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Abstract

Diabetes is a major metabolic disorder and type 2 diabetes (T2D) is the most prevalent form of diabetes where insulin resistance serves as the reason for hyperglycemia. Insulin receptors are a crucial part of the insulin signaling pathway that mediates glucose uptake in skeletal muscles and adipose tissues as well as in other organs. Insulin signaling promotes glycogen and protein synthesis, cell growth, inhibits apoptosis through several downstream pathways. Different aspects of Insulin receptor depletion have been conducted in mice and zebrafish yet the implication with microvascular complications in zebrafish has not been carried out. Thus, this study was directed towards finding the abnormalities caused by insulin receptor knockout in zebrafish. My study was conducted in zebrafish where I have taken advantage of zebrafish as a model organism and the availability of Tg(fli1:EGFP) and Tg(wt1b:EGFP) transgenic zebrafish. Zebrafish depleted of Insulin receptors (insulin receptor a: insra-/- and insulin receptor b: insrb-/-) were generated using CRISPR/Cas9 gene-editing technology and then I characterized the morphology of the mutants during the early and adult stages. I have found that the larvae showed no hyperglycemia, however, overfeeding can lead to fasting high glucose in insra-/- fish. I also observed that while trunk vasculature is affected only in insra-/- larvae, retinal hyaloid vasculature is affected in both insra-/- and insrb-/- larvae. Furthermore, abnormalities in retinal vasculature were also found in over-fed insra-/- fish and in normalfed insrb-/- fish. I have observed metabolic shift in those mutants as saturated & unsaturated fatty acids and cholesterol increased in insra-/- and insrb-/- larvae. Also in adult fish, we found a higher amount of fatty acids in skeletal muscle. Altogether, the data acquired from this study show that despite maintaining a euglycemic state, microvascular complications can arise when insulin receptors are knocked out in zebrafish. Therefore it can be said that high glucose is not the only factor behind the development of microvascular complications in zebrafish.