Impact of hepatic HSP72 on insulin signaling.

Heat shock protein 72 (HSP72) is a major inducible molecule in the heat shock response that enhances intracellular stress tolerance. Decreased expression of HSP72 is observed in type 2 diabetes, which may contribute to the development of insulin resistance and chronic inflammation. We used HSP72 knockout (HSP72-KO) mice to investigate the impact of HSP72 on glucose metabolism and endoplasmic reticulum (ER) stress, particularly in the liver. Under a high-fat diet (HFD) condition, HSP72-KO mice showed glucose intolerance, insulin resistance, impaired insulin secretion, and enhanced hepatic gluconeogenic activity. Furthermore, activity of the c-Jun NH2-terminal kinase (JNK) was increased and insulin signaling suppressed in the liver. Liver-specific expression of HSP72 by lentivirus (lenti) in HFD-fed HSP72-KO mice ameliorated insulin resistance and hepatic gluconeogenic activity. Furthermore, increased adipocyte size and hepatic steatosis induced by the HFD were suppressed in HSP72-KO lenti-HSP72 mice. Increased JNK activity and ER stress upon HFD were suppressed in the liver as well as the white adipose tissue of HSP72-KO lenti-HSP72 mice. Thus, HSP72 KO caused a deterioration in glucose metabolism, hepatic gluconeogenic activity, and ß-cell function. Moreover, liver-specific recovery of HSP72 restored glucose homeostasis. Therefore, hepatic HSP72 may play a critical role in the pathogenesis of type 2 diabetes.

The clinical course and pathophysiological investigation of adolescent gestational diabetes insipidus: a case report.

BACKGROUND: Gestational diabetes insipidus (GDI) is a rare endocrine complication during pregnancy that is associated with vasopressinase overproduction from the placenta. Although increased vasopressinase is associated with placental volume, the regulation of placental growth in the later stage of pregnancy is not well known. CASE PRESENTATION: A 16-year-old pregnant woman was urgently transferred to our hospital because of threatened premature labor when the Kumamoto earthquakes hit the area where she lived. During her hospitalization, she complained of gradually increasing symptoms of polyuria and polydipsia. The serum level of arginine vasopressin (AVP) was 1.7 pg/mL, which is inconsistent with central DI. The challenge of diagnostic treatment using oral 1-deamino-8-D-AVP (DDAVP) successfully controlled her urine and allowed for normal delivery. DDAVP tablets were not necessary to control her polyuria thereafter. Based on these observations, clinical diagnosis of GDI was confirmed. Pathophysiological analyses revealed that vasopressinase expression was more abundant in the GDI patient's syncytiotrophoblast in placenta compared with that in a control subject. Serum vasopressinase was also observed during gestation and disappeared soon after delivery. Vasopressinase is reportedly identical to oxytocinase or insulin regulated aminopeptidase (IRAP), which is an abundant cargo protein associated with the glucose transporter 4 (GLUT4) storage vesicle. Interestingly, the expression and subcellular localization of GLUT4 appeared to occur in a vasopressinase (IRAP)-dependent manner. CONCLUSION: Because placental volume may be associated with vasopressinase overproduction in GDI, vasopressinase (IRAP)/GLUT4 association appears to contribute to the growth of placenta in this case.

Effects of combination therapy with vildagliptin and valsartan in a mouse model of type 2 diabetes.

BACKGROUND: Dipeptidyl peptidase-4 (DPP-4) inhibitors modulate incretin hormones and exert anti-diabetic effects in type 2 diabetes mellitus. Treatment with angiotensin II type 1 receptor blockers (ARB) is a proven successful intervention for hypertension with type 2 diabetes. The present study investigated the combined effects of the DPP-4 inhibitor vildagliptin and the ARB valsartan in a mouse model of type 2 diabetes. METHODS: C57BL/6 J mice fed with high-fat diet (HFD) or db/db mice were treated with placebo, phloridzin (PHZ), vildagliptin alone (ViL), valsartan alone (VaL) or ViL with VaL (ViLVaL) for 8 weeks. RESULTS: Glucose metabolism was improved in response to PHZ, ViL and ViLVaL in both HFD and db/db mice. Upon glucose challenge, ViLVaL showed the greatest suppression of blood glucose excursions, with increased insulin secretion, in db/db mice. ViLVaL treatment also showed an improvement of insulin sensitivity in db/db mice. Serum inflammatory cytokines were significantly decreased, and adiponectin was highest, in the ViLVaL group. ViLVaL improved insulin signaling and attenuated stress signaling in liver with amelioration of hepatic steatosis due to activated fatty acid oxidation in db/db mice. Furthermore, immunohistochemical analysis of the pancreas revealed that the combination treatment resulted in an increased expression of insulin and PDX-1, and increased insulin content. CONCLUSIONS: The combination therapy of ViL and VaL improves both pancreatic beta-cell function and insulin sensitivity, with a reduction of the inflammatory and cell stress milieu in mouse models of T2DM. Our results suggest that this combination therapy exerts additive or even synergistic benefits to treat T2DM.

The Amount of Residual Incretin Regulates the Pancreatic ß-cell Function and Glucose Homeostasis.

The gastrointestinal tract is considered an important endocrine organ for controlling glucose homeostasis via the production of incretins. A 21-year-old man emergently underwent total colectomy due to severe ulcerative colitis, and overt diabetes became evident. Weekly administration of a glucagon-like peptide (GLP)-1 receptor agonist (RA) dramatically improved his glucose control. Levels of GLP-1 or gastric inhibitory polypeptide (GIP) were low at the baseline in the duodenum and serum of the patient. After 11 months of GLP-1RA treatment, his HbA1c worsened again, and intensive insulin therapy was necessary to control his glucose levels. Our report may explain the significance of residual incretin for maintaining the pancreatic ß-cell function.

Activation of heat shock response improves biomarkers of NAFLD in patients with metabolic diseases.

Nonalcoholic fatty liver disease (NAFLD) is often accompanied by metabolic disorders such as metabolic syndrome and type 2 diabetes (T2DM). Heat shock response (HSR) is one of the most important homeostatic abilities but is deteriorated by chronic metabolic insults. Heat shock (HS) with an appropriate mild electrical stimulation (MES) activates HSR and improves metabolic abnormalities including insulin resistance, hyperglycemia and inflammation in metabolic disorders. To analyze the effects of HS + MES treatment on NAFLD biomarkers, three cohorts including healthy men (two times/week, n = 10), patients with metabolic syndrome (four times/week, n = 40), and patients with T2DM (n = 100; four times/week (n = 40) and two, four, seven times/week (n = 20 each)) treated with HS + MES were retrospectively analyzed. The healthy subjects showed no significant alterations in NAFLD biomarkers after the treatment. In patients with metabolic syndrome, many of the NAFLD steatosis markers, including fatty liver index, NAFLD-liver fat score, liver/spleen ratio and hepatic steatosis index and NAFLD fibrosis marker, aspartate aminotransferase/alanine aminotransferase (AST/ALT) ratio, were improved upon the treatment. In patients with T2DM, all investigated NAFLD steatosis markers were improved and NAFLD fibrosis markers such as the AST/ALT ratio, fibrosis-4 index and NAFLD-fibrosis score were improved upon the treatment. Thus, HS + MES, a physical intervention, may become a novel treatment strategy for NAFLD as well as metabolic disorders.

Mineralocorticoid Receptor May Regulate Glucose Homeostasis through the Induction of Interleukin-6 and Glucagon-Like peptide-1 in Pancreatic Islets.

Because the renin-angiotensin-aldosterone system influences glucose homeostasis, the mineralocorticoid receptor (MR) signal in pancreatic islets may regulate insulin response upon glucose load. Glucagon-like peptide-1 (GLP-1) production is stimulated by interleukin-6 (IL-6) in pancreatic α-cells. To determine how glucose homeostasis is regulated by interactions of MR, IL-6 and GLP-1 in islets, we performed glucose tolerance and histological analysis of islets in primary aldosteronism (PA) model rodents and conducted in vitro experiments using α-cell lines. We measured active GLP-1 concentration in primary aldosteronism (PA) patients before and after the administration of MR antagonist eplerenone. In PA model rodents, aldosterone decreased insulin-secretion and the islet/pancreas area ratio and eplerenone added on aldosterone (E+A) restored those with induction of IL-6 in α-cells. In α-cells treated with E+A, IL-6 and GLP-1 concentrations were increased, and anti-apoptotic signals were enhanced. The E+A-treatment also significantly increased MR and IL-6 mRNA and these upregulations were blunted by MR silencing using small interfering RNA (siRNA). Transcriptional activation of the IL-6 gene promoter by E+A-treatment required an intact MR binding element in the promoter. Active GLP-1 concentration was significantly increased in PA patients after eplerenone treatment. MR signal in α-cells may stimulate IL-6 production and increase GLP-1 secretion, thus protecting pancreatic ß-cells and improving glucose homeostasis.

Evaluation of metabolic changes in oxalate-rich plant Rumex obtusifolius L. caused by ion beam irradiation.

Some Rumex species such as sorrel are edible as baby leaf salad greens. On the other hand, Rumex plants accumulate soluble oxalate, a toxic metabolite which causes serious diseases such as renal syndrome. We attempted to produce low-oxalate plants of R. obtusifolius, a perennial weed which has higher vitamin C and amino acid content and higher tolerance to stress than many other Rumex species. Ion beams are ionising radiation with high linear energy transfer that causes a wide spectrum of mutations. Thus, in the present study we evaluated the effects of ion beams on oxalate and other primary metabolites in leaves of R. obtusifolius using CE-MS. The results showed that oxalate content was increased by irradiation with carbon ion beams. Metabolome analysis revealed that ion beams affected carbon flow to the isocitrate pathway, which is involved in oxalate synthesis. These observations suggested that modulation of carbon flow to the isocitrate pathway is important to regulate oxalate levels in plants.

Identification of microRNA that represses IRS-1 expression in liver.

MicroRNAs (miRNAs) are short, non-coding RNAs that post-transcriptionally regulate gene expression and have been shown to participate in almost every cellular process. Several miRNAs have recently been implicated in glucose metabolism, but the roles of miRNAs in insulin-resistant conditions, such as obesity or type 2 diabetes, are largely unknown. Herein, we focused on miR-222, the expression of which was increased in the livers of high fat/high sucrose diet-fed mice injected with gold thioglucose (G+HFHSD). Overexpression of miR-222 in primary mouse hepatocytes attenuated Akt phosphorylation induced by insulin, indicating that miR-222 negatively regulates insulin signaling. As per in silico analysis, miR-222 potentially binds to the 3' untranslated region (3' UTR) of the IRS-1 gene, a key insulin signaling molecule. In fact, IRS-1 protein expression was decreased in the livers of G+HFHSD-fed mice. We further confirmed a direct interaction between miR-222 and the 3' UTR of IRS-1 via luciferase assays. Our findings suggest that up-regulation of miR-222 followed by reduction in IRS-1 expression may be a viable mechanism of insulin resistance in the liver.

Activation of heat shock response to treat obese subjects with type 2 diabetes: a prospective, frequency-escalating, randomized, open-label, triple-arm trial.

Activation of heat shock response (HSR) improves accumulated visceral adiposity and metabolic abnormalities in type 2 diabetes. To identify the optimal intervention strategy of the activation of the HSR provided by mild electrical stimulation (MES) with heat shock (HS) in type 2 diabetes. This study was a prospective, frequency-escalating, randomized, open-label, triple-arm trial in Japan. A total of 60 obese type 2 diabetes patients were randomized into three groups receiving two, four, or seven treatments per week for 12 weeks. No adverse events were identified. MES + HS treatment (when all three groups were combined), significantly improved visceral adiposity, glycemic control, insulin resistance, systemic inflammation, renal function, hepatic steatosis and lipid profile compared to baseline. The reduction in HbA1c was significantly greater among those treated four times per week (-0.36%) or seven times per week (-0.65%) than among those treated two times per week (-0.10%). The relative HbA1c levels in seven times per week group was significantly decreased when adjusted by two times per week group (-0.55%. p = 0.001). This research provides the positive impact of MES + HS to treat obese patients with type 2 diabetes mellitus.

Mild Electrical Stimulation with Heat Shock Reduces Visceral Adiposity and Improves Metabolic Abnormalities in Subjects with Metabolic Syndrome or Type 2 Diabetes: Randomized Crossover Trials.

BACKGROUND: The induction of heat shock protein (HSP) 72 by mild electrical stimulation with heat shock (MES + HS), which improves visceral adiposity and insulin resistance in mice, may be beneficial in treating metabolic syndrome (MS) or type 2 diabetes mellitus (T2DM). METHODS: Using open-label crossover trials, 40 subjects with MS or T2DM were randomly assigned using computer-generated random numbers to 12 weeks of therapeutic MES + HS followed by 12 weeks of no treatment, or vice versa. During the intervention period, physical and biochemical markers were measured. FINDINGS: Compared to no treatment, MES + HS treatment was associated with a significant decrease in visceral adiposity (- 7.54 cm(2) (- 8.61%), 95% CI - 8.55 to - 6.53 (p = 0.037) in MS, - 19.73 cm(2) (- 10.89%), 95% CI - 20.97 to - 18.49 (p = 0.003) in T2DM). Fasting plasma glucose levels were decreased by 3.74 mg/dL (- 5.28%: 95% CI - 4.37 to - 3.09 mg/dL, p = 0.029) in MS and by 14.97 mg/dL (10.40%: 95% CI - 15.79 to 14.15 mg/dL, p < 0.001) in T2DM, and insulin levels were also reduced by 10.39% and 25.93%, respectively. HbA1c levels showed a trend toward reduction (- 0.06%) in MS, and was significantly declined by - 0.43% (95% CI - 0.55 to - 0.31%, p = 0.009) in T2DM. HbA1c level of less than 7.0% was achieved in 52.5% of the MES + HS-treated T2DM patients in contrast to 15% of the non-treated period. Several insulin resistance indices, inflammatory cytokines or adipokines, including C-reactive protein, adiponectin, and tumor necrosis factor-α, were all improved in both groups. In isolated monocytes, HSP72 expression was increased and cytokine expression was reduced following MES + HS treatment. Glucose excursions on meal tolerance test were lower after using MES + HS in T2DM. INTERPRETATION: This combination therapy has beneficial impacts on body composition, metabolic abnormalities, and inflammation in subjects with MS or T2DM. Activation of the heat shock response by MES + HS may provide a novel approach for the treatment of lifestyle-related diseases. FUNDING: Funding for this research was provided by MEXT KAKENHI (Grants-in-Aid for Scientific Research from Ministry of Education, Culture, Sports, Science and Technology, Japan).