Decreased beige adipocyte number and mitochondrial respiration coincide with increased histone methyl transferase (G9a) and reduced FGF21 gene expression in Sprague-Dawley rats fed prenatal low protein and postnatal high-fat diets.

We have shown that prenatal low-protein (LP) followed by postnatal high-fat (HF) diets result in a rapid increase in subcutaneous adipose tissue (subc-AT) mass in the offspring, contributing to development of obesity and insulin resistance. Studies have shown that a key transcription factor, PR domain containing 16 (PRDM16), and fibroblast growth factor 21 (FGF21) are involved in conversion of precursor cells into mitochondria (mt)-enriched beige adipocytes (BA). Our hypothesis is that a maternal LP and postnatal HF diets increase the risk of obesity and insulin resistance in offspring, in part, by reducing the conversion of precursor cell into BA in the subc-AT of offspring. Using obese-prone Sprague-Dawley rats fed 8% LP or 20% normal-protein (NP) diets for 3 weeks prior to conception and throughout pregnancy and lactation followed by 12 weeks of 10% normal-fat (NF) or 45% HF diet feeding, we investigated whether prenatal LP and postnatal HF diets affect BA number and oxidative respiratory function in subc-AT. Results showed that subc-AT and liver FGF21, PRDM16 and BA marker CD137 mRNA increase with postnatal HF diet in maternal NP group rats. In contrast, rats fed maternal LP and postnatal HF diets showed no increase in subc-AT mt copy number, oxygen consumption rate, FGF21, PRDM16 and CD137 mRNA, whereas protein expression of an inhibitor for FGF21 transcription (histone methyltransferase, G9a) increased. These findings suggest that LPHF diets cause offspring metabolic alterations by reduced BA and FGF21 mRNA and increased G9a protein expression in subc-AT.

Evaluation of markers of beige adipocytes in white adipose tissue of the mouse.

BACKGROUND: There is a growing interest in exploiting the induction of beige or "brite" (brown in white) adipocytes (beigeing) to combat obesity and its comorbidities. However, there is some uncertainty regarding the best markers to evaluate the occurrence or magnitude of beigeing in white adipose tissue in the mouse model. METHODS: We evaluated the transcript expression of several thermoregulatory genes and proposed beige markers employing cell culture, whole white adipose tissue, and the adipocyte and stromal vascular fractions. RESULTS: Most beige markers tested with the exception of TMEM26 can discriminate white from beige adipocytes in culture. Markers FGF21, P2RX5, PAT2, or CAR4 can successfully mark beigeing in whole tissue of younger mice, or in the adipocyte subfraction of older mice. However, markers for the thermoregulatory genes UCP1, CIDEA, and Cox8b displayed the greatest dynamic range and were consistently elevated in vitro, in vivo, and in the adipocyte fraction by treatments that induce beige adipogenesis. CONCLUSIONS: While most putative beige markers are clearly expressed in beige adipocytes in vitro, in vivo the small dynamic range of most of these markers, the strength of the beigeing stimulus, and the age of the mice may limit their utility, although this limitation may be overcome by specifically evaluating these markers in the adipocyte fraction. Thermoregulatory markers like UCP1, CIDEA, or Cox8b represent the best options to evaluate the beigeing of white adipose tissue in vivo.

Butyrate and deoxycholic acid play common and distinct roles in HCT116 human colon cell proliferation.

Consumption of a high-fat diet causes an increase in bile acid deoxycholic acid (DCA) in colon lumen and colon cancer risk, while butyrate, an intestinal microbiota metabolite of dietary fiber, has been shown to exhibit colon cancer-preventive effects. To distinguish these opposing effects of DCA and butyrate (two major metabolites in colon lumen), we examined the effects of physiologically relevant doses of butyrate (0.5-2 mmol/l) and DCA (0.05-0.3 mmol/l) on colon cell proliferation. We hypothesize that butyrate and DCA each modulates the cell cycle and apoptosis via common and distinct cellular signaling targets. In this study, we demonstrated that both butyrate and DCA inhibited cell proliferation by up to 89% and 92% and increased cell apoptosis rate by up to 3.1- and 4.5-fold, respectively. Cell cycle analyses revealed that butyrate led to an increase in G1 and G2 fractions with a concomitant drop in the S-phase fraction, but DCA induced an increase in only G1 fraction with a concomitant drop in the S-phase fraction when compared with the untreated cells. The examination of early cellular signaling revealed that DCA but not butyrate increased intracellular reactive oxygen species, genomic DNA breakage, the activation of ERK1/2, caspase-3 and PARP. In contrast, DCA decreased activated Rb protein level, and butyrate but not DCA increased p21 expression. Collectively, although both butyrate and DCA inhibit colonic cell proliferation, butyrate increases tumor suppressor gene expression, whereas DCA decreases tumor suppressor activation in cell cycle and apoptosis pathways.

Maternal low-protein diet causes body weight loss in male, neonate Sprague-Dawley rats involving UCP-1-mediated thermogenesis.

Brown adipose tissue (BAT) plays an important role in regulating body weight (BW) by modifying thermogenesis. Maternal low protein (LP) diets reduce offspring birth weight. Increased BAT thermogenesis in utero may be one mechanism for the lower BW. However, whether maternal LP nutrition alters BAT thermogenesis and BW of offspring in utero is not yet known. We fed obese-prone Sprague-Dawley dams 8% LP or 20% normal protein (NP) diets for 3 weeks prior to breeding and through pregnancy. BW and gene expression of interscapular BAT (iBAT) thermogenic markers were measured in male fetal (gestation day 18) and neonatal (day 0 or 1) offspring. BW of neonatal LP males was lower than NP males but no difference was observed in females. Gene and protein expression of UCP-1 and transcription factors PRDM16 and PPARα in iBAT were 2- to 6-fold greater in LP than in NP male neonatal offspring. FNDC5, a precursor of irisin and activator of thermogenesis, was expressed 2-fold greater in neonatal LP iBAT than NP males. However, fetal iBAT UCP-1, PRDM16, PPARα and irisin mRNA did not differ between LP and NP groups. Maternal LP diet had no effects on placental irisin and UCP-2 expression. These results suggest that prenatal protein restriction increases the risk for low BW through mechanisms affecting full-term offspring iBAT thermogenesis but not greatly altering fetal iBAT or placental thermogenesis.

Epigenetics of inflammation, maternal infection, and nutrition.

Studies have demonstrated that epigenetic changes such as DNA methylation, histone modification, and chromatin remodeling are linked to an increased inflammatory response as well as increased risk of chronic disease development. A few studies have begun to investigate whether dietary nutrients play a beneficial role by modifying or reversing epigenetically induced inflammation. Results of these studies show that nutrients modify epigenetic pathways. However, little is known about how nutrients modulate inflammation by regulating immune cell function and/or immune cell differentiation via epigenetic pathways. This overview will provide information about the current understanding of the role of nutrients in the epigenetic control mechanisms of immune function.

Skeletal muscle Sirt3 expression and mitochondrial respiration are regulated by a prenatal low-protein diet.

Malnutrition during the fetal growth period increases risk for later obesity and type 2 diabetes mellitus (T2DM). We have shown that a prenatal low-protein (8% protein; LP) diet followed by postnatal high-fat (45% fat; HF) diet results in offspring propensity for adipose tissue catch-up growth, obesity and T2DM in Sprague-Dawley rats. Skeletal muscle is the major tissue for insulin-mediated glucose uptake. Dysfunctional skeletal muscle mitochondrial function, particularly reduction in expression of mitochondrial protein sirtuin protein 3 (Sirt3) contributes to development of T2DM by reducing mitochondrial respiration. Therefore, we hypothesized that maternal LP and postnatal HF diets would increase T2DM risk due to Sirt3 dysfunction within skeletal muscle mitochondria. Using our maternal LP and postnatal HF diet model, we showed that skeletal muscle mitochondrial oxygen consumption rate was decreased by maternal LP diet. Mitochondria copy number, mitochondrial thermogenesis (UCP-1) expression and mitochondrial biogenic factors including nuclear respiratory factor 1 and cytochrome c oxidases 1 and 4 were unaffected by maternal LP and postnatal HF diets. Skeletal muscle Sirt3 mRNA decreased with maternal LP diet. A mitochondrial substrate of Sirt3, succinate dehydrogenase (SDH), is regulated by Sirt3 via lysine residue acetylation status of SDH. Acetylated SDH protein (inactive form) levels were moderately decreased by maternal LP diet. Taken together, these data suggest that maternal LP and postnatal HF diets may increase the risk for T2D by decreasing skeletal muscle oxidative respiration via increased Sirt3 and possibly by decreased amounts of the active form of SDH enzyme.

Epigenetics in adipose tissue, obesity, weight loss, and diabetes.

Given the role that diet and other environmental factors play in the development of obesity and type 2 diabetes, the implication of different epigenetic processes is being investigated. Although it is well known that external factors can cause cell type-dependent epigenetic changes, including DNA methylation, histone tail modifications, and chromatin remodeling, the regulation of these processes, the magnitude of the changes and the cell types in which they occur, the individuals more predisposed, and the more crucial stages of life remain to be elucidated. There is evidence that obese and diabetic people have a pattern of epigenetic marks different from nonobese and nondiabetic individuals. The main long-term goals in this field are the identification and understanding of the role of epigenetic marks that could be used as early predictors of metabolic risk and the development of drugs or diet-related treatments able to delay these epigenetic changes and even reverse them. But weight gain and insulin resistance/diabetes are influenced not only by epigenetic factors; different epigenetic biomarkers have also been identified as early predictors of weight loss and the maintenance of body weight after weight loss. The characterization of all the factors that are able to modify the epigenetic signatures and the determination of their real importance are hindered by the following factors: the magnitude of change produced by dietary and environmental factors is small and cumulative; there are great differences among cell types; and there are many factors involved, including age, with multiple interactions between them.

Effects of voluntary running and soy supplementation on diet-induced metabolic disturbance and inflammation in mice.

We investigated the effects of diet (AIN93G or high-fat), physical activity (sedentary or voluntary running), and protein source (casein or soy protein isolate (SPI)) and their interactions on metabolic disturbance and inflammation in mice. After 14 weeks of feeding, the high-fat diet increased body weight gain by 34.5% (p < 0.01), whereas running reduced weight gain by 30.5% (p < 0.01) compared to their respective AIN93G and sedentary controls; SPI did not affect weight gain. The high-fat diet significantly increased plasma concentrations of insulin, glucose, triglycerides, leptin, and monocyte chemotactic protein-1 (MCP-1); running and SPI significantly reduced these parameters compared to their respective controls. The high-fat diet significantly increased and running significantly reduced plasma plasminogen activator inhibitor-1. A unique finding was that SPI supplementation to the high-fat diet reduced plasma insulin by 11% (p < 0.05), MCP-1 by 21% (p = 0.03), and tumor necrosis factor-α (TNF-α) by 50% (p = 0.05) compared to casein. As adipose tissues produce many adipocytokines, including MCP-1 and TNF-α, that contribute to a state of chronic low grade systemic inflammation and facilitate metabolic disturbance in obesity, further investigations are warranted into the roles of soy protein in reducing the risk of obesity.

Nutritional epigenomics: a portal to disease prevention.

Epigenetics can be defined as inheritable and reversible phenomena that affect gene expression without altering the underlying base pair sequence. Epigenomics is the study of genome-wide epigenetic modifications. Because gene expression changes are critical in both normal development and disease progression, epigenetics is widely applicable to many aspects of biological research. The influences of nutrients and bioactive food components on epigenetic phenomena such as DNA methylation and various types of histone modifications have been extensively investigated. Because an individual's epigenetic patterns are established during early gestation and are changed and personalized by environmental factors during our lifetime, epigenetic mechanisms are quite important in the development of transgenerational and adult obesity as well as in the development of diabetes mellitus. Aging and cancer demonstrate profound genome-wide DNA methylation changes, suggesting that nutrition may affect the aging process and cancer development through epigenetic mechanisms.

Prenatal low-protein and postnatal high-fat diets induce rapid adipose tissue growth by inducing Igf2 expression in Sprague Dawley rat offspring.

Maternal low-protein diets result in lower birth weight followed by accelerated catch-up growth that is accompanied by the development of obesity and glucose intolerance in later life. Whether postnatal high-fat (HF) diets further contribute to the development of obesity and insulin resistance in offspring by affecting adipose tissue metabolism and DNA methylation is currently unknown. Obese-prone Sprague-Dawley rats were fed 8% low protein (LP) or 20% normal protein diets for 3 wk prior to conception and throughout pregnancy and lactation to investigate whether prenatal LP and postnatal HF diets affect the rate of adipose tissue growth, insulin-like growth factor 2 (Igf2) expression, and DNA methylation in male offspring. At weaning, the offspring were fed 10% normal fat or 45% HF diets for 12 wk. The adipose tissue growth rate was increased (up to 26-fold) by the LP prenatal and HF postnatal diets. Adipose tissue Igf2 mRNAs and DNA methylation were increased by the LP prenatal and HF postnatal diets. The LP prenatal and HF postnatal diet increased the number of small adipocytes in adipose tissue and decreased insulin sensitivity. These findings suggest that prenatal LP and postnatal HF intake result in adipose tissue catch-up growth through alterations in the expression of the Igf2 gene and DNA methylation within adipocytes. These alterations in adiposity are accompanied by an increased risk of development of type 2 diabetes.

Leptin differentially regulate STAT3 activation in ob/ob mouse adipose mesenchymal stem cells.

BACKGROUND: Leptin-deficient ob/ob mice exhibit adipocyte hypertrophy and hyperplasia as well as elevated adipose tissue and systemic inflammation. Multipotent stem cells isolated from adult adipose tissue can differentiate into adipocytes ex vivo and thereby contribute toward increased adipocyte cell numbers, obesity, and inflamm ation. Currently, information is lacking regarding regulation of adipose stem cell numbers as well as leptin-induced inflammation and its signaling pathway in ob/ob mice. METHODS: Using leptin deficient ob/ob mice, we investigated whether leptin injection into ob/ob mice increases adipose stem cell numbers and adipose tissue inflammatory marker MCP-1 mRNA and secretion levels. We also determined leptin mediated signaling pathways in the adipose stem cells. RESULTS: We report here that adipose stem cell number is significantly increased following leptin injection in ob/ob mice and with treatment of isolated stem cells with leptin in vitro. Leptin also up-regulated MCP-1 secretion in a dose- and time-dependent manner. We further showed that increased MCP-1 mRNA levels were due to increased phosphorylation of Signal Transducer and Activator of Transcription 3 (STAT3) Ser727 but not STAT3 Tyr705 phosphorylation, suggesting differential regulation of MCP-1 gene expression under basal and leptin-stimulated conditions in adipose stem cells. CONCLUSIONS: Taken together, these studies demonstrate that leptin increases adipose stem cell number and differentially activates STAT3 protein resulting in up-regulation of MCP-1 gene expression. Further studies of mechanisms mediating adipose stem cell hyperplasia and leptin signaling in obesity are warranted and may help identify novel anti-obesity target strategies.

Synergistic inhibition of interleukin-6 production in adipose stem cells by tart cherry anthocyanins and atorvastatin.

Studies have shown positive correlations between inflammatory cytokines such as interleukin-6 (IL-6) and the development of chronic diseases including cardiovascular disease by activating C-reactive protein (CRP). Both atorvastatin calcium (lipitor) as well as flavonoid rich fruit such as tart cherry demonstrate potent anti-inflammatory effects on IL-6 secretion. In this study, we investigated whether tart cherry extract or specific anthocyanins contained in the tart cherry show synergistic anti-inflammatory effects with lipitor. Results showed that LPS-induced adipose stem cell secretion of IL-6 reduced with the addition of tart cherry extract, a mixture of tart cherry anthocyanins, and pure tart cherry cyanidin-3-O-glucoside (C3G) in a dose-dependent manner. Furthermore, lipitor and C3G exhibited synergistic effects in reducing LPS-induced IL-6 secretion from adipose stem cells. In conclusion, these results support potential benefits of using dietary phytochemicals in conjunction with pharmacological therapies to decrease adipose inflammation, drug doses, and ultimately, drug-induced adverse effects.

n-3 and n-6 polyunsaturated fatty acids differentially regulate adipose angiotensinogen and other inflammatory adipokines in part via NF-κB-dependent mechanisms.

Excessive secretion of proinflammatory adipokines has been linked to metabolic disorders. We have previously documented anti-inflammatory effects of n-3 polyunsaturated fatty acids (n-3 PUFAs) in adipose tissue; however, the mechanisms by which these fatty acids regulate adipokine secretion remain unclear. Here, we determined differential effects of eicosapentaenoic acid (EPA, n-3 PUFA) vs. arachidonic acid (AA, n-6 PUFA) on expression and secretion of angiotensinogen (Agt), interleukin 6 (IL-6) and monocyte chemotactic protein (MCP-1) in 3T3-L1 adipocytes. While both PUFAs increased intracellular Agt protein and mRNA expression, Agt secretion into culture media was increased only by AA treatment, which in turn was prevented by co-treatment with EPA. At various AA/EPA ratios, increasing AA concentrations significantly increased secretion of the above three adipokines, whereas increasing EPA dose-dependently, while lowering AA, decreased their secretion. Moreover, IL-6 and MCP-1 were more significantly reduced by EPA treatment compared to Agt (IL-6>MCP>Agt). Next, we tested whether nuclear factor-κB (NF-κB), a major proinflammatory transcription factor, was involved in regulation of these adipokines by PUFAs. EPA significantly inhibited NF-κB activation compared to control or AA treatments. Moreover, EPA attenuated tumor necrosis factor-α-induced MCP-1 and further reduced its secretion in the presence of an NF-κB inhibitor. Taken together, we reported here novel beneficial effects of EPA in adipocytes. We demonstrated direct anti-inflammatory effects of EPA, which are at least in part due to the inhibitory effects of this n-3 PUFA on the NF-κB pathway in adipocytes. In conclusion, these studies further support beneficial effects of n-3 PUFAs in adipocyte inflammation and metabolic disorders.

Immunity as a link between obesity and insulin resistance.

Obesity is a major public health problem in the United States and worldwide. Further, obesity is causally linked to the pathogenesis of insulin resistance, metabolic syndrome and type-2 diabetes (T2D). A chronic low-grade inflammation occurring in adipose tissue is at least in part responsible for the obesity-induced insulin resistance. This adipose tissue inflammation is characterized by changes in immune cell populations giving rise to altered adipo/cytokine profiles, which in turn induces skeletal muscle and hepatic insulin resistance. Detailed molecular mechanisms of insulin resistance, adipose tissue inflammation and the implications of these findings on therapeutic strategies are discussed in this review.

Stearidonic and eicosapentaenoic acids inhibit interleukin-6 expression in ob/ob mouse adipose stem cells via Toll-like receptor-2-mediated pathways.

Increased adipose tissue positively correlates with circulating inflammatory cytokines such as IL-6. We previously reported that adipose stem cells from genetically obese ob/ob mice produce significantly higher levels of IL-6 compared with other cell types such as adipocytes and macrophages within adipose tissue. We also demonstrated that (n-3) PUFA have antiinflammatory effects on adipocyte IL-6 secretion. Based on these findings, we hypothesized that EPA [20:5 (n-3)] and stearidonic acid [SDA, 18:4 (n-3)] would decrease LPS (200 µg/L)-induced IL-6 secretion and IL-6 mRNA content in the adipose stem cells. SDA (100 µmol/L) and EPA (100 µmol/L) significantly reduced LPS-induced IL-6 secretion and decreased IL-6 mRNA expression. To determine the underlying intracellular mechanisms, we tested whether LPS-induced Toll-like-receptor (TLR) 4 and TLR2 expression were modulated by these fatty acids using Western-blot analysis. EPA and SDA suppressed LPS-induced TLR2 but not TLR4 protein expression in the adipose stem cells. Furthermore, SDA and EPA significantly lowered the activation and translocation of NF-κB, a TLR2 downstream signaling target, while protein expression of extracellular signal-regulated kinases-1/2 were unaffected. Collectively, our results suggest that EPA and SDA inhibit LPS-induced IL-6 secretion and IL-6 mRNA expression in the adipose stem cells by decreasing TRL2-mediated signaling pathways.

(n-3) Fatty acids alleviate adipose tissue inflammation and insulin resistance: mechanistic insights.

Obesity is associated with the metabolic syndrome, a significant risk factor for developing type 2 diabetes and cardiovascular diseases. Chronic low-grade inflammation occurring in the adipose tissue of obese individuals is causally linked to the pathogenesis of insulin resistance and the metabolic syndrome. Although the exact trigger of this inflammatory process is unknown, adipose tissue hypoxia, endoplasmic reticular stress, and saturated fatty acid-mediated activation of innate immune processes have been identified as important processes in these disorders. Furthermore, macrophages and T lymphocytes have important roles in orchestrating this immune process. Although energy restriction leading to weight loss is the primary dietary intervention to reverse these obesity-associated metabolic disorders, other interventions targeted at alleviating adipose tissue inflammation have not been explored in detail. In this regard, (n-3) PUFA of marine origin both prevent and reverse high-fat-diet-induced adipose tissue inflammation and insulin resistance in rodents. We provide an update on the pathogenesis of adipose tissue inflammation and insulin resistance in obesity and discuss potential mechanisms by which (n-3) PUFA prevent and reverse these changes and the implications in human health.

Activation of autophagy through modulation of 5'-AMP-activated protein kinase protects pancreatic beta-cells from high glucose.

Chronic hyperglycaemia is detrimental to pancreatic beta-cells by causing impaired insulin secretion and diminished beta-cell function through glucotoxicity. Understanding the mechanisms underlying beta-cell survival is crucial for the prevention of beta-cell failure associated with glucotoxicity. Autophagy is a dynamic lysosomal degradation process that protects organisms against metabolic stress. To date, little is known about the physiological function of autophagy in the pathogenesis of diabetes. In the present study, we explored the roles of autophagy in the survival of pancreatic beta-cells exposed to high glucose using pharmacological and genetic manipulation of autophagy. We demonstrated that chronic high glucose increases autophagy in rat INS-1 (832/13) cells and pancreatic islets, and that this increase is enhanced by inhibition of 5'-AMP-activated protein kinase. Our results also indicate that stimulation of autophagy rescues pancreatic beta-cells from high-glucose-induced cell death and inhibition of autophagy augments caspase-3 activation, suggesting that autophagy plays a protective role in the survival of pancreatic beta-cells. Greater knowledge of the molecular mechanisms linking autophagy and beta-cell survival may unveil novel therapeutic targets needed to preserve beta-cell function.

n3 and n6 polyunsaturated fatty acids differentially modulate prostaglandin E secretion but not markers of lipogenesis in adipocytes.

A dramatic rise in the incidence of obesity in the U.S. has accelerated the search for interventions that may impact this epidemic. One recently recognized target for such intervention is adipose tissue, which secretes a variety of bioactive substances including prostaglandins. Prostaglandin E2 (PGE2) has been shown to decrease lipolysis in adipocytes, but limited studies have explored alternative mechanisms by which PGE2 might impact obesity, such as adipogenesis or lipogenesis. Studies conducted on ApcMin/+ mice indicated that selective inhibition of the cyclooxygenase (COX)-2 enzyme led to significant reductions in fatty acid synthase (FAS) activity in adipose tissue suggesting lipogenic effects of PGE2. To further investigate whether these lipid mediators directly regulate lipogenesis, we used 3T3-L1 adipocytes to determine the impact of eicosapentaenoic acid (EPA) and celecoxib on PGE2 formation and FAS used as a lipogenic marker. Both arachidonic acid (AA) and EPA dose-dependently increased PGE secretion from adipocytes. AA was expectedly more potent and exhibiting at 150 uM dose a 5-fold increase in PGE2 secretion over EPA. Despite higher secretion of PGE by EPA and AA compared to control, neither PUFA significantly altered FAS activity. By contrast both AA and EPA significantly decreased FAS mRNA levels. Addition of celecoxib, a selective COX-2 inhibitor, significantly decreased PGE2 secretion (p < 0.05) versus control, and also significantly decreased FAS activity (p < 0.05). Unexpectedly, the combination of exogenous PGE2 and celecoxib further decreased the FAS activity compared to PGE2 alone or untreated controls. In conclusion, EPA-mediated inhibition of AA metabolism did not significantly alter FAS activity while both AA and EPA significantly decreased FAS mRNA expression. COX-2 inhibition significantly decreased PGE2 production resulting in a decrease in FAS activity and expression that was not reversed with the addition of exogenous PGE2, suggesting an additional mechanism that is independent of COX-2.