Role of HCA2 in Regulating Intestinal Homeostasis and Suppressing Colon Carcinogenesis.

Hydroxycarboxylic acid receptor 2 (HCA2) is vital for sensing intermediates of metabolism, including ß-hydroxybutyrate and butyrate. It also regulates profound anti-inflammatory effects in various tissues, indicating that HCA2 may serve as an essential therapeutic target for mediating inflammation-associated diseases. Butyrate and niacin, endogenous and exogenous ligands of HCA2, have been reported to play an essential role in maintaining intestinal homeostasis. HCA2, predominantly expressed in diverse immune cells, is also present in intestinal epithelial cells (IECs), where it regulates the intricate communication network between diet, microbiota, and immune cells. This review summarizes the physiological role of HCA2 in intestinal homeostasis and its pathological role in intestinal inflammation and cancer.

Whole-slide image analysis outperforms micrograph acquisition for adipocyte size quantification.

The distinction between biological processes of adipose tissue expansion is crucial to understanding metabolic derangements, but a robust method for quantifying adipocyte size has yet to be standardized. Here, we compared three methods for histological analysis in situ: one conventional approach using individual micrographs acquired by digital camera, and two with whole-slide image analysis pipelines involving proprietary (Visiopharm) and open-source software (QuPath with a novel ImageJ plugin). We found that micrograph analysis identified 10-40 times fewer adipocytes than whole-slide methods, and this small sample size resulted in high variances that could lead to statistical errors. The agreement of the micrograph method to measure adipocyte area with each of the two whole-slide methods was substantially less (R2 of 0.6644 and 0.7125) than between the two whole-slide methods (R2 of 0.9402). These inconsistencies were more pronounced in samples from high-fat diet fed mice. While the use of proprietary software resulted in the highest adipocyte count, the lower cost, ease of use, and minimal variances of the open-source software provided a distinct advantage for measuring the number and size of adipocytes. In conclusion, we recommend whole-slide image analysis methods to consistently measure adipocyte area and avoid unintentional errors due to small sample sizes.

The Absence of Adiponectin Alters Niacin's Effects on Adipose Tissue Inflammation in Mice.

Obesity is an immunometabolic disease associated with chronic inflammation and the dysregulation of pro- and anti-inflammatory cytokines. One hallmark of obesity is reduced concentrations of the anti-inflammatory adipokine, adiponectin. Pharmacologic doses of niacin produce multiple metabolic benefits, including attenuating high-fat diet (HFD)-induced adipose tissue inflammation and increasing adiponectin concentrations. To determine if adiponectin mediates the anti-inflammatory effects of niacin, male C57BL/6J (WT) and adiponectin null (Adipoq-/-) mice were maintained on a low-fat diet (LFD) or HFD for 6 weeks, before being administered either vehicle or niacin (360 mg/kg/day) for 5 weeks. HFD-fed mice had increased expression of genes associated with macrophage recruitment (Ccl2) and number (Cd68), and increased crown-like structure (CLS) number in adipose tissue. While niacin attenuated Ccl2 expression, there were no effects on Cd68 or CLS number. The absence of adiponectin did not hinder the ability of niacin to reduce Ccl2 expression. HFD feeding increased gene expression of inflammatory markers in the adipose tissue of WT and Adipoq-/- mice. While niacin tended to decrease the expression of inflammatory markers in WT mice, niacin increased their expression in HFD-fed Adipoq-/- mice. Therefore, our results indicate that the absence of adiponectin alters the effects of niacin on markers of adipose tissue inflammation in HFD-fed mice, suggesting that the effects of niacin on tissue cytokines may involve adiponectin.

Niacin increases diet-induced hepatic steatosis in B6129 mice.

Nonalcoholic fatty liver disease (NAFLD) is a very common disorder affecting between 20 and 30% of adults in the United States. However, there is no effective pharmacotherapy for treating NAFLD. Niacin, a water-soluble vitamin (B3), at pharmacological doses, decreases hepatic triglyceride (TG) content in NAFLD through inhibition of diacylglycerol acyltransferase 2, a key enzyme that catalyzes the final step in TG synthesis. Alternatively, some studies indicate that niacin induces fatty liver in high-fat diet (HFD)-fed rats. Therefore, in this study we investigated whether niacin is beneficial in treating NAFLD in two strains of mice, C57BL/6J (B6) and B6129SF2/J (B6129) mice, with 20 weeks of HFD feeding. Niacin treatment was started from week 5 until the end of the study. Niacin treatment increased normalized liver weight, hepatic TG content and NAFLD score in HFD-fed B6129 mice but had no impact on B6 mice. Metabolomics analysis revealed that in B6129 mice, 4-hydroxyphenylpyruvic acid (4-HPP), which is associated with fatty acid oxidation, did not change with HFD feeding but significantly decreased with niacin treatment. Lipidomics analysis discovered that the abundance of phosphocholine (PC), which is critical for very low-density lipoprotein (VLDL)-TG production and secretion, was decreased in HFD-fed B6129 with niacin treatment. In conclusion, niacin had no impact on diet-induced NAFLD development in B6 mice but potentiated hepatic steatosis in HFD-fed B6129 mice due to impaired fatty acid oxidation and decreased VLDL-TG production and secretion.

Rapid lipolytic oscillations in ex vivo adipose tissue explants revealed through microfluidic droplet sampling at high temporal resolution.

Our understanding of adipose tissue biology has steadily evolved. While structural and energy storage functionalities have been in the forefront, a key endocrine role for adipocytes was revealed only over the last few decades. In contrast to the wealth of information on dynamic function of other endocrine tissues, few studies have focused on dynamic adipose tissue function or on tool development toward that end. Here, we apply our unique droplet-based microfluidic devices to culture, perfuse, and sample secretions from primary murine epididymal white adipose tissue (eWAT), and from predifferentiated clusters of 3T3-L1 adipocytes. Through automated control, oil-segmented aqueous droplets (∼2.6 nL) were sampled from tissue or cells at 3.5 second temporal resolution (including sample and reference droplets), with integrated enzyme assays enabling real-time quantification of glycerol (down to 1.9 fmol per droplet). This high resolution revealed previously unreported oscillations in secreted glycerol at frequencies of 0.2 to 2.0 min-1 (∼30-300 s periods) present in the primary tissue but not in clustered cells. Low-level bursts (∼50 fmol) released in basal conditions were contrasted with larger bursts (∼300 fmol) during stimulation. Further, both fold changes and burst magnitudes were decreased in eWAT of aged and obese mice. These results, combined with immunostaining and photobleaching analyses, suggest that gap-junctional coupling or nerve cell innervation within the intact ex vivo tissue explants play important roles in this apparent tissue-level, lipolytic synchronization. High-resolution, quantitative sampling by droplet microfluidics thus permitted unique biological information to be observed, giving an analytical framework poised for future studies of dynamic oscillatory function of adipose and other tissues.

Pharmacodynamic Effects of Pioglitazone on High Molecular Weight Adiponectin Concentrations and Insulin Response After Oral Sugar in Equids.

Chronic insulin dysregulation is challenging to manage with pharmaceuticals in horses. Pioglitazone improves insulin sensitivity in humans, and the pharmacokinetics of pioglitazone have been evaluated in horses. The objectives of this study were to assess the pharmacodynamic effects of oral pioglitazone on morphometric parameters, hepatic enzyme activity and function, adipokines, and enteroinsular response to oral sugar. A prospective pilot study was performed using fifteen adult equids (8 ponies, 7 horses) to evaluate the effects of short-term pioglitazone administration (2 mg/kg PO q 24 hours, 28 days). Oral sugar tests (OST) were performed before and after treatment. Adipokines were measured at day 0, 14, and 28 of administration. Plasma drug concentrations were measured at day 14 and 28 of administration. The subjects were grouped into horses, ponies, and insulin dysregulated (ID) animals. Baseline values for all parameters were compared with values obtained at day 14 and 28 using one-way or two-way analysis of variance. Mild changes were noted in morphometric parameters and hepatic enzymes. No differences were found in leptin concentrations or the blood glucose response to the OST. Significant decreases were found in the insulin response to OST at 90 and 120 minutes time points and the area under the curve after pioglitazone treatment in the pony and ID groups. High-molecular-weight (HMW) adiponectin concentrations were significantly increased in all groups after pioglitazone treatment. Decreased insulin concentrations in response to oral sugar and increased HMW adiponectin concentrations indicate positive effects of pioglitazone for treatment of metabolic derangements in equine metabolic syndrome, which warrant future clinical study.

Adiponectin Regulation and Function.

Adipose tissue is now recognized as an important endocrine organ, capable of secreting a large number of endocrine factors which regulate a wide variety of physiological functions. Adiponectin is one such factor, secreted in large quantities primarily from adipose tissue. Adiponectin is posttranslationally modified from a 30-kDa monomeric protein into different multimers (low molecular weight or trimer, middle molecular weight or hexamer, and high molecular weight) and secreted into the circulation. Upon binding to its receptors, AdipoR1 and R2, adiponectin initiates a series of tissue-dependent signal transduction events, including phosphorylation of adenosine monophosphate (AMPK) and p38 mitogen-activated protein kinase (p38 MAPK), and increased peroxisome proliferator-activated receptor alpha (PPARα) ligand activity. These signal transduction events are regulated by adaptor protein containing a pleckstrin homology domain, phosphotyrosine binding domain, and leucine zipper motif (APPL1), which binds directly to the intracellular regions of AdipoR1 and R2. AdipoR1 and R2 also possesses inherent ceramidase activity, resulting in a decrease in intracellular ceramide, a sphingolipid that has been implicated in insulin resistance, cell death, inflammation, and atherosclerosis. Adiponectin stimulates fatty acid oxidation in skeletal muscle and inhibits glucose production in the liver, resulting in an improvement in whole-body energy homeostasis. Adiponectin is also a classic anti-inflammatory agent, reducing inflammation in various cell types through AdipoR1 and R2 signaling mechanisms. Adiponectin's anti-inflammatory and anti-apoptotic properties results in protection of the vasculature, heart, lung, and colon. In this review, we provide a comprehensive overview of the discovery, protein structure, receptors, expression, regulation, and physiological functions of adiponectin. © 2017 American Physiological Society. Compr Physiol 8:1031-1063, 2018.

Changes in hepatic phase I and phase II biotransformation enzyme expression and glutathione levels following atrazine exposure in female rats.

1. To determine the effects of repeated atrazine (ATR) treatment on hepatic phase I and II enzymes, adult female rats were treated with vehicle or 100 mg/kg of ATR for 1, 2, 3 or 4 days. Glutathione-s-transferases (GST) mRNA expression, protein levels (mu, pi, alpha, omega), and activity (cytosolic and microsomal), along with bioavailable glutathione (GSH) were assayed. 2. GST expression, concentrations and activity were increased, along with GSH levels, in animals treated with ATR for 3 and 4 days. 3. A subsequent study was performed with animals treated with vehicle, 6.5, 50 or 100 mg/kg/day for 4, 8 or 14 days. Expression of hepatic phase I CYP 450 enzymes was evaluated in conjugation with GST expression, protein and activity. Nineteen of the 45 CYP enzymes assayed displayed increased mRNA levels after eight days of treatment in animals treated with 50 or 100 mg/kg/day. After 14 days of treatment, all CYP expression levels returned to control levels except for CYP2B2, CYP2B3, CYP2C7, CYP2C23, CYP2E1, CYP3A9, CYP4A3 and CYP27A1, which remained elevated. 4. Results indicate that there may be a habituation or adaptation of liver phase I and phase II expression following repeated ATR treatment.

Regulation of intracellular trafficking and secretion of adiponectin by myosin II.

Adiponectin is a protein secreted by white adipocytes that plays an important role in insulin action, energy homeostasis and the development of atherosclerosis. The intracellular localization and trafficking of GLUT4 and leptin in adipocytes has been well studied, but little is known regarding the intracellular trafficking of adiponectin. Recent studies have demonstrated that constitutive adiponectin secretion is dependent on PIP2 levels and the integrity of cortical F-actin. Non-muscle myosin II is an actin-based motor that is associated with membrane vesicles and participates in vesicular trafficking in mammalian cells. Therefore, we investigated the role of myosin II in the trafficking and secretion of adiponectin in 3T3-L1 adipocytes. Confocal microscopy revealed that myosin IIA and IIB were dispersed throughout the cytoplasm of the adipocyte. Both myosin isoforms were localized in the Golgi/TGN region as evidenced by colocalization with the cis-Golgi marker, p115 and the trans-Golgi marker, γ-adaptin. Inhibition of myosin II activity by blebbistatin or actin depolymerization by latrunculin B dispersed myosin IIA and IIB towards the periphery while significantly inhibiting adiponectin secretion. Therefore, the constitutive trafficking and secretion of adiponectin in 3T3-L1 adipocytes occurs by an actin-dependent mechanism that involves the actin-based motors, myosin IIA and IIB.

Culture and Sampling of Primary Adipose Tissue in Practical Microfluidic Systems.

Microfluidic culture of primary adipose tissue allows for reduced sample and reagent volumes as well as constant media perfusion of the cells. By continuously flowing media over the tissue, microfluidic sampling systems can more accurately mimic vascular flow in vivo. Quantitative measurements can be performed on or off chip to provide time-resolved secretion data, furthering insight into the dynamics of the function of adipose tissue. Buoyancy resulting from the large lipid storage capacity in this tissue presents a unique challenge for culture, and it is important to account for this buoyancy during microdevice design. Herein, we describe approaches for microfluidic device fabrication that utilize 3D-printed interface templating to help counteract cell buoyancy. We apply such methods to the culture of both isolated, dispersed primary adipocytes and epididymal adipose explants. To facilitate more widespread adoption of the methodology, the devices presented here are designed for user-friendly operation. Only handheld syringes are needed to control flow, and devices are inexpensive and disposable.

Anti-inflammatory effects of the hydroxycarboxylic acid receptor 2.

The hydroxycarboxylic acid receptors (HCA1-3) are a family of G-protein-coupled receptors that are critical for sensing endogenous intermediates of metabolism. All three receptors are predominantly expressed on adipocytes and mediate anti-lipolytic effects. In addition to adipocytes, HCA2 is highly expressed on immune cells, including macrophages, monocytes, neutrophils and dermal dendritic cells, among other cell types. The endogenous ligand for HCA2 is beta-hydroxybutyrate (ß-OHB), a ketone body produced by the liver through ß-oxidation when an individual is in a negative energy balance. Recent studies demonstrate that HCA2 mediates profound anti-inflammatory effects in a variety of tissues, indicating that HCA2 may be an important therapeutic target for treating inflammatory disease processes. This review summarizes the roles of HCA2 on inflammation in a number of tissues and clinical states.

Metabolic phenotype and adipose and liver features in a high-fat Western diet-induced mouse model of obesity-linked NAFLD.

nonalcoholic fatty liver disease (NAFLD), an obesity and insulin resistance associated clinical condition - ranges from simple steatosis to nonalcoholic steatohepatitis. To model the human condition, a high-fat Western diet that includes liquid sugar consumption has been used in mice. Even though liver pathophysiology has been well characterized in the model, little is known about the metabolic phenotype (e.g., energy expenditure, activity, or food intake). Furthermore, whether the consumption of liquid sugar exacerbates the development of glucose intolerance, insulin resistance, and adipose tissue dysfunction in the model is currently in question. In our study, a high-fat Western diet (HFWD) with liquid sugar [fructose and sucrose (F/S)] induced acute hyperphagia above that observed in HFWD-fed mice, yet without changes in energy expenditure. Liquid sugar (F/S) exacerbated HFWD-induced glucose intolerance and insulin resistance and impaired the storage capacity of epididymal white adipose tissue (eWAT). Hepatic TG, plasma alanine aminotransferase, and normalized liver weight were significantly increased only in HFWD+F/S-fed mice. HFWD+F/S also resulted in increased hepatic fibrosis and elevated collagen 1a2, collagen 3a1, and TGFß gene expression. Furthermore, HWFD+F/S-fed mice developed more profound eWAT inflammation characterized by adipocyte hypertrophy, macrophage infiltration, a dramatic increase in crown-like structures, and upregulated proinflammatory gene expression. An early hypoxia response in the eWAT led to reduced vascularization and increased fibrosis gene expression in the HFWD+F/S-fed mice. Our results demonstrate that sugary water consumption induces acute hyperphagia, limits adipose tissue expansion, and exacerbates glucose intolerance and insulin resistance, which are associated with NAFLD progression.

Comparison of Chemiluminescence vs. Infrared Techniques for Detection of Fetuin-A in Saliva.

The western blotting technique for transfer and detection of proteins, named following the discovery of southern and northern blotting for DNA- and RNA-blotting, respectively, has traditionally relied on the use of X-ray films to capture chemiluminescence. Recent advancements use super-cooled charge coupled devices (CCD) cameras to capture both chemiluminescence and fluorescence images, which exhibit a greater dynamic range compared to traditional X-ray film. Chemiluminescence detected by a CCD camera records photons and displays an image based on the amount of light generated as a result of a dynamic chemical reaction. Fluorescent detection with a CCD camera, on the other hand, is measured in a static state. Despite this advantage, researchers continue to widely use chemiluminescent detection methods due to the generally poor performance of fluorophores in the visible spectrum. Infrared imaging systems offer a solution to the dynamic reactions of chemiluminescence and the poor performance of fluorophores detected in the visible spectrum, by imaging fluorophores in the infrared spectrum. Infrared imaging is static, has a wide linear range, high sensitivity, and reduced autofluorescence and light scatter. A distinct advantage of infrared imaging is the ability to detect two target proteins simultaneously on the same blot which increases accuracy of quantification and comparison, while minimizing the need for stripping and reprobing. Here, we compare the methodology for chemiluminescent (UVP BioChemi) and infrared (UVP Odyssey) detection of salivary total and phosphorylated fetuin-A, a multifunctional protein associated with cardio-metabolic risk, and discuss the advantages and disadvantages of these methodologies.

A microfluidic interface for the culture and sampling of adiponectin from primary adipocytes.

Secreted from adipose tissue, adiponectin is a vital endocrine hormone that acts in glucose metabolism, thereby establishing its crucial role in diabetes, obesity, and other metabolic disease states. Insulin exposure to primary adipocytes cultured in static conditions has been shown to stimulate adiponectin secretion. However, conventional, static methodology for culturing and stimulating adipocytes falls short of truly mimicking physiological environments. Along with decreases in experimental costs and sample volume, and increased temporal resolution, microfluidic platforms permit small-volume flowing cell culture systems, which more accurately represent the constant flow conditions through vasculature in vivo. Here, we have integrated a customized primary tissue culture reservoir into a passively operated microfluidic device made of polydimethylsiloxane (PDMS). Fabrication of the reservoir was accomplished through unique PDMS "landscaping" above sampling channels, with a design strategy targeted to primary adipocytes to overcome issues of positive cell buoyancy. This reservoir allowed three-dimensional culture of primary murine adipocytes, accurate control over stimulants via constant perfusion, and sampling of adipokine secretion during various treatments. As the first report of primary adipocyte culture and sampling within microfluidic systems, this work sets the stage for future studies in adipokine secretion dynamics.

Bisphenol A regulation of testicular endocrine function in male rats is affected by diet.

There is concern that early-life exposure to bisphenol A (BPA) may alter developmental programming and predispose individuals to obesity and reproductive anomalies. The present study was designed to determine if a high fat diet at sexual maturation moderates testicular toxicity occasioned by exposure to BPA during reproductive development. Therefore, male rats were exposed to BPA by maternal gavage (0, 2.5 or 25 µg/kg body weight/day) from gestational day 12 to postnatal day 21. At weaning, control and BPA-exposed animals were placed on a regular normal fat diet (NFD) until 70 days of age when they were continued on the NFD or were maintained on a high fat diet (HFD) until euthanasia at 98 days. Adult male rats maintained on HFD were generally heavier than NFD animals due to greater energy intake but energy intake per unit body weight gain was similar in all animals. However, perinatal exposure to BPA decreased (P<0.05) serum adiponectin as well as adiponectin and AdipoR2 protein expression levels in Leydig cells. Importantly, the combination of BPA exposure and HFD consumption promoted lipid peroxidation evidenced by elevated serum thiobarbituric acid reactive substances and glutathione concentrations. These findings imply that interaction between BPA and HFD potentially causes testicular dysfunction to a greater degree than would be due to BPA exposure or HFD consumption. Given the relationship that exists between energy homeostasis and reproductive activity, additional studies are warranted to investigate the consequences of BPA-diet interactions on testicular function.

Niacin increases adiponectin and decreases adipose tissue inflammation in high fat diet-fed mice.

AIMS: To determine the effects of niacin on adiponectin and markers of adipose tissue inflammation in a mouse model of obesity. MATERIALS AND METHODS: Male C57BL/6 mice were placed on a control or high-fat diet (HFD) and were maintained on such diets for the duration of the study. After 6 weeks on the control or high fat diets, vehicle or niacin treatments were initiated and maintained for 5 weeks. Identical studies were conducted concurrently in HCA2 (-/-) (niacin receptor(-/-)) mice. RESULTS: Niacin increased serum concentrations of the anti-inflammatory adipokine, adiponectin by 21% in HFD-fed wild-type mice, but had no effect on lean wild-type or lean or HFD-fed HCA2 (-/-) mice. Niacin increased adiponectin gene and protein expression in the HFD-fed wild-type mice only. The increases in adiponectin serum concentrations, gene and protein expression occurred independently of changes in expression of PPARγ C/EBPα or SREBP-1c (key transcription factors known to positively regulate adiponectin gene transcription) in the adipose tissue. Further, niacin had no effect on adipose tissue expression of ERp44, Ero1-Lα, or DsbA-L (key ER chaperones involved in adiponectin production and secretion). However, niacin treatment attenuated HFD-induced increases in adipose tissue gene expression of MCP-1 and IL-1ß in the wild-type HFD-fed mice. Niacin also reduced the expression of the pro-inflammatory M1 macrophage marker CD11c in HFD-fed wild-type mice. CONCLUSIONS: Niacin treatment attenuates obesity-induced adipose tissue inflammation through increased adiponectin and anti-inflammatory cytokine expression and reduced pro-inflammatory cytokine expression in a niacin receptor-dependent manner.

Lipid-lowering drugs and circulating adiponectin.

Pharmacological agents used to treat primary and combined hyperlipidemia reduce cardiovascular disease morbidity and mortality. Risk reduction has been attributed to improvements in blood lipid and lipoprotein characteristics. However, each class of available lipid-lowering drugs has been shown to exhibit pleiotropic effects that broaden their anticipated actions. Indeed, the results of a growing number of available studies suggest that a strong relationship exists between pharmacological reductions in blood lipids and circulating concentrations of the adipose tissue derived protein, adiponectin. Adiponectin is the most abundantly secreted protein from adipose tissue and has been shown to decrease hepatic glucose production, increase fatty acid oxidation in liver and skeletal muscle, and decrease vascular inflammation. In this chapter, we present a comprehensive analysis of the effects of the available classes of lipid-lowering drugs (statins, fibrates, niacin, and omega-3-fatty acids) on circulating adiponectin and the known mechanisms which produce these important events.

Evaluation of high-molecular weight adiponectin in horses.

OBJECTIVE: To characterize adiponectin protein complexes in lean and obese horses. ANIMALS: 26 lean horses and 18 obese horses. Procedures-Body condition score (BCS) and serum insulin activity were measured for each horse. Denaturing and native western blot analyses were used to evaluate adiponectin complexes in serum. A human ELISA kit was validated and used to quantify high-molecular weight (HMW) complexes. Correlations between variables were made, and HMW values were compared between groups. RESULTS: Adiponectin was present as a multimer consisting of HMW (> 720-kDa), low-molecular weight (180-kDa), and trimeric (90-kDa) complexes in serum. All complexes were qualitatively reduced in obese horses versus lean horses, but the percentage of complexes < 250 kDa was higher in obese versus lean horses. High-molecular weight adiponectin concentration measured via ELISA was negatively correlated with serum insulin activity and BCS and was lower in obese horses (mean ± SD, 3.6 ± 3.9 µg/mL), compared with lean horses (8.0 ± 4.6 µg/mL). CONCLUSIONS AND CLINICAL RELEVANCE: HMW adiponectin is measurable via ELISA, and concentration is negatively correlated with BCS and serum insulin activity in horses. A greater understanding of the role of adiponectin in equine metabolism will provide insight into the pathophysiology of metabolic disease conditions.

Effects of high fat diet on GPR109A and GPR81 gene expression.

GPR109A (PUMA-G, NIACR1, HCA(2)) and GPR81 (HCA(1)) are G protein-coupled receptors located predominantly on adipocytes that mediate anti-lipolytic effects. These cell surface receptors give the adipocyte the ability to "sense" metabolic changes in the environment and respond through lipolytic regulation and release of products including free fatty acids and pro- or anti-inflammatory adipokines. The endogenous ligands for GPR109A and GPR81 are ß-hydroxybutyrate and lactate, respectively, both of which are hydroxycarboxylic acids and intermediates of energy metabolism. Circulating ß-hydroxybutyrate levels are increased during a 2-3 day fast and prolonged starvation, while lactate levels are elevated during times of intense exercise. Therefore, regulation of expression of these receptors is crucial for the metabolic sensing ability of the adipocyte and ultimately whole body energy homeostasis. We investigated the effects of high fat diet-induced obesity on expression of GPR109A and GPR81. Sixteen male C57BL/6 mice were placed on a control (10% kcal fat; n=8) or a high fat (60% kcal fat; n=8) diet for 11 weeks. Diet-induced obesity significantly reduced GPR109A and GPR81 gene expression in epididymal fat pads. This decrease in GPR109A and GPR81 gene expression was positively correlated with a decrease in adipose tissue PPARγ gene expression. In contrast, acute treatment of both 3T3-L1 adipocytes and RAW 264.7 macrophages with lipopolysaccharide significantly increased GPR109A gene expression, but had no effect on GPR81 expression in 3T3-L1 adipocytes. In conclusion, chronic obesity reduces GPR109A and GPR81 expression in the adipose tissue, while acute in vitro LPS treatment increases expression of GPR109A in adipocytes and macrophages.

Regulation of adiponectin secretion by soy isoflavones has implication for endocrine function of the testis.

Testicular Leydig cells are the predominant source of the male sex steroid hormone testosterone (T), which is required to maintain male fertility. There is now growing evidence that environmental stressors, including chemicals present in food, air and water, may affect energy balance. A relationship between energy balance and reproductive capacity has been proposed for a long time. In the present study, developmental exposures of male rats to soy isoflavones in the maternal diet from gestational day 12 to day 21 post-partum enhanced adiponectin expression in adipose tissue and increased serum adiponectin concentrations in adulthood. However, exposure to soy isoflavones caused a decrease in T production and expression of adiponectin and its receptor (adipoR2) in Leydig cells. In separate experiments, incubation of Leydig cells with recombinant adiponectin in the absence of isoflavones caused a decrease in T biosynthesis associated with diminished expression of the cholesterol transporter steroidogenic acute regulatory protein (StAR). Thus, chemical-induced alterations in serum adiponectin concentrations have implication for steroid hormone secretion. The results also imply that changes in adipose tissue metabolism occasioned by exposure to dietary estrogens, and perhaps other estrogenic agents, possibly contribute to deficiencies in reproductive capacity attributed to these compounds.