Dnmt2 mediates intergenerational transmission of paternally acquired metabolic disorders through sperm small non-coding RNAs.

The discovery of RNAs (for example, messenger RNAs, non-coding RNAs) in sperm has opened the possibility that sperm may function by delivering additional paternal information aside from solely providing the DNA 1 . Increasing evidence now suggests that sperm small non-coding RNAs (sncRNAs) can mediate intergenerational transmission of paternally acquired phenotypes, including mental stress2,3 and metabolic disorders4-6. How sperm sncRNAs encode paternal information remains unclear, but the mechanism may involve RNA modifications. Here we show that deletion of a mouse tRNA methyltransferase, DNMT2, abolished sperm sncRNA-mediated transmission of high-fat-diet-induced metabolic disorders to offspring. Dnmt2 deletion prevented the elevation of RNA modifications (m5C, m2G) in sperm 30-40 nt RNA fractions that are induced by a high-fat diet. Also, Dnmt2 deletion altered the sperm small RNA expression profile, including levels of tRNA-derived small RNAs and rRNA-derived small RNAs, which might be essential in composing a sperm RNA 'coding signature' that is needed for paternal epigenetic memory. Finally, we show that Dnmt2-mediated m5C contributes to the secondary structure and biological properties of sncRNAs, implicating sperm RNA modifications as an additional layer of paternal hereditary information.

Activation of AMPK alleviates cardiopulmonary bypass-induced cardiac injury via ameliorating acute cardiac glucose metabolic disorder.

Recent years, studies have demonstrated that hyperglycemia is one of the main manifestations after cardiac surgeries, which contributes to myocardial injuries and increases the chance of subsequent complications and mortality in such patients. However, strategies targeting at glucose metabolic disorder after cardiac surgeries to attenuate myocardial injuries are inadequately studied. In this study, a rat model of cardiopulmonary bypass (CPB) was applied to investigate the role of Adenosine 5'-monophosphate-activated protein kinase (AMPK) in modulating myocardial glucose metabolic-induced cardiac injuries after cardiac surgery. The results revealed that CPB elicited significant cardiac dysfunction, and pronouncedly elevated the markers of myocardial injuries including serum creatine kinase MB and cardiac troponin I. Additionally, blunted myocardial glucose uptake after CPB was associated with decreased membrane glucose transporter 4 (GLUT4) content. However, pretreatment of AMPK agonist 5-aminoimidazole-4-carboxamide1-ß-D-ribofuranoside (AICAR) at the beginning of CPB activated AMPK, enhanced phosphorylation of Akt substrate 160 (AS160), and increased myocardial membrane content of GLUT4. Meanwhile, improved myocardial glucose uptake and more importantly alleviated cardiac injury were also observed after CPB pretreated with AICAR. Moreover, the application of a mutant form of AS160 (AS160-4P) abolished the beneficial effect of AICAR, as evidenced by impaired cardiac glucose uptake, reduced myocardial membrane GLUT-4 translocation, increased cardiac injury markers, and deterioration of cardiac function after CPB. In conclusion, it was suggested in this study that preactivation of AMPK by AICAR improved myocardial glucose uptake by promoting AS160 dependent myocardial membrane GLUT-4 translocation, which ultimately provided a potent cardioprotective effect.

Suksdorfin Promotes Adipocyte Differentiation and Improves Abnormalities in Glucose Metabolism via PPARγ Activation.

Although the Apiaceae herb family has been traditionally used for the management of type 2 diabetes, its molecular mechanism has not been clarified. Coumarin derivatives, which are abundant in plants of the Apiaceae family, were evaluated for their effects on adipogenesis. We found that suksdorfin significantly promoted adipocyte differentiation and enhanced production of adiponectin, an anti-diabetic adipokine. We also demonstrated that suksdorfin activates peroxisome proliferator-activated receptor gamma (PPARγ), a master regulator of adipogenesis. Furthermore, we showed metabolic disorders in obese diabetic KK-Ay mice were attenuated by suksdorfin feeding. Suksdorfin intake induced adipocyte miniaturization and increased expression levels of PPARγ target genes related to adipocyte differentiation. These results indicated that suksdorfin induces adipogenesis in white adipose tissue (WAT) via the activation of PPARγ, leading to improvement of obesity-induced metabolic disorders. Therefore, suksdorfin-mediated amelioration of WAT dysfunctions might be responsible for the anti-diabetic effects of traditional herbal medicine therapy with Apiaceae.

Unraveling the actions of AMP-activated protein kinase in metabolic diseases: Systemic to molecular insights.

AMP-activated protein kinase (AMPK) plays a critical role both in sensing and regulating cellular energy state. In experimental animals, its activation has been shown to reduce the risk of obesity and diabetes-related co-morbidities such as insulin resistance, the metabolic syndrome and atherosclerotic cardiovascular disease. However, in humans, AMPK activation alone often does not completely resolve these conditions. Thus, an improved understanding of AMPK action and regulation in metabolic and other diseases is needed. Herein, we provide a brief description of the enzymatic regulation of AMPK and review its role in maintaining energy homeostasis. We then discuss tissue-specific actions of AMPK that become distorted during such conditions as obesity, type 2 diabetes and certain cancers. Finally, we explore recent findings regarding the interactions of AMPK with mammalian target of rapamycin complex 1 and the lysosome and discuss how changes in these relationships during overnutrition may lead to AMPK dysfunction. A more thorough understanding of AMPK's molecular interactions during diseases of overnutrition may provide key insights for the development of AMPK-based combinatorial treatments for metabolic disease.

Visfatin concentrations in obese patients in relation to the presence of newly diagnosed glucose metabolism disorders.

INTRODUCTION: Visfatin, protein secreted by visceral adipose tissue, exerts insulin-mimetic actions. Visfatin concentration increases in patients with longer-standing diabetes type 2 with progressive b-cell dysfunction. Data about the role of visfatin in newly diagnosed glucose metabolism abnormalities are limited. Evaluation of visfatin concentration in patients with obesity, in relation to the presence of newly diagnosed glucose metabolism disorders. MATERIAL AND METHODS: The study included 68 subjects with obesity, without a previous diagnosis of abnormal glucose metabolism. In all subjects we performed an oral glucose tolerance test, and according to the results the group was divided into the subgroups: A (n = 31), with glucose metabolism disorders (impaired fasting glucose, impaired glucose tolerance and type 2 diabetes); and B (n = 37), without abnormalities. In all subjects serum lipids, uric acid, C-peptide, glycated haemoglobin (HbA1c), creatinine, and serum visfatin concentrations were measured. The control group comprised 30 lean, healthy individuals with normal glucose tolerance. RESULTS: We found elevated visfatin levels in obese individuals versus the control group (50.0 ± 48 vs. 26.7 ± 22.1 ng/mL; p = 0.01). Visfatin concentrations in both subgroups, A and B, did not differ (40.86 ± 27.84 vs. 57.7 ± 59.79 ng/mL; p = 0.19). In subgroup A visfatin concentration correlated significantly with triglycerides (r = 0.37, p = 0.038), HbA1c (r = -0.43, p = 0.02), C-peptide (r = -0.38,p = 0.048), and waist-hip ratio (r = -0.41, p = 0.036). CONCLUSIONS: The presence of newly diagnosed glucose metabolism abnormalities in obese subjects had no influence on the visfatin level, probably due to preserved endogenous insulin secretion and relatively short exposure to hyperglycaemia in patients with prediabetes or at early stage of type 2 diabetes.

Cryptotanshinone reverses ovarian insulin resistance in mice through activation of insulin signaling and the regulation of glucose transporters and hormone synthesizing enzymes.

OBJECTIVE: To investigate the effects of cryptotanshinone (CRY), an active component of Chinese medicine, on ovarian androgen production, insulin resistance (IR), and glucose metabolism in mice. DESIGN: Animal model and in vitro tissue model. SETTING: University-affiliated laboratory. ANIMAL(S): Mice. INTERVENTION(S): Ovarian IR was induced by dexamethasone (DEX) in vivo. Animals were randomized to receive CRY treatment for 3 days or not. Ovulation rates, serum steroid levels, and glucose uptake in ovaries were quantified, and proteins in the phosphatidylinositol 3-hydroxy kinase pathway were measured. In vitro ovarian IR was also induced by DEX for 3 days. Ovarian steroid hormone secretion and glucose uptake were measured, and the hormone-synthesizing enzymes were determined by semiquantitative reverse transcription-polymerase chain reaction. MAIN OUTCOME MEASURE(S): Ovarian glucose uptake, in vivo ovulation rate, serum and culture medium steroid level, and molecular expression of phosphatidylinositol 3-hydroxy kinase and steroidogenic enzymes. RESULT(S): Dexamethasone significantly increased ovulation rates in vivo and increased T and E2 production and decreased ovarian glucose uptake in vivo and in vitro. Cryptotanshinone significantly reduced ovulation rates in vivo and decreased T and estrogen production in vitro. Cryptotanshinone attenuated the inhibition of DEX on AKT2 and suppressed the up-regulation of CYP11 and CYP17 expression by DEX. CONCLUSION(S): Cryptotanshinone reversed DEX-induced androgen excess and ovarian IR in mice through activation of insulin signaling and the regulation of glucose transporters and hormone-synthesizing enzymes. This suggests a potential role for CRY in treating the ovulatory dysfunction associated with PCOS.

Regulation of lipid and glucose homeostasis by mango tree leaf extract is mediated by AMPK and PI3K/AKT signaling pathways.

Ethanolic extract of Mangifera indica (mango) dose-dependently decreased serum glucose and triglyceride in KK-A(y) mice. Our in vitro and in vivo investigations revealed that the effect of mango leave extract (ME) on glucose and lipid homeostasis is mediated, at least in part, through the PI3K/AKT and AMPK signaling pathway. ME up-regulated the expression of PI3K, AKT and GYS genes by 2.0-fold, 3.2-fold, and 2.7-fold, respectively, leading to a decrease in glucose level. On the other hand, ME up-regulated AMPK and altered lipid metabolism. ME also down-regulated ACC (2.8-fold), HSL (1.6-fold), FAS (1.8-fold) and PPAR-γ (4.0-fold). Finally, we determined that active metabolites of benzophenone C-glucosides, Iriflophenone 3-C-ß-glucoside and Foliamangiferoside A from ME, may play a dominant role in this integrated regulation of sugar and lipid homeostasis.

Recent progress on the role of ChREBP in glucose and lipid metabolism.

Carbohydrate response element binding protein (ChREBP) is a transcription factor activated by glucose that is highly expressed in liver, pancreatic ß-cells, brown and white adipose tissues, and muscle. We reported that hepatic suppression of the Chrebp gene improves hepatic steatosis, glucose intolerance, and obesity in genetically obese mice. Moreover, we have studied the role of ChREBP with special reference to feedforward and feedback looping in liver and pancreatic ß-cells. Recently, several groups reported that (1) glucose activates ChREBP-α transactivity and in turn ChREBP-α induces ChREBP-ß on both transcriptional and translational levels in adipose tissues, and (2) ChREBP regulates glucose transporter type 4 mRNA levels, which may affect glucose uptake in adipose tissues. Moreover, in adipose tissues of obese patients, Chrebpb mRNA levels were much lower than those in lean subjects, while the levels were much higher in liver of obese patients than those in lean subjects. These findings suggest that Chrebpb mRNA levels are different in various tissues and probably in the stages of diabetes mellitus. Herein, we review recent progress in the study of ChREBP with special references to (1) the mechanisms regulating ChREBP transactivity (posttranslational modifications, intramolecular glucose sensing module, feedforward mechanism, and the feedback loop between ChREBP and its target genes), and (2) the role of ChREBP in liver, pancreatic islets and adipose tissues. Understanding the role of ChREBP in each tissue will provide important insight into the pathogenesis of metabolic syndrome.

[Relationship between liver fat content and liver enzymes in individuals with various statuses of glucose metabolism].

OBJECTIVE: To study the relationship between liver fat content (LFC) and liver enzymes in individuals with various statuses of glucose metabolism. METHODS: A total of 109 subjects including with impaired glucose regulation (IGR) (n = 31), newly diagnosed type 2 diabetes (NT2DM) (n = 31) and normal glucose tolerance (NGT) (n = 47) were recruited. The level of LFC was measured by (1)H magnetic resonance spectroscopy ((1)H-MRS) to study the relationship between liver fat content (LFC) and alanine aminotransferase (ALT), aspartate aminotransferase (AST), alkaline phosphatase (AKP) and γ-glutamyltransferase (GGT). The receiver operating characteristic curve (ROC) was employed to obtain the optimal cut-off point of ALT to predict the occurrence of nonalcoholic fatty liver disease (NAFLD). RESULTS: (1) The levels of LFC were progressively raised in NGT, IGR and NT2DM groups respectively [3.83 (2.35 - 7.59)%, 12.82 (8.10 - 21.37)% and 21.99 (11.89 - 34.43)%, P < 0.01]; (2) the subjects were divided into four subgroups by the method of LFC quartile. And quartile subgroups Q1-4 were associated with the increase of LFC. Waist, BMI, systolic blood pressure, triglyceride, total cholesterol, fasting plasma glucose, OGTT 2 h postprandial glucose and HOMA-IR had a rising trend from Q2. But HDL-C showed a declining trend from Q2; (3) ALT and GGT significantly increased from Q3 (P < 0.01) while AST and AKP significantly increased in Q4 (P < 0.01); (4) adjusted by gender, age and body mass index (BMI), LFC was positively correlated with AST (r = 0.329, P < 0.05), ALT (r = 0.454) and GGT (r = 0.378) (All P < 0.01). But it was negatively correlated with AST/ALT (r = -0.364, P < 0.01); (5) the analysis of stepwise regression demonstrated that LFC was a predictor of ALT, AST, GGT and AST/ALT; (6) ALT had a ROC(AUC) of 0.813 (male) and 0.769 (female) (All P < 0.01). The optimal cut-off point of 23.5 U/L (male) and 17.5 U/L (female) might predict the occurrence of NAFLD. CONCLUSIONS: Liver enzymes are correlated with LFC even in normal range. The optimal cut-off point of 23.5 U/L (male) and 17.5 U/L (female) might predict the occurrence of NAFLD. The current used ALT upper limit could underestimate the NAFLD.

Pharmacokinetic, pharmacodynamic, and efficacy profiles of alogliptin, a novel inhibitor of dipeptidyl peptidase-4, in rats, dogs, and monkeys.

The aim of the present research was to characterize the pharmacokinetic, pharmacodynamic, and efficacy profiles of alogliptin, a novel quinazolinone-based dipeptidyl peptidase-4 (DPP-4) inhibitor. Alogliptin potently inhibited human DPP-4 in vitro (mean IC(50), ~ 6.9 nM) and exhibited > 10,000-fold selectivity for DPP-4 over the closely related serine proteases DPP-2, DPP-8, DPP-9, fibroblast activation protein/seprase, prolyl endopeptidase, and tryptase (IC(50) > 100,000 nM). Absolute oral bioavailability of alogliptin in rats, dogs, and monkeys was 45%, 86%, and 72% to 88%, respectively. After a single oral dose of alogliptin, plasma DPP-4 inhibition was observed within 15 min and maximum inhibition was > 90% in rats, dogs, and monkeys; inhibition was sustained for 12 h in rats (43%) and dogs (65%) and 24 h in monkeys (> 80%). From E(max) modeling, 50% inhibition of DPP-4 activity was observed at a mean alogliptin plasma concentration (EC(50)) of 3.4 to 5.6 ng/ml (10.0 to 16.5 nM) in rats, dogs, and monkeys. In Zucker fa/fa rats, a single dose of alogliptin (0.3, 1, 3, and 10 mg/kg) inhibited plasma DPP-4 (91% to 100% at 2 h and 20% to 66% at 24 h), increased plasma GLP-1 (2- to 3-fold increase in AUC(0-20 min)) and increased early-phase insulin secretion (1.5- to 2.6-fold increase in AUC(0-20 min)) and reduced blood glucose excursion (31%-67% decrease in AUC(0-90 min)) after oral glucose challenge. Alogliptin (30 and 100 mg/kg) had no effect on fasting plasma glucose in normoglycemic rats. In summary, these data suggest that alogliptin is a potent and highly selective DPP-4 inhibitor with demonstrated efficacy in Zucker fa/fa rats and potential for once-daily dosing in humans.

Glucokinase thermolability and hepatic regulatory protein binding are essential factors for predicting the blood glucose phenotype of missense mutations.

To better understand how glucokinase (GK) missense mutations associated with human glycemic diseases perturb glucose homeostasis, we generated and characterized mice with either an activating (A456V) or inactivating (K414E) mutation in the gk gene. Animals with these mutations exhibited alterations in their blood glucose concentration that were inversely related to the relative activity index of GK. Moreover, the threshold for glucose-stimulated insulin secretion from islets with either the activating or inactivating mutation were left- or right-shifted, respectively. However, we were surprised to find that mice with the activating mutation had markedly reduced amounts of hepatic GK activity. Further studies of bacterially expressed mutant enzymes revealed that GK(A456V) is as stable as the wild type enzyme, whereas GK(K414E) is thermolabile. However, the ability of GK regulatory protein to inhibit GK(A456V) was found to be less than that of the wild type enzyme, a finding consistent with impaired hepatic nuclear localization. Taken together, this study indicates that it is necessary to have knowledge of both thermolability and the interactions of mutant GK enzymes with GK regulatory protein when attempting to predict in vivo glycemic phenotypes based on the measurement of enzyme kinetics.

Functional significance of the LAR receptor protein tyrosine phosphatase family in development and diseases.

The protein tyrosine phosphatases (PTPs) have emerged as critical players in diverse cellular functions. The focus of this review is the leukocyte common antigen-related (LAR) subfamily of receptor PTPs (RPTPs). This subfamily is composed of three vertebrate homologs, LAR, RPTP-sigma, and RPTP-delta, as well as few invertebrates orthologs such as Dlar. LAR-RPTPs have a predominant function in nervous system development that is conserved throughout evolution. Proteolytic cleavage of LAR-RPTP proproteins results in the noncovalent association of an extracellular domain resembling cell adhesion molecules and intracellular tandem PTPs domains, which is likely regulated via dimerization. Their receptor-like structures allow them to sense the extracellular environment and transduce signals intracellularly via their cytosolic PTP domains. Although many interacting partners of the LAR-RPTPs have been identified and suggest a role for the LAR-RPTPs in actin remodeling, very little is known about the mechanisms of action of RPTPs. LAR-RPTPs recently raised a lot of interest when they were shown to regulate neurite growth and nerve regeneration in transgenic animal models. In addition, LAR-RPTPs have also been implicated in metabolic regulation and cancer. This RPTP subfamily is likely to become important as drug targets in these various human pathologies, but further understanding of their complex signal transduction cascades will be required.