A comprehensive lipidomic screen of pancreatic β-cells using mass spectroscopy defines novel features of glucose-stimulated turnover of neutral lipids, sphingolipids and plasmalogens

Gemma L Pearson; Natalie Mellett; Kwan Yi Chu; Ebru Boslem; Peter J Meikle; Trevor J Biden

doi:10.1016/j.molmet.2016.04.003

A comprehensive lipidomic screen of pancreatic β-cells using mass spectroscopy defines novel features of glucose-stimulated turnover of neutral lipids, sphingolipids and plasmalogens

Mol Metab. 2016 Apr 13;5(6):404-414. doi: 10.1016/j.molmet.2016.04.003. eCollection 2016 Jun.

Authors

Gemma L Pearson¹, Natalie Mellett², Kwan Yi Chu³, Ebru Boslem¹, Peter J Meikle⁴, Trevor J Biden⁵

Affiliations

¹ Diabetes and Metabolism Division, Garvan Institute of Medical Research, 384 Victoria St, Darlinghurst, NSW, 2010, Australia; St. Vincent's Clinical School, Faculty of Medicine, University of New South Wales, Australia.
² Baker IDI Heart and Diabetes Institute, Melbourne, Australia.
³ Diabetes and Metabolism Division, Garvan Institute of Medical Research, 384 Victoria St, Darlinghurst, NSW, 2010, Australia.
⁴ Baker IDI Heart and Diabetes Institute, Melbourne, Australia. Electronic address: peter.meikle@bakeridi.edu.au.
⁵ Diabetes and Metabolism Division, Garvan Institute of Medical Research, 384 Victoria St, Darlinghurst, NSW, 2010, Australia; St. Vincent's Clinical School, Faculty of Medicine, University of New South Wales, Australia. Electronic address: t.biden@garvan.org.au.

Abstract

Objective: Glucose promotes lipid remodelling in pancreatic β-cells, and this is thought to contribute to the regulation of insulin secretion, but the metabolic pathways and potential signalling intermediates have not been fully elaborated.

Methods: Using mass spectrometry (MS) we quantified changes in approximately 300 lipid metabolites in MIN6 β-cells and isolated mouse islets following 1 h stimulation with glucose. Flux through sphingolipid pathways was also assessed in (3)H-sphinganine-labelled cells using TLC.

Results: Glucose specifically activates the conversion of triacylglycerol (TAG) to diacylglycerol (DAG). This leads indirectly to the formation of 18:1 monoacylglycerol (MAG), via degradation of saturated/monounsaturated DAG species, such as 16:0_18:1 DAG, which are the most abundant, immediate products of glucose-stimulated TAG hydrolysis. However, 16:0-containing, di-saturated DAG species are a better direct marker of TAG hydrolysis since, unlike the 18:1-containing DAGs, they are predominately formed via this route. Using multiple reaction monitoring, we confirmed that in islets under basal conditions, 18:1 MAG is the most abundant species. We further demonstrated a novel site of glucose to enhance the conversion of ceramide to sphingomyelin (SM) and galactosylceramide (GalCer). Flux and product:precursor analyses suggest regulation of the enzyme SM synthase, which would constitute a separate mechanism for localized generation of DAG in response to glucose. Phosphatidylcholine (PC) plasmalogen (P) species, specifically those containing 20:4, 22:5 and 22:6 side chains, were also diminished in the presence of glucose, whereas the more abundant phosphatidylethanolamine plasmalogens were unchanged.

Conclusion: Our results highlight 18:1 MAG, GalCer, PC(P) and DAG/SM as potential contributors to metabolic stimulus-secretion coupling.

Keywords: (O), ether lipid; (P), plasmalogen; ATGL, adipose tissue glycerolipase; CE, cholesterol ester; COH, free cholesterol; Ceramide; DAG, diacylglycerol; Diacylglycerol; FA, fatty acid; GSIS, glucose-stimulated insulin secretion; GalCer, galactosylceramide; GluCer, glucosylceramide; HSL, hormone sensitive lipase; Insulin secretion; KRHB, Krebs Ringer Hepes Buffer; MAG, monacylglycerol; MHC, monohexosylceramide; MS, mass spectrometry; Monacylglycerol; PC, phosphatidylcholine; PE, phosphatidylethanolamine; PI, phosphatidylinositol; PKD, protein kinase D; PLA2, phospholipase A2; Pancreatic β-cell; Plasmalogen; SM, sphingomyelin; TAG, triacylglycerol.