CIDEA expression in SAT from adolescent girls with obesity and unfavorable patterns of abdominal fat distribution

Abstract

Objective: This study investigated whether variations in cell death-inducing DNA fragmentation factor alpha subunit-like effector A (CIDEA) mRNA expression and protein levels are modulated by the pattern of abdominal fat distribution in adolescent girls with obesity.

Methods: This study recruited 35 adolescent girls with obesity and characterized their abdominal fat distribution by magnetic resonance imaging. Participants had only a periumbilical/abdominal (n = 14) or a paired abdominal and gluteal subcutaneous adipose tissue (SAT) biopsy (n = 21). CIDEA expression was determined by reverse transcription-polymerase chain reaction, CIDEA protein level by Western blot, and the turnover of adipose lipids and adipocytes by ² H₂ O labeling. In six girls, a second abdominal SAT biopsy was performed (after ~34.2 months) to explore the weight gain effect on CIDEA expression in abdominal SAT.

Results: CIDEA expression decreased in abdominal SAT from participants with high visceral adipose tissue (VAT)/(VAT+SAT); CIDEA inversely correlated with number of small adipocytes, with the increase in preadipocyte proliferation, and with adipogenesis. A strong inverse correlation was found between CIDEA protein level with the newly synthetized glycerol (r = -0.839, p = 0.0047). Following weight gain, an increase in adipocytes' cell diameter with a decrease in CIDEA expression and RNA-sequencing transcriptomic profile typical of adipocyte dysfunction was observed.

Conclusions: Reduced expression of CIDEA in girls with high VAT/(VAT+SAT) is associated with adipocyte hypertrophy and insulin resistance.

Figure 1.. CIDEA mRNA expression is reduced in abdominal SAT in high VAT/(VAT+SAT) group and correlates with an increase in markers associated to insulin resistance.

(A) CIDEA mRNA expression in abdominal SAT (Low VAT/(VAT+SAT): n=21 subjects, High VAT/(VAT+SAT): n=14 subjects) and gluteal SAT (Low VAT/(VAT+SAT): n=7 subjects, High VAT/(VAT+SAT): n=14 subjects). (B) Representative blots showing CIDEA levels in abdominal and gluteal SAT in low and high VAT/(VAT+SAT) groups and CIDEA protein quantification showing significant reduction in abdominal SAT in high VAT/(VAT+SAT) group and no variation in gluteal SAT. (Abdominal low VAT/(VAT+SAT): n=7 subjects, abdominal high VAT/(VAT+SAT): n=5 subjects; gluteal low VAT/(VAT+SAT): n=5 subjects, gluteal high VAT/(VAT+SAT): n=6 subjects). Data are expressed as mean ± SEM. All data were analyzed using multiple linear regression adjusted for age, race and BMI. (C-D) CIDEA mRNA expression significantly correlates with HOMA-IR and WBISI, (E) inversely correlates with Adipose tissue Insulin Resistance, (F) fasting insulin, (G) fasting C-peptide, and (H) fasting serum FFA. Data were analyzed using Pearson’s correlation after logarithmic transformation of x and y variables and using all the subjects enrolled including both Low and High VAT/(VAT+SAT) (n=32–35 subjects).

Figure 2.. Association between CIDEA mRNA expression and insulin resistance, adipocyte measurements and lipolysis.

(A) CIDEA mRNA expression correlates with percentage of new pre-adipocytes (n=12 subjects), and (C) with the percentage of new mature adipocytes (n=13 subjects). (D) CIDEA protein level correlates with the percentage of newly synthesized glycerol as index of lipolysis (n=8 subjects). (B-D) Data were analyzed using Spearman correlation. (E-F) Blots and protein quantification showing significant increase in both ATGL and HSL phosphorylation levels in abdominal SAT in high vs low VAT/(VAT+SAT) groups (Low VAT/(VAT+SAT): n=4 subjects, high VAT/(VAT+SAT): n=5 subjects). (G) CIDEA mRNA expression in subjects grouped by VAT/(VAT+SAT) and characterized by insulin sensitivity (IS) or insulin resistance (IR). Data are expressed as mean ± SEM and analyzed using multiple linear regression adjusted by age, BMI, and race. IS Low VAT/(VAT+SAT) n=14 subjects, IR Low VAT/(VAT+SAT) n=7, IS High VAT/(VAT+SAT) n=7, IR High VAT/(VAT+SAT) n=7.

Figure 3.. CIDEA mRNA expression significantly decreases in abdominal SAT after weight gain.

(A) CIDEA mRNA expression in SAT collected at baseline and after gaining weight (follow-up). A linear model was fitted using generalized least squares with unstructured covariance, corrected for change in age and BMI (n=6 subjects each group) (B) Inverse correlation between percent change in CIDEA mRNA expression and percent change in cell peak. Data were analyzed using Spearman correlation (n=6 subjects each group). (C) Heatmap originated from RNA-seq analysis of SAT collected at baseline and during follow-up biopsy. (D-E) Canonical pathways enrichment analysis for down-/up-regulated genes in follow up SAT biopsy compared to baseline biopsy. The bar represents the percent of genes up-/down-regulated within the specific pathways. The solid line represents the -log(p value) for each pathway (n=3 subjects each group).