Liver fat accumulation may be dissociated from adiposity gain in ovariectomized rats.

OBJECTIVE: The purpose of the present study was to establish a model of rats prone and resistant to intra-abdominal fat accumulation in response to ovariectomy (Ovx-P and Ovx-R) and to determine its relationship with molecular biomarkers. DESIGN: Two experiments were conducted in which female rats were either sham-operated (Sham) or ovariectomized (Ovx). In the first experiment, ovariectomized rats were stratified into three tertiles based on intra-abdominal adipose tissue mass. To strengthen the Ovx-P/Ovx-R model, we conducted a second experiment in which the numbers of rats in each group were extended and in which different molecular markers were measured. At the end of a 6-8-week period, ovariectomized rats that displayed the lower abdominal fat accumulation (lower tertile) were labelled as Ovx-R and those in the upper tertile as Ovx-P. RESULTS: Ovx-R rats displayed similar abdominal fat gain to Sham rats whereas Ovx-P rats depicted abdominal fat mass twice as high as that of Sham and Ovx-R rats. Despite the difference in abdominal adiposity, liver fat content was ~50% higher (p < 0.01) in both Ovx-R and Ovx-P rats compared to Sham rats. In addition, both Ovx-R and Ovx-P rats depicted higher HOMA-IR scores (p < 0.05) and lower (p < 0.01) hepatic gene expression of leptin receptor-b and -e, microsomal transfer protein (MTP), and diacylglycerol acyltransferase-2 (DGAT-2) compared to Sham rats. CONCLUSION: The present findings indicate that estrogen withdrawal-induced hepatic steatosis and associated insulin resistance may be dissociated from abdominal fat accumulation and suggest that a decrease in leptin action through a down-regulation of leptin receptors and a decrease in very low density lipoprotein production through a down-regulation of MTP and DGAT-2 may be factors responsible for this observation in the absence of peripheral fat gain.

Relationship between the percentage of predicted cardiorespiratory fitness and cardiovascular disease risk factors in premenopausal women: a MONET study.

OBJECTIVE: To determine the relationships between the percentage predicted cardiorespiratory fitness (%CRF) and the anthropometric and metabolic cardiovascular disease risk factors in asymptomatic, premenopausal women. METHODS: Data are baseline values obtained in 97 healthy premenopausal women (age 49.9 +/- 1.9 years; body mass index 23.2 +/- 2.2 kg/m(2)) participating in a longitudinal study from 2004 to 2009. The outcome measures were peak oxygen consumption (VO(2) peak), body mass index, body composition (percentage fat, fat mass, fat-free mass), waist circumference, abdominal subcutaneous fat, visceral fat, resting blood pressure and fasting lipids, glucose and insulin levels. RESULTS: The %CRF was negatively associated with body mass index, fat mass, percentage fat, waist circumference, abdominal subcutaneous fat, visceral fat, triglycerides, triglyceride/high density lipoprotein cholesterol, total cholesterol, total cholesterol/high density lipoprotein cholesterol, fasting insulin levels and HOMA-IR (- 0.59 < or = r < or = - 0.20; 0.01 < p < 0.05) and positively associated with insulin sensitivity index (r = 0.23; p < 0.05). VO(2) peak was associated with the same variables; however, correlations were slightly better (- 0.70 < or = r < or = 0.30; 0.01 < p < 0.05). Stepwise multiple regression analysis showed that %CRF was only independently correlated with plasma triglyceride levels. CONCLUSION: The results of this study suggest that %CRF was not a major predictor of anthropometric and metabolic variables associated with an increased risk of cardiovascular disease in asymptomatic premenopausal women. Finally, the VO(2) peak is a better predictor than the %CRF to assess the risk of cardiovascular disease in asymptomatic premenopausal women.

Does exercise training prior to ovariectomy protect against liver and adipocyte fat accumulation in rats?

OBJECTIVE: To determine whether a training state protects against the metabolically deleterious effects of ovariectomy on liver and adipocyte fat accumulation in rats. DESIGN: Female rats were randomly assigned to each group (n = 8 rats/group). The animals were first either exercise-trained (Tr) for 6 weeks or kept sedentary (Sed) before being sham-operated (Sham), ovariectomized (Ovx), or ovariectomized with 17beta-estradiol supplementation (OvxE2). Following surgery, sedentary rats either remained sedentary (Sed-Sed) or undertook exercise training for 6 weeks (Sed-Tr) while exercise-trained rats either became sedentary (Tr-Sed) or resumed exercise training (Tr-Tr). RESULTS: Body weight and energy intake along with intra-abdominal and subcutaneous fat pad weights and homeostasis model assessment of insulin resistance (HOMA-IR) were significantly (p < 0.01) increased in the Ovx group compared to the Sham and OvxE2 groups. Rats kept in a sedentary state after surgery showed the higher (p < 0.05) values for all of these variables whether they were trained or not before surgery (Sed-Sed and Tr-Sed), indicating no protective effect of a previous exercise-trained state. On the other hand, training conducted after surgery resulted in a lowering of fat mass and HOMA-IR whether rats had been trained or not before surgery (Sed-Tr and Tr-Tr), indicating the effectiveness of exercise training even initiated after surgery. These responses were independent of surgery. Interestingly, liver triacylglycerol concentrations followed a pattern of responses identical to fat mass with the exception that all of the responses were observed only in the Ovx group (p < 0.05). CONCLUSION: There is no protective effect of a previous exercise-training state on ovariectomy-induced liver and adipocyte fat accumulation if rats remain sedentary after ovariectomy. However, training conducted concurrently with estrogen withdrawal has protective effects, especially on liver fat accumulation, whether or not rats were previously trained.

Substituting food restriction by resistance training prevents liver and body fat regain in ovariectomized rats.

OBJECTIVE: Fat mass gain and regain following weight loss are major concerns and may be even more critical after menopause. The present study was undertaken to evaluate the effect of a resistance training protocol on body weight and fat mass in ovariectomized Sprague-Dawley rats following diet-induced weight loss. DESIGN: Rats were randomly divided into ovariectomized (Ovx) and sham-operated (Sham) groups. Five weeks after ovariectomy, Ovx rats were subjected to a 26% food restriction (OvxFR) for 8 weeks. Following this period, OvxFR rats went back to a normal ad libitum feeding and were divided into two groups: either sedentary or undergoing a resistance training program for an additional 5 weeks, which consisted of climbing a 6-m vertical grill, 20-40 times, with progressively increasing load four times/week. RESULTS: The food restriction program decreased (p < 0.01) body mass, fat pad weight (intra-abdominal and subcutaneous), and liver triacylglycerol (TAG) levels as compared to normally fed Ovx rats. Stopping the food restriction program over a 5-week period resulted in a partial regain in body weight and intra-abdominal fat pad weight (p < 0.05), and in an almost complete regain in liver TAG compared to normally fed Ovx rats. On the other hand, no significant increases in these variables were noted when the food restriction was replaced by resistance training over the same 5-week period. CONCLUSION: These results indicate that a resistance training program could be useful in preventing body weight as well as adipose tissue and liver fat regain in Ovx rats, following diet-induced weight loss. It is suggested that changing from a food restriction regimen to a resistance training program can be an interesting strategy to promote successful long-term weight reduction in postmenopausal women.