Treatment with Streptozotocin (STZ) causes hypoglycemia and alters the stability of reference genes for real‐time PCR analysis in the liver of channel catfish

Abstract

Genetically selected channel catfish for increased growth often develops phenotype similar to human obesity, suggesting that channel catfish may be a model organism to investigate human metabolic disorders. Streptozotocin (STZ) treatment induces hyperglycemia in mammals and some fish species. However, the effects of STZ treatment on blood glucose level as well as other physiological parameters in channel catfish have never been examined in detail. In this study, we tested the hypothesis that treatment with STZ affects body weight, blood glucose level, and hepatic expression of house‐keeping genes. Juvenile channel catfish (28.3 ± 2g) were treated with 0, 3.6, 36, 180, or 360 mg/kg STZ intraperitoneally on day 0 (n=4 fish/treatment). On day 7, blood glucose level was measured and blood, liver, muscle and brain samples were collected. Expression of five common housekeeping genes (beta‐macroglobulin, alpha‐tubulin, 18s ribosomal RNA, beta‐actin, and GAPDH) were measured using real‐time PCR. The weight of fish did not change between days 0 and 7 among all treatments. Blood glucose levels were lower in fish treated with 180 or 360 mg/kg STZ compared to fish treated with 0 mg/kg STZ. Treatment with STZ at higher doses altered expression of 4 housekeeping genes. Expression of beta‐macroglobulin, alpha‐tubulin, and beta‐actin mRNA was higher in fish treated with higher doses of STZ compared to 0 mg/kg STZ. In contrast, expression of GAPDH mRNA tended to be less in 360 mg/kg STZ than 0 mg/kg STZ. Expression of 18s rRNA was not affected by STZ treatment. Rather than causing hyperglycemia, treatment with high doses of STZ decreased blood glucose level in channel catfish, suggesting a difference in glucose metabolism exists between channel catfish and humans.Support or Funding InformationThis study is supported by APS IOSP fellowship program and Kansas Idea Network of Biomedical Research Excellence (P20GM10348).