New insights on intestinal microorganisms and carbohydrate metabolism in fish

Fish intestinal tract harbors numerous microorganisms, which exert a critical function in maintaining intestinal health and regulating nutrition metabolism. Although the most economical energy source, carbohydrates cannot be efficiently utilized by some carnivorous fish and even bring serious metabolic diseases. Therefore, how to improve carbohydrate utilization is an essential direction in fish nutrition research. It is well acknowledged that intestinal microorganisms play a crucial part in the host’s growth, digestion, metabolism, and immunity, but the information about their roles in fish carbohydrate metabolism is very limited. Here, we review the progress of intestinal microorganisms and carbohydrate metabolism in fish, focusing on carbohydrate and fish health, carbohydrate metabolism disorders and the possible mechanisms, and the roles of intestinal microorganisms in carbohydrate metabolism and relative metabolic disease control. This review provides theoretical support for improving the utilization of carbohydrates and preventing relative metabolic diseases in fish from the perspective of intestinal microorganisms.