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Don't fill adipocytes beyond their capacity

Posted by pbio on 07 May 2009 at 22:26 GMT

Author: Isabel Azevedo
Position: Professor of Biochemistry
Institution: Depart Biochemistry, Fac. Medicine, University of Porto, Portugal
Additional Authors: Rosário Monteiro, Conceição Calhau, Manuel NMP Alçada
Submitted Date: September 25, 2008
Published Date: October 3, 2008
This comment was originally posted as a “Reader Response” on the publication date indicated above. All Reader Responses are now available as comments.

The interesting and lucid essay by Samuel Virtue and Antonio Vidal-Puig [1] on how obesity causes insulin resistance (and associated diseases) strongly emphasises the adipose tissue expandability hypothesis. We fully agree with this vision, and would like to add a further dimension to this expandability hypothesis.
While the mentioned expandability limits refer to overall capacity of an individual to expand his fat mass, the existence of a limit to the expandability of adipocytes themselves has not been considered.
We have published on the tendency of adipocytes to rupture, this rupture being more facile the bigger the adipocyte [2]. Cinti et al [3] had already provided sound evidence for macrophage aggregation around dead adipocytes, a phenomenon more frequent in adipose tissue with larger adipocytes. Our proposal added another putative mechanism relating adipocyte hypertrophy (a phenomenon related to the conflict between fat expansion and capacity to produce new adipocytes) with obesity related inflammation.
Adipocyte rupture at the basis of inflammation is in good agreement with the fact that adipose tissue localization markedly influences its consequences on health, the most pathogenic obesity being the visceral one [4, 5,]. As a matter of fact, adipocytes in abdominal cavity are subject to suddenly varying pressures, as occurs for example during cough, abdominal crunch or diverse physical exercises [6], as well as during obstructive sleep apnoea [7].
Both the adipose tissue expandability hypothesis as put forward by Samuel Virtue and Antonio Vidal-Puig, and the adipocyte expandability hypothesis we suggest, point to the advantage of increasing the number and decreasing the size of adipocytes. We recently verified that chronic consumption of green tea exerts those effects, at least in the rat [8].

1. Virtue S, Vidal-Puig A (2008) It's not how fat you are, it's what you do with it that counts. PLoS Biol 6(9): e237.doi:10.1371/journal.pbio.0060237
2. Monteiro R, de Castro PM, Calhau C, Azevedo I (2006) Adipocyte size and liability to cell death. Obes Surg 16: 804-806.
3. Cinti S, Mitchell G, Barbatelli G, Murano I, Ceresi E, et al. (2005) Adipocyte death defines macrophage localization and function in adipose tissue of obese mice and humans. J Lip Res 46: 2347-2355.
4. Carey VJ, Walters EE, Colditz GA, Solomon CG, Willett WC, et al. (1997) Body fat distribution and risk of non-insulin-dependent diabetes mellitus in women. The Nurses' Health Study. Am J Epidemiol 145: 614-619.
5. Lean MEJ, Han TS, Seidell JC (1998) Impairment of health and quality of life in people with large waist circumference. Lancet 351: 853-856.
6. Cobb WS, Burns JM, Kercher KW, Matthews BD, Norton HJ, Heniford BT (2005) Normal intraabdominal pressure in healthy adults. J Surg Res 129(2): 231-235.
7. Monteiro R, Calhau C, Azevedo I (2007) Obstructive sleep apnoea and adipocyte death. Eur J Heart Fail.9(1):103-104
8. Monteiro R, Assunção M, Andrade JP, Neves D, Calhau C, Azevedo I (2007) Chronic green tea consumption decreases body mass, induces aromatase expression, and changes proliferation and apoptosis in adult male rat adipose tissue. J Nutr (in press).

No competing interests declared.