Department of Clinical Chemistry and Transfusion Medicine, Institute of Biomedicine, Sahlgrenska Academy, University of Gothenburg, S-405 30 Gothenburg, Sweden.
BMC Endocr Disord. 2014 Jan 22;14:7. doi: 10.1186/1472-6823-14-7.
Adipose tissue (AT) contributes to metabolic dysfunction through imbalanced production of adipokines, including cytokines. Visceral AT in particular is associated with metabolic disorders, indicating a specific secretory status. The relative significance of different human AT depots in adipokine release is not fully known. Further, previous in vitro systems usually included medium containing bovine serum albumin (BSA), which may induce cytokine release. Our aim was to compare release of a number of adipokines/cytokines - all implicated in insulin resistance - from human subcutaneous and visceral AT in a short-term incubation system minimizing cytokine induction and including repeated measurements during 24 h. A prerequisite was to evaluate a potential alternative to BSA in the incubation medium.
Subcutaneous and/or visceral AT from 17 patients (age 20-68 years; BMI 22.6-56.7 kg/m2) undergoing elective surgery was incubated for 2, 4, 6, 8, and 24 h in medium with or without 1% BSA or human serum albumin (HSA). Medium concentrations of adiponectin, chemerin, nine cytokines, dipeptidyl peptidase 4 (DPP4), and omentin were analyzed by multiplex immunoassay or ELISA. Adipocyte size, AT macrophage density, and medium concentrations of endotoxin were determined.
Cytokine release was induced by BSA but not by HSA. In evaluation of the final incubation protocol including 1% HSA, and as expected, adiponectin release was higher from subcutaneous biopsies of nonobese than of obese subjects and inversely associated with adipocyte size; omentin was released almost exclusively from visceral AT. Exploratory incubations revealed more abundant release of chemerin, cytokines (except IL-6), and DPP4 from the visceral depot, while adiponectin release was higher from subcutaneous than visceral AT. Release was linear for a maximum of 2-6 h. Macrophage density was higher in visceral than subcutaneous AT. Levels of endotoxin in the medium were negligible.
Adiponectin, chemerin, many cytokines, and DPP4 are released from human AT in a depot-dependent manner. These results highlight functional differences between visceral and subcutaneous AT, and a mechanistic link between regional fat accumulation and metabolic disorders. Supplementation of human AT incubation medium with HSA rather than BSA is recommended to minimize induction of cytokine release.
脂肪组织（AT）通过产生不平衡的脂肪因子，包括细胞因子，导致代谢功能障碍。特别是内脏 AT 与代谢紊乱有关，表明其具有特定的分泌状态。不同人体 AT 储存库在脂肪因子释放中的相对重要性尚不完全清楚。此外，以前的体外系统通常包括含有牛血清白蛋白（BSA）的培养基，这可能会诱导细胞因子释放。我们的目的是比较人体皮下和内脏 AT 在短期孵育系统中释放多种脂肪因子/细胞因子的情况，这些细胞因子都与胰岛素抵抗有关，并且在 24 小时内尽量减少细胞因子诱导和重复测量。前提是评估孵育培养基中 BSA 的潜在替代物。
对 17 名（年龄 20-68 岁；BMI 22.6-56.7kg/m2）接受择期手术的患者的皮下和/或内脏 AT 进行孵育，在含有或不含有 1%BSA 或人血清白蛋白（HSA）的培养基中孵育 2、4、6、8 和 24 小时。通过多重免疫测定或 ELISA 分析脂肪因子、趋化因子、9 种细胞因子、二肽基肽酶 4（DPP4）和网膜素的浓度。测定脂肪细胞大小、AT 巨噬细胞密度和培养基中内毒素浓度。
BSA 诱导细胞因子释放，但 HSA 不诱导。在评估最终孵育方案（包括 1%HSA）时，与预期的一样，非肥胖者的皮下活检释放的脂联素高于肥胖者，并且与脂肪细胞大小呈负相关；网膜素几乎仅从内脏 AT 中释放。探索性孵育显示，内脏储存库中趋化因子、细胞因子（除 IL-6 外）和 DPP4 的释放更为丰富，而脂肪因子从皮下比内脏 AT 释放更多。释放在 2-6 小时内呈线性。内脏 AT 中的巨噬细胞密度高于皮下 AT。培养基中的内毒素水平可忽略不计。
脂联素、趋化因子、多种细胞因子和 DPP4 以依赖储存库的方式从人 AT 中释放。这些结果突出了内脏和皮下 AT 之间的功能差异，以及区域脂肪堆积与代谢紊乱之间的机制联系。建议在人 AT 孵育培养基中补充 HSA 而不是 BSA，以尽量减少细胞因子释放的诱导。
