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Biomedical subjects

A Tremblay

Publications and source records attributed to A Tremblay.

At least 127 records · Page 7Linked to original sources
PubMed1998

Fat balance and ageing: results from the Québec Family Study.

The aim of the present study was to evaluate changes in participation in physical activity and in fat and alcohol intake associated with ageing. This issue was examined in adults (n 207) who were tested between 1978 and 1982 and re-tested 12 years later. These adults were 42.3 (SD 4.9) years of age at baseline. Their children (n 122) were tested over the same follow-up period. They were, on average, 12.5 (SD 1.9) years at entry into the study. A decrease in the proportion of daily energy intake as fat and an increase in participation in vigorous physical activities were observed over the 12-year period in both groups. The proportion of dietary energy as alcohol remained stable in adults whereas it increased markedly in children. Correlation analyses between baseline and follow-up levels were significant for dietary fat and alcohol intake in adults. In children, the levels of these variables in the growing years did not predict the levels attained 12 years later. Even though the adults displayed changes in fat balance generally following current public health recommendations, a substantial increase in skinfold thicknesses was observed in these subjects during follow-up. This observation suggests that there is a strong effect of age-related factors on fat balance.

Adult↗
PubMed1998

EM-800, a novel antiestrogen, acts as a pure antagonist of the transcriptional functions of estrogen receptors alpha and beta.

Estrogens act as potent mitogens in a large number of breast cancers, and the use of estrogen receptor (ER) antagonists is, therefore, considered the endocrine therapy of choice in the management of this disease. We describe the molecular properties of EM-652, the active metabolite of EM-800, a novel nonsteroidal antiestrogen compound, on the transcriptional functions of ER alpha and ER beta. Using RT-PCR, we show that ER alpha and ER beta are expressed in mouse mammary glands, suggesting that both receptors should be considered putative targets for antiestrogen action in the breast. In cotransfection assays using a synthetic estrogen-responsive promoter, EM-652 shows no agonistic activity on ER alpha and ER beta transcriptional function and blocks the estradiol (E2)-mediated activation of both ER alpha and ER beta. EM-652 is also very effective in abrogating E2-stimulated ER alpha and ER beta trans-activation of the pS2 promoter in HeLa cells. EM-652 does not alter binding of ER alpha and ER beta to DNA. The Ras-mediated induction of ER alpha and ER beta transcriptional activity in the presence of E2 is also completely abolished by EM-652. In addition, EM-652 blocks the E2-dependent activation of ER alpha and ER beta by the steroid hormone receptor coactivator-1 as well as the in vitro interaction between SRC-1 and the ligand-binding domains of both ERs. These results demonstrate that the novel antiestrogen EM-800 fully impedes AF-1 and AF-2 activities of ER alpha and ER beta and can, therefore, be considered a potent and pure antagonist of both ER subtypes.

Animals↗
PubMed1998

Plasma adrenal, gonadal, and conjugated steroids before and after long-term overfeeding in identical twins.

An analysis of the data collected in the Quebec Overfeeding Study of identical twins was undertaken to determine any evidence of a genotype effect on plasma levels of adrenal and gonadal steroids arising from long term positive energy balance. Plasma levels of sex hormone-binding globulin (SHBG), testosterone, dihydrotestosterone (DHT), dehydroepiandrosterone sulfate (DHEA-S), androsterone glucuronide, androstane-3 alpha, 17 beta-diol glucuronide (3 alpha-DIOL-G), and cortisol were measured in 12 pairs of young, sedentary, male monozygotic twins before and after 100 days of overfeeding. The dietary energy excess of 4.2 MJ/day (1000 Cal), 6 days a week, resulted in a total positive energy balance of 353 MJ (84,000 Cal). Overfeeding induced significant changes (P < 0.0001) in body weight and other measures of body composition. Within-twin pair resemblance was observed at baseline in all steroids, except cortisol [intraclass correlation range: DHEA-S, 0.50 (P < 0.05); DHT, 0.77 (P < 0.001)] and was lost with overfeeding, except for DHT and SHBG (P < 0.05). SHBG levels fell and 3 alpha-DIOL-G rose with the gain in body fatness. The change in testosterone was a significant correlate of the change in upper body fat (r = -0.48; P < 0.05). The change in 3 alpha-DIOL-G correlated positively with increases in all measures of central adiposity (r = 0.52; P < 0.01). A decrease in DHEA-S occurred with a higher, but not with a lower, gain in abdominal visceral fat (P < 0.05). Thus, analysis of adrenal and gonadal steroids and of conjugated metabolites before and after overfeeding in monozygous twins supports the idea that there is a genotype effect on steroid circulating steroid levels and that these blood levels are correlated with the pattern of body fat distribution. Moreover, the baseline within-twin pairs similarity in steroid levels was attenuated by prolonged positive energy balance and body fat gain.

Adipose Tissue↗
PubMed1998

Postprandial triglyceride response in visceral obesity in men.

Although metabolic disturbances are often observed in obese patients, increased accumulation of visceral adipose tissue (AT) has been shown to be more closely associated with high fasting triglyceride (TG) and insulin levels as well as with low HDL cholesterol concentrations than with excess body fatness per se. Interestingly, the fasting concentration of plasma TGs has been shown to be an important determinant of the magnitude and duration of the postprandial TG response. Yet little is known about the respective contributions of obesity versus excess visceral AT to the variation in postprandial TG clearance. In the present study, we examined potential differences in postprandial triglyceride-rich lipoprotein (TRL) responses in subjects characterized by high versus low levels of visceral AT. In a sample of 43 men (mean age: 41.3 +/- 9.6 years), we found that both excess body fat and visceral obesity were associated with increased postprandial TG responses in total TRL (r = 0.33-0.45). We also found a strong relationship between fasting plasma TG levels and postprandial total TRL-TG concentrations (r = 0.79, P < 0.0001). When matched for total body fat mass, individuals with high levels of visceral AT (> or =130 cm2; n = 10) as assessed by computed tomography were characterized by increased medium- and small-TRL-TG responses (P < 0.05) compared with subjects with low visceral AT accumulation (<130 cm2; n = 10). Moreover, this elevated response of small-TRL triglycerides noted in men with high levels of visceral AT was not accompanied by a concomitant increased retinyl palmitate response in this TRL fraction, suggesting that visceral obesity in men is accompanied by higher postprandial VLDL production than is found in obese men with lower levels of visceral AT. Increased postprandial insulin and free fatty acid (FFA) responses were also noted in men with high levels of visceral AT. Finally, postheparin plasma lipoprotein lipase activity was negatively correlated with the total-TRL-TG response in a subsample of 32 individuals (r = -0.37, P < 0.05). The results of the present study suggest that visceral obesity is associated with an impaired postprandial TG clearance. Furthermore, the exaggerated postprandial FFA response observed in subjects with high visceral AT suggests that visceral obesity may contribute to fasting and postprandial hypertriglyceridemia by altering FFA metabolism in the postprandial state.

Adipose Tissue↗
PubMed1998

Adult respiratory failure.

Pulmonary complications following thoracic surgery are common and associated with significant morbidity and mortality. In particular, acute respiratory distress syndrome (ARDS) can occur postoperatively or after trauma. This syndrome, when complicated by multisystem organ failure, often leads to a poor outcome. This article describes the etiology and pathophysiology of ARDS and evaluates recent advances in pharmacological and nonpharmacological therapies. In addition, newer modalities of mechanical ventilatory support are reviewed.

Acute Disease↗
PubMed1997

Association between median episiotomy and severe perineal lacerations in primiparous women.

OBJECTIVE: To evaluate the association between median episiotomy and severe (third- and fourth-degree) perineal lacerations in primiparous women. DESIGN: Retrospective cohort study. SETTING: University-affiliated hospital providing secondary obstetric care in Quebec City. PATIENTS: A total of 6522 primiparous women who gave birth vaginally to a single live baby in cephalic position between 1985 and 1993. OUTCOME MEASURE: Incidence of third- and fourth-degree perineal lacerations. RESULTS: Median episiotomy was performed in 4390 women (67.3%). A total of 1002 women (15.4%) had a third- or fourth-degree laceration. The frequency of severe perineal lacerations was 20.6% with episiotomy and 4.5% without episiotomy (relative risk [RR] 4.58, 95% confidence interval [CI] 3.74-5.62). This association persisted after adjustment by stratified analysis for type of delivery and birth weight (RR 3.03, 95% CI 2.52-3.63) and by logistic regression for type of delivery, birth weight, epidural analgesia, shoulder dystocia, baby's head circumference, experience of the physician and year of delivery (odds ratio 3.58, 95% CI 2.84-4.50). CONCLUSION: Median episiotomy is strongly associated with third- and fourth-degree perineal lacerations in primiparous women. Reducing the use of this procedure could decrease the occurrence of severe perineal tears.

Adult↗
PubMed1997

The MspI polymorphism of the apolipoprotein A-II gene as a modulator of the dyslipidemic state found in visceral obesity.

The aim of the present study was to examine the effect of variation at the apolipoprotein (apo) A-II gene locus on lipoprotein levels in visceral obesity. A total of 145 sedentary men, free from metabolic disorders requiring pharmacotherapy, were classified into two groups on the basis of their apo A-II-MspI genotype determined by the polymerase chain reaction: 1) 43 M1 carriers or M1M2, including two M1M1 homozygotes and 41 M1M2 heterozygotes, and 2) 102 M2M2 homozygotes for the presence of a MspI restriction site. The two genotypic groups did not differ for body mass index (BMI, expressed in kg/m2), body fat mass, visceral adipose tissue (AT) accumulation, as well as for insulin, glucose and free fatty acids levels measured in the fasting state and in response to an oral glucose tolerance test. In addition, 65 and 63% of M1 carriers had plasma HDL2 cholesterol levels and a HDL2/HDL3 cholesterol ratio below the 50th percentile of their distributions compared with 45%(P < 0.05) and 46%(P = 0.06), respectively, in M2M2 homozygotes. When subjects were further divided on the basis of visceral AT accumulation (below and above a value of 130 cm2), M1 carriers with low levels of visceral AT were characterized by high plasma HDL cholesterol and HDL2 cholesterol concentrations as well as by a higher HDL2/HDL3 ratio, compared with M1 carriers with high levels of visceral AT (> 130 cm2), or with M2M2 homozygotes with either a high or a low accumulation of visceral AT. Furthermore, M1 carriers with high levels of visceral AT showed a trend for lower plasma HDL2 cholesterol levels and were characterized by a significantly lower HDL2/HDL3 cholesterol ratio compared with the other three groups. No difference in HDL and HDL2 cholesterol levels and in the HDL2/HDL3 cholesterol ratio was noted when M2 homozygotes with lower versus higher levels of visceral AT were compared. The contribution of hyperinsulinemia was also examined by dividing subjects on the basis of the 50th percentile of the integrated insulin response to an oral glucose challenge. Significantly lower plasma HDL2 cholesterol levels and a reduced HDL2/HDL3 cholesterol ratio were noted among M1 carriers with high plasma insulin responses compared with M1 carriers with low insulin responses. Among M2M2 homozygotes, no difference was noted in plasma HDL cholesterol and in HDL2 cholesterol concentrations between men with low versus high insulin responses to the oral glucose load. These results suggest that the apo A-II-MspI polymorphism could modulate plasma HDL cholesterol levels among visceral obese, insulin-resistant men.

Adipose Tissue↗
PubMed1997

Abdominal visceral fat is associated with a BclI restriction fragment length polymorphism at the glucocorticoid receptor gene locus.

Several investigations have suggested that body fat distribution is influenced by nonpathologic variations in the responsiveness to cortisol. Genetic variations in the glucocorticoid receptor (GRL) could therefore potentially have an impact on the level of abdominal fat. A restriction fragment length polymorphism (RFLP) has previously been detected with the BclI restriction enzyme in the GRL gene identifying two alleles with fragment lengths of 4.5 and 2.3 kb. This study investigates whether abdominal fat areas measured by computerized tomography (CT) are associated with this polymorphism in 152 middle-aged men and women. The less frequent 4.5-kb allele was found to be associated with a higher abdominal visceral fat (AVF) area independently of total body fat mass (4.5/4.5 vs. 2.3/2.3 kb genotype; men: 190.7 +/- 30.1 vs. 150.7 +/- 33.3 cm2, p = 0.04; women: 132.7 +/- 37.3 vs. 101.3 +/- 34.5 cm2, p = 0.06). However, the association with AVF was seen only in subjects of the lower tertile of the percent body fat level. In these subjects, the polymorphism was found to account for 41% (p = 0.003) and 35% (p = 0.007), in men and women, respectively, of the total variance in AVF area. The consistent association between the GRL polymorphism detected with BclI and AVF area suggests that this gene or a locus in linkage disequilibrium with the BclI restriction site may contribute to the accumulation of AVF.

Abdomen↗
PubMed1997

Plasma leptin concentrations: gender differences and associations with metabolic risk factors for cardiovascular disease.

The cloning of the obese gene and the characterization of its protein product, leptin, has permitted the study of a new hormone potentially involved in the regulation of adipose tissue mass. The present study examined the gender differences in fasting plasma leptin concentration and its relationship to body fatness, adipose tissue distribution and the metabolic profile in samples of 91 men (mean age +/- SD: 37.3 +/- 4.8 years) and 48 women (38.5 +/- 6.8 years). Plasma leptin concentrations were strongly associated with body fat mass measured by underwater weighing [men: r = 0.80, p < 0.0001; women: r = 0.85, p < 0.0001]. In both genders, plasma leptin levels were also strongly correlated with waist girth as well as cross-sectional areas of abdominal subcutaneous and visceral adipose tissue measured by computed tomography. Women had, on average, plasma leptin concentrations that were three times higher than men. Furthermore, this gender difference remained significant when comparing men and women matched for similar levels of body fat mass. The associations between plasma leptin and lipoprotein concentrations were dependent of adiposity. In both men and women, elevated fasting plasma leptin levels were associated with higher plasma insulin concentrations, but only in women was the association maintained after correction for fat mass. Thus, results of the present study show that women have higher plasma leptin levels compared to men, independent of the concomitant variation in total body fat mass. Furthermore, our results also suggest that, in women, the association between plasma leptin and insulin concentrations is independent of adiposity, a finding which provides further support to the observation that adipose tissue leptin secretion may be upregulated by insulin.

Adipose Tissue↗
PubMed1997

Relationships between endogenous steroid hormone, sex hormone-binding globulin and lipoprotein levels in men: contribution of visceral obesity, insulin levels and other metabolic variables.

Excess visceral adipose tissue (AT) and hyperinsulinemia are important correlates of an altered lipoprotein profile. It has also been reported that testosterone, adrenal C19 steroids and sex hormone-binding globulin (SHBG) concentrations are associated with plasma lipoprotein levels. The aim of the present study was to investigate the relative contributions of endogenous steroid hormone and SHBG levels, of visceral AT accumulation measured by computed tomography, and of fasting insulin and free fatty acid (FFA) concentrations to the variation of plasma lipoprotein levels in men. For this purpose, plasma concentrations of testosterone, dehydroepiandrosterone (DHEA), androstene-3beta,17beta-diol (delta5-DIOL), androstenedione (delta4-DIONE), estrone and estradiol, as well as SHBG levels were determined in a sample of 76 men covering a wide range of body fatness values. Higher testosterone levels were associated with a more favorable lipoprotein profile as it showed significant correlations with triglyceride (TG), total cholesterol and LDL-cholesterol (LDL-C) concentrations (r= -0.25, -0.25 and -0.27, respectively; P < 0.05). Higher plasma adrenal C19 steroid levels were also associated with a favorable lipoprotein profile as DHEA, delta4-DIONE and delta5-DIOL levels were negatively correlated with total cholesterol (r = -0.24, -0.33 and -0.24, respectively; P < 0.05) and LDL-C (r = -0.23, -0.31 and -0.28, respectively; P < 0.05). SHBG levels were negatively correlated with TG concentrations (r = -0.33; P < 0.005) whereas delta5-DIOL, testosterone and SHBG were negatively correlated with apolipoprotein B levels (-0.32 < or = r < or = -0.43; P < 0.005). Statistical adjustment for visceral AT area, fasting insulin, fasting free fatty acid (FFA) levels and total body fat mass eliminated most of the correlations between steroid and lipoprotein levels, while SHBG remained significantly correlated with lipoprotein concentrations after such adjustments. Multivariate analyses revealed that SHBG, delta4-DIONE, delta5-DIOL and metabolic variables all contributed to the variance in plasma lipoprotein concentrations (from 10 to 29% of explained variance). Visceral AT, fasting FFA and insulin levels as well as SHBG concentrations appeared to be independent correlates of lipoprotein concentrations. Thus, metabolic and anthropometric variables examined in the present study could have represented important confounding factors in previous studies which have examined the relationship of steroid hormones to plasma lipoprotein concentrations.

Adipose Tissue↗
PubMed1997

Endurance training with constant energy intake in identical twins: changes over time in energy expenditure and related hormones.

The effects of exercise training and of its interaction with the genotype on components of energy expenditure and related hormones were examined in young male monozygotic twins. Energy intake was maintained at the pretraining level for a 93-day training period. The estimated net energy deficit induced by training was 244 MJ and was associated with a 5-kg body weight loss that was almost entirely explained by body fat loss. Resting metabolic rate (RMR) was significantly decreased by 8% after training despite the preservation of fat-free mass (FFM). Accordingly, plasma norepinephrine (NE) concentrations, NE appearance rate, and plasma levels of triiodothyronine (T3), free T3, and total thyroxine (T4) were lower after training. The energy cost of standardized exercise was also reduced after the training program. A modest to significant within-twin-pair resemblance was observed for absolute changes in the RMR, thermic effect of food, energy cost of exercise, NE clearance, and plasma concentrations of thyroid hormones. These results suggest that when exercise training is associated with a substantial negative energy balance, energy expenditure and levels of related hormones are decreased, and this effect is partly accounted for by heredity.

Adult↗
PubMed1997

Fat gain in female swimmers.

The association between diet and body composition was investigated in 6 elite female swimmers subjected to a 13-month nutritional supervision and in 11 female untrained subjects matched for fat-free mass. The impact of a 2-month interruption of training on diet and body composition was also studied in the swimmers. A positive correlation was observed between the percentage of dietary energy as fat and percent body fat in the untrained subjects (r = 0.68, p < 0.05). When values of the swimmers were incorporated in the regression analysis, the correlation coefficient remained the same. Following detraining for 2 months, a 4.8-kg body weight gain, including 4.3 kg fat mass, was observed. The energy equivalent of these morphological changes was 170 MJ and corresponded to about the amount of energy that would have been normally expended during this detraining period. In conclusion, these results suggest that the association between diet and body composition is not altered by exercise training, and that body fat gain occurs in response to detraining, perhaps to promote the restoration of energy and fat balance.

Adolescent↗
PubMed1997

Food intake, energy balance and body weight control.

Obesity is a multifactorial and complex affectation that is characterized by a long-term excess energy intake (EI) above energy expenditure (EE). Since fat oxidation seems to be dependent on SNS activation and also seems to remain acutely unaffected by fat intake, this macronutrient is certainly partly responsible for this situation. In addition, high-fat intake does not induce as potent satiety signals or a compensation effect on subsequent EI as do diets rich in carbohydrates or proteins. Moreover, since alcohol intake acutely inhibits fat oxidation and does not promote subsequent compensation for its energy content, it should consequently be regarded as a substrate which can induce a positive energy balance under free-living conditions. Thus, in a weight reducing context, each energy substrate should be manipulated while taking into account its specific characteristics. Obesity has also often been associated to a decreased sympathetic nervous system (SNS) activity, hence sympathomimetic agents have been proposed as a possible way to partially correct this situation. Two of these agents are the widely consumed caffeine (CAF) and the pungent principle of hot red pepper, capsaicin (CAP), which acutely increase EE and reduce EI under some circumstances. Furthermore, other factors like dietary fibers, that have been shown to increase satiety and fullness, and reduce EI in some cases, should also be considered.

Alcohol Drinking↗
PubMed1997

Energy and macronutrient balances for humans in a whole body metabolic chamber without control of preceding diet and activity level.

OBJECTIVE: To examine the relationships between 24 h energy and macronutrient balances in a whole body metabolic chamber subsequent to periods when subjects maintained their normal food intake and physical activity levels. SUBJECTS: Thirteen males and 17 females were studied for two 24 h sessions while consuming an estimated isocaloric diet with a food quotient of 0.85. MEASUREMENTS: Energy expenditure and macronutrient oxidation rates were measured twice for 24 h in whole body indirect calorimeter. RESULTS: Positive and significant correlations were evident between energy and lipid balances (r = 0.38, P < 0.05 and r = 0.54, P < 0.01, respectively) and differences between the two sessions for energy and lipid balances were also significantly correlated (r = 0.40, P < 0.05). Accounting for carbohydrate or protein balances improved the strength of each of these associations. CONCLUSION: These results indicate that for subjects in a small but significant positive energy balance, with uncontrolled diet and activity preceding their metabolic chamber sessions, that 24 h energy balance is positively correlated with lipid balance. Accounting for associations between lipid, carbohydrate, protein and energy balances, improved the strength of the association between 24 h lipid and energy balances. The implications of these results are that in these conditions modifications to lipid balance are important for weight maintenance.

Adult↗
PubMed1997

Acute effect of exercise and low-fat diet on energy balance in heavy men.

OBJECTIVE: To quantify the acute effect of the exercise-low-fat diet combination on energy balance compared with sedentarity and a high fat diet in overweight individuals. DESIGN AND MEASUREMENTS: We assessed the acute effect of exercise and ad libitum intake of low-fat foods on daily energy balance. Six heavy men participated in two randomly assigned sessions which required a 24 h stay in a whole body indirect calorimeter. Sessions were preceded by either a 60 min aerobic exercise at 50% VO2 max or a 60 min rest. Subjects were fed a low-fat diet (mean FO = 0.89) after exercise and a mixed diet (mean FQ = 0.85) after the resting period. RESULTS: The difference in energy balance between the two conditions was 7.3 MJ. About half of the effect was attributable to the energy surplus expended during exercise whereas the remaining fraction was explained by the difference in post-exercise energy balance. CONCLUSION: In heavy men, the combination of a low-fat diet and exercise has a strong acute effect on energy balance compared to a rest-mixed diet condition.

Adult↗