FN1 and type 2 diabetes mellitus: Furthermore, our study shows that untreated T2DM rats exhibited a significant increase in glycogen deposition and interstitial cardiac fibrosis when compared to control rats (p < 0.05), as assessed by PAS and Masson’s trichrome staining (Figure 4A–C), and increased mRNA expression of collagen I and fibronectin (Figure 4D,E).