Dietary Restriction Ameliorates Diabetic Nephropathy through Anti-Inflammatory Effects and Regulation of the Autophagy via Restoration of Sirt1 in Diabetic Wistar Fatty (fa/fa) Rats: A Model of Type 2 Diabetes

Abstract

Aim. Despite the beneficial effects of dietary restriction (DR) on lifespan, age-related diseases, including diabetes and cardiovascular diseases, its effects on type 2 diabetic nephropathy remain unknown. This study examined the renoprotective effects of DR in Wistar fatty (fa/fa) rats (WFRs). Methods. WFRs were treated with DR (40% restriction) for 24 weeks. Urinary albumin excretion, creatinine clearance, renal histologies, acetylated-NF-κB (p65), Sirt1 protein expression, and p62/Sqstm 1 accumulation in the renal cortex, as well as electron microscopic observation of mitochondrial morphology and autophagosomes in proximal tubular cells were estimated. Results. DR ameliorated renal abnormalities including inflammation in WFRs. The decrease in Sirt1 levels, increase in acetylated-NF-κB, and impaired autophagy in WFRs were improved by DR. Conclusions. DR exerted anti-inflammatory effects and improved the dysregulation of autophagy through the restoration of Sirt1 in the kidneys of WFRs, which resulted in the amelioration of renal injuries in type 2 diabetes.

A very-low-protein diet ameliorates advanced diabetic nephropathy through autophagy induction by suppression of the mTORC1 pathway in Wistar fatty rats, an animal model of type 2 diabetes and obesity

“…However, autophagy in renal tubular cells is induced through cellular stresses, including hypoxia and proteinuria, and the activation of autophagy protects tubular cells from cellular dysfunction and apoptosis. Previous studies have shown that the impairment of autophagy is associated with the pathogenesis of kidney diseases, including HFD-induced renal dysfunction [30], ageing kidneys [31] and diabetic nephropathy [28]. In this study we showed that fragmented mitochondria accumulated in diabetic PTCs, possibly due to impaired autophagy, resulted in increased apoptosis.…”

“…Morphological analysis and immunohistochemistry, western blot analysis and real-time PCR The kidney sections were stained with Masson's trichrome (MT)/periodic acid-Schiff (PAS) reagent, and immunohistochemical staining was performed using antibodies against CD68 (1:50), kidney injury molecule-1 (KIM-1) (1:100), p62 (1:100) and p-S6 ribosomal protein (S6RP) (1:100), as previously described [28,30,31]. (For further details of morphological and immunohistochemical analysis, see ESM Methods.)…”

“…Western blotting was performed using antibodies to cleaved caspase-3 (1:1000), β-actin (1:1000), p-S6RP (1:1000), S6RP (1:1000), p-Akt (1:1000), Akt (1:1000) and microtubule-associated protein light chain 3 (LC3)-I/II (1:1000). The isolation of total RNA from the renal cortex, cDNA synthesis and quantitative realtime PCR were performed, as previously described [28]. TaqMan probes for type III collagen, CD68, IL-6, TNF-α, monocyte chemotactic protein 1 (MCP-1) and toll-like receptor 2 (TLR2) were purchased from Thermo Fisher Scientific (Waltham, MA, USA).…”

“…Transmission electron microscopy Mitochondrial morphology and fragmented mitochondria in the proximal tubular cells (PTCs) were observed using transmission electron microscopy, as previously described [28,32]. (For further details regarding electron microscopic mitochondrial morphology, see ESM Methods.…”

Calorie restriction and sirtuins revisited

“…In addition, SIRT1 is required for CR-induced renal protection against hypoxia, in this case by deacetylating of FOXO3 and activating autophagy (Kume et al 2010). Finally, CR is also renal-protective in a diabetes model in rats, and this is associated with activation of SIRT1 and deacetylation of NF-kB (Kitada et al 2011).…”