Type 2 Diabetes And Related Metabolic Disorders, Molecular Genetic Studies

Objeetive To estimate the prevalence of the metabolic syndrome (MS) and its main components in diabetic patients and non-diabetic first degree relatives(FDR) in families with type 2 diabetes mellitus(T2DM), and estimate the heritabilities of MS and its related features.Methods (1) 1312 subjects(587male and 725 female) from 247 Chongqing Han families were enrolled. 1178 of them came from T2DM family, and 134 of them were their spouses. Anthropometry, blood pressure, oral glucose tolerance test (OGTT), lipid levels,high-sensitivity C-reactive protein (hsCRP),non-esterified fatty acid (NEFA) were examined. MS was defied according to International Diabetes Federation(IDF) definition and National Cholesterol Education Program Adult Treatment PanelⅢ(NCEP-ATPⅢ) guideline with Asian criteria for obesity. (2)Except second degree relatives and spouses who had diabetic relatives or who per se were diabetic, all the subjects were divided into three groups: T2DM, first degree relatives (FDR)and control group. The clinical and metabolic characteristics and the prevalence of MS and its main components were compared among three groups. (3) The Statistical Analysis for Genetic Epidemiology (S.A.G.E.) program was applied to calculate heritability of the metabolic traits.Results After adjusted for age, waist circumferences and WHR in FDR group were higher than those in controls(P＜0.05and P＜0.01). After adjusted for age and BMI, the levels of SBP, OGTT 2h glucose, fasting insulin, and HomaIR in FDR group were higher than those in controls(P＜0.05 or P＜0.01), and HDL-C lower than that in controls(P＜0.05). Although there were higher TG, fasting glucose, OGTT 2h insulin, hsCRP in FDR group than in control group, there were no statistic difference between two groups(P＞0.05). In FDR group, the prevalence of IGR, obesity, central obesity, hypertension, hypertriglyceridemia, decreased blood HDL-C, MS(IDF criterion) and MS (NCEP-ATPⅢcriterion) were 44.9%, 33.3%, 34.1%, 21.1%, 28.2%, 30.1%, 20.8% and 19.2% respectively. After adjusted for age and sex, the risk of MS and its main components increased in FDR than in controls: IGR (OR 13.2, 95%CI=5.91～29.46), obesity(OR 2.13, 95% CI=1.23～3.68), central obesity(OR 1.92, 95 %CI=1.14～3.21), decreased blood HDL-C (OR 1.73, 95%CI=1.01～2.98), MS (IDF OR 2.57, 95%CI=1.14～3.21; NCEP-ATPⅢOR 2.35, 95%CI=1.17～4.71). There were higher prevalence of MS in T2DM than in controls, the risk of obesity was 3.81 (95% CI=2.22～6.56), obesity(OR 3.91, 95% CI=2.34～6.51), central obesity(OR 3.91, 95% CI=2.34～6.51), hypertension (OR 3.82, 95% CI=2.17～6.74), MS (IDF OR 7.96, 95%CI=4.03～15.74, NCEP-ATPⅢOR 12.13, 95%CI=6.14～23.96 ), hyper- triglyceridemia(OR 2.51, 95%CI=1.53～4.11), decreased blood HDL-C (OR 2.31, 95%CI=1.38～3.89). In T2DM family, there were moderate heritability estimates of metabolic phenotypes. Fasting glucose concentration, fasting insulin and Homaβhad the highest heritability estimates of 0.71, 0.68 and 0.68 respectively. The heritability estimate of Homaβwas higher than HomaIR(0.68 vs 0.54). Heritability estimates for the features of BMI, waist, hsCRP, TG and HDL-C were also high (0.32～0.55). Among all of the metabolic traits, SBP and DBP had the lowest heritability(0.25 and 0.28 respectively). Conclusion There is significant familial aggregation of T2DM and related phenotypes including obesity, hypertension and dyslipidaemia There are more or less metabolic abnormalities in the non-diabetic FDR. The moderate heritability of metabolic traits in T2DM family is due to both genetic and environmental factors. Objective To study the association of single nucleotide polymorphisms (SNPs) in peroxisome proliferators- activated receptorγcoactivator-1β(PGC- 1β) with T2DM and with related metabolic disease.Methods (1) The DNA samples of 18 controls and 39 T2DM patients were selected to identify SNPs in PGC- 1βgene. all of 12 exons, including exon-intron boundaries and promoter region (□31.6 kb) were amplificated, and the PCR products were examined by denaturing high performance liquid chromatography(DHPLC) followed by sequencing to search SNPs, then pairwise linkage disequilibrium (LD) test and haplotype were examined. (2)The missense variants were genotyped in 474 T2DM patients and in 313 controls in Chongqqing area to investigate their genetic association with T2DM and obesity.Results A total of 9 SNPs were identified in PGC- 1βgene, including four missense variants(Ala203Pro,Arg265Gln,Val279Ile, Arg292Ser)in exon 5, one silent variant (Leu42Leu), two SNPs in promoter region (-1263G＞A, -985C＞T) and two SNPs in intron (IVS2-132 G＞A, IVS9-31G＞C). The four missense variants were in LD and in a haplotype block. Because the four missense SNPs were 268bp apart, sequencing was used for genotyping. There was no association between Ala203Pro, Arg265Gln, rg292Ser and T2DM (P＞0.05). The SNP of Arg265Gln showed an increased risk with obesity (additive model: OR=1.436, 95% CI=1.079～1.921, P=0.013; dominant model: OR=1.424, 95%CI=1.029～1.970, P=0.033: recessive model: OR=2.648, 95%CI=1.008～6.961, P= 0.048). In male, subjects with Arg265Gln GA/AA genotype had higher BMI, waist and Waist-to-hip ratio(WHR) than those with GG genotype(P＜0.05). Among four missense SNPs genotyped, three common haplo- types (frequency＞0.05) accounted for 95.3% of the observed haplotypes. There were no association between the three haplotypes and T2DM (P＞0.05). The frequency of haplotype H3 was higher in obesity group than in controls(16.6%vs12.8%, P=0.039).Conclusion There is no association between PGC- 1βSNPs and T2DM in Chongqing area. Arg265Gln and a common haplotypes in PGC-1βgene may contribute to the pathogenesis of obesity, especially in male. Objective To investigate the impact of peroxisome proliferators-activated receptorγcoactivator-1α(PGC- 1α) and of Peroxisome proliferators- activated receptorγ(PPARγ) polymorphisms on T2DM and on obesity. To explore the effects of gene to gene interactions among PGC- 1α,PGC- 1βand PPARyon the risk of T2DM and obesity.Methods Genotyping was performed by means of RFLE Case-control analysis were studied to investigate genetic association of SNPs (PGC-1αGly482Ser and Thr394Thr,PPARγPro 12Ala and C161T) with T2DM and obesity. Multifactor dimensionality reduction (MDR) and logistic regression were used to analyze gene-gene interactions of PGC-1α,PGC- 1βand PPARy.Results There was no association between the four SNPs and T2DM (P＞0.05). The PGC-1αThr394Thr showed an increased risk of obesity with an dominant model (OR=0.697, 95%CI=0.497～0.977, P=0.036). There was no relationship between Gly482Ser,Pro 12Ala, C161T polymorphisms and obesity (P＞0.05). Subjects with PPARγC161T CT/TT genotype had higher fasting insulin and higher HomaIR than those with CC genotype (11.13±5.36 mU/L vs 9.83±5.50 mU/L, P=0.030 and 2.47±1.23 vs 2.18±1.30, P=0.033 respectively). No interaction among the three candidate genes associated with T2DM. Using the MDR method, a significant two-locus interaction between PGC-1αGly482Ser and PGC-1βArg265Gln was found among 5 loci in three genes on the risk of obesity. This model showed a cross-validation consistency of 10 of 10 and a testing accuracy of 0.5432 (P =0.0010). The odds ratio of the high-risk to low-risk group was 1.6034 (95 %CI0.5493～4.6804, X~2=7.7275, P=0.0054) .The gene-gene interactions could be validated by Logistic regression analysis.Conclusion There is no association between the four SNPs of PGC- 1α, PPARγ, and T2DM, but PGC-1αThr394Thr could be related to obesity ,and PPARγC161T may be contribute to insulin resistance. Using the MDR method, a significant interaction between PGC-1αGly482Ser and PGC-1β,Arg265Gln for obesity has been shown. MDR analysis could be a useful method to study polygenetic disease.