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Biomedical subjects

A Tremblay

Publications and source records attributed to A Tremblay.

At least 181 records · Page 10Linked to original sources
PubMed1995

Nutritional determinants of the insulin resistance syndrome.

Recent data show that fat balance is the only component of macronutrient balance which is not precisely regulated. The adherence to a lifestyle characterized by high fat food habits and sedentariness thus favor a positive fat balance which may persist for a long period of time. The resulting body fat gain contributes to the restoration of fat and energy balance because of the enhancing effect of fat gain on fat oxidation. Individuals predisposed to obesity seem to be particularly vulnerable to a positive lipid balance because they are characterized by a reduced fat oxidation when their body weight is normal and by a reduced capacity to increase fat oxidation when exposed to a high fat diet. Body fat gain, particularly in the deep abdominal area, is also associated with an increase in insulinemia which is known to acutely inhibit fat mobilization and oxidation. Beyond these peripheral metabolic effects, hyperinsulinemia with euglycemia can influence neuronal regulation of energy balance which ultimately results in an increase in sympathetic nervous system activity. An increased sympathetic tonus exerts an enhancing effect on fat oxidation and energy expenditure and a reducing effect on food intake. As discussed in this report, hyperinsulinemia thus appears to be an adaptation which is part of a regulatory system aimed at restoring fat and energy balance under conditions favoring body fat accumulation.

Body Composition↗
PubMed1995

Exercise-training, macronutrient balance and body weight control.

It is well established that exercise-training can induce body weight and fat losses provided that mean daily energy expenditure exceeds mean energy intake. Recent experimental data show that under free living conditions, the composition of macronutrient intake tends to differ from the composition of macronutrient utilization when the body is in energy imbalance, even over a short period of time. Since protein and carbohydrate balances are precisely regulated under unrestricted food intake conditions, a body energy deficit is necessarily equivalent to a lipid deficit. In the context of an aerobic training program, a body lipid deficit should be spontaneously reached by performing prolonged vigorous exercise on a regular basis and by preventing a diet with a high fat content. However, as body fat decreases with exercise there is an associated decrease in the lipid content of the fuel mix oxidized and this acts to progressively decrease the lipid deficit. Ultimately, a new lipid balance will be reached at a reduced level of body fatness when the proportion of lipid in the substrate mix will become similar to the proportion of lipid in the diet. Recent research observations show that such a program has the potential to induce a substantial fat loss, particularly in the abdominal area, and a significant improvement of the metabolic profile of obese individuals. These beneficial effects cannot be maintained on a long-term basis if the new exercise and food habits are not incorporated in the lifestyle of these individuals.

Adipose Tissue↗
PubMed1995

Body fatness in active individuals reporting low lipid and alcohol intake.

OBJECTIVES: To evaluate body fatness in subjects complying with common public health guidelines for lipid and alcohol intake as well as physical activity participation. SUBJECTS: A sample of 358 male subjects who participated in phase 1 of the Quebec Family Study. DESIGN: The association between adiposity, lipid and alcohol intake and physical activity participation was analyzed in the overall sample. A comparison of body fatness in individuals adhering or not to public health recommendations was also performed. RESULTS: Significant positive correlations were observed between the percentage of dietary energy as lipid and adiposity indicators. Accordingly, subjects classified as low-fat consumers displayed significantly lower levels of fat mass and subcutaneous adiposity compared to high-fat consumers. When subjects reporting low lipid and alcohol intake and regular participation in vigorous physical activities were compared to those exhibiting opposite behaviors, the between-group difference in subcutaneous adiposity was doubled and this was essentially explained by an increase in the difference for truncal subcutaneous adiposity. CONCLUSION: These results indicate that the adherence to a lifestyle characterized by high-fat and alcohol intake as well as sedentariness promotes fat gain, particularly in the trunk area.

Adult↗
PubMed1995

Exercise, macronutrient preferences and food intake.

The impact of physical training on body weight and fat depends on the ability of exercise to promote a negative fat balance. This effect is more likely to occur in individuals who are good responders in fat oxidation to exercise and who adhere to a dietary regimen containing a low to moderate amount of fat. Experimental evidence suggests that exercise per se may also increase the preference for carbohydrates, i.e. reduce the relative fat content of the diet, and this might be related to the composition of the substrate mix oxidized during exercise. The body fat loss resulting from a long-term negative fat balance is associated with a progressive decrease in fat oxidation which is likely involved in the occurrence of resistance to lose fat in reduced obese individuals. This suggests that fat loss related factors represent signals for neurosystems controlling feeding behavior. Further research pertaining to exercise and the control of food intake should focus on the mechanisms by which exercise may influence neurosystems which are known to affect food intake.

Dietary Carbohydrates↗
PubMed1995

Social class interacts with the association between macronutrient intake and subcutaneous fat.

BACKGROUND: A large amount of evidence shows that adiposity is associated both with macronutrient composition of the habitual diet and socio-economic variables. Since dietary habits may covariate with social status, these two groups of factors may act as mutual confounders when studying their independent impact on adiposity. OBJECTIVE: To investigate the independent relationship between educational level and dietary habits with adiposity. To study interactive effects of educational level on the association between macronutrient intake and adiposity. DESIGN: This cross-sectional study was based on dietary records, interviews and anthropometry of 358 men and 368 women of the Québec Family Study. STATISTICS: Partial correlation analyses were applied to clarify independent correlations of body fatness with educational level, dietary habits and other behavioural factors. ANCOVA was used to detect interactive effects of educational level on macronutrient versus adiposity relationships. RESULTS: Inverse associations between educational level and BMI, percent body fat, truncal skinfolds were found in women but not in men. Both protein and lipid intake correlated or tended to correlate positively with some of the adiposity measures in women. Protein intake correlated positively with truncal skinfolds in men of lower but not higher educational level. CONCLUSIONS: The results emphasize the importance of including demographic variables like social status in surveys dealing with the relationships between adiposity and dietary habits.

Adipose Tissue↗
PubMed1995

Differences in fat balance underlying obesity.

Energy balance occurs under free-living conditions when macronutrient balance is achieved (i.e., the intake of each macronutrient corresponds to its use). Among the components of macronutrient balance, fat balance is the one which is at greater risk of large deviations because of a reduced potential of fat to decrease food intake acutely and to promote its oxidation. This may represent a problem for individuals predisposed to obesity who are characterized by an increased taste preference for fat and a reduced capacity to oxidize fat when their body weight is normal. When these individuals are exposed to a lifestyle favouring a positive fat balance, a greater demand is imposed on sympathetic nervous system activity which is stimulated by hyperinsulinaemia. Accordingly, muscle sympathetic nerve activity (MSNA) is greater in obese hyperinsulinaemic individuals in the basal state, whereas they display a blunted response in MSNA to the acute administration of insulin. In this context, where the ability to further stimulate sympathetic activity is low, fat gain and its related increased lipid mobilization and oxidation remain the ultimate means to restore fat balance.

Body Composition↗
PubMed1994

Transgenic glutathione peroxidase mouse models for neuroprotection studies.

Seleno-glutathione peroxidase (GSHPx) is considered to be the major enzymatic activity in charge of removing excess cytosolic and mitochondrial H2O2 in most tissues including brain. Intracellular GSHPx activity is therefore hypothesized to be one important factor that contributes to minimize hydroxyl radical formation via Fenton-type reactions. An animal model was developed to challenge this hypothesis in vivo and evaluate the role of GSHPx in hydroperoxide metabolism and oxidative stress homeostasis. Three lines of transgenic mice, homozygous for the integration of 1 to 3 GSHPx transgene copies, have been generated. The transgene was placed under transcriptional control of a metallothionein promoter (hMT-IIA). This promoter was chosen because metallothionein expression, normally low in most tissues, can be induced by several inflammatory cytokines, protein kinase C activators, and stress agents including heavy metals. The data reported here provide information on the constitutive expression of GSHPx mRNA and enzyme in various brain regions of healthy untreated adult tg-MT-GPx mice. Northern and/or Western analysis indicated that transgenic GSHPx was expressed constitutively in all brain regions investigated in tg-MT-GPx-6 mice, including the cerebral cortex, brainstem, hippothalamus, cerebellum, substantia nigra, and striatum. Similar results were obtained with the two other transgenic lines, tg-MT-GPx-11 and -13. Depending on the brain region, the GSHPx immunoreactivity detected in tissue extracts with an immunoaffinity-purified polyclonal antibody was about 2- to 5-fold stronger in transgenic extracts than in their non-tg counterparts (western blots). In contrast, the corresponding increase in GSHPx activity measured in these extracts was smaller, for example, about 1.5-fold in transgenic mesencephalon. Immunocytochemical data indicated that GSHPx-like staining was distinctly more intense in transgenic midbrain brain sections than in corresponding non-tg sections. Interestingly, only a subset of the cells displayed higher density staining that most likely reflects increased amounts of GSHPx protein. This observation suggests that the stained cells, not yet identified, may have larger GSHPx activity increments than the cell-average increments measured in tissue extracts. Current work is in progress to determine whether transgenic GSHPx expression may be induced by inflammatory processes or perturbations of heavy metal metabolism.

Animals↗
PubMed1994

Waist circumference and abdominal sagittal diameter: best simple anthropometric indexes of abdominal visceral adipose tissue accumulation and related cardiovascular risk in men and women.

The amount of abdominal visceral adipose tissue measured by computed tomography is a critical correlate of the potentially "atherogenic" metabolic disturbances associated with abdominal obesity. In this study conducted in samples of 81 men and 70 women, data are presented on the anthropometric correlates of abdominal visceral adipose tissue accumulation and related cardiovascular disease risk factors (triglyceride and high-density lipoprotein cholesterol levels, fasting and postglucose insulin and glucose levels). Results indicate that the waist circumference and the abdominal sagittal diameter are better correlates of abdominal visceral adipose tissue accumulation than the commonly used waist-to-hip ratio (WHR). In women, the waist circumference and the abdominal sagittal diameter also appeared more closely related to the metabolic variables than the WHR. When the samples were divided into quintiles of waist circumference, WHR or abdominal sagittal diameter, it was noted that increasing values of waist circumference and abdominal sagittal diameter were more consistently associated with increases in fasting and postglucose insulin levels than increasing values of WHR, especially in women. These findings suggest that the waist circumference or the abdominal sagittal diameter, rather than the WHR, should be used as indexes of abdominal visceral adipose tissue deposition and in the assessment of cardiovascular risk. It is suggested from these data that waist circumference values above approximately 100 cm, or abdominal sagittal diameter values > 25 cm are most likely to be associated with potentially "atherogenic" metabolic disturbances.

Abdomen↗
PubMed1994

The response to exercise with constant energy intake in identical twins.

Seven pairs of young adult male identical twins completed a negative energy balance protocol during which they exercised on cycle ergometers twice a day, 9 out of 10 days, over a period of 93 days while being kept on a constant daily energy and nutrient intake. The total energy deficit caused by exercise above the estimated energy cost of body weight maintenance reached 244 +/- 9.8 MJ (Mean +/- SEM). Baseline energy intake was estimated over a period of 17 days preceding the negative energy balance protocol. Mean body weight loss was 5.0 kg (SEM = 0.6) (p < 0.001) and it was entirely accounted for by the loss of fat mass (p < 0.001). Fat-free mass was unchanged. Body energy losses reached 191 MJ (SEM = 24) (p < 0.001) which represented about 78% of the estimated energy deficit. Subcutaneous fat loss was slightly more pronounced on the trunk than on the limbs as estimated from skinfolds, circumferences, and computed tomograply (CT). The reduction in CT-assessed abdominal visceral fat was quite striking, from 81 cm2 (SEM = 5) to 52 cm2 (SEM = 6) (p < 0.001). At the same submaximal power output level, subjects oxidized more lipids than carbohydrates after the program as indicated by the changes in the respiratory exchange ratio (p < or = 0.05). Intrapair resemblance was observed for the changes in body weight (p < 0.05), fat mass (P < 0.01), percent fat (p < 0.01), body energy content (p < 0.01), sum of 10 skinfolds (p < 0.01), abdominal visceral fat (p < 0.01), fasting plasma triglycerides (p < 0.05) and cholesterol (p < 0.05), maximal oxygen uptake (p < 0.05), and respiratory exchange ratio during submaximal work (p < 0.01). We conclude that even though there were large individual differences in response to the negative energy balance and exercise protocol, subjects with the same genotype were more alike in responses than subjects with different genotypes particularly for body fat, body energy, and abdominal visceral fat changes. High lipid oxidizers and low lipid oxidizers during submaximal exercise were also seen despite the fact that all subjects had experienced the same exercise and nutritional conditions for about three months.

Adipose Tissue↗
PubMed1994

Are gender differences in cardiovascular disease risk factors explained by the level of visceral adipose tissue?

It has been suggested that the lower prevalence of cardiovascular disease in women before menopause in comparison with men may be explained by differences in body fat distribution, plasma lipoprotein levels and indices of plasma glucose-insulin homeostasis. Thus, gender differences in visceral adipose tissue accumulation measured by computed tomography and metabolic variables were studied in 80 men and 69 pre-menopausal women, aged 23-50 years. Despite the fact that women had higher levels of total body fat (p < 0.0001), they displayed lower areas of abdominal visceral adipose tissue (p < 0.06) and a lower ratio of abdominal visceral to mid-thigh adipose tissue areas than men (p < 0.0001). After adjustment for body fat mass, women generally displayed a more favourable risk profile than men which included higher plasma HDL2-cholesterol and lower plasma insulin, apolipoprotein B and triglyceride levels (p < 0.01). Metabolic variables adjusted for body fat mass were then compared between genders after control for differences in abdominal visceral adipose tissue area. After such controls, variables related to plasma glucose-insulin homeostasis were no longer significantly different between men and women. Gender differences for plasma concentrations of triglyceride, apolipoprotein B and the ratio of HDL2-cholesterol/HDL3-cholesterol also disappeared, whereas plasma concentrations of HDL-cholesterol, HDL2-cholesterol as well as the ratio of HDL-cholesterol/total cholesterol remained significantly higher in women than in men (p < 0.01). These results suggest that abdominal visceral adipose tissue is an important correlate of gender differences in cardiovascular disease risk. However, additional factors are likely to be involved in gender differences in plasma HDL-cholesterol levels.

Adipose Tissue↗
PubMed1994

Systolic blood pressure during submaximal exercise: an important correlate of cardiovascular disease risk factors in normotensive obese women.

Body fatness, plasma lipids, lipoproteins, indicators of glucose metabolism, and resting as well as submaximal treadmill exercise systolic blood pressures (BPs) were measured in a sample of 25 normotensive obese premenopausal women. No association was observed between body fatness, risk factors for cardiovascular disease, and resting BP. However, body fatness and plasma cholesterol, low-density lipoprotein cholesterol (LDL-CHOL), LDL apolipoprotein B (apo B), and apo B concentrations, as well as the high-density lipoprotein cholesterol to cholesterol (HDL-CHOL/CHOL) ratio, showed significant correlations with systolic BP measured during submaximal exercise. In addition, fasting plasma insulin concentrations and the glucose and insulin areas under the oral glucose tolerance test (OGTT) curve were both significantly associated with systolic BP during submaximal exercise. Partial correlation analyses revealed that the associations between submaximal exercise systolic BP and plasma apo B and LDL apo B levels were in part independent from the level of obesity. These results indicate that plasma concentrations of lipoproteins and insulin are important correlates of the systolic BP during submaximal exercise in obese premenopausal women. Further analyses performed on two subgroups indicated that women with high exercise systolic BP values exhibited significant differences in their metabolic profile in comparison to women with low BP during exercise. These results suggest that the absolute systolic BP recorded during submaximal exercise may be useful in the early detection of individuals at risk for the development of cardiovascular disease in resting normotensive obese women.

Adult↗
PubMed1994

Impact of exercise intensity on body fatness and skeletal muscle metabolism.

The impact of two different modes of training on body fatness and skeletal muscle metabolism was investigated in young adults who were subjected to either a 20-week endurance-training (ET) program (eight men and nine women) or a 15-week high-intensity intermittent-training (HIIT) program (five men and five women). The mean estimated total energy cost of the ET program was 120.4 MJ, whereas the corresponding value for the HIIT program was 57.9 MJ. Despite its lower energy cost, the HIIT program induced a more pronounced reduction in subcutaneous adiposity compared with the ET program. When corrected for the energy cost of training, the decrease in the sum of six subcutaneous skinfolds induced by the HIIT program was ninefold greater than by the ET program. Muscle biopsies obtained in the vastus lateralis before and after training showed that both training programs increased similarly the level of the citric acid cycle enzymatic marker. On the other hand, the activity of muscle glycolytic enzymes was increased by the HIIT program, whereas a decrease was observed following the ET program. The enhancing effect of training on muscle 3-hydroxyacyl coenzyme A dehydrogenase (HADH) enzyme activity, a marker of the activity of beta-oxidation, was significantly greater after the HIIT program. In conclusion, these results reinforce the notion that for a given level of energy expenditure, vigorous exercise favors negative energy and lipid balance to a greater extent than exercise of low to moderate intensity. Moreover, the metabolic adaptations taking place in the skeletal muscle in response to the HIIT program appear to favor the process of lipid oxidation.

Adipose Tissue↗
PubMed1994

Diet composition and postexercise energy balance.

This study was aimed at investigating the effect of exercise on energy balance under dietary conditions differing by the relative lipid content of foods. Nine healthy men performed a 60-min treadmill exercise followed by a 48-h observation period during which they maintained their habitual daily activities and had free access to either a low-fat, a mixed, or a high-fat diet. Energy balance, summing up the excess of energy expended during exercise and the 48-h postexercise energy balance, was -6.4, -4.5, and 0.9 MJ under low-fat, mixed, and high-fat diet conditions, respectively. These observations suggest that exercise can induce a substantial energy deficit when a low-fat diet conforming to nutritional recommendations is consumed after exercise. They also suggest that the increase in energy intake associated with a high-fat diet is sufficient to fully compensate for the energy deficit resulting from the energy cost of exercise and the increase in postexercise energy expenditure.

Adult↗
PubMed1994

DNA variation in the genes of the Na,K-adenosine triphosphatase and its relation with resting metabolic rate, respiratory quotient, and body fat.

The aim of this study was to investigate in 261 subjects from 58 families the association between DNA variation at the genes coding for the Na,K-ATPase peptides and resting metabolic rate (RMR), respiratory quotient (RQ), and percent body fat (%FAT). Five restriction fragment length polymorphisms (RFLP) at three Na,K-ATPase genes were determined: one at the alpha 1 locus (BglII), and two at the beta locus (beta MspI and beta PvuII). Haplotypes were determined from the two variable sites of the alpha 2 gene (alpha 2 haplotypes) and the beta gene (beta haplotypes). There was a strong trend for %FAT to be related to the RFLP generated by BglII at the alpha 2 exons 21-22 in males (P = 0.06) and females (P = 0.05). RQ was (a) associated with the BglII RFLP at the alpha 2 exon 1 (P = 0.02) and with the alpha 2 8.0 kb/4.3 kb haplotype (P = 0.04) and (b) linked with the beta gene MspI marker (P = 0.04) and with the beta 5.3 kb/5.1 kb haplotype (P = 0.008) based on sib-pair analysis. The present study suggests that the genes encoding Na,K-ATPase may be associated or linked with RQ and perhaps with %FAT but not with RMR.

Adipose Tissue↗