Plasma lipid relationships, effect

Recognition of a beneficial effect of exercise on the Incidence of CHD has led to numerous cross-sectional and longitudinal studies designed to examine the Influence of physical activity on major coronary risk factors, with particular emphasis on plasma lipids and lipoproteins. A number of comprehensive reviews have summarized these studies (14-18). In general. In cross-sectional studies, high density lipoprotein (HDL) cholesterol is elevated (14) and total plasma and very low density lipoprotein (VLDL) triglycerides are lower In endurance trained subjects than In sedentary control subjects (14). In a study of 23 top-level male athletes, Lehtonen and Vllkarl (19) found a statistically significant relationship between the number of kilometers that the athletes ran or skied weekly and their plasma HDL cholesterol concentration (P<0.05 r=0.554). Low density lipoprotein (LDL) cholesterol Is frequently lower, and plasma total cholesterol Is Inconsistently lower In trained subjects (19). 

The plasma concentration of a P-adrenoceptor blocker may have a complex relationship with its effect, for several reasons. First-order kinetics usually apply to elimination of drug from plasma, but the decline in receptor block is zero-order. The practical application is important within 4 h of giving propranolol 20 mg i.v. the plasma concentration falls by 50%, but the receptor block (as measured by exerdse-induced tachycardia) falls by only 35%. The relationship between the concentration of the parent drug in plasma and its effect is further obscured if pharmacologically active metabolites are also present. Additionally, for some of the lipid-soluble p-blockers, especially timolol, plasma t/ may not reflect the duration of P-blockade since the drug remains boimd to the tissues near the receptor when the plasma concentration is negligible. 

A number of plants and phytochemicals have attracted attention for their ability to reduce many of the risk factors associated with cardiovascular disease. Research into these diseases has shown the relationship between lesions, fatty streaking and plaque formation in blood vessels and the development of strokes and myocardial infarctions. These effects are linked to levels of plasma lipids which comprise triglycerides, cholesterol and other fat substances. It is known that the biosynthesis of lipids involves the condensation of several molecules of acetylcoenzyme A and malonylcoenzyme A in a gradual process of elongation of the fatty acid chain involving the sequential addition of two carbon units giving rise to fatty acids such as lauric acid (12 carbons) and eventually to palmitic acid (16 carbons). Palmitic acid is the precursor... 

The relationship between dietary fats and cardiovascular disease (CVD), especially CHD, has been extensively investigated, with strong and consistent associations emerging from a wide body of evidence accrued from animal experiments, as well as observational studies, clinical trials, and metabolic studies conducted in diverse human populations. This relationship was initially considered to be mediated mainly through the atherogenic effects of plasma lipids (total cholesterol, lipoprotein fractions, and triglycerides). The effects of dietary fats on... 

The role of the antioxidant properties of vitamins C, E, and p-carotene in the prevention of cardiovascular disease has been the focus of several recent studies. Antioxidants reduce the oxidation of low-density lipoproteins, which may play a role in the prevention of atherosclerosis. However, an inverse relationship between the intake or plasma levels of these vitamins and the incidence of coronary heart disease has been found in only a few epidemiological studies. One study showed that antioxidants lowered the level of high-density lipoprotein 2 and interfered with the effects of lipid-altering therapies given at the same time. While many groups recommend a varied diet rich in fruits and vegetables for the prevention of coronary artery disease, empirical data do not exist to recommend antioxidant supplementation for the prevention of coronary disease. 

Nasta et al. also tried to investigate the relationship between cholesterol and mood states in the initial puerperal period. Their results showed that reduced plasma cholesterol concentration was associated with major feelings of fatigue and depressed mood [79]. In addition, West et al. compared the effects of transdermal versus oral estrogens on the vascular resistance index, mean arterial pressure, serum lipid concentrations, norepinephrine, and left ventricular structure in 10 postmenopausal women. The results showed that oral and transdermal estrogen significantly decreased the vascular resistance index, mean arterial pressure, norepinephrine, and total and low-density lipoprotein cholesterol to a similar extent [80],... 

Sorci-Thomas, M., Prack, M.M., Dashti, N., Johnson, F., Rudel, LI.., and Williams, D.L. (1989) Differential Effects of Dietary Fat on the Tissue-Specific Expression of the Apolipoprotein A-I Gene Relationship to Plasma Concentration of High-Density Lipoproteins, 7. Lipid Res. 30, 1397-1403. 

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