ABSTRACT
AIMS: Trimethylamine N-oxide (TMAO), choline and betaine serum levels have been associated with metabolic diseases including type 2 diabetes (T2D) and non-alcoholic fatty liver disease (NAFLD). These associations could be mediated by insulin resistance. However, the relationships among these metabolites, insulin resistance and NAFLD have not been thoroughly investigated. Moreover, it has recently been suggested that TMAO could play a role in NAFLD by altering bile acid metabolism. We examined the association between circulating TMAO, choline and betaine levels and NAFLD in obese subjects. METHODS: Serum TMAO, choline, betaine and bile acid levels were measured in 357 Mexican obese patients with different grades of NAFLD as determined by liver histology. Associations of NAFLD with TMAO, choline and betaine levels were tested. Moreover, association of TMAO levels with non-alcoholic steatohepatitis (NASH) was tested separately in patients with and without T2D. RESULTS: TMAO and choline levels were significantly associated with NAFLD histologic features and NASH risk. While increased serum TMAO levels were significantly associated with NASH in patients with T2D, in non-T2D subjects this association lost significance after adjusting for sex, BMI and HOMA2-IR. Moreover, circulating secondary bile acids were associated both with increased TMAO levels and NASH. CONCLUSIONS: In obese patients, circulating TMAO levels were associated with NASH mainly in the presence of T2D. Functional studies are required to evaluate the role of insulin resistance and T2D in this association, both highly prevalent in NASH patients.
Subject(s)
Diabetes Mellitus, Type 2 , Methylamines/blood , Non-alcoholic Fatty Liver Disease , Adult , Betaine/blood , Bile Acids and Salts/blood , Biomarkers/blood , Biopsy , Choline/blood , Diabetes Mellitus, Type 2/complications , Diabetes Mellitus, Type 2/epidemiology , Female , Humans , Insulin Resistance , Liver/pathology , Male , Mexican Americans , Middle Aged , Non-alcoholic Fatty Liver Disease/complications , Non-alcoholic Fatty Liver Disease/epidemiology , Obesity/complications , Obesity/epidemiologyABSTRACT
Based on our previously reported solution assay protocol, a solid-phase assay for the tyrosine kinase activity of the epidermal growth factor receptor has been developed. Glucose-6-phosphate dehydrogenase, immobilized noncovalently on microtiter plates, was used as the substrate in the solid-phase assay. Phosphorylation of the immobilized substrate takes place in the presence of ATP and a solubilized epidermal growth factor receptor preparation. After washing off the soluble reaction mixture, the phosphotyrosine-containing dehydrogenase produced on the well surface is quantitated by an ELISA method using a polyclonal antiphosphotyrosine antibody, a second antibody conjugated with horseradish peroxidase, and finally the o-phenylenediamine reaction. The absorbance at 492 nm developed in the wells is a measure of the kinase activity of the solubilized receptor preparation. Putative inhibitors of receptor kinase can be conveniently incorporated in this assay system to test for potential inhibitory activity. This assay, being rapid and convenient, is useful in drug screening programs where a high through-put rate is required.
Subject(s)
Enzyme-Linked Immunosorbent Assay/methods , Enzymes, Immobilized/metabolism , ErbB Receptors/analysis , ErbB Receptors/metabolism , Glucosephosphate Dehydrogenase/metabolism , Antibody Specificity , Biotechnology , Cell Line , ErbB Receptors/antagonists & inhibitors , Humans , In Vitro Techniques , Solubility , Spectrophotometry , Substrate SpecificityABSTRACT
1. A single i.p. dose of taurine (25 mg/mouse) given to mice 3 hr before an i.p. injection of morphine (0.1 mg/mouse) decreased the analgesic response of the animals to morphine. 2. Neither a lower dose of taurine nor the same dose of another amino acid was effective. 3. The analgesic response to morphine was also reduced by inclusion of taurine in the drinking water. 4. The results of the present study indicate that peripherally administered taurine antagonized morphine-induced analgesia, similar to a previous report that taurine administered centrally, diminished the analgesic response to a centrally injected opioid peptide.
Subject(s)
Analgesia , Morphine/antagonists & inhibitors , Taurine/pharmacology , Animals , Dose-Response Relationship, Drug , Injections, Intraperitoneal , Male , Mice , Mice, Inbred ICR , Taurine/administration & dosageABSTRACT
Different tissues of the black sea bream Mylio macrocephalus including the liver, gills, intestine, muscle, gonad, swim bladder, spleen, heart and kidney were examined for the presence of prolactin and growth hormone receptors. Membranes were prepared from the tissues and 125I-labeled ovine prolactin and bovine growth hormone were used as ligands. It was found that the liver contained the highest level of specific 125I-labeled ovine prolactin and bovine growth hormone binding, suggesting the existence of hepatic prolactin and growth hormone receptors. The protein nature of the hepatic growth hormone receptor was revealed by the reduction of specific 125I-labeled growth hormone binding after treatment of hepatic membranes with trypsin and chymotrypsin.
