J. F. Oberlin University

Calf circumference serves as a surrogate marker of skeletal muscle mass. However, its ability to reflect changes in skeletal muscle mass remains unclear. This longitudinal study aimed to assess the relationship between changes in calf circumference and appendicular skeletal muscle mass (ASM) and to explore the effects of age and obesity.

The two-wave cohort data of 227 adults aged 40-87 years were analyzed. The maximum calf circumference was measured in a standing position, whereas body composition, including ASM, was measured using dual-energy X-ray absorptiometry. Pearson's correlation coefficient was calculated to assess this relationship.

The mean follow-up period was 8.0 ± 0.4 years. The mean changes in calf circumference and ASM (follow-up - baseline value) were -0.1 ± 1.2 cm and -0.7 ± 1.0 kg, respectively. Changes in calf circumference and ASM showed a positive correlation in men and women (r = 0.71 and 0.71, respectively). A 1.0 cm reduction in calf circumference corresponded to a 1.4 and 0.9 kg reduction in ASM for men and women, respectively. As in the primary analysis, subgroup analysis based on age and obesity exhibited similar positive correlations between changes in calf circumference and ASM (r = 0.70, 0.67, 0.69, and 0.72 for middle-aged, older, non-obese, and obese adults, respectively).

Longitudinal changes in calf circumference were positively correlated with those in ASM, regardless of age and obesity status. As such, changes in calf circumference could serve as a reliable indicator of variations in skeletal muscle mass.

The present study clarified the relationship between the temperature of bath water, the presence of systolic hypertension, the presence of antihypertensive medication, and the pulse rate during bathing, focusing on the variation of systolic blood pressure.

Twenty community-dwelling men 61 to 87 years old were included in the study. The subjects were randomly divided into 2 groups, based on bath temperature 39°C and 41°C. They were then given a full-body bath for 10 minutes.

The variables significantly related to the change in systolic blood pressure from 2 to 8 minutes after bathing were the presence or absence of antihypertensive medication, and the interaction between the presence of antihypertensive medication and the change in pulse rate from 2 to 8 minutes after bathing.

Antihypertensive medication had a favorable effect on the reduction of systolic blood pressure during bathing.

MOTS-c is a mitochondrial microprotein that improves metabolism. Here, we demonstrate CK2 is a direct and functional target of MOTS-c. MOTS-c directly binds to CK2 and activates it in cell-free systems. MOTS-c administration to mice prevented skeletal muscle atrophy and enhanced muscle glucose uptake, which were blunted by suppressing CK2 activity. Interestingly, the effects of MOTS-c are tissue-specific. Systemically administered MOTS-c binds to CK2 in fat and muscle, yet stimulates CK2 activity in muscle while suppressing it in fat by differentially modifying CK2-interacting proteins. Notably, a naturally occurring MOTS-c variant, K14Q MOTS-c, has reduced binding to CK2 and does not activate it or elicit its effects. Male K14Q MOTS-c carriers exhibited a higher risk of sarcopenia and type 2 diabetes (T2D) in an age- and physical-activity-dependent manner, whereas females had an age-specific reduced risk of T2D. Altogether, these findings provide evidence that CK2 is required for MOTS-c effects.