Calorie restriction enhances cell adaptation to hypoxia through Sirt1-dependent mitochondrial autophagy in mouse aged kidney

Abstract

Mitochondrial oxidative damage is a basic mechanism of aging, and multiple studies demonstrate that this process is attenuated by calorie restriction (CR). However, the molecular mechanism that underlies the beneficial effect of CR on mitochondrial dysfunction is unclear. Here, we investigated in mice the mechanisms underlying CR-mediated protection against hypoxia in aged kidney, with a special focus on the role of the NAD-dependent deacetylase sirtuin 1 (Sirt1), which is linked to CR-related longevity in model organisms, on mitochondrial autophagy. Adult-onset and long-term CR in mice promoted increased Sirt1 expression in aged kidney and attenuated hypoxia-associated mitochondrial and renal damage by enhancing BCL2/adenovirus E1B 19-kDa interacting protein 3-dependent (Bnip3-dependent) autophagy. Culture of primary renal proximal tubular cells (PTCs) in serum from CR mice promoted Sirt1-mediated forkhead box O3 (Foxo3) deacetylation. This activity was essential for expression of Bnip3 and p27Kip1 and for subsequent autophagy and cell survival of PTCs under hypoxia. Furthermore, the kidneys of aged Sirt1 +/-mice were resistant to CR-mediated improvement in the accumulation of damaged mitochondria under hypoxia. These data highlight the role of the Sirt1-Foxo3 axis in cellular adaptation to hypoxia, delineate a molecular mechanism of the CR-mediated antiaging effect, and could potentially direct the design of new therapies for age-and hypoxia-related tissue damage. IntroductionIncreasing age causes progressive postmaturational deterioration of tissues and organs, leading to impairment of tissue functioning, increased vulnerability to challenges, and death. The kidney is a typical target organ of age-associated tissue damage, and the increased incidence of chronic kidney disease (CKD) in the elderly is a health problem worldwide (1-3). However, there is little or no information on the mechanisms underlying age-associated kidney damage. Thus, studies designed to determine such molecular mechanisms could help formulate interventions that delay the onset and/or progression of CKD in elderly patients.Among the several proposed theories on the pathogenesis of ageassociated tissue damage, the mitochondrial ROS theory provides the basic mechanism of age-associated tissue dysfunction (4, 5): that age-dependent alteration in mitochondrial DNA (mtDNA) plays a fundamental role in the age-associated increase in ROS and subsequent tissue damage (6, 7). Further evidence linking alterations in mtDNA with progressive age-dependent tissue dysfunction can be found in individuals with mitochondrial genetic diseases and mice with deletion mutation of mtDNA, which display a phenotype that resembles premature aging, including kidney dysfunction (8,9). Hypoxia is the cause of age-associated mitochondrial dysfunction (10) and is involved in age-dependent tissue damage affecting the brain (11), heart (12), and kidney (13). Furthermore, hypoxia modulates various cellular processes, such as apoptosis, cell cycle, autophagy, and glucose me...

Role of dietary amino acid balance in diet restriction‐mediated lifespan extension, renoprotection, and muscle weakness in aged mice

“…Thus, we decided to use 24 months as the end‐point of this study, which enabled us to analyze the effect of each dietary regimen on survival, cardiac function, glucose metabolism, muscle function, histology, and serum parameters in living middle aged and older mice, but not in very old mice. The amount of food given to DR groups was reduced by 40% of the dietary amount of the ad libitum group (Kume et al., 2010). The amount of each amino acid in the DR plus either NEAAs or EAAs groups was supplemented to the level of the ad libitum group.…”

“…Urinary creatinine was measured using the LabAssay Creatinine assay kit (Wako, Osaka, Japan). Plasma cystatin C levels were measured using the cystatin C (mouse) ELISA Kit (ALEXIS Biochemicals) (Kume et al., 2010). Glucose and insulin tolerance tests were performed as previously described (Tanaka et al., 2011).…”

“…Periodic acid–Schiff (PAS), hematoxylin–eosin (HE), Masson's trichrome, and immunohistochemical stains were performed as described previously (Kume et al., 2010). Antibodies to fibronectin (#AB2033, Chemicon, Temecula, CA), F4/80 (#MCA497GA, Serotec, Oxford, U.K.), CGL (#ab151769, Abcam, Cambridge, MA), CBS (#ab135626, Abcam, Cambridge, MA), klotho (Cosmo Bio.…”

“…Dietary restriction (DR) can extend lifespan in numerous species, including mammals, and prevent age‐related impairment in organ function, including kidney dysfunction (Colman et al., 2014; Kume et al., 2010; Lin, Ford, Haigis, Liszt, & Guarente, 2004; Shimokawa et al., 2015). In contrast, DR has only one principal negative effect: muscle weakness due to protein wasting (Lopes, Russell, Whitwell, & Jeejeebhoy, 1982; Thomas, 2007), which also represents a health problem in both elderly subjects and patients with kidney disease (Goodpaster et al., 2006; Workeneh & Mitch, 2010).…”

“…Of particular note is that, in a study conducted in Drosophila , recovering dietary EAA, but not NEAA, prevented DR‐induced lifespan extension (Grandison, Piper, & Partridge, 2009). Given that the beneficial effect of simple DR on lifespan is observed in most living organisms (Colman et al., 2014; Kume et al., 2010; Lin et al., 2004), the distinct effects of dietary EAA and NEAA on DR‐mediated longevity may be conserved across species. We therefore hypothesized that the balance between the dietary content of EAAs and NEAAs would affect DR‐induced lifespan extension and modify age‐related organ dysfunction in mammals, with implications for the design of an improved dietary regimen aimed at extending healthy lifespan.…”