Alternative Day Fasting Protocol Attenuates High Fructose-induced Activation Of The Tgf-beta/smad Signaling Pathway

Abstract

Purpose: This study aims to explore the protective effects of alternate-day fasting (ADF) against metabolic disturbances induced by high fructose (HF) intake, with a particular focus on modulating the transforming growth factor-beta1 (TGF-β1) / mother against decapentaplegic homolog 2 (Smad2) signaling pathway. Materials and methods: Four groups of rats (n=7 per group) were included: Control, ADF, HF (20% fructose in drinking water), and HF+ADF. The ADF protocol was applied with 24 hours of ad libitum feeding followed by 24 hours of fasting over a 5-week period. After five weeks, body weight (BW), muscle, and fat mass were measured. Serum samples were analyzed using ELISA to assess levels of TGF-β1, Smad2, connective tissue growth factor (CTGF), and total oxidant-antioxidant status (TOS-TAS). Results: Results indicated that HF significantly increased final BW, and ADF reduced this weight gain (p=0.001). ADF also led to lower gastrocnemius-soleus muscle weights compared to controls (p=0.001), but mitigated fructose-induced retroperitoneal fat accumulation. TAS levels were higher (ADF vs control (p=0.01); HF vs HF+ADF (p=0.001)), and TOS levels were lower (ADF vs control (p=0.022); HF vs HF+ADF (p=0.001)) in the ADF groups, showing an antioxidant shift. Moreover, ADF significantly attenuated the TGF-β1/Smad2 pathway activation by decreasing serum TGF-β1 (ADF vs control (p=0.011); HF vs HF+ADF (p=0.008)), Smad2 (ADF vs control (p=0.001); HF vs HF+ADF (p=0.001)), and CTGF (ADF vs control (p=0.018); HF vs HF+ADF (p=0.001)) levels, suggesting a protective role against fructose-induced metabolic dysregulation. Conclusions: These findings suggest that ADF could be an effective dietary intervention for mitigating the metabolic impact of excessive fructose intake, particularly by regulating oxidative stress and the TGF-β1/Smad2 pathway. © 2025, Pamukkale University. All rights reserved.