Identification and Functional Analysis of Mutations in FAD-Binding Domain of Mitochondrial Glycerophosphate Dehydrogenase in Caucasian Patients with Type 2 Diabetes Mellitus

Abstract

Ca2+-responsive mitochondrial FAD-linked glycerophosphate dehydrogenase (mGPDH) is a key component of the pancreatic beta-cell glucose-sensing device. The purpose of this study was to examine the association of mutations in the cDNA coding for the FAD-binding domain of mGPDH and to explore the functional consequences of these mutations in vitro. To investigate this association in type 2 diabetes mellitus, we studied a cohort of 168 patients with type 2 diabetes and 179 glucose-tolerant control subjects of Spanish Caucasian origin by single-stranded conformational polymorphism analysis. In vitro site-directed mutagenesis was performed in the mGPDH cDNA sequence to reproduce those mutations that produce amino acid changes in a patient with type 2 diabetes. We detected mutations in the mGPDH FAD-binding domain in a single patient, resulting in a Gly to Arg amino acid change at positions 77, 78, and 81 and a Thr to Pro at position 90. In vitro expression of the mutated constructs in Xenopus oocytes resulted in a significantly lower enzymatic activity than in cells expressing the wild-type form of the enzyme. Our results indicate that although mutations in the mGPDH gene do not appear to have a major role in type 2 diabetes mellitus, the reduction in mGPDH enzymatic activity associated with the newly described mGPDH mutations suggests that they may contribute to the disease in some patients.

Haploinsufficiency of the GPD2 gene in a patient with nonsyndromic mental retardation

“…However, the involvement of this mutation in the pathogenesis of T2DM remained unclear, as it was not present in his diabetic brother. In addition, neither linkage studies nor mutation analysis has failed to Wnd an association between GPD2 gene and T2DM suggesting that mutations in the GPD2 gene do not appear to have a major role in T2DM (MacDonald et al 1997;Gudayol et al 2001). Additionally, four loci (not including GPD2 gene) containing variants that confer T2DM risk have been recently identiWed using highdensity arrays (Sladek et al 2007).…”

Closely spaced multiple mutations as potential signatures of transient hypermutability in human genes

“…a C4T SNS mutation and an A4G SNS mutation are also present at 1,450 bp 5 0 and 143 bp 3 0 to the mutation cluster, respectively, in the KNG1 gene. C: A quadruplet mutation identified in the GPD2 gene [Gudayol et al, 2001]. Barred sequences denote deleted bases whereas base substitutions are indicated below the wild-type sequence.…”

A Refined Analysis of Superoxide Production by Mitochondrial sn-Glycerol 3-Phosphate Dehydrogenase

“…Tissues with characteristically low expression of mGPDH, such as liver, kidney, and heart, show increased enzyme activity in response to thyroid and steroid hormones, whereas those with high expression are generally insensitive to this regulation (3,(5)(6)(7). Variations in mGPDH expression, activity, or genetic sequence have been associated with increased plasma levels of glycerol and free fatty acids (8), mental retardation (9), cancers (5, 10 -12), and diabetes (13,14). Despite its important role in various metabolic processes, mGPDH remains poorly characterized relative to other components of the electron transport chain.…”