Molecular genetics of diabetes mellitus in Chinese subjects: identification of mutations in glucokinase and hepatocyte nuclear factor-1alpha genes in patients with early-onset type 2 diabetes mellitus/MODY.

AIMS: To examine the prevalence of identified MODY-related genes in Chinese subjects with early onset Type 2 diabetes mellitus and a positive family history of diabetes and to look for possible associations between the gene mutations and the development of diabetes. METHODS: Ninety-two unrelated Chinese subjects with diabetes diagnosed before the age of 40 years who had a positive family history of diabetes were screened for mutations in hepatocyte nuclear factors (HNF-1alpha and HNF-4alpha) and glucokinase genes by direct sequencing. The family members of patients with mutations and 100 healthy controls were also examined. RESULTS: Mutations in the HNF-1alpha and the glucokinase genes were found in 5% and 3% of the diabetic subjects, respectively but no mutations were found in the coding region of the HNF-4alpha gene. Three mutations found in the glucokinase gene were novel missense mutations (I110T, A119D and G385V). The mutations in the HNF-1alpha gene were also new and included four missense mutations (G20R, R203H, S432C, I618M) and one splice acceptor site mutation (IVS2nt-1G-->A). Patients with mutations in these genes were clinically heterogeneous with respect to phenotype and basal pancreatic beta cell function. CONCLUSIONS: Genetic factors such as mutations in the HNF-1alpha and glucokinase genes may be important in the development of diabetes in Chinese people, especially when the disease is of early onset.     

The hepatic nuclear factor-1alpha G319S variant is associated with early-onset type 2 diabetes in Canadian Oji-Cree

Mutations in the gene encoding hepatic nuclear factor-1alpha (HNF-1alpha) have been found in patients with maturity-onset diabetes of the young. We identified a new variant in the HNF-1alpha gene, namely G319S, in Ontario Oji-Cree with type 2 diabetes. G319S is within the proline II-rich domain of the trans-activation site of HNF-1alpha and alters a glycine residue that is conserved throughout evolution. S319 was absent from 990 alleles taken from subjects representing six other ethnic groups, suggesting that it is private for Oji-Cree. We found that 1) the S319 allele was significantly more prevalent in diabetic than nondiabetic Oji-Cree (0.209 vs. 0.087; P = 0.000001); 2) S319/S319 homozygotes and S319/G319 heterozygotes, respectively, had odds ratios for type 2 diabetes of 4.00 (95% confidence interval, 2.65-6.03) and 1.97 (95% confidence interval, 1.44-2.70) compared with G319/G319 homozygotes; 3) there was a significant difference in the mean age of onset of type 2 diabetes, with G319/G319, S319/G319, and S319/S319 subjects affected in the fifth, fourth, and third decades of life, respectively. In subjects with type 2 diabetes, we also found significantly lower body mass index and significantly higher post-challenge plasma glucose in S319/S319 and S319/G319 compared with G319/G319 subjects. Finally, among nondiabetic subjects, S319/G319 heterozygotes had significantly lower plasma insulin than G319/G319 homozygotes. The presence of the private HNF-1alpha G319S variant in a large number of Oji-Cree with type 2 diabetes and its strong association with type 2 diabetes susceptibility are unique among human populations. Also, G319S is associated with a distinct form of type 2 diabetes, characterized by onset at an earlier age, lower body mass, and a higher postchallenge plasma glucose.     

Clinical characteristics, beta-cell function, HLA class II and mutations in MODY genes in non-paediatric subjects with Type 1 diabetes without pancreatic autoantibodies.

OBJECTIVE: To study clinical characteristics, beta-cell function, HLA typing and mutations in the hepatocyte nuclear factor (HNF)-1alpha and HNF-4alpha genes in Type 1 diabetes mellitus (T1D) patients without pancreatic autoantibodies. DESIGN AND METHODS: Twenty patients without pancreatic autoantibodies (Ab neg) and 20 with autoantibodies (Ab pos), age/gender matched, were included (age 17-34 years). Islet cell, glutamic acid decarboxylase, tyrosine phosphatase and insulin autoantibodies, basal and stimulated C-peptide were measured. HLA-DRB1-DQA1-DQB1 typing and screening for mutations in the HNF-1alpha and HNF-4alpha genes were performed. RESULTS: No differences were found in clinical presentation, metabolic control and beta-cell function in the two groups (onset or after 12 months). DRB1*0301-DQA1*0501-DQB1*0201 was the most frequent haplotype in both groups but we found a higher proportion of protective T1D haplotypes and Asp(beta57) in the Ab neg group, but in all the cases in combination with susceptible T1D haplotypes. We found two previously reported polymorphisms (HNF-1alpha, Ala98Val; HNF-4alpha, Thr130Ile) in Ab neg and a new variant (Ser165Gly) in the HNF-4alpha gene in an Ab pos subject. Conclusions In a non-paediatric population with newly diagnosed T1D, the absence of islet antibodies does not imply clinical or metabolic differences when compared with those cases with islet antibodies. Despite a similar HLA-DR/DQ typing, the presence of protective alleles and molecular properties in a higher proportion in the Ab neg group suggests that these factors could modulate the presence or absence of islet antibodies. Variants in HNF-1alpha and HNF-4alpha are unlikely to be major contributors to the pathogenesis of diabetes in antibody-negative T1D.     

Genetic variants of hepatocyte nuclear factor-1beta in Chinese young-onset diabetic patients with nephropathy

In Hong Kong, the prevalence of diabetes is estimated to be 2% in the young population. In the diabetic population, 30% of patients have diagnosis before the age of 40 years. Besides, 30% of young diabetic patients have varying degrees of albuminuria. Mutations in the gene encoding the hepatocyte nuclear factor (HNF)-1beta are associated with a subtype of maturity-onset diabetes of the young (MODY 5) characterized by urogenital abnormalities. We examined 74 unrelated Chinese subjects with young-onset diabetes complicated by nephropathy for variants in this gene.The HNF-1beta gene was screened by direct sequencing and the functional properties of wild-type and mutant proteins were analyzed by transactivation analysis.A novel variant in exon 3 (E260D) was found in one patient. Extended family analysis revealed four other siblings carrying this variant. One subject had diabetes and another had impaired glucose tolerance. Another sibling had microalbuminuria but normal glucose tolerance. Transfection studies showed insignificant differences in transactivation ability between wild-type and mutated HNF-1beta. A silent polymorphism Q378Q was identified in another unrelated subject.These results suggest genetic variants in HNF-1beta are not a common cause of young-onset diabetes or diabetic nephropathy in Chinese, but may modify disease manifestation and progression. Other potential candidate genes should be looked for to account for the high prevalence of young-onset diabetes and nephropathy in this population.     

Heterogeneity in young adult onset diabetes: aetiology alters clinical characteristics.

AIMS: To describe the characteristics of hepatocyte nuclear factor (HNF) 1 alpha mutation carriers diagnosed with diabetes after 25 years and compare them with young-onset Type 2 diabetic patients (YT2D) diagnosed at the same age. SUBJECTS AND METHODS: We studied 44 (21 male, 23 female) patients with HNF-1 alpha mutations diagnosed with diabetes at ages 25-45 years and 44 YT2D subjects matched for sex and age of diagnosis. RESULTS: Median age of onset of diabetes was 35 years in both groups. The HNF-1 alpha group demonstrated: lower body mass index (25.1 vs. 30.7 kg/m2; P < 0.001) and lower fasting triglycerides (1.37 vs. 2.96 mmol/l; P = 0.001) with similar fasting cholesterol level. They had lower glycated haemoglobin A1c (7.3 vs. 8.5%; P = 0.015) despite greater duration of diabetes (24 vs. 16 years; P = 0.02) and less frequent treatment with insulin (21% vs. 55%; P = 0.002). They were less likely to be treated for hypertension (13.3% vs. 56.3%; P = 0.009). Importantly, no difference was observed in reported parental history of diabetes between the two groups (65.9% vs. 63.6%; P = 0.92). Logistic regression showed that triglyceride levels and presence of anti-hypertensive treatment were the most important independent variables. CONCLUSIONS: Patients with HNF-1 alpha mutations may present with diabetes as young adults between the ages of 25-45 years. In this age range a wide differential diagnosis of diabetes is observed. Conventional criteria of age of onset and family history will not differentiate HNF-1 alpha mutation carriers from YT2D subjects in this age range, but features of the metabolic syndrome, in particular fasting triglycerides and hypertension, are helpful. In patients diagnosed before 45 years without features of insulin resistance the diagnosis of HNF-1 alpha should be considered.     

Prevalence of the missense mutation Gly574Ser in the hepatocyte nuclear factor-1alpha in Africans with diabetes

BACKGROUND: Clinical presentation and natural history of diabetes are somewhat different in Black Africans compared to Caucasians. This peculiar disease course could be at least partly related to a specific genetic profile that has not been studied in this population.METHODS: Medical backgrounds, anthropometric and biologic parameters were obtained from 69 diabetic subjects in Dakar, Senegal, in 1998. Blood anti GAD and Islet Cell Antibodies were studied, using RIA and immunofluorescence assay. The HNF-1alpha gene was sequenced searching the Gly574Ser mutation, previously described in MODY 3.RESULTS: Among these 69 diabetic patients, 11 (16%) were found to have the G574S mutation affecting the HNF-1alpha. These 11 patients carrying the mutation were compared respectively with the 58 non carriers. Mean age (57.5 yr. +/- 11 vs 51.1 yr. +/- 15) and duration of diabetes (11.9 vs 6.7 yr), were similar in the two groups. BMI was not different in patients with the mutation (26.3 vs 23.3, p=0.06). Metabolic control (Glycosylated hemoglobin) was poor in the two groups (9.5% vs 9.2%). Chronic complications were equally found in the patients, but no mutation carrier had macroangiopathy. None of the anti GAD positive or ICA positive patients had the mutation. CONCLUSIONS: The HNF-1alpha Gly574Ser mutation was found in 16% of cases in a 69 diabetic patients group in Senegal. Diabetes was as severe as in non carriers of mutation. This mutation has been implicated in atypical diabetes of Afro-American children. The study confirms its prevalence in Africans with diabetes.     

The Gly482Ser variant of the PPARGC1 gene is associated with Type 2 diabetes mellitus in northern Chinese, especially men.

AIMS: To investigate the prevalence of the Gly482Ser polymorphism of the PPARGC1 gene in a northern Chinese population and to clarify the susceptibility of individuals with the Gly482Ser polymorphism to insulin resistance and related diseases. METHODS: We studied the association of the Gly482Ser polymorphism identified in the PPARGC1 gene with Type 2 diabetes mellitus (T2DM) in 390 unrelated patients with T2DM and 525 control subjects with normal glucose tolerance. Clinical parameters and measures of insulin resistance were recorded. Genotypes were determined by the polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) method, which was further confirmed by direct sequencing in 20 randomly selected cases. RESULTS: The Gly482Ser polymorphism was common in the northern Chinese population. Univariate analysis indicated no statistically significant differences in allele frequencies or genotype frequencies of the Gly482Ser polymorphism in diabetic and control subjects (minor 482Ser allele frequency 44.4 vs. 41.4%, P = 0.169). However, logistic regression analysis demonstrated a positive 1.645-fold higher risk of the Ser/Ser genotype for T2DM (P = 0.039, 95% CI = 1.026-2.632). After stratification by gender, the risk of Type 2 diabetes in men was increased 1.852-fold (95% CI = 1.125-3.049) in those with the Ser/X genotype compared with those with the Gly/Gly genotype (P = 0.015). No associations were observed between the Gly482Ser polymorphism and parameters of insulin resistance, obesity and hypertension. CONCLUSION: The Gly482Ser variant of the PPARGC1 gene might contribute to susceptibility to T2DM in northern Chinese subjects. The Ser/X genotype of the Gly482Ser polymorphism in the PPARGC1 gene appears to be a risk factor for T2DM in northern Chinese men.     

IRS1, KCNJ11, PPARγ2 and HNF‐1α: do amino acid polymorphisms in these candidate genes support a shared aetiology between type 1 and type 2 diabetes?

AIMS: Type 1 diabetes mellitus (T1DM) is a chronic disorder primarily triggered by environmental and immunological factors in genetically susceptible individuals. Despite the fact that there are indications of common aetiological features of T1DM and type 2 diabetes (T2DM), variation in genes involved in insulin secretion and insulin signalling has to a large extent been ignored as potential modifiers in the pathogenesis of T1DM. Recent studies suggest, however, that proven T2DM susceptibility gene variants may be involved in the pathogenesis of T1DM. The objective of this study was to estimate the impact of four selected amino acid polymorphisms -IRS-1 Gly972Arg, Kir6.2 Glu23Lys, HNF-1alpha Ala98Val and PPARgamma2 Pro12Ala in a Danish population of T1DM families. METHODS: All variants were genotyped in 490 simplex- and multiplex-T1DM families applying polymerase chain reaction-restriction fragment length polymorphism, and results were evaluated by means of a transmission disequilibrium test (TDT) analysis. RESULTS: TDT analysis revealed that the Arg972 IRS-1, the Lys23 Kir6.2 and the Val98 HNF-1alpha variants were transmitted from heterozygous parents to affected probands at frequencies of 49.1%, 47.0% and 54.1%, respectively (p > 0.05 for all). This was similar to the rate of transmission to unaffected siblings. The transmission rate of the Ala12 PPARgamma2 variant to affected probands was 46.5% (p > 0.05) which differed significantly from the transmission to unaffected offspring (p = 0.024). A combined analysis of the present and published pertinent data of 1691 transmissions showed a significantly decreased transmission of the PPARgamma2 Ala12 allele to affected probands (p = 0.0045). CONCLUSIONS: The Pro12Ala variant of PPARgamma2 is associated with T1DM, the minor Ala allele conferring a reduced risk. This same finding has been reported in patients with T2DM.     

老年糖尿病PAI-1与IR的相关性分析

目的探讨老年糖尿病患者血浆纤溶酶原激活物抑制物-1(PAI-1)活性及基因启动子区4G/5G多态性与胰岛素抵抗(IR)的关系。方法运用等位基因特异性PCR扩增技术对136例老年糖尿病患者PAI-14G/5G多态位点的基因型进行检测,发色底物法测血浆PAI-1活性。结果1老年糖尿病患者血浆PAI-1活性明显升高,空腹胰岛素(FPG)、胰岛素抵抗指数(HOMA-IR)、体重指数(BMI)、4G/5G基因类型与PAI-1活性升高密切相关(P<0.05)。2对照组和伴IR的糖尿病患者的4G/4G基因型频率分别为47.2%和32,5%,两组比较无明显差异(P>0.05),IR组不同基因型患者的PAI-1活性差异显著(P<0.01),4G/4G型者PAI-1活性明显高于4G/5G和5G/5G者(P<0.05)。3胰岛素对PAI-1活性的影响无基因依赖性。结论老年糖尿病患者PAI-1活性升高,FPG、HOMA-IR、BMI与PAI-1活性升高有关,甘油三酯对PAI-1活性的调节存在基因型依赖性。     

Familial liver adenomatosis associated with hepatocyte nuclear factor 1alpha inactivation

Background & Aims:

Germline mutations in hepatocyte nuclear factor 1α (TCF1/HNF-1α) are associated with maturity-onset diabetes of the young type 3 (MODY3), and somatic biallelic inactivations of the gene are found in hepatocellular adenomas and liver adenomatosis. This study investigated cosegregation of HNF-1α germline mutations with diabetes and liver adenomatosis in 2 families.

Methods:

Two unrelated patients with liver adenomatosis and harboring HNF-1α germline and somatic mutations were studied. Subsequently, we screened 9 relatives in the 2 independent families for diabetes, hepatocellular adenomas, and HNF-1α germline mutations.

Results:

In family A, a father and his son presented with an intraperitoneal hemorrhagic rupture of a liver adenomatosis without diabetes. A heterozygous R229X germline mutation was identified in HNF-1α in the father and his son and also in his second 27-year-old son without hepatocellular adenomas. In family B, a diagnosis of liver adenomatosis was made fortuitously in a 14-year-old girl. A heterozygous G55fsX57 germline mutation in HNF-1α was identified in this patient, her diabetic father, and her 2 sisters. Systematic exploration showed liver adenomatosis in the 2 sisters. Somatic inactivation of the second HNF-1α allele was found in liver tumors in both families.

Conclusions:

This study describes familial liver adenomatosis and shows the association with germline HNF-1α mutations in adults and children. It also highlights the importance of screening for hepatocellular adenomas, diabetes, and HNF-1α germline mutations in relatives of patients with liver adenomatosis. Finally, prevalence of liver adenomatosis remains to be evaluated in MODY3 subjects.     

Early-onset type 2 diabetes: metabolic and genetic characterization in the mexican population

The objective of this study was to investigate possible defects in the insulin sensitivity and/or the acute insulin response in a group of Mexican patients displaying early-onset type 2 diabetes and to evaluate the contribution of mutations in three of the genes linked to maturity-onset diabetes of the young. We studied 40 Mexican patients with an age of diagnosis between 20 and 40 yr in which the insulin sensitivity as well as the insulin secretory response were measured using the minimal model approach. A partial screening for possible mutations in 3 of the 5 genes linked to maturity-onset diabetes of the young was carried out by PCR-single strand conformation polymorphism analysis. A low insulin secretory capacity (AIRg = 68.5 +/- 5 muU/mL.min) and a near-normal insulin sensitivity (3.43 +/- 0.2 min/muU.mL x 10(4)) were found in these patients. Among this group we found two individuals carrying missense mutations in exon 4 of the hepatocyte nuclear factor-1alpha (HNF-4alpha) gene (Asp(126)-->His/Tyr and Arg(154)-->Gln, respectively) and one carrying a nonsense mutation in exon 7 of the HNF-1alpha gene (Gln(486)-->stop codon); 7.5% had positive titers for glutamic acid decarboxylase antibodies. Thirty-five percent of cases had insulin resistance; these subjects had the lipid abnormalities seen in the metabolic syndrome. A defect in insulin secretion is the hallmark in Mexican diabetic patients diagnosed between 20 and 40 yr of age. Mutations in either the HNF-1alpha or the HNF-4alpha genes are present among the individuals who develop early-onset diabetes in our population. These particular sequence changes have not been previously reported and therefore represent putative new mutations. Even in the absence of endogenous hyperinsulinemia, insulin resistance is associated with an adverse lipid profile.