Vitamin A Biosynthesis through gut bacteria

Biosynthesis of Vitamin A

The scientific predictions that are underpinning the hypothesis “Biosynthesis of retinoids from carotenoids dependent and independent pathways through gut microbiota is a highlight research area. First, the liver and or intestine of the animals are the storage and bioconversion sites for synthesizing retinoids from carotenoids. The carotenoids are metabolized through the carotenoid cleavage enzymes synthesized by the epithelial cells that include the cells lining the liver. Since, a diverse group of microbes in the liver and intestine relay on that organ for its nutritional requirements, they could have developed the capability to take part or entire metabolism of carotenoids and retinoids. Also, the microbial role in retinol transportation to multiple sites of the body through bacterial compounds mimicking the retinol-binding protein (RBP) is an area of concern. Second, the host-symbiont interactions through the hologenome adaptation effect. The microbes could have remodeled its genetic make-up, generation by generation through various intragenomic recombination processes with the host cells to increase the adaptability with the gut environment. Third, through lateral or horizontal gene transfer phenomenon, the genes for the biosynthesis and catabolism of carotenoids and retinoids might have been transferred to bacteria from the host tissues. Fourth, some putative enzymes that synthesis retinoids of different biological activity could have been synthesized and utilized by microbes to sustain the niche. Finally, there is always a bidirectional pressure exists between the prokaryotic cells and the host eukaryotic cells in the organs. The demand could have resulted in inter-bacterial changes that alter the microbes to play a role in vitamin A synthesis. A vital organ, nutritional powerhouse and one of the top vitamin A source is the beef liver. The liver also acts as a downstream of the gastrointestinal tract in the digestive system and harbors trillions of bacteria (Hartstra, Nieuwdorp, and Herrema 2016 Hartstra, A. V., M. Nieuwdorp, and H. Herrema. 2016. Interplay between gut microbiota, its metabolites and human metabolism: dissecting cause from consequence. Trends in Food Science and Technology 57:233–243. doi: 10.1016/j.tifs.2016.08.009.[Crossref], [Web of Science ®], , [Google Scholar]). Hence, this review strongly emphasizes and proposes a critical role for the liver or intestine-friendly bacteria in Vitamin A biosynthesis. These proposed conceptual points with literature evidence have been detailed, and the alternative strategies to overcome VAD are illustrated.