Diet-induced changes in gene expression of lactase in rat
jejunum.
Goda, Toshinao, Hiromitsu Yasutake, Yuko Suzuki, Sachiko Takase, and
Koldovsky, O.
Department of Nutrition, School of Food and Nutritional Sciences,
The University of Shizuoka, Shizuoka-city, Shizuoka 422, Japan; and
Departments of Pediatrics and Physiology, University of Arizona,
Health Sciences Center, Tucson, Arizona 85724
APStracts 2:0032G, 1995.
To explore the mechanisms by which jejunal lactase activity is
modified by carbohydrate and/or fat intake, mRNA levels and absolute
synthesis rate of lactase-phlorizin hydrolase (LPH) were determined
in six-week-old rats which were fed either low-starch diets
containing long-chain triacylglycerol (73 energy% as corn oil; LCT)
or medium-chain triacylglycerol (66 energy% as MCT, 7 energy% as corn
oil; MCT), or a high-starch diet (70 energy% as cornstarch) for 7
days. The LPH mRNA levels in the jejunum were similar between LCT-fed
and MCT-fed rats, but the 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 the rats fed the high-starch
diet than other groups. A short-term force feeding experiment
revealed that sucrose was able to evoke LPH mRNA levels within 12h,
but that a non-metabolizable sugar ( -methylglucoside) was unable to
enhance it. By contrast, the animals fed the high-LCT diet showed a
lower (by 30%) lactase activity than the rats fed the low-starch,
high-MCT diet, which was accompanied not only by the reduction of
immunoreactive LPH in the brush border membranes, but also by the
reduction in the lactase activity per unit weight of immunoreactive
LPH. These results suggest that both gene expression and post
-translational 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.
Received 24 May 1994; accepted in final form 8 February 1995.
APS Manuscript Number G195-4.
Article publication pending Am. J. Physiol. (Gastrointest. Liver
Physiology).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 10 March 1995.