一项研究发现，上半身和下半身的脂肪组织增加的重量不同，这部分是由于脂肪细胞前体的差异。此前的研究提示上半身脂肪增加会提高代谢疾病的风险，而下半身脂肪的增加会减少这种风险，但是其中的原因尚不清楚。为了确定人体脂肪积累如何增长，Michael D. Jensen及其同事检验了过度进食对于人的上半身和下半身皮下脂肪组织的影响。这组作者招募了28位健康的成年志愿者，在8周的时间里要求他们进食直到比平常的程度饱很多。
此外，这组志愿者食用了冰激凌奶昔、大号士力架和Boost Plus能量饮料等补充食物。这组作者发现，在经过8周之后，这组志愿者上半身脂肪增加了大约2千克，下半身的脂肪增加了大约1.5千克。这组作者报告说，上半身脂肪细胞的平均尺寸而非细胞数量在过度进食之后增加，而大腿脂肪细胞的情况正好相反。上半身而非大腿的脂肪细胞前体显示出了参与脂肪合成的蛋白质的RNA信息浓度更高。这组作者说，这些发现可能为所谓的大腿脂肪的有益作用提供一个可能的解释。（生物谷Bioon.com）
生物谷推荐英文摘要：
PNAS doi: 10.1073/pnas.1005259107
Regional differences in cellular mechanisms of adipose tissue gain with overfeeding
Yourka D. Tchoukalovaa,b, Susanne B. Votrubaa, Tamara Tchkoniac, Nino Giorgadzec, James L. Kirklandc, and Michael D. Jensena,1
aEndocrine Research Unit and
cRobert and Arlene Kogod Center on Aging, Mayo Clinic, Rochester, MN 55905; and
bPennington Biomedical Research Center, Baton Rouge, LA 70808
Body fat distribution is an important predictor of the metabolic consequences of obesity, but the cellular mechanisms regulating regional fat accumulation are unknown. We assessed the changes in adipocyte size (photomicrographs) and number in response to overfeeding in upper- and lower-body s.c. fat depots of 28 healthy, normal weight adults (15 men) age 29 ± 2 y. We analyzed how these changes relate to regional fat gain (dual energy X-ray absorptiometry and computed tomography) and baseline preadipocyte proliferation, differentiation [peroxisome proliferator-activated receptor-γ2 (PPARγ2) and CCAAT/enhancer binding protein-α (C/EBPα) mRNA]), and apoptotic response to TNF-α. Fat mass increased by 1.9 ± 0.2 kg in the upper body and 1.6 ± 0.1 kg in the lower body. Average abdominal s.c. adipocyte size increased by 0.16 ± 0.06 μg lipid per cell and correlated with relative upper-body fat gain (r = 0.74, P & 0.0001). However, lower-body fat responded to overfeeding by fat-cell hyperplasia, with adipocyte number increasing by 2.6 ± 0.9 × 109 cells (P & 0.01). We found no depot-differences in preadipocyte replication or apoptosis that would explain lower-body adipocyte hyperplasia and abdominal s.c. adipocyte hypertrophy. However, baseline PPARγ2 and C/EBPα mRNA were higher in abdominal than femoral s.c. preadipocytes (P & 0.005 and P & 0.03, respectively), consistent with the ability of abdominal s.c. adipocytes to achieve a larger size. Inherent differences in preadipocyte cell dynamics may contribute to the distinct responses of different fat depots to overfeeding, and fat-cell number increases in certain depots in adults after only 8 wk of increased food intake.
