Metabolic and Hepatic Effects Of Partial Lipectomy In Ovariectomized young and aged rats

Abstract

The present study was planned to investigate and evaluate the early and late metabolic and hepatic effects of partial subcutaneous adipose tissue reduction )by lipectomy( in ovariectomized young and aged rats and to identify the relation between these effects and the adipose tissue endocrine secretions, in order to throw more light on the impact of lipectomy on metabolic and hepatic activities in menopausal females. The study was done on 160 female white Wistar rats, that were allocated into two main groups according to age: group I, the young adult rats, and group II, the aged rats. Each group was subdivided into two main subgroups: the short-term groups IS and IIS, in which rats were studied one week after lipectomy operation, and the long-term groups IL and IIL, in which rats were studied six weeks after the lipectomy operation. Rats in each of the short-term and long-term subgroups were further subdivided into 3 subgroups as follows: (a) Sham-operated (control) groups, in which rats were subjected to all steps of the ovariectomy operation, without removal of the ovaries and served as control group. These groups include: ●subgroup IS.C and ●subgroup IIS.C in which rats were sacrificed and studied 5 wks after the operation and ●subgroup IL.C and ●subgroup IIL.C in which rats were sacrificed and studied 10wks after the operation. (b) Only ovariectomized groups: in which rats were subjected to ovariectomy operation. These groups include: ●subgroup IS.OVX and ●subgroup IIS.OVX in which rats were sacrificed and studied 5wks after the operation and ●subgroup IL.OVX and ●subgroup IIL.OVX in which rats were sacrificed and studied 10 wks after the operation. (c) Ovariectomized-lipectomized groups, in which rats were subjected to ovariectomy operation followed 4 weeks later by lipectomy operation. These groups include: ●subgroup IS.OVX.L1W and ●subgroup IIS.OVX.L1W in which rats were sacrificed and studied one week after the lipectomy operation and ●subgroup IL.OVX.L6W and ●subgroup IIL.OVX.L6W in which rats were sacrificed and studied 6 wks after the lipectomy operation. Subcutaneous belt lipectomy was performed according to Weber et al. (2000). The removed fat weight was on the average 2.39 % of body weight in young rats, and on the average 1.46 % of body weight in aged rats. All rats were subjected to determination of body weight, BMI, perirenal and liver fat weights, plasma triglycerides, total cholesterol, LDL-C, HDL-C, atherogenic index, fasting blood sugar, plasma total proteins, albumin, plasma levels of liver enzymes (ALT & AST), plasma malondialdehyde (MDA), blood and hepatic reduced glutathione, plasma leptin and adiponectin, besides histological examination of samples from the liver, aorta and the perirenal fat together with assessment of the perirenal fat cell size. The encountered results revealed that there was a decrease in BMI in the 5wks ovariectomized-1wk lipectomized young and aged rats compared to the 5wks only ovariectomized ones. However, 6wks following lipectomy, the young rat group appeared to have compensated for the removed fat tissue manifested in increased BMI, perirenal fat cell size and marked hepatic tissue fatty infiltration, whereas aged rats couldn’t compensate for the removed fat. Further, there were unfavourable metabolic effects one week after lipectomy in both the young and aged rats compared to the only ovariectomized rats, manifested by further increase in the fasting blood sugar and disturbed lipid profile associated with early atherosclerotic changes in the wall of abdominal aorta. Six weeks after subcutaneous lipectomy, there was a continuation of the unfavourable metabolic effects in the young rats compared to their only ovariectomized peers, but there was an improvement in the metabolic profile in aged rats together with increased adiponectin level, the adiponectin level being increased only in the aged lipectomized rats. Moreover, increased MDA, decreased antioxidant capacities, increased visceral fat cell size, accompanied by hepatic cell vacuolation and inflammatory cell infiltration were all observed in both the young and the aged groups one week after lipectomy. However, improvement of the liver histological findings was noticed six weeks after lipectomy, which was more marked in aged rats.