Introduction and Objective: Adipose tissue (AT) inflammation, a hallmark of obesity, promotes metabolic disorders such as type 2 diabetes. B-1 cells, an innate-like B cell subset, mitigate diet-induced AT inflammation, in part via the anti-inflammatory cytokine interleukin (IL)-10, whereas B-2 cells, comprised of follicular B cells and marginal zone B cells, exacerbate AT inflammation. Whether mechanistic relationships link AT and B cell function remains a major knowledge gap in this field. The objective of this study was to investigate whether adipocytes and preadipocytes can regulate IL-10 production by B cells. Methods: I.29µ+ B cells (murine B cell lymphoma with B-1 characteristics) and murine splenic B cells (predominantly follicular B-2 cells) were separately cultured for various intervals with or without lipopolysaccharide (LPS) stimulation, in control media or conditioned media prepared from murine 3T3-L1 adipocytes and preadipocytes. IL-10 production by B cells was assessed by real-time RT-PCR and ELISA. Data obtained for conditioned media and control media cultures were compared using t-tests. Results: Conditioned media from both 3T3-L1 adipocytes and preadipocytes increased IL-10 production by LPS-stimulated splenic B cells. Both sources of conditioned media induced IL-10 secretion by I.29µ+ B cells, but diminished IL-10 production by LPS-activated I.29µ+ B cells. This inhibitory effect was not abrogated by 0.1-micron filtration of conditioned media. Conclusion: These data indicate that adipocytes and preadipocytes can regulate IL-10 production by B cells. Further, the results suggest this regulatory effect can be positive or negative depending on the type of B cell and its activation status and is mediated by a soluble factor(s) < 0.1-micron rather than exosomes. These findings support the hypothesis that AT can influence anti-inflammatory functions of B cells and warrant further studies of adipocyte and preadipocyte communication with primary B-1 and B-2 cells. Disclosure J.W. Brewer: None. O.L. Doud: None. R. Josepher: None. C. Leeling: None. C. Lovelady: None. K. Sparkman: None. R.L. Judd: None.

Nitric oxide (NO) is a ubiquitous signaling molecule known to modulate various physiological processes, with specific implications in skeletal muscle and broader applications in exercise performance. This review focuses on the modulation of skeletal muscle function, mitochondrial adaptation and function, redox state by NO, and the effect of nitrate supplementation on exercise performance. In skeletal muscle function, NO is believed to increase the maximal shortening velocity and peak power output of muscle fibers. However, its effect on submaximal contraction is still undetermined. In mitochondria, NO may stimulate biogenesis and affect respiratory efficiency. NO also plays a role in the redox state within the skeletal muscle, partially through its interaction with respiratory chain enzymes and transcriptional regulators of antioxidant production. Nitrate supplementation leads to an increased bioavailability of NO in skeletal muscle. Thus, nitrate supplementation has been investigated for its ability to impact performance outcomes in endurance and resistance exercise. The effect of nitrate supplementation on endurance exercise is currently indecisive, although evidence indicates that it may extend the time to exhaustion in endurance exercise. Alternatively, the effect of nitrate supplementation on resistance exercise performance has been less studied. Limited research indicates that nitrate supplementation may improve repetitions to failure. Further research is needed to investigate the influence of training status, age, sex, and duration of supplementation to further elucidate the impact of nitrate supplementation on exercise performance.

Obesity is characterized by the enlargement of adipose tissue due to an increased calorie intake exceeding the body’s energy expenditure. Changes in the size of adipose tissue can lead to harmful consequences, with excessive fat accumulation resulting in adipocyte hypertrophy and promoting metabolic dysfunction. These adiposity-associated pathologies can be influenced by dietary components and their potential health benefits. Lupeol, a pharmacologically active pentacyclic triterpenoid found in medicinal plants, vegetables, and fruits, has been shown to exhibit antioxidant and anti-inflammatory properties. This study investigated the role of lupeol on adipocyte hypertrophy by evaluating key adipogenic regulators in vitro. First, 3T3-L1 MBX mouse embryonic cells were differentiated into adipocytes and hypertrophy was induced using 500 µM palmitic acid. The treated adipocytes showed a significantly increased lipid droplet size, confirming adipocyte hypertrophy. Both adipocytes and hypertrophied adipocytes were then treated with or without 60 µM lupeol, following a dose-dependent study. Lipid droplet size was assessed and validated by Oil Red O staining. Western blot analysis was performed to measure the expression of adipogenic and inflammatory markers. Differentiated adipocytes showed increased fatty acid-binding protein 4 (FABP4) expression and Oil Red O staining, indicating an increased lipid content. Western blot analysis revealed that lupeol treatment reduced the expression of FABP4, peroxisome proliferator-activated receptor-γ (PPARγ), and adipokines. In conclusion, the results suggest that lupeol reverts the inflammatory and adipogenic markers that are enhanced in adipocyte hypertrophy. Through its anti-inflammatory effects, lupeol offers protective effects against adipocyte hypertrophy and contributes to reducing hypertrophic adiposity.

Pathologies in adipose (fat) tissue function are linked with human diseases such as diabetes, obesity, metabolic syndrome, and cancer. Dynamic, rapid release of metabolites has been observed in adipocyte cells and tissue, yet higher temporal resolution is needed to adequately study this process. In this work, a microfluidic device with precise and regular valve-automated droplet sampling, termed a microfluidic analog-to-digital converter (µADC), was used to sample secretions from ~0.75 mm diameter adipose explants from mice, and on-chip salt water electrodes were used to merge sampled droplets with reagent droplets from two different fluorometric coupled enzyme assays. By integrating sampling and assays on-chip, either glycerol or non-esterified fatty acids (NEFA), or both, were quantified optically within merged 12-nanoliter droplets using a fluorescence microscope with as high as 20-second temporal resolution. Limits of detection were 6 µM for glycerol (70 fmol) and 0.9 µM for NEFA (10 fmol). Multiple ex vivo adipose tissue explants were analyzed with this system, all showing clear increases in lipolytic function after switching from feeding to fasting conditions. Enabled by high temporal resolution, lipolytic oscillations of both glycerol and NEFA were observed for the first time in the range of 0.2 to 1.6 min-1. Continuous wavelet transform (CWT) spectrograms and burst analyses (0.1 to 4.0 pmol bursts) revealed complex dynamics, with multiplexed assays (duplex for glycerol and NEFA) from the same explants showing mostly discordant bursts. These data support separate mechanisms of NEFA and glycerol release, although the connection to intracellular metabolic oscillations remains unknown. Overall, this device allowed automated and highly precise temporal sampling of tissue explants at high resolution and programmable downstream merging with multiple assay reagents, revealing unique biological information. Such device features should be applicable to various other tissue or spheroid types and to other assay formats.

Phosphoprotein enriched in astrocytes 15kDa (PEA15) is a ubiquitously expressed cytosolic protein with high expression in the brain, and enhanced expression in the hypothalamus. Humans with type 2 diabetes mellitus have increased expression of PEA15 in adipose tissue and skeletal muscle, and overexpression of PEA15 in transgenic mice and pigs results in peripheral insulin resistance. Despite these findings, studies of PEA15 in high fat diet (HF)-mediated obesity are limited. Male and female Pea15-/- mice (KO) and littermate controls (WT) were fed a control diet (CD) or HF for 20 weeks, with a GTT at 19 weeks and metabolic cage data at 20 weeks, just prior to serum and tissue collection. The effects of PEA15 on metabolic parameters varied based on sex. Female KO mice fed HF had a significant increase in body weight due to increased inguinal adipose and liver weight, and impaired insulin sensitivity compared to HF-fed WT females. The KO mice had similar food intake but decreased activity during the light cycle compared to HF-fed WT female mice. In contrast, a genotypic effect in male mice was noted in CD-fed mice with KO mice having an increased body weight and corresponding increases in inguinal and gonadal adipose compared to WT with no significant change in insulin sensitivity, food intake or energy expenditure. KO males on CD were significantly more active during the light phase than WT controls despite increased body weight. Substrate utilization and its associated diurnal switch were altered in both sexes of KO mice compared to WT, with KO male mice having increased preference towards carbohydrate utilization while female KO mice had increased lipid utilization. These findings suggest that PEA15 regulates metabolism in a sex-dependent manner through alterations in metabolic flexibility, energy substrate utilization, and diurnal rhythms. Further work will investigate the sex-dependent role of PEA15 on central and peripheral regulators of diurnal rhythm and metabolism. Disclosure T.J.Towns: None. E.Graff: None. E.Brinker: None. R.Watanabe: None. I.A.Odeniyi: None. K.J.Mccafferty: None. N.Grabau: None. D.Kroeger: None. M.W.Greene: None. R.L.Judd: None. Funding Auburn University

Obesity, a global health problem, leads to chronic inflammation of adipose tissue (AT), an immune-mediated process linked to metabolic dysfunction and disease, including type II diabetes mellitus. Adipocytes, the most abundant cellular constituent of AT, store lipids and secrete adipokines, a group of hormone-like molecules such as adiponectin and adipsin that regulate metabolism and immune cell functions. In mouse models of diet-induced obesity, distinct subsets of B lymphocytes have been implicated in both exacerbating and mitigating AT inflammation and insulin resistance, but the immunoregulatory mechanisms underlying these effects are incompletely understood. Similarly, whether B lymphocytes and adipocytes engage in regulatory interactions with each other is not known. To investigate this question, we performed in vitro co-culture studies using murine 3T3-L1 adipocytes and I.29µ+ B cells, a murine B cell lymphoma that initiates robust secretion of IgM antibodies and the anti-inflammatory cytokine interleukin (IL)-10 upon activation by lipopolysaccharide (LPS). The induction of IgM and IL-10 secretion was markedly attenuated when I.29µ+ B cells were stimulated with LPS while co-cultured in direct contact with 3T3-L1 adipocytes. This inhibitory effect was also observed, albeit to a lesser degree, when the two cell types were co-cultured but separated by a semipermeable membrane. Conversely, secretion of adiponectin and adipsin by 3T3-L1 adipocytes was reduced when the adipocytes were co-cultured with I.29µ+ B cells, both in direct contact and when separated by a semipermeable membrane. This reduction of adipokine output was observed in both the absence and presence of LPS to activate the B cells. These data support the hypothesis that B lymphocytes and adipocytes can engage in reciprocal interactions that modulate the functions of these two secretory cell types and, in turn, may influence AT homeostasis and inflammation in healthy and obese states. Disclosure J. W. Brewer: None. R. L. Judd: None. M. K. Allman: None. S. R. Carroll: None. S. Granger: None. A. Hall: None. K. Pownall: None. J. Quintana: None. N. Arellano rangel: None. J. Thomas: None. Funding Edward Via College of Osteopathic Medicine Center for One Health

Hydroxycarboxylic acid receptor 2 (HCA2) , formally known as GPR109A, is a metabolite-sensing receptor expressed predominately on adipocytes, immune cells and intestinal epithelial cells. The primary endogenous ligand of HCA2 is β-hydroxybutyrate (βOHB) , which is elevated during periods of nutrient deprivation including fasting. Previous in vitro studies have suggested that βOHB activation of HCA2 on adipocytes inhibits lipolysis and serves as a negative feedback mechanism to prevent excess fat loss during fasting. However, the metabolic implications of this feedback mechanism have not been tested in vivo during a prolonged fast. To address this question, male and female C57BL/6J (WT) and HCA2 knockout (KO) mice were fasted in metabolic cages for 36 hours. No significant differences were observed for genotype or sex in RER, EE, or VO2. Following the fast, KO males exhibited a significant decrease in body weight compared to their WT counterparts. However, body weight was not significantly different between female WT and KO mice after fasting. Gonadal white adipose tissue (gWAT) depot weights were significantly lower in KO male mice compared to WT male mice, with no significant difference in gWAT weight between female WT and KO mice. Inguinal white adipose tissue (iWAT) depot weights were significantly lower for both sexes in KO mice compared to WT mice. KO males displayed significantly lower levels of circulating NEFAs compared to WT males. However, no differences in NEFAs were observed between female WT and KO mice. No significant differences were shown between groups for glucose, insulin, or βOHB. Therefore, this study demonstrates that mice lacking HCA2 possess a diminished capacity to regulate body and adipose tissue weight during a fast, which is observed to a greater extent in male mice. Disclosure K.J.Mccafferty: None. E.Brinker: None. E.Graff: None. T.D.Steury: None. M.W.Greene: None. R.L.Judd: None.

Hydroxycarboxylic acid receptor 2 (HCA2) , formally known as GPR109A, is a metabolite-sensing receptor expressed predominately on adipocytes, immune cells and intestinal epithelial cells. The primary endogenous ligand of HCA2 is β-hydroxybutyrate (βOHB) , which is elevated during periods of nutrient deprivation including fasting. Previous in vitro studies have suggested that βOHB activation of HCA2 on adipocytes inhibits lipolysis and serves as a negative feedback mechanism to prevent excess fat loss during fasting. However, the metabolic implications of this feedback mechanism have not been tested in vivo during a prolonged fast. To address this question, male and female C57BL/6J (WT) and HCA2 knockout (KO) mice were fasted in metabolic cages for 36 hours. No significant differences were observed for genotype or sex in RER, EE, or VO2. Following the fast, KO males exhibited a significant decrease in body weight compared to their WT counterparts. However, body weight was not significantly different between female WT and KO mice after fasting. Gonadal white adipose tissue (gWAT) depot weights were significantly lower in KO male mice compared to WT male mice, with no significant difference in gWAT weight between female WT and KO mice. Inguinal white adipose tissue (iWAT) depot weights were significantly lower for both sexes in KO mice compared to WT mice. KO males displayed significantly lower levels of circulating NEFAs compared to WT males. However, no differences in NEFAs were observed between female WT and KO mice. No significant differences were shown between groups for glucose, insulin, or βOHB. Therefore, this study demonstrates that mice lacking HCA2 possess a diminished capacity to regulate body and adipose tissue weight during a fast, which is observed to a greater extent in male mice. Disclosure K.J.Mccafferty: None. E.Brinker: None. E.Graff: None. T.D.Steury: None. M.W.Greene: None. R.L.Judd: None.

Hydroxycarboxylic acid receptor 2 (HCA 2 ) is vital for sensing intermediates of metabolism, including β-hydroxybutyrate and butyrate. It also regulates profound anti-inflammatory effects in various tissues, indicating that HCA 2 may serve as an essential therapeutic target for mediating inflammation-associated diseases. Butyrate and niacin, endogenous and exogenous ligands of HCA 2 , have been reported to play an essential role in maintaining intestinal homeostasis. HCA 2 , 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 HCA 2 in intestinal homeostasis and its pathological role in intestinal inflammation and cancer.

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.

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, with integrated enzyme assays enabling real-time quantification of glycerol (down to 1.9 fmol droplet-1). 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.

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.

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.

Adiponectin is an adipokine that has recently been under investigation for potential neuroprotective effects in various brain disorders including Alzheimer's disease, stroke, and depression. Adiponectin receptors (AdipoR1 and AdipoR2) are found throughout various brain regions, including the hippocampus. However, the role of these receptors in synaptic and cognitive function is not clear. Therefore, the goal of the current study was to evaluate synaptic and cognitive function in the absence of adiponectin. The current study utilized 12-month-old adiponectin knockout (APN-KO) mice and age-matched controls to study cognitive and hippocampal synaptic alterations. We determined that AdipoR1 and AdipoR2 are present in the synaptosome, with AdipoR2 displaying increased presynaptic vs. postsynaptic localization, whereas AdipoR1 was enriched in both the presynaptic and postsynaptic fractions. APN-KO mice displayed cognitive deficits in the novel object recognition (NOR) and Y-maze tests. This was mirrored by deficits in long-term potentiation (LTP) of the hippocampal Schaefer collateral pathway in APN-KO mice. APN-KO mice also displayed a reduction in basal synaptic transmission and an increase in presynaptic release probability. Deficits in LTP were rescued through hippocampal slice incubation with the adiponectin receptor agonist, AdipoRon, indicating that acute alterations in adiponectin receptor signaling influence synaptic function. Along with the deficits in LTP, altered levels of key presynaptic and postsynaptic proteins involved in glutamatergic neurotransmission were observed in APN-KO mice. Taken together, these results indicate that adiponectin is an important regulator of cognition and synaptic function in the hippocampus. Future studies should examine the role of specific adiponectin receptors in synaptic processes.

Recent studies have demonstrated significant metabolic changes in different strains of mice fed a high-fat diet (HFD). Pharmacological doses of niacin can improve nonalcoholic fatty liver disease (NAFLD) in HFD-fed rodents. However, previous study from our lab demonstrated that niacin increases the hepatic triglyceride content and histological score in HFD-fed B6129SF2/J (B6129) mice but has no effect in C57BL/6J (B6) mice. Therefore, the aim of this study was to identify the mechanism responsible for niacin-induced fatty liver in B6129 mice using targeted liver metabolomic analysis. Livers were collected from B6 and B6129 mice, which were fed either a chow (10% fat) or HFD (60% fat) for 20 weeks with niacin (360 mg/kg/day) or vehicle supplementation from week 5 to week 20. Two hundred polar metabolites were identified in these livers. A total of 21 and 26 metabolites identified as different between chow and HFD group in B6 and B6129 mice, respectively. In B6 mice, only 6 metabolites were identified as different with niacin treatment and no specific pathways appeared to be impacted. In contrast to B6 mice, 16 metabolites and 5 pathways were impacted by niacin in HFD-fed B6129 mice. Of the metabolites that were changed in these pathways, only hydroxyphenylpyruvate (also known as 4-Hydroxyphenylpyruvate, 4-HPP) did not change with HFD feeding but significantly decreased with niacin treatment. 4-HPP is an intermediate in the metabolism of phenylalanine/tyrosine and improves mitochondrial oxidation in rats subjected to hemorrhagic shock. Therefore, decreased 4-HPP by niacin may lead to decreased beta-oxidation in the liver and subsequent lipid accumulation and liver damage in B6129 mice. Further lipidomic analysis suggested different hepatic lipid profiles with HFD and niacin treatment in B6129 mice, which may explain the increased NAFLD development in these mice with niacin treatment. Disclosure H. Fang: None. Z. Li: None. E. Graff: Research Support; Self; Elanco Animal Health. K.J. McCafferty: None. R.L. Judd: None. Funding Boshell Diabetes and Metabolic Diseases Research Program

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, the most abundant plasma adipokine, plays an important role in the regulation of glucose and lipid metabolism. Adiponectin also possesses insulin-sensitizing, anti-inflammatory, angiogenic, and vasodilatory properties which may influence central nervous system (CNS) disorders. Although initially not thought to cross the blood-brain barrier, adiponectin enters the brain through peripheral circulation. In the brain, adiponectin signaling through its receptors, AdipoR1 and AdipoR2, directly influences important brain functions such as energy homeostasis, hippocampal neurogenesis, and synaptic plasticity. Overall, based on its central and peripheral actions, recent evidence indicates that adiponectin has neuroprotective, antiatherogenic, and antidepressant effects. However, these findings are not without controversy as human observational studies report differing correlations between plasma adiponectin levels and incidence of CNS disorders. Despite these controversies, adiponectin is gaining attention as a potential therapeutic target for diverse CNS disorders, such as stroke, Alzheimer's disease, anxiety, and depression. Evidence regarding the emerging role for adiponectin in these disorders is discussed in the current review.

Pharmacological doses of niacin improve adipose tissue (AT) inflammation and nonalcoholic fatty liver disease (NAFLD) in rodents chronically fed a high-fat diet (HFD). However, recent mouse studies have demonstrated significant metabolic changes in different strains of mice fed a HFD. Therefore, the aim of this study was to assess the effect of niacin on both AT inflammation and liver steatosis in two mouse strains, C57BL6/J (B6) and B6129SF2/J (B6129), under HFD feeding. Thirty-two male B6 and 32 male B6129 mice were randomized into four groups: Chow/Vehicle (CV), Chow/Niacin (CN), HFD/Vehicle (HV), and HFD/Niacin (HN). They were fed either a chow (10% fat) or HFD (60% fat) for 20 weeks. Niacin (360 mg/kg/day) or vehicle was added to the drinking water from week 5 until the end of the study. As expected, HFD-fed mice gained more weight than chow-fed mice in both strains, with no difference in weight gain between strains. Crown-like structure (CLS) number, a hallmark of AT inflammation, was increased in HV mice of both strains compared to CV mice. In addition, HV B6 mice had higher CLS number than HV B6129 mice. In B6129 mice, niacin decreased CLS number in HN compared to HV mice, while this decrease was not observed in B6 mice. Liver weight to body weight (L/B) ratio, liver triglyceride (TG) content and NASH score was increased in HV compared to CV B6 mice. In contrast, in B6129 mice, only NASH score was increased in HV compared to CV controls. Niacin had no impact on L/B ratio, TG content, or NASH score in B6 mice. However, in B6129 mice, niacin increased all three parameters in HN compared to HV mice. In conclusion, there are strain differential effects on AT inflammation and NAFLD induced by HFD feeding. Interestingly, liver steatosis is significantly increased in HFD-fed B6129 mice treated with niacin. This increase is potentially due to methyl deficiency, as niacin is a potent hepatic methyl consumer and 129 mice are more sensitive to methyl deficiency. Disclosure H. Fang: None. E. Graff: None. Z. Li: None. R.L. Judd: None.