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

Relationships Between the Apolipoprotein Levels and Sarcopenia in Inpatients with Type 2 Diabetes Mellitus: A Cross-Sectional Study

Background

Apolipoprotein (Apo) may be associated with sarcopenia in elderly inpatients with type 2 diabetes mellitus (T2DM), but fewer studies are available. In this study, we explored the association of ApoA1, ApoB, and ApoB/ApoA1 with sarcopenia and compared the predictive role of Apo indicators for sarcopenia in an elderly T2DM.

Objective

To investigate the relationships between the Apo and sarcopenia in elderly inpatients with T2DM.

Methods

This study included 253 inpatients with T2DM (mean age of 70.11±5.44 years, 32.8% male). The inpatients were divided into the sarcopenic group (n = 100) and non-sarcopenic group (n = 153). The associations among the Apo and sarcopenia were assessed using multivariate analyses.

Results

Inpatients in the sarcopenia group showed lower ApoA1 levels than those in the non-sarcopenia group (1.25±0.21 vs 1.36±0.20 g/L, P < 0.05) and showed higher ApoB/ApoA1 and ApoB levels than those in the non-sarcopenia group (0.82±0.27 vs 0.69±0.19 g/L, P < 0.05;1.00±0.32 vs 0.93±0.24 g/L, P < 0.05, respectively). After adjusting for age and BMI, the logistic regression model indicated that ApoA1 was a protective factor for elderly inpatients with T2DM sarcopenia.(OR =0.079,95% CI: 0.021~0.306, P < 0.05);ApoB and AopB/AopA1 were risk factors for elderly inpatients with T2DM sarcopenia.(OR =3.578,95% CI:1.318~9.715, P < 0.05;OR =16.440,95% CI:4.437~60.427, P < 0.05, respectively). AopB/AopA1 provided an AUC value of 0.765 in elderly men.(95% CI: 0.665~0.866, P<0.05).

Conclusion

ApoA1, AopB, and AopB/AopA1 are associated with sarcopenia in elderly inpatients with T2DM, and AopB/AopA1 may be a potential predictor of sarcopenia in elderly men with T2DM.

Evidence That Skeletal Muscles Modulate HDL-Cholesterol in Metabolic Healthy Young Adults

The aim of this study was to investigate whether skeletal muscle (SM) mass correlates with plasma lipids in metabolic healthy young adults. The study was designed as a retrospective observational monocentric study. Data on plasma lipids and SM mass of subjects attending our institution from 1999 to 2014 were analyzed. Inclusion criteria were being 18-45 years old and in apparently good health. SM mass was evaluated by bioelectrical impedance analysis (BIA) using the equation proposed by Janssen and normalized to height as skeletal muscle index (SMI: SM mass/height2). The association between SMI and plasma lipids levels was examined using a crude and adjusted linear regression model including age, sex, BMI and waist circumference as additional covariates. The study population consisted of 450 subjects (273 females) without metabolic syndrome (12.2% with normal body weight, 33.1% overweight, and 54.7% with obesity). SMI, total-cholesterol, LDL-cholesterol, and Triglycerides were higher, whereas HDL-cholesterol was lower in overweight and obese patients as compared with normal weight subjects. SMI was inversely associated with HDL-cholesterol in female patients with obesity but not in male patients with obesity, in normal- or over-weight subjects (p < 0.05). These results suggest that changes in SM mass occurring in obesity could have a role in worsening lipid profile with special reference to HDL-cholesterol.

Skeletal muscle morphology and risk of cardiovascular disease in elderly men

BACKGROUND

While it is well known that physical inactivity is a major risk factor for cardiovascular disease, there is still a search for the mechanisms by which exercise exerts its positive effect. Skeletal muscle fibre type can be affected to some extent by exercise, and different fibre types possess different anti-inflammatory and glucometabolic properties that may influence cardiovascular disease risk.

DESIGN

Population-based cohort study.

METHODS

We investigated relations of skeletal muscle morphology to risk of cardiovascular events in a sample of 466 71-year-old men without cardiovascular disease, of which 295 were physically active (strenuous physical activity at least 3 h/week).

RESULTS

During a median of 13.1 years of follow up, 173 major cardiovascular events occurred. Among physically active men, 10% higher proportion of type-I (slow-twitch oxidative) fibres was associated with a hazard ratio (HR) of 0.84 (95% confidence interval 0.74-0.95) for cardiovascular events, and 10% higher proportion of type-IIx (fast-twitch glycolytic) fibres was associated with a HR of 1.24 (1.06-1.45), adjusting for age. Similar results were observed in several sets of multivariable-adjusted models. No association of muscle fibre type with risk of cardiovascular events was observed among physically inactive men.

CONCLUSIONS

Higher skeletal muscle proportion of type-I fibres was associated with lower risk of cardiovascular events and a higher proportion of type-IIx fibres was associated with higher risk of cardiovascular events. These relations were only observed in physically active men. Skeletal muscle fibre composition may be a mediator of the protective effects of exercise against cardiovascular disease.

The low-fitness phenotype as a risk factor: more than just being sedentary?

Higher levels of fitness are associated with reduced risk of a wide variety of illnesses and chronic conditions. For cardiovascular disease (CVD) and many metabolic conditions, the fitness-morbidity/mortality curve is not linear but curvilinear, with lower levels of fitness being associated with significantly higher levels of risk compared to moderate and high levels of fitness. We have a very poor understanding of what the low fit phenotype represents as it is clearly more than just low physical activity levels. For example, there are likely some metabolic disadvantaged individuals with intrinsically low fitness and low oxidative capacity that are also prone to being sedentary due to easy fatigability. For these individuals, there exists a worse case scenario of a sedentary lifestyle superimposed on metabolically disadvantaged muscle resulting in the exaggerated CVD and metabolic risk. There is clearly a need for more work exploring the risk associated with low fitness and developing strategies to address the risk of low fitness. For example, we need to (i) define the mechanisms responsible for the exceptional risk associated with being low fit, (ii) identify best physical activity programs for reversing low fitness, (iii) examine whether exercise training nonresponders receive health benefits from exercise training despite the failure to improve fitness, and (iv) explore methods to identify individuals with the "low fit" phenotype without conducting a maximal exercise test. Individuals in the low fit category typically account for the majority of accumulated metabolic/CVD events, thus reducing this risk in this category would have substantial public health and clinical payoff.

Muscle fiber type I influences lipid oxidation during low-intensity exercise in moderately active middle-aged men

The simultaneous effects of body composition, cardiorespiratory fitness, physical activity, and muscle fiber characteristics on lipid oxidation at basal state and during exercise were studied in a population-based group (n = 70) of middle-aged men. Body composition, oxygen uptake, and lipid oxidation were determined in a volitional maximal exercise test, physical activity with a questionnaire, muscle fiber characteristics with muscle biopsy, and resting metabolic rate and lipid oxidation at basal state with indirect calorimetry. In regression analysis, type I muscle fibers contributed significantly to lipid oxidation at basal state (r = 0.30, r2 = 0.07, P<0.05) and during low-intensity exercise (r = 0.35, r2 = 0.10, P<0.05). ANOVA revealed 7.7% (P = 0.268) lower lipid oxidation at basal state, 14% (P<0.05) lower lipid oxidation in low-intensity exercise, and 10.5% (P = 0.088) lower lipid oxidation in moderate-intensity exercise in muscle fiber tertile I (type I muscle fiber count 28.8%) compared with muscle fiber tertile III (type I muscle fiber count 71.4%). In conclusion, the muscle fiber distribution contributed significantly to lipid oxidation during low-intensity exercise in moderately active middle-aged men.

Muscle fiber-type distribution predicts weight gain and unfavorable left ventricular geometry: a 19 year follow-up study

Background

Skeletal muscle consists of type-I (slow-twitch) and type-II (fast-twitch) fibers, with proportions highly variable between individuals and mostly determined by genetic factors. Cross-sectional studies have associated low percentage of type-I fibers (type-I%) with many cardiovascular risk factors.

Methods

We investigated whether baseline type-I% predicts left ventricular (LV) structure and function at 19-year follow-up, and if so, which are the strongest mediating factors. At baseline in 1984 muscle fiber-type distribution (by actomyosin ATPase staining) was studied in 63 healthy men (aged 32–58 years). The follow-up in 2003 included echocardiography, measurement of obesity related variables, physical activity and blood pressure.

Results

In the 40 men not using cardiovascular drugs at follow-up, low type-I% predicted higher heart rate, blood pressure, and LV fractional shortening suggesting increased sympathetic tone. Low type-I% predicted smaller LV chamber diameters (P ≤ 0.009) and greater relative wall thickness (P = 0.034) without increase in LV mass (concentric remodeling). This was explained by the association of type-I% with obesity related variables. Type-I% was an independent predictor of follow-up body fat percentage, waist/hip ratio, weight gain in adulthood, and physical activity (in all P ≤ 0.001). After including these risk factors in the regression models, weight gain was the strongest predictor of LV geometry explaining 64% of the variation in LV end-diastolic diameter, 72% in end-systolic diameter, and 53% in relative wall thickness.

Conclusion

Low type-I% predicts obesity and weight gain especially in the mid-abdomen, and consequently unfavourable LV geometry indicating increased cardiovascular risk.

Muscle fiber-type distribution as a predictor of blood pressure: a 19-year follow-up study

The known association between physical activity and low blood pressure may be influenced by inherited characteristics. Skeletal muscle consists of type I (slow-twitch) and type II (fast-twitch) muscle fibers, with proportions highly variable between individuals and mostly determined by genetic factors. A high percentage of type I fibers (type I%) has been associated with low blood pressure in cross-sectional studies. We investigated whether type I percentage predicts future blood pressure levels and explains part of the association between physical activity and blood pressure. At baseline, in 1984, muscle fiber-type distribution, physical activity, and body mass index (BMI) were determined in 64 healthy men (age, 32 to 58 years). At follow-up, in 2003, blood pressure, physical activity, and BMI were determined in these men. In subjects without antihypertensive medication (n=43), type I percentage accounted for 5%/18% of the variation in systolic/diastolic blood pressure. A high type I percentage predicted, independent of both baseline (in 1984) and follow-up (in 2003), physical activity, BMI, and low systolic and diastolic blood pressure. Adjusted for all baseline covariates, a 20-unit higher type I percentage predicted a 11.6-mm Hg lower systolic blood pressure (P=0.018) and a 5.0-mm Hg lower diastolic blood pressure (P=0.018). High levels of physical activity in 1984 predicted low diastolic blood pressure, but this association was lost when type I percentage was included into the model. A high proportion of type I fibers in skeletal muscle is an independent predictor of low blood pressure and explains part of the known association between high levels of physical activity and low blood pressure.

Occurrence of chronic disease in former top-level athletes. Predominance of benefits, risks or selection effects?

Former elite athletes from most sports disciplines have lower overall morbidity risk and enjoy better self-rated health in later years compared with the general population and matched controls who were healthy at young age. This is seen particularly among former endurance athletes who have a lower incidence of coronary heart disease and type 2 diabetes mellitus. Most often data are available only for men. Based on the available data, participation in elite sports cannot be regarded as an overall health hazard. However, aside from a high risk of acute injury in specific sports, possible negative effects of long-standing athletic activity on the development of osteoarthritis should not be neglected. It should also be remembered that elite athletes are a biologically and genetically select group who are not representative of the population at large. Given the nature of the available data, the possible health consequences of recent changes in different characteristics of sports, such as training practices, professionalism and use of doping, cannot be properly predicted.

Effects of low intensity aerobic training on skeletal muscle capillary and blood lipoprotein profiles

The effects of low intensity endurance training on skeletal muscle capillary density and serum lipoprotein levels were studied in 11 non-obese men (18-25 years). The subjects performed a 6-week training regimen (60 min, 5 times per week) at the lactate threshold (LT). Capillary density was determined in biopsy specimens obtained from the vastus lateralis muscle before and after the training. The number of capillaries per fiber (cap/fiber ratio) before training was 1.97 +/- 0.47, and increased to 2.49 +/- 0.69 after training (p < 0.05). The maximal oxygen uptake (VO2 max) and LT- VO2 increased significantly by 5% (p < 0.01) and 27% (p < 0.01), respectively, whereas no change was observed in body weight. Low density lipoprotein cholesterol (LDL-C) tended to decrease (p = 0.06). The change in the cap/fiber ratio correlated inversely with the change in the ratio of LDL-C to high density lipoprotein cholesterol (HDL-C) (r = -0.61, p < 0.05). It was also, positively associated with the change in HDL2-C (r = 0.82, p < 0.01) and inversely associated with the change in HDL3-C (r = -0.63, p < 0.05). The change in LT- VO2 was inversely associated with the change in LDL-C (r = -0.62, r < 0.05). These results indicate that low intensity training increases capillary density in skeletal muscle, which may explain in part the changes in the lipoprotein profiles.

Muscle morphology, self-reported physical activity and insulin resistance syndrome

In a population-based sample of 475 men the associations between muscle morphology, self-reported physical activity (PA) and insulin resistance (IR) syndrome were investigated. Also, we studied to what degree muscle morphology contributes to the association between PA and IR syndrome. Muscle morphology and the components of IR syndrome were compared in four groups categorized according to self-reported habitual PA data. We found a significantly higher percentage of type I fibres, fibre area and number of capillaries around the fibres and a lower proportion of type IIB fibres with higher level of PA. The relative distribution of type I fibres and capillarization were positively related to high density lipoprotein (HDL) cholesterol and negatively to serum triglycerides (TG) and plasminogen activator inhibitor-1 (PAI-1) activity. The percentage of type IIB fibres was were inversely related to HDL cholesterol and positively to serum TG, PAI-1 activity and resting heart rate. Insulin sensitivity was positively and independently related to PA level (P < 0.001). Regression analysis including all relevant variables regarding insulin sensitivity indicated that the significant explanatory variables left in the equation were body mass index (BMI), glucose intolerance, PAI-1 activity, serum free fatty acid concentration, proportion of type IIB fibres, HDL cholesterol level, drug treatment, PA level, and waist-to-hip ratio, which together explained 55% of the variation in the insulin sensitivity index. In conclusion, both fibre type distribution and muscle capillary density might contribute to the beneficial effect of PA on IR syndrome.

Blood lipids and lipoproteins in child and adolescent athletes

The purpose of this review is to describe the age- and gender-associated variation in blood lipids of young athletes and examine the association between training status, peak oxygen consumption (VO(2peak)), and body fatness with blood lipids in young athletes. Results from cross-sectional studies suggest similar levels of total cholesterol (TC), lower levels of triglycerides (TG) and low-density lipoprotein-cholesterol (LDL-C), and higher levels of high-density lipoprotein-cholesterol (HDL-C) in young athletes compared with controls. Longitudinal data show that the age- and gender-associated variation in blood lipids in young distance runners is similar to youth in the general population; TC and LDL-C remain stable, HDL-C declines during adolescence (especially in males), and TG increases with age. Considerable heterogeneity exists in the blood lipids of young athletes, including dyslipidaemic values. Age, sexual maturity status, training status, VO(2peak) and body fatness are determinants of blood lipids in young athletes. VO(2peak) is a significant predictor of HDL-C independent of body fatness. Further research is warranted to examine: the prevalence rates of dyslipidaemia in various sport groups; and the complex interactions of genes, biological maturation, exercise training, dietary intake and composition, skeletal muscle and adipose tissue properties on lipoprotein metabolism in young athletes.

Steroid use and long-term health risks in former athletes

This article focuses on anabolic steroid adverse effects on the cardiovascular system and mental health issues as well as the possible increase in the incidence of neoplasms in anabolic steroid users. On the basis of findings in the literature, the authors consider these three issues as the most significant concerning morbidity and mortality among anabolic steroid users. A study by Pärssinen et al. (2000) has shown an increased incidence of premature mortality among power lifters. Anabolic steroids and other concomitantly used drugs are the probable cause of this increased mortality, as power training itself does not increase health risks and all types of physical activity promote health.

Differential global gene expression in red and white skeletal muscle

The differences in gene expression among the fiber types of skeletal muscle have long fascinated scientists, but for the most part, previous experiments have only reported differences of one or two genes at a time. The evolving technology of global mRNA expression analysis was employed to determine the potential differential expression of approximately 3,000 mRNAs between the white quad (white muscle) and the red soleus muscle (mixed red muscle) of female ICR mice (30-35 g). Microarray analysis identified 49 mRNA sequences that were differentially expressed between white and mixed red skeletal muscle, including newly identified differential expressions between muscle types. For example, the current findings increase the number of known, differentially expressed mRNAs for transcription factors/coregulators by nine and signaling proteins by three. The expanding knowledge of the diversity of mRNA expression between white and mixed red muscle suggests that there could be quite a complex regulation of phenotype between muscles of different fiber types.

Natural selection to sports, later physical activity habits, and coronary heart disease

OBJECTIVES

To investigate the associations between natural selection to sports at a young age, continuity of physical activity, and occurrence of coronary heart disease.

DESIGN

Prospective cohort study.

SETTING

Finland.

PARTICIPANTS

Former top level male athletes participating at a young age (1920-1965) in different types of sport (endurance (n = 166), power speed (n = 235), "other" (n = 834)) and controls healthy at the age of 20 years (n = 743).

MAIN OUTCOME MEASURES

Data on the occurrence of coronary heart disease were obtained from death certificates, three nationwide registers, and questionnaire studies in 1985 and 1995, and data on later physical activity were obtained from the questionnaires.

RESULTS

In 1985 all groups of former athletes were more physically active than controls (p<0.001). Despite similar total volumes of physical activity, compared with power speed athletes, former endurance athletes participated more often in vigorous activity (p = 0.006) and had less coronary heart disease (adjusted odds ratio 0.34, 95% confidence interval 0.17 to 0.73; p = 0.004). In 1985 and 1995, both endurance and other athletes had less coronary heart disease than controls. From 1986 to 1995, the incidence of new coronary heart disease was lower among those who participated in vigorous physical activity in 1985.

CONCLUSIONS

Both a previous aptitude for endurance athletic events and continuity of vigorous physical activity seem to be associated with protection against coronary heart disease, but an aptitude for power speed events does not give protection against coronary heart disease.

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.

Heart attacks and lower-limb function in master endurance athletes

PURPOSE

Whether very vigorous physical activity bestows on the participant more health benefits or more adverse effects is unclear: we investigated whether men participating in competitive endurance sports in middle and old age are at increased risk of heart attacks as well as of lower-limb osteoarthritis and disability.

METHODS

In our cohort study with an 11-yr follow-up, we studied 269 male orienteering runners (mean age 48.6 yr at baseline; range 37-61), who in 1984 were placed among the 60 best in their master orienteer age-class in Finland, and 188 male nonsmoking controls (mean age 50.4 yr; range 39-61) classified as healthy at 20 yr of age and without overt ischemic heart disease up until 1985. We followed mortality and studied the prevalence of questionnaire-reported physician-diagnosed diseases and disabilities at the end of the follow-up in late 1995.

RESULTS

Two (0.7%) of the 269 runners and 10 (5.3%) of the 188 controls had suffered myocardial infarctions during the follow-up, the age-adjusted odds ratio (95% confidence interval) being 0.15 (0.03-0.67) in runners compared with controls (P = 0.0059). At follow-up, orienteering runners reported knee osteoarthritis and knee pain more often than did the controls, whereas the occurrence of hip osteoarthritis and hip pain did not differ. Disability due to hip or knee pain after the same everyday activities tended to be less in the runners.

CONCLUSION

In top-level master endurance athletes having a long-term training background and participating in competitive endurance sports, the risk both of heart attack and of lower-limb disability is low.

Significance of skeletal muscle properties on fitness, long-term physical training and serum lipids

The percentage of slow-twitch (ST) fibers in a person's skeletal muscle, e.g. muscle fiber composition (ST-%), may have a significant impact on physical activity, fitness level, serum high density lipoprotein cholesterol (HDL-C) concentration, and ultimately, on the risk of coronary heart disease (CHD). We studied the effect of a 12 month home-based exercise training program on skeletal muscle metabolic activity, serum lipids, and hormones in 12 healthy middle-aged men (sedentary men) with a low level of fitness and leisure-time physical activity (LTPA). Their parameters and changes in them were compared with 12 men of the same age with defined CHD and with two groups (15 each) of physically active men, who had either a high ST-% (high-ST-men) or a low ST-% (low-ST-men). In the sedentary men, CHD-patients and low-ST-men, the mean ST-% (42, 44, and 49%, respectively) was similar but was significantly higher in the high-ST-men (73%). The sedentary men whose LTPA mean was 34 and 19% of the mean of low-ST-men (mean of 2137 kcal/week) and high-ST-men (mean of 3845 kcal/week), respectively, increased their LTPA from a mean of 728-1526 kcal/week (P < 0.01). After training, we found an increase in serum HDL-C by 21%, (P < 0.01) and apo A-I by 36% (P < 0.01), and a decrease in serum LDL-C by 8%. The cholesterol/HDL-C ratio decreased by 17(% (P < 0.01) and the LDL-C/HDL-C ratio decreased by 22% (P < 0.01). Skeletal muscle lipoprotein lipase (LPL) activity increased by 65% (P < 0.001). Moreover, the increase in LPL as well as in HDL-C concentration tended to be more pronounced the higher the level was before training. The oxidative enzyme activity of alpha-ketoglutarate dehydrogenase (KGDH) in skeletal muscle and the activity of carnitine palmitoyltransferase (CPT) in lipid metabolism increased, whereas glycolytic phosphofructokinase (PFK) did not change but the PFK to CPT ratio decreased, which was reflected as a decrease of lactate accumulation during exercise. Increase in CPT activity correlated significantly (r(s) = 0.81, P < 0.01) with the increase in HDL-C concentration. In all men (n = 54), the CPT activity correlated negatively with serum triglyceride concentration (r(s) = -0.34, P < 0.05) but positively with serum HDL-C concentration and ST-% (r(s) = 0.34, P < 0.05 and r(s) = 0.47, P < 0.01, respectively). In all healthy men, (n = 42) LTPA correlated with both Vo2max, and ST-% (r(s) = 0.76, P < 0.001 and r(s) = 0.54, P < 0.001, respectively) and with serum HDL-C and apo A-I concentrations (r(s) = 0.35, P < 0.05 and r(s) = 0.54, P < 0.001, respectively). Serum sex hormones did not show significant associations with serum lipids, but in sedentary men, serum total and free testosterone as well as the ratio of free testosterone to free estradiol decreased significantly after training. These findings confirm the pronounced effects of a home-based exercise training program on CHD risk factors and they underline the importance of considering skeletal muscle properties when studying serum lipids and lipoproteins and their modifications in the field of health-related fitness and physical activity.

High blood pressure and muscle morphology/metabolism--causal relationship or only associated factors?

As muscle tissue constitutes a main target organ for glucose metabolism and is responsible for the development of insulin resistance, it seems plausible to elucidate the relationship between blood pressure and muscle morphology and metabolism. The association between blood pressure and capillarization/morphology of the vastus lateralis muscle and metabolic variables was evaluated in 24 perimenopausal obese women [body mass index (BMI) 34.9 +/- 1.1; waist-hip ratio (WHR) 0.90 +/- 0.02]. The muscle enzyme activity of lipoprotein lipase (LPL), citrate synthase and glycogen synthase was determined. There was a significant negative correlation between the percentage of type I fibres and relative fibre area of type I on the one hand and systolic and diastolic blood pressure on the other. There was a negative correlation between the capillary density (i.e. number of capillaries/muscle fibre) and a positive correlation between the diffusion distance (fibre area supplied by one capillary) and diastolic blood pressure. The activities of LPL and citrate synthase were positively correlated with the percentage of type I and negatively correlated with the percentage of type II muscle fibres. The activity of LPL was also negatively correlated with plasma glucose and the insulin/C-peptide ratio. The insulin/C-peptide ratio was positively correlated with the percentage of type II muscle fibres. In stepwise multiple regression analyses, 20-30% of the variation in systolic and diastolic blood pressure could be explained by the variables of muscle fibre distribution. Excluding muscle morphological variables from the regression model, the insulin/C-peptide ratio accounted for 13% of the variation in systolic and diastolic blood pressure. The results of the study show the close association between muscle morphology and blood pressure. It remains to be elucidated whether this association indicates a causal relationship.

Associations between skeletal muscle properties, physical fitness, physical activity and coronary heart disease risk factors in men

High physical fitness and physical activity are associated with favourable lipid levels, especially a high level of high density lipoprotein cholesterol (HDL-C). A person's skeletal muscle properties, metabolism and percentage of different muscle fibres (ST-%), which may modify coronary heart disease (CHD) risk factors, such as serum insulin, obesity and serum sex hormones may also influence his fitness level and leisure-time physical activity. We studied the associations of physical fitness, physical activity and ST-% with serum lipids and lipoproteins in 72 healthy men. Their parameters were compared with those of 20 men with defined CHD. Significant interrelationships between ST-%, fitness and leisure-time physical activity index (LTPAI) were observed. Multiple regression analysis showed that ST-%, fitness and leisure-time physical activity explained about 32% of the variation in HDL-C in the healthy men. In healthy men ST-% correlated positively with fitness (r(s) = 0.62, P < 0.001) and with LTPAI (r(s) = 0.62, P < 0.001). Fitness level also correlated significantly with LTPAI (r(s) = 0.81, P < 0.001). Serum insulin showed negative associations with ST-% (r(s) = -0.63, P < 0.001) and fitness (r(s) = -0.54, P < 0.001) and LTPAI (r(s) = -0.62, P < 0.001). Free fraction of testosterone correlated negatively with serum HDL-C level (r(s) = -0.34, P < 0.01), with fitness (r(s) = -0.41, P < 0.001) and with LTPAI (r(s) = -0.54, P < 0.001). In sedentary men with the lowest fitness and physical activity the mean of ST-% (45%) was similar to that in CHD patients (44%). However, ST-% in men in the highest tertile of physical activity and fitness (68%) was significantly higher than in CHD patients and in men in the lowest tertile of physical activity and fitness. Skeletal muscle enzyme activity in lipid metabolism was significantly lower in both CHD patients and in sedentary and low-fit men than that in fitter and physically active men. The present data imply that skeletal muscle properties are important determinants of risk profiles, such as physical activity, fitness and serum lipid and lipoprotein patterns. Although fitness is a graded, independent predictor of mortality from CHD, a relatively high fitness level is not enough. This was clearly observed in the clustering analysis, in which the healthy men, according to their ST-%, fitness, leisure-time physical activity and serum sex hormone binding globulin (SHBG), fell into three natural groups: (i) Inactive men with lowest ST-% (mean 42%), lowest fitness (10.7 METs) and lowest HDL-C (1.36 mm/l); (ii) Fit men with high ST-% (66%), high fitness (14.5 METs) and moderately high HDL-C (1.54 mol/l); (iii) Active men with high ST-% (66%), highest fitness (14.9 METs) and highest serum HDL (1.83 mmol/l). The results support the idea that both fitness and physical activity give further protection against CHD by modifying risk factors. Our findings also suggest that skeletal muscle properties should be considered in the studies which assess CHD risk factors and their modifications especially in the field of health-related fitness.

Skeletal muscle fiber distribution influences serum high-density lipoprotein cholesterol level

Earlier we have shown a significant positive association between muscle fiber distribution, i.e. percentage of slow-twitch (ST) fibers in the vastus lateralis muscle, and serum high-density lipoprotein cholesterol (HDL-C) level. This association may be due to the fact that ST fibers have a high capacity for oxidative energy metabolism and a high number of surrounding capillaries. These fibers have a high capacity to metabolize fatty acids liberated by lipoprotein lipase (LPL) from triglyceride-rich lipoproteins. This in turn elevates serum HDL-C levels. Thus, a high percentage of ST fibers (ST-%) may be one factor having a beneficial effect on serum HDL-C concentration. A high ST-% may also increase the likelihood that a person will become involved in an endurance type of physical activity, which further increases serum HDL-C concentration by increasing further LPL activity in the capillary bed of skeletal muscle. In this paper we present a hypothetical background of the role that ST fibers may have on serum lipid and lipoprotein profile.

The association among fat distribution, physical fitness, and the risk factors of cardiovascular disease in obese women

The purpose of this study was to see whether fat distribution and physical fitness are independent risk factors of cardiovascular diseases in obese women. Seventy-four obese women aged 19 to 65 years participated in this study. The data were collected on plasma lipid profiles, plasma glucose and insulin during an oral glucose tolerance test, blood pressure, fat distribution determined by the waist to hip ratio (WHR), total body fat determined by the hydrostatic weighing method and a direct measurement of blood lactate threshold. Significant correlations were found between WHR and plasma cholesterol (TC), plasma LDL cholesterol (LDL-c) and LDL-c to the plasma HDL cholesterol ratio (LDL-c/HDL-c), independent of age, percent body fat, and VO2 per lean body mass at blood lactate threshold (LT). On the other hand, LT was significantly related to the area under the curve of insulin during OGTT (insulin area) and DBP, independent of age, percent body fat, and WHR. In conclusion, both fat distribution and physical fitness are considered to be independently related to some important risk factors in obese women after adjustment for percent body fat.

The effects of weight loss by exercise or by dieting on plasma high-density lipoprotein (HDL) levels in men with low, intermediate, and normal-to-high HDL at baseline

To assess whether baseline plasma high-density lipoprotein (HDL) cholesterol levels affected the HDL response to weight loss, we examined lipoprotein changes in overweight men aged 30 to 59 years who were randomized to lose weight by exercise training (primarily running, n = 46) or by caloric restriction (ie, dieting, n = 42) or to remain sedentary, nondieting controls (n = 42) in a 1-year study. In exercisers, absolute increases in HDL (mg/dL) were greatest in men with normal-to-high baseline HDL and least in men with low baseline HDL. Specifically, when divided into groups of low (< or = 37 mg/dL), intermediate (38 to 47 mg/dL), and normal-to-high HDL cholesterol (> or = 48 mg/dL) at baseline, the exercisers increased HDL cholesterol by 2.3 +/- 1.9, 4.9 +/- 1.1, and 7.0 +/- 1.3 mg/dL, respectively; HDL2 cholesterol by 0.8 +/- 1.6, 2.3 +/- 1.2, and 5.1 +/- 1.3 mg/dL; and HDL2 mass by 2.8 +/- 5.1, 9.5 +/- 8.9, and 31.7 +/- 11.0 mg/dL. Relative increases in HDL cholesterol were more similar in the low (7.1% +/- 6.1%), intermediate (12.4% +/- 3.9%), and normal-to-high men (13.2% +/- 4.0%). Regression analyses were performed to assess whether baseline HDL cholesterol was related to the amount of absolute HDL change per unit of weight loss. In exercisers, the increase in HDL3 cholesterol concentrations was significantly greater in men with low HDL than in those with normal-to-high HDL at entry (2.0 +/- 0.8 v 0.2 +/- 0.8 mg/dL per kg/m2 lost).(ABSTRACT TRUNCATED AT 250 WORDS)

Relationships between subcutaneous fat and muscle distributions and serum HDL-cholesterol

To evaluate the relationship between human body composition and serum lipids levels, the distributions of subcutaneous adipose tissue (AT) and muscle thickness were evaluated in Japanese 449 males and 542 females, aged from 35 to 77 years. Among males, a significant positive correlation was observed between AT thicknesses and total cholesterol, and negative relationships between the AT and HDL-C as well as HDL-C/TC ratio. Among females, similar but weaker relationships were found for AT at the upper arm and trunk sites. However, the thigh AT thickness was positively correlated with HDL-C and HDL-C/TC ratio only among women. The muscle thickness in the abdomen and the thigh correlated significantly with HDL-C/TC for both sexes. Furthermore, the regional trend observed in both sexes remained significant after correction for concomitant variables such as age, tobacco and alcohol intake. We conclude that it is necessary to evaluate not only total body fat but muscle and AT thickness distributions when evaluating the relationship between body composition and serum lipids and lipoproteins.