Author(s): FUNA, K., SANDO, E., KOIKE, T., AKIMA, H., TANAKA, N., Institution: NAGOYA UNIVERSITY , Country: JAPAN, Abstract-ID: 991

INTRODUCTION:
Intramuscular adipose tissue (IntraMAT) is know as one of the ectopic fat which accumulates within skeletal muscle (1,2). IntraMAT content is higher in older individuals compared to young ones (3). IntraMAT content is significantly related to sarcopenia, physical activity, and eating habits (4,5). Older individuals with low body mass index (BMI) (underweight) are generally at high risk of sarcopenia (6). However, it is unknown whether there are differences in factors associated with IntraMAT content between underweight and normal-weight individuals. Therefore, the purpose of this study was to explore the differences in factors associated with trunk IntraMAT content between underweight and normal-weight older women.
METHODS:
Thirty five older women aged 66 to 77 years (BMI: 21.9 ± 3.1 kg/m2) participated. Participants were divided into two groups based on BMI category based on dietary reference intakes for Japanese (2025) (7), namely, underweight group (UW, BMI: < 21.5 kg/m2, n = 20) and normal-weight group (NW, BMI: 21.5 to 24.5 kg/m2, n = 15). Trunk IntraMAT content and cross-sectional areas in 4 skeletal muscle groups (rectus abdominis, abdominal oblique, erector spinae, and iliopsoas) at the third lumbar vertebra were assessed by magnetic resonance imaging. Height, body weight, brachial blood pressure, fasting blood glucose, total cholesterol, HDL-cholesterol, and LDL-cholesterol levels were evaluated. We also assessed daily physical activity using global physical activity questionnaire. Eating behavior was assessed using scores derived from a questionnaire included in the obesity guidelines issued by the Japan Society for the Study of Obesity. The questionnaire evaluated perception of body weight and body constitution, external eating behavior, emotional eating behavior, sense of hunger, eating style, food preference, and regularity of eating habits. (8,9). Physical functional tests such as the five-meter maximal gait speed and times taken for ten-time-repeated sit-to-stand were also measured.
RESULTS:
Trunk IntraMAT content in UW was significantly lower (26.2 ± 6.5 %) than that in NW (28.1 ± 7.4 %) (p<0.05). In UW, trunk IntraMAT content was significantly and positively correlated with LDL-cholesterol level and the score of eating styles (r = 0.485 and 0.512, p<0.05, respectively). In NW, trunk IntraMAT content had significant correlations with sit-to-stand (r　= 0.389, p<0.05) and trunk skeletal muscle cross-sectional area (r = -0.540, p<0.05).
CONCLUSION:
The factors associated with trunk IntraMAT content differ depending on BMI. In underweight older women, metabolic and behavioral factors may significantly affect to trunk IntraMAT content. In normal-weight older women, risk factors of sarcopenia such as skeletal muscle mass and physical functions may significantly relate to trunk IntraMAT content.