title: FVB/NJ Mice Are a Useful Model for Examining Cardiac Adaptations to Treadmill Exercise.
abstract: Mice are commonly used to examine the mechanisms by which exercise improves cardiometabolic health; however, exercise compliance and adaptations are often strain-dependent or are variable due to inconsistency in exercise training protocols. In this study, we examined nocturnal/diurnal behavior, treadmill exercise compliance, and systemic as well as cardiac-specific exercise adaptations in two commonly used mouse strains, C57BL/6J, and FVB/NJ mice. Metabolic cage analysis indicated a strong nocturnal nature of C57BL/6J mice, whereas FVB/NJ mice showed no circadian element to activity, food or water intake, VO2, or VCO2. Initial exercise capacity tests revealed that, compared with C57BL/6J mice, FVB/NJ mice are capable of achieving nearly 2-fold higher workloads prior to exhaustion. FVB/NJ mice tested during the day were capable of achieving significantly more work compared with their night-tested counterparts. Following 4 weeks of training, FVB/NJ mice showed significant increases in exercise capacity as well as physiologic cardiac growth characterized by enlarged myocytes and higher mitochondrial DNA content. C57BL/6J mice showed no increases in exercise capacity or cardiac growth regardless of whether they exercised during the day or the night. This lack of adaptation in C57BL/6J mice was attributable, at least in part, to their progressive loss of compliance to the treadmill training protocol. We conclude that the FVB/NJ strain is a useful and robust mouse model for examining cardiac adaptations to treadmill exercise and that treadmill training during daytime hours does not negatively affect exercise compliance or capacity.
authors.affiliation: Department of Medicine, Institute of Molecular Cardiology, University of LouisvilleLouisville, KY, USA; Diabetes and Obesity Center, University of LouisvilleLouisville, KY, USA; Department of Physiology, University of LouisvilleLouisville, KY, USA.
authors.forename: Andrew A
authors.initials: AA
authors.lastname: Gibb
authors.affiliation: Department of Medicine, Institute of Molecular Cardiology, University of LouisvilleLouisville, KY, USA; Diabetes and Obesity Center, University of LouisvilleLouisville, KY, USA.
authors.forename: Lindsey A
authors.initials: LA
authors.lastname: McNally
authors.affiliation: Department of Medicine, Institute of Molecular Cardiology, University of LouisvilleLouisville, KY, USA; Diabetes and Obesity Center, University of LouisvilleLouisville, KY, USA.
authors.forename: Daniel W
authors.initials: DW
authors.lastname: Riggs
authors.affiliation: Department of Medicine, Institute of Molecular Cardiology, University of LouisvilleLouisville, KY, USA; Diabetes and Obesity Center, University of LouisvilleLouisville, KY, USA.
authors.forename: Daniel J
authors.initials: DJ
authors.lastname: Conklin
authors.affiliation: Department of Medicine, Institute of Molecular Cardiology, University of LouisvilleLouisville, KY, USA; Diabetes and Obesity Center, University of LouisvilleLouisville, KY, USA; Department of Physiology, University of LouisvilleLouisville, KY, USA; Department of Biochemistry and Molecular Genetics, University of LouisvilleLouisville, KY, USA.
authors.forename: Aruni
authors.initials: A
authors.lastname: Bhatnagar
authors.affiliation: Department of Medicine, Institute of Molecular Cardiology, University of LouisvilleLouisville, KY, USA; Diabetes and Obesity Center, University of LouisvilleLouisville, KY, USA; Department of Physiology, University of LouisvilleLouisville, KY, USA; Department of Biochemistry and Molecular Genetics, University of LouisvilleLouisville, KY, USA.
authors.forename: Bradford G
authors.initials: BG
authors.lastname: Hill
keywords: cardiac hypertrophy; circadian; compliance; exercise; metabolism; mitochondria; mouse strain; physical activity