Relation of serum irisin level with metabolic and antropometric parameters in obese children

The association of serum irisin with anthropometric, metabolic, and bone parameters in obese children and adolescents

Background

Irisin is an adipomyokine secreted by muscle and adipose cells, and it plays a role in glucose, fat, and bone metabolism. This study aimed to determine the correlation of serum irisin levels with anthropometric, metabolic, and bone parameters in obese children and adolescents.

Methods

This single-center study included 103 Korean children and adolescents: 54 (52.4%) obese participants with a body mass index (BMI) ≥95th percentile and 49 (47.6%) healthy controls with BMI within the 15th to 85th percentile. Various parameters were measured, including fasting blood glucose, fasting insulin, homeostasis model assessment of insulin resistance (HOMA-IR), triglyceride and glucose (TyG) index, lipid profile, alkaline phosphatase (ALP), osteocalcin, and 25(OH)-Vitamin D levels. Bone mineral density (BMD) was measured using dual-energy X-ray absorptiometry (DEXA) in 33 healthy subjects.

Results

Serum irisin was significantly higher in the obese group than in the control group (mean 18.1 ± 3.5 vs. 16.2 ± 2.0 ng/mL; p = 0.001). Serum irisin level was positively correlated with chronological age (r = 0.28; p = 0.004), height SDS (r = 0.24; p = 0.02), BMI SDS (r = 0.37; p < 0. 001), fasting glucose (r = 0.27; p = 0.007), fasting insulin (r = 0.23; p = 0.03), HOMA-IR (r = 0.21; p = 0.04), osteocalcin (r = 0.27; p = 0.006) and negatively correlated with HDL cholesterol (r = -0.29; p = 0.005). All these correlations were evident in obese subjects but not in healthy subjects. ALP and 25(OH)-Vitamin D were unrelated to irisin levels. Among 33 healthy subjects, total body-less head (TBLH) BMD Z-score was positively correlated with serum irisin (r = 0.39; p = 0.03), osteocalcin (r = 0.40; p = 0.02), fasting insulin (r = 0.39; p = 0.04), and HOMA-IR (r = 0.38; p = 0.047).

Conclusion

This study demonstrated an association between irisin levels and glucose, lipid, and bone parameters in children and adolescents. Our findings suggest that irisin has a potential role in metabolic disorders and bone health in obese children and adolescents.

Association of Serum Irisin Levels with Body Composition, Metabolic Profile, Leptin, and Adiponectin Levels in Lean and Obese Children

Background and Objectives: Irisin is an adipo-myokine with potential metabolic effects in the body, and its association with childhood obesity is still controversial. This study aimed to investigate the relationship between serum irisin levels and anthropometric parameters, body composition, metabolic profiles, leptin, and adiponectin in obese and normal-weight children. Methods: The study sample consisted of a total of 80 children aged 6-10, including 44 obese children (BMI ≥ 97th percentile) and 36 normal-weight children. Anthropometric parameters were measured. Body composition was determined with the use of the Bioelectrical Impedance Analysis (BIA) method. Metabolic profiles, as well as irisin, leptin, and adiponectin levels, were analyzed. Results: Anthropometric parameters and body composition were found to be significantly different between the obese and normal-weight groups (p < 0.05). Fasting blood glucose, insulin, HOMA-IR, and leptin levels were found to be significantly higher in the obese group, while the normal-weight group had significantly higher HDL cholesterol and adiponectin levels (p < 0.05). Serum irisin levels did not differ between the obese and normal-weight groups, or based on sex, vitamin D levels, and insulin resistance status. There was also no statistically significant correlation between serum irisin levels and anthropometric parameters, metabolic profile, leptin, and adiponectin. Conclusions: The study concluded that the obese children who participated in this study had high leptin levels and low adiponectin levels, with no significant difference in the irisin levels between the groups. More comprehensive clinical studies are needed to investigate the relationship between irisin and adipokines in children.

[Adipomyokines in children with obesity]

BACKGROUND

Adipomyokines are synthesized and secreted into the bloodstream by cells of both muscle and adipose tissue. They can have both a negative metabolic effect, acting as pro-inflammatory adipokines in obesity, and a positive one, increasing in response to physical exertion in the form of myokines.

AIM

To study the features of adipocytokine secretion in children with constitutionally exogenous obesity.

MATERIALS AND METHODS

The study included 80 patients: 60 adolescents aged 15 [13; 16] years with constitutionally exogenous obesity SDS BMI: 3.0 [2.6; 3.3] and 20 control group children aged 16 [15; 17] years without excess weight SDS BMI: -0.3 [-1.25; 0.33]. Commercial enzyme immunoassay kits were used to determine the level of adipomyokines. The compositional composition of the body was evaluated by bioimpedance analysis (InBody 770 analyzer, South Korea) in the morning, on an empty stomach. Statistical processing was carried out using STATISTICA v.12.0 (StatSoft Inc., USA). The results are presented in the form of median (Me) and quartiles (Q1; Q3) corresponding to 25 and 75 percentiles. The critical significance level (p) was assumed to be <0.05.

RESULTS

Levels of IL-6 and irisin are statistically significantly higher in obese adolescents compared to the control group: 0.55 [0.226; 1.35] pg/ml vs 0.202 [0.128; 0.652] pg/ml (p=0.041) and 11.16 [6.6; 22.76] mcg/ml vs 7.36 [6.48; 9.68] mcg/ml (p=0.043), respectively. Concentrations of IL-6, myostatin and decorin increase with an increase in the degree of obesity: grade I vs III: 0.226 [0.224; 0.398] vs 0.80 [0.36; 1.81] pg/ml (p=0,0197), 25,85 [21,53; 28,23] vs 31.41 [24.36; 35.06] ng/ml (p=0.03), 4065.3 [3244.9; 5245.5] vs 5322.5 [4199.8; 7702.4] pg/ml (p=0.0376), respectively. In obese children, IL-6 levels positively correlate with BMI, SDS BMI and the amount of adipose tissue, and myostatin - with BMI and SDS BMI. The concentration of irisin in the blood serum is significantly higher in obese girls than in obese boys and healthy girls. Obese patients, compared with lean peers, are characterized by a statistically significantly higher content of both fat and lean mass. With the progression of obesity, there is a statistically significant increase in the ratio of fat to lean mass (I degree - 0.66 [0.56; 0.7], III - 0.78 [0.68; 0.98] (p=0.0073).

CONCLUSION

Patients with obesity and normal body weight have different levels of adipomyokines. An increase in the level of IL-6 with the progression of obesity is directly related to an increase in the content of adipose tissue. Further study of the features of adipocytokine secretion, their relationship with the features of the body composition and metabolic complications in obesity is required.

Serum irisin levels increase in girls with central precocious puberty not dependent on BMI: a pilot study

OBJECTIVE

The objective of this study is to investigate the role of serum irisin level in diagnosis of central precocious puberty (CPP) in girls and its major determinants.

METHODS

This study was conducted in 67 girls with CPP, 19 girls with premature thelarche (PT) and 59 normal controls. The major determinants of irisin were assessed by multivariate linear regression (MLR) analysis. Propensity score matching (PSM) analysis was performed to minimize the bias that can result from BMI. A receiver operating characteristic curve was used to obtain the optimal threshold value of irisin.

RESULTS

The girls with CPP and PT had higher irisin levels than controls (P < 0.05). The optimal cutoff value of irisin levels for predicting CPP was 91.88 ng/mL, with a sensitivity of 70.1% and a specificity of 72.9%. MLR analysis showed that BMI was a predictor of irisin (P < 0.05). Serum irisin levels remained higher in the CPP girls than the controls with adjustment for BMI (P < 0.05).

CONCLUSIONS

Increased serum irisin levels with CPP suggest that irisin is involved in puberty. However, due to low sensitivity and specificity, irisin level can only be used as an auxiliary indicator rather than a single diagnostic indicator of CPP.

Irisin response to acute moderate intensity exercise and high intensity interval training in youth of different obesity statuses: A randomized crossover trial

Limited data exist regarding the impact of an acute bout of exercise with varying intensities on irisin levels in the youth of different obesity statuses. The objectives were to (1) compare an acute bout of moderate continuous intensity (MCI) exercise and an acute bout of high‐intensity interval training (HIIT) on irisin response in youth with different obesity statuses and, (2) investigate whether changes in irisin levels are correlated with exploratory outcomes. A randomized crossover design study was conducted on 25 youth aged 12–18 years old. Participants were classified as either healthy weight (BMI percentile <85; n = 14) or overweight/obese (BMI percentile ≥85; n = 11). Participants performed an MCI exercise session at 50% of heart rate reserve for 35 min and a HIIT exercise session for 35 min, with intervals every 5 min increasing from 50% heart rate reserve to 85–90% for 2 min. Irisin was measured using an enzyme‐linked immunoabsorbent assay from plasma sampling obtained throughout the exercise (at times 0, 7, 14, 21, 28, and 35 min). A time effect was observed throughout the HIIT session [F(1,5) = 6.478, p < 0.001]. Bonferonni post‐hoc analysis revealed significant differences in irisin levels post‐exercise (35 min) compared to times 7, 14, 21, and 28 min. Irisin increased during HIIT (81.0% ± 71.3; p = 0.012) in youth with a healthy weight. No differences were observed for youth living as overweight or with obesity. Overall, HIIT elicits a higher peak irisin response compared to MCI exercise training in youth.

Changes of Circulating Irisin and High-Sensitivity C-Reactive Protein Levels in Morbidly Obese Individuals with Type 2 Diabetes After Roux-en-Y Gastric Bypass

Background: Irisin has been recently reported to provide beneficial effects in obesity and diabetes. Elevation of high-sensitivity C-reactive protein (hs-CRP) reflects the inflammatory state that has been shown to play a key role in obesity and its comorbidities. Objective: Our study aimed to compare the changes of circulating irisin levels in an obese diabetic population who underwent laparoscopic Roux-en-Y gastric bypass (LRYGB) versus a control-matched population who underwent usual medical care plus diabetes support education (DSE) program. In addition, we aimed to explore the association between circulating irisin and hs-CRP levels after the interventions. Methods: In a prospective controlled trial, we studied 58 obese individuals with type 2 diabetes before and 12 months after intervention. Twenty-nine subjects underwent LRYGB and 29 subjects received DSE. Results: At 12-month follow-up, compared with the DSE group, patients who underwent LRYGB lost more weight (LRYGB; -33.4 ± 11.2, and DSE; 0.2 ± 4.9 kg; P < .001), fat mass (P < .001), and fat-free mass (P < .05). Circulating irisin (P < .05) and hs-CRP level (P < .05) were also significantly lower. Within the LRYGB group, the reduction of irisin level was positively associated with the changes of hs-CRP levels (r = 0.39, P < .05). Conclusions: To the best of our knowledge, this is the first study showing that LRYGB significantly reduces circulating irisin levels compared with usual medical care and DSE, in an obese diabetic population. After LRYGB, the irisin reduction significantly correlates with the reduction of hs-CRP. The elevation of circulating irisin levels suggests irisin resistance in the obese state and its decrease after LRYGB might reflect the resolution of irisin resistance. Future investigations are needed to confirm and explore the mechanisms of irisin resistance in obesity, its resolution after LRYGB, and the pathophysiological significance.

Circulating Irisin in Children and Adolescents With Prader-Willi Syndrome: Relation With Glucose Metabolism

Irisin is a myokine involved in the browning of white adipose tissue and regulation of energy expenditure, glucose homeostasis and insulin sensitivity. Debated evidence exists on the metabolic role played by irisin in children with overweight or obesity, while few information exist in children with Prader Willi Syndrome (PWS), a condition genetically prone to obesity. Here we assessed serum irisin in relation to the metabolic profile and body composition in children and adolescents with and without PWS. In 25 PWS subjects [age 6.6-17.8y; body mass index standard deviation score (BMI SDS) 2.5 ± 0.3] and 25 age, and BMI-matched controls (age 6.8-18.0y; BMI SDS, 2.8 ± 0.1) we assessed irisin levels and metabolic profile inclusive of oral glucose tolerance test (OGTT), and body composition by dual-energy X-ray absorptiometry (DXA). In PWS, we recorded lower levels of fat-free mass (FFM) (p <0.05), fasting (p<0.0001) and 2h post-OGTT insulin (p<0.05) and lower insulin resistance as expressed by homeostatic model of insulin resistance (HOMA-IR) (p<0.0001). Irisin levels were significantly lower in PWS group than in controls with common obesity (p<0.05). In univariate correlation analysis, positive associations linked irisin to insulin OGTT₀ (p<0.05), insulin OGTT₁₂₀ (p<0.005), HOMA-IR (p<0.05) and fasting C-peptide (p<0.05). In stepwise multivariable regression analysis, irisin levels were independently predicted by insulin OGTT₁₂₀. These results suggest a link between irisin levels and insulin sensitivity in two divergent models of obesity.

Emerging evidence for the opposite role of circulating irisin levels and brown adipose tissue activity measured by infrared thermography in anthropometric and metabolic profile during childhood

Irisin is an adipomyokine that increases browning of adipose tissue and thermogenesis, thereby protecting against obesity and insulin resistance. However, the correlation between irisin, brown adipose tissue (BAT), and childhood obesity, as well as its association with an increased risk of developing metabolic diseases, has not been completely elucidated. This study aimed to investigate the association between irisin levels and BAT activity measured by infrared thermography among children and verify their correlation with anthropometric and metabolic parameters. This study included 42 children with normal weight and 18 overweight/obese children. Anthropometric data, irisin levels, lipid and glucose profile were evaluated. The percentage of the thermally active portion of the supraclavicular area (%Area_SCR) before and after a cold stimulus was measured by infrared thermography, and the differences between the percentages of thermally active (Δ%Area_SCR) was calculated as an index of BAT activation. The results were correlated with anthropometric and metabolic parameters. Circulating irisin levels was positive correlated with age (rho=0.327, P= 0.011), body mass index (BMI) (rho=0.707, P<0.001), waist circumference (rho=0.624, P<0.001), total cholesterol (rho=0.361, P=0.044), triglycerides (rho=0.419, P=0.001), and low-density lipoprotein cholesterol (LDLc) (rho=0.381, P= 0.003). Active BAT was negatively correlated with BMI, waist circumference, triglycerides, LDLc and irisin levels. We observed that normal weight children increased significantly the Δ% Area_SCR as compared to overweight/obese children. In conclusion, circulating irisin levels and BAT activity appear to have opposing roles, since normal weight children had greater BAT activity and lower circulating levels of irisin.

The Physiological Role of Irisin in the Regulation of Muscle Glucose Homeostasis

Irisin is a myokine that primarily targets adipose tissue, where it increases energy expenditure and contributes to the beneficial effects of exercise through the browning of white adipose tissue. As our knowledge has deepened in recent years, muscle has been found to be a major target organ for irisin as well. Several studies have attempted to characterize the role of irisin in muscle to improve glucose metabolism through mechanisms such as reducing insulin resistance. Although they are very intriguing reports, some contradictory results make it difficult to grasp the whole picture of the action of irisin on muscle. In this review, we attempted to organize the current knowledge of the role of irisin in muscle glucose metabolism. We discussed the direct effects of irisin on glucose metabolism in three types of muscle, that is, skeletal muscle, smooth muscle, and the myocardium. We also describe irisin’s effects on mitochondria and its interactions with other hormones. Furthermore, to consider the relationship between the irisin-induced improvement of glucose metabolism in muscle and systemic disorders of glucose metabolism, we reviewed the results from animal interventional studies and human clinical studies.

Associations of apelin, leptin, irisin, ghrelin, insulin, glucose levels, and lipid parameters with physical activity during eight weeks of regular exercise training

OBJECTIVES

This study aims to evaluate the effects of 8 weeks of basketball training on apelin, leptin, irisin, ghrelin, insulin, glucose, and blood lipids among basketball players.

METHODS

The exercise groups were given 2 h of basketball training for 5 d a week and for 8 weeks. The control group was randomly selected among the adolescents who did not regularly exercise.

RESULTS

The apelin and ghrelin levels significantly increased; however, leptin, irisin, and insulin levels statistically decreased in the post-exercise group compared to the other groups (p < .05). The results suggest low levels of cholesterol, triglyceride, high-density lipoprotein (HDL), and low-density lipoprotein (LDL) parameters (p < .05).

CONCLUSIONS

This study demonstrated that after 8 weeks of chronic exercise training, apelin and ghrelin levels increased; in contrast, leptin, irisin, and insulin levels decreased. The decrease in leptin and irisin levels is compatible with the pattern of decrease in the lipid levels as a result of chronic exercise.

The Effect of a Life-Style Intervention Program of Diet and Exercise on Irisin and FGF-21 Concentrations in Children and Adolescents with Overweight and Obesity

Overweight and obesity in childhood and adolescence represent major public health problems of our century, and account for increased morbidity and mortality in adult life. Irisin and Fibroblast Growth Factor 21 (FGF-21) have been proposed as prognostic and/or diagnostic biomarkers in subjects with obesity and metabolic syndrome, because they increase earlier than other traditional biomarkers. We determined the concentrations of Irisin and FGF-21 in children and adolescents with overweight and obesity before and after one year of a life-style intervention program of diet and physical exercise and explored the impact of body mass index (BMI) reduction on the concentrations of Irisin, FGF-21 and other cardiometabolic risk factors. Three hundred and ten (n = 310) children and adolescents (mean age ± SD: 10.5 ± 2.9 years) were studied prospectively. Following one year of the life-style intervention program, there was a significant decrease in BMI (p = 0.001), waist-to-hip ratio (p = 0.024), waist-to-height ratio (p = 0.024), and Irisin concentrations (p = 0.001), and an improvement in cardiometabolic risk factors. There was no alteration in FGF-21 concentrations. These findings indicate that Irisin concentrations decreased significantly as a result of BMI reduction in children and adolescents with overweight and obesity. Further studies are required to investigate the potential role of Irisin as a biomarker for monitoring the response to lifestyle interventions and for predicting the development of cardiometabolic risk factors.

Serum Irisin Levels in Central Precocious Puberty and Its Variants

AIM

The exact mechanisms that trigger the onset of puberty are not well known. Adipomyokines are postulated to stimulate the central neural network. In the present study, we investigated irisin levels in girls with central precocious puberty (CPP), slowly progressing precocious puberty (SPPP), or premature thelarche (PT); we also studied prepubertal girls and to determine if this adipomyokine could be used as a marker in this context.

METHODS

A total of 94 girls including 33 with CPP, 31 with precocious puberty (PP) variants (SPPP or PT), and 30 healthy controls were enrolled to the study. The mean irisin levels were compared between groups. The bivariate correlations of irisin levels with clinical and laboratory parameters were assessed. Multivariate linear regression analysis was performed to determine independent predictive factors of irisin levels.

RESULTS

Irisin levels were higher in the CPP group compared with the other groups (CPP group: 723.25 ± 62.35 ng/mL; PP variants group: 529.60 ± 39.66 ng/mL; and control group: 325.03 ± 27.53 ng/mL) (P < 0.001). Irisin levels were positively correlated with body mass index standard deviation scores (BMI-SDS), height-SDS, weight-SDS, bone age, uterus long axis, ovary size, baseline FSH and LH, and peak LH levels. Multivariate linear regression analysis revealed that irisin levels had the strongest correlation with peak LH. The other independent predictive factor of irisin levels was BMI-SDS.

CONCLUSIONS

The mean irisin levels were higher in patients with CPP compared with other groups. The results of this study imply that increased irisin levels may be used as a marker of CPP provided that these findings are confirmed in larger prospective studies.

Effects of Hypnotherapy on Weight Loss and thus on Serum Leptin, Adiponectin, and Irisin Levels in Obese Patients

Objective: This study aimed to investigate effects of hypnotherapy on weight loss and thus on leptin, adiponectin (ADP), and irisin levels in obese patients who presented to the psychiatry outpatient clinic to participate in hypnotherapy sessions to develop a healthy and balanced diet. Methods: The study sample included 32 individuals with a body mass index (BMI) of ≥30 and who completed the 10-week hypnotherapy. First, the Personal Information Form was handed out to the participants and then each participant's weight (in the morning on an empty stomach) and height were measured and BMI was determined. Five-milliliter blood samples were drawn before the first session, and then irisin, leptin, and ADP levels were measured using the enzyme-linked immunosorbent assay method. Then, they participated in hypnotherapy sessions once a week for 10 weeks. At the end of the 10-week hypnotherapy, 5 mL of blood was taken again and the aforementioned biochemical analyses were performed. BMIs were measured again. Results: The mean BMI values of the patients were 33.43 ± 5.28 and 31.45 ± 4.98 at the beginning and end of the hypnotherapy sessions, respectively. Serum leptin, ADP, and irisin levels, which were 9.48 ± 5.48, 6.73 ± 3.27, and 1.43 ± 1.14, respectively, at the beginning of the hypnotherapy sessions, were 6.47 ± 2.69, 7.68 ± 3.34, and 1.53 ± 1.21, respectively, at the end of the hypnotherapy sessions. The results showed that BMI and serum leptin levels decreased significantly after the hypnotherapy sessions, whereas serum ADP and irisin levels increased significantly. Conclusions: This study indicates that hypnotherapy in obesity treatment leads to weight loss in obese patients and thus to considerable changes in leptin, ADP, and irisin levels. Hypnotherapy is easy to apply, cheap, and effective; has no potential for side effects; and can be applied both alone and in combination with other treatments. However, to confirm its effects, further studies should be conducted on this issue.

Association between Irisin, hs-CRP, and Metabolic Status in Children and Adolescents with Type 2 Diabetes Mellitus

Proinflammatory cytokines and the novel myokine irisin, a cleavage product of FNDC5, have been found to play a role in obesity and type 2 diabetes mellitus (T2DM). Irisin has been shown to increase browning of adipose tissue, thermogenesis, energy expenditure, and insulin sensitivity, yet its association with inflammatory markers is still limited. Circulating irisin has been found to be increased in obesity, while in adult subjects with T2DM decreased levels have been found. However, data establishing the association of circulating irisin in children and adolescents with T2DM has not been described in the literature. The objective of this study was to determine irisin plasma concentration and its association with metabolic and adiposity markers and with hs-CRP, a surrogate marker of inflammation used in clinical practice, in a pediatric population with T2DM. A cross-sample of 40 Mexican children and adolescents aged 7-17 were recruited, 20 diagnosed with T2DM and 20 healthy controls. Plasma irisin levels were found to be lower in the T2DM group compared with controls, which could be attributed to a reduced PGC-1α activity in muscle tissue with a consequent decrease in FNDC5 and irisin expression. Irisin concentration was found to be positively correlated with HDL-c, LDL-c, and total cholesterol, while negatively correlated with BMI, waist circumference, and triglycerides. However, after multiple regression analysis, only HDL-c correlation remained significant. hs-CRP was higher in the T2DM group and positively associated with adiposity markers, unfavorable lipid profile, insulin levels, and HOMA-IR, but no association with irisin was found. Given the favorable metabolic effects attributed to irisin, the low plasma levels found in children and adolescents with T2DM could exacerbate the inflammatory and metabolic imbalances and the intrinsic cardiovascular risk of this disease. We propose an "irisin-proinflammatory/anti-inflammatory axis" to explain the role of irisin as a metabolic regulator in obesity and T2DM.

Circulating Irisin Levels in Children With GH Deficiency Before and After 1 Year of GH Treatment

PURPOSE

To evaluate circulating irisin levels in children with GH deficiency (GHD) and any relation with clinical and metabolic parameters.

PATIENTS

Fifty-four prepubertal children (mean age, 7.4 ± 0.8 years) with idiopathic GHD treated with GH for at least 12 months and 31 healthy short children as control subjects.

METHODS

Body height, body mass index (BMI), waist circumference (WC), IGF-I, HbA1c, lipid profile, fasting and after-oral glucose tolerance test glucose and insulin, insulin sensitivity indices, and irisin levels were evaluated at baseline and after 12 months of GH replacement (GHR).

RESULTS

At baseline, children with GHD, in addition to having lower growth velocity (P < 0.001), GH peak after stimulation tests (both P < 0.001), and IGF-I (P < 0.001), showed significantly lower irisin (P < 0.001) and higher BMI (P < 0.001) and WC (P = 0.001), without any difference in metabolic parameters, than control subjects. After GHR, children with GHD showed a significant increase in height (P < 0.001), growth velocity (P < 0.001), IGF-I (P < 0.001), fasting glucose (P = 0.002) and insulin (P < 0.001), homeostasis model assessment estimate of insulin resistance (P < 0.001), and irisin (P = 0.005), with a concomitant decrease in BMI (P = 0.001) and WC (P = 0.003). In multivariate analysis, the independent variables significantly associated with irisin were BMI (P = 0.002) and GH peak (P = 0.037) at baseline and BMI (P = 0.005), WC (P = 0.018), and IGF-I (P < 0.001) during GHR.

CONCLUSIONS

We report that GHR leads to an increase in irisin levels, strongly related to a decrease in BMI and WC, and to an increase in IGF-I; these changes are among the main goals of GHR. These data confirm the favorable effects of GHR in children.

Myokine-adipokine cross-talk: potential mechanisms for the association between plasma irisin and adipokines and cardiometabolic risk factors in Mexican children with obesity and the metabolic syndrome

BACKGROUND

Adipokines and the myokine irisin, involved in mechanisms associated with obesity and metabolic syndrome (MS), are understudied in the pediatric population.

OBJECTIVE

To investigate the relationship between irisin, and leptin, resistin, adiponectin, adipsin, anthropometric and cardiovascular risk factors in Mexican children.

METHODS

A cross-sample of 126 Mexican children aged 6-12 years old were classified as normal weight (n = 46), obese (n = 40), and MS (n = 40) according to CDC's and Cook's age-modified criteria for obesity and MS. Anthropometric parameters and blood pressure were determined and percentiles calculated for age and gender. Irisin, leptin, adiponectin, adipsin, resistin, triglycerides, glucose, high-density lipoprotein cholesterol (HDL-c) levels, and physical activity were determined. Statistical tests for differences between groups, correlation, and multiple regression analyses were performed.

RESULTS

Irisin plasma levels were significantly lower in the obese (6.08 [4.68-6.65]) and MS groups (6.46 [5.74-7.02]) compared with the normal-weight group (8.05 [7.24-8.94]) (p < 0.001). Irisin levels were not influenced by age or gender, but significant dispersion was observed in obese girls (95% CI median [2.29-6.30]). Leptin, resistin, and adipsin levels were significantly increased in the obese and MS groups. Lean-fat ratio was significantly higher in the NW group. Irisin correlated negatively with leptin (- 0.310), resistin (- 0.389), adipsin (- 0.362), BMI% (-0.472), WC% (- 0.453), BMI z-score (- 0.496), fat free mass (- 0.257), fat percentage (- 0.532), fat mass (- 0.515), triglycerides (- 0.291), the number of cardiometabolic risk factors (- 0.443) (p < 0.001); positively with lean-fat ratio (0.489) and HDL-c (0.328) (p < 0.001) and none with physical activity (p < 0.001). Following stepwise multiple linear regression analysis, the lean-fat ratio was the only determinant of irisin levels (B = 1.168, p < 0.001).

CONCLUSIONS

Lean-fat ratio, more than the absolute amount of muscle or fat mass, as well as potential myokine-adipokine cross-talk mechanisms may explain the lower irisin levels in children with obesity and MS, through blunted compensatory responses interfering with tissue-dependent irisin secretion, contributing to a continuous deleterious effect cycle.

Relationship of Circulating Irisin with Body Composition, Physical Activity, and Cardiovascular and Metabolic Disorders in the Pediatric Population

Exercise-induced irisin, a recently discovered myokine, has been linked to insulin resistance, obesity, and other diseases in adults; however, information in children is scarce and contradictory. We analyzed the limited evidence of irisin’s effects in children and adolescents, and its association with body composition, exercise training, cardiovascular risk factors, and metabolic diseases, as well as the results of dietetic interventions. Both positive and negative correlations between irisin concentrations and body mass index, fat mass, fat-free mass, and other anthropometric parameters were found. Likewise, contradictory evidence was shown associating irisin plasma levels with cardiovascular and metabolic parameters such as glucose, insulin resistance, and cholesterol and other lipid and fatty acid plasma levels in healthy children, as well as in those with obesity and the metabolic syndrome. Gender, puberty, and hormonal differences were also examined. Furthermore, important contradictory findings according to the type and duration of exercise and of dietetic interventions in healthy and unhealthy subjects were demonstrated. In addition, correlations between mother–infant relations and circulating irisin were also identified. This review discusses the potential role of irisin in health and disease in the pediatric population.

High irisin levels in overweight/obese children and its positive correlation with metabolic profile, blood pressure, and endothelial progenitor cells

BACKGROUND AND AIMS

Irisin is involved in the compensatory mechanisms for metabolic regulation and appears to be associated with glucose homeostasis and lipid profile. However, it's possible implications on obesity-associated cardiometabolic complications have not been completely elucidated. This study aimed to investigate the association between irisin level and anthropometric data, metabolic parameters, blood pressure, and endothelial progenitor cells (EPCs) level among children with overweight/obesity.

METHODS AND RESULTS

This study included 24 children with overweight/obesity (9 girls and 15 boys) and 63 children with normal weight (25 girls and 38 boys). The anthropometric data, blood pressure, blood biochemistry, EPCs and irisin levels were evaluated. Children with overweight/obesity had significantly higher circulating irisin and EPCs levels than those with normal weight (P < 0.001). Additionally, we found that irisin level was positively correlated with BMI (rho = 0.407), waist circumference (rho = 0.449), triglycerides (rho = .334), glucose (rho = 0.226), insulin (rho = 0.533), HOMA (rho = 0.545), and negatively correlated with HDL cholesterol level (rho = -0.218). Importantly, we also found that irisin levels were significantly correlated with systolic (rho = 0.420), diastolic (rho = 0.331) blood pressure and circulating EPCs level (rho = 0.391).

CONCLUSION

Our study provides evidence that overweight/obese children had elevated circulating levels of both irisin and EPCs and address the gap in the literature with regard to the understanding of the implications of irisin on obesity-related cardiometabolic complications among these children and also highlight the possible involvement of irisin regulation on insulin resistance and endothelial function in childhood overweight and obesity.

Irisin promotes proliferation but inhibits differentiation in osteoclast precursor cells

The receptor activator of NF-κB ligand-induced osteoclast differentiation has a critical role in the process of bone metabolism. Overactivation of osteoclastogenesis may result in a series of diseases. Irisin, a novel myokine, which was first reported in 2012, has been proposed to mediate the beneficial metabolic effects of exercise. Studies have demonstrated that irisin targets osteoblasts by promoting osteoblast proliferation and differentiation; however, the underlying mechanism regarding the effect of irisin on osteoclasts remains elusive. Using 2 types of osteoclast precursor cells, RAW264.7 cells and mouse bone marrow monocytes, we showed that irisin promoted osteoclast precursor cell proliferation but inhibited osteoclast differentiation. Irisin down-regulated the expression of osteoclast differentiation marker genes, including receptor activators of NF-κB, nuclear factor of activated T cells, cytoplasmic 1, cathepsin K, and tartrate-resistant acid phosphatase (TRAP), as well as decreasing the number of TRAP-positive multinucleated cells and hydroxyapatite resorption pits. Furthermore, we showed that irisin suppressed the NF-κB signaling pathway, but activated the p38 and JNK signaling pathways. In the presence of an inhibitor of p38 and JNK, irisin-induced promotion of RAW264.7 cell proliferation was attenuated. However, irisin-induced inhibition of osteoclast differentiation was not affected by either the p38 or JNK signaling pathway. Our study suggested the direct effect of irisin on osteoclastogenesis and revealed the mechanism responsible for the therapeutic potential of irisin in bone metabolism disease.-Ma, Y., Qiao, X., Zeng, R., Cheng, R., Zhang, J., Luo, Y., Nie, Y., Hu, Y., Yang, Z., Zhang, J., Liu, L., Xu, W., Xu, C. C., Xu, L. Irisin promotes proliferation but inhibits differentiation in osteoclast precursor cells.

Metabolic syndrome, leptin-insulin resistance and uric acid: a trinomial foe for Algerian city-dweller adolescents' health

Background Adolescence is one of the critical periods where increased risk for long-term obesity-related complications is an important health concern. This highlights the need to perform early diagnostics based on precise biomarkers to decrease the risk of complications in adolescents with obesity. Objective To determine the relationships between serum levels of uric acid (UA), leptin and insulin with metabolic syndrome (MS) components in Algerian adolescents. Subjects Nondiabetic adolescents (n = 204). Methods Blood pressure (BP) and anthropometric measurements were performed using standardized techniques. Blood samples were taken for determination of glycemia, triglyceridemia, uricemia, cholesterolemia, leptinemia and insulinemia. Results The rate of MS among an excess weight group was 17.4% [95% confidence interval (CI)]. Serum levels of UA, leptin and insulin were significantly higher in the excess weight group compared to a normal weight group (279.4 ± 86.05 vs. 204.9 ± 50.34 μmol/L and 25.65 ± 14.01 vs. 4.09 ± 2.60 μg/L, p < 0.001; 24.58 ± 13.85 vs. 13.34 ± 6.41 μIU/L, p < 0.05). Serum levels of UA, leptin and insulin were significantly higher in adolescents with MS compared to those without MS (304.86 ± 111.41 vs. 224.72 ± 77.81 μmol/L, 30.26 ± 12.46 vs. 16.93 ± 14.97 μg/L and 30.91 ± 17.30 vs. 18.71 ± 10.14 μIU/L, p < 0.05, respectively). Significant correlations were found between UA and leptin with waist circumference (r = 0.50 and 0.76), diastolic blood pressure (r = 0.58 and 0.43), triglycerides (r = 0.42 and 0.35) and high-density lipoprotein-cholesterol (r = -0.36 and -0.35). Conclusion Serum levels of UA and leptin may be useful biomarkers for early diagnosis of the risk of MS in our Algerian adolescent population.

Association of circulating irisin levels with metabolic and metabolite profiles of Korean adolescents

CONTEXT

Irisin, a novel exercise-induced myokine, has been suggested to regulate energy metabolism.

OBJECTIVE

We studied the relationship between circulating irisin and metabolic and metabolite profiles of Korean adolescents, and investigated the effects of physical activity, obesity, and metabolic syndrome (MetS) on irisin levels.

MATERIALS AND METHODS

Data were obtained from the Korean Children-Adolescents Study. Our cross-sectional study included 618 adolescents (370 normal-weight and 248 obese adolescents; 316 boys and 302 girls) aged 12-15years. Body composition was determined using an impedance body composition analyzer and general participant characteristics and lifestyle information were obtained from questionnaires. Serum irisin levels were measured using a commercial kit.

RESULTS

Mean body mass index (BMI) was 19.4kg/m² in normal-weight adolescents and 31.4kg/m² in obese adolescents. Circulating irisin was positively correlated with adiposity indices, including BMI z-score, waist circumference, percent body fat, fat mass, fat-free mass, fat mass to fat-free mass ratio, and lipid and glucose metabolism markers, including total cholesterol, low-density lipoprotein cholesterol (LDL-C), triglycerides, glucose, insulin, and homeostasis model assessment-estimated insulin resistance (all p≤0.006). Of these, increased body fat mass [standardized (Std) ß, 0.23; p<0.0001], LDL-C (Std ß, 0.14; p=0.0005) and fasting glucose (Std ß, 0.08; p=0.0383) were the main independent factors associated with higher irisin levels. Moreover, elevated serum irisin was associated with the risk of obesity [odds ratio (OR], 2.2; confidence interval (CI), 1.19-3.87] and MetS (OR, 2.0; CI, 1.15-3.47). Furthermore, irisin and branched-chain amino acids were positively associated (p<4×10^-4 for Bonferroni correction). Additionally, in the normal-weight group, girls had higher irisin levels than boys (p=0.006) and adolescents who engaged in regular physical activity had higher levels of irisin than sedentary adolescents (p=0.0388). The relationship between physical activity and irisin levels was not observed in obese adolescents.

CONCLUSIONS

Elevated serum irisin was independently associated with the risk of obesity and positively correlated with unhealthy metabolic parameters and metabolites. Moreover, irisin levels were higher in active versus sedentary adolescents in the normal-weight group, but not in the obese group. Our findings suggest that irisin plays an important role in metabolic disorders and may be affected by physiopathological status.

Serum Irisin and Oxytocin Levels as Predictors of Metabolic Parameters in Obese Children

OBJECTIVE

Irisin and oxytocin can affect energy homeostasis and it has been suggested that they may play an important role in reducing obesity and diabetes. In this study, we aimed to determine the relationship between metabolic parameters (including irisin and oxytocin levels) and anthropometric parameters in obese children.

METHODS

Ninety obese children (mean age, 13.85±1.63 years) and 30 healthy controls (mean age, 14.32±1.58 years) were enrolled in this study. Anthropometric and laboratory parameters (glucose, insulin, lipid, oxytocin, and irisin levels) were analyzed. The serum irisin and oxytocin levels were measured by enzyme-linked immunosorbent assay. Bioelectrical impedance was used to determine body composition.

RESULTS

Irisin level was higher in the patients than in the controls (p=0.018), and this higher irisin level was correlated with increased systolic blood pressure, body mass index, waist/hip ratio, fat percentage, fat mass, glucose level, insulin level, and homeostasis model assessment of insulin resistance. Serum oxytocin level was significantly decreased in obese children compared to the controls (p=0.049). Also, among the 60 obese patients, oxytocin level was significantly lower in patients with than in those without metabolic syndrome (8.65±2.69 vs. 10.87±5.93 ng/L, respectively), while irisin levels were comparable (p=0.049 and p=0.104, respectively). There were no statistically significant relationships between oxytocin or irisin levels and lipid levels (p>0.05).

CONCLUSION

Obese children had significantly higher irisin levels than the healthy controls. Additionally, this study shows for the first time that oxytocin level is significantly lower in obese compared with non-obese children and also lower in obese children with metabolic syndrome compared to those without.

Association of Irisin Plasma Levels with Anthropometric Parameters in Children with Underweight, Normal Weight, Overweight, and Obesity

The correlations between irisin levels, physical activity, and anthropometric measurements have been extensively described in adults with considerable controversy, but little evidence about these relationships has been found in children. The objective of this study is to correlate the plasma levels of irisin in underweight, normal weight, overweight, and obese children with anthropometric parameters and physical activity levels. A cross-sample of 40 children was divided into the following groups on the basis of body mass index (BMI) percentile. The correlations of plasma irisin levels with physical activity, anthropometric, and metabolic measurements were determined. Plasma irisin levels (ng/mL) were lower for the underweight group (164.2 ± 5.95) than for the normal weight and obese groups (182.8 ± 5.58; p < 0.05). Irisin levels correlated positively with BMI percentile (0.387), waist circumference (0.373), and fat-free mass (0.353; p < 0.05), but not with body muscle mass (−0.027). After a multiple linear regression analysis, only BMI percentile (0.564; p < 0.008) showed a positive correlation with irisin. Our results indicated no association with metabolic parameters. A negative correlation with physical activity was observed. Interrelationships among body components might influence irisin levels in children.