Lopes P A, Martins A P, Martins S V, Madeira M S, Santos N C, Moura T F, Prates J A M, Soveral G
1CIISA, Faculdade de Medicina Veterinária,Universidade de Lisboa,1300-477 Lisboa,Portugal.
2Research Institute for Medicines (iMed.ULisboa), Faculdade de Farmácia,Universidade de Lisboa,1649-003 Lisboa,Portugal.
Animal. 2017 Apr;11(4):713-719. doi: 10.1017/S1751731116001968. Epub 2016 Oct 17.
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.
对于肉类行业而言，生产出肌内脂肪（IMF）含量适中且皮下脂肪不增加的猪肉是非常理想的。多项研究表明，在猪的生长育肥期减少日粮蛋白质可提高IMF含量，但其对胴体脂肪沉积的影响仍存在矛盾。在本研究中，我们假设，减少蛋白质日粮（RPD），无论是否用限制性氨基酸赖氨酸进行校正，对不同基因型猪皮下脂肪沉积的影响是由脂肪细胞膜生物物理特性介导的。总共36头杂种猪（大白猪×长白猪×皮特兰猪——瘦肉型基因型）和纯种猪（阿连特雅纳猪品种——脂肪型基因型）雄性猪被随机分配到对照组、RPD组或赖氨酸平衡的减少蛋白质日粮（RPDL）组，形成2×3析因设计（n = 6）。阿连特雅纳猪的背膘厚度和总脂肪酸含量高于杂种猪。尽管日粮处理未改变背膘厚度，但RPD和RPDL增加了皮下脂肪的总脂肪酸含量。为了理解这种效应，使用1,6-二苯基-1,3,5-己三烯（DPH）和1-(4-(三甲基氨基)-苯基)-6-苯基-1,3,5-己三烯（TMA-DPH）探针，对从猪皮下脂肪分离的脂肪组织膜进行甘油渗透性和流动性测定。甘油跨脂肪细胞膜的转运不是由水甘油通道蛋白介导的，并且在各日粮组之间保持不变。无论赖氨酸校正情况如何，RPD均增加了两种基因型猪在烃区域的膜流动性（较低的DPH荧光各向异性）。这一结果与膜脂肪酸组成中油酸与亚油酸的比例较低有关。脂肪细胞膜的胆固醇含量与基因型和日粮无关。综上所述，本研究表明，减少日粮蛋白质成功维持了背膘厚度，尽管在皮下脂肪总脂肪酸方面观察到了负面效应，这可能是由于脂肪细胞膜流动性的变化所致。
