Insulin-sensitizing Activity Research Articles

Incretin-Based Therapies: A Promising Approach for Modulating Oxidative Stress and Insulin Resistance in Sarcopenia.

Recent studies have linked sarcopenia development to the hallmarks of diabetes, oxidative stress, and insulin resistance. The anti-oxidant and insulin sensitivityenhancing effects of incretin-based therapies may provide a promising option for the treatment of sarcopenia. This review aimed to unveil the role of oxidative stress and insulin resistance in the pathogenesis of sarcopenia and explore the potential benefits of incretin-based therapies in individuals with sarcopenia. PubMed, the Cochrane Library, and Google Scholar databases were searched by applying keywords relevant to the main topic, to identify articles that met our selection criteria. Incretin-based therapies manifested anti-oxidant effects by increasing the anti-oxidant defense system and decreasing free radical generation or by indirectly minimizing glucotoxicity, which was mainly achieved by improving insulin signaling and glucose homeostasis. Likewise, these drugs exhibit insulin-sensitizing activities by increasing insulin secretion, transduction, and β-cell function or by reducing inflammation and lipotoxicity. Incretin-based therapies, as modulators of oxidation and insulin resistance, may target the main pathophysiological factors of sarcopenia, thus providing a promising strategy for the treatment of this disease.

Bombax ceiba calyx extract promotes insulin sensitivity in L6 myotubes and modulates glucose metabolism in BRL3A cells through multiple pathways: A cell metabolomics approach

BackgroundBombax ceiba calyces are highly valued as a medicinal and nutritional vegetable, and have been traditionally used to treat various ailments. Recent studies have shown that extracts derived from Bombax ceiba calyces (BCE) can decrease insulin resistance and increase insulin secretion in hyperglycemic conditions, while reducing the formation of advanced glycation end products. However, the mechanism by which BCE promotes insulin sensitivity in high glucose condition remains unclear and requires further investigation. PurposeIn this study, our objective was to elucidate the molecular mechanism responsible for the effects of BCE and high glucose (Glu 33.6 mM) treatments on insulin sensitivity and glucose metabolism in L6 myotubes and BRL3A cells. By investigating these mechanisms, we aim to provide a better understanding of how BCE promotes insulin sensitivity and enhances glucose metabolism under conditions of high glucose. MethodsThe insulin-sensitizing activity of BCE (10 µg and 20 µg) was evaluated in L6 myotubes under high glucose conditions (G33.6 mM). After the treatment period, protein isolation was performed, and western blot analysis was conducted to assess the levels of specific markers, including AKT, pAKT, Nrf2, PI3K, and NFκB. Mitochondrial dysfunction was measured by evaluating the activity of complexes I-IV, TCA enzymes such as succinate dehydrogenase (SDH) and aconitase. Additionally, a Q-RT-PCR study was performed to determine the expression levels of PGC1α, PDK4, UCP2, and UCP3. The effect of BCE (10 µg and 20 µg) on glucose utilization and gluconeogenesis was determined by using BRL3A cells under hyperglycemic conditions (G33.6 mM). Glucose uptake and glycogen content were measured, while gluconeogenesis was inhibited by assessing the expression of AKT, pAKT, AMPK, pAMPK, and PEPCK proteins using western blot analysis. ResultsOur results indicate that, BCE promotes insulin signaling and enhances insulin sensitivity in L6 myotubes treated with high glucose by activating the PI3K/AKT pathway. Our analysis revealed that BCE restores mitochondrial respiration by restoring complexes I-IV, UCP2, and UCP3, and enhances metabolism through the activation of PGC1α, PDK4, and TCA enzymes such as aconitase and SDH. Moreover, BCE activates antioxidant pathways, such as Nrf2 and NF-kB, in high glucose-treated L6 myotubes, and improves insulin sensitivity by modulating the glycerophospholipid pathway. Furthermore, BCE promotes glycogenesis through AKT and AMPK phosphorylation and inhibits gluconeogenesis by downregulating PEPCK expression in BRL3A cells treated with high glucose. ConclusionOur study has demonstrated that, BCE promotes insulin sensitivity and modulates glucose metabolism through multiple mechanisms under hyperglycemic conditions. Our findings suggest that BCE has the potential to be used as a functional food for the treatment of hyperglycemia.

Surface Engineering Promoted Insulin-Sensitizing Activities of Sub-Nanoscale Vanadate Clusters through Regulated Pharmacokinetics and Bioavailability.

The therapeutic application of vanadium compounds is plagued by their poor bioavailability and potential adverse effects. Herein, 1nm polyoxovanadate (POV) clusters are functionalized with alkyl chains of various lengths and studied for the effect of surface engineering on their preclinical pharmacokinetics and typical insulin-sensitizing activity. The concentrations of surface engineered POVs in plasma, urine, and feces are monitored after a single administration to rats. The POVs exhibit a two-compartment profile of in vivo kinetics, and the surface engineering effect plays an important role in renal clearance of the POVs comparable to small molecules. POVs functionalized with long alkyl chains show much shorter elimination half time t1/2β and higher elimination fractions (50%) within 48h than pristine POVs, suggesting favorable elimination kinetics to mitigate the possible side effects of vanadium. Meanwhile, long alkyl chain modification leads to a 76% increment of oral bioavailability in contrast to unmodified POVs. As suggested by glucose tolerance tests and sub-chronic toxicity tests, the above two factors contribute to the enhanced therapeutic efficacy of POVs while mitigating their adverse effects. The surface engineering protocol provides a feasible approach to the optimization of the bioavailability and pharmacokinetic properties of POVs for promoted insulin-sensitizing activities.

Diabetes medications and risk of HCC.

Type 2 diabetes mellitus is a recognized risk factor for HCC in patients with liver disease, independent from the etiology of their liver disease. Hence, prevention and treatment of type 2 diabetes mellitus and its underlying cause, insulin resistance, should be considered a treatment target for patients with liver disease. The drug armamentarium for diabetes is wide and consists of agents with insulin-sensitizing activity, agents that stimulate insulin secretion, insulin itself, and agents that reduce gastrointestinal and urinary glucose absorption. From an endocrinology perspective, the main goal of treatment is the achievement of euglycemia; however, in patients at risk of, or with known underlying liver disease, the choice of diabetic medication as it relates to potential hepatic carcinogenesis remains complex and should be carefully considered. In the last decade, increasing evidence has suggested that metformin may reduce the risk of HCC, whereas evidence for other classes of diabetic medications, particularly some of the newer agents including the sodium glucose cotransporter-2 inhibitors and glucagon-like peptide-1 receptor agonists, is fewer and often inconsistent. In this review, we aim to summarize the current evidence on the potential effects of the most widely used diabetic agents on liver cancer tumorigenesis.

Preliminary Phytochemical Screening, In Vitro Antidiabetic, Antioxidant Activities, and Toxicity of Leaf Extracts of Psychotria malayana Jack.

Psychotria malayana Jack belongs to the Rubiacea and is widespread in Southeast Asian countries. It is traditionally used to treat diabetes. Despite its potential medicinal use, scientific proof of this pharmacological action and the toxic effect of this plant are still lacking. Hence, this study aimed to investigate the in vitro antidiabetic and antioxidant activities, toxicity, and preliminary phytochemical screening of P. malayana leaf extracts by gas chromatography-mass spectrometry (GC-MS) after derivatization. The antidiabetic activities of different extracts of this plant were investigated through alpha-glucosidase inhibitory (AGI) and 2-NBDG glucose uptake using 3T3-L1 cell line assays, while the antioxidant activity was evaluated using DPPH and FRAP assays. Its toxicological effect was investigated using the zebrafish embryo/larvae (Danio rerio) model. The mortality, hatchability, tail-detachment, yolk size, eye size, beat per minute (BPM), and body length were taken into account to observe the teratogenicity in all zebrafish embryos exposed to methanol extract. The LC50 was determined using probit analysis. The methanol extract showed the AGI activity (IC50 = 2.71 ± 0.11 μg/mL), insulin-sensitizing activity (at a concentration of 5 µg/mL), and potent antioxidant activities (IC50 = 10.85 μg/mL and 72.53 mg AAE/g for DPPH and FRAP activity, respectively). Similarly, the water extract exhibited AGI activity (IC50 = 6.75 μg/mL), insulin-sensitizing activity at the concentration of 10 μg/mL, and antioxidant activities (IC50 = 27.12 and 33.71 μg/mL for DPPH and FRAP activity, respectively). The methanol and water extracts exhibited the LC50 value higher than their therapeutic concentration, i.e., 37.50 and 252.45 µg/mL, respectively. These results indicate that both water and methanol extracts are safe and potentially an antidiabetic agent, but the former is preferable since its therapeutic index (LC50/therapeutic concentration) is much higher than for methanol extracts. Analysis using GC-MS on derivatized methanol and water extracts of P. malayana leaves detected partial information on some constituents including palmitic acid, 1,3,5-benzenetriol, 1-monopalmitin, beta-tocopherol, 24-epicampesterol, alpha-tocopherol, and stigmast-5-ene, that could be a potential target to further investigate the antidiabetic properties of the plant. Nevertheless, isolation and identification of the bioactive compounds are required to confirm their antidiabetic activity and toxicity.

Ameliorative potential of phloridzin in type 2 diabetes-induced memory deficits in rats

Diabetes associated oxidative stress and impaired cholinergic neurotransmission causes cognitive deficits. Although phloridzin shows antioxidant- and insulin sensitizing-activities, its ameliorative potential in diabetes-induced memory dysfunction remains unexplored. In the present study, type 2 diabetes (T2D) was induced by streptozotocin (35 mg/kg, intraperitoneal) in rats on ad libitum high-fat diet. Diabetic animals were treated orally with phloridzin (10 and 20 mg/kg) for four weeks. Memory functions were evaluated by passive avoidance test (PAT) and novel object recognition (NOR) test. Brains of rats were subjected to biochemical analysis of glutathione (GSH), brain-derived neurotrophic factor (BDNF), malonaldehyde (MDA) and acetylcholinesterase (AChE). Role of cholinergic system in the effects of phloridzin was evaluated by scopolamine pre-treatment in behavioral studies. While diabetic rats showed a significant decrease in step through latency in PAT, and exploration time and discrimination index in NOR test; a substantial increase in all parameters was observed following phloridzin treatment. Phloridzin reversed abnormal levels of GSH, BDNF, MDA and AChE in the brain of diabetic animals. Moreover, in silico molecular docking study revealed that phloridzin acts as a potent agonist at M1 receptor as compared to acetylcholine. Viewed collectively, reversal of T2D-induced memory impairment by phloridzin might be attributed to upregulation of neurotrophic factors, reduced oxidative stress and increased cholinergic signaling in the brain. Therefore, phloridzin may be a promising molecule in the management of cognitive impairment comorbid with T2D.

WSF-CT-11, a Sesquiterpene Derivative, Activates AMP-Activated Protein Kinase with Anti-diabetic Effects in 3T3-L1 Adipocytes

Background: AMP-activated protein kinase (AMPK) is a therapeutic target against type II diabetes (T2D). Synthetic sesquiterpene derivatives were investigated to identify novel AMPK activators as anti-diabetic drugs because the leading drugs like metformin and thiazolidinediones (TZDs) activate AMPK by inhibiting the synthesis of adenosine 5′-triphosphate and thus are associated with some side effects. Results: We identified WSF-CT-11 as an AMPK activator in HEK293T cells and found that WSF-CT-11 activates AMPK by the activation of transient receptor potential vanilloid type 1 (TRPV1), a Ca2+-permeable cation channel. The increased Ca2+ influx then activates phosphoinositide 3-kinase (PI3K), protein kinase B (PKB/Akt), and Ca2+/calmodulin-dependent protein kinase II (CaMKII), which in turn phosphorylates TRPV1 and facilitates the formation of a TRPV1/Akt/CaMKII/AMPK complex. This complex might be important for the regulation of AMPK activity. In 3T3-L1 adipocytes, WSF-CT-11-induced AMPK activation has three anti-diabetic effects. It promotes the assembly of high-molecular-weight adiponectin, which has stronger insulin-sensitizing activity than other multimers. It improves translocation of the glucose transporter type 4, increases glucose uptake, and induces the inhibitory phosphorylation of peroxisome proliferator-activated receptor γ and thus suppresses adipogenesis. Conclusion: WSF-CT-11 is a novel AMPK activator and potential drug against T2D without the side effects of metformin and TZDs.

Status of Adiponectin and hs-C-reactive Protein in Metabolic Syndrome in a Tertiary Care Teaching Hospital

Background: The metabolic syndrome (MetS), a cluster of abdominal obesity, dyslipidemia, hypertension and hyperglycemia, is a common basis for atherosclerotic vascular diseases in industrial countries exposed to overnutrition. Adiponectin is an adipose-derived plasma protein with anti-atherogenic and insulin-sensitizing activities. Materials and Methods: There were 46 subjects with MetS and 46 control groups. Mean serum level of adiponectin and high sensitive C-reactive protein (CRP) were lower and higher in subjects with MetS than control groups, respectively. Results: The serum adiponectin in the cases 2.43 ± 0.83 μg/ml was lower compared to the controls 7.54 ± 0.94 μg/ml (P value was 0.001), the difference was statistically significant. The serum hs-CRP in the cases 3.8 ± 1.26 μg/ml was lower compared to the controls 1.4 ± 0.74 μg/ml (P value was 0.001), the difference was statistically significant. Conclusion: The high hs-CRP and low adiponectin have a positive and negative relationship with certain MetS components. High sensitive C-reactive protein (hs-CRP) was found to have a stronger link to the MetS than adiponectin. It appears that high-sensitivity CRP (hs-CRP) may be a substantial risk factor for MetS. In contrast to prior findings, this study suggests that hs-CRP is more relevant than adiponectin as a diagnostic biomarker for MetS. These variations could be related to changes in lifestyle and food habits among Sambalpur residents with MetS.

In Search for Multi-Target Ligands as Potential Agents for Diabetes Mellitus and Its Complications-A Structure-Activity Relationship Study on Inhibitors of Aldose Reductase and Protein Tyrosine Phosphatase 1B.

Diabetes mellitus (DM) is a complex disease which currently affects more than 460 million people and is one of the leading cause of death worldwide. Its development implies numerous metabolic dysfunctions and the onset of hyperglycaemia-induced chronic complications. Multiple ligands can be rationally designed for the treatment of multifactorial diseases, such as DM, with the precise aim of simultaneously controlling multiple pathogenic mechanisms related to the disease and providing a more effective and safer therapeutic treatment compared to combinations of selective drugs. Starting from our previous findings that highlighted the possibility to target both aldose reductase (AR) and protein tyrosine phosphatase 1B (PTP1B), two enzymes strictly implicated in the development of DM and its complications, we synthesised 3-(5-arylidene-4-oxothiazolidin-3-yl)propanoic acids and analogous 2-butenoic acid derivatives, with the aim of balancing the effectiveness of dual AR/PTP1B inhibitors which we had identified as designed multiple ligands (DMLs). Out of the tested compounds, 4f exhibited well-balanced AR/PTP1B inhibitory effects at low micromolar concentrations, along with interesting insulin-sensitizing activity in murine C2C12 cell cultures. The SARs here highlighted along with their rationalization by in silico docking experiments into both target enzymes provide further insights into this class of inhibitors for their development as potential DML antidiabetic candidates.

Insulin‐Sensitizing Activity of Sub‐Nanoscaled Polyalkoxyvanadate Clusters

Sub-nanoscaled polyalkoxyvanadates (PAOVs) functionalized with various aliphatic acids are evaluated for their insulin-sensitizing activity in lowering the blood glucose levels of diabetic mice in typical glucose tolerance tests. All the PAOVs can restore the blood glucose to normal levels after a single oral administration of PAOVs. Among them, the myristic acid-modified PAOVs enable the response of insulin to the repeated glucose challenges, lasting for up to 13 h. The combined administration of PAOVs exerts better glucose control over insulin alone, while the capric acid- and myristic acid-modified ones can enhance the responsiveness of insulin to glucose challenge and is comparable to a clinical-used derivative of insulin. Interestingly, continuous glucose monitoring shows that myristic acid-modified PAOV derivatives sensitize the responsiveness of insulin, almost matching with that of a healthy pancreas. These discoveries open up new opportunities for the application of PAOVs to promote glucose-responsive and long-lasting activity of insulin, which are expected to aid the accurate blood glucose control in insulin therapy while reducing the number of insulin administrations.

Cyclin-Dependent Kinase 5 Inhibitor Butyrolactone I Elicits a Partial Agonist Activity of Peroxisome Proliferator-Activated Receptor γ.

Adiponectin is an adipocyte-derived cytokine having an insulin-sensitizing activity. During the phenotypic screening of secondary metabolites derived from the marine fungus Aspergillus terreus, a poly cyclin-dependent kinase (CDK) inhibitor butyrolactone I affecting CDK1 and CDK5 was discovered as a potent adiponectin production-enhancing compound in the adipogenesis model of human bone marrow-derived mesenchymal stem cells (hBM-MSCs). CDK5 inhibitors exhibit insulin-sensitizing activities by suppressing the phosphorylation of peroxisome proliferator-activated receptor γ (PPARγ). However, the adiponectin production-enhancing activities of butyrolactone I have not been correlated with the potency of CDK5 inhibitor activities. In a target identification study, butyrolactone I was found to directly bind to PPARγ. In the crystal structure of the human PPARγ, the ligand-binding domain (LBD) in complex with butyrolactone I interacted with the amino acid residues located in the hydrophobic binding pockets of the PPARγ LBD, which is a typical binding mode of the PPARγ partial agonists. Therefore, the adiponectin production-enhancing effect of butyrolactone I was mediated by its polypharmacological dual modulator activities as both a CDK5 inhibitor and a PPARγ partial agonist.

Lanostane Triterpenoids with Glucose-Uptake-Stimulatory Activity from Peels of the Cultivated Edible Mushroom Wolfiporia cocos.

A chemical study on the peels of the cultivated edible mushroom Wolfiporia cocos led to the isolation and identification of 47 lanostane triterpenoids including 16 new compounds (1-16). The structures of the new compounds were determined by analysis of the NMR, MS, and electronic circular dichroism (ECD) data. Compounds 1 and 2 represent new members of the family of 4,5-secolanostane triterpenes. Compound 3 is a new aromatic lanostane triterpene with an unusual methyl rearrangement from C-10 to C-6. The absolute configurations of 1 and 8 were assigned by ECD spectra calculation. All compounds were evaluated for cytotoxicity (K562, SW480, and HepG2) and glucose-uptake-stimulating effects. Compounds 23, 25, 29, and 31 showed weak inhibition on the K562 cells with IC50 in the range of 25.7 to 68.2 μM, respectively. Compounds 21, 28, and 30 increased the glucose uptake in 3T3-L1 cells by 25%, 14%, and 50% at 5 μM, respectively. In addition, compounds 14, 23, 29, 35, and 43 showed insulin-sensitizing activity by increasing the insulin-stimulated glucose uptake at 2.5 μM in 3T3-L1 adipocytes. A preliminary structure-activity relationship analysis indicates that the 6/6/6/5 ring skeleton and the double bond between C-8 and C-9 are beneficial for the glucose-uptake-stimulating and insulin-sensitizing activities. Furthermore, the alkaline-insoluble fraction mainly containing compounds 22, 24, 28, and 31 were confirmed to have hypoglycemic and hypolipidemic activity on high-fat-diet-induced obese mice. This work confirms the potential of the peels' extracts of W. cocos as a functional food or dietary supplements.

1332-P: Complement C3 and C4 Levels Predict Cardiometabolic Risk in Healthy Adolescents

Complement, in addition to its immunologic functions, also helps regulate inflammation and fat metabolism. Thus, complement may play a role in the development of the metabolic syndrome. In adults complement component C3 is a risk factor for the development of type 2 diabetes, and a determinant of cardiometabolic risk. Adult cardiometabolic disease has its origins in childhood and adolescence. Therefore, if we are to fully understand the role of complement in cardiometabolic disease we need to study this age group. 56 healthy, non-Hispanic white adolescents (28 F, age 15.4±1.7 years; BMI 22.0±4.9 kg/m2 (mean±SD) were studied. Cardiometabolic risk factors were studied in the fasting state and included measures of vascular function [reactive hyperemia (RH), augmentation index (AI)], lipids, inflammation [white blood cell (WBC) and neutrophil (ANC) count, c-reactive protein (CRP), interleukin 6 (IL6)], carbohydrate metabolism [OGTT: insulin sensitivity (ISEN), insulin secretion (ISEC), disposition index, DI], endothelin 1 and plasminogen activator inhibitor 1 (PAI-1). RH worsened, HDL decreased and ANC, LDL, triglycerides and ISEC increased with increasing C3. RH and HDL were also negatively related to C4 while WBC, ANC, IL6 and DI were positively related to C4. Adjustment for body habitus eliminated the relationships of HDL, LDL and ISEC but not ANC or triglycerides to C3 and/or C4. Adjusted PAI-1 was significantly related to C3. Except for the positive relationship between C4 and DI these relationships demonstrate that increasing levels of C3 and C4 are associated with increasing cardiometabolic risk in healthy, non-Hispanic white adolescents. Increasing C3 levels may influence increasing triglyceride levels while increasing C4 is more closely related to increasing inflammation. Disclosure R.P. Hoffman: Other Relationship; Self; Novo Nordisk A/S. C. Yu: None. Funding American Heart Association; National Institutes of Health

Synergistic Effect of Two Major Components of Malva verticillata in the Recovery of Alloxan-Damaged Pancreatic Islet Cells in Zebrafish.

Malva verticillata (Chinese mallow) has long been used in traditional medicines and herbal teas in Asia. The n-BuOH fraction (Fr) from M. verticillata promoted significant recovery of alloxan-damaged (AXD) pancreatic islets (PIs) in zebrafish (ZF). Two major components were isolated from M. verticillata through repeated-column chromatography. Based on several spectroscopic methods, including nuclear magnetic resonance (NMR), infrared spectroscopy (IR), and fast atom bombardment-mass spectrometry (FAB-MS), the chemical structures of compounds 1 and 2 were determined. In addition, the quantity of both compounds in the n-BuOH Fr was investigated through high-performance liquid chromatography (HPLC) and the quantities of compounds 1 and 2 in the n-BuOH Fr were determined to be 5.58% ± 0.16% and 2.85% ± 0.13%, respectively. The n-BuOH Fr, compounds 1 and 2, and the mixture of compounds 1 and 2 (MX, 1 and 2, the ratio of both compounds in n-BuOH Fr, 1.96:1) were evaluated for their ability to recover AXD PIs and for their KATP channel-blocking mechanism using diazoxide in ZF. The n-BuOH Fr (10 μg/mL) and compounds 1 and MX (1 μg/mL) exhibited a recovery effect on AXD PIs. The n-BuOH Fr (10 μg/mL) and MX (1 μg/mL) were also confirmed to be useful KATP channel activators. A synergistic effect of MX in the recovery of AXD PIs was first confirmed in ZF, and it was discovered that 2 acted as an insulin sensitivity activator that increased the activity of compound 1.

Histochemistry, phenolic content, antioxidant, and anti-diabetic activities of Vernonia amygdalina leaf extract.

Vernonia amygdalina leaves were investigated for their histochemical properties and antidiabetic activities. Histochemical analysis of the leaf revealed distributions of acidic lipid, mucilage, and pectin, lipids, polyphenols, and alkaloids at the mid rib, glandular trichome, and epidermis. HPLC analysis of the leaves hot water infusion revealed the presence of quercetin and (-)-epi-catechin. The infusion had significant (p<0.05) 2,2'-diphenyl-1-picrylhydrazyl scavenging activity and ferric reducing antioxidant power. Ex vivo antioxidative analysis revealed the ability of the infusion to increase glutathione level, superoxide dismutase, and catalase activities, while concomitantly depleting malondialdehyde level and DNA fragmentation in Fe2+ -induced hepatic injury. The infusion showed significant (p<0.05) inhibitory activity against α-glucosidase and pancreatic lipase. It also inhibited intestinal glucose absorption and enhanced muscle glucose uptake, respectively. The ability of the infusion to abate oxidative stress, DNA fragmentation and stimulate muscle glucose uptake may suggest the antioxidative, anti-apoptotic, and insulin-sensitizing activity of V. amygdalina. PRACTICAL APPLICATIONS: Vernonia amygdalina (bitter leaf) is among the common leafy vegetables in West Africa reported for its various medicinal and nutritional properties. It is utilized as a food ingredient as well as supplement for the treatment and management of type 2 diabetes (T2D). Its ability to inhibit intestinal glucose absorption, enhance muscle glucose uptake, and protect against hepatic oxidative stress gives more credence to its reported antidiabetic properties. Being a common leafy vegetable, V. amygdalina can be a cheap source of nutraceutical for the treatment and management of T2D and its complications.

Chungkookjang with High Contents of Poly-γ-Glutamic Acid Improves Insulin Sensitizing Activity in Adipocytes and Neuronal Cells.

We hypothesized that soybeans fermented with Bacillus spp. for 48 h (chungkookjang) would be rich in poly-γ-glutamate (γ-PGA) and would have greater efficacy for improving insulin sensitivity and insulin secretion in 3T3-L1 adipocytes, min6 cells, and PC12 neuronal cells. We screened 20 different strains of B. subtillus and B. amyloliquefaciens spp. for γ-polyglutamate (PGA) production and their anti-diabetic and anti-dementia activities in cell-based studies. Chungkookjang made with two B. amyloliquefaciens spp. (BA730 and BA731) were selected to increase the isoflavonoid and γ-PGA. Insulin-stimulated glucose uptake was higher in 3T3-L1 adipocytes given both chungkookjang extracts than in the cells given vehicle (control). The ethanol extract of BA731 (BA731-E) increased the uptake the most. Triglyceride accumulation decreased in BA731-E and BA731-W and the accumulation increased in BA730-W and BA730-E. The mRNA expression of fatty acid synthetase and acetyl CoA carboxylase was much lower in BA731-E and BA731-W and it was higher in BA730-W than the control. BA730-E and BA730-W also increased peroxisome proliferator-activated receptor (PPAR)-γ activity. Glucose-stimulated insulin secretion increased with the high dosage of BA730-W and BA730-E in insulinoma cells, compared to the control. Insulin contents and cell survival in high glucose media were higher in cells with both BA731-E and BA730-E. Triglyceride deposition and TNF-α mRNA expression were lower in BA731 than the control. The high-dosage treatment of BA730-E and BA731-E increased differentiated neuronal cell survival after treating amyloid-β(25-35) compared to the control. Brain-derived neurotrophic factor and ciliary neurotrophic factor, indices of neuronal cell proliferation, were higher in BA730 and BA731 than in the control. Tau expression was also reduced in BA731 more than the control and it was a similar level of the normal-control. In conclusion, BA730 increased PPAR-γ activity and BA731 enhanced insulin sensitivity in the brain and periphery. BA730 and BA731 prevented and alleviated the symptoms of type 2 diabetes and Alzheimer’s disease with different pathways.

Lavatera critica controls systemic insulin resistance by ameliorating adipose tissue inflammation and oxidative stress using bioactive compounds identified by GC–MS

BackgroundLavatera critica, a leafy green herb, is reported to have many pharmacological activities; but, the improvement of insulin sensitivity against the high gram-fat diet (HGFD)-caused insulin resistance (IR) has not yet been studied. ObjectiveThis study evaluated the role of Lavatera critica leaf extract (LCE) in systemic insulin resistance through the alleviation of adipose tissue inflammation and oxidative damage in HGFD fed mice. MethodsThe mice were fed with HGFD for 10 weeks and the diet was supplemented with LCE each day for the next five weeks. Body weight, food intake, leptin, blood glucose, insulin, insulin resistance, and pro- and anti-inflammatory genes expression were assessed on day 106. ResultsThe HGFD control mice displayed markedly elevated adipose tissue inflammation, oxidative stress, insulin inactivity, and hyperglycemia. Administration of LCE in the HGFD mice, especially a dose of 100 mg/kg, lowered the body weight, food intake, plasma leptin, plasma glucose, plasma insulin, insulin resistance, and increased the food efficacy ratio when compared with the HGFD control mice. The oral glucose tolerance test (OGTT) revealed that LCE prevented further increase in the circulating levels after the glucose load. LCE-treated mice demonstrated a marked suppression of pro-inflammatory cytokines mRNA expression. On the other hand, the mice showed a higher anti-inflammatory genes mRNA expression in the adipose tissue. In addition, LCE treatment improved the oxidative damage as evidenced by the reduced levels of lipid hydroperoxides and thiobarbituric acid reactive substances coupled with the increased antioxidants (superoxide dismutase, total glutathione, glutathione/glutathione disulfide ratio and glutathione peroxidase) in the adipose tissue, plasma and erythrocytes. Gas chromatography-mass spectrometry analysis of the bioactive compounds revealed the presence of 9, 12, 15-octadecatrienoic acid, vitamin E, phytol, hexadecanoic acid, benzenepropanoic acid, and stigmasterol. ConclusionsThese findings prove that LCE improves the insulin-sensitizing activity in the mouse model of HGFD-caused IR, probably due to the amelioration of adipose tissue inflammation and oxidative damage. Hence, the LCE could serve as a useful anti-diabetic agent.

Sufficient NADPH supply and pknG deletion improve 4-hydroxyisoleucine production in recombinant Corynebacterium glutamicum

Cofactor engineering is a common strategy to improve amino acid production. 4-hydroxyisoleucine (4-HIL), a nonproteinogenic amino acid, exhibits unique insulinotropic and insulin-sensitizing activities, therefore has potential medical value in treating diabetes. In our previous study, l-isoleucine (Ile) dioxygenase gene ido was overexpressed in an Ile-producing Corynebacterium glutamicum strain, and 4-HIL was de novo synthesized from glucose. In this study, to increase the NADPH supply, the endogenous NAD+ kinase gene ppnK and glucose-6-phosphate dehydrogenase gene zwf were co-expressed with ido. The resulting strain SL01 produced 81.12 ± 5.96 mM 4-HIL, 62% higher than the ido-mere expressing strain SN02. However, the strain SL02 co-expressing exogenous NADH kinase gene POS5 with ido grew slowly and its 4-HIL production decreased by 12%, perhaps due to the lower 2-oxoglutarate (OG) level and slightly weaker membrane permeability. To increase OG availability for 4-HIL conversion, the serine/threonine protein kinase G gene pknG was deleted and replaced by ido gene in SL02. The growth of the resulting strain SL04 was restored and 4-HIL production was improved to 84.14 ± 6.38 mM; meanwhile, the conversion ratio of Ile to 4-HIL reached up to 0.98 ± 0.01 mol/mol. Therefore, sufficient NADPH supply and OG availability may be benefit to 4-HIL de novo biosynthesis in recombinant C. glutamicum.

Chlorogenic acid alleviates autophagy and insulin resistance by suppressing JNK pathway in a rat model of nonalcoholic fatty liver disease

Non-alcoholic fatty liver disease (NAFLD) is one of the leading causes of chronic liver diseases around the world and commonly associated with insulin resistance and hyperlipidemia. Chlorogenic acid (CG) was reported to have insulinsensitizing activity and exert hypocholesterolemic and hypoglycemic effect. However, the involvement of CG in NAFLD remains far from being addressed. In this study, a high-fat diet-induced NAFLD rat model was used to investigate the biological roles and underlying mechanism of CG in NAFLD. The results showed that high-fat diet-fed rats exhibited an increase in body weight, glucose tolerance, liver injury, insulin resistance, as well as autophagy and C-Jun N-terminal kinase (JNK) pathway. Nevertheless, all these effects were alleviated by CG treatment. Moreover, angiotensin treatment in CG group activated the JNK pathway, and promoted autophagy, insulin resistance, and liver injury. In conclusion, our findings demonstrated that CG ameliorated liver injury and insulin resistance by suppressing autophagy via inactivation of JNK pathway in a rat model of NAFLD. Therefore, CG might be a potential application for the treatment of NAFLD.

Baicalein improves insulin resistance via regulating SOCS3 and enhances the effect of acarbose on diabetes prevention

Baicalein, a major component in Scutellaria baicalensis and Oroxylum indicum, is used as dietary supplement in Asia. In this study, we characterized the insulin-sensitizing activity of baicalein and found that baicalein improved insulin resistance by reducing the expression of SOCS3, increasing the phosphorylation of IRS1 and Akt1, reducing the phosphorylation of GSK3β and increasing hepatic glycogen level. We further evaluated the preventive effect of baicalein combined with acarbose in mice, aiming to enhance the therapeutic effect and reduce the side-effects of acarbose. The combination reduced the relative risk of progression from prediabetes to diabetes by 83.3% and the dose of acarbose by 80%. The underlying mechanisms include reducing postprandial hyperglycemia, improving insulin resistance, improving lipid metabolism, and reducing oxidative stress. Our results suggest that the consumption of 195–780mg/d baicalein might improve the efficacy of acarbose on diabetes prevention and reduce the side-effects of acarbose in long-term acarbose users.