Changes of essential amino acids in thyropathies

Urinary metabolomics reveals glycemic and coffee associated signatures of thyroid function in two population-based cohorts

Background

Triiodothyronine (T3) and thyroxine (T4) as the main secretion products of the thyroid affect nearly every human tissue and are involved in a broad range of processes ranging from energy expenditure and lipid metabolism to glucose homeostasis. Metabolomics studies outside the focus of clinical manifest thyroid diseases are rare. The aim of the present investigation was to analyze the cross-sectional and longitudinal associations of urinary metabolites with serum free T4 (FT4) and thyroid-stimulating hormone (TSH).

Methods

Urine Metabolites of participants of the population-based studies Inter99 (n = 5620) and Health2006/Health2008 (n = 3788) were analyzed by ¹H-NMR spectroscopy. Linear or mixed linear models were used to detect associations between urine metabolites and thyroid function.

Results

Cross-sectional analyses revealed positive relations of alanine, trigonelline and lactic acid with FT4 and negative relations of dimethylamine, glucose, glycine and lactic acid with log(TSH). In longitudinal analyses, lower levels of alanine, dimethylamine, glycine, lactic acid and N,N-dimethylglycine were linked to a higher decline in FT4 levels over time, whereas higher trigonelline levels were related to a higher FT4 decline. Moreover, the risk of hypothyroidism was higher in subjects with high baseline trigonelline or low lactic acid, alanine or glycine values.

Conclusion

The detected associations mainly emphasize the important role of thyroid hormones in glucose homeostasis. In addition, the predictive character of these metabolites might argue for a potential feedback of the metabolic state on thyroid function. Besides known metabolic consequences of TH, the link to the urine excretion of trigonelline, a marker of coffee consumption, represents a novel finding of this study and given the ubiquitous consumption of coffee requires further research.

Urinary excretion of 3-methylhistidine and creatinine and plasma concentrations of amino acids in hyperthyroid patients following preoperative treatment with antithyroid drug or beta-blocking agent: results from a prospective, randomized study

The aim of this investigation was to compare the effects of a beta 1-selective adrenoceptor blocking agent and an antithyroid drug on urinary excretion of creatinine (Cr) and 3-methylhistidine (3-MH) and plasma concentrations of amino acids in hyperthyroid patients. beta-adrenoceptor blocking agents are increasingly used in the treatment of hyperthyroid patients, and the effects on clinical signs and symptoms mainly reflect beta 1-adrenoceptor blockade. The consequences of this treatment on metabolic alterations in hyperthyroidism are not fully known. In the present study, 30 hyperthyroid patients were randomized to preoperative treatment with the antithyroid drug methimazole + thyroxine (group I) or the beta 1-selective adrenoceptor blocking agent metoprolol (group II). Urinary excretion of Cr and 3-MH and plasma concentrations of amino acids were measured at the time of diagnosis, following preoperative treatment and 6 months postoperatively. Serum triiodothyronine (T3) was comparably elevated in the two groups of patients at the time of diagnosis and was normalized during preoperative treatment in group I but remained elevated during preoperative treatment in group II. Urinary excretion of creatinine was lower at the time of diagnosis than postoperatively, suggesting reduced muscle mass during hyperthyroidism. Urinary excretion of Cr increased during preoperative treatment in group I but was not significantly altered during treatment with metoprolol. The 3-MH/Cr ratio, which was higher at the time of diagnosis than postoperatively, indicating accelerated protein breakdown in skeletal muscle during hyperthyroidism, was reduced during preoperative treatment in group I but not in group II.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of thyroid hormone and beta-adrenoceptor blocking agents on urinary excretion of 3-methylhistidine and plasma amino acids in man

The aim of this investigation was to study the effect of beta-adrenoceptor blockade on alterations in protein metabolism induced by administration of 3,5,3'-triiodothyronine (T3) to man. Urinary excretion of 3-methylhistidine and plasma concentrations of amino acids were measured in seven healthy subjects following 1 weeks's administration of T3 alone or T3 in combination with the selective beta 1-adrenoceptor blocking agent metoprolol or the non-selective beta-adrenoceptor blocking agent propranolol. Urinary excretion of 3-methylhistidine and plasma concentrations of valine, methionine, lysine, tyrosine, phenylalanine, isoleucine, leucine, and total essential and branched chain amino acids increased following administration of T3, probably in part reflecting accelerated muscle proteolysis. Neither metoprolol nor propranolol normalized 3-methylhistidine excretion or plasma concentrations of amino acids during T3 treatment. The results indicate that metabolic alterations induced by T3 and giving rise to enhanced 3-methylhistidine excretion and elevated concentrations of plasma amino acids are not normalized by beta-adrenoceptor blockade.