Jun Takeda

Variants in KCNQ1 are associated with susceptibility to type 2 diabetes mellitus

We carried out a multistage genome-wide association study of type 2 diabetes mellitus in Japanese individuals, with a total of 1,612 cases and 1,424 controls and 100,000 SNPs. The most significant association was obtained with SNPs in KCNQ1, and dense mapping within the gene revealed that rs2237892 in intron 15 showed the lowest P value (6.7 × 10−13, odds ratio (OR) = 1.49). The association of KCNQ1 with type 2 diabetes was replicated in populations of Korean, Chinese and European ancestry as well as in two independent Japanese populations, and meta-analysis with a total of 19,930 individuals (9,569 cases and 10,361 controls) yielded a P value of 1.7 × 10−42 (OR = 1.40; 95% CI = 1.34–1.47) for rs2237892. Among control subjects, the risk allele of this polymorphism was associated with impairment of insulin secretion according to the homeostasis model assessment of β-cell function or the corrected insulin response. Our data thus implicate KCNQ1 as a diabetes susceptibility gene in groups of different ancestries.

The ratio of leptin to adiponectin can be used as an index of insulin resistance

The level of leptin increases with obesity, whereas that of adiponectin decreases with obesity. It is reported that the ratio of leptin to adiponectin (L/A) is associated with insulin resistance. It is difficult to evaluate insulin resistance in diabetic patients who have a dysfunction of insulin secretion. The aim of this study was to examine whether the L/A ratio is a useful marker for insulin resistance in diabetic patients. We examined L/A in the serum of a total of 139 Japanese patients with type 2 diabetes mellitus (66 women and 73 men) and 7 healthy individuals recruited in our hospital. Changes in the levels of leptin and adiponectin were observed using the oral glucose tolerance test and a hyper- and euglycemic clamp test. Twenty-one patients with type 2 diabetes mellitus were observed for more than 6 months after treatment with pioglitazone, and 31 patients with type 2 diabetes mellitus were observed for more than 6 months after the treatment with metformin. The mean value of L/A in 139 Japanese patients with type 2 diabetes mellitus was 1.22 +/- 1.41 (1.68 +/- 1.76 in women, 0.81 +/- 0.80 in men; P = .0002). In the clamp tests, L/A correlated with glucose infusion rate (GIR) (r(2) = 0.26, P = .0034). The correlation of L/A and GIR indicated a stronger correlation than either leptin (r(2) = 0.144, P = .03) or adiponectin alone (r(2) = 0.023, P = .41), or the homeostasis model assessment of insulin resistance (r(2) = 0.103, P = .08). The average hemoglobin A(1c) (HbA(1c)) improved from 10.2% +/- 1.2% to 9.2% +/- 1.6% (P = .0037) in 6 months after treatment with pioglitazone. Our results indicate pioglitazone to be effective for HbA(1c) improvement in subjects with high L/A and low L/A. The average HbA(1c) improved from 9.2% +/- 0.9% to 8.0% +/- 1.2% (P = .0002) in 6 months after treatment with metformin. Our results indicate metformin to be effective for HbA(1c) improvement in subjects with a low L/A. In conclusion, we demonstrate that L/A is different between male and female subjects. The correlation of L/A and GIR by the euglycemic hyperinsulinemic clamp test suggests that L/A is a useful indicator for the choice of drug to treat diabetes mellitus.

Replication of Genome-Wide Association Studies of Type 2 Diabetes Susceptibility in Japan

BACKGROUNDnIn Europeans and populations of European origin, several groups have recently identified novel type 2 diabetes susceptibility genes, including FTO, SLC30A8, HHEX, CDKAL1, CDKN2B, and IGF2BP2, none of which were in the list of functional candidates.nnnOBJECTIVE AND DESIGNnThe aim of this study was to replicate in a Japanese population previously identified associations of single nucleotide polymorphisms (SNPs) within 10 candidate loci with type 2 diabetes using a relatively large sample size: 1921 subjects with type 2 diabetes and 1622 normal controls.nnnRESULTSnA total of 15 SNPs were genotyped. Eight SNPs in five loci were found to be associated with type 2 diabetes: rs3802177 [odds ratio (OR) = 1.16 (95% confidence interval (CI) 1.05-1.27); P = 4.5 x 10(-3)] in SLC30A8; rs1111875 [OR = 1.27 (95% CI 1.14-1.40); P = 1.4 x 10(-5)] and rs7923837 [OR = 1.27 (95% CI 1.13-1.43); P = 1.0 x 10(-4)] in HHEX; rs10811661 [OR = 1.27 (95% CI 1.15-1.40); P = 1.9 x 10(-6)] in CDKN2B; rs4402960 [OR = 1.23 (95% CI 1.11-1.36); P = 8.1 x 10(-5)] and rs1470579 [OR = 1.18 (95% CI 1.07-1.31); P = 8.3 x 10(-4)] in IGF2BP2; and rs7754840 [OR = 1.28 (95% CI 1.17-1.41); P = 4.5 x 10(-7)] and rs7756992 [OR = 1.27 (95% CI 1.15-1.40); P = 9.8 x 10(-7)] in CDKAL1. The first and second strongest associations were found at variants in CDKAL1 and CDKN2B, both of which are involved in the regenerative capacity of pancreatic beta-cells.nnnCONCLUSIONnSome of these variants represent common type 2 diabetes-susceptibility genes in both Japanese and Europeans.

Association of TCF7L2 polymorphisms with susceptibility to type 2 diabetes in 4,087 Japanese subjects

AbstractTranscription factor 7-like 2 (TCF7L2) has been shown to be associated with type 2 diabetes mellitus in multiple ethnic groups. Regarding the Asian population, Horikoshi et al. (Diabetologia 50:747–751, 2007) and Hayashi et al. (Diabetologia 50:980–984, 2007) reported that single nucleotide polymorphisms (SNPs) in TCF7L2 were associated with type 2 diabetes in the Japanese population, while contradictory results were reported for Han Chinese populations. The aim of this study was to investigate the associations of the TCF7L2 gene with type 2 diabetes using a relatively large sample size: 2,214 Japanese individuals with type 2 diabetes and 1,873 normal controls. The minor alleles of rs7903146, rs11196205, and rs12255372 showed significant associations with type 2 diabetes (OR = 1.48, P = 2.7 × 10−4; OR = 1.39, P = 4.6 × 10−4; OR = 1.70, P = 9.8 × 10−5, respectively) in the combined sample sets. However, neither rs11196218 nor rs290487 showed a significant association. These results indicate that TCF7L2 is an important susceptibility gene for type 2 diabetes in the Japanese population.

Sonographic Evaluation of the Peripheral Nerve in Diabetic Patients The Relationship Between Nerve Conduction Studies, Echo Intensity, and Cross-sectional Area

Objective. Early detection of nerve dysfunction is important to provide appropriate care for patients with diabetic polyneuropathy. The aim of this study was to assess the echo intensity of the peripheral nerve and to evaluate the relationship between nerve conduction study results and sonographic findings in patients with type 2 diabetes mellitus. Methods. Thirty patients with type 2 diabetes (mean ± SD, 59.8 ± 10.2 years) and 32 healthy volunteers (mean, 53.7 ± 13.9 years) were enrolled in this study. The cross‐sectional area (CSA) and echo intensity of the peripheral nerve were evaluated at the carpal tunnel and proximal to the wrist (wrist) of the median nerve and in the tibial nerve at the ankle. Results. There was a significant increase in the CSA and hypoechoic area of the nerve in diabetic patients compared with controls (wrist, 7.1 ± 2.0 mm2, 62.3% ± 3.0%; ankle, 8.9 ± 2.8 mm2, 57.6% ± 3.9%; and wrist, 9.8 ± 3.7 mm2, 72.3% ± 6.6%; ankle, 15.0 ± 6.1 mm2, 61.4% ± 5.3% in controls and diabetic patients, respectively; P < .05). Cross‐sectional areas were negatively correlated with reduced motor nerve conduction velocity and delayed latency. Conclusions. These results suggest that sonographic examinations are useful for the diagnosis of diabetic neuropathy.

Construction of a prediction model for type 2 diabetes mellitus in the Japanese population based on 11 genes with strong evidence of the association.

Prediction of the disease status is one of the most important objectives of genetic studies. To select the genes with strong evidence of the association with type 2 diabetes mellitus, we validated the associations of the seven candidate loci extracted in our earlier study by genotyping the samples in two independent sample panels. However, except for KCNQ1, the association of none of the remaining seven loci was replicated. We then selected 11 genes, KCNQ1, TCF7L2, CDKAL1, CDKN2A/B, IGF2BP2, SLC30A8, HHEX, GCKR, HNF1B, KCNJ11 and PPARG, whose associations with diabetes have already been reported and replicated either in the literature or in this study in the Japanese population. As no evidence of the gene–gene interaction for any pair of the 11 loci was shown, we constructed a prediction model for the disease using the logistic regression analysis by incorporating the number of the risk alleles for the 11 genes, as well as age, sex and body mass index as independent variables. Cumulative risk assessment showed that the addition of one risk allele resulted in an average increase in the odds for the disease of 1.29 (95% CI=1.25–1.33, P=5.4 × 10−53). The area under the receiver operating characteristic curve, an estimate of the power of the prediction model, was 0.72, thereby indicating that our prediction model for type 2 diabetes may not be so useful but has some value. Incorporation of data from additional risk loci is most likely to increase the predictive power.

Associations of coronary artery calcification and carotid intima-media thickness with plasma concentrations of vascular calcification inhibitors in type 2 diabetic patients

Vascular calcification is frequently accompanied by intima-media thickening, but the associations among these atherosclerotic features and bone-related peptides in diabetic patients are unclear. We enrolled 168 type 2 diabetic patients and 40 non-diabetic subjects consecutively admitted to our hospital. Mean intima-media thickness (mean-IMT) in common carotid arteries was measured by B-mode ultrasonography. Agatston coronary artery calcium score (CACS) was obtained using multidetector-row computed tomography (MDCT). Plasma bone-related peptides osteopontin and osteoprotegerin levels were measured. Diabetic patients had higher mean-IMT (p=0.0002) and log(CACS+1) (p<0.0001) and similar bone-related peptides compared to non-diabetic subjects. In diabetic patients classified into tertiles according to their CACS levels, those with the highest scores showed the highest mean-IMT (p=0.0004) and bone-related peptides (p<0.05) among the groups. log(CACS+1) and mean-IMT were associated (p<0.0001) and were positively correlated with osteopontin (p<0.01) and osteoprotegerin (p<0.01) in diabetic patients. Multivariate analyses revealed that the significant independent determinants of log(CACS+1) were age, duration of diabetes and osteopontin (p<0.0001) and those of mean-IMT were age, hypertension, osteopontin and osteoprotegerin (p<0.0001), respectively. We have demonstrated that vascular calcification in type 2 diabetic patients is frequently accompanied by intima-media thickening, and osteopontin may act as a vascular calcification inhibitor by increasing intima-media thickness.

Correlation between left ventricular mass and urinary sodium excretion in specific genotypes of CYP11B2.

Background Aldosterone has essential roles in regulating intravascular volume and blood pressure, and is suggested to influence cardiac structure. However, the association of polymorphisms in the aldosterone synthase gene (CYP11B2) with hypertension or cardiac hypertrophy remains controversial. Objective To evaluate the distribution of polymorphisms in the CYP11B2 gene and the possible associations between genotypes and blood pressure, urinary excretion of aldosterone or electrolytes and echocardiographic measurements, in a Japanese population. Methods and results We examined the association of two common diallelic polymorphisms within CYP11B2, one in the promoter −344T/C and the other an intron 2 gene conversion, with blood pressure, 24-h urinary excretion of aldosterone and electrolytes, and echocardiographic measurements, in a Japanese population. We confirmed significant linkage disequilibrium between these polymorphic loci and ethnic differences in frequency of the alleles. The −344C and −344T haplotypes apparently diverged before the intron conversion polymorphism was generated on the latter haplotype. Allele frequencies did not differ between 535 normotensive and 360 hypertensive individuals or between hypertensive individuals with higher and lower concentrations of renin. The only significant correlation was a positive correlation of left ventricular mass with 24-h urinary excretion of sodium, which occurred only in individuals with the −344CC genotype or the intron 2 conversion (−/−) genotype. Conclusions The −344CC or intron 2 conversion (−/−) genotype in CYP11B2 may be a risk factor for developing sodium-sensitive cardiac hypertrophy. Ethnic differences in the distribution of CYP11B2 genotypes combined with differences in salt intake might account for inconsistencies between previous reports.

Effect of fasting on PPARγ and AMPK activity in adipocytes

We investigated the effects of fasting on gene expression and intracellular signals regulating energy metabolism in adipose tissue. Following fasting for 15h or 39h, epididymal fat pads were isolated from Wistar rats. PPARgamma mRNA levels decreased in the adipose tissues isolated from rats fasted for 39h, whereas adipocyte lipid-binding protein (aP2) and lipoprotein lipase (LPL) mRNA levels increased. Overnight fasting increased the AMP/ATP ratio and AMP-activated protein kinase (AMPK) in adipose tissue, but not in muscle or liver tissue. In addition, the effect of 5-aminoimidazole-4-carboxyamide-ribonucleoside (AICAR) on PPARgamma expression in primary cultured adipocytes was investigated. AICAR reduced PPARgamma mRNA levels but increased aP2 and LPL mRNA levels. Thus, fasting-induced AMPK activation may affect on the regulation of gene expression in adipocytes.

Higher arterial stiffness, greater peripheral vascular resistance and lower blood flow in lower-leg arteries are associated with long-term hyperglycaemia in type 2 diabetic patients with normal ankle-brachial index.

Higher arterial stiffness and greater peripheral vascular resistance reduce blood flow in lower‐leg arteries and contribute to the development of ischaemic limb in diabetic patients even without peripheral artery occlusive disease. The aim of this study was to clarify whether these vascular parameters are associated with long‐term hyperglycaemia in diabetic patients.