Adipose tissue macrophages secrete small extracellular vesicles that mediate rosiglitazone-induced insulin sensitization.

The obesity epidemic continues to worsen worldwide, driving metabolic and chronic inflammatory diseases. Thiazolidinediones, such as rosiglitazone (Rosi), are PPARγ agonists that promote 'M2-like' adipose tissue macrophage (ATM) polarization and cause insulin sensitization. As ATM-derived small extracellular vesicles (ATM-sEVs) from lean mice are known to increase insulin sensitivity, we assessed the metabolic effects of ATM-sEVs from Rosi-treated obese male mice (Rosi-ATM-sEVs). Here we show that Rosi leads to improved glucose and insulin tolerance, transcriptional repolarization of ATMs and increased sEV secretion. Administration of Rosi-ATM-sEVs rescues obesity-induced glucose intolerance and insulin sensitivity in vivo without the known thiazolidinedione-induced adverse effects of weight gain or haemodilution. Rosi-ATM-sEVs directly increase insulin sensitivity in adipocytes, myotubes and primary mouse and human hepatocytes. Additionally, we demonstrate that the miRNAs within Rosi-ATM-sEVs, primarily miR-690, are responsible for these beneficial metabolic effects. Thus, using ATM-sEVs with specific miRNAs may provide a therapeutic path to induce insulin sensitization.

Targeting Clic1 for the treatment of obesity: A novel therapeutic strategy to reduce food intake and body weight.

OBJECTIVE: Despite great advances in obesity therapeutics in recent years, there is still a need to identify additional therapeutic targets for the treatment of this disease. We previously discovered a signature of genes, including Chloride intracellular channel 1 (Clic1), whose expression was associated with drug-induced weight gain, and in these studies, we assess the effect of Clic1 inhibition on food intake and body weight in mice. METHODS: We studied the impact of Clic1 inhibition in mouse models of binge-eating, diet-induced obese mice and genetic models of obesity (Magel2 KO mice). RESULTS: Clic1 knockout (KO) mice ate significantly less and had a lower body weight than WT littermates when either fed chow or high fat diet. Furthermore, pharmacological inhibition of Clic1 in diet-induced obese mice resulted in suppression of food intake and promoted highly efficacious weight loss. Clic1 inhibition also reduced food intake in binge-eating models and hyperphagic Magel2 KO mice. We observed that chronic obesity resulted in a significant change in subcellular localization of Clic1 with an increased ratio of Clic1 in the membrane in the obese state. These observations provide a novel therapeutic strategy to block Clic1 translocation as a potential mechanism to reduce food intake and lower body weight. CONCLUSIONS: These studies attribute a novel role of Clic1 as a driver of food intake and overconsumption. In summary, we have identified hypothalamic expression of Clic1 plays a key role in food intake, providing a novel therapeutic target to treat overconsumption that is the root cause of modern obesity.

Nuclear receptor 5A2 regulation of Agrp underlies olanzapine-induced hyperphagia.

Antipsychotic (AP) drugs are efficacious treatments for various psychiatric disorders, but excessive weight gain and subsequent development of metabolic disease remain serious side effects of their use. Increased food intake leads to AP-induced weight gain, but the underlying molecular mechanisms remain unknown. In previous studies, we identified the neuropeptide Agrp and the transcription factor nuclear receptor subfamily 5 group A member 2 (Nr5a2) as significantly upregulated genes in the hypothalamus following AP-induced hyperphagia. While Agrp is expressed specifically in the arcuate nucleus of the hypothalamus and plays a critical role in appetite stimulation, Nr5a2 is expressed in both the CNS and periphery, but its role in food intake behaviors remains unknown. In this study, we investigated the role of hypothalamic Nr5a2 in AP-induced hyperphagia and weight gain. In hypothalamic cell lines, olanzapine treatment resulted in a dose-dependent increase in gene expression of Nr5a2 and Agrp. In mice, the pharmacological inhibition of NR5A2 decreased olanzapine-induced hyperphagia and weight gain, while the knockdown of Nr5a2 in the arcuate nucleus partially reversed olanzapine-induced hyperphagia. Chromatin-immunoprecipitation studies showed for the first time that NR5A2 directly binds to the Agrp promoter region. Lastly, the analysis of single-cell RNA seq data confirms that Nr5a2 and Agrp are co-expressed in a subset of neurons in the arcuate nucleus. In summary, we identify Nr5a2 as a key mechanistic driver of AP-induced food intake. These findings can inform future clinical development of APs that do not activate hyperphagia and weight gain.

Metabolomic profiles associated with a mouse model of antipsychotic-induced food intake and weight gain.

Antipsychotic drugs (AP) are used to treat a multitude of psychiatric conditions including schizophrenia and bipolar disorder. However, APs also have metabolic side effects including increased food intake and body weight, but the underlying mechanisms remain unknown. We previously reported that minocycline (MINO) co-treatment abrogates olanzapine (OLZ)-induced hyperphagia and weight gain in mice. Using this model, we investigated the changes in the pharmacometabolome in the plasma and hypothalamus associated with OLZ-induced hyperphagia and weight gain. Female C57BL/6 mice were divided into groups and fed either i) control, CON (45% fat diet) ii) CON + MINO, iii) OLZ (45% fat diet with OLZ), iv) OLZ + MINO. We identified one hypothalamic metabolite indoxylsulfuric acid and 389 plasma metabolites (including 19 known metabolites) that were specifically associated with AP-induced hyperphagia and weight gain in mice. We found that plasma citrulline, tricosenoic acid, docosadienoic acid and palmitoleic acid were increased while serine, asparagine and arachidonic acid and its derivatives were decreased in response to OLZ. These changes were specifically blocked by co-treatment with MINO. These pharmacometabolomic profiles associated with AP-induced hyperphagia and weight gain provide candidate biomarkers and mechanistic insights related to the metabolic side effects of these widely used drugs.

Adipocyte PU.1 knockout promotes insulin sensitivity in HFD-fed obese mice.

Insulin resistance is a key feature of obesity and type 2 diabetes. PU.1 is a master transcription factor predominantly expressed in macrophages but after HFD feeding PU.1 expression is also significantly increased in adipocytes. We generated adipocyte specific PU.1 knockout mice using adiponectin cre to investigate the role of PU.1 in adipocyte biology, insulin and glucose homeostasis. In HFD-fed obese mice systemic glucose tolerance and insulin sensitivity were improved in PU.1 AKO mice and clamp studies indicated improvements in both adipose and liver insulin sensitivity. At the level of adipose tissue, macrophage infiltration and inflammation was decreased and glucose uptake was increased in PU.1 AKO mice compared with controls. While PU.1 deletion in adipocytes did not affect the gene expression of PPARg itself, we observed increased expression of PPARg target genes in eWAT from HFD fed PU.1 AKO mice compared with controls. Furthermore, we observed decreased phosphorylation at serine 273 in PU.1 AKO mice compared with fl/fl controls, indicating that PPARg is more active when PU.1 expression is reduced in adipocytes. Therefore, in obesity the increased expression of PU.1 in adipocytes modifies the adipocyte PPARg cistrome resulting in impaired glucose tolerance and insulin sensitivity.

Low-Protein Diets with Fixed Carbohydrate Content Promote Hyperphagia and Sympathetically Mediated Increase in Energy Expenditure.

SCOPE: Dietary protein restriction elicits hyperphagia and increases energy expenditure; however, less is known of whether these responses are a consequence of increasing carbohydrate content. The effects of protein-diluted diets with fixed carbohydrate content on energy balance, hormones, and key markers of protein sensing and thermogenesis in tissues are determined. METHODS AND RESULTS: Obesity-prone rats (n = 13-16 per group) are randomized to diets containing fixed carbohydrate (52% calories) and varying protein concentrations: 15% (control), 10% (mild protein restriction), 5% (moderate protein restriction) or 1% (severe protein restriction) protein calories, or protein-matched to 5% protein, for 21 days. Propranolol and ondansetron are administered to interrogate the roles of sympathetic and serotonergic systems, respectively, in diet-induced changes in energy expenditure. It is found that mild-to-moderate protein restriction promotes transient hyperphagia, whereas severe protein restriction induces hypophagia, with alterations in meal patterns. Protein restriction enhances energy expenditure that is partly attenuated by propranolol, but not ondansetron. Moderate to severe protein restriction decreases gains in body weight, lean and fat mass, decreased postprandial glucose and leptin, but increased fibroblast growth factor-21 concentrations. Protein-matching retains lean mass suggesting that intake of dietary protein, but not calories, is important for preserving lean mass. Notably, protein restriction increases the protein and/or transcript abundance of key amino acid sensing molecules in liver and intestine (PERK, eIF2α, ATF2, CHOP, 4EBP1, FGF21), and upregulated thermogenic markers (ß2AR, Klotho, HADH, UCP-1) in brown adipose tissue. CONCLUSION: Low-protein diets promote hyperphagia and sympathetically mediated increase in energy expenditure, prevent gains in tissue reserves, and concurrently upregulate hepatic and intestinal amino acid sensing intermediaries and thermogenic markers in brown adipose tissue.

Short communication: Expression of transcripts for proglucagon, glucose-dependent insulinotropic peptide, peptide YY, and their cognate receptors, in feline peripheral tissues.

Gastrointestinal hormone based therapies are being investigated for treating diabetes in cats; however, the tissue distribution of these hormones and their cognate receptors remain largely understudied. We determined the distribution of transcripts for the gut hormones proglucagon (Gcg), glucose-dependent insulinotropic peptide (Gip), peptide YY (Pyy), and their receptors (Glp1r, Gipr, Npy2r), in feline peripheral tissues. The Gcg, Gip and Pyy mRNA were expressed in the gut, with higher Gcg and Pyy abundance in the lower gut. Interestingly, Glp1r and Npy2r mRNA were expressed in multiple peripheral tissues including the gut, pancreas and liver, whereas, Gipr mRNA was restricted to the stomach and adipose tissues. The localized mRNA expression of Gcg and Pyy in the gut, but the extensive distribution of Glp1r and Npy2r in several peripheral tissues suggests that these hormones may have pleiotropic physiological functions in cats.

Dietary Tryptophan Restriction Dose-Dependently Modulates Energy Balance, Gut Hormones, and Microbiota in Obesity-Prone Rats.

OBJECTIVE: To determine the effects of graded dietary restriction of tryptophan on food intake, energy expenditure, body composition, gut hormones, and select fecal bacterial populations in obesity-prone rats. METHODS: Obesity-prone rats were randomized to isocaloric diets with varying degrees of tryptophan restriction: control (100% requirements), 70% tryptophan (70TRP), 40% tryptophan (40TRP), or 10% tryptophan (10TRP) for 21 days. The sympathetic system was challenged with a subcutaneous injection of propranolol on days 15 to 17. Measurements included food intake, energy expenditure, body composition, metabolic hormones, and fecal concentrations of select bacteria. RESULTS: Moderate tryptophan restriction (70TRP) induced thermogenesis without altering body composition, whereas severe degrees of restriction (40TRP, 10TRP) produced profound hypophagia and decreased energy expenditure and body weight. The thermogenic effects of moderate tryptophan restriction were sympathetically mediated. Severe tryptophan restriction decreased fasting circulating concentrations of glucose, insulin, C-peptide, and leptin, but increased glucagon, pancreatic polypeptide, and glucagon-like peptide-1. Severe tryptophan restriction decreased fecal concentrations of Enterobacteriaceae, Lactobacillus, Bacteroides, and Clostridium coccoides while increasing Roseburia groups. CONCLUSIONS: Our findings demonstrate that dietary tryptophan restriction dose-dependently modulates energy balance, with severe restriction causing hypophagia and weight loss and moderate restriction promoting sympathetically driven thermogenesis as well as concurrent changes in gut microbiota and hormones.

Peptide YY mediates the satiety effects of diets enriched with whey protein fractions in male rats.

Dairy proteins-whey protein, in particular-are satiating and often recommended for weight control; however, little is known about the mechanisms by which whey protein and its components promote satiety and weight loss. We used diet-induced obese rats to determine whether the hypophagic effects of diets that are enriched with whey and its fractions, lactalbumin and lactoferrin, are mediated by the gut hormone, peptide YY (PYY). We demonstrate that high protein diets that contain whey, lactalbumin, and lactoferrin decreased food intake and body weight with a concurrent increase in PYY mRNA abundance in the colon and/or plasma PYY concentrations. Of importance, blockade of PYY neuropeptide Y receptor subtype 2 (Y2) receptors with a peripherally restricted antagonist attenuated the hypophagic effects of diets that are enriched with whey protein fractions. Diets that are enriched with whey fractions were less preferred; however, in a modified conditioned taste preference test, PYY Y2 receptor blockade induced hyperphagia of a lactoferrin diet, but caused a reduction in preference for Y2 antagonist-paired flavor, which suggested that PYY signaling is important for lactoferrin-induced satiety, but not essential for preference for lactoferrin-enriched diets. Taken together, these data provide evidence that the satiety of diets that are enriched with whey protein components is mediated, in part, via enhanced PYY secretion and action in obese male rats.-Zapata, R. C., Singh, A., Chelikani, P. K. Peptide YY mediates the satiety effects of diets enriched with whey protein fractions in male rats.

Diets enriched in whey or casein improve energy balance and prevent morbidity and renal damage in salt-loaded and high-fat-fed spontaneously hypertensive stroke-prone rats.

High-fat diets induce obesity and increase risks of diabetes and cardiovascular and renal disorders. Whey- or casein-enriched diets decrease food intake and weight gain; however, their cardiovascular and renal benefits are unclear. We determined whether whey- and casein-enriched diets improve energy balance and are protective against renal damage and morbidity associated with stroke in an obesogenic and hypertensive experimental setting. We also assessed whether the hypophagic effects of these diets were due to reduced diet preference. In experiment 1, spontaneously hypertensive stroke-prone rats were randomized to (a) control (CON; 14% kcal protein, 33% fat), (b) whey (WHY; 40% protein, 33% fat), (c) casein (CAS; 40% protein, 33% fat) or (d) chow (CHW; 24% protein, 13% fat) for 12 weeks with 1% salt in drinking water for CON, WHY and CAS groups. Our results demonstrated that both WHY and CAS produced short-term hypophagia, moderately increased energy expenditure and decreased respiratory quotient, body weight and lean mass, with effects of WHY being more prolonged. Further, only WHY decreased fat mass and blood pressure. Importantly, both WHY and CAS prevented morbidity associated with stroke and decreased indices of renal inflammation (tumor necrosis factor-α, interleukin-6) and damage (osteopontin, renal lesions). In experiment 2, following four initial conditioning trials, the preference for CON, WHY or CAS diet was determined. Both WHY and CAS decreased food intake during conditioning and decreased preference. In conclusion, diets enriched in whey or casein improved energy balance, increased survival and prevented renal damage in salt-loaded and high-fat-fed spontaneously hypertensive stroke-prone rats.