Rate-of-living theory

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The rate-of-Living Theory ( dt. "Survival theory") is an explanatory model for the aging of organisms that reproduce sexually . The hypothesis is one of the first contributions to the aging theory and was proposed in 1928 by the American biogerontologist Raymond Pearl .

description

Pearl's rate of living theory is based on Max Rubner's metabolic theory published in 1908 . Rubner observed that the life expectancy of an organism is inversely proportional to its mass-specific metabolic rate . This means that the higher the mass-specific metabolic rate, the shorter the life span. Together with the observation made by Jacques Loeb and John Howard Northrop that the life expectancy of fruit flies ( Drosophila ) increases with decreasing ambient temperature, Pearl concluded - like Rubner before him - that the basal metabolic rate is inversely proportional to the maximum life expectancy of an organism. Raymond Pearl suspected that life expectancy was limited by cell components that would be broken down or damaged more quickly with an increased metabolism.

As a result, different variants of the rate-of-living theory were put forward. Other life-limiting factors have been postulated. This includes, for example, the maximum number of heartbeats that an organism can have in the course of its life.

With the 1956 by Denham Harman established free-radical theory of aging , as new aging theory, the circle was closed to Pearl's theory. Harman's theory is based on the rate-of-living theory. The higher the metabolism rate of an organism, the higher its breathing rate and, as a result, the uptake of oxygen , which in turn leads to a correspondingly increased production of reactive species ( free radicals ) in the cells. The free radicals in turn - according to Harman's theory - lead to an accelerated aging process.

reception

For many years the rate of living theory has been the leading aging theory. The simplest interpretation of the rate-of-living theory is that lowering an organism's metabolism increases its life expectancy. Numerous experiments, for example calorie restriction in a number of model organisms , seem to confirm the theory.

However, some observations contradict the rate of living theory. For example, exercise is generally associated with a higher metabolic rate. However, sport does not shorten life expectancy, neither in rats nor in humans. In individuals of a species there is apparently no correlation between life expectancy and mass-specific metabolic rate. No correlation could be found, at least for mice and fruit flies. Even if the calorie restriction increases life expectancy, it does not reduce the metabolic rate. Birds and mammals have similar metabolic rates, but birds generally live significantly longer than mammals of comparable size.

further reading

  • U. Neuhäuser-Berthold and P. Lührmann: The metabolic rate as the clock of life. (PDF; 366 kB) In: Spiegel der Forschung 24, 2007, pp. 49–53.
  • K. Brys et al .: Testing the rate-of-living / oxidative damage theory of aging in the nematode model Caenorhabditis elegans. In: Exp Gerontol 42, 2007, pp. 845-851. PMID 17379464 (Review)
  • WA Van Voorhies et al .: Testing the "rate of living" model: further evidence that longevity and metabolic rate are not inversely correlated in Drosophila melanogaster. In: J Appl Physiol 97, 2004, pp. 1915-1922. doi : 10.1152 / japplphysiol.00505.2004 PMID 15234957
  • M. Rubner: About the influence of body size on metabolism and strength change. In: Z Biol 19, 1883, pp. 535-562.

Individual evidence

  1. M. Rubner: The problem of lifespan and its relationship to growth and nutrition. Munich, Oldenbourg, 1908.
  2. ^ J. Loeb and JH Northrop: On the influence of food and temperature upon the duration of life. In: The Journal of Biological Chemistry 32, 1917, pp. 103-121.
  3. ^ R. Pearl: The Rate of Living, Being an Account of Some Experimental Studies on the Biology of Life Duration. New York, Alfred A. Knopf, 1928
  4. ^ R. Klatz and R. Goldman: Stopping the clock or How to stop time. Keats Publishing, Vier Flamingos Verlag, Rheine, 1999, pp. 27-42. ISBN 3-928-30622-7
  5. NM Nitschke: The influence of the carotenoids lycopene and lutein on the antioxidant status of the dog. Dissertation, LMU Munich, 2005, p. 57.
  6. JO Holloszy include: Effect of voluntary exercise on longevity of rats. In: J Appl Physiol 59, 1985, pp. 826-831. PMID 4055572
  7. ^ IM Lee et al.: Exercise intensity and longevity in men. The Harvard Alumni Health Study. In: J Am Med Assoc 273, 1995, pp. 1179-1184. PMID 7707624
  8. JR Speakman et al .: Living fast and dying old: cross sectional variation in daily energy expenditure is positively linked to lifespan in female mice. In: Energy Metabolism in Animals A Chwalibog and K. Jakobsen (editors), Wageningen Press, 2000, pp. 269-272. ISBN 9-074-13483-1
  9. AJ Hulbert et al .: Metabolic rate is not reduced by dietary restriction or by lowered insulin / IGF-1 signaling and is not correlated with individual lifespan in Drosophila melanogaster. In: Exp Gerontol 39, 2004, pp. 1137-1143. PMID 15288688
  10. AJ Hulbert et al.: Life and death: metabolic rate, membrane composition, and life span of animals. In: Physiol Rev 87, 2007, pp. 1175-1213. PMID 17928583 (Review)