Combination of the anthocyanidins malvidin and peonidin attenuates lipopolysaccharide-mediated inflammatory gene expression in primary human adipocytes.

We recently demonstrated that California table grapes and a methanol-extractable, polyphenol-rich fraction decreased adiposity, insulin resistance, or markers of inflammation in high-fat fed mice. Malvidin and peonidin glycosides were the 2 most abundant anthocyanins in the polyphenol-rich fraction. We hypothesized that a blood borne combination of anthocyanidins malvidin and peonidin derived from intestinal ß-glycosidase metabolism of these 2 anthocyanins are responsible, in part, for the beneficial health effects observed in vivo. Therefore, we supplemented primary human adipocytes with malvidin or peonidin, alone or together, followed by acute lipopolysaccharide (LPS) treatment. Neither peonidin nor malvidin alone consistently decreased the expression of several inflammatory genes. However, supplementing adipocytes with an equal combination of malvidin plus peonidin followed by LPS treatment decreased the mRNA levels of interleukin (IL)-6, IL-1ß, IL-8, monocyte chemoattractant protein-1, toll-like receptor-2, tumor necrosis factor alpha, cyclooxygenase-2, and interferon gamma-induced protein-10. The highest combination dose of malvidin plus peonidin decreased or increased the expression of protein tyrosine phosphatase-1B and hormone sensitive lipase, respectively, genes encoding proteins associated with insulin resistance or lipolysis. These data indicate that a combination of malvidin plus peonidin have potentiating interactions that reduce inflammatory gene expression; however, in vivo studies are needed to support these in vitro data.

Nutrient Regulation: Conjugated Linoleic Acid's Inflammatory and Browning Properties in Adipose Tissue.

Obesity is the most widespread nutritional disease in the United States. Developing effective and safe strategies to manage excess body weight is therefore of paramount importance. One potential strategy to reduce obesity is to consume conjugated linoleic acid (CLA) supplements containing isomers cis-9, trans-11 and trans-10, cis-12, or trans-10, cis-12 alone. Proposed antiobesity mechanisms of CLA include regulation of (a) adipogenesis, (b) lipid metabolism, (c) inflammation, (d) adipocyte apoptosis, (e) browning or beiging of adipose tissue, and (f) energy metabolism. However, causality of CLA-mediated responses to body fat loss, particularly the linkage between inflammation, thermogenesis, and energy metabolism, is unclear. This review examines whether CLA's antiobesity properties are due to inflammatory signaling and considers CLA's linkage with lipogenesis, lipolysis, thermogenesis, and browning of white and brown adipose tissue. We propose a series of questions and studies to interrogate the role of the sympathetic nervous system in mediating CLA's antiobesity properties.

Table grape consumption reduces adiposity and markers of hepatic lipogenesis and alters gut microbiota in butter fat-fed mice.

Our objective was to determine if consuming table grapes reduces adiposity and its metabolic consequences and alters gut microbiota in mice fed a high-fat (HF), butter-rich diet. C57BL/6J mice were fed a low-fat (LF) diet or HF diet with 3% or 5% grapes for 11weeks. Total body and inguinal fat were moderately but significantly reduced in mice fed both levels of grapes compared to their controls. Mice fed 5% grapes had lower liver weights and triglyceride levels and decreased expression of glycerol-3-phosphate acyltransferase (Gpat1) compared to the 5% controls. Mice fed 3% grapes had lower hepatic mRNA levels of peroxisome proliferator-activated receptor gamma 2, sterol-CoA desaturase 1, fatty-acid binding protein 4 and Gpat1 compared to the 3% controls. Although grape feeding had only a minor impact on markers of inflammation or lipogenesis in adipose tissue or intestine, 3% of grapes decreased the intestinal abundance of sulfidogenic Desulfobacter spp. and the Bilophila wadsworthia-specific dissimilatory sulfite reductase gene and tended to increase the abundance of the beneficial bacterium Akkermansia muciniphila compared to controls. In addition, Bifidobacterium, Lactobacillus, Allobaculum and several other genera correlated negatively with adiposity. Allobaculum in particular was increased in the LF and 3% grapes groups compared to the HF-fed controls. Notably, grape feeding attenuated the HF-induced impairment in epithelial localization of the intestinal tight junction protein zonula occludens. Collectively, these data indicate that some of the adverse health consequences of consuming an HF diet rich in saturated fat can be attenuated by table grape consumption.

Intestinal and systemic inflammatory responses are positively associated with sulfidogenic bacteria abundance in high-fat-fed male C57BL/6J mice.

Recent studies have highlighted the relation between high-fat (HF) diets, the gut microbiota, and inflammation. However, the role of sulfidogenic bacteria in mediating these effects has been explored only recently. Therefore, we tested the hypothesis that an HF diet rich in saturated fat stimulates sulfidogenic bacteria and that these increases correlate with intestinal and systemic inflammatory responses. Forty C57BL/6J male mice were fed a low-fat (LF; 10% of energy) or an HF lard-based (60% of energy) diet for 6 or 20 wk. Mucosa samples were collected from the ileum, cecum, and colon and used for measuring 16S ribosomal RNA and functional genes of sulfidogenic bacteria. Matching intestinal samples and visceral and subcutaneous white adipose tissue (WAT) depots were used to measure mRNA abundance for inflammatory genes. Mice fed the HF diet had greater (P < 0.05) abundance of 3 types of sulfidogenic bacteria, primarily in colonic mucosa, compared with LF-fed mice at week 20. Although HF feeding did not increase intestinal inflammation at week 6, ileal markers of macrophage infiltration and inflammation were upregulated (P < 0.05) 1- to 6-fold at week 20. HF feeding impaired the localization of the tight junction protein zonula occludens 1 at the apical area of the ileal epithelium at weeks 6 and 20. Mice fed the HF diet had 1- to 100-fold greater (P < 0.05) mRNA levels of markers of macrophage infiltration in visceral and subcutaneous WAT at week 20, but not at week 6, compared with LF-fed mice. These results provide evidence that chronic, but not acute, consumption of an HF lard-based diet may be linked with pathways of microbial metabolism that potentially contribute to chronic intestinal and systemic inflammation. Such linkage provides further support for reducing consumption of saturated fats.

Influence of dietary fat on intestinal microbes, inflammation, barrier function and metabolic outcomes.

Recent studies using germ-free, gnotobiotic microbial transplantation/conventionalization or antibiotic treatment in rodent models have highlighted the critical role of intestinal microbes on gut health and metabolic functions of the host. Genetic and environmental factors influence the abundance and type of mutualistic vs. pathogenic bacteria, each of which has preferred substrates for growth and unique products of fermentation. Whereas some fermentation products or metabolites promote gut function and health, others impair gut function, leading to compromised nutrient digestion and barrier function that adversely impact the host. Such products may also influence food intake, energy harvest and expenditure, and insulin action, thereby influencing adiposity and related metabolic outcomes. Diet composition influences gut microbiota and subsequent fermentation products that impact the host, as demonstrated by prebiotic studies using oligosaccharides or other types of indigestible fiber. Recent studies also show that dietary lipids affect specific populations of gut microbes and their metabolic end products. This review will focus on studies examining the influence of dietary fat amount and type on the gut microbiome, intestinal health and positive and negative metabolic consequences. The protective role of omega-3-rich fatty acids on intestinal inflammation will also be examined.

Differential effects of grape powder and its extract on glucose tolerance and chronic inflammation in high-fat-fed obese mice.

The objective of this study was to determine the anti-inflammatory properties of grape powder (GP) or GP extract (GE) and examine (1) which polyphenol metabolites in GE were bioavailable, (2) the impact of GP and GE on glucose tolerance and inflammation in obese mice, and (3) if bioavailable polyphenols in GE decrease markers of inflammation in primary adipocytes. In experiment 1, C57BL/6J mice were gavaged with GE and serum polyphenols were measured. In experiment 2, mice were fed high-fat diets supplemented with 3% GP or 0.02% GE for 18 weeks and markers of inflammation were measured. In experiment 3, human adipocytes were treated with the bioavailable polyphenols quercetin 3-O-glucoside (Q3G) or quercetin 3-O-glucuronide (Q3GN) and markers of inflammation were measured. Serum Q3G and Q3GN increased at 1 h post-GE gavage and decreased thereafter. GP supplementation improved glucose tolerance at 5 weeks and decreased markers of inflammation ∼20-50% in serum and adipose tissue at 18 weeks. Q3G, but not Q3GN, attenuated TNFα-mediated inflammatory gene expression ∼30-40% in human adipocytes, possibly by suppressing c-Jun-NH(2) terminal kinase and c-Jun activation. In summary, (1) Q3G and Q3GN are bioavailable polyphenols in GE, (2) GP acutely improves glucose tolerance and chronically reduces markers of inflammation in obese mice, and (3) Q3G reduces several markers of inflammation in human adipocytes.

JNK inhibition by SP600125 attenuates trans-10, cis-12 conjugated linoleic acid-mediated regulation of inflammatory and lipogenic gene expression.

Supplementation with a mixture of trans-10, cis-12 (t10,c12) and cis-9, trans-11 (c9,t11) isomers of conjugated linoleic acid (CLA), or t10,c12 CLA alone, reduces body weight and fat deposition in animals and some humans. However, these anti-obesity actions of t10,c12 CLA are routinely accompanied by increased markers of inflammation and insulin resistance. Thus, we examined the extent to which blocking c-Jun NH2-terminal kinase (JNK) signaling using the JNK inhibitor SP600125 attenuated markers of inflammation and insulin resistance in primary human adipocytes treated with t10,c12 CLA. SP600125 attenuated t10,c12 CLA-mediated phosphorylation of cJun and increased protein levels of activating transcription factor (ATF) 3, two downstream targets of JNK. SP600125 attenuated t10,c12 CLA-mediated induction of inflammatory genes, including interleukin (IL)-6, IL-8, IL-1ß, ATF3, monocyte chemoattractant protein (MCP)-1, and cyclooxygenase-2. Consistent with these data, SP600125 prevented t10,c12 CLA-mediated secretion of IL-8, IL-6, and MCP-1. SP600125 prevented t10,c12 CLA suppression of lipogenic genes including peroxisome proliferator activated receptor gamma, liver X receptor, sterol regulatory element binding protein, acetyl-CoA carboxylase, and stearoyl-CoA desaturase. Additionally, SP600125 blocked t10,c12 CLA-mediated induction of suppressor of cytokine synthesis-3 and suppression of adiponectin and insulin-dependent glucose transporter 4 mRNA levels. Collectively, these data suggest that JNK signaling plays an important role in t10,c12 CLA-mediated regulation of inflammatory and lipogenic gene expression in primary cultures of human adipocytes.

Potential mechanisms by which polyphenol-rich grapes prevent obesity-mediated inflammation and metabolic diseases.

Obesity and metabolic disease-related health problems (e.g., type 2 diabetes, atherosclerosis, and hypertension) are the most prevalent nutrition-related issues in the United States. An emerging feature of obesity and type 2 diabetes is their linkage with chronic inflammation that begins in white adipose tissue and eventually becomes systemic. One potential strategy to reduce inflammation and insulin resistance is consumption of polyphenol-rich foods like grapes or their by-products, which have anti-inflammatory properties. Polyphenols commonly found in grape products have been reported to reduce inflammation by (a) acting as an antioxidant or increasing antioxidant gene or protein expression, (b) attenuating endoplasmic reticulum stress signaling, (c) blocking proinflammatory cytokines or endotoxin-mediated kinases and transcription factors involved in metabolic disease, (d) suppressing inflammatory- or inducing metabolic-gene expression via increasing histone deacetylase activity, or (e) activating transcription factors that antagonize chronic inflammation. Thus, polyphenol-rich grape products may reduce obesity-mediated chronic inflammation by multiple mechanisms, thereby preventing metabolic diseases.

Grape powder extract attenuates tumor necrosis factor α-mediated inflammation and insulin resistance in primary cultures of human adipocytes.

Grapes are rich in phenolic phytochemicals that possess anti-oxidant and anti-inflammatory properties. However, the ability of grape powder extract (GPE) to prevent inflammation and insulin resistance in human adipocytes caused by tumor necrosis factor α (TNFα), a cytokine elevated in plasma and white adipose tissue (WAT) of obese, diabetic individuals, is unknown. Therefore, we examined the effects of GPE on markers of inflammation and insulin resistance in primary cultures of newly differentiated human adipocytes treated with TNFα. We found that GPE attenuated TNFα-induced expression of inflammatory genes including interleukin (IL)-6, IL-1ß, IL-8, monocyte chemoattractant protein (MCP)-1, cyclooxygenase (COX)-2 and Toll-like receptor (TLR)-2. GPE attenuated TNFα-mediated activation of extracellular signal-related kinase (ERK) and c-Jun NH(2)-terminal kinase (JNK) and activator protein-1 (AP-1, i.e., c-Jun). GPE also attenuated TNFα-mediated IκBα degradation and nuclear factor-kappa B (NF-κB) activity. Finally, GPE prevented TNFα-induced expression of protein tyrosine phosphatase (PTP)-1B and phosphorylation of serine residue 307 of insulin receptor substrate-1 (IRS-1), which are negative regulators of insulin sensitivity, and suppression of insulin-stimulated glucose uptake. Taken together, these data demonstrate that GPE attenuates TNFα-mediated inflammation and insulin resistance in human adipocytes, possibly by suppressing the activation of ERK, JNK, c-Jun and NF-κB.

Quercetin is equally or more effective than resveratrol in attenuating tumor necrosis factor-{alpha}-mediated inflammation and insulin resistance in primary human adipocytes.

BACKGROUND: Quercetin and trans-resveratrol (trans-RSV) are plant polyphenols reported to reduce inflammation or insulin resistance associated with obesity. Recently, we showed that grape powder extract, which contains quercetin and trans-RSV, attenuates markers of inflammation in human adipocytes and macrophages and insulin resistance in human adipocytes. However, we do not know how quercetin and trans-RSV individually affected these outcomes. OBJECTIVE: The aim of this study was to examine the extent to which quercetin and trans-RSV prevented inflammation or insulin resistance in primary cultures of human adipocytes treated with tumor necrosis factor-α (TNF-α)-an inflammatory cytokine elevated in the plasma and adipose tissue of obese, diabetic individuals. DESIGN: Cultures of human adipocytes were pretreated with quercetin and trans-RSV followed by treatment with TNF-α. Subsequently, gene and protein markers of inflammation and insulin resistance were measured. RESULTS: Quercetin, and to a lesser extent trans-RSV, attenuated the TNF-α-induced expression of inflammatory genes such as interleukin (IL)-6, IL-1ß, IL-8, and monocyte chemoattractant protein-1 (MCP-1) and the secretion of IL-6, IL-8, and MCP-1. Quercetin attenuated TNF-α-mediated phosphorylation of extracellular signal-related kinase and c-Jun-NH2 terminal kinase, whereas trans-RSV attenuated only c-Jun-NH2 terminal kinase phosphorylation. Quercetin and trans-RSV attenuated TNF-α-mediated phosphorylation of c-Jun and degradation of inhibitory κB protein. Quercetin, but not trans-RSV, decreased TNF-α-induced nuclear factor-κB transcriptional activity. Quercetin and trans-RSV attenuated the TNF-α-mediated suppression of peroxisome proliferator-activated receptor γ (PPARγ) and PPARγ target genes and of PPARγ protein concentrations and transcriptional activity. Quercetin prevented the TNF-α-mediated serine phosphorylation of insulin receptor substrate-1 and protein tyrosine phosphatase-1B gene expression and the suppression of insulin-stimulated glucose uptake, whereas trans-RSV prevented only the TNF-α-mediated serine phosphorylation of insulin receptor substrate-1. CONCLUSION: These data suggest that quercetin is equally or more effective than trans-RSV in attenuating TNF-α-mediated inflammation and insulin resistance in primary human adipocytes.

Trans-10, cis-12 conjugated linoleic acid antagonizes ligand-dependent PPARgamma activity in primary cultures of human adipocytes.

We previously demonstrated that trans-10, cis-12 (10,12) conjugated linoleic acid (CLA) causes human adipocyte delipidation, insulin resistance, and inflammation in part by attenuating PPARgamma target gene expression. We hypothesized that CLA antagonizes the activity of PPARgamma in an isomer-specific manner. 10,12 CLA, but not cis-9, trans-11 (9,11) CLA, suppressed ligand-stimulated activation of a peroxisome proliferator response element-luciferase reporter. This decreased activation of PPARgamma by 10,12 CLA was accompanied by an increase in PPARgamma and extracellular signal-related kinase (ERK)1/2 phosphorylation, followed by decreased PPARgamma protein levels. To investigate if 10,12 CLA-mediated delipidation was preventable with a PPARgamma ligand (BRL), cultures were treated for 1 wk with 10,12 CLA or 10,12 CLA + BRL and adipogenic gene and protein expression, glucose uptake, and triglyceride (TG) were measured. BRL cosupplementation completely prevented 10,12 CLA suppression of adipocyte fatty acid-binding protein, lipoprotein lipase, and perilipin mRNA levels without preventing reductions in PPARgamma or insulin-dependent glucose transporter 4 (GLUT4) expression, glucose uptake, or TG. Lastly, we investigated the impact of CLA withdrawal in the absence or presence of BRL for 2 wk. CLA withdrawal did not rescue CLA-mediated reductions in adipogenic gene and protein expression. In contrast, BRL supplementation for 2 wk following CLA withdrawal rescued mRNA levels of PPARgamma target genes. However, the levels of PPARgamma and GLUT4 protein and TG were only partially rescued by BRL. Collectively, we demonstrate for the first time, to our knowledge, that 10,12 CLA antagonizes ligand-dependent PPARgamma activity, possibly via PPARgamma phosphorylation by ERK.

Preadipocytes mediate lipopolysaccharide-induced inflammation and insulin resistance in primary cultures of newly differentiated human adipocytes.

Recent data suggest that proinflammatory cytokines secreted from adipose tissue contribute to the morbidity associated with obesity. However, characterization of the cell types involved in inflammation and how these cells promote insulin resistance in human adipocytes are unclear. We simulated acute inflammation using the endotoxin lipopolysaccharide (LPS) to define the roles of nonadipocytes in primary cultures of human adipocytes. LPS induction of the mRNA levels of proinflammatory cytokines (e.g. IL-6, TNF-alpha, and IL-1beta) and chemokines (e.g. IL-8, monocyte chemoattractant protein-1) occurred primarily in the nonadipocyte fraction of newly differentiated human adipocytes. Nonadipocytes were characterized as preadipocytes based on their abundant mRNA levels of preadipocyte markers preadipocyte factor-1 and adipocyte enhancer protein-1 and only trace levels of markers for macrophages and myocytes. The essential role of preadipocytes in inflammation was confirmed by modulating the degree of differentiation in the cultures from approximately 0-90%. LPS-induced proinflammatory cytokine/chemokine expression and nuclear factor-kappaB and MAPK signaling decreased as differentiation increased. LPS-induced cytokine/chemokine expression in preadipocytes was associated with: 1) decreased adipogenic gene expression, 2) decreased ligand-induced activation of a peroxisome proliferator activated receptor (PPAR)-gamma reporter construct and increased phosphorylation of PPARgamma, and 3) decreased insulin-stimulated glucose uptake. Collectively, these data demonstrate that LPS induces nuclear factor-kappaB- and MAPK-dependent proinflammatory cytokine/chemokine expression primarily in preadipocytes, which triggers the suppression of PPARgamma activity and insulin responsiveness in human adipocytes.

Conjugated linoleic acid promotes human adipocyte insulin resistance through NFkappaB-dependent cytokine production.

We previously demonstrated that trans-10, cis-12 conjugated linoleic acid (CLA) reduced the triglyceride content of human adipocytes by activating mitogen-activated protein kinase kinase/extracellular signal-related kinase (MEK/ERK) signaling via interleukins (IL) 6 and 8. However, the upstream mechanism is unknown. Here we show that CLA increased (>or=6 h) the secretion of IL-6 and IL-8 in cultures containing both differentiated adipocytes and stromal vascular (SV) cells, non-differentiated SV cells, and adipose tissue explants. CLA isomer-specific induction of IL-6 and tumor necrosis factor-alpha was associated with the activation of nuclear factor kappaB (NFkappaB) as evidenced by 1) phosphorylation of IkappaBalpha, IkappaBalpha kinase, and NFkappaB p65, 2) IkappaBalpha degradation, and 3) nuclear translocation of NFkappaB. Pretreatment with selective NFkappaB inhibitors and the MEK/ERK inhibitor U0126 blocked CLA-mediated IL-6 gene expression. Trans-10, cis-12 CLA suppression of insulin-stimulated glucose uptake at 24 h was associated with decreased total and plasma membrane glucose transporter 4 proteins. Inhibition of NFkappaB activation or depletion of NFkappaB by RNA interference using small interfering NFkappaB p65 attenuated CLA suppression of glucose transporter 4 and peroxisome proliferator-activated receptor gamma proteins and glucose uptake. Collectively, these data demonstrate for the first time that trans-10, cis-12 CLA promotes NFkappaB activation and subsequent induction of IL-6, which are at least in part responsible for trans-10, cis-12 CLA-mediated suppression of peroxisome proliferator-activated receptor gamma target gene expression and insulin sensitivity in mature human adipocytes.

Conjugated linoleic acid induces human adipocyte delipidation: autocrine/paracrine regulation of MEK/ERK signaling by adipocytokines.

Dietary conjugated linoleic acid (CLA) reduces body fat in animals and some humans. Here we show that trans-10, cis-12 CLA, but not cis-9, trans-11 CLA, when added to cultures of stromal vascular cells containing newly differentiated human adipocytes, caused a time-dependent decrease in triglyceride content, insulin-stimulated glucose and fatty acid uptake, incorporation into lipid, and oxidation compared with controls. In parallel, gene expression of peroxisome proliferator-activated receptor-gamma and many of its downstream targets were diminished by trans-10, cis-12 CLA, whereas leptin gene expression was increased. Prior to changes in gene expression and metabolism, trans-10, cis-12 CLA caused a robust and sustained activation of mitogen-activated protein kinase kinase/extracellular signal-related kinase (MEK/ERK) signaling. Furthermore, the trans-10, cis-12 CLA-mediated activation of MEK/ERK could be attenuated by pretreatment with U0126 and pertussis toxin. In parallel, pretreatment with U0126 blocked the ability of trans-10, cis-12 CLA to alter gene expression and attenuate glucose and fatty acid uptake of the cultures. Intriguingly, the induction by CLA of MEK/ERK signaling was linked to hypersecretion of adipocytokines interleukin-6 and interleukin-8. Collectively, these data demonstrate for the first time that trans-10, cis-12 CLA decreases the triglyceride content of newly differentiated human adipocytes by inducing MEK/ERK signaling through the autocrine/paracrine actions of interleukins-6 and 8.

Conjugated linoleic acid in humans: regulation of adiposity and insulin sensitivity.

Conjugated linoleic acid (CLA) isomers, a group of positional and geometric isomers of linoleic acid [18:2(n-6)], have been studied extensively due to their ability to modulate cancer, atherosclerosis, obesity, immune function and diabetes in a variety of experimental models. The purpose of this review was to examine CLA's isomer-specific regulation of adiposity and insulin sensitivity in humans and in cultures of human adipocytes. It has been clearly demonstrated that specific CLA isomers or a crude mixture of CLA isomers prevent the development of obesity in certain rodent and pig models. This has been attributed mainly to trans-10, cis-12 CLA, both in vivo and in vitro. However, CLA's ability to modulate human obesity remains controversial because data from clinical trials using mixed isomers are conflicting. In support of some studies in humans, our group demonstrated that trans-10, cis-12 CLA prevents triglyceride (TG) accumulation in primary cultures of differentiating human preadipocytes. In contrast, cis-9, trans-11 CLA increases TG content. Closer examination has revealed that CLA's antiadipogenic actions are due, at least in part, to regulation of glucose and fatty acid uptake and metabolism. This review presents our current understanding of potential isomer-specific mechanisms by which CLA reduces human adiposity and insulin sensitivity.

Isomer-specific regulation of metabolism and PPARgamma signaling by CLA in human preadipocytes.

Trans-10,cis-12 conjugated linoleic acid (CLA) has previously been shown to be the CLA isomer responsible for CLA-induced reductions in body fat in animal models, and we have shown that this isomer, but not the cis-9,trans-11 CLA isomer, specifically decreased triglyceride (TG) accumulation in primary human adipocytes in vitro. Here we investigated the mechanism behind the isomer-specific, CLA-mediated reduction in TG accumulation in differentiating human preadipocytes. Trans-10,cis-12 CLA decreased insulin-stimulated glucose uptake and oxidation, and reduced insulin-dependent glucose transporter 4 gene expression. Furthermore, trans-10,cis-12 CLA reduced oleic acid uptake and oxidation when compared with all other treatments. In parallel to CLA's effects on metabolism, trans-10,cis-12 CLA decreased, whereas cis-9,trans-11 CLA increased, the expression of peroxisome proliferator-activated receptor gamma (PPARgamma) and several of its downstream target genes when compared with vehicle controls. Transient transfections demonstrated that both CLA isomers antagonized ligand-dependent activation of PPARgamma. Collectively, trans-10,cis-12, but not cis-9, trans-11, CLA decreased glucose and lipid uptake and oxidation and preadipocyte differentiation by altering preadipocyte gene transcription in a manner that appeared to be due, in part, to decreased PPARgamma expression.