Rate Of Glycogen Synthesis Research Articles

Identification and Function Analysis of Novel Hypoglycemic and Antioxidant Peptides from Chickpea.

Chickpea is rich in protein and has been demonstrated to possess hypoglycaemic effects. However, the specific bioactive ingredients and mechanisms underlying their hypoglycaemic effects remain unclear. In this study, enzymatic hydrolysis and gel permeation chromatography were used to extract chickpea bioactive peptide (CBP) from chickpea protein. One of the products, CBP-75-3, was found to inhibit α-glucosidase (GAA) activity and significantly increase the viability of insulin resistant (IR) cells. Moreover, CBP-75-3 significantly increased the rate of glucose consumption and glycogen synthesis in IR-HepG2 cells. Moreover, CBP-75-3 decreased the levels of malondialdehyde and increased the levels of superoxide dismutase, glutathione, and glutathione peroxidase. Subsequently, 29 novel bioactive peptides in CBP-75-3 were identified by LC‒MS/MS, and the potential hypoglycaemic targets of these novel bioactive peptides were investigated using molecular docking. Based on the results, the residues of the novel bioactive peptides interact with GAA through hydrogen bonding (especially LLR, FH, RQLPR, KGF and NFQ by binding to the substrate binding pocket or the active centre of GAA), thereby inhibiting GAA activity and laying a foundation for its hypoglycaemic activity. In short, the novel bioactive peptides isolated and identified from chickpea can effectively exert hypoglycaemic effects and increase the antioxidant capacity of IR-HepG2 cells. This study reveals that CBP-75-3, a natural hypoglycaemic ingredient, has potential for applications in functional foods and provides a theoretical basis for the development and application of CBP in the future.

Meta-analytic comparison of the effects of consuming carbohydrate with and without protein on postexercise plasma insulin and glucagon responses in healthy, trained males

This meta-analysis evaluates how hydrolysed protein and carbohydrate (CHO) mixtures compare with intact protein and CHO mixtures regarding post-exercise plasma insulin and glucagon responses in healthy endurance trained males. Studies measuring insulin and/or glucagon following an exercise bout with ingestion of CHO vs. CHO+ protein were included. Random-effects meta-analyses were conducted on the insulin peaks over time. Overall, 33 trials from 20 articles were included. The ingestion of CHO+ protein induced significantly higher insulin peaks than ingestion of CHO only from 30 to 240 minutes postexercise (30-180 min: p < .001, 210-240 min: p < .01), higher insulin area under the curve (p < .001), and greater muscle FSR ( p < .001). No statistically significant differences on insulin peaks over time were found between the ingestion of CHO+ intact protein and CHO+ hydrolysed protein or differences in muscle glycogen synthesis rate or glycogen peaks. Findings provide evidence the co-ingestion of CHO+ protein is a better strategy for recovery for endurance-type male athletes than the ingestion of CHO only. However, more research is warranted to understand whether there are differences between the ingestion of intact protein and its hydrolysed counterpart with CHO, and the impact on glucagon responses.

The Relationship Between Subclinical Hypothyroidism and Gestational Diabetes Mellitus

The most common metabolic disorder during pregnancy is gestational diabetes mellitus (GDM). GDM can occur in anywhere between 1.7 and 11.6 percent of people. In hypothyroidism, the rates of glucose oxidation and glycogen synthesis are reduced, and the peripheral tissues' consumption of glucose is also delayed. Patients with subclinical and overt hypothyroidism develop insulin resistance because insulin is unable to adequately maintain the muscles' use of glucose. According to the literature, hypothyroidism is linked to 6–15 percent of GDM pregnancies. Additionally, the chance of having GDM is 4.3 times higher in pregnant women who have hypothyroidism. This study aimed to reveal the relationship between first-trimester thyroid function tests and GDM. This retrospective cohort study was conducted between May 2021 and May 2022. 100 pregnant patients diagnosed with GDM and 500 healthy controls were included in the study. Using a 75 g glucose challenge test, GDM was identified. The trimester-specific recognized normal limits were used to evaluate the TSH and fT4 readings. There was a statistically significant difference in terms of SCH between patients with and without GDM (p=0.04). TSH's performance in predicting GDM was evaluated using AUC and ROC (AUC=0.586 and p=0.006). To forecast GDM, the TSH level cut-off value was discovered to be 1.58. The AUC was found to be 0.586 (0.521-0.652). Furthermore, the selectivity is 58% and the sensitivity is 41%. There are many studies in the literature investigating thyroid functions and the development of gestational diabetes mellitus. Our study also found a correlation between the diagnosis of subclinical hypothyroidism in the first trimester and GDM. The study adds to the literature the importance of being cautious and vigilant in terms of the development of gestational diabetes mellitus based on the results of the thyroid function test in the first trimester.

Subklinik Hipotiroidizm ile Gestasyonel Diabetes Mellitus Arasındaki İlişki

Aim: The most common metabolic disorder during pregnancy is gestational diabetes mellitus (GDM). GDM can occur in anywhere between 1.7 and 11.6 percent of people. In hypothyroidism, the rates of glucose oxidation and glycogen synthesis are reduced, and the peripheral tissues' consumption of glucose is also delayed. Patients with subclinical and overt hypothyroidism develop insulin resistance because insulin is unable to adequately maintain the muscles' use of glucose. According to the literature, hypothyroidism is linked to 6–15 percent of GDM pregnancies. Additionally, the chance of having GDM is 4.3 times higher in pregnant women who have hypothyroidism. This study aimed to reveal the relationship between first-trimester thyroid function tests and GDM. 
 Material and Method: This retrospective cohort study was conducted between May 2021 and May 2022. 100 pregnant patients diagnosed with GDM and 500 healthy controls were included in the study. Using a 75 g glucose challenge test, GDM was identified. The trimester-specific recognized normal limits were used to evaluate the TSH and fT4 readings.
 Results: There was a statistically significant difference in terms of SCH between patients with and without GDM (p=0.04). TSH's performance in predicting GDM was evaluated using AUC and ROC (AUC=0.586 and p=0.006). To forecast GDM, the TSH level cut-off value was discovered to be 1.58. The AUC was found to be 0.586 (0.521-0.652). Furthermore, the selectivity is 58% and the sensitivity is 41%
 Conclusion: There are many studies in the literature investigating thyroid functions and the development of gestational diabetes mellitus. Our study also found a correlation between the diagnosis of subclinical hypothyroidism in the first trimester and GDM. The study adds to the literature the importance of being cautious and vigilant in terms of the development of gestational diabetes mellitus based on the results of the thyroid function test in the first trimester.

The effect of coffee consumption on glucose homeostasis and redox-inflammatory responses in high-fat diet-induced obese rats

Coffee effects on glucose homeostasis in obesity remain controversial. We investigated whether coffee mitigates the negative effects on glucose metabolism induced by a high-fat diet and the interrelationships with redox-inflammatory responses. Rats were treated with: control (CT-); coffee (CT+) 3.9 g of freeze-dried coffee/kg of diet; high-fat (HF-); or high-fat + coffee 3.9 g of freeze-dried coffee/kg of diet (HF+) diet. The high-fat diet increased weight gain, feed efficiency, HOMA β, muscle and hepatic glycogen, intestinal CAT and SOD activity, hepatic protein (CARB) and lipid oxidation (MDA), muscle Prkaa1 mRNA and IL6 levels, and decreased food intake, hepatic GR, GPX and SOD activities, intestinal CARB, intestinal Slc2a2 and Slc5a1 and hepatic Prkaa1 and Prkaa2 mRNA levels, hepatic glucose-6-phosphatase and muscle hexokinase (HK) activities, compared to the control diet. The high-fat diet with coffee increased hepatic GST activity and TNF and decreased IL6 and intestinal glucosidase activity compared with the high-fat diet. The coffee diet increased muscle glycogen, hepatic CARB and PEPCK activity, and decreased hepatic GR and SOD activities and intestinal CARB, compared with the control diet. Coffee increased insulin levels, HOMA IR/β, FRAP, muscle Prkaa1 mRNA levels and hepatic and muscle phosphofructokinase-1, and it decreased intestinal CAT, hepatic Slc2a2 mRNA levels and muscle HK activity, regardless of the diet type. In conclusion, chronic coffee consumption improves antioxidant and anti-inflammatory responses, but does not ameliorate glucose homeostasis in a high-fat diet-induced obesity model. In addition, coffee consumption increases insulin secretion and promotes muscle glycogen synthesis in rats maintained on a control diet.

Impaired glucose partitioning in primary myotubes from severely obese women with type 2 diabetes.

The purpose of this study was to determine whether intramyocellular glucose partitioning was altered in primary human myotubes derived from severely obese women with type 2 diabetes. Human skeletal muscle cells were obtained from lean nondiabetic and severely obese Caucasian females with type 2 diabetes [body mass index (BMI): 23.6 ± 2.6 vs. 48.8 ± 1.9 kg/m2, fasting glucose: 86.9 ± 1.6 vs. 135.6 ± 12.0 mg/dL, n = 9/group]. 1-[14C]-Glucose metabolism (glycogen synthesis, glucose oxidation, and nonoxidized glycolysis) and 1- and 2-[14C]-pyruvate oxidation were examined in fully differentiated myotubes under basal and insulin-stimulated conditions. Tricarboxylic acid cycle intermediates were determined via targeted metabolomics. Myotubes derived from severely obese individuals with type 2 diabetes exhibited impaired insulin-mediated glucose partitioning with reduced rates of glycogen synthesis and glucose oxidation and increased rates of nonoxidized glycolytic products, when compared with myotubes derived from the nondiabetic individuals (P < 0.05). Both 1- and 2-[14C]-pyruvate oxidation rates were significantly blunted in myotubes from severely obese women with type 2 diabetes compared with myotubes from the nondiabetic controls. Lastly, concentrations of tricarboxylic acid cycle intermediates, namely, citrate (P < 0.05), cis-aconitic acid (P = 0.07), and α-ketoglutarate (P < 0.05), were lower in myotubes from severely obese women with type 2 diabetes. These data suggest that intramyocellular insulin-mediated glucose partitioning is intrinsically altered in the skeletal muscle of severely obese women with type 2 diabetes in a manner that favors the production of glycolytic end products. Defects in pyruvate dehydrogenase and tricarboxylic acid cycle may be responsible for this metabolic derangement associated with type 2 diabetes.

Coingestion of Carbohydrate and Protein on Muscle Glycogen Synthesis after Exercise: A Meta-analysis.

Evidence suggests that carbohydrate and protein (CHO-PRO) ingestion after exercise enhances muscle glycogen repletion to a greater extent than carbohydrate (CHO) alone. However, there is no consensus at this point, and results across studies are mixed, which may be attributable to differences in energy content and carbohydrate intake relative to body mass consumed after exercise. The purpose of this study was determine the overall effects of CHO-PRO and the independent effects of energy and relative carbohydrate content of CHO-PRO supplementation on postexercise muscle glycogen synthesis compared with CHO alone. Meta-analysis was conducted on crossover studies assessing the influence of CHO-PRO compared with CHO alone on postexercise muscle glycogen synthesis. Studies were identified in a systematic review from PubMed and Cochrane Library databases. Data are presented as effect size (95% confidence interval [CI]) using Hedges' g. Subgroup analyses were conducted to evaluate effects of isocaloric and nonisocaloric energy content and dichotomized by median relative carbohydrate (high, ≥0.8 g·kg-1⋅h-1; low, <0.8 g·kg-1⋅h-1) content on glycogen synthesis. Twenty studies were included in the analysis. CHO-PRO had no overall effect on glycogen synthesis (0.13, 95% CI = -0.04 to 0.29) compared with CHO. Subgroup analysis found that CHO-PRO had a positive effect (0.26, 95% CI = 0.04-0.49) on glycogen synthesis when the combined intervention provided more energy than CHO. Glycogen synthesis was not significant (-0.05, 95% CI = -0.23 to 0.13) in CHO-PRO compared with CON when matched for energy content. There was no statistical difference of CHO-PRO on glycogen synthesis in high (0.07, 95% CI = -0.11 to 0.22) or low (0.21, 95% CI = -0.08 to 0.50) carbohydrate content compared with CHO. Glycogen synthesis rates are enhanced when CHO-PRO are coingested after exercise compared with CHO only when the added energy of protein is consumed in addition to, not in place of, carbohydrate.

Abscisic acid enriched fig extract promotes insulin sensitivity by decreasing systemic inflammation and activating LANCL2 in skeletal muscle

Abscisic acid is a phytohormone found in fruits and vegetables and is endogenously produced in mammals. In humans and mice, lanthionine synthetase C-like 2 (LANCL2) has been characterized as the natural receptor for ABA. Herein, we characterize the efficacy of a fig fruit extract of ABA in promoting glycemic control. This ABA-enriched extract, at 0.125 µg ABA/kg body weight, improves glucose tolerance, insulin sensitivity and fasting blood glucose in diet-induced obesity (DIO) and db/db mouse models. In addition to decreasing systemic inflammation and providing glycemic control without increasing insulin, ABA extract modulates the metabolic activity of muscle. ABA increases expression of important glycogen synthase, glucose, fatty acid and mitochondrial metabolism genes and increases direct measures of fatty acid oxidation, glucose oxidation and metabolic flexibility in soleus muscle cells from ABA-treated mice with DIO. Glycolytic and mitochondrial ATP production were increased in ABA-treated human myotubes. Further, ABA synergized with insulin to dramatically increase the rate of glycogen synthesis. The loss of LANCL2 in skeletal muscle abrogated the effect of ABA extract in the DIO model and increased fasting blood glucose levels. This data further supports the clinical development of ABA in the treatment of pre-diabetes, type 2 diabetes and metabolic syndrome.

Coingestion of protein and carbohydrate in the early recovery phase, compared with carbohydrate only, improves endurance performance despite similar glycogen degradation and AMPK phosphorylation.

The present study compared the effects of postexercise carbohydrate plus protein (CHO+PROT) and carbohydrate (CHO)-only supplementation on muscle glycogen metabolism, anabolic cell signaling, and subsequent exercise performance. Nine endurance-trained males cycled twice to exhaustion (muscle glycogen decreased from ~495 to ~125 mmol/kg dry wt) and received either CHO only (1.2 g·kg-1·h-1) or CHO+PROT (0.8/0.4 g·kg-1·h-1) during the first 90 min of recovery. Glycogen content was similar before the performance test after 5 h of recovery. Glycogen synthase (GS) fractional activity increased after exhaustive exercise and remained activated 5 h after, despite substantial glycogen synthesis (176.1 ± 19.1 and 204.6 ± 27.0 mmol/kg dry wt in CHO and CHO+PROT, respectively; P = 0.15). Phosphorylation of GS at site 3 and site 2+2a remained low during recovery. After the 5-h recovery, cycling time to exhaustion was improved by CHO+PROT supplementation compared with CHO supplementation (54.6 ± 11.0 vs. 46.1 ± 9.8 min; P = 0.009). After the performance test, muscle glycogen was equally reduced in CHO+PROT and CHO. Akt Ser473 and p70s6k Thr389 phosphorylation was elevated after 5 h of recovery. There were no differences in Akt Ser473, p70s6k Thr389, or TSC2 Thr1462 phosphorylation between treatments. Nitrogen balance was positive in CHO+PROT (19.6 ± 7.6 mg nitrogen/kg; P = 0.04) and higher than CHO (-10.7 ± 6.3 mg nitrogen/kg; P = 0.009). CHO+PROT supplementation during exercise recovery improved subsequent endurance performance relative to consuming CHO only. This improved performance after CHO+PROT supplementation could not be accounted for by differences in glycogen metabolism or anabolic cell signaling, but may have been related to differences in nitrogen balance.NEW & NOTEWORTHY Endurance athletes competing consecutive days need optimal dietary intake during the recovery period. We report that coingestion of protein and carbohydrate soon after exhaustive exercise, compared with carbohydrate only, resulted in better performance the following day. The better performance after coingestion of protein and carbohydrate was not associated with a higher rate of glycogen synthesis or activation of anabolic signaling compared with carbohydrate only. Importantly, nitrogen balance was positive after coingestion of protein and carbohydrate, which was not the case after intake of carbohydrate only, suggesting that protein synthesis contributes to the better performance the following day.

205-OR: Hepatic Protein Kinase C-e Is Necessary and Sufficient in Mediating Lipid-Induced Hepatic Insulin Resistance

Nonalcoholic fatty liver disease (NAFLD) is strongly associated with hepatic insulin resistance (HIR), however the key lipid species and molecular mechanisms linking these conditions are widely debated. In order to address these questions, we examined the metabolic impact of a liver-specific antisense oligonucleotide against PKCε and found that liver-specific PKCε knockdown ameliorated high-fat diet-induced HIR in rats, reflected by ∼2x increase in insulin-stimulated hepatic glycogen synthesis rate and improved insulin-mediated suppression of endogenous glucose production during a hyperinsulinemic-hyperglycemic (HH) clamp. This was associated with increased IRK Y1162 and Akt S473 phosphorylation and could be attributed to decreased PKCε-mediated IRK T1160 phosphorylation. Overexpressing a constitutively active PKCε (A159E) in the liver induced HIR in regular chow-fed rats, reflected by reduced insulin-stimulated glycogen synthesis rate during an HH clamp. This was associated with impaired IRK Y1162 and Akt S473 phosphorylation and could be attributed to increased PKCε-mediated IRK T1160 phosphorylation. We also developed a subcellular fractionation method to quantify diacylglycerol (DAG) stereoisomers and ceramides in the endoplasmic reticulum, mitochondria, plasma membrane (PM), lipid droplet and cytosol and applied this method to a cohort of obese human subjects with and without NAFLD and HIR. Liver PM sn-1,2 DAG content was ∼5x higher in HIR individuals with NAFLD compared to insulin-sensitive individuals without NAFLD, associated with ∼3x higher IRK T1160 phosphorylation, supporting the importance of PM sn-1,2 DAG-PKCε-IRK pT1160 pathway to mediate HIR in humans with NAFLD. In contrast there were no significant differences in ceramide content in any of the subcellular compartments. Conclusion: These data identify PM sn-1,2 DAGs as the key lipids that activate PKCε, and that hepatic PKCε is both necessary and sufficient in mediating HIR. Disclosure K. Lyu: None. D. Zhang: None. M. Kahn: None. M.R.S. Rodrigues: None. S. Hirabara: None. P. Luukkonen: None. S. Lee: None. S. Bhanot: None. J. Rinehart: None. N. Blume: Employee; Self; Novo Nordisk A/S. Stock/Shareholder; Self; Novo Nordisk A/S. M. Rasch: Employee; Self; Novo Nordisk A/S. Stock/Shareholder; Self; Novo Nordisk A/S. M.J. Serlie: None. J. Bogan: None. G. Cline: None. V. Samuel: None. G.I. Shulman: Advisory Panel; Self; AstraZeneca, Janssen Research &amp; Development, LLC, Merck &amp; Co., Inc. Advisory Panel; Spouse/Partner; Merck &amp; Co., Inc. Consultant; Self; Novo Nordisk A/S. Consultant; Spouse/Partner; Novo Nordisk A/S. Other Relationship; Self; Gilead Sciences, Inc., iMetabolic Biopharma Corporation. Other Relationship; Spouse/Partner; iMetabolic Biopharma Corporation. Other Relationship; Self; Maze Therapeutics. Funding U.S. Public Health Service (R01DK116774, R01DK119968, R01DK113984, P30DK045735, R01 DK092661); U.S. Department of Veternas Affairs (I01BX000901)

Differential effects of REV-ERBα/β agonism on cardiac gene expression, metabolism, and contractile function in a mouse model of circadian disruption.

Cell-autonomous circadian clocks have emerged as temporal orchestrators of numerous biological processes. For example, the cardiomyocyte circadian clock modulates transcription, translation, posttranslational modifications, ion homeostasis, signaling cascades, metabolism, and contractility of the heart over the course of the day. Circadian clocks are composed of more than 10 interconnected transcriptional modulators, all of which have the potential to influence the cardiac transcriptome (and ultimately cardiac processes). These transcriptional modulators include BMAL1 and REV-ERBα/β; BMAL1 induces REV-ERBα/β, which in turn feeds back to inhibit BMAL1. Previous studies indicate that cardiomyocyte-specific BMAL1-knockout (CBK) mice exhibit a dysfunctional circadian clock (including decreased REV-ERBα/β expression) in the heart associated with abnormalities in cardiac mitochondrial function, metabolism, signaling, and contractile function. Here, we hypothesized that decreased REV-ERBα/β activity is responsible for distinct phenotypical alterations observed in CBK hearts. To test this hypothesis, CBK (and littermate control) mice were administered with the selective REV-ERBα/β agonist SR-9009 (100 mg·kg-1·day-1 for 8 days). SR-9009 administration was sufficient to normalize cardiac glycogen synthesis rates, cardiomyocyte size, interstitial fibrosis, and contractility in CBK hearts (without influencing mitochondrial complex activities, nor normalizing substrate oxidation and Akt/mTOR/GSK3β signaling). Collectively, these observations highlight a role for REV-ERBα/β as a mediator of a subset of circadian clock-controlled processes in the heart.

Metabolic control analysis of hepatic glycogen synthesis in vivo

Multiple insulin-regulated enzymes participate in hepatic glycogen synthesis, and the rate-controlling step responsible for insulin stimulation of glycogen synthesis is unknown. We demonstrate that glucokinase (GCK)-mediated glucose phosphorylation is the rate-controlling step in insulin-stimulated hepatic glycogen synthesis in vivo, by use of the somatostatin pancreatic clamp technique using [13C6]glucose with metabolic control analysis (MCA) in three rat models: 1) regular chow (RC)-fed male rats (control), 2) high fat diet (HFD)-fed rats, and 3) RC-fed rats with portal vein glucose delivery at a glucose infusion rate matched to the control. During hyperinsulinemia, hyperglycemia dose-dependently increased hepatic glycogen synthesis. At similar levels of hyperinsulinemia and hyperglycemia, HFD-fed rats exhibited a decrease and portal delivery rats exhibited an increase in hepatic glycogen synthesis via the direct pathway compared with controls. However, the strong correlation between liver glucose-6-phosphate concentration and net hepatic glycogen synthetic rate was nearly identical in these three groups, suggesting that the main difference between models is the activation of GCK. MCA yielded a high control coefficient for GCK in all three groups. We confirmed these findings in studies of hepatic GCK knockdown using an antisense oligonucleotide. Reduced liver glycogen synthesis in lipid-induced hepatic insulin resistance and increased glycogen synthesis during portal glucose infusion were explained by concordant changes in translocation of GCK. Taken together, these data indicate that the rate of insulin-stimulated hepatic glycogen synthesis is controlled chiefly through GCK translocation.

Athletes feature greater rates of muscle glucose transport and glycogen synthesis during lipid infusion.

BACKGROUNDInsulin resistance results from impaired skeletal muscle glucose transport/phosphorylation, linked to augmented lipid availability. Despite greater intramuscular lipids, athletes are highly insulin sensitive, which could result from higher rates of insulin-stimulated glycogen synthesis or glucose transport/phosphorylation and oxidation. Thus, we examined the time course of muscle glycogen and glucose-6-phosphate concentrations during low and high systemic lipid availability.METHODSEight endurance-trained and 9 sedentary humans (VO2 peak: 56 ± 2 vs. 33 ± 2 mL/kg/min, P < 0.05) underwent 6-hour hyperinsulinemic-isoglycemic clamp tests with infusions of triglycerides or saline in a randomized crossover design. Glycogen and glucose-6-phosphate concentrations were monitored in vastus lateralis muscles using 13C/31P magnetic resonance spectroscopy.RESULTSAthletes displayed a 25% greater (P < 0.05) insulin-stimulated glucose disposal rate (Rd) than sedentary participants. During Intralipid infusion, insulin sensitivity remained higher in the athletes (ΔRd: 25 ± 3 vs. 17 ± 3 μmol/kg/min, P < 0.05), supported by higher glucose transporter type 4 protein expression than in sedentary humans. Compared to saline infusion, AUC of glucose-6-phosphate remained unchanged during Intralipid infusion in athletes (1.6 ± 0.2 mmol/L vs. 1.4 ± 0.2 [mmol/L] × h, P = n.s.) but tended to decrease by 36% in sedentary humans (1.7 ± 0.4 vs. 1.1 ± 0.1 [mmol/L] × h, P < 0.059). This drop was accompanied by a 72% higher rate of net glycogen synthesis in the athletes upon Intralipid infusion (47 ± 9 vs. 13 ± 3 μmol/kg/min, P < 0.05).CONCLUSIONAthletes feature higher skeletal muscle glucose disposal and glycogen synthesis during increased lipid availability, which primarily results from maintained insulin-stimulated glucose transport with increased myocellular glucose-6-phosphate levels for subsequent glycogen synthesis.TRIAL REGISTRATIONClinicalTrials.gov NCT01229059.FUNDINGGerman Federal Ministry of Health (BMG).

Glucokinase activators — a promising class of antidiabetic drugs

Type 2 diabetes mellitus is an urgent problem of the modern healthcare. Despite a wide choice of oral hypoglycemic drugs, today there is a great need to create and introduce into clinical practice new, effective, and safe drugs for the treatment of diabetes. One of the promising targets for the creation of new antidiabetics is a glucokinase. It has an exceptionally high influence on glucose homeostasis, serving as a glucose “sensor” in pancreatic β-cells and controlling the rate of glycogen synthesis in the liver. In the present work, the molecular-genetic structure of the enzyme, as well as its interrelation with the organs and tissues of the organism, is presented. The modern ideas about activators of glucokinase as a promising class of antidiabetic drugs are outlined, their hypoglycemic and general antidiabetic effects proved in preclinical and clinical studies are considered. The most advanced activators of glucokinase, undergoing clinical trials, are indicated.

Differential Impacts of Insulin Analogs Lispro and Glulisine on Glucose and Lipid Homeostasis during Hyperinsulinemic Euglycemic Clamp in Streptozotocin-Induced Diabetic Rats

In addition to their benefits on glycemia, the specific actions of insulin analogs on glucose and lipid metabolism should be depicted. Here we analyzed the effects of Lispro (LIS) and Glulisine (GLU) insulin-analogs in diabetic rats. Diabetes was induced in Wistar male rats following an i.v. injection of streptozotocin (STZ) at 60mg/kg. Conscious rats underwent a 2-hour hyperinsulinemic (LIS or GLU at 0.8U/kg/h) euglycemic clamp with a constant infusion of 3H-glucose (4µCi/kg/min), with n=8 rats per each group. Glycemia was monitored continuously to adjust glucose infusion rate (GIR) to maintain euglycemia during the LIS or GLU perfusion. Blood, muscle and liver samples were collected for biochemical and radioactivity analysis. Compared to GLU, mean GIR was 51% higher in LIS treated rats (LIS: 18 +/- 1mg/kg/min, GLU: 12 +/- 1 mg/kg/min, p&amp;lt;0.01). Importantly, the higher GIR observed with LIS was associated with a strong inhibition of hepatic glucose production, which remained elevated in rats treated with GLU (LIS: 0.4 +/- 0.9mg/kg/min, GLU: 6.4 +/-1.6 mg/kg/min, p&amp;lt;0.01). Whole body glycolysis, glycogen, as well as liver and muscle glycogen synthesis rates remain similar between groups. Compared with LIS, rats treated with GLU showed a better reduction in plasma free fatty acids and glycerol levels during the clamp experiment, with a 50% and 139% lower plasma free fatty acids and glycerol area under the curve (p&amp;lt;0.and p&amp;lt;0.01 vs. LIS, respectively). 3H-glucose incorporation in muscle and liver lipid stores was not different, indicating that lipolysis rather than lipogenesis was differentially impacted. In conclusion, hyperinsulinemic euglycemic clamps in STZ rats enabled to detect a strong inhibition of hepatic glucose production by LIS, while GLU better suppresses lipolysis. Our experimental setting should help to differentiate other insulin analogs and dissect their mechanisms of action. Disclosure F. Briand: Employee; Self; Physiogenex S.A.S.. Stock/Shareholder; Self; Physiogenex S.A.S. E. Brousseau: Employee; Self; Physiogenex S.A.S. R. Burcelin: Stock/Shareholder; Self; Physiogenex S.A.S. T. Sulpice: Employee; Self; Physiogenex S.A.S.. Stock/Shareholder; Self; Physiogenex S.A.S..

Melatonin attenuates smoking-induced hyperglycemia via preserving insulin secretion and hepatic glycogen synthesis in rats.

Epidemiology survey indicated that cigarette smoking is a risk factor of diabetes. However, the precise mechanisms remain to be clarified. In this study, we found that smoking caused metabolic malfunctions on pancreas and liver in experimental animal model. These were indicated by hyperglycemia, increased serum hemoglobin A1c level and decreased insulin secretion, inhibition of liver glycogen synthase (LGS), and hepatic glycogen synthesis. Mechanistic studies revealed that all these alterations were caused by the inflammatory reaction and reactive oxygen species (ROS) induced by the smoking. Melatonin treatment significantly preserved the functions of both pancreas and liver by reducing β cell apoptosis, CD68‐cell infiltration, ROS production, and caspase‐3 expression. The siRNA‐knockdown model identified that the protective effects of melatonin were mediated by melatonin receptor‐2 (MT2). This study uncovered potentially underlying mechanisms related to the association between smoking and diabetes. In addition, it is, for first time, to report that melatonin effectively protects against smoking‐induced glucose metabolic alterations and the signal transduction pathway of melatonin is mainly mediated by its MT2 receptor. These observations provide solid evidence for the clinically use of melatonin to reduce smoking‐related diabetes, and the therapeutic regimens are absent currently.

A 2D & 3D fluorescent toxicity pathway reporter platform for high throughput imaging-based evaluation of hepatotoxicity liabilities

Real-time dose-response curves for fructose have been non-invasively determined in primary rat hepatocyte alginate spheroids cultured in a NMR-compatible fluidized-bed bioreactor. Using 13C–labeled glucose and glycine culture medium, fructose dose was compared to glucose uptake and glycogen synthesis rate using 13C NMR spectroscopy, and to ATP and fructose-1-phosphate concentration using 31P NMR spectroscopy. A highly efficient multicoaxial perfusion system maintains high density 3-D hepatocyte cultures, permitting 13C and 31P NMR spectral time courses with 1 min time points. The perfusion system was turned off to demonstrate its efficiency and effect on the metabolites. Within 16 min, glycogen plummeted, lactate became the largest 13C–glucose metabolite via anaerobic glycolysis, while glutathione was the largest 13C–glycine metabolite. ATP depletion and fructose-1-phosphate formation demonstrated a dose response with a 3 h EC50 of 19 mM ± 8.9 mM and 17.4 mM ± 3.7 mM, respectively. Computational modeling of mass transfer corroborated experimental results and helped determine the optimal bioreactor loading densities, oxygen concentration, and perfusion rates to maintain physiologically-relevant nutrient levels. The total bioreactor plus perfusion loop has a dead volume of 2 ml, and contains 5 million hepatocytes. Due to the non-invasive measurements, there is a reduction of animal tissue by an order-of-magnitude, depending on the number of time points in an experiment. This dynamic flux approach may have generic utility for dose-response studies monitoring multiple metabolic reactions in other primary mammalian cells, such as human, that have strict oxygen demands.

Dose-response in a high density three-dimensional liver device with real-time bioenergetic and metabolic flux quantification

Real-time dose-response curves for fructose have been non-invasively determined in primary rat hepatocyte alginate spheroids cultured in a NMR-compatible fluidized-bed bioreactor. Using 13C–labeled glucose and glycine culture medium, fructose dose was compared to glucose uptake and glycogen synthesis rate using 13C NMR spectroscopy, and to ATP and fructose-1-phosphate concentration using 31P NMR spectroscopy. A highly efficient multicoaxial perfusion system maintains high density 3-D hepatocyte cultures, permitting 13C and 31P NMR spectral time courses with 1min time points. The perfusion system was turned off to demonstrate its efficiency and effect on the metabolites. Within 16min, glycogen plummeted, lactate became the largest 13C–glucose metabolite via anaerobic glycolysis, while glutathione was the largest 13C–glycine metabolite. ATP depletion and fructose-1-phosphate formation demonstrated a dose response with a 3h EC50 of 19mM±8.9mM and 17.4mM±3.7mM, respectively. Computational modeling of mass transfer corroborated experimental results and helped determine the optimal bioreactor loading densities, oxygen concentration, and perfusion rates to maintain physiologically-relevant nutrient levels. The total bioreactor plus perfusion loop has a dead volume of 2ml, and contains 5 million hepatocytes. Due to the non-invasive measurements, there is a reduction of animal tissue by an order-of-magnitude, depending on the number of time points in an experiment. This dynamic flux approach may have generic utility for dose-response studies monitoring multiple metabolic reactions in other primary mammalian cells, such as human, that have strict oxygen demands.

Protective effects of asiatic acid in a spontaneous type2 diabetic mouse model.

Asiatic acid (AA) has been demonstrated to exhibit anti-diabetic activity. However, the mechanisms and underlying signaling pathways remain to be elucidated. The present study was performed to confirm the protective effect of AA and demonstrate its ability to regulate the phosphatidylinositol 3-kinase (PI3K)/protein kinase B (AKT)/glycogen synthase kinase-3β (GSK-3β) signaling pathway in db/db mice. Db/db mice fed on a high-fat diet were used to model diabetes mellitus. Modeled mice were divided randomly into the model control, pioglitazone hydrochloride tablet (PH) and AA groups. Age-matched C57 BL/6J mice served as normal controls. Lipid and glucose levels, and glycogen synthesis rates were assessed following treatment. Pathological changes were detected using hematoxylin and eosin staining. Expression of the PI3K/AKT/GSK-3β signaling pathway at the mRNA level was measured using quantitative polymerase chain reaction analysis. The model control group revealed typical characteristics of obesity and diabetes, including high glucose and lipid levels, and decreased glycogen synthesis. Four weeks of treatment with AA or PH ameliorated these abnormalities. AA and PH treatments mitigated the upregulation of PI3K, AKT, insulin receptor, and insulin receptor substrate-1 mRNA expression in modeled mice. Furthermore, AA and PH treatments decreased GSK-3β and glucose-6-phosphatase mRNA expression compared with the normal control group. The results of the present study confirmed that AA possesses anti-diabetic activity in db/db mice. The PI3K/AKT/GSK-3β signaling pathway may mediate this protective effect.

Flux balance analysis of photoautotrophic metabolism: Uncovering new biological details of subsystems involved in cyanobacterial photosynthesis

We have constructed and experimentally tested a comprehensive genome-scale model of photoautotrophic growth, denoted iSyp821, for the cyanobacterium Synechococcus sp. PCC 7002. iSyp821 incorporates a variable biomass objective function (vBOF), in which stoichiometries of the major biomass components vary according to light intensity. The vBOF was constrained to fit the measured cellular carbohydrate/protein content under different light intensities. iSyp821 provides rigorous agreement with experimentally measured cell growth rates and inorganic carbon uptake rates as a function of light intensity. iSyp821 predicts two observed metabolic transitions that occur as light intensity increases: 1) from PSI-cyclic to linear electron flow (greater redox energy), and 2) from carbon allocation as proteins (growth) to carbohydrates (energy storage) mode. iSyp821 predicts photoautotrophic carbon flux into 1) a hybrid gluconeogenesis-pentose phosphate (PP) pathway that produces glycogen by an alternative pathway than conventional gluconeogenesis, and 2) the photorespiration pathway to synthesize the essential amino acid, glycine. Quantitative fluxes through both pathways were verified experimentally by following the kinetics of formation of 13C metabolites from 13CO2 fixation. iSyp821 was modified to include changes in gene products (enzymes) from experimentally measured transcriptomic data and applied to estimate changes in concentrations of metabolites arising from nutrient stress. Using this strategy, we found that iSyp821 correctly predicts the observed redistribution pattern of carbon products under nitrogen depletion, including decreased rates of CO2 uptake, amino acid synthesis, and increased rates of glycogen and lipid synthesis.