title: Long-term caloric restriction reduces metabolic rate and heart rate under cool and thermoneutral conditions in FBNF1 rats.
abstract: The long-term metabolic and cardiovascular responses to caloric restriction (CR) are poorly understood. We examined the responses to one year of CR in FBNF1 rats housed in cool (COOL; T(a)=15 °C) or thermoneutral (TMN; T(a)=30 °C) conditions. Rats were acclimated to COOL or TMN for 2 months, instrumented for cardiovascular telemetry and studied in calorimeters. Baseline caloric intake, oxygen consumption (VO(2)), mean arterial blood pressure (MAP), and heart rate (HR) were determined prior to assignment to ad lib (AL) or CR groups (30-40% CR) within each T(a) (n = 8). Groups of rats were studied after 10 weeks CR, one year CR, and after 4 days of re-feeding. Both 10 weeks and one year of CR reduced HR and VO(2) irrespective of T(a). Evaluation of the relationship between metabolic organ mass (liver, heart, brain, and kidney mass) and energy expenditure revealed a clear shift induced by CR to reduce expenditure per unit metabolic mass in both COOL and TMN groups. Re-feeding resulted in prompt elevations of HR and VO(2) to levels observed in control rats. These findings are consistent with the hypothesis that long term CR produces sustained reductions in metabolic rate and heart rate in rats.
authors.affiliation: Department of Biomedical Sciences and Program in Neuroscience, Florida State University, College of Medicine, Tallahassee, FL 32306-4340, USA.
authors.forename: W David
authors.initials: WD
authors.lastname: Knight
authors.forename: M M
authors.initials: MM
authors.lastname: Witte
authors.forename: A D
authors.initials: AD
authors.lastname: Parsons
authors.forename: M
authors.initials: M
authors.lastname: Gierach
authors.forename: J Michael
authors.initials: JM
authors.lastname: Overton
mesh_terms: D000818:Animals; D031204:Caloric Restriction; D003080:Cold Temperature; D002149:Energy Intake / Q000502:physiology; D006339:Heart Rate / Q000502:physiology*; D008297:Male; D009929:Organ Size / Q000502:physiology; D010101:Oxygen Consumption / Q000502:physiology; D051381:Rats; D013997:Time Factors