title: Docosahexaenoic acid attenuates macrophage-induced inflammation and improves insulin sensitivity in adipocytes-specific differential effects between LC n-3 PUFA.
abstract: OBJECTIVE
  Adipose tissue inflammation with immune cell recruitment plays a key role in obesity-induced insulin resistance (IR). Long-chain (LC) n-3 polyunsaturated fatty acids (PUFA) eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) have anti-inflammatory potential; however, their individual effects on adipose IR are ill defined. We hypothesized that EPA and DHA may differentially affect macrophage-induced IR in adipocytes.
  
  
  METHODS
  J774.2 macrophages pretreated with EPA or DHA (50 μM for 5 days) were stimulated with lipopolysaccharide (LPS, 100 ng/ml for 30 min-48 h). Cytokine secretion profiles and activation status of macrophages were assessed by enzyme-linked immunosorbent assay and flow cytometry. Pretreated macrophages were seeded onto transwell inserts and placed over 3T3-L1 adipocytes for 24-72 h; effects on adipocyte-macrophage cytokine cross-talk and insulin-stimulated ³H-glucose transport into adipocytes were monitored.
  
  
  RESULTS
  DHA had more potent anti-inflammatory effects relative to EPA, with marked attenuation of LPS-induced nuclear factor (NF)κB activation and tumor necrosis factor (TNF)α secretion in macrophages. DHA specifically enhanced anti-inflammatory interleukin (IL)-10 secretion and reduced the expression of proinflammatory M1 (F4/80⁺/CD11⁺) macrophages. Co-culture of DHA-enriched macrophages with adipocytes attenuated IL-6 and TNFα secretion while enhancing IL-10 secretion. Conditioned media (CM) from DHA-enriched macrophages attenuated adipocyte NFκB activation. Adipocytes co-cultured with DHA-enriched macrophages maintained insulin sensitivity with enhanced insulin-stimulated ³H-glucose transport, GLUT4 translocation and preservation of insulin-receptor substrate-1 expression compared to co-culture with untreated macrophages. We confirmed that IL-10 expressed by DHA-enriched macrophages attenuates the CM-induced proinflammatory IR phenotype in adipocytes.
  
  
  CONCLUSIONS
  We demonstrate an attenuated proinflammatory phenotype of DHA-pretreated macrophages, which when co-cultured with adipocytes partially preserved insulin sensitivity.
authors.affiliation: Nutrigenomics Research Group, UCD Conway Institute, & UCD Institute of Food and Health, University College Dublin, Dublin 4, Ireland.
authors.forename: Elizabeth
authors.initials: E
authors.lastname: Oliver
authors.forename: Fiona C
authors.initials: FC
authors.lastname: McGillicuddy
authors.forename: Karen A
authors.initials: KA
authors.lastname: Harford
authors.forename: Clare M
authors.initials: CM
authors.lastname: Reynolds
authors.forename: Catherine M
authors.initials: CM
authors.lastname: Phillips
authors.forename: Jane F
authors.initials: JF
authors.lastname: Ferguson
authors.forename: Helen M
authors.initials: HM
authors.lastname: Roche
mesh_terms: D041721:3T3-L1 Cells; D052438:Adipocytes, White / Q000276:immunology / Q000378:metabolism*; D000818:Animals; D000894:Anti-Inflammatory Agents, Non-Steroidal / Q000378:metabolism*; D001692:Biological Transport; D002450:Cell Communication; D002461:Cell Line, Transformed; D018920:Coculture Techniques; D017077:Culture Media, Conditioned; D016207:Cytokines / Q000378:metabolism; D004281:Docosahexaenoic Acids / Q000378:metabolism*; D015118:Eicosapentaenoic Acid / Q000378:metabolism; D005947:Glucose / Q000378:metabolism; D051275:Glucose Transporter Type 4 / Q000378:metabolism; D007328:Insulin / Q000378:metabolism; D055504:Insulin Receptor Substrate Proteins / Q000378:metabolism; D007333:Insulin Resistance; D016753:Interleukin-10 / Q000378:metabolism*; D008262:Macrophage Activation; D008264:Macrophages / Q000276:immunology* / Q000378:metabolism; D051379:Mice; D021381:Protein Transport
chemical_list: D000894:Anti-Inflammatory Agents, Non-Steroidal; D017077:Culture Media, Conditioned; D016207:Cytokines; D051275:Glucose Transporter Type 4; C556062:IL10 protein, mouse; D007328:Insulin; D055504:Insulin Receptor Substrate Proteins; C526295:Irs1 protein, mouse; C495693:Slc2a4 protein, mouse; D016753:Interleukin-10; D004281:Docosahexaenoic Acids; D015118:Eicosapentaenoic Acid; D005947:Glucose