Skeletal muscle is a major target tissue for insulin action and plays a central role in regulating glucose metabolism and maintaining whole-body energy homeostasis. The biological effects of insulin and insulin-like growth factor 1 (IGF-1) are mediated through the insulin receptor (IR) and the insulin-like growth factor 1 receptor (IGF-1R). Owing to their high structural homology, these receptors activate numerous common intracellular signaling pathways while performing distinct physiological functions. Understanding their expression in different skeletal muscle models is essential for elucidating the signaling mechanisms involved in the regulation of muscle metabolism, growth, and regeneration. The aim of this bachelor's thesis was to determine the relative expression of the INSR and IGF1R genes in differentiated primary human skeletal muscle cells and the Insr and Igf1r genes in differentiated rat L6 skeletal muscle cells. Total RNA was isolated from the cells, cDNA was synthesized, and relative gene expression was determined using quantitative polymerase chain reaction. The results showed that both genes were expressed in both cell models. The relative mRNA levels of both genes were statistically significantly higher in the L6 cell line than in primary human skeletal muscle cells. In the L6 cell line, the relative Igf1r mRNA level was statistically significantly higher than that of Insr, whereas the relative mRNA levels of IGF1R and INSR did not differ statistically significantly in primary human skeletal muscle cells. A comparable pattern of results was obtained with all three normalization approaches, using PPIA and 18S rRNA as reference genes. This study contributes to a better understanding of the expression of insulin and IGF-1 receptors in two widely used in vitro models of skeletal muscle and provides a basis for future investigations of their expression and functional role in skeletal muscle.
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