Porphyromonas gingivalis induces entero-hepatic metabolic derangements with alteration of gut microbiota in a type 2 diabetes mouse model.

Periodontal infection induces systemic inflammation; therefore, aggravating diabetes. Orally administered periodontal pathogens may directly alter the gut microbiota. We orally treated obese db/db diabetes mice using Porphyromonas gingivalis (Pg). We screened for Pg-specific peptides in the intestinal fecal specimens and examined whether Pg localization influenced the intestinal microbiota profile, in turn altering the levels of the gut metabolites. We evaluated whether the deterioration in fasting hyperglycemia was related to the changes in the intrahepatic glucose metabolism, using proteome and metabolome analyses. Oral Pg treatment aggravated both fasting and postprandial hyperglycemia (P < 0.05), with a significant (P < 0.01) increase in dental alveolar bone resorption. Pg-specific peptides were identified in fecal specimens following oral Pg treatment. The intestinal Pg profoundly altered the gut microbiome profiles at the phylum, family, and genus levels; Prevotella exhibited the largest increase in abundance. In addition, Pg-treatment significantly altered intestinal metabolite levels. Fasting hyperglycemia was associated with the increase in the levels of gluconeogenesis-related enzymes and metabolites without changes in the expression of proinflammatory cytokines and insulin resistance. Oral Pg administration induced gut microbiota changes, leading to entero-hepatic metabolic derangements, thus aggravating hyperglycemia in an obese type 2 diabetes mouse model.

Hypothalamic AMP-Activated Protein Kinase Regulates Biphasic Insulin Secretion from Pancreatic ß Cells during Fasting and in Type 2 Diabetes.

Glucose-stimulated insulin secretion (GSIS) by pancreatic ß cells is biphasic. However, the physiological significance of biphasic GSIS and its relationship to diabetes are not yet fully understood. This study demonstrated that impaired first-phase GSIS follows fasting, leading to increased blood glucose levels and brain glucose distribution in humans. Animal experiments to determine a possible network between the brain and ß cells revealed that fasting-dependent hyperactivation of AMP-activated protein kinase in the hypothalamus inhibited first-phase GSIS by stimulating the ß-adrenergic pancreatic nerve. Furthermore, abnormal excitability of this brain-ß cell neural axis was involved in diabetes-related impairment of first-phase GSIS in diabetic animals. Finally, pancreatic denervation improved first-phase GSIS and glucose tolerance and ameliorated severe diabetes by preventing ß cell loss in diabetic animals. These results indicate that impaired first-phase GSIS is critical for brain distribution of dietary glucose after fasting. Furthermore, ß cells in individuals with diabetes mistakenly sense that they are under conditions that mimic prolonged fasting. The present study provides additional insight into both ß cell physiology and the pathogenesis of ß cell dysfunction in type 2 diabetes.

A fish-based diet intervention improves endothelial function in postmenopausal women with type 2 diabetes mellitus: a randomized crossover trial.

OBJECTIVE: The beneficial effects of fish and n-3 polyunsaturated fatty acids (PUFAs) consumption on atherosclerosis have been reported in numerous epidemiological studies. However, to the best of our knowledge, the effects of a fish-based diet intervention on endothelial function have not been investigated. Therefore, we studied these effects in postmenopausal women with type 2 diabetes mellitus (T2DM). MATERIALS/METHODS: Twenty-three postmenopausal women with T2DM were assigned to two four-week periods of either a fish-based diet (n-3 PUFAs ≧ 3.0 g/day) or a control diet in a randomized crossover design. Endothelial function was measured with reactive hyperemia using strain-gauge plethysmography and compared with the serum levels of fatty acids and their metabolites. Endothelial function was determined with peak forearm blood flow (Peak), duration of reactive hyperemia (Duration) and flow debt repayment (FDR). RESULTS: A fish-based dietary intervention improved Peak by 63.7%, Duration by 27.9% and FDR by 70.7%, compared to the control diet. Serum n-3 PUFA levels increased after the fish-based diet period and decreased after the control diet, compared with the baseline (1.49 vs. 0.97 vs. 1.19 mmol/l, p < 0.0001). There was no correlation between serum n-3 PUFA levels and endothelial function. An increased ratio of epoxyeicosatrienoic acid/dihydroxyeicosatrienoic acid was observed after a fish-based diet intervention, possibly due to the inhibition of the activity of soluble epoxide hydrolase. CONCLUSIONS: A fish-based dietary intervention improves endothelial function in postmenopausal women with T2DM. Dissociation between the serum n-3 PUFA concentration and endothelial function suggests that the other factors may contribute to this phenomenon.

Altered unfolded protein response is implicated in the age-related exacerbation of proteinuria-induced proximal tubular cell damage.

Aging is a dominant risk factor for end-stage renal disease. We analyzed the mechanism involved in age-related exacerbation of proteinuria-induced proximal tubular cell (PTC) damage by focusing on endoplasmic reticulum-related unfolded protein response (UPR). After equal-degree induction of proteinuria in 24-month-old (aged) and 3-month-old (young) mice by intraperitoneal free fatty acid-bound albumin overload, tubulointerstitial lesions were more severe in aged than in young mice. In aged PTCs, proteinuria-induced cell-adaptive UPR resulting from induction of the molecular chaperone BiP was significantly suppressed, whereas proapoptotic UPR with CHOP overexpression was enhanced. Treatment with the exogenous molecular chaperone tauroursodeoxycholic acid (TUDCA) ameliorated proteinuria-induced tubulointerstitial lesions and PTC apoptosis in aged mice. Among the three UPR branches, alterations in the inositol-requiring 1α (IRE1α) pathway, but not the activating transcription factor 6 or PERK pathway, were associated with impaired BiP induction in aged kidneys. Moreover, siRNA-mediated suppression of BiP and IRE1α exacerbated free fatty acid-bound albumin-induced apoptosis in cultured PTCs, whereas siRNA-mediated CHOP suppression ameliorated apoptosis. Finally, proteinuria-induced BiP induction in PTCs was diminished in kidney specimens from elderly patients. These results indicate that maladaptive UPRs are involved in proteinuria-induced tubulointerstitial lesions exacerbation in aged kidneys, and that supplementation of chaperones may be used to treat elderly patients with persistent proteinuria. These results should improve understanding of cell vulnerability in aged kidneys.

Haematopoietic cells produce BDNF and regulate appetite upon migration to the hypothalamus.

Brain-derived neurotrophic factor (BDNF) suppresses food intake by acting on neurons in the hypothalamus. Here we show that BDNF-producing haematopoietic cells control appetite and energy balance by migrating to the hypothalamic paraventricular nucleus. These haematopoietic-derived paraventricular nucleus cells produce microglial markers and make direct contacts with neurons in response to feeding status. Mice with congenital BDNF deficiency, specifically in haematopoietic cells, develop hyperphagia, obesity and insulin resistance. These abnormalities are ameliorated by bone marrow transplantation with wild-type bone marrow cells. Furthermore, when injected into the third ventricle, wild-type bone marrow mononuclear cells home to the paraventricular nucleus and reverse the hyperphagia of BDNF-deficient mice. Our results suggest a novel mechanism of feeding control based on the production of BDNF by haematopoietic cells and highlight a potential new therapeutic route for the treatment of obesity.

Low concentration of 4-hydroxy hexenal increases heme oxygenase-1 expression through activation of Nrf2 and antioxidative activity in vascular endothelial cells.

Large-scale clinical studies have shown that n-3 polyunsaturated fatty acids (n-3 PUFAs) such as eicosapentaenoic and docosahexaenoic acids reduce cardiovascular events without improving classical risk factors for atherosclerosis. Recent studies have proposed that direct actions of n-3 PUFAs themselves, or of their enzymatic metabolites, have antioxidative and anti-inflammatory effects on vascular cells. Although a recent study showed that plasma 4-hydroxy hexenal (4-HHE), a peroxidation product of n-3 PUFA, increased after supplementation of docosahexaenoic acid, the antiatherogenic effects of 4-HHE in vascular cells remain unclear. In the present study, we tested the hypothesis that 4-HHE induces the antioxidative enzyme heme oxygenase-1 (HO-1) through activation of nuclear factor erythroid 2-related factor 2 (Nrf2), a master regulatory transcriptional factor, and prevents oxidative stress-induced cytotoxicity in vascular endothelial cells. This mechanism could partly explain the cardioprotective effects of n-3 PUFAs. Human umbilical vein endothelial cells were stimulated with 1-10µM 4-HHE or 4-hydroxy nonenal (4-HNE), a peroxidation product of n-6 PUFAs. Both 4-HHE and 4-HNE dose-dependently increased HO-1 mRNA and protein expression, and intranuclear expression and DNA binding of Nrf2 at 5µM. Small interfering RNA for Nrf2 significantly reduced 4-HHE- or 4-HNE-induced HO-1 mRNA and protein expression. Furthermore, pretreatment with 4-HHE or 4-HNE prevented tert-butyl hydroperoxide-induced cytotoxicity. In conclusion, 4-HHE, a peroxidation product of n-3 PUFAs, stimulated expression of the antioxidant enzyme HO-1 through the activation of Nrf2 in vascular endothelial cells. This resulted in prevention of oxidative stress-induced cytotoxicity, and may represent a possible mechanism to partly explain the cardioprotective effects of n-3 PUFAs.

Marine-derived n-3 fatty acids and atherosclerosis in Japanese, Japanese-American, and white men: a cross-sectional study.

OBJECTIVES: We sought to examine whether marine-derived n-3 fatty acids are associated with less atherosclerosis in Japanese versus white populations in the U.S. BACKGROUND: Marine-derived n-3 fatty acids at low levels are cardioprotective through their antiarrhythmic effect. METHODS: A population-based cross-sectional study in 281 Japanese (defined as born and living in Japan), 306 white (defined as white men born and living in the U.S.), and 281 Japanese-American men (defined as Japanese men born and living in the U.S.) ages 40 to 49 years was conducted to assess intima-media thickness (IMT) of the carotid artery, coronary artery calcification (CAC), and serum fatty acids. RESULTS: Japanese men had the lowest levels of atherosclerosis, whereas whites and Japanese Americans had similar levels. Japanese had 2-fold higher levels of marine-derived n-3 fatty acids than whites and Japanese Americans in the U.S. Japanese had significant and nonsignificant inverse associations of marine-derived n-3 fatty acids with IMT and CAC prevalence, respectively. The significant inverse association with IMT remained after adjusting for traditional cardiovascular risk factors. Neither whites nor Japanese Americans had such associations. Significant differences between Japanese and whites in multivariable-adjusted IMT (mean difference 39 mum, 95% confidence interval [CI]: 21 to 57mum, p < 0.001) and CAC prevalence (mean difference 10.7%, 95% CI: 2.9% to 18.4%, p = 0.007) became nonsignificant after we adjusted further for marine-derived n-3 fatty acids (22 mum, 95% CI: -1 to 46 mum, p = 0.065 and 5.0%, 95% CI: -5.3% to 15.4%, p = 0.341, respectively). CONCLUSIONS: Very high levels of marine-derived n-3 fatty acids have antiatherogenic properties that are independent of traditional cardiovascular risk factors and may contribute to lower the burden of atherosclerosis in Japanese, a lower burden that is unlikely the result of genetic factors.

Serum concentrations of trace elements in patients with Crohn's disease receiving enteral nutrition.

We investigated the trace element status in Crohn's disease (CD) patients receiving enteral nutrition, and evaluated the effects of trace element-rich supplementation. Thirty-one patients with CD were enrolled in this study. All patients were placed on an enteral nutrition regimen with Elental(R) (Ajinomoto pharmaceutical. Ltd., Tokyo, Japan). Serum selenium, zinc and copper concentrations were determined by atomic absorption spectroscopy. Serum selenoprotein P levels were determined by an ELISA system. Average serum levels of albumin, selenium, zinc and copper were 4.1 +/- 0.4 g/dl, 11.2 +/- 2.8 microg/dl, 71.0 +/- 14.8 microg/dl, and 112.0 +/- 25.6 microg/dl, respectively. In 9 patients of 31 CD patients, serum albumin levels were lower than the lower limit of the normal range. Serum selenium, zinc and copper levels were lower than lower limits in 12 patients, 9 patients and 1 patient, respectively. Serum selenium levels significantly correlated with both serum selenoprotein P levels and glutathione peroxidase activity. Supplementation of selenium (100 microg/day) and zinc (10 mg/day) for 2 months significantly improved the trace element status in CD patients. In conclusion, serum selenium and zinc levels are lower in many CD patients on long-term enteral nutrition. In these patients, supplementation of selenium and zinc was effective in improving the trace element status.

Diet high in lipid hydroperoxide by vitamin E deficiency induces insulin resistance and impaired insulin secretion in normal rats.

To clarify the effect of dietary lipid hydroperoxide (LPO) on development of glucose intolerance, we fed Sprague-Dawley rats on a diet containing elevated LPO level for 10 weeks and measured both insulin sensitivity and insulin secretion. The contents of LPO in both plasma and skeletal muscle in the LPO-fed rats were significantly higher than those in the controls. Both insulin resistance evaluated by steady-state blood glucose (SSBG) methods and impaired insulin secretion evaluated by oral glucose tolerance test (OGTT) were found in the LPO-fed rats as compared with control rats. Furthermore, the levels of insulin receptor substrate (IRS)-1 protein in the skeletal muscle were significantly lower in the LPO-fed rats. Those impairments were not reversed in LPO-fed rats with supernormal levels of plasma vitamin E following vitamin E supplementation for 5 weeks. Moreover, the immunohistochemical study revealed that NF-kappaB-p50 protein was found in the nucleus of pancreatic beta-cells of the LPO-fed rats, whereas it was not observed in the nucleus of the islets in the control rats. These findings indicate that NF-kappaB is activated in response to oxidative stress in pancreatic islet cells in LPO-fed rats. In conclusion, our studies reveal that diet high in LPO by vitamin E deficiency accelerates glucose intolerance through impairments of both sensitivity and secretion of insulin.

Protein-tyrosine phosphatase 1B as new activator for hepatic lipogenesis via sterol regulatory element-binding protein-1 gene expression.

Like hyperglycemia, postprandial (diet-induced) hypertriglyceridemia is thought to play crucial roles in the pathogenesis of insulin resistant/metabolic syndrome. Sterol regulatory element-binding protein-1 (SREBP-1) is a key transcription factor to induce postprandial hypertriglyceridemia. We found that insulin-resistant rats fed a diet high in fructose showed an increased proteintyrosine phosphatase 1B (PTP1B) content with strong expression of SREBP-1 mRNA in the liver. To clarify the association of PTP1B with SREBP-1 gene expression, we overexpressed PTP1B in rat hepatocytes, which led to increased mRNA content and promoter activity of SREBP-1a and -1c, resulting in the increased mRNA expression of fatty-acid synthase, one of the SREBP-1-responsive lipogenic genes. Because PTP1B overexpression increased phosphatase 2A (PP2A) activity, we inhibited PP2A activity by expression of its selective inhibitor, SV40 small T antigen and found that this normalized the PTP1B-enhanced SREBP-1a and -1c mRNA expressions through activation of the Sp1 site. These results indicate that PTP1B may regulate gene expression of SREBP-1 via enhancement of PP2A activity, thus mediating hepatic lipogenesis and postprandial hypertriglyceridemia. We demonstrate here a unique serial activation of the PTP1B-PP2A axis as a novel mechanism for the regulation of gene expression in the biosynthesis of triglyceride.