# Impaired Mitochondrial DNA Copy Number in Visceral Adipose Tissue of Insulin-Resistant Individuals: Implications for Metabolic Dysregulation

## TL;DR

This study shows that insulin-resistant individuals have lower mitochondrial DNA in visceral fat, linking it to metabolic issues and suggesting new treatment approaches.

## Contribution

The study reveals a significant reduction in mitochondrial DNA copy number in visceral adipose tissue of insulin-resistant individuals.

## Key findings

- Mitochondrial DNA copy number in visceral adipose tissue was about two-fold lower than in subcutaneous adipose tissue.
- Insulin-resistant individuals had significantly reduced mitochondrial DNA in both SAT and VAT compared to insulin-sensitive subjects.
- mtDNA copy number in VAT correlated with BMI and insulin signaling gene expression.

## Abstract

Insulin resistance is a fundamental pathophysiological mechanism contributing to the development of type 2 diabetes and metabolic syndrome. Recently, attention has focused on mitochondria’s role in glucose and lipid metabolism. Mitochondrial dysfunction is strongly associated with impaired energy metabolism and elevated oxidative stress. We investigated the mitochondrial DNA (mtDNA) copy number in subcutaneous adipose tissue (SAT) and visceral adipose tissue (VAT) in insulin-sensitive (IS) and insulin-resistant (IR) individuals. Twenty-seven paired adipose tissue biopsies were obtained during elective abdominal surgery. DNA and RNA were extracted, and mtDNA copy number was quantified using Real-Time PCR. We found that mtDNA content in VAT was approximately two-fold lower than in SAT. Furthermore, in IR individuals, mtDNA copy number was significantly reduced in both SAT and VAT compared to IS subjects. A strong positive correlation was observed between mtDNA content in VAT and body mass index (BMI), and a negative correlation was found with the QUICKI index. Additionally, mtDNA copy number in VAT positively correlated with the expression of several genes involved in insulin signalling, lipid metabolism, and other metabolic pathways. These findings underscore the central role of mitochondrial function in VAT in the context of metabolic disorders and suggest that targeting mitochondrial regulation in this tissue may represent a promising therapeutic approach.