Effects of exercise and fat ingestion on high density lipoprotein production by peripheral tissues

High-Density Lipoprotein Subfractions and Cholesterol Efflux Capacity Are Not Affected by Supervised Exercise but Are Associated with Baseline Interleukin-6 in Patients with Peripheral Artery Disease

OBJECTIVE

To quantify the association between high-density lipoprotein (HDL) subfractions, efflux capacity, and inflammatory markers at baseline and the effect of supervised exercise on these HDL parameters in patients with peripheral artery disease (PAD).

METHODS

The study to improve leg circulation (SILC) was a randomized trial of supervised treadmill exercise, leg resistance training, or control in individuals with PAD. In a post hoc cross-sectional analysis, we quantified the associations between baseline HDL subfraction concentrations (HDL2 and HDL3), HDL-C efflux capacity, and inflammatory markers [C-reactive protein (CRP) and interleukin-6 (IL-6)]. We then examined the effect of supervised exercise on changes in these lipoprotein parameters and inflammatory markers in 88 patients from SILC.

RESULTS

Baseline HDL-C efflux capacity was associated with baseline concentrations of HDL2 (β = 0.008, p = 0.0106), HDL3 (β = 0.013, p < 0.0001), and IL-6 (β = -0.019, p = 0.03). Baseline HDL3 concentration was inversely associated with IL-6 concentration (β = -0.99, p = 0.008). Compared to control, changes in HDL2, HDL3, normalized HDL-C efflux capacity, CRP, or IL-6 were not significantly different at 6 months following the structured exercise intervention.

CONCLUSION

HDL efflux and HDL3 were inversely associated with IL-6 in PAD patients. Structured exercise was not associated with changes in HDL subfractions, HDL-C efflux capacity, CRP, and IL-6 in PAD patients. Our preliminary findings support the theory that inflammation may adversely affect HDL structure and function; however, further studies are needed to evaluate these findings.

Single session exercise stimulates formation of pre beta 1-HDL in leg muscle

Physical activity can raise the level of circulating HDL cholesterol. Pre beta 1-HDL is thought to be either the initial acceptor of cellular cholesterol or virtually the first particle in the pathway of the formation of HDL from apolipoprotein A-I and cellular lipids. We have therefore sought to identify pre beta 1-HDL in arterial and venous circulations of exercising legs in healthy individuals and in subjects with stable Type 2 diabetes mellitus. Blood samples were taken simultaneously from the femoral artery and vein before and after 25 min cycling exercise. The major findings were, first, that exercise significantly increased plasma concentration of pre beta 1-HDL (20% increase, P < 0.05) and second, that the pre beta 1-HDL concentration was significantly higher in the venous compared with the arterial blood both before and after exercise in both diabetics and controls. In the combined population, formation of pre beta 1-HDL at rest was 9.9 +/- 5.2 mg/min and exercise enhanced pre beta 1-HDL formation 6.6-fold in both groups.

Health effects resulting from exercise versus those from body fat loss

OBJECTIVE

The purpose of this review was to assess whether body weight confounds the relationships between physical activity and its health benefits.

METHODS

The review includes 80 reports from population-based studies (Evidence Category C) of physical activity or fitness and cardiovascular disease (CVD) or coronary heart disease (CHD).

RESULTS

Eleven of 64 reports on activity found no relationship between physical activity and disease. Of the remaining 53 reports, 11 did not address the possible confounding effects of body weight, nine cited reasons that weight differences should not explain their observed associations, and 33 statistically adjusted for weight (as required). Only three of these changed their associations from significant to nonsignificant when adjusted. Ten of 16 reports on cardiorespiratory fitness and CHD or CVD used statistical adjustment, and none of these changed their findings to nonsignificant. Population studies show that vigorously active individuals also have higher high-density lipoprotein (HDL)-cholesterol concentration, a major risk factor for CHD and CVD, than sedentary individuals when statistically adjusted for weight. In contrast, intervention studies, which relate dynamic changes in weight and HDL, suggest that adjustment for weight loss largely eliminates the increase in HDL-cholesterol in sedentary men who begin exercising vigorously. Adjusting the cross-sectional HDL-cholesterol differences for the dynamic effects of weight loss eliminates most of the HDL-cholesterol difference between active and sedentary men.

CONCLUSION

Population studies show that the lower incidence of CHD and CVD and higher HDL of fit, active individuals are not because of lean, healthy individuals choosing to be active (i.e., self-selection bias). Nevertheless, metabolic processed associated weight loss may be primarily responsible for the HDL differences between active and sedentary men, and possibly also their differences in CHD and CVD.

Decreased skeletal muscle capillary density is related to higher serum levels of low-density lipoprotein cholesterol and apolipoprotein B in men

The relationships between skeletal muscle morphology, particularly muscle fiber capillary density, and serum lipid profiles were evaluated in 25 non-obese men aged 18 to 36 years (body mass index [BMI], 22.7 +/- 2.5 kg/m2; body fat, 13.6% +/- 4.0%, maximal oxygen uptake [VO2max], 46.2 < or = 6.3 mL/kg/min). Skeletal muscle samples were taken from the vastus lateralis using the needle-biopsy method. The fiber types (I, IIa, and IIx) and their percent distribution, the indices of capillary density, and the diffusion index expressed as the cross-sectional area occupied by one capillary were determined. Blood samples were drawn from the antecubital vein after a 12-hour fast. Based on Pearson's correlation analysis, the number of capillaries around type IIx fiber correlated inversely with the serum level of low-density lipoprotein cholesterol ([LDL-C] r = -.50, P < .05). The number of capillaries per fiber (cap/fiber ratio), number of capillaries per area (cap/mm2), and capillaries around each fiber type correlated inversely with the serum level of apolipoprotein B ([apo B] r = -.40 to -.54, P < .05 to .01). Further, the diffusion index for each fiber type correlated positively with LDL-C and apo B (r = .42 to .50, P < .05 to .01). Among 14 subjects in whom high-density lipoprotein cholesterol (HDL-C) subfractions were analyzed, a positive correlation was found between cap/mm2 and HDL2-C (r = .64, P < .05). Partial correlation analysis showed that these correlations either remain or improve after adjusting for age, VO2max, and body fatness. These results indicate that skeletal muscle capillary density and diffusion capacity are related to lipid and apolipoprotein concentrations for both type I and type II fibers.

The influence of exercise on postprandial triacylglycerol metabolism

Trained people exhibit low plasma concentrations of triacylglcyeride (TAG) in both fasted and postprandial states. This mainly reflects enhanced uptake of TAG into skeletal muscle, via enhanced activity of lipoprotein lipase, the rate-limiting step in TAG removal. Endurance athletes possess a large, well-vascularised muscle mass and this may contribute through the increased availability of endothelial binding sites for LPL. However, each session of exercise stimulates a delayed increase in LPL activity so that prior exercise enhances uptake into muscle. Intramuscular TAG is one source of energy for muscular contraction so this may serve to replenish muscle nutrient stores which have been diminished by exercise. Regular, frequent aerobic exercise may oppose the atherogenic disturbances to lipoprotein metabolism evident during the postprandial period. It may also, by favouring the disposition of dietary fatty acids in muscle, improve the matching of fat oxidation to fat intake and hence help with maintenance of a desirable level of body fatness.

Effect of a high or a low fat diet on cardiovascular risk factors in male and female runners

Dietary fat may be associated with coronary heart disease (CHD). Studies suggest that restricting fat intake may compromise endurance performance and that increasing fat intake may improve endurance performance. We studied the effects of varying dietary fat intake on CHD risk factors in runners. Twelve male and 13 female runners increased fat from 16% to 30% of daily calories (4 wk each). Of this group, six males and six females increased fat to 42% of daily calories (4 wk). Physiological and lipoprotein risk factors were measured after each diet. Results were analyzed by repeated measures ANOVA. Increasing dietary fat from 16% to 42% of daily calories did not change adiposity, weight, heart rate, blood pressure, serum triglycerides, total cholesterol, LDL cholesterol. Apolipoprotein B, or the Apo A1/Apo B ratio. Compared with those eating higher fat, subjects eating 16% fat had lower HDL cholesterol (50 +/- 3 vs 62 +/- 3 mg.dl-1, P < 0.0001) and Apolipoprotein A1 (111 +/- 6 v. 134 +/- 6 mg/dl, P < 0.0005) and a higher TC/HDL-C ratio (4.05 +/- 0.27 vs 3.42 +/- 0.24, P < 0.0005). Runners who increased fat intake to 42% further raised HDL cholesterol (64 +/- 6 to 69 +/- 5 mg.dl-1, P < 0.04) without adversely affecting other lipoproteins. In conclusion, a 42% fat diet maintained favorable CHD risk factors in female and male runners whereas a 16% fat diet lowered Apo A1 and HDL-C and raised the TC/HDL-C ratio.

The associations of high-density lipoprotein subclasses with insulin and glucose levels, physical activity, resting heart rate, and regional adiposity in men with coronary artery disease: the Stanford Coronary Risk Intervention Project baseline survey

We used nondenaturing polyacrylamide gradient gel electrophoresis to examine the associations of high-density lipoprotein (HDL) subclasses with adiposity, physical activity, resting heart rate (an indicator of sympathetic drive), and plasma insulin and glucose levels in 97 men with angiographically documented coronary artery disease. These men neither smoked nor used medications known to affect lipoproteins. The absorbency of protein stain was used as an index of mass concentrations at intervals of 0.01 nm within five HDL subclasses: HDL3c (7.2 to 7.8 nm), HDL3b (7.8 to 8.2 nm), HDL3a (8.2 to 8.8 nm), HDL2a (8.8 to 9.7 nm), and HDL2b (9.7 to 12 nm). HDL peak diameter was determined from the predominant peak of the HDL particle distribution when plotted against particle diameter. Four men who were non-insulin-dependent diabetics as defined by a fasting glucose exceeding 140 mg/dL had significantly higher plasma HDL3b levels and significantly smaller HDL peak diameters than nondiabetic men, and were therefore excluded from further analyses. In the remaining 93 nondiabetic men, plasma HDL3b levels correlated positively with indices of truncal obesity (waist to hip ratio and subscapular skinfold), whereas plasma HDL2b levels correlated negatively with indices of total adiposity (body mass index [BMI]) and truncal obesity (subscapular and abdominal skinfold). Fasting plasma insulin levels correlated negatively with HDL3a, HDL2a, and HDL2b. Obesity significantly affected the relationships of resting heart rate with insulin and HDL subclasses.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of low-fat diet, calorie restriction, and running on lipoprotein subfraction concentrations in moderately overweight men

We studied the effects of exercise (primarily running), calorie restriction (dieting), and a low-fat, high-carbohydrate diet on changes in lipoprotein subfractions in moderately overweight men in a randomized controlled clinical trial. After 1 year, complete data were obtained for 39 men assigned to lose weight through dieting without exercise, 37 men assigned to lose weight through dieting with exercise (primarily running), and 40 nondieting sedentary controls. We instructed both diet groups to consume no more than 30% total fat, 10% saturated fat, and 300 mg/d of cholesterol, and at least 55% carbohydrates, and the controls were instructed to maintain their usual food choices. Analytic ultracentrifugation was used to measure changes in plasma lipoprotein mass concentrations. In addition, the absorbance of protein-stained polyacrylamide gradient gels was used as an index of concentrations for five high-density lipoprotein (HDL) subclasses that have been identified by their particle sizes, ie, HDL3c (7.2 to 7.8 nm), HDL3b (7.8 to 8.2 nm), HDL3a (8.2 to 8.8 nm), HDL2a (8.8 to 9.7 nm), and HDL2b (9.7 to 12 nm). Relative to controls, weight decreased significantly in men who dieted with exercise (net difference +/- SE, -3.3 +/- 0.4 kg/m2) and in men who dieted without exercise (-2.0 +/- 0.4 kg/m2). Dieting with exercise significantly decreased very-low-density lipoprotein (VLDL)-mass concentrations and significantly increased plasma HDL2-mass, HDL3a, HDL2a, and HDL2b relative to both control and dieting without exercise. There were no significant changes in lipoprotein mass and HDL protein for dieters who did not run.(ABSTRACT TRUNCATED AT 250 WORDS)

A comparison of the effects of the selective peripheral alpha 1-blocker terazosin with the selective beta 1-blocker atenolol on blood pressure, exercise performance and the lipid profile in mild-to-moderate essential hypertension

The effects of six weeks of treatment with the selective peripheral alpha 1-adrenoceptor blocker terazosin, or the selective beta 1-adrenoceptor blocker atenolol on blood pressure, exercise performance and blood lipid profile were compared in a single-blind, randomized, crossover study of 17 patients with mild-to-moderate essential hypertension. Although both drugs significantly reduced blood pressure at rest, atenolol caused a larger fall in supine blood pressure (11/11 and 7.5/7.0 mmHg, atenolol and terazosin, respectively; p < 0.001). Both treatments controlled the pressor response to exercise, although a greater reduction in diastolic blood pressure was observed at the end of exercise on terazosin (74.0 +/- 5.7 and 91.6 +/- 4.0 mmHg, terazosin and atenolol, respectively; p < 0.01). Alpha 1-blocker therapy was not associated with any measurable improvement or deterioration in cardiopulmonary performance and exercise duration. Unlike atenolol, terazosin therapy had the potentially beneficial effect of reducing serum total cholesterol levels and increasing the high-density lipoprotein-cholesterol/low-density lipoprotein-cholesterol ratio.

Relationship of skeletal muscle fiber type to serum high density lipoprotein cholesterol and apolipoprotein A-I levels

We measured the percentage of slow-twitch (ST) muscle fibers in the lateral portion of the quadriceps femoris muscle in 41 healthy sedentary male controls, 35 active male joggers, and 26 male coronary heart disease (CHD) patients. We then compared these percentages with serum levels of total cholesterol (TC), triglycerides (TG), high density lipoprotein cholesterol (HDL-C) and apolipoprotein A-I (apo A-I) found in these 102 middle-aged men. The percentage of ST muscle fibers in all men correlated positively with serum HDL-C (r = 0.57, P less than 0.001) and with apo A-I (r = 0.60, P less than 0.001) and negatively with triglycerides (r = -0.43, P less than 0.001). The proportion of ST fibers in joggers (65%; 61-69%, 95% confidence interval) was higher (P less than 0.001) than in sedentary controls (48%; 44-52%) or in CHD patients (44%; 39-49%). Moreover, 89% of the joggers had a proportion of ST fibers higher than 50%, whilst in sedentary controls and in CHD patients these values were 46% and 38%, respectively. Positive correlations were found between the percentage of ST fibers and both HDL-C and apo A-I in controls (r = 0.33, P less than 0.05 and r = 0.34, P less than 0.05) and in joggers (r = 0.46, P less than 0.01, and r = 0.40, P less than 0.05), respectively. Negative correlations in controls (r = -0.34, P less than 0.05) and in CHD patients (r = -0.43, P less than 0.05) were also found between the percentage of ST fibers and serum TG.(ABSTRACT TRUNCATED AT 250 WORDS)

An investigation of the role of lecithin:cholesterol acyltransferase and triglyceride-rich lipoproteins in the metabolism of pre-beta high density lipoproteins

Small high density lipoproteins (HDL) with pre-beta electrophoretic mobility (pre-beta HDL) have recently been shown to be the primary acceptor of cholesterol from cultured cells. We studied the metabolism of these particles by incubating serum at 37 degrees C in the presence and absence of active lecithin: cholesterol acyltransferase (LCAT). We found that the serum pre-beta HDL concentration decreased in the presence of LCAT, but when LCAT was inhibited the concentration remained constant, or increased, depending on the method of inhibition. This suggests that pre-beta HDL are a substrate for LCAT. We also found a significant negative correlation between levels of LCAT activity and pre-beta HDL in 28 fasting healthy subjects, this provides evidence that the activity of LCAT regulates, at least in part the concentration of these particles in vivo. During the early phase of incubation there was a more rapid decrease in pre-beta HDL concentration which was greater in the post-prandial than fasting state. When we infused a triglyceride emulsion into 6 subjects or added this to serum in vitro we observed an immediate fall in pre-beta HDL concentration. These findings suggest that pre-beta HDL interact with triglyceride rich particles. We investigated the origin of pre-beta HDL from blood lipoproteins during their lipolysis, in vivo and in vitro and found that they were produced from both triglyceride-rich and high-density lipoproteins. Formation from triglyceride-rich lipoproteins was evident by the rise in pre-beta HDL concentration during heparin-induced lipolysis when fasting and post-prandially. The rise was greater post-prandially and particularly marked in 4 hypertriglyceridaemic patients following a fat load. Generation from alpha-HDL was evident when we prolonged the action of the heparin-released lipases by incubation of post-heparin sera at 37 degrees C. Continued formation of pre-beta HDL occurred at an equal rate in the fasting and post-prandial samples suggesting release by lipolysis of alpha-HDL. This was supported by the action of lipases on serum and isolated HDL in vitro, where triglyceride lipase rather than phospholipase activity appeared more effective at releasing pre-beta HDL. These findings suggest binding and release of pre-beta HDL by triglyceride-rich lipoproteins depending on the prandial state and production from alpha-HDL through the action of lipases.

The role of cold in ischaemic heart disease: a review

A review of the literature suggests that the geographical and social class distribution of ischaemic heart disease (IHD) could be partly explained by variations in degrees of cold exposure, which includes wind and rain as well as temperature, with frequent exposure to cold being more harmful than steady exposure. Blood pressure (BP) and serum cholesterol are raised in response to acute and chronic exposure to cold. Smoking and cold produce similar physiological changes which increase the risk of IHD, while regular exercise blunts the physiological effects of cold and other stresses. There are many acute responses to cold which could trigger a myocardial infarction (MI) and therefore cold is probably a major precipitating factor in many cases of MI. Public health measures to improve domestic housing and the working environment may produce a significant impact on the incidence of IHD.

Lifestyle determinants of HDL2- and HDL3-cholesterol levels in a hypercholesterolemic male population

In this cross-sectional study we investigated the role of lifestyle and other factors in determining serum HDL2- and HDL3-cholesterol levels among 82 dyslipidemic (total cholesterol minus HDL-cholesterol greater than or equal to 5.2 mmol/l) middle-aged participants of the Helsinki Heart Study. Alcohol consumption correlated positively with both subfractions of HDL-cholesterol, while leisure time physical activity had a significant correlation with the HDL3-subfraction only. HDL levels were lower in smokers than in non-smokers but the differences were not statistically significant. Using the multiple linear regression model, alcohol consumption emerged as the only significant factor influencing both HDL cholesterol subfraction levels. Leisure time physical activity had an independent contribution to HDL3-level, but lifestyle variables other than alcohol consumption did not contribute significantly to HDL2-cholesterol level. The model incorporating alcohol consumption, physical activity, smoking and relative body weight explained 13.4% of the variation in HDL2 and 17.5% in HDL3-cholesterol.

Diet and exercise as regulators of lipid risk factors

Comparisons of different countries have shown that populations with a low dietary intake of saturated fat also have a low mortality from coronary heart disease. Controlled-feeding experiments have shown that the potential for altering plasma cholesterol levels and, consequently, altering the risk of coronary heart disease by dietary modification is great. However, in practice the influence of dietary advice to the general population on plasma cholesterol levels has been less pronounced. Several investigators have shown that by decreasing the intake of saturated fats and dietary cholesterol and increasing the intake of polyunsaturated fats and foods providing soluble fibre, plasma cholesterol levels can be reduced by up to 29% and low density lipoprotein (LDL)-cholesterol by over 33%. In most studies, levels of high density lipoprotein (HDL)-cholesterol are not materially altered by modern lipid-lowering diets; generally, plasma levels are maintained, or increased after correction of overweight is is achieved. It has been calculated that the risk of fatal coronary heart disease is 32% lower in subjects consuming such a diet than in those following a typical American diet, and life expectancy is 5 years greater in the former group. Life expectancy is also 2 to 3 years longer in populations habitually following low fat diets than in Western populations. Frequent exercise has been inversely related to risk of coronary heart disease. Physically active individuals have a more favourable lipoprotein profile than sedentary individuals but the extent of a direct effect of exercise on lipoprotein levels is not known.