title: Surfactant protein d, a marker of lung innate immunity, is positively associated with insulin sensitivity.
abstract: OBJECTIVE
  Impaired lung function and innate immunity have both attracted growing interest as a potentially novel risk factor for glucose intolerance, insulin resistance, and type 2 diabetes. We aimed to evaluate whether surfactant protein D (SP-D), a lung-derived innate immune protein, was behind these associations.
  
  
  METHODS
  Serum SP-D was evaluated in four different cohorts. The cross-sectional associations between SP-D and metabolic and inflammatory parameters were evaluated in two cohorts, the cross-sectional relationship with lung function in one cohort, and the longitudinal effects of weight loss on fasting and circadian rhythm of serum SP-D and cortisol concentrations in one prospective cohort.
  
  
  RESULTS
  In the cross-sectional studies, serum SP-D concentration was significantly decreased in subjects with obesity and type 2 diabetes (P = 0.005) and was negatively associated with fasting and postload serum glucose. SP-D was also associated with A1C, serum lipids, insulin sensitivity, inflammatory parameters, and plasma insulinase activity. Smoking subjects with normal glucose tolerance, but not smoking patients with type 2 diabetes, showed significantly higher serum SP-D concentration than nonsmokers. Serum SP-D concentration correlated positively with end-tidal carbon dioxide tension (r = 0.54, P = 0.034). In the longitudinal study, fasting serum SP-D concentration decreased significantly after weight loss (P = 0.02). Moreover, the main components of cortisol and SP-D rhythms became synchronous after weight loss.
  
  
  CONCLUSIONS
  These findings suggest that lung innate immunity, as inferred from circulating SP-D concentrations, is at the cross-roads of inflammation, obesity, and insulin resistance.
authors.affiliation: Department of Diabetes, Endocrinology, and Nutrition, Institut d'Investigació Biomèdica deGirona, Girona, Spain. jmfernandezreal.girona.ics@gencat.cat
authors.forename: José Manuel
authors.initials: JM
authors.lastname: Fernández-Real
authors.forename: Sergio
authors.initials: S
authors.lastname: Valdés
authors.forename: Melania
authors.initials: M
authors.lastname: Manco
authors.forename: Berta
authors.initials: B
authors.lastname: Chico
authors.forename: Patricia
authors.initials: P
authors.lastname: Botas
authors.forename: Arantza
authors.initials: A
authors.lastname: Campo
authors.forename: Roser
authors.initials: R
authors.lastname: Casamitjana
authors.forename: Elías
authors.initials: E
authors.lastname: Delgado
authors.forename: Javier
authors.initials: J
authors.lastname: Salvador
authors.forename: Gema
authors.initials: G
authors.lastname: Fruhbeck
authors.forename: Geltrude
authors.initials: G
authors.lastname: Mingrone
authors.forename: Wifredo
authors.initials: W
authors.lastname: Ricart
mesh_terms: D015415:Biomarkers / Q000097:blood; D001786:Blood Glucose / Q000032:analysis; D003430:Cross-Sectional Studies; D003924:Diabetes Mellitus, Type 2 / Q000097:blood; D006801:Humans; D007113:Immunity, Innate / Q000276:immunology*; D007328:Insulin; D007333:Insulin Resistance / Q000502:physiology*; D009765:Obesity / Q000097:blood; D037663:Pulmonary Surfactant-Associated Protein D / Q000097:blood*
chemical_list: D015415:Biomarkers; D001786:Blood Glucose; D007328:Insulin; D037663:Pulmonary Surfactant-Associated Protein D