Association of ghrelin Leu72Met polymorphism with type 2 diabetes mellitus in Chinese population

Background

Ghrelin, a novel endogenous ligand for the growth hormone secretagogue receptor, is considered to implicate the development of the type 2 diabetes mellitus (T2DM). The Leu72Met (+ 408 C > A) polymorphism of the preproghrelin, has been linked to obesity, insulin resistance and diabetes.

Objective

To investigate the distribution of ghrelin gene Leu72Met polymorphism and its association with the type 2 diabetes mellitus in Chinese population.

Methods

We conducted a case–control study on 877 patients with T2DM and 864 controls, which were genotyped by the polymerase chain reaction (PCR) technique, denaturing high performance liquid chromatography (DHPLC) and DNA sequence analysis. Laboratory analyses were carried out in the hospital laboratory.

Results

No significant difference in the Leu72Met genotype distributions and allele frequency was observed between type 2 diabetes mellitus and controls (both P > 0.05). The polymorphism was not associated with T2DM. However, among the T2DM group, the patients carrying Leu72Leu genotype had significantly increased levels of FPG and serum creatinine compared with variant genotypes (Leu72Met and Met72Met) (P < 0.05). In the control group, the subjects with variant genotypes had significantly increased levels of FINS, HOMA-IR compared with Leu72Leu genotype (P < 0.05).

Conclusion

The Leu72Met polymorphism of the preproghrelin gene was not associated with T2DM in Chinese population. However, it may have some roles in the etiology of insulin resistance.     

Association of adiponectin gene functional polymorphisms (-11377C/G and +45T/G) with nonalcoholic fatty liver disease

Adiponectin levels are reduced in NAFLD patients and genetic variants of adiponectin have been frequently associated with type 2 diabetes and insulin resistance. To determine the genotypic frequencies of adiponectin functional polymorphisms (-11377C/G and +45T/G) and their subsequent effect on disease progression and plasma adiponectin levels in the patients with NAFLD. A total of 137 NAFLD patients and 250 matched controls were enrolled in the study. DNA sequencing and genotyping were performed to identify the genetic variants. The plasma adiponectin levels were assessed by ELISA. Homozygous mutant genotype of adiponectin SNPs, -11377C/G and +45T/G, were significantly more prevalent in NAFLD patients than controls (Bonferroni corrected p=0.014 and 0.018, respectively). Plasma adiponectin levels were significantly lower in the NAFLD patients as compared to controls. Moreover, presence of 'G' allele at position -11377C/G and +45T/G was found to be associated with necroinflammatory grade and reduced adiponectin levels, (p values 0.02 and 0.01) respectively. -11377G and +45G alleles are associated with severity of liver disease and hypoadiponectemia, in the patients with NAFLD, respectively.     

Uncoupling protein 2 − 866G/A and uncoupling protein 3 − 55C/T polymorphisms in young South African Indian coronary artery disease patients

Background

Uncoupling proteins (UCPs) 2 and 3 play an important role in the regulation of oxidative stress which contributes to chronic inflammation. Promoter polymorphisms of these genes have been linked to chronic diseases including heart disease and type II diabetes mellitus in several populations. This is the first investigation of the UCP2 − 866G/A rs659366 and UCP3 − 55C/T rs1800849 polymorphisms in young South African (SA) Indians with coronary artery disease (CAD).

Methods

A total of 300 subjects were recruited into this study of which 100 were SA Indian males with CAD, 100 age- (range 24–45 years), gender- and race-matched controls and 100 age-matched black SA males. The frequency of the UCP2 − 866G/A and UPC3 − 55C/T genotypes was assessed by polymerase chain reaction restriction fragment length polymorphism (PCR-RFLP).

Results

The heterozygous UCP2 − 866G/A and homozygous UCP3 − 55C/C genotypes occurred at highest frequency in CAD patients (60% and 64%, respectively) compared to SA Indian controls (52% and 63%) and SA Black controls (50% and 58%). The UCP2 − 886G/A (OR = 1.110; 95% CI = 0.7438–1.655; p = 0.6835) and UCP3 − 55C/T (OR = 0.788; 95% CI = 0.482–1.289; p = 0.382) polymorphisms did not influence the risk of CAD.The rare homozygous UCP3 − 55T/T genotype was associated with highest fasting glucose (11.87 ± 3.7 mmol/L vs. C/C:6.11 ± 0.27 mmol/L and C/T:6.48 ± 0.57 mmol/L, p = 0.0025), HbA1c (10.05 ± 2.57% vs. C/C:6.44 ± 0.21% and C/T:6.76 ± 0.35%, p = 0.0006) and triglycerides (6.47 ± 1.7 mmol/L vs. C/C:2.33 ± 0.17 mmol/L and C/T:2.06 ± 0.25 mmol/L, p < 0.0001) in CAD patients.

Conclusion

The frequency of the UCP2 − 866G/A and UCP3 − 55C/T polymorphisms was similar in our SA Indian and SA Black groups. The presence of the UCP2 − 866G/A and UCP3 − 55C/T polymorphisms does not influence the risk of CAD in young South African Indian CAD patients.     

In vitro effect of gliclazide on DNA damage and repair in patients with type 2 diabetes mellitus (T2DM)

Type 2 diabetes mellitus is associated with elevated level of oxidative stress, which is one of the most important factors responsible for the development of chronic complications of this disease. Moreover, it was shown that diabetic patients had increased level of oxidative DNA damage and decreased effectiveness of DNA repair. These changes may be associated with increased risk of cancer in T2DM patients, since DNA damage and DNA repair play a pivotal role in malignant transformation. It was found that gliclazide, an oral hypoglycemic drug with antioxidant properties, diminished DNA damage induced by free radicals. Therefore, the aim of the present study was to evaluate the in vitro impact of gliclazide on: (i) endogenous basal and oxidative DNA damage, (ii) DNA damage induced by hydrogen peroxide and (iii) the efficacy of DNA repair of such damage. DNA damage and DNA repair in peripheral blood lymphocytes of 30 T2DM patients and 30 non-diabetic individuals were evaluated by alkaline single cell electrophoresis (comet) assay. The extent of oxidative DNA damage was assessed by DNA repair enzymes: endonuclease III and formamidopyrimidine-DNA glycosylase. The endogenous basal and oxidative DNA damages were higher in lymphocytes of T2DM patients compared to non-diabetic subjects and gliclazide decreased the level of such damage. The drug significantly decreased the level of DNA damage induced by hydrogen peroxide in both groups. Gliclazide increased the effectiveness of DNA repair in lymphocytes of T2DM patients (93.4% (with gliclazide) vs 79.9% (without gliclazide); P< or =0.001) and non-diabetic subjects (95.1% (with gliclazide) vs 90.5% (without gliclazide); P< or =0.001). These results suggest that gliclazide may protect against the oxidative stress-related chronic diabetes complications, including cancer, by decreasing the level of DNA damage induced by reactive oxygen species.     

Association of P213S polymorphism of the L-selectin gene with type 2 diabetes and insulin resistance in Chinese population

Aims

L-selectin belongs to selectin family of adhesion molecule and participates in the generation and development of type 2 diabetes (T2D). In this study, we evaluated the relationship between the P213S polymorphism of L-selectin gene and T2D and insulin resistance in the Chinese population.

Methods

We genotyped P213S polymorphism in 801 patients with T2D and 834 healthy controls in the Chinese population using polymerase chain reaction–ligase detection reaction (PCR–LDR) technique. Plasma glucose, insulin, lipid, blood urea nitrogen, creatinine and uric acid levels were measured by biochemical technique.

Results

The frequency of 213PP genotype and P allele of the L-selectin gene in patients with T2D was significantly higher than that in controls (P = 0.007; P = 0.019, respectively). The relative risk of allele P suffered from T2D was 1.191 times higher than that of allele S. Moreover, the levels of FPG and HOMA-IR of PP and PS genotype carriers were significantly higher than those of SS genotype carriers in the T2D group (P < 0.05).

Conclusion

These findings indicated that the P213S polymorphism of L‐selectin gene may contribute to susceptibility to T2D and insulin resistance in the Chinese population, and P allele appears to be a risk factor for T2D.     

Association analysis of common variants in FOXO3 with type 2 diabetes in a South Indian Dravidian population

Recent studies have identified common variants in forkhead box O3 gene (FOXO3) to be strongly associated with longevity in different populations. But studies have not been carried out to analyse the role of common variants in FOXO3 with type 2 diabetes. Since type 2 diabetes is an age related disorder and FOXO proteins play an important role in the regulation of metabolism, we studied the role of common variants in FOXO3 for association with type 2 diabetes. The study was carried out in 994 type 2 diabetic samples and 984 normoglycemic control samples from a South Indian Dravidian population. In our analysis, we found that there was no association between any of the selected SNPs in FOXO3 with type 2 diabetes. Analysis of these SNPs with diabetes related biochemical and clinical parameters also did not reveal any significant association. Haplotype association of SNPs in FOXO3 with type 2 diabetes was observed, but the frequency of the haplotypes was considerably lower and they do not remain significant after correction for multiple testing. In conclusion, we did not observe any association of SNPs in FOXO3 with type 2 diabetes and related parameters suggesting an entirely different mechanism by which these SNPs influence longevity. However additional studies in other populations are required to completely rule out the association of common variants in FOXO3 with type 2 diabetes.     

Associations of the PTEN − 9C>G polymorphism with insulin sensitivity and central obesity in Chinese

Background

Phosphatase and tensin homolog on chromosome 10 gene (PTEN) is known as a tumor-suppressor gene. Previous studies demonstrated that PTEN dysfunction affects the function of insulin. However, investigations of PTEN single nucleotide polymorphisms (SNPs) and IR-related disease associations are limited. The aim of the present study was to investigate whether its polymorphism could be involved in the risk of metabolic syndrome (MetS).

Methods

The genotype frequency of PTEN − 9C>G polymorphism was determined by using a Matrix-Assisted Laser Desorption/Ionization Time of Flight Mass Spectrometry (MALDI-TOF MS) method in 530 subjects with MetS and 202 healthy control subjects of the Han Ethnic Chinese population in a case–control analysis.

Results

The PTEN − 9C>G polymorphism was not associated with MetS or its hyperglycemia, hypertension and hypertriglyceridemia components. In the control individuals aged < 60 years or ≥ 60 years, the CG genotype individuals had lower insulin sensitivity than CC individuals (P < 0.05). In the < 60-year-old MetS group and normal glucose tolerance (NGT) subgroup, the CG individuals had lower insulin sensitivity and higher waist circumference (WC) and waist-height-ratio (WHtR) than CC individuals (P < 0.05). Multiple linear regression analysis showed that the PTEN polymorphism (P = 0.001) contributed independently to 4.2% (adjusted R²) of insulin sensitivity variance (estimated by Matsuda ISI), while age (P = 0.004), gender (P = 0.000) and the PTEN polymorphism (P = 0.032) contributed independently to 5.6% (adjusted R²) of WHtR variance.

Conclusions

The CG genotype of PTEN − 9C>G polymorphism was not associated with MetS and some of its components as well. However, it may not only decrease insulin sensitivity in the healthy control and MetS in pre-elderly or NGT subjects, but may also increase the risk of central obesity among these MetS individuals.