Garcinia linii extracts exert the mediation of anti-diabetic molecular targets on anti-hyperglycemia.

Different portions (stem GIS and leaf GIL) of Garcinia linii were extracted by ethanol/water and crude extracts were employed to investigate the contents of total phenol and flavonoids, antioxidation activities, and inhibitory activities of α-amylase and α-glucosidase via enzymatic assay and OGTT and OSTT for lowering glucose levels. The data revealed that GlS and GlL contained different levels of flavonoids and total phenol. Furthermore, the results showed the extracts exhibited remarkable antioxidation activities and inhibitory activities of α-amylase and α-glucosidase. In silico docking studies were done using Gold software and the probable molecules retrieved from PubChem were docked with several anti-diabetic relate targets, the results showed several components of G. linii could potentially inhibit diabetic molecules when compared with clinic drugs. The cell glucose uptake data also confirmed that GlL and GlS could retain the active component in the regulation of insulin, AMPK, PPARγ, and DPP4. In vivo, the evidence showed G. linii extracts including syringaldehyde suppressed effect of hyperglycemia on OSTT and OGTT assays. These results suggest that G. linii extract has a potential therapeutic value for the treatment of diabetes in humans.

HM-chromanone inhibits adipogenesis by regulating adipogenic transcription factors and AMPK in 3T3-L1 adipocytes.

Portulaca oleracea L. is used as a folk medicine in many countries because of its wide range of pharmacological effects. HM-chromanone, isolated from P. oleracea using bioassay-guided fractionation and HPLC, belongs to the homoisoflavonoid group and has been shown to exert several biological effects. In this study, we evaluated whether HM-chromanone inhibits adipogenesis by regulating adipogenic transcription factors in 3T3-L1 adipocytes. The results showed that HM-chromanone suppresses adipocyte differentiation and adipogenesis in a dose-dependent manner in 3T3-L1 adipocytes. The HM-chromanone-treated adipocytes exhibited lower triglyceride accumulation and leptin secretion, and higher glycerol and adiponectin secretion than the control adipocytes. Microscopic observation using oil red O staining revealed a dose-dependent reduction in the number of lipid droplets in the HM-chromanone-treated adipocytes compared to the control group. HM-chromanone significantly down-regulated the protein expression of major adipogenic transcription factors sterol regulatory element binding protein-1c (SREBP-1c), peroxisome proliferator-activated receptor γ (PPARγ), and CCAAT/enhancer binding protein α (C/EBPα) and markedly inhibited several key adipogenic enzymes including fatty acid synthase (FAS) and acetyl-CoA carboxylase (ACC). In addition, adipose triglyceride lipase (ATGL) and hormone-sensitive lipase (HSL) were both more activated in the HM-chromanone-treated adipocytes than in the control adipocytes. HM-chromanone also promoted the phosphorylation of 5' Adenosine monophosphate-activated protein kinase (AMPK), which inhibits adipogenesis through the regulation of adipogenic transcription factors. These results suggest that HM-chromanone may be an effective anti-adipogenesis agent that functions via the suppression of adipogenic transcription factors and the activation of AMPK.

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

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

Cinnamon Polyphenol Extract and Insulin Regulate Diacylglycerol Acyltransferase Gene Expression in Mouse Adipocytes and Macrophages.

Cinnamon polyphenol extract (CPE) improves people with insulin resistance. The objective was to investigate CPE and insulin on diacylglycerol acyltransferase (DGAT) gene expression important for lipid biosynthesis and compared it to anti-inflammatory tristetraprolin/zinc finger protein 36 (TTP/ZFP36) gene expression known to be regulated by both agents. Mouse 3T3-L1 adipocytes and RAW264.7 macrophages were treated with insulin and CPE followed by qPCR evaluation of DGAT and TTP mRNA levels. Insulin decreased DGAT1 and DGAT2 mRNA levels in adipocytes but had no effect on DGAT1 and increased DGAT2 mRNA levels 3-fold in macrophages. Insulin increased TTP mRNA levels 3-fold in adipocytes but had no effect in macrophages. CPE effect on DGAT1 gene expression was minimal but increased DGAT2 mRNA levels 2-4 fold in adipocytes and macrophages. CPE increased TTP mRNA levels 2-7 fold in adipocytes and macrophages. We conclude that CPE and insulin exhibited overlapping and independent effects on DGAT and TTP gene expression and suggest that CPE and insulin have profound effects on fat biosynthesis and inflammatory responses.

n-Butanol Extract of Lotus Seeds Exerts Antiobesity Effects in 3T3-L1 Preadipocytes and High-Fat Diet-Fed Mice via Activating Adenosine Monophosphate-Activated Protein Kinase.

In this study, the antiobesity effects of n-butanol extract of lotus seeds (LBE) were evaluated in cultured 3T3-L1 preadipocytes and in high-fat diet (HFD)-fed mice. LBE decreased lipid contents in mature 3T3-L1 cells without obvious cytotoxicity. Meanwhile, LBE supplementation also led to weight loss and improved plasma lipid profiles in HFD-fed mice. Furthermore, LBE could activate AMP-activated protein kinase (AMPK) accompanied by down-regulation of lipogenesis related genes (PPARγ, aP2, LPL, C/EBPα, FAS, SREBP-1c) and up-regulation of lipolysis genes (adiponectin and PPARα) in vitro and in vivo. Collectively, our data demonstrated LBE possesses antiadipogenic and antilipogenic activities which are, at least partially, mediated by the activation of AMPK signaling pathways.

Replacement of soybean oil by fish oil increases cytosolic lipases activities in liver and adipose tissue from rats fed a high-carbohydrate diets.

Several studies have demonstrated that fish oil consumption improves metabolic syndrome and comorbidities, as insulin resistance, nonalcoholic fatty liver disease, dyslipidaemia and hypertension induced by high-fat diet ingestion. Previously, we demonstrated that administration of a fructose-rich diet to rats induces liver lipid accumulation, accompanied by a decrease in liver cytosolic lipases activities. In this study, the effect of replacement of soybean oil by fish oil in a high-fructose diet (FRUC, 60% fructose) for 8 weeks on lipid metabolism in liver and epididymal adipose tissue from rats was investigated. The interaction between fish oil and FRUC diet increased glucose tolerance and decreased serum levels of triacylglycerol (TAG), VLDL-TAG secretion and lipid droplet volume of hepatocytes. In addition, the fish oil supplementation increased the liver cytosolic lipases activities, independently of the type of carbohydrate ingested. Our results firmly establish the physiological regulation of liver cytosolic lipases to maintain lipid homeostasis in hepatocytes. In epididymal adipose tissue, the replacement of soybean oil by fish oil in FRUC diet did not change the tissue weight and lipoprotein lipase activity; however, there was increased basal and insulin-stimulated de novo lipogenesis and glucose uptake. Increased cytosolic lipases activities were observed, despite the decreased basal and isoproterenol-stimulated glycerol release to the incubation medium. These findings suggest that fish oil increases the glycerokinase activity and glycerol phosphorylation from endogenous TAG hydrolysis. Our findings are the first to show that the fish oil ingestion increases cytosolic lipases activities in liver and adipose tissue from rats treated with high-carbohydrate diets.

3,3'-Diindolylmethane Suppresses Adipogenesis Using AMPKα-Dependent Mechanism in 3T3-L1 Adipocytes and Caenorhabditis elegans.

3,3'-diindolylmethane is a major in vivo metabolite of indole-3-carbinol, a bioactive compound found in cruciferous vegetables. Although 3,3'-diindolylmethane has been implicated to possess antitumorigenic and anti-inflammatory properties, the effect of 3,3'-diindolylmethane on adipogenesis has not been explored previously. Thus, the present study was conducted to determine if 3,3'-diindolylmethane affects adipogenesis using 3T3-L1 adipocytes and Caenorhabditis elegans. Treatment of 3,3'-diindolylmethane significantly reduced fat accumulation without affecting viability in 3T3-L1 adipocytes. 3,3'-diindolylmethane suppressed expression of peroxisome proliferator-activated receptor γ (PPARγ), CCAAT-enhancer-binding protein α (C/EBPα), fatty acid binding protein 4 (FABP4), and perilipin. In addition, 3,3'-diindolylmethane activated AMP-activated protein kinase α (AMPKα), which subsequently inactivated acetyl CoA carboxylase (ACC), resulting in reduced fat accumulation. These observations were further confirmed in C. elegans as treatment with 3,3'-diindolylmethane significantly reduced body fat accumulation, which was partly associated with aak-1, but not aak-2, orthologs of AMPKα catalytic subunits α1 and α2, respectively. The current results demonstrate that 3,3'-diindolylmethane, a biologically active metabolite of indole-3-carbinol, may prevent adipogenesis through the AMPKα-dependent pathway.

Nandinine, a Derivative of Berberine, Inhibits Inflammation and Reduces Insulin Resistance in Adipocytes via Regulation of AMP-Kinase Activity.

Nandinine is a derivative of berberine that has high efficacy for treating cardiovascular diseases. This study investigated the effects of berberine and nandinine on the regulation of insulin sensitivity in adipocytes. Through treatment with macrophage-derived conditioned medium in 3T3-L1 adipocytes, dysregulation of adipokine production and activation of the IκB kinase ß/nuclear factor-kappa B pathway was induced. However, these phenomena were effectively reversed by berberine, nandinine, and salicylate pretreatments. Furthermore, both berberine and nandinine inhibited serine phosphorylation of insulin receptor substrate-1 induced by IκB kinase ß and increased tyrosine phosphorylation of insulin receptor substrate-1 to activate the PI3K/Akt pathway, which finally led to insulin-mediated glucose uptake. In addition, berberine and nandinine significantly increased AMP-activated protein kinase activity, thereby contributing to their anti-inflammatory effect by inhibiting IκB kinase ß activation. Finally, in vivo studies demonstrated that both berberine (100 or 200 mg/kg) and nandinine (100 or 200 mg/kg) effectively ameliorated glucose intolerance and induced the insulin sensitivity index in mice. In conclusion, berberine and nandinine attenuated insulin resistance in adipocytes by inhibiting inflammation in an AMP-activated protein kinase-dependent manner. Berberine and nandinine may be used as dietary supplements and nandinine is a new candidate for obesity treatment.

The flower of Edgeworthia gardneri (wall.) Meisn. suppresses adipogenesis through modulation of the AMPK pathway in 3T3-L1 adipocytes.

ETHNOPHARMACOLOGICAL RELEVANCE: The flower of Edgeworthia gardneri (Wall.) Meisn., locally named "Lvluohua, ", has been widely used as Tibetan folk medicine for the treatment of metabolic diseases for a long time. AIM OF THIS STUDY: To evaluate the anti-adipogenesis effect of ethyl acetate extract of the flower of E. gardneri (EEG extract) in 3T3-L1 adipocytes. MATERIALS AND METHODS: Obesity-related parameters such as lipid accumulation and TG content were determined by Oil red O staining and enzymatic kit, respectively. Western blotting was used to determine the expressions of peroxisome proliferator-activated receptor γ (PPARγ), CCAAT/enhancer-binding protein-α (C/EBPα), phosphorylated adenosine 5'-monophosphate (AMP)-activated protein kinase (AMPK) and acetyl-CoA carboxylase (ACC). Moreover, main constituents of EEG extract were analyzed by high performance liquid chromatography (HPLC). RESULTS: EEG extract decreased the lipid and triglyceride (TG) accumulations during the differentiation process and down-regulated the adipogenesis-related transcriptional factors PPARγ and C/EBPα. EEG extract treatment increased AMPK and ACC phosphorylation. In addition, pretreatment with AMPK inhibitor, weakened the inhibitory effects of EEG extract on the expressions of PPARγand C/EBPα. HPLC analysis indicated that tiliroside was the main constituent in EEG extract. CONCLUSIONS: These results suggest that EEG extract may exert anti-adipogenic effects through modulation of the AMPK signaling pathway.

In vitro studies on anti-obesity activity of Korean Memilmuk through AMPK activation.

The anti-obesity effect of Korean traditional food, Memilmuk, was examined through inhibition of differentiation of 3T3-L1 preadipocytes by buckwheat flour extract. Oil-Red O staining showed that lipid accumulation in adipocytes was reduced upon adding buckwheat flour extract, indicating effective inhibition of adipocyte differentiation. Buckwheat flour extract also inhibited the expression of adipogenic transcription factor, peroxisome proliferator-activated receptor γ (PPARγ), and AMP-activated protein kinase (AMPK), an intracellular regulator of energy balance. Overall, the anti-obesity effect of Korean Memilmuk might be mediated through down-regulation of PPARγ expression via AMPK activation by buckwheat flour.

Cell type-specific modulation of lipid mediator's formation in murine adipose tissue by omega-3 fatty acids.

Mutual interactions between adipocytes and immune cells in white adipose tissue (WAT) are involved in modulation of lipid metabolism in the tissue and also in response to omega-3 polyunsaturated fatty acids (PUFA), which counteract adverse effects of obesity. This complex interplay depends in part on in situ formed anti- as well as pro-inflammatory lipid mediators, but cell types engaged in the synthesis of the specific mediators need to be better characterized. We used tissue fractionation and metabolipidomic analysis to identify cells producing lipid mediators in epididymal WAT of mice fed for 5 weeks obesogenic high-fat diet (lipid content 35% wt/wt), which was supplemented or not by omega-3 PUFA (4.3 mg eicosapentaenoic acid and 14.7 mg docosahexaenoic acid per g of diet). Our results demonstrate selective increase in levels of anti-inflammatory lipid mediators in WAT in response to omega-3, reflecting either their association with adipocytes (endocannabinoid-related N-docosahexaenoylethanolamine) or with stromal vascular cells (pro-resolving lipid mediator protectin D1). In parallel, tissue levels of obesity-associated pro-inflammatory endocannabinoids were suppressed. Moreover, we show that adipose tissue macrophages (ATMs), which could be isolated using magnetic force from the stromal vascular fraction, are not the major producers of protectin D1 and that omega-3 PUFA lowered lipid load in ATMs while promoting their less-inflammatory phenotype. Taken together, these results further document specific roles of various cell types in WAT in control of WAT inflammation and metabolism and they suggest that also other cells but ATMs are engaged in production of pro-resolving lipid mediators in response to omega-3 PUFA.

Ice Plant (Mesembryanthemum crystallinum) Extract Promotes Lipolysis in Mouse 3T3-L1 Adipocytes Through Extracellular Signal-Regulated Kinase Activation.

The antiobesity effect of ice plant (IP) (Mesembryanthemum crystallinum), a salt-resistant African plant, has recently attracted increased attention. IP is rich in pinitol, which lowers blood sugar, and myo-inositol, which prevents fatty liver disease. Furthermore, IP can potentially prevent or reduce the symptoms of metabolic syndrome. However, the details of the physiological mechanisms and mechanisms of action of IP are unclear. A previous study by our group demonstrated the capability of IP extract to prevent adipogenesis in 3T3-L1 preadipocytes. In this study, we analyzed the physiological function of IP extract on lipolysis in 3T3-L1 cells and the underlying mechanisms of this process. We found that the release of glycerol from cells treated with IP extract increased in an IP dose-dependent manner. IP extract exhibited cytotoxic activity at concentrations above 4 mg/mL. Real-time polymerase chain reaction and western blotting showed that IP extract downregulated peroxisome proliferator-activated receptor (PPAR-)γ, hormone-sensitive lipase (HSL), and adipose triglyceride lipase (ATGL) in a concentration-dependent manner, but did not affect HSL-Ser563, HSL-Ser660, or perilipin phosphorylation. Although the cAMP-dependent protein kinase A (PKA)-specific inhibitor H89 did not affect IP extract-induced lipolysis, the extracellular signal-regulated kinase (ERK1/2) inhibitor U0126 significantly abrogated IP extract-activated glycerol release. Furthermore, IP extract strongly enhanced ERK1/2 phosphorylation at the concentrations used in the study. These results suggest that IP extract augments lipolysis by enhancing ERK phosphorylation.

Omental adipocyte hypertrophy relates to coenzyme Q10 redox state and lipid peroxidation in obese women.

Occurrence of oxidative stress in white adipose tissues contributes to its dysfunction and the development of obesity-related metabolic complications. Coenzyme Q10 (CoQ10) is the single lipophilic antioxidant synthesized in humans and is essential for electron transport during mitochondrial respiration. To understand the role of CoQ10 in adipose tissue physiology and dysfunction, the abundance of the oxidized and reduced (CoQ10red) isoforms of the CoQ10 were quantified in subcutaneous and omental adipose tissues of women covering the full range of BMI (from 21.5 to 53.2 kg/m(2)). Lean women displayed regional variations of CoQ10 redox state between the omental and subcutaneous depot, despite similar total content. Obese women had reduced CoQ10red concentrations in the omental depot, leading to increased CoQ10 redox state and higher levels of lipid hydroperoxide. Women with low omental CoQ10 content had greater visceral and subcutaneous adiposity, increased omental adipocyte diameter, and higher circulating interleukin-6 and C-reactive protein levels and were more insulin resistant. The associations between abdominal obesity-related cardiometabolic risk factors and CoQ10 content in the omental depot were abolished after adjustment for omental adipocyte diameter. This study shows that hypertrophic remodeling of visceral fat closely relates to depletion of CoQ10, lipid peroxidation, and inflammation.

Can low-level laser therapy when associated to exercise decrease adipocyte area?

Obesity affects approximately 20% of the world population, and exercise is the primary non-pharmacological therapy. The combined use of exercise and low-level laser therapy (LLLT) may potentiate the effects promoted by exercise. The objective of this study was to investigate the effects of exercise in combination with phototherapy on adipocyte area, activity of the enzyme citrate synthase and muscle morphological analysis. We used 64 Wistar rats, which were divided into eight groups with 8 rats each: sedentary chow-diet (SC); sedentary chow-diet plus laser therapy (SCL), exercised chow-diet (EC); exercised chow-diet plus laser therapy (ECL); sedentary high-fat diet (SH); sedentary high-fat diet plus laser therapy (SHL); exercised high-fat diet (EH); exercised high-fat diet, laser therapy (EHL). The animals were submitted to a program of swimming training for 90min/5 times per week for 8weeks and LLLT (GA-Al-AS, 830nm) at a dose of 4.7J/point and a total energy of 9.4J/animal, with duration of 47s, which was applied to both gastrocnemius muscles after exercise. We conclude that the combined use of exercise and phototherapy increases the activity of the enzyme citrate synthase and decreases the white adipocyte area epididymal, retroperitoneal and visceral in obese rats, enhancing the effects of exercise.

Glitazones inhibit human monoamine oxidase but their anti-inflammatory actions are not mediated by VAP-1/semicarbazide-sensitive amine oxidase inhibition.

Glitazones are peroxisome proliferator-activated receptor gamma (PPARγ) agonists widely used as antidiabetic drugs also known as thiazolidinediones. Most of them exert other effects such as anti-inflammatory actions via mechanisms supposed to be independent from PPARγ activation (e.g., decreased plasma monocyte chemoattractant protein-1 (MCP-1) levels). Recently, pioglitazone has been shown to inhibit the B form of monoamine oxidase (MAO) in mouse, while rosiglitazone and troglitazone were described as non-covalent inhibitors of both human MAO A and MAO B. Since molecules interacting with MAO might also inhibit semicarbazide-sensitive amine oxidase (SSAO), known as vascular adhesion protein-1 (VAP-1), and since VAP-1/SSAO inhibitors exhibit anti-inflammatory activity, our aim was to elucidate whether VAP-1/SSAO inhibition could be a mechanism involved in the anti-inflammatory behaviour of glitazones. To this aim, MAO and SSAO activities were measured in human subcutaneous adipose tissue biopsies obtained from overweight women undergoing plastic surgery. The production of hydrogen peroxide, an end-product of amine oxidase activity, was determined in tissue homogenates using a fluorometric method. The oxidation of 1 mM tyramine was inhibited by pargyline and almost resistant to semicarbazide, therefore predominantly MAO-dependent. Rosiglitazone was more potent than pioglitazone in inhibiting tyramine oxidation. By contrast, benzylamine oxidation was only abolished by semicarbazide: hence SSAO-mediated. Pioglitazone hampered SSAO activity only when tested at 1 mM while rosiglitazone was inefficient. However, rosiglitazone exhibited anti-inflammatory activity in human adipocytes by limiting MCP-1 expression. Our observations rule out any involvement of VAP-1/SSAO inhibition and subsequent limitation of leukocyte extravasation in the anti-inflammatory action of glitazones.

Effect of germinated brown rice extracts on pancreatic lipase, adipogenesis and lipolysis in 3T3-L1 adipocytes.

BACKGROUND: This study investigated anti-obesity effects of seven different solvent (n-hexane, toluene, dicholoromethane, ethyl acetate, absolute methanol, 80% methanol and deionized water) extracts of germinated brown rice (GBR) on pancreatic lipase activity, adipogenesis and lipolysis in 3T3-L1 adipocytes. METHODS: GBR were extracted separately by employing different solvents with ultrasound-assisted. Pancreatic lipase activity was determined spectrophotometrically by measuring the hydrolysis of p-nitrophenyl butyrate (p-NPB) to p-nitrophenol at 405 nm. Adipogenesis and lipolysis were assayed in fully differentiated 3T3-L1 adipocytes by using Oil Red O staining and glycerol release measurement. RESULTS: GBR extract using hexane showed the highest inhibitory effect (13.58 ± 0.860%) at concentration of 200 µg/ml followed by hexane extract at 100 µg/ml (9.98 ± 1.048%) while ethyl acetate extract showed the lowest (2.62 ± 0.677%) at concentration of 200 µg/ml on pancreatic lipase activity. Water extract at 300 µg/ml showed 61.55 ± 3.824% of Oil Red O staining material (OROSM), a marker of adipogenesis. It significantly decrease (p < 0.05) lipid accumulation than control (OROSM = 100%), follow by ethyl acetate extract at 300 µg/ml (OROSM = 65.17 ± 3.131%). All the GBR extracts induced lipolysis with 1.22-1.83 fold of greater glycerol release than control. CONCLUSIONS: GBR extracts especially the least polar and intermediate polar solvent extracts exhibited inhibitory effect on pancreatic lipase, decrease fat accumulation by adipocyte differentiation inhibition, and stimulate lipolysis on adipocytes. Therefore, GBR could be furthered study and developed as a functional food in helping the treatment and/or prevention of obesity.

Pycnogenol supplementation promotes lipolysis via activation of cAMP-dependent PKA in ob/ob mice and primary-cultured adipocytes.

This study investigated the PKA-dependent inhibitory effect of pycnogenol (Pyc) on lipolysis using ob/ob mice and primary mouse adipocytes. Supplementation of Pyc at 30 mg/kg significantly reduced body weight gain and visceral fat mass. The serum and hepatic triglyceride (TG) and total cholesterol (TC) levels were reduced by Pyc supplementation, and high density lipoprotein (HDL)-cholesterol level significantly increased. In addition, hormone sensitive lipase (HSL) and adipose triglyceride lipase (ATGL) mRNA levels increased with Pyc supplementation in adipose tissue of ob/ob mice. The treatment of primary cultured adipocytes with Pyc at 100 µg/mL significantly increased glycerol release, cAMP level by reduction of phosphodiestersae-3B (PDE3B), and HSL levels, but decreased protein levels of perilipin A and fatty acid synthetase (FAS). The PKA inhibitor (H89) clearly blocked the cellular levels of perilipin A and HSL, suggesting that Pyc promotes lipolysis of adipocytes through activation of cAMP-dependent PKA, resulting in induction of HSL and reduction of perilipin A. Therefore, this study may elucidate the possible mechanism of Pyc, which is a candidate for weight loss through stimulation of lipolysis.

FoxO1 controls lysosomal acid lipase in adipocytes: implication of lipophagy during nutrient restriction and metformin treatment.

Finding new molecular pathways and strategies modulating lipolysis in adipocytes is an attractive goal of the current research. Indeed, it is becoming clear that several human age-related pathologies are caused by adipose tissue expansion and altered lipid metabolism. In the present work, we show that transcription factor forkhead homeobox type protein O1 (FoxO1) is upregulated by nutrient restriction (NR) in adipocytes and exerts the transcriptional control of lipid catabolism via the induction of lysosomal acid lipase (Lipa). An increased autophagy and colocalization of lipid droplets (LDs) with lysosomes was observed implying lipophagy in Lipa-mediated LDs degradation. Interestingly, we found that metformin (Metf), a biguanide drug commonly used to treat type-2 diabetes, exerts effects comparable to that of NR. Actually, it was able to elicit FoxO1-dependent Lipa induction as well as LDs degradation through lipophagy. Moreover, we demonstrate that, during NR or Metf treatment, free fatty acids released by Lipa are directed toward AMP-activated protein kinase-mediated mitochondrial oxidation, thus maintaining energetic homeostasis in adipocytes. In conclusion, our data show that lysosomal-mediated lipid catabolism is activated by NR in adipocytes and give further support to the use of Metf as a NR mimetic to combat age-related diseases associated with altered lipid metabolism.

Inhibition of stearoyl-CoA desaturase 1 reduces lipogenesis in primary bovine adipocytes.

The objectives were to determine the effect of stearoyl-CoA desaturase (SCD1) inhibition on adipocyte proliferation, differentiation and cellular lipid metabolism in bovine primary adipocytes. Inhibition of SCD1 activity by sterculic acid (SA) or conjugated linoleic acid, trans-10 cis-12 isomer, (t10, c12-CLA) did not alter adipocyte cellular proliferation, viability or differentiation. In 1,2-[(13)C]-acetate supplemented cells, the mass isotopomer distribution analysis showed that the fractional synthesis rate of [(13)C]-16:0 was reduced (P < 0.01) in SA and t10, c12-CLA treatments compared to control. Of the lipogenic genes, t10, c12-CLA treatment decreased (P < 0.05) the expression of SCD1, acetyl-CoA carboxylase (ACC), fatty acid synthase; whereas SA supplementation decreased (P < 0.05) the expression of ACC. Both SA and t10, c12-CLA increased (P < 0.05) the expression of hormone-sensitive lipase and carnitine palmitoyl transferase involved in lipolysis and oxidation. Inhibition of SCD1 in bovine adipocytes decreases de novo fatty acid synthesis by down-regulating genes involved in lipogenesis and up-regulating genes involved in lipolysis and oxidation.

PIP3 but not PIP2 increases GLUT4 surface expression and glucose metabolism mediated by AKT/PKCζ/λ phosphorylation in 3T3L1 adipocytes.

Phosphatidylinositol-3,4,5-triphosphate (PIP3) and phosphatidylinositol-4,5-biphosphate (PIP2) are two well-known membrane bound polyphosphoinositides. Diabetes is associated with impaired glucose metabolism. Using a 3T3L1 adipocyte cell model, this study investigated the role of PIP3 and PIP2 on insulin stimulated glucose metabolism in high glucose (HG) treated cells. Exogenous PIP3 supplementation (1, 5, or 10 nM) increased the phosphorylation of AKT and PKCζ/λ, which in turn upregulated GLUT4 total protein expression as well as its surface expression, glucose uptake, and glucose utilization in cells exposed to HG (25 mM); however, PIP2 had no effect. Comparative signal silencing studies with antisense AKT2 and antisense PKCζ revealed that phosphorylation of PKCζ/λ is more effective in PIP3 mediated GLUT4 activation and glucose utilization than in AKT phosphorylation. Supplementation with PIP3 in combination with insulin enhanced glucose uptake and glucose utilization compared to PIP2 with insulin, or insulin alone, in HG-treated adipocytes. This suggests that a decrease in cellular PIP3 levels may cause impaired insulin sensitivity in diabetes. PIP3 supplementation also prevented HG-induced MCP-1 and resistin secretion and lowered adiponectin levels. This study for the first time demonstrates that PIP3 but not PIP2 plays an important role in GLUT4 upregulation and glucose metabolism mediated by AKT/PKCζ/λ phosphorylation. Whether PIP3 levels in blood can be used as a biomarker of insulin resistance in diabetes needs further investigation.