Interleukin-16 is increased in obesity and alters adipogenesis and inflammation in vitro.

Introduction: Obesity is a chronic condition associated with low-grade inflammation mainly due to immune cell infiltration of white adipose tissue (WAT). WAT is distributed into two main depots: subcutaneous WAT (sWAT) and visceral WAT (vWAT), each with different biochemical features and metabolic roles. Proinflammatory cytokines including interleukin (IL)-16 are secreted by both adipocytes and infiltrated immune cells to upregulate inflammation. IL-16 has been widely studied in the peripheral proinflammatory immune response; however, little is known about its role in adipocytes in the context of obesity. Aim & Methods: We aimed to study the levels of IL-16 in WAT derived from sWAT and vWAT depots of humans with obesity and the role of this cytokine in palmitate-exposed 3T3-L1 adipocytes. Results: The results demonstrated that IL-16 expression was higher in vWAT compared with sWAT in individuals with obesity. In addition, IL-16 serum levels were higher in patients with obesity compared with normal-weight individuals, increased at 6 months after bariatric surgery, and at 12 months after surgery decreased to levels similar to before the intervention. Our in vitro models showed that IL-16 could modulate markers of adipogenesis (Pref1), lipid metabolism (Plin1, Cd36, and Glut4), fibrosis (Hif1a, Col4a, Col6a, and Vegf), and inflammatory signaling (IL6) during adipogenesis and in mature adipocytes. In addition, lipid accumulation and glycerol release assays suggested lipolysis alteration. Discussion: Our results suggest a potential role of IL-16 in adipogenesis, lipid and glucose homeostasis, fibrosis, and inflammation in an obesity context.

Claudin-1 as a novel target gene induced in obesity and associated to inflammation, fibrosis, and cell differentiation.

OBJECTIVE: T lymphocytes from visceral and subcutaneous white adipose tissues (vWAT and sWAT, respectively) can have opposing roles in the systemic metabolic changes associated with obesity. However, few studies have focused on this subject. Claudin-1 (CLDN1) is a protein involved canonically in tight junctions and tissue paracellular permeability. We evaluated T-lymphocyte gene expression in vWAT and sWAT and in the whole adipose depots in human samples. METHODS: A Clariom D-based transcriptomic analysis was performed on T lymphocytes magnetically separated from vWAT and sWAT from patients with obesity (Cohort 1; N = 11). Expression of candidate genes resulting from that analysis was determined in whole WAT from individuals with and without obesity (Cohort 2; patients with obesity: N = 13; patients without obesity: N = 14). RESULTS: We observed transcriptional differences between T lymphocytes from sWAT compared with vWAT. Specifically, CLDN1 expression was found to be dramatically induced in vWAT T cells relative to those isolated from sWAT in patients with obesity. CLDN1 was also induced in obesity in vWAT and its expression correlates with genes involved in inflammation, fibrosis, and adipogenesis. CONCLUSION: These results suggest that CLDN1 is a novel marker induced in obesity and differentially expressed in T lymphocytes infiltrated in human vWAT as compared with sWAT. This protein may have a crucial role in the crosstalk between T lymphocytes and other adipose tissue cells and may contribute to inflammation, fibrosis, and alter homeostasis and promote metabolic disease in obesity.

Cold exposure modulates potential brown adipokines in humans, but only FGF21 is associated with brown adipose tissue volume.

OBJECTIVE: The study objective was to investigate the effect of cold exposure on the plasma levels of five potential human brown adipokines (chemokine ligand 14 [CXCL14], growth differentiation factor 15 [GDF15], fibroblast growth factor 21 [FGF21], interleukin 6 [IL6], and bone morphogenic protein 8b [BMP8b]) and to study whether such cold-induced effects are related to brown adipose tissue (BAT) volume, activity, or radiodensity in young humans. METHODS: Plasma levels of brown adipokines were measured before and 1 h and 2 h after starting an individualized cold exposure in 30 young adults (60% women, 21.9 ± 2.3 y; 24.9 ± 5.1 kg/m2 ). BAT volume, 18 F-fluorodeoxyglucose uptake, and radiodensity were assessed by a static positron emission tomography-computerized tomography scan after cold exposure. RESULTS: Cold exposure increased the concentration of CXCL14 (Δ2h = 0.58 ± 0.98 ng/mL; p = 0.007), GDF15 (Δ2h = 19.63 ± 46.2 pg/mL; p = 0.013), FGF21 (Δ2h = 33.72 ± 55.13 pg/mL; p = 0.003), and IL6 (Δ1h = 1.98 ± 3.56 pg/mL; p = 0.048) and reduced BMP8b (Δ2h = -37.12 ± 83.53 pg/mL; p = 0.022). The cold-induced increase in plasma FGF21 was positively associated with BAT volume (Δ2h: ß = 0.456; R2 = 0.307; p = 0.001), but not with 18 F-fluorodeoxyglucose uptake or radiodensity. None of the changes in the other studied brown adipokines was related to BAT volume, activity, or radiodensity. CONCLUSIONS: Cold exposure modulates plasma levels of several potential brown adipokines in humans, whereas only cold-induced changes in FGF21 levels are associated with BAT volume. These findings suggest that human BAT might contribute to the circulatory pool of FGF21.

Lipidome Profiling in Childhood Obesity Compared to Adults: A Pilot Study.

The objective is to assess the circulating lipidome of children with obesity before and after lifestyle intervention and to compare the data to the circulating lipidome of adults with obesity before and after bariatric surgery. Ten pediatric (PE) and thirty adult (AD) patients with obesity were prospectively recruited at a referral single center. The PE cohort received lifestyle recommendations. The AD cohort underwent bariatric surgery. Clinical parameters and lipidome were analyzed in serum before and after six months of metabolic intervention. The abundance of phosphatidylinositols in the PE cohort and phosphatidylcholines in the AD significantly increased, while O-phosphatidylserines in the PE cohort and diacyl/triacylglycerols in the AD decreased. Fifteen lipid species were coincident in both groups after lifestyle intervention and bariatric surgery. Five species of phosphatidylinositols, sphingomyelins, and cholesteryl esters were upregulated. Eight species of diacylglycerols, glycerophosphoglycerols, glycerophosphoethanolamines, and phosphatidylcholines were downregulated. Most matching species were regulated in the same direction except for two phosphatidylinositols: PI(O-36:2) and PI(O-34:0). A specific set of lipid species regulated after bariatric surgery in adult individuals was also modulated in children undergoing lifestyle intervention, suggesting they may constitute a core circulating lipid profile signature indicative of early development of obesity and improvement after clinical interventions regardless of individual age.

Birth Weight and Early Postnatal Outcomes: Association with the Cord Blood Lipidome.

Being born small or large for gestational age (SGA and LGA, respectively), combined with suboptimal early postnatal outcomes, can entail future metabolic alterations. The exact mechanisms underlying such risks are not fully understood. Lipids are a highly diverse class of molecules that perform multiple structural and metabolic functions. Dysregulation of lipid metabolism underlies the onset and progression of many disorders leading to pathological states. The aim of this pilot study was to investigate the relationships between birth weight, early postnatal outcomes, and cord blood serum lipidomes. We performed a non-targeted lipidomics-based approach to ascertain differences in cord blood lipid species among SGA, LGA, and appropriate-for-GA (AGA) newborns. Moreover, we longitudinally assessed (at birth and at ages of 4 and 12 months) weight and length, body composition (DXA), and clinical parameters. We disclosed distinct cord blood lipidome patterns in SGA, LGA, and AGA newborns; target lipid species distinctly modulated in each SGA, AGA, and LGA individual were associated with parameters related to growth and glucose homeostasis. The distinct lipidome patterns observed in SGA, AGA, and LGA newborns may play a role in adipose tissue remodeling and future metabolic risks. Maternal dietary interventions may potentially provide long-term benefits for the metabolic health of the offspring.

The armadillo-repeat containing X-linked protein 3, ARMCX3, is a negative regulator of the browning of adipose tissue associated with obesity.

OBJECTIVES: To determine the role of armadillo repeat-containing X-linked protein 3 (ARMCX3) in the thermogenic plasticity of adipose tissue. METHODS: Adipose tissues were characterized in Armcx3-KO male mice. Armcx3 gene expression was analyzed in adipose tissue from mice exposed to thermogenic inducers (cold, ß3-adenergic stimulus) and in differentiating brown and beige cells in culture. Analyses encompassed circulating metabolite and hormonal profiling, tissue characterization, histology, gene expression patterns, and immunoblot assays. Armcx3 gene expression was assessed in subcutaneous adipose tissue from lean individuals and individuals with obesity and was correlated with expression of marker genes of adipose browning. The effects of adenoviral-mediated overexpression of ARMCX3 on differentiating brown adipocyte gene expression and respiratory activity were determined. RESULTS: Male mice lacking ARMCX3 showed significant induction of white adipose tissue browning. In humans, ARMCX3 expression in subcutaneous adipose tissue was inversely correlated with the expression of marker genes of thermogenic activity, including CIDEA, mitochondrial transcripts, and creatine kinase-B. Armcx3 expression in adipose tissues was repressed by thermogenic activation (cold or ß3-adrenergic stimulation) and was upregulated by obesity in mice and humans. Experimentally-induced increases in Armcx3 caused down-regulation of thermogenesis-related genes and reduced mitochondrial oxidative activity of adipocytes in culture, whereas siRNA-mediated Armcx3 knocking-down enhanced expression of thermogenesis-related genes. CONCLUSION: ARMCX3 is a novel player in the control of thermogenic adipose tissue plasticity that acts to repress acquisition of the browning phenotype and shows a direct association with indicators of obesity in mice and humans.

White adipose tissue dysfunction in obesity and aging.

Both obesity and aging are associated with the development of metabolic diseases such as type 2 diabetes and cardiovascular disease. Chronic low-grade inflammation of adipose tissue is one of the mechanisms implicated in the progression of these diseases. Obesity and aging trigger adipose tissue alterations that ultimately lead to a pro-inflammatory phenotype of the adipose tissue-resident immune cells. Obesity and aging also share other features such as a higher visceral vs. subcutaneous adipose tissue ratio and a decreased lifespan. Here, we review the common characteristics of obesity and aging and the alterations in white adipose tissue and resident immune cells. We focus on the adipose tissue metabolic derangements in obesity and aging such as inflammation and adipose tissue remodeling.

Increasing breast milk betaine modulates Akkermansia abundance in mammalian neonates and improves long-term metabolic health.

Accelerated postnatal growth is a potentially modifiable risk factor for future obesity. To study how specific breast milk components contribute to early growth and obesity risk, we quantified one-carbon metabolism-related metabolites in human breast milk and found an inverse association between milk betaine content and infant growth. This association was replicated in an independent and geographically distinct cohort. To determine the potential role of milk betaine in modulating offspring obesity risk, we performed maternal betaine supplementation experiments in mice. Higher betaine intake during lactation increased milk betaine content in dams and led to lower adiposity and improved glucose homeostasis throughout adulthood in mouse offspring. These effects were accompanied by a transient increase in Akkermansia spp. abundance in the gut during early life and a long-lasting increase in intestinal goblet cell number. The link between breast milk betaine and Akkermansia abundance in the gut was also observed in humans, as infants exposed to higher milk betaine content during breastfeeding showed higher fecal Akkermansia muciniphila abundance. Furthermore, administration of A. muciniphila to mouse pups during the lactation period partially replicated the effects of maternal breast milk betaine, including increased intestinal goblet cell number, lower adiposity, and improved glucose homeostasis during adulthood. These data demonstrate a link between breast milk betaine content and long-term metabolic health of offspring.

Oxidative Stress and Inflammatory Markers in Abdominal Aortic Aneurysm.

Abdominal aortic aneurysm (AAA) is increasing due to aging of the population and is a major cause of death among the elderly. Ultrasound screening programs are useful in early diagnosis, but aneurysm size is not always a good predictor of rupture. Our aim was to analyze the value of circulating molecules related to oxidative stress and inflammation as new biomarkers to assist the management of AAA. The markers were quantified by ELISA, and their expression in the aneurysmal wall was studied by real-time PCR and by immunostaining. Correlation analysis of the studied markers with aneurysm diameter and peak wall stress (PWS), obtained by finite element analysis, and multivariate regression analysis to assess potential confounding factors were performed. Our study shows an extensive inflammatory infiltration in the aneurysmal wall, mainly composed by T-cells, macrophages and B-cells and altered levels of reactive oxygen species (ROS), IgM, IgG, CD38, GDF15, S100A4 and CD36 in plasma and in the aneurysmal tissue of AAA patients compared with controls. Circulating levels of IgG, CD38 and GDF15 positively correlated with abdominal aortic diameter, and CD38 was correlated with PWS. Our data show that altered levels of IgG, CD38 and GDF15 have potential diagnostic value in the assessment of AAA.

White adipose tissue-infiltrated CD11b+ myeloid cells are a source of S100A4, a new potential marker of hepatic damage.

CONTEXT: The endocrine and immunological properties of subcutaneous vs visceral adipose tissue (sWAT and vWAT, respectively) have turned a milestone in the study of metabolic diseases. The cytokine S100A4 is increased in obesity and has a role in adipose tissue dysfunction. However, the cellular source and its potential role in hepatic damage in obesity has not been elucidated. OBJECTIVE: We aim to study the regulation of S100A4 in immune cells present in sWAT and vWAT, as well as its potential role as a circulating marker of hepatic inflammation and steatosis. DESIGN: A cohort of 60 patients with obesity and distinct metabolic status was analyzed. CD11b+ myeloid cells and T cells were isolated from sWAT and vWAT by magnetic-activating cell sorting, and RNA was obtained. S100A4 gene expression was measured, and correlation analysis with clinical data was performed. Liver biopsies were obtained from 20 patients, and S100A4 circulating levels were measured to check the link with hepatic inflammation and steatosis. RESULTS: S100A4 gene expression was strongly upregulated in sWAT- vs vWAT-infiltrated CD11b+ cells, but this modulation was not observed in T cells. S100A4 mRNA levels from sWAT (and not from vWAT) CD11b+ cells positively correlated with glycemia, triglycerides, TNF-α gene expression and proliferation markers. Finally, circulating S100A4 directly correlated with liver steatosis and hepatic inflammatory markers. CONCLUSION: Our data suggest that sWAT-infiltrated CD11b+ cells could be a major source of S100A4 in obesity. Moreover, our correlations identify circulating S100A4 as a potential novel biomarker of hepatic damage and steatosis.

The chemokine CXCL14 is negatively associated with obesity and concomitant type-2 diabetes in humans.

Chemokine (C-X-C motif) ligand-14 (CXCL14) levels are downregulated in experimental rodent models of obesity. Moreover, CXCL14 reportedly favors insulin sensitization in obese mice. Here we examined, for the first time, the role of CXCL14 in human obesity. We found that circulating levels of CXCL14 were decreased in patients with obesity and, especially, those with concomitant type-2 diabetes. CXCL14 levels were negatively associated with BMI and with indices of impaired glucose/insulin homeostasis. CXCL14 expression was decreased in subcutaneous adipose tissue from patients with obesity and type-2 diabetes. In adipose tissue, CXCL14 expression was negatively correlated with the expression of genes encoding pro-inflammatory molecules, and positively correlated with GLUT4 and adiponectin expression. In conclusion, obesity, and especially, concomitant type-2 diabetes are associated with abnormally decreased levels of CXCL14 in blood and impaired CXCL14 expression in adipose tissue. CXCL14 downregulation may be a novel biomarker of altered metabolism in obesity. CXCL14 also deserves further research as a therapeutic candidate.

Altered GDF15 and FGF21 Levels in Response to Strenuous Exercise: A Study in Marathon Runners.

BACKGROUND: Recreational marathon runners face strong physiological challenges. Assessment of potential biomarkers for the biological responses of runners will help to discriminate individual race responsiveness and their physiological consequences. This study sought to analyze the changes in the plasma levels of GDF15 and FGF21, novel endocrine factors related to metabolic stress, in runners following the strenuous exercise of a marathon race. METHODS: Blood samples were obtained from eighteen male runners (mean ±SD, age: 41.7 ±5.0 years, BMI: 23.6 ± 1.8) 48 h before, immediately after, and 48 h after a marathon race, and from age-matched sedentary individuals. The level of GDF15, FGF21, and 38 additional biochemical and hematological parameters were determined. RESULTS: The basal levels of GDF15 and FGF21 did not differ between runners before the race and sedentary individuals. Significant increases in the mean levels of GDF15 (4.2-fold) and FGF21 (20-fold) were found in runners immediately after the race. The magnitudes of these increases differed markedly among individuals and did not correlate with each other. The GDF15 and FGF21 levels had returned to the basal level 48 h post-race. The post-race value of GDF15 (but not FGF21) correlated positively with increased total white cell count (r = 0.50, P = 0.01) and neutrophilia (r = 0.10, P = 0.01). CONCLUSION: GDF15 and FGF21 are transiently increased in runners following a marathon race. The induction of GDF15 levels is associated with alterations in circulating immune cells levels.

Effects of Bifidobacterium animalis Subsp. lactis (BPL1) Supplementation in Children and Adolescents with Prader-Willi Syndrome: A Randomized Crossover Trial.

Prader-Willi syndrome (PWS) is a rare genetic disorder characterized by a wide range of clinical manifestations, including obesity, hyperphagia, and behavioral problems. Bifidobacterium animalis subsp. lactis strain BPL1 has been shown to improve central adiposity in adults with simple obesity. To evaluate BPL1's effects in children with PWS, we performed a randomized crossover trial among 39 patients (mean age 10.4 years). Participants were randomized to placebo-BPL1 (n = 19) or BPL1-placebo (n = 20) sequences and underwent a 12-week period with placebo/BPL1 treatments, a 12-week washout period, and a 12-week period with the crossover treatment. Thirty-five subjects completed the study. The main outcome was changes in adiposity, measured by dual-energy X-ray absorptiometry. Secondary outcomes included lipid and glucose metabolism, hyperphagia, and mental health symptoms. Generalized linear modeling was applied to assess differences between treatments. While BPL1 did not modify total fat mass compared to placebo, BPL1 decreased abdominal adiposity in a subgroup of patients older than 4.5 years (n = 28). BPL1 improved fasting insulin concentration and insulin sensitivity. Furthermore, we observed modest improvements in some mental health symptoms. A follow-up trial with a longer treatment period is warranted to determine whether BPL1 supplementation can provide a long-term therapeutic approach for children with PWS (ClinicalTrials.gov NCT03548480).

Liver CPT1A gene therapy reduces diet-induced hepatic steatosis in mice and highlights potential lipid biomarkers for human NAFLD.

The prevalence of nonalcoholic fatty liver disease (NAFLD) has increased drastically due to the global obesity pandemic but at present there are no approved therapies. Here, we aimed to revert high-fat diet (HFD)-induced obesity and NAFLD in mice by enhancing liver fatty acid oxidation (FAO). Moreover, we searched for potential new lipid biomarkers for monitoring liver steatosis in humans. We used adeno-associated virus (AAV) to deliver a permanently active mutant form of human carnitine palmitoyltransferase 1A (hCPT1AM), the key enzyme in FAO, in the liver of a mouse model of HFD-induced obesity and NAFLD. Expression of hCPT1AM enhanced hepatic FAO and autophagy, reduced liver steatosis, and improved glucose homeostasis. Lipidomic analysis in mice and humans before and after therapeutic interventions, such as hepatic AAV9-hCPT1AM administration and RYGB surgery, respectively, led to the identification of specific triacylglyceride (TAG) specie (C50:1) as a potential biomarker to monitor NAFFLD disease. To sum up, here we show for the first time that liver hCPT1AM gene therapy in a mouse model of established obesity, diabetes, and NAFLD can reduce HFD-induced derangements. Moreover, our study highlights TAG (C50:1) as a potential noninvasive biomarker that might be useful to monitor NAFLD in mice and humans.

Differential association between S100A4 levels and insulin resistance in prepubertal children and adult subjects with clinically severe obesity.

OBJECTIVES: S100A4 has been recently identified as an adipokine associated with insulin resistance (IR) in adult subjects with obesity. However, no data about its levels in children with obesity and only a few approaches regarding its potential mechanism of action have been reported. To obtain a deeper understanding of the role of S100A4 in obesity, (a) S100A4 levels were measured in prepubertal children and adult subjects with and without obesity and studied the relationship with IR and (b) the effects of S100A4 in cultured human adipocytes and vascular smooth muscle cells (VSMCs) were determined. METHODS: Sixty-five children (50 with obesity, age 9.0 ±1.1 years and 15 normal weight, age 8.4 ±0.8 years) and fifty-nine adults (43 with severe obesity, age 46 ±11 years and 16 normal weight, age 45 ±9 years) were included. Blood from children and adults and adipose tissue samples from adults were obtained and analysed. Human adipocytes and VSMC were incubated with S100A4 to evaluate their response to this adipokine. RESULTS: Circulating S100A4 levels were increased in both children (P = .002) and adults (P < .001) with obesity compared with their normal-weight controls. In subjects with obesity, S100A4 levels were associated with homeostatic model assessment-insulin resistance (HOMA-IR) in adults (ßstd = .42, P = .008) but not in children (ßstd = .12, P = .356). Human adipocytes were not sensitive to S100A4, while incubation with this adipokine significantly reduced inflammatory markers in VSMC. CONCLUSIONS: Our human data demonstrate that higher S100A4 levels are a marker of IR in adults with obesity but not in prepubertal children. Furthermore, the in vitro results suggest that S100A4 might exert an anti-inflammatory effect. Further studies will be necessary to determine whether S100A4 can be a therapeutic target for obesity.

Use of Infrared Thermography to Estimate Brown Fat Activation After a Cooling Protocol in Patients with Severe Obesity That Underwent Bariatric Surgery.

BACKGROUND: In contrast to the energy-storing role of white adipose tissue (WAT), brown adipose tissue (BAT) acts as the main site of non-shivering thermogenesis in mammals and has been reported to play a role in protection against obesity and associated metabolic alterations in rodents. Infrared thermography (IRT) has been proposed as a novel non-invasive, safe, and quick method to estimate BAT thermogenic activation in humans. The aim of this study is to determine whether the IRT could be a potential new tool to estimate BAT thermogenic activation in patients with severe obesity in response to bariatric surgery. METHODS: Supraclavicular BAT thermogenic activation was evaluated using IRT in a cohort of 31 patients (50 ± 10 years old, BMI = 44.5 ± 7.8; 15 undergoing laparoscopy sleeve gastrectomy and 16 Roux-en-Y gastric bypass) at baseline and 6 months after a bariatric surgery. Clinical parameters were determined at these same time points. RESULTS: Supraclavicular BAT-related activity was detected in our patients by IRT after a cooling stimulus. The BAT thermogenic activation was higher at 6 months after laparoscopy sleeve gastrectomy (0.06 ± 0.1 vs 0.32 ± 0.1), while patients undergoing to a roux-en-Y gastric bypass did not change their thermogenic response using the same cooling stimulus (0.09 ± 0.1 vs 0.08 ± 0.1). CONCLUSIONS: Our study postulates the IRT as a potential tool to evaluate BAT thermogenic activation in patients with obesity before and after a bariatric surgery. Further studies are needed to evaluate differences between LSG technique and RYGB on BAT activation.

Elevated Levels of Circulating miR-92a Are Associated with Impaired Glucose Homeostasis in Patients with Obesity and Correlate with Metabolic Status After Bariatric Surgery.

INTRODUCTION: miRNAs are small non-coding RNAs, some of which are expressed in adipose tissues, are present in the circulation, and are regulated in obesity. Bariatric surgery (BS) has been proposed to lead to activation of brown adipose tissue, an effect that may be related to beneficial effects of BS on systemic metabolism. Here, we evaluated circulating levels of miR-92a and miR-99b, two miRNAs proposed as biomarkers of brown fat activity, in a cohort of patients with severe obesity before and after BS, and studied their potential relationship with BS-associated improvements in metabolic parameters. METHODS: Circulating levels of miR-92a and miR-99b were quantified in a cohort of 26 patients (age, 48 ± 10 years; BMI, 45 ± 7 kg/m2) before and 6 months after BS. Clinical parameters were determined at different time points and correlations among them were studied. RESULTS: Basal levels of miR-92a were significantly increased in patients with obesity relative to lean controls. Serum miR-92a levels were strongly reduced at 6 months after BS, reaching levels similar to those in controls. Serum miR-99b levels were unchanged in relation to both the obese condition and BS. Elevated levels of miR-92a were directly correlated with worsened glucose homeostasis parameters and poor BS outcome. CONCLUSIONS: Our findings show that miR-92a is elevated in conditions of obesity, and its reduction after BS correlates with metabolic improvement. Further studies would be necessary to establish miR-92a as serum biomarker and potential predictor of the BS success in improving the metabolic status of patients with obesity.

A Role for Oncostatin M in the Impairment of Glucose Homeostasis in Obesity.

CONTEXT: Oncostatin M (OSM) plays a key role in inflammation, but its regulation and function during obesity is not fully understood. OBJECTIVE: The aim of this study was to evaluate the relationship of OSM with the inflammatory state that leads to impaired glucose homeostasis in obesity. We also assessed whether OSM immunoneutralization could revert metabolic disturbances caused by a high-fat diet (HFD) in mice. DESIGN: 28 patients with severe obesity were included and stratified into two groups: (1) glucose levels <100 mg/dL and (2) glucose levels >100 mg/dL. White adipose tissue was obtained to examine OSM gene expression. Human adipocytes were used to evaluate the effect of OSM in the inflammatory response, and HFD-fed C57BL/6J mice were injected with anti-OSM antibody to evaluate its effects. RESULTS: OSM expression was elevated in subcutaneous and visceral fat from patients with obesity and hyperglycemia, and correlated with Glut4 mRNA levels, serum insulin, homeostatic model assessment of insulin resistance, and inflammatory markers. OSM inhibited adipogenesis and induced inflammation in human adipocytes. Finally, OSM receptor knockout mice had increased Glut4 mRNA levels in adipose tissue, and OSM immunoneutralization resulted in a reduction of glucose levels and Ccl2 expression in adipose tissue from HFD-fed mice. CONCLUSIONS: OSM contributes to the inflammatory state during obesity and may be involved in the development of insulin resistance.

Adipocyte Oncostatin Receptor Regulates Adipose Tissue Homeostasis and Inflammation.

Adipocytes are the largest cell type in terms of volume, but not number, in adipose tissue. Adipocytes are prominent contributors to systemic metabolic health. Obesity, defined by excess adipose tissue (AT), is recognized as a low-grade chronic inflammatory state. Cytokines are inflammatory mediators that are produced in adipose tissue (AT) and function in both AT homeostatic as well as pathological conditions. AT inflammation is associated with systemic metabolic dysfunction and obesity-associated infiltration and proliferation of immune cells occurs in a variety of fat depots in mice and humans. AT immune cells secrete a variety of chemokines and cytokines that act in a paracrine manner on adjacent adipocytes. TNFα, IL-6, and MCP-1, are well studied mediators of AT inflammation. Oncostatin M (OSM) is another proinflammatory cytokine that is elevated in AT in human obesity, and its specific receptor (OSMRß) is also induced in conditions of obesity and insulin resistance. OSM production and paracrine signaling in AT regulates adipogenesis and the functions of AT. This review summarizes the roles of the oncostatin M receptor (OSMRß) as a modulator of adipocyte development and function its contributions to immunological adaptations in AT in metabolic disease states.

Infrared Thermography for Estimating Supraclavicular Skin Temperature and BAT Activity in Humans: A Systematic Review.

OBJECTIVE: Brown adipose tissue (BAT) is a thermogenic tissue with potential as a therapeutic target in the treatment of obesity and related metabolic disorders. The most used technique for quantifying human BAT activity is the measurement of 18 F-fluorodeoxyglucose uptake via a positron emission tomography/computed tomography scan following exposure to cold. However, several studies have indicated the measurement of the supraclavicular skin temperature (SST) by infrared thermography (IRT) to be a less invasive alternative. This work reviews the state of the art of this latter method as a means of determining BAT activity in humans. METHODS: The data sources for this review were PubMed, Web of Science, and EBSCOhost (SPORTdiscus), and eligible studies were those conducted in humans. RESULTS: In most studies in which participants were first cooled, an increase in IRT-measured SST was noted. However, only 5 of 24 such studies also involved a nuclear technique that confirmed increased activity in BAT, and only 2 took into account the thickness of the fat layer when measuring SST by IRT. CONCLUSIONS: More work is needed to understand the involvement of tissues other than BAT in determining IRT-measured SST; at present, IRT cannot determine whether any increase in SST is due to increased BAT activity.