Exercise training blunts microvascular rarefaction in the metabolic syndrome

Area of Science:

• Physiology
• Exercise Science
• Metabolic Syndrome Research

Background:

• Obesity and metabolic syndrome are linked to reduced skeletal muscle microvessel density (MVD).
• This reduction is associated with decreased vascular nitric oxide (NO) bioavailability and potentially increased matrix metalloproteinase (MMP) activity.
• Exercise is known to improve NO bioavailability and reduce inflammation.

Purpose of the Study:

• To investigate the effects of chronic exercise on MVD, NO bioavailability, MMP activity, and plasma cytokine levels in obese Zucker rats (OZR).
• To determine if exercise can ameliorate microvascular rarefaction in OZR.

Main Methods:

• Obese Zucker rats underwent a 10-week treadmill exercise program.
• Measurements included body mass, insulin, triglycerides, gastrocnemius MVD, arteriolar dilation, NO release, functional hyperemia, and vascular resistance.
• Skeletal muscle MMP-2 and MMP-9 expression and activity were assessed via Western blotting and zymography.
• Plasma levels of inflammatory cytokines (monocyte chemoattractant protein-1, IL-1beta, IL-13) were analyzed.

Main Results:

• Exercise reduced body mass, insulin, and triglyceride levels in OZR.
• Gastrocnemius MVD, arteriolar dilation, and methacholine-induced NO release were significantly increased in exercised OZR.
• Functional hyperemia improved, and vascular resistance decreased with exercise.
• Neither MMP-2 nor MMP-9 expression or activity was altered by exercise.
• Exercise training reduced pro-inflammatory cytokines (monocyte chemoattractant protein-1, IL-1beta) and increased IL-13.

Conclusions:

• Chronic exercise improves skeletal muscle MVD in obese rats.
• These improvements are associated with enhanced NO bioavailability.
• The beneficial effects appear to be mediated by alterations in plasma inflammatory profiles rather than changes in MMP-2 or MMP-9 activity.