METABOLISM OF BETA-CAROTENE IN HYPOCAROTENEMIC PATIENTS

点击翻译按钮获取中文摘要

Some of the patients (pts) with cerebro-vascular accident (CVA) develop a severe motility disorder of the hypopharinx and upper esophagus resulting in inability to swallow and require permanent enteral feeding. After several weeks, such pts develop hypocarotenemia because their enteral feeding formulas are devoid of carotenoids while containing adequate amount of micro and macronutrients. Such pts offer a unique opportunity to study the metabolism of Beta-Carotene (BC) since their gastrointestinal tract is intact and their diet can be strictly controlled over a prolonged period of observation. This research aims to study: 1) absorption of BC; 2) plasma, skin and fat tissue levels of BC; 3) the physiological or pathological effects various tissue levels of this compound on lipid peroxidation, and leukocyte functions; and 4) lipid and water soluble antioxidants levels in pts who are hypocarotenemic and later supplemented with graded doses of BC. Initially, the serum levels of carotenoids and other antioxidants of CVA pts on enteral feeding will be screened. Only those that are in normal nutritional condition and develop a serum BC level below 1 1/2 SD of normal (mean 33 + or -20.5 ug/dl) will be admitted to this study. Forty pts will be recruited, five of them will be studied in the framework of a pilot study in order to refine the testing methodology and its coordination. The remaining 35 pts will be randomized into 5 groups of 7 pts. These groups are: 1) Group I no BC (control), and 2) Groups II, III, IV and V will receive BC in doses of 3, 15, 30 and 180 mg per day respectively for a period of 10 wks. At the beginning of the study, they will be assessed for their acute response to their assigned doses of BC by taking a placebo on Day 0 and their assigned dose on Day 1. On Day 0, they will be evaluated for baseline levels of serum and tissues stores of BC, serum lipid peroxidation parameters (LPP), (breath hydrocarbons, serum lipid peroxides, GSSG, GSH), leukocyte functions, water and lipid soluble antioxidants and vitamin A absorption. On Day 1, pts will be assessed for their acute response to BC over a 12 hour time period. They will continue their supplementation and will be tested every 2 wks for serum retinoids, carotenoids, other antioxidants, serum LPP and breath hydrocarbons. After 10 wks of supplementation, they will go through the same type of evaluation as Days 0 and 1. At 4 and 10 wks after withdrawal of BC, serum levels of retinoids carotenoids, other antioxidants, breath hydrocarbons and serum LPP will be repeated.