EFFECT OF A NOVEL HYPOGLYCEMIC AGENT, KAD-1229 ON GLUCOSE-METABOLISM AND FRUCTOSE-2,6-BISPHOSPHATE CONTENT IN ISOLATED HEPATOCYTES OF NORMAL RATS

The effects of a novel hypoglycemic agent, -2-benzyl-3-(cis-hexahydro- 2-isoindolinylcarbonyl) propionate dihydrate (KAD-1229), which is a be nzyl succinate derivative, on liver metabolism were investigated using isolated hepatocytes from normal rats. In the presence of 10 mM gluco se, KAD-1229 increased the L-lactate production (41.1 +/- 0.9 versus 6 0.9 +/- 2.6 mu mol of lactate/g of cells/30 min; P < 0.05) and inhibit ed gluconeogenesis in hepatocytes (0.94 +/- 0.02 versus 0.70 +/- 0.03 mu mol of [2-C-14]-pyruvate converted to glucose/g of cells/20 min; P< 0.05). These effects by KAD-1229 were accompanied by an increase in th e cellular content of fructose-2, 6-bisphosphate (F-2,6-P-2), which is one of the important regulators of hepatic glucose metabolism, in a d ose-dependent manner (0.05-2.5 mM). KAD-1229 also stimulated the oxida tion of [2-C-14]-pyruvate and [6-C-14]-glucose in the tricarboxylic ac id cycle (+18 and +31%, respectively), indicating that stimulation of tricarboxylic acid cycle activity and/or enhancement of the glycolytic flux rate had occurred. Moreover, KAD-1229 did not modify the activit ies of 6-phosphofructo 2-kinase or fructose-2,6-bisphosphatase, but in creased significantly the accumulation of fructose 6-phosphate in hepa tocytes. These results suggest that KAD-1229 has extrapancreatic effec ts on hepatic glucose metabolism, that its actions are mediated throug h the inhibition of fructose-1,6-bisphosphatase and stimulation of bot h the 6-phosphofructo 1-kinase reaction and tricarboxylic acid cycle a ctivity by increasing the F-2,6-P-2 content in hepatocytes, and that t hese multiple effects may account in part for the ability of KAD-1229 to reduce blood glucose levels in vivo.