Visceral fat and total body fat mass correlate differently with hormones in rat.

Forty-eight 67-day-old male Wistar rats (330+/-5g) were fed ad libitum either with a lipid enriched diet or a standard laboratory chow. Half of each sub-group was submitted to training. Training and difference in diet composition induced nonsignificant changes in body adiposity. Visceral fat (perirenal adipose tissue mass) was correlated with leptin (r=0.35, p=0.02) and insulin (r=0.38, p=0.01). Total body fat mass (measured by DEXA) was correlated with leptin only (r=0.58, p=0.003). Other correlations between perirenal adipose tissue or fat mass and adiponectin or insulin like growth factor 1 were nonsignificant. These results suggest that, in rat like in human, visceral fat development is linked with insulin insensitivity.

Effect of a lipid-enriched diet on body composition and some regulatory hormones of food intake in growing rats.

OBJECTIVE: The aim of the present study was to investigate the effects of a lipid-enriched diet on body composition and on main regulatory hormones of food intake (insulin, adiponectin, leptin, ghrelin). METHOD: Two groups of 16 rats, 35 days old, weighing 80+/-6 g, were constituted. One group (S) was given a standard diet during 10 weeks and served as control. The second group (L) was given a lipidic-enriched diet (containing: G: 41.5, L: 38.5, P: 20% calorie). Food and water were given "ad libitum". RESULTS: Total food intake, body weight, skeletal area and lean body mass of rats eating lipid-enriched diet were lowered (6694+/-178 vs. 8160+/-184 kcal, P=0.01; 431+/-38 vs. 468+/-25 g, P=0.003; 72.19+/-0.96 vs. 76.07+/-1.31 cm2, P=0.03; 369+/-18 vs. 409+/-23 g, P=0.0006), fat mass difference was not statistically significant (82.5+/-17 vs. 80+/-17 g, P=0.7). Blood ghrelin, adiponectin levels were lowered (1517+/-224 vs. 1915+/-579 pg/ml, P=0.03; 10+/-3 vs. 19+/-3 microg/ml, P=0.003) whereas insulin and leptin were unchanged (1.8+/-1.5 vs. 2.6+/-1.4 ng/ml, P=0.1; 16+/-11 vs. 13+/-10 ng/ml, P=0.4). CONCLUSION: A period of high fat diet in growing rats leads to a hypophagia, resulting in a lower lean body mass development. Some regulatory hormones of food intake did not change, while others significantly decreased, notably ghrelin being possible causal factor of the observed hypophagia linked to high fat diet.

Progressive isometric force training and bone mass in rats.

In ten growing male Wistar rats, isometric strength training for 69 days (3-6 times vertical gripping position on a wire-netting during 2 x 30 s, with progressive loading of the tail through a 50-200 g indwelling clip), fat mass and plasma leptin concentrations were lower on day 70 than in ten sedentary controls. Muscle mass and femoral trabecular and cortical bone mineral density were simultaneously higher in exercised animals than in controls. Such an effect might result from decreased bone resorption. At the end of the training period no difference concerning plasma osteocalcin concentration was observed between exercised and resting rats while urinary deoxypyridinoline excretion was lower in the former than in the latter.

Influence of clenbuterol on bone metabolism in exercised or sedentary rats.

This paper reports that the selective beta(2)-adrenergic receptor agonist clenbuterol affects bone metabolism in growing 3-mo-old male Wistar rats treated over 8 wk. Thirty-two 3-mo-old growing Wistar rats weighing 234 +/- 2 g were assigned to a progressive isometric force, strength-training exercise program plus oral clenbuterol (2 mg x kg body wt(-1) x day(-1)) for 5 days each week, exercise program without clenbuterol 5 days each week, no exercise program plus oral clenbuterol (2 mg x kg(-1) x day(-1)) for 5 days each week, or no exercise without clenbuterol 5 days each week. At the end of 8 wk, lean mass, fat mass, and right total femoral, distal metaphyseal femoral, and diaphyseal femoral bone mineral density were measured by Hologic QDR 4,500 dual X-ray absorptiometry (DEXA) technique. Left femoral bones were harvested after death on day 58, and femoral resistance was determined by three-point bending testing. We found that fat mass was decreased in rats given strength training exercise and decreased further in rats treated with clenbuterol. Lean mass was increased in clenbuterol-treated animals. Strength-training exercise appeared to have no effect on bone mineral density, serum osteocalcin, or urinary deoxypyridinoline. However, clenbuterol treatment decreased femoral length, diameter, bone mineral density, and mechanical resistance. Clenbuterol had no effect on osteocalcin but increased urinary deoxypyridinoline. We concluded that clenbuterol treatment decreased bone mineral density and increased bone resorption independent of the level of exercise rats were given.

A rat model of progressive isometric strength training.

This study presents an isometric model of strength resistance training in rats. Seven rats were trained for five weeks with increasing load, once a day for six days per week while seven rats served as control group. Mechanical strength of the hindlimb muscle group was measured on anaesthetised rats with a force transducer linked to the Achilles tendon after electrical stimulation of the sciatic nerve. Training resulted in a 74 +/- 2% strength gain in experimental (E) vs control (C) rats and in a reduction of fatigability with no change in gastrocnemius, soleus and extensor digitorum longus weights. The fibres composition of the gastrocnemius showed a 50% increase of IIA fibres and a 17% fall of IIB fibres. Consequently, this new model of isometric training is suitable for physiological studies.