[C-13]NMR STUDIES OF THE EFFECT OF THE SOMATOSTATIN ANALOG OCTREOTIDEON HEPATIC GLYCOGENESIS AND GLYCOGENOLYSIS

NMR spectroscopy is a useful tool for monitoring multiple intermediate metabolic pathways in different organs in intact animals and humans. We report the effect of the somatostatin analogue octreotide on the fa te of C-13-labeled glucose administered to fasted and well-fed rats as determined by NMR spectroscopy. The production of C-13-labeled glycog en and its subsequent breakdown after the end of infusion was identifi ed with a time resolution of 7 min. Hepatic glycogen synthesis was not different between control and octreotide-treated animals but persiste d for 15 min after the end of the infusion only in control animals. Gl ycogenolysis, however, was initiated immediately after the end of infu sion in octreotide-treated animals where the half-life of glycogen was 40 min compared with 68 min in control animals. However, once intiate d, the rate of glycogenolysis was not significantly altered by octreot ide. Although octreotide had no effect on glucose signal intensities i n fasted animals, C-13 glucose signals were more intense in octreotide compared with control well-fed animals. In conclusion, octreotide alt ers rat hepatic metabolism by accelerating the onset of glycogenolysis and stimulating glucose accumulation without significantly interferin g with glycogen synthesis.