Near-infrared light control of membrane potential by an electron donor-acceptor linked molecule.

Near-infrared (NIR) light control of living cellular activities is a highly desired technique for living cell manipulation because of its advantage of high penetrability towards living tissue. In this study, (π-extended porphyrin)-fullerene linked molecules are designed and synthesized to achieve NIR light control of the membrane potential. A donor-(π-extended porphyrin)-acceptor linked molecule exhibited the formation of the charge-separated state with a relatively long lifetime (0.68 µs) and a moderate quantum yield (27-31%). The hydrophilic trimethylammonium-linked triad molecule successfully altered PC12 cells' membrane potential via photoinduced intramolecular charge separation.

Optical control of neuronal firing via photoinduced electron transfer in donor-acceptor conjugates.

A series of porphyrin-fullerene linked molecules has been synthesized to evaluate the effects of substituents and molecular structures on their charge-separation yield and the lifetime of a final charge-separated state in various hydrophilic environments. The selected high-performance molecule effectively achieved depolarization in a plasma cell membrane by visible light as well as two-photon excitation using a near-infrared light laser. Moreover, it was revealed that the depolarization can trigger neuronal firing in rat hippocampal neurons, demonstrating the potential and versatility for controlling cell functions using light.

Decreased serum chemerin levels in male Japanese patients with type 2 diabetes: sex dimorphism.

Chemerin, a recently discovered adipocytokine plays an important role in obesity and obesity-associated metabolic complications. However, the role of chemerin in the pathogenesis of type 2 diabetes mellitus (T2DM) has not fully been elucidated. We compared the serum chemerin levels and metabolic parameters between 88 control subjects, 86 patients with metabolic syndrome (MS), and 147 patients with T2DM in a Japanese population and further analyzed their correlation. Enzyme-linked immunosorbent assay was used to measure the serum chemerin levels. The chemerin levels were significantly higher in male than in female control subjects (p < 0.005), with significant decreases in patients with T2DM compared with those with MS and control subjects (164.9 ± 6.3 ng/mL vs. 209.8 ± 7.7 and 218.7 ± 7.3 ng/mL; p < 0.0001 vs. p < 0.0001, respectively) but no significant differences in female subjects. The multiple regression analysis revealed that the chemerin levels negatively correlated with the fasting glucose and HbA1c levels in total and male subjects. In the patients with T2DM, the chemerin levels negatively correlated with fasting glucose and high-density lipoprotein cholesterol but positively correlated with body mass index (BMI), and total cholesterol and triglyceride levels. The negative correlation between the chemerin and fasting glucose levels remained significant after adjustment for age, sex, and BMI in the total and male subjects and those with T2DM. These results suggest the role of chemerin in sex dimorphism and a potential link between chemerin levels and T2DM pathogenesis in a Japanese population.

Kir6.2 variant E23K increases ATP-sensitive K+ channel activity and is associated with impaired insulin release and enhanced insulin sensitivity in adults with normal glucose tolerance.

OBJECTIVE: The E23K variant in the Kir6.2 subunit of the ATP-sensitive K(+) channel (K(ATP) channel) is associated with increased risk of type 2 diabetes. The present study was undertaken to increase our understanding of the mechanisms responsible. To avoid confounding effects of hyperglycemia, insulin secretion and action were studied in subjects with the variant who had normal glucose tolerance. RESEARCH DESIGN AND METHODS: Nine subjects with the E23K genotype K/K and nine matched subjects with the E/E genotype underwent 5-h oral glucose tolerance tests (OGTTs), graded glucose infusion, and hyperinsulinemic-euglycemic clamp with stable-isotope-labeled tracer infusions to assess insulin secretion, action, and clearance. A total of 461 volunteers consecutively genotyped for the E23K variant also underwent OGTTs. Functional studies of the wild-type and E23K variant potassium channels were conducted. RESULTS: Insulin secretory responses to oral and intravenous glucose were reduced by approximately 40% in glucose-tolerant subjects homozygous for E23K. Normal glucose tolerance with reduced insulin secretion suggests a change in insulin sensitivity. The hyperinsulinemic-euglycemic clamp revealed that hepatic insulin sensitivity is approximately 40% greater in subjects with the E23K variant, and these subjects demonstrate increased insulin sensitivity after oral glucose. The reconstituted E23K channels confirm reduced sensitivity to inhibitory ATP and increase in open probability, a direct molecular explanation for reduced insulin secretion. CONCLUSIONS: The E23K variant leads to overactivity of the K(ATP) channel, resulting in reduced insulin secretion. Initially, insulin sensitivity is enhanced, thereby maintaining normal glucose tolerance. Presumably, over time, as insulin secretion falls further or insulin resistance develops, glucose levels rise resulting in type 2 diabetes.

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 x 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.

Two related cases of type A insulin resistance with compound heterozygous mutations of the insulin receptor gene.

We describe two sisters with type A insulin resistance. In contrast to common situation for this genetic disorder, the sisters harbored compound heterozygous mutations in the insulin receptor gene associated with mild glucose intolerance. The cases highlight the diversity of clinical phenotypes associated with mutations of the insulin receptor gene.

Association of serum MCP-1 concentration and MCP-1 polymorphism with insulin resistance in Japanese individuals with obese type 2 diabetes.

Monocyte chemoattractant protein-1 (MCP-1, also known as CCL2) secreted by adipocytes is a member of the CC chemokine family and plays a pivotal role in the inflammatory process. A polymorphism, the -2518 A/G of MCP-1 gene, has been associated with type 2 diabetes, type 1 diabetes, parameters of insulin resistance and obesity. Therefore, we investigated the effects of MCP-1 single nucleotide polymorphisms (SNPs) on the susceptibility to type 2 diabetes or insulin resistance in the Japanese population. We also assessed the correlation between serum MCP-1 concentration and other clinical characteristics in Japanese type 2 diabetic subjects. The serum MCP-1 concentration was significantly correlated with HOMA-IR and the visceral fat area, but not with BMI. Although there was no association between this SNP and type 2 diabetes, the -2518A/G polymorphism was associated with the serum MCP-1 concentration. In subgroup analysis, Japanese obese diabetic -2518AA carriers had a higher MCP-1 concentration and increased insulin resistance than obese diabetic -2518G carriers. These data indicated that the MCP-1 polymorphism was associated with insulin resistance in Japanese obese diabetic subjects and that MCP-1 was implicated in the pathogenesis of insulin resistance, especially associated with obesity, in humans.

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 Pvalue (6.7 x 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 x 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 beta-cell function or the corrected insulin response. Our data thus implicate KCNQ1 as a diabetes susceptibility gene in groups of different ancestries.

Lack of association of LRP5 and LRP6 polymorphisms with type 2 diabetes mellitus in the Japanese population.

AIMS: A missense mutation in the low density lipoprotein receptor-related protein 6 gene (LRP6) was recently shown to be responsible for a disorder characterized by early-onset coronary artery disease as well as diabetes mellitus (DM), hyperlipidemia, hypertension, and osteoporosis. Mice deficient in LRP5, a closely related paralog of LRP6, manifest a marked impairment in glucose tolerance. The aim of the present study was to examine whether common variants of LRP5 and LRP6 are associated with Type 2 DM or dyslipidemia in Japanese individuals. METHODS: Thirteen single nucleotide polymorphisms (SNPs) of LRP6 and nine SNPs of LRP5 were genotyped in a total of 608 Type 2 DM patients and 366 nondiabetic control subjects (initial study). An association analysis was then performed for each SNP and for haplotypes. For some of the SNPs, we provided another sample panel of 576 cases and 576 controls for the replication study. The relation to clinical characteristics was also examined in diabetic subjects. RESULTS: In the initial study, three SNPs of LRP6 were found to be associated with susceptibility to Type 2 DM. However, this association was not detected in the replication panel. None of SNPs in LRP5 were associated with Type 2 DM in the initial panel. Neither LRP6 nor LRP5 was associated with body mass index, HOMA-beta, HOMA-IR or serum lipid concentrations. CONCLUSIONS: We found no evidence for a substantial effect of LRP5 or LRP6 SNPs on susceptibility to type 2 diabetes or clinical characteristics of diabetic subjects in Japanese population.

Replication of genome-wide association studies of type 2 diabetes susceptibility in Japan.

BACKGROUND: In 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. OBJECTIVE AND DESIGN: The 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. RESULTS: A 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. CONCLUSION: Some 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.

Transcription 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 x 10(-4); OR=1.39, P=4.6 x 10(-4); OR=1.70, P=9.8 x 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.

Association study of the effect of WFS1 polymorphisms on risk of type 2 diabetes in Japanese population.

Mutations of WFS1 gene cause Wolfram syndrome, which is a rare autosomal recessive disorder characterized by juvenile diabetes mellitus, optic atrophy, deafness and diabetes insipidus. The product encoded by WFS1 gene, wolframin, could be involved in ER stress response causing beta-cell loss through impaired cell cycle progression and increased apoptosis. Recently, polymorphisms in the WFS1 gene were strongly associated with type 2 diabetes in Caucasians. The aim of the present study was to examine whether the variants of WFS1 are associated with risk of type 2 diabetes in Japanese individuals. Four single nucleotide polymorphisms, rs6446482, rs12511742, rs1801208 (R456H) and rs734312 (H611R) were genotyped in a total of 536 diabetic patients and 398 nondiabetic control subjects. Among the four variants, rs12511742 showed a marginal association with susceptibility to type 2 diabetes (odds ratio = 1.32, 95% confidence interval = 1.02-1.71, P = 0.033). Carriers of the risk allele at rs12511742 exhibited lower pancreas beta-cell function (P = 0.017). However, this association disappeared after adjustment for sex, age and BMI (Adjusted P = 0.24). Although we found no evidence for a substantial effect of WFS1 polymorphisms on risk of type 2 diabetes or clinical characteristics of diabetic subjects in Japanese population, this gene is still a good candidate for a type 2 diabetes susceptibility gene, potentially, through impaired insulin secretion.

Identification of type 2 diabetes genes in Mexican Americans through genome-wide association studies.

OBJECTIVE: The objective of this study was to identify DNA polymorphisms associated with type 2 diabetes in a Mexican-American population. RESEARCH DESIGN AND METHODS: We genotyped 116,204 single nucleotide polymorphisms (SNPs) in 281 Mexican Americans with type 2 diabetes and 280 random Mexican Americans from Starr County, Texas, using the Affymetrix GeneChip Human Mapping 100K set. Allelic association exact tests were calculated. Our most significant SNPs were compared with results from other type 2 diabetes genome-wide association studies (GWASs). Proportions of African, European, and Asian ancestry were estimated from the HapMap samples using structure for each individual to rule out spurious association due to population substructure. RESULTS: We observed more significant allelic associations than expected genome wide, as empirically assessed by permutation (14 below a P of 1 x 10(-4) [8.7 expected]). No significant differences were observed between the proportion of ancestry estimates in the case and random control sets, suggesting that the association results were not likely confounded by substructure. A query of our top approximately 1% of SNPs (P < 0.01) revealed SNPs in or near four genes that showed evidence for association (P < 0.05) in multiple other GWAS interrogated: rs979752 and rs10500641 near UBQLNL and OR52H1 on chromosome 11, rs2773080 and rs3922812 in or near RALGPS2 on chromosome 1, and rs1509957 near EGR2 on chromosome 10. CONCLUSIONS: We identified several SNPs with suggestive evidence for replicated association with type 2 diabetes that merit further investigation.

Lack of association of CPT1A polymorphisms or haplotypes on hepatic lipid content or insulin resistance in Japanese individuals with type 2 diabetes mellitus.

Accumulation of fat in the liver is associated with insulin resistance and type 2 diabetes mellitus. The carnitine palmitoyltransferase (CPT) enzyme system facilitates the transport of long-chain fatty acids into mitochondria, and the gene for the hepatic isoform of CPT1 (CPT1A) is a candidate gene for metabolic disorders such as insulin resistance associated with fatty liver. We have now investigated the contribution of the CPT1A locus to hepatic lipid content (HLC), insulin resistance, and susceptibility to type 2 diabetes mellitus. A total of 324 type 2 diabetic patients and 300 nondiabetic individuals were enrolled in the study. Eighty-seven of the type 2 diabetic patients who had not been treated with insulin or lipid-lowering drugs were evaluated by homeostasis model assessment for insulin resistance and were subjected to nuclear magnetic resonance for determination of HLC. A total of 19 single nucleotide polymorphisms (SNPs) were identified at the CPT1A locus, and linkage disequilibrium analysis revealed a strong linkage disequilibrium block between SNP8 (intron 5) and SNP17 (intron 14). Neither haplotypes nor SNPs of CPT1A were found to be associated either with susceptibility to type 2 diabetes mellitus or with HLC or insulin resistance in type 2 diabetic patients.

GEL: a novel genotype calling algorithm using empirical likelihood.

MOTIVATION: Preliminary results on the data produced using the Affymetrix large-scale genotyping platforms show that it is necessary to construct improved genotype calling algorithms. There is evidence that some of the existing algorithms lead to an increased error rate in heterozygous genotypes, and a disproportionately large rate of heterozygotes with missing genotypes. Non-random errors and missing data can lead to an increase in the number of false discoveries in genetic association studies. Therefore, the factors that need to be evaluated in assessing the performance of an algorithm are the missing data (call) and error rates, but also the heterozygous proportions in missing data and errors. RESULTS: We introduce a novel genotype calling algorithm (GEL) for the Affymetrix GeneChip arrays. The algorithm uses likelihood calculations that are based on distributions inferred from the observed data. A key ingredient in accurate genotype calling is weighting the information that comes from each probe quartet according to the quality/reliability of the data in the quartet, and prior information on the performance of the quartet. AVAILABILITY: The GEL software is implemented in R and is available by request from the corresponding author at nicolae@galton.uchicago.edu.

A polymorphism in the AMPKalpha2 subunit gene is associated with insulin resistance and type 2 diabetes in the Japanese population.

AMP-activated protein kinase (AMPK) acts as a fuel gauge for glucose and lipid metabolism. The gene encoding the alpha2 isoform of the catalytic subunit of AMPK (PRKAA2) is located at one of the Japanese type 2 diabetes loci mapped by our previous genome scan (1p36-32). PRKAA2 is, therefore, a good candidate gene for insulin resistance and type 2 diabetes. We screened all nine exons, their exon-intron boundaries, and the 5' and 3' flanking regions of PRKAA2 to identify single nucleotide polymorphisms (SNPs), and we genotyped 192 type 2 diabetic patients and 272 nondiabetic subjects to assess possible associations between genotypes or haplotypes and type 2 diabetes. None of the 10 SNPs genotyped was associated with type 2 diabetes, but the haplotype analysis, consisting of six representative SNPs, revealed one haplotype, with the A (minor) allele for rs2051040 and a major allele for the other five SNPs, to be associated with type 2 diabetes (P = 0.009). This finding was confirmed in two larger replication samples (657 case and 360 control subjects, P = 0.021; and 356 case and 192 control subjects from the same area in Japan, P = 0.007) and a significant P value was obtained in the joint haplotype analysis of all samples (1,205 case and 824 control subjects, P = 0.0001). Furthermore, insulin resistance was associated with rs2051040 in nondiabetic subjects, and those with the A (minor) allele had a higher homeostasis model assessment of insulin resistance index than those who did not (initial control subjects [n = 272], P = 0.002; and joint replication control subjects [n = 552], P = 0.037). We speculate that the PRKAA2 gene influences insulin resistance and susceptibility to type 2 diabetes in the Japanese population.

Inverse correlation between serum adiponectin concentration and hepatic lipid content in Japanese with type 2 diabetes.

Adiponectin is an adipose tissue-specific protein and plays an important role in insulin sensitivity. On the other hand, intramyocellular lipid content and hepatic lipid content (HLC) are related to insulin resistance in humans. In the present study, the possible relations between the serum concentration of adiponectin and intracellular triglyceride content in skeletal muscle and in the liver were investigated in individuals with type 2 diabetes mellitus. Fifty Japanese sedentary subjects (34 men, 16 women) with type 2 diabetes who had neither been treated with insulin nor with thiazolidinediones were enrolled in the study. Insulin sensitivity in vivo was evaluated by measurement of the glucose infusion rate during a hyperinsulinemic-euglycemic clamp and of the homeostasis model of assessment-insulin resistance index. The intracellular triglyceride content in skeletal muscle and the liver was determined by nuclear magnetic resonance. The serum adiponectin concentration was inversely correlated with both HLC ( r = -0.39, P < .01) and the homeostasis model of assessment-insulin resistance index ( r = -0.32, P < .05), but it was not significantly related to either intramyocellular lipid content or glucose infusion rate during the hyperinsulinemic-euglycemic clamp in individuals with type 2 diabetes. These results suggest that adiponectin might play an important role in the regulation of HLC and basal insulin sensitivity in individuals with type 2 diabetes.

Role of Krüppel-like factor 15 in PEPCK gene expression in the liver.

Regulation of hepatic gene expression is important for energy homeostasis. We now show that hepatic expression of the gene for the transcription factor Kruppel-like factor 15 (KLF15) is increased by food deprivation and reduced by feeding in mice. Expression of the KLF15 gene in mouse liver was also down-regulated by a euglycemic-hyperinsulinemic clamp and was increased by inhibition of phosphatidylinositol 3-kinase. In cultured rat hepatocytes, KLF15 gene expression was induced by dexamethasone and a non-hydrolyzing analog of cAMP, and this effect was inhibited by insulin in a manner dependent on phosphatidylinositol 3-kinase signaling. Forced expression of KLF15 in cultured hepatocytes increased both the expression and the promoter activity of the gene for phosphoenolpyruvate carboxykinase (PEPCK). These results suggest that insulin and its counteracting hormones regulate the hepatic expression of KLF15, and that this transcription factor contributes to the regulation of PEPCK gene expression in the liver.

The IHPK1 gene is disrupted at the 3p21.31 breakpoint of t(3;9) in a family with type 2 diabetes mellitus.

Type 2 diabetes mellitus (T2DM) is a group of multifactorial disorders due to either defective insulin secretion or action. Despite the fact that numerous genetic researches of T2DM have been pursued, the pathogenic mechanisms remain obscure. We encountered a T2DM family associated with a balanced reciprocal translocation, t(3;9)(p21.31;q33.1). To isolate a candidate gene susceptible to T2DM, we constructed physical maps covering both the 3p and 9q breakpoints of the translocation in the family. Consequently, the inositol hexaphosphate kinase 1 gene ( IHPK1) (OMIM *606991) was found to be disrupted at the 3p21.31 breakpoint. We then carried out sequence analysis for all coding regions of IHPK1 in 405 unrelated T2DM patients in order to validate whether aberrations of the gene are common in T2DM patients, but we failed to detect any pathogenic changes. The disruption of IHPK1 or another predisposing gene affected by position effect of the translocation may explain the T2DM phenotype at least in this family. Alternatively, the IHPK1 disruption in the family is a chance association.