Gastrointestinal tolerance and plasma status of carotenoids, EPA and DHA with a fiber-enriched tube feed in hospitalized patients initiated on tube nutrition: Randomized controlled trial.

BACKGROUND & AIMS: During the first days of tube feeding (TF) gastrointestinal (GI) complications are common and administration of sufficient nutrition is a challenge. Not all standard nutritionally complete formulas contain dietary fiber, fish oil or carotenoids, key dietary nutrients for health and wellbeing. The aim of this study was to investigate the effects of a fiber, fish oil and carotenoid enriched TF formula on diarrhea, constipation and nutrient bioavailability. METHODS: A multi-center randomized, double-blind, controlled, parallel trial compared the effects of a dietary fiber, fish oil and carotenoid-enriched TF formula (test) with an isocaloric non-enriched formula (control) in 51 patients requiring initiation of TF. Incidence of diarrhea and constipation (based on stool frequency and consistency) was recorded daily. Plasma status of EPA, DHA and carotenoids was measured after 7 days. RESULTS: The incidence of diarrhea was lower in patients receiving the test formula compared with the control group (19% vs. 48%, p = 0.034). EPA and DHA status (% of total plasma phospholipids) was higher after 7 days in test compared with control group (EPA: p = 0.002, DHA: p = 0.082). Plasma carotenoid levels were higher after 7 days in the test group compared with control group (lutein: p = 0.024, α-carotene: p = 0.005, lycopene: p = 0.020, ß-carotene: p = 0.054). CONCLUSIONS: This study suggests that the nutrient-enriched TF formula tested might have a positive effect on GI tolerance with less diarrhea incidence and significantly improved EPA, DHA and carotenoid plasma levels during the initiation of TF in hospitalized patients who are at risk of diarrhea and low nutrient status. CLINICAL TRIAL REGISTRATION: This trial was registered at trialregister.nl; registration number 2924.

Permissive and suppressive effects of dexamethasone on enzyme induction in hepatocyte co-cultures.

1. Steroids are known to act as permissive factors in hepatocytes. This study shows that dexamethasone (DEX) is a permissive factor for induction of CYP2B1/2, CYP3A1, CYP2A1 and probably also CYP2C11 in cultures with primary rat hepatocytes. 2. The induction factor of phenobarbital (PB)-induced formation of 16beta-hydroxytestosterone (OHT), a testosterone biotransformation product predominantly formed by CYP2B1, is increased 18-fold by the addition of 32 nM DEX to the culture medium. Interestingly, higher concentrations of DEX up to 1000 nM led to a concentration-dependent maximally 5-fold decrease (p = 0.002) of phenobarbital-induced 16beta-OHT formation compared with the effect observed with 32 nM DEX. Thus, DEX shows permissive and suppressive effects on enzyme induction depending on the concentration of the glucocorticoid. 3. Qualitatively similar but smaller permissive and suppressive effects of DEX were observed for PB-induced CYP3A1 activity as evidenced by formation of 2beta-, 6beta- and 15beta-OHT. 4. DEX is a permissive factor for induction of CYP2A1 activity by 3-methylcholanthrene (3MC), as evidenced by the formation of 7alpha-OHT. Without addition of DEX, 3MC did not induce formation of 7alpha-OHT, whereas an almost 3-fold induction occurred in the presence of DEX. In contrast to CYP2B and CYP3A, concentrations up to 1000 nM DEX were not suppressive for the induction of CYP2A1. 5. We described recently a technique that allows preparation of cultures from cryopreserved hepatocytes. An almost identical influence of dexamethasone on enzyme induction was observed here in cultures from cryopreserved compared with freshly isolated hepatocytes. 6. Cultures with primary hepatocyte cultures represent a well-established technique for the study of drug-drug interactions. However, a large interlaboratory variation is known. Our study provides evidence that differences in glucocorticoid concentration in the culture medium contribute to this variation.

Cultures with cryopreserved hepatocytes: applicability for studies of enzyme induction.

The use of hepatocyte cultures is well established for the study of drug-drug interactions. However, the major hindrance for the use of human hepatocyte cultures is that human hepatocytes are only occasionally available. This problem could be overcome by cryopreservation. Although cryopreserved hepatocytes have been recommended for short term applications in suspension, studies on induction of enzyme activity, requiring a more prolonged maintenance of cryopreserved hepatocytes in culture, represent a new field of research. In the present study, we established a technique that allows preparation of rat hepatocyte co-cultures, using cryopreserved hepatocytes. After incubation with phenobarbital (0.75 mM; 72 h) induction factors for the isoenzyme-dependent regio and stereoselective testosterone hydroxylations were 1.6, 2.2, 1.0, 2.1, 5.6, 2.4, 3.6, 4.5 and 0.9 for 2alpha-, 2beta-, 6alpha-, 6beta-, 7alpha-, 15beta-, 16alpha- and 16beta-hydroxytestosterone and 4-androsten-3,17 dione. Regarding induction factors of less than 2-fold, as questionable these induction factors were similar to those of cultures with freshly isolated hepatocytes and the induction pattern of the individual hydroxylation products was similar to the in vivo situation. In addition 3-methylcholanthrene (5 microM; 72 h) induced exclusively the formation of 7alpha-hydroxytestosterone (6.6-fold) in cultures with cryopreserved hepatocytes. This specificity also correlates to that obtained in rats. Although these induction factors were clearly satisfactory in cryopreserved cultures, the absolute activities of the main testosterone hydroxylation products were reduced when compared to fresh cultures. For instance, 6beta-hydroxytestosterone, the main metabolite in solvent controls was reduced to 79%, 7alpha-hydroxytestosterone, the main metabolite after induction with 3-MC, was reduced to 66% and 16beta-hydroxytestosterone, the main metabolite after induction with PB, was reduced to 52%. Similarly, EROD activity after induction with 3-methylcholanthrene in cryopreserved cultures was reduced to 62%, compared with that in fresh cultures. Although further optimization and validation is required, the data show that cytochrome P450 activities can clearly be induced in co-cultures of cryopreserved hepatocytes, in a fashion which for the investigated inducers, is similar to that in cultures from freshly isolated hepatocytes and similar to the in vivo situation.