The effects of high fat diet and negative energy balance methods on adipocyte size and concentrations of adiponectin in fat depots of abdominal cavity in obese rats

The aim of the present study was to investigate the effect of 10-week negative energy balance (NEB) methods on adipocyte size and adiponectin levels in different abdominal fat depots as well as glucose and lipid variables and insulin resistance in high-fat-diet obese male wistar rats. Study sample were consisted of sixty-four Wistar male rats (average weight; 194.5±12.6g). Blood samples were collected at 1st, 18th and 28th weeks after an overnight fasting. After first sampling, remaining 56 rats were randomly divided into control (n=16) and high-fat-diet (n=40) groups. After 18 weeks High-fat-diet group randomly divided into high-fat-diet (HFD) and negative energy balance consisted of calorie restriction, exercise training and combination (exercise training with calorie restriction) subgroups. Negative energy balance subgroups underwent an aerobic training (running) with intensity of 70 to 75% of VO2max, %25 calorie restriction and interval of both methods for 10 weeks. Adiponectin Levels and adipocyte size in retroperitoneal and mesenteric fat depots, insulin and glucose levels and lipid profile were measured. HOMA-IR was also calculated. The results of this study indicated that in comparison to high-fat-diet, negative energy balance methods despite consumption of high fat diet, decreased adipocyte size in retroperitoneal and mesenteric fat depots (P<0.05) and insulin resistance index improved in line with decrease of serum concentrations of insulin, glucose and triglyceride in obese male rats (P<0.05). However although lipid profile improved, only triglyceride concentration significantly decreased (P<0.05). From negative energy balance subgroups only combination showed significant increase in adiponectin levels of studied depots compared to high-fat-diet (P>0.05). This study indicated that negative energy balance methods can actually decrease adipocyte size of retroperitoneal and mesenteric fat depots even with simultaneous consumption of high-fat-diet which is largely congruent with improvement in lipid and metabolic profile Results also indicate a superiority of aerobic training in improving the lipid profile compare to other NEB methods.