Bile Acid Sequestration Reduces Plasma Glucose Levels in db/db Mice by Increasing Its Metabolic Clearance Rate Maxi Meissner 1 *, Hilde Herrema 1,3,4 , Theo H. van Dijk 2 , Albert Gerding 2 , Rick Havinga 1 , Theo Boer 2 , Michael Mu ¨ ller 3,4 , Dirk-Jan. Reijngoud 2 , Albert K. Groen 1,2 , Folkert Kuipers 1,2 1 Department of Pediatrics, Center for Liver, Digestive and Metabolic Diseases, University Medical Center Groningen, University of Groningen, Groningen, The Netherlands, 2 Department of Laboratory Medicine, Center for Liver, Digestive and Metabolic Diseases, University Medical Center Groningen, University of Groningen, Groningen, The Netherlands, 3 Nutrigenomics Consortium, TI Food and Nutrition, Wageningen, The Netherlands, 4 Nutrition, Metabolism and Genomics Group, Division of Human Nutrition, Wageningen University, Wageningen, The Netherlands Abstract Aims/Hypothesis: Bile acid sequestrants (BAS) reduce plasma glucose levels in type II diabetics and in murine models of diabetes but the mechanism herein is unknown. We hypothesized that sequestrant-induced changes in hepatic glucose metabolism would underlie reduced plasma glucose levels. Therefore, in vivo glucose metabolism was assessed in db/db mice on and off BAS using tracer methodology. Methods: Lean and diabetic db/db mice were treated with 2% (wt/wt in diet) Colesevelam HCl (BAS) for 2 weeks. Parameters of in vivo glucose metabolism were assessed by infusing [U- 13 C]-glucose, [2- 13 C]-glycerol, [1- 2 H]-galactose and paracetamol for 6 hours, followed by mass isotopologue distribution analysis, and related to metabolic parameters as well as gene expression patterns. Results: Compared to lean mice, db/db mice displayed an almost 3-fold lower metabolic clearance rate of glucose (p = 0.0001), a ,300% increased glucokinase flux (p = 0.001) and a ,200% increased total hepatic glucose production rate (p = 0.0002). BAS treatment increased glucose metabolic clearance rate by ,37% but had no effects on glucokinase flux nor total hepatic or endogenous glucose production. Strikingly, BAS-treated db/db mice displayed reduced long-chain acylcarnitine content in skeletal muscle (p = 0.0317) but not in liver (p = 0.189). Unexpectedly, BAS treatment increased hepatic FGF21 mRNA expression 2-fold in lean mice (p = 0.030) and 3-fold in db/db mice (p = 0.002). Conclusions/Interpretation: BAS induced plasma glucose lowering in db/db mice by increasing metabolic clearance rate of glucose in peripheral tissues, which coincided with decreased skeletal muscle long-chain acylcarnitine content. Citation: Meissner M, Herrema H, van Dijk TH, Gerding A, Havinga R, et al. (2011) Bile Acid Sequestration Reduces Plasma Glucose Levels in db/db Mice by Increasing Its Metabolic Clearance Rate. PLoS ONE 6(11): e24564. doi:10.1371/journal.pone.0024564 Editor: Irina Agoulnik, Florida International University, United States of America Received December 10, 2010; Accepted August 15, 2011; Published November 7, 2011 Copyright: ß 2011 Meissner et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Funding: This study was funded by an unrestricted research grant of the Groningen Expert Center for Kids with Obesity (GECKO) and DaiichiSankyo (Pirsipanny, NJ). Neither GECKO nor DaiichiSankyo took part in the data collection nor the preparation of the manuscript. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. Competing Interests: The authors have declared that no competing interests exist. * E-mail: meissner.maxi@gmail.com Introduction Type 2 diabetes is a major health problem worldwide [1]. The predominant features of type 2 diabetes entail increased fasting blood glucose levels, increased plasma triglycerides and LDL- cholesterol levels, as well as disturbed peripheral glucose utilization [2–4]. The use of bile acid sequestrants (BAS) for lowering of LDL- cholesterol levels is well established [5–7]. More recently, Colesevelam HCl, a BAS, has been indicated by the FDA to improve glycemic control in patients with type 2 diabetes [8–10]. So far, however, the actual changes in hepatic and/or peripheral glucose metabolism upon BAS supplementation are not understood. Bile acids are synthesized from cholesterol in the liver. Upon secretion into bile, bile acids function to emulsify fats in the small intestine. Most of the secreted biliary bile acids are reabsorbed in the ileum (enterohepatic circulation). Sequestrants interfere with the enterohepatic circulation of bile acids by binding them in the intestine, thereby inhibiting their reabsorption and promoting their fecal loss. As a consequence, the liver increases bile acid synthesis and subsequently cholesterol uptake from the circulation thereby reducing LDL-cholesterol levels [11,12]. To date, there is a lack of understanding how BAS reduce plasma glucose levels. However, a large body of research suggests that bile acids modulate hepatic glucose metabolism via signaling pathways mediated by the nuclear receptor NRH1H4 (Fxr) in diabetes [13–19]. Fxr is expressed in the liver, intestine, adrenal gland and kidney [20], and it acts to inhibit de novo bile acid synthesis when activated by bile acids in the liver [21]. Paradoxically, both agents that inhibit de novo bile acid synthesis, such as bile acids themselves and synthetic Fxr ligands [14,22], as well as agents that increase de novo bile acid synthesis such as BAS, were shown to reduce plasma glucose levels in diabetic mice [23,24]. Thus, regulation of bile acid-mediated changes in blood glucose levels remains elusive. PLoS ONE | www.plosone.org 1 November 2011 | Volume 6 | Issue 11 | e24564