Search

Objective: The aims of this study were to investigate some features of the metabolic profile and the body composition of male Lou/C rats and to examine whether these characteristics are strictly related to the food-intake reduction., Research Methods and Procedures: Fourteen-week-old male Lou/C rats were compared with age-matched male Wistar rats fed ad libitum (WAL) and another group of male Wistar rats whose food was chronically restricted (WFR) to the same amount as the Lou/C rats from weeks 3 to 14., Results: Food intake and body weight were significantly (p < 0.01) reduced in Lou/C compared with WAL rats, whereas these reductions were perfectly reproduced in WFR rats. Lou/C rats demonstrated lower relative weights of retroperitoneal (0.97 +/- 0.07 vs. 1.67 +/- 0.16 and 1.88 +/- 0.15 g/100 g body) and epididymal (1.01 +/- 0.02 vs. 1.62 +/- 0.12 and 1.80 +/- 0.11 g/100g body) fat depots than did the two other groups and no decrease in the percentage of carcass proteins, which was observed in the WFR rats. In addition, compared with the WFR group, the Lou/C rats showed lower plasma glucose levels (3.65 +/- 0.14 vs. 4.72 +/- 0.15 and 4.7 +/- 0.19 mM); a tendency (p < 0.1) for lower liver glycogen concentrations; and similar levels of glycerol, free fatty acids, and beta-hydroxybutyrate concentrations. Epinephrine and the relative weight of the adrenal glands were significantly (p < 0.01) lower in the Lou/C rats than in the WAL rats and the two other groups, respectively., Discussion: The ability of the Lou/C rats to accumulate less body fat than their equally food-restricted Wistar counterparts (WFR) suggests a difference in basal metabolism in this strain of rats that resembles obesity-resistant rats.

OBJECTIVE:: We recently reported that an 8-week high-fat diet-induced hepatic steatosis was completely prevented if an exercise training programme was introduced and pursued concurrently with the diet. The purpose of the present study was to determine the extent to which introducing exercise training at mid-point in the course of a 16-week high-fat diet regimen contributes to the reversal of liver lipid infiltration and the reduction of blood lipid profile deterioration and body fat accumulation. DESIGN AND SUBJECTS:: Two groups of rats were fed a high-fat diet (42% kcal) for 16 weeks, one remaining sedentary during this entire period (HF-Sed) and the other being exercise trained for the last 8 weeks (HF-Tr). A third group was fed a standard diet and remained sedentary for all 16 weeks (SD-Sed). Training (5 days/week for 8 weeks) began 8 weeks after introducing the high-fat diet and consisted of treadmill running that was progressively increased to reach 60?min at 26 m/min, 10% grade, for the last 4 weeks. MEASUREMENTS:: Various parameters including liver lipid infiltration, fat depots and blood lipids. RESULTS:: Unexpectedly, liver lipid infiltration was not significantly higher in HF-Sed than in SD-Sed rats (means±s.e.: 14.9±1.7 vs 12.3±0.4?mg/g; P>0.05). High-fat compared to age-matched standard fed rats also showed an absence of difference (P>0.05) in the weight of total visceral fat pads (13%), plasma nonesterified fatty acids (NEFA), and leptin concentrations, but depicted significantly (P<0.01) higher values for subcutaneous fat pad weight and plasma triacyglycerol. Exercise training largely decreased visceral and subcutaneous fat accumulation by 30 and 26%, respectively (P<0.01) as well as NEFA, triacylglycerol, and leptin concentrations (P<0.01). CONCLUSION:: Liver lipid infiltration does not seem to progress linearly over 16 weeks of high-fat feeding in light of what has previously been observed after 8 weeks of high-fat feeding. Introducing a training programme in the course of a 16-week high-fat diet protocol reduced adiposity, plasma NEFA, and leptin concentrations below the levels observed in standard fed rats. These data indicate that, exercise training, whether conducted concurrently or introduced during the course of a high-fat diet, is an asset to reduce the deleterious effects of a high-fat diet.International Journal of Obesity (2004) 28, 1064-1071. doi:10.1038/sj.ijo.0802628 [ABSTRACT FROM AUTHOR]

OBJECTIVE:: Lou/C rats are a substrain of Wistar rats that exhibit a spontaneous low caloric intake and no development of obesity with age. Recently, we reported that Lou/C rats, compared to equally food-restricted Wistar counterparts, show lower resting levels of plasma glucose, epinephrine and liver glycogen. To further explore this metabolic particularity, we used exercise (swimming 60?min) as a situation of high-energy demand, to test the ability of Lou/C rats to maintain euglycemia. DESIGN:: Male Lou/C rats (14-week-old) were compared to age-matched male Wistar rats fed either ad libitum (WAL) or Wistar rats whose food was chronically restricted (WFR) to the same caloric intake as the Lou/C rats. RESULTS:: In spite of low liver glycogen stores (~50% of normal values), Lou/C rats were able to maintain euglycemia during exercise even though liver glycogen breakdown was blunted. The decreased use of glycogen during exercise in Lou/C rats was associated with a reduced epinephrine response compared to WFR animals. By contrast, WFR were also able to maintain euglycemia during exercise but at the expense of a significant (P<0.01) decrease in liver and muscle glycogen content. Plasma free fatty acid and glycerol concentrations were increased (P<0.01) similarly in all three groups during exercise. In a separate experiment conducted in isolated hepatocytes from 24?h fasted Lou/C and Wistar rats, it was found that gluconeogenic flux from glycerol was found to be significantly (P<0.01) higher in Lou/C than in Wistar rats (5.4±0.2 vs 3.7±0.1 µmol/min/g dry cells). Resting and exercising plasma leptin levels were also significantly (P<0.05) lower in Lou/C than in the two other groups. CONCLUSION:: It is concluded that Lou/C rats have the particularity to rely spontaneously less on their liver glycogen stores to meet their energy demands during exercise while maintaining euglycemia.International Journal of Obesity (2004) 28, 972-978. doi:10.1038/sj.ijo.0802717 Published online 22 June 2004 [ABSTRACT FROM AUTHOR]