Neuropsychopharmacology (2016) 41, 3070–3079 © 2016 American College of Neuropsychopharmacology. All rights reserved 0893-133X/16 www.neuropsychopharmacology.org Brain-Derived Neurotrophic Factor Val66Met Human Polymorphism Impairs the Beneficial Exercise-Induced Neurobiological Changes in Mice *,1 1 1 2 1 Alessandro Ieraci , Alessandro I Madaio , Alessandra Mallei , Francis S Lee and Maurizio Popoli 1Laboratory of Neuropsychopharmacology and Functional Neurogenomics, Dipartimento di Scienze Farmacologiche e Biomolecolari and Center of 2 Excellence on Neurodegenerative Diseases, Università di Milano, Milano, Italy; Department of Psychiatry, Weill Medical College of Cornell University, New York, NY, USA Several studies have shown that exercise improves cognitive functions and emotional behaviors. Positive effects of exercise have been associated with enhanced brain plasticity, adult hippocampal neurogenesis, and increased levels of brain-derived neurotrophic factor (BDNF). However, a substantial variability of individual response to exercise has been described, which may be accounted for by individual genetic variants. Here, we have assessed whether and how the common human BDNF Val66Met polymorphism influences the Val/Val neurobiological effects modulated by exercise in BDNF Val66Met knock-in male mice. Wild-type (BDNF ) and homozygous BDNF Met/Met Val66Met (BDNF ) male mice were housed in cages equipped with or without running wheels for 4 weeks. Changes in behavioral phenotype, hippocampal adult neurogenesis, and gene expression were evaluated in exercised and sedentary control mice. We found that Val/Val exercise reduced the latency to feed in the novelty suppressed feeding and the immobility time in the forced swimming test in BDNF but not in BDNFMet/Met mice. Hippocampal neurogenesis was reduced in BDNFMet/Met mice compared with BDNFVal/Val mice. BDNFMet/Met mice had lower basal BDNF protein levels in the hippocampus, which was not recovered following exercise. Moreover, exercise-induced expression of total BDNF, BDNF splice variants 1, 2, 4, 6 and fibronectin type III domain-containing protein 5 (FNDC5) Met/Met α mRNA levels were absent or reduced in the dentate gyrus of BDNF mice. Exercise failed to enhance PGC-1 and FNDC5 mRNA Met/Met levels in the BDNF muscle. Overall these results indicate that, in adult male mice, the BDNF Val66Met polymorphism impairs the beneficial behavioral and neuroplasticity effects induced by physical exercise. Neuropsychopharmacology (2016) 41, 3070–3079; doi:10.1038/npp.2016.120; published online 10 August 2016 INTRODUCTION Stranahan et al,2007;vanPraaget al, 1999; Vivar et al, 2013). One of the major mechanisms proposed whereby exercise Several studies have shown that regular physical exercise is beneficial for physical and mental health at all ages, including affects brain plasticity and function is the increase of the elderly. Exercise improves mental health by reducing brain-derived neurotrophic factor (BDNF), a neurotrophin anxiety, depression, negative mood and by improving self- implicated in anxiety, depression, learning, and memory esteem and cognitive functions (Deslandes et al, 2009; disabilities (Hopkins et al, 2011; Ieraci et al, 2015; Intlekofer Duman et al, 2008; Schuch et al, 2016; Voss et al, 2013). et al, 2013; Phillips et al, 2014; Vaynman et al, 2004; Voss Moreover, some lines of evidence strongly suggest that et al, 2013). However, the mechanism underlying the individuals who are physically active during adulthood tend exercise-induced BDNF expression in the hippocampus is to have better cognitive performances later in life (Mattson, still poorly understood. 2015). Exercise-induced improvement in brain function has Recently, it has been reported that exercise enhances the been associated with increased adult hippocampal neurogen- expression of fibronectin type III domain-containing protein esis, synaptogenesis, and enhanced activity-dependent 5 (FNDC5) in the muscle, in a peroxisome proliferator- synaptic plasticity (Christie et al, 2008; Farmer et al,2004; activated receptor-γ coactivator-1α (PGC-1α)-dependent manner (Wrann et al, 2013). FNDC5 is a transmembrane *Correspondence: Dr A Ieraci, Laboratory of Neuropsychopharmacol- protein released in the blood stream after proteolytic ogy and Functional Neurogenomics, Dipartimento di Scienze Farm- cleavage (Bostrom et al, 2012). Importantly, overexpression acologiche e Biomolecolari, Università di Milano, Via Balzaretti 9, of FNDC5 into liver via adenovirus infection significantly Milano 20133, Italy. Tel: +39 0250318351; Fax: +39 0250318278. E-mail: [email protected] enhances BDNF expression in the hippocampus (Wrann Received 3 May 2016; revised 15 June 2016; accepted 27 June 2016; et al, 2013). Interestingly, BDNF in turn is able to reduce the accepted article preview online 8 July 2016 expression of FNDC5 suggesting a homeostatic feedback BDNF Val66Met impairs exercise-induced changes A Ieraci et al 3071 loop (Wrann et al, 2013). However, whether BDNF genetic controlled room (21 ± 1 °C), with free access to food variants may alter this pathway is still unknown. and water. Despite the well-documented positive effects of exercise in All experimental procedures involving animals were humans, substantial variability in the individual response has performed in accordance with the European Community been reported. This variability may be accounted for by Council Directive 86/609/EEC, and were approved by Italian genetic factors that interfere with the benefit of exercise on legislation on animal experimentation (Decreto Legislativo cognitive functions and mood. 116/1992). A number of common single-nucleotide polymorphisms (SNPs) have been identified in the human BDNF gene. The Behavioral Tests rs6265 SNP leads to a Valine to Methionine substitution at position 66 (Val66Met) in the pro-domain of BDNF, which Behavioral tests were conducted between 0900 and 1600 h. impairs the activity-dependent release of BDNF. Val66Met See Supplementary Materials and Methods for more details. SNP is associated with increased susceptibility to cognitive deficits and neuropsychiatric disorders (Egan et al, 2003; BrdU Treatment and Immunohistochemistry Hariri et al, 2003; Lim et al, 2014; Notaras et al, 2015; Verhagen et al, 2010). Despite the strong evidence that Detailed information can be found in Supplementary exercise increases BDNF expression, only a few human Materials and Methods. studies have been conducted to address the potential role of Val66Met SNP in moderating exercise response, showing BDNF ELISA inconclusive results, probably due to confounding factors (Brown et al, 2014; Gujral et al, 2014; Hopkins et al, 2012; BDNF levels were measured by an enzyme-linked immuno- Lemos et al, 2016; Mata et al, 2010; Nascimento et al, 2015). sorbent assay (ELISA) according to the manufacturer’s Animal models may offer a useful tool to better address instructions (BDNF Emax Immunoassay System, Promega). such question in a well-controlled environment and genetic setting. A knock-in mouse carrying the human BDNF Val66Met Western Blot SNP has been generated (Chen et al, 2006). BDNFMet/Met Detailed western blot procedures can be found in homozygous mice recapitulate the phenotypic hallmarks of Supplementary Materials and Methods. humans carrying the BDNF Met allele. Indeed, BDNFMet/Met mice display reduced hippocampal volume, reduced den- dritic arborization in the dentate gyrus (DG), reduced BDNF RNA Isolation and Quantitative Real-Time PCR levels, and NMDA receptor-dependent synaptic plasticity in Detailed information is reported in Supplementary Materials the hippocampus (Chen et al, 2006; Ninan et al, 2010). and Methods. Furthermore, we have recently found decreased expression and dendritic trafficking for selected BDNF transcripts in BDNFMet/Met hippocampus (Mallei et al, 2015). Interestingly, Statistical Analysis Met/Met BDNF mice are unresponsive to treatment with some Statistical analyses were performed using GraphPad Prism 6 antidepressant drugs, in particular it has been reported that (GraphPad Software, La Jolla, CA). Data are presented chronic fluoxetine treatment and acute ketamine adminis- as mean ± standard error of the mean (SEM). Statistical tration do not promote anxiolytic and antidepressant-like analyses were made using unpaired t-test or two-way Met/Met effects, respectively, in BDNF mice (Chen et al, 2006; analysis of variance (ANOVA), and Fischer’s LSD post hoc Liu et al, 2012). Thus, this mouse may provide an ideal test was used for multiple comparison analysis. model to explore whether and by what mechanism(s) the Val66Met SNP moderates the effects of environmental and pharmacological treatments. RESULTS In this study, we assessed the effect of exercise on anxious- Val/Val Physical Exercise-Induced Reduction of Body Weight and depressive-like behaviors in BDNF wild-type and Gain BDNFMet/Met mutant adult male mice. We explored the possible mechanisms underlying the exercise-induced Adult male BDNFVal/Val and BDNFMet/Met mice underwent behavioral changes by measuring the levels of neurogenesis 4 weeks of free voluntary exercise. BDNFVal/Val and and BDNF expression in the hippocampus of BDNFVal/Val BDNFMet/Met displayed similar daily running distance and BDNFMet/Met mice exposed to exercise. Finally, we (P = 0.3001; Figure 1a). However, we found a main body investigated whether exercise-induced PGC-1α and FNDC5 weight gain effect for exercise and genotype (exercise: Met/Met = = = = expressions were altered in