Intrinsic differences in adipocyte precursor cells from different white fat depots

Abstract

Obesity and body fat distribution are important risk factors for the development of type 2 diabetes and metabolic syndrome. Evidence has accumulated that this risk is related to intrinsic differences in behavior of adipocytes in different fat depots. In the current study, we demonstrate that adipocyte precursor cells (APCs) isolated from visceral and subcutaneous white adipose depots of mice have distinct patterns of gene expression, differentiation potential, and response to environmental and genetic influences. APCs derived from subcutaneous fat differentiate well in the presence of classical induction cocktail, whereas those from visceral fat differentiate poorly but can be induced to differentiate by addition of bone morphogenetic protein (BMP)-2 or BMP-4. This difference correlates with major differences in gene expression signature between subcutaneous and visceral APCs. The number of APCs is higher in obesity-prone C57BL/6 mice than obesity-resistant 129 mice, and the number in both depots is increased by up to 270% by exposure of mice to high-fat diet. Thus, APCs from visceral and subcutaneous depots are dynamic populations, which have intrinsic differences in gene expression, differentiation properties, and responses to environmental/genetic factors. Regulation of these populations may provide a new target for the treatment and prevention of obesity and its metabolic complications.

FIG. 1.

Frequency of APCs and other SVF cells in SC vs. Vis depots. Typical FACS sorting analysis of APCs and other SVF cells from SC and Vis depots isolated from male mice aged 7–9 weeks. Data were calculated using only live cells. Double positive CD34, SCA1 (and CD45⁻, CD31⁻, and Ter119⁻) cells were considered APCs, whereas CD45⁺, CD31⁺, and Ter119⁺ cells were considered as other SVF cells. A: Number of cells per depot. B: Percent of APCs in both depots relative to other SVF cells. Data are mean ± SEM of n = 4 independent experiments. Statistics were analyzed by Student t test (two-way, unequal variance). *P < 0.05.

FIG. 2.

Higher differentiation capacity in APCs from SC than from Vis depots. After FACS sorting, APCs from SC and Vis depots were placed in culture; upon 80% confluence, they were treated with or without BMP2 or BMP4 and 2 days later, were induced to differentiate (insulin, isobutylmethylxanthine, dexamethasone, and rosiglitazone). Seven days after induction of differentiation, they were photographed to evaluate for lipid-containing mature adipocytes (A and B) or lysed, mRNA extracted, and processed for quantitative PCR to evaluate expression changes on adipocyte differentiation genes (C and D). Graphs show fold changes vs. N Vis. N, control without BMPs or IC; BMP4 IC, BMP4 pretreatment followed by IC. Data are mean ± SEM of n = 2 independent experiments. Statistics were analyzed by Student t test (two-way, unequal variance). *P < 0.05.

FIG. 3.

Genetic and environmental impact on number (#) and percentage (%) of APCs and other SVF cells from Vis and SC fat depots. FACS sorting analysis of Vis and SC APCs and other SVF cells. Data were calculated using only live cells. Double positive CD34, SCA1 (and CD45⁻, CD31⁻, and Ter119⁻) cells were considered APCs, whereas CD45⁺, CD31⁺, and Ter119⁺ cells were considered as other SVF cells. A: 8-week-old vs. 1-year-old C57BL/6 mice. m, month. B: C57BL/6 (B6) vs. 129 mice (3 months old). C: C57BL/6 male (M) vs. female (F) mice (6 months old). Five mice per group were used in two independent experiments. Data are mean ± SEM. Statistics were analyzed by Student t test (two-way, unequal variance). *P < 0.05.

FIG. 4.

Effect of HFD on number (#) and percentage (%) of APCs and other SVF cells from Vis and SC fat depots. FACS sorting analysis of Vis and SC APCs and other SVF cells. Data were calculated using only live cells. Double positive CD34, SCA1 (and CD45⁻, CD31⁻, and Ter119⁻) cells were considered APCs, whereas CD45⁺, CD31⁺, and Ter119⁺ cells were considered as other SVF cells. FACS sorted cells from mice placed on chow diet (CD) or HFD for 1, 2, and 4 weeks starting at age 4 weeks (A) or 8 weeks (B). Three to five mice per group were used in two independent experiments. Data are mean ± SEM. Statistics were analyzed by Student t test (two-way, unequal variance). *P < 0.05.