Fig. 8. Defective 4-HNE detoxification and the elevation of 4-HNE induced the imbalance of glucose homeostasis after Aldh3a1 loss. (A). Aldh3a1−/− zebrafish larvae showed unaltered ALDH activity, Glo1 activity when MG as substrate and unchanged MG amount at 96 hpf. (B–C). Aldh3a1−/− zebrafish larvae showed decreased ALDH activity when 4-HNE as substrate, increased 4-HNE amount and decreased free cysteine at 96 hpf, but pdx1 morphants showed no significant change in ALDH activity and 4-HNE amount. (D–F). 10 μM 4-HNE treatment in wild type zebrafish larvae caused: (D). Decreased ins and pdx1 mRNA expression at 48 hpf. Expression of mRNA was analysed by RT-qPCR and was normalized to b2m; (E). Reduced glycogenic amino acids Asn and Met at 96hpf; (F). Elevated glucose at 120 hpf. (G). 4-HNE and ALDH dependent 4-HNE detoxification ability were not changed in zebrafish larvae with pdx1 silencing at 96hpf. (H). Concise mechanism flow chart showed the consequence of defective 4-HNE detoxification after Aldh3a1 loss. n = 3–7 clutches as each plot showed with 30–50 larvae per group. For statistical analysis paired samples t-tests were applied. *p < 0.05, **p < 0.01, ***p < 0.0010.4-HNE, 4-Hydroxynonenal; Glo1, glyoxalase 1; MG, methylglyoxal.