Youichi Sato

Interrelationship of dipeptidyl peptidase IV (DPP4) with the development of diabetes, dyslipidaemia and nephropathy: a streptozotocin-induced model using wild-type and DPP4-deficient rats

We examined the role of dipeptidyl peptidase IV (DPP4) in the development of diabetes, dyslipidaemia and renal dysfunction induced by streptozotocin (STZ). F344/DuCrlCrlj rats, which lack DPP4 activity, and wild-type rats were treated with STZ. Plasma DPP4 activity and biochemical parameters were measured until 42 days after STZ treatment. At the end of the experiment, renal function and DPP4 expressions of the kidney, liver, pancreas and adipose tissues were determined. Increases in blood glucose, cholesterol and triglycerides were evoked by STZ in both rat strains; however, the onset of hyperglycaemia was delayed in DPP4-deficient rats as compared with wild-type rats. By contrast, more severe dyslipidaemia was observed in DPP4-deficient rats than in wild-type rats after STZ treatment. Plasma DPP4 activity increased progressively with time after STZ treatment in wild-type rats. The kidney of wild-type rats showed decreased DPP4 activity with increased Dpp4 mRNA after STZ treatment. In addition, kidney weight, serum creatinine and excreted amounts of urinary protein, glucose and DPP4 enzyme were enhanced by STZ. DPP4-deficient rats showed increased serum creatinine in accordance with decreased creatinine clearance as compared with wild-type rats after STZ treatment. In conclusion, plasma DPP4 activity increased after STZ treatment, positively correlating to blood glucose. DPP4-deficient rats were resistant to developing diabetes, while susceptible to dyslipidaemia and reduction of glomerular filtration rate by STZ. DPP4 activation may be responsible for hyperglycaemia, lipid metabolism and preservation of renal function.

Altered dipeptidyl peptidase-4 activity during the progression of hyperinsulinemic obesity and islet atrophy in spontaneously late-stage type 2 diabetic rats

Altered dipeptidyl peptidase-4 (DPP4) activity during the progression of late-stage type 2 diabetes was measured in Otsuka Long-Evans Tokushima fatty (OLETF) rats. Compared with OLETF rats subjected to 30% food restriction, food-satiated OLETF rats exhibited spontaneous hyperphagic obesity, insulin resistance, hyperglycemia, hyperinsulinemia, and increased plasma DPP4 activity during the early phase of the experiment (up to ∼30 wk). Subsequently, their plasma DPP4 activity as well as their body weight, body fat, and plasma insulin concentration declined to control levels during the late phase, resulting in excessive polyuria, proteinuria, dyslipidemia, pancreatic islet atrophy, hypoinsulinemia, and diabetes, which changed from insulin-resistant diabetes to hypoinsulinemic diabetes secondary to progressive islet insufficiency, and their fasting blood glucose level remained high. Since plasma DPP4 activity demonstrated significant positive correlations with body weight and the fasting plasma insulin level but not with the fasting blood glucose level during the late stage of diabetes, body fat and fasting plasma insulin levels may be useful factors for predicting the control of plasma DPP4 activity. In contrast, pancreatic DPP4 activity was significantly increased, and the expression of pancreatic insulin was significantly reduced in late-stage diabetic OLETF rats, suggesting that a relationship exists between the activation of pancreatic DPP4 and insulin depletion in pancreatic islet atrophy. In conclusion, it is suggested that plasma DPP4 activity changes in accordance with the progression of hyperinsulinemic obesity and pancreatic islet atrophy. DPP4 activity may play an important role in insulin homeostasis.

An association study of four candidate loci for human male fertility traits with male infertility

STUDY QUESTION Are the four candidate loci (rs7867029, rs7174015, rs12870438 and rs724078) for human male fertility traits, identified in a genome-wide association study (GWAS) of a Hutterite population in the USA, associated with male infertility in a Japanese population? SUMMARY ANSWER rs7867029, rs7174015 and rs12870438 are significantly associated with the risk of male infertility in a Japanese population. WHAT IS KNOWN ALREADY Recently, a GWAS of a Hutterite population in the USA revealed that 41 single-nucleotide polymorphisms (SNPs) were significantly correlated with family size or birth rate. Of these, four SNPs (rs7867029, rs7174015, rs12870438 and rs724078) were found to be associated with semen parameters in ethnically diverse men from Chicago. STUDY DESIGN, SIZE, DURATION This is a case-control association study in a total of 917 Japanese subjects, including 791 fertile men, 76 patients with azoospermia and 50 patients with oligozoospermia. PARTICIPANTS/MATERIALS, SETTING, METHODS Azoospermia was diagnosed on the basis of semen analysis (the absence of sperm in ejaculate), serum hormone levels and physical examinations. Oligozoospermia was defined as a sperm concentration of <20 × 10(6)/ml. We excluded patients with any known cause of infertility (i.e. obstructive azoospermia, varicocele, cryptorchidism, hypogonadotropic hypogonadism, karyotype abnormalities or complete deletion of AZF a, b or c). The SNPs rs7867029, rs7174015, rs12870438 and rs724078 were genotyped using DNA from peripheral blood samples and either restriction fragment length polymorphism PCR or TaqMan probes. Genetic associations between the four SNPs and male infertility were assessed using a logistic regression analysis under three different comparative models (additive, recessive or dominant). MAIN RESULTS AND THE ROLE OF CHANCE The genotypes of all four SNPs were in Hardy-Weinberg equilibrium in the fertile controls. The SNPs rs7867029 and rs7174015 are associated with oligozoospermia [rs7867029: odds ratio (OR) = 1.70, 95% confidence interval (CI) = 1.07-2.68, P = 0.024 (log-additive); rs7174015: OR = 6.52, 95% CI = 1.57-27.10, P = 0.0099 (dominant)] and rs12870438 is associated with azoospermia (OR = 10.90, 95% CI = 2.67-44.60, P = 0.00087 (recessive)] and oligozoospermia [OR = 8.54, 95% CI = 1.52-47.90, P = 0.015 (recessive)]. The association between rs7174015 and oligozoospermia under a dominant model and between rs12870438 and azoospermia under additive and recessive models remained after correction for multiple testing. There were no associations between rs724078 and azoospermia or oligozoospermia. LIMITATIONS, REASONS FOR CAUTION Even though the sample size of case subjects was not very large, we found that three SNPs were associated with the risk of male infertility in a Japanese population. WIDER IMPLICATIONS OF THE FINDINGS The three infertility-associated SNPs may be contributing to a quantitative reduction in spermatogenesis. STUDY FUNDING/COMPETING INTERESTS This study was supported in part by the Ministry of Health and Welfare of Japan (1013201) (to T.I.), Grant-in-Aids for Scientific Research (C) (23510242) (to A.Ta.) from the Japan Society for the Promotion of Science, the European Union (BMH4-CT96-0314) (to T. I.) and the Takeda Science Foundation (to A.Ta.). None of the authors has any competing interests to declare.

6,7-Dihydroxyflavone Dramatically Intensifies the Susceptibility of Methicillin-Resistant or -Sensitive Staphylococcus aureus to β-Lactams

ABSTRACT We have demonstrated that 6,7-dihydroxyflavone by itself has only a weak antibacterial effect on methicillin-resistant Staphylococcus aureus (MRSA) but that at concentrations less than MIC it synergistically elevates the susceptibility of clinically isolated MRSA and methicillin-sensitive S. aureus strains to β-lactam antibiotics from 8- to 32,800-fold.

Replication Study and Meta-Analysis of Human Nonobstructive Azoospermia in Japanese Populations

ABSTRACT Recently, a Chinese genomewide association study (GWAS) identified four autosomal single-nucleotide polymorphism (SNP) loci as being significantly associated with risk factors for nonobstructive azoospermia (NOA; P < 5 × 10−8). In the present study, we performed a replication study on two Japanese cohorts from different institutions in order to evaluate whether SNP loci are associated with NOA. The four SNPs (rs12097821, rs2477686, rs10842262, and rs6080550) reported in the Chinese GWAS were genotyped in 490 NOA patients and 1167 controls. To assess the significance of the associations between each of the four SNPs and NOA in the Japanese population, the association results for the two cohorts were combined by meta-analysis. In the meta-analysis, the combined per-allele odds ratios (ORs) for the four SNPs and their respective 95% confidence intervals (CIs) were as follows: rs12097821, OR = 1.10 (CI = 0.89–1.37); rs2477686, OR = 1.11 (CI = 0.87–1.43); rs10842262, OR = 1.11 (CI = 0.94–1.32); and rs6080550, OR = 0.96 (CI = 0.76–1.21). None of the SNPs was significantly associated with NOA (P > 0.05). However, three of four SNPs (rs12097821, rs2477686, and rs10842262) showed associations in the same direction in Japanese men as those reported in the Chinese GWAS. To determine whether the four SNPs are genetic risk factors for NOA, the effect sizes of NOA risk factors require further investigation using larger independent sets of case-control samples of populations, including Japanese and Chinese populations.

Y chromosome haplogroup d2* lineage is associated with azoospermia in Japanese males.

ABSTRACT Several studies have investigated whether particular Y chromosome haplogroups are associated with spermatogenic failure in Japanese males; however, they produced differing results. In this study, to investigate the association of Y chromosome haplogroup with spermatogenic failure, we recruited 451 infertile patients and 730 fertile men from a Japanese population and typed their Y chromosome haplogroups. The infertile patients were suffering from varicocele, azoospermia, oligozoospermia, asthenozoospermia, obstructive azoospermia, karyotype abnormalities, microdeletions of the long arm of the Y chromosome, or other conditions that affect fertility. The frequency of haplogroup D2* was significantly higher (odds ratio = 2.28, 95% confidence interval = 1.44–3.61, P = 0.00034 using chi-square test) among the men with azoospermia than among the fertile men. None of the other Y haplogroups displayed associations with particular types of infertility. In conclusion, Y chromosome haplogroup D2* is associated with spermatogenic failure in Japanese males, suggesting that the Y chromosome lineage can have significant effects on spermatogenesis.

Role of dipeptidyl peptidase IV (DPP4) in the development of dyslipidemia: DPP4 contributes to the steroid metabolism pathway

AIMS We previously reported that dipeptidyl peptidase IV (DPP4)-deficient rats were susceptible to dyslipidemia induced by streptozotocin (STZ). Hence, it is suggested that DPP4 is important for lipid metabolism. MAIN METHODS In this study, to verify the role of DPP4 in the development of dyslipidemia, we carried out a microarray analysis of the livers of STZ-treated wild-type and DPP4-deficient rats and showed that the expression levels of genes involved in metabolic processes (steroid metabolic processes and cellular lipid metabolic processes) were significantly altered by STZ treatment. KEY FINDINGS In the wild-type rats, the expression of hydroxysteroid (17-beta) dehydrogenase 2 (Hsd7b2), which catalyzes sex steroid synthesis from cholesterol, was significantly increased by about 15-fold after STZ treatment; however, it did not change in the DPP4-deficient rats. In the STZ untreated group of DPP4-deficient rats, the expression levels of cytochrome P450, subfamily 51 (Cyp51) and sterol-C4-methyl oxidase-like (Sc4mol), which catalyze intermediate steps in cholesterol synthesis, were significantly elevated compared to those of other groups. Similar results were demonstrated in HuH7-cells after DPP4 overexpression or the addition of human sera containing DPP4. SIGNIFICANCE DPP4 is crucial for regulating the expression of factors related to steroid metabolism such as Cyp51, Sc4mol, and Hsd17b2, and DPP4 deficiency or inhibition may cause dyslipidemia.

Proteasome Subunits mRNA Expressions Correlate With Male BMI: Implications for a Role in Obesity

Obesity as well as its associated chronic diseases and adverse health consequences such as type 2 diabetes mellitus, dyslipidemia, hypertension, and coronary artery disease are afflicting middle‐aged adults and an ever greater number of children globally. We planned to investigate new obesity‐related factors using proteomics approaches in a randomly selected three high and three low BMI samples of Epstein‐Barr‐transformed B (EBV‐B) lymphoblastoid cell lines prepared from two groups of young Japanese men with different BMI. To search novel obesity‐related factors, comparisons of protein expressions between high and low BMI groups were carried out by two‐dimensional gel electrophoresis (2‐DE). Gene transcripts of proteasome subunits found out from 2‐DE were further determined by quantitative real‐time PCR. Results from proteomics approach showed that the expression of proteasome α subunit type 5 (PSMA5) was significantly lower in the high BMI male group than in those with low BMI (P < 0.05). To validate these results, we expanded the study to include 20 more men and used real‐time PCR to quantify the mRNA expression level in their EBV‐B cells. Both PSMA5 and PSMA2 of EBV‐B cells showed negative correlation with BMI. Furthermore, the mRNA levels measured in the peripheral blood B lymphocytes for many proteasome subunits in 75 healthy men and women showed significant negative correlation with BMI in healthy men. Our findings suggest that proteasome expression may play a key role in obesity.

Molecular analysis of TBL1Y, a Y-linked homologue of TBL1X related with X-linked late-onset sensorineural deafness

AbstractRecent progress in sequencing the human Y chromosome has unveiled a series of X-Y homologous genes. In the present study, we focused on Transducin beta-like 1Y (TBL1Y), which is a Y-linked homologue of TBL1X that is related with X-linked late-onset sensorineural deafness. Recently, it has been shown that TBLR1, another homologue whose gene resides on chromosome 3, and TBL1X act as a corepressor/coactivator exchanger for several nuclear receptors and transcription factors. However, the expression pattern and function of TBL1Y remain unknown. The RT-PCR analysis of the TBL1 family revealed that TBL1Y was expressed in all 13 tissues examined but not in leukocytes. Among the cell lines tested, however, it was only expressed in NT2/D1 cells and in lymphoblasts transformed with Epstein Barr (EB) virus. To compare the functions of the TBL1 family, we generated a series of expression plasmids for GAL4DBD-fused proteins of the TBL1 family. We carried out dual luciferase assays using these plasmids in combination with a plasmid having a luciferase reporter gene harboring 5×GAL4 binding sites. Unlike the other constructs, GAL4DBD-fused TBL1Y did not repress the promoter activity. Moreover, we found three novel polymorphisms in the TBL1Y gene, IVS7+9G>A, G268C, and IVS7+1G>C, which is presumed to cause splicing error. These polymorphisms are found in males within Y-haplogroup O3 (XO3e), which is defined as the Y-haplogroup O3 excluding O3e, a branch of O3. The results show that TBL1Y differs from other members of the TBL1 family in expression and function, suggesting other roles in maleness.

Y Chromosome gr/gr Subdeletion Is Associated with Lower Semen Quality in Young Men from the General Japanese Population but Not in Fertile Japanese Men

ABSTRACT Several case-control studies have investigated whether Y chromosome haplogroups or deletions are associated with spermatogenic failure. However, the relationships between Y chromosome haplogroups or deletions and semen quality in general population have not been elucidated. In this study, we assessed relationships between Y chromosome haplogroups or deletions and semen parameters in 791 fertile Japanese men and 1221 young men from the general Japanese population. We found that the haplogroup D2 (M55 lineage) was significantly associated with lower semen parameters, especially total motile sperm count (P = 0.00051, beta = −0.097), in men from the general population but not in fertile men. In addition, we found that the gr/gr subdeletion was associated with semen quality and in particular, strongly associated with decreased sperm motility (P = 0.00041, beta = −3.14) and total motile sperm count (P = 0.00031, beta = −0.099) in men from the general population but not in fertile men. The combined analysis of fertile Japanese men and men from the general Japanese population showed that the haplogroup D2 (M55 lineage) and the gr/gr subdeletion were strongly associated with reduced sperm motility (P = 0.00056, beta = −2.71, and P = 7.7 × 10−5, beta = −3.05, respectively) and that haplogroup O2b1 was strongly associated with elevated sperm motility (P = 0.00089, beta = 2.94). These observations add further support for the view that the gr/gr subdeletion diminishes sperm motility that consequently may result in male infertility.