Analysis of the HepG2/erythrocyte glucose transporter locus in a family with type 2 (non-insulin-dependent) diabetes and obesity

HepG2/erythrocyte glucose transporter (GLUT1) gene in NIDDM: a population association study and molecular scanning in Japanese subjects

To evaluate the role of mutations in the glucose transporter (GLUT1) gene in Japanese patients with non-insulin-dependent diabetes mellitus (NIDDM), we first conducted a population association study using the XbaI polymorphism of the gene. A polymerase chain reaction (PCR)-based assay was developed and used for the analysis. When analysed in 91 diabetic patients and 87 non-diabetic control subjects, the distribution of the genotype frequency was significantly different between the two groups (p = 0.0025). The (-) allele was significantly associated with NIDDM (odds ratio 2.317, 95% confidence interval 1.425-3.768). To identify possible mutation(s) in the GLUT1 gene, which was in linkage disequilibrium with the (-) allele, all ten exons of the gene were analysed by PCR single-strand conformation polymorphism (SSCP) analysis in 53 diabetic patients with at least one (-) allele. Variant SSCP patterns were detected in exons 2, 4, 5, 7, 9 and 10. Sequence analysis revealed that all the variants represented silent mutations. One of the variants in exon 2, GCT (Ala15)-->GCC(Ala), created a HaeIII restriction site. This polymorphism was common in Japanese subjects with heterozygosity of 0.36 and polymorphism information content 0.29. We conclude that the structural mutation of GLUT1 is rare and not likely to be a major genetic determinant of NIDDM in Japanese subjects. The XbaI (-) allele of the GLUT1 gene appeared to be a genetic marker of NIDDM in Japanese subjects. The possibility of the presence of mutation(s) in the regulatory region of the gene or in another locus nearby could not be excluded.

The molecular biology of glucose transport: relevance to insulin resistance and non-insulin-dependent diabetes mellitus

The structure of the glucose transporter and the characteristics of the identified members of the facilitative glucose transporter gene family (GLUT1-5) are reviewed. The role of glucose transport in insulin resistance and non-insulin-dependent diabetes mellitus (NIDDM) is discussed. The potential contributions of genetic mutation and disruption of short- or long-term regulation of glucose transporters, particularly GLUT4, in insulin-sensitive tissues to the etiology of NIDDM are examined.

Molecular studies of the genetics of non-insulin-dependent diabetes mellitus

Non-insulin-dependent mellitus (NIDDM) is a common, multifactorial disease with a significant genetic component to disease susceptibility. Biometrical analysis of family data has consistently found evidence of the action of a major gene in determining susceptibility to NIDDM in families. However, the identity of the gene or genes that contribute to NIDDM in the general population is still not known. Recent advances in molecular biology have given investigators access to a number of plausible candidate genes for NIDDM and these have been used as test loci in association and linkage studies with inconsistent results. A review of the candidate gene studies in NIDDM suggests that the failure of these studies to identify specific loci involved in conferring susceptibility to NIDDM is, in part, due to failure to incorporate a number of biological features of the disease. The frequency of NIDDM in the population suggests that the alleles involved in NIDDM are common and their individual impact too small to be detected by simple single locus methods of analysis. Studies of other phenotypic forms of diabetes mellitus suggest that susceptibility to NIDDM is probably determined by alleles at more than one locus acting independently or in concert. The evolutionary history of certain populations may have isolated alleles conferring susceptibility to NIDDM in ethnically defined populations at high risk of NIDDM. These populations may provide a unique opportunity to identify specific genes involved in the complex etiology of NIDDM. © 1993 Wiley-Liss, Inc.

Missense glucokinase mutation in maturity-onset diabetes of the young and mutation screening in late-onset diabetes

We describe a codon 299 mutation in the glucokinase gene in a British pedigree with maturity-onset diabetes of the young (MODY) resulting in a substitution of glycine to arginine. One out of fifty patients diagnosed with classical late-onset type 2 diabetes mellitus was also found to have this mutation. All nine relatives of this patient who have inherited the mutation have type 2 diabetes, although six others without the mutation are also present with diabetes. The discovery that glucokinase mutations can cause MODY and was also found in ten affected members of a pedigree with type 2 diabetes in which MODY had not previously been considered indicates that diagnosis based on molecular pathology will be helpful in understanding the aetiology of type 2 diabetes.

Polymorphisms at the GLUT1 (HepG2) and GLUT4 (muscle/adipocyte) glucose transporter genes and non-insulin-dependent diabetes mellitus (NIDDM)

In order to determine the possible contribution of the GLUT1 (HepG2) glucose transporter gene to the inheritance of non-insulin-dependent diabetes mellitus (NIDDM), two restriction fragment length polymorphisms (RFLPs) and the related haplotypes at this locus were studied in 48 Italian diabetic patients and 58 normal subjects. Genotype frequencies for the XbaI polymorphism were significantly different between patients and controls (XbaI: chi 2 = 9.80, df = 2, P less than 0.0079). A significant difference was also found in the allele frequencies between NIDDM patients and controls (chi 2 = 9.39, df = 1, P less than 0.0022), whereas no differences were found for the StuI RFLP. No linkage disequilibrium was detected between the XbaI and StuI RFLPs in this sample. The analysis of the four haplotype frequencies (X1S1, X1S2, X2S1, X2S2) revealed a significant difference between diabetic patients and controls (chi 2 = 14.26, df = 3, P less than 0.002). By comparing single haplotype frequencies, a significant difference between the two groups was found for the X1S1 and X2S2 haplotypes. A two-allele RFLP at the GLUT4 (muscle/adipocyte) glucose transporter gene, detected with the restriction enzyme KpnI, was also examined; no differences were found between patients and controls for this RFLP. The finding of an association between polymorphic markers at the GLUT1 transporter and NIDDM suggests that this locus may contribute to the inherited susceptibility to the disease in this Italian population.

Genetics of non-insulin dependent diabetes mellitus

It is probable that NIDDM has a multifactorial origin in which environmental factors hasten the progression of the disease in genetically predisposed individuals. The importance of the genetic contribution to NIDDM has been established by the study of certain inbred populations, the almost 100% concordance of disease in monozygotic twins and by familial clustering. However, progress in identifying specific genetic factors involved in NIDDM has been slow and no consistent evidence has emerged supporting a major aetiological role for any of the genes so far studied. This may be due in part to methodological problems encountered in the identification of such disease susceptibility genes.