Enhancement of ajoene-induced apoptosis by conjugated linoleic acid in 3T3-L1 adipocytes

Management of Obesity-Related Inflammatory and Cardiovascular Diseases by Medicinal Plants: From Traditional Uses to Therapeutic Targets

Inflammation is a crucial factor in the development and progression of cardiovascular diseases (CVD). Cardiac remodeling in the presence of persistent inflammation leads to myocardial fibrosis and extracellular matrix changes, which reduce cardiac function, induce arrhythmias, and finally, cause heart failure. The majority of current CVD treatment plans concentrate on reducing risk factors such as hyperlipidemia, type 2 diabetes, and hypertension. One such strategy could be inflammation reduction. Numerous in vitro, animal, and clinical studies indicate that obesity is associated with low-grade inflammation. Recent studies have demonstrated the potential of medicinal plants and phytochemicals to cure and prevent obesity and inflammation. In comparison to conventional therapies, the synergistic effects of several phytochemicals boost their bioavailability and impact numerous cellular and molecular targets. Focusing on appetite, pancreatic lipase activity, thermogenesis, lipid metabolism, lipolysis and adipogenesis, apoptosis in adipocytes, and adipocyte life cycle by medicinal plants and phytochemicals represent an important goal in the development of new anti-obesity drugs. We conducted an extensive review of the literature and electronic databases, including Google Scholar, PubMed, Science Direct, and MedlinePlus, for collecting data on the therapeutic effects of medicinal plants/phytochemicals in curing obesity and its related inflammation and CVD diseases, including cellular and molecular mechanisms, cytokines, signal transduction cascades, and clinical trials.

The immunomodulation and anti-inflammatory effects of garlic organosulfur compounds in cancer chemoprevention

Garlic (Allium sativum) has been used for centuries as a prophylactic and therapeutic medicinal agent. Importantly, garlic has been suggested to have both cancer-preventive potential as well as significant enhancing effects on the immune system. While these observations are supported experimentally both in vitro and in vivo, the impact of garlic in assisting the immune system in the prevention of cancer still lacks experimental confirmation. Studies addressing the immunomodulatory effects of garlic reveal conflicting data as to pro- or anti-inflammatory responses depending on the particular experimental set-ups and the garlic preparation used (i.e. garlic extract versus chemically pure garlic compounds). Here we provide an overview of the chemistry of the major garlic organosulfur compounds, summarize the current understanding and propose a link between the immunomodulating activity of garlic and the prevention of cancer. We hypothesize that garlic rather elicits anti-inflammatory and anti-oxidative responses that aid in priming the organism towards eradication of an emerging tumor.

The combination of resveratrol and conjugated linoleic acid is not useful in preventing obesity

Scientific research is constantly looking for new molecules to be used as functional ingredients to combat obesity. The aim of the present study was to analyse whether resveratrol and conjugated linoleic acid (CLA) together could reduce body fat more efficiently than their separate administration. Thirty-six male Wistar rats were randomly divided into four groups: controls rats (C), rats treated with resveratrol (RSV), rats treated with CLA (CLA) and rats treated with a combination of resveratrol and CLA (RSV+CLA). All rats were fed on an obesogenic diet. In RSV and RSV+CLA groups, the rats received 30 mg resveratrol/kg body weight/day. In CLA and RSV+CLA groups, an equimolecular mixture of trans-10,cis-12 and cis-9,trans-11 was added to the diet to reach 0.5% of the active isomer trans-10,cis-12. After 6 weeks of treatment, white adipose tissue from different anatomical locations was dissected and weighed. Serum triacylglycerols, total and HDL cholesterols, glucose, insulin, fructosamine and TNF-α were measured. A glucose tolerance test was also performed. Separately, resveratrol and CLA significantly reduced body fat but did not do so when combined: 20% in the RSV group and 18% in CLA group but 7% in the RSV+CLA group. Resveratrol reduced serum triacylglycerols. No differences were found among groups in serum cholesterol. Resveratrol, as well as the combination RSV+CLA, improved glycaemic control. These results demonstrate that the combination RSV+CLA reduces the effectiveness of each compound on body fat-lowering action, but it maintains the positive effect of resveratrol on glycaemic control. Consequently, this combination has no usefulness in obesity prevention.

Ajoene, a stable garlic by-product, inhibits high fat diet-induced hepatic steatosis and oxidative injury through LKB1-dependent AMPK activation

Hepatic steatosis, a hepatic component of metabolic syndrome, is common and may progress to steatohepatitis and cirrhosis. The liver X receptor-α (LXRα)-sterol regulatory element binding protein-1c (SREBP-1c) pathway plays a key role in hepatic steatosis. This study investigated the potential of ajoene, a stable garlic by-product, to inhibit high fat diet (HFD)-induced hepatic steatosis and the underlying mechanism. Ajoene treatment attenuated fat accumulation and induction of lipogenic genes in the liver of HFD-fed mice. Blood biochemical analyses and histopathologic examinations showed that ajoene prevented liver injury with the inhibition of oxidative stress, as evidenced by thiobarbituric acid reactive substances formation and nitrotyrosinylation. Moreover, ajoene treatment inhibited LXRα agonist (T0901317)-mediated SREBP-1c activation, and transactivation of the lipogenic target genes in hepatocytes. Ajoene was found to activate AMP-activated protein kinase (AMPK) via LKB1, responsible for the inhibition of p70 ribosomal S6 kinase-1 (S6K1). The ability of ajoene to repress T0901317-induced SREBP-1c expression was antagonized by inhibition of AMPK or activation of S6K1, supporting the role of these kinases in the antisteatotic effect. Our results demonstrate that ajoene has an effect of activating AMPK through LKB1 and inhibit S6K1 activity, contributing to the prevention of SREBP-1c-mediated hepatic lipogenesis via the inhibition of LXRα activity.

Ajoene, a stable garlic by-product, has an antioxidant effect through Nrf2-mediated glutamate-cysteine ligase induction in HepG2 cells and primary hepatocytes

Cytoprotective effects of chemopreventive agents may be attributed to the induction of antioxidant enzymes. Among these, the induction of glutamate-cysteine ligase (GCL) protects cells from oxidative injury by increasing glutathione (GSH) content. Nuclear factor erythroid-2-related factor 2 (Nrf2) transcriptionally regulates the expression of genes encoding for GCL and other cysteine-metabolizing enzymes. Despite extensive studies on the components in garlic, little information is available on organosulfur by-products made from garlic. In this study, we investigated whether ajoene, a chemically stable garlic by-product, has the ability to activate Nrf2 and induce GCL, and, if so, what is the role of activating Nrf2 in cytoprotection against oxidative stress. Immunoblottings and reporter gene assays were performed in HepG2 cells. Ajoene treatment activated Nrf2, as indicated by increased phosphorylation and nuclear accumulation of Nrf2, decreased interaction with Kelch-like ECH-associated protein-1, and decreased Nrf2 ubiquitination. Consistently, treatment of ajoene increased antioxidant response element reporter gene activity and the mRNA and protein levels of GCL subunits. Ajoene activated protein kinase C-delta (PKCdelta). Inhibition of PKCdelta activation by rottlerin abrogated its ability to activate Nrf2 and induce GCL, suggesting that ajoene promotes the Nrf2-dependent antioxidant defense system via PKCdelta activation. Consequently, ajoene prevented cell death, GSH depletion, and hydrogen peroxide production elicited by tert-butylhydroperoxide. The important role of Nrf2 in cytoprotection was verified by the reversal of ajoene's ability to protect hepatocytes in Nrf2-knockout mice. Our results demonstrate that ajoene increases PKCdelta-dependent Nrf2 activation, GCL induction, and the cellular GSH concentration, which may contribute to protecting cells from oxidative stress.

Mouse 3T3-L1 cells acquire resistance against oxidative stress as the adipocytes differentiate via the transcription factor FoxO

Repression of excessive increase and enlargement of adipocytes that is closely associated with obesity is effective in the prevention and treatment of metabolic syndrome. Generally, apoptosis is induced in cells via a wide variety of intracellular or extracellular substances, and recently, it has been suggested that the FoxO subfamily is involved in the induction of apoptosis. We aimed to elucidate the mechanism of FoxO-mediated apoptosis-induction in the adipocytes under the reactive oxygen species (ROS) stimulus. The treatment of differentiated and undifferentiated 3T3-L1 cells with glucose oxidase (GOD), an enzyme that generates H(2)O(2), induced apoptosis and led to the accumulation of 8-OHdG. Apoptosis analysis revealed that GOD treatment induced apoptosis in differentiated 3T3-L1 cells less efficiently than in undifferentiated preadipocytes. GOD remarkably increased the levels of Bad, Bax, and Bim-the genes that are actively involved in cell apoptosis. GOD treatment also increased the expression of FoxO3a mRNA and protein. The introduction of FoxO3a-siRNA into 3T3-L1 cells suppressed the oxidative stress-induced expression of Bim mRNA, as well as the GOD-induced apoptosis. Furthermore, the expression of MnSOD, Cu/ZnSOD, and catalase, as well as of FoxO, increased significantly along with the progression of adipocyte differentiation. These results indicated that ROS-induced apoptosis in undifferentiated 3T3-L1 cells via the expression of FoxO3a, whereas FoxO expression suppressed the ROS-induced apoptosis in differentiated 3T3-L1 cells via the expression of ROS-scavenging enzymes.

Anti-obesity effects of xanthohumol plus guggulsterone in 3T3-L1 adipocytes

Xanthohumol (XN) and guggulsterone (GS) have each been shown to inhibit adipogenesis and induce apoptosis in adipocytes. In the present study effects of the combination of XN + GS on 3T3-L1 adipocyte apoptosis and adipogenesis were investigated. Mature adipocytes were treated with XN and GS individually and in combination. XN and GS individually decreased cell viability, but XN + GS caused an enhanced decrease in viability and potentiated induction of apoptosis. Likewise, XN + GS caused a potentiated increase in caspase-3/7 activation, whereas neither of the compounds showed any effect individually. In addition, western blot analysis revealed that XN + GS increased Bax expression and decreased Bcl-2 expression, whereas individual compounds did not show any significant effect. XN and GS both decreased lipid accumulation. Individually, XN at 1.5 microM and GS at 3.12 microM decreased lipid accumulation by 26 +/- 4.5% (P < .001) each, whereas XN1.5 + GS3.12 decreased lipid accumulation by 78.2 +/- 1.8% (P < .001). Moreover, expression of the adipocyte-specific proteins was down-regulated with XN1.5 + GS3.12, but no effect was observed with the individual compounds. Finally, XN + GS caused an enhanced stimulation of lipolysis. Thus, combination of XN and GS is more potent in exerting anti-obesity effects than additive effects of the individual compounds.

Enhanced inhibition of adipogenesis and induction of apoptosis in 3T3-L1 adipocytes with combinations of resveratrol and quercetin

Certain flavonoids have been shown to have specific effects on biochemical and metabolic functions of adipocytes. In this study, we investigated the effects of combinations of resveratrol and quercetin on adipogenesis and apoptosis in 3T3-L1 cells. In maturing preadipocytes resveratrol and quercetin at 25 microM individually suppressed intracellular lipid accumulation by 9.4+/-3.9% (p<0.01) and 15.9+/-2.5%, respectively, (p<0.001). The combination of resveratrol and quercetin at the same dose, however, decreased lipid accumulation by 68.6+/-0.7% (p<0.001). In addition, combinations of resveratrol and quercetin at 25 microM significantly decreased the expression of peroxisome proliferators-activated receptor gamma (PPAR gamma) and CCAAT/enhancer-binding protein (C/EBP)alpha, both of which act as key transcription factors. In mature adipocytes resveratrol and quercetin at 100 microM individually decreased viability by 18.1+/-0.6% (p<0.001) and 15.8+/-1% (p<0.001) and increased apoptosis (100 microM) by 120.5+/-8.3% (p<0.001) and 85.3+/-10% (p<0.001) at 48 h, respectively. Combinations of resveratrol and quercetin further decreased viability (73.5+/-0.9%, p<0.001) and increased apoptosis (310.3+/-9.6%, p<0.001) more than single compounds alone. The combination of resveratrol and quercetin at 100 muM increased release of cytochrome c from mitochondria to cytosol and decreased ERK 1/2 phosphorylation. Taken together, our data indicate that combinations of resveratrol and quercetin can exert potential anti-obesity effects by inhibiting differentiation of preadipocytes and inducing apoptosis of mature adipocytes.