Markers for obese and non-obese Type 2 diabetes identified using whole blood metabolomics.

Definitive differences in blood metabolite profiles between obese and non-obese Type 2 diabetes (T2D) have not been established. We performed an LC-MS-based non-targeted metabolomic analysis of whole blood samples collected from subjects classified into 4 types, based on the presence or absence of obesity and T2D. Of the 125 compounds identified, 20, comprising mainly nucleobases and glucose metabolites, showed significant increases or decreases in the T2D group. These included cytidine, UDP-glucuronate, UMP, 6-phosphogluconate, and pentose-phosphate. Among those 20 compounds, 11 enriched in red blood cells (RBCs) have rarely been studied in the context of diabetes, indicating that RBC metabolism is more extensively disrupted than previously known. Correlation analysis revealed that these T2D markers include 15 HbA1c-associated and 5 irrelevant compounds that may reflect diabetic conditions by a different mechanism than that of HbA1c. In the obese group, enhanced protein and fatty acid catabolism causes increases in 13 compounds, including methylated or acetylated amino acids and short-chain carnitines. Our study, which may be considered a pilot investigation, suggests that changes in blood metabolism due to obesity and diabetes are large, but essentially independent.

Activity of xanthine oxidase in plasma correlates with indices of insulin resistance and liver dysfunction in patients with type 2 diabetes mellitus and metabolic syndrome: A pilot exploratory study.

AIMS/INTRODUCTION: There is controversy as to whether hyperuricemia is an independent risk factor for cardiometabolic diseases. The serum level of uric acid is affected by a wide variety of factors involved in its production and excretion. In contrast, evidence has accumulated that locally- and systemically-activated xanthine oxidase (XO), a rate-limiting enzyme for production of uric acid, is linked to metabolic derangement in humans and rodents. We therefore explored the clinical implication of plasma XO activity in patients with type 2 diabetes mellitus and metabolic syndrome (MetS). MATERIALS AND METHODS: We enrolled 60 patients with type 2 diabetes mellitus and MetS. MetS was defined according to the 2005 International Diabetes Federation guidelines. Plasma XO activity was measured by highly-sensitive fluorometric assay measuring the conversion of pterin to isoxanthopterin, and explored associations between the value of plasma XO activity and metabolic parameters. RESULTS: The value of plasma XO activity was correlated with indices of insulin resistance and the level of circulating liver transaminases. In contrast, the level of serum uric acid was not correlated with indices of insulin resistance. The value of plasma XO activity was not correlated with the serum uric acid level. CONCLUSIONS: Plasma XO activity correlates with indices of insulin resistance and liver dysfunction in Japanese patients with type 2 diabetes mellitus and MetS. Through assessing the plasma XO activity, patients showing normal levels of serum uric acid with higher activity of XO can be screened, thereby possibly providing a clue to uncovering metabolic risks in type 2 diabetes mellitus and MetS patients.

A novel insulinotropic mechanism of whole grain-derived γ-oryzanol via the suppression of local dopamine D2 receptor signalling in mouse islet.

BACKGROUND AND PURPOSE: γ-Oryzanol, derived from unrefined rice, attenuated the preference for dietary fat in mice, by decreasing hypothalamic endoplasmic reticulum stress. However, no peripheral mechanisms, whereby γ-oryzanol could ameliorate glucose dyshomeostasis were explored. Dopamine D2 receptor signalling locally attenuates insulin secretion in pancreatic islets, presumably via decreased levels of intracellular cAMP. We therefore hypothesized that γ-oryzanol would improve high-fat diet (HFD)-induced dysfunction of islets through the suppression of local D2 receptor signalling. EXPERIMENTAL APPROACH: Glucose metabolism and regulation of molecules involved in D2 receptor signalling in pancreatic islets were investigated in male C57BL/6J mice, fed HFD and treated with γ-oryzanol . In isolated murine islets and the beta cell line, MIN6 , the effects of γ-oryzanol on glucose-stimulated insulin secretion (GSIS) was analysed using siRNA for D2 receptors and a variety of compounds which alter D2 receptor signalling. KEY RESULTS: In islets, γ-oryzanol enhanced GSIS via the activation of the cAMP/PKA pathway. Expression of molecules involved in D2 receptor signalling was increased in islets from HFD-fed mice, which were reciprocally decreased by γ-oryzanol. Experiments with siRNA for D2 receptors and D2 receptor ligands in vitro suggest that γ-oryzanol suppressed D2 receptor signalling and augmented GSIS. CONCLUSIONS AND IMPLICATIONS: γ-Oryzanol exhibited unique anti-diabetic properties. The unexpected effects of γ-oryzanol on D2 receptor signalling in islets may provide a novel; natural food-based, approach to anti-diabetic therapy.

γ-Oryzanol protects pancreatic ß-cells against endoplasmic reticulum stress in male mice.

Endoplasmic reticulum (ER) stress is profoundly involved in dysfunction of ß-cells under high-fat diet and hyperglycemia. Our recent study in mice showed that γ-oryzanol, a unique component of brown rice, acts as a chemical chaperone in the hypothalamus and improves feeding behavior and diet-induced dysmetabolism. However, the entire mechanism whereby γ-oryzanol improves glucose metabolism throughout the body still remains unclear. In this context, we tested whether γ-oryzanol reduces ER stress and improves function and survival of pancreatic ß-cells using murine ß-cell line MIN6. In MIN6 cells with augmented ER stress by tunicamycin, γ-oryzanol decreased exaggerated expression of ER stress-related genes and phosphorylation of eukaryotic initiation factor-2α, resulting in restoration of glucose-stimulated insulin secretion and prevention of apoptosis. In islets from high-fat diet-fed diabetic mice, oral administration of γ-oryzanol improved glucose-stimulated insulin secretion on following reduction of exaggerated ER stress and apoptosis. Furthermore, we examined the impact of γ-oryzanol on low-dose streptozotocin-induced diabetic mice, where exaggerated ER stress and resultant apoptosis in ß-cells were observed. Also in this model, γ-oryzanol attenuated mRNA level of genes involved in ER stress and apoptotic signaling in islets, leading to amelioration of glucose dysmetabolism. Taken together, our findings demonstrate that γ-oryzanol directly ameliorates ER stress-induced ß-cell dysfunction and subsequent apoptosis, highlighting usefulness of γ-oryzanol for the treatment of diabetes mellitus.

Lipid deposition in various sites of the skeletal muscles and liver exhibits a positive correlation with visceral fat accumulation in middle-aged Japanese men with metabolic syndrome.

Objective In addition to excess visceral fat, lipid deposition in the liver and skeletal muscle has been implicated in the pathophysiology of type 2 diabetes and metabolic syndrome. This study was designed to explore the relationship between hepatic and muscular lipid deposition and visceral fat accumulation in 105 middle-aged men with metabolic syndrome. Methods Abdominal computed tomography (CT) was used to simultaneously evaluate the visceral fat area (VFA) and CT Hounsfield unit (HU) values of three different portions of skeletal muscle and the liver. Results A significant inverse correlation was observed between the VFA and the CT HU values of the iliopsoas muscle, back muscle, rectus abdominis muscle and liver. Three types of interventions, i.e., lifestyle modification and treatment with antidiabetic drugs, such as Pioglitazone or Miglitol, caused significant decreases in visceral fat accumulation. The extent of lipid deposition in the liver was strongly correlated with the levels of glucose-lipid metabolic markers, which decreased significantly following Pioglitazone treatment. On the other hand, the amount of lipid deposition in the three skeletal muscles and the liver did not decrease after Miglitol treatment. Conclusion Visceral fat accumulation is accompanied by excess lipid deposition in skeletal muscle and the liver in patients with metabolic syndrome. The CT-based simultaneous, concise evaluations of ectopic lipid deposition and visceral fat mass used in the present study may provide unique information for assessing cardiometabolic risks and the therapeutic impact in patients with diabetes-obesity syndrome.

Brown rice and its component, γ-oryzanol, attenuate the preference for high-fat diet by decreasing hypothalamic endoplasmic reticulum stress in mice.

Brown rice is known to improve glucose intolerance and prevent the onset of diabetes. However, the underlying mechanisms remain obscure. In the current study, we investigated the effect of brown rice and its major component, γ-oryzanol (Orz), on feeding behavior and fuel homeostasis in mice. When mice were allowed free access to a brown rice-containing chow diet (CD) and a high-fat diet (HFD), they significantly preferred CD to HFD. To reduce hypothalamic endoplasmic reticulum (ER) stress on an HFD, mice were administered with 4-phenylbutyric acid, a chemical chaperone, which caused them to prefer the CD. Notably, oral administration of Orz, a mixture of major bioactive components in brown rice, also improved glucose intolerance and attenuated hypothalamic ER stress in mice fed the HFD. In murine primary neuronal cells, Orz attenuated the tunicamycin-induced ER stress. In luciferase reporter assays in human embryonic kidney 293 cells, Orz suppressed the activation of ER stress-responsive cis-acting elements and unfolded protein response element, suggesting that Orz acts as a chemical chaperone in viable cells. Collectively, the current study is the first demonstration that brown rice and Orz improve glucose metabolism, reduce hypothalamic ER stress, and, consequently, attenuate the preference for dietary fat in mice fed an HFD.

Association of an A/C single nucleotide polymorphism in programmed cell death-ligand 1 gene with Graves' disease in Japanese patients.

OBJECTIVE: Programmed cell death-1 (PD-1) and its ligands (PD-L1 and PD-L2) inhibit T-cell proliferation and activation. This inhibition down-regulates the immune responses. The association of a PD-L1 polymorphism with Graves' disease (GD) was studied. DESIGN: The association of an A/C polymorphism at position 8923 in PD-L1 intron 4 with GD was studied. PATIENTS: The study included 327 GD patients and 192 controls, of which 252 GD patients were followed over 5-10 years. MEASUREMENTS: PD-L1 intron 4 position 8923 A/C polymorphism was typed using the PCR-restriction fragment length polymorphism method. RESULTS: The A/C genotype frequencies were significantly different between GD patients and controls. The A/C and C/C frequencies were higher in GD patients than in controls. The A/A frequencies were lower in GD patients than in controls. C-allele frequency was higher in GD patients than in controls. A total of 252 GD patients were followed over 5-10 years; 200 had discontinued antithyroid drugs (ATD) while 52 continued to take ATD. Of these 200, 176 continued to be in remission and 24 had relapsed into hyperthyroidism. Significant differences in the duration of positive TBII, positive thyroid-stimulating antibodies, and ATD treatment were noted between the patients in remission and those that had relapsed. Significant differences in the A- and C-allele frequencies were noted between the two. The C-allele frequency was higher in GD patients who did not achieve remission than in those who achieved remission. CONCLUSION: An A/C polymorphism at position 8923 in PD-L1 is associated with GD. The PD-L1 polymorphism plays a role in GD development. GD patients with the C allele at position 8923 in PD-L1 gene had difficulty in achieving remission.