Hyperinsulinemia induces insulin resistance and immune suppression via Ptpn6/Shp1 in zebrafish

Abstract

Type 2 diabetes, obesity, and metabolic syndrome are pathologies where insulin resistance plays a central role, and that affect a large population worldwide. These pathologies are usually associated with a dysregulation of insulin secretion leading to a chronic exposure of the tissues to high insulin levels (i.e. hyperinsulinemia), which diminishes the concentration of key downstream elements, causing insulin resistance. The complexity of the study of insulin resistance arises from the heterogeneity of the metabolic states where it is observed. To contribute to the understanding of the mechanisms triggering insulin resistance, we have developed a zebrafish model to study insulin metabolism and its associated disorders. Zebrafish larvae appeared to be sensitive to human recombinant insulin, becoming insulin-resistant when exposed to a high dose of the hormone. Moreover RNA-seq-based transcriptomic profiling of these larvae revealed a strong downregulation of a number of immune-relevant genes as a consequence of the exposure to hyperinsulinemia. Interestingly, as an exception, the negative immune modulator protein tyrosine phosphatase nonreceptor type 6 (ptpn6) appeared to be upregulated in insulin-resistant larvae. Knockdown of ptpn6 was found to counteract the observed downregulation of the immune system and insulin signaling pathway caused by hyperinsulinemia. These results indicate that ptpn6 is a mediator of the metabolic switch between insulin-sensitive and insulin-resistant states. Our zebrafish model for hyperinsulinemia has therefore demonstrated its suitability for discovery of novel regulators of insulin resistance. In addition, our data will be very useful in further studies of the function of immunological determinants in a non-obese model system.

GLUT12 deficiency during early development results in heart failure and a diabetic phenotype in zebrafish

“…Moreover, our data also show that, in agreement with the observations in mammals, its expression is regulated by insulin. Recently, it has been published by our group that human insulin is effective in zebrafish larvae (Marín-Juez et al 2014b). In that work, we showed how 4 dpf larvae injected with 100 nM insulin experienced transient hypoglycemia between 15 and 45 min post injection, becoming insulin resistant at 4 hpi (Marín-Juez et al 2014b).…”

“…Recently, it has been published by our group that human insulin is effective in zebrafish larvae (Marín-Juez et al 2014b). In that work, we showed how 4 dpf larvae injected with 100 nM insulin experienced transient hypoglycemia between 15 and 45 min post injection, becoming insulin resistant at 4 hpi (Marín-Juez et al 2014b). Interestingly, the expression of glut12 is stimulated at 0.5 and 4 hpi, times at which zebrafish larvae are insulin sensitive and resistant respectively.…”

“…The fast response observed at 0.5 hpi could indicate that glut12 expression is rapidly stimulated in the presence of insulin to ensure an efficient glucose uptake. The latter stimulation could be explained as an attempt to compensate for the hyperglycemia that these larvae experience as a consequence of the hyperinsulinemia-induced insulin resistance that they experience at 4 hpi (Marín-Juez et al 2014b).…”

“…Insulin was injected into the zebrafish larvae as described previously (Marín-Juez et al 2014b). For exposure to 250 mM metformin, zebrafish embryos were dechorionated at 48 hpf and treated with the compound for 48 h at 28 8C.…”

“…To better characterize the mechanisms regulating zebrafish glut12, we stimulated zebrafish larvae with insulin using a newly developed technique (Marín-Juez et al 2014b). Zebrafish larvae at 4 days post fertilization (dpf) were injected into the caudal aorta with 100 nM and 1 mM human recombinant insulin.…”