Poster Presentation Australian Diabetes Society and the Australian Diabetes Educators Association Annual Scientific Meeting 2016

Lipid Droplet Proteome Reveals Role of Key Proteins in the Pathogenesis of Hepatic Insulin Resistance (#202)

Shilpa Nagarajan 1 , Zhiduan Su 2 , Amanda E Brandon 3 4 , Harrison Shtein 1 , Thinh Nguyen 1 , Rima Chaudhuri 2 , Eurwin Suryana 3 , David E James 1 2 , Gregory J Cooney 3 4 , Daniel J Fazakerley 2 , Andrew J Hoy 1 5
  1. Discipline of Physiology, School of Medical Sciences & Bosch Institute, Charles Perkins Centre, University of Sydney, Sydney, NSW, Australia
  2. School of Molecular Bioscience, Charles Perkins Centre, The University of Sydney, Sydney, NSW, Australia
  3. Diabetes and Metabolism Division, Garvan Institute of Medical Research, Sydney, NSW, Australia
  4. St Vincent’s Clinical School, Faculty of Medicine, University of New South Wales, Sydney, NSW, Australia
  5. Boden Institute of Obesity, Nutrition, Exercise & Eating Disorders, University of Sydney, Sydney, NSW, Australia

Lipid droplets (LDs) are cytoplasmic organelles composed of a neutral lipid core of triglycerides and cholesterol esters surrounded by dynamic membrane-associated proteins that govern the turnover of these lipids. Ectopic lipid accumulation in the LDs of key glucoregulatory tissues, namely the liver, has been associated with pathological metabolic responses and perturbed insulin signaling. However, our understanding of the mechanisms linking LD biology, in particular how insulin regulates LD dynamics, and the development of insulin resistance is incomplete. The aim of this study was to identify changes in the in vivo proteome of rat liver LDs under conditions of acute insulin stimulation in insulin-sensitive and insulin resistant rats.

A group of 16 Male Wistar rats were fed either a chow or high fat (HF) diet for 4 weeks. A cohort from the two diet groups received intravenous insulin for 10 mins. LDs were isolated from rat liver lysates using density-gradient centrifugation. LD proteins were subjected to tryptic digest, isobaric labelling and quantitative LC-MS/MS analysis. We identified 4831 proteins in hepatic LDs with 4115 proteins in all 16 rats across the 4 conditions. Systematic analysis to identify candidate proteins that are perturbed in insulin resistance identified 338 LD-associated proteins that were predicted to behave differently with impaired insulin action. Bioinformatic analysis of these 338 proteins identified KEGG pathway enrichment for metabolic, proteasomal, NAFLD, and insulin signaling pathways, and a number of novel candidates for their possible role in the pathogenesis of hepatic insulin resistance have been identified.

In conclusion, the lipid droplet proteome is sensitive to changes in diet and insulin stimulation and impairment in these pathways may underpin the development of insulin. Ongoing studies aim to delineate the function of candidate proteins in hepatic insulin resistance.