ATP-binding cassette transporter A1 (ABCA1) expression in adipose tissue and its modulation with insulin resistance in obesity

Figures & data

Table 1 Clinical characteristics of participants

Variables	Control group (lean) (n=28)		Study group (obese) (n=34)		P-value
	Mean ± SEM	Range	Mean ± SEM	Range
Anthropometrics
Age (years)	37±2	18–58	38±2	25–60	0.94
BMI (kg/m^2)	22.33±0.34	18.03–24.61	44.48±0.92	34.01–54.20	<0.0001
WC (cm)	81.1±0.6	75.0–87.0	120.1±2.1	101.0–139.0	<0.0001
Lipid profile
Total cholesterol (mg/dL)	135.4±5.4	75.0–198.0	156.2±5.7	96.0–266.0	0.01
HDL cholesterol (mg/dL)	45.9±1.2	35.0–60.0	44.4±1.2	34.0–65.0	0.4
LDL cholesterol (mg/dL)	90.9±4.1	47.0–142.0	108.0±4.8	65.0–195.0	0.01
VLDL cholesterol (mg/dL)	13.8±0.9	7.0–26.0	17.2±0.9	9.0–33.0	0.01
TG (mg/dL)	105.1±8.6	44.0–215.0	140.5±7.5	66.0–250.0	0.002
NEFA (mmol/L)	0.30±0.03	0.09–0.64	0.67±0.03	0.38–1.08	<0.0001
Glucose homeostasis
Fasting glucose (mmol/L)	4.81±0.07	4.17–5.83	5.50±0.13	3.89–6.94	<0.0001
Fasting insulin (µIU/mL)	7.34±1.00	1.90–21.40	13.68±1.23	1.00–30.20	0.0003
HOMA-IR	1.58±0.22	0.38–5.02	3.40±0.33	0.31–7.60	<0.0001
Adipo-IR	14.40±2.56	1.03–53.76	57.42±6.32	3.18–146.5	<0.0001

Abbreviations: adipo-IR, adipose tissue insulin resistance; BMI, body mass index; HDL, high-density lipoprotein; HOMA-IR, homeostatic model assessment for insulin resistance; LDL, low-density lipoprotein; NEFA, non-esterified fatty acids; SEM, standard error of mean; TG, triglyceride; VLDL, very low-density lipoprotein; WC, waist circumference.

Figure 1 Expression of ABCA1, adiponectin and GLUT4 in the adipose tissue from individuals who were lean and individuals who were obese.

Notes: Expression of (A) abca1 (P=0.04 and 0.4), adipoq (P=0.001 and 0.5) and glut4 (slc2a4) (P=0.0004 and 0.0002) at the mRNA level in specified adipose tissue compartments from individuals who were lean and obese. Expression levels normalized to geometric mean of three reference genes (actb, hprt1 and polr2a). Statistical test: Wilcoxon rank sum test (P-value: ns = not significant, *P<0.05, **P<.01, ***P<0.001. (B) Representative images of immunohistochemical staining for ABCA1 in specified adipose tissue compartments. Magnification 10×. Scale bar =100 µm. (C) Heat map showing immunoreactivity scoring for the expression of ABCA1 and GLUT4 (SLC2A4) at the protein level in visceral and subcutaneous adipose tissue compartments from individuals who were lean and obese (lean, n=28; obese, n=34).
Abbreviation: ns, nonsignificant.

Table 2 Clinical characteristics of individuals grouped as insulin sensitive and insulin resistant

Variables	Insulin sensitive (n=36)		Insulin resistant (n=26)		P-value
	Mean ± SEM	Range	Mean ± SEM	Range
Anthropometrics
Age (years)	38±2	18–60	37±2	20–59	0.78
BMI (kg/m^2)	29.82±1.79	18.03–51.78	40.93±2.03	18.34–54.20	0.0001
WC (cm)	95.17±3.42	75.0–136.0	112.6±3.8	77.0–139.0	<0.001
Lipid profile
Total cholesterol (mg/dL)	140.6±5.9	75.0–266.0	155.5±5.4	96.0–216.0	0.08
HDL cholesterol (mg/dL)	44.7±1.1	35.0–60.0	45.7±1.4	34.0–65.0	0.57
LDL cholesterol (mg/dL)	95.5±4.5	47.0–195.0	106.9±4.8	65.0–157.0	0.1
VLDL cholesterol (mg/dL)	14.9±0.9	7.0–33.0	16.7±1.0	9.0–29.0	0.18
TG (mg/dL)	111.0±7.8	44.0–215.0	143.1±8.4	70.0–250.0	0.007
NEFA (mmol/L)	0.41±0.04	0.09–1.04	0.63±0.05	0.14–1.08	0.0003
Glucose homeostasis
Fasting glucose (mmol/L)	4.83±0.09	4.17–5.83	5.69±0.12	4.78–6.89	<0.0001
Fasting insulin (µIU/mL)	6.08±0.51	1.00–10.90	17.38±1.13	9.60–30.20	<0.0001
HOMA-IR	1.28±0.10	0.31–2.30	4.38±0.29	2.54–7.60	<0.0001
Adipo-IR	17.10±2.56	1.03–65.52	66.93±7.07	14.62–146.5	<0.0001

Abbreviations: adipo-IR, adipose tissue insulin resistance; BMI, body mass index; HDL, high-density lipoprotein; HOMA-IR, homeostatic model assessment for insulin resistance; LDL, low-density lipoprotein; NEFA, non-esterified fatty acids; SEM, standard error of mean; TG, triglyceride; VLDL, very low-density lipoprotein; WC, waist circumference.

Figure 2 Expression of ABCA1, adiponectin and GLUT4 in adipose tissue from IS and IR individuals.

Notes: Expression of (A) abca1 (P=0.0001 and 0.97), adipoq (P=0.04 and 0.24) and glut4 (slc2a4) (P=0.001 and 0.008) at the mRNA level. (B) Heat map showing immunoreactivity scoring for ABCA1 and GLUT4 (SLC2A4) in specified adipose tissue compartments from individuals who were IS and IR (IS, n=36; IR, n=26). (C) Expression of abca1 mRNA and (D) protein in visceral adipose tissue compartment in specified groups (n=23, 13 and 21, respectively). Statistical test: Wilcoxon rank sum test (P-value: *P<0.05, **P<.01, ***P<0.001.
Abbreviations: IR, insulin resistant; IS, insulin sensitive; ns, not significant.

Figure 3 Correlation between abca1 mRNA expression in the visceral adipose tissue with insulin resistance markers and mean adipocyte area.

Notes: Correlation between abca1 mRNA in the visceral adipose tissue with (A) HOMA-IR (n=62) and (B) adipo-IR (n=62). (C) Correlation between mean visceral adipocyte area in µm² and abca1 mRNA expression in the visceral adipose tissue (n=48). Statistical test: Pearson correlation.
Abbreviations: adipo-IR, adipose tissue insulin resistance; HOMA-IR, homeostatic model assessment for insulin resistance.