Polymorphism of the glucagon receptor gene and non-insulin-dependent diabetes mellitus in the Russian population

Role of Glucagon and Its Receptor in the Pathogenesis of Diabetes

Various theories for the hormonal basis of diabetes have been proposed and debated over the past few decades. Insulin insufficiency was previously regarded as the only hormone deficiency directly leading to metabolic disorders associated with diabetes. Although glucagon and its receptor are ignored in this framework, an increasing number of studies have shown that they play essential roles in the development and progression of diabetes. However, the molecular mechanisms underlying the effects of glucagon are still not clear. In this review, recent research on the mechanisms by which glucagon and its receptor contribute to the pathogenesis of diabetes as well as correlations between GCGR mutation rates in populations and the occurrence of diabetes are summarized. Furthermore, we summarize how recent research clearly establishes glucagon as a potential therapeutic target for diabetes.

Linkage study of the glucagon receptor gene with type 2 diabetes mellitus in Italians

Type 2 diabetes mellitus (T2DM) is a common complex trait disorder. Multiple genome scans have identified different loci in linkage with T2D, including a locus on chromosome 17q24-25. Because the glucagon receptor gene ( GCR ) resides on chromosome 17q25, it might be responsible for the linkage identified in the same region. In a combined French-Sardinian study of GCR , there is an association of Gly 40 Ser mutation with T2DM, confirmed by a UK study but not by others. Our goal was to study this selected region of chromosome 17 in a group of Italian patients with late- and early-onset T2DM by genotyping the microsatellites D17S801, D17S937, and D17S1806 and by performing nonparametric multipoint linkage analysis (Merlin 2000-2002) with allele frequencies calculated from sib-pairs data. We recruited from the center of Italy late-onset sib pairs with T2DM and families with maturity-onset diabetes of the young/early-onset T2DM (N = 503). The linkage analysis at chromosome 17q25 reported no positive lod scores in the total T2D sib pairs, in the late-onset T2D group, and in the early-onset T2D group. Although the study does not show evidence for linkage in this chromosomal region in our Italian cohort, we cannot a priori exclude the possibility of an allelic or genotypic association. Nevertheless, we may conclude that GCR does not play a major role in the pathogenesis of T2DM in Italians.

Genetics of Type 2 diabetes

Type 2 diabetes (T2D) has become a health-care problem worldwide, with the rise in disease prevalence being all the more worrying as it not only affects the developed world but also developing nations with fewer resources to cope with yet another major disease burden. Furthermore, the problem is no longer restricted to the ageing population, as young adults and children are also being diagnosed with T2D. In recent years, there has been a surge in the number of genetic studies of T2D in attempts to identify some of the underlying risk factors. In this review, I highlight the main genes known to cause uncommon monogenic forms of diabetes (e.g. maturity-onset diabetes of the young--MODY--and insulin resistance syndromes), as well as describe some of the main approaches used to identify genes involved in the more common forms of T2D that result from the interaction between environmental risk factors and predisposing genotypes. Linkage and candidate gene studies have been highly successful in the identification of genes that cause the monogenic variants of diabetes and, although progress in the more common forms of T2D has been slow, a number of genes have now been reproducibly associated with T2D risk in multiple studies. These are discussed, as well as the main implications that the diabetes gene discoveries will have in diabetes treatment and prevention.

Analysis of the Gly40Ser polymorphism in the glucagon receptor gene in a German non-insulin-dependent diabetes mellitus population

A heterozygous polymorphism changing GGT40 (Gly) to AGT40 (Ser) in the glucagon receptor gene (GCG-R) was reported to be associated with non-insulin-dependent diabetes mellitus (NIDDM). A possible involvement of this polymorphism in impaired glucose tolerance was also suggested in a French population. However, the prevalence of this polymorphism differs markedly among different ethnic groups, whereby the results in German populations were found to be contradictory. We thus investigated the association of this mutation with NIDDM and healthy subjects in 508 German subjects (196 NIDDM, and 312 controls). None of the control subjects, but one of the NIDDM patients demonstrated the Gly40Ser polymorphism. Since no first-degree relative of the index patient had this genetic variance, a de novo mutation is suggested. Although the frequency of the Gly40Ser polymorphism in NIDDM observed in France is not confirmed in our population, this genetic variance is also evident in Germany.