ABSTRACT
CONTEXT: Visceral adipose tissue (VAT) is a key contributor to chronic inflammation in obesity. The 12/15-lipoxygenase pathway (ALOX) is present in adipose tissue (AT) and leads to inflammatory cascades that are causal for the onset of insulin resistance in rodent models of obesity. OBJECTIVE: The pathophysiology of the ALOX 12/15 pathway in human AT is unknown. We characterized the ALOX pathway in different AT depots in obese humans with or without type 2 diabetes (T2D). DESIGN: This study includes a cross-sectional cohort of 46 morbidly obese (body mass index >39 kg/m(2)) nondiabetic (n = 25) and T2D (n = 21) subjects. SETTING: This study was conducted at Eastern Virginia Medical School (Norfolk, Virginia) in collaboration with Sentara Metabolic and Weight Loss Surgery Center (Sentara Medical Group, Norfolk, Virginia). PATIENTS: Twenty-five obese (body mass index 44.8 ± 4.4 kg/m(2)) nondiabetic (hemoglobin A1c 5.83% ± 0.27%) and 21 obese (43.4 ± 4.1 kg/m(2)) and T2D (hemoglobin A1c 7.66% ± 1.22%) subjects were included in the study. The subjects were age matched and both groups had a bias toward female gender. MAIN OUTCOMES AND MEASURES: Expression of ALOX isoforms along with fatty acid substrates and downstream lipid metabolites were measured. Correlations with depot-specific inflammatory markers were also established. RESULTS: ALOX 12 expression and its metabolite 12(S)-hydroxyeicosatetraenoic acid were significantly increased in the VAT of T2D subjects. ALOX 15A was exclusively expressed in VAT in both groups. ALOX 12 expression positively correlated with expression of inflammatory genes IL-6, IL-12a, CXCL10, and lipocalin-2. CONCLUSIONS: ALOX 12 may have a critical role in regulation of inflammation in VAT in obesity and T2D. Selective ALOX 12 inhibitors may constitute a new approach to limit AT inflammation in human obesity.
Subject(s)
Arachidonate 12-Lipoxygenase/metabolism , Arachidonate 15-Lipoxygenase/metabolism , Diabetes Mellitus, Type 2/enzymology , Intra-Abdominal Fat/enzymology , Obesity, Morbid/enzymology , Adolescent , Adult , Aged , Arachidonate 12-Lipoxygenase/genetics , Arachidonate 15-Lipoxygenase/genetics , Biomarkers/metabolism , Cross-Sectional Studies , Diabetes Mellitus, Type 2/genetics , Diabetes Mellitus, Type 2/immunology , Fatty Acids/metabolism , Female , Gene Expression Regulation, Enzymologic/immunology , Glycated Hemoglobin/metabolism , Humans , Inflammation/enzymology , Inflammation/genetics , Inflammation/immunology , Intra-Abdominal Fat/immunology , Lipid Metabolism/genetics , Lipid Metabolism/immunology , Male , Middle Aged , Obesity, Morbid/genetics , Obesity, Morbid/immunology , Young AdultABSTRACT
Migration of human eosinophils is regulated by integrin expression, conformational change, and activation of cytosolic phospholipase A2 (cPLA2). Corticosteroids have been shown to inhibit cPLA2 hydrolysis in human eosinophils. The objective of this study was to determine the mechanisms of fluticasone propionate (FP) alone or in combination with salmeterol (SM) in blocking adhesion mediated by beta 2-integrin in human eosinophils. Human eosinophils were isolated by negative magnetic selection. beta 2-integrin-mediated eosinophil adhesion was measured by residual eosinophil peroxidase activity. Eosinophils were pretreated for 12 h to 24 h with FP and with or without SM for 30 min. Both SM alone and FP alone inhibited eosinophil adhesion in concentration- and time-dependent manner. SM alone modestly (approximately 30%) inhibited interleukin (IL)-5-induced eosinophil adhesion. Blockade of IL-5-induced eosinophil adhesion caused by 10(-7) M FP at 24 h was augmented by 10(-7) M SM from 41.5% to 72.5%. Similar blockade was also observed for eotaxin-induced eosinophil adhesion. Neither SM, FP, nor FP + SM blocked either: 1) upregulation of CD11b surface expression; or 2) phosphorylation of cPLA2. Blockade of beta 2-integrin-mediated eosinophil adhesion by fluticasone propionate is augmented by salmeterol. Decreased adhesion results from augmented blockade of nuclear translocation of cytosolic phospholipase A2 caused by addition of salmeterol to fluticasone.
Subject(s)
Adrenergic beta-Agonists/therapeutic use , Albuterol/analogs & derivatives , Albuterol/therapeutic use , Androstadienes/therapeutic use , Anti-Inflammatory Agents/therapeutic use , Bronchodilator Agents/therapeutic use , CD18 Antigens/drug effects , Eosinophils/drug effects , Adult , Cell Adhesion/drug effects , Cell Movement/drug effects , Chemokine CCL11 , Chemokines, CC/pharmacology , Chemotactic Factors, Eosinophil/pharmacology , Cytosol/enzymology , Dose-Response Relationship, Drug , Drug Synergism , Female , Fluticasone , Humans , Interleukin-5/pharmacology , Male , Middle Aged , Phospholipases A/drug effects , Phospholipases A2 , Salmeterol XinafoateABSTRACT
OBJECTIVE: To study the effects of intravenous atrial natriuretic peptide (ANP) on antigen-induced bronchoconstriction, propranolol-induced bronchoconstriction (PIB) after antigen challenge, and histamine-induced bronchoconstriction in guinea pigs. METHODS: Allergic bronchoconstriction was evoked by inhalation of ovalbumin (OA) and PIB was caused when 10 mg/mL of propranolol was inhaled 20 min after OA challenge in passively sensitized and artificially ventilated guinea pigs. 25, 50, 100 and 200 microg/mL of histamine were inhaled for 20 s at 5-min intervals in non-sensitized guinea pigs. RESULTS: Pretreatment with ANP in doses of 0.1 and 1.0 nmol/kg injected intravenously 15 min after antigen challenge reduced PIB in a dose-dependent manner, and 5 min before antigen challenge significantly attenuated PIB but not antigen-induced bronchoconstriction. Intravenous ANP significantly reduced bronchial responses to increasing concentrations of inhaled histamine in a dose-dependent manner. CONCLUSION: These results suggest that ANP possesses protective effects against propranolol-induced and histamine-induced bronchoconstriction, albeit by a non-specific mechanism in guinea pig in vivo.
