Short Term Effects of Leptin on Hepatic Gluconeogenesis and in Vivo Insulin Action

Long term administration of leptin decreases caloric intake and fat mass and improves glucose tolerance. Here we examine whether leptin acutely regulates peripheral and hepatic insulin action. Recombinant mouse leptin (0.3 mg/kg·h, Leptin +) or vehicle (Leptin −) were administered for 6 h to 4-month-old rats (n = 20), and insulin (3 milliunits/kg·min) clamp studies were performed. During physiologic hyperinsulinemia (plasma insulin ∼65 microunits/ml), the rates of whole body glucose uptake, glycolysis, and glycogen synthesis and the rates of 2-deoxyglucose uptake in individual tissues were similar inLeptin − and Leptin +. Post-absorptive hepatic glucose production (HGP) was similar in the two groups. However, leptin enhanced insulin's inhibition of HGP (4.1 ± 0.7 and 6.2 ± 0.7 mg/kg·min; p 95% pure by SDS-polyacrylamide gel electrophoresis) at the rate of 5 μg/kg·min for 6 h (Leptin +). Rats were housed in individual cages and subjected to a standard light (6 a.m. to 6 p.m.)/dark (6 p.m. to 6 a.m.) cycle. One week before the in vivostudy, rats were anesthetized with an intraperitoneal injection of pentobarbital (50 mg/kg body weight), and indwelling catheters were inserted in the right internal jugular vein and in the left carotid artery. The venous was to the of the right and the was to the of the J.F. Biochem. Biophys. Res. Commun. 1996; PubMed Scopus Google Scholar, E. D. A. P. J. Google Scholar, A. L. J. PubMed Scopus Google Scholar, L. N. T. D. C.E. J. Biol. Chem. 1996; 271: Full Text Full Text PDF PubMed Scopus Google Scholar). were in and rats L. Smith D. D. J. Clin. Invest. PubMed Scopus Google Scholar, L. A. J. Clin. Invest. PubMed Scopus Google Scholar). mass and fat mass were the whole body of distribution of by injection in N. D. L. Biochem. J. 1995; PubMed Scopus Google Scholar). of of were on the of the for in rats is 5 were 1 and 2 h The distribution of was by the by the of plasma was to of the plasma mass was the whole body distribution by were in rats the insulin clamp L. Smith D. D. J. Clin. Invest. PubMed Scopus Google L. A. J. Clin. Invest. PubMed Scopus Google Scholar, L. A. N. G. M. J. Clin. Invest. PubMed Scopus Google Scholar), in with and L. A. N. G. M. J. Clin. Invest. PubMed Scopus Google Scholar, A. L. J. Clin. Invest. PubMed Scopus Google Scholar). was for h before the in vivo studies and a for of the of distribution of a for of the rates of glucose and a hyperinsulinemic clamp At the of the and before the a infusion of was and the h of the of was before the end of the was the of the The the insulin clamp was similar to that L. Smith D. D. J. Clin. Invest. PubMed Scopus Google Scholar, L. A. J. Clin. Invest. PubMed Scopus Google Scholar, L. A. N. G. M. J. Clin. Invest. PubMed Scopus Google Scholar, A. L. J. Clin. Invest. PubMed Scopus Google Scholar). a infusion of insulin (3 milliunits/kg·min) was and a infusion of a glucose was at and to clamp the plasma glucose at To control for effects of leptin on the J.F. Biochem. Biophys. Res. Commun. 1996; PubMed Scopus Google Scholar), was also to inhibit insulin in both groups. for of and were at the and clamp for the plasma glucose and were in both the and clamp of the studies for of plasma insulin and concentrations were at the for of plasma were at and the clamp The of was to and a of of by of the and was at a rate of Furthermore, following cells were in and the were also on vein at the end of the At the end of the in vivo rats were anesthetized mg/kg body weight, the was vein was and and and were in in The the injection of the of the tissues was than were at for The was and by the and of the of glucose was by the glucose and leptin Leptin Inc., concentrations were by The plasma of free fatty was by an with an to the was in in the of and of plasma to to The rates of were L. A. J. Clin. Invest. PubMed Scopus Google Scholar). was by of the before and to on of glucose is to glycolysis, it can that plasma is in or To plasma were and an of the was in a of of and 5 of To were and in of 1 in a at for 1 with of 1 2 were One was with and and the with The both and whereas the and the The in the two the of E. D. A. P. J. Google Scholar). and phosphoenolpyruvate concentrations and in the were two L. A. N. G. M. J. Clin. Invest. PubMed Scopus Google Scholar, A. L. J. Clin. Invest. PubMed Scopus Google Scholar, A. L. J. PubMed Scopus Google Scholar, L. N. T. D. C.E. J. Biol. Chem. 1996; 271: Full Text Full Text PDF PubMed Scopus Google Scholar). glucokinase and phosphoenolpyruvate carboxykinase mRNA abundance was by analysis N. L. J. Biol. Chem. Full Text PDF PubMed Google Scholar, D. N. M. L. J. Biol. Chem. 1996; 271: Full Text Full Text PDF PubMed Scopus Google Scholar, D. N. M. D. L. Diabetes. 1997; PubMed Google Scholar). was on tissues to the The was for by the of were on a gel in 1 The was with and to a The and PEPCK were with the and were the The were to for h at with of and PEPCK mRNA was by for to for The term glucose is in vivo The term hepatic glucose production (HGP) is the rates of to glucose is the of glucose the by of the for plasma glucose the rate of glucose the rate of glucose The was the of the rate of infusion of and the plasma exogenous glucose was the rate of glucose production was the and the infusion rate of The rate of 2-deoxyglucose uptake was by E. D. A. P. J. Google Scholar). The of the hepatic glucose directly plasma glucose was the of and plasma The of the hepatic glucose gluconeogenesis was the of the of and 2 following in vivo with L. A. N. G. M. J. Clin. Invest. PubMed Scopus Google Scholar, A. L. J. Clin. Invest. PubMed Scopus Google Scholar). groups were with for and the ± of the The discovery by of the (1Zhang Y. Proenca R. Maffei M. Barone M. Leopold L. Friedman J. Nature. 1994; 372: 425-432Crossref PubMed Scopus (11935) Google Scholar) and of its product, a protein leptin J.L. Gajiwala K.S. Maffei M. Cohen S.L. Chait B.T. Rabinowitz D. Lallone R.L. Burley S.K. Friedman J.M. Science. 1995; 269: 543-546Crossref PubMed Scopus (4280) Google Scholar), has of energy metabolism (8Flier J.S. Proc. Natl. Acad. Sci. U. S. A. 1997; 94: 4242-4245Crossref PubMed Scopus (195) Google Scholar). However, it is well established that leptin is by adipose cells (1Zhang Y. Proenca R. Maffei M. Barone M. Leopold L. Friedman J. Nature. 1994; 372: 425-432Crossref PubMed Scopus (11935) Google Scholar, M.A. Cullen M.J. Baker M.B. Hecht R. Winters D. Boone T. Collins F. Science. 1995; 269: 540-543Crossref PubMed Scopus (3914) Google Scholar, 3Mantzoros C.S. Qu D. Frederich R.C. Susulic V.S. Lowell B.B. Maratos-Flier E. Flier J.S. Diabetes. 1996; 45: 909-914Crossref PubMed Scopus (318) Google Scholar, 6Frederich R.C. Hamann A. Anderson S. Lollmann B. Lowell B.B. Flier J.S. Nat. Med. 1995; 1: 1311-1314Crossref PubMed Scopus (1438) Google Scholar, 15Halaas J.L. Gajiwala K.S. Maffei M. Cohen S.L. Chait B.T. Rabinowitz D. Lallone R.L. Burley S.K. Friedman J.M. Science. 1995; 269: 543-546Crossref PubMed Scopus (4280) Google Scholar, S. Frederich R.C. R. Flier J.S. Lowell B.B. 1997; PubMed Scopus Google Scholar) and marked effects L. Smith F.J. Guisez Y. Devos R. Burn P. Science. 1995; 269: 546-549Crossref PubMed Scopus (3089) Google Scholar, 14Schwartz M.W. Baskin D.G. Bukowski T.R. Kuijper J.L. Foster D. Lasser G. Prunkard D.E. Porte D.J. Woods S.C. Seeley R. Weigle D. Diabetes. 1996; 45: 531-535Crossref PubMed Google Scholar, M.W. Seeley Burn P. Baskin D.G. J. Clin. Invest. 1996; PubMed Scopus Google Scholar, M.W. E. M. Porte D.J. Nat. Med. 1996; PubMed Scopus Google Scholar, J. M.B. P. S. During M. Diabetes. 1997; PubMed Scopus Google Scholar, R.V. Considine Caro J.F. Diabetes. 1996; 45: PubMed Google Scholar), is on of leptin in carbohydrate or of the leptin and insulin action have been to in (9Cohen B. Novick D. Rubinstein M. Science. 1996; 274: 1185-1188Crossref PubMed Scopus (656) Google Scholar, G. Ertl J. Gerl M. Preibisch G. J. Biol. Chem. 1997; 272: 10585-10593Abstract Full Text Full Text PDF PubMed Scopus (410) Google Scholar). the and insulin can regulate the gene expression of ob in adipose cells and leptin in plasma R.C. Hamann A. Anderson S. Lollmann B. Lowell B.B. Flier J.S. Nat. Med. 1995; 1: 1311-1314Crossref PubMed Scopus (1438) Google Scholar, J.S. Proc. Natl. Acad. Sci. U. S. A. 1997; 94: 4242-4245Crossref PubMed Scopus (195) Google Scholar, 10Considine R.V. Sinha M.K. Heiman M.L. Kriauciunas A. Stephens T.W. Nyce M.R. Ohannesian J.P. Marco C.C. McKee L.J. Bauer T. Caro J. N. Engl. J. Med. 1996; 334: 324-325Crossref PubMed Scopus (5641) Google Scholar, 11Kolaczynski J.W. Considine R.V. Ohannesian J. Marco C. Opentanova I. Nyce M.R. Myint M. Caro J.F. Diabetes. 1996; 45: 1511-1515Crossref PubMed Google Scholar), it is presently unknown whether leptin role in the regulation vivo insulin action and hepatic glucose fluxes. To examine the effect of the acute administration of leptin on whole and insulin action, 12 rats were with 5 μg/kg·min leptin for 6 h and were compared with 8 control rats receiving a vehicle were in the body food intake, and mass the two groups of rats. following the plasma and concentrations were similar in the rats to the two of rats receiving of vehicle (Leptin −) or leptin (Leptin ± ± intake ± ± of body ± ± glucose ± ± insulin ± ± ± ± were for 5 h to plasma the ± of at in intake the ± of the and mass was the of plasma at h following the injection of a of in a new Rats were for 5 h to plasma the ± of at in intake the ± of the and mass was the of plasma at h following the injection of a of To the effects of insulin in vivo, a physiologic increase in the plasma insulin concentrations was for and the plasma glucose concentrations were at the by a glucose Thus, conscious rats were compared in the presence of similar hyperinsulinemia and in the presence or of exogenous leptin for plasma glucose and were both the and clamp The plasma not its following the vehicle infusion and However, was a increase in the plasma concentrations and the leptin of the plasma concentrations were decreased at a similar the hyperinsulinemic clamp The plasma leptin concentrations the leptin ± The rates of glucose infusion to the plasma glucose at the the hyperinsulinemic clamp studies were similar in the rats receiving vehicle and leptin plasma and free fatty concentrations and rate of glucose infusion in Leptin − and Leptin + rats the and the clamp studies ± ± ± ± ± ± < versus ± ± < versus ± ± < versus ± < versus Leptin ± < versus ± ± the ± the of p < versus p < versus Leptin −. in a new the ± the of The effect of a similar increase in the insulin concentrations on the rates of glucose uptake glycolysis, and glycogen synthesis in were the of the clamp a were for plasma glucose and insulin and rates of glucose The rates of whole body glucose ± and ± 0.7 in Leptin − and Leptin respectively; were similar in the two groups. Thus, leptin not alter the whole body glucose disposal in to physiologic in the plasma insulin We examined whether leptin the of glucose fluxes the two of glucose disposal, glycogen synthesis and in 2 the rates of glycogen synthesis and the hyperinsulinemic clamp studies were also similar in Leptin + compared with Leptin − rats. Thus, short term leptin infusion not the whole body fluxes of glucose glycogen synthesis and Since hyperinsulinemia markedly the uptake of glucose in and adipose the rates of glucose uptake were in and fat at the of the in vivo The rate of glucose uptake the of the hyperinsulinemic clamp studies was The rates of 2-deoxyglucose in and and fat were similar in Leptin + and Leptin −. with the on the whole body glucose fluxes, these the of hyperinsulinemic clamp short term leptin administration does not insulin action on glucose the rate of glucose production (HGP) the and its suppression by that it is that glucose production to glucose production in were for and we had that marked decreases in mass has effect on HGP in conscious rats S. L. L. PubMed Scopus Google Scholar). HGP was similar in the Leptin − and Leptin + rats. However, the inhibition of HGP the hyperinsulinemic clamp studies was increased in the Leptin + compared with the Leptin − rats. the decrease in HGP was ± 6 and ± in Leptin + and Leptin −, Furthermore, the HGP the clamp studies was also in Leptin + than in Leptin −. We examined whether leptin the of plasma and glycogenolysis to the hepatic glucose Leptin its most effect on the intrahepatic of glucose fluxes. a marked increase in the contribution of gluconeogenesis to HGP was demonstrated in the rats receiving exogenous leptin with gluconeogenesis for the and and the that used to the contribution of plasma glucose in to the hepatic glucose The the with and the two The of the of hepatic and vein plasma glucose an of the contribution of the in the of the to the hepatic at the end of the clamp studies were similar in the Leptin + compared with the Leptin − of hepatic used to the and the at the end of the in the rats receiving vehicle (Leptin −) or leptin (Leptin ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± < versus ± < versus abbreviations used are: plasma of the hepatic plasma the of the of or and of the hepatic the of the of or and 2 p < versus in a new The abbreviations used are: plasma of the hepatic plasma the of the of or and of the hepatic the of the of or and 2 also the and and the that used to the contribution of gluconeogenesis in to the hepatic glucose The for of the hepatic in the contribution was than in the rats receiving leptin for 6 to the in vivo fluxes and the rates of glucose and glycogenolysis in Leptin − and Leptin + rats. in the decreased HGP in Leptin + was by similar decreases in the rates of glucose and glucose compared with the Leptin − rats. The glucose in HGP can gluconeogenesis and/or the hyperinsulinemic of these studies glycogenolysis for the of HGP in the control group (Leptin − in However, following leptin infusion gluconeogenesis was markedly increased and for of were also in rats with the with a leptin infusion of μg/kg·min (plasma leptin = ± this gluconeogenesis for an of ± of Thus, short term administration of the of the ob to marked in the intrahepatic distribution of hepatic glucose fluxes with of gluconeogenesis and inhibition of The abundance of and PEPCK was by analysis of at the end of the in vivo of is in that the rats receiving leptin for 6 h a increase in PEPCK mRNA concentrations compared with rats. this marked of PEPCK gene expression by leptin was in the presence of and plasma insulin Thus, leptin to antagonize the effect of insulin on PEPCK gene expression in The effect of leptin the effects of the on PEPCK mRNA in an (9Cohen B. Novick D. Rubinstein M. Science. 1996; 274: 1185-1188Crossref PubMed Scopus (656) Google Scholar). the effect of leptin on the hepatic abundance of mRNA was to that of rats receiving leptin a decrease in mRNA concentrations compared with rats. that short term administration of exogenous leptin the action of insulin on the gene expression of and PEPCK in the may that this the by leptin regulates the intrahepatic of glucose fluxes with marked increase in gluconeogenesis and decrease in However, it to whether these effects of leptin in the regulation of hepatic glucose metabolism physiologic and whether peripheral and/or that leptin may play a role in the regulation of energy and in the of to (8Flier J.S. Proc. Natl. Acad. Sci. U. S. A. 1997; 94: 4242-4245Crossref PubMed Scopus (195) Google Scholar, G. Ertl J. Gerl M. Preibisch G. J. Biol. Chem. 1997; 272: 10585-10593Abstract Full Text Full Text PDF PubMed Scopus (410) Google Scholar, M. G. F. Lee Y. Proc. Natl. Acad. Sci. U. S. A. 1997; 94: PubMed Scopus Google Scholar). Since the rate of is a of the hepatic of and has been to for the regulation of to in the M. G. F. Lee Y. Proc. Natl. Acad. Sci. U. S. A. 1997; 94: PubMed Scopus Google Scholar), that leptin the hepatic of by of in the with the effects of leptin on adipose cells (12Muller G. Ertl J. Gerl M. Preibisch G. J. Biol. Chem. 1997; 272: 10585-10593Abstract Full Text Full Text PDF PubMed Scopus (410) Google Scholar, 13Bai Y. Zhang S. Kim K.-S. Lee J.-K. Kim K.-H. J. Biol. Chem. 1996; 271: 13939-13942Abstract Full Text Full Text PDF PubMed Scopus (216) Google Scholar) and cells M. G. F. Lee Y. Proc. Natl. Acad. Sci. U. S. A. 1997; 94: PubMed Scopus Google Scholar). studies to the by leptin the hepatic energy to Since is a key of the of in the a effect of leptin on the hepatic of the inhibition on 1 Foster J. Clin. Invest. PubMed Scopus Google Scholar, J. Clin. Invest. 1996; PubMed Scopus Google Scholar). The effect by or both increased gluconeogenesis and decreased intrahepatic in the and/or inhibition of by leptin Y. Zhang S. Kim K.-S. Lee J.-K. Kim K.-H. J. Biol. Chem. 1996; 271: 13939-13942Abstract Full Text Full Text PDF PubMed Scopus (216) Google Scholar). We (Amgen, Inc., Thousand for leptin and for and and for