Masaru Sakurai

A liver-derived secretory protein, selenoprotein P, causes insulin resistance.

The liver may regulate glucose homeostasis by modulating the sensitivity/resistance of peripheral tissues to insulin, by way of the production of secretory proteins, termed hepatokines. Here, we demonstrate that selenoprotein P (SeP), a liver-derived secretory protein, causes insulin resistance. Using serial analysis of gene expression (SAGE) and DNA chip methods, we found that hepatic SeP mRNA levels correlated with insulin resistance in humans. Administration of purified SeP impaired insulin signaling and dysregulated glucose metabolism in both hepatocytes and myocytes. Conversely, both genetic deletion and RNA interference-mediated knockdown of SeP improved systemic insulin sensitivity and glucose tolerance in mice. The metabolic actions of SeP were mediated, at least partly, by inactivation of adenosine monophosphate-activated protein kinase (AMPK). In summary, these results demonstrate a role of SeP in the regulation of glucose metabolism and insulin sensitivity and suggest that SeP may be a therapeutic target for type 2 diabetes.

Gender differences in the association between anthropometric indices of obesity and blood pressure in Japanese.

To investigate which of four anthropometric variables of obesity has the strongest association with blood pressure (BP), and to investigate whether there are gender differences in these relationships in Asian adults, we evaluated the associations of four anthropometric variables, body mass index (BMI), waist circumference, waist-to-hip ratio and waist-to-height ratio, with BP and the prevalence of hypertension in a cross-sectional study. A total of 4,557 employees of a metal-products factory in Toyama, Japan (2,935 men and 1,622 women, aged 35 to 59 years) were included in the study. Waist circumference in men and BMI in women had the strongest associations with BP. As for the age-adjusted rate ratio (RR) of the prevalence of hypertension for one standard deviation increase in each anthropometric variable, RR was the highest for waist circumference in men (RR, 1.44; 95% confidence interval [CI], 1.31–1.58), and for BMI in women (RR, 1.61; 95% CI, 1.38–1.88). The associations of waist circumference in men and BMI in women remained significant after adjustment for each of the other variables. The associations of waist-to-height ratio with BP and the prevalence of hypertension were a little weaker than those of waist circumference for both men and women. In conclusion, among four anthropometric variables of obesity—i.e., BMI, waist circumference, waist-to-hip ratio, and waist-to-height ratio—waist circumference had the strongest association with BP and the prevalence of hypertension in men and BMI had the strongest association with BP and hypertension in women. Waist circumference in men and BMI in women should be given more importance in the screening of and guidelines on hypertension in Asians.

Obesity Upregulates Genes Involved in Oxidative Phosphorylation in Livers of Diabetic Patients

Obesity is a major cause of insulin resistance and contributes to the development of type 2 diabetes. The altered expression of genes involved in mitochondrial oxidative phosphorylation (OXPHOS) has been regarded as a key change in insulin‐sensitive organs of patients with type 2 diabetes. This study explores possible molecular signatures of obesity and examines the clinical significance of OXPHOS gene expression in the livers of patients with type 2 diabetes. We analyzed gene expression in the livers of 21 patients with type 2 diabetes (10 obese and 11 nonobese patients; age, 53.0 ± 2.1 years; BMI, 24.4 ± 0.9 kg/m2; fasting plasma glucose, 143.0 ± 10.6 mg/dl) using a DNA chip. We screened 535 human pathways and extracted those metabolic pathways significantly altered by obesity. Genes involved in the OXPHOS pathway, together with glucose and lipid metabolism pathways, were coordinately upregulated in the liver in association with obesity. The mean centroid of OXPHOS gene expression was significantly correlated with insulin resistance indices and the hepatic expression of genes involved in gluconeogenesis, reactive oxygen species (ROS) generation, and transcriptional factors and nuclear co‐activators associated with energy homeostasis. In conclusion, obesity may affect the pathophysiology of type 2 diabetes by upregulating genes involved in OXPHOS in association with insulin resistance markers and the expression of genes involved in hepatic gluconeogenesis and ROS generation.

Impact of diabetes on recurrence of hepatocellular carcinoma after surgical treatment in patients with viral hepatitis.

OBJECTIVES: Consensus has been reached that diabetes is a risk factor for development of HCC, but the impact on postoperative recurrence is still controversial. To clarify this point, we analyzed the relationship of postoperative recurrence rate of HCC and coexistence of diabetes in the patients with viral hepatitis.METHODS: A total of 90 patients who had undergone curative resection for HCC were analyzed. They were divided into two groups with and without diabetes, and the recurrence-free survival rates after surgical treatment and the factors contributing to recurrence were examined.RESULTS: Kaplan-Meier survival analysis showed the recurrence-free survival rates in the diabetic group were significantly lower than those in the nondiabetic group (P = 0.005) and overall survival rates in the diabetic group were significantly lower than those in the nondiabetic group (P = 0.005). These results were emphasized in the analysis of patients infected with hepatitis C virus. Univariate and multivariate analyses showed diabetes was a significant factor contributing to HCC recurrence after treatment. Furthermore, multivariate analysis in HCC patients with diabetes showed Child-Pugh classification B (P = 0.001) and insulin therapy (P = 0.049) were significant factors contributing to HCC recurrence after treatment.CONCLUSIONS: The results of the present study suggest that diabetes is a risk factor for the recurrence of HCV-related HCC and decreases the overall survival rates after surgical treatment. HCV-related HCC patients with diabetes should be closely followed for postoperative recurrence.

Genes involved in oxidative phosphorylation are coordinately upregulated with fasting hyperglycaemia in livers of patients with type 2 diabetes.

Aims/hypothesisMitochondrial oxidative phosphorylation (OXPHOS) plays an important role in the pathophysiology of type 2 diabetes. Genes involved in OXPHOS have been reported to be down-regulated in skeletal muscle from patients with type 2 diabetes; however, hepatic regulation is unknown.Materials and methodsWe analysed expression of genes involved in OXPHOS from the livers of 14 patients with type 2 diabetes and 14 subjects with NGT using serial analysis of gene expression (SAGE) and DNA chip analysis. We evaluated the correlation between expression levels of genes involved in OXPHOS and the clinical parameters of individuals with type 2 diabetes and NGT.ResultsBoth gene analyses showed that genes involved in OXPHOS were significantly upregulated in the type 2 diabetic liver. In the SAGE analysis, tag count comparisons of mitochondrial transcripts showed that ribosomal RNAs (rRNA) were 3.5-fold over-expressed, and mRNAs were 1.2-fold over-expressed in the type 2 diabetes library. DNA chip analysis revealed that expression of genes involved in OXPHOS, which correlated with several nuclear factors, including estrogen-related receptor-α or peroxisome proliferator-activated receptor-γ, was a predictor of fasting plasma glucose levels, independently of age, BMI, insulin resistance and fasting insulin levels (pu2009=u20090.04). Surprisingly, genes involved in OXPHOS did not correlate with peroxisome proliferator-activated receptor-γ coactivator-1α or nuclear respiratory factor 1.Conclusions/interpretationOur results indicate that upregulation of genes involved in OXPHOS in the liver, which are regulated by different mechanisms from genes in the skeletal muscle, is associated with fasting hyperglycaemia in patients with type 2 diabetes.

Genes for systemic vascular complications are differentially expressed in the livers of type 2 diabetic patients.

Aims/hypothesisType 2 diabetes is characterised by excessive hepatic glucose production and frequently leads to systemic vascular complications. We therefore analysed the relationship between the gene expression profile in the liver and the pathophysiology of Type 2 diabetes.MethodsLiver biopsy samples were obtained from twelve patients with Type 2 diabetes and from nine non-diabetic patients. To assay gene expression globally in the livers of both groups, we made complementary DNA (cDNA) microarrays consisting of 1080 human cDNAs. Relative expression ratios of individual genes were obtained by comparing cyanine 5-labelled cDNA from the patients with cyanine 3-labelled cDNA from reference RNA from the liver of a non-diabetic patient.ResultsOn assessing the similarities of differentially expressed genes, the gene expression profiles of the twelve diabetic patients formed a separate cluster from those of the non-diabetic patients. Of the 1080 genes assayed, 105 (9.7%) were up-regulated and 134 (12%) were down-regulated in the diabetic livers (p<0.005). The genes up-regulated in the diabetic patients included those encoding angiogenic factors such as vascular endothelial growth factor, endothelin and platelet-derived growth factor. They also included TGF superfamily genes such as TGFA and TGFB1 as well as bone morphogenetic proteins. Among the down-regulated genes in the diabetic patients were molecules defending against stress, e.g. flavin-containing monooxygenase and superoxide dismutase.Conclusions/interpretationThese findings suggest that livers of patients with Type 2 diabetes have gene expression profiles indicative of an increased risk of systemic vascular complications.

Sugar-sweetened beverage and diet soda consumption and the 7-year risk for type 2 diabetes mellitus in middle-aged Japanese men.

PurposeThis cohort study investigated the association between sugar-sweetened beverage (SSB) and diet soda consumption and the incidence of type 2 diabetes in Japanese men.MethodsThe participants were 2,037 employees of a factory in Japan. We measured consumption of SSB and diet soda using a self-administered diet history questionnaire. The incidence of diabetes was determined in annual medical examinations over a 7-year period. Hazard ratios (HRs) with 95xa0% confidence intervals (CIs) for diabetes were estimated after adjusting for age, body mass index, family history, and dietary and other lifestyle factors.ResultsDuring the study, 170 participants developed diabetes. The crude incidence rates (/1,000 person-years) across participants who were rare/never SSB consumers, <1 serving/week, ≥1 serving/week and <1 serving/day, and ≥1 serving/day were 15.5, 12.7, 14.9, and 17.4, respectively. The multivariate-adjusted HR compared to rare/never SSB consumers was 1.35 (95xa0% CI 0.80–2.27) for participants who consumed ≥1 serving/day SSB. Diet soda consumption was significantly associated with the incident risk of diabetes (P for trendxa0=xa00.013), and multivariate-adjusted HRs compared to rare/never diet soda consumers were 1.05 (0.62–1.78) and 1.70 (1.13–2.55), respectively, for participants who consumed <1 serving/week and ≥1 serving/week.ConclusionsConsumption of diet soda was significantly associated with an increased risk for diabetes in Japanese men. Diet soda is not always effective at preventing type 2 diabetes even though it is a zero-calorie drink.

HbA1c and the Risks for All-Cause and Cardiovascular Mortality in the General Japanese Population: NIPPON DATA90

OBJECTIVE Associations between HbA1c and cardiovascular diseases (CVD) have been reported mainly in Western countries. It is not clear whether HbA1c measurements are useful for assessing CVD mortality risk in East Asian populations. RESEARCH DESIGN AND METHODS The risk for cardiovascular death was evaluated in a large cohort of participants selected randomly from the overall Japanese population. A total of 7,120 participants (2,962 men and 4,158 women; mean age 52.3 years) free of previous CVD were followed for 15 years. Adjusted hazard ratios (HRs) and 95% CIs among categories of HbA1c (<5.0%, 5.0–5.4%, 5.5–5.9%, 6.0–6.4%, and ≥6.5%) for participants without treatment for diabetes and HRs for participants with diabetes were calculated using a Cox proportional hazards model. RESULTS During the study, there were 1,104 deaths, including 304 from CVD, 61 from coronary heart disease, and 127 from stroke (78 from cerebral infarction, 25 from cerebral hemorrhage, and 24 from unclassified stroke). Relations to HbA1c with all-cause mortality and CVD death were graded and continuous, and multivariate-adjusted HRs for CVD death in participants with HbA1c 6.0–6.4% and ≥6.5% were 2.18 (95% CI 1.22–3.87) and 2.75 (1.43–5.28), respectively, compared with participants with HbA1c <5.0%. Similar associations were observed between HbA1c and death from coronary heart disease and death from cerebral infarction. CONCLUSIONS High HbA1c levels were associated with increased risk for all-cause mortality and death from CVD, coronary heart disease, and cerebral infarction in general East Asian populations, as in Western populations.

Selenoprotein P as a diabetes-associated hepatokine that impairs angiogenesis by inducing VEGF resistance in vascular endothelial cells.

Aims/hypothesisImpaired angiogenesis induced by vascular endothelial growth factor (VEGF) resistance is a hallmark of vascular complications in type 2 diabetes; however, its molecular mechanism is not fully understood. We have previously identified selenoprotein P (SeP, encoded by the SEPP1 gene in humans) as a liver-derived secretory protein that induces insulin resistance. Levels of serum SeP and hepatic expression of SEPP1 are elevated in type 2 diabetes. Here, we investigated the effects of SeP on VEGF signalling and angiogenesis.MethodsWe assessed the action of glucose on Sepp1 expression in cultured hepatocytes. We examined the actions of SeP on VEGF signalling and VEGF-induced angiogenesis in HUVECs. We assessed wound healing in mice with hepatic SeP overexpression or SeP deletion. The blood flow recovery after ischaemia was also examined by using hindlimb ischaemia model with Sepp1-heterozygous-knockout mice.ResultsTreatment with glucose increased gene expression and transcriptional activity for Sepp1 in H4IIEC hepatocytes. Physiological concentrations of SeP inhibited VEGF-stimulated cell proliferation, tubule formation and migration in HUVECs. SeP suppressed VEGF-induced reactive oxygen species (ROS) generation and phosphorylation of VEGF receptor 2 (VEGFR2) and extracellular signal-regulated kinase 1/2 (ERK1/2) in HUVECs. Wound closure was impaired in the mice overexpressing Sepp1, whereas it was improved in SeP−/−mice. SeP+/−mice showed an increase in blood flow recovery and vascular endothelial cells after hindlimb ischaemia.Conclusions/interpretationThe hepatokine SeP may be a novel therapeutic target for impaired angiogenesis in type 2 diabetes.

Family history of diabetes, lifestyle factors, and the 7-year incident risk of type 2 diabetes mellitus in middle-aged Japanese men and women.

This cohort study of middle‐aged Japanese participants investigated the relationship between family history of diabetes, the incident risk of type 2 diabetes and the interaction of these variables with other factors.