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Biomedical subjects

A Tremblay

Publications and source records attributed to A Tremblay.

At least 253 records · Page 14Linked to original sources
PubMed1990

The response to long-term overfeeding in identical twins.

We undertook this study to determine whether there are differences in the responses of different persons to long-term overfeeding and to assess the possibility that genotypes are involved in such differences. After a two-week base-line period, 12 pairs of young adult male monozygotic twins were overfed by 4.2 MJ (1000 kcal) per day, 6 days a week, for a total of 84 days during a 100-day period. The total excess amount each man consumed was 353 MJ (84,000 kcal). During overfeeding, individual changes in body composition and topography of fat deposition varied considerably. The mean weight gain was 8.1 kg, but the range was 4.3 to 13.3 kg. The similarity within each pair in the response to overfeeding was significant (P less than 0.05) with respect to body weight, percentage of fat, fat mass, and estimated subcutaneous fat, with about three times more variance among pairs than within pairs (r approximately 0.5). After adjustment for the gains in fat mass, the within-pair similarity was particularly evident with respect to the changes in regional fat distribution and amount of abdominal visceral fat (P less than 0.01), with about six times as much variance among pairs as within pairs (r approximately 0.7). We conclude that the most likely explanation for the intrapair similarity in the adaptation to long-term overfeeding and for the variations in weight gain and fat distribution among the pairs of twins is that genetic factors are involved. These may govern the tendency to store energy as either fat or lean tissue and the various determinants of the resting expenditure of energy.

Adult↗
PubMed1990

Correlates of plasma very-low-density lipoprotein concentration and composition in premenopausal women.

Potential correlates of plasma very-low-density lipoprotein (VLDL) concentration and composition were studied in a sample of 75 premenopausal women. Fasting plasma free fatty acid (FFA) levels, as well as plasma glucose and insulin levels in the fasting state and during an oral glucose tolerance test, displayed significant positive correlations with plasma triglyceride (TG) and VLDL-TG levels (P less than .005). Plasma post-heparin lipoprotein lipase (LPL) activity, measured in a subsample of 31 women from the original sample, was negatively correlated with plasma TG, VLDL-cholesterol (CHOL), VLDL-TG, and VLDL-apolipoprotein (apo) B concentrations (.005 greater than P less than .05). Multivariate analyses showed that, after LPL was considered, the insulin area was the only other metabolic variable studied that was significantly correlated with VLDL-apo B concentration, whereas fasting FFA levels were significantly correlated with plasma TG and VLDL-TG levels. ANOVA revealed that plasma VLDL-CHOL, VLDL-TG, and VLDL-apo B levels were not associated with the glucose area, but were significantly associated with the insulin area (P less than .005). When the effect of insulin area was controlled for, the plasma FFA levels did not contribute significantly to the variance in VLDL-CHOL and VLDL-apo B, but showed an independent effect on VLDL-TG levels (P less than .05). Finally, stepwise multiple regression analyses indicated that once the variance explained by plasma LPL activity and by the insulin area was considered, no other metabolic variable could account for the variation in VLDL-CHOL and VLDL-apo B levels, whereas fasting FFA levels explained a further 5% of the VLDL-TG variance and one third of the variance observed in the VLDL-TG/apo B ratio.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1990

Counterregulatory response to insulin-induced hypoglycemia in trained and nontrained humans.

The aim of the present series of experiments was to investigate the hormonal counterregulatory response to insulin-induced hypoglycemia in trained and nontrained healthy individuals. Five endurance athletes and six controls were administered intravenous insulin infusion at a rate of 0.15 U/kg/h until plasma glucose reached 50 mg/dL. The mean duration of the infusion in the trained and nontrained subjects corresponded to 18.6 and 26.3 minutes (P less than .01), suggesting that the former were characterized by an increased insulin sensitivity. Plasma glucose levels were similar in the two groups at the end of the insulin infusion, as well as during the postinfusion recovery period. Forty-five minutes after the end of the infusion, plasma glucose levels were not significantly different from the preinfusion levels in the two groups. During this period of glycemia recovery, the increases in plasma glucagon, epinephrine, norepinephrine, and growth hormone were at least 50% lower in the trained than in the nontrained subjects. The increase in heart rate and oxygen uptake during the same period of time was significantly higher in the trained subjects. To determine whether this reduced hormonal response to hypoglycemia was due to reduced insulin levels or to an increased sensitivity to counterregulatory hormones, we investigated the effect of epinephrine on plasma glucose in two other groups of trained and nontrained subjects. In response to a constant epinephrine infusion of 0.01 or 0.1 micrograms/kg fat-free mass (FFM)/min, plasma glucose levels increased similarly in the two groups. In conclusion, these results indicate that trained subjects are characterized by a normal recovery from hypoglycemia despite a reduced response of counterregulatory factors.(ABSTRACT TRUNCATED AT 250 WORDS)

Blood Glucose↗
PubMed1990

Effect of intensity of physical activity on body fatness and fat distribution.

To evaluate the effect of intensity of physical activity on body fatness and fat distribution, observations of 1366 women and 1257 men who participated in the 1981 Canada Fitness Survey were analyzed. Subjects were tested for energy expenditure of leisure-time activities and estimated maximal oxygen uptake (VO2max), body fatness was measured by subcutaneous skinfold thicknesses, and anthropometric measurements were made. Subjects of both sexes were categorized into four subgroups on the basis of their participation in leisure-time activities of various intensities. In general, subjects practicing vigorous activities on a regular basis had lower subcutaneous skinfold thicknesses and waist-to-hip ratios (WHRs) than those not performing these activities. These differences remained statistically significant after a covariance analysis was used to remove the effect of total energy expenditure of leisure-time activities on subcutaneous fat and fat distribution. Moreover, the WHR remained significantly lower in subjects performing high-intensity exercise after the effect of subcutaneous fat on fat distribution was adjusted for.

Adipose Tissue↗
PubMed1990

Abdominal fat cell lipolysis, body fat distribution, and metabolic variables in premenopausal women.

It is well established that abdominal obesity is related to numerous metabolic abnormalities and that this correlation represents a significant risk factor for coronary heart disease and related mortality. In the present study the relationships among the regional distribution of body fat, selected metabolic variables, and abdominal adipose cell lipolysis were investigated in 30 premenopausal women, 34 +/- 8 yr (mean +/- SD) of age, with body mass indices ranging from 17-45 kg/m2. Basal as well as epinephrine- and isoproterenol-stimulated lipolyses were positively correlated with fasting plasma insulin and triglyceride levels (0.48 less than r less than 0.64; 0.05 greater than P less than 0.0005 and 0.46 less than r less than 0.60; 0.05 greater than P less than 0.005, respectively) and with the insulin area measured during an oral glucose tolerance test (0.49 less than r less than 0.67; 0.005 greater than P less than 0.0005). With the exception of epinephrine-stimulated lipolysis, these correlations remained significant when lipolysis was corrected for cell surface area. Basal and maximal epinephrine- and isoproterenol-induced lipolyses were also negatively related to plasma high density lipoprotein cholesterol (-0.52 less than r less than -0.36; 0.05 greater than P less than 0.005). However, these relationships were no longer significant after control for fat cell surface. The associations between abdominal lipolysis and fat distribution did not remain significant when data were adjusted for total adiposity. Taken together, these results support the notion that variations in abdominal adipocyte lipolysis 1) depend more on total body fatness than on fat distribution, and 2) may be involved in the metabolic complications associated with abdominal obesity, particularly those pertaining to plasma insulin and triglyceride metabolism.

Abdominal Muscles↗
PubMed1990

Effect of dietary fat content on total and regional adiposity in men and women.

The relationship between dietary fat intake, adiposity and regional subcutaneous fat distribution was studied in 344 men and 335 women (aged 35-55 years). Three-day food records were used to estimate total energy intake (EI) and percent intake of all macronutrients. Subjects were categorized as having an EI that was low (lower quantile) or high (upper quantile) in fat. Results showed that both men and women with a higher percent of EI in the form of fat weighed significantly (P less than 0.05) more, and had higher subcutaneous adiposity indices than subjects with a low fat intake. There was also a significant difference for both sexes between low and high fat intake groups in trunk and extremity skinfolds and trunk/extremity skinfolds ratio adjusted for the sum of skinfolds. However, this effect was not present when correlations between percent fat intake and body composition or regional fat distribution variables adjusted for total fat intake per unit of body mass were computed. These results suggest that a greater EI in the form of fat influences total adiposity, as well as regional subcutaneous fat distribution, only when high fat consumers are compared to low fat consumers.

Adipose Tissue↗
PubMed1990

Altered plasma free carnitine response to exercise in type 1 diabetic subjects.

The plasma carnitine response to prolonged exercise in 12 postprandial insulin-dependent diabetics was compared with that of eight normal controls. The diabetics reduced their morning dose of intermediate acting insulin and regular insulin to two-thirds and one-half, respectively. Insulin was injected subcutaneously into the abdominal wall. Exercise was performed on a treadmill for 90 min at 60% VO2 max. Respiratory exchange ratios (RER) decreased significantly (p less than 0.0001) during exercise in both the control and diabetic group. However, RER values were higher (p less than 0.05) in the diabetic group during most of the exercise period, corresponding to a significantly (p less than 0.05) lower proportion of the energy utilized from the oxidation of fat. In the diabetic group, mean plasma glucose at rest was 278 +/- 26 mg/dl, and decreased significantly (p less than 0.01) to 107 +/- 12 mg/dl after 90 min of exercise. In the control group, mean resting plasma glucose was 78 +/- 6 mg/dl, and dropped (p less than 0.05) to 67 +/- 3 mg/dl at 30 min of exercise. Thereafter, it showed no change. Mean resting plasma free insulin in the control group was lower compared to the diabetic group (10.2 +/- 2.0 vs 23.5 +/- 2.0 microU/ml, p less than 0.001). During exercise, insulin levels decreased significantly (p less than 0.01) in the control group while there was no change in the diabetic group. In both control and diabetic groups, percent basal total carnitine increased significantly (p less than 0.01) throughout exercise.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1990

Long-term exercise training with constant energy intake. 1: Effect on body composition and selected metabolic variables.

The effects of long-term negative energy balance generated by exercise while maintaining a constant energy intake were studied in five healthy young males (25 +/- 3 years; mean +/- s.d.). After 2 weeks of monitoring to determine habitual energy intake, they were subjected to a 100-day experimental period during which they exercised on a cycle ergometer, 6 days a week, twice a day at 55 per cent of VO2 max. The daily energy deficit was 4.2 MJ for a total of 353 MJ for the duration of the treatment. Body weight decreased from 86.7 to 78.7 kg (P less than 0.001). More than 80 per cent of the weight loss was accounted for by the reductions in fat mass. Fat-free mass did not change significantly. The data suggest that subcutaneous fat was lost about evenly from the trunk and from the limbs as estimated from skinfolds. Cardiorespiratory and metabolic responses to submaximal work loads indicate that the low intensity exercise regimen was capable of inducing some of the known adaptations of exercise training such as a decrease in plasma insulin and norepinephrine concentrations during exercise, reductions in heart rate, pulmonary ventilation and blood lactate concentration at a given exercise intensity, and an increase in skeletal muscle oxidative capacity. The energy cost of sitting and standing was not decreased in spite of the loss in body mass. However, the energy cost of submaximal cycling and walking exercises was reduced considerably. These results clearly demonstrate that it is quite possible to lose fat while preserving fat-free mass through regular prolonged exercise of moderate intensity if energy intake is kept constant at baseline level. They also emphasize the importance of the individual differences in response to negative energy balance.

Adult↗
PubMed1990

Long-term exercise training with constant energy intake. 2: Effect on glucose metabolism and resting energy expenditure.

The effect of exercise training on glucose and insulin metabolism as well as on resting energy expenditure was investigated in five young men (mean BMI = 27.5 +/- 2.9 (s.d)). Subjects performed cycle-ergometer exercise 6 days/week over a 100 day period and the quantity of daily exercise was calculated to induce a 4.2 MJ/day surplus in energy expenditure during the days of training. As expected, significant weight and fat losses were observed in response to the training program. Exercise training induced a significant reduction in fasting levels and in the responses of insulin to a 4.2 MJ meal or an oral glucose load. Most of the training effects were noted after only 25 days of training. However, a significant decrease in plasma C-peptide concentrations during the oral glucose tolerance test was observed only at the end of the exercise program whereas essentially no change occurred during the first 25 days of training. The resting metabolic rate (RMR) and the thermic effect of food (TEF) were not significantly modified by training. Results show that the reduction in plasma insulin induced by training occurred earlier than that for C-peptide. Moreover, the absence of change in RMR in the presence of a substantial weight loss may represent a beneficial effect of training in comparison to the documented effect of diet-induced weight loss on RMR.

Adult↗
PubMed1990

Genetic effects in human energy expenditure components.

It is increasingly recognized that variations in human energy expenditure are partly due to an influence of the genotype, even after control for the well established concomitants of energy expenditure. Using the technique of genetic epidemiology, we have found that about 40 percent of the variance in resting metabolic rate, thermic effect of food and energy cost of low to moderate intensity exercise (less than or equal to 5 times the resting metabolic rate) is explained by inherited characteristics. A significant genetic effect has also been reported for the level of habitual physical activity. The existence of a genotype-environment interaction has also been investigated. Thus, we have demonstrated that in response to chronic overfeeding, as well as negative energy balance, changes in the components of energy expenditure are partly determined by one's genotype. Taken as a whole, these observations consistently support the hypothesis that heredity plays a significant role on the variations in the various components of energy expenditure in humans. Further research should now be focused more on the identification of biochemical and molecular markers of these energy expenditure characteristics.

Adult↗
PubMed1990

Long-term exercise training with constant energy intake. 3: Effects on plasma lipoprotein levels.

The composition and concentration of plasma lipoproteins were studied in five young men (mean BMI = 27.5 +/- 2.9 (s.d.] before, during (after 25 and 50 days of training), and after the completion of a 100 day exercise training program that induced daily 4.2 MJ calorie deficit. Along with reductions in body weight (from 86.7 +/- 20.0 to 78.7 +/- 17.1 kg, P less than 0.01) and in fat mass (from 17.0 +/- 9.7 to 10.4 +/- 7.4 kg, P less than 0.01), the exercise training program induced numerous changes in plasma lipoprotein levels. Plasma total cholesterol level fell significantly after 25 days of training (P less than 0.05) and remained significantly reduced at the end of the training experiment (P less than 0.05). This reduction in total plasma cholesterol was accompanied by reductions in plasma apoprotein (apo) B, LDL-cholesterol and LDL-apo B levels (P less than 0.05). There were trends for reductions in plasma triglyceride and VLDL components that were significant only for VLDL-triglycerides (P less than 0.05). Plasma HDL-cholesterol levels increased significantly only at the end of the training program (P less than 0.01). This increase in plasma HDL-cholesterol was not accompanied by an increase in plasma apo A-I levels suggesting that exercise training produced an increase in HDL cholesterol content rather than an increase in HDL particle number. Ratios of HDL-cholesterol/cholesterol (P less than 0.01) and apo A-I/apo B (P less than 0.05) were significantly increased by exercise training, suggesting a decreased risk of cardiovascular disease. These results indicate that a reduction in fat mass solely induced by aerobic exercise training has substantial beneficial effects on plasma lipoprotein levels.

Adult↗
PubMed1990

Serum osteocalcin or bone Gla-protein, a biochemical marker for bone metabolism in horses: differences in serum levels with age.

Levels of alkaline phosphatase and osteocalcin or bone Gla-protein, a new marker of bone metabolism, were analyzed in blood samples of 50 clinically normal female Standardbred horses between four months and twenty years of age. Samples were collected in the morning before exercise. Serum osteocalcin was measured by radioimmunoassay using bovine antibodies. There was a significant inverse correlation between alkaline phosphatase, osteocalcin and the age of the animals up to 48 months. The decrease in osteocalcin levels in serum was very marked during the first 30 months of life. The mean osteocalcin concentration was respectively 47.3, 35.7 and 6.7 ng/mL for animals less than one year, between 1.5 and 2.5 years of age and older than 3.5 years. Alkaline phosphatase serum activity was higher in foals less than one year of age (means = 856 U/L) than in the two older groups (meansII = 339, meansIII = 351 U/L). We believe that osteocalcin is a useful parameter for the evaluation of bone metabolism in growing animals and in adults and is probably more specific than alkaline phosphatase.

Aging↗
PubMed1990

Associations between regional body fat distribution, fasting plasma free fatty acid levels and glucose tolerance in premenopausal women.

The associations between total adiposity, body fat distribution measured by computed tomography (CT) and estimated by the waist-to-hip ratio (WHR), regional fat cell morphology, fasting plasma free fatty acid (FFA) levels and glucose tolerance were studied in a sample of 37 premenopausal women aged 35.3 +/- 4.6 years (mean +/- s.d.). Body fat mass, CT-derived abdominal and femoral fat areas, as well as the abdominal fat cell weight were all significantly associated with fasting plasma FFA levels (0.34 less than r less than 0.49, 0.005 less than P less than 0.05), and with the glucose and insulin areas during the oral glucose tolerance test (OGTT) (0.36 less than r less than 0.70, 0.0001 less than P less than 0.05). No associations were found between the WHR, the femoral fat cell weight and fasting plasma FFA levels or glucose area during the OGTT. However, the WHR and the femoral fat cell weight were positively associated with insulin area. Plasma FFA levels were positively correlated with the glucose area during the OGTT, whereas no association was found between plasma FFA levels and the insulin area. Covariance analysis indicated that this effect of plasma FFA levels on the magnitude of glucose response to OGTT was independent from that of total adiposity or regional body fat distribution variables. These results emphasize the importance of plasma FFA levels as a correlate of glucose tolerance and suggest that the associations previously reported between obesity, regional body fat distribution, fat cell size and glucose tolerance are, at least partly, mediated by variations in plasma FFA levels.

Abdomen↗
PubMed1990

Apolipoprotein E polymorphism alters the association between body fatness and plasma lipoproteins in women.

The aim of the present study was to investigate the associations between total adiposity, body fat distribution, and plasma lipoprotein levels within groups of women defined on the basis of apolipoprotein E phenotypes, in order to verify whether apoE polymorphism could modify these associations. In women having only apolipoprotein E3 isoforms (n = 24), body fat mass, the waist: hip circumference ratio, and computed tomography-derived total and intra-abdominal fat areas were all positively correlated with very low density lipoprotein (VLDL) and low density lipoprotein (LDL) lipids and apolipoprotein B concentrations. These body fatness variables were also negatively correlated with plasma high density lipoprotein (HDL) cholesterol concentration. These associations were, however, altered in the groups of women carrying either apoE2 or E4 isoforms. Indeed, in women carrying the apoE2 isoform (n = 22), body fatness variables were predominantly associated with VLDL components concentration (0.05 greater than P less than 0.01) and with LDL triglyceride content. No association was found between adiposity and LDL cholesterol or apolipoprotein B levels in these women. In contrast, no relationship was found between total adiposity, regional fat accumulation, and VLDL fraction in women carrying the apolipoprotein E4 isoform (n = 17). In this latter group, computed tomography-measured total abdominal fat accumulation was positively correlated with LDL apolipoprotein B (r = 0.58, P less than 0.05) concentration, whereas intra-abdominal fat accumulation was positively correlated with both LDL cholesterol and apolipoprotein B concentrations (P less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Abdomen↗
PubMed1990

Effects of experimenters and different blood sampling procedures on blood metabolite values in growing pigs.

The aims of the present study were firstly to verify if sera obtained by jugular venipuncture and those obtained from an anterior vena cava cannula were comparable and secondly to observe the effect of different experimenters on the biochemical profile of pigs. In the first experiment, 16 Yorkshire pigs with a mean weight of 48.9 +/- 2.3 kg were venipunctured using either a vacuum tube system or a syringe. The experiment was conducted on two separate days, seven days apart, in a crossover design experiment. At the time of obtaining blood via venipuncture, blood was also withdrawn from the jugular cannula. The tip of the latter was in the anterior vena cava. No effect of the sampling system was observed. However, a significant decrease in serum concentrations of Na, P and CO2 and a significant increase in anion gap, total protein, albumin, globulin, total bilirubin, aspartate amniotransferase, L-gamma glutamyl-transferase and creatine kinase were observed from blood samples obtained by venipuncture. In the second experiment, ten pigs from the first experiment were sampled by an inexperienced manipulator. Variations of the same magnitude as observed in the first experiment were observed in sera obtained by venipuncture and anterior vena cava but 18 of the 22 biochemical variables of sera obtained from the anterior vena cava were significantly different than those from the first experiment. The results show that blood samples obtained by jugular venipuncture in pigs can differ from samples obtained from an anterior vena cava cannula, specially in enzyme concentrations, and the dexterity of the experimenter may have a major effect on blood values.

Animals↗