Ubiquitination of glucose and lipid metabolic proteins is altered in diabetic rat livers

Authors

Ehab M. Abo-Ali, St. John's University and CUNY New York City College of TechnologyFollow
Divya K. Shetty, St. John's University
Rhema Khairnar, St. John's University
Sunil Kumar, St. John's University
Vikas V. Dukhande, St. John's University

Document Type

Article

Publication Date

1-15-2026

Abstract

Aim: Post-translational modifications in the form of phosphorylation of key insulin signaling proteins are known to contribute to insulin resistance by regulating the activity and function of proteins such as IR, IRS, and Akt. However, little is known about the ubiquitination code in an insulin-resistant state. Several studies have connected the ubiquitin-proteasome system to dysfunctional insulin signaling. We aimed to investigate how reduced sensitivity to insulin affects hepatic ubiquitination in vivo.

Materials and methods: We studied hepatic ubiquitination patterns in a high-fat diet and low-dose (40 mg/kg) streptozotocin (HF-STZ) animal model of diabetes. Affinity pull-down and proteomics techniques were employed to explore differential ubiquitination as well as lysine-48 (K48)- and lysine-63 (K63)-linkage-specific differences between control and diabetic animals. Bioinformatic tools such as gene ontology, KEGG pathway, and STRING analysis were used to categorize the ubiquitinated proteins. Western blotting and immunoprecipitation were used to validate the proteomics results of selected hits. Lipid metabolism was further investigated using triglyceride content assay and expression of lipid metabolic proteins.

Key findings: Proteomics data showed that both the overall and linkage-specific ubiquitination were higher in diabetic rat livers. Bioinformatic analysis of the top 150 protein hits in each ubiquitination category revealed enrichment in metabolic processes involving glucose and lipid metabolism. Glycogen synthase 2 (GYS2) levels were moderately elevated with reduced total and K48-polyubiquitination in HF-STZ rat livers.

Significance: Our study provides insight into hepatic ubiquitination in an animal model of insulin resistance; further studies could tease out potential targets for the pharmacotherapy of metabolic disorders

Comments

This is the author's accepted manuscript of an article originally published in Life Sciences, available at https://doi.org/10.1016/j.lfs.2025.124120.