Near-infrared spectroscopy detects age-related differences in skeletal muscle oxidative function: promising implications for geroscience

Age is the greatest risk factor for chronic disease and is associated with a marked decline in functional capacity and quality of life. A key factor contributing to loss of function in older adults is the decline in skeletal muscle function. While the exact mechanism(s) remains incompletely understood, age-related mitochondrial dysfunction is thought to play a major role. To explore this question further, we studied 15 independently living seniors (age: 72 ± 5 years; m/f: 4/11; BMI: 27.6 ± 5.9) and 17 young volunteers (age: 25 ± 4 years; m/f: 8/9; BMI: 24.0 ± 3.3). Skeletal muscle oxidative function was measured in forearm muscle from the recovery kinetics of muscle oxygen consumption using near-infrared spectroscopy (NIRS). Muscle oxygen consumption was calculated as the slope of change in hemoglobin saturation during a series of rapid, supra-systolic arterial cuff occlusions following a brief bout of exercise. Aging was associated with a significant prolongation of the time constant of oxidative recovery following exercise (51.8 ± 5.4 sec vs. 37.1 ± 2.1 sec, P = 0.04, old vs. young, respectively). This finding suggests an overall reduction in mitochondrial function with age in nonlocomotor skeletal muscle. That these data were obtained using NIRS holds great promise in gerontology for quantitative assessment of skeletal muscle oxidative function at the bed side or clinic

Impact of Optimized Breastfeeding on the Costs of Necrotizing Enterocolitis in Extremely Low Birthweight Infants

To estimate risk of NEC for ELBW infants as a function of preterm formula and maternal milk (MM) intake and calculate the impact of suboptimal feeding on NEC incidence and costs

Near-infrared spectroscopy detects age-related differences in skeletal muscle oxidative function: promising implications for geroscience

Age is the greatest risk factor for chronic disease and is associated with a marked decline in functional capacity and quality of life. A key factor contributing to loss of function in older adults is the decline in skeletal muscle function. While the exact mechanism(s) remains incompletely understood, age-related mitochondrial dysfunction is thought to play a major role. To explore this question further, we studied 15 independently living seniors (age: 72 ± 5 years; m/f: 4/11; BMI: 27.6 ± 5.9) and 17 young volunteers (age: 25 ± 4 years; m/f: 8/9; BMI: 24.0 ± 3.3). Skeletal muscle oxidative function was measured in forearm muscle from the recovery kinetics of muscle oxygen consumption using near-infrared spectroscopy (NIRS). Muscle oxygen consumption was calculated as the slope of change in hemoglobin saturation during a series of rapid, supra-systolic arterial cuff occlusions following a brief bout of exercise. Aging was associated with a significant prolongation of the time constant of oxidative recovery following exercise (51.8 ± 5.4 sec vs. 37.1 ± 2.1 sec, P = 0.04, old vs. young, respectively). This finding suggests an overall reduction in mitochondrial function with age in nonlocomotor skeletal muscle. That these data were obtained using NIRS holds great promise in gerontology for quantitative assessment of skeletal muscle oxidative function at the bed side or clinic

Dual Wavelength Diffuse Correlation Spectroscopy: A Novel Tool for Identifying Determinants of Oxygen Consumption

Near-infrared diffuse correlation spectroscopy (DCS) is a novel method for measuring microvascular skeletal muscle blood flow. Our lab recently found excellent agreement between single wavelength DCS and Doppler ultrasound of the brachial artery during rhythmic handgrip exercise. PURPOSE: Here, we report new data utilizing a dual wavelength DCS system (785nm and 852nm), which extends our prior work by combining novel microvascular perfusion assessment with real-time quantification of tissue oxygenation. METHODS: We enrolled eight individuals (male/female: 3/5, mean: age 48±22 (range: 22-76 years), height 170±8cm, and weight 75±12kg). Subjects were instrumented with the DCS probe placed over the belly of the flexor digitorum profundus. Duplex ultrasound of the brachial artery was performed concurrently to provide and additional measure of skeletal muscle blood flow. Each subject performed two bouts of rhythmic hand grip exercise at 20% of their maximum voluntary contraction (MVC). Resting baseline data were acquired prior to each bout of exercise, and each period of data collection were separated by a minimum of 10 minutes of rest. The data derived from both rest and exercise periods were averaged. RESULTS: As reported previously using our single wavelength DCS device, blood flow index (BFI, the primary output from DCS) increased significantly (119+37%) with exercise. We also observed a 1.9+1.1% change in oxyhemoglobin and 21.8+10.0% change in deoxyhemoglobin resulting in a -5.9±2.6% change in tissue saturation with exercise. Using these data, relative muscle oxygen consumption (rmVO2) was calculated and found to increase by 160.2+55.4%. The novelty of this new approach is best illustrated by a case-comparison between two subjects, who performed nearly equivalent absolute (11 vs 10 kg) and relative work (20%), and yet achieved strikingly different levels of oxygen utilization during exercise (ΔrmO2 = 307% vs. 214%, Case A vs. Case B respectively). This disparity appears to be attributable to muscle oxygen extraction as both brachial artery blood flow and microvascular perfusion (by DCS) were similar in both subjects. By contrast, Case A exhibited a much greater change in StO2 (-17.8%) compared to Case B, whose StO2 more closely mirrored the group average (-6.8%). To aid in the interpretation of these results, we evaluated skeletal muscle oxidative capacity in both subjects using an established NIRS-based cuff occlusion protocol (Rosenberry et al. 2018. JoVE). Remarkably, these additional data corroborated our hypothesis; Case A exhibited a much faster muscle oxygen consumption recovery time (34 seconds) whereas Case B’s recovery time was 93 seconds. CONCLUSION: Taken together, these data establish strong proof-of-concept that dual wavelength DCS can provide valuable mechanistic insight into the determinants of oxygen consumption

Where and With Whom Does a Brief Social-Belonging Intervention Promote Progress in College?

A promising way to mitigate inequality is by addressing students’ worries about belonging. But where and with whom is this social-belonging intervention effective? Here we report a team-science randomized controlled experiment with 26,911 students at 22 diverse institutions. Results showed that the social-belonging intervention, administered online before college (in under 30 minutes), increased the rate at which students completed the first year as full-time students, especially among students in groups that had historically progressed at lower rates. The college context also mattered: The intervention was effective only when students’ groups were afforded opportunities to belong. This study develops methods for understanding how student identities and contexts interact with interventions. It also shows that a low-cost, scalable intervention generalizes its effects to 749 4-year institutions in the United States

Impact of Optimized Breastfeeding on the Costs of Necrotizing Enterocolitis in Extremely Low Birthweight Infants

To estimate risk of NEC for ELBW infants as a function of preterm formula and maternal milk (MM) intake and calculate the impact of suboptimal feeding on NEC incidence and costs