Development of a new Sonovue™ contrast-enhanced ultrasound approach reveals temporal and age-related features of muscle microvascular responses to feeding.
Level 3 - non-randomized controlled study
non-randomized comparative cohort study evaluating age-related physiological responses
PubMed 24303186 · doi:10.1002/phy2.119
What was done
Researchers developed a contrast-enhanced ultrasound protocol using continuous Sonovue infusion and a quadriceps-fixed probe with microbubble destruction-replenishment kinetics to quantify real-time microvascular blood volume (MBV), microvascular flow velocity (MFV), and microvascular blood flow (MBF). They measured these parameters alongside Doppler leg blood flow (LBF) and serum insulin before and after an oral bolus of 15 g essential amino acids in young men (~20 years, n = 6) and older men (~70 years, n = 7). Interindividual variability was assessed across N = 36.
What was found
Steady-state contrast concentration was reached in <150 seconds, with measurements completed in <120 seconds. Interindividual coefficients of variation for MBV and MFV were 35-40% (N = 36). In young men (n = 6), feeding elicited an early increase in MBV (+36%, P < 0.008 at 45 min) synchronized with peak insulin but without altered LBF, followed by late increases in MFV (+77%, P < 0.008) and MBF (+130%, P < 0.007 at 195 min) accompanied by increased LBF after insulin normalized. In older men (n = 7), all vascular and microvascular responses to feeding were absent.
Why it matters
This study demonstrates age-related blunting of postprandial muscle microvascular perfusion and capillary recruitment, providing a potential hemodynamic mechanism for impaired muscle protein anabolism and sarcopenia in older adults.
Limits
The comparative cohort was very small (6 young vs. 7 old men), all participants were male, and direct downstream metabolic or clinical outcomes such as muscle protein synthesis were not reported.
Cited by
- supports Aging impairs insulin-mediated capillary recruitment and vasodilation in skeletal muscle without necessarily causing overt glycemic insulin resistance.