Depot-specific differences in visceral and subcutaneous adipose tissue from patients with obesity.
This study highlights that subcutaneous adipose tissue has larger adipocytes and higher basal lipolysis compared to visceral adipose tissue in patients with obesity.
Where it sits
this study against the rest of the dsip corpusSummary and findings
This study measured adipocyte cell size, gene expression, glucose uptake, and lipolysis in visceral and subcutaneous adipose tissues from 22 patients with obesity undergoing gastric bypass surgery. The findings indicated that subcutaneous adipocytes were larger and exhibited higher basal lipolysis compared to visceral adipocytes. Additionally, visceral adipocytes showed greater glucose uptake in response to insulin stimulation.
Abstract
Factors limiting fat cell expandability remain scarcely explored, and comprehensive functional comparisons of adipose depots in humans are limited. In the present study, we collected visceral adipose tissue (VAT) and subcutaneous adipose tissue (SAT) paired-samples from 22 patients with obesity undergoing elective Roux-en-Y gastric bypass surgery. Whole tissue samples were used to determine adipocyte cell size using a coulter counter and gene expression levels using bulk mRNA sequencing. Isolated adipocytes from the same tissue samples were used to functionally assess glucose uptake using glucose tracer assay, and lipolysis by measuring glycerol release. Western blotting was used to determine Caveolin 1 levels in adipocytes. The relationship between <i>COL3A1</i> expression and systemic health outcomes was assessed using data from the Adipose Tissue Knowledge Portal. We found that SAT adipocytes were larger in size, displayed higher basal lipolysis and higher lipolysis-related gene expression than VAT adipocytes. Isoprenaline-induced lipolytic responsiveness, as well as basal and insulin-stimulated glucose uptake were higher in VAT than in SAT adipocytes. SAT displayed higher levels of extracellular matrix components associated with cellular flexibility and higher cellular Caveolin 1 levels than VAT. Further, we identified subcutaneous adipose tissue <i>COL3A1</i> as a potential contributor to insulin resistance in obesity, positively associated with BMI, HOMA-IR and adipocyte size. In summary, our findings underscore distinct metabolic properties of subcutaneous and visceral adipocytes in obesity, with SAT adipose tissue exhibiting characteristics that possibly promote greater cellular expandability.
Background
This paper addresses the metabolic differences between visceral and subcutaneous adipose tissues in patients with obesity. Prior research has indicated that adipose tissue depots have distinct functional roles, but comprehensive comparisons in humans remain limited. Understanding these differences is important for elucidating the mechanisms underlying obesity-related metabolic disorders.
Methods
The study utilized paired samples of visceral adipose tissue (VAT) and subcutaneous adipose tissue (SAT) from 22 patients with obesity who were undergoing elective Roux-en-Y gastric bypass surgery. Adipocyte cell size was measured using a coulter counter, and gene expression levels were assessed via bulk mRNA sequencing. Functional assessments included glucose uptake using a glucose tracer assay and lipolysis measurement through glycerol release. Western blotting was employed to determine Caveolin 1 levels.
Results
Subcutaneous adipocytes were found to be larger in size compared to visceral adipocytes. Basal lipolysis was higher in subcutaneous adipocytes, while visceral adipocytes exhibited greater lipolytic responsiveness to isoprenaline. Additionally, visceral adipocytes demonstrated higher basal and insulin-stimulated glucose uptake. The study also identified a positive association between subcutaneous adipose tissue COL3A1 expression and systemic health outcomes, including BMI and HOMA-IR.
Interpretation
The findings suggest that subcutaneous adipose tissue has distinct metabolic properties compared to visceral adipose tissue, which may influence cellular expandability in obesity. While the study provides valuable insights, the clinical significance of these differences remains uncertain due to the small sample size and specific patient population. Further research is needed to explore these relationships in broader populations.
Key findings
- Larger adipocyte size in subcutaneous adipose tissue compared to visceral adipose tissue, n=22.
- Higher basal lipolysis in subcutaneous adipocytes than in visceral adipocytes, n=22.
- Isoprenaline-induced lipolytic responsiveness was higher in visceral adipocytes than in subcutaneous adipocytes, n=22.
- Higher basal and insulin-stimulated glucose uptake in visceral adipocytes compared to subcutaneous adipocytes, n=22.
- Positive association of subcutaneous adipose tissue COL3A1 with BMI, HOMA-IR, and adipocyte size, not quantified.
Limitations
- small n=22
- single-site study
- focused on patients undergoing gastric bypass surgery
- no long-term follow-up reported
- not all associations quantified