Ciglitazone, a new hypoglycaemic agent. 3. Effect on glucose disposal and gluconeogenesis in vivo in C57BL/6J-ob/ob and -+/? mice.

Ciglitazone is orally active in preventing and reversing the hyperglycaemic syndrome in C57BL/6J-ob/ob mice and it is only mildly and transiently hypoglycaemic in lean littermates (C57BL/6J-+/?). Its effect on glucose disposal in vivo was estimated by injecting glucose-6-3H/14C and following the specific activity of radiolabelled glucose at 15, 30, 45, and 60 min after injection. The rate constants of glucose turnover were calculated to be as follows in decreasing order: treated obese (0.046/min), treated lean (0.032/min), control lean (0.026/min), and control obese (0.022/min). The obese mice showed less futile Cori cycle activity than the lean mice and ciglitazone had negligible effect on glucose recycling. The control obese mice incorporated more radiolabels in hepatic lipids, glycogen, and proteins than the control lean mice and ciglitazone further enhanced the incorporations. Ciglitazone also increased hepatic accumulations of radiolabels in the glycogen and lipid fractions in the lean littermates. Using lactate-14C as precursor, gluconeogenesis in vivo was measured in control and treated obese and lean mice. Ciglitazone significantly lowered the rate of conversion of lactate-14C to glucose-14C in the obese mice but not in the lean littermates.