Background: Fibrosis induced by transforming growth factor-β1 (TGF-β1) activity and the Wnt/β-catenin pathway is a significant hallmark of progressive kidney disease and kidney aging. We aimed to investigate the effects of pharmacological silent mating type information regulation 2 homolog-2 (SIRT2) inhibition on renal functions, histopathological changes, fibrosis, TGF-β1/β-catenin and klotho signaling, and apoptosis in D-galactose (D-Gal)-induced aging model.

Methods: The study was conducted with three months old male rats divided into four groups: control (Saline solution (0.9%, 0.5 mL/day) was administered subcutaneously (sc) for ten weeks) (n = 6), D-Gal (D-galactose saline solution (150 mg/kg/day) was administered sc for ten weeks) (n = 8), D-Gal+DMSO (D-galactose (150 mg/kg/day) and 4% dimethyl sulfoxide (DMSO) in phosphate-buffered saline (PBS) (10 μL/bw/day) were administered sc for ten weeks) (n = 8), and D-Gal+acylglycerol kinase (AGK)-2 (D-galactose (150 mg/kg/day) and AGK-2 in 4% DMSO-PBS (10 μM/bw/day) was administered sc for ten weeks) (n = 8). The kidney index was calculated, renal function markers (sodium (Na⁺), creatinine (Cr), blood urea nitrogen (BUN)) in plasma and urine samples were analyzed, and fractional excretion of sodium (FeNa%) was calculated. Glomerular diameter, fibrosis, and basement membrane thickness were analyzed with histopathological methods. TGF-β1 and β-catenin mRNA expression were determined with quantitative real-time polymerase chain reaction (qRT-PCR), klotho protein levels were determined with the enzyme linked immunosorbent assay (ELISA) method, and SIRT2 protein expression was determined with western blot. The immunohistochemical method was employed to determine the immunoreactivities of β-catenin, klotho, SIRT2, and fibronectin. Apoptosis was determined with the terminal deoxynucleotidyl transferase deoxyuridine triphosphate (dUTP) nick end labeling (TUNEL) method.

Results: AGK-2 and D-galactose co-administration increased kidney index and decreased plasma and urine Na⁺ and Cr levels, as well as BUN and FeNa% (p < 0.05). AGK-2 improved the histopathological changes induced by D-galactose, reducing fibrosis and basal membrane thickness (p < 0.05). Furthermore, AGK-2 administration decreased TGF-β1, β-catenin, SIRT2, and fibronectin in the kidney (p < 0.05). AGK-2 and D-galactose co-administration increased klotho protein levels in the kidney; however, the increase was not statistically significant in klotho immunoreactivity (p > 0.05). D-galactose induced apoptosis in the kidney (p < 0.05); however, AGK-2 did not significantly mitigate apoptosis (p > 0.05).

Conclusion: Our findings suggested that pharmacological SIRT2 inhibition could ameliorate alterations in functional, histopathological, and fibrosis protein pathway activities in the kidney that are associated with aging.

Metabolic syndrome (MetS) is a multifactorial disorder characterized by insulin resistance, dyslipidemia, central obesity, and hypertension, leading to an increased risk of cardiovascular diseases and type-2 diabetes. Although conventional drugs have been used to treat MetS and its associated complications, they are often linked with undesirable side effects. Consequently, there is a growing interest in herbal remedies as potential alternatives. Among these remedies is Withania somnifera, commonly known as Ashwagandha, a revered medicinal herb in traditional Chinese medicine and Ayurveda due to its numerous health-promoting properties. Withanolides, such as withaferin-A and withanolid-D, are the primary active compounds in W. somnifera and suggested to play a pivotal role in managing MetS. Moreover, Ashwagandha exhibits hypotensive, anti-obesity, anti-diabetic, and anti-hyperlipidemic properties, influencing multiple molecular and cellular pathways associated with MetS. W. somnifera has been demonstrated its potential to considerably reduce atherosclerotic plaque formation, as well as lower levels of very low-density lipoprotein (VLDL), triglycerides (TG), and low-density lipoproteins (LDL). This comprehensive review provides valuable insights into the latest research findings on the preventive potential of W. somnifera against MetS. Furthermore, recent studies on Ashwagandha highlight the need for additional clinical trials to evaluate its optimal dosage, safety profile, efficacy, and precise mechanisms of action.