title: Higher membrane fluidity mediates the increased subcutaneous fatty acid content in pigs fed reduced protein diets.
abstract: The production of pork with moderate amounts of intramuscular fat (IMF) without an increase in subcutaneous fat is highly desirable for the meat industry. Several studies indicate that dietary protein reduction during the growing-finishing period of pigs enhances IMF content, but its consequence on carcass fat deposition is still contradictory. In this study, we hypothesized that the effects of reduced protein diets (RPD), corrected or not with the limiting amino acid lysine, on subcutaneous fat deposition from pigs with distinct genotypes are mediated by adipose membranes biophysical properties. In total, 36 crossbred (Large White×Landrace×Pietrain - a lean genotype) and purebred (Alentejana breed - a fatty genotype) male pigs were randomly assigned to the control group, the RPD group or the reduced protein diet equilibrated for lysine (RPDL) group, allowing a 2×3 factorial arrangement (n=6). Backfat thickness and total fatty acid content were higher in Alentejana relative to crossbred pigs. Although dietary treatments did not change backfat thickness, RPD and RPDL increased total fatty acids content of subcutaneous fat. In order to understand this effect, adipose tissue membranes isolated from pig's subcutaneous fat were assayed for glycerol permeability and fluidity, using 1,6-diphenyl-1,3,5-hexatriene (DPH) and 1-(4-(trimethylamino)-phenyl)-6-phenyl-1,3,5-hexatriene (TMA-DPH) probes. The glycerol transport across adipose membranes was not mediated by aquaglyceroporins and remained unchanged across dietary groups. Regardless of lysine correction, RPD increased membrane fluidity at the hydrocarbon region (lower DPH fluorescence anisotropy) in both genotypes of pigs. This result was associated with a lower ratio between oleic acid and linoleic acid on membrane's fatty acid composition. Adipose membrane's cholesterol content was independent from genotype and diet. Taken together, the present study shows that dietary protein reduction is successful in maintaining backfat thickness, although a negative side effect was observed on total fatty acids in subcutaneous fat, which may be due to changes in the fluidity of adipose membranes.
authors.affiliation: 1CIISA, Faculdade de Medicina Veterinária,Universidade de Lisboa,1300-477 Lisboa,Portugal.
authors.forename: P A
authors.initials: PA
authors.lastname: Lopes
authors.affiliation: 2Research Institute for Medicines (iMed.ULisboa), Faculdade de Farmácia,Universidade de Lisboa,1649-003 Lisboa,Portugal.
authors.forename: A P
authors.initials: AP
authors.lastname: Martins
authors.affiliation: 1CIISA, Faculdade de Medicina Veterinária,Universidade de Lisboa,1300-477 Lisboa,Portugal.
authors.forename: S V
authors.initials: SV
authors.lastname: Martins
authors.affiliation: 1CIISA, Faculdade de Medicina Veterinária,Universidade de Lisboa,1300-477 Lisboa,Portugal.
authors.forename: M S
authors.initials: MS
authors.lastname: Madeira
authors.affiliation: 3Instituto de Medicina Molecular, Faculdade de Medicina,Universidade de Lisboa,1649-028 Lisboa,Portugal.
authors.forename: N C
authors.initials: NC
authors.lastname: Santos
authors.affiliation: 2Research Institute for Medicines (iMed.ULisboa), Faculdade de Farmácia,Universidade de Lisboa,1649-003 Lisboa,Portugal.
authors.forename: T F
authors.initials: TF
authors.lastname: Moura
authors.affiliation: 1CIISA, Faculdade de Medicina Veterinária,Universidade de Lisboa,1300-477 Lisboa,Portugal.
authors.forename: J A M
authors.initials: JA
authors.lastname: Prates
authors.affiliation: 2Research Institute for Medicines (iMed.ULisboa), Faculdade de Farmácia,Universidade de Lisboa,1649-003 Lisboa,Portugal.
authors.forename: G
authors.initials: G
authors.lastname: Soveral
mesh_terms: D000273:Adipose Tissue / Q000378:metabolism; D000818:Animals; D001823:Body Composition; D001947:Breeding; D018753:Diet, Protein-Restricted / Q000662:veterinary*; D004044:Dietary Proteins / Q000008:administration & dosage / Q000378:metabolism; D004161:Diphenylhexatriene / Q000031:analogs & derivatives; D005227:Fatty Acids / Q000032:analysis*; D008239:Lysine / Q000378:metabolism; D008297:Male; D008560:Membrane Fluidity; D009765:Obesity / Q000378:metabolism; D000069466:Red Meat / Q000592:standards*; D050151:Subcutaneous Fat / Q000737:chemistry* / Q000378:metabolism; D013552:Swine / Q000502:physiology*
chemical_list: D004044:Dietary Proteins; D005227:Fatty Acids; D004161:Diphenylhexatriene; C033628:1-(4-(trimethylamino)phenyl)-6-phenylhexa-1,3,5-triene; D008239:Lysine
keywords: glycerol permeability; membrane fluidity; pigs; reduced protein diets; subcutaneous fat