363-OR: ChREBP-Beta Controls Both Proliferation and Cell Death of Pancreatic Beta Cells

Abstract

Glucose is a key physiological driver of adaptive beta cell mass expansion, promoting beta cell proliferation both in vitro and in vivo. Carbohydrate response element binding protein β (ChREBPβ) is upregulated in response to glucose and is required for glucose-stimulated beta cell proliferation. To study the role of ChREBPβ in beta cells, we knocked out (KO) or overexpressed (OE) ChREBPβ in mouse pancreatic beta cells using Cre LoxP approaches with either MIP-CreERT (induced by tamoxifen at 3 months of age), or the RIP-Cre model which leads to recombination specifically in β cells, early during embryogenesis (E9). We performed intraperitoneal glucose tolerance tests (IPGTTs) and assessed pancreata for proliferation (Ki67), cell death (TUNEL) and beta cell mass in the 4 mouse models. ChREBPβ MIP-CreERT KO mice displayed impaired glucose tolerance, with an increase of 25.3 ± 7.9% (N=3-4, P<0.05) in the area under the curve (AUC) of IPGTT. Heterozygous or complete Chrebpβ KOs in the RIP-Cre model resulted in an increase in the AUC of IPGTT compared with control littermates (20.1 ± 13.7% and 56 ± 7.1%, respectively; n=2-4). Beta cells from isolated ChREBPβ KO islets had 60.4 ± 17.4% less proliferation compared to control islets in 6 mM glucose, and 22.9 ± 2.4% (P<0.05, N=5) less in 20 mM glucose. Inducible OE of ChREBPβ resulted in 97.7 ± 6% increase in AUC of IPGTT (N=3, p<0.01) and fasting blood glucose levels were increased by 89 ± 13.2% (P<0.01). Similarly, when ChREBPβ was OE early in the embryogenesis of β cells, we observed AUC for GTT was increased by 2.4 ± 0.5 fold compared to non-Cre expressing litter mates (N=5, p<0.05). In both mouse models, the OE of ChREBPβ resulted in β cell death as assessed by TUNEL along with increased in Ki67 staining. Remarkably, the RIP-Cre mice had almost no remaining β cells at 4 months of age and were overtly diabetic. Taken these data together, we propose a molecular regulatory mechanism where ChREBPβ controls both beta cell proliferation and cell death depending on its abundance. Disclosure L.S. Katz: None. G. Brill: None. M.A. Herman: None. D. Scott: None. Funding National Institutes of Health