Ursolic acid and rosiglitazone combination alleviates metabolic syndrome in high fat diet fed C57BL/6J mice

The effects of ursolic acid on cardiometabolic risk factors: a systematic review and meta-analysis

Aim: Ursolic acid (UA) has an important biological role in the fight against fat accumulation, insulin resistance, obesity and inflammation. Therefore, in the current review and meta-analysis work, we investigate the effects of UA (dosage range is 50.94 to 450 mg/day) on cardiometabolic risk factors. Materials & methods: After searching the studies up to February 2023, six articles were included in the study. Results: The pooled effect size showed that UA supplementation didn't significantly change body weight, body mass index, waist circumference, body fat percentage, lean body mass, systolic blood pressure, diastolic blood pressure, fasting blood glucose, insulin, triglyceride and high-density lipoprotein compared with control groups. Conclusion: UA supplementation had no significant effect on the cardiometabolic risk factors in adults.

Biochanin A, a soy isoflavone, diminishes insulin resistance by modulating insulin-signalling pathway in high-fat diet-induced diabetic mice

AIM

The objective of this study was to evaluate the probable mechanism of action of Biochanin A (BCA) on high-fat diet-induced insulin resistance mice.

METHODS

Twenty-four male C57/BL/6J mice were divided into two and fed either control diet or a high fat-high diet (HFD). After 6 weeks, mice were grouped into: Control, Control + BCA, HFD and HFD + BCA (n = 6). Mice were made diabetic by feeding them an HFD.

RESULTS

Body weight, plasma glucose, insulin, leptin levels and HOMA values were significantly lower in the BCA supplemented HFD group when related to the HFD group. Furthermore, BCA supplementation significantly increased Insulin receptor substrate 1 (IRS 1), PI3K, Akt and Glucose transporter type 4 (GLUT-4) protein abundance in skeletal muscle when equated with HFD.

CONCLUSION

This study demonstrates that BCA can improve insulin sensitivity by activating insulin signalling, suggesting that it may possess antidiabetic activities.

AMPK-Regulated Autophagy Contributes to Ursolic Acid Supplementation-Alleviated Hepatic Steatosis and Liver Injury in Chronic Alcohol-Fed Mice

Alcoholic liver disease (ALD) is a chronic liver disease caused by long-term heavy consumption of alcohol. The pathogenesis of ALD is complex, and there is no effective clinical treatment at present. Ursolic acid (UA), a general triterpenoid with multiple biological roles, is widely distributed in plants. This study aims to explore the therapeutic effect and potential mechanisms of UA that protect against liver injury and hepatic steatosis in an ALD mouse model. In this study, we analyzed the lipid accumulation and the effect of UA treatment in a mouse model of ALD; AML12 and HepG2 cells were used to study the biological effect and potential mechanisms of UA on ethanol-induced hepatotoxicity. The morphologic and histological detections showed that UA significantly reduced alcohol-induced liver injury and hepatic steatosis. In addition, UA dramatically ameliorated alcohol-induced metabolic disorders, oxidative stress, and inflammation. Furthermore, UA treatment activated autophagy via the AMPK-ACC pathway to protect hepatocytes from lipotoxicity. Thus, these findings demonstrate that UA treatment alleviates alcoholic-induced liver injury by activating autophagy through the AMPK-ACC pathway. Therefore, UA may represent a promising candidate for the treatment of ALD.

The protective effects of Aster yomena (Kitam.) Honda on high-fat diet-induced obese C57BL/6J mice

BACKGROUND/OBJECTIVES

Aster yomena (Kitam.) Honda (AY) has remarkable bioactivities, such as antioxidant, anti-inflammation, and anti-cancer activities. On the other hand, the effects of AY against obesity-induced insulin resistance have not been reported. Therefore, this study examined the potential of AY against obesity-associated insulin resistance in high-fat diet (HFD)-fed mice.

MATERIALS/METHODS

An obesity model was established by feeding C57BL/6J mice a 60% HFD for 16 weeks. The C57BL6/When ethyl acetate fraction from AY (EFAY) at doses of 100 and 200 mg/kg/day was administered orally to mice fed a HFD for the last 4 weeks. Normal and control groups were administered water orally. The body weight and fasting blood glucose were measured every week. Dietary intake was measured every other day. After dissection, blood and tissues were collected from the mice.

RESULTS

The administration of EFAY reduced body and organ weights significantly compared to HFD-fed control mice. The EFAY-administered groups also improved the serum lipid profile by decreasing the triglyceride, total cholesterol, and low-density lipoprotein compared to the control group. In addition, EFAY ameliorated the insulin resistance-related metabolic dysfunctions, including the fasting blood glucose and serum insulin level, compared to the HFD-fed control mice. The EFAY inhibited lipid synthesis and insulin resistance by down-regulation of hepatic fatty acid synthase and up-regulation of the AMP-activated protein kinase pathway. EFAY also reduced lipid peroxidation in the liver, indicating that EFAY protected hepatic injury induced by obesity.

CONCLUSIONS

These results suggest that EFAY improved obesity-associated insulin resistance by regulating the lipid and glucose metabolism, suggesting that AY could be used as a functional food to prevent obesity and insulin resistance.

Ursolic Acid and Related Analogues: Triterpenoids with Broad Health Benefits

Ursolic acid (UA) is a well-studied natural pentacyclic triterpenoid found in herbs, fruit and a number of traditional Chinese medicinal plants. UA has a broad range of biological activities and numerous potential health benefits. In this review, we summarize the current data on the bioavailability and pharmacokinetics of UA and review the literature on the biological activities of UA and its closest analogues in the context of inflammation, metabolic diseases, including liver and kidney diseases, obesity and diabetes, cardiovascular diseases, cancer, and neurological disorders. We end with a brief overview of UA’s main analogues with a special focus on a newly discovered naturally occurring analogue with intriguing biological properties and potential health benefits, 23-hydroxy ursolic acid.

Administration of ursolic acid to new-born pups prevents dietary fructose-induced non-alcoholic fatty liver disease in Sprague Dawley rats

Overconsumption of fructose time dependently induces the development of non-alcoholic fatty liver disease (NAFLD). We investigated whether ursolic acid (UA) intake by new-born rats would protect against fructose-induced NAFLD. One hundred and seven male and female Sprague Dawley rat pups were randomly grouped and gavaged (10 ml/kg body weight) with either 0.5% dimethylsulphoxide (vehicle control), 0.05% UA, 50% fructose mixed with UA (0.05%) or 50% fructose alone, from postnatal day 6 (P6) to P20. Post-weaning (P21-P69), the rats received normal rat chow (NRC) and water to drink. On P70, the rats in each group were continued on water or 20% fructose to drink, as a secondary high fructose diet during adulthood. After 8 weeks, body mass, food and fluid intake, circulating metabolites, visceral adiposity, surrogate markers of liver function and indices of NAFLD were determined. Food intake was reduced as a result of fructose feeding in both male and female rats (p < 0.0001). Fructose consumption in adulthood significantly increased fluid intake and visceral adiposity in female rats (p < 0.05) and had no apparent effects in male rats (p > 0.05). In both sexes of rats, fructose had no significant (p > 0.05) effects on body mass, circulating metabolites, total calorie intake and surrogate markers of hepatic function. Fructose consumption in both early life and adulthood in female rats promoted hepatic lipid accumulation (p < 0.001), hypertrophy, microvesicular and macrovesicular steatosis (p < 0.05). Early-life UA intake significantly (p < 0.001) reduced fructose-induced hepatic lipid accumulation in both male and female rats. Administration of UA during periods of developmental plasticity shows prophylactic potential against dietary fructose-induced NAFLD.

Ursolic acid induces the production of IL6 and chemokines in both adipocytes and adipose tissue

Adipose tissue inflammation plays an important role in the regulation of glucose and lipids metabolism. It is unknown whether Ursolic acid (UA) could regulate adipose tissue inflammation, though it can regulate inflammation in many other tissues. In this study, 3T3-L1 adipocytes, DIO mice and lean mice were treated with UA or vehicle. Gene expression of inflammatory factors, chemokines and immune markers in adipocytes and adipose tissue, cytokines in cell culture medium and serum, and inflammation regulatory pathways in adipocytes were detected. Results showed that UA increased the expression of interleukins and chemokines, but not TNFα, in both adipocytes and adipose tissue. IL6 and MCP1 levels in the cell culture medium and mouse serum were induced by UA treatment. Cd14 expression level and number of CD14+ monocytes were higher in UA treated adipose tissue than those in the control group. Glucose tolerance test was impaired by UA treatment in DIO mice. Mechanistically, UA induced the expression of Tlr4 and the phosphorylation levels of ERK and NFκB in adipocytes. In conclusion, our study indicated that short-term UA administration could induce CD14+ monocytes infiltration by increasing the production of interleukins and chemokines in mouse adipose tissue, which might further impair glucose tolerance test.

Antidiabetic effect of mangiferin in combination with oral hypoglycemic agents metformin and gliclazide

BACKGROUND

Diabetes mellitus poses serious threat to the global population due to the alarming diabetic complications it leads to. The current therapeutic options available can be improved for better efficiency and maximum benefits. Combination therapy has been commonly used to improve the efficacy and to minimize the side effects of drugs in current clinical use.

PURPOSE

The present study aims to assess the interaction between a natural molecule mangiferin with the commercially available oral hypoglycemic drugs metformin and gliclazide in diabetic rats.

METHODS

In this study, the in vitro cytotoxicity and glucose uptake studies were performed in HepG2 cells. Based on experimental data, the combination index of the hypoglycemic drugs like metformin and gliclazide in combination with different doses of mangiferin was determined using COMPUSYN software. Further, in vivo studies were performed in HFD + STZ induced diabetic male Sprague Dawley rats. Serum parameters, enzyme markers, hepatic oxidative stress markers, gene and protein expression studies and histopathological analyses were performed in rat liver to identify the mode of action of the combination drug administration.

RESULTS

The in vitro studies on HepG2 cells suggest a positive interaction of mangiferin with both metformin and gliclazide at specific concentrations as evidenced by glucose uptake. The hepatic enzymes, oxidative stress markers, carbohydrate metabolizing enzymes, gene (AMPK, Akt, ACC β and Glut-2) and protein (PPARα, PPARγ) expression confirmed the results of the in vitro studies. Both the combinations of mangiferin with metformin and mangiferin with gliclazide exhibited potent antidiabetic effect. The combination of mangiferin with metformin was insulin dependent (Akt pathway) whereas the combination of mangiferin and gliclazide was insulin independent (AMPK pathway).

CONCLUSION

The overall results suggest that combination of mangiferin with both metformin and gliclazide alleviates diabetic conditions potentially at specific doses and modulates the adverse effect of high dose of commonly used OHD's. This combination therapy can be translated for its clinical use as a diabetes management strategy.

Rosiglitazone Improves Insulin Resistance Mediated by 10,12 Conjugated Linoleic Acid in a Male Mouse Model of Metabolic Syndrome

Trans-10, cis-12 conjugated linoleic acid (10,12 CLA) is a dietary fatty acid that promotes weight loss and disproportionate fat loss. Obese mice fed a high-fat, high-sucrose (HFHS) diet containing 10,12 CLA are resistant to weight gain and contain markedly reduced subcutaneous fat and adiponectin, with a concurrent lack of improvement in insulin sensitivity despite significant weight loss. Taken together, 10,12 CLA promotes a phenotype resembling peroxisome proliferator-activated receptor (PPAR)γ antagonism. Because thiazolidinediones such as rosiglitazone (Rosi) are used clinically to improve insulin sensitivity by activating PPARγ, with particular efficacy in subcutaneous white adipose tissue, we hypothesized that Rosi would improve glucose metabolism in mice losing weight with 10,12 CLA. Obese low-density lipoprotein receptor-deficient mice were fed a HFHS control diet, or supplemented with 1% 10,12 CLA with or without Rosi (10 mg/kg) for 8 weeks. Body composition, glucose and insulin tolerance tests, tissue gene expression, and plasma lipid analyses were performed. Mice consuming 10,12 CLA with Rosi lost weight and body fat compared with control groups, but with a healthier redistribution of body fat toward more subcutaneous adipose tissue than with 10,12 CLA alone. Further, Rosi improved 10,12 CLA-mediated insulin resistance parameters and increased plasma and subcutaneous adipose tissue adiponectin levels without adverse effects on plasma or hepatic lipids. We conclude that cotreatment of mice with 10,12 CLA and Rosi promotes fat loss with a healthier fat distribution that leads to improved insulin sensitivity, suggesting that the combination treatment strategy of 10,12 CLA with Rosi could have therapeutic potential for obesity treatment.

Ursolic acid derivatives for pharmaceutical use: a patent review (2012-2016)

INTRODUCTION

Ursolic acid (UA), belongs to a group of pentacyclic triterpenoids and is known to possess some very interesting biological properties. Protocols have been developed in order to synthesize bioactive UA analogs which have resulted in numerous ursolic acid analogs being synthesized during the period 2012-2016. Ursolic acid and its analogues can be employed to treat various cancers, inflammatory diseases, diabetes, Parkinson's disease, Alzheimer's disease, hepatitis B, hepatitis C and AIDS to mention but a few. Areas covered: This review covers patents on therapeutic activities of ursolic acid (UA) and its synthetic derivatives published during the four year period 2012-2016. A discussion about structure-activity relationships (SAR) of these analogs is also included. Expert opinion: Ursolic acid and its synthetic derivatives demonstrated excellent anticancer, antidiabetic, antiarrhythmic, anti-hyperlipidemic, antimicrobial, anti-hypercholesterolemic, and anti-cardiovascular properties. Additionally, various ursolic acid analogues have been synthesized through modification at positions C2-OH, C3-OH and C17-CO2H. It is noteworthy that the C-17 amide and amino analogs of UA possessed better anticancer activity compared to the parent compound (UA). Most importantly, UA has the potential to conjugate with other anticancer drugs or be transformed into its halo derivatives since this will greatly facilitate scientists to get lead compounds in cancer drug discovery.

Effect of Ursolic Acid on Metabolic Syndrome, Insulin Sensitivity, and Inflammation

To evaluate the effect of ursolic acid on metabolic syndrome, insulin sensitivity, and inflammation, a randomized, double-blind, placebo-controlled clinical trial was carried out in 24 patients (30-60 years) with a diagnosis of metabolic syndrome without treatment. They were randomly assigned to two groups of 12 patients, each to receive orally 150 mg of ursolic acid or homologated placebo once a day for 12 weeks. Before and after the intervention, the components of metabolic syndrome, insulin sensitivity (Matsuda index), and inflammation profile (interleukin-6 and C-reactive protein) were evaluated. After ursolic acid administration, the remission of metabolic syndrome occurred in 50% of patients (P = .005) with significant differences in body weight (75.7 ± 11.5 vs. 71 ± 11 kg, P = .002), body mass index (BMI) (29.9 + 3.6 vs. 24.9 ± 1.2 kg/m2, P = .049), waist circumference (93 ± 8.9 vs. 83 + 8.6 cm, P = .008), fasting glucose (6.0 ± 0.5 vs. 4.7 ± 0.4 mmol/L, P = .002), and insulin sensitivity (3.1 ± 1.1 vs. 4.2 ± 1.2, P = .003). Ursolic acid administration leads to transient remission of metabolic syndrome, reducing body weight, BMI, waist circumference and fasting glucose, as well as increasing insulin sensitivity.

Ursolic acid and mechanisms of actions on adipose and muscle tissue: a systematic review

This systematic review aimed at addressing the ursolic acid actions as an adjunctive treatment of the obesity-mediated metabolic abnormalities. To explore our aims, we used the literature search including clinical and animal studies using the Medline and Google Scholar (up to December 2015). Out of 63 screened studies, 17 presented eligibility criteria, such as the use of ursolic acid on adiposity, energy expenditure and skeletal muscle mass in mice and humans. In the literature, we found that several physiological and molecular mechanisms are implicated in the effects of ursolic acid on obesity, energy expenditure, hepatic steatosis, skeletal muscle mass loss and physical fitness, such as (1) increase of thermogenesis by modulation adipocyte transcription factors, activation of 5' adenosine monophosphate-activated protein kinase and overexpression of the uncoupling protein 1 thermogenic marker; (2) enhancement of skeletal muscle mass by activation in bloodstream growth hormone and insulin-like growth factor-1 concentrations secretion, as well as in the activation of mammalian target of rapamycin and inhibition of ring-finger protein-1; and (3) improvement of physical fitness by skeletal muscle proliferator-activated receptor gamma co-activator alpha and sirtuin 1 expression. Therefore, supplementation with ursolic acid may be an adjunctive therapy for prevention and treatment of obesity-mediated and muscle mass-mediated metabolic consequences.

Aqueous seed extract of Hunteria umbellata (K. Schum.) Hallier f. (Apocynaceae) palliates hyperglycemia, insulin resistance, dyslipidemia, inflammation and oxidative stress in high-fructose diet-induced metabolic syndrome in rats

ETHNOPHARMACOLOGICAL RELEVANCE

Hunteria umbellata is used in the management and treatment of diabetes and obesity in Nigeria. This study evaluates the effect of aqueous seed extract of Hunteria umbellata on insulin resistance, dyslipidemia, inflammation and oxidative stress in high-fructose diet-induced metabolic syndrome MATERIALS AND METHODS: Rats were randomized into seven groups (A-G). Control (group A) and group C rats received control diet for nine weeks while rats in groups B, D - G were placed on high-fructose diet for 9 weeks. In addition to the diets, groups C - F rats orally received 400, 100, 200 and 400mg/kg body weight aqueous seed extract of Hunteria umbellata for 3 weeks starting from 6th - 9th week.

RESULTS

High-fructose diet (when compared to control rats) mediated a significant (p<0.05) increase in body weight, body mass index and abdominal circumference. Similarly, levels of blood glucose, insulin, leptin, adiponectin and insulin resistance were increased. It also caused a significant increase in the levels of cholesterol, triglycerides, low-density lipoprotein cholesterol, very low-density lipoprotein cholesterol, atherogenic index, cardiac index and coronary artery index while high-density lipoprotein cholesterol was decreased significantly. Levels of proinflammatory factor, tumour necrosis factor-α, interleukin-6 and 8 were also increased by the high fructose diet. Moreover, it mediated decrease in activities of superoxide dismutase, catalase, glutathione peroxidase, glutathione reductase, glucose 6-phosphate dehydrogenase and level of glutathione reduced. Conversely, levels of malondialdehyde, conjugated dienes, lipid hydroperoxides, protein carbonyl and fragmented DNA were elevated. Aqueous seed extract of Hunteria umbellata significantly ameliorated the high fructose diet-mediated alterations.

CONCLUSIONS

From this study, it is concluded that aqueous seed extract of Hunteria umbellata possesses hypoglycemic, hypolipidemic and antioxidants abilities as evident from its capability to extenuate insulin resistance, dyslipidemia, inflammation and oxidative stress in high-fructose diet-induced metabolic syndrome rats.

Effect of Bergenin on the Kidney of C57BL/6J Mice with High Fat-Diet Induced Oxidative Stress

The present study evaluated the protective effect of bergenin on high fat diet (HFD) induced diabetic mice. C57BL/6J mice were segregated in two groups, one fed standard diet (NC) and the other fed HFD for 16 weeks. Mice were fed continuously with high fat diet for 16 weeks and subjected to intragastric administration of bergenin (10, 20 and 40 mg/kg body weight (BW)), metformin (25 mg/kg BW) 9 to 16 weeks. At the end of the treatment nephritic markers, lipid peroxidation product, antioxidant and histopathological examination were carried out to assess the efficacy of the treatment. HFD fed mice showed increased plasma glucose, insulin, altered nephritic markers, antioxidant and histopathological abnormalities. Oral Treatment with bergenin (40 mg/kg BW) showed near normalized levels of plasma glucose, lipid peroxidation product, antioxidants, improved insulin and reduced kidney damage. The effects of bergenin were comparable with standard drug, metformin. These data suggest that bergenin protect kidney from deleterious effect of glucose.

Effect of Bergenin on the Kidney of C57BL/6J Mice with High Fat-Diet Induced Oxidative Stress

The present study evaluated the protective effect of bergenin on high fat diet (HFD) induced diabetic mice. C57BL/6J mice were segregated in two groups, one fed standard diet (NC) and the other fed HFD for 16 weeks. Mice were fed continuously with high fat diet for 16 weeks and subjected to intragastric administration of bergenin (10, 20 and 40 mg/kg body weight (BW)), metformin (25 mg/kg BW) 9 to 16 weeks. At the end of the treatment nephritic markers, lipid peroxidation product, antioxidant and histopathological examination were carried out to assess the efficacy of the treatment. HFD fed mice showed increased plasma glucose, insulin, altered nephritic markers, antioxidant and histopathological abnormalities. Oral Treatment with bergenin (40 mg/kg BW) showed near normalized levels of plasma glucose, lipid peroxidation product, antioxidants, improved insulin and reduced kidney damage. The effects of bergenin were comparable with standard drug, metformin. These data suggest that bergenin protect kidney from deleterious effect of glucose.

Oleanolic, Ursolic, and Betulinic Acids as Food Supplements or Pharmaceutical Agents for Type 2 Diabetes: Promise or Illusion?

Oleanolic (OA), ursolic (UA), and betulinic (BA) acids are three triterpenic acids (TAs) with potential effects for treatment of type 2 diabetes (T2DM). Mechanistic studies showed that these TAs act as hypoglycemic and antiobesity agents mainly through (i) reducing the absorption of glucose; (ii) decreasing endogenous glucose production; (iii) increasing insulin sensitivity; (iv) improving lipid homeostasis; and (v) promoting body weight regulation. Besides these promising beneficial effects, it is believed that OA, UA, and BA protect against diabetes-related comorbidities due to their antiatherogenic, anti-inflammatory, and antioxidant properties. We also highlight the protective effect of OA, UA, and BA against oxidative damage, which may be very relevant for the treatment and/or prevention of T2DM. In the present review, we provide an integrative description of the antidiabetic properties of OA, UA, and BA, evaluating the potential use of these TAs as food supplements or pharmaceutical agents to prevent and/or treat T2DM.

1-Deoxynojirimycin Alleviates Liver Injury and Improves Hepatic Glucose Metabolism in db/db Mice

The present study investigated the effect of 1-Deoxynojirimycin (DNJ) on liver injury and hepatic glucose metabolism in db/db mice. Mice were divided into five groups: normal control, db/db control, DNJ-20 (DNJ 20 mg·kg⁻¹·day⁻¹), DNJ-40 (DNJ 40 mg·kg⁻¹·day⁻¹) and DNJ-80 (DNJ 80 mg·kg⁻¹·day⁻¹). All doses were treated intravenously by tail vein for four weeks. DNJ was observed to significantly reduce the levels of serum triglyceride (TG), total cholesterol (TC), low density lipoprotein cholesterol (LDL-C) and liver TG, as well as activities of serum alanine aminotransferase (ALT), and aspartate transaminase (AST); DNJ also alleviated macrovesicular steatosis and decreased tumor necrosis factor α (TNF-α), interleukin-1 (IL-1), interleukin-6 (IL-6) levels in liver tissue. Furthermore, DNJ treatment significantly increased hepatic glycogen content, the activities of hexokinase (HK), pyruvate kinase (PK) in liver tissue, and decreased the activities of glucose-6-phosphatase (G6Pase), glycogen phosphorylase (GP), and phosphoenolpyruvate carboxykinase (PEPCK). Moreover, DNJ increased the phosphorylation of phosphatidylinositol 3 kinase (PI3K) on p85, protein kinase B (PKB) on Ser473, glycogen synthase kinase 3β (GSK-3β) on Ser9, and inhibited phosphorylation of glycogen synthase (GS) on Ser645 in liver tissue of db/db mice. These results demonstrate that DNJ can increase hepatic insulin sensitivity via strengthening of the insulin-stimulated PKB/GSK-3β signal pathway and by modulating glucose metabolic enzymes in db/db mice. Moreover, DNJ also can improve lipid homeostasis and attenuate hepatic steatosis in db/db mice.

Fucoidan from sea cucumber may improve hepatic inflammatory response and insulin resistance in mice

Nutrition excess-induced inflammation positively contributed to insulin resistance. Fucoidan from sea cucumber can increase glucose translocation in skeletal muscle. However, its effects on inflammation-associated insulin resistance are not understood. We investigated fucoidan from Isostichopus badionotus (Ib-FUC)-alleviated inflammatory response and signaling as well as -improved insulin resistance in the liver of obesity mice. The results showed that Ib-FUC reduced body weight and glucose levels, increased insulin sensitivity, and inhibited serum lipid concentrations. Meanwhile, Hepatic glycogen synthesis was promoted by Ib-FUC via activation of the PI3K/PKB/GSK-3β signaling and regulation of glucose metabolism-related enzymatic activities. Ib-FUC regulated serum inflammatory cytokines and their mRNA expression in the liver. Ib-FUC-induced inactivation of the JNK and IKKβ/NFκB pathways was involved in the activation of insulin signal cascade and inflammatory factor production. These findings suggested that Ib-FUC supplementary-induced alleviation of inflammatory response could be a mechanism responsible for its beneficial effects against hepatic insulin resistance.

Ursolic acid increases energy expenditure through enhancing free fatty acid uptake and β-oxidation via an UCP3/AMPK-dependent pathway in skeletal muscle

SCOPE

Ursolic acid (UA) is a triterpenoid compound with multifold biological functions. Our previous studies have reported that UA protects against high-fat diet-induced obesity and improves insulin resistance (IR). However, the potential mechanisms are still undefined. Free fatty acid (FFA) metabolism in skeletal muscle plays a central role in obesity and IR. Therefore, in this study, we investigated the effect and the potential mechanisms of UA on skeletal muscle FFA metabolism.

METHODS AND RESULTS

In diet-induced obese rats, 0.5% UA supplementation for 6 weeks markedly reduced body weight, increased energy expenditure, decreased FFA level in serum and skeletal muscle and triglyceride content in skeletal muscle. In vitro, the data provided directly evidence that UA significantly increased fluorescently labeled FFA uptake and (3) H-labeled palmitic acid β-oxidation. UA-activated AMP-activated protein kinase (AMPK) and downstream targets were involved in the increase of FFA catabolism. Moreover, upregulated uncoupling protein 3 (UCP3) by UA contributed to AMPK activation via elevating adenosine monophosphate/adenosine triphosphate ratio.

CONCLUSION

UA increases FFA burning through enhancing skeletal muscle FFA uptake and β-oxidation via an UCP3/AMPK-dependent pathway, which provides a novel perspective on the biological function of UA against obesity and IR.

Fucosylated chondroitin sulfate from sea cucumber improves insulin sensitivity via activation of PI3K/PKB pathway

This study was to investigate the effects of fucosylated chondroitin sulfate (CHS) from sea cucumber on insulin sensitivity in skeletal muscle of type 2 diabetic mice induced by a high-fat high-sucrose diet (HFSD). CHS supplementation for 19 wk significantly improved insulin sensitivity by 20%, and reduced blood glucose and insulin levels. Western blotting assay showed that CHS significantly increased insulin-stimulated glucose transporter 4 (GLUT4) translocation to 1.7-fold, phosphorylation of phosphoinositide 3-kinase (PI3K) at p85 to 5.0-fold, protein kinase B (PKB) at Ser473 to 1.5-fold, and Thr308 to 1.6-fold in skeletal muscle. However, PI3K, PKB, and GLUT4 total proteins expression were unchangeable. In addition, qRT-PCR analysis proved that the insulin signaling was activated by CHS treatment, showing the increased mRNA expressions of glucose uptake-related key genes. It indicated that CHS improved insulin sensitivity by activation of PI3K/PKB signaling in skeletal muscle of type 2 diabetic mice. Identification of potential mechanism by which CHS increased insulin sensitivity might provide a new functional food or pharmaceutical application of sea cucumber.

Use of mRNA expression signatures to discover small molecule inhibitors of skeletal muscle atrophy

PURPOSE OF REVIEW

Here, we discuss a recently developed experimental strategy for discovering small molecules with potential to prevent and treat skeletal muscle atrophy.

RECENT FINDINGS

Muscle atrophy involves and requires widespread changes in skeletal muscle gene expression, which generate complex but measurable patterns of positive and negative changes in skeletal muscle mRNA levels (a.k.a. mRNA expression signatures of muscle atrophy). Many bioactive small molecules generate their own characteristic mRNA expression signatures, and by identifying small molecules whose signatures approximate mirror images of muscle atrophy signatures, one may identify small molecules with potential to prevent and/or reverse muscle atrophy. Unlike a conventional drug discovery approach, this strategy does not rely on a predefined molecular target but rather exploits the complexity of muscle atrophy to identify small molecules that counter the entire spectrum of pathological changes in atrophic muscle. We discuss how this strategy has been used to identify two natural compounds, ursolic acid and tomatidine, that reduce muscle atrophy and improve skeletal muscle function.

SUMMARY

Discovery strategies based on mRNA expression signatures can elucidate new approaches for preserving and restoring muscle mass and function.

Therapeutic role of ursolic acid on ameliorating hepatic steatosis and improving metabolic disorders in high-fat diet-induced non-alcoholic fatty liver disease rats

BACKGROUND

Non-alcoholic fatty liver disease (NAFLD) is one of the most prevalent liver diseases around the world, and is closely associated with obesity, diabetes, and insulin resistance. Ursolic acid (UA), an ubiquitous triterpenoid with multifold biological roles, is distributed in various plants. This study was conducted to investigate the therapeutic effect and potential mechanisms of UA against hepatic steatosis in a high-fat diet (HFD)-induced obese non-alcoholic fatty liver disease (NAFLD) rat model.

METHODOLOGY/PRINCIPAL FINDINGS

Obese NAFLD model was established in Sprague-Dawley rats by 8-week HFD feeding. Therapeutic role of UA was evaluated using 0.125%, 0.25%, 0.5% UA-supplemented diet for another 6 weeks. The results from both morphologic and histological detections indicated that UA significantly reversed HFD-induced hepatic steatosis and liver injury. Besides, hepatic peroxisome proliferator-activated receptor (PPAR)-α was markedly up-regulated at both mRNA and protein levels by UA. Knocking down PPAR-α significantly inhibited the anti-steatosis role of UA in vitro. HFD-induced adverse changes in the key genes, which participated in hepatic lipid metabolism, were also alleviated by UA treatment. Furthermore, UA significantly ameliorated HFD-induced metabolic disorders, including insulin resistance, inflammation and oxidative stress.

CONCLUSIONS/SIGNIFICANCE

These results demonstrated that UA effectively ameliorated HFD-induced hepatic steatosis through a PPAR-α involved pathway, via improving key enzymes in the controlling of lipids metabolism. The metabolic disorders were accordingly improved with the decrease of hepatic steatosis. Thereby, UA could be a promising candidate for the treatment of NAFLD.