Csad, or cysteine sulfinic acid decarboxylase, is an enzyme involved in the pyridoxal-5'-phosphate (PLP)-dependent biosynthesis of taurine [2]. It is thought to be the rate-limiting enzyme in taurine biosynthesis [5]. Taurine, in turn, is involved in multiple physiological functions such as plasma glucose regulation, bile acid conjugation, and membrane stabilization [5].

In homozygous knockout mice lacking Csad (Csad-KO), there are significant physiological changes. These mice show hypoglycemia and substantial retinal degeneration, which can be rectified by taurine supplementation [3]. Additionally, Csad-KO and Taurine transporter (TauT) knockout mice exacerbate dextran sulfate sodium (DSS)-induced colitis symptoms, highlighting Csad's role in maintaining intestinal health [4]. In high-fat-diet-fed mice, overexpression of Csad alleviates non-alcoholic fatty liver disease (NAFLD)-associated pathologies, including reducing body weight, hepatic lipid levels, and the degree of steatosis [1]. Genome-wide association studies have also associated SNPs in Csad/lnc-ITGB7-1 on chromosome 12q13.13 with susceptibility to fulminant type 1 diabetes [6,7].

In conclusion, Csad plays essential roles in multiple biological processes, especially those related to taurine biosynthesis. Studies using Csad-KO mouse models have revealed its significance in glucose homeostasis, retinal structure, intestinal barrier function, NAFLD development, and susceptibility to fulminant type 1 diabetes. These findings contribute to a better understanding of the pathophysiology of related diseases and may potentially lead to new therapeutic strategies.