Relationship between physical activity and circulating fibroblast growth factor 21 in middle-aged and older adults

Different Effects of Cyclical Ketogenic vs. Nutritionally Balanced Reduction Diet on Serum Concentrations of Myokines in Healthy Young Males Undergoing Combined Resistance/Aerobic Training

Myokines represent important regulators of muscle metabolism. Our study aimed to explore the effects of a cyclical ketogenic reduction diet (CKD) vs. a nutritionally balanced reduction diet (RD) combined with regular resistance/aerobic training in healthy young males on serum concentrations of myokines and their potential role in changes in physical fitness. Twenty-five subjects undergoing regular resistance/aerobic training were randomized to the CKD (n = 13) or RD (n = 12) groups. Anthropometric and spiroergometric parameters, muscle strength, biochemical parameters, and serum concentrations of myokines and cytokines were assessed at baseline and after 8 weeks of intervention. Both diets reduced body weight, body fat, and BMI. Muscle strength and endurance performance were improved only by RD. Increased musclin (32.9 pg/mL vs. 74.5 pg/mL, p = 0.028) and decreased osteonectin levels (562 pg/mL vs. 511 pg/mL, p = 0.023) were observed in RD but not in the CKD group. In contrast, decreased levels of FGF21 (181 pg/mL vs. 86.4 pg/mL, p = 0.003) were found in the CKD group only. Other tested myokines and cytokines were not significantly affected by the intervention. Our data suggest that changes in systemic osteonectin and musclin levels could contribute to improved muscle strength and endurance performance and partially explain the differential effects of CKD and RD on physical fitness.

Association between physical activity, growth differentiation factor 15 and bodyweight in older adults: A longitudinal mediation analysis

BACKGROUND

Late-life aging is often associated with appetite reduction and weight loss. Physical activity (PA) may prevent these processes, but the molecular mechanisms involved remain elusive. The present study investigated the putative mediating aspect of growth differentiation factor 15 (GDF-15), a stress signalling protein involved in aging, exercise and appetite control, on the association between PA and late-life-associated weight loss.

METHODS

One thousand eighty-three healthy adults (63.8% women) aged 70 years and over who participated in the Multidomain Alzheimer Preventive Trial were included. Bodyweight (kg) and PA levels (square root of metabolic equivalent of task-min/week) were assessed repeatedly from baseline to the 3-year visit, whereas plasma GDF-15 (pg/mL) was measured at the 1-year visit. Multiple linear regressions were performed to test the association between first-year mean PA level, 1-year visit GDF-15 concentration and subsequent bodyweight changes. Mediation analyses were used to investigate whether GDF-15 mediated the association between first-year mean PA levels and consecutive bodyweight changes.

RESULTS

Multiple regression analyses demonstrated that higher first-year mean PA levels significantly predicted lower GDF-15 and bodyweight at 1 year (B = -2.22; SE = 0.79; P = 0.005). In addition, higher 1-year visit GDF-15 levels were associated with faster subsequent bodyweight loss (Time × GDF-15 interaction B = -0.0004; SE = 0.0001; P = 0.003). Mediation analyses confirmed that GDF-15 mediated the association between first-year mean PA levels and subsequent bodyweight changes (mediated effect ab = 0.0018; bootstrap SE = 0.001; P < 0.05) and revealed that mean PA had no direct effect on subsequent bodyweight changes (c' = 0.006; SE = 0.008; P > 0.05).

CONCLUSIONS

This study suggests that GDF-15 may be one of the molecules mediating the link between PA and late-life weight loss, but mechanistic studies are necessary to further support the present findings.

Circulating fibroblast growth factor 21 links hemodynamics with kidney function in middle-aged and older adults: A mediation analysis

Altered hemodynamics are commonly observed in individuals with declining renal function; however, the pathophysiological mechanisms linking renal dysfunction and hemodynamics have not been fully elucidated. Fibroblast growth factor 21 (FGF21), which upregulates sympathetic nerve activity, can alter systemic hemodynamics, and its level can increase as renal function declines. This study aimed to determine the associations among circulating FGF21 levels, hemodynamics, and renal function in middle-aged and older adults. In a total of 272 middle-aged and older adults (age range: 46-83 years), estimated glomerular filtration rate (eGFR), hemodynamics (brachial and aortic blood pressure and aortic pulse wave velocity [PWV]), and serum FGF21 levels were measured. For mediation analysis, hemodynamic parameters were entered as outcomes. eGFR or log-transformed urinary albumin and creatinine ratio (UACR) and log-transformed serum FGF21 levels were set as the predictors and mediator, respectively. According to multivariable regression models after adjusting for potential covariates, serum FGF21 levels were significantly associated with brachial systolic blood pressure (β = 0.140), pulse pressure (β = 0.136), and aortic PWV (β = 0.144). Mediation analyses showed that serum FGF21 levels significantly mediated the relationship of eGFR with brachial systolic blood pressure (indirect effect [95% confidence interval]: -0.032 [-0.071, -0.002]), pulse pressure (-0.019 [-0.041, -0.001]), and aortic PWV (-0.457 [-1.053, -0.021]) and the relationship of UACR with aortic PWV (7.600 [0.011, 21.148]). These findings suggest that elevated circulating FGF21 levels partially mediate the association of elevated blood pressure and/or aortic stiffness with renal dysfunction in middle-aged and older adults.