Contrasting cellularity on fat deposition in the subcutaneous adipose tissue and longissimus lumborum muscle from lean and fat pigs under dietary protein reduction

Abstract

The production of pork with high amounts of intramuscular fat (IMF) without an increase in subcutaneous fat is highly desirable for the pig industry and consumers. Herein, we question the impact of dietary protein reduction (18% v. 13%) on fat deposition in the subcutaneous adipose tissue (SAT) and longissimus lumborum (LL) muscle using genetically diverse pigs for body fatness (lean v. fat). A clear effect of genotype was observed on plasma insulin (P = 0.004) and leptin (P < 0.001), as well as on backfat thickness (P < 0.001), with the fat pigs having higher values. Accordingly, IMF was higher in the fat pigs, when compared with their lean counterparts (P = 0.003), which was supported by enlarged adipocytes (P < 0.001). The area of lipid droplets within the LL fibres (P = 0.039) and extramyocellular lipids number (P = 0.017) were increased in pigs fed reduced protein diets, regardless of genotype, which is consistent with higher levels of plasma triacylglycerols (P = 0.002). The gene-expression pattern of lipogenic factors in the SAT was distinct from the LL muscle. In the SAT, PPARG expression was similar among genotypes (P > 0.05), whereas in the LL muscle it was higher in the lean pigs (P = 0.023), especially when fed on low protein diet (P = 0.057). The CEBPA and FABP4 mRNA levels were increased in the SAT of fat pigs (P < 0.001), without changes in the LL muscle (P > 0.05). The influence of diet on FABP4 expression in the SAT was dependent on pig's genetic background (P = 0.005). In conclusion, fat deposition was clearly influenced by genotype and, to a lesser extent, by dietary protein level, the SAT being more sensitive than the LL muscle. One can speculate that the pathways involved in lipid metabolism are downregulated in intramuscular adipocytes when compared with SAT fat cells. This result might be a direct consequence of the relatively low proportion of adipocytes found in the LL muscle.

Effects of Effective Microorganisms on Meat Quality, Microstructure of the Longissimus Lumborum Muscle, and Electrophoretic Protein Separation in Pigs Fed on Different Diets

“…Although the authors showed a slight increase in IMF content (from 1.78% to 2.06%) in Alentejana purebred pigs, this is still a small amount. This was clearly confirmed by studies by Lopez et al [ 52 ], who reported a significantly higher intramuscular fat content with a 5% reduction in protein levels in the diet ( p < 0.003). According to research by Olivares et al [ 53 ], the addition of high levels of vitamin A (dVitA; 100,000 IU) to the diet of Duroc boars resulted in a 20% increase in the IMF of their offspring.…”

Changes in Biceps femoris Transcriptome along Growth in Iberian Pigs Fed Different Energy Sources and Comparative Analysis with Duroc Breed

“…The size of the IMF adipocytes in the BF muscle was studied in the growing Iberian and Duroc animals, with larger adipocytes being observed in the Iberian breed than in the Duroc breed (86.3 microns versus 70.10 microns, respectively; p -value < 0.0001). Although there are histological studies comparing the adipocytes of fat and lean breeds [ 40 ], to the best of our knowledge, this is the first study that compares, at the histological level, the IMF adipocytes between Iberian and Duroc pure growing pigs. The micrographs of Iberian and Duroc intramuscular adipocytes are shown in Figure 1 .…”

Differences in histomorphology and expression of key lipid regulated genes of four adipose tissues from Tibetan pigs

“…Economically important pig breeds such as the Large White and Duroc have thin subcutaneous fat, while Tibetan pigs have high fat-deposition levels and delicious and nutritious meat ( Gan et al, 2019 ; Shen et al, 2014 ). Differences in morphology and lipid-regulated genes also exist between breeds and adipose tissue types ( Lopes et al, 2014 ).…”