Diet-induced changes in gene expression of lactase in rat jejunum.
To explore the mechanisms by which jejunal lactase activity is modified by carbohydrate and/or fat intake, mRNA levels and the absolute synthesis rate of lactase-phlorizin hydrolase (LPH) were determined in 6-wk-old rats that were fed either low-starch diets containing long-chain triacylglycerol (LCT, 73% energy as corn oil) or medium-chain triacylglycerol (MCT, 66% energy as MCT, 7% energy as corn oil), or a high-starch diet (70% energy as cornstarch) for 7 days. LPH mRNA levels in the jejunum were similar between LCT-fed and MCT-fed rats, but animals fed the high-starch diet exhibited a greater (2x) LPH mRNA level than other groups. The absolute synthesis rate of LPH, estimated by the flooding dose technique using [3H]phenylalanine, was greater (2.4x) in rats fed the high-starch diet than in other groups. A short-term force-feeding experiment revealed that sucrose was able to evoke LPH mRNA levels within 12 h but that a nonmetabolizable sugar (alpha-methylglucoside) was unable to enhance it. By contrast, animals fed the high-LCT diet showed a lower (by 30%) lactase activity than rats fed the low-starch, high-MCT diet, which was accompanied by not only a reduction of immunoreactive LPH in brush-border membranes but also a reduction in lactase activity per unit weight of immunoreactive LPH. These results suggest that both gene expression and posttranslational events of LPH might be influenced by dietary manipulations; carbohydrate intake primarily increases LPH mRNA levels, and LCT accelerates inactivation and/or degradation of lactase.
Goda
T
T
Department of Nutrition, School of Food and Nutritional Sciences, University of Shizuoka, Japan.
Yasutake
H
H
Suzuki
Y
Y
Takase
S
S
Koldovský
O
O
D000818:Animals; D001483:Base Sequence; D015152:Blotting, Northern; D003001:Cloning, Molecular; D003314:Corn Oil / Q000494:pharmacology; D017931:DNA Primers; D004040:Dietary Carbohydrates / Q000494:pharmacology*; D004041:Dietary Fats / Q000494:pharmacology*; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects; D006801:Humans; D007413:Intestinal Mucosa / Q000201:enzymology*; D007583:Jejunum; D043322:Lactase; D008297:Male; D008757:Methylglucosides / Q000494:pharmacology; D008969:Molecular Sequence Data; D010649:Phenylalanine / Q000378:metabolism; D016133:Polymerase Chain Reaction; D014176:Protein Biosynthesis; D012333:RNA, Messenger / Q000032:analysis / Q000096:biosynthesis; D051381:Rats; D017207:Rats, Sprague-Dawley; D013213:Starch / Q000494:pharmacology; D013395:Sucrose / Q000494:pharmacology; D014280:Triglycerides / Q000494:pharmacology; D001616:beta-Galactosidase / Q000096:biosynthesis*
D017931:DNA Primers; D004040:Dietary Carbohydrates; D004041:Dietary Fats; D008757:Methylglucosides; D012333:RNA, Messenger; D014280:Triglycerides; D010649:Phenylalanine; C027020:methylglucoside; D013395:Sucrose; D003314:Corn Oil; D013213:Starch; D043322:Lactase; D001616:beta-Galactosidase