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Biomedical subjects

A Tremblay

Publications and source records attributed to A Tremblay.

At least 37 records · Page 2Linked to original sources
PubMed2004

Thermogenesis and weight loss in obese individuals: a primary association with organochlorine pollution.

The main objective of this study was to investigate the potential impact of body organochlorine (OC) pollution on the adaptive change in thermogenesis induced by body weight loss. Fat mass (FM), fat-free mass (FFM), and sleeping metabolic rate (SMR) were measured in obese individuals before and after a weight-reducing program. The measured values of SMR were then compared to those predicted from a reference equation established from FM and FFM in control subjects. Plasma OC, leptin, total tri-iodothyronine, and free thyroxine concentrations were also measured in obese subjects before and after weight loss. After weight loss, the measured decrease in SMR was greater than that predicted by changes in FM and FFM. Increased plasma OC concentration was the factor explaining the greatest proportion of the difference between predicted and measured SMR changes induced by body weight loss. OC pollution seems to be a new factor affecting the control of thermogenesis in some obese individuals experiencing body weight loss.

Adult↗
PubMed2004

Impaired fasting glucose vs. glucose intolerance in pre-menopausal women: distinct metabolic entities and cardiovascular disease risk?

BACKGROUND: Impaired glucose tolerance (IGT) is associated with an increased cardiovascular disease risk. Less is known about cardiovascular disease risk among subjects with impaired fasting glucose (IFG) or with combined IFG and IGT. AIMS: To compare body composition, body fat distribution, plasma glucose-insulin homeostasis and plasma lipid-lipoprotein profile between pre-menopausal women having either a normal glucose tolerance (NGT), isolated IFG, isolated IGT or combined IFG and IGT. METHODS: Three hundred and thirty-four women with NGT, 11 women with IFG, 35 women with IGT and 10 women with both IFG and IGT were studied. RESULTS: Women with IFG were characterized by a higher visceral adipose tissue (AT) accumulation than women with NGT (P < 0.05). Also, they were characterized by a higher subcutaneous AT area and by higher body fat mass than NGT and IGT women (P < 0.05). However, their lipid-lipoprotein profile was comparable with that of NGT women, except for reduced HDL-cholesterol concentrations (P < 0.05). After adjustment for visceral AT, women with IFG had lower total cholesterol, LDL-cholesterol and apolipoprotein B (apoB) levels than the three other groups. They also had lower HDL(2)-cholesterol than NGT women and lower total cholesterol/HDL-cholesterol ratio than IGT women. Women with IGT showed higher triglyceride and apoB concentrations and a higher total cholesterol/HDL-cholesterol ratio than women with NGT (P < 0.05). Overall, women with combined IFG and IGT showed body fatness characteristics and alterations in their metabolic risk profile which were essentially similar to women with isolated IGT. CONCLUSIONS: These results indicate that there are significant differences in anthropometric and metabolic variables between pre-menopausal women with IFG vs. IGT and that the association between body fatness-body fat distribution indices and the metabolic profile may differ between IFG and IGT women.

Adolescent↗
PubMed2004

Altering dietary cation-anion difference in lactating dairy cows to reduce phosphorus excretion to the environment.

Four early-lactating dairy cows were randomly allocated to 4 diets with dietary cation-anion difference [DCAD; (Na + K) - (Cl- + S2-) mEq/100 g dry matter)] values of +14, +18, +24, and +45. Diets were formulated to be isoenergetic and isonitrogenous, and supplied similar levels of P (0.46%) and Ca (0.77%). The salts, MgCl2, MgSO4, K2CO3, and NaHCO3 were used to alter DCAD. The main objective of the study was to ascertain whether a decrease in DCAD would reduce fecal P excretion in lactating dairy cattle. The experiment was conducted as a 4 x 4 Latin square design with 21-d periods. During the last 5 d, diets were offered at a restricted level and samples of blood, milk, feces, and urine were collected. Measures of acid-base status of the cows were linearly related to DCAD, but the animals did not experience metabolic acid stress. Neither fecal P nor urinary P was affected by DCAD, and there was no change in overall P balance. Plasma P tended to increase and blood concentrations of ionized Ca were enhanced as DCAD decreased; P excretion in milk showed a quadratic response to DCAD. Milk yield and milk composition were unaffected by changes in DCAD. Although DCAD may have influenced P homeostasis in lactating cows, there was no evidence that, within the range of + 14 to + 45 mEq/ 100 g dry matter, DCAD could be used as a nutritional strategy to reduce manure P from dairy cattle.

Acid-Base Equilibrium↗
PubMed2003

Effect of malnutrition during the first year of life on adult plasma insulin and glucose tolerance.

There is evidence linking intrauterine growth retardation with increased cardiovascular risk and diabetes mellitus (DM) later in life. However, little is known about the association between malnutrition during the first year of life and metabolic abnormalities in adulthood. The objective of this study was to assess the effect of documented malnutrition during the first year of life on glucose tolerance, plasma insulin, lipid profile, and blood pressure in early adulthood, as well as to assess the interaction between body mass index (BMI) and malnutrition on these variables. A study group of young men with a documented history of malnutrition during their first year of life was recruited from 4 pediatric hospitals in Mexico City and compared with a control group. Subjects included were 52 men, aged 20.2 +/- 3.6 years, with a mean birth weight of 3.0 +/- 0.7 kg and documented malnutrition in their first year of life; controls were 50 men, aged 23.3 +/- 1.8 years, with a mean birth weight of 3.2 +/- 0.5 kg. Insulin and glucose concentrations, fasting and in response to an oral glucose load, plasma lipids, blood pressure, and an insulin sensitivity index (ISI) were measured. The areas under the curves of glucose (AUCG) and insulin (AUCI) were significantly higher in cases (P =.012 and <.002, respectively), independent of birth weight, BMI, or age. BMI was significantly associated with fasting plasma insulin (FPI), AUCI, ISI, triglyceride, and high-density lipoprotein (HDL)-cholesterol concentrations in cases, but not in controls. These data suggest that early malnutrition in extrauterine life, independently of birth weight, has an adverse effect on insulin metabolism and glucose tolerance in young men, and it worsens as body mass increases even within the normal range of BMI. Therefore, it is advisable to prevent obesity in individuals exposed to early malnutrition.

Adult↗
PubMed2003

Genetic variation at the adipsin locus and response to long-term overfeeding.

OBJECTIVES: The role of adipsin and adipsin Hinc II polymorphisms on the metabolic and body composition changes in response to overfeeding was studied. SUBJECTS: A total of 12 pairs of male monozygotic twins ate a 4.2 MJ/day energy surplus, 6 days a week, during a period of 100 days. RESULTS: The preoverfeeding plasma adipsin concentration correlated positively with the change in CT-measured abdominal total and subcutaneous (P<0.05) fat. The changes in abdominal total fat and abdominal subcutaneous fat correlated negatively with changes in plasma adipsin concentrations (P<0.005). Overfeeding induced greater increases in body weight, fat mass, abdominal total and subcutaneous fat (P<0.05) in 6.1 kb noncarriers (n=10) than in 6.1 kb carriers (n=14) of the adipsin Hinc II polymorphism. The 6.1 kb noncarriers had a greater increase in plasma leptin levels (P<0.01). Also the total (P<0.01) and very-low-density lipoprotein (VLDL)-triglycerides (P<0.05), apolipoprotein B (P<0.05) and VLDL-cholesterol (P<0.05) levels increased more in the 6.1 kb noncarriers than in the 6.1 kb carriers. CONCLUSIONS: Adipsin plasma level could be a predictor of the changes in abdominal subcutaneous fat during times of increased energy intake. However, a greater increase in the abdominal subcutaneous fat was related to a lower increase in the plasma adipsin level. The adipsin Hinc II 6.1 kb allele noncarriers gained more abdominal subcutaneous fat and had a greater increase in plasma levels of leptin- and triglyceride-rich lipoproteins when exposed to a long-term positive energy balance. These findings provide new information on the role of adipsin on individual differences in response to chronically elevated food intake.

Abdomen↗
PubMed2003

Insulin resistance and abdominal adiposity in young men with documented malnutrition during the first year of life.

OBJECTIVE: The main objective of the study was to examine the effect of early life malnutrition on the relation between insulin sensitivity and abdominal adiposity in adulthood. It was hypothesised that participants with early life malnutrition would display a more pronounced deterioration of insulin sensitivity in association with a gain in abdominal fat. DESIGN: As a first attempt to investigate this issue, we studied the effect of body fat gains in a cross-sectional context. SUBJECTS: A total of 26 young adult men with evidence of malnutrition during the first year of life and 27 control subjects were recruited for this study. Malnutrition status was determined from medical files of paediatric hospitals in the Mexico City metropolitan area. MEASUREMENTS: Insulin sensitivity was measured by hyperinsulinaemic euglycaemic clamp, and body composition was measured by anthropometrics, bioelectrical impedance and computed tomography. RESULTS: There was a negative correlation between total abdominal adipose tissue area and insulin sensitivity in the previously malnourished and control groups (r(2)=0.65 and 0.35, P<0.01, respectively). When matched for low amounts of abdominal fat (114 cm(2)), participants with and without early life malnutrition had similar insulin sensitivity (9.03 vs 8.88 mg kg(-1) x min(-1)). However, when matched for high amounts of abdominal fat (310 cm(2)) participants who were malnourished during the first year of life had lower insulin sensitivity (4.74 vs 6.85 mg kg(-1) x min(-1), P<0.05). CONCLUSION: Higher levels of abdominal adipose tissue are more detrimental to insulin sensitivity in previously malnourished individuals.

Abdomen↗
PubMed2003

Do 6-y changes in eating behaviors predict changes in body weight? Results from the Québec Family Study.

OBJECTIVE: This study was performed to examine changes in eating behaviors as assessed by the three-factor eating questionnaire (TFEQ) and to quantify the potential associations between these eating behaviors and body weight changes in a 6-follow-up study. DESIGN AND SUBJECTS: Prospective study performed in men and women who were tested twice (Visit 1=1989-1995 and Visit 2=6 y later) in the Québec Family Study (QFS). RESULTS: Women were more restrained and less hungry than men. To reduce food intake, women relied more on strategic dieting behavior and avoided more fattening food. However, they had higher emotional and situational susceptibility to eat than men. Significant decreases in the disinhibition score were noted over time in women (P<0.01), which resulted from a decrease in habitual susceptibility behavior to increase food intake. In men, we observed an increase in the avoidance of fattening food (P<0.05). In both genders, we found that the 6-y change in restraint behavior was negatively correlated with body weight changes (P<0.05). In women, a high restraint behavior seems to promote weight gain, whereas in men, it is associated with the opposite trend. CONCLUSION: These results suggest that variables reflecting some eating behaviors are associated with body weight changes in a free-living context. However, these behaviors are expressed differently between men and women. These behaviors should be considered in clinical interventions for individuals seeking a better body weight control.

Adult↗
PubMed2003

Energy balance and pollution by organochlorines and polychlorinated biphenyls.

Organochlorines are fat-soluble chemical compounds resistant to degradation, so they are stored in the adipose tissue of practically every organism on the planet, including humans. Accumulation of these compounds in the body seems to be related to fat mass, obese individuals having a higher plasma organochlorine concentration than lean subjects. During body weight loss, lipid mobilization and a decrease in fat mass result in increased concentrations of organochlorines in plasma and adipose tissue. Organochlorines may have adverse health effects. For example, they have been associated with altered immune and thyroid functions and with some types of cancer. As these compounds may reach their target organs whilst in the circulation, their increase in plasma during weight loss might be associated with some physiological changes occurring during weight loss. Relationships have indeed been reported among weight loss-induced increase in plasma organochlorine concentration and decreased triiodothyronine (T3) concentration, resting metabolic rate, and skeletal muscle markers for fat oxidation. Although further studies are needed to assess the causality of these relationships, they raise concern about some potential undesirable effects of weight loss. Indeed, the effects of organochlorines on energy balance could complicate body weight loss and even favour weight regain. These notions lend support for weight-loss strategies favouring a moderate weight loss, which would reduce risks for cardiovascular diseases, diabetes and hypertension, without resulting in a substantial release of organochlorines.

Adipose Tissue↗
PubMed2003

How much physical activity is enough to prevent unhealthy weight gain? Outcome of the IASO 1st Stock Conference and consensus statement.

A consensus meeting was held in Bangkok, 21-23 May 2002, where experts and young scientists in the field of physical activity, energy expenditure and body-weight regulation discussed the different aspects of physical activity in relation to the emerging problem of obesity worldwide. The following consensus statement was accepted unanimously. 'The current physical activity guideline for adults of 30 minutes of moderate intensity activity daily, preferably all days of the week, is of importance for limiting health risks for a number of chronic diseases including coronary heart disease and diabetes. However for preventing weight gain or regain this guideline is likely to be insufficient for many individuals in the current environment. There is compelling evidence that prevention of weight regain in formerly obese individuals requires 60-90 minutes of moderate intensity activity or lesser amounts of vigorous intensity activity. Although definitive data are lacking, it seems likely that moderate intensity activity of approximately 45 to 60 minutes per day, or 1.7 PAL (Physical Activity Level) is required to prevent the transition to overweight or obesity. For children, even more activity time is recommended. A good approach for many individuals to obtain the recommended level of physical activity is to reduce sedentary behaviour by incorporating more incidental and leisure-time activity into the daily routine. Political action is imperative to effect physical and social environmental changes to enable and encourage physical activity. Settings in which these environmental changes can be implemented include the urban and transportation infrastructure, schools, and workplaces.'

Adult↗
PubMed2003

Is visceral obesity a physiological adaptation to stress?

Visceral obesity represents an important risk factor associated with hypertension, diabetes and cardiovascular diseases. Since this condition is associated with a disruption of the functioning of the HPA axis, stress-induced HPA axis activation has been identified to play an important role in this preferential body fat accumulation. HPA axis activation increases cortisol (corticosterone) production which has been shown to exert hyperphagic and antithermogenic effects. Since abdominal adipose tissue has more cells per mass units, higher blood flow and more glucocorticoid receptors, glucocorticoids affect abdominal fat to a greater extent than subcutaneous adipose tissue. Cushing's syndrome in humans is the best evidence showing a link between hypercortisolemia and accumulation of central fat. The Hervey's hypothesis which suggests that fat cells take up and catabolize glucocorticoids is one of the possible regulatory effect that supports the adaptive role of visceral fat in response to stress. This is also supported by other evidence showing that abdominal obesity is associated with an increased cortisol clearance. Hormonal and enzymatic changes have been implicated in this preferential body fat accumulation in response to stress. Specific genetic background may also accentuate this visceral fat accumulation in some individuals exposed to stress. Alternatively, obesity could also be a source of stress promoting the visceral fat accumulation since visceral fat is able to release cytokines which stimulate the HPA axis. Even if the available literature does not permit to establish clearly which comes first, it suggests that visceral obesity could represent a non optimal physiological adaptation to stress. In this context, visceral obesity treatment should focus on stress management and weight loss strategies in order to stop this vicious circle.

Abdomen↗
PubMed2002

Metabolic impact of body fat distribution.

Many studies have shown that fat distribution influences metabolism independently of the effects of total body fat stores. The accumulation of fat in the abdominal area, particularly in the visceral fat compartment, seems to be associated with an increased risk to display complications such as insulin resistance, diabetes, dyslipidemias and atherosclerosis. As reviewed in this paper, the mechanisms explaining this impact of fat distribution is not clearly established, although evidence suggests that free-fatty acids, leptin, TNF-alpha, PPAR-gamma, and F are directly or indirectly involved in this process. Despite a lot of research has yet to be performed to mechanistically characterize the impact of visceral fat on the metabolic profile, there is enough consensus in the literature about its effect to justify its consideration in a clinical setting. In this regard, the use of waist circumference as a clinical marker of variations in visceral fat is highly relevant and should be encouraged. This review also presents an evolutionary perspective according to which body fat gain would have been and may still remain an adaptation that helps to deal with stress and inflammation.

Adaptation, Physiological↗
PubMed2002

Reduction of visceral adipose tissue during weight loss.

OBJECTIVE: The aims of the present study were to retrospectively: (1) compare how weight loss affects the reduction of adipose tissue from three different sites between men and women; and (2) to verify whether gender differences in the reduction of adipose tissue are influenced by changes in fat mass (FM) and initial levels of fat in different compartments. DESIGN: Double-blind randomized treatment with fenfluramine once daily coupled to a non-macronutrient specific energy restriction. SUBJECTS: Seventeen obese men (age 43.9+/-1.5 and body mass index (BMI) 34.3+/-0.7) and 17 obese women (age 41.2+/-1.2 and BMI 35.7+/-0.6). INTERVENTIONS: Subjects were given fenfluramine (60 mg) or placebo once daily and were also subjected to a non-macronurient specific energy restriction of -2.9 MJ/day (-700 kcal/day) for 15 weeks. RESULTS: Body weight, FM, fat-free mass (FFM), waist circumference, BMI, as well as visceral (VAT), subcutaneous abdominal (SAT) and thigh (TAT) adipose tissue were all significantly reduced. Men lost significantly more VAT (-41.6%) than SAT (-22.5%), or than TAT (-20.5%) while no site difference in fat loss was observed in women when changes were calculated as a percentage of initial levels. Men lost about twice as much fat from the VAT compartment than did women (P<0.05), even after having considered changes in FM as a potential covariate. In absolute values, TAT was reduced to a lesser extent in men than in women. However, when initial levels of respective fat depots were also taken into account, gender differences in VAT and TAT loss were no longer statistically significant. CONCLUSION: These results suggest that gender differences in VAT reduction during weight loss are independent of changes in FM. However, once initial levels of VAT are also taken into account, gender differences in the reduction of this tissue during weight loss are no longer apparent.

Adipose Tissue↗
PubMed2002

Lipoprotein lipase polymorphisms and responses to long-term overfeeding.

OBJECTIVES: The role of the lipoprotein lipase (LPL) gene Hind III, S447X, Bam HI and Pvu II polymorphisms on body composition and lipid and lipoprotein changes in response to long-term overfeeding was studied. SUBJECTS: Twelve pairs of male monozygotic twins ate a 4.2 MJ day-1 energy surplus, 6 days a week, during a period of 100 days. RESULTS: Overfeeding induced a decrease in high-density lipoprotein 2 cholesterol (HDL2-C) and HDL2-C to HDL3-C ratio in the H2H2 (n = 12) subjects of the LPL Hind III polymorphism. In contrast, the H1H1/H1H2 (n = 12) subjects experienced increases both in the HDL2-C and HDL2-C to HDL3-C ratio (P = 0.009 and 0.007, respectively, for differences in percentage changes between H2H2 and H1H1/H1H2). In addition, the H2H2 genotype was associated with higher levels of very-low-density lipoprotein triglyceride (VLDL-TG) (P < 0.03) and VLDL-C (P < 0.05) before and after overfeeding and higher HDL-TG levels (P < 0.003) after overfeeding. Postheparin lipoprotein lipase (PH-LPL) activity tended to increase in H1H1/H1H2 and decrease in H2H2 subjects. The H2H2 subjects had lower total HDL-C than those with the genotype H1H1/H1H2 4 months and 5 years after overfeeding (P = 0.04 and 0.10, respectively). The plasma lipid differences were similar amongst subjects with the S447S (n = 4) genotype of the S447X and H2H2 genotype of the Hind III polymorphisms. Body composition changes in response to overfeeding were not different between the Hind III genotypes. LPL Pvu II and Hind III polymorphisms were associated weakly with body weight gain (P = 0.015-0.039) but strongly with adipose tissue LPL activity (P < 0.01) after the caloric surplus. CONCLUSIONS: We conclude that the H2H2 subjects of the LPL gene Hind III polymorphism experience a decrease in the concentration of antiaterogenic lipoproteins when they are exposed to long-term positive energy balance. This may have been partly caused by a diminished catabolism of TG-rich particles in H2H2 subjects. LPL Pvu II and Bam HI polymorphisms were associated with body weight gain and adipose tissue LPL activity. Genetic variation at the LPL locus could thus be one of the factors responsible for the inter-individual differences observed in plasma lipid and lipoprotein responses to chronic positive energy balance. It must be kept in mind that the sample size for this study was small. Nonetheless, it provides useful information on the genes and pathways that should be further explored.

Adult↗
PubMed2002

Increase in plasma pollutant levels in response to weight loss is associated with the reduction of fasting insulin levels in men but not in women.

Environmental pollutants can act as endocrine modulators. In this study, we examined whether weight loss-induced changes in plasma organochlorine compounds (OC) were associated with those in plasma insulin levels. Fasting insulin and the area under the curve (AUC) of insulin after a 75-g oral glucose load, plasma levels of 1 commercial polychlorinated biphenyl (PCB) mixture (Aroclor 1260), 1 PCB congener (PCB 153), and 3 pesticides (2,2'-bis(4-chlorophenyl)-1,1-dichloroethylene (p,p'-DDE), beta-hexachlorocyclohexane (beta-HCH), and hexachlorobenzene (HCB)) were measured before and after a 15-week weight loss program induced by a caloric restriction in a sample of obese men and women. Both genders showed a similar reduction in body weight (approximately 11 kg) in response to treatment, although men lost significantly more fat mass than women (mean +/- SD 9.4 +/- 4.1 v 5.9 +/- 5 kg, respectively, P <.05). Fasting insulin and AUC of insulin significantly decreased in men and women after the treatment. In response to weight loss, a significant increase in OC was observed in both genders, and this effect was more pronounced in men. The greater the increase in plasma OC levels, the greater the reduction in fasting insulin was in response to weight loss in men (-.49 < r < -.59, P <.05), but not in women (-.22 < r <.01, not significant [NS]). In both genders, no relationship was observed between changes in plasma OC levels and changes in AUC of insulin (-.41 < r < -.08, NS). In men, relationships between changes in plasma HCB, Aroclor 1260, and PCB-153 concentrations and those in fasting insulin levels in response to weight loss remained significantly correlated after correction for fat mass loss (-.46 < partial r < -.51, P values ranging from.05 to.07). These results suggest that weight loss-induced increase in plasma pollutant levels tends to be independently associated with the reduction of fasting insulin levels in men, but not in women. Further studies are needed to verify whether these findings are causally related.

Adipose Tissue↗
PubMed2001

T-tubule localization of the inward-rectifier K(+) channel in mouse ventricular myocytes: a role in K(+) accumulation.

1. The properties of the slow inward 'tail currents' (I(tail)) that followed depolarizing steps in voltage-clamped, isolated mouse ventricular myocytes were examined. Depolarizing steps that produced large outward K(+) currents in these myocytes were followed by a slowly decaying inward I(tail) on repolarization to the holding potential. These currents were produced only by depolarizations: inwardly rectifying K(+) currents, I(K1), produced by steps to potentials negative to the holding potential, were not followed by I(tail). 2. For depolarizations of equal duration, the magnitude of I(tail) increased as the magnitude of outward current at the end of the depolarizing step increased. The apparent reversal potential of I(tail) was dependent upon the duration of the depolarizing step, and the reversal potential shifted to more depolarized potentials as the duration of the depolarization was increased. 3. Removal of external Na(+) and Ca(2+) had no significant effect on the magnitude or time course of I(tail). BaCl(2) (0.25 mM), which had no effect on the magnitude of outward currents, abolished I(tail) and I(K1) simultaneously. 4. Accordingly, I(tail) in mouse ventricular myocytes probably results from K(+) accumulation in a restricted extracellular space such as the transverse tubule system (t-tubules). The efflux of K(+) into the t-tubules during outward currents produced by depolarization shifts the K(+) Nernst potential (E(K)) from its 'resting' value (close to -80 mV) to more depolarized potentials. This suggests that I(tail) is produced by I(K1) in the t-tubules and is inward because of the transiently elevated K(+) concentration and depolarized value of E(K) in the t-tubules. 5. Additional evidence for the localization of I(K1) channels in the t-tubules was provided by confocal microscopy using a specific antibody against Kir2.1 in mouse ventricular myocytes.

Animals↗