Biotin high intakes

Fenech, M., Baghurst, P., Luderer, W., Turner, J., Record, S., Ceppi, M., and Bonassi, S. (2005). Low intake of calcium, folate, nicotinic acid, vitamin E, retinol, beta-carotene and high intake of pantothenic acid, biotin and riboflavin are significantly associated with increased genome instability—Results from a dietary intake and micronucleus index survey in South Australia. Carcinogenesis 26, 991-999. 

Biotin uptake into enterocytes is by a sodium-dependent carrier, which also transports pantothenic acid (Section 12.2) and lipoic acid, but is inhibited by biocytin and dethiobiotin. The carrier is found in both the small intestine and the colon, so both biotin and pantothenic acid synthesized by intestinal bacteria can be absorbed (Chatterjee etal., 1999 Ramaswamy, 1999 Said, 1999 Prasad and Ganapathy, 2000). Even at relatively high intakes (up to 80 /rmol), biotin is more-or-less completely absorbed (Zempleni and Mock, 1999b). 

Long-term regulation of acetyl-CoA carboxylase involves nutritional, hormonal (e.g., insulin, thyroxine), and other factors. In animals on high-carbohydrate diets, fat-free diets, choline deprivation, or vitamin B12 deprivation, the activity is enhanced. However, fasting, high intake of fat or of polyunsaturated fatty acids, and prolonged biotin deficiency leads to decreased activity. In diabetes, the enzyme activity is low, but insulin administration raises it to normal levels. 

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