Fat Infiltration in the Leg is Associated with Bone Geometry and Physical Function in Healthy Older Women

Abstract

The objective of this study was to estimate the associations between muscular fat infiltration, tibia bone mineral quantity and distribution, and physical function in healthy older women. Thirty-five women (aged 60-75 years, mean 70 years) were recruited from the community. Percent intramuscular fat (%IntraMF) within the right leg tibialis anterior, soleus, and gastrocnemius muscles and total intermuscular fat (IMF) were segmented from magnetic resonance imaging scans at the mid-calf. Intramyocellular lipid (IMCL) content in the right tibialis anterior was measured with proton magnetic resonance spectroscopy. Right tibia bone content, area, and strength were measured at the 4, 14, and 66% sites using peripheral quantitative computed tomography. Physical function was assessed by gait speed on the 20 m walking test. After adjusting for age, body size, and activity level, %IntraMF had a negative association with bone content and area at all tibia sites (r = -0.31 to -0.03). Conversely, greater IMF was associated with increased bone content and area (r = 0.04-0.32). Correlation coefficients for the association between IMCL and bone were negative (r = -0.44 to -0.03). All measures of fat infiltration had a negative association with observed physical function (r = -0.42 to -0.04). Our findings suggest that muscular fat infiltration in the leg of healthy postmenopausal women has a compartment-specific relationship with bone status and physical function. Minimizing fat accumulation within and between muscle compartments may prevent bone fragility and functional decline in women.

Mid-calf skeletal muscle density and its associations with physical activity, bone health and incident 12-month falls in older adults: The Healthy Ageing Initiative

“…Lower gluteus maximus and abductor muscle densities are associated with lower hip areal bone mineral density (aBMD) in hip fracture patients (14), and measures of 'bone qualities', such as peripheral volumetric BMD (vBMD) and bone geometry (15), also appear to be poorer in those with lower muscle density. Indeed, we recently reported that lower mid-calf muscle density is associated with lower proximal tibial cortical vBMD and area in older adults (16), and high relative lower-leg intra-muscular fat has also been associated with lower tibial bone content and area (17). The findings of these studies suggest a potential negative localised effect of lower skeletal muscle density on bone health in older adults, but no study has reported associations between muscle density and bone density and architecture at multiple anatomical sites.…”

Aging and Imaging Assessment of Body Composition: From Fat to Facts

“…MRI was used to study intramuscular adipose tissue in frail and non-frail individuals, showing that more muscle fat infiltration was detectable in older frail subjects (18.0 vs. 11.7%) (51). In women over 50 years old, MRI-measured muscle fat infiltration was reported to be positively associated with increased fracture risk (52), while lower extremity muscle fat infiltration was shown to be negatively associated with performance based measures of physical function (53).…”

The Effects of Dietary Omega-3s on Muscle Composition and Quality in Older Adults

“…This finding differs to in intact humans where the deterioration in muscle function occurs at ~2–3-fold greater rate than the loss of muscle mass (declines of ~2–3% vs. ~0.5–1.0% per year, respectively) [29, 30]. The reduction in muscle quality (i.e., strength per unit of muscle mass) with aging has been postulated to be occur due to changes in the muscle architecture [31], an increase in intermuscular fat infiltration [32–34], greater muscle fibrosis [35, 36], and reduced neuromuscular activation [37, 38]. …”

“…However, results from our recent study, where increases in strength following omega-3 fatty acid supplementation were ~2-fold greater than the gain in muscle volume [78], provide at least some circumstantial evidence for an omega-3 fatty acid-induced improvement in muscle quality. Additionally, omega-3 fatty acid supplementation has been reported to improve neuromuscular function [85, 86] and reduce intermuscular fat infiltration [78], both of which help determine muscle quality and have been implicated in aging-induced declines in muscle function [37, 38, 32–34]. Changes in other factors that influence muscle quality such as muscle architecture [31], and fibrosis [35, 36] have to the author’s knowledge not been examined in response to omega-3 fatty acids.…”