Improved Glucose Uptake Research Articles

Structure characterization and anti-fatigue activity of an acidic polysaccharide from Panax ginseng C. A. Meyer

Ethnopharmacological relevancePanax ginseng C. A. Meyer is a traditional Chinese herbal medicine, which has been used in China for more than 2000 years. Its traditional effect of “invigorating vitality” is mainly reflected in anti-fatigue. However, due to the difficulty of identification of polysaccharide structure, there are few reports on homogeneous ginseng polysaccharide, and the molecular mechanism of its anti-fatigue effect remains to be further explored. Aim of the studyIn order to find the homogenous ginseng polysaccharide with the most anti-fatigue effect, this study is for the first time extracted, isolated and structurally identified polysaccharide monomer from Mountain Cultivated Ginseng (MCG). Then the anti-fatigue activity and molecular mechanism were studied. Materials and methodsThe structure of ginseng acidic polysaccharide APS-1 prepared by high performance gel permeation chromatography (HPGPC) was determined by acid hydrolysis/HPLC, methylation/GC-MS and NMR analysis. Anti-fatigue effect was evaluated by exhaustive swimming model, and AMPK axis-related proteins were detected by Western blot. ResultsAPS-1 significantly prolonged fatigue tolerance time, alleviated accumulation of BLA, LDH and BUN, increased activities of SOD and CAT, alleviated oxidative damage caused by MDA, increased activity of CK, regulated glycolysis, and alleviated muscle fiber contraction. The expressions of LKB1, p-AMPK, PGC-1α and Glut4 in muscle were significantly up-regulated. ConclusionsThe anti-fatigue effect of APS-1 was significantly, and the molecular mechanism may be related to the activation of AMPK axis signaling pathway to improve glucose uptake and mitochondrial function.

Placental mesenchymal stem cells restore glucose and energy homeostasis in obesogenic adipocytes.

Obesity (Ob) depicts a state of energy imbalance(s) being characterized by the accumulation of excessive fat and which predisposes to several metabolic diseases. Mesenchymal stem cells (MSCs) represent a promising option for addressing obesity and its associated metabolic co-morbidities. The present study aims at assessing the beneficial effects of human placental MSCs (P-MSCs) in mitigating Ob-associated insulin resistance (IR) and mitochondrial dysfunction both in vivo and in vitro. Under obesogenic milieu, adipocytes showed a significant reduction in glucose uptake, and impaired insulin signaling with decreased expression of UCP1 and PGC1α, suggestive of dysregulated non-shivering thermogenesis vis-a-vis mitochondrial biogenesis respectively. Furthermore, obesogenic adipocytes demonstrated impaired mitochondrial respiration and energy homeostasis evidenced by reduced oxygen consumption rate (OCR) and blunted ATP/NAD+/NADP+ production respectively. Interestingly, co-culturing adipocytes with P-MSCs activated PI3K-Akt signaling, improved glucose uptake, diminished ROS production, enhanced mitochondrial OCR, improved ATP/NAD+/NADP+ production, and promoted beiging of adipocytes evidenced by upregulated expression of PRDM16, UCP1, and PGC1α expression. In vivo, P-MSCs administration increased the peripheral blood glucose uptake and clearance, and improved insulin sensitivity and lipid profile with a coordinated increase in the ratio of ATP/ADP and NAD+ and NADP+ in the white adipose tissue (WAT), exemplified in WNIN/GR-Ob obese mutant rats. In line with in vitro findings, there was a significant reduction in adipocyte hypertrophy, increased mitochondrial staining, and thermogenesis. Our findings advocate for a therapeutic application of P-MSCs for improving glucose and energy homeostasis, i.e., probably restoring non-shivering thermogenesis towards obesity management.

Cinnamic Acid Improves Glucose Uptake and Utilization with Concomitant Improvement of Redox and Bioenergetic Homeostasis, While Modulating Glucose-Lipid Metabolic Switch in Isolated Psoas Muscle

Cinnamic Acid Improves Glucose Uptake and Utilization with Concomitant Improvement of Redox and Bioenergetic Homeostasis, While Modulating Glucose-Lipid Metabolic Switch in Isolated Psoas Muscle

Heartwood Extract of Pterocarpus marsupium Roxb. Offers Defense against Oxyradicals and Improves Glucose Uptake in HepG2 Cells.

Diabetes mellitus leads to cellular damage and causes apoptosis by oxidative stress. Heartwood extract of Pterocarpus marsupium has been used in Ayurveda to treat various diseases such as leprosy, diabetes, asthma, and bronchitis. In this study, we worked out the mechanism of the antidiabetic potential of methanolic heartwood extract of Pterocarpus marsupium (MPME). First, metabolic profiling of MPME was done using gas chromatography-mass spectrometry (GCMS), ultra-performance liquid chromatography-mass spectroscopy (UPLC-MS), and high-performance thin-layer chromatography (HPTLC) to identify phenols, flavonoids, and terpenoids in MPME. Biological studies were carried out in vitro using the HepG2 cell line. Many antidiabetic compounds were identified including Quercetin. Methanolic extract of MPME (23.43 µg/mL–93.75 µg/mL) was found to be safe and effective in reducing oxyradicals in HepG2 cells. A concentration of 93.75 µg/mL improved glucose uptake efficiently. A significant decrease in oxidative stress, cell damage, and apoptosis was found in MPME-treated HepG2 cells. The study suggests that the heartwood of Pterocarpus marsupium offers good defense in HepG2 cells against oxidative stress and improves glucose uptake. The results show the significant antidiabetic potential of MPME using a HepG2 cell model. The effect seems to occur by reducing oxidative stress and sensitizing the cells towards glucose uptake, hence lowering systemic glucose levels, as well as rescuing ROS generation.

Novel active compounds and the anti-diabetic mechanism of mulberry leaves.

Mulberry (Morus alba L.) leaves have long been considered beneficial in traditional Chinese medicine to treat infectious and internal diseases. Recently studies have discovered that the mulberry leaf’s total flavonoids (MLF) display excellent hypoglycemia properties. However, the active ingredients and their molecular mechanisms are still uncharacterized. In this study, we explored the hypoglycemic effects of MLF and mulberry leaf polysaccharides (MLP) on ob/ob mice, an animal model of type 2 diabetes mellitus (T2DM), compared with Ramulus Mori (Sangzhi) alkaloid (RMA). Network pharmacology was employed to identify the potential available targets and active compounds of MLF and RMA against hyperglycemia. Molecular docking, an insulin-resistant cell model and qPCR were employed to verify the antidiabetic activity of the critical compounds and the gene expression profiles of the top molecular targets. Here, the results showed that MLF and MLP improved glucose uptake in insulin-resistant hepatocytes. MLF, MLP and RMA alleviated insulin resistance and glucose intolerance in ob/ob mice. Unlike MLF and MLP, RMA administration did not influence the accumulation of intrahepatic lipids. Network pharmacology analysis revealed that morusin, kuwanon C and morusyunnansin L are the main active compounds of MLF and that they amend insulin resistance and glycemia via the PI3K- Akt signaling pathway, lipid and atherosclerosis pathways, and the AGE-RAGE signaling pathway. Moreover, 1-deoxynojirimycin (DNJ), fagomine (FA), and N-methyl-1-deoxynojirimycin are the primary active ingredients of RMA and target carbohydrate metabolism and regulate alpha-glucosidase activity to produce a potent anti-diabetic effect. The molecular docking results indicated that morusin, kuwanon C and morusyunnansin L are the critical bioactive compounds of MLF. They had high affinities with the key targets adenosine A1 receptor (ADORA1), AKT serine/threonine kinase 1 (AKT1), peroxisome proliferator-activated receptor gamma (PPARγ), and glycogen synthase kinase 3 beta (GSK3β), which play crucial roles in the MLF-mediated glucose-lowering effect. Additionally, morusin plays a role in amending insulin resistance of hepatocytes by repressing the expression of the ADORA1 and PPARG genes. Our results shed light on the mechanism behind the glucose-lowering effects of MLF, suggesting that morusin, kuwanon C, and morusyunnansin L might be promising drug leads for the management of T2DM.

MiR-17-5p Promotes Glucose Uptake of HTR8/SVneo Trophoblast Cells by Inhibiting TXNIP/NLRP3 Inflammasome Pathway.

Gestational diabetes mellitus (GDM) is one of the common metabolic disorders of pregnancy and results in poor pregnancy outcomes for both mother and fetus. MiR-17-5p is considered as the strongest predictor of metabolic syndrome status, but the relationship between GDM and miR-17-5p remains unclear. TXNIP, which leads to activation of NLRP3, is considered as a potential target of miR-17-5p, and the miR-17-5p/TXNIP/NLRP3 axis has been shown to play a major role in the occurrence and development of many metabolic diseases but has not been validated in GDM. MiR-17-5p was detected by RT-qPCR. The expression of TXNIP and NLRP3 in placenta was detected by immunofluorescence, RT-qPCR and Western blot. To explore the effect of miR-17-5p on TXNIP and NLRP3 and glucose uptake of HTR8/SVneo cells, miR-17-5p mimic and miR-17-5p inhibitor were transfected to achieve overexpression and inhibition. The interaction between miR-17-5p and TXNIP was confirmed by dual-luciferase reporter assay. Besides, glucose consumption of trophoblast cells was detected by glucose assay kit. MiR-17-5p expression was down-regulated, while the expression of TXNIP and NLRP3 was up-regulated in GDM placental tissues. MiR-17-5p targeted TXNIP and inhibited its expression. MiR-17-5p also regulated NLRP3 expression and glucose uptake of HTR8/SVneo cells, which could be reversed by overexpression of TXNIP, suggesting that miR-17-5p improved glucose uptake of HTR8/SVneo cells by TXNIP/NLRP3 axis. The results were consistent with the above findings in high-glucose treated HTR8/SVneo cells. Our results suggested that miR-17-5p ameliorates the glucose uptake of HTR8/SVneo cells by TXNIP/NLRP3 axis, which may provide a new idea for offspring health of GDM patients.

HM-Chromanone, a Major Homoisoflavonoid in Portulaca oleracea L., Improves Palmitate-Induced Insulin Resistance by Regulating Phosphorylation of IRS-1 Residues in L6 Skeletal Muscle Cells.

This study investigated the effect of (E)-5-hydroxy-7-methoxy-3-(2-hydroxybenzyl)-4-chromanone (HM-chromanone) on palmitate-induced insulin resistance and elucidated the underlying mechanism in L6 skeletal muscle cells. Glucose uptake was markedly decreased due to palmitate-induced insulin resistance in these cells; however, 10, 25, and 50 µM HM-chromanone remarkably improved glucose uptake in a concentration-dependent manner. HM-chromanone treatment downregulated protein tyrosine phosphatase 1B (PTP1B) and phosphorylation of c-Jun N-terminal kinase (JNK) and inhibitor of nuclear factor kappa-B kinase subunit beta (IKKβ), which increased because of palmitate mediating the insulin-resistance status in cells. HM-chromanone promoted insulin receptor substrate-1 (IRS-1) tyrosine phosphorylation and suppressed palmitate-induced phosphorylation of IRS-1 serine. This activated phosphoinositide 3-kinase (PI3K) and stimulated protein kinase B (AKT) phosphorylation. Phosphorylated AKT promoted the translocation of Glucose transporter type 4 to the plasma membrane and significantly enhanced glucose uptake into muscle cells. Additionally, HM-chromanone increased glycogen synthesis through phosphorylating glycogen synthase kinase 3 alpha/beta (GSK3 α/β) via AKT. Consequently, HM-chromanone may improve insulin resistance by downregulating the phosphorylation of IRS-1 serine through inhibition of negative regulators of insulin signaling and inflammation-activated protein kinases in L6 skeletal muscle cells.

Investigating Anti-diabetic Effects of Autoclaved Curcuma longa Linn (turmeric) Extracts using Mouse Tissues in vitro

Curcumin, the active compound found in turmeric, is believed to delay the development of diabetes through several mechanisms. This study aimed to investigate if an aqueous extract of turmeric can improve glucose uptake and uric acid in mouse tissues in vitro, after inclusion of turmeric in the diet for four weeks. Fourteen adult male Swiss mice were divided into three groups. The first group was the control (n=6) that was given clean water, the second group of mice (n=4) was given 5% autoclaved turmeric extract in drinking water, and the third group (n=4) was given 5% non-autoclaved turmeric extract in drinking water. After four weeks, the cardiac muscle, skeletal muscle, pancreas, and liver tissues were dissected and used for analysis. The results showed that the aqueous 5% turmeric extract reduced glucose in cardiac tissues while the plasma glucose was not changed. Cardiac muscle, liver, pancreas, and skeletal muscle showed glucose absorption after the 5% turmeric treatment. This research shows that turmeric did improve glucose uptake in most tissues, although it was not significant due to the limitations of this study. Tissues may need to be cultured longer and media processed quicker to prevent evaporation. Turmeric continues to show great potential in the treatment of type 2 diabetes and may present an alternative way of treating diabetes.

Halophila beccarii extract ameliorate glucose uptake in 3T3-L1 adipocyte cells and improves glucose homeostasis in streptozotocin-induced diabetic rats

The regulation of carbohydrate metabolizing enzymes is an effective way of reducing blood glucose levels and improving glycogen synthesis during the management of type 2 diabetes. The present investigation was conducted to explain the detailed mechanism with which a Seagrass, Halophila beccarii extract (HBE) enhances the glucose uptake in the 3T3-L1 adipocyte cell culture system in invitro. HBE stimulates the glucose uptake by the translocation of glucose transporter 4 (GLUT4) on to plasma cell membrane through induction of insulin receptor substrate 1 (IRS-1)/protein kinase B (Akt) signaling pathways. To assess the effect of HBE on T2DM, we used invivo experimental diabetes rat models induced with streptozotocin (STZ) to perform oral GTT and ITT. Furthermore, we assessed the enzymatic profile of Glycolysis, Pentose phosphate pathway, and gluconeogenesis from liver tissue homogenate. After long-term exposure with HBE, our results confirmed, that HBE improves the glucose uptake in 3T3-L1 cell lines by up-regulation of glucose transporter type 4 (GLUT4) through uptake of glucose by the adipocytes. The resulting data indicated that HBE had a great potentiality in preventing diabetes and maintaining glucose homeostasis through improving glucose uptake. The present data also showed that HBE with its insulin mimetic activity activates glycogen synthesis and enhances glucose utilization by regulating the carbohydrate metabolic enzymes. The similarity between HBE and insulin indicates that the HBE follows the mechanisms same as the insulin signaling pathway to show the antidiabetic activity.

Antihyperglycemic activity of verbenone and L-arginine in nicotinamide-streptozotocin-induced diabetic mice: in vitro and in vivo studies

BackgroundNatural products are utilized globally for the management of diseases such as diabetes mellitus. Carrot seeds are ethnobotanically used in the management of diabetes mellitus. This study investigated the in vitro and in vivo antihyperglycemic activities of verbenone and L-arginine, which are compounds found in carrot seed.ResultsVerbenone, L-arginine, and their ratios combination expressed significantly in vitro α-amylase inhibitory activity with IC50 of 13.00, 12.69, and 13.30 µg/mL respectively compared with acarbose (IC50 = 12.64 µg/mL) and significant in vitro α-glucosidases inhibitory activity with IC50 of 29.01, 23.76 and 30.11 µg/mL respectively compared with acarbose (IC50 = 16.80 µg/mL). Furthermore, the compounds improved glucose uptake in yeast cells and inhibited haemoglobin glycation in vitro. In the in vivo study, the compounds significantly reduced the levels of blood glucose, the levels of liver total cholesterol, and liver triacylglycerol, the calculated cardiovascular indices, whereas the level of plasma high density lipoprotein (HDL) cholesterol was significantly elevated in all diabetic treated mice.ConclusionThe data revealed the in vitro antidiabetic activity of verbenone and L-arginine. Also, the compounds ameliorated hyperglycemia, hyperlipidemia and other diabetic-induced biochemical alterations in NAD-STZ-induced diabetic mice model.

Novel soybean peptide iglycin ameliorates insulin resistance of high-fat diet fed C57BL/6J mice and differentiated 3T3L1 adipocytes with improvement of insulin signaling and mitochondrial function

Soy consumption has been associated with potential health benefits in reducing chronic diseases. These physiological functions have been attributed to soy proteins or more commonly to bioactive peptides. Thus, more studies are required to identify these bioactive peptides, and elucidate their biological mechanisms of action. In the present study, a novel peptide iglycin was purified from soybean seeds with a molecular mass of 3.88 kDa. Thereafter, iglycin reduced fasting blood glucose and restored insulin sensitivity of C57BL/6J mice on a high-fat diet with increased phosphorylation of insulin receptor substrate 1 (IRS1) and AKT in adipose tissue. Furthermore, it improved glucose uptake, induced translocation of intracellular GLUT4 to plasma membrane and activation of insulin signaling in adipocytes under insulin-resistant condition. In addition, it decreased reactive oxygen species production, lipid peroxidation and inhibited adipocyte apoptosis with improved mitochondrial function as evidenced by up-regulation of succinate dehydrogenase activity, mitochondrial membrane potential and intracellular ATP store. These data suggested that iglycin ameliorated insulin resistance via activation of insulin signaling, which was associated with inhibition of oxidative stress, adipocyte apoptosis, and improvement of mitochondrial function.

Antidiabetic effects of Psidium x durbanensis Baijnath & Ramcharun ined. (Myrtaceae) leaf extract on streptozotocin-induced diabetes in rats

Ethnopharmacological relevancePsidium guajava L. leaves are used to treat diabetes in South African folkloric medicine and in other parts of the world. Psidium x durbanensis Baijnath & Ramcharun ined. (PD) is a natural sterile hybrid and congener of Psidium guajava that is expected to share the medicinal properties of the genus Psidium and is widely distributed in South Africa.Aim of the study: This study investigates the antioxidant, antidiabetic effects, and mechanisms of action of hydro-methanolic leaf extracts of PD on streptozotocin-induced diabetes in rats. Material and methodsPhytochemical constituents of hydro-methanolic extract of PD were analyzed by gas chromatography-mass spectrometry (GC-MS). Male Wistar rats 250–300 g body weight (BW) were rendered diabetic after a single intraperitoneal injection with streptozotocin, 45 mg/kg BW. The diabetic rats were treated with hydro-methanolic (20:80 v/v) leaf extracts of PD (400 mg/kg/BW) or subcutaneous injections of regular insulin (2.0U/kg/BW, bid) for 56 days. The body weights of the animals were recorded daily. Fasting blood glucose, glucose tolerance tests, and insulin resistance index were measured. The effects of the extracts on total superoxide dismutase, catalase, and reduced glutathione activities, histopathology, and gene expression of insulin receptor substrate 1 and glucose transporter 4 were determined in the liver, pancreas, and gastrocnemius muscles of the rats. ResultsIn the acute toxicity studies, there were no signs of toxicity observed for PD up to 2000 mg/kg BW doses. Diabetic animals showed significant weight loss, elevated and reduced fasting blood glucose and insulin, respectively, impaired glucose tolerance and diminished antioxidant enzymes’ activities compared to controls. Treatment with PD hydro-methanolic leaf extracts improved body weight, glucose tolerance, insulin resistance, and antioxidant enzymes but not plasma insulin in diabetic animals compared to controls, respectively. GC-MS analysis identified organic acids, alcohols, vitamins, terpenoids, and esters in the extracts. Treatment with PD improved glucose uptake by stimulating mRNA expression of GLUT 4 in gastrocnemius muscles of diabetic animals compared to the untreated control and also restored histological aberrations in the pancreas and liver of diabetic rats compared with the untreated control rats. ConclusionCollectively, the present study suggests that treatment with PD leaf extracts significantly ameliorated diabetes symptoms and oxidative stress in rats, and these effects may be linked to the bioactive phytoconstituents present in the plant. This study further suggests that PD improves insulin resistance by increasing glucose uptake in gastrocnemius muscles in an insulin-independent manner.

Complexation potentiated promising anti‐diabetic and anti‐oxidative synergism between ZN(ii) and ferulic acid: A multimode study

This study was done to investigate the anti-diabetic and anti-oxidative synergism between zinc(II) and ferulic acid through complexation. Zinc sulphate was complexed with ferulic acid in a 1:2 molar ratio. The complex was characterized using Fourier-transform infrared spectroscopy, proton NMR and high-resolution mass spectroscopy techniques and evaluated for cellular toxicity. In silico, in vitro, cell-based and tissue experimental models were used to test the anti-diabetic and anti-oxidant activities of the complex relative to its precursors. A zinc(II)-biferulate.2H2 O complex was formed. The in vitro radical scavenging, anti-lipid peroxidative and α-glucosidase and α-amylase inhibitory activity of the complex was 1.7-2.1 folds more potent than ferulic acid. Zn(II) complexation increased the anti-glycation activity of ferulic acid by 1.5 folds. The complex suppressed lipid peroxidation (IC50 =48.6 and 331 μM) and GHS depletion (IC50 =33.9 and 33.5μM) in both Chang liver cells and isolated rat liver tissue. Its activity was 2.3-3.3 folds more potent than ferulic acid and statistically comparable to ascorbic acid. Zn(II) complexation afforded ferulic acid improved glucose uptake activity in L-6 myotube (EC50 =11.7 vs. 45.7μM) and isolated rat muscle tissue (EC50 =501 and 1510 μM). Complexation increased muscle tissue zinc(II) uptake and hexokinase activity. Docking scores of the complex (-7.24 to -8.25 kcal/mol) and ferulic acid (-5.75 to 6.43 kcal/mol) suggest the complex had stronger interaction with protein targets related to diabetes, which may be attributed to the 2 ferulic acid moieties and Zn(II) in the complex. Moreover, muscle tissue showed increased phospho-Akt/pan-Akt ratio upon treatment with complex. The complex was not hepatotoxic and myotoxic at in vitro cellular level. Zn(II) complexation may be promising therapeutic approach for improving the glycaemic control and anti-oxidative potential of natural phenolic acids.

The Combined Therapy of Insulin and Zinc Improves Glucose Uptake and Utilization by Testicular Cells in Diabetic Rats

Glucose uptake by the Sertoli cells of the testes is essential for spermatogenesis. Diabetes mellitus (DM) alters the uptake and utilization of glucose by the testicular cells. This manifests as one of the causes of male subfertility/infertility in diabetes mellitus. With onset of complications even before diagnosis, especially in developing countries, there may be need for therapy beyond the standard therapy. Five normal and twenty diabetic male rats were assigned into groups as follows; normal control had five normal rats with access to food and water only. DM group had five diabetic rats with no treatment. DM and insulin group had five diabetic rats and given subcutaneous insulin twice daily. DM and zinc group had five diabetic rats and given 10mg/kg oral zinc. The final group had five diabetic rats and given both insulin and zinc as above. Treatments in all cases only commenced after fourteen days. Testes were harvested after ten days of treatment for assay. DM decreased both glucose and lactate in the testes. Insulin and zinc improved the uptake of glucose and its utilization as evident in increased production of lactate.

Modulating effects of steviol and steviol glycosides on adipogenesis, lipogenesis, glucose uptake and insulin resistance in 3T3-L1 adipocyte model

• Stevia-derived compounds modulate adipogenic and lipogenic gene expression. • Steviol decreases lipid accumulation in mature 3T3-L1 adipocytes. • Steviol and stevioside improve glucose uptake and mitigate insulin resistance. Stevia rebaudiana Bertoni is famous for sweetness due to the content of steviol glycosides (SG). This study aimed to determine the effect of SG (stevioside, rebaudioside A) and steviol on adipogenesis and lipogenesis in the 3T3-L1 model. Test compounds were also analysed for their ability to affect glucose uptake in hypertrophied insulin-resistant 3T3-L1 adipocytes. The most active compound in modulating adipogenesis, lipogenesis and insulin resistance was steviol, SG metabolism product. Steviol (10 μM, 100 μM) significantly down-regulated the expression of adipogenic transcription factors (PPARγ, C/EBPα, SREBP1) and lipogenic genes (FAS, aP2, LPL), which caused decreased lipid accumulation and triglyceride content in adipocytes. Treatment of insulin-resistant adipocytes with steviol (1 μM) and stevioside (1 μM, 10 μM) increased GLUT-4 transcript level and improved glucose uptake. Steviol also lowered resistin gene expression, which may mitigate insulin resistance in hypertrophied adipocytes. This study promotes SG as potential health-promoting ingredients in low-calorie functional foods.

Heteroleptic oxidovanadium(IV)-malate complex improves glucose uptake in HepG2 and enhances insulin action in streptozotocin-induced diabetic rats.

Diabetes mellitus, a complex and heterogeneous disease associated with hyperglycemia, is a leading cause of mortality and reduces life expectancy. Vanadium complexes have been studied for the treatment of diabetes. The effect of complex [VO(bpy)(mal)]·H2O (complex A) was evaluated in a human hepatocarcinoma (HepG2) cell line and in streptozotocin (STZ)-induced diabetic male Wistar rats conditioned in seven groups with different treatments (n = 10 animals per group). Electron paramagnetic resonance and 51V NMR analyses of complex A in high-glucose Dulbecco's Modified Eagle Medium (DMEM) revealed the oxidation and hydrolysis of the oxidovanadium(IV) complex over a period of 24h at 37°C to give low-nuclearity vanadates "V1" (H2VO4-), "V2" (H2V2O72-), and "V4" (V4O124-). In HepG2 cells, complex A exhibited low cytotoxic effects at concentrations 2.5 to 7.5μmol L-1 (IC50 10.53μmol L-1) and increased glucose uptake (2-NBDG) up to 93%, an effect similar to insulin. In STZ-induced diabetic rats, complex A at 10 and 30mgkg-1 administered by oral gavage for 12days did not affect the animals, suggesting low toxicity or metabolic impairment during the experimental period. Compared to insulin treatment alone, complex A (30mgkg-1) in association with insulin was found to improve glycemia (30.6 ± 6.3mmol L-1 vs. 21.1 ± 8.6mmol L-1, respectively; p = 0.002), resulting in approximately 30% additional reduction in glycemia. The insulin-enhancing effect of complex A was associated with low toxicity and was achieved via oral administration, suggesting the potential of complex A as a promising candidate for the adjuvant treatment of diabetes.

Structure-function analysis of the AMPK activator SC4 and identification of a potent pan AMPK activator.

The AMP-activated protein kinase (AMPK) αβγ heterotrimer is a primary cellular energy sensor and central regulator of energy homeostasis. Activating skeletal muscle AMPK with small molecule drugs improves glucose uptake and provides an opportunity for new strategies to treat type 2 diabetes and insulin resistance, with recent genetic and pharmacological studies indicating the α2β2γ1 isoform combination as the heterotrimer complex primarily responsible. With the goal of developing α2β2-specific activators, here we perform structure/function analysis of the 2-hydroxybiphenyl group of SC4, an activator with tendency for α2-selectivity that is also capable of potently activating β2 complexes. Substitution of the LHS 2-hydroxyphenyl group with polar-substituted cyclohexene-based probes resulted in two AMPK agonists, MSG010 and MSG011, which did not display α2-selectivity when screened against a panel of AMPK complexes. By radiolabel kinase assay, MSG010 and MSG011 activated α2β2γ1 AMPK with one order of magnitude greater potency than the pan AMPK activator MK-8722. A crystal structure of MSG011 complexed to AMPK α2β1γ1 revealed a similar binding mode to SC4 and the potential importance of an interaction between the SC4 2-hydroxyl group and α2-Lys31 for directing α2-selectivity. MSG011 induced robust AMPK signalling in mouse primary hepatocytes and commonly used cell lines, and in most cases this occurred in the absence of changes in phosphorylation of the kinase activation loop residue α-Thr172, a classical marker of AMP-induced AMPK activity. These findings will guide future design of α2β2-selective AMPK activators, that we hypothesise may avoid off-target complications associated with indiscriminate activation of AMPK throughout the body.

Docosahexaenoic Acid Ester of Phloridzin Reduces Inflammation and Insulin Resistance via AMPK.

Docosahexaenoic acid-acylated phloridzin (PZ-DHA), a novel polyphenol fatty acid ester derivative, is synthesized through an acylation reaction of phloridzin (PZ) and docosahexaenoic acid (DHA). PZ-DHA is more stable than DHA and exhibits higher cellular uptake and bioavailability than PZ. The study aims to investigate the effects of PZ-DHA on insulin resistance in the skeletal muscle and the related mechanisms; we used palmitic acid (PA)-treated C2C12 myotubes as an insulin resistance model. We found that PZ-DHA increased the activity of AMP-activated protein kinase (AMPK) and improved glucose uptake and mitochondrial function in an AMPK-dependent manner in untreated C2C12 myotubes. PZ-DHA treatment of the myotubes reversed PA-induced insulin resistance; this was indicated by increases in glucose uptake and the expression of membrane glucose transporter 4 (Glut4) and phosphorylated Akt. Moreover, PZ-DHA treatment reversed PA-induced inflammation and oxidative stress. These effects of PZ-DHA were mediated by AMPK. Furthermore, the increase in AMPK activity, improvement in insulin resistance, and decrease in inflammatory and oxidative responses after PZ-DHA treatment diminished upon co-treatment with a liver kinase B1 (LKB1) inhibitor, suggesting that PZ-DHA improved AMPK activity by regulating its upstream kinase, LKB1. The effects of PZ-DHA on insulin resistance in C2C12 myotubes may be mediated by the LKB1- AMPK signaling pathway. Hence, PZ-DHA is a promising therapeutic agent for insulin resistance in type 2 diabetes.

Three hours of Moderate Intensity Exercise Training Reduces Glucose Tolerance in Endurance Trained Athletes

Objectives:It is well accepted that exercise training improves glucose uptake and insulin sensitivity, and that endurance trained athletes in general show a high capacity for these parameters. However, some studies have observed negative effects on glucose regulation in healthy, trained subjects the day after exercise. These, often unexpected, results have been postulated to be caused by excessive training loads, muscle damage, energy deficit, differences in glucose uptake in the exercised and non-exercised musculature and a metabolic interaction through increased fatty acid metabolism. The mode or volume of exercise that can lead to glucose intolerance in trained athletes as well as its relevance for health and performance are, however, not fully understood. We here studied the metabolic response to a glucose load the day after a session of high intensity interval training (HIIT) or three hours of continuous exercise (3h) in endurance trained athletes and compared the results with measurements during rest.Methods:Nine endurance trained athletes underwent oral glucose tolerance tests (OGTT) after rest and ˜14 hours after exercise on a cycle ergometer (HIIT 5x4 minutes at ˜95% of VO2max or 3h at 65% of VO2max). Concentrations of glucose, insulin, free fatty acids (FFA) and ketones (β-hydroxybutyrate) were measured. Statistical analysis was performed using a RM one-way ANOVA.Results:The area under the curve (AUC) during the OGTT increased greatly after 3h (668±124 mM · min) (p<0.01) compared to rest (532±89) but was found to be unchanged after HIIT (541±96). Resting values of FFA and ketones were increased after 3h (p<0.01 and p<0.05, respectively) but not after HIIT. Insulin was found to be unaltered during all conditions.Conclusion:Here, we show manifestation of glucose intolerance in endurance trained athletes together with concomitant increases in plasma concentrations of FFA and ketones the day after a session of prolonged exercise training but not after HIIT. This could be a protective response for securing glucose delivery to the brain and therefore have a positive effect on endurance. It also has the potential to reduce the recovery of glycogen depots, glucose uptake during exercise and performance at higher work rates.

Meroterpenoids containing benzopyran or benzofuran motif from Ganoderma cochlear

Five undescribed benzopyran containing meroterpenoids, ganodercins Q－U, two undescribed benzofuran containing meroterpenoids, ganodercins V and W, and two known meroterpenoids were isolated from Ganoderma cochlear. Their structures were elucidated by using HRESIMS, NMR spectroscopy and computational methods. The results of biochemical studies using a palmitic acid (PA) induced insulin resistance (IR) model show that (−)-ganodercin Q, (+)-ganodercins R and W activate phospho-AKT (p-AKT) at 20 μM and improve glucose uptake in a concentration dependent manner. The results of renoprotection studies show that (+)-ganodercin S, cochlearol F, (+)- and (−)-ganodercins V reduce the expression of collagen I.