The Effect of Gonadectomy on Fat and Protein Metabolism in VMH Lesioned Rats

Summary

The effects of castration on weight gain and on fat and protein metabolism were studied in ventromedial hypothalamic (VMH) lesioned adult male rats and controls.

Compared to control rats VMH lesioned ad libitum fed animals had an increased capacity for fat deposition (increased glucose incorporation into fatty acids and glyceride-glycerol in the fat cells, and considerably elevated LPL activity in fat tissue). Plasma urea concentrations were elevated, indicating increased amino acid catabolism. Weight gain was not affected by VMH lesions alone.

The combination of castration and VMH lesion caused an increase in weight gain and a further increase in plasma urea. The rate of lipolysis was decreased while LPL activity and glucose incorporation in fatty acids and glyceride-glycerol were unchanged. The only effect of castration seen in normal controls was a lower rate of lipolysis.

In animals fed an isocaloric diet gonadectomy did not affect nitrogen excretion in the urine. VMH lesions increased the nitrogen excretion which was further potentiated by gonadectomy.

In conclusion, our results indicate that the increased obesity after castration of adult male VMH-lesioned rats may be due, at least in part, to a combination of decreased lipolysis and increased protein catabolism.

Key-Words:

Hypothalamic Lesions - Gonadectomy - Fat Cells - Weight Gain - Fatty Acid Synthesis - Lipoprotein Lipase - Lipolysis - Nitrogen Balance