Possible involvement of normalized Pin1 expression level and AMPK activation in the molecular mechanisms underlying renal protective effects of SGLT2 inhibitors in mice

Abstract

Background Recently, clinical studies have shown the protective effects of sodium glucose co-transporter2 (SGLT2) inhibitors against progression of diabetic nephropathy, but the underlying molecular mechanisms remain unclear. Methods Diabetic mice were prepared by injecting nicotinamide and streptozotocin, followed by high-sucrose diet feeding (NA/STZ/Suc mice). The SGLT2 inhibitor canagliflozin was administered as a 0.03% (w/w) mixture in the diet for 4 weeks. Then, various parameters and effects of canagliflozin on diabetic nephropathy were investigated. Results Canagliflozin administration to NA/STZ/Suc mice normalized hyperglycemia as well as elevated renal mRNA of collagen 1a1, 1a2, CTGF, TNFα and MCP-1. Microscopic observation revealed reduced fibrotic deposition in the kidneys of canagliflozin-treated NA/STZ/Suc mice. Interestingly, the protein level of Pin1, reportedly involved in the inflammation and fibrosis affecting several tissues, was markedly increased in the NA/STZ/Suc mouse kidney, but this was normalized with canagliflozin treatment. The cells showing increased Pin1 expression in the kidney were mainly mesangial cells, along with podocytes, based on immunohistochemical analysis. Furthermore, it was revealed that canagliflozin induced AMP-activated kinase (AMPK) activation concentration-dependently in CRL1927 mesangial as well as THP-1 macrophage cell lines. AMPK activation was speculated to suppress mesangial cell proliferation and exert anti-inflammatory effects in hematopoietic cells. Conclusion Therefore, we can reasonably suggest that normalized Pin1 expression and AMPK activation contribute to the molecular mechanisms underlying SGLT2 inhibitor-induced suppression of diabetic nephropathy, possibly at least in part by reducing inflammation and fibrotic change.

Autophagy stimulation and intracellular sodium reduction as mediators of the cardioprotective effect of sodium–glucose cotransporter 2 inhibitors

“…Experimental studies indicates that SGLT2 inhibitors can activate AMPK, SIRT1 and HIF‐1α in the myocardium, thereby potentially contributing to their actions to reduce heart failure and adverse renal events ( Figure ). Canagliflozin increases the expression, phosphorylation and activation of AMPK; although similar effects have been reported for empagliflozin and dapagliflozin, the evidence is less certain . Both canagliflozin and empagliflozin have been shown to upregulate SIRT1, and both empagliflozin and dapagliflozin induce the expression of HIF‐1α .…”

“…The overlap in the mechanism of action between metformin and SGLT2 inhibitors (with respect to AMPK activation) may explain why the magnitude of the benefit of SGLT2 inhibitors in large‐scale randomized controlled trials appears to be attenuated in patients receiving metformin, especially when it is used together with SGLT2 inhibitors that robustly activate AMPK (i.e. canagliflozin) . In the CANVAS trials, canagliflozin reduced the risk of cardiovascular death or hospitalization for heart failure by 36% in patients not receiving metformin, but by only 12% in those receiving metformin (interaction P = 0.03) .…”

SGLT2 Inhibitors Produce Cardiorenal Benefits by Promoting Adaptive Cellular Reprogramming to Induce a State of Fasting Mimicry: A Paradigm Shift in Understanding Their Mechanism of Action

“…1) (27). These drugs activate SIRT1/AMPK and suppress Akt/mTOR signaling and, consequently, they can promote autophagy, independent of their effects on glucose or insulin (28)(29)(30)(31). Importantly, the effect of SGLT2 to stimulate the activity of low-energy sensors is not mediated by interference with SGLT2 protein on an individual cellular level, since it is seen in organs that do not express SGLT2 (30,32).…”

Interplay of adenosine monophosphate‐activated protein kinase/sirtuin‐1 activation and sodium influx inhibition mediates the renal benefits of sodium‐glucose co‐transporter‐2 inhibitors in type 2 diabetes: A novel conceptual framework

“…The resulting shift in the transcriptional paradigm includes activation of AMPK and SIRT1. SGLT2 inhibitors lead to the phosphorylation of AMPK and/or upregulation of SIRT1 and induce biomarkers of autophagy in the kidney, and experimental knockout of SGLT2 in the renal proximal tubule may promote autophagic flux . Interestingly, although reports concerning the effects of SGLT2 inhibitors on HIF‐1α expression in renal tubular cells have yielded conflicting results, these drugs may stimulate HIF‐2α (through their effect to enhance SIRT1 signalling), which promotes lysosome‐mediated clearance of dysfunctional peroxisomes.…”

“…Stimulation of HIF‐2α (which transactivates the gene for erythropoietin) may explain why SGLT2 inhibitors cause erythrocytosis in clinical trials . The enhanced interplay of AMPK, SIRT1 and HIF‐2α may underlie the action of SGLT2 inhibitors to ameliorate oxidative and endoplasmic reticular stress, and thereby minimize glomerular and tubular injury and inflammation, and attenuate the development of nephropathy . An increase in AMPK and SIRT1 may also directly enhance tubuloglomerular feedback, thereby linking changes in the activity of these energy sensors to the action of SGLT2 inhibitors to ameliorate glomerular hyperfiltration.…”