CERS2-Dependent Sphingolipid Control of Human Beta-Cell Function and Resilience

About This Grant

PROJECT SUMMARY Type 1 diabetes (T1D) is an autoimmune disease characterized by the destruction of insulin-producing pancreatic β-cells, leading to chronic hyperglycemia and insulin deficiency. Emerging evidence suggests that disrupted β-cell lipid metabolism accelerates dysfunction, highlighting the importance of lipid pathways for β- cell health. Human β-cells store excess fatty acids in lipid droplets and depend on sphingolipids (SLs) - particularly very-long-chain SLs (VLCSLs) - for proper insulin processing and secretion. Significantly, islets from individuals with recent-onset T1D exhibit reduced SL levels and diminished expression of ceramide synthase 2 (CERS2), the enzyme responsible for VLCSL synthesis. Decreased CERS2 activity shifts the lipid balance toward shorter-chain ceramides, impairing β-cell function, while elevated VLCSL levels provide protection. Moreover, CERS2 loss-of-function variants strongly correlate with increased diabetes risk. Despite this knowledge, it remains unclear how specific SL subtypes influence insulin secretion and β-cell viability in human islets. Our long-term goal is to identify the cellular and molecular networks essential for maintaining human β-cell identity and function, thereby preventing insulin deficiency. Our preliminary data indicate that perturbations in β-cell lipid metabolism - such as lipid droplet depletion or CERS2 knockdown - cause impaired insulin secretion and activate of stress responses, including ER stress, oxidative stress, and inflammation. We hypothesize CERS2-derived VLCSLs constitute a vital lipid hub linking fatty acid storage to gene networks crucial for insulin maturation, insulin granule trafficking, and β-cell survival. To test this hypothesis, we propose two aims using human islets. Aim 1 will define how CERS2-dependent pathways influence β-cell function by β- cell-specific CERS2 knockdown. We will employ integrated lipidomic and transcriptomic profiling to map the CERS2-regulated sphingolipidome and gene network alterations, while assessing insulin secretion, stress responses, and β-cell integrity in vitro and in vivo. Aim 2 will test whether boosting CERS2 expression in β- cells shifts the shingolipidome toward protective VLCSLs and protects β-cells from diabetogenic stressors, as assessed by insulin secretion, cell viability, and stress markers. The proposed research addresses a critical and unresolved question regarding how CERS2-derived VLCSLs influence insulin secretion and viability in human β-cells – representing an innovative exploration of lipid mechanisms underpinning β-cell function and failure in T1D. This research aligns with HIRN’s mission to understand β-cell loss in T1D and develop novel strategies to preserve or restore functional β-cell mass. It also meets objectives outlined in RFA-DK-26-009 by advancing innovative, early-stage T1D research. Ultimately, this work will inform lipid-based therapeutic strategies to maintain insulin-producing β-cell mass, addressing critical challenges in diabetes prevention and treatment.