Summary
The metabolic consequences of ventromedial hypothalamic lesion were studied in a group
of aged male rats which were obese and had decreased response to insulin. The effects
of hyperphagia and ventromedial hypothalamic lesion per se were separated by comparing
experimental animals fed isocalorically with controls and animals fed ad libitum.
Ventromedial hypothalamic lesion as such led to increases in the glucose conversion
to fatty acid and in lipoprotein lipase activity in adipose tissue. Protein catabolism
as reflected by plasma urea levels, was enhanced. The lipoprotein lipase activity
in heart tended to be lower after VMH lesion. These metabolic changes were amplified
in the VMH lesioned rats fed ad libitum. The liver glycogen content was lowered by
VMH lesion, but this effect was abolished by hyperphagia. In parallel experiments
the influence of diet composition was studied by feeding similar groups with diet
of high fat content. The glucose incorporation in fatty acids was in all groups markedly
and similarly inhibited by the high fat diet. The increase in lipoprotein lipase activity
in heart and adipose tissue of control rats with high fat intake could not be demonstrated
in any of the groups with ventromedial hypothalamic lesion. The plasma urea level
in the control group was not affected by the diet, but tended to increase in the ventromedial
hypothalamic lesioned groups on high fat intake. These findings demonstrate that the
well known metabolic effects of ventromedial hypothalamic lesions are also manifest
in obese insulin resistant male rats. Furthermore, the responses to changes in diet
composition are different from those of the control rats.
Key-Words:
Hypothalamic Lesion
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Hyperphagia
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Dietary Effects
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Adipose Tissue Metabolism
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Liver Glycogen
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LPL in Heart
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Plasma Cholesterol
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Protein Catabolism
