Insulin Responsiveness in Vitro of Diaphragm and Adipose Tissue from Weanling Rats with Hypothalamic Obesity[*]

Abstract

Studies were undertaken in order to evaluate the responsiveness to insulin in vitro of adipose tissue and diaphragm of weanling rats with obesity secondary to destruction of the ventromedial hypothalamic nuclei (VMN). Quartered diaphragm and adipose tissue fragments were obtained from normal and VMN rats and incubated with U-¹⁴C-glucose in the presence or absence of several concentrations of insulin. Glucose oxidation was measured as was the incorporation of glucose into total lipid, saponifiable fatty acid and glycogen. In the absence of insulin VMN diaphragm and adipose tissue incorporated more glucose into total lipid and fatty acid than did tissue from normal rats. Glucose oxidation in adipose tissue was greater in VMN rats and in diaphragm was equal in both groups. Glycogen labelling of diaphragm and adipose tissue was the same in both groups of rats in the absence of insulin. Glucose metabolism by tissues from VMN and normal rats responded similarly to the addition of insulin except for glycogen labelling in which insulin resistance was demonstrated in tissues from VMN rats. The interpretation of these findings and their possible significance is discussed.

Key words

Insulin Resistance - Obesity - Hypothalamus

1 This work was supported by USPHS Grants AM-11746 and AM-14418, a V.A. Clinical Investigatorship and V.A. Research Grant 01/3193-1/69-01 (J.K.G.)

1 This work was supported by USPHS Grants AM-11746 and AM-14418, a V.A. Clinical Investigatorship and V.A. Research Grant 01/3193-1/69-01 (J.K.G.)