Targeting hepatic glucokinase in type 2 diabetes: weighing the benefits and risks

EpiGePT: a Pretrained Transformer model for epigenomics

The inherent similarities between natural language and biological sequences have given rise to great interest in adapting the transformer-based large language models (LLMs) underlying recent breakthroughs in natural language processing (references), for applications in genomics. However, current LLMs for genomics suffer from several limitations such as the inability to include chromatin interactions in the training data, and the inability to make prediction in new cellular contexts not represented in the training data. To mitigate these problems, we propose EpiGePT, a transformer-based pretrained language model for predicting context-specific epigenomic signals and chromatin contacts. By taking the context-specific activities of transcription factors (TFs) and 3D genome interactions into consideration, EpiGePT offers wider applicability and deeper biological insights than models trained on DNA sequence only. In a series of experiments, EpiGePT demonstrates superior performance in a diverse set of epigenomic signals prediction tasks when compared to existing methods. In particular, our model enables cross-cell-type prediction of long-range interactions and offers insight on the functional impact of genetic variants under different cellular contexts. These new capabilities will enhance the usefulness of LLM in the study of gene regulatory mechanisms. We provide free online prediction service of EpiGePT through http://health.tsinghua.edu.cn/epigept/.

New-Generation Glucokinase Activators: Potential Game-Changers in Type 2 Diabetes Treatment

Achieving glycemic control and sustaining functional pancreatic β-cell activity remains an unmet medical need in the treatment of type 2 diabetes mellitus (T2DM). Glucokinase activators (GKAs) constitute a class of anti-diabetic drugs designed to regulate blood sugar levels and enhance β-cell function in patients with diabetes. A significant progression in GKA development is underway to address the limitations of earlier generations. Dorzagliatin, a dual-acting GKA, targets both the liver and pancreas and has successfully completed two phase III trials, demonstrating favorable results in diabetes treatment. The hepato-selective GKA, TTP399, emerges as a strong contender, displaying clinically noteworthy outcomes with minimal adverse effects. This paper seeks to review the current literature, delve into the mechanisms of action of these new-generation GKAs, and assess their efficacy and safety in treating T2DM based on published preclinical studies and recent clinical trials.

A link between energy metabolism and plant host adaptation states in the two-spotted spider mite, Tetranychus urticae (Koch)

Energy metabolism is a highly conserved process that balances generation of cellular energy and maintenance of redox homeostasis. It consists of five interconnected pathways: glycolysis, tricarboxylic acid cycle, pentose phosphate, trans-sulfuration, and NAD+ biosynthesis pathways. Environmental stress rewires cellular energy metabolism. Type-2 diabetes is a well-studied energy metabolism rewiring state in human pancreatic β-cells where glucose metabolism is uncoupled from insulin secretion. The two-spotted spider mite, Tetranychus urticae (Koch), exhibits a remarkable ability to adapt to environmental stress. Upon transfer to unfavourable plant hosts, mites experience extreme xenobiotic stress that dramatically affects their survivorship and fecundity. However, within 25 generations, mites adapt to the xenobiotic stress and restore their fitness. Mites' ability to withstand long-term xenobiotic stress raises a question of their energy metabolism states during host adaptation. Here, we compared the transcriptional responses of five energy metabolism pathways between host-adapted and non-adapted mites while using responses in human pancreatic islet donors to model these pathways under stress. We found that non-adapted mites and human pancreatic β-cells responded in a similar manner to host plant transfer and diabetogenic stress respectively, where redox homeostasis maintenance was favoured over energy generation. Remarkably, we found that upon host-adaptation, mite energy metabolic states were restored to normal. These findings suggest that genes involved in energy metabolism can serve as molecular markers for mite host-adaptation.

Glucokinase regulatory protein: a balancing act between glucose and lipid metabolism in NAFLD

Non-alcoholic fatty liver disease (NAFLD) is a common liver disease worldwide, affected by both genetics and environment. Type 2 diabetes (T2D) stands as an independent environmental risk factor that precipitates the onset of hepatic steatosis and accelerates its progression to severe stages of liver damage. Furthermore, the coexistence of T2D and NAFLD magnifies the risk of cardiovascular disease synergistically. However, the association between genetic susceptibility and metabolic risk factors in NAFLD remains incompletely understood. The glucokinase regulator gene (GCKR), responsible for encoding the glucokinase regulatory protein (GKRP), acts as a regulator and protector of the glucose-metabolizing enzyme glucokinase (GK) in the liver. Two common variants (rs1260326 and rs780094) within the GCKR gene have been associated with a lower risk for T2D but a higher risk for NAFLD. Recent studies underscore that T2D presence significantly amplifies the effect of the GCKR gene, thereby increasing the risk of NASH and fibrosis in NAFLD patients. In this review, we focus on the critical roles of GKRP in T2D and NAFLD, drawing upon insights from genetic and biological studies. Notably, prior attempts at drug development targeting GK with glucokinase activators (GKAs) have shown potential risks of augmented plasma triglycerides or NAFLD. Conversely, overexpression of GKRP in diabetic rats improved glucose tolerance without causing NAFLD, suggesting the crucial regulatory role of GKRP in maintaining hepatic glucose and lipid metabolism balance. Collectively, this review sheds new light on the complex interaction between genes and environment in NAFLD, focusing on the GCKR gene. By integrating evidence from genetics, biology, and drug development, we reassess the therapeutic potential of targeting GK or GKRP for metabolic disease treatment. Emerging evidence suggests that selectively activating GK or enhancing GK-GKRP binding may represent a holistic strategy for restoring glucose and lipid metabolic balance.

Effect of anthocyanin-rich blackberry juice on endoplasmic reticulum stress in streptozotocin-induced diabetic rats

This study investigates blackberry juice's effects on glucose metabolism, oxidative stress, inflammation, and endoplasmic reticulum stress (ER) in streptozotocin (STZ)-induced diabetic rats. Fifty Wistar rats were distributed to five groups randomly of ten rats each: Normal control, diabetic control, 9 mL/kg body weight (b.wt) blackberry juice only, blackberry juice plus diabetes, and 500 mg/kg b.wt metformin plus diabetes. A single intraperitoneal injection of 50 mg/kg b.wt STZ induced diabetes in the rats. This animal study continued for 56 days after the confirmation of diabetes. The levels of liver function and renal function, as well as insulin, glucose-6-phosphatase, glucokinase, and malondialdehyde (MDA) levels, and the activities of catalase (CAT) and superoxide dismutase (SOD), were determined. Additionally, interleukin-6 (IL-6) levels, tumor necrosis factor-alpha (TNF-α), and activated transcription factor 4 (ATF4) expressions were examined in the liver homogenate of rats. Furthermore, the liver tissues were utilized for histopathological examination. The results showed that blackberry juice prevented drastic loss of body weight and reduced food consumption in diabetic rats. Additionally, the levels of blood glucose, total protein, aspartate aminotransferase (AST), albumin, alanine aminotransferase (ALT), uric acid, creatinine, and urea improved after the administration of blackberry juice in diabetic rats. Blackberry juice significantly increased glucose metabolism and antioxidant status while reducing ER stress and inflammation in diabetic rats. Moreover, blackberry juice improved glucose metabolism by increasing insulin levels and improving the dysregulated activities of glucose-metabolizing enzymes. The microstructure of liver tissues in diabetic rats was also improved with blackberry juice treatment. Therefore, blackberry juice has the potential to alleviate diabetes in rats and could be considered as a functional food for people with diabetes.

Targeting human Glucokinase for the treatment of type 2 diabetes: an overview of allosteric Glucokinase activators

Diabetes mellitus is a worldwide impacting disorder and the ratio through which the number of diabetic patients had increased worldwide, puts medical professionals to serious stress for its effective management. Due to its polygenic origin and involvement of multiple genes to its pathophysiology, leads to understanding of this ailment more complex. It seems that current interventions, such as dietary changes, life style changes and drug therapy such as oral hypoglycaemics and insulin, are unable to halt the trend. There are various novel and emerging targets on which the researchers are paying attention to combat with this ailment successfully. Human glucokinase (GK) enzyme is one of these novel and emerging targets for management of diabetes. Its availability in the pancreas and liver cells makes this target more lucrative. GK's presence in the pancreatic and hepatic cells plays a very important function for the management of glucose homoeostasis. Small molecules that activate GK allosterically provide an alternative strategy for restoring/improving glycaemic regulation, especially in type 2 diabetic patients. Although after enduring many setbacks in the development of the GK activators, interest has been renewed especially due to introduction of novel dual acting GK activator dorzagliatin, and a novel hepato-selective GK activator, TTP399. This review article has been formulated to discuss importance of GK in glucose homeostasis, recent updates on small molecules of GK activators, clinical status of GK activators and challenges in development of GK activators.

Dorzagliatin in drug-naïve patients with type 2 diabetes: a randomized, double-blind, placebo-controlled phase 3 trial

Improving glucose sensitivity remains an unmet medical need in treating type 2 diabetes (T2D). Dorzagliatin is a dual-acting, orally bioavailable glucokinase activator that enhances glucokinase activity in a glucose-dependent manner, improves glucose-stimulated insulin secretion and demonstrates effects on glycemic control in patients with T2D. We report the findings of a randomized, double-blind, placebo-controlled phase 3 clinical trial to evaluate the efficacy and safety of dorzagliatin in patients with T2D. Eligible drug-naïve patients with T2D (n = 463) were randomly assigned to the dorzagliatin or placebo group at a ratio of 2:1 for 24 weeks of double-blind treatment, followed by 28 weeks of open-label treatment with dorzagliatin for all patients. The primary efficacy endpoint was the change in glycated hemoglobin from baseline to week 24. Safety was assessed throughout the trial. At week 24, the least-squares mean change in glycated hemoglobin from baseline (95% confidence interval) was -1.07% (-1.19%, -0.95%) in the dorzagliatin group and -0.50% (-0.68%, -0.32%) in the placebo group (estimated treatment difference, -0.57%; 95% confidence interval: -0.79%, -0.36%; P < 0.001). The incidence of adverse events was similar between the two groups. There were no severe hypoglycemia events or drug-related serious adverse events in the dorzagliatin group. In summary, dorzagliatin improved glycemic control in drug-naïve patients with T2D and showed a good tolerability and safety profile.

An fgf21-like gene from swamp eel (Monopterus albus): Recombinant expression and its potential roles in glucose and lipid homeostasis

Fibroblast growth factor 21 (FGF21) plays important roles in the regulation of glucose and lipid metabolism and energy balance in mammals. In this study, the full-length cDNA of swamp eel fgf21 was cloned. Sequence analysis showed that swamp eel FGF21 displayed high similarity with FGF21 of other vertebrates. Subsequently, a prokaryotic expression vector for swamp eel fgf21 was constructed, and recombinant FGF21 (rFGF21) was successfully induced and purified. To investigate the potential roles of swamp eel FGF21 in glucose and lipid metabolism, we examined the effects of rFGF21 on regulation of glucose and lipid homeostasis in type 1 diabetes mellitus (T1DM) mice as well as swamp eels under glucose stress. In T1DM mice, the levels of blood glucose, serum triglyceride (TG), liver TG, serum total cholesterol (TC), and liver TC were significantly downregulated after repeated daily injection of rFGF21 for 15 days. In addition, liver pathological section analysis indicated that rFGF21 alleviated the degree of damage to liver cells in T1DM mice. Furthermore, rFGF21 significantly upregulated the mRNA expression levels of peroxisome proliferators-activated receptor alpha (Pparα), β-Klotho, fibroblast growth factor receptor 1 (Fgfr1), phosphoenolpyruvate carboxykinase (Pepck), glucose transporter 1 (Glut1), and glucose transporter 4 (Glut4) in T1DM mouse livers. Moreover, in swamp eels, rFGF21 significantly decreased blood glucose and liver TC levels under glucose stress and upregulated the mRNA expression levels of fgf21, pparα, β-klotho, and fgfr1 in liver tissue. These results suggested that FGF21 plays important roles in the regulation of glucose and lipid homeostasis in swamp eel.

In vitro toxic interaction of arsenic and hyperglycemia in mitochondria: an important implication of increased vulnerability in pre-diabetics

Environmental pollutants and lifestyle both contribute to the rapidly increasing prevalence of type 2 diabetes mellitus (T2DM) worldwide. Evidence suggests that exposure to environmental contaminants such as arsenic is associated with impaired glucose metabolism and insulin signaling. In the present study, isolated rat liver mitochondria (1 mg/ml) were co-exposed to low concentration of arsenic trioxide (ATO) ( IC₂₅ = 40 µM) and hyperglycemic condition (20, 40, 80, 160 mM glucose or 20, 40, 80, 160 mM pyruvate (PYR)). Mitochondrial dehydrogenase activity (complex II), glutathione content (GSH), reactive oxygen species (ROS), lipid peroxidation, mitochondrial membrane potential (ΔΨ), and mitochondrial swelling were then evaluated in the presence of ATO 40 µM and PYR 40 mM. Unexpectedly, glucose alone (20, 40, 80, 160 mM) had no toxic effect on mitochondria, even at very high concentrations and even when combined with ATO. Interestingly, PYR at low concentrations (≤ 10 mM) has a protective effect on mitochondria, but at higher concentrations (≥ 40 mM) with ATO, it decreased the complex II activity and increased mitochondrial ROS production, lipid peroxidation, GSH depletion, mitochondrial membrane damage, and swelling (p < 0.05). In conclusion, PYR but not glucose increased ATO mitochondrial toxicity even at low concentrations. These results suggest that pre-diabetics with non-clinical hyperglycemia, who are inevitably exposed to low concentrations of arsenic through food and water, may develop mitochondrial dysfunction that accelerates their progression to diabetes over time.

The association between rs1260326 with the risk of NAFLD and the mediation effect of triglyceride on NAFLD in the elderly Chinese Han population

Background: Accumulated studies have pointed out the striking association between variants in or near APOC3, GCKR, PNPLA3, and nonalcoholic fatty liver disease (NAFLD) at various ages from multiple ethnic groups. This association remained unclear in the Chinese Han elderly population, and whether this relationship correlated to any clinical parameters was also unclear.

Objectives: This study aims to decipher the complex relevance between gene polymorphisms, clinical parameters, and NAFLD by association study and mediation analysis.

Methods: Eight SNPs (rs2854116, rs2854117, rs780093, rs780094, rs1260362, rs738409, rs2294918, and rs2281135) within APOC3, GCKR, and PNPLA3 were genotyped using the MassARRAY® platform in a large Chinese Han sample comprising of 733 elderly NAFLD patients and 824 age- and ethnic-matched controls. Association and mediation analysis were employed by R.

Results: The genotypic frequencies of rs1260326 and rs780094 were significantly different between NAFLD and control (rs1260326: P=0.004, P_corr=0.020, OR [95%CI]= 0.69 [0.54-0.89]; rs780094: P=0.005, P_corr=0.025, OR [95%CI]= 0.70 [0.55-0.90]). Particularly, an increased triglyceride level was observed in carriers of rs1260326 T allele (1.94±1.19 mmol/L) compared with non-carriers (1.73±1.05 mmol/L).no significant results were observed in rs780094. Notably, triglyceride levels had considerably indirect impacts on association between NAFLD and rs1260326 (β =0.01, 95% CI: 0.01–0.02), indicating that 12.7% of the association of NAFLD with rs1260326 was mediated by triglyceride levels.

Conclusions: Our results identified a prominent relationship between GCKR rs1260326 and NAFLD, and highlighted the mediated effect of triglyceride levels on the that association in the Chinese Han elderly.

Multi-Targeted Molecular Docking, Pharmacokinetics, and Drug-Likeness Evaluation of Okra-Derived Ligand Abscisic Acid Targeting Signaling Proteins Involved in the Development of Diabetes

Diabetes mellitus is a global threat affecting millions of people of different age groups. In recent years, the development of naturally derived anti-diabetic agents has gained popularity. Okra is a common vegetable containing important bioactive components such as abscisic acid (ABA). ABA, a phytohormone, has been shown to elicit potent anti-diabetic effects in mouse models. Keeping its anti-diabetic potential in mind, in silico study was performed to explore its role in inhibiting proteins relevant to diabetes mellitus- 11β-hydroxysteroid dehydrogenase (11β-HSD1), aldose reductase, glucokinase, glutamine-fructose-6-phosphate amidotransferase (GFAT), peroxisome proliferator-activated receptor-gamma (PPAR-gamma), and Sirtuin family of NAD(+)-dependent protein deacetylases 6 (SIRT6). A comparative study of the ABA-protein docked complex with already known inhibitors of these proteins relevant to diabetes was compared to explore the inhibitory potential. Calculation of molecular binding energy (ΔG), inhibition constant (pKi), and prediction of pharmacokinetics and pharmacodynamics properties were performed. The molecular docking investigation of ABA with 11-HSD1, GFAT, PPAR-gamma, and SIRT6 revealed considerably low binding energy (ΔG from −8.1 to −7.3 Kcal/mol) and predicted inhibition constant (pKi from 6.01 to 5.21 µM). The ADMET study revealed that ABA is a promising drug candidate without any hazardous effect following all current drug-likeness guidelines such as Lipinski, Ghose, Veber, Egan, and Muegge.

Combined effect of metformin and gallic acid on inflammation, antioxidant status, endoplasmic reticulum (ER) stress and glucose metabolism in fructose-fed streptozotocin-induced diabetic rats

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Metformin, gallic acid and a combination of both improved glucose metabolism and antioxidant status in diabetic rats.

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Metformin, gallic acid and a combination of both lowered levels of IL-6 and TNF-α in liver and pancreas of diabetic rats.

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Metformin, gallic acid and a combination of both decreased the expression of ATF4 in liver and pancreas of diabetic rats.

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Metformin/GA combination appeared more effective than metformin only and gallic acid only.

Over time, diabetes patients usually need combination therapy involving two or more agents, including phytonutrients to attain therapeutic targets. The purpose of this research is to elucidate the combined effect of metformin and gallic acid (GA) on glucose metabolism, inflammation as well as oxidative and endoplasmic reticulum (ER) stresses in fructose-fed diabetic rats. Thirty-five rats of Wistar strain were arbitrarily distributed into five groups, each containing seven animals as follows: normal control, diabetic control, groups administered 100 mg/kg bw metformin only, 50 mg/kg bw gallic acid only and a combination of both. Experimental animals were made diabetic by single injection of 40 mg/kg streptozotocin (intraperitoneally) subsequent to 14 days administration of 10 % fructose prior. Treatment of rats continued for 21 days following diabetes confirmation. Glucose and insulin levels as well as lipid profile were evaluated in the serum, while activities of catalase and superoxide dismutase were estimated in both liver and pancreas. In addition, levels of malondialdehyde, interleukin-6 and tumor necrosis factor-alpha, as well as expression of activating transcription factor-4 were evaluated in liver and pancreas of diabetic rats. Activities of glucose-6-phosphatase and glucokinase were also determined in liver of diabetic animals. Metformin only, GA only and combination of metformin and GA significantly improved antioxidant status and glucose homeostasis while inflammation and endoplasmic reticulum stress were significantly ameliorated in diabetic rats. Metformin/GA combination appeared to improve glucose metabolism by increasing insulin level and ameliorating the dysregulated activities of glucose metabolizing enzymes and ER stress better than either metformin only or GA only. It could be concluded that coadministration of metformin/GA produced a combined effect in ameliorating diabetes in Wistar rats and could be considered in treatment of diabetes.

Increased insulin and GLUT2 gene expression and elevated glucokinase activity in β-like cells of islets of langerhans differentiated from human haematopoietic stem cells on treatment with Costus igneus leaf extract

In the quest to understand lost β-cells regeneration in the diabetic condition, we have demonstrated successful differentiation of human haematopoietic stem cells (HSCs) to functional β-like cells. Costus igneus (Ci) leaf extract is known to exhibit anti-diabetic properties by lowering the blood glucose level as demonstrated in mice models. To establish the anti-diabetic properties of Ci leaf extract on human subjects, we studied the effect of Ci on these differentiated β-like cells. Ci leaf extract showed its anti-diabetic property through elevated glucokinase activity which catalyzes the rate-limiting step of glucose catabolism in β-like cells and acts as a sensor for insulin production while decreasing the glucose-6-phosphatase activity. Upon increasing the concentrations of Ci leaf extract (25, 65, 105, 145, 185 µg/ml) and glucose concentrations (5.5, 11.1, and 25 mM) Ci leaf extract treated β-like cells showed enhanced glucokinase and decreased glucose-6-phosphatase activities and an exponential rise in gene expressions of INS and GLUT2 was observed. The present study shows enhanced INS and GLUT2 gene expression and elevated glucokinase activity in β-like cells differentiated from HSCs upon treatment with Ci leaf extract explain the anti-diabetic property of Ci leaf extract. This extract can be effectively used in the management of diabetes.

Vanillic acid mitigates the impairments in glucose metabolism in HepG2 cells through BAD-GK interaction during hyperinsulinemia

Glucokinase (GK), a key regulator of hepatic glucose metabolism in the liver and glucose sensor and mediator in the secretion of insulin in the pancreas, is not studied in detail for its therapeutic application in diabetes. Herein, we study the alteration in GK activity during hyperinsulinemia-induced insulin resistance in HepG2 cells. We also investigated the link between GK and Bcl-2-associated death receptor (BAD) during hyperinsulinemia. There are emerging demands for GK activators from natural resources, and we selected vanillic acid (VA) to evaluate its potential as GK activators during hyperinsulinemia in HepG2 cells. VA is a phenolic compound and a commonly used food additive in many food industries. We found that VA safeguarded GK inhibition during hyperinsulinemia significantly in HepG2 cells. VA also prevented the depletion of glycogen synthesis during hyperinsulinemia, which is evident from protein expression studies of phosphoenolpyruvate carboxykinase, glucose-6-phosphatase, glycogen synthase, and glycogen synthase kinase-3β. This was associated with activation of BAD activity, which was also confirmed by Western blotting. Molecular docking revealed strong binding between GK active site and VA, supporting their strong interaction. These are the first in vitro data to indicate the beneficial properties of VA with respect to insulin resistance induced by hyperinsulinemia by GK activation. Since it is activated via BAD, the hypoglycemia associated with general GK activation is not expected here and therefore has significant implications for future therapies against diabetes.

Myricitrin Ameliorates Hyperglycemia, Glucose Intolerance, Hepatic Steatosis, and Inflammation in High-Fat Diet/Streptozotocin-Induced Diabetic Mice

To test the hypothesis that myricitrin (MYR) improves type 2 diabetes, we examined the effect of MYR on hyperglycemia, glucose intolerance, hepatic steatosis, and inflammation in high-fat diet (HFD) and streptozotocin (STZ)-induced type 2 diabetic mice. Male C57BL/6J mice were randomly divided into three groups: non-diabetic, diabetic control, and MYR (0.005%, w/w)-supplemented diabetic groups. Diabetes was induced by HFD and STZ, and MYR was administered orally for 5 weeks. Myricitrin exerted no significant effects on food intake, body weight, fat weight, or plasma lipids levels. However, MYR significantly decreased fasting blood glucose levels, improved glucose intolerance, and increased pancreatic β-cell mass compared to the diabetic control group. Myricitrin administration also markedly increased glucokinase mRNA expression and activity as well as lowered glucose-6-phosphatase and phosphoenolpyruvate carboxykinase mRNA expression and activity in the liver. In addition, liver weight, hepatic triglyceride content, and lipid droplet accumulation were markedly decreased following MYR administration. These changes were seemingly attributable to the suppression of the hepatic lipogenic enzymes—fatty acid synthase and phosphatidate phosphohydrolase. Myricitrin also significantly lowered plasma MCP-1 and TNF-α levels and the mRNA expression of hepatic pro-inflammatory genes. These results suggest that MYR has anti-diabetic potential.

Synergistic effect of novel chitosan combined metformin drug on streptozotocin-induced diabetes mellitus rat

Metformin is widely used as a frontline medicine of type-II diabetes. Frequent overdose side-effects and their consequent adversative need to be reduced. The novel source of marine hydrozoa, Thyroscyphus ramosus derived chitosan combined metformin drug was administrated to evaluate the antidiabetic potential on a high-fat diet (HFD) with streptozotocin (STZ) induced diabetic rats. The primary analysis of In vitro antioxidant activity was tested for various solvent dissolved chitosan. Based on their IC₅₀ dose values, CsnAA was chosen for further experiments. The chitosan was combined with metformin by sonication and confirmed through XRD, FTIR and SEM analysis. The enhanced activity was observed in 100 mg/kg metformin combined with CSN500mg/kg. The level of serum bilirubin, total protein, SGH, liver glycogen, Glucose-6-phosphatase and fructose-1,6- phosphatase values were significantly similar to metformin 300 mg/kg treated group. With this beneficiary, the novel chitosan was recommended to administrate with metformin to improve the drug efficacy and reduction of overdose lethal effects.

The peptide hormone adropin regulates signal transduction pathways controlling hepatic glucose metabolism in a mouse model of diet-induced obesity

The peptide hormone adropin regulates energy metabolism in skeletal muscle and plays important roles in the regulation of metabolic homeostasis. Besides muscle, the liver has an essential role in regulating glucose homeostasis. Previous studies have reported that treatment of diet-induced obese (DIO) male mice with adropin34-76 (the putative secreted domain) reduces fasting blood glucose independently of body weight changes, suggesting that adropin suppresses glucose production in the liver. Here, we explored the molecular mechanisms underlying adropin's effects on hepatic glucose metabolism in DIO mice. Male DIO B6 mice maintained on a high-fat diet received five intraperitoneal injections of adropin34-76 (450 nmol/kg/injection) over a 48-h period. We found that adropin34-76 enhances major intracellular signaling activities in the liver that are involved in insulin-mediated regulation of glucose homeostasis. Moreover, treatment with adropin34-76 alleviated endoplasmic reticulum stress responses and reduced activity of c-Jun N-terminal kinase in the liver, explaining the enhanced activities of hepatic insulin signaling pathways observed with adropin34-76 treatment. Furthermore, adropin34-76 suppressed cAMP activated protein kinase A (PKA) activities, resulting in reduced phosphorylation of inositol trisphosphate receptor, which mediates endoplasmic reticulum calcium efflux, and of cAMP-responsive element-binding protein, a key transcription factor in hepatic regulation of glucose metabolism. Adropin34-76 directly affected liver metabolism, decreasing glucose production and reducing PKA-mediated phosphorylation in primary mouse hepatocytes in vitro Our findings indicate that major hepatic signaling pathways contribute to the improved glycemic control achieved with adropin34-76 treatment in situations of obesity.

Targeting hepatic glucokinase to treat diabetes with TTP399, a hepatoselective glucokinase activator

The therapeutic success of interventions targeting glucokinase (GK) activation for the treatment of type 2 diabetes has been limited by hypoglycemia, steatohepatitis, and loss of efficacy over time. The clinical characteristics of patients with GK-activating mutations or GK regulatory protein (GKRP) loss-of-function mutations suggest that a hepatoselective GK activator (GKA) that does not activate GK in β cells or affect the GK-GKRP interaction may reduce hyperglycemia in patients with type 2 diabetes while limiting hypoglycemia and liver-associated adverse effects. Here, we review the rationale for TTP399, an oral hepatoselective GKA, and its progression from preclinical to clinical development, with an emphasis on the results of a randomized, double-blind, placebo- and active-controlled phase 2 study of TTP399 in patients with type 2 diabetes. In this 6-month study, TTP399 (800 mg/day) was associated with a clinically significant and sustained reduction in glycated hemoglobin, with a placebo-subtracted least squares mean HbA1c change from baseline of −0.9% (P < 0.01). Compared to placebo, TTP399 (800 mg/day) also increased high-density lipoprotein cholesterol (3.2 mg/dl; P < 0.05), decreased fasting plasma glucagon (−20 pg/ml; P < 0.05), and decreased weight in patients weighing ≥100 kg (−3.4 kg; P < 0.05). TTP399 did not cause hypoglycemia, had no detrimental effect on plasma lipids or liver enzymes, and did not increase blood pressure, highlighting the importance of tissue selectivity and preservation of physiological regulation when targeting key metabolic regulators such as GK.

Type 2 diabetes mellitus in children and adolescent: an Indonesian perspective

The prevalence of type 2 diabetes mellitus (T2DM) in children and adolescents has increased globally over the past 2 decades. Metabolic syndrome, including obesity and overweight at a young age, increases the occurrence of T2DM. Studies in Indonesia have found that obese children and adolescents are more likely to have insulin resistance, a risk factor for T2DM. There are no data on the current incidence of T2DM in youth in Indonesia, but there has been a significant rise in the prevalence of overweight in adolescents. The diagnosis of T2DM in youth is similar to that in adults, with special consideration of when to test asymptomatic children. Management of T2DM in Indonesia follows the recommendations of the Indonesian Pediatric Society, which include lifestyle modifications, such as improving dietary habits and exercise, as well as appropriate medications. Metformin is the drug of choice for young T2DM patients; if marked hyperglycemia is present, basal insulin is given with metformin. Monitoring of T2DM is generally done through selfmonitoring of blood glucose and glycosylated hemoglobin.

Krüppel-Like Factors in Metabolic Homeostasis and Cardiometabolic Disease

Members of the Krüppel-like factor (KLF) family of transcription factors, which are characterized by the presence of three conserved Cys₂/His₂ zinc-fingers in their C-terminal domains, control a wide variety of biological processes. In particular, recent studies have revealed that KLFs play diverse and essential roles in the control of metabolism at the cellular, tissue and systemic levels. In both liver and skeletal muscle, KLFs control glucose, lipid and amino acid metabolism so as to coordinate systemic metabolism in the steady state and in the face of metabolic stresses, such as fasting. The functions of KLFs within metabolic tissues are also important contributors to the responses to injury and inflammation within those tissues. KLFs also control the function of immune cells, such as macrophages, which are involved in the inflammatory processes underlying both cardiovascular and metabolic diseases. This review focuses mainly on the physiological and pathological functions of KLFs in the liver and skeletal muscle. The involvement of KLFs in inflammation in these tissues is also summarized. We then discuss the implications of KLFs' control of metabolism and inflammation in cardiometabolic diseases.

The role of FGF21 in type 1 diabetes and its complications

Data from the International Diabetes Federation show that 347 million people worldwide have diabetes, and the incidence is still rising. Although the treatment of diabetes has been advanced, the current therapeutic options and outcomes, e.g. complications, are yet far from ideal. Therefore, an urgent need exists for the development of more effective therapies. Numerous studies have been conducted to establish and confirm whether FGF21 exerts beneficial effects on obesity and diabetes along with its complications. However, most of the studies associated with FGF21 were conducted in the patients with type 2 diabetes. Subsequently, the effect of FGF21 in the prevention or treatment of type 1 diabetes and its complications were also increasingly reported. In this review, we summarize the findings available on the function of FGF21 and the status of FGF21's treatment for type 1 diabetes. Based on the available information, we found that FGF21 exerts a hypoglycemic effect, restores the function of brown fat, and inhibits various complications in type 1 diabetes patients. Although these features are predominantly similar to those observed in the studies that showed the beneficial impact of FGF21 on type 2 diabetes and its complications, there are also certain distinct features and findings that may be of provide important and instructive for us to understand mechanistic insights and further promote the prevention and treatment of type 1 diabetes.

Pharmacological efficacy of FGF21 analogue, liraglutide and insulin glargine in treatment of type 2 diabetes

Fibroblast growth factor 21 (FGF21) is a promising regulator of glucose and lipid metabolism with multiple beneficial effects including hypoglycemic and lipid-lowering. Previous studies have reported that FGF21 is expected to become a new drug for treatment of diabetes. Liraglutide and insulin glargine are the two representative anti-diabetic biological drugs. In the current study, we aim to compare the long-term pharmacological efficacy of mFGF21 (an FGF21 analogue), liraglutide and insulin glargine in type 2 diabetic db/db mice. Db/db mice were initially treated with three kinds of proteins (25nmol/kg/day) by subcutaneous injection once a day for 4weeks, then subsequently be treated with once every two days for next 4weeks. After 8weeks of treatments, the blood glucose levels, body weights, glycosylated hemoglobin levels, fasting insulin levels, serum lipid profiles, hepatic biochemical parameters, oral glucose tolerance tests and hepatic mRNA expression levels of several proteins (GK, G6P, GLUT-1 and GLUT-4) associated with glucose metabolism of the experimental mice were detected. Results demonstrated that three proteins could significantly decrease the fed blood glucose levels of db/db mice. After treatment for 1week, the fed blood glucose levels of db/db mice in liraglutide group were significantly lower than those in mFGF21 and insulin glargine groups. However, after 2weeks of administration, the long-lasting hypoglycemic effect of mFGF21 was superior to liraglutide and insulin glargine up to the end of the experiments. Compared with liraglutide and insulin glargine, mFGF21 significantly reduced the glycosylated hemoglobin levels and improved the ability on glycemic control, insulin resistance, serum lipid and liver function states in db/db mice after 8weeks treatments. In addition, mFGF21 regulated glucose metabolism through increasing the mRNA expression levels of GK and GLUT-1, and decreasing the mRNA expression level of G6P. But liraglutide and insulin glargine could only up-regulate the mRNA expression of GLUT-4. In summary, as a hypoglycemic drug for long-term treatment, mFGF21 has the potential to be an ideal drug candidate for the therapy of type 2 diabetes.

Oat bran β-glucan improves glucose homeostasis in mice fed on a high-fat diet

The changes of body weight (A) and food intake (B) of mice fed on different diets of low-fat (LF), high-fat (HF), HF + grain form β-glucan (HFGF), and HF + extracted β-glucan (HFEX).

O-GlcNAcylation of Orphan Nuclear Receptor Estrogen-Related Receptor γ Promotes Hepatic Gluconeogenesis

Estrogen-related receptor γ (ERRγ) is a major positive regulator of hepatic gluconeogenesis. Its transcriptional activity is suppressed by phosphorylation signaled by insulin in the fed state, but whether posttranslational modification alters its gluconeogenic activity in the fasted state is not known. Metabolically active hepatocytes direct a small amount of glucose into the hexosamine biosynthetic pathway, leading to protein O-GlcNAcylation. In this study, we demonstrate that ERRγ is O-GlcNAcylated by O-GlcNAc transferase in the fasted state. This stabilizes the protein by inhibiting proteasome-mediated protein degradation, increasing ERRγ recruitment to gluconeogenic gene promoters. Mass spectrometry identifies two serine residues (S317, S319) present in the ERRγ ligand-binding domain that are O-GlcNAcylated. Mutation of these residues destabilizes ERRγ protein and blocks the ability of ERRγ to induce gluconeogenesis in vivo. The impact of this pathway on gluconeogenesis in vivo was confirmed by the observation that decreasing the amount of O-GlcNAcylated ERRγ by overexpressing the deglycosylating enzyme O-GlcNAcase decreases ERRγ-dependent glucose production in fasted mice. We conclude that O-GlcNAcylation of ERRγ serves as a major signal to promote hepatic gluconeogenesis.

The relative importance of kinetic mechanisms and variable enzyme abundances for the regulation of hepatic glucose metabolism--insights from mathematical modeling

Background

Adaptation of the cellular metabolism to varying external conditions is brought about by regulated changes in the activity of enzymes and transporters. Hormone-dependent reversible enzyme phosphorylation and concentration changes of reactants and allosteric effectors are the major types of rapid kinetic enzyme regulation, whereas on longer time scales changes in protein abundance may also become operative. Here, we used a comprehensive mathematical model of the hepatic glucose metabolism of rat hepatocytes to decipher the relative importance of different regulatory modes and their mutual interdependencies in the hepatic control of plasma glucose homeostasis.

Results

Model simulations reveal significant differences in the capability of liver metabolism to counteract variations of plasma glucose in different physiological settings (starvation, ad libitum nutrient supply, diabetes). Changes in enzyme abundances adjust the metabolic output to the anticipated physiological demand but may turn into a regulatory disadvantage if sudden unexpected changes of the external conditions occur. Allosteric and hormonal control of enzyme activities allow the liver to assume a broad range of metabolic states and may even fully reverse flux changes resulting from changes of enzyme abundances alone. Metabolic control analysis reveals that control of the hepatic glucose metabolism is mainly exerted by enzymes alone, which are differently controlled by alterations in enzyme abundance, reversible phosphorylation, and allosteric effects.

Conclusion

In hepatic glucose metabolism, regulation of enzyme activities by changes of reactants, allosteric effects, and reversible phosphorylation is equally important as changes in protein abundance of key regulatory enzymes.

Electronic supplementary material

The online version of this article (doi:10.1186/s12915-016-0237-6) contains supplementary material, which is available to authorized users.

Antidiabetic potential of a novel dual-target activator of glucokinase and peroxisome proliferator activated receptor-γ

BACKGROUND AND PURPOSE

Glucokinase (GK) balances blood glucose levels via regulation of glucose metabolism and insulin secretion. Peroxisome proliferator activated receptor-γ (PPARγ) regulates gene expression in glucose and lipid metabolism. In this study, we investigated the therapeutic effect of a novel compound, SHP289-03, which activates both GK and PPARγ.

METHODS

Glucose metabolism was tested in primary hepatocytes of normal ICR mice, and insulin secretion was measured in NIT-1 insulinoma cells as well as in primary islets of normal ICR mice. The in vivo pharmacodynamics of SHP289-03 was assessed using the spontaneous type 2 diabetic mouse model, KKA(y).

KEY RESULTS

In hepatocytes, SHP289-03 promoted glucose consumption. In NIT-1 cells, it increased the concentration of intracellular ATP and calcium, and subsequently enhanced glucose-stimulated insulin secretion in both NIT-1 cells and primary islets. Moreover, SHP289-03 decreased the blood glucose level, improved glucose tolerance and reduced blood lipid levels in KKA(y) mice. It restored islet morphology and increased the beta cell/alpha cell mass ratio, in addition to up-regulating GK gene expression in the liver of KKA(y) mice.

DISCUSSION AND CONCLUSIONS

SHP289-03 has significant therapeutic potential for the treatment of diabetes mellitus.

Long-lasting anti-diabetic efficacy of PEGylated FGF-21 and liraglutide in treatment of type 2 diabetic mice

Fibroblast growth factor-21 (FGF-21) is a new member of the FGF family and potential drug candidate for the treatment of type 2 diabetes mellitus. However, FGF-21 protein has short half-life in vivo, which severely affects its clinical application. In the present study, PEGylated FGF-21 was prepared by modifying the N-terminus of hFGF-21 with 20 kDa mPEG-ALD. The long-acting hypoglycemic effect of PEGylated FGF-21 and liraglutide was compared on type 2 diabetic db/db mice. The pharmacological efficacy of the compounds was evaluated by blood glucose levels, body weight, glycosylated hemoglobin levels, insulin levels, oral glucose tolerance test, lipid levels, and liver function parameters. We noticed that both PEGylated FGF-21 and liraglutide could significantly decrease plasma glucose in db/db mice. However, comparing to liraglutide treatments, PEGylated FGF-21 therapy resulted in more significant effect in lowering blood glucose levels and glycosylated hemoglobin levels, alleviating insulin resistance, improving lipid profile, liver function, and glucose control of the experimental mice. Our results suggest that PEGylated FGF-21 appears more beneficial anti-diabetic effect in type 2 diabetic mice than liraglutide, which holds significant promise as an ideal candidate for the treatment of type 2 diabetic patients.

S 50131 and S 51434, two novel small molecule glucokinase activators, lack chronic efficacy despite potent acute antihyperglycaemic activity in diabetic mice

BACKGROUND AND PURPOSE

Small molecule glucokinase activators (GKAs) have been associated with potent antidiabetic efficacy and hepatic steatosis in rodents. This study reports the discovery of S 50131 and S 51434, two novel GKAs with an original scaffold and an atypical pharmacological profile.

EXPERIMENTAL APPROACH

Activity of the compounds was assessed in vitro by measuring activation of recombinant glucokinase, stimulation of glycogen synthesis in rat hepatocytes and increased insulin secretion from rat pancreatic islets of Langerhans. Efficacy and safety in vivo were evaluated after oral administration in db/db mice by measuring glycaemia, HbA1c and dyslipidaemia-associated events.

KEY RESULTS

S 50131 and S 51434 activated GK and stimulated glycogen synthesis in hepatocytes and insulin secretion from pancreatic islets. Unexpectedly, while both compounds effectively lowered glycaemia after acute oral administration, they did not decrease HbA1c after a 4-week treatment in db/db mice. This lack of antidiabetic efficacy was associated with increased plasma free fatty acids (FFAs), contrasting with the effect of GKA50 and N00236460, two GKAs with sustained HbA1c lowering activity but neutral regarding plasma FFAs. S 50131, but not S 51434, also induced hepatic steatosis, as did GKA50 and N00236460. However, a shorter, 4-day treatment resulted in increased hepatic triglycerides without changing the plasma FFA levels, demonstrating dynamic alterations in the lipid profile over time.

CONCLUSIONS AND IMPLICATIONS

In addition to confirming the occurrence of dyslipidaemia with GKAs, these findings provide new insights into understanding how such compounds may sustain or lose efficacy over time.

Molecular docking studies of (4Z, 12Z)-cyclopentadeca-4, 12-dienone from Grewia hirsuta with some targets related to type 2 diabetes

Background

Management of diabetes without any side effects is still a challenge to the medical system. This leads to increasing demand for natural products with antidiabetic activity with fewer side effects. Grewia hirsuta (Tiliaceae) is a traditional herbal medicinal plant and is reported to possess a variety of pharmacological actions. In the present research, a compound (4Z, 12Z)-cyclopentadeca-4, 12-dienone isolated from Grewia hirsuta was taken as ligand for molecular docking studies. Evaluation of hypoglycemic activity through an extensive in silico docking approach with molecular targets such as aldose reductase, glucokinase, pyruvate dehydrogenase kinase isoform 2, peroxisome proliferator-activated receptor-gamma, glycogen synthase kinase-3, 11β-Hydroxysteroid dehydrogenase, and glutamine: fructose-6-phosphate amidotransferase were performed.

Methods

Isolation of the (4Z, 12Z)-cyclopentadeca-4,12-dienone from the methanol extract of the leaves of Grewia hirsuta was performed by the column chromatography to yield different fractions. These fractions were then subjected to purification and the structure was elucidated and confirmed by spectroscopic methods including UV, FTIR, ¹H, ¹³C NMR and the accurate mass determination was carried out using the Q-TOF mass spectrometer. In-vivo experimentation was performed with evaluation of α-glucosidase, α-amylase and MTT assay that had been reported by the author in the earlier paper. Molecular docking study was performed with GLIDE docking software.

Results

The docking studies of the ligand (4Z, 12Z)-cyclopentadeca-4, 12-dienone with seven different target proteins showed that this is a good inhibitor, which docks well with various targets related to diabetes mellitus. Hence (4Z, 12Z)-cyclopentadeca-4,12-dienone can be considered for developing into a potent anti-diabetic drug.

Conclusion

The results of the current study have revealed that the leaves of the selected plant Grewia hirsuta contains a potential inhibitor for diabetes (4Z, 12Z)-cyclopentadeca-4,12-dienone. Thus enabling a possibility of this plant extract as a new alternative to existing diabetic approaches.

Transporter-mediated tissue targeting of therapeutic molecules in drug discovery

Tissue concentrations of endogenous chemicals and nutrients are in large part regulated by membrane transporters through their substrate specificity and differential tissue distributions. These transporters also play a key role in the disposition of therapeutic agents thus affecting their efficacy and safety profile. A transporter-mediated tissue targeting strategy, where the structural features recognized by the transporters are incorporated into the therapeutic molecule, is emerging as an effective approach in drug discovery. In this digest, we review this phenomenon and highlight recent cases in the design of liver and kidney targeted drug molecules.

Long-acting hypoglycemic effects of PEGylated FGF21 and insulin glargine in mice with type 1 diabetes

OBJECTIVE

In this study, we compared the long-acting hypoglycemic effect of PEGylated FGF21 (PEG-FGF21) with insulin glargine in mice with STZ-induced type 1 diabetes.

METHODS

PEG-FGF21 and insulin glargine were administered once daily for two months, and blood glucose was measured prior to the next administration. Real-time PCR was used to measure mRNA expression of glucokinase (GK), glucose 6-phosphatase (G6pase), phosphoenolpyruvate carboxykinase (PEPCK), glucose transporter 1 (GLUT1) and glucose transporter 4 (GLUT4).

RESULTS

During long-term treatment, the blood glucose of untreated mice remained at 25.0 to 28.0mmol/L for the whole experiment, and the blood glucose of mice treated with insulin glargine remained at 16.5 to 18.0mmol/L. However, mice treated with PEG-FGF21 had lower blood glucose levels of 8.0 to 9.0mmol/L on day 10 and maintained this level until the end of the experiment. qRT-PCR showed that PEG-FGF21 up-regulated mRNA expression of GK and GLUT1, and down-regulated mRNA expression of G6Pase and PEPCK. Insulin glargine up-regulated mRNA expression of GLUT4, but had no effect on GK, G6Pase, PEPCK or GLUT1.

CONCLUSIONS

PEG-FGF21 has a better long-acting efficacy than insulin glargine. PEG-FGF21 achieves glucose clearance by accelerating glycolysis by up-regulating expression of GK and GLUT1 and inhibiting gluconeogenesis via down-regulation of G6Pase and PEPCK expression.

Increased risk of insulin resistance in rat offsprings exposed prenatally to white rice

White rice (WR) is a major staple food for people in developing countries and it may be responsible for the growing incidence of type 2 diabetes. Nonpregnant Female Sprague Dawley rats fed with WR or brown rice (BR) for 8 weeks were mated with age-matched male rats maintained on normal pellet over the same period. Offsprings were fed normal pellet after weaning until 8 weeks postdelivery. Rats fed with WR and their offsprings showed worsened oral glucose tolerance test, lower serum adiponectin levels, and higher weights, homeostatic model assessment of insulin resistance, serum retinol binding protein-4 levels, and leptin levels, compared with the normal and BR groups, suggesting an increased risk of insulin resistance. Furthermore, transcriptional levels of genes involved in insulin signaling showed different expression patterns in the liver, muscle, and adipose tissues of mothers and offsprings in both WR and BR groups. The results propose that the cycle of WR-induced insulin resistance in offsprings due to prenatal exposure, followed by their consumption of WR later in life may contribute to diabetes incidents. These findings are worth studying further.

Comparison of PEGylated FGF-21 with insulin glargine for long-lasting hypoglycaemic effect in db/db mice

AIM

This study investigated the long-acting antidiabetic efficacy of PEGylated fibroblast growth factor (FGF)-21 in type 2 diabetic db/db mice.

METHODS

PEGylated FGF-21 was prepared by modifying the N-terminus of human FGF-21 (hFGF-21) using mPEG-ALD. To compare the long-lasting hypoglycaemic effects of PEGylated FGF-21 and insulin glargine in diabetic db/db mice, their pharmacological efficacy was evaluated by changes in blood glucose levels, body weight, insulin levels, glycosylated haemoglobin levels, lipid profile and liver function parameters, and by oral glucose tolerance tests (OGTTs).

RESULTS

Both PEGylated FGF-21 and insulin glargine decreased plasma glucose in db/db mice. However, compared with insulin glargine treatment, PEGylated FGF-21 therapy had more significant effects in lowering blood glucose and glycosylated haemoglobin levels, improving lipid profile and liver function parameters, alleviating insulin resistance and reducing the glucose area under the curve in OGTTs.

CONCLUSION

Our results suggest that PEGylated FGF-21 is an ideal candidate as a long-acting antidiabetes drug, and holds significant promise as an effective therapeutic agent in the treatment of type 2 diabetes patients.

Small molecule glucokinase activators disturb lipid homeostasis and induce fatty liver in rodents: a warning for therapeutic applications in humans

BACKGROUND AND PURPOSE

Small-molecule glucokinase activators (GKAs) are currently being investigated as therapeutic options for the treatment of type 2 diabetes (T2D). Because liver overexpression of glucokinase is thought to be associated with altered lipid profiles, this study aimed at assessing the potential lipogenic risks linked to oral GKA administration.

EXPERIMENTAL APPROACH

Nine GKA candidates were qualified for their ability to activate recombinant glucokinase and to stimulate glycogen synthesis in rat hepatocytes and insulin secretion in rat INS-1E cells. In vivo activity was monitored by plasma glucose and HbA1c measurements after oral administration in rodents. Risk-associated effects were assessed by measuring hepatic and plasma triglycerides and free fatty acids, as well as plasma aminotransferases, and alkaline phosphatase.

KEY RESULTS

GKAs, while efficiently decreasing glycaemia in acute conditions and HbA1c levels after chronic administration in hyperglycemic db/db mice, were potent inducers of hepatic steatosis. This adverse outcome appeared as soon as 4 days after daily oral administration at pharmacological doses and was not transient. GKA treatment similarly increased hepatic triglycerides in diabetic and normoglycaemic rats, together with a pattern of metabolic phenotypes including different combinations of increased plasma triglycerides, free fatty acids, alanine and aspartyl aminotransferases, and alkaline phosphatase. GKAs belonging to three distinct structural families induced hepatic steatosis in db/db mice, arguing in favour of a target-mediated, rather than a chemical class-mediated, effect.

CONCLUSION AND IMPLICATIONS

Given the risks associated with fatty liver disease in the general population and furthermore in patients with T2D, these findings represent a serious warning for the use of GKAs in humans.

LINKED ARTICLE

This article is commented on by Rees and Gloyn, pp. 335-338 of this issue. To view this commentary visit http://dx.doi.org/10.1111/j.1476-5381.2012.02201.x.

Structural Variations of Human Glucokinase Glu256Lys in MODY2 Condition Using Molecular Dynamics Study

Glucokinase (GK) is the predominant hexokinase that acts as glucose sensor and catalyses the formation of Glucose-6-phosphate. The mutations in GK gene influence the affinity for glucose and lead to altered glucose levels in blood causing maturity onset diabetes of the young type 2 (MODY2) condition, which is one of the prominent reasons of type 2 diabetic condition. In view of the importance of mutated GK resulting in hyperglycemic condition, in the present study, molecular dynamics simulations were carried out in intact and 256 E-K mutated GK structures and their energy values and conformational variations were correlated. Energy variations were observed in mutated GK (3500 Kcal/mol) structure with respect to intact GK (5000 Kcal/mol), and it showed increased γ-turns, decreased β-turns, and more helix-helix interactions that affected substrate binding region where its volume increased from 1089.152 Ų to 1246.353 Ų. Molecular docking study revealed variation in docking scores (intact = −12.199 and mutated = −8.383) and binding mode of glucose in the active site of mutated GK where the involvement of A53, S54, K56, K256, D262 and Q286 has resulted in poor glucose binding which probably explains the loss of catalytic activity and the consequent prevailing of high glucose levels in MODY2 condition.

Metabolite profiling reveals normal metabolic control in carriers of mutations in the glucokinase gene (MODY2)

Mutations in the gene encoding glucokinase (GCK) cause a mild hereditary form of diabetes termed maturity-onset diabetes of the young (MODY)2 or GCK-MODY. The disease does not progress over time, and diabetes complications rarely develop. It has therefore been suggested that GCK-MODY represents a metabolically compensated condition, but experimental support for this notion is lacking. Here, we profiled metabolites in serum from patients with MODY1 (HNF4A), MODY2 (GCK), MODY3 (HNF1A), and type 2 diabetes and from healthy individuals to characterize metabolic perturbations caused by specific mutations. Analysis of four GCK-MODY patients revealed a metabolite pattern similar to that of healthy individuals, while other forms of diabetes differed markedly in their metabolite profiles. Furthermore, despite elevated glucose concentrations, carriers of GCK mutations showed lower levels of free fatty acids and triglycerides than healthy control subjects. The metabolite profiling was confirmed by enzymatic assays and replicated in a cohort of 11 GCK-MODY patients. Elevated levels of fatty acids are known to associate with β-cell dysfunction, insulin resistance, and increased incidence of late complications. Our results show that GCK-MODY represents a metabolically normal condition, which may contribute to the lack of late complications and the nonprogressive nature of the disease.

Safety, pharmacokinetics and pharmacodynamics of multiple-ascending doses of the novel glucokinase activator AZD1656 in patients with type 2 diabetes mellitus

AIMS

To assess the safety, pharmacokinetics and pharmacodynamics of multiple-ascending doses of the novel glucokinase activator AZD1656 in patients with type 2 diabetes mellitus (T2DM).

METHODS

This randomized, single-blind, placebo-controlled, monotherapy study was carried out in two parts. In part A, 32 patients received AZD1656 (7, 20, 40 or 80 mg) twice daily or placebo for 8 days in hospital. In part B, another 20 patients received, as outpatients, individually titrated AZD1656 15-45 mg twice daily or placebo for 28 days. Safety, pharmacokinetics and pharmacodynamic variables were evaluated.

RESULTS

AZD1656 was generally well tolerated. Pharmacokinetics of AZD1656 were virtually dose- and time-independent. AZD1656 was rapidly absorbed and eliminated. An active metabolite was formed which had a longer half-life than AZD1656, but showed ∼15% of the area under the plasma concentration versus time curve from 0 to 24 h compared with that of AZD1656. Renal excretion of AZD1656 and the metabolite was low. In part A, fasting plasma glucose (FPG) was reduced by up to 21% and mean 24-h plasma glucose was reduced by up to 24% with AZD1656 versus placebo, depending on dose. No dose-related changes in serum insulin or C-peptide were observed with AZD1656 at the end of treatment. Results in part B confirmed the glucose-lowering effect of AZD1656 versus placebo.

CONCLUSIONS

AZD1656 was well tolerated with predictable pharmacokinetics in patients with T2DM. Dose-dependent reductions in plasma glucose were observed.

Effects of a glucokinase activator on hepatic intermediary metabolism: study with 13C-isotopomer-based metabolomics

GKAs (glucokinase activators) are promising agents for the therapy of Type 2 diabetes, but little is known about their effects on hepatic intermediary metabolism. We monitored the fate of (13)C-labelled glucose in both a liver perfusion system and isolated hepatocytes. MS and NMR spectroscopy were deployed to measure isotopic enrichment. The results demonstrate that the stimulation of glycolysis by GKA led to numerous changes in hepatic metabolism: (i) augmented flux through the TCA (tricarboxylic acid) cycle, as evidenced by greater incorporation of (13)C into the cycle (anaplerosis) and increased generation of (13)C isotopomers of citrate, glutamate and aspartate (cataplerosis); (ii) lowering of hepatic [Pi] and elevated [ATP], denoting greater phosphorylation potential and energy state; (iii) stimulation of glycogen synthesis from glucose, but inhibition of glycogen synthesis from 3-carbon precursors; (iv) increased synthesis of N-acetylglutamate and consequently augmented ureagenesis; (v) increased synthesis of glutamine, alanine, serine and glycine; and (vi) increased production and outflow of lactate. The present study provides a deeper insight into the hepatic actions of GKAs and uncovers the potential benefits and risks of GKA for treatment of diabetes. GKA improved hepatic bioenergetics, ureagenesis and glycogenesis, but decreased gluconeogenesis with a potential risk of lactic acidosis and fatty liver.

Glucokinase links Krüppel-like factor 6 to the regulation of hepatic insulin sensitivity in nonalcoholic fatty liver disease

The polymorphism, KLF6-IVS1-27A, in the Krüppel-like factor 6 (KLF6) transcription factor gene enhances its splicing into antagonistic isoforms and is associated with delayed histological progression of nonalcoholic fatty liver disease (NAFLD). To explore a potential role for KLF6 in the development of insulin resistance, central to NAFLD pathogenesis, we genotyped KLF6-IVS1-27 in healthy subjects and assayed fasting plasma glucose (FPG) and insulin sensitivities. Furthermore, we quantified messenger RNA (mRNA) expression of KLF6 and glucokinase (GCK), as an important mediator of insulin sensitivity, in human livers and in liver tissues derived from a murine Klf6 knockdown model (DeltaKlf6). Klf6 overexpression studies in a mouse hepatocyte line were utilized to mechanistically link KLF6 with Gck promoter activity. KLF6-IVS1-27Gwt (i.e., less KLF6 splicing) was associated with stepwise increases in FPG and insulin and reduced hepatic insulin sensitivity. KLF6 binds to the liver-specific Gck promoter and activates a GCK promoter-reporter, identifying GCK as a KLF6 direct transcriptional target. Accordingly, in DeltaKlf6 hepatocytes Gck expression was reduced and stable transfection of Klf6 led to up-regulation of Gck. GCK and KLF6 mRNAs correlate directly in human NAFLD tissues and immunohistochemistry studies confirm falling levels of both KLF6 and GCK in fat-laden hepatocytes. In contrast to full-length KLF6, splice variant KLF6-SV1 increases in NAFLD hepatocytes and inversely correlates with glucokinase regulatory protein, which negatively regulates GCK activity.

CONCLUSION

KLF6 regulation of GCK contributes to the development of hepatic insulin resistance. The KLF6-IVS1-27A polymorphism, which generates more KLF6-SV1, combats this, lowering hepatic insulin resistance and blood glucose.

Berberine ameliorates hyperglycemia in alloxan-induced diabetic C57BL/6 mice through activation of Akt signaling pathway

Recently, it is implicated that the abnormality of Akt signaling pathway is involved in the diabetic pathology. Previous studies have demonstrated that berberine could decrease blood glucose by elevating liver glycogen synthesis. However, the underlying mechanism is still unclear. In the present study, we investigated the effects of berberine on fasting blood glucose, liver glycogen, Akt, Glycogen synthase kinase-3, glucokinase and insulin receptor substrate (IRS) in alloxan-induced diabetic mice, exploring its possible hypoglycemic mechanism. We found that in alloxan-induced diabetic mice, the high blood glucose was significantly lowered by berberine treatment. Liver glycogen content, the expression and activity of glucokinase and the phosphorylated Akt and IRS were all significantly reduced in diabetic mice whereas berberine blocked these changes. Berberine also depressed the increasing of phosphorylated GSK-3β in diabetic mice. Collectively, Berberine upregulates the activity of Akt possibly via insulin signaling pathway, eventually lowering high blood glucose in alloxan-induced diabetic mice.