Masaya Shimada

(-)-Epigallocatechin gallate enhances the expression of genes related to insulin sensitivity and adipocyte differentiation in 3T3-L1 adipocytes at an early stage of differentiation

OBJECTIVE (-)-Epigallocatechin gallate (EGCG) is thought to enhance insulin sensitivity in adipocytes, although doses used in in vitro experiments have been shown to promote apoptosis. To explore the effects of EGCG on insulin sensitivity in adipocytes, the expression of genes related to insulin sensitivity and adipocyte differentiation in 3T3-L1 adipocytes were measured in response to low doses of EGCG. METHODS Increasing concentrations of low-dose EGCG were administered for 8 d to differentiating 3T3 adipocytes, either at days 0-8 (early stage) or at days 8-16 (late stage). Fat accumulation and cell activity were measured by Oil Red O staining and 1-(4,5-dimethylthiazol-2-yl)-3,5-diphenylformazan assay, respectively. The expression of genes related to insulin sensitivity and adipocyte differentiation was measured by real-time reverse transcriptase-polymerase chain reaction. RESULTS Fat accumulation and cell activity in 3T3-L1 cells at the early and late stages were reduced at EGCG concentrations > or = 50 microM. However, EGCG doses of 5-10 microM reduced fat accumulation and induced the expression of genes related to insulin sensitivity (including Fabp4, Cd36, Lpl, Pck1, Acox1, Lypla3, and Ucp2) and adipocyte differentiation (Pparg1, Pparg2, Cebps, and Ppargc1a). These increases were only seen at the early, and not late, stages of differentiation. CONCLUSION These data indicate that low doses of EGCG, despite reducing triacylglycerol accumulation, induce the expression of genes related to insulin sensitivity in the early stage of differentiation.

Dietary Supplementation with Epigallocatechin Gallate Elevates Levels of Circulating Adiponectin in Non-Obese Type-2 Diabetic Goto-Kakizaki Rats

Epigallocatechin gallate (EGCG) reportedly enhances plasma adiponectin levels in models of insulin resistance and obesity. In this study, we found that EGCG increases plasma adiponectin levels and decreases plasma triacylglycerol levels in non-obese diabetic Goto-Kakizaki rats with insulin secretory dysfunction. These results suggest that EGCG ameliorates lipid metabolic abnormality even in non-obese rats, probably by increasing adiponectin production.

The regulation of jejunal induction of the maltase-glucoamylase gene by a high-starch/low-fat diet in mice

Maltase and glucoamylase are derived from the same mRNA and are responsible for digestion of starch in the small intestine. Their jejunal activities in rodents are induced by a high-starch/low-fat (HS)-diet. However, it is unknown whether jejunal expression of the maltase-glucoamylase (Mgam) gene is enhanced by the HS-diet. In this study, we found that jejunal Mgam mRNA was increased by a HS-diet in mice. We showed that the HS-diet increased acetylation of histones, bindings of a coactivator, Creb binding protein (CREBBP), and the transcriptional factors caudal type homeobox 2 (CDX2) and HNF1 homeobox (HNF1) in the promoter/enhancer and transcriptional regions of Mgam gene. This suggests that the increase in the jejunal activity of maltase and glucoamylase caused by a HS-diet in mice is regulated at the mRNA level through histone acetylation and binding of CREBBP, CDX2 and HNF1 in the promoter/enhancer and transcriptional regions of Mgam gene.

The α-glucosidase inhibitor miglitol decreases glucose fluctuations and gene expression of inflammatory cytokines induced by hyperglycemia in peripheral leukocytes

OBJECTIVE Postprandial hyperglycemia is thought to cause inflammation in many tissues. In this study, we examined whether the gene expression of inflammatory cytokines/cytokine-like factors in peripheral leukocytes are altered by feeding streptozotocin-treated rats a diet containing an alpha-glucosidase inhibitor, miglitol. METHODS Upregulated gene expression in peripheral leukocytes of streptozotocin-induced hyperglycemic rats was determined by microarray analysis. We examined whether gene expression was altered by supplementing the diet with miglitol. RESULTS Microarray analysis revealed that gene expression of interleukin-1beta and putative inflammatory cytokines, S100a4/6/8/9, was induced by streptozotocin treatment. Dietary supplementation with miglitol to the streptozotocin-induced hyperglycemic rats for 20 d not only increased plasma concentrations of a marker for glucose fluctuations, 1,5-anhydroglucitol, the concentration of which is decreased by sustained or postprandial elevated blood glucose levels, but also suppressed the induction of interleukin-1beta and S100a4/6/8/9 genes by hyperglycemia. CONCLUSION These results suggest that miglitol inhibits the gene expression of inflammatory cytokines/cytokine-like factors in peripheral leukocytes by suppressing glucose fluctuations.

Plasma interleukin-1β concentrations are closely associated with fasting blood glucose levels in healthy and preclinical middle-aged nonoverweight and overweight Japanese men

Plasma interleukin (IL)-1β and IL-6 are markers that predict the risk of inflammation in diabetes. In the current study, we examined the relationship between fasting glucose and plasma inflammatory cytokines (IL-1β and IL-6) concentrations in healthy and preclinical middle-aged Japanese men (mean ± SD, 58.7 ± 7.8 years old) divided according to body mass index (<25 kg/m(2), nonoverweight group; ≥25 kg/m(2), overweight group). We conducted a cross-sectional study of 413 healthy and preclinical men aged 40 to 69 years who participated in health checkups in Japan. We measured their clinical parameters, lifestyle factors, and plasma IL-1β and IL-6 concentrations. Participants were classified according to their fasting blood glucose levels, and we compared their plasma cytokine levels. Plasma IL-1β and IL-6 levels in nonoverweight subjects were positively and strongly associated with fasting blood glucose and hemoglobin A(1c); in contrast, these cytokines were strongly associated with homeostasis model assessment of insulin resistance and fasting glucose in overweight subjects. Significant positive associations between plasma IL-1β and glucose concentrations were observed within the groups classified according to glucose concentrations, after adjustment for age and body mass index. The results of our current study show that plasma IL-1β levels are strongly associated with fasting blood glucose concentrations in healthy and preclinical nonoverweight and overweight Japanese men.

The α-glucosidase inhibitor miglitol suppresses postprandial hyperglycaemia and interleukin-1β and tumour necrosis factor-α gene expression in rat peripheral leucocytes induced by intermittent sucrose loading

Postprandial hyperglycaemia is thought to increase inflammation in leucocytes. In the present study, we examined whether sucrose loading in rats with moderate postprandial hyperglycaemia induces the expression of cytokines in peripheral leucocytes and whether these inductions are suppressed by inhibiting postprandial hyperglycaemia with the alpha-glucosidase inhibitor miglitol. One group of streptozotocin-treated rats and age-matched saline-treated rats were orally administered sucrose only, and another group of streptozotocin-treated rats was administered sucrose with miglitol, at a single daily dose for 4 d, under 4 h fasting conditions. Blood glucose levels at 0, 0.25, 0.5, 1, 2 and 3 h and cytokine mRNA in peripheral leucocytes at 0 and 3 h after sucrose loading on days 1 and 4 from the start of sucrose loading were determined. Streptozotocin-treated rats showed moderate postprandial hyperglycaemia (>2000 mg/l) at 0.25-1 h after sucrose loading on days 1 and 4. Postprandial hyperglycaemia was not observed in the miglitol-treated rats loaded with sucrose. Gene expression levels of IL-1beta and TNF-alpha were higher in the streptozotocin-treated rats at fasting on day 1 than in saline-treated rats. Fasting IL-1beta and TNF-alpha gene expression on day 1 were not only increased at 3 h on the same day of sucrose loading, but was also increased at the fasting period on day 4. These inductions on day 4 by intermittent sucrose administration were inhibited by miglitol. The present results suggest that miglitol decreases postprandial hyperglycaemia and intermittent sucrose-induced expression of the IL-1beta and TNF-alpha genes in rat peripheral leucocytes.

Feeding Rats Dietary Resistant Starch Shifts the Peak of SGLT1 Gene Expression and Histone H3 Acetylation on the Gene from the Upper Jejunum toward the Ileum.

Sodium glucose cotransporter 1 (SGLT1) participates in the incorporation of glucose from the lumen to enterocytes in the small intestine. We examined whether dietary resistant starch (RS), an autoclaved high amylose starch that is digested more slowly than regular cornstarch in the small intestine, alters SGLT1 mRNA levels along the jejunum-ileum of rats. The SGLT1 mRNA level was lower in the upper jejunum in rats fed an RS diet than in those fed a regular cornstarch diet, whereas it was higher in the lower jejunum/upper ileum. Furthermore, using chromatin immunoprecipitation (ChIP) assay, we demonstrated that histone H3 acetylation on the promoter/enhancer and transcriptional regions was reduced in the upper jejunum and elevated in the lower jejunum/upper ileum by feeding rats an RS diet. On the other hand, HNF-1 binding on the region around transcription start site of the SGLT1 gene was not altered in each jejunoileal segment by feeding rats an RS diet. Our results suggest that a shift of the expressional peak of the SGLT1 gene from the upper jejunum toward the ileum by dietary RS is associated with a change of histone H3 acetylation rather than that of HNF-1 binding on the gene.

Dietary Resistant Starch Reduces Levels of Glucose-Dependent Insulinotropic Polypeptide mRNA along the Jejunum-Ileum in Both Normal and Type 2 Diabetic Rats

It has been reported that the circulating glucose-dependent insulinotropic polypeptide (GIP) levels were reduced by an intake of some foods/drugs capable of delaying carbohydrate digestion/absorption. In this study, we revealed that feeding rats with dietary resistant starch reduced the GIP mRNA levels along the entire length of the jejunoileum in both Wistar and type 2 diabetic GK rats.

Variation in Gene Expression of Inflammatory Cytokines in Leukocyte-Derived Cells of High-Fat-Diet-Induced Insulin-Resistant Rats

A high-fat diet is thought to enhance inflammation in various tissues by increasing insulin resistance. In this study, we determined the mRNA levels of inflammatory cytokines in leukocyte-derived cells in the blood of rats with high-fat-diet-induced insulin resistance. Feeding rats a high-fat diet for 77 d induced moderate insulin resistance, which was determined by increased plasma glucose and insulin concentrations, following an oral glucose tolerance test. The interleukin (IL)-1β mRNA level was higher in the insulin-resistant rats than in control rats at the fasting stage, whereas the tumor necrosis factor (TNF)-α mRNA level was greatly elevated at 180 min after glucose administration in the insulin-resistant rats. The results suggest that feeding rats a high-fat diet enhances the expression of fasting IL-1β and postprandial TNF-α genes in leukocyte-derived cells.

A higher rate of eating is associated with higher circulating interluekin-1β concentrations in Japanese men not being treated for metabolic diseases

OBJECTIVE In this study, we examined the relations between the rate of eating and circulating interleukin (IL)-1β and IL-6 levels in Japanese men not being treated for metabolic diseases. METHODS We conducted a cross-sectional study of 170 men 40 to 59 y old (mean ± standard deviation, 51.4 ± 5.7 y old) who participated in health checkups in Japan and were not being treated for metabolic diseases. We measured clinical serum parameters and plasma IL-1β and IL-6 concentrations and assessed by questionnaire lifestyle factors such as the dietary intake of food/nutrition and the rate of eating. Using multivariate linear regression analysis, we analyzed the relations between the rate of eating and IL-1β and IL-6 concentrations, clinical parameters, and lifestyle factors. RESULTS Significant Spearman correlation coefficients with the rate of eating were observed for IL-1β and IL-6 (0.250 and 0.195, respectively). The rate of eating was positively associated with IL-1β independently of IL-6, body mass index, homeostasis model assessment for insulin resistance, alcohol intake, energy intake, smoking status, and physical activity. CONCLUSIONS These results indicate that a higher rate of eating is positively and independently associated with circulating IL-1β concentrations in Japanese men not being treated for metabolic diseases.