Inhibition of Citrate Cotransporter Slc13a5/mINDY by RNAi Improves Hepatic Insulin Sensitivity and Prevents Diet-Induced Non-Alcoholic Fatty Liver Disease in Mice

Mol Metab. 2016 Aug 13;5(11):1072-1082. doi: 10.1016/j.molmet.2016.08.004. eCollection 2016 Nov.

Abstract

Objective: Non-alcoholic fatty liver disease is a world-wide health concern and risk factor for cardio-metabolic diseases. Citrate uptake modifies intracellular hepatic energy metabolism and is controlled by the conserved sodium-dicarboxylate cotransporter solute carrier family 13 member 5 (SLC13A5, mammalian homolog of INDY: mINDY). In Drosophila melanogaster and Caenorhabditis elegans INDY reduction decreased whole-body lipid accumulation. Genetic deletion of Slc13a5 in mice protected from diet-induced adiposity and insulin resistance. We hypothesized that inducible hepatic mINDY inhibition should prevent the development of fatty liver and hepatic insulin resistance.

Methods: Adult C57BL/6J mice were fed a Western diet (60% kcal from fat, 21% kcal from carbohydrate) ad libitum. Knockdown of mINDY was induced by weekly injection of a chemically modified, liver-selective siRNA for 8 weeks. Mice were metabolically characterized and the effect of mINDY suppression on glucose tolerance as well as insulin sensitivity was assessed with an ipGTT and a hyperinsulinemic-euglycemic clamp. Hepatic lipid accumulation was determined by biochemical measurements and histochemistry.

Results: Within the 8 week intervention, hepatic mINDY expression was suppressed by a liver-selective siRNA by over 60%. mINDY knockdown improved hepatic insulin sensitivity (i.e. insulin-induced suppression of endogenous glucose production) of C57BL/6J mice in the hyperinsulinemic-euglycemic clamp. Moreover, the siRNA-mediated mINDY inhibition prevented neutral lipid storage and triglyceride accumulation in the liver, while we found no effect on body weight.

Conclusions: We show that inducible mINDY inhibition improved hepatic insulin sensitivity and prevented diet-induced non-alcoholic fatty liver disease in adult C57BL6/J mice. These effects did not depend on changes of body weight or body composition.

Keywords: 2-DG, 2-Deoxy-d-glucose; Citrate transport; EE, energy expenditure; EGP, endogenous glucose production; FA, fatty acids; FLD, fatty liver disease; GIR, glucose infusion rate; HE clamp, hyperinsulinemic-euglycemic clamp; HFD, high-fat diet; IEX, anion-exchange high-performance liquid chromatography; INDY, ‘I'm not dead Yet’; INDY/Slc13a5; Insulin resistance; KO, knockout; Lipid accumulation; ORO, oil red O; RER, respiratory exchange ratio; SCR, non-silencing scrambled control siRNA; SKM, skeletal muscle; Steatosis; T2D, type-2 diabetes; TCA, tricarboxylic acid; WAT, white adipose tissue; WD, western diet; e, epididymal; mINDY, Slc13a5/SLC13A5; p, perirenal; s, subcutaneous; siINDY, mINDY-specific siRNA; siRNA; solute carrier family 13, member 5.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Citrates
  • Citric Acid
  • Dicarboxylic Acid Transporters / physiology*
  • Diet
  • Insulin Resistance*
  • Lipid Metabolism*
  • Mice
  • Mice, Inbred C57BL
  • Non-alcoholic Fatty Liver Disease*
  • RNA Interference*
  • Symporters / physiology*

Substances

  • Citrates
  • Dicarboxylic Acid Transporters
  • Slc13a5 protein, mouse
  • Symporters
  • Citric Acid