Localized increases in CEPT1 and ATGL elevate plasmalogen phosphatidylcholines in HDLs contributing to atheroprotective lipid profiles in hyperglycemic GCK-MODY

Glucokinase-maturity onset diabetes of the young (GCK-MODY) represents a rare genetic disorder due to mutation in the glucokinase (GCK) gene. The low incidence of vascular complications in GCK-MODY makes it a natural paradigm for interrogating molecular mechanisms promoting vascular health under prolonged hyperglycemia. Clinical rate of misdiagnosis has remained high, and a reliable serum lipid biomarker that precedes genetic screening can facilitate correct diagnosis and treatment. Herein, we comprehensively quantitated 565 serum lipids from 25 classes in 105 subjects (42 nondiabetic controls, 30 GC K-MODY patients, 33 drug-naive, and newly-onset T2D patients). At false-discovery rate (FDR) < 0.05, several phosphatidylcholines (PCs) and plasmalogen PCs were specifically increased in GCK-MODY, while triacylglycerols (TAGs) and diacylglycerols (DAGs) were reduced. Correlation matrices between lipids uncovered coregulation between plasmalogen PCs (PCps) and glycerolipid precursors was distinctly enhanced in GCK-MODY compared to T2D. Strengthened positive correlations between serum PCps and circulating HDLs was specifically observed in hyperglycemic subjects (i.e. T2D and GCK-MODY) compared to normglycemic controls, suggesting that HDL-PCps may elicit distinct physiological effects under hyperglycemia. Amongst GCK-MODY patients, individuals harboring variants of GCK mutations with elevated PCps also exhibited higher HDLs. Isolated HDLs displayed localized increases (p < 0.05) in very-long-chain PUFA-PCs and PCps in GCK-MODY. Protein analyses revealed elevated levels of HDLresident ATGL (P = 0.003) and CEPT1 (P < 0.0001), which mediate critical steps of PCps production along the TAG-DAG-PC axis, in GCK-MODY relative to T2D. A panel of four lipids differentiated GCK-MODY from T2D with AUC of 0.950 (95% CI 0.903-9.997). This study provides the first evidence that enhanced recruitment of CEPT1 and ATGL onto HDLs essentially underlie the atheroprotective profiles associated with GCK-MODY. Resultant increases in the production of HDL-PCps and PUFA-PCs provides an active, circulating form of protection towards the vasculature of GCK-MODY, thereby lowering the incidence of vascular complications despite chronic exposure to hyperglycemia since birth.

Automated summary

GCK-MODY is a rare genetic disorder caused by mutations in the GCK gene, with low incidence of vascular complications, making it a model for studying molecular mechanisms promoting vascular health under prolonged hyperglycemia. Analysis of serum lipids in GCK-MODY patients revealed specific lipid abnormalities that can aid in diagnosis and treatment. The study also showed enhanced regulation of lipid metabolism and potential protective effects on the vasculature in GCK-MODY patients compared to T2D.