Effects of acute exercise on markers of inflammation in pediatric chronic kidney disease: a pilot study

Height-adjusted lean body mass and its associations with physical activity and kidney function in pediatric kidney transplantation

BACKGROUND

Although LBM is positively associated with health outcomes, studies assessing determinants for the accrual of ht-LBM, such as physical activity, are limited. This study aimed to assess ht-LBM levels in pediatric kidney transplant recipients and test its association with baseline and contemporaneous variables, including physical activity.

METHODS

A retrospective cross-sectional review was performed on 46 pediatric kidney transplant recipients, and a longitudinal review was performed on a subset of recipients with serial post-transplant (n = 21) and pre/post-transplant (n = 11) ht-LBM measurements. Ht-LBM measurements were obtained using DXA scans.

RESULTS

This cohort was 16.0 (IQR 12.3, 17.7) years old, 56.5% male and 46 ± 45 months post-transplant with a mean ht-LBM of 15.1 ± 2.5 kg/m² . A median ht-LBM increase of 1.6 kg/m² (IQR - 0.1, 2.6 kg/m² ; p < .01) was observed, over 29.2 ± 12.0 months from the earliest post-transplant scan obtained at 46 ± 25 months post-transplant until the most recent post-transplant scan. A 1.7 ± 1.4 kg/m² (p < .01) increase was observed between pre- and post-transplant DXA scans which were taken at 12 ± 11 months pre-transplant and 13 ± 6 months post-transplant, respectively. In separate adjusted models, lower physical activity questionnaire scores (n = 17, beta = 1.55, p = .02), faster rate of estimated glomerular filtration rate decline (beta = 0.05, p < .048) adjusted for annualized change in BSA, and younger age at scan (beta = 0.32, p < .01) were each significant predictors of lower ht-LBM.

CONCLUSIONS

Physical activity and kidney function may influence ht-LBM in the pediatric kidney transplant population.

Muscle-bone axis in children with chronic kidney disease: current knowledge and future perspectives

Bone and muscle tissue are developed hand-in-hand during childhood and adolescence and interact through mechanical loads and biochemical pathways forming the musculoskeletal system. Chronic kidney disease (CKD) is widely considered as both a bone and muscle-weakening disease, eventually leading to frailty phenotype, with detrimental effects on overall morbidity. CKD also interferes in the biomechanical communication between two tissues. Pathogenetic mechanisms including systemic inflammation, anorexia, physical inactivity, vitamin D deficiency and secondary hyperparathyroidism, metabolic acidosis, impaired growth hormone/insulin growth factor 1 axis, insulin resistance, and activation of renin-angiotensin system are incriminated for longitudinal uncoordinated loss of bone mineral content, bone strength, muscle mass, and muscle strength, leading to mechanical impairment of the functional muscle-bone unit. At the same time, CKD may also interfere in the biochemical crosstalk between the two organs, through inhibiting or stimulating the expression of certain osteokines and myokines. This review focuses on presenting current knowledge, according to in vitro, in vivo, and clinical studies, concerning the pathogenetic pathways involved in the muscle-bone axis, and suggests approaches aimed at preventing bone loss and muscle wasting in the pediatric population. Novel therapeutic targets for preserving musculoskeletal health in the context of CKD are also discussed.

Endocrine Mechanisms Connecting Exercise to Brown Adipose Tissue Metabolism: a Human Perspective

PURPOSE OF REVIEW

To summarize the state-of-the-art regarding the exercise-regulated endocrine signals that might modulate brown adipose tissue (BAT) activity and/or white adipose tissue (WAT) browning, or through which BAT communicates with other tissues, in humans.

RECENT FINDINGS

Exercise induces WAT browning in rodents by means of a variety of physiological mechanism. However, whether exercise induces WAT browning in humans is still unknown. Nonetheless, a number of protein hormones and metabolites, whose signaling can influence thermogenic adipocyte's metabolism, are secreted during and/or after exercise in humans from a variety of tissues and organs, such as the skeletal muscle, the adipose tissue, the liver, the adrenal glands, or the cardiac muscle. Overall, it seems plausible to hypothesize that, in humans, exercise secretes an endocrine cocktail that is likely to induce WAT browning, as it does in rodents. However, even if exercise elicits a pro-browning endocrine response, this might result in a negligible effect if blood flow is restricted in thermogenic adipocyte-rich areas during exercise, which is still to be determined. Future studies are needed to fully characterize the exercise-induced secretion (i.e., to determine the effect of the different exercise frequency, intensity, type, time, and volume) of endocrine signaling molecules that might modulate BAT activity and/or WAT browning or through which BAT communicates with other tissues, during exercise. The exercise effect on BAT metabolism and/or WAT browning could be one of the still unknown mechanisms by which exercise exerts beneficial health effects, and it might be pharmacologically mimicked.

Muscle wasting in chronic kidney disease

Loss of lean body mass is a relevant component of the cachexia, or protein energy wasting (PEW), syndrome. Reduced muscle mass seems to be the most solid criterion for the presence of cachexia/PEW in patients with chronic kidney disease (CKD), and those with greater muscle mass loss have a higher risk of death. Children with CKD have many risk factors for lean mass and muscle wasting, including poor appetite, inflammation, growth hormone resistance, and metabolic acidosis. Mortality risks in patients with CKD increases as body mass index (BMI) and weight decreases. However, data regarding cachexia/PEW and muscle wasting in children with CKD is scarce due to lack of consensus in diagnostic criteria and an appropriate investigative methodology. Further research is urgently needed to address this important complication in the pediatric CKD setting, which may have fundamental impact on clinical outcomes.

Physical activity and screen time in adolescents in the chronic kidney disease in children (CKiD) cohort

BACKGROUND

Self-reported physical activity (PA) and screen time exposure in adolescents with chronic kidney disease (CKD) has not been evaluated.

METHODS

We performed a cross-sectional analysis of PA and screen time in 224 adolescents at entry into the Chronic Kidney Disease in Children (CKiD) cohort. We compared proportions of CKiD vs. healthy 2012 National Health and Nutrition Examination Survey (NHANES) participants reporting the recommended 60 min of PA 7 days/week or ≤ 2 h/day of entertainment screen time (binomial probability test). Within CKiD, we assessed correlates of PA and screen time using multivariable logistic and linear regression and examined longitudinal data for 136 participants.

RESULTS

Median age of CKiD participants was 15 years, and 60 % were male. Median estimated glomerular filtration rate (eGFR) was 41.3 (IQR 30.8, 52.3) ml/min/1.73 m(2). Only 13 % of CKiD participants met recommendations for PA vs. 25 % of NHANES (p < 0.001), while 98 % in CKiD exceeded the recommended screen time vs. 73 % in NHANES (p < 0.001). Within CKiD, obesity (p = 0.04) and lower eGFR (p = 0.02) were independently associated with greater screen time.

CONCLUSIONS

Adolescents with CKD engage in significantly less PA and greater screen time than healthy youth in the United States, and this may worsen over time.

Circulating Progenitor Cells and Childhood Cardiovascular Disease

Circulating progenitor cells have been extensively studied in the context of heart disease in adults. In these patients, they have been demonstrated to be markers of myocardial injury and recovery as well as potential therapeutic agents. However, studies in children are much more limited. Here we review current knowledge pertaining to circulating progenitor cells in the context of childhood cardiovascular disease. Priorities for further research are also highlighted.

Effects of acute exercise on circulating endothelial and progenitor cells in children and adolescents with juvenile idiopathic arthritis and healthy controls: a pilot study

BACKGROUND

Youth with juvenile idiopathic arthritis (JIA) may be at risk of poor cardiovascular health. Circulating endothelial progenitor cells (EPCs) and circulating endothelial cells (CECs) are markers of cardiovascular repair and damage, respectively, and respond to exercise. The objectives of this study were to compare resting levels of EPCs and CECs in JIA and controls, and to assess the effects of distinct types of exercise on EPCs and CECs in JIA and controls.

METHODS

Seven youth with JIA and six controls completed 3 visits. First, aerobic fitness was assessed. Participants then performed either moderate intensity, continuous exercise (MICE) or high intensity, intermittent exercise (HIIE) on separate days. Blood samples were collected at the beginning (REST), mid-point (MID) and end of exercise (POST) for determination of EPCs (CD31(+)CD34(bright)CD45(dim)CD133(+)) and CECs (CD31(bright)CD34(+)CD45(-)CD133(-)) by flow cytometry. Between group differences in EPCs and CECs were examined using two-way ANOVA, followed by Tukey's HSD post hoc, where appropriate. Statistical significance set at p ≤ 0.05.

RESULTS

Both EPCs and CECs were similar between groups at REST (p = 0.18-0.94). During MICE, EPCs remained unchanged in JIA (p = 0.95) but increased significantly at POST in controls (REST: 0.91 ± 0.55 × 10(6) cells/L vs. POST: 1.53 ± 0.36 × 10(6) cells/L, p = 0.04). Compared with controls, lower levels of EPCs were observed in JIA at MID (0.48 ± 0.50 × 10(6) cells/L vs. 1.10 ± 0.39 × 10(6) cells/L, p = 0.01) and POST (0.38 ± 0.34 × 10(6) cells/L vs. 1.53 ± 0.36 × 10(6) cells/L, p < 0.001) during MICE. No changes were detected in CECs with MICE in JIA and controls (p = 0.69). Neither EPCs nor CECs were modified with HIIE (p = 0.28-0.69).

CONCLUSION

Youth with JIA demonstrated a blunted EPC response to MICE when compared with controls. Future work should examine factors that may increase or normalize EPC mobilization in JIA.