An INS-1 832/13 𝛽-Cell Proteome Highlights the Rapid Regulation of Fatty Acid Biosynthesis in Glucose-Stimulated Insulin Secretion.

Pancreatic beta cells secrete insulin in response to rising glucose levels, a process known as glucose-stimulated insulin secretion (GSIS). Here, we acquire proteomes of rat pancreatic INS-1 832/13 beta cells that were short-term stimulated with 11 different glucose concentrations from 0 to 20 mM, quantifying the response of 3703 proteins. Ensemble clustering of proteome profiles revealed unique response patterns of proteins expressed by INS-1 832/13 cells. Three hundred and fourteen proteins, amongst them proteins associated with vesicular SNARE interactions, protein export, and pancreatic secretion, increased in abundance upon glucose stimulation. In contrast, many proteins implicated in metabolic glucose sensing processes such as glycolysis, the TCA cycle, and the respiratory chain, did not respond. Interestingly, we observe that enzymes participating in fatty acid metabolism showed a "switch-on" response upon release of complete glucose starvation with no further changes in abundance upon increasing glucose levels. We speculate that increased activity of fatty acid metabolic activity might either be part of GSIS by replenishing membrane lipids required for vesicle-mediated exocytosis and/or by providing an electron sink to compensate for the increase in glucose catabolism. These findings offer new insights into beta cell function and may inform future strategies for targeting metabolic pathways in diabetes treatment. SUMMARY: We used high-throughput proteomics to capture comprehensive proteome changes 30 min post stimulation in the INS-1 832/13 beta cell line, a commonly used cell model in studying glucose-induced insulin secretion. Our results show that specific parts of the proteome respond promptly upon glucose exposure in this cell line. Furthermore, while many proteins canonically associated with GSIS did not change in abundance in the time frame and cell line investigated, our results attribute a specific role to fatty acid biosynthesis in the early steps of insulin secretion. By documenting protein abundance alterations in the initial phase of GSIS in the INS-1 832/13 beta cell line, our study highlights the necessity of sampling early time points, well-controlled study design and biological replicates in the study of beta cell function.