Associations between white matter lesions, adiposity, and systemic inflammation in late adulthood: Results from the IGNITE study.

The relationship between relative visceral adipose tissue (rVAT) and white matter lesion (WML) volume was statistically mediated by IL-6 and TNF-α.

• Baseline data from n=648 participants from the IGNITE multisite study were used (mean age=69.9 ± 3.8 years, 70.5% females).
• rVAT was measured using dual-energy x-ray absorptiometry (DXA) as VAT relative to total body adiposity.
• IL-6 and TNF-α served as markers of systemic inflammation included in mediation analyses.
• Age, sex, years of education, hypertension status, and study site were included as covariates.
• The original hypothesis that rVAT would be associated with greater WML volume was partially supported through inflammatory mediation.

The relationship between relative abdominal subcutaneous adipose tissue (rASAT) and WML volume was also statistically mediated by IL-6 and TNF-α.

• Contrary to the initial hypothesis, rASAT (not only rVAT) was associated with WML burden.
• rASAT was measured using DXA as abdominal subcutaneous adipose tissue relative to total body adiposity.
• Both IL-6 and TNF-α mediated the rASAT–WML association, paralleling the findings for rVAT.
• This finding suggests that both visceral and subcutaneous fat compartments relate to white matter lesion burden through shared inflammatory mechanisms.

IL-1RA was included as a marker of systemic inflammation alongside IL-6 and TNF-α, but the primary mediation findings centered on IL-6 and TNF-α.

• Three inflammatory cytokines were examined: IL-6, IL-1RA, and TNF-α.
• IL-1RA did not emerge as a significant mediator in the adiposity–WML associations in contrast to IL-6 and TNF-α.
• This differential pattern suggests specificity in the inflammatory pathways linking adipose tissue compartments to white matter burden.

White matter lesions are associated with cardiometabolic factors including excess adiposity and markers of systemic inflammation in late adulthood.

• WMLs increase the risk for cognitive impairment and dementia.
• Few prior studies had examined whether specific compartments of adipose tissue differentially relate to WML volume.
• The IGNITE study sample had a mean age of 69.9 ± 3.8 years with 70.5% females across multiple study sites.
• The study used baseline cross-sectional data from 648 participants enrolled in an exercise intervention trial.

The findings establish a testable mechanistic pathway suggesting that managing low-grade systemic inflammation and intentional weight loss may support brain health in older adults.

• Authors conclude that both higher rVAT and rASAT are associated with higher WML burden through an elevated inflammatory state.
• The results are described as setting 'a testable mechanistic pathway for future longitudinal and intervention studies.'
• Specific targets identified include managing low-grade systemic inflammation and intentional weight loss as potential strategies.
• The study design is cross-sectional (baseline data), limiting causal inference and highlighting the need for longitudinal follow-up.