Genetic Polymorphisms and Zinc Status: Implications for Supplementation in Metabolic Diseases.

BACKGROUND: Zinc is an essential component for all living organisms, representing the second most abundant trace element, after iron. This element is widely distributed in the tissues of a human body where it is involved in normal growth, reproduction and several biological functions including immunity, energy metabolism and antioxidant processes. Because of its essential role, zinc levels in the human body must remain constant, independently of dietary intake fluctuations. The homeostasis of zinc is a well-regulated cellular process and has been reported to be chiefly mediated by the expression and activity of zinc-binding proteins such as metallothioneins and zinc transporters. Genes encoding for these proteins are subjected to genetic variants. METHODS: We performed a multi-database electronic search to provide an overview on the relationship between specific polymorphisms (SNP) of genes encoding for metallothioneins and zinc transporters and their relationship with zinc status, immune function and some non-communicable diseases. RESULTS: A number of SNP are implicated in a range of metabolic disease. Some SNP may affect the impact of zinc supplementation on immune function, diabetes, and obesity. CONCLUSION: New studies are needed to clarify the interaction between individual genetic profile and zinc status. Moreover, there is a need for a better interaction between the scientific bodies and health professionals to allow better dietary and behavioural recommendations to promote human health, with particular concern to elderly people.

Choline supplementation and measures of choline and betaine status: a randomised, controlled trial in postmenopausal women.

Choline is an essential nutrient and can also be obtained by de novo synthesis via an oestrogen responsive pathway. Choline can be oxidised to the methyl donor betaine, with short-term supplementation reported to lower plasma total homocysteine (tHcy); however, the effects of longer-term choline supplementation are less clear. We investigated the effect of choline supplementation on plasma concentrations of free choline, betaine and tHcy and B-vitamin status in postmenopausal women, a group more susceptible to low choline status. We also assessed whether supplementation altered plasma lipid profiles. In this randomised, double-blinded, placebo-controlled study, forty-two healthy postmenopausal women received 1 g choline per d (as choline bitartrate), or an identical placebo supplement with their habitual diet. Fasting blood samples were collected at baseline, week 6 and week 12. Administration of choline increased median choline and betaine concentrations in plasma, with significant effects evident after 6 weeks of supplementation (P<0·001) and remaining significant at 12 weeks (P<0·001); no effect was observed on folate status or on plasma lipids. Choline supplementation induced a median (25th, 75th percentile) change in plasma tHcy concentration at week 6 of -0·9 (-1·6, 0·2) µmol, a change which, when compared to that observed in the placebo group 0·6 (-0·4, 1·9) µmol, approached statistical significance (P=0·058). Choline supplementation at a dose of 1 g/d significantly increases the circulating concentration of free choline, and can also significantly increase the concentration of the methyl donor, betaine, thereby potentially enhancing the betaine-homocysteine methyltransferase-mediated remethylation of tHcy.