The prevalence of childhood obesity has increased dramatically in recent decades, becoming a global public health problem (1). Pathological conditions associated with obesity, such as diabetes, hyperlipidemia, or hypertension (2), have been observed mainly in adults. As the prevalence of childhood obesity increases, these conditions are becoming more common among infants and teenagers (3–8).

Obesity is associated with a chronic inflammatory state in adipose tissue (9–11). In this context, we can observe altered levels of molecules involved in the regulation of inflammation, called cytokines (12–14).

Research on cytokines has increased during the last years in order to identify risk and protective factors of cardiovascular disease and to generate potential target treatments (15, 16).

Tumor Necrosis Factor Weak Inducer of Apoptosis (TWEAK), also known as Tumor Necrosis Factor (TNF) ligand superfamily member 12, is a cytokine involved in multiple biological functions (12, 17, 18). It seems to play a protective role in the regulation of obesity and insulin resistance (15, 19, 20). It was observed that serum levels of soluble TWEAK are lower in adults with severe obesity, and they increase in these patients after a significant weight loss (21).

Cluster of Differentiation 163 (CD163) is a macrophage-specific protein that increases in the context of inflammation (22). In vitro, it has been identified as a scavenger receptor of TWEAK, promoting its degradation (23). Serum levels of CD163 are higher in obesity and insulin resistance, being a strong predictor of type 2 diabetes in adults (24). In cardiovascular diseases, a high CD163/TWEAK ratio was found (25).

Little is known about TWEAK and CD163 in children. The main objective of the study was to evaluate if a significant weight loss in children with obesity may induce changes in these parameters after a 2-year lifestyle intervention program. In addition, the investigation aimed to evaluate serum levels of TWEAK, CD163, and CD163/TWEAK ratio in prepubertal children with obesity compared to lean children.

Seventy-three prepubertal children with obesity were included, from an outpatient long-term intervention program over a period of 2 years. Inclusion criteria were the presence of obesity as defined by body mass index (BMI) > 2 standard deviation (SD) scores for age and sex upon Spanish normative charts (26), aged between 6 and 10 years and prepubertal according to Tanner staging (27, 28). Controls were forty-seven prepubertal healthy children attending for preoperative blood tests before minor surgery. They were matched by age and gender. Exclusion criteria were the presence of endocrinopathies, obesity-associated syndrome, and any infectious or inflammatory disease in the past 10 days, or taking medication that affected weight, lipid metabolism, or arterial blood pressure (BP). Written informed consent was obtained from all patients’ parents, and all investigations followed the Helsinki Declaration. The study was approved by the Ethics Committee of our Institution (reference code 2004104).

73 children with obesity and 47 controls were included in the study. Characteristics of subjects are shown in Table 1. Comparing cases and controls, CD163 levels were higher in children with obesity. No statistically significant differences were found in TWEAK and CD163/TWEAK ratio.

After a 2-year follow-up of the cases, 62 completed the study and 11 dropped out (15%). 31 patients achieved a significant weight loss. Comparing patients with and without weight loss after the intervention program, TWEAK decreased in both groups after the intervention program. However, we observed that this parameter was higher in patients who achieved weight loss, before and after the intervention program. Serum levels of CD163 decreased after 2 years in both groups, and the decrease was more pronounced in patients with weight loss (Figure 1). CD163/TWEAK ratio was higher in children without weight loss, and it increased after 2 years in this group (Figure 2). Data are shown in Table 2.

To further understand the relationship between TWEAK and CD163 and the rest of the variables, we carried out some bivariate correlation analysis with each of them. Age, sex, HOMA, and lipid profile were included as independent variables. No significant correlation among all these variables was found.

Forty-nine percent of the patients began puberty (assessed by Tanner stage) during the follow-up phase. After adjusting the regression model by Tanner, results were not modified.

TWEAK and CD163 have been linked to obesity and associated cardiovascular diseases in adults (15). However, there are still few data about these cytokines in children.

Our investigation did not find statistically significant differences in TWEAK or CD163/TWEAK ratio of children with obesity compared to controls. A possible explanation for this might be that this cytokine is involved in processes such as cell proliferation and differentiation (36), present in childhood growth. The protective role of TWEAK in obesity is not demonstrated in prepubertal children, although some studies observed an anti-inflammatory role of this cytokine in obese adults (25, 37).

Regarding CD163, this cytokine is higher in adults with obesity, and known as a biomarker of insulin resistance (23). Carolan et al. observed elevated CD163 in children with obesity, suggesting that it could be a biomarker to prioritize lifestyle intervention in childhood (38). In our study, CD163 serum levels were also higher in children with obesity compared to lean.

The present study is the first to observe a favorable effect of a 2-year lifestyle intervention program in prepubertal children who achieved a significant weight loss compared with those who did not. We observed expected higher levels of TWEAK, lower CD163/TWEAK ratio, and a more pronounced decrease of CD163 in the group of patients who achieved weight loss.

This study is the first one to observe the evolution of these parameters in prepubertal children, supporting the hypotheses that these cytokines may play a role in childhood obesity. One study found similar results in adults with severe obesity after weight loss achieved by bariatric surgery (25). Kazankov et al. observed a decrease in CD163 after 10 weeks of a lifestyle intervention in children with a mean age of 12 years (39).

This research has some limitations. It has a weak external validity because all subjects were only from one center. However, inclusion criteria for subjects are enough to guarantee a strong internal validity in our results. Unfortunately we don’t have estradiol, testosterone levels or TWEAK evolution of control group after two years of follow-up.

Our findings show that TWEAK and CD163 may be involved in the pathogenesis of obesity in prepubertal children. Childhood is a necessary stage for the prevention of consequences derived from obesity. This study opens an interesting line of research aimed at this objective.

The original contributions presented in the study are included in the article/supplementary material. Further inquiries can be directed to the corresponding author.

The studies involving human participants were reviewed and approved by CEIC from FUNDACIÓ INSTITUT D’INVESTIGACIÓ I INNOVACIÓ PARC TAULÍ (I3PT). Written informed consent to participate in this study was provided by the participants’ legal guardian/next of kin.

AC, RC, and JG-C conceived the study. RC obtained informed consent and clinical variables. JV analyzed samples. MF and RE performed literature search. All authors were involved in writing the paper and had final approval of the submitted and published versions.

This project was supported by a grant from Fundació Parc Taulí 2004104.

The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

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