Biotin forms a covalent bond to the following carboxylase enzymes: pyruvate carboxylase for glucose metabolism, acetyl CoA carboxylase for fatty acid oxidation, and propinonyl-CoA carboxylase and βmethylcrotonyl-CoA carboxylase for amino acid metabolism. It is thought that biotin supports healthy glucose metabolism by stimulating glucose-induced insulin secretion in pancreatic beta cells and by accelerating glycolysis in the liver and pancreas.†Biotin also enhances muscle insulin sensitivity by increasing guanylate cyclase activity.
In a Japanese study, oral supplementation of 3 mg biotin three times daily for one month supported healthy fasting glucose levels by 45%; no effect was observed in subjects taking placebo. Immune cell function is also affected by biotin levels.†Effects of biotin on gene expression are likely to modulate the response of immune cells to antigens. In vivo studies showed that
biotin increases the amount of mRNA encoding for interferon-ỿ, interleukin-1, and 3-methylcrotonyl-CoA
carboxylase.
Optimal levels of biotin support nerve function and play a role in activating acetyl CoA carboxylase, a potentially rate-limiting enzyme in myelin synthesis. Clinical studies indicate that biotin may adjust the cellular arrangement of the nail bed, helping to reinforce the keratin structure, promote strength and thickness, and reduce splitting.