Regulation of fatty acid and carbohydrate metabolism by insulin, growth hormone and tri-iodothyronine in hepatocyte cultures from normal and hypophysectomized rats

Abstract

The interactions of insulin, growth hormone (somatotropin) and tri-iodothyronine (T3) in the long-term (24 h) regulation of fatty acid and carbohydrate metabolism were studied in hepatocyte primary cultures isolated from normal or hypophysectomized Sprague-Dawley rats. Hepatocytes from hypophysectomized rats had similar rates of palmitate metabolism, but lower rates of ketogenesis, than hepatocytes from normal rats. They also had a lower endogenous triacylglycerol content and lower activities of NADP-linked dehydrogenases than did cells from normal rats. The inhibitions of ketogenesis and gluconeogenesis by insulin were more marked in hepatocytes from hypophysectomized than from normal rats. Insulin caused a 7-10-fold increase in cellular glycogen in hepatocytes from hypophysectomized rats, compared with a 2-3-fold increase in cells from normal rats, and it increased cellular triacylglycerol by 65% in cells from hypophysectomized rats, compared with 11% in cells from normal rats. In hepatocytes from hypophysectomized rats, growth hormone and T3 increased ketogenesis both separately and in combination (12% and 23% respectively; P less than 0.05), whereas in hepatocytes from normal rats only the combination of growth hormone and T3 caused a significant increase in ketogenesis. In cells from hypophysectomized rats, T3 and growth hormone had different effects on carbohydrate metabolism: T3, but not growth hormone, potentiated the anti-gluconeogenic and glycogenic effects of insulin. It is concluded that hypophysectomy increases the responsiveness of hepatocytes to insulin, growth hormone and T3, and that growth hormone and T3 regulate fatty acid and carbohydrate metabolism by different mechanisms.

The metabolic role of growth hormone in humans with particular reference to fasting

“…Co-incubation of rat hepatocytes with GH leads to inhibition of the activity of lipogenic enzymes [182]. When GH is added to primary cultures of rat hepatocytes, ketogenesis is increased in the presence of unaltered total lipid clearance, whereas no effect on gluconeogenesis is observed [183]. In contrast, GH may stimulate gluconeogenesis in sheep hepatocytes, without affecting ketogenesis from fatty acids [184], an effect which has also been noted in suspensions of canine renal proximal tubules, where GH also stimulates gluconeogenesisdependent glucose release [185].…”

Evidence for dissociation of gluconeogenesis stimulated by non-esterified fatty acids and changes in fructose 2,6-bisphosphate in cultured rat hepatocytes

“…Each perfusion routinely yielded 80-110 plates of cultured cells (3.5 x 106 cells/plate) from a single rat liver. Evidence of sustained viability of hepatocytes in cultures has been provided by reports from this laboratory and elsewhere [15,16]. All cultures used in these experiments were > 90% viable, judged by the criterion of Trypan Blue exclusion.…”

“…The plates were swirled carefully to ensure even distribution of cells over the surface of the plate and were then incubated under air/CO2 (19: 1) at 37 'C. Within 4 h, the cells had attached to the Matrigel surface, and by [12][13][14][15][16][17][18][19][20][21][22][23][24] h they had formed a confluent monolayer. Culture medium was changed every 24 h and consisted of Eagle's minimal essential medium vitamin mixture plus amino acids and salts of Hanks' medium 199, with the following modifications: ornithine (20 mg/l) was substituted for arginine, hydroxyproline and Fe(NO3)3 were omitted, and NaHCO3 was added at a concentration of 1.26 g/l.…”

Metabolic Stability of D-Allulose in Biorelevant Media and Hepatocytes: Comparison with Fructose and Erythritol

“…Dietary carbohydrates are readily absorbed in the intestines and pass through the liver via the portal vein before reaching the systemic circulation. Primary hepatocytes are viewed as a physiologically relevant system for the evaluation of nutrient metabolism, and thus, have been used in metabolic studies of drugs and nutrient (e.g., lipids and carbohydrates) [20,21,22]. Furthermore, cryopreserved hepatocytes held in suspension have been recommended for use in short-term metabolic and toxicity studies [22], and reports have consistently shown good correlations between results obtained in vitro using hepatocytes and in vivo derived data [23].…”