PLoS One: Relationship between serum indirect bilirubin levels and skeletal muscle mass in older men and women with type 2 diabetes

Background: In aging societies, such as Japan and many Western countries, the prevalence of frailty and its adverse consequences increase
.
Activities of daily living disorder (ADL) is an undesirable outcome of frailty, which places a high burden
on the frail, nursing professionals, and the health care system.
Older diabetics are at risk of frailty, and frail diabetics have a higher mortality rate than non-frail diabetics
.
Therefore, it is important to
understand what factors can predict frailty and ADL disability in older people with diabetes.
In recent years, oxidative stress has received attention as one of the important causative factors of weakness, and there have been reports of increased oxidative stress and pro-inflammatory biomarkers in frail and pre-frailty subjects
.
Bilirubin is a strong endogenous antioxidant
.
There is growing evidence of a relationship
between serum bilirubin levels and oxidative stress-related conditions such as diabetes, diabetic nephropathy, and cardiovascular disease.
In addition, in previous reports, we found that serum bilirubin levels are a strong predictive biomarker of ADL disability in older diabetic patients (70 years and older
).
However, the mechanism of the link between serum bilirubin levels and ADL disability has not been fully elucidated
.

Decreased skeletal muscle mass or skeletal muscle loss is one of
the main features of weakness and ADL disability.
Many studies have shown that diabetes is a risk factor
for sarcopenia.
Since oxidative stress is thought to be involved in age-related skeletal muscle abnormalities through multiple pathways, it may also play a role
in diabetes-induced skeletal muscle abnormalities.

Objective: Therefore, the purpose of this study is to assess whether serum bilirubin levels are associated with
skeletal muscle mass in older patients with diabetes.

Methods: From April 2020 to July 2020, 272 patients with type 2 diabetes mellitus aged 60 and above (152 males and 120 females)
were continuously enrolled.
Bioelectrical impedance analysis evaluates body composition
.
The Skeletal Muscle Mass Index (SMI) is calculated as the mass of the appendicemus divided by the square of height (m2).

Results: The SMI of elderly patients (75 years old and above) was significantly lower than that of younger patients (60 ~ 74 years old) (7.
1±0.
8 kg/m2 vs 7.
6±0.
9 kg/m2, P<0.
001; 5.
5±0.
9 kg/m2 vs 6.
3±0.
8 kg/m2, P<0.
001).

Multivariate regression analysis showed that SMI was associated with body mass index (BMI) (p<0.
001) and age (p=0.
048) in male juvenile patients, and BMI (p<0.
001), age (p=0.
008), and serum indirect bilirubin level (p=0.
038)
in older men 。 In women, SMI was associated with BMI (p<0.
001) and age (p=0.
042) in young elderly patients, while only BMI (p<0.
001)
was associated in older patients.

Table 1 Univariate analysis of factors related to male skeletal muscle mass index (SMI).

Table 2 Univariate analysis
of factors related to female skeletal muscle mass index (SMI).

Table 3 Multiple linear regression analysis was used to evaluate the influencing factors
of skeletal muscle mass index (SMI).

Conclusion: The decline in skeletal muscle mass in elderly patients with type 2 diabetes mellitus aged 75 years and older may be related to
serum indirect bilirubin levels.

Original source:

Inoguchi Y, Inoguchi T, Eto T,,et al.
Relationship between serum indirect bilirubin levels and skeletal muscle mass in older male and female patients with type 2 diabetes.
PLoS One 2022; 17(11)