Author(s): SANDO, E., KITAGAWA, F., KOIKE, T., TANAKA, N., AKIMA, H., Institution: NAGOYA UNIVERSITY, Country: JAPAN, Abstract-ID: 2283

INTRODUCTION:
Skeletal muscle size decreases and intramuscular adipose tissue (IntraMAT) content increases with aging, which induces decline of skeletal muscle strength and physical function (Goodpaster et al, 2006; Tuttle et al, 2012). IntraMAT content is known to be associated with metabolic diseases such as type Ⅱ diabetes (Goodpaster et al, 2000). Therefore, it is important to take measures to prevent the decrease in skeletal muscle size and the accumulation of IntraMAT. One of the factors that may affect changes in the amount and proportion of skeletal muscle and adipose tissue is habitual dietary intake. It has been clarified that protein intake helps maintain and increase skeletal muscle size; however, it is not well known how protein intake affects adipose tissue. Previous studies examined the relationships among skeletal muscle cross-sectional area (CSA), IntraMAT content, and protein intake (Sjoholm et al, 2016; Dicks et al, 2020); however, a consistent consensus has not been observed in these relationships. A possible cause of the inconsistency in these relationships is the difference in age. Therefore, the purpose of this study was to clarify the relationships among skeletal muscle CSA, IntraMAT content, and protein intake in younger and older adults.
METHODS:
Twenty-three young women (19.9 ± 1.6 years) and 25 older women (72.4 ± 3.2 years) participated in this study. Skeletal muscle CSA and IntraMAT content (%) of the quadriceps femoris (QF), hamstrings (HM), adductors (AD), and total thigh (i.e. sum of QF, HM, and AD) at the mid-thigh were measured using magnetic resonance imaging. The percentages of energy from protein were assessed using a simple self-administered dietary history questionnaire. Protein was classified into total protein, animal protein, or plant protein.
RESULTS:
No significant correlations were observed between skeletal muscle CSA and percentage of energy from protein (i.e. total protein, animal protein, and plant protein) in both groups. In younger group, IntraMAT content of the QF significantly correlated with the percentages of energy from total protein (r = 0.528, P < 0.05) and animal protein (r = 0.484, P < 0.05). In older group, IntraMAT content of the three skeletal muscle groups (i.e. QF, HM, and AD) and the total thigh were inversely correlated with the percentages of energy from plant protein (r = -0.538 to -0.455, P < 0.01).
CONCLUSION:
These results suggest that the relationship between IntraMAT content and protein intake varies with age, and particularly in older group, a higher percentage of energy from plant protein affect reduce the accumulation of IntraMAT content.