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APPETITE, OBESITY, DIGESTION, AND METABOLISM

Intraportal administration of neuropeptide Y and hepatic glucose metabolism

¹Department of Molecular Physiology and Biophysics and ²Diabetes Research and Training Center, Vanderbilt University School of Medicine, Nashville, Tennessee

Submitted 17 December 2007 ; accepted in final form 28 January 2008

We examined whether intraportal delivery of neuropeptide Y (NPY) affects glucose metabolism in 42-h-fasted conscious dogs using arteriovenous difference methodology. The experimental period was divided into three subperiods (P1, P2, and P3). During all subperiods, the dogs received infusions of somatostatin, intraportal insulin (threefold basal), intraportal glucagon (basal), and peripheral intravenous glucose to increase the hepatic glucose load twofold basal. Following P1, in the NPY group (n = 7), NPY was infused intraportally at 0.2 and 5.1 pmol·kg^–1·min^–1 during P2 and P3, respectively. The control group (n = 7) received intraportal saline infusion without NPY. There were no significant changes in hepatic blood flow in NPY vs. control. The lower infusion rate of NPY (P2) did not enhance net hepatic glucose uptake. During P3, the increment in net hepatic glucose uptake (compared with P1) was 4 ± 1 and 10 ± 2 µmol·kg^–1·min^–1 in control and NPY, respectively (P < 0.05). The increment in net hepatic fractional glucose extraction during P3 was 0.015 ± 0.005 and 0.039 ± 0.008 in control and NPY, respectively (P < 0.05). Net hepatic carbon retention was enhanced in NPY vs. control (22 ± 2 vs. 14 ± 2 µmol·kg^–1·min^–1, P < 0.05). There were no significant differences between groups in the total glucose infusion rate. Thus, intraportal NPY stimulates net hepatic glucose uptake without significantly altering whole body glucose disposal in dogs.

dog; liver; nerves