Protein ubiquitination in rat liver is insulin sensitive and is altered in insulin resistant high-fat fed rats — ASN Events
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  3. Protein ubiquitination in rat liver is insulin sensitive and is altered in insulin resistant high-fat fed rats

Protein ubiquitination in rat liver is insulin sensitive and is altered in insulin resistant high-fat fed rats (#253)

Shilpa Nagarajan 1 , Jessie McKenna 2 , Amanda E Brandon 3 4 , Harrison Shtein 1 , Eurwin Suryana 4 , Greg J Cooney 3 4 , Darren N Saunders 2 5 , Andrew J Hoy 1 6
  1. University of Sydney, Sydney, NSW, Australia
  2. Kinghorn Cancer Centre, Garvan Institute of Medical Research, Darlinghurst, NSW, Australia
  3. St Vincent’s Clinical School, Faculty of Medicine, University of New South Wales, Sydney, NSW, Australia
  4. Diabetes and Metabolism Division, Garvan Institute of Medical Research, Darlinghurst, NSW , Australia
  5. School of Medical Sciences, Faculty of Medicine, University of New South Wales, Sydney, NSW, Australia
  6. Boden Institute of Obesity, Nutrition, Exercise & Eating Disorders, University of Sydney, Sydney, NSW , Australia

Ubiquitin is a crucial post-translational modification in cellular signalling, regulating numerous processes such as metabolism, transcription, and translation. Dysfunction of the ubiquitin proteasome system is associated with multiple diseases including cancer but its role in metabolic disease is not well characterised. The aim of this study was to identify the in vivo ubiquitinated proteome in rat liver and determine changes in the ubiquitome under conditions of insulin resistance and acute insulin stimulation.

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. Ubiquitinated proteins were isolated from rat liver lysates using ubiquitin affinity purification followed by nano LC-MS/MS identification and label-free quantification.

HF fed rats were heavier, had increased epidydimal fat mass and liver TAG content compared to chow fed controls. Insulin stimulation resulted in similar final insulin levels between diet groups yet insulin-stimulated liver pAkt was blunted in HF fed rats compared to chow. We identified 1267 ubiquitinated proteins in rat liver with 882 identified in all conditions. Bioinformatics analysis of these 882 proteins identified the KEGG pathway enrichment for metabolic pathways, TCA cycle, glycolysis/gluconeogenesis, fatty acid metabolism, and carbon metabolism. We also identified ubiquitinated proteins that were unique to each treatment group. For example, 67 proteins were only identified in animals fed a chow diet where as 163 proteins were uniquely identified in HF fed animals. 

In conclusion, the rat liver ubiquitinome is sensitive to diet and insulin stimulation and this is perturbed in insulin resistance. Further studies will validate these observations and investigate their significance in liver biology.