Fig 2: Quercetin (Quer) protected PC-12 cells through activating Adenosine 5‘-monophosphate (AMP)-activated protein kinase (AMPK) and Wnt/ß-catenin signaling pathways. (A) miR-122 regulated the effect of Quer on activation of AMPK signaling pathway. (B) miR-122 regulated the effect of Quer on activation of Wnt/ß-catenin signaling pathway

Fig 3: Scheme depicting proposed mechanisms involved in empagliflozin-offered protection against microvasculature damage in diabetes. Empagliflozin activates AMPK pathways through regulation of the AMP/ATP ratio. Activated AMPK pathways regulates Drp1 posttranscriptional phosphorylation modifications at Ser616 and Ser637, leading to the inability of Drp1 to translocate onto mitochondria and mitochondrial fission impairment. The loss of mitochondrial fission retards cellular senescence and preserves endothelial barrier/permeability by suppressing superfluous ROS. In consequence, endothelial migration and vascularization are improved by balanced F-actin degradation. Moreover, empagliflozin reduces CMEC apoptosis, increases cardiac microvessel density, promotes eNOS phosphorylation and alleviates vascular collagen deposition, leading to improved endothelial function and preserved vascular remodeling, ultimately lower levels of inflammatory cell penetration and better vascular relaxation. Through these aforementioned mechanisms, empagliflozin eventually facilitates diabetic myocardial perfusion and protects the heart against hyperglycemic injury.

Fig 4: AMPKa inhibited the inflammatory responses in the high-glucose-cultured HK-2 cells by activating PPARa and downregulating NF-?B. (A) Adenosine 5'-monophosphate (AMP)-activated protein kinase (AMPK) and phosphorylated AMPK detected by Western blotting in rat renal tissues. Levels of the inflammatory factors (B) and oxidation-related factors (C) in the cell culture supernatants were quantified by ELISA. (D) Expression levels of PPARa and NF-?B in HK-2 cells detected by Western blotting. (E) Protein expression detected by Western blotting. All data represented the mean ± SD. *p < 0.05 [compared with the control (Con) group]; #p < 0.05 [compared with the diabetic nephropathy (DN) group].

Fig 5: HG blocked the AMPK signal pathway in neonatal ventricular myocytes and in mice. (A) Effect of HG was not eliminated in the presence of CGP20712a (1 µM), ICI118551 (0.5 µM), and LY294002 (1 µM). (B) Western blot representative images and analysis of the expression of phosphorylated and total AMPK in neonatal ventricular cardiomyocytes. (C) Western blot representative images confirmed the efficacy of the agonist AICAR. (D) In the absence of agonist AICAR, HG could inhibit DOX-induced cardiomyocyte apoptosis. (E) AICAR blocked the inhibitory effect of HG on DOX-induced cardiomyocyte apoptosis. (F) Immunohistochemical staining of the phosphorylated and total AMPK in each group of 4 weeks and the phosphorylated AMPK-positive cell for quantitative analysis in mice hearts; scale bar: 100 µM. The aforementioned experiments were repeated more than three times. All values are presented as mean ± SEM; statistical analysis was performed using Prism 8.0 one-way ANOVA. * p < 0.05 DOX vs control C, AICAR vs control C, DOX vs NS; # p < 0.05 DOX + HG vs DOX; ns, p > 0.05 DOX + HG + AICAR vs DOX + AICAR. Animal numbers: NS, n = 8; HG, n = 7; DOX, n = 10; DOX + HG, n = 10.