Mutation-function analysis in the lipoprotein lipase gene of Chinese patients with hypertriglyceridemic type 2 diabetes

Abstract

OBJECTIVE: To investigate the role of lipoprotein lipase (LPL) gene on Chinese patients with hypertriglyceridemic type 2 diabetes. METHODS: Three subject groups, including hypertriglyceridemic group, normalipidemic type 2 diabetes group and healthy controls, were recruited and screened for sequence changes in LPL gene with PCR, SSCP, restriction analysis and direct DNA sequencing. LPL mass and activity in post-heparin plasma and in in vitro expression were investigated. Comparative modeling was performed via Swiss-PDB Viewer to provide the potential 2-D structures of wildtype and mutant proteins. RESULTS: Four missense mutations, Ala71Thr, Val18Ile, Gly188Glu and Glu242Lys, were identified in patients with hypertriglyceridemic type 2 diabetes, and not in both normalipidemic diabetes and the control subjects. The four missense mutations were located in the highly conserved amino acid sites, which are involved in highly conserved exon 3, 5, or 6 regions. They led to reduced LPL mass and enzyme activities in both post-heparin plasma and in vitro expression. The modeled structures displayed the differences to a great extent between the mutant and wide-type molecules. CONCLUSION: These results indicated that the 4 missense mutations lead to LPL deficiency and subsequent hypertriglyceridemia. The LPL deficiency predispose a progressive diabetic pathway to those affected individuals. LPL gene is one of susceptibility gene for hypertriglyceridemic type 2 diabetes.