LETTERS TCF1 links GIPR signaling to the control of beta cell function and survival Jonathan E Campbell1, John R Ussher1,7, Erin E Mulvihill1, Jelena Kolic2,3, Laurie L Baggio1, Xiemen Cao1, Yu Liu1, Benjamin J Lamont1,7, Tsukasa Morii1,7, Catherine J Streutker4, Natalia Tamarina5, Louis H Philipson5, Jeffrey L Wrana1, Patrick E MacDonald2,3 & Daniel J Drucker1,6 The glucagon-like peptide-1 (GLP-1) receptor and the glucose- and survival1, rendering them attractive targets for the treatment dependent insulinotropic polypeptide (GIP) receptor transduce of type 2 diabetes (T2D). Indeed, the prevention of incretin degrada- nutrient-stimulated signals to control beta cell function1. tion by inhibiting dipeptidyl peptidase-4 (DPP4)5 and the augmenta- Although the GLP-1 receptor (GLP-1R) is a validated drug tion of incretin receptor signaling using GLP-1R agonists or emerging target for diabetes1, the importance of the GIP receptor co- and tri-agonists that target this pathway6,7 represent established (GIPR) for the function of beta cells remains uncertain2–4. and investigational strategies for the treatment of T2D. We demonstrate that mice with selective ablation of GIPR in The receptors for GLP-1 and GIP are highly related in structure; beta cells (MIP-Cre:GiprFlox/Flox; Gipr−/−βCell) exhibit lower both are regulated by transcription factor 7-like 2 (TCF7L2)8 in islets levels of meal-stimulated insulin secretion, decreased and control beta cell function and survival through cAMP-dependent expansion of adipose tissue mass and preservation of insulin pathways. Although genetic variation within the coding region of the sensitivity when compared to MIP-Cre controls. Beta cells from GLP1R gene has been linked to differences in fasting glucose levels Gipr−/−βCell mice display greater sensitivity to apoptosis and and in beta cell function in humans9, interpretation of the impor- markedly lower islet expression of T cell–specific transcription tance of the GIPR for beta cell function is confounded by genetic and factor-1 (TCF1, encoded by Tcf7), a protein not previously physiological data in humans and in mice and rats that suggest roles characterized in beta cells. GIP, but not GLP-1, promotes beta for the GIPR in the regulation of adipose-tissue accretion, body cell Tcf7 expression via a cyclic adenosine monophosphate weight and insulin sensitivity2–4,10. (cAMP)-independent and extracellular signal–regulated kinase GLP-1R agonists are increasingly used for the treatment of T2D (ERK)-dependent pathway. Tcf7 (in mice) or TCF7 (in humans) and obesity and are under investigation for the treatment of type 1 levels are lower in islets taken from diabetic mice and in diabetes1,11. By contrast, there is less interest in the GIPR as a drug humans with type 2 diabetes; knockdown of TCF7 in human target because of reports of defective GIP action in people with and mouse islets impairs the cytoprotective responsiveness to diabetes who are severely hyperglycemic12. Nevertheless, a brief GIP and enhances the magnitude of apoptotic injury, whereas period of insulin therapy markedly restores GIP responsiveness in restoring TCF1 levels in beta cells from Gipr−/−βCell mice lowers subjects with T2D (ref. 13), and GIPR activation is a key component of the number of apoptotic cells compared to that seen in MIP- the action of several novel co- and tri-agonists that are under investi- Cre controls. Tcf7−/− mice show impaired insulin secretion, gation as potential treatments for diabetes and obesity6,7. Accordingly, deterioration of glucose tolerance with either aging and/or to delineate the importance of GIPR signaling in beta cells inde- high-fat feeding and increased sensitivity to beta cell injury pendently of its potentially confounding actions in extrapancreatic relative to wild-type (WT) controls. Hence the GIPR-TCF1 axis tissues, we mated MIP-CreERT mice with GiprFlox/Flox mice to generate represents a potential therapeutic target for preserving both the mice with conditional and selective inactivation of Gipr in adult beta function and survival of vulnerable, diabetic beta cells. cells (Gipr−/−βCell) (Supplementary Fig. 1a). Levels of Gipr mRNA transcripts were 90% lower in the islets of Gipr−/−βCell mice than in The ingestion of nutrients triggers the secretion of multiple gut peptides, those of MIP-Cre mice, GiprFlox/Flox mice and WT mice (Fig. 1a and including GLP-1 and GIP, both of which are incretin hormones that Supplementary Fig. 1b), whereas Gipr expression in adipose tissue amplify insulin secretion. GLP-1 and GIP also control beta cell growth was not perturbed (Supplementary Fig. 1b). GIP robustly reduced 1Lunenfeld-Tanenbaum Research Institute, Mt. Sinai Hospital, Toronto, Ontario, Canada. 2Department of Pharmacology, University of Alberta, Edmonton, Alberta, Canada. 3Alberta Diabetes Institute, University of Alberta, Edmonton, Alberta, Canada. 4St. Michael’s Hospital, University of Toronto, Toronto, Ontario, Canada. 5Department of Medicine, Kovler Diabetes Center, University of Chicago, Chicago, USA. 6Department of Medicine, University of Toronto, Toronto, Ontario, Canada. 7Present addresses: Faculty of Pharmacy and Pharmaceutical Sciences, University of Alberta, Edmonton, Alberta, Canada (J.R.U.); Department of Medicine, University of Melbourne, Melbourne, Australia (B.J.L.); Akita University Graduate School of Medicine, Akita, Japan (T.M.). Correspondence should be addressed to D.J.D. ([email protected]). Received 24 August; accepted 26 October; published online 7 December 2015 ; doi:10.1038/nm.3997 NATURE MEDICINE ADVANCE ONLINE PUBLICATION 1 LETTERS G 0 min a G c 0 min 0 min b G G d 1,500 10 min Veh DPP4i 6.7 mM nM GIP 10 min 10 min 1,000 1 Veh DPP4i 25 * 2.5 30 min 6.7 mM 10 2.7 mM 1 2.7 mM + * 500 ) 2.5 20 * 2.0 1.5 0.15 * 20 400 2.5 * 20 500 0 * MIP-Cre 300 * 400 * * 200 * 300 2.0 * 15 1.5 Gipr –/–�Cell 15 2.0 15 200 ession 1.0 0.10 100 100 1.5 0 0 10 1.0 elease 1.5 xpr 10 tal insulin) 10 mRNA 1.0 5 MIP-Cre 0.5 Glucose (mM) Insulin (ng/ml) to e 1.0 0.5 0.05 Gipr –/–�Cell 5 0.5 5 Insulin (ng/ml) Gipr 0.5 0 0 Glucose (mM) Glucose (mM) Insulin r Insulin (ng/ml) elativ * (% of 0 0 30 60 90 120 e ell 0 0 C (R 0 0 0 -Cr � h Time (min) –/– e ell 0 8 16 24 32 –30 0 30 60 90 120 h –30 0 30 60 90 120 Ve MIP C -Cr � Ve DPP4i Gipr –/– Time (min) Time (min) DPP4i Time (min) MIP-Cre MIP Gipr –/–�Cell Gipr 8,000 * 6,000 * 2,000 0 min 8,000 2.0 100 e f MIP-Cre h 4,000 20 30 1,500 150 6,000 2,000 * 1,000 5 10 min 4,000 40 Gipr –/–�Cell 0 500 30 min 2,000 1.5 75 15 0 4 0 20 * 100 30 3 * Glucose 50 10 20 1.0 2 (% of baseline) at mass Glucose at mass 10 50 MIP-Cre F F MIP-Cre MIP-Cre 25 5 1 10 Glucose (mM) 0.5 (% of baseline) –/– Cell –/– Cell Insulin (ng/ml) � Gipr � Gipr –/–�Cell Gipr Insulin (ng/ml) 0 30 60 90 (% of body weight) (% of body weight) 0 0 0 0 0 Time (min) e ell 0 8 10 12 14 16 18 0 30 60 90 120 C 0 30 60 90 8 14 20 26 -Cr � –/– 0 7 14 Age (weeks) Time (min) MIP r Time (min) Age (weeks) Gip Pellet (mg) MIP-Cre MIP-Cre Gipr –/–�Cell Gipr –/–�Cell g MIP-Cre MIP-Cre MIP-Cre MIP-Cre i 15 –/–�Cell 4 –/–�Cell 15 –/–�Cell –/–�Cell Gipr Gipr Gipr Gipr 20 20 20 1,200 20 1,200 3 2 * 900 * 900 10 10 15 15 15 600 15 600 * 300 300 2 0 0 1 10 10 10 10 5 5 at mass 1 at mass F F Glucose (mM) Insulin (ng/ml) Glucose (mM) Insulin (ng/ml) 5 MIP-Cre 5 MIP-Cre 5 5 Glucose (mM) –/–�Cell Glucose (mM) 0 0 0 0 Gipr Gipr –/–�Cell (% of body weight) (% of body weight) 0 0 0 0 0 0 0 0 :0 :0 :0 :0 4:00 4:00 4:00 4:00 8 10 12 14 16 18 8 10 12 14 16 18 0 30 60 90 120 0 30 60 90 120 07:0008:00 11 1 07:0008:00 11 1 07:0008:00 11 1 07:0008:00 11 1 Time of day (h) Time of day (h) Time of day (h) Time of day (h) Age (weeks) Age (weeks) Time (min) Time (min) + −/− βCell G Figure 1 The phenotype of Gipr mice. (a) Gipr expression in mouse islets j MIP-Cre 0 min G G 6.7 mM G –/–�Cell 30 min 1 (n = 5). (b) Insulin release from mouse islets from 18-week-old mice on LFD Gipr 6.7 mM 2.7 mM 1 2.7 mM 1 nM Ex4 30 2.5 * 0.15 (n = 7). G, glucose. (c) Oral glucose tolerance test (OGTT) and plasma insulin MIP-Cre * ** 2.0 levels in 12-week-old (two left panels) and −/− βCell (two right panels) –/–�Cell MIP-Cre Gipr 20 0.10 Gipr * 1.5 * elease mice administered vehicle (veh) or sitagliptin (a dipeptidyl peptidase-4 inhibitor; tal insulin) 1.0 to DPP4i) (MIP-Cre, n = 5; Gipr−/−βCell, n = 9). (d) Glycemic (left) and insulin 10 * 0.05 0.5 Insulin (ng/ml) Insulin r Glucose (mM) (middle) response during OGTT, and glycemic (bottom) response during an insulin 0 0 (% of 0 tolerance test (ITT), all in 18-week-old LFD mice ( = 7).