The obese healthy paradox: is inflammation the answer?

Area of Science:

• Metabolic Health
• Obesity Research
• Immunology

Background:

• Obesity is often linked to metabolic dysfunction, but some individuals remain 'metabolically healthy'.
• Understanding the differences between metabolically healthy and unhealthy obese individuals is crucial for targeted interventions.
• Visceral adipose tissue (VAT) plays a key role in obesity-related metabolic alterations.

Purpose of the Study:

• To investigate inflammatory and insulin signaling pathway differences in visceral adipose tissue (VAT).
• To compare morbidly obese individuals who are insulin-resistant (IR-MO) versus insulin-sensitive (NIR-MO).
• To identify mechanisms linking adipose tissue expansion to metabolic health in obesity.

Main Methods:

• Analysis of inflammatory markers and insulin signaling pathways in VAT.
• Comparison of gene expression and protein activation between IR-MO and NIR-MO groups.
• Assessment of macrophage infiltration in VAT.

Main Results:

• All morbidly obese patients showed increased tumor necrosis factor-alpha (TNFalpha) and c-Jun N-terminal kinase 1/2 (JNK1/2) activation.
• Insulin-resistant morbidly obese (IR-MO) individuals had elevated interleukin-1beta (IL-1beta) and interleukin-6 (IL-6) levels and increased macrophage infiltrates compared to NIR-MO.
• Inhibitor of NF-kappaB alpha (IkappaBalpha), extracellular-signal-regulated kinase 1/2 (ERK1/2), and nuclear factor kappaB (NF-kappaB) activation, along with insulin receptor substrate 1 (IRS-1) expression and Akt activation, differed significantly between IR-MO and NIR-MO groups.

Conclusions:

• Metabolically healthy obese (NIR-MO) individuals exhibit a reduced inflammatory response in VAT compared to IR-MO individuals.
• Interleukin-6 (IL-6), interleukin-1beta (IL-1beta), extracellular-signal-regulated kinase (ERK), and nuclear factor kappaB (NF-kappaB) are key mediators of inflammation that promote insulin resistance in obesity.
• These findings highlight distinct inflammatory profiles associated with metabolic health in obesity.