Contents lists available at ScienceDirect Gene journal homepage: www.elsevier.com/locate/gene Research paper Effects of 2-week HMB-FA supplementation with or without eccentric resistance exercise on expression of some genes related to muscle protein turnover and serum irisin and IGF-1 concentrations Hossein Shirvani a , Saleh Rahmati-Ahmadabad b , Elias Kowsari a , Hillary Fry c , Maryam Kazemi c , Mojtaba Kaviani d, ⁎ a Exercise Physiology Research Center, Life Style Institute, Baqiyatallah University of Medical Sciences, Tehran, Iran b Department of Physical Education, Pardis Branch, Islamic Azad University, Pardis, Iran c Division of Nutritional Sciences, Human Metabolic Research Unit, Cornell University, Ithaca, NY, USA d School of Nutrition and Dietetics, Acadia University, Wolfville, Nova Scotia, Canada ARTICLE INFO Keywords: Resistance training Atrophy Hypertrophy Caspase Myostatin Leucine ABSTRACT Protein turnover is a process that is regulated by several factors and can lead to muscle hypertrophy or atrophy. The purpose of the present study was to determine the effects of β-hydroxy-β-methylbutyrate free acid (HMB-FA) and eccentric resistance exercise on variables related to protein turnover in rats. Thirty-two male rats were randomly assigned into four groups of eight, including control, control-HMB, exercise, and exercise-HMB. Animals in HMB groups received 340 mg/kg/day for two weeks. Animals in the exercise groups performed one session of eccentric resistance exercise consisting of eight repetitions descending from a ladder with a slope of 80 degree, with an extra load of two times body weight (100% 1RM). Twenty-four hours after the exercise session, triceps brachii muscle and serum were collected for further analysis. Exercise and HMB-FA induced lower muscle myostatin and higher muscle Fibronectin type III domain containing 5 (FNDC5), P70-S6 kinase 1 gene expres- sion, as well as higher serum irisin and IGF-1 concentrations. Exercise alone induced higher caspase-3 and caspase-8 gene expression while HMB-FA alone induced lower caspase 3 gene expression. HMB-FA supplement increased the effect of exercise on muscle FNDC5, myostatin, and P70-S6 kinase 1 gene expression. The inter- action of exercise and HMBFA resulted in an additive effect, increasing serum irisin and IGF-1 concentrations. In conclusion, a 2-week HMB-FA supplementation paired with acute eccentric resistance exercise can positively affect some genes related to muscle protein turnover. 1. Introduction Protein turnover is a constant cellular process of muscle protein synthesis and breakdown in all living organs of biological systems (Poortmans et al., 2012; Li et al., 2016). In skeletal muscle, inequality in this process can lead to muscle hypertrophy (protein accrual) or atrophy (muscle loss) (Bonaldo and Sandri, 2013; Phillips et al., 2009). Several factors including sedentary lifestyle (Lund et al., 2018), pre- sence of chronic diseases (Reeds and Jahoor, 2001) and aging (Volpi et al., 2004) have been reported to increase muscle loss. In response to this relationship, physical activity, nutrients, and how these factors could attenuate muscle protein breakdown through metabolic path- ways and genetic expression, has become a topic of study. Recent studies have shown that eccentric resistance exercise (even one session) (Li et al., 2016; Tipton et al., 2018) and β-hydroxy-β-me- thylbutyrate-free acid (HMB-FA) supplementation (Wilkinson et al., 2013; Arazi et al., 2018) positively affect some major factors involved in protein turnover. Acute resistance exercise can impact protein turnover via several pathways including: ubiquitin-proteasome medi- ated muscle proteolysis (muscle atrophy f-box/atrogin-1 and muscle RING finger 1), translation initiation of muscle protein synthesis (mammalian target of rapamycin signaling), satellite cell-mediated myogenesis, and myostatin gene expression through ERK pathway (Bell et al., 2016; Murton, 2008; Rennie and Tipton, 2000). HMB is the active metabolite of leucine, one of the branched-chain amino acids (BCAA), which plays a key role in protein metabolism https://doi.org/10.1016/j.gene.2020.145018 Received 26 March 2020; Received in revised form 6 July 2020; Accepted 30 July 2020 Abbreviations: FNDC5, fibronectin type III domain containing 5; IGF-1, insulin-like growth factor 1; HMB-FA, myostatin, β-hydroxy-β-methylbutyrate free acid; MPS, Muscle protein synthesis; 1RM, one repeated maximum ⁎ Corresponding author. E-mail address: mojtaba.kaviani@acadiau.ca (M. Kaviani). Gene 760 (2020) 145018 Available online 03 August 2020 0378-1119/ © 2020 Elsevier B.V. All rights reserved. T