Use of simulated intestinal fluid for Caco-2 permeability assay of lipophilic drugs.

The most commonly used method to assess intestinal permeability is the measurement of compound flux across a Caco-2 cells monolayer by using Hanks balanced salt solution (HBSS)-like buffers. Nevertheless, lipophilic acid drugs are poorly or not at all soluble in these types of buffers and their adsorption on the transwell plate is commonly observed. To reduce adsorption and increase solubility, permeability assays need to be developed in conditions other than classic conditions for lipophilic compounds. The best model to increase recovery of lipophilic compounds was determined as fasted state simulated intestinal fluid (FaSSIF) in the apical compartment and HBSS with 1% bovine serum albumin (BSA) in basolateral compartment. This model allows a correlation between absorption on Caco-2 cells and absorbed fraction in humans. For 35 compounds, only 2 outliers were observed in the Caco-2 assay using the FaSSIF model. These two outliers were the same outlier compounds as those observed with a classic Caco-2 method. Furthermore, a permeability assay of Pgp substrates evidenced efflux transport in both models and addition of a Pgp inhibitor suppressed Pgp efflux transport. FaSSIF in the apical compartment and HBSS with 1% BSA in the basolateral compartment is the model of choice to predict in vivo absorption for lipophilic acid drugs.

Subclinical protein malnutrition is a determinant of hyperhomocysteinemia.

OBJECTIVES: Hyperhomocysteinemia is regarded as a public health problem of increasing importance likely to contribute to vascular disorders and premature mortality. Folate, cobalamin, pyridoxine, and riboflavin dietary deficiencies are currently regarded as causative factors. However, several investigations have indicated that the theory of vitamin B deprivation provides only a partial explanation for the observed abnormalities of sulfur-containing amino acids. We investigated the potential contributory role played by protein malnutrition. METHODS: For that purpose, three cohorts of 20 adult patients presenting stage I, II, and III goiter underwent careful medical history, dietary inquiry, and clinical examination. Their overall health and nutrition states were assessed with classic anthropometry, measurement of vitamin B blood parameters, visceral protein markers, essential amino acids, total homocysteine, and cystathionine. RESULTS: The concentrations of transthyretin, seven essential amino acids, and cystathionine progressively decreased as the thyroid gland increased. Methionine was the sole essential amino acid whose values did not change; total homocysteine was unique in that increased levels correlated negatively with transthyretin values. Taken together, the data point to a progressive deterioration of protein nutrition status impairing the transsulfuration pathway and is best explained by an acquired defect of cystathionine-beta-synthase activity. CONCLUSIONS: Hyperhomocysteinemia may arise from the shrinking of endogenous nitrogen pools as a result of decreased protein intake or stress-induced increased losses. Raised total homocysteine may result from the attempt of the malnourished and/or stressed body to preserve methionine homeostasis.