Altered distribution and increased IL-17 production by mucosal-associated invariant T cells in adult and childhood obesity.

Mucosal-associated invariant T (MAIT) cells are innate MHC-unrestricted cells that regulate inflammatory responses through the rapid production of cytokines. In this article, we show that circulating MAIT cells are depleted in obese adults, and depletion is associated with diabetic status. Circulating MAIT cells more frequently produced IL-17 upon stimulation ex vivo, a cytokine implicated in insulin resistance. MAIT cells were enriched in adipose tissue (AT) compared with blood. AT MAIT cells, but not circulating MAIT cells, were capable of producing IL-10. In AT from obese subjects, MAIT cells were depleted, were less likely to produce IL-10, and more frequently produced IL-17. Finally, we show that IL-17(+) MAIT cells are also increased in childhood obesity, and altered MAIT cell frequencies in obese children are positively associated with insulin resistance. These data indicate that MAIT cells are enriched in human AT and display an IL-17(+) phenotype in both obese adults and children, correlating with levels of insulin resistance. The alterations in MAIT cells may be contributing to obesity-related sterile inflammation and insulin resistance.

Glucagon-like peptide 1 analogue therapy directly modulates innate immune-mediated inflammation in individuals with type 2 diabetes mellitus.

AIMS/HYPOTHESIS: Glucagon-like peptide 1 (GLP-1) is a gut hormone used in the treatment of type 2 diabetes mellitus. There is emerging evidence that GLP-1 has anti-inflammatory activity in humans, with murine studies suggesting an effect on macrophage polarisation. We hypothesised that GLP-1 analogue therapy in individuals with type 2 diabetes mellitus would affect the inflammatory macrophage molecule soluble CD163 (sCD163) and adipocytokine profile. METHODS: We studied ten obese type 2 diabetes mellitus patients starting GLP-1 analogue therapy at a hospital-based diabetes service. We investigated levels of sCD163, TNF-α, IL-1ß, IL-6, adiponectin and leptin by ELISA, before and after 8 weeks of GLP-1 analogue therapy. RESULTS: GLP-1 analogue therapy reduced levels of the inflammatory macrophage activation molecule sCD163 (220 ng/ml vs 171 ng/ml, p < 0.001). This occurred independent of changes in body weight, fructosamine and HbA1c. GLP-1 analogue therapy was associated with a decrease in levels of the inflammatory cytokines TNF-α (264 vs 149 pg/ml, p < 0.05), IL-1ß (2,919 vs 748 pg/ml, p < 0.05) and IL-6 (1,379 vs 461 pg/ml p < 0.05) and an increase in levels of the anti-inflammatory adipokine adiponectin (4,480 vs 6,290 pg/ml, p < 0.002). CONCLUSIONS/INTERPRETATION: In individuals with type 2 diabetes mellitus, GLP-1 analogue therapy reduces the frequency of inflammatory macrophages. This effect is not dependent on the glycaemic or body weight effects of GLP-1.

Cigarette smoke alters the invariant natural killer T cell function and may inhibit anti-tumor responses.

Invariant natural killer T (iNKT) cells are a minor subset of human T cells which express the invariant T cell receptor Vα24 Jα18 and recognize glycolipids presented on CD1d. Invariant NKT cells are important immune regulators and can initiate anti-tumor responses through early potent cytokine production. Studies show that iNKT cells are defective in certain cancers. Cigarette smoke contains many carcinogens and is implicated directly and indirectly in many cancers. We investigated the effects of cigarette smoke on the circulating iNKT cell number and function. We found that the iNKT cell frequency is significantly reduced in cigarette smoking subjects. Invariant NKT cells exposed to cigarette smoke extract (CSE) showed significant defects in cytokine production and the ability to kill target cells. CSE inhibits the upregulation of CD107 but not CD69 or CD56 on iNKT cells. These findings suggest that CSE has a specific effect on iNKT cell anti-tumor responses, which may contribute to the role of smoking in the development of cancer.

iNKT Cells Induce FGF21 for Thermogenesis and Are Required for Maximal Weight Loss in GLP1 Therapy.

Adipose-resident invariant natural killer T (iNKT) cells are key players in metabolic regulation. iNKT cells are innate lipid sensors, and their activation, using their prototypic ligand α-galactosylceramide (αGalCer), induces weight loss and restores glycemic control in obesity. Here, iNKT activation induced fibroblast growth factor 21 (FGF21) production and thermogenic browning of white fat. Complete metabolic analysis revealed that iNKT cell activation induced increased body temperature, V02, VC02, and fatty acid oxidation, without affecting food intake or activity. FGF21 induction played a major role in iNKT cell-induced weight loss, as FGF21 null mice lost significantly less weight after αGalCer treatment. The glucagon-like peptide 1 (GLP-1) receptor agonist, liraglutide, also activated iNKT cells in humans and mice. In iNKT-deficient mice, liraglutide promoted satiety but failed to induce FGF21, resulting in less weight loss. These findings reveal an iNKT cell-FGF21 axis that defines a new immune-mediated pathway that could be targeted for glycemic control and weight regulation.

Invariant Natural Killer T Cell Deficiency and Functional Impairment in Sleep Apnea: Links to Cancer Comorbidity.

STUDY OBJECTIVES: Emerging evidence links obstructive sleep apnea (OSA) with increased cancer incidence and mortality. Invariant natural killer T (iNKT) cells play an important role in cancer immunity. We hypothesized that patients with OSA have low number of circulating invariant natural killer T (iNKT) cells, which may also be functionally impaired. This study aims to evaluate the frequency of circulating iNKT cells in OSA. DESIGN: We evaluated the frequency of circulating iNKT cells by flow cytometry in 33 snorers being assessed for possible OSA. Using iNKT cell lines, we also evaluated the effect of exposure to hypoxia over 24 hours on apoptosis, cytotoxicity, and cytokine production. SETTING: Teaching hospital based sleep unit and research laboratory. PATIENTS: Thirty-three snorers were evaluated: 9 with no OSA (apnea-hypopnea frequency [AHI] < 5/h), 12 with mild-moderate OSA (AHI 5-30) and 12 with severe OSA (AHI > 30). MEASUREMENTS AND RESULTS: Patients with severe OSA had considerably fewer iNKT cells (0.18%) compared to patients with mild-moderate (0.24%) or no OSA (0.35%), P = 0.0026. The frequency of iNKT cells correlated negatively with apnea-hypopnea index (r = -0.58, P = 0.001), oxygen desaturation index (r = -0.58, P = 0.0003), and SpO2% < 90% (r = -0.5407, P = 0.005). The frequency of iNKT cells increased following 12 months of nCPAP therapy (P = 0.015). Hypoxia resulted in increased apoptosis (P = 0.016) and impaired cytotoxicity (P = 0.035). CONCLUSION: Patients with obstructive sleep apnea (OSA) have significantly reduced levels of circulating invariant natural killer T (iNKT) cells and hypoxia leads to impaired iNKT cell function. These observations may partly explain the increased cancer risk reported in patients with OSA.

Cornea preservation time study: methods and potential impact on the cornea donor pool in the United States.

PURPOSE: The aim of this study was to describe the aims, methods, donor and recipient cohort characteristics, and potential impact of the Cornea Preservation Time Study (CPTS). METHODS: The CPTS is a randomized clinical trial conducted at 40 clinical sites (70 surgeons) designed to assess the effect of donor cornea preservation time (PT) on graft survival 3 years after Descemet stripping automated endothelial keratoplasty (DSAEK). Eyes undergoing surgery for Fuchs endothelial corneal dystrophy or pseudophakic/aphakic corneal edema were randomized to receive donor corneas stored ≤7 days or 8 to 14 days. Donor and patient characteristics, tissue preparation and surgical parameters, recipient and donor corneal stroma clarity, central corneal thickness, intraocular pressure, complications, and a reading center-determined central endothelial cell density were collected. Surveys were conducted to evaluate pre-CPTS PT practices. RESULTS: The 1330 CPTS donors were: 49% >60 years old, 27% diabetic, had a median eye bank-determined screening endothelial cell density of 2688 cells/mm, and 74% eye bank prepared for DSAEK. A total of 1090 recipients (1330 eyes including 240 bilateral cases) had: median age of 70 years, were 60% female, 90% white, 18% diabetic, 52% phakic, and 94% had Fuchs endothelial corneal dystrophy. Before the CPTS, 19 eye banks provided PT data on 20,852 corneas domestically placed for DSAEK in 2010 to 2011; 96% were preserved ≤7 days. Of 305 American Academy of Ophthalmology members responding to a pre-CPTS survey, 233 (76%) set their maximum PT preference at 8 days or less. CONCLUSIONS: The CPTS will increase understanding of factors related to DSAEK success and, if noninferiority of longer PT is shown, will have great potential to extend the available pool of endothelial keratoplasty donors.Clinical Trial Registration-URL: http://www.clinicaltrials.gov. Unique identifier: NCT01537393.

The impact of childhood obesity on inflammation, innate immune cell frequency, and metabolic microRNA expression.

BACKGROUND: Obesity is characterized by chronic inflammation, immune dysregulation, and alteration of gene expression, associated with type 2 diabetes mellitus and cardiovascular disease. The degree to which these changes occur in childhood obesity is not fully defined. AIMS AND METHODS: The aim was to investigate the effect of childhood obesity on immune cell frequency, macrophage activation, cytokine production, and specific regulators of metabolic gene expression. Profiling was performed on peripheral blood from 29 obese and 20 nonobese children using real-time PCR, ELISA, and flow cytometry. RESULTS: Fasting glucose was similar in both groups, but there was a higher degree of insulin resistance in obese subjects (homeostasis model of assessment for insulin resistance, 4.8 vs 0.84; P < .001). Soluble CD163, a marker of macrophage polarization to a proinflammatory profile, was elevated in the obese compared to nonobese children (135 vs 105 ng/mL; P = .03). Invariant natural killer T cells were reduced in the obese children (CD3 T cells, 0.31 vs 0.53%; P = .001). Cytokine profiling revealed significantly elevated TNF-α (6.7 vs 5.1 pg/mL; P = .01) and leptin (1186 vs 432 pg/mL; P < .001) and reduced adiponectin (884 vs 1321 pg/mL; P = .001) in obese compared to nonobese children. Stimulation of peripheral blood mononuclear cells from obese children resulted in higher levels of IL-1ß (2100 vs 1500 pg/mL; P = .018). There was a 4-fold increase in expression of microRNA33a (P = .001) and a 3-fold increase in microRNA33b (P = .017) in obese children. CONCLUSION: Childhood obesity is associated with changes in immune cell frequency, inflammatory environment, and regulation of metabolic gene expression. These changes have been causally linked to the onset of metabolic disease in adulthood and suggest the future trajectory of obese children to the development of type 2 diabetes mellitus and premature cardiovascular disease.

Endogenous oils derived from human adipocytes are potent adjuvants that promote IL-1α-dependent inflammation.

Obesity is characterized by chronic inflammation associated with neutrophil and M1 macrophage infiltration into white adipose tissue. However, the mechanisms underlying this process remain largely unknown. Based on the ability of oil-based adjuvants to induce immune responses, we hypothesized that endogenous oils derived from necrotic adipocytes may function as an immunological "danger signal." Here we show that endogenous oils of human origin are potent adjuvants, enhancing antibody responses to a level comparable to Freund's incomplete adjuvant. The endogenous oils were capable of promoting interleukin (IL)-1α-dependent recruitment of neutrophils and M1-like macrophages, while simultaneously diminishing M2-like macrophages. We found that endogenous oils from subcutaneous and omental adipocytes, and from healthy and unhealthy obese individuals, promoted comparable inflammatory responses. Furthermore, we also confirmed that white adipocytes in visceral fat of metabolically unhealthy obese (MUO) individuals are significantly larger than those in metabolically healthy obese individuals. Since adipocyte size is positively correlated with adipocyte death, we propose that endogenous oils have a higher propensity to be released from hypertrophied visceral fat in MUO individuals and that this is the key factor in driving inflammation. In summary, this study shows that adipocytes contain a potent oil adjuvant which drives IL-1α-dependent proinflammatory responses in vivo.

Glycemic, insulinemic, and appetite responses of patients with type 2 diabetes to commonly consumed breads.

PURPOSE: The purpose of this study was to identify the breads most commonly consumed by adults with type 2 diabetes (T2DM) and then examine the postprandial glycemic, insulinemic, and appetite responses that these breads elicit. METHODS: One hundred people with T2DM were surveyed to identify the varieties of bread they most frequently consumed. According to a randomized crossover design, 11 fasting participants with T2DM consumed 50 g of available carbohydrate from 4 breads. Glucose and insulin concentrations and appetite ratings were determined over 270 minutes. RESULTS: Three commonly consumed varieties (white, whole wheat buttermilk, whole grain) identified in the survey-plus a lower-glycemic-index "control" bread (pumpernickel rye)-were tested in the second phase. Despite perceived differences between "brown" and "white" breads, the white, whole wheat buttermilk, and wholegrain breads promoted similar glycemic and insulinemic responses. Pumpernickel bread resulted in a significantly lower peak glucose (P < .01) than all other breads and a lower peak insulin (P < .001) than white or wholegrain bread. Similar appetite responses were found with all 4 breads. CONCLUSIONS: Adults with T2DM are choosing a variety of breads with perceived differential effects on glycemic, insulinemic, and appetite responses. Appreciable benefits, however, are not conferred by the commonly consumed breads. If breads known to promote favorable metabolic responses are unavailable, the primary emphasis in education should be placed on portion control. Conveying this information to patients is crucial if nutrition education is to achieve its aim of empowering individuals to manage their diabetes through their food choices.