Adipose tissue is highly
plastic and can respond rapidly to changes in nutrient intake through fat-cell
hypertrophy or hyperplasia.
Previously it was thought that
the number of adipocytes remained constant, and that fat gain during adulthood
was the result of adipocyte hypertrophy, not hyperplasia (1). However that
supposition didn’t quite fit well with the fact that fat-cell progenitors from
different body-fat depots have distinct properties (2,3,4).
The notion of fix adipocyte
cell number was challenged by an overfeeding study and measurement of adipocyte
size and number (5). This study reported a quick increase in femoral adipose
tissue through formation of new fat cells, gain of only ∼1.6 kg of lower-body fat (femoral fat) resulted in
the creation of ∼2.6 billion new adipocytes
within 8 weeks (5).
Newly formed mature adipocytes
arise from preadipocytes, resident in fat depots (6,7,8,9). In principle if
adipocytes exceed an average lipid content of ∼0.7–0.8 μg per cell new cells are created (5), in other words when adipocytes reach
a critical volume or threshold they secrete factors that recruit new adipocytes
(10,11,12). This response to overfeeding depends partially on sex and baseline
adipocyte size.
The number of leg fat cells is
greater in overweight than in normoweight persons (13), and obesity is
associated with abdominal s.c. adipocyte hyperplasia (13,14,15).
This adipose tissue plasticity coupled
with the fact that morbid obesity can be developed to a body mass index (BMI)
higher than 40 and even 50 (16), illustrates the immense capacity for the
body to store fat, unlike stores for carbohydrates and protein.
Would you like to know more? Subscribe!
References:
1. Spalding KL,
et al. (2008) Dynamics of fat cell turnover in humans. Nature 453:783–787
2. Tchkonia T, et al. (2002) Fat depot origin affects adipogenesis in primary cultured and cloned human preadipocytes. Am J Physiol Regul Integr Comp Physiol 282:R1286–R1296.
3. Kirkland JL, Tchkonia T, Pirtskhalava T, Han J, Karagiannides I (2002) Adipogenesis and aging: Does aging make fat go MAD? Exp Gerontol 37:757–767.
2. Tchkonia T, et al. (2002) Fat depot origin affects adipogenesis in primary cultured and cloned human preadipocytes. Am J Physiol Regul Integr Comp Physiol 282:R1286–R1296.
3. Kirkland JL, Tchkonia T, Pirtskhalava T, Han J, Karagiannides I (2002) Adipogenesis and aging: Does aging make fat go MAD? Exp Gerontol 37:757–767.
4.
Karagiannides I, et al. (2001) Altered expression of C/EBP family members
results indecreased adipogenesis with aging. Am J Physiol Regul Integr Comp
Physiol 280:
R1772–R1780.
5. Yourka D.
Tchoukalova, Susanne B. Votruba, Tamara Tchkonia, Nino Giorgadze, James L.
Kirkland and Michael D. Jensen. Regional differences in cellular mechanisms of
adipose tissue gain with overfeeding. Proc Natl Acad Sci U S A. 2010 Oct
19;107(42):18226-31
6. Crossno JT,
Jr., Majka SM, Grazia T, Gill RG, Klemm DJ (2006) Rosiglitazone promotes
development of a novel adipocyte population from bone marrow-derived
circulating progenitor cells. J Clin Invest 116:3220–3228.
7. Koh YJ, et
al. (2007) Bone marrow-derived circulating progenitor cells fail to transdifferentiate
into adipocytes in adult adipose tissues in mice. J Clin Invest 117:3684–3695.
8. Scadden DT
(2007) The weight of cell identity. J Clin Invest 117:3653–3655.
9. Tang W, et
al. (2008) White fat progenitor cells reside in the adipose vasculature. Science
322:583–586.
10. Faust IM,
Johnson PR, Stern JS, Hirsch J (1978) Diet-induced adipocyte number increase in
adult rats: A new model of obesity. Am J Physiol 235:E279–E286.
11. DiGirolamo
M, Fine JB, Tagra K, Rossmanith R (1998) Qualitative regional differences in
adipose tissue growth and cellularity in male Wistar rats fed ad libitum. Am J
Physiol 274:R1460–R1467.
12. Marques BG,
Hausman DB, Martin RJ (1998) Association of fat cell size and paracrine growth
factors in development of hyperplastic obesity. Am J Physiol 275: R1898–R1908.
13. Tchoukalova
YD, et al. (2008) Subcutaneous adipocyte size and body fat distribution. Am J
Clin Nutr 87:56–63.
14. Tchoukalova
Y, Koutsari C, Jensen M (2007) Committed subcutaneous preadipocytes are reduced
in human obesity. Diabetologia 50:151–157.
15. Drolet R,
et al. (2008) Hypertrophy and hyperplasia of abdominal adipose tissues in
women. Int J Obes (Lond) 32:283–291.
16. Sturm R. Increases in clinically severe obesity in the
US: 1986–2000. Archives of Internal Medicine. 2003;163(18):2146–2148.
