Pro-Inflammatory Endothelial Activation Detected by Molecular Imaging in Obese Non-Human Primates Coincides with the Onset of Insulin Resistance and Progressively Increases with Duration of Insulin Resistance
Background—Inflammation and insulin resistance (IR) are associated processes that potentiate risk for cardiovascular disease in obesity. The temporal relation between IR and inflammation is not completely characterized. We hypothesized that endothelial cell adhesion molecule (ECAM) expression in large arteries is an early event that coincides with diet-induced obesity and IR in primates.
Methods and Results—Ten adult male rhesus macaques were studied at baseline and every 4-6 months on high-fat diet (HFD) for 2 years. Truncal fat, carotid intima-media thickness (IMT), plasma inflammatory biomarkers, and carotid P-selectin and VCAM-1 expression by contrast-enhanced ultrasound molecular imaging were assessed. Intravenous glucose tolerance test (IVGTT) was performed at baseline, 4 and 18 months. HFD produced a rapid increase (p<0.01) in weight, truncal fat, and degree of IR indicated by the insulin area-under-the-curve and glucose disappearance rate on IVGTT; all of which worsened minimally thereafter. Molecular imaging detected a progressive increase in ECAM expression over time (5-7-fold greater than control agent signal at 2 yrs, p<0.01). Changes in IMT were not detected until 2 years and, while there was a trend toward an increase in plasma markers of inflammation (MCP-1, CRP), the pattern of increase varied considerably over time.
Conclusions—In primates with diet-induced obesity, endothelial inflammatory activation is an early event that occurs coincident with the development of IR and long before any measurable change carotid IMT. Endothelial activation is more related to the duration rather than severity of IR and is not mirrored by changes in plasma biomarkers.
- Received May 7, 2013.
- Revision received October 11, 2013.
- Accepted October 16, 2013.