Associations of physical activity and fitness with adipocytokines in adolescents: the AFINOS Study

Lower adiponectin is associated with higher anthropometry and insulin resistance but not with low cardiorespiratory fitness in adolescents

PURPOSE

The aim of this study was to analyze the relationship between adiposity, cardiometabolic risk and cardiorespiratory fitness (CRF) according to different groups of adiponectin concentration.

METHODS

255 adolescents of both sexes, aged 11-17 years old, participated. Anthropometric and biochemical parameters such as body mass, height, abdominal circumference (AC), waist circumference (WC), fat mass, fat-free mass, total cholesterol (TC), high-density lipoprotein (HDL-c), low-density lipoprotein (LDL-c), triglycerides (TG), glucose, insulin, adiponectin, blood pressure, peak oxygen consumption (VO2peak) were measured. Body mass index (BMI), z-score BMI (BMI-z), triponderal mass index (TMI), waist-to-height ratio (WHtR), homeostasis model to assessment insulin resistance (HOMA-IR), and quantitative insulin sensitivity check index (QUICKI) were calculated. Adiponectin was categorized: low adiponectin concentration (LAC  ≤ 5.18 µg/mL-1), intermediate (IAC = 5.18 and 7.63 µg/mL-1) and high (HAC ≥ 7.63 µg/ml-1).

RESULTS

LAC showed higher BMI, BMI-z and TMI than the other groups (p < 0.05) and higher AC, WC and WHtR that the HAC (p < 0.05). IAC showed lower values of TC, LDL-c and TG, and the LAC presented the highest values of insulin, HOMA-IR and QUICKI (p < 0.05) to the IAC and HAC. HAC presented the lower VO2peak than the other groups (p < 0.01). BMI, TMI, glucose, insulin, HOMA-IR showed inverse, and QUICKI a direct and weak correlation with adiponectin (p < 0.05). No significant association was found between adiponectin and VO2peak (p > 0.05).

CONCLUSION

The LAC group had higher means in the anthropometric variables and the worst results related to insulin resistance and sensitivity. Thus, adiponectin may play an important role in obesity and reduced concentration may be a factor in the development of obesity-associated morbidities.

Moderating role of 1-minute abdominal test in the relationship between cardiometabolic risk factors and adiponectin concentration in adolescents

BACKGROUND

Adiponectin is an anti-inflammatory cytokine secreted by adipose tissue, has been associated with adiposity and cardiometabolic risk, and has controversial results with muscular fitness. The aim of this study was to analyze the interaction of 1-minute abdominal test in the relationship between adiposity, body composition, cardiometabolic risk and adiponectin concentration in adolescents.

METHODS

This is a cross-sectional study conducted with 62 adolescents of both sexes, aged 11 to 16 years, approved by the Ethics Committee of Research in Humans (CAEE: 62963916.0.0000.5223). Body mass, height, abdominal circumference (AC), waist circumference (WC), fat mass (FM), fat-free mass (FFM), high density lipoprotein (HDL-c), low density lipoprotein (LDL-c), triglycerides (TG), adiponectin, systolic blood pressure (SBP), diastolic blood pressure (DBP) and mean blood pressure (MBP), 1-minute abdominal test (ABD) were measured. Body mass index (BMI), z-score BMI (BMI-z), triponderal mass index (TMI), and waist-to-height ratio (WHtR) were calculated. The macro PROCESS for SPSS v.24.0 was used for moderation analyses, with linear regression models.

RESULTS

Inverse interactions were found for adiposity (BMI, BMI-z, TMI, AC, WC, WHtR), body composition (FM, FFM) and CMRF (SBP, DBP, MBP, TG) versus 1-minute abdominal test with adiponectin concentration, demonstrating that abdominal test is a moderator in these relationships.

CONCLUSION

We conclude that 1-minute abdominal test may play an important role in the relationship between obesity and cardiometabolic risk. We found that muscular fitness can confer a protective effect on adolescents with high levels of abdominal test.

Moderation of Physical Activity between Cardiometabolic Risk and Adiponectin in Adolescents

The aims of the study were to examine the moderating role of physical activity in the relationship between cardiometabolic risk factors and adiponectin concentration in adolescents. This is a cross-sectional study conducted with 96 adolescents of both sexes, between 11 and 17 years old. Body mass, height, fat mass (FM), fat-free mass, systolic blood pressure, diastolic blood pressure, high density lipoprotein, low density lipoprotein (LDL-c), triglycerides, insulin, adiponectin, C-reactive protein, and level of physical activity (energy expenditure questionnaire) were measured. Body mass index (BMI), triponderal mass index (TMI), homeostasis model to assessment insulin resistance (HOMA-IR), and quantitative insulin sensitivity check index (QUICKI) were calculated. Macro-PROCESS for SPSS was used for moderation analyses. Direct interactions were found for BMI, TMI, FM, insulin, and HOMA-IR and inverse for LDL-c, and QUICKI. Protection against cardiometabolic risk was found when the PA-coeff was completed above 1.57 coeff (BMI), 1.62 coeff (TMI), 1.55 coeff (FM), 1.41 coeff (LDL-c)1.60 coeff (insulin), 1.59 coeff (HOMA-IR) and 1.35 coeff (QUICKI). We conclude that physical activity was a moderator in the relationship with adiposity, insulin resistance and sensitivity, LDL-c, and adiponectin. In this context, we evidenced a relevant clinical impact on the health of adolescents, demonstrating the interaction between anthropometrics variables and physical activity.

Serum Adiponectin and Leptin Is Not Related to Skeletal Muscle Morphology and Function in Young Women

Adipokines secreted from adipose tissue, such as adiponectin and leptin, enhance skeletal muscle metabolism. Animal studies have shown that adipokine knockout leads to a reduction in muscle function. Muscle function is determined by muscle size and quality; therefore, it is speculated that lower adipokine levels affect skeletal muscle size and quality, eventually leading to lower muscle function. This study aimed to investigate the relationship between adipokines and skeletal muscle morphology and function in young individuals. A total of 21 young women participated in this study. Adiponectin and leptin levels were analyzed using fasting blood samples from all participants. B-mode ultrasound images of the thigh and calf were obtained, and the muscle thickness and echo intensity were measured in the vastus lateralis (VL) and medial gastrocnemius (MG). The shear modulus was measured from the VL and MG using shear wave elastography. Knee extension and plantar flexion peak torques were measured as muscle functions. Adiponectin and leptin were not related to echo intensity, shear modulus, and muscle thickness in the VL and MG (r_s = -0.26-0.37, P > .05). Furthermore, no relationship was observed between adiponectin, leptin, knee extension, and dorsiflexion peak torque (r_s = -0.28-0.41, P > .05). These negative results suggest that adiponectin and leptin levels in young women are not associated with muscle size and quality, nor are they related to muscle function.

Low leptin levels are associated with elevated physical activity among lean school children in rural Tanzania

BACKGROUND

In Sub-Saharan African countries, rapid urbanization and increasing socio-economic status are associated with a transition to decreased physical activity (PA). A more sedentary lifestyle is linked to increased body fat leading to increments in leptin levels. Since rodent and human studies in high-income countries have shown that starvation-induced hypoleptinemia triggers high PA, efforts are warranted to pursue the hypothesis that low leptin levels in lean children of low- and middle-income countries (LMIC) are also associated with high PA.

METHODS

In this cross-sectional study, we assessed seven-day PA with triaxial accelerometry (ActiGraph GT3X) among 223 primary school children (9 to 12 years of age) in rural Tanzania. Moderate-to-vigorous PA (MVPA) and total accelerometer counts per day were outcome variables. Leptin was determined using enzyme linked immunosorbent assay tests from dried blood spots. Anthropometric assessments were conducted and food insecurity and socio-demographic data were gathered using semi-structured interviews.

RESULTS

In this sample of school children in rural Tanzania, leptin concentrations (median: 0.91 ng/mL, P25: 0.55, P75: 1.69), body mass index z-scores (median: -1.35, P25: -1.93, P75: -0.82), and height-for-age-z-scores (median: -1.16, P25: -1.96, P75: -0.61) were low. In contrast, PA levels were high with a median MVPA time of 119 min/day. Linear regression confirmed that leptin levels were negatively associated with MVPA (beta: -18.1; 95%CI: -29.7; -6.5; p = 0.002) and total accelerometer counts (beta: -90,256; 95%CI: -154,146; -26,365; p = 0.006). Children residing in areas with better infrastructure had lower MVPA levels (p < 0.001) and tended to have higher leptin levels (p = 0.062) than children residing in areas only reachable via dirt roads.

CONCLUSION

Our cross-sectional field study is the first that supports the hypothesis of low leptin levels as a potential endocrine trigger of high PA in lean children of a LMIC. We observed early signs of a PA transition towards a less active lifestyle in a subgroup residing in areas with better infrastructure that concomitantly tended to have higher leptin concentrations. Considering that area-dependent PA differences were more pronounced among girls than boys, whereas differences in leptin levels were less pronounced, not only biological, but also external factors explain PA transition.

Fitness Levels and Gender Are Related With the Response of Plasma Adipokines and Inflammatory Cytokines in Prepubertal Children

Background and Aim

Changes in adipokines have been related with the development of metabolic syndrome, frequently associated with obesity, and other risk factors. Fitness seems to promote a healthy cardiovascular status and could be a protector factor, just from childhood. Therefore, the present study aimed to evaluate the relationship between fitness levels with plasma adipokines and inflammatory biomarkers in prepubertal children.

Methods

One hundred and thirty-seven healthy normal-weight prepubertal children were recruited from local schools and divided after performing the fitness tests, into two groups according to fitness level—low cardiovascular fitness group (LF) and equal or higher cardiovascular fitness group (HF). Anthropometric variables, blood pressure (BP) and plasma insulin, and leptin, resistin, adiponectin, tumor necrosis factor-alpha, hepatic growth factor, interleukin (IL)-8, monocyte chemoattractant protein-1, nerve growth factor (NGF), and plasminogen activator inhibitor-1 (PAI-1) were measured fasting in both groups to be compared. Univariate analysis of variance, comparative analysis, binary logistic regression, stepwise linear regression, and principal component analysis were conducted to evaluate the association between fitness, BMI, gender, and the biochemical parameters.

Results

Girls and boys with HF presented lower waist circumference Z-score, BMI Z-score, systolic BP (only boys) as well as lower levels of leptin and NGF compared with their respective LF group. Regarding the association between variables, fitness showed an inverse relationship with BMI Z-score, leptin, PAI-1, HOMA-IR, resistin, IL-8, and NGF.

Conclusion

An adequate level of fitness seems to protect against risk factors related to low-grade inflammation and altered adipokines that are related to the onset of obesity just from the prepubertal stage.

Inflammation, oxidative stress and altered heat shock response in type 2 diabetes: the basis for new pharmacological and non-pharmacological interventions

Type 2 diabetes mellitus (DM2) is a chronic disease characterised by variable degrees of insulin resistance and impaired insulin secretion. Besides, several pieces of evidence have shown that chronic inflammation, oxidative stress, and 70 kDa heat shock proteins (HSP70) are strongly involved in DM2 and its complications, and various pharmacological and non-pharmacological treatment alternatives act in these processes/molecules to modulate them and ameliorate the disease. Besides, uncontrolled hyperglycaemia is related to several complications as diabetic retinopathy, neuropathy and hepatic, renal and cardiac complications. In this review, we address discuss the involvement of different inflammatory and pro-oxidant pathways related to DM2, and we described molecular targets modulated by therapeutics currently available to treat DM2.

Muscular Fitness and Cardiometabolic Variables in Children and Adolescents: A Systematic Review

BACKGROUND

The importance of muscular fitness (MF) in the performance of activities of daily living is unequivocal. Additionally, emerging evidence has shown MF can reduce cardiometabolic risk in children and adolescents.

OBJECTIVES

The purpose of this study was to examine and summarize the evidence regarding the relationship between MF phenotypes (i.e., maximum muscular strength/power, muscular endurance, and maximum muscular strength/power/endurance) and cardiometabolic variables (obesity, blood pressure, lipids, glucose homeostasis, inflammatory markers, and clustered cardiometabolic variables) in children and adolescents.

DESIGN

This systematic review was conducted in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement and was registered with PROSPERO, number CRD42020179273.

DATA SOURCES

A systematic review was performed on five databases (PubMed, EMBASE, SciELO, Scopus, and Web of Knowledge) from database inception to May 2020, with complementary searches in reference lists.

ELIGIBILITY CRITERIA FOR SELECTING STUDIES

Eligibility criteria included (1) a study sample of youth aged ≤ 19 years, (2) an assessment of MF with individual or clustered cardiometabolic variables derived from adjusted models (regardless of test/measurement adopted or direction of reported association), and (3) a report of the association between both, using observational studies. Only original articles published in peer-reviewed journals in English, Portuguese, and Spanish languages were considered. The quality of the included studies was assessed by using the National Heart, Lung, and Blood Institute checklist. The percentage of results reporting a statistically significant inverse association between each MF phenotype and cardiometabolic variables was calculated.

RESULTS

Of the 23,686 articles initially identified, 96 were included (77 cross-sectional and 19 longitudinal), with data from children and adolescents from 35 countries. The score for the quality of evidence ranged from 0.33 to 0.92 (1.00 maximum). MF assessed by maximum muscular strength/power was inversely associated with lower obesity (64/113 total results (56.6%)) and reduction in clustered cardiometabolic risk (28/48 total results (58.3%)). When assessed by muscular endurance, an inverse association with obesity (30/44 total results (68.1%)) and cardiometabolic risk (5/8 total results (62.5%)) was identified. Most of the results for the relationship between MF phenotypes with blood pressure, lipids, glucose homeostasis, and inflammatory markers indicated a paucity of evidence for these interrelationships (percentage of results below 50.0%).

CONCLUSION

MF assessed by maximum muscular strength/power or muscular endurance is potentially associated with lower obesity and lower risk related to clustered cardiometabolic variables in children and adolescents. There is limited support for an inverse association between MF with blood pressure, lipids, glucose homeostasis biomarkers, and inflammatory markers in children and adolescents.

Impact of Physical Activity Intensity Levels on the Cardiometabolic Risk Status of Children: The Genobox Study

Childhood obesity has been related to metabolic syndrome and low-grade chronic inflammation. This study aimed to evaluate the impact of physical activity intensities and practice on inflammation, endothelial damage, and cardiometabolic risk factors in children. There were 513 participants, aged 6-14 years, recruited for the study. Physical activity was measured by accelerometry, and the children were classified into four groups according to quartiles of moderate to vigorous physical activity (MVPA) practice as very low active, low active, moderate active, and high active. Anthropometric measures, blood pressure, and plasma metabolic and proinflammatory parameters were analyzed. Very low active group presented a worse lipid profile and higher insulin, leptin, adiponectin, resistin, matrix metallopeptidase-9, and tissue plasminogen activator inhibitor-1, while lower levels of tumor necrosis factor-alpha, Type 1 macrophages, and interleukin 8 than high-active children. Regression analyses showed that a higher MVPA practice was associated with lower levels of triacylglycerols (β: -0.118; p = .008), resistin (β: -0.151; p = .005), tPAI (β: -0.105; p = .046), and P-selectin (β: -0.160; p = .006), independently of sex, age, and body mass index (BMI). In contrast, a higher BMI was associated with higher levels of insulin (β: 0.370; p < .001), Homeostasis Model Assessment (β: 0.352; p < .001), triacylglycerols (β: 0.209; p < .001), leptin (β: 0.654; p < .001), tumor necrosis factor-alpha (β: 0.182; p < .001), Type 1macrophages (β: 0.181; p < .001), and tissue plasminogen activator inhibitor (β: 0.240; p < .001), independently of sex, age, and MVPA. A better anthropometric, metabolic, and inflammatory profile was detected in the most active children; however, these differences were partly due to BMI. These results suggest that a higher MVPA practice and a lower BMI in children may lead to a better cardiometabolic status.

The genetic case for cardiorespiratory fitness as a clinical vital sign and the routine prescription of physical activity in healthcare

BACKGROUND

Cardiorespiratory fitness (CRF) and physical activity (PA) are well-established predictors of morbidity and all-cause mortality. However, CRF is not routinely measured and PA not routinely prescribed as part of standard healthcare. The American Heart Association (AHA) recently presented a scientific case for the inclusion of CRF as a clinical vital sign based on epidemiological and clinical observation. Here, we leverage genetic data in the UK Biobank (UKB) to strengthen the case for CRF as a vital sign and make a case for the prescription of PA.

METHODS

We derived two CRF measures from the heart rate data collected during a submaximal cycle ramp test: CRF-vo2max, an estimate of the participants' maximum volume of oxygen uptake, per kilogram of body weight, per minute; and CRF-slope, an estimate of the rate of increase of heart rate during exercise. Average PA over a 7-day period was derived from a wrist-worn activity tracker. After quality control, 70,783 participants had data on the two derived CRF measures, and 89,683 had PA data. We performed genome-wide association study (GWAS) analyses by sex, and post-GWAS techniques to understand genetic architecture of the traits and prioritise functional genes for follow-up.

RESULTS

We found strong evidence that genetic variants associated with CRF and PA influenced genetic expression in a relatively small set of genes in the heart, artery, lung, skeletal muscle and adipose tissue. These functionally relevant genes were enriched among genes known to be associated with coronary artery disease (CAD), type 2 diabetes (T2D) and Alzheimer's disease (three of the top 10 causes of death in high-income countries) as well as Parkinson's disease, pulmonary fibrosis, and blood pressure, heart rate, and respiratory phenotypes. Genetic variation associated with lower CRF and PA was also correlated with several disease risk factors (including greater body mass index, body fat and multiple obesity phenotypes); a typical T2D profile (including higher insulin resistance, higher fasting glucose, impaired beta-cell function, hyperglycaemia, hypertriglyceridemia); increased risk for CAD and T2D; and a shorter lifespan.

CONCLUSIONS

Genetics supports three decades of evidence for the inclusion of CRF as a clinical vital sign. Given the genetic, clinical and epidemiological evidence linking CRF and PA to increased morbidity and mortality, regular measurement of CRF as a marker of health and routine prescription of PA could be a prudent strategy to support public health.

A lifestyle pattern during adolescence is associated with cardiovascular risk markers in young adults: results from the DONALD cohort study

Lifestyle score approaches combining individual lifestyle factors, e.g. favourable diet, physical activity or normal body weight, showed inverse associations with cardiovascular disease (CVD) risk. However, research mainly focussed on adult behaviour and is scarce for vulnerable time windows for adult health like adolescence. We investigated associations between an adolescent lifestyle score and CVD risk markers in young adulthood. Overall, we analysed 270 participants of the open DONALD cohort study with 1–6 complete measurements of five lifestyle factors (healthy diet, moderate-to-vigorous physical activity, sedentary behaviour, sleep duration and BMI standard deviation score) during adolescence (females: 8⋅5–15⋅5 years and males: 9⋅5–16⋅5 years). Multivariable linear regression models were used to investigate the prospective association between the adolescent lifestyle score (0–5 points) and CVD risk markers in young adulthood (18–30 years). On average, participants obtained a mean adolescent lifestyle score of 2⋅9 (0–5) points. Inverse associations between the adolescent lifestyle score and waist circumference, waist-to-height ratio and percentage of body fat were observed (4⋅1, 4⋅1 and 9⋅2 % decrease per 1 point increase in adolescent lifestyle score, respectively, P < 0⋅05). For the remaining CVD risk markers (glucose, blood lipids, blood pressure and a proinflammatory score), no associations were observed. A healthy adolescent lifestyle is particularly associated with CVD risk-related favourable anthropometric markers in adulthood. A more comprehensive understanding of lifestyle patterns in the life course might enable earlier, targeted preventive measures to assist vulnerable groups in prevention of chronic diseases.

Handgrip Strength and Its Relationship with White Blood Cell Count in U.S. Adolescents

BACKGROUND

The role of muscular fitness (as a protecting factor for an optimal immune system) and WBC count remains unclear. To the best of our knowledge, this is the first study to investigate the relationship between the total count of WBC and groups based on handgrip strength and body composition. The aim of this study was to elucidate the relationship between handgrip strength and WBC count in a nationally representative sample of adolescents from the U.S.

METHODS

We used data from the NHANES cross-sectional study (waves 2011 to 2014). The final analysis included 917 adolescents from 12-17 years old (51.0% boys). Normalized handgrip strength (kg) (NHS) was relativized by body composition parameters (body weight [NHSw], total body fat [NHSf], and trunk fat [NHSt]) assessed with dual energy X-ray absorptiometry.

RESULTS

An inverse association was found between total WBC count and all assessments of low NHS in both sexes (p < 0.05). Both boys and girls with low NHS had higher WBC counts in all estimations of NHS than those with high NHS (p < 0.05 for all). All estimations of low NHS showed significant differences with those with intermediate NHS (only in girls) (p < 0.05 for all). Girls with intermediate NHSt exhibited higher WBC count than those with high NHSt (p = 0.004).

CONCLUSIONS

Our findings suggest that greater levels of NHS are linked to lower total WBC counts. From a public health perspective, our findings are clinically significant and emphasize the relevance of improving muscular fitness during adolescence since it may contribute to boosting the immune system among adolescents.

Cardiorespiratory Fitness Predicted by Fibrinogen and Leptin Concentrations in Children with Obesity and Risk for Diabetes: A Cross-Sectional Study and a ROC Curve Analysis

Obesity is defined as abnormal or excessive fat accumulation that presents a risk to health. The ability to exercise is affected by adiposity, and this mechanism involves low-grade chronic inflammation and homeostatic stress produced mainly in adipocytes, which can result in abnormal adipokine secretion. To date, the gold standard for cardiorespiratory fitness assessment is considered to be the maximum oxygen uptake (VO_2max). The aim of the present study was to assess the prognostic value of hematological parameters of childhood obesity, as potential predictors of cardiorespiratory fitness (VO_2max), using a sample of children and adolescents with obesity and risk for diabetes. A total of 84 clinically healthy children and adolescents were recruited, of which 21 were considered lean, 22 overweight and 41 obese, with a mean age of 12.0 ± 1.9, 11.4 ± 2.0, and 11.2 ± 2.1 years old, in each weight status category, respectively. Age and sex did not differ between groups. Hematologic testing was performed after 12 h of fasting including glucose, serum lipids, insulin, hc-CRP, adiponectin, leptin and fibrinogen levels. Cardiorespiratory capacity for exercise was assessed to determine VO_2max, using a cycle ergometer. The VO_2max was negatively correlated with progressive strength to the BMIz (-0.656, p ≤ 0.001), hs-CRP (r = -0.341, p ≤ 0.002), glucose (r = -0.404, p ≤ 0.001) and insulin levels (r = -0.348, p ≤ 0.001), the homeostasis model assessment of insulin resistance (HOMA-IR) (r = -0.345, p ≤ 0.002), as well as to the leptin (r = -0.639, p ≤ 0.001) and fibrinogen concentrations (r = -0.520, p ≤ 0.001). The multivariate analysis revealed that only leptin and fibrinogen concentrations could predict the VO_2max adjusted for the BMIz of participants. The receiver operating characteristic (ROC) curve for the diagnostic accuracy of leptin, hs-CRP and fibrinogen concentrations for the prediction of VO_2max revealed a good diagnostic ability for all parameters, with leptin being the most promising one (area under the curve (AUC): 99%). The results verify that in children with obesity, VO_2max may be predicted from hematological parameters (leptin and fibrinogen), possibly bypassing more invasive methods.

The longitudinal relationship between dietary intake, physical activity and muscle strength among adolescents

The longitudinal relationship between muscle strength, dietary intake and physical activity among adolescents is not well understood. We investigated the trend and longitudinal effects of dietary intakes and physical activity scores on muscle strength in adolescents. This prospective cohort study consisted of 436 adolescents (134 males; 302 females) aged 13 years at baseline (2012) who were followed up at the ages of 15 (2014) and 17 (2016) years, respectively. We measured muscle strength using a calibrated hand dynamometer, estimated dietary intake with a 7-d dietary history and physical activity scores with a validated physical activity questionnaire for older children. A generalised estimating equation was used to examine the effect of dietary intakes and physical activity on muscle strength changes. The analysis was performed separately by sex. The muscle strength for males and females had increased within the 5-year period. The dietary intakes (energy and macronutrients) also increased initially but plateaued after the age of 15 years for both sexes. Females recorded a significant declining trend in physical activity scores compared with males as they grew older. A significant positive longitudinal relationship was found between protein (β = 0·035; P = 0·016), carbohydrate intake (β = 0·002; P = 0·013) and muscle strength among males. However, no longitudinal relationship was found between dietary intake, physical activity and muscle strength among females. Higher protein and carbohydrate intake among males was associated with higher muscle strength but was not observed in females. Nutrition and physical activity focusing on strength building are required in early adolescence and need to be tailored to males and females accordingly.

Cardiorespiratory fitness, physical activity, sedentary behavior, and circulating white blood cells in US youth

The white blood cell (WBC) provides a clue to the presence of illness. Cardiorespiratory fitness (CRF) and physical activity levels are negatively associated with circulating total WBC counts in adults. To date, only a scarce number of studies have investigated these associations among youths. The aim was to elucidate the relationship between CRF and accelerometer-assessed physical activity and sedentary behavior with WBC counts and subfraction concentrations of particular WBC (neutrophils, lymphocytes, monocytes, basophils, and eosinophils) in a large representative national sample of US children and adolescents. Participants accumulating 60 min/day or more of moderate-to-vigorous physical activity (MVPA) were considered active or inactive otherwise. Participants were also categorized into low, average, and high CRF level. The final sample consisted of 1623 children and adolescents (11.9 years old) from 2003 to 2006 cycle and 2624 (14.5 years old) from 1999 to 2004 cycle. CRF was inversely associated with total WBC and segmented neutrophils concentration in both sexes, and MVPA only in boys. Further, active children and adolescents had higher odds of a normal range of WBC count in boys (Odds Ratio [OR] = 1.41 95% CI, 1.02 to 2.34) and girls (OR = 3.52 95% CI, 1.01 to 12.23). In conclusion, our observations indicate that interventions targeting CRF and MVPA could strength the immune system of children and adolescents.

High levels of adiponectin attenuate the detrimental association of adiposity with insulin resistance in adolescents

BACKGROUND AND AIM

This study aimed to: i) examine the differences in insulin resistance (IR) across adiposity levels; and ii) ascertain whether high levels of adiponectin attenuate the detrimental association of adiposity with IR in adolescents.

METHODS AND RESULTS

A total of 529 adolescents aged 12-18 years participated in this cross-sectional study (267 girls). Anthropometry and body adiposity parameters [body mass index (BMI), sum of skinfolds, body fat percentage (BF %) by bio-impedance analysis and waist circumference (WC)], were measured according to standardized procedures and categorized into age- and sex-specific quartiles. Socioeconomic status, pubertal stage and lifestyle determinants (Mediterranean diet adherence and cardiorespiratory fitness) were gathered and used as confounders. Serum adiponectin and IR (homeostasis model assessment of insulin resistance [HOMA-IR] estimated from fasting serum insulin and glucose were assessed. Analysis of covariance (ANCOVA) showed that HOMA-IR increased in a linear fashion throughout the quartiles of all adiposity measures (p < 0.001 for all), independently of age, sex, pubertal stage, socioeconomic status, adherence to the Mediterranean diet and cardiorespiratory fitness. Two-way ANCOVA showed that adolescents in the higher quartile of adiposity for BF%, BMI, WC and skinfolds sum (Q4) presented the highest adiponectin levels, and had 0.77 Standard Deviation (SD), 0.8 SD, 0.85 SD and 0.8 SD lower HOMA-IR, respectively (p < 0.01) than their low adiponectin group counterparts, after adjustments for potential confounders.

CONCLUSION

Higher adiponectin levels may attenuate the detrimental association between adiposity and IR, particularly in subjects with higher adiposity.

Physical activity attenuates metabolic risk of adolescents with overweight or obesity: the ICAD multi-country study

BACKGROUND

Although the benefits of physical activity (PA) at an early age are well established, there is no robust evidence of the role of PA as well as its intensities in attenuating the association between weight status and metabolic risk among adolescents. In this investigation, we analyzed the association between weight status, intensities of PA, and metabolic risk among adolescents.

METHODS

Data from six cross-sectional studies in the International Children's Accelerometry Database were used (N = 5216 adolescents; boys 14.6 ± 2.1 years and girls 14.7 ± 2.0 years). Weight status was assessed and classified according to body mass index. Fasting glucose, triglycerides, inverse high-density lipoprotein cholesterol, and blood pressure composed the metabolic risk indicator (z-score). PA was measured by accelerometers. The estimated age of peak height velocity was used as a covariate for somatic maturation.

RESULTS

We observed that increase in weight status showed a strong positive relationship with metabolic risk. However, adolescents with overweight or obesity in the highest tertile of PA (moderate-to-vigorous and vigorous intensity) showed a similar metabolic risk score as the normal weight groups. Moderate intensity PA seemed related to metabolic risk even within some categories of vigorous PA.

CONCLUSIONS

We conclude that PA attenuates the metabolic risk of adolescents with overweight or obesity. Although this attenuation is largely explained by vigorous PA, moderate intensity seems also important for better metabolic profile.

Ability of 2 estimation methods of body fat percentage in identifying unfavorable levels of cardiometabolic biomarkers in adolescents: Results from the LabMed study

Background:

To assess and compare the ability of body fat percentage (BF%) estimated by 2 methods, bioelectrical impedance analysis (BIA) and by the Slaughter et al equations for triceps and subscapular skinfold thickness (SKF), in identifying unfavorable levels of several biomarkers of cardiometabolic risk.

Methods:

Cross-sectional school-based study with 529 apparently healthy adolescents (267 girls), aged 14.3 ± 1.7 years.

Results:

BF% estimated by both methods always showed higher areas under the curve (AUC) for each biomarker in girls than in boys (with the exception of BIA for leptin). BF% estimated by BIA and by SKF presented a discriminatory ability in identifying unfavorable levels in all biomarkers of cardiometabolic risk in girls; however, BF% estimated by BIA displayed the highest AUC (except for C-reactive protein). In boys, BF% estimated by SKF presented higher AUC for C-reactive protein, fibrinogen and erythrocyte sedimentation rate; and BF% estimated by BIA for complement C3 and leptin. Positive and significant associations between BIA and SKF with all biomarkers (P < .05) were found (except for SKF and complement C4 in girls, and SKF and fibrinogen and erythrocyte sedimentation rate in boys), after adjustments for pubertal stage, cardiorespiratory fitness, adherence to the Mediterranean diet and socioeconomic status.

Conclusions:

Overall, diagnostic performance was more accurate in girls. BF% estimated by BIA presented a slightly better overall discriminatory ability for each biomarker than BF% estimated by SKF in girls, while in boys no method clearly prevailed over the other.

Toward Active Living: SES- and Race-Based Disparities in Knowledge and Behaviors

OBJECTIVE

The purpose of this study was to examine the potential differences in knowledge and behaviors related to active living between two schools with contrasting socioeconomic status (SES) and racial characteristics.

DESIGN

The sample involved 523 adolescents from two public middle schools in a southern US state including 243 Black (46.5%), 223 White (42.6%), and 67 others (12.8%). Physical activity (PA) and sedentary behavior (SB) were measured using the validated Youth Activity Profile (YAP), while knowledge of physical activity and fitness (PAF knowledge) was measured using the grade-appropriate PE Metrics written test. Socio-demographic characteristics were self-reported or obtained via secondary government database.

RESULTS

The medium SES school showed higher PA outside of school (ΔM = 0.27, d = 0.26), lower SB (ΔM = - 0.35, d = - 0.45), and higher PAF knowledge (ΔM = 8.3%, d = 0.54) than the low SES school. Statistically significant differences were observed for after-school PA, evening PA, weekend PA, TV viewing, video games, and cell phone use (d = - 0.38 to 0.39). Group difference by race was also found with White participants demonstrating higher PA outside of school, lower SB, and higher PAK knowledge than Black participants (d = - 0.43 to 0.57).

CONCLUSIONS

The lower SES school (mostly Black) showed less favorable PA, SB, and knowledge results than the higher SES school. SES is a significant school-level characteristic influencing the determinants (i.e., knowledge and behaviors) of the active living habit in youth.

Dietary intake, physical activity and muscle strength among adolescents: the Malaysian Health and Adolescents Longitudinal Research Team (MyHeART) study

OBJECTIVE

To examine the role of dietary intake and physical activity in muscle strength among adolescents.

DESIGN

Cross-sectional analysis.

SETTING

The Malaysian Health and Adolescents Longitudinal Research Team (MyHeART) study.

PARTICIPANTS

Fifteen-year-old secondary school children who have given consent and who participated in the MyHeART study in 2014.

PRIMARY OUTCOME MEASURE

Muscle strength was measured in relation to dietary intake (energy and macronutrients) and physical activity by using a hand grip dynamometer.

RESULTS

Among the 1012 participants (395 male; 617 female), the hand grip strength of the males was higher than that of the females (27.08 kg vs 18.63 kg; p<0.001). Also, males were more active (2.43vs2.12; p<0.001) and consumed a higher amount of energy (2047 kcal vs 1738 kcal; p<0.001), carbohydrate (280.71 g vs 229.31 g; p<0.001) and protein (1.46 g/kg body weight (BW) vs 1.35 g/kg BW; p<0.168). After controlling for ethnicity, place of residency and body mass index, there was a positive relationship between hand grip strength and the intake of energy (r=0.14; p=0.006), carbohydrate (r=0.153; p=0.002) and fat (r=0.124; p=0.014) and the physical activity score (r=0.170; p=0.001) and a negative relationship between hand grip strength and the intake of protein (r=-0.134; p=0.008), for males. However, this was not observed among females.

CONCLUSIONS

Energy, carbohydrate and fat intakes and physical activity score were positively correlated with hand grip strength while protein intake was negatively correlated with hand grip strength in males but not in females.

Cardiorespiratory fitness and site-specific risk of cancer in men: A systematic review and meta-analysis

BACKGROUND

Cardiorespiratory fitness is a strong predictor of all-cause morbidity and mortality; nevertheless, the association between cardiorespiratory fitness and the risk of cancer remains unclear. Thus, the aim of this study was to synthetize the evidence on the relationship between cardiorespiratory fitness and the risk of several sites of cancer in men.

METHODS

A computerised search in MEDLINE, EMBASE and Web of Science databases from their inception to 13th February 2019 was performed. Both fixed and random-effects models were used to calculate the pooled hazard ratio (HR) estimates and their 95% confidence intervals (CIs) to examine the effect of high and moderate versus low cardiorespiratory fitness on site-specific cancer (lung, colon/rectum, prostate) and all-sites cancer.

RESULTS

Ten studies were included in the qualitative review, and seven of them were included in the meta-analysis. Using low cardiorespiratory fitness as the reference group, moderate and high levels of cardiorespiratory fitness were associated with a lower risk (HRs) of lung cancer, 0.53 (95% confidence interval [CI], 0.39 to 0.68) and 0.52 (95% CI, 0.42 to 0.61); colorectal cancer, 0.74 (95% CI, 0.55 to 0.93) and 0.77 (95% CI, 0.62 to 0.92) and all cancer sites, 0.86 (95% CI, 0.79 to 0.93) and 0.81 (95% CI, 0.75 to 0.87), respectively.

CONCLUSIONS

Among men, cardiorespiratory fitness plays an important role in protecting against the risk of lung and colorectal cancer. Additionally, this protective effect was observed for all-sites cancer risk. These results show the importance of good cardiorespiratory fitness as a potential factor in cancer prevention.

Independent and combined associations of physical fitness components with inflammatory biomarkers in children and adolescents

BACKGROUND

We aimed to examine the independent and combined associations of cardiorespiratory fitness, muscular fitness, and motor ability with single and clustered inflammatory biomarkers in children and adolescents.

METHODS

This study included 503 children and adolescents. Cardiorespiratory fitness, upper- and lower-muscular fitness, and motor ability were assessed using field-based tests. Fasting blood samples were obtained to determine the levels of a set of inflammatory biomarkers. Global physical fitness and clustered inflammatory biomarker scores were computed. Associations between physical fitness and inflammatory biomarkers were analyzed through linear regression. Differences in inflammatory biomarker levels between physical fitness tertiles were tested.

RESULTS

Global physical fitness was inversely associated with single and clustered inflammatory biomarkers in children (p < 0.05); and with C-reactive protein, complement factor C4, leptin, and clustered inflammatory biomarkers in adolescents (p < 0.025). Cardiorespiratory fitness and upper-muscular fitness were negatively and independently associated with several single and clustered inflammatory biomarkers in children and adolescents (p < 0.05). Differences were found between the lowest and the highest tertiles of global physical fitness in clustered inflammatory biomarker levels (p < 0.010).

CONCLUSION

Physical fitness was negatively associated with single and clustered inflammatory biomarkers, independently of body mass index. Increasing physical fitness levels in youth might contribute to reduce the cardiovascular risk.

Fitness and academic performance in adolescents. The mediating role of leptin: DADOS study

We tested the mediating effect of leptin on the association between physical fitness (PF) components and academic performance indicators in healthy adolescents. A total of 263 adolescents (13.9 ± 0.3 years, 47.5% girls, 12.5% overweight) from the DADOS (Deporte, ADOlescencia y Salud) Study were included in the analysis. PF components were assessed by the handgrip test for upper-limb muscular strength, standing long jump test for lower-limb muscular strength, 4 × 10-m shuttle run test for speed-agility, and 20-m shuttle run test for cardiorespiratory fitness. Plasma leptin concentration was assessed from antecubital vein blood after an overnight fast using a sensitive ELISA kit. Academic performance indicators were assessed through final school grades and through the Spanish version of the SRA Test of Educational Ability. Body composition was assessed by body mass index and skinfold thicknesses. Boot-strapped mediation procedures were performed and indirect effects with confidence intervals not including zero were interpreted as statistically significant. Our findings suggest that the positive associations observed between cardiorespiratory fitness and lower-limb muscular strength with academic performance indicators were mediated by leptin concentration after adjusting for sex, pubertal stage, socioeconomic status, and adiposity (percentage of mediation ranging from 54.61 to 82.02%).

CONCLUSIONS

Improvements on PF components, particularly in cardiorespiratory fitness and lower-limb muscular strength, might reduce leptin concentration with potential benefits on academic performance in adolescents, independently of adiposity. What is Known: • Academic performance is associated with physical fitness and leptin concentration in children and adolescents. • Fitness modulates leptin concentration levels, regardless of physical activity and adiposity. What is New: • Leptin concentration mediates the association of cardiorespiratory fitness and muscular strength with academic performance in adolescents. • Improvements in cardiorespiratory fitness and muscular strength might reduce leptin concentration levels enhancing academic performance.

Physical Fitness and Its Relationship to Plasma Leptin, Leptin Soluble Receptor, and Free Leptin Index in a Saudi Population: A Comparison Between Diabetic and Non-Diabetic Individuals

Background

Low physical activity is considered to be a risk factor for type 2 diabetes mellitus (T2DM). One theory suggest that leptin resistance is involved in the pathophysiology of impaired glucose metabolism. In this study we aimed to assess the correlation of physical fitness scores (PFS) with serum total leptin (TL), serum leptin soluble receptor (LSR), and free leptin index (FLI) in a group of Saudi patients with T2DM.

Material/Methods

This cross-sectional study involved 115 subjects: 52 healthy control subjects and 63 patients with T2DM. All subjects underwent body composition analysis. Blood samples were analyzed for fasting blood glucose (FBG), glycosylated hemoglobin (HbA1c), serum total leptin (TL), and serum leptin soluble receptor (LSR). Based on ideal body composition and our previous studies, physical fitness scores (PFS) were recorded for each subject.

Results

In patients with T2DM, levels of LSR were positively correlated with PFS (r=0.281, p=0.025), while the levels of TL (r=−0.425, p=0.001) and FLI (r=−0.439, p=0.001) were negatively correlated with PFS. In control subjects, TL and FLI levels were negatively correlated (r=−0.612, p=0.001and r=−0.543, p=0.001 respectively) with PFS. In linear regression analysis, after adjustment for age and BMI, TL and FLI were independent predictors of PFS.

Conclusions

Serum TL and FLI were negatively correlated while LSR was positively correlated with PFS in patients with T2DM. Therefore, they may be important biomarkers for predicting the outcomes of physical fitness and exercise programs.

Associations of serum leptin, ghrelin and peptide YY levels with physical activity and cardiorespiratory fitness in adolescent boys with different BMI values

The aim of this study was to investigate the differences in associations of serum acylated and des-acylated ghrelin, peptide YY (PYY) and leptin levels with physical activity (PA) and cardiorespiratory fitness (CReF) in adolescent boys (mean age of 14.0 years) with overweight (OWB; n=55) and with normal weight (NWB; n=154).

METHODS

Total PA was measured by 7-day accelerometry (counts/min) and CReF by peak oxygen consumption (VO²peak/kg).

RESULTS

No differences were found in serum PYY, acylated ghrelin or des-acyl ghrelin levels, whereas mean leptin (11.6±10.6 vs. 2.0±2.7 ng/ml; p<0.05) and insulin (18.1±8.7 vs. 11.0±6.2 mU/l; p<0.05) levels were significantly higher in OWB compared to NWB. Mean CReF was significantly lower in OWB compared to NWB (39.7±8.7 vs. 50.5±6.8 ml/min/kg; p<0.05). Leptin was negatively correlated with CReF in both groups (r=-0.43; p<0.05), des-acylated ghrelin with CReF only in OWB (r =-0.36; p<0.05). In OWB leptin was negatively correlated with total PA (r=-0.32; p<0.05) and positively with sedentary time of PA (r=0.35; p<0.05). In NWB 28.1% of the variability of CReF was determined by leptin and insulin resistance index (HOMA-IR), whereas in OWB 71.9% was determined by trunk FM and BMI.

CONCLUSIONS

Leptin concentration was inversely associated with CReF in adolescent boys independently of BMI in both groups, while des-acylated ghrelin was associated with CReF only in OWB. Low PA in OWB was associated with high serum leptin level.

The hyperleptinemia state can downregulate cardiorespiratory fitness and energy expenditure in obese women

INTRODUCTION

In general, in obese people a state of hyperleptinemia may impair both energy balance and the inflammatory process. However, it has not been fully investigated whether there is a relationship between hyperleptinemia and cardiorespiratory fitness (CRF) and resting energy expenditure (REE), in obese women.

METHODS

83 obese women were enrolled in this cross-sectional study. Anthropometric measures, body composition, REE, CRF and serum concentration of leptin were measured. Pearson's correlation coefficient was performed to examine the relationship between circulating leptin level and other clinical variables. Multiple regression analysis was applied to determine predictors of REE and CRF. Effects were considered significant at p≤0.05.

RESULTS

The most important finding in the present study is that the hyperleptinemia state was inversely correlated with CRF (r=-0.382, p=0.001) and REE (r=-0.447, p<0.001). Moreover, a positive correlation with fat mass was confirmed (r=0.419, p<0.001). In addition, hyperleptinemia was an independent negative predictor of REE (r²=-2.649, p=0.010) and CRF (r²=-2.335, p=0.023).

CONCLUSION

Together our results may suggest a vicious cycle between the state of hyperleptinemia and a decrease in energy expenditure and cardiorespiratory fitness in obese women, which can impair whole body energy homeostasis. This information is important to contribute to clinical practices.

Association between Leptin, Adiponectin, and Leptin/Adiponectin Ratio with Clustered Metabolic Risk Factors in Portuguese Adolescents: The LabMed Physical Activity Study

Introduction: Circulating leptin and adiponectin levels have been associated with impaired vascular function, insulin resistance, and acute cardiovascular evens. This study aimed to evaluate the associations of leptin, adiponectin, and the leptin/adiponectin (L/A) ratio with a clustering of metabolic risk factors (MRF) in adolescents aged 12-18 years. Methods: This is a cross-sectional analysis with 529 Portuguese adolescents aged 12-18 years. Blood samples were taken to analyze total cholesterol (TC) and high-density lipoprotein (HDL) cholesterol (HDL-c), triglycerides glucose, insulin, leptin, and adiponectin levels. A continuous variable of clustered MRF score (sum of Z-scores of body fat percentage, systolic blood pressure, ratio TC/HDL, triglycerides, homeostatic model assessment insulin resistance, and cardiorespiratory fitness*[-1]) was computed. Results: Regression analyses showed that adiponectin was a significant and negative predictor of MRF score (boys: β = -0.199; p < 0.001; girls: β = -0.200; p < 0.001); whereas leptin was a significant positive predictor of MRF score (boys: β = 0.553; p < 0.001; girls: β = 0.399; p < 0.001). The L/A ratio was also a significant positive predictor of MRF score in both sexes (boys: β = 0.593; p < 0.001; girls: β = 0.461; p < 0.001), after adjustments for age, pubertal stage, adherence to the Mediterranean diet, and socioeconomic status. In addition, adiponectin, leptin, and L/A ratio were accurate to predict MRF among adolescents, but L/A ratio showed the highest area under receiver operating characteristic curve. Conclusion: Leptin, adiponectin, and L/A ratio are associated with the clustering of MRF in adolescents after adjustments for age, sex, pubertal stage, adherence to the Mediterranean diet, and socioeconomic status. L/A ratio was more strongly associated with MRF score than adiponectin or leptin.

Comparisons of physical activity, adipokines, vitamin D status and dietary vitamin D intake among adolescents

BACKGROUND

Considering that lifestyle and diet are key factors responsible for the increases in adiposity in youth, it is important to understand how vitamin D, adipokines and markers of glucose metabolism are related to physical activity level (PAL) during growth. The present study aimed to investigate associations between physical activity level, adiponectin/leptin ratio, vitamin D status and dietary vitamin D intake among adolescents.

METHODS

A cross-sectional study was conducted with adolescents aged 14-18 years old who were living in São Paulo, Brazil. Serum 25 hydroxyvitamin D [25(OH)D], adiponectin (A), leptin (L), glucose and insulin were obtained after 12 h of fasting. Dietary calcium and vitamin D intake were measured by 24-h food record, as repeated in 62.6% of the sample. PAL was measured by the International Physical Activity Questionnaire (IPAQ). Pearson's chi-square test, Pearson correlation and linear regression analysis were performed.

RESULTS

A total of 198 subjects, mean (SD) age 16.3 (1.4) years, 51% male, were enrolled in the study. Some 9% of participants were sedentary, 22% were insufficiently active (IA), 51% were active and 18% were very active (VA). The A/L ratio was lower among sedentary/IA subjects [2.2 (4.0) versus 5.6 (12.3); P = 0.01] compared to active/VA subjects. PAL was not associated with vitamin D status or markers of glucose metabolism. Serum 25(OH)D positively associated with vitamin D intake, after adjusting for sex, sun exposure and season of the year in regression analysis (partial r² =0.026, P = 0.02).

CONCLUSIONS

Low PAL was associated with a lower A/L ratio. Vitamin D status was not associated with sun exposure habits, although it was positively correlated with vitamin D intake.

Response to the Commentary: "Methodological Considerations for Analysing the Relation of Physical Activity with Leptin Levels in Children: Comment on the Study by Cicchella et al. (2013)" by David Jiménez-Pavon

This is a response to commentary by Jiménez-Pavon (2015) on the relationships of leptin levels with children's physical activity. The present response suggests actigraphs are superior to questionnaires for measuring children's physical activity. Cicchella, Stefanelli, Jurimae, Saar and Purge (2013) pointed out some interesting methodological issues related to the relationships of leptin and physical activity in normal weight children. The questions dealt with the reliability of the questionnaires in assessing physical activity in children, choices of the cut-off points for considering levels of physical activity as moderate or intense, and the association of leptin with PA levels. Some considerations in Jiménez-Pavon (2015) remain unclear.

Association between serum adiponectin levels and muscular fitness in Portuguese adolescents: LabMed Physical Activity Study

BACKGROUND AND AIM

Paradoxically, recent investigations have showed that adiponectin levels are inversely associated with muscle strength. However, to date, there is a lack of knowledge on the relationship between muscular fitness (MF) and adiponectin levels in adolescents. We aimed to examine the independent associations between MF and adiponectin levels in adolescents, controlling for several potential confounders.

METHODS AND RESULTS

This is a cross-sectional analysis with 529 Portuguese adolescents aged 12-18 years. A MF score was computed as the mean of the handgrip strength and standing long jump standardized values by age and gender. We measured fasting glucose, insulin, HDL-cholesterol, C-reactive protein and adiponectin. Linear regression analysis showed a significant inverse association between adiponectin (Z-score by age and sex) and MF score, after adjustments for age, sex, pubertal stage, socioeconomic status, adherence to the Mediterranean diet, body mass index, HOMA-IR, HDL-cholesterol, C-reactive protein and cardiorespiratory fitness (unstandardized β = -0.176; p < 0.005). Analysis of covariance showed a significant difference between the Low MF/Non-overweight group and the High MF/Non-overweight Group (p < 0.05) and between the Low MF/Non-overweight and High MF/Overweight Group (p < 0.05) (F (5, 523) = 2.262, p = 0.047).

CONCLUSION

Adiponectin circulating levels are inversely and independently associated with MF. In non-overweight adolescents, those with high levels of MF presented lower levels of adiponectin compared to those with Low MF. Likewise, overweight adolescents with High MF presented lower levels of serum adiponectin than non-overweight adolescents with Low MF.

Ability of Measures of Adiposity in Identifying Adverse Levels of Inflammatory and Metabolic Markers in Adolescents

BACKGROUND

Overweight and obesity have been associated with a pro-inflammatory state. We aimed to assess the ability of different measures of overall and abdominal adiposity for identifying adverse levels of inflammatory and metabolic markers in adolescents.

METHODS

This is a cross-sectional analysis with 529 Portuguese adolescents (267 girls), mean age 14.3 ± 1.7 years. Weight, height, sitting height, waist circumference (WC), and body fat percentage (BF%) were measured; and BMI, waist-to-height ratio (WHtR), and waist-to-sitting-height ratio (WsHtR) were calculated. We measured C-reactive protein (CRP), fibrinogen, erythrocyte sedimentation rate (ESR), complements C3 and C4, leptin, and adiponectin levels. Receiver operating characteristic (ROC) curves were used to estimate the ability of the adiposity measures to discriminate between low/high values of biomarkers.

RESULTS

The highest areas under the ROC curves were presented by BF% for fibrinogen and complement C3 in both sexes and for ESR, complement C4, and adiponectin only in girls; by BMI for CRP in girls and for leptin in both sexes; by WHtR for leptin in both sexes and for CRP, fibrinogen, and adiponectin only in girls; by waist circumference for CRP, fibrinogen, and complement C3 only in boys and for complement C4 in girls; and by WsHtR for complement C3 in girls; p < 0.05 for all.

CONCLUSIONS

The measures that more often presented discriminatory power were, for overall adiposity, BF% in both sexes, and for abdominal adiposity, WHtR in girls and WC in boys. However, small differences in discriminatory capabilities don't allow us to clearly defend the adoption of a single measure above all others.

The health benefits of muscular fitness for children and adolescents: a systematic review and meta-analysis

BACKGROUND

Physical fitness during childhood and adolescence has been identified as an important determinant of current and future health status. While research has traditionally focused on the association between cardio-respiratory fitness and health outcomes, the association between muscular fitness (MF) and health status has recently received increased attention.

OBJECTIVE

The aim of this systematic review and meta-analysis was to evaluate the potential physiological and psychological benefits associated with MF among children and adolescents.

METHODS

A systematic search of six electronic databases (PubMed, SPORTDiscus, Scopus, EMBASE, PsycINFO and OVID MEDLINE) was performed on the 20th May, 2013. Cross-sectional, longitudinal and experimental studies that quantitatively examined the association between MF and potential health benefits among children and adolescents were included. The search yielded 110 eligible studies, encompassing six health outcomes (i.e., adiposity, bone health, cardiovascular disease [CVD] and metabolic risk factors, musculoskeletal pain, psychological health and cognitive ability). The percentage of studies reporting statistically significant associations between MF and the outcome of interest was used to determine the strength of the evidence for an association and additional coding was conducted to account for risk of bias. Meta-analyses were also performed to determine the pooled effect size if there were at least three studies providing standardised coefficients.

RESULTS

Strong evidence was found for an inverse association between MF and total and central adiposity, and CVD and metabolic risk factors. The pooled effect size for the relationship between MF and adiposity was r = -0.25 (95% CI -0.41 to -0.08). Strong evidence was also found for a positive association between MF and bone health and self-esteem. The pooled effect size for the relationship between MF and perceived sports competence was r = 0.39 (95% CI 0.34-0.45). The evidence for an association between MF and musculoskeletal pain and cognitive ability was inconsistent/uncertain. Where evidence of an association was found, the associations were generally low to moderate.

CONCLUSION

The findings of this review highlight the importance of developing MF in youth for a number of health-related benefits.

METHODOLOGICAL CONSIDERATIONS TO ANALYZE THE RELATION OF PHYSICAL ACTIVITY WITH LEPTIN LEVELS IN CHILDREN: COMMENT ON CICCHELLA, ET AL. (2013)

A positive correlation was found between self-reported physical activity, leptin level, and Tanner stage 2 in children aged 10 to 12 years. However, several methodological considerations on the accuracy for assessing physical activity, misclassification of physical activity levels and weight status, the inclusion of possible confounds, and interpretation of the current findings should be examined to clarify the final interpretation.

High circulating adiponectin levels predict decreased muscle strength among older adults aged 70 years and over: A prospective cohort study

BACKGROUND AND AIMS

Population-based researches indicate that circulating adiponectin is inversely associated with muscle strength. However, interpretation of the findings has been limited by the use of a cross-sectional design. This study aimed to examine the prospective relationship between baseline circulating adiponectin concentration and change in muscular function-related physical performance in older adults.

METHODS AND RESULTS

A 1-year prospective cohort study of Japanese community-dwelling elderly was conducted between 2002 and 2003. Four hundred thirty-four older persons participated in the measurements of physical function, including leg extension power, functional reach, timed up-and-go test, and 10-m maximum walking speed, at baseline and follow-up. After adjustment for potential covariates, higher serum adiponectin concentration was found to be significantly associated with poorer physical performance at baseline (leg extension power [watt], P < 0.001; functional reach [cm], P < 0.001; log timed up-and-go test, P = 0.007; log 10-m maximum walking speed, P < 0.001). The results of the prospective analysis by analysis of covariance indicated that the elderly with higher serum adiponectin concentrations (tertiles) at baseline tended to have a decreased performance in leg extension power (means [95% confidence interval]: lowest, -105 [-125, -85.7]; middle, -117 [-135, -97.8]; highest, -140 [-160, -120], watt, P for trend = 0.021) and timed up-and-go test (lowest, -0.08 [-0.28, -0.12]; middle, -0.10 [-0.29, 0.10]; highest, 0.28 [0.07, 0.48], s, P for trend = 0.019), but not two other functioning.

CONCLUSION

High circulating adiponectin concentration may be an indicator of decreased physical performance, especially muscle strength, in older adults.

Muscular strength, aerobic capacity, and adipocytokines in obese youth after resistance training: A pilot study

BACKGROUND

Exercise has shown positive training effects on obesity-related inflammation, however, resistance training has shown mixed results concerning adipocytokine levels.

AIMS

The purpose of this pilot study was to explore the effects of resistance training on blood adipocytokine concentrations in obese youth, with specific examination of the relationship between these biomarkers and improved fitness (i.e., aerobic capacity, muscular strength).

METHODS

Fourteen obese adolescents (16.1 ±1.6 y; BMI: 32.3 ±3.9 kg/m(2)) participated in a 16-week resistance training intervention. Body composition, fasting blood concentrations of interleukin-6 (IL-6), tumour necrosis factor-alpha (TNF-ɑ), adiponectin, and leptin were measured pre- and post-training. Aerobic capacity was assessed via a maximal discontinuous exercise test. The rate of gain in muscular strength was calculated as the slope of progression in 1-repetition maximum throughout the intervention.

RESULTS

Resistance training increased lean mass (total, trunk) and decreased per cent body fat (total, trunk). The training also caused moderate clear decreases in IL-6 and TNF-ɑ concentrations. A small increase in adiponectin was also observed before and after intervention. When the group was stratified by changes in aerobic capacity, there were substantially larger decreases in leptin levels for those with improved capacity. Correlation analyses also revealed a negative relationship between log-transformed leptin and aerobic capacity at rest. Improvement in quadriceps strength was positively correlated with IL-6 and TNF-ɑ, while improvement in shoulder adductor strength was positively correlated with IL-6 only.

CONCLUSION

Resistance training improved adipocytokine markers, which were partially associated with improved physical fitness. Specifically, the relationship between strength improvements and IL-6 and TNF-ɑ suggests an exercise-induced signalling pathway that results in overall adaptive decreases in systemic inflammation in obese youth.

Circulating leptin levels are associated with physical activity or physical fitness in Japanese

OBJECTIVE

The aim of this study was to evaluate the link between circulating leptin levels and physical activity and/or physical fitness in apparently healthy Japanese.

METHODS

A total of 85 men and 111 women who were not taking any medication were enrolled in this cross-sectional study. Circulating leptin levels, physical activity measured by tri-axial accelerometers and peak oxygen uptake were evaluated. We also assessed anthropometric data, blood pressure, blood examinations and energy intake.

RESULTS

Circulating leptin levels were 3.2 ± 2.3 ng/mL in men and 5.9 ± 3.8 ng/mL in women. Circulating leptin levels were significantly and positively correlated with body weight, body mass index, abdominal circumference, insulin and the homeostasis model assessment index, and significantly and negatively correlated with peak oxygen uptake in both sexes. Stepwise multiple regression showed that peak oxygen uptake in men and physical activity evaluated by Σ[metabolic equivalents h per week(METs h/w)]. in women were determinant factors for circulating leptin levels after adjusting for confounding factors.

Cardiorespiratory fitness as predictor of cancer mortality: a systematic review and meta-analysis

BACKGROUND

Epidemiologic studies have reported that cardiorespiratory fitness is inversely associated with mortality from cancer. However, the evidence relating cardiorespiratory fitness to cancer mortality has not yet been quantitatively summarized.

METHODS

Following the preferred reporting items for sytematic reviews and meta-analyses (PRISMA) checklist, we conducted a systematic review and meta-analysis of the association between cardiorespiratory fitness and total cancer mortality. Relevant studies were identified through a literature search in PubMed up to August 2013 and by screening reference lists of qualifying articles. Data extraction was carried out independently by both authors and summary risk estimates were obtained using random-effects models.

RESULTS

Six prospective studies with an overall number of 71 654 individuals and 2002 cases of total cancer mortality were included. The median follow-up time in the studies was 16.4 years. Cardiorespiratory fitness showed a strong, graded, inverse association with total cancer mortality. Using low cardiorespiratory fitness as the reference group, intermediate and high levels of cardiorespiratory fitness were related to statistically significant decreased summary relative risks (RRs) of total cancer mortality of 0.80 [95% confidence interval (CI) 0.67-0.97] and 0.55 (95% CI 0.47-0.65), respectively. Studies that adjusted for adiposity yielded similar results to those that did not adjust for adiposity.

CONCLUSION

Increased cardiorespiratory fitness represents a strong predictor of decreased total cancer mortality risk, independent of adiposity.

Top 10 research questions related to musculoskeletal physical fitness testing in children and adolescents

The purpose of this article is to bring attention to the 10 most pressing questions relevant to musculoskeletal physical fitness testing in children and adolescents. The goal is to stimulate research to answer these questions. The most pressing needs include establishing definitive links between valid, reliable, and feasible field test measures of muscular strength, endurance, power, and flexibility and health risk factors/markers in children and adolescents; determining the effects of exercise training on these relationships; and documenting the tracking of these relationships. The role of flexibility in health-related physical fitness (HRPF) needs to be carefully and specifically examined. Although body weight/composition is a separate component of health-related fitness, it is also a factor that can influence the performance of musculoskeletal test items. The role of body weight, body fat, and central adiposity and the possibility of adjustment of tests results are important research questions. Several questions relate to which field tests are best for use in schools. Finally, actual health-related criterion-referenced cutoff values need to be developed. In conclusion, more quality research is needed to firmly establish the musculoskeletal area for HRPF in youth.

Circulating adiponectin levels are associated with peak oxygen uptake in Japanese

OBJECTIVE

The aim of this study was to investigate the link between circulating adiponectin levels and peak oxygen uptake and/or physical activity in Japanese.

METHODS

A total of 528 subjects (188 men and 340 women) were enrolled in this cross-sectional study. Circulating adiponectin levels, physical activity measured by tri-axial accelerometers, peak oxygen uptake and metabolic risk parameters were evaluated. We also assessed anthropometric factors, blood pressure, blood examinations and energy intake.

RESULTS

Circulating adiponectin levels were 6.7 ± 3.0 μg/mL in men and 11.0 ± 4.9 μg/mL in women. Circulating adiponectin levels were positively correlated with physical fitness after adjusting for age, physical activity evaluated by Σ [metabolic equivalents × h per week (METs h/w)], cigarette smoking habit and energy intake in both sexes. However, these associations were attenuated further after adjusting for body mass index including other confounding factors, especially in men. However, circulating adiponectin levels were not associated with physical activity in either sex.

CONCLUSION

Circulating adiponectin levels were associated with peak oxygen uptake rather than physical activity.

Moderate physical activity correlates with elevated leptin in physically active 10-12-year-old boys with normal BMI

The aim of this study is to examine the relations between physical activity of differing intensity and duration with body energy-balance hormone leptin in 10-12-year-old boys (N = 94) who participated in moderate-to-vigorous physical activity at least four to five times per week. The boys reported their physical activity using a questionnaire. They had normal body mass index (BMI, kg/ m2), and were at Tanner Stage 2 of development. Boys were divided into three subgroups by leptin levels: normal serum leptin (M +/- .5 SD, n = 44, 1.2-3.9 ng/ml), low leptin (< or = M - .5 SD; n = 31, < 1.2 ng/ml), and high leptin (> or = M + .5 SD; n = 19, > 3.9 ng/ml). There were significant differences between subgroups in anthropometric parameters and serum leptin levels, but not in physical activity. A significant correlation was found between leptin and moderate physical activity of at least five times per week for at least 30 minutes each time in the high leptin group (r = .61). In conclusion, the correlations between physical activity and leptin are weak; only moderate physical activity was correlated with leptin levels in the high leptin

Inverse association between circulating adiponectin levels and skeletal muscle strength in Japanese men and women

BACKGROUND AND AIMS

Increased levels of circulating adiponectin in the elderly cause a negative impact on physical function and health status, which suggests that circulating adiponectin may be related to skeletal muscle function. However, data on the relationship between circulating adiponectin levels and skeletal muscle function is limited. Our objective was to investigate the association between serum adiponectin levels and muscle strength in adults.

METHODS AND RESULTS

This cross-sectional study is a part of the Oroshisho Study of adult employees in Japan from 2008 to 2011. In our study, we used data gathered in 2008-2010 that had included serum adiponectin measurements (n = 1378; age, 19-83 years). From this population, 1259 subjects were evaluated for grip strength (949 men, 310 women), and 965 subjects were evaluated for leg extension power (716 men, 249 women). Multivariate linear regression analyses showed that adiponectin was associated significantly and negatively with both grip strength (β and standard error [SE]: men, -0.09 [0.01], p = 0.010; women, -0.20 [0.03], kg, p = 0.002) and leg extension power (men, -0.09 [0.02], p = 0.014; women, -0.14 [0.07], W, p = 0.032) after adjusting for age, physical activity, nutrient intake, depressive symptoms, metabolic syndrome, C-reactive protein, body mass index, and other lifestyle-related potential confounders.

CONCLUSION

This population-based cross-sectional study indicates an inverse association between serum adiponectin levels and muscle strength in adults. Further studies are necessary to confirm this association and to clarify causality.

Ethnic differences in leptin and adiponectin levels between Greenlandic Inuit and Danish children

Objective

In a recent study, we found that Greenlandic Inuit children had a more adverse metabolic profile than Danish children. Aerobic fitness and adiposity could only partly account for the differences. Therefore, we set out to evaluate and compare plasma leptin and adiponectin levels in Danish and Inuit children.

Methods

In total, 187 Inuit and 132 Danish children (5.7–17.1 years) had examinations of anthropometrics, body fat content, pubertal staging, fasting blood and aerobic fitness.

Results

Plasma leptin was higher in Danish boys [3,774 (4,741–3,005)] [pg/mL unadjusted geometric mean (95% CI)] compared to both northern [2,076 (2,525–1,706)] (p<0.001) and southern (2,515 (3,137–2,016)) (p<0.001) living Inuit boys and higher in Danish girls [6,988 (8,353–5,847)] compared to southern living Inuit girls [4,910 (6,370–3,785)] (p=0.021) and tended to be higher compared to northern living Inuit girls [5,131 (6,444–4,085)] (p=0.052). Plasma adiponectin was higher for both Danish boys [22,359 (2,573–19,428)] [ng/mL unadjusted geometric mean (95% CI)] and girls [26,609 (28,994–24,420)] compared to southern living Inuit boys [15,306 (18,406–12,728)] and girls [18,864 (22,640–15,717)] (both p<0.001), respectively. All differences remained after adjustment for body fat percentage (BF%), aerobic fitness, age and puberty. The leptin/adiponectin ratio was higher in Danish boys and tended to be higher in Danish girls compared to northern living Inuit boys and girls, respectively. These differences were eliminated after adjustment for BF%, aerobic fitness, age and puberty.

Conclusions

In contrast to our hypothesis, plasma leptin was higher in Danish children despite a more healthy metabolic profile compared to Inuit children. As expected, plasma adiponectin was lowest in Inuit children with the most adverse metabolic profile.

Fitness and adiposity are independently associated with cardiometabolic risk in youth

Purpose. The purpose of the study was to examine the independent associations of adiposity and cardiorespiratory fitness with clustered cardiometabolic risk. Methods. A cross-sectional sample of 192 adolescents (118 boys), aged 14–16 years, was recruited from a South Lanarkshire school in the West of Scotland. Anthropometry and blood pressure were measured, and blood samples were taken. The 20 m multistage fitness test was the indicator of cardiorespiratory fitness (CRF). A clustered cardiometabolic risk score was constructed from HDL-C (inverted), LDL-C, HOMA, systolic blood pressure, and triglycerides. Interleukin-6, C-reactive protein, and adiponectin were also measured and examined relative to the clustered cardiometabolic risk score, CRF, and adiposity. Results. Although significant, partial correlations between BMI and waist circumference (WC) and both CRF and adiponectin were negative and weak to moderate, while correlations between the BMI and WC and CRP were positive but weak to moderate. Weak to moderate negative associations were also evident for adiponectin with CRP, IL-6, and clustered cardiometabolic risk. WC was positively associated while CRF was negatively associated with clustered cardiometabolic risk. With the additional adjustment for either WC or CRF, the independent associations with cardiometabolic risk persisted. Conclusion. WC and CRF are independently associated with clustered cardiometabolic risk in Scottish adolescents.

Circulating levels of adipokines and IGF-1 are associated with skeletal muscle strength of young and old healthy subjects

It is known that adipose tissue mass increases with age, and that a number of hormones, collectively called adipokines, are produced by adipose tissue. For most of them it is not known whether their plasmatic levels change with age. Moreover, it is known that adipose tissue infiltration in skeletal muscle is related to sarcopenia and loss of muscle strength. In this study we investigated the age-related changes of representative adipokines and insulin-like growth factor (IGF)-1 and their effect on muscle strength. We studied the association between circulating levels of adiponectin, leptin, resistin and IGF-1 and muscle strength. This cross-sectional study included 412 subjects of different age (152 subjects aged 18-30 years and 260 subjects aged 69-81 years) recruited within the framework of the European research network project "Myoage". The levels of adiponectin (both in male and female subjects) and leptin (only in males) were significantly higher in old subjects compared to young, while those of IGF-1 were lower in old subjects. In old subjects adiponectin, resistin and the resistin/IGF-1 ratio (but not IGF-1 alone) were inversely associated with quadriceps torque, while only adiponectin was inversely associated with handgrip strength independently from percentage of fat mass, height, age, gender and geographical origin. The ratio of leptin to adiponectin was directly associated with handgrip strength in both young and old subjects. These results suggest that in humans the age-associated loss of strength is associated with the levels of representative adipokines and IGF-1.

The associations between peak O2 consumption and leptin in 10- to 12-year-old boys

The aim of this study was to assess the associations of circulating levels of leptin with the peak O(2) consumption (VO(2)peak ) in 10- to 12-year-old boys of different BMI selected by Cole et al. (BMJ, 320,2000,1-6): total group (n = 248), normal (n = 190), overweight (n = 34) and obese (n = 24). We hypothesized that there is a close relationship in overweight and obese subgroups of boys with relative VO(2)peak kg (-1) (ml min(-1) kg(-1)) and leptin. Most of the subjects were Tanner stage 2. Peak O(2) consumption was measured directly using an increasing incremental protocol until volitional exhaustion on an electronically braked cycle ergometer. The expired gas was sampled continuously breadth-by-breadth mode for the measurement of oxygen consumption (MetaMax, Germany). Blood samples were obtained after an overnight fast from an antecubital vein for leptin measurements. Peak O(2) consumption (l min(-1)) was higher or lower (ml min(-1) kg(-1)) in overweight and obese groups, compared with normal BMI group. Leptin was higher in overweight and obese groups, compared with normal BMI group. Peak O(2) consumption (l min(-1)) correlated significantly with leptin only in total group (n = 248, r = 0·196). Contrary, relative VO(2)peak kg (-1) correlated significantly and negatively with leptin. The relationship was highest on the total group (r = -0·674). We can conclude that leptin first of all correlated negatively with relative peak O(2) consumption. Absolute VO(2)peak correlated with leptin only in total group.

A consideration of biomarkers to be used for evaluation of inflammation in human nutritional studies

To monitor inflammation in a meaningful way, the markers used must be valid: they must reflect the inflammatory process under study and they must be predictive of future health status. In 2009, the Nutrition and Immunity Task Force of the International Life Sciences Institute, European Branch, organized an expert group to attempt to identify robust and predictive markers, or patterns or clusters of markers, which can be used to assess inflammation in human nutrition studies in the general population. Inflammation is a normal process and there are a number of cells and mediators involved. These markers are involved in, or are produced as a result of, the inflammatory process irrespective of its trigger and its location and are common to all inflammatory situations. Currently, there is no consensus as to which markers of inflammation best represent low-grade inflammation or differentiate between acute and chronic inflammation or between the various phases of inflammatory responses. There are a number of modifying factors that affect the concentration of an inflammatory marker at a given time, including age, diet and body fatness, among others. Measuring the concentration of inflammatory markers in the bloodstream under basal conditions is probably less informative compared with data related to the concentration change in response to a challenge. A number of inflammatory challenges have been described. However, many of these challenges are poorly standardised. Patterns and clusters may be important as robust biomarkers of inflammation. Therefore, it is likely that a combination of multiple inflammatory markers and integrated readouts based upon kinetic analysis following defined challenges will be the most informative biomarker of inflammation.