[Liver Fibrosis is Associated with Loss of Skeletal Muscle Mass in Community-Dwelling Older Adults with No History of Liver Diseases]

The gut microbiota genus Blautia is associated with skeletal muscle mass reduction in community-dwelling older Japanese adults: the Wakayama Study

PURPOSE

This cross-sectional study examined the gut microbiota species associated with skeletal muscle mass reduction in a community-based sample of older Japanese adults.

METHODS

The study included 744 participants (320 men and 424 women) aged 65-89 years (mean age: 73 years) with no history of treatment for colorectal, chronic kidney, or liver diseases. Bioelectrical impedance analysis was performed to estimate the appendicular skeletal muscle mass (ASM) of each participant. The gut microbiota composition was assessed using next-generation sequencing targeting the V3-V4 regions of the prokaryotic 16S rRNA genes. A self-administered questionnaire was used to evaluate daily living habits, including food intake associated with maintaining the gut microbiota.

RESULTS

Among the participants, those with reduced muscle mass (defined as an ASM index of less than 4.4 kg/m2 for men and 3.7 kg/m2 for women) had significantly higher levels of the genus Blautia when compared with those with normal muscle mass (P = 0.009). Logistic regression analysis revealed that the association between the genus Blautia and skeletal muscle mass remained significant even after adjusting for multiple confounding factors (P = 0.012). Additionally, an increase in the genus Blautia was positively associated with excessive alcohol consumption (≥ 20 g/day, β = 0.125, P = 0.002) and negatively associated with regular yogurt intake (≥ 1 time/week, β = -0.101, P = 0.010), independent of other lifestyle and dietary factors.

CONCLUSION

Elevated levels of the genus Blautia were associated with reduced skeletal muscle mass in older Japanese adults, suggesting that improving the gut microbiota may be a potential approach to preserving muscle mass among this population.

Spot urinary sodium-to-potassium ratio is associated with blood pressure levels in healthy adolescents: the Wakayama Study

The spot urinary sodium-to-potassium (Na/K) ratio is a simple measure of salt loading and has been shown to be associated with elevated blood pressure (BP) in middle-aged and older adults. This study aimed to evaluate the association between the spot urinary Na/K ratio and BP in 457 healthy adolescents aged 12-15 years in a school-based setting. The mean urinary Na/K ratio was 4.99 ± 2.76, and no significant difference was found between the boys and girls. When the participants were stratified based on urinary Na/K ratio quartile, age- and sex-adjusted systolic and diastolic BP gradually increased as Na/K ratio increased (systolic BP: 106.1, 106.9, 108.2, and 111.5 mmHg, Ptrend < 0.001; diastolic BP: 62.0, 62.4, 63.1, 64.3 mmHg, Ptrend = 0.022). The systolic and diastolic BP were more closely associated with urinary Na/K ratio than with Na and K levels, as well as estimated daily salt intake. In the multiple regression analysis, the urinary Na/K ratio was significantly associated with systolic BP (β = 0.144, P < 0.001) and diastolic BP (β = 0.114, P = 0.015) independent of potential confounding factors. An additional subgroup analysis revealed that the BP of the group with both high salt intake (≥8.5 g/day) and high Na/K ratio (≥6.60) was significantly higher than that of the group with high salt intake alone (systolic BP, 115.0 vs. 109.1 mmHg, P < 0.001; diastolic BP, 66.0 vs. 62.5 mmHg, P = 0.017). These results suggest that the urinary Na/K ratio is associated with BP levels in healthy adolescents and may be useful for assessing salt loading and its effects on BP elevation.

Effects of cigarette smoking on the association between respiratory muscle strength and skeletal muscle mass in middle-aged and older adults: the Wakayama Study

PURPOSE

This study aimed to examine whether cumulative smoking exposure affects the association between peak expiratory flow rate (PEFR) and skeletal muscle mass in middle-aged and older adults.

METHODS

The study participants comprised 832 community-dwelling individuals aged 50-89 years (mean age: 69 years) without chronic obstructive pulmonary disease. Bioelectrical impedance analysis was performed to estimate the skeletal muscle mass of each participant. PEFR was assessed using an electronic spirometer. Cumulative smoking exposure was expressed in pack years, that is a product of the average number of packs of cigarettes smoked per day and smoking duration in years.

RESULTS

The whole-body skeletal muscle mass progressively reduced with decreasing PEFR levels in both males and females. In the multiple regression analysis, PEFR was found to be significantly associated with skeletal muscle mass, independent of the potential confounding factors. When participants were stratified based on the cumulative smoking exposure, the association between low PEFR and reduced skeletal muscle mass persisted in individuals with non-smoking and light-to-moderate smoking exposure (< 30 pack-years). However, this association was not clearly observed in individuals with heavy smoking exposure (≥ 30 pack-years).

CONCLUSION

The findings of this study support the notion that PEFR declines with a reduction in systemic skeletal muscle mass due to aging. However, chronic cigarette smoking induces respiratory dysfunction exceeding the expected values by age, and thus a low PEFR level may not be used as a marker of reduced muscle mass in older adults exposed to heavy smoking.

Excessive alcohol intake and liver fibrosis are associated with skeletal muscle mass reduction in elderly men: the Wakayama study

BACKGROUND

Excessive alcohol intake complicated by liver dysfunction has been presumed to affect skeletal muscles. This study aimed to examine the association between excessive alcohol intake, liver fibrosis, and loss of skeletal muscle mass in elderly men.

METHODS

The study participants comprised 799 community-dwelling elderly men (age, 71 ± 3 years) with no history of treatment for liver disease. Bioelectrical impedance analysis was performed to estimate the appendicular skeletal muscle mass (ASM) of each participant. The ASM values were also normalized for height (ASM index). Liver fibrosis was evaluated using the Fib4 index, which was calculated using participant age, AST level, ALT level, and platelet count. Usual alcohol intake was estimated based on the type of alcohol, frequency of drinking, and amount of alcohol consumed per day.

RESULTS

Among the excess drinkers (≥ 20 g/day), the ASM index of the subgroup with liver fibrosis (Fib4 index ≥ 2.67) was significantly lower than that of the subgroup with no liver fibrosis (Fib4 index < 2.67). However, no significant difference between the subgroups was found in the non-drinkers and moderate drinkers (< 20 g/day). In multiple regression analysis, the Fib4 index was significantly associated with the ASM index, independent of potential confounding factors. The association between the Fib4 index and ASM index was more pronounced in excess drinkers than in non-drinkers and moderate drinkers.

CONCLUSION

These results suggest that liver fibrosis is associated with loss of skeletal muscle mass in elderly men, and excessive alcohol intake combined with liver fibrosis may lead to greater muscle mass reduction than each individual condition.