Molecular Mechanisms of Biotin in Modulating Inflammatory Diseases

Biotin, also known as vitamin B7 or vitamin H, is a water-soluble B-complex vitamin and serves as an essential co-enzyme for five specific carboxylases. Holocarboxylase synthase (HCS) activates biotin and facilitates its covalent attachment to these enzymes, while biotinidase releases free biotin in the biotin cycle. The transport of biotin, primarily from the intestine, is mediated by the sodium-dependent multi-vitamin transporter (SMVT). Severe biotin deficiency leads to multiple carboxylase deficiency. Moreover, biotin is crucial to glucose and lipid utilization in cellular energy production because it modulates the expression of metabolic enzymes via various signaling pathways and transcription factors. Biotin also modulates the production of proinflammatory cytokines in the immune system through similar molecular mechanisms. These regulatory roles in metabolic and immune homeostasis connect biotin to conditions such as diabetes, dermatologic manifestations, and multiple sclerosis. Furthermore, deficiencies in biotin and SMVT are implicated in inflammatory bowel disease, affecting intestinal inflammation, permeability, and flora. Notably, HCS and probably biotin directly influence gene expression through histone modification. In this review, we summarize the current knowledge on the molecular aspects of biotin and associated molecules in diseases related to both acute inflammatory responses and chronic inflammation, and discuss the potential therapeutic applications of biotin.