Adipokine signatures of subcutaneous and visceral abdominal fat in normal-weight and obese women with different metabolic profiles

Abstract

Introduction: Metabolic syndrome arises from abnormal adipose function accompanied by insulin resistance. As early factors reflecting/impacting lipid storage dysfunction of adipose tissues, we sought to determine adipokine levels in subcutaneous and visceral adipose tissues (SAT and VAT).

Material and methods: Gene and protein expression levels of leptin, adiponectin, and resistin were analysed in SAT and VAT of normal-weight and overweight/obese women, subclassified according to insulin resistance index, triglyceride, total, low-density lipoprotein (LDL) and high-density lipoprotein (HDL) cholesterol levels into metabolically healthy and "at risk" groups.

Results: Compared with normal-weight women, obese women had higher serum leptin levels (p < 0.05), as well as increased leptin gene and protein expression in VAT. Conversely, expression levels of leptin were lower in SAT of obese women, and minor in the SAT of "at risk" groups of women, compared with weight-matched healthy groups. In addition, lower adiponectin levels were detected in SAT of metabolically healthy obese women (p < 0.01), and lower in SAT and VAT (p < 0.05) of "at risk" obese women compared to healthy, obese women. Significant differences in resistin levels were only observed in obese women; resistin gene expression was higher in VAT and SAT of obese, compared to normal-weight women. However, higher gene expression was not consistent with protein expression of resistin.

Conclusions: Low adiponectin in both examined adipose tissues and inappropriate leptin expression levels in SAT appear to be important characteristics of obesity-related metabolic syndrome. Intriguingly, this adipokine dysregulation is primary seen in SAT, suggesting that endocrine dysfunction in this abdominal depot may be an early risk sign of metabolic syndrome.

Keywords: abdominal obesity; adiponectin; leptin; metabolic syndrome; resistin.

Conflict of interest statement

The authors declare no conflict of interest.

Copyright: © 2021 Termedia & Banach.

Figures

Figure 1

Relationship between serum leptin levels and BMI. Serum leptin levels are shown in relation to each subject’s BMI (A), and in normal-weight (n = 20) (B) and obese groups (n = 20) (C)

Figure 2

mRNA and protein expression levels of leptin in the visceral (A, C) and subcutaneous adipose tissues (B, D) of metabolically healthy normal-weight, metabolically obese normal-weight, metabolically healthy obese, and metabolically obese (“at risk”) women. The protein content is expressed relative to that of a metabolically healthy normal-weight control, which was standardised to be 100%. The results of a representative example from three observations are shown. The data were quantified as described in the Materials and methods section. The values represent the mean ± SEM *Comparison with metabolically healthy normal-weight group, *p

Figure 3

Leptin immunohistochemistry in the visceral (VAT) and subcutaneous (SAT) adipose tissues of metabolically healthy normal-weight, metabolically obese normal-weight, metabolically healthy obese and “at risk” obese women. Immunoreactivity for leptin is visible in the cytoplasm of the visceral and subcutaneous adipocytes of all investigated groups, whereas the highest immunoreactivity is visible in the VAT of the “at risk” obese women compared with that in the controls. Omission of the primary antibody completely eliminated the immunoreactivity (NK). Scale bars: 20 μm

Figure 4

mRNA and protein expression levels of adiponectin in the visceral (A, C) and subcutaneous adipose tissues (B, D) of metabolically healthy normal-weight, metabolically obese normal-weight, metabolically healthy obese, and metabolically obese (“at risk”) women. The protein content is expressed relative to that of a metabolically healthy normal-weight control, which was standardised to be 100%. The results of a representative example from three observations are shown. The data were quantified as described in the Material and methods section. The values represent the mean ± SEM *Comparison with metabolically healthy normal-weight group, *p

Figure 5

mRNA and protein expression levels of resistin in the visceral (A, C) and subcutaneous adipose tissues (B, D) of metabolically healthy normal-weight, metabolically obese normal-weight, metabolically healthy obese, and metabolically obese (“at risk”) women. The protein content is expressed relative to that of a metabolically healthy normal-weight control, which was standardised to be 100%. The results of a representative example from three observations are shown. The data were quantified as described in the Materials and methods section. The values represent the mean ± SEM *Comparison with metabolically healthy normal weight group, *p

Figure 6

Relative protein expression levels of leptin (A), adiponectin (B) and resistin (C) in paired biopsies of subcutaneous and visceral adipose tissues in metabolically healthy normal-weight, metabolically obese normal-weight, metabolically healthy obese, and metabolically obese (“at risk”) women. The protein content is expressed relative to that of a visceral adipose tissue, which was standardised to be 100%. The results of a representative example from three observations are shown. The data were quantified as described in the Material and methods section