Lactase Phlorizin Hydrolase Synthesis Is Decreased In Protein-Malnourished Pigs

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Abstract
We have examined the effect of protein malnutrition on brush border (BB) lactase phlorizin hydrolase (LPH) synthesis in young pigs. Two groups of four 3-wk-old pigs were fed diets containing either 19 g soy protein, 63 g carbohydrate and 5 g fat per 100 g diet (a protein-sufficient diet) or 3 g soy protein, 85 g carbohydrate and 5 g fat per 100 g diet (a protein-deficient diet). After 8 wk of consuming the diets, pigs were infused intravenously with 2H3-leucine for 8 h, then killed. The jejunum was collected for measurement of lactase activity, LPH mRNA abundance and the rate of LPH post-translational synthesis. Lactase activities did not differ between groups (mean 8.1 ± 1.2 μmol⋅min−1⋅g mucosa−1). LPH mRNA abundance relative to elongation factor-1α mRNA (the constitutive/reference mRNA) was significantly (P < 0.05) higher in well-nourished pigs (0.36 ± 0.03%) than in protein-malnourished pigs (0.21 ± 0.02%). The rate constants of BB LPH post-translational synthesis were also significantly higher in the well-nourished (103 ± 9%⋅d−1) than in the protein-malnourished pigs (66 ± 8%⋅d−1). Further, the absolute synthesis rate of BB LPH, a measure of the amount of enzyme synthesized per gram of tissue, was significantly higher in well-nourished than in protein-malnourished pigs (in arbitrary units, 892 ± 90 vs. 450 ± 34, respectively). Thus, protein malnutrition affects both LPH mRNA abundance and post-translational processing in young pigs.