Matrine counteracts obesity in mice via inducing adipose thermogenesis by activating HSF1/PGC-1α axis.

Promoting energy expenditure is known to curb obesity and can be exploited for its treatment. Our previous study has demonstrated that activation of HSF1/PGC-1α axis efficiently induced mitochondrial biogenesis and adaptive oxidation and thus ameliorating lipid accumulation, however, whether it can be a therapeutic approach for metabolic disorders treatment needs explored. Here, a high-efficient and specific HSF1/PGC-1α activator screening system was established and the natural clinical liver-protecting agent matrine was identified as a robust HSF1/PGC-1α activator. Matrine treatment efficiently induced mitogenesis and thermogenic program in primary mouse adipose stem cell derived adipocytes by enriching HSF1 to the promoter of Pgc-1α. Deficiency of PGC-1α in adipocytes diminished the browning induction ability of matrine. Oral administration of matrine to the obese mice induced by high fat and high cholesterol diet increased energy expenditure and corrected the degeneration of thermogenesis in brown adipose tissue (BAT). Also, matrine treatment markedly induced the transformation of brown-like adipocytes in subcutaneous white adipose tissue (sWAT) via a mechanism of HSF1/PGC-1α, thereby attenuating obesity and myriads of metabolic disorders. This led to an improvement in adaptive thermogenesis to cold stimuli. These findings are of great significance in understanding the regulation mechanisms of the HSF1/PGC-1α axis in thermogenesis and providing a novel therapeutic approach for obesity treatment. Matrine may have potential therapeutic implications for the treatment of obesity in clinics.

Role of the mTOR-autophagy-ER stress pathway in high fructose-induced metabolic-associated fatty liver disease.

Metabolic-associated fatty liver disease (MAFLD) is the most common metabolic disease with a global prevalence of 25%. While MAFLD is serious and incurable at the later stage, it can be controlled or reversed at the early stage of hepatosteatosis originating from unhealthy diets. Recent laboratory evidence implicates a critical role of the mammalian target of rapamycin (mTOR)-autophagy signaling pathway in the pathogenesis of MAFLD induced by a high-fructose diet mimicking the overconsumption of sugar in humans. This review discusses the possible molecular mechanisms of mTOR-autophagy-endoplasmic reticulum (ER) stress in MAFLD. Based on careful analysis of recent studies, we suggest possible new therapeutic concepts or targets that can be explored for the discovery of new anti-MAFLD drugs.

Exposure to cigarette smoke precipitates simple hepatosteatosis to NASH in high-fat diet fed mice by inducing oxidative stress.

Consumption of diet rich in fat and cigarette smoking (CS) are independent risk factors of non-alcoholic steatohepatitis (NASH), and they often occur together in some populations. The present study investigated the mechanisms of high-fat diet (HFD) and CS, individually and in combination, on the pathogenesis of NASH in mice. C57BL/6 male mice were subjected to either a low-fat chow (CH) or HFD with or without mainstream CS-exposure (4 cigarettes/day, 5 days/ week for 14 weeks). HFD alone caused hepatosteatosis (2.5-fold increase in TG content) and a significant increase in 3-nitrotyrisine (by ∼40-fold) but without an indication of liver injury, inflammation or fibrosis. CS alone in CH-fed mice increased in Tnfα expression and macrophage infiltration by 2-fold and relatively less increase in 3-nitrotyrosine (18-fold). Combination of HFD and CS precipitated hepatosteatosis to NASH reflected by exacerbated makers of liver inflammation and fibrosis which were associated with much severe liver oxidative stress (90-fold increase in 3-nitrotyrisine along with 6-fold increase in carbonylated proteins and 56% increase in lipid oxidations). Further studies were performed to administer the antioxidant tempol to CS exposed HFD mice and the results showed that the inhibition of liver oxidative stress prevented inflammatory and fibrotic changes in liver despite persisting hepatosteatosis. Our findings suggest that oxidative stress is a key mechanism underlying CS-promoted progression of simple hepatosteatosis to NASH. Targeting hepatic oxidative stress may be a viable strategy in halting the progression of metabolic associated fatty liver disease.

Cigarette smoking blocks the benefit from reduced weight gain for insulin action by shifting lipids deposition to muscle.

Cigarette smoking (CS) is known to reduce body weight and this often masks its real effect on insulin action. The present study tested the hypothesis that CS can divert lipid deposition to muscles to offset the supposed benefit of reduced body weight gain on insulin signalling in this major site for glucose tolerance (or insulin action). The study was conducted in mice exposed to chronic CS followed by either a chow (CH) diet or a high-fat (HF) diet. CS increased triglyceride (TG) levels in both plasma and muscle despite a reduced body weight gain and adiposity. CS led to glucose intolerance in CH-fed mice and they retained the glucose intolerance that was induced by the HF diet. In adipose tissue, CS increased macrophage infiltration and the mRNA expression of TNFα but suppressed the protein expression of adipose triglyceride lipase and PPARγ. While CS increased hormone-sensitive lipase and suppressed the mRNA expression of leptin, these effects were blunted in HF-fed mice. These results imply that CS impairs insulin signalling in skeletal muscle via accumulated intramuscular lipids from lipolysis and lipodystrophy of adipose tissues. This may explain why smokers may not benefit from insulin sensitising effects of reduced body weight gain.

Matrine reduces cigarette smoke-induced airway neutrophilic inflammation by enhancing neutrophil apoptosis.

Chronic Obstructive Pulmonary Disease (COPD) is a major incurable global health burden and will become the third largest cause of death in the world by 2030. It is well established that an exaggerated inflammatory and oxidative stress response to cigarette smoke (CS) leads to, emphysema, small airway fibrosis, mucus hypersecretion, and progressive airflow limitation. Current treatments have limited efficacy in inhibiting chronic inflammation and consequently do not reverse the pathology that initiates and drives the long-term progression of disease. In particular, there are no effective therapeutics that target neutrophilic inflammation in COPD, which is known to cause tissue damage by degranulation of a suite of proteolytic enzymes including neutrophil elastase (NE). Matrine, an alkaloid compound extracted from Sophora flavescens Ait, has well known anti-inflammatory activity. Therefore, the aim of the present study was to investigate whether matrine could inhibit CS-induced lung inflammation in mice. Matrine significantly reduced CS-induced bronchoalveolar lavage fluid (BALF) neutrophilia and NE activity in mice. The reduction in BALF neutrophils in CS-exposed mice by matrine was not due to reductions in pro-neutrophil cytokines/chemokines, but rather matrine's ability to cause apoptosis of neutrophils, which we demonstrated ex vivo Thus, our data suggest that matrine has anti-inflammatory actions that could be of therapeutic potential in treating CS-induced lung inflammation observed in COPD.

Small molecule IVQ, as a prodrug of gluconeogenesis inhibitor QVO, efficiently ameliorates glucose homeostasis in type 2 diabetic mice.

Gluconeogenesis is a major source of hyperglycemia in patients with type 2 diabetes mellitus (T2DM), thus targeting gluconeogenesis to suppress glucose production is a promising strategy for anti-T2DM drug discovery. In our preliminary in vitro studies, we found that a small-molecule (E)-3-(2-(quinoline-4-yl)vinyl)-1H-indol-6-ol (QVO) inhibited the hepatic glucose production (HGP) in primary hepatocytes. We further revealed that QVO suppressed hepatic gluconeogenesis involving calmodulin-dependent protein kinase kinase ß- and liver kinase B1-adenosine monophosphate-activated protein kinase (AMPK) pathways as well as AMPK-independent mitochondrial function-related signaling pathway. To evaluate QVO's anti-T2DM activity in vivo, which was impeded by the complicated synthesis route of QVO with a low yield, we designed and synthesized 4-[2-(1H-indol-3-yl)vinyl]quinoline (IVQ) as a prodrug with easier synthesis route and higher yield. IVQ did not inhibit the HGP in primary hepatocytes in vitro. Pharmacokinetic studies demonstrated that IVQ was quickly converted to QVO in mice and rats following administration. In both db/db and ob/ob mice, oral administration of IVQ hydrochloride (IVQ-HCl) (23 and 46 mg/kg every day, for 5 weeks) ameliorated hyperglycemia, and suppressed hepatic gluconeogenesis and activated AMPK signaling pathway in the liver tissues. Furthermore, IVQ caused neither cardiovascular system dysfunction nor genotoxicity. The good druggability of IVQ has highlighted its potential in the treatment of T2DM and the prodrug design for anti-T2DM drug development.

Nitazoxanide, an anti-parasitic drug, efficiently ameliorates learning and memory impairments in AD model mice.

The pathogenesis of Alzheimer's disease (AD) is characterized by both accumulation of ß-amyloid (Aß) plaque and formation of neurofibrillary tangles in the brain. Recent evidence shows that autophagy activation may potently promote intracellular Aß clearance. Thus targeting autophagy becomes a promising strategy for discovery of drug leads against AD. In the present study, we established a platform to discover autophagy stimulator and screened the lab in-house FDA-approved drug library. We found that anti-parasitic drug nitazoxanide (NTZ) was an autophagy activator and could efficiently improve learning and memory impairments in APP/PS1 transgenic mice. In BV2 cells and primary cortical astrocytes, NTZ stimulated autophagy and promoted Aß clearance by inhibiting both PI3K/AKT/mTOR/ULK1 and NQO1/mTOR/ULK1 signaling pathways; NTZ treatment attenuated LPS-induced inflammation by inhibiting PI3K/AKT/IκB/NFκB signaling. In SH-SY5Y cells and primary cortical neurons, NTZ treatment restrained tau hyperphosphorylation through inhibition of PI3K/AKT/GSK3ß pathway. The beneficial effects and related signaling mechanisms from the in vitro studies were also observed in APP/PS1 transgenic mice following administration of NTZ (90 mg·kg-1·d-1, ig) for 100 days. Furthermore, NTZ administration decreased Aß level and senile plaque formation in the hippocampus and cerebral cortex of APP/PS1 transgenic mice, and improved learning and memory impairments in Morris water maze assay. In conclusion, our results highlight the potential of NTZ in the treatment of AD.

Repurposing matrine for the treatment of hepatosteatosis and associated disorders in glucose homeostasis in mice.

The present study investigated the efficacy of the hepatoprotective drug matrine (Mtr) for its new application for hepatosteatosis and associated disorders in glucose homeostasis. The study was performed in two nutritional models of hepatosteatosis in mice with various abnormal glucose homeostasis: (1) high-fructose diet (HFru) induced hepatosteatosis and glucose intolerance from hepatic, and (2) hepatosteatosis and hyperglycemia induced by high-fat (HF) diet in combination with low doses of streptozotocin (STZ). Administration of Mtr (100 mg/kg every day in diet for 4 weeks) abolished HFru-induced hepatosteatosis and glucose intolerance. These effects were associated with the inhibition of HFru-stimulated de novo lipogenesis (DNL) without altering hepatic fatty acid oxidation. Further investigation revealed that HFru-induced endoplasmic reticulum (ER) stress was inhibited, whereas heat-shock protein 72 (an inducible chaperon protein) was increased by Mtr. In a type 2 diabetic model induced by HF-STZ, Mtr reduced hepatosteatosis and improved attenuated hyperglycemia. The hepatoprotective drug Mtr may be repurposed for the treatment of hepatosteatosis and associated disorders in glucose homeostasis. The inhibition of ER stress associated DNL and fatty acid influx appears to play an important role in these metabolic effects.

Endoplasmic reticulum stress up-regulates Nedd4-2 to induce autophagy.

The accumulation of unfolded proteins within the endoplasmic reticulum (ER) causes ER stress and activation of unfolded protein response (UPR). This response can trigger ER-associated degradation and autophagy, which clear unfolded proteins and restore protein homeostasis. Recently, it has become clear that ubiquitination plays an important role in the regulation of autophagy. In the present study, we investigated how the E3 ubiquitin ligase neural precursor cell-expressed, developmentally down-regulated protein 4-2 (Nedd4-2) interacts with ER stress and autophagy. In mice, we found that an increase in the expression of Nedd4-2, which was concomitant with the activation of the UPR and autophagy, was caused by a prolonged high-fructose and high-fat diet that induces ER stress in the liver. Pharmacologic induction of ER stress also led to an increase in Nedd4-2 expression in cultured cells, which was coincident with UPR and autophagy activation. The inhibition of inositol-requiring enzyme 1 significantly suppressed Nedd4-2 expression. Moreover, increased Nedd4-2 expression in vivo was closely associated with the activation of inositol-requiring enzyme 1 and increased expression of the spliced form of X-box binding protein 1. Furthermore, knockdown of Nedd4-2 in cultured cells suppressed both basal autophagy and ER stress-induced autophagy, whereas overexpression of Nedd4-2-induced autophagy. Taken together, our findings provide evidence that Nedd4-2 is up-regulated in response to ER stress by the spliced form of X-box binding protein 1 and that this is important in the induction of an appropriate autophagic response.-Wang, H. Sun, R.-Q., Camera, D., Zeng, X.-Y., Jo, E., Chan, S. M. H., Herbert, T. P., Molero, J. C., Ye, J.-M. Endoplasmic reticulum stress up-regulates Nedd4-2 to induce autophagy.

IRE1 impairs insulin signaling transduction of fructose-fed mice via JNK independent of excess lipid.

The unfolded protein response (UPR) pathways have been implicated in the development of hepatic insulin resistance during high fructose (HFru) feeding. The present study investigated their roles in initiating impaired insulin signaling transduction in the liver induced by HFru feeding in mice. HFru feeding resulted in hepatic steatosis, increased de novo lipogenesis and activation of two arms of the UPR pathways (IRE1/XBP1 and PERK/eIF2α) in similar patterns from 3days to 8weeks. In order to identify the earliest trigger of impaired insulin signaling in the liver, we fed mice a HFru diet for one day and revealed that only the IRE1 branch was activated (by 2-fold) and insulin-mediated Akt phosphorylation was blunted (~25%) in the liver. There were significant increases in phosphorylation of JNK (~50%) and IRS at serine site (~50%), protein content of ACC and FAS (up to 2.5-fold) and triglyceride level (2-fold) in liver (but not in muscle or fat). Blocking IRE1 activity abolished increases in JNK activity, IRS serine phosphorylation and protected insulin-stimulated Akt phosphorylation without altering hepatic steatosis or PKCε activity, a key link between lipids and insulin resistance. Our findings together suggest that activation of IRE1-JNK pathway is a key linker of impaired hepatic insulin signaling transduction induced by HFru feeding.

Fenofibrate insulates diacylglycerol in lipid droplet/ER and preserves insulin signaling transduction in the liver of high fat fed mice.

Hepatic steatosis is often associated with insulin resistance as a hallmark of the metabolic syndrome in the liver. The present study investigated the effects of PPARα activation induced by fenofibrate (FB) on the relationship of insulin resistance and hepatic steatosis in mice fed a high-fat (HF) diet, which increases lipid influx into the liver. Mice were fed HF diet to induce insulin resistance and hepatic steatosis with or without FB. FB activated PPARα and ameliorated HF diet-induced glucose intolerance and hepatic insulin resistance without altering either hepatic steatosis or inflammation signaling (JNK or IKK). Interestingly, FB treatment simultaneously increased fatty acid (FA) synthesis (50%) and oxidation (66%, both p<0.01) into intermediate lipid metabolites, suggesting a FA oxidation-synthesis cycling in operation. Associated with these effects, diacylglycerols (DAGs) were sequestered within the lipid droplet/ER compartment, thus reducing their deposition in the cellular membrane, which is known to impair insulin signal transduction. These findings suggest that the reduction in membrane DAGs (rather than total hepatic steatosis) may be critical for the protection by fenofibrate-induced PPARα activation against hepatic insulin resistance induced by dietary fat.

Liver glycogen in type 2 diabetic mice is randomly branched as enlarged aggregates with blunted glucose release.

Glycogen is a vital highly branched polymer of glucose that is essential for blood glucose homeostasis. In this article, the structure of liver glycogen from mice is investigated with respect to size distributions, degradation kinetics, and branching structure, complemented by a comparison of normal and diabetic liver glycogen. This is done to screen for differences that may result from disease. Glycogen α-particle (diameter ∼ 150 nm) and ß-particle (diameter ∼ 25 nm) size distributions are reported, along with in vitro γ-amylase degradation experiments, and a small angle X-ray scattering analysis of mouse ß-particles. Type 2 diabetic liver glycogen upon extraction was found to be present as large loosely bound, aggregates, not present in normal livers. Liver glycogen was found to aggregate in vitro over a period of 20 h, and particle size is shown to be related to rate of glucose release, allowing a structure-function relationship to be inferred for the tissue specific distribution of particle types. Application of branching theories to small angle X-ray scattering data for mouse ß-particles revealed these particles to be randomly branched polymers, not fractal polymers. Together, this article shows that type 2 diabetic liver glycogen is present as large aggregates in mice, which may contribute to the inflexibility of interconversion between glucose and glycogen in type 2 diabetes, and further that glycogen particles are randomly branched with a size that is related to the rate of glucose release.

Discovery of natural alkaloid bouchardatine as a novel inhibitor of adipogenesis/lipogenesis in 3T3-L1 adipocytes.

Bouchardatine (1), a naturally occurring ß-indoloquinazoline alkaloid, was synthesized. For the first time, the lipid-lowering effect and mechanism of 1 was investigated in 3T3-L1 adipocytes. Our study showed that 1 could significantly reduce lipid accumulation without cytotoxicity and mainly inhibited early differentiation of adipocyte through proliferation inhibition and cell cycle arrested in dose-dependent manner. Furthermore, the inhibition of early differentiation was reflected by down-regulation of key regulators of adipogenesis/lipogenesis, including CCAAT enhancer binding proteins (C/EBPß, C/EBPδ, C/EBPα), peroxisome proliferator-activated receptors γ (PPARγ) and sterol-regulatory element binding protein-1c (SREBP-1c), in both of mRNA and protein levels. Subsequently decreasing the protein levels of acetyl CoA carboxylase (ACC), fatty acid synthase (FAS), and stearyl coenzyme A desaturated enzyme 1 (SCD-1), the rate-limited metabolic enzymes of fatty acid synthesis, were also observed. Further studies revealed that 1 persistently activated adenosine 5'-monophosphate (AMP)-activated protein kinase (AMPK) during differentiation, suggesting that the AMPK may be an upstream mechanism for the effect of 1 on adipogenesis and lipogenesis. Our data suggest that 1 can be a candidate for the development of new therapeutic drugs against obesity and related metabolic disorders.

Strategies for the discovery and development of anti-diabetic drugs from the natural products of traditional medicines.

This review discusses issues largely from the biological point of view about the targeted approaches for the use of natural products for the discovery of anti-diabetic drugs in collaboration with medicinal chemists and computer-aided drug design. A major thrust of this review reflects the collaborative research of four institutions: RMIT University (Australia), Garvan Institute of Medical Research (Australia), Shanghai Institute of Materia Medica of the Chinese Academy of Science (China) and Sun-Yat Sen University (China) in the past eight years. By joining forces of biomedical research in diabetes and medicinal chemistry with a focus on traditional medicine, they are trying to bridge the West (the latest research discoveries in biomedical research) with the East (traditional medicine) to step forward in drug discovery from natural products.

Arctigenin alleviates ER stress via activating AMPK.

AIM: To investigate the protective effects of arctigenin (ATG), a phenylpropanoid dibenzylbutyrolactone lignan from Arctium lappa L (Compositae), against ER stress in vitro and the underlying mechanisms. METHODS: A cell-based screening assay for ER stress regulators was established. Cell viability was measured using MTT assay. PCR and Western blotting were used to analyze gene and protein expression. Silencing of the CaMKKß, LKB1, and AMPKα1 genes was achieved by RNA interference (RNAi). An ATP bioluminescent assay kit was employed to measure the intracellular ATP levels. RESULTS: ATG (2.5, 5 and 10 µmol/L) inhibited cell death and unfolded protein response (UPR) in a concentration-dependent manner in cells treated with the ER stress inducer brefeldin A (100 nmol/L). ATG (1, 5 and 10 µmol/L) significantly attenuated protein synthesis in cells through inhibiting mTOR-p70S6K signaling and eEF2 activity, which were partially reversed by silencing AMPKα1 with RNAi. ATG (1-50 µmol/L) reduced intracellular ATP level and activated AMPK through inhibiting complex I-mediated respiration. Pretreatment of cells with the AMPK inhibitor compound C (25 µmol/L) rescued the inhibitory effects of ATG on ER stress. Furthermore, ATG (2.5 and 5 µmol/L) efficiently activated AMPK and reduced the ER stress and cell death induced by palmitate (2 mmol/L) in INS-1 ß cells. CONCLUSION: ATG is an effective ER stress alleviator, which protects cells against ER stress through activating AMPK, thus attenuating protein translation and reducing ER load.

A novel HSF1 activator ameliorates non-alcoholic steatohepatitis by stimulating mitochondrial adaptive oxidation.

BACKGROUND AND PURPOSE: Non-alcoholic steatohepatitis (NASH) is the more severe form of metabolic associated fatty liver disease (MAFLD) and no pharmacological treatment as yet been approved. Identification of novel therapeutic targets and their agents is critical to overcome the current inadequacy of drug treatment for NASH. EXPERIMENTAL APPROACH: The correlation between heat shock factor 1 (HSF1) levels and the development of NASH and the target genes of HSF1 in hepatocyte were investigated by chromatin-immunoprecipitation sequencing. The effects and mechanisms of SYSU-3d in alleviating NASH were examined in relevant cell models and mouse models (the Ob/Ob mice, high-fat and high-cholesterol diet and the methionine-choline deficient diet-fed mice). The actions of SYSU-3d in vivo were evaluated. KEY RESULTS: HSF1 is progressively reduced with mitochondrial dysfunction in NASH pathogenesis and activation of this transcription factor by its newly identified activator SYSU-3d effectively inhibited all manifestations of NASH in mice. When activated, the phosphorylated HSF1 (Ser326) translocated to nucleus and bound to the promoter of PPARγ coactivator-1α (PGC-1α) to induce mitochondrial biogenesis. Thus, increasing mitochondrial adaptive oxidation and inhibiting oxidative stress. The deletion of HSF1 and PGC-1α or recovery of HSF1 in HSF1-deficiency cells showed the HSF1/PGC-1α pathway was mainly responsible for the anti-NASH effects of SYSU-3d independent of AMP-activated protein kinase (AMPK). CONCLUSION AND IMPLICATIONS: Activation of HSF1 is a practical therapeutic approach for NASH treatment via the HSF1/PGC-1α/mitochondrial pathway and SYSU-3d can be considered as a potential candidate for the treatment of NASH.

Involvement of the Autophagy-ER Stress Axis in High Fat/Carbohydrate Diet-Induced Nonalcoholic Fatty Liver Disease.

Nonalcoholic fatty liver disease (NAFLD) is the most common chronic liver disease that can progress from simple hepatic steatosis to nonalcoholic steatohepatitis (NASH), and even further to liver cirrhosis or liver cancer. Overconsumption of high fat and/or carbohydrate are among the most common lifestyle factors that drive the development and progression of NAFLD. This review evaluates recent reports on the involvement of autophagy and endoplasmic reticulum (ER) stress in the pathogenesis of NAFLD. Here, we reveal a mechanism of an intrinsically linked axis of impaired autophagy and unresolved ER stress that mediates the development and progression of NAFLD resulting from the overconsumption of high fat and/or carbohydrate.

Discovery of a promising agent IQZ23 for the treatment of obesity and related metabolic disorders.

Discovery of novel anti-obesity agents is a challenging and promising research area. Based on our previous works, we synthesized 40 novel ß-indoloquinazoline analogues by altering the skeleton and introducing preferential side chains, evaluated their lipid-lowering activity and summarized the structure-activity relationships. In combination with an evaluation of the lipid-lowering efficacies, AMP-dependent activated protein kinase (AMPK) activating ability and liver microsomal stability, compound 23 (named as IQZ23) was selected for further studies. IQZ23 exerted a high efficacy in decreasing the triglyceride level (EC50 = 0.033 µM) in 3T3-L1 adipocytes. Mechanistic studies revealed the lipid-lowering activity of IQZ23 was dependent on the AMPK pathway by modulating ATP synthase activity. This activation was accompanied by mitochondrial biogenesis and oxidation capacity increased, and insulin sensitivity enhanced in pertinent cell models by various interventions. Correspondingly, IQZ23 (20 mg/kg, i.p.) treatment significantly reversed high fat and cholesterol diet (HFC)- induced body weight increases and accompanying clinical symptoms of obesity in mice but without indicative toxicity. These results indicate that IQZ23 could be a useful candidate for the treatment of obesity and related metabolic disorders.

Antidiabetic activities of triterpenoids isolated from bitter melon associated with activation of the AMPK pathway.

Four cucurbitane glycosides, momordicosides Q, R, S, and T, and stereochemistry-established karaviloside XI, were isolated from the vegetable bitter melon (Momordica charantia). These compounds and their aglycones exhibited a number of biologic effects beneficial to diabetes and obesity. In both L6 myotubes and 3T3-L1 adipocytes, they stimulated GLUT4 translocation to the cell membrane--an essential step for inducible glucose entry into cells. This was associated with increased activity of AMP-activated protein kinase (AMPK), a key pathway mediating glucose uptake and fatty acid oxidation. Furthermore, momordicoside(s) enhanced fatty acid oxidation and glucose disposal during glucose tolerance tests in both insulin-sensitive and insulin-resistant mice. These findings indicate that cucurbitane triterpenoids, the characteristic constituents of M. charantia, may provide leads as a class of therapeutics for diabetes and obesity.

Characterization of the Therapeutic Profile of Albiflorin for the Metabolic Syndrome.

Albiflorin (AF) is a small molecule (MW 481) isolated from Paeoniae radix, a plant used as a remedy for various conditions with pathogenesis shared by metabolic diseases. Reported here is our characterization of its therapeutic profiles in three mouse models with distinctive pathological features of metabolic syndrome (MetS). Our results firstly showed that AF alleviated high fat (HF) induced obesity and associated glucose intolerance, suggesting its therapeutic efficacy for MetS. In the type 2 diabetes (T2D) model induced by a combination of HF and low doses of streptozotocin, AF lowered hyperglycaemia and improved insulin-stimulated glucose disposal. In the non-alcoholic steatohepatitis-like model resulting from a HF and high cholesterol (HF-HC) diet, AF reversed the increased liver triglyceride and cholesterol, plasma aspartate aminotransferase, and liver TNFα mRNA levels. Consistent with its effect in promoting glucose disposal in HF-fed mice, AF stimulated glucose uptake and GLUT4 translocation to the plasma membrane in L6 myotubes. However, these effects were unlikely to be associated with activation of insulin, AMPK, ER, or cellular stress signalling cascades. Further studies revealed that AF increased the whole-body energy expenditure and physical activity. Taken together, our findings indicate that AF exerts a therapeutic potential for MetS and related diseases possibly by promoting physical activity associated whole-body energy expenditure and glucose uptake in muscle. These effects are possibly mediated by a new mechanism distinct from other therapeutics derived from Chinese medicine.