[Influence of indole-3-alkanecarboxylic acids on glucose utilization in rats]

The influence of various indole-3-alkane-carboxylic acids (indole-3-propionic acid, indole-3-butyric acid and derivatives of this substance) on some parameters of carbohydrate, fat and insulin metabolism were studied in normal and experimentally induced diabetic rats. Earlier it had been shown, by Schillinger and Loge (1973) using rat liver slices for in vitro studies and adrenalectomized rates for in vivo experiments that indole-3-butyric acid and its analogues investigated suppress gluconeogenesis from pyruvate and that these substances have a hypoglycaemic effect when administered orally at doses of 50-250 mg/kg. Indole-3-propionic acid, indole-3-butyric acid, 1-methyl-indole-3-butyric acid, 2-methyl-indole-3-butyric acid and 1-carboxy-6-fluor-1,2,3,4-tetrahydrocarbazol, administered orally at doses up to 1000 mg/kg, had either only a slight or no hypoglycaemic effect at all in intact and streptozotocin-diabetic rats. The suppression of gluconeogenesis observed in vitro thus only has an appreciable effect on blood glucose in vivo when the capacity of the liver to synthetize glucose is reduced. In normal rats indole-3-propionic acid and indole-3-butyric acid led to a deterioration of glucose tolerance following i.v. glucose loading and to a reduction of 14C-U-glucose oxidation. An increase in the concentration of serum free fatty acids (FFA) measured after treatment with indole-3-butyric acid and its 1- and 2-methylated derivatives was not--in accordance with a theory of an interference of the glucose and fatty acid utilization published in literature--considered to be the primary cause since the reduced formation of 14CO2 from radioactive glucose is not normalized when the increased FFA content is reduced by an inhibitor of lipolysis (5-methyl-isoxazol-3-carboxylic acid)...