Animal. 2016 Oct 17:1-7. [Epub ahead of print]
- 11CIISA, Faculdade de Medicina Veterinária,Universidade de Lisboa,1300-477 Lisboa,Portugal.
- 22Research Institute for Medicines (iMed.ULisboa), Faculdade de Farmácia,Universidade de Lisboa,1649-003 Lisboa,Portugal.
- 33Instituto de Medicina Molecular, Faculdade de Medicina,Universidade de Lisboa,1649-028 Lisboa,Portugal.
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.
KEYWORDS:
glycerol permeability; membrane fluidity; pigs; reduced protein diets; subcutaneous fat
