Improved Glucose Uptake Research Articles

Exercise-induced myokines and their effect on prostate cancer.

Exercise is recognized by clinicians in the field of clinical oncology for its potential role in reducing the risk of certain cancers and in reducing the risk of disease recurrence and progression; yet, the underlying mechanisms behind this reduction in risk are not fully understood. Studies applying post-exercise blood serum directly to various types of cancer cell lines provide insight that exercise might have a role in inhibiting cancer growth via altered soluble and cell-free blood contents. Myokines, which are cytokines produced by muscle and secreted into the bloodstream, might offer multiple benefits to cellular metabolism (such as a reduction in insulin resistance, improved glucose uptake and reduced adiposity), and blood myokine levels can be altered with exercise. Alterations in the levels of myokines such as IL-6, IL-15, IL-10, irisin, secreted protein acidic risk in cysteine (SPARC), myostatin, oncostatin M and decorin might exert a direct inhibitory effect on cancer growth via inhibiting proliferation, promoting apoptosis, inducing cell-cycle arrest and inhibiting the epithermal transition to mesenchymal cells. The association of insulin resistance, hyperinsulinaemia and hyperlipidaemia with obesity can create a tumour-favourable environment; exercise-induced myokines can manipulate this environment by regulating adipose tissue and adipocytes. Exercise-induced myokines also have a critical role in increasing cytotoxicity and the infiltration of immune cells into the tumour.

Genistein improves systemic metabolism and enhances cold resistance by promoting adipose tissue beiging

Genistein, a naturally occurring phytoestrogen and a member of the large class of compounds known as isoflavones, exerts protective effects in several diseases. Recent studies indicate that genistein plays a critical role in controlling body weight, obesity-associated insulin resistance, and metabolic disorders, but its target organs in reversing obesity and related pathological conditions remain unclear. In this study, we showed that mice supplemented with 0.2% genistein in a high-fat diet for 12 weeks showed enhanced metabolic homeostasis, including reduced obesity, improved glucose uptake and insulin sensitivity, and alleviated hepatic steatosis. We also observed a beiging phenomenon in the white adipose tissue and reversal of brown adipose tissue whitening in these mice. These changes led to enhanced resistance to cold stress. Altogether, our data suggest that the improved metabolic profile in mice treated with genistein is likely a result of enhanced adipose tissue function.

Antidiabetic Flavonoids from Fruits of Morus alba Promoting Insulin-Stimulated Glucose Uptake via Akt and AMP-Activated Protein Kinase Activation in 3T3-L1 Adipocytes.

Morus alba (Moraceae), known as white mulberry, has been used to treat fever, protect against liver damage, improve eyesight, and lower blood sugar levels in traditional oriental medicine. Few studies have been conducted on the antidiabetic compounds identified from M. alba and their underlying mechanisms of action. Consequently, in this study, the fruits of M. alba were investigated for potential antidiabetic natural products using 3T3-L1 adipocytes. Phytochemical analysis of the ethanolic extract of M. alba fruits, followed by high-performance liquid chromatography (HPLC), purification led to the isolation of two main compounds: rutin and quercetin-3-O-β-d-glucoside (Q3G). Long-term use of available drugs for treating type 2 diabetes ((T2D) is often accompanied by undesirable side effects, which have generated increased interest in the development of more effective and safer antidiabetic agents. Examination of the isolated compounds, rutin and Q3G, for antidiabetic or anti-obesity properties or both in 3T3-L1 adipocytes demonstrated that they both improved glucose uptake via Akt-mediated insulin signaling pathway or AMP-activated protein kinase (AMPK) activation in 3T3-L1 adipocytes. The compounds also showed a positive effect on lipid accumulation in adipocytes, suggesting that glucose uptake occurred through activation of the Akt and AMPK signaling pathway without inducing adipogenesis. Taken together, our findings suggest that rutin and Q3G in M. alba fruits have the potential to induce fewer side effects such as weight gain, and these active compounds could be potential therapeutic candidates for the management of T2D.

The triterpene, methyl-3β-hydroxylanosta-9,24-dien-21-oate (RA3), attenuates high glucose-induced oxidative damage and apoptosis by improving energy metabolism

BackgroundHyperglycemia-induced cardiovascular dysfunction has been linked to oxidative stress and accelerated apoptosis in the diabetic myocardium. While there is currently no treatment for diabetic cardiomyopathy (DCM), studies suggest that the combinational use of anti-hyperglycemic agents and triterpenes could be effective in alleviating DCM. HypothesisTo investigate the therapeutic effect of methyl-3β-hydroxylanosta-9,24-dien-21-oate (RA3), in the absence or presence of the anti-diabetic drug, metformin (MET), against hyperglycemia-induced cardiac injury using an in vitro H9c2 cell model. MethodsTo mimic a hyperglycemic state, H9c2 cells were exposed to high glucose (HG, 33 mM) for 24 h. Thereafter, the cells were treated with RA3 (1 μM), MET (1 μM) and the combination of MET (1 μM) plus RA3 (1 μM) for 24 h, to assess the treatments therapeutic effect. ResultsBiochemical analysis revealed that RA3, with or without MET, improves glucose uptake via insulin-dependent (IRS-1/PI3K/Akt signaling) and independent (AMPK) pathways whilst ameliorating the activity of antioxidant enzymes in the H9c2 cells. Mechanistically, RA3 was able to alleviate HG-stimulated oxidative stress through the inhibition of reactive oxygen species (ROS) and lipid peroxidation as well as the reduced expression of the PKC/NF-кB cascade through decreased intracellular lipid content. Subsequently, RA3 was able to mitigate HG-induced apoptosis by decreasing the activity of caspase 3/7 and DNA fragmentation in the cardiomyoblasts. ConclusionRA3, in the absence or presence of MET, demonstrated potent therapeutic properties against hyperglycemia-mediated cardiac damage and could be a suitable candidate in the prevention of DCM.

Peptide Analogues of VPP and IPP with Improved Glucose Uptake Activity in L6 Myotubes can be Released from Cereal Proteins.

VPP (Val-Pro-Pro) and IPP (Ile-Pro-Pro) are two famous antihypertensive peptides with possible benefits for type 2 diabetes mellitus (T2DM). The study was aimed to investigate the effect of peptide analogues of VPP and IPP on glucose uptake activity in L6 myotubes. The analogues were designed by replacing the N-terminal, middle, or C-terminal amino acid residues of VPP and IPP with one amino acid at a time from five amino acid groups (polar, nonpolar, basic, acidic, and aromatic amino acids). Among 26 tripeptides tested, IQP, IPQ, VPE, and VEP showed significantly higher glucose uptake activity than their parent peptides, and all were successfully released from rice proteins at the contents of 5415.82 ± 63.34, 1586.77 ± 14.94, 354.07 ± 6.56, and 596.10 ± 2.32 ng/mg dry basis, respectively, and quantified by liquid chromatography-mass spectrometry (MS)/MS using multiple reaction monitoring. All four peptides were shown to promote glucose uptake via the adenosine monophosphate-activated protein kinase pathway accompanied by glucose transporter type 4 (Glut4) translocation rather than the insulin signaling pathway.

Insight Into The Molecular Basis Of The Anti‑Hyperglycemic Activity Of Ra‑3 In Type 2 Diabetic Rats And Its Cardioprotective Potential In Cultured Cardiomyoblasts

Insulin resistance, a hallmark of type 2 diabetes mellitus (T2DM), is the underlying cause of various metabolic changes observed in type 2 diabetic patients. This study investigated the molecular basis of the anti-hyperglycemic activity of RA-3, the lanosteryl triterpene from Protorhus longifolia, in type 2 diabetic rats and its cardioprotective potential in cultured cardiomyoblasts. To mimic a hyperglycemic state, H9c2 cells were exposed to high glucose concentration (33 mM) for 24 hours. Thereafter, the cells wells were treated with RA3 (1 μM). The high-fat diet fed (HFD) and STZ-induced T2DM in rat model was used to evaluate the anti-hyperglycemic activity of RA-3. The T2DM mimetic rats were orally administered with RA-3 (100 mg/kg) daily for 28 days. Blood and skeletal muscles were collected for biochemical and protein (IRS-1, AKT, GSK and GLUT 4) expression analysis. Biochemical analysis of the cell extracts revealed that RA3 improves glucose uptake via insulin- dependent (IRS-1/PI3K/Akt signaling) and independent (AMPK) pathways whilst ameliorating the activity of antioxidant enzymes defense in the H9c2 cells. The in vivo results showed significant decrease in p-GSK-3β and p-AKT expression, whereas the expression of IRS- 1ser307 were increased when compared to the model control group. This effect was ablated upon treatment of the animals with RA-3 and this was concomitant to an observed increase in GLUT 4 expression. It was concluded that the anti-hyperglycemic effect of RA-3 could partly be associated with its ability to improve cellular glucose uptake in muscle tissue and thus alleviating hyperglycemia- induced tissue damage.

Myricitrin, a Glycosyloxyflavone in Myrica esculenta Bark Ameliorates Diabetic Nephropathy via Improving Glycemic Status, Reducing Oxidative Stress, and Suppressing Inflammation.

The present study evaluated the therapeutic potential of myricitrin (Myr), a glycosyloxyflavone extracted from Myrica esculenta bark, against diabetic nephropathy. Myr exhibited a significant hypoglycemic effect in high fat-fed and a single low-dose streptozotocin-induced type 2 diabetic (T2D) rats. Myr was found to improve glucose uptake by the skeletal muscle via activating IRS-1/PI3K/Akt/GLUT4 signaling in vitro and in vivo. Myr significantly attenuated high glucose (HG)-induced toxicity in NRK cells and in the kidneys of T2D rats. In this study, hyperglycemia caused nephrotoxicity via endorsing oxidative stress and inflammation resulting in the induction of apoptosis, fibrosis, and inflammatory damages. Myr was found to attenuate oxidative stress via scavenging/neutralizing oxidative radicals and improving endogenous redox defense through Nrf-2 activation in both in vitro and in vivo systems. Myr was also found to attenuate diabetes-triggered renal inflammation via suppressing NF-κB activation. Myr inhibited hyperglycemia-induced apoptosis and fibrosis in renal cells evidenced by the changes in the expressions of the apoptotic and fibrotic factors. The molecular docking predicted the interactions between Myr and different signal proteins. An in silico absorption, distribution, metabolism, excretion, and toxicity (ADMET) study predicted the drug-likeness character of Myr. Results suggested the possibility of Myr to be a potential therapeutic agent for diabetic nephropathy in the future.

WATER EXTRACT OF CAESALPINIA PULCHERRIMA FLOWERS INCREASES GLUCOSE UPTAKE IN INSULIN RESISTANT ADIPOCYTES IN A DOSEDEPENDENT MANNER

Caesalpinia pulcherrima (CP) flower extract has been shown to have antidiabetic effects on pancreatic beta cell regeneration and improved skeletal muscle glucose utilisation. However, little is known about its effect on adipocytes, particularly insulin resistant adipocytes. This study investigated the possibility of improving glucose uptake in adipocytes obtained from chickens which are naturally insulin resistant via direct effects of water extract of Caesalpinia pulcherrima flowers. The extract was prepared by boiling air dried CP flowers in a water based modified Krebs Ringer Bicarbonate buffer for 5mins and sterilizing the filtrate via vacuum filtration. A glucose load of 18mM and 10% ITS was added to the extract. In the absence of adipocytes, the glucose concentration of the CP extract remained unchanged (p=0.5087). Insulin resistance in the chicken adipocytes was confirmed by delayed and limited glucose uptake (maximum 2.9% + 1.62% in 60mins). This was reversed via the addition of the water extract of the CP flowers as concentrations as low as 2.8mg/ml doubled glucose uptake and concentrations as low as 5.6mg/ml increased the rate of glucose uptake to that of insulin sensitive cells. These results suggest that water extract of CP flowers directly modulate glucose uptake into insulin resistant cells at concentrations as low as 2.8mg/ml following a 5mins decoction preparation.

Alpha lipoic acid attenuates ER stress and improves glucose uptake through DNAJB3 cochaperone

Persistent ER stress, mitochondrial dysfunction and failure of the heat shock response (HSR) are fundamental hallmarks of insulin resistance (IR); one of the early core metabolic aberrations that leads to type 2 diabetes (T2D). The antioxidant α-lipoic acid (ALA) has been shown to attenuate metabolic stress and improve insulin sensitivity in part through activation of the heat shock response (HSR). However, these studies have been focused on a subset of heat shock proteins (HSPs). In the current investigation, we assessed whether ALA has an effect on modulating the expression of DNAJB3/HSP40 cochaperone; a potential therapeutic target with a novel role in mitigating metabolic stress and promoting insulin signaling. Treatment of C2C12 cells with 0.3 mM of ALA triggers a significant increase in the expression of DNAJB3 mRNA and protein. A similar increase in DNAJB3 mRNA was also observed in HepG2 cells. We next investigated the significance of such activation on endoplasmic reticulum (ER) stress and glucose uptake. ALA pre-treatment significantly reduced the expression of ER stress markers namely, GRP78, XBP1, sXBP1 and ATF4 in response to tunicamycin. In functional assays, ALA treatment abrogated significantly the tunicamycin-mediated transcriptional activation of ATF6 while it enhanced the insulin-stimulated glucose uptake and Glut4 translocation. Silencing the expression of DNAJB3 but not HSP72 abolished the protective effect of ALA on tunicamycin-induced ER stress, suggesting thus that DNAJB3 is a key mediator of ALA-alleviated tunicamycin-induced ER stress. Furthermore, the effect of ALA on insulin-stimulated glucose uptake is significantly reduced in C2C12 and HepG2 cells transfected with DNAJB3 siRNA. In summary, our results are supportive of an essential role of DNAJB3 as a molecular target through which ALA alleviates ER stress and improves glucose uptake.

Vagus nerve stimulation optimized cardiomyocyte phenotype, sarcomere organization and energy metabolism in infarcted heart through FoxO3A-VEGF signaling

Vagus nerve stimulation (VNS) restores autonomic balance, suppresses inflammation action and minimizes cardiomyocyte injury. However, little knowledge is known about the VNS’ role in cardiomyocyte phenotype, sarcomere organization, and energy metabolism of infarcted hearts. VNS in vivo and acetylcholine (ACh) in vitro optimized the levels of α/β-MHC and α-Actinin positive sarcomere organization in cardiomyocytes while reducing F-actin assembly of cardiomyocytes. Consistently, ACh improved glucose uptake while decreasing lipid deposition in myocytes, correlating both with the increase of Glut4 and CPT1α and the decrease of PDK4 in infarcted hearts in vivo and myocytes in vitro, attributing to improvement in both glycolysis by VEGF-A and lipid uptake by VEGF-B in response to Ach. This led to increased ATP levels accompanied by the repaired mitochondrial function and the decreased oxygen consumption. Functionally, VNS improved the left ventricular performance. In contrast, ACh-m/nAChR inhibitor or knockdown of VEGF-A/B by shRNA powerfully abrogated these effects mediated by VNS. On mechanism, ACh decreased the levels of nuclear translocation of FoxO3A in myocytes due to phosphorylation of FoxO3A by activating AKT. FoxO3A overexpression or knockdown could reverse the specific effects of ACh on the expression of VEGF-A/B, α/β-MHC, Glut4, and CPT1α, sarcomere organization, glucose uptake and ATP production. Taken together, VNS optimized cardiomyocytes sarcomere organization and energy metabolism to improve heart function of the infarcted heart during the process of delaying and/or blocking the switch from compensated hypertrophy to decompensated heart failure, which were associated with activation of both P13K/AKT-FoxO3A-VEGF-A/B signaling cascade.

Aronia melanocarpa anthocyanin extracts are an effective regulator of suppressor of cytokine signaling 3-dependent insulin resistance in HepG2 and C2C12 cells

Insulin resistance (IR) is involved in the development of type 2 diabetes mellitus (T2DM). Plant anthocyanins can attenuate IR, but the related mechanisms are still incompletely understood. We found that Aronia melanocarpa anthocyanin extracts (AMAE) could improve glucose uptake by upregulating glucose transporter-4, enhance insulin action in IR HepG2 and C2C12 cells, increase IRS-1 and p-GSK-3β (Ser9) levels, and decrease p-IRS-1 (Ser307) and GSK-3β levels, thereby promoting glycogen synthesis. Suppressor of cytokine signaling 3 (SOCS3), a negative regulator of insulin signaling, was reduced by AMAE after palmitic acid induction. Importantly, siSOCS3 transfection significantly amplified the insulin-sensitizing effects of AMAE. These findings indicated that AMAE could enhance insulin sensitivity and glycogen synthesis in IR HepG2 and C2C12 cells by downregulating SOCS3. This research was conducive to supplement the molecular mechanisms of AMAE alleviating IR, providing support for application of A. melanocarpa anthocyanins in the prevention and treatment of T2DM.

The impact of preconditioning exercise on the vascular response to an oral glucose challenge.

Exercise elicits direct benefits to insulin sensitivity but may also indirectly improve glucose uptake by hemodynamic conditioning of the vasculature. The purpose of this study was to examine the modifying effect of 3 different types of exercise on the vascular response to an oral glucose challenge. Twenty healthy adults (9 women, 11 men; aged 23 ± 3 years) completed a standard oral glucose tolerance test (OGTT) at rest, as well as 1.5 hours after moderate continuous cycling exercise (30min; 65% peak oxygen consumption), high-intensity interval cycling exercise (10 × 1 min at 90% peak heart rate), and lower-load higher-repetition resistance exercise (25-35 repetitions/set, 3 sets). Brachial and superficial femoral artery blood flow, conductance, and oscillatory shear index were measured throughout the OGTT. Regardless of rested state or exercise preconditioning, the OGTT induced reductions in brachial artery blood flow and conductance (p< 0.001), and transient increases in brachial and superficial femoral artery oscillatory shear index and retrograde blood flow (p< 0.01). Continuous cycling and resistance exercise were followed with a small degree of protection against prolonged periods of oscillatory flow. Our findings imply transient peripheral vasoconstriction and decreased limb blood flow during a standard OGTT, for which prior exercise was unable to prevent in healthy adults. Novelty: We investigated the impact of continuous, interval, and resistance exercise on the hemodynamic response to an OGTT. Our findings suggest decreased upper-limb blood flow during an OGTT is not prevented by prior exercise in healthy adults.

Tankyrase inhibition augments neuronal insulin sensitivity and glucose uptake via AMPK-AS160 mediated pathway

Tankyrase, a member of poly (ADP-ribose) polymerase (PARP) family, regulates various cellular pathways including wnt signaling, telomere maintenance and mitosis, has become a prime target for the development of cancer therapeutics. Inhibition of tankyrase, which leads to its increased cellular accumulation, reveal the role of tankyrase in the regulation of Glucose transporter type 4 (GLUT4) translocation and glucose homeostasis in peripheral insulin responsive tissues. While in adipocytes inhibition of tankyrase improves insulin sensitivity and glucose uptake, its inhibition in skeletal muscle leads to development of insulin resistance. Evidently further studies are required to determine the broader perspective of tankyrase in other cellular systems in regulating insulin signaling and insulin resistance. Role of tankyrase in neuronal tissues/cells has not been tested. In the present study, we investigated the effect of tankyrase inhibition in insulin-sensitive and insulin-resistant Neuro-2a cells. Here, we report that XAV939 treatment, a tankyrase inhibitor, improves insulin-stimulated glucose uptake in insulin-sensitive as well as in insulin-resistant neuronal cells via AMP-activated protein kinase (AMPK) - AKT Substrate of 160 kDa (AS160) mediated pathway without affecting the phosphorylation/activation of AKT. AMPK inhibition by Compound C repressed XAV939 treatment mediated increase in glucose uptake, confirming the role of tankyrase in glucose uptake via AMPK. We show for the first time that inhibition of tankyrase significantly improves glucose uptake and insulin sensitivity of insulin-resistant neuronal cells via AMPK-AS160 mediated pathway. Our study demonstrates new mechanistic insights of tankyrase mediated regulation of insulin sensitivity as well as glucose uptake in neuronal cells.

2,3,5,6-Tetramethylpyrazine improves diet-induced whole-body insulin resistance via suppressing white adipose tissue lipolysis in mice

Ectopic lipid accumulation in skeletal muscle and liver arises when nutrient storage systems are exposed to chronic energy surplus, leading to whole-body insulin resistance and metabolic disorders. One recent study has shown 2,3,5,6-tetramethylpyrazine (TMP), highly enriched in roasted foodstuffs, such as cocoa and peanuts, significantly decreases blood lipids levels and ameliorates ApoE-defect induced atherosclerosis suggesting a potent role of TMP in lipid dysregulation improvement. Here, we evaluated the impact of TMP treatment on high fat diet (HFD)-induced insulin resistance. Using hyperinsulinemic-euglycemic mouse clamp, we demonstrated 4-week TMP treatment improved whole-body insulin resistance in HFD-fed mice through suppressing lipolysis in white adipose tissue associated with reduced triglyceride in liver and improved glucose uptake in skeletal muscle. Collectively, our work provides proof-of-concept data to support the development of white adipose tissue-targeted medicine for the treatment of metabolic disorder.

Mechanisms Underlying Absent Training-Induced Improvement in Insulin Action in Lean, Hyperandrogenic Women With Polycystic Ovary Syndrome.

Women with polycystic ovary syndrome (PCOS) have been shown to be less insulin sensitive compared with control (CON) women, independent of BMI. Training is associated with molecular adaptations in skeletal muscle, improving glucose uptake and metabolism in both healthy individuals and patients with type 2 diabetes. In the current study, lean hyperandrogenic women with PCOS (n = 9) and healthy CON women (n = 9) completed 14 weeks of controlled and supervised exercise training. In CON, the training intervention increased whole-body insulin action by 26% and insulin-stimulated leg glucose uptake by 53% together with increased insulin-stimulated leg blood flow and a more oxidative muscle fiber type distribution. In PCOS, no such changes were found, despite similar training intensity and improvements in VO2max In skeletal muscle of CON but not PCOS, training increased GLUT4 and HKII mRNA and protein expressions. These data suggest that the impaired increase in whole-body insulin action in women with PCOS with training is caused by an impaired ability to upregulate key glucose-handling proteins for insulin-stimulated glucose uptake in skeletal muscle and insulin-stimulated leg blood flow. Still, other important benefits of exercise training appeared in women with PCOS, including an improvement of the hyperandrogenic state.

Histone deacetylase 5 regulates interleukin 6 secretion and insulin action in skeletal muscle

ObjectivePhysical exercise training is associated with increased glucose uptake in skeletal muscle and improved glycemic control. HDAC5, a class IIa histone deacetylase, has been shown to regulate transcription of the insulin-responsive glucose transporter GLUT4 in cultured muscle cells. In this study, we analyzed the contribution of HDAC5 to the transcriptional network in muscle and the beneficial effect of muscle contraction and regular exercise on glucose metabolism. MethodsHDAC5 knockout mice (KO) and wild-type (WT) littermates were trained for 8 weeks on treadmills, metabolically phenotyped, and compared to sedentary controls. Hdac5-deficient skeletal muscle and cultured Hdac5-knockdown (KD) C2C12 myotubes were utilized for studies of gene expression and glucose metabolism. Chromatin immunoprecipitation (ChIP) studies were conducted to analyze Il6 promoter activity using H3K9ac and HDAC5 antibodies. ResultsGlobal transcriptome analysis of Hdac5 KO gastrocnemius muscle demonstrated activation of the IL-6 signaling pathway. Accordingly, knockdown of Hdac5 in C2C12 myotubes led to higher expression and secretion of IL-6 with enhanced insulin-stimulated activation of AKT that was reversed by Il6 knockdown. Moreover, Hdac5-deficient myotubes exhibited enhanced glucose uptake, glycogen synthesis, and elevated expression levels of the glucose transporter GLUT4. Transcription of Il6 was further enhanced by electrical pulse stimulation in Hdac5-deficient C2C12 myotubes. ChIP identified a ∼1 kb fragment of the Il6 promoter that interacts with HDAC5 and demonstrated increased activation-associated histone marker AcH3K9 in Hdac5-deficient muscle cells. Exercise intervention of HDAC5 KO mice resulted in improved systemic glucose tolerance as compared to WT controls. ConclusionsWe identified HDAC5 as a negative epigenetic regulator of IL-6 synthesis and release in skeletal muscle. HDAC5 may exert beneficial effects through two different mechanisms, transcriptional control of genes required for glucose disposal and utilization, and HDAC5-dependent IL-6 signaling cross-talk to improve glucose uptake in muscle in response to exercise.

Poncirin, an orally active flavonoid exerts antidiabetic complications and improves glucose uptake activating PI3K/Akt signaling pathway in insulin resistant C2C12 cells with anti-glycation capacities

Poncirin, a natural flavanone glycoside present abundantly in many citrus fruits, contains an extensive range of biological activities. However, the antidiabetic mechanism of poncirin is unexplored yet. In this study, we examined the anti-diabetic prospective of poncirin by evaluating its ability to inhibit protein tyrosine phosphatase 1B (PTP1B), α-glucosidase, human recombinant AR (HRAR), rat lens aldose reductase (RLAR), and advanced glycation end-product (AGE) formation (IC50 = 7.76 ± 0.21, 21.31 ± 1.26, 3.56 ± 0.33, 11.91 ± 0.21, and 3.23 ± 0.09 µM, respectively). Kinetics data and docking studies showed the lowest binding energy and highestaffinityforthemixed and competitivetypeof inhibitorsof poncirin. Moreover, the molecular mechanisms underlying the antidiabetic outcomes of poncirin in insulin resistant C2C12 skeletal muscle cells were explored, which significantly increased glucose uptake and decreased the expression of PTP1B in C2C12 cells. Consequently, poncirin increased GLUT-4 expression level by activating the IRS-1/PI3K/Akt/GSK-3 signaling pathway. Moreover, poncirin (0.5–50 µM) remarkably inhibited the formation of fluorescent AGE, nonfluorescent CML, fructosamine, and β-cross amyloid structures in glucose-fructose-induced BSA glycation during 4 weeks of study. Poncirin also notably prevented protein oxidation demonstrated with decreasing the protein carbonyl and the consumption of protein thiol in the dose-dependent manner. The results clearly expressed the promising activity of poncirin for the therapy of diabetes and its related complications.

Conditioned medium of adipose derived Mesenchymal Stem Cells reverse insulin resistance through downregulation of stress induced serine kinases

Insulin resistance (IR) is a constituent part of Type 2 Diabetes Mellitus (T2DM). Conditioned medium from Adipose derived Mesenchymal Stem Cells (ADMSCs-CM) has been shown to reverse IR. However, its effect on cellular stress is not well established. The objective of this study was to explore the effect of ADMSCs-CM on reactive oxygen species, mitochondrial membrane potential (ΔΨm), endoplasmic reticulum (ER) stress and expression of oxidative and inflammatory stress induced serine kinases (SISK) which are pathophysiologically linked to IR. In insulin resistant, 3T3-L1 adipocytes and C2C12 myoblast cell culture models, glucose uptake was assayed by 2-NBDG uptake. Immunomodulatory cytokines, intracellular reactive oxygen species generation, ΔΨm and protein expression of JNK1, IKKβ and phospho-IRS1 (307) were analyzed using FACS. mRNA expression of ER stress markers (CHOP1 and IRE1) and SISK (JNK1, IKKβ, ERK1 and S6K1) were analyzed using RT-PCR. ADMSCs-CM effectively improve glucose uptake as evidenced by 2-NBDG uptake assay. FACS analysis showed that ADMSCs-CM possessed significantly higher levels of IL-6 and IL-10. ADMSCs-CM decreased intracellular generation of reactive oxygen species where it restored ΔΨm in C2C12cells. ADMSCs-CM mediated reduction in ER stress was confirmed by down-regulation in CHOP1 and IRE1 mRNA expression. ADMSCs-CM treatment showed significant down-regulation of SISK mRNA expression including IKKβ, JNK, ERK and S6K1. Our results unequivocally demonstrate for the first time the mechanism of action of ADMSCs-CM in amelioration IR by reducing oxidative and inflammatory cellular stress. This study identifies SISK as potential therapeutic targets for T2DM therapy.

Isoorientin ameliorates lipid accumulation by regulating fat browning in palmitate-exposed 3T3-L1 adipocytes

Stimulation of fat browning using natural bioactive products is regarded as one of the promising approaches to treat obesity and insulin resistance. Here, we investigated the physiological effects of isoorientin on glucose uptake and lipid accumulation in insulin resistant 3T3-L1 adipocytes. To achieve this, 3T3-L1 adipocytes were exposed to 0.75 mM palmitate for 24 h, to induce insulin resistance, before treatment with 10 μM isoorientin or the comparative controls such as CL-316,243 (10 μM), pioglitazone (10 μM) and compound C (1 μM) for 4 h. Relevant bioassays and Western blot analysis were conducted on these insulin resistant cells. Our results showed that palmitate exposure could induce insulin resistance and mitochondrial dysfunction as measured by reduction in glucose uptake and impaired mitochondrial bioenergetics parameters. However, treatment with isoorientin reversed these effects by improving glucose uptake, blocking lipid accumulation, and modulating the process of mitochondrial respiration. Mechanistically, isoorientin could mediate lipid metabolism by activating 5′ AMP-activated protein kinase (AMPK), while also effectively modulating the expression of genes involved in fat browning such as peroxisome proliferator-activated receptor gamma (PPAR)γ/α and uncoupling protein 1 (UCP1). In conclusion, isoorientin impacts insulin resistance in vitro by improving glucose uptake and mitochondrial function, consistent to modulating the expression of genes involved in energy metabolism and fat browning.

Evaluation of the antidiabetic potential of Psidium guajava L. (Myrtaceae) using assays for α-glucosidase, α-amylase, muscle glucose uptake, liver glucose production, and triglyceride accumulation in adipocytes

Ethnopharmacological relevancePsidium guajava L. (Myrtaceae) leaves are used as an herbal antidiabetic remedy in several parts of the world. On Madagascar, both the bark and leaves are used for treatment of diabetes. Materials and methodsDilution series of ethanolic extracts of P. guajava leaves and bark were used for determining inhibitory activities against yeast α-glucosidase and porcine α-amylase. Skeletal muscle glucose uptake was measured using 2-deoxy-D-(1–3H)-glucose in murine C2C12 skeletal muscle cells. Hepatic glucose-6-phosphatase activity in rat hepatoma H4IIE cells and triglyceride accumulation in murine 3T3-L1 adipocyte-like cells were assessed using Wako AutoKit Glucose assays and AdipoRed reagent, respectively. Cells were incubated for 18 h with the maximal non-toxic concentrations of the plant extracts determined by the lactate dehydrogenase cytotoxicity assay. ResultsEthanolic extracts of P. guajava leaf and bark inhibited α-glucosidase with IC50 values of 1.0 ± 0.3 and 0.5 ± 0.01 μg/mL, respectively. In the α-amylase inhibition assay, the ethanolic extract of bark of P. guajava showed an IC50 value of 10.6 ± 0.4 μg/mL. None of the extracts were able to reduce glucose-6-phosphatase activity in rat hepatoma H4IIE cells. In contrast, P. guajava leaf extract significantly increased 2-deoxy-D-[1–3H]-glucose uptake in C2C12 muscle cells (161.4 ± 10.1%, p = 0.0015) in comparison to the dimethyl sulfoxide (DMSO) vehicle control, as did the reference compounds metformin (144.0 ± 7.7%, p = 0.0345) and insulin (141.5 ± 13.8%, p = 0.0495). Furthermore, P. guajava leaf and bark extracts, as well as the reference compound rosiglitazone, significantly enhanced triglyceride accumulation in 3T3-L1 cells (252.6 ± 14.2%, p < 0.0001, 211.1 ± 12.7%, p < 0.0001, and 201.1 ± 9.2%, p < 0.0001, respectively) to levels higher than the DMSO vehicle control. Moreover, P. guajava leaf extract significantly enhanced the triglyceride accumulation in 3T3-L1 cells compared to rosiglitazone. ConclusionThe results demonstrated that P. guajava leaf and bark extracts can be used as a natural source of α-glucosidase inhibitors. In addition, the bark extract of P. guajava was an effective α-amylase inhibitor. Moreover, P. guajava leaf extract improved glucose uptake in muscle cells, while both leaf and bark extracts enhanced the triglyceride content in adipocytes in culture. P. guajava leaf and bark extracts may thus hypothetically have future applications in the treatment of type 2 diabetes.