Regulation of Gluconeogenesis by Aldo-keto-reductase 1a1b in Zebrafish

Abstract

Regulation of glucose homeostasis is a fundamental process to maintain blood glucose at a physiological level, and its dysregulation is associated with the development of several metabolic diseases. Here, we report on a zebrafish mutant for Aldo-keto-reductase 1a1b (akr1a1b) as a regulator of gluconeogenesis. Adult akr1a1b À/À mutant zebrafish developed fasting hypoglycemia, which was caused by inhibiting phosphoenolpyruvate carboxykinase (PEPCK) expression as ratelimiting enzyme of gluconeogenesis. Subsequently, glucogenic amino acid glutamate as substrate for gluconeogenesis accumulated in the kidneys, but not in livers, and induced structural and functional pronephros alterations in 48-hpf akr1a1b À/À embryos. Akr1a1b À/À mutants displayed increased nitrosative stress as indicated by increased nitrotyrosine, and increased protein-S-nitrosylation. Inhibition of nitrosative stress using the NO synthase inhibitor L-NAME prevented kidney damage and normalized PEPCK expression in akr1a1b À/À mutants. Thus, the data have identified Akr1a1b as a regulator of gluconeogenesis in zebrafish and thereby controlling glucose homeostasis.

Reduced Acrolein Detoxification in akr1a1a Zebrafish Mutants Causes Impaired Insulin Receptor Signaling and Microvascular Alterations

“…Last, different from previous studies regarding Akr1a1b, [26] the entirely loss of Akr1a1a did not up-regulate S-nitrosylated proteins (Figure S6, Supporting Information). At the meantime, akr1a1b −/− mutants displayed unaltered insra/insrb mRNA expression, internal ACR level and normal hyaloid vasculature (Figures S7,S8, Supporting Information).…”

“…cDNA Synthesis and qPCR reaction were proceeded as previously described. [ 26 ] Primers are listed in Table S2 , Supporting Information.…”

“…S‐Nitrosylation was detected by using the Biotin Switch Assay Kit (Abcam, ab236207) as described previously. [ 26 ]…”

“…[13,23,24] The first discovered AKR, the Aldehyde Reductase Akr1a1, is a cytosolic, NADPH-dependent, monomeric oxidoreductase, which has two separate homologs in zebrafish, namely, Akr1a1a and Akr1a1b. [25,26] Akr1a1 possesses a broad substrate spectrum, and it prefers carboxyl-group containing negatively charged substrates. [27,28] In addition to detoxifying common RCS, such as 3-deoxyglucosone (3DG), glyoxal, and MG, Akr1a1 also has a high affinity to ACR.…”

“…[ 29 ] In a previous study, Akr1a1b was identified as a gluconeogenesis regulator via adjusting S‐nitrosyaltion in zebrafish. [ 26 ] However, whether Akr1a1a functions closely to Akr1a1b or completely separate and whether a permanent loss of Akr1a1a causes accumulated internal ACR and results in diabetes and relevant complications in the end require further elucidation.…”