Organ-o-penia

Abstract

INVITED EDITORIALSOrgan-o-peniaT. M. ManiniT. M. ManiniPublished Online:01 Jun 2009https://doi.org/10.1152/japplphysiol.00315.2009This is the final version - click for previous versionMoreSectionsPDF (81 KB)Download PDF ToolsExport citationAdd to favoritesGet permissionsTrack citations ShareShare onFacebookTwitterLinkedInEmailWeChat the loss in appendicular muscle and bone mass with increasing age is a well-defined event (4, 11). While this event has been acknowledged for centuries, in vivo data to quantify the degree of age-related changes in muscle and bone mass have only become available, primarily due to new imaging technologies, in the past two decades. Investigators in these fields of research even gave names to the age-related conditions: sarcopenia and osteopenia. The placement of specific names has sparked research into discovering the causes and consequences in hopes of developing interventions for reducing the burden of these conditions.While scientists in the field have a clear understanding of the changes in appendicular muscle and bone mass, information is lacking about the age-related changes in other organ systems that compose total fat-free mass (FFM). The first report of age-related change in organ mass occurred in 1926 where autopsy studies were performed on ∼2,200 men and women (2). These data suggested a 32% reduction in liver mass, a 23% reduction in kidney mass, a 55% reduction in spleen mass, but a 10% increase in heart mass from age 20 to 80 yr. While this and other autopsy studies demonstrated an age-related decline in mass of most organs (6), these data are criticized because of the lack of information regarding the cause of death and the delay in which the organs are harvested that may affect fluid retention. Although other evidence exists to support age-related decline in organ mass (5), there are no in vivo data addressing such an issue. Knowledge about how other organ systems change with age would develop an understanding of the aging process from a mechanistic standpoint, as well as establish potential consequences similar to what has occurred for both bone and muscle mass.Eighty-three years later, new data have filled an important gap in the literature. Using the exact but tedious procedure of analyzing whole body magnetic resonance scans, He and colleagues (8), in their study in the Journal of Applied Physiology, bring to the forefront that most organs demonstrate a similar phenomenon as that seen in muscle and bone. Magnetic resonance images were used to calculate organ volumes to estimate the mass of the liver, brain, kidney, spleen, and left ventricle of the heart. Additionally, because the loss in FFM may explain changes in organ mass, the authors also measured whole body FFM using dual-energy X-ray absorptiometry. The results demonstrate that aging is associated with a striking decline in all organs except the left ventricle of the heart, regardless of sex, race, and FFM. To demonstrate the relative changes in organ mass, I have generated Fig. 1 using the regression equations provided by the authors. Figure 1, scaled for percent change from 20 to 80 yr of age, was determined for an African-American female with a body mass of 70 kg and height of 1.6 m. It should be noted that the results would look similar in men and Caucasians. For comparison purposes, published data on appendicular muscle mass (4) and bone mass (11) were added. Figure 1 demonstrates that mass of the brain, bone, kidney, liver, and muscle decline at relatively similar rates, between 10 and 20% from the ages of 20 and 80 yr. The spleen, however, demonstrates a dramatic 38% loss in mass.An important question remains. How do these changes in mass influence the function of the organ? We learned from evidence in muscle that the decline in maximal strength is approximately three times greater than the loss of muscle mass (7). As such, what once was thought to be a major pathway toward physical limitations in the elderly, the loss in muscle mass has been found to be a poor predictor when considering muscle strength simultaneously (3). Similarly, the staggering decline in spleen mass should predispose the elderly to infections, autoimmune problems, and thrombosis. However, splenic function measured by assessing pitted blood cell percentage is only modestly reduced, and splenic dysfunction is not a common ailment in the elderly (10). Therefore, it seems plausible that age-related decline in organ mass is reflective of a systemic tissue degradation process with built-in regulators to partially preserve function of that organ. The mechanisms of why organs decline and how they compensate for this change are certainly interesting and worthwhile to pursue.Data by He and colleagues (8) support a systemic process(es) that works in conjunction to degrade tissues. This result is ultimately due to an imbalance of protein synthesis and degradation. For example, several studies in human muscle suggest that the ability to synthesize proteins at rest (1) and following anabolic stimuli (9) is reduced while protein breakdown is not typically altered with aging (12). Very little information is available on how protein balance is misregulated in other organ systems with age, and for obvious reasons no work has been performed in humans (e.g., biopsies from organ tissues are not regularly acceptable). Discovery of such mechanisms may eventually lead to targeted interventions for preserving the structure of organs with hopes that these effects will transfer to maintained organ function.In summary, the study by He and coworkers (8) highlights the degree and consistency of atrophy in most organs with increasing age. This investigation also provides a stepping stone for future research aimed at understanding fundamental concepts in aging. Fig. 1.Predicted organ mass change from 20 to 80 yr of age. Regression coefficients from He et al. (8) were used to estimate a percent change in the left ventricle (LV) of the heart, brain, kidney, liver, and spleen mass. The predicted values were derived by fitting the model for an African-American women with a height of 1.6 m and body mass of 70 kg. Kidney and spleen masses estimated with the natural logarithm were exponentiated for calculating values presented. Appendicular muscle mass was estimated using regression coefficients from Gallagher et al. (4), where body mass and height were used to predict age-related change in African-American women. Bone mass (i.e., bone mineral content) was estimated using data in women from Rico et al. (11). Data from Rico et al. were not adjusted for body mass, and no information was given as to the race distribution of the subject sample.Download figureDownload PowerPointREFERENCES1 Balagopal P, Ljungqvist O, Nair KS. Skeletal muscle myosin heavy-chain synthesis rate in healthy humans. Am J Physiol Endocrinol Metab 272: E45–E50, 1997.Link | ISI | Google Scholar2 Bean B. Composite study of weight of vital organs in man. Am J Phys Anthropol 9: 293–317, 1926.Crossref | Google Scholar3 Clark BC, Manini TM. Sarcopenia =/= dynapenia. J Gerontol 63: 829–834, 2008.Google Scholar4 Gallagher D, Visser M, De Meersman RE, Sepulveda D, Baumgartner RN, Pierson RN, Harris T, Heymsfield SB. Appendicular skeletal muscle mass: effects of age, gender, and ethnicity. J Appl Physiol 83: 229–239., 1997.Link | ISI | Google Scholar5 Gallagher D, Visser M, Wang Z, Harris T, Pierson RN Jr, Heymsfield SB. Metabolically active component of fat-free body mass: influences of age, adiposity, and gender. Metabol Clin Exper 45: 992–997, 1996.Crossref | PubMed | ISI | Google Scholar6 Garby L, Lammert O, Kock K, Thobo-Carlsen B. Weights of brain, heart, liver, kidneys, and spleen in health and apparently healthy adult Danish subjects. Am J Hum Biol 5: 291–296, 1993.Crossref | PubMed | ISI | Google Scholar7 Goodpaster BH, Park SW, Harris TB, Kritchevsky SB, Nevitt M, Schwartz AV, Simonsick EM, Tylavsky FA, Visser M, Newman AB. The loss of skeletal muscle strength, mass, and quality in older adults: The Health, Aging and Body Composition Study. J Gerentol Med Sci 61: 1059–1064, 2006.Crossref | PubMed | ISI | Google Scholar8 He Q, Heshka S, Albu J, Boxt L, Krasnow N, Elia M, Gallagher D. Smaller organ mass with greater age, except for heart. J Appl Physiol (March 26, 2009). doi:10.1152/japplphysiol.90454.2008.Link | ISI | Google Scholar9 Katsanos CS, Kobayashi H, Sheffield-Moore M, Aarsland A, Wolfe RR. A high proportion of leucine is required for optimal stimulation of the rate of muscle protein synthesis by essential amino acids in the elderly. Am J Physiol Endocrinol Metab 291: E381–E387, 2006.Link | ISI | Google Scholar10 Ravaglia G, Forti P, Biagi F, Maioli F, Boschi F, Corazza GR. Splenic function in old age. Gerontology 44: 91–94, 1998.Crossref | ISI | Google Scholar11 Rico H, Revilla M, Villa LF, Alvarez de Buergo M. Age-related differences in total and regional bone mass: a cross-sectional study with DXA in 429 normal women. Osteoporos Int 3: 154–159, 1993.Crossref | ISI | Google Scholar12 Volpi E, Kobayashi H, Sheffield-Moore M, Mittendorfer B, Wolfe RR. Essential amino acids are primarily responsible for the amino acid stimulation of muscle protein anabolism in healthy elderly adults. Am J Clin Nutr 78: 250–258, 2003.Crossref | PubMed | ISI | Google ScholarAUTHOR NOTESAddress for reprint requests and other correspondence: T. M. Manini, Univ. of Florida, Institute on Aging, Dept. of Aging and Geriatric Research, 210 E. Mowry Rd., PO Box 112610, Gainesville, FL 32611-2610 (e-mail: [email protected]) Download PDF Previous Back to Top Next FiguresReferencesRelatedInformationCited ByGeriatric Phenotypes and Their Impact on Oral HealthDental Clinics of North America, Vol. 32Muscle weakness in the elderly: role of sarcopenia, dynapenia, and possibilities for rehabilitation4 May 2012 | European Review of Aging and Physical Activity, Vol. 9, No. 2Vieillissement général normal et pathologiqueAspects physiologiques du vieillissement orofacialEnergy expenditure and agingAgeing Research Reviews, Vol. 9, No. 1 More from this issue > Volume 106Issue 6June 2009Pages 1759-1760 Copyright & PermissionsCopyright © 2009 the American Physiological Societyhttps://doi.org/10.1152/japplphysiol.00315.2009PubMed19359616History Published online 1 June 2009 Published in print 1 June 2009 Metrics