Early life stress increases preadipocyte number and early markers of differentiation in female mice fed a high fat diet

Abstract

Adipogenenic and lipogenenic functions are complex processes influenced by many mechanisms that become dysregulated with obesity. We have previously shown that Maternal Separation and Early Weaning (MSEW), a mouse model of early life stress, exacerbates high fat diet (HF)‐induced fat deposition in female mice, but not male mice. Therefore, the aim of this study was to determine the effects of MSEW on energy expenditure and on adipogenesis in response to diet‐induced obesity. MSEW and control mice were weaned either a low fat diet (LF, 10 Kcal from fat) or HF (60 % Kcal from fat) for 20 weeks. The adiposity of female MSEW mice fed a HF increased significantly compared to controls (42.09 ± 09 vs. 33.40±1.5 % body weight, respectively, P<0.05). The respiratory exchange ratio (RER), a function of macronutrient utilization and molecular interconversion, was not different between HF‐fed MSEW and control mice (0.84±0.03 vs. 0.83±0.01). In addition, MSEW and control females showed similar resting energy expenditure (REE, 0.50±0.02 vs. 0.47±0.02 kcal/hr), and food intake (38.6±1 vs. 41.03±1.0 kcals, respectively). Preadipocyte number was determined in subcutaneous white adipose tissue (scWAT) and gonadal WAT (gWAT) by cell sorting via flow cytometry. The percentage of CD45‐/CD31‐/CD34+/Sca1+ committed preadipocytes found in the stromal vascular fraction from scWAT was similar in MSEW and control mice (65.25±1.01 vs. 71.25±3.4 %, respectively). However, MSEW increased the total percentage of committed preadipocytes found in gWAT compared to controls (78.3±2.45 vs. 65.75±2.95%, respectively, p=0.063). In a subset of mice, fresh scWAT and gWAT were collagenase‐digested for adipocyte differentiation studies. Preadipocytes were harvested at day 0 of confluence (T0) or differentiated into mature adipocytes (after 8 days of differentiation, T8) to determine the expression of genes involved in early and late stage of adipocyte differentiation. At T0, the expression of leptin, a fat‐derived hormone from mature adipocytes, was significantly increased in scWAT from MSEW mice compared to controls (1.8 ± 0.3 vs. 0.65 ± 0.1 2^ddCT, p<0.05). At T8, female MSEW mice fed a HF showed increased CEBPa (1.13±0.4 vs 0.44 ±1.3 2^ddCT, p<0.05) and CEBPb (3.38±1.5 vs. 0.96±0.3 2^ddCT, p<0.05) and decreased PPARg mRNA (1.41±0.5 vs. 7.19±3.1 2^ddCT, p<0.05). Overall, MSEW‐mediated fat gain was not associated with decreased energy expenditure. However, chronologic expression of genes controlling the maturation process of preadipocytes from scWAT was altered, as well as the percentage of committed preadipocytes found in gWAT was increased from obese MSEW mice. Altogether, this data suggests that adipose tissue from MSEW mice may undergo a second cycle of differentiation more rapidly than control counterparts; this combined with the increased percentage of preadipocytes may be a possible origin of exacerbated HF‐induced obesity due to MSEW.Support or Funding InformationR01 HL135158 and R01 HL135158S1