Basal metabolic rate has been found to decline with age in a number of species including humans, dogs and passerine birds. Basal metabolic rate is one of the most widely measured physiological traits, ,, , and because this trait represents an animals' maintenance cost, is easy to obtain and believed to reflect the rate of living it has been used to investigate age related changes in energy metabolism. Basal metabolic rate (BMR) is defined as the rate of energy transformation in an endothermic organism at rest in a postabsorptive state, measured within its thermoneutral zone. Consequently, in addition to being a potential predictor of lifespan, metabolism may itself change as an effect of ageing. Thus, although energy metabolism is likely to play a role in the ageing process, the seemingly complex relationship between energy metabolism, ageing and longevity is far from being fully understood.Īgeing is associated with a decline in physiological performance. This paints a rather complex picture of the relationship between energy metabolism, free radical production and ageing. However, later findings have revealed that ROS production is not necessary positively correlated to aerobic metabolism, and that oxidative damage is not only influenced by the production of ROS, but also antioxidant defence and repair mechanisms,. According to the free radical theory the production of ROS correlates with the rate of aerobe metabolism thereby linking energy metabolism with ageing and ultimately lifespan. After discovering that reactive oxygen species (ROS), which can cause damage to various cell components, was generated during energy metabolism, the free radical theory (also known as the oxidative stress theory) emerged as a mechanistic explanation to the rate of living theory. One of the first theories of ageing, the rate of living theory, was put forward by Pearl predicting that the rate of life, in other words the energy metabolism, was a key determinant of lifespan. In spite of being a biological phenomenon that has received much attention and given rise to numerous theories, there are still many unanswered questions regarding the ageing process. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.Ĭompeting interests: The authors have declared that no competing interests exist. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.įunding: This work was supported by grants from the Research Council of Norway, nos. Received: JanuAccepted: SeptemPublished: September 29, 2014Ĭopyright: © 2014 Rønning et al. Thus, the effect of BMR on the rate of functional deterioration with age, if any, was not strong enough to influence neither the rate of metabolic ageing nor survival in the zebra finches.Ĭitation: Rønning B, Moe B, Berntsen HH, Noreen E, Bech C (2014) Is the Rate of Metabolic Ageing and Survival Determined by Basal Metabolic Rate in the Zebra Finch? PLoS ONE 9(9): In female zebra finches there was a tendency for survival to decrease with increasing BMR, but the effect did not reach significance ( P<0.1). Furthermore, survival was not affected by BMR in the males. However, we found no effect of BMR on the rate of metabolic ageing. If so, we would expect the rate of metabolic ageing to increase and survival to decrease with increasing BMR. This loss of functionality could be due to accumulated oxidative damage, believed to increase with increasing metabolic rate, c.f. Basal metabolic rate declined with age in both sexes after controlling for the effect of body mass, indicating a loss of functionality with age. We conducted a longitudinal study on captive zebra finches where we tested the effect of age on basal metabolic rate (BMR), as well as the effect of BMR on the rate of metabolic ageing (decline in BMR with age) and survival. The relationship between energy metabolism and ageing is of great interest because aerobic metabolism is the primary source of reactive oxygen species which is believed to be of major importance in the ageing process.
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