Summary
Lean (Fa/?) and obese (fa/fa) Zucker rats were adrenalectomized (ADX) in order to
assess the contribution of adrenal hormones to insulin resistance of the obese Zucker
rat. Glucose utilization was measured using an insulin suppression test.
Sham-operated obese rats gained almost twice as much weight as sham-operated lean
littermates. However, body weight gain of ADX animals was comparable in both genotypes.
It was significantly less than that of the respective sham-operated controls. Body
weight differences can be accounted for almost entirely by a marked loss of adipose
tissue.
Although insulin resistance may be attributable to obesity in part, steroid hormones
are thought to be directly antagonistic to insulin for glucose metabolism. Adrenalectomy
resulted in a decrease in serum glucose concentrations for both lean and obese Zucker
rats compared with their respective sham-operated groups. Serum insulin concentration
of lean ADX rats was 23% of sham-operated controls; in obese ADX rats, it was 9% of
controls. Elevated levels of steady state serum glucose (SSSG) levels in sham-operated
obese rats demonstrate a marked resistance to insulin induced glucose uptake compared
with sham-operated lean animals. Adrenalectomy caused a marked improvement in insulin
sensitivity of obese rats. The hyperglycemic SSSG levels of the obese rats were reduced
2.5 times by ADX.
These results indicate that insulin resistance of Zucker obese rats can be ameliorated
by ADX, suggesting adrenal hormones contribute to insulin resistance in these animals.
Key-Words
Adrenalectomy
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Glucose Metabolism
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Insulin Resistant Zucker Obese Rat
