Preferential deposition of dairy derived fatty acids in muscle tissue is partially due to the upregulation of CD36 in a low-birth-weight swine model

Abstract

Metabolic syndrome is a worldwide health issue. Previous research has revealed that low-birth weight (LBW) swine fed a high-fat (HF) diet were susceptible to insulin resistance (IR) and developed a preferential intestinal lipid absorption, hypertriglyceridemia, and muscle steatosis. We hypothesized that fatty acid transporters such as CD36, FATP4, and FABP2 could potentially explain the development of these conditions. In addition, dairy-derived fatty acids have been shown to be valid biomarkers to assess dairy intake, which can be utilized to investigate muscle lipid deposition in LBW swine. The overall aim of this study was to delineate molecular transport candidates responsible for intestinal lipid absorption and muscle lipid deposition in LBW swine; and secondly to determine what dietary fatty acids might accumulate preferentially in pork muscle when consuming dairy products. At 5 weeks of age, normal birth weight (NBW) and LBW piglets were randomly assigned to three experimental diets: 1-chow diet, 2-HF diet, or 3-isocaloric HF diet supplemented with full fat dairy products. At 12 weeks of age, piglets were euthanized, and carcass, fasting plasma, biceps femoris and jejunum mucosal scrapings were collected. Results showed that HF-fed LBW swine exhibited early signs of IR (fasting glucose, P < 0.05; fasting insulin, P = 0.091; HOMA-IR, P = 0.086) compared with NBW-Chow, which were attenuated with increased dairy intake. Muscle samples from HF-fed LBW swine contained significantly more triglyceride compared to Chow-fed NBW swine (P < 0.05). Increased dairy intake significantly increased myristic acid (C14:0) and DPA (C22:5n3) relative to HF feeding alone (P < 0.05). All HF-fed LBW swine (regardless of dairy intake) exhibited an upregulation of CD36 expression (but not FABP2) compared with NBW littermates in both the small intestine and muscle (P < 0.05). Interestingly, increased dairy intake significantly increased the Canadian Lean Yield percentage in LBW swine fed an HF diet (P < 0.05). Findings from this study provide evidence on the mechanistic pathway of intestinal and muscle lipid metabolism in an innovative LBW swine model. We have also revealed that increasing dairy intake can enhance the incorporation of dietary long-chain polyunsaturated fatty acids into pork, as well as increasing the predicted lean yield of the carcass.

Keywords: dairy fat; dyslipidemia; fatty acid transporter; metabolic syndrome; pigs.

Figure 1.

Study design to investigate intestinal and muscle lipid metabolism under the impact of dairy products in LBW swine model of insulin resistance. Abbreviations: CHO: carbohydrate; NBW: normal birth weight; LBW: low-birth weight; HF: high-fat diet; HF + Dairy: HF diet supplemented with dairy products.

Figure 2.

Comparison of TG levels (mg/dL) in mucosal scrapings (A) and biceps femoris (B) in NBW and LBW swine fed experimental diets at 12 weeks of age. Abbreviations: TG: triglyceride; NBW: normal birth weight; LBW: low birth weight; HF: high fat diet; HF + Dairy: HF diet supplemented with dairy products. Values are presented as mean ± SE. Groups that do not share similar letters are statistically significant according to the Tukey’s HSD test for multiple comparisons. NBW–Chow: n = 5; NBW–HF: n = 6; LBW–HF: n = 8; LBW–HF + Dairy: n = 5.

Figure 3.

Expressions of CD36 and FABP2 relative to beta-actin in mucosal scrapings (A, B, C) and/or biceps femoris (D, E) in NBW and LBW swine fed experimental diets at 12 weeks of age. Abbreviations: CD36: cluster of differentiation 36; FABP2: fatty acid binding protein 2; NBW: normal birth weight; LBW: low-birth weight; HF: high-fat diet; HF + Dairy: HF diet supplemented with dairy products. Values are presented as mean ± SE. Groups that do not share similar letters are statistically significant according to the Tukey’s HSD test for multiple comparisons. NBW–Chow: n = 5; NBW–HF: n = 6; LBW–HF: n = 8; LBW–HF + Dairy: n = 5.

Figure 4.

Correlation loading plot of both X- and Y- variables by the partial least squares regression. The red dot is Y-variable and blue dots are X-variables. m_TG: muscle triglyceride level; m_CD36: muscle CD36 level; p_TG: plasma triglyceride level; p_insulin: plasma insulin level; p_glucose: plasma glucose level; HOMA–IR: Homeostatic Model Assessment for Insulin Resistance.