Comparison of red meat versus high carbohydrate diet using the gilt biomedical model: Myofiber and adipocyte molecular biology

Abstract Text: The objective of this study was to determine if differences in body composition, blood chemistry, and insulin receptor (IR) density of adipocyte and muscle fibers are associated with a high calorie, high glycemic diet. Yorkshire x Duroc x Hampshire gilts (N = 21) born over a five-day period from the same sire were provided ad libitum access to a low lysine diet (Lys = 0.45%) to promote hyperphagia and adiposity. Upon reaching 3 cm subcutaneous backfat (10BF; 10/11th rib interface), dietary treatments were allocated across BW and BF to either a ground beef (GB; n = 5) or control (CON; n = 5) treatment. The GB diet was 99.9% cooked ground beef (65:35 lean:fat) plus 0.1% calcium carbonate while CON comprised 83% ground corn, 10% distillers dried grains plus solubles, and 5% soybean meal. Both rations met NRC requirements for gilts of this size and weight. Intake and orts were recorded daily. Body weights (BW) and blood draws were collected on d0, 28, 56, and 84. Gilts were humanely slaughtered on d85 for tissue collections and body composition analysis. One gilt was removed from the GB due to foot infection. Samples of longissimus thoracis muscle (LT; 10/11th rib interface), gracilis muscle (GM), 10BF, and liver tissues were snap frozen for IR qPCR analysis, and fixed in formalin for immunohistochemical evaluation of IR density. The GB gilts had a greater percent change in BW (P = 0.002) and 10BF (P < 0.02). Control gilts had more (P = 0.04) perirenal fat than GB (5.05 vs. 5.50 Kg, respectively). Image analyses of photomicrographs of tissues stained for IR did not differ between treatments for IR density in 10BF or pooled muscle, however GB GM IR density was significantly greater (P = 0.04) than CON GM, CON LT, and GB LT. No differences were observed for qPCR analysis for expression of IR in the LT, GM, 10BF, and liver (P = 0.43, 0.2, 0.13, and 0.19, respectively). Despite the CON (high carbohydrate) gilts gaining more 10BF and BW, no significant differences were observed between the treatments for IR density and IR expression.

Keywords: Gilts, Insulin receptor, biomedical