Circulating leptin did not associate with the development of the hyperglycemia accompanied by insulin insensitivity in spontaneous noninsulin dependent diabetes mellitus model Otsuka-Long-Evans-Tokushima-Fatty rats

Effects of ileal interposition on glucose metabolism in obese rats with diabetes

BACKGROUND

Ileal interposition (IT), in which the distal ileum is transposed isoperistaltically into the proximal jejunum, is considered as a procedure for metabolic or antidiabetes surgery. Our aim was to study the effects of IT on glycemic control, fat metabolism, and hormonal changes in obese rats with spontaneous diabetes.

METHODS

Animals were divided into either an IT or a sham (SH) group. They underwent an oral glucose tolerance test (OGTT) before and 4 and 8 weeks after the operation. All animals were killed 10 weeks after operation for analyses of tissue weight (liver, pancreas, epididymal fat, brown fat), immunoblotting of uncoupling protein-1 (UCP1) protein in brown adipose tissue (BAT), and fasting plasma levels of glucose, insulin, glucagon-like peptide (GLP)-1, peptide YY (PYY), glucose-dependent insulinotropic polypeptide (GIP), and leptin.

RESULTS

Body weight increased postoperatively in both groups compared with preoperative weight, but it did not differ between the 2 groups. Eight weeks postoperatively, integrated blood glucose levels during the OGTT were decreased in IT compared with SH (P < .05). Fasting plasma levels of insulin, GLP-1, and GIP did not differ between the 2 groups, but PYY levels were higher in the IT animals (P < .01). The weight of epididymal and BATs, homeostasis model assessment insulin resistance, and fasting plasma leptin levels were decreased in the IT group (P < .05). Expression of UCP1 was higher in IT than SH animals (P < .05).

CONCLUSION

These results suggest that IT improves glucose and lipid metabolism by decreasing insulin resistance and epididymal fat, and increased expression of UCP1 in BAT might be among the mechanisms responsible.

The obesity in bilateral ovariectomized rats is related to a decrease in the expression of leptin receptors in the brain

We investigated the expression levels of leptin receptors in the brain of ovariectomized (OVX) rats. The mean expression level of ob mRNA in adipose tissues of OVX rats was significantly (P < 0.01) lower than that in the SHAM operation group rats, and the mean body weight of OVX rats was significantly (P < 0.01) greater than that in the SHAM group rats. However, there were no differences between serum leptin concentrations in these two groups. The mean level of leptin receptor (OB-R) mRNA expression in the brain tissue and the mean level of long form type OB-R (OB-RL) mRNA expression in the hypothalamus of the OVX rats were significantly (P < 0.05) lower than those in the SHAM group rats. These changes were cancelled by supplementation with 17 beta-estradiol in OVX rats. These results suggested that not only changes in the expression level of ob mRNA in adipose tissue and the serum leptin concentration but also changes in the OB-R mRNA in the brain are involved in the body weight increase in OVX rats and that a decrease in OB-R makes transmission of signals to suppress the amount of food intake difficult, thus leading to an increase in body weight.

The effect of high-fat diet on the development of obesity and serum leptin level in rats

Ten male Wistar-albino rats were overfed with high-fat diet (margarine at the dose 40 g/kg body weight/day in addition to standard rat diet) during six months from the age of between 8-12 weeks. Ten male rats received a standard chow for the same period. The body weights of the overfed rats increased time dependently (basal 171.5 +/- 5, at sixth month 268 +/- 19 g), whereas those of the rats fed with standard chow did not increase significantly (basal 177 +/- 6.4, at sixth month 220 +/- 10 g). At the sixth month, mean body fat percentages were 36.3 +/- 6.7% and 24.2 +/- 5.4% respectively. Both total cholesterol-triglyceride levels and mean serum leptin levels were also higher than in the overfed rats (p < 0.01 and p < 0.05 respectively). The livers of all rats were histopathologically normal.

CONCLUSION

High-fat diet resulting in an increased body fat percentage in rats is associated with hyperleptinemia, hypercholesterolemia and hypertriglyceridemia.