, and of fibrates or fish oil, to decrease LDL and triglycerides, respectively. Despite perceptions to the contrary, very-low-fat diets can meet with good compliance in well-motivated subjects given appropriate instruction.

The porphyrin pathway: the final common pathway?

When I was learning pathology a wise and knowledgeable mentor described a final common pathway that allows many diseases to overlap in their presentation. This pathway was never identified for it was unknown. Recent books by physicians have suggested that maintaining body balance and/or treatment by a substance could halt or repair damage caused by a wide array of diseases, once again suggesting a common thread amongst diseases. Again no mention was made regarding what was this common denominator. I have been interested in people who have more than one disease, feeling that there must be a link. My interest in the porphyrin pathway has strengthened that impression. Since finding Doss's list of diseases having porphyrin abnormalities unrelated to a porphyria, I have worked on models that would allow me to show a way where porphyrin abnormalities may be a part of the final common pathway for all disease. I have finally decided that a spider's web is that model. The following discussion will attempt to demonstrate that this hypothesis could be true.

Polycyclic aromatic hydrocarbons present in cigarette smoke cause endothelial cell apoptosis by a phospholipase A2-dependent mechanism

Smoking is a major risk factor for endothelial cell injury and subsequent coronary artery disease. Epidemiological studies implicate the phospholipase A2/arachidonic acid cascade in the mechanism by which smoking causes heart disease. However, specific components of cigarette smoke that activate this pathway have not been identified. The purpose of this study was to investigate the effects of polycyclic aromatic hydrocarbons contained in cigarette smoke on phospholipase A2 (PLA2) activity and apoptosis of human coronary artery endothelial cells. 1-methylanthracene (1-MA), phenanthrene (PA), and benzo(a)pyrene (B(a)P) caused significant release of 3H-arachidonate from endothelial cells. 1-MA and PA, but not B(a)P, also caused significant release of 3H-linoleic acid. Release of fatty acids from membrane phospholipids preceded the onset of apoptosis. 3H-arachidonate release and apoptosis induced by 1-MA, B(a)P, and PA were inhibited by methylarachidonoyl-fluorophosphonate, an inhibitor of Groups IV and VI PLA2s. Bromoenol lactone, an inhibitor of Group VI enzymes, inhibited both 3H-arachidonate release and apoptosis induced by 1-MA and PA, but not B(a)P. MJ33, an inhibitor of the acidic calcium-independent PLA2, attenuated 3H-arachidonate release and apoptosis by PA, but not 1-MA or B(a)P. The presence of Groups IV and VI and the acidic iPLA2 in endothelial cells was demonstrated by reverse transcriptase-polymerase chain reaction and Western analysis. These data suggest that 1-MA, B(a)P and PA induce apoptosis of endothelial cells by a mechanism that involves activation of these three distinct isoforms of PLA2.

Complementary measures for promoting insulin sensitivity in skeletal muscle

Insulin resistance of skeletal muscle is fundamental to both syndrome X and its frequent sequel, type II diabetes. In these disorders, excessive exposure of muscle to free fatty acids (FFAs) and their metabolic derivatives appears to play a prominent role in the induction of insulin resistance. Recent evidence suggests that activation of novel isoforms of protein kinase C (PKC) by diacylglycerol may mediate at least part of the adverse impact of FFAs on muscle insulin sensitivity. Vitamin E and fish oil omega-3s, by promoting the activity of diacylglycerol kinase and inhibiting that of phosphatidate phosphohydrolase, should reduce diacylglycerol levels, thus accounting for their documented favorable impact on insulin sensitivity. Thiazolidinediones such as troglitazone, on the other hand, appear to intervene in the signaling pathway whereby PKC down-regulates insulin function. The insulin-sensitizing activity of chromium picolinate may be attributable, at least in part, to increased expression of insulin receptors. In combination with lifestyle modifications which reduce FFA exposure--weight loss, very-low-fat eating, excessive training--these measures can be expected to work in a complementary way to promote increased numbers of insulin receptors that are more functionally competent. As these measures appear to be safe and well-tolerated, they may have utility for the prevention of diabetes as well as its therapy. When they do not prove sufficient to achieve optimal glycemic control, excessive hepatic glucose output and impaired cell response to glucose can be addressed with metformin and sulfonylureas, respectively. The prospects for a rational medical management of type II diabetes, obviating the need for injectible insulin, have never been brighter.

A central role for protein kinase C overactivity in diabetic glomerulosclerosis: implications for prevention with antioxidants, fish oil, and ACE inhibitors

The primary etiologic factor in diabetic glomerulosclerosis appears to be an overproduction of transforming growth factor-beta by mesangial cells, which in turn reflects a hyperglycemically mediated overactivation of protein kinase C (PKC) throughout the glomerulus. Membrane-active antioxidants, fish oil, and angiotensin-converting enzyme inhibitors can act to down-regulate glomerular PKC activity, via a variety of mechanisms that may include activation of diacylglycerol kinase and suppression of phosphatidate phosphohydrolase, support of endothelial nitric oxide and heparan sulfate production, inhibition of thromboxane and angiotensin synthesis/activity, and correction of glomerular hypertension. The beneficial impact of these measures on vascular endothelial function may be of more general utility in the prevention of diabetic complications such as retinopathy, neuropathy, and atherosclerosis. Adjunctive use of gamma-linolenic acid is indicated for prevention of neuropathy, and it is conceivable that bioactive chromium will have protective activity not solely attributable to improved glycemic control. Re-establishing euglycemia must clearly remain the core strategy for preventing diabetic complications, but when glycemic control remains suboptimal, practical, safe measures are at hand for decreasing risk.