Effect of Acute Feeding of Diets of Varying Fatty Acid Composition on Intestinal Apolipoprotein Expression in the Newborn Swine

Abstract

The purpose of this study was to determine the effects of dietary fatty acids of varying chain lengths and degrees of saturation on intestinal apolipoprotein (apo) B and A-I expression in the newborn piglet. Two-day-old female piglets received one of three isocaloric formulas containing 48% of total calories (120 kcal/kg/24 h) as medium-chain triglycerides (MCT) from MCT oil, intermediate-chain saturated triglycerides (ICST) from coconut oil, or long-chain polyunsaturated triglycerides (LCPUT) from safflower oil by continuous duodenal infusion for 24 h. After in situ radiolabeling, jejunal and ileal mucosal apo B-48 and A-I were immunoprecipitated, and synthesis was expressed as percentage of total protein synthesis. Mucosal apo B and A-I mass was measured by ELISA as nanograms of apoprotein/microgram of total protein. Fifty percent less apo B jejunal synthesis was present in the ICST group versus the MCT and LCPUT groups (0.67 +/- 0.07, 1.19 +/- 0.20, and 1.25 +/- 0.15, respectively, mean +/- SEM, p < 0.05). Jejunal apo B mass was lower in the MCT group versus the ICST and LCPUT groups (0.10 +/- 0.02, 0.21 +/- 0.03, and 0.16 +/- 0.03, respectively, p < 0.05). Ileal apo B synthesis was lowest in the ICST group. No differences were found in ileal apo B mass. Two-fold higher jejunal apo A-I synthesis was found in the LCPUT group versus the MCT and ICST groups (14.18 +/- 1.69, 7.56 +/- 2.63, and 6.36 +/- 0.58, respectively, p < 0.01). No differences were found for jejunal apo A-I mass. In the ileum, the only difference was a higher apo A-I mass in the LCPUT group (p < 0.05). We conclude that in the newborn piglet intestinal apo B and A-I expression is acutely and differentially regulated by dietary lipid varying in fatty acid chain length and saturation. The patterns of regulation are complex and vary among specific apolipoproteins and regions of the small intestine and include co- and posttranslational mechanisms.

Response of ApoA-IV in pigs to long-term increased dietary oil intake and to the degree of unsaturation of the fatty acids

“…2). The present results corroborate the observation of a coordinated regulation of duodenal ApoA-I and ApoC-III in a postprandial regimen in newborn pigs (Black et al 1996;Wang et al 1996;Wang et al 1998) and in the long-term administration of lipid-rich diets to transgenic mice (Baroukh et al 2001). This indicates that this intestinal coordination in long-term diets is preserved in adult animals only for the ApoA-I and ApoC-III genes.…”

Development of Intestinal Transport Function in Mammals

“…Similarly, the effect of a high-fructose diet on the expression of GLUT5 but not SGLT1 (360) reflects luminal but not systemic endocrine regulation (262,361). Recent findings indicate that luminal lipids also have a direct effect on lipid absorption, particularly on apolipoprotein synthesis (34,420).…”

Regulation of MTP expression in developing swine

“…For reverse transcription, 5 g total RNA was used. Reverse transcription was performed at 42 Њ C for 15 min in a final volume of 20 l in buffer containing 10 mM Tris-HCl (pH 8.3), 90 mM KCl, 1 mM MnCl 2 , 200 M of each deoxynucleotide triphosphate (dNTP), 0.5 g oligodT (15) as primer, and 15 units Avian Myeloblastosis virus (AMV) reverse transcriptase (Promega). Following reverse transcription, the single-strand cDNA was amplified using the Qiagen Taq PCR core kit (Qiagen, Santa Clarita, CA) with 1 l cDNA and 100 pmol of each specific primer (MTP527 and MTP862 for MTP large subunit, Actin F and Actin R for ␤ -actin, and B2MGF and B2MGR for ␤ 2 -microglobulin) in a total volume of 50 l. After incubation for 3 min at 95 Њ C, PCR was performed for 21 cycles for ␤ 2 -microglobulin, 23 cycles for ␤ -actin, and 25 cycles for MTP large subunit in a thermal cycler (Perkin-Elmer, Boston, MA) as follows: 60 s at 94 Њ C, 10 s at 94 Њ C, 15 s at 58 Њ C, and 45 s at 72 Њ C. For each RNA sample, a negative control was run to check for DNA contamination using AmpliTaq (Perkin-Elmer), leaving the sample on ice during reverse transcription.…”

“…One reason for the paucity of data in this area has been the lack of suitable in vitro and in vivo model systems. Over the past several years, our laboratory has focused on the neonatal swine as a model system for studies of the regulation of intestinal and hepatic apolipoprotein expression and lipid synthesis by dietary lipids during development (8)(9)(10)(11)(12)(13)(14)(15)(16)(17). This model offers several advantages for such studies.…”