Type IV hyperlipoproteinemia: effects of a caloric restricted type IV diet versus physical training plus isocaloric type IV diet

Changes in plasma lipids and lipoproteins following 10-days of prolonged walking: influence of age and relationship to physical activity level

The aim of the present study was to examine (1) the influence of 10 days of prolonged walking on plasma total-cholesterol (TC), high-density lipoprotein cholesterol (HDL-C) and low-density lipoprotein cholesterol (LDL-C) concentrations, (2) the effect of age on any changes in plasma cholesterol and lipoprotein concentration, and (3) whether any changes in cholesterol and lipoprotein concentrations are correlated to the participants' physical activity level (PAL). Seventeen male participants were divided into two groups according to their age. The nine participants in group 1 constituted the younger group (age 24 +/- 3 (SD) years), whereas eight older participants were in group 2 (age 56 +/- 3 years). Both groups completed 10 consecutive days of high-intensity hill walking. Mean (range) daily distances and ascent were 21 km (10-35 km) and 1,160 m (800-2,540 m), respectively. Identical distances and ascents were covered by each group. For each participant, PAL was calculated from energy expenditure, assessed by the doubly-labeled water technique, divided by the individual's basal metabolic rate. Venous blood was sampled immediately prior to, and following, the 10 consecutive days of walking. Following these 10 days, the older group showed a greater decrease in both TC (-25 +/- 11% vs. -10 +/- 11%; P < 0.05) and LDL-C (-26 +/- 12% vs. -4 +/- 13%; P < 0.05) when compared with the young. Likewise, the older group showed a greater increase in HDL-C (38 +/- 15%; P < 0.05), after the 10 days, whereas no significant change was evident in the younger group. In the older participants, there were strong positive relationships between PAL and the decreases in TC (r = 0.79, P < 0.05) and LDL-C (r = 0.74, P < 0.05). Conversely, in the younger group there were strong negative relationships between PAL and the decreases in TC (r = -0.74, P < 0.05) and LDL-C (r = -0.86, P < 0.01). These correlations persisted when changes in lipid concentrations were corrected for changes in plasma volume. These data suggest an 'age-dependant' threshold for PAL, rather than a specific exercise intensity or duration, may be critical for inducing favourable changes in HDL-C, LDL-C and TC.

The effects of physical exercise on plasma prebeta-1 high-density lipoprotein

The impact of physical exercise on high-density lipoprotein (HDL) metabolism is recognized as a major mechanism of coronary artery disease (CAD) risk reduction. Prebeta-1 HDL subparticle species play a pivotal role in initiating reverse cholesterol transport (RCT). We examined the effect of acute physical exercise on plasma prebeta-1 HDL levels. Nineteen nonsmoking, healthy men (n = 11) and women (n = 8) not receiving lipid-altering medications completed dietary surveys, and had percent body fat determinations, and fasting blood drawn for measurements of plasma lipids, lipoproteins, apolipoprotein A-I (Apo A-I), and absolute and percent prebeta-1 HDL. Each subject completed cardiopulmonary exercise stress testing to Vo(2max) followed by a 4-km course of run-jogging. Laboratory measurements were repeated from blood drawn immediately after exercise. Mean +/- SD values were determined for age, percent body fat, dietary calories, dietary cholesterol, dietary fat, and plasma lipids, lipoproteins, Apo A-I, and absolute and percent prebeta-1 HDL using 1-way analysis of variance (ANOVA). One-way ANOVA comparisons were made for measurements of plasma lipids, lipoproteins, Apo A-I, and absolute and percent prebeta HDL measurements taken before and after exercise for all subjects combined. Entry characteristics showed the following (mean +/-SD): age, 24 +/- 5.8 years; body mass index (BMI), 22.4 +/- 2.6; percent body fat, 13 +/- 5.7; and Vo(2max), 49.1 +/- 7.9 mL O(2)/kg/min. Exercise significantly increased absolute plasma prebeta HDL (0.10 +/- 0.05 to 0.130 +/- 0.07 microg/mL, P =.039) and decreased plasma HDL-triglycerides (23.3 +/- 10.8 to 12.5 +/- 5.6 mg/dL, P =.012). Our findings indicate that prebeta-1 HDL and HDL-triglyceride metabolism are significant components of the effect of acute exercise on RCT. These findings have important relevance for studies pertaining to exercise-related effects on HDL metabolism as pertains to CAD risk reduction.

Low-intensity endurance exercise training, plasma lipoproteins and the risk of coronary heart disease

Physically active individuals generally show a reduced risk of coronary heart disease (CHD) compared to the sedentary population. However, whether such reduction in CHD risk mainly results from the concomitant improvement in cardiorespiratory fitness or from the alterations in CHD risk factors has yet to be clearly established. Furthermore, there is still some controversy regarding the potential associations between endurance training-induced changes in metabolic variables considered as CHD risk factors (plasma glucose, insulin and lipoprotein levels) and the magnitude of improvement in cardiorespiratory fitness. From the results of several studies discussed in this article, it is proposed that prolonged endurance exercise of low intensity (approximately 50% VO2max), performed on an almost daily basis, seems to significantly improve metabolic variables considered as CHD risk factors through mechanisms that are likely to be independent from the training-related changes in cardiorespiratory fitness. The notion of 'metabolic fitness' is introduced and can be defined as the state of a ste of metabolic variables relevant to CHD risk and affected by the level of physical activity. Evidence available suggests that these metabolic variables are not closely related to the adaptation of cardiorespiratory fitness in response to exercise training. The concept of metabolic fitness has several implications for the prescription of exercise and for the primary and secondary prevention of CHD. Indeed, emphasis should not be placed on aiming at increasing VO2max through high-intensity exercise, but rather on producing a substantial increase in daily energy expenditure that will eventually lead to weight loss and related improvements in carbohydrate and lipid metabolism. Therefore, from a practical standpoint, although a 1 h daily walk may not have marked effects on cardiorespiratory fitness, it probably represents an exercise prescription that is likely to substantially improve 'metabolic fitness', thereby reducing the risk of CHD.

The effect of exercise on lipid metabolism in men and women

Lipoprotein abnormalities constitute a major risk for development of cardiovascular disease. These substances, which are comprised of various lipids and proteins (apoproteins), are influenced by specific enzymes which effect their concentrations. It has been demonstrated that elevated total cholesterol and LDL cholesterol are directly associated with the development of coronary artery disease, whereas HDL cholesterol has an inverse relationship with coronary heart disease (CHD). Although more controversial, triglycerides may also be directly associated with coronary atherosclerosis. Favourable changes in lipid levels have been shown to reduce coronary mortality. Exercise may constitute a non-pharmacological approach to lipoprotein therapy. Many exogenous factors also influence lipoprotein concentrations. Changes in diet, body composition, age, as well as medication and alcohol usage may directly alter lipid levels. In addition, they can be artificially affected by the analytical method. The immediate effects of one to several bouts of physical activity appear to influence lipoprotein level. A reduction in triglycerides has been shown after physical exertion, especially among trained individuals and those with hypertriglyceridaemia. These acute changes may reflect the utilisation of both muscle and plasma triglycerides as fuels during exertion. After more prolonged training, changes in lipoproteins may also occur. However, since exercise is accompanied by many co-variables which also favourably alter these levels (e.g. lower percentage of body fat, dietary alterations), it is difficult to determine the direct effect of regular physical activity. Initial studies of exercise training's effects on total cholesterol did not differentiate changes in HDL and LDL cholesterol. Subsequent research has observed these specific cholesterol fractions. Consistent reduction in LDL cholesterol levels have not been convincingly demonstrated. Although HDL cholesterol has been shown to increase in certain studies, the response has been variable in other investigations. These latter responses may have been due to the fact that HDL cholesterol changes may be dependent on levels prior to conditioning. Assessment of HDL cholesterol subfractions (HDL2 and HDL3), which could additionally impact on cardiovascular risk reduction, have shown favourable increases in HDL2, but as yet these HDL moieties have not been adequately investigated. Reductions in triglyceride levels after training among those with elevated values and beneficial apoprotein changes post-training have been reported, although few studies exist.(ABSTRACT TRUNCATED AT 400 WORDS)

Physical training and insulin sensitivity

In conclusion, a large body of available evidence indicates that the degree of physical conditioning is an important determinant of insulin sensitivity and overall glucose tolerance. Both acute exercise and chronic physical training are associated with enhanced disposal of a glucose load. Conversely, physical inactivity leads to a deterioration in glucose tolerance. The primary tissue responsible for accelerated glucose disposal following exercise is muscle. After an acute bout of exercise, enhanced glucose transport and augmented glycogen synthesis are largely responsible for the improvement in glucose tolerance. The beneficial effects of chronic physical training on glucose metabolism appear to be explained by multiple factors, including increased muscle mass, augmented muscle blood flow and capillary area, enhanced mitochondrial oxidative enzyme capacity, and activation of the glucose transport system. Despite these well-documented effects of training on glucose metabolism, the precise role of exercise in the treatment of diabetic patients remains to be established. In insulin-dependent (type I) diabetic individuals, acute exercise has been shown to be a helpful adjunct in establishing good glycemic control. However, the role of acute exercise in helping to smooth out glycemic control in non-insulin-dependent (type II) diabetic patients has received little attention. The role of chronic physical training in the treatment of both insulin-dependent (type I) and non-insulin-dependent (type II) diabetic individuals remains to be established.

Atherosclerosis: an insulin-dependent disease?

Evidence is reviewed that dietary habits in industrially developed countries, especially an increased frequency of ingestion of foods of high energy density, may contribute to excessive hepatic cholesterol synthesis and to a preponderance of lipogenic versus lipolytic effects on the arterial intima, thereby favoring the formation and progression of atheroma. These effects are mediated by the rise and fall of circulating insulin levels. The evidence is suggestive of the possibility that frequent and prolonged exposure of the arterial wall to high circulating levels of insulin may favor the development of atherosclerotic lesions. Research on diet-atherosclerosis relationships should take into account not only overall diet composition but individual meal composition and size and their effects on serum insulin levels, as well as meal spacing and the relative durations of absorptive and postabsorptive periods during the 24-hour daily cycle.

Effect of exercise training on glucose tolerance, in vivo insulin sensitivity, lipid and lipoprotein concentrations in middle-aged men with mild hypertriglyceridemia

The effects of 9 weeks of aerobic exercise training with maintenance of stable body weight upon insulin sensitivity and upon glucose, lipid, and lipoprotein concentrations were studied in 10 middle-aged men with mild hypertriglyceridemia. Following training, mean maximum oxygen consumption improved from 33.5 +/- 1.9 to 39.3 +/- 1.9 mL/kg/min (means +/- SEM), (P less than 0.01). Glucose concentrations, both fasting and during oral glucose tolerance testing, remained stable but both fasting insulin concentrations and insulin responses to oral glucose decreased (P less than 0.1 and less than 0.01, respectively). In vivo insulin sensitivity improved 25 +/- 6.1% (P less than 0.01) following training. Exercise training resulted in decreases in fasting serum triglyceride concentrations from 203 +/- 12.6 to 126 +/- 9.0 mg/dL (P less than 0.01), primarily as a result of the reduction in VLDL-triglycerides (P less than 0.01). The magnitude in percentage decrease of VLDL-triglycerides was found to be significantly correlated (r = 0.71, P less than 0.05) with the magnitude in percent increase in max VO2. Serum cholesterol levels declined from 211 +/- 8.9 to 193 +/- 11.9 mg/dL (P less than 0.01), and the ratio of HDL-cholesterol to total cholesterol was improved. This study demonstrates that exercise training at a level of intensity feasible for many middle-aged men has beneficial effects on several factors that have been associated with an increased risk of cardiovascular disease.

Exercise and risk factors for arteriosclerosis in 42 married couples followed over four years

Forty-two married couples (30-69 years of age) were followed for 4 years with yearly measurements of risk factors for arteriosclerosis. Advice was given concerning relaxed, enjoyable exercise (mainly running at 10-13 km hr-1). Each person served as his own control by comparison of the first and the last yearly status. Both the group of women and the group of men significantly improved (two sided p less than 0.005) their maximum oxygen uptake, and reduced their blood glucose concentration (two-sided p less than 0.01). S-cholesterol (for the group of men) was reduced statistically significantly (two-sided p less than 0.01). At the first examination the groups of women and men with the lowest maximum oxygen uptake (group I) had higher average values for risk factors than the more active groups (group II). At the final examination almost all persons had improved their maximum oxygen uptake, so none of the other risk factor differences between groups I and II were statistically significant. Both the women and the men improved their well being and their health profile as evaluated in terms of risk factors for arteriosclerosis. Exhaustive exercise was not necessary for beneficial effects.

Sustained effect of zinc-protamin-glucagon in hyperlipidaemic patients

Is is well known from laboratory investigations and acute intervention studies that glucagon is involved in lipid metabolism. The present study was undertaken in order to evaluate a possible sustained effect of zinc-protamin-glucagon in moderately hyperlipidaemic patients. 4 patients were investigated after an acute bolus dose of glucagon 5 mg intravenously and 16 patients were given zinc-protamin-glucagon 5 mg subcutaneously, b.i.d. for 5 days. A similar degree of decrease of plasma cholesterol and triglycerides was obtained in the acute and chronic study, while the increase in fasting blood sugar and plasma insulin seen in the acute study was not present after 5 days treatment. The effect on plasma triglycerides was much more variable than the effect on plasma cholesterol. Five days after treatment the lipid concentrations had returned to the pretreatment values. The effect could not be predicted from the pretreatment lipid concentrations, neither by the type of hyperlipidaemia present. The decrease in plasma cholesterol and triglycerides were not correlated. The drug might prove useful in the long term research of lipid metabolism and the various complex hormonal interactions.