Increased serum IgG and IgA in overweight children relate to a less favourable metabolic phenotype

Hypogammaglobulinemia Class G Is Present in Compensated and Decompensated Patients with Propionate Defects, Independent of Their Nutritional Status

Propionate defects (PDs) mainly include methylmalonic (MMA) and propionic acidemia (PA) defects. Lifelong PD patients progress from the compensated to the decompensated stages, the latter of which are characterized by life-threatening acidemia and hyperammonemia crises. PD patients can suffer immunocompromise, especially during the decompensation stage. There is a significant gap in the research regarding the humoral immune response in PD patients. Here, we analyzed serum immunoglobulin concentrations and hemograms across compensated and decompensated stages in PD patients. Nutritional status and crisis triggers of decompensation were also explored. Twenty patients were studied, and 25 decompensation events (DE) and 8 compensation events (CE) were recorded. Compared with those in the CE group, the IgG levels in the DE group (513.4 ± 244.5 mg/dL) were significantly lower than those in the CE group (860.8 ± 456.5 mg/dL) (p < 0.0087). The mean hemoglobin concentration was significantly lower in the DE group (11.8 g/dL) than in the CE group (13.4 g/dL) (p < 0.05). The most frequent (48%) possible decompensation trigger factor was infection. Most of the events were registered in eutrophic patients (87.9%), despite which 65.2% and 50% of patients who experienced decompensated and compensated events, respectively, presented with hypogammaglobulinemia G. These findings provide evidence of the immunodeficiency of PD patients, independent of their nutritional status. We suggest that PD patients be managed as immunocompromised independently of their nutritional status or metabolic state (compensated or decompensated).

Obesity and Adipose Tissue Dysfunction: From Pediatrics to Adults

Obesity is a growing health problem that affects both children and adults. The increasing prevalence of childhood obesity is associated with comorbidities such as cardiovascular disease, type 2 diabetes and metabolic syndrome due to chronic low-grade inflammation present at early stages of the disease. In pediatric patients suffering from obesity, the role of epigenetics, the gut microbiome and intrauterine environment have emerged as causative factors Interestingly, pediatric obesity is strongly associated with low birth weight. Accelerated weight gain oftentimes occurs in these individuals during the post-natal period, which can lead to increased risk of adiposity and metabolic disease. The pathophysiology of obesity is complex and involves biological and physiological factors compounded by societal factors such as family and community. On a cellular level, adipocytes contained within adipose tissue become dysregulated and further contribute to development of comorbidities similar to those present in adults with obesity. This review provides an overview of the current understanding of adipose tissue immune, inflammatory and metabolic adaptation of the adipose tissue in obesity. Early cellular changes as well as the role of immune cells and inflammation on the progression of disease in pivotal pediatric clinical trials, adult studies and mouse models are emphasized. Understanding the initial molecular and cellular changes that occur during obesity can facilitate new and improved treatments aimed at early intervention and subsequent prevention of adulthood comorbidities.

Leptin-reactive antibodies are distinctly correlated with body composition parameters and metabolic risk indexes in children and adolescents

Studies have demonstrated the presence of low-affinity immunoglobulins (Igs) directed to leptin, a key hormone of the neuroendocrine axis that regulates appetite and metabolism, in adult healthy subjects, patients with obesity, and type 2 diabetes mellitus. In the present exploratory study, IgG leptin-reactive antibodies were analyzed for the first time in children and adolescents according to body mass index (BMI) and were correlated with biochemical profile (lipid profile, insulin, glucose, and leptin) and metabolic risk indexes [homeostasis model assessment for insulin resistance (HOMA-IR), homeostasis model assessment for β-cell function (HOMA-β), atherogenic index of plasma (AIP)]. One hundred and thirty-six participants were included (children n = 63, adolescents n = 73). An in-house enzyme-linked immunosorbent assay (ELISA) test was performed to measure IgG anti-leptin antibodies (free, total, and immune complexes). In adolescents, free and total IgG anti-leptin antibodies levels were higher in groups with overweight or obesity than in normal-weight group (P < 0.01), while in children, the total fractions were lower in groups with overweight and obesity than in normal weight (P < 0.02). Immune complexes percentage showed opposite correlations with BMI in children (r = 0.4004, P = 0.0473) and adolescents (r = -0.3983, P = 0.0133). IgG anti-leptin antibodies were also correlated with HOMA-IR in children (r = -0.4569, P = 0.0217) and adolescents (r = -0.3589, P = 0.0316), and with AIP (r = -0.3608, P = 0.0261) in adolescents. Our data suggest that the production and affinity of IgG anti-leptin antibodies can be affected by age, body composition, and metabolic conditions; additionally, in normal conditions, IgG anti-leptin antibodies may have a protective role in insulin resistance and cardiovascular events.

Influence of adipose tissue immune dysfunction on childhood obesity

In recent decades, a dramatic rise has been observed in the prevalence of obesity in childhood and adolescence, along with an increase in fetal microsomia rates. The increased risk of obesity during this key period in development negatively affects the health of the individual later in life. Immune cells residing and recruited to white adipose tissue have been highlighted as important factors contributing to the pathogenesis of childhood obesity. Immune dysfunction in the context of obesity begins early in childhood, which is different from the pathological characteristics and influencing factors of adipose immunity in adults. Here, we explore the current understanding of the roles of childhood and early life events that result in high risks for obesity by influencing adipose tissue immune dysfunction under the pathological condition of obesity. Such knowledge will help in determining the mechanisms of childhood and early life obesity in efforts to ameliorate chronic inflammation-related metabolic diseases.

Longitudinal association of the anti-inflammatory serum marker GDF-15 with serum IgA and IgG in apparently healthy children

Both the innate and adaptive immune responses are deregulated in individuals with obesity and are key drivers of its associated metabolic alterations. Although the anti-inflammatory growth differentiation factor 15 (GDF-15) is a candidate protein against obesity, its mechanisms regulating the immune responses are not fully cleared. We examined whether GDF-15 was related to serum immunoglobulins in a children’s cohort assessed longitudinally during childhood. Results showed that circulating GDF-15 positively associated with IgA (p < 0.002) and IgG (p < 0.001) levels and the IgA*IgG product (p < 0.001) in apparently healthy children at both baseline (age 9) and follow-up (age 13). The associations were readily observed in heavier children (those with BMI-SDS above the median) as well as in children with higher renal fat accumulation (those with renal fat-to-height ratio above the median) and remained significant after correcting for possible confounding variables. Serum GDF-15 levels accounted for up to 16% of the variance of follow-up IgG levels and up to 14% of the variance of follow-up IgA*IgG product. The longitudinal associations of the anti-inflammatory GDF-15 with IgA, IgG and the IgA*IgG product in children with higher BMI or higher renal fat accumulation suggest a role of GDF-15 in human obesity through the regulation of the immune adaptive system.

Insulin resistance is linked to a specific profile of immune activation in human subjects

We tested the hypothesis that a particular immune activation profile might be correlated with insulin resistance in a general population. By measuring 43 markers of immune, endothelial, and coagulation activation, we have previously shown that five different immune activation profiles may be distinguished in 150 volunteers. One of these profiles, Profile 2, characterized by CD4+ T cell senescence, inflammation, monocyte, B cell, and endothelial activation, presented elevated insulinemia, glycemia, triglyceridemia, and γ-glutamyl transferase, a marker of liver injury, in comparison with other profiles. Our data are compatible with a model in which a particular immune activation profile might favor the development of insulin resistance and metabolic syndrome. In this hypothesis, identification of this profile, that is feasible with only 3 markers with an error rate of 5%, might allow to personalize the screening and prevention of metabolic syndrome-driven morbidities as liver steatosis.

Hormonal Dysregulation and Unbalanced Specialized Pro-Resolving Mediator Biosynthesis Contribute toward Impaired B Cell Outcomes in Obesity

Diet-induced obesity is associated with impaired B-cell-driven humoral immunity, which coincides with chronic inflammation and has consequences for responses to infections and vaccinations. Key nutritional, cellular, and molecular mechanisms by which obesity may impair aspects of humoral immunity such as B cell development, class switch recombination, and formation of long-lived antibody secreting cells are reviewed. A key theme to emerge is the central role of white adipose tissue on the formation and function of pro-inflammatory B cell subsets that exacerbate insulin resistance. The underlying role of select hormones such as leptin is highlighted, which may be driving the formation of pro-inflammatory B cells in the absence of antigen stimulation. This review also extensively covers the regulatory role of lipid metabolites such as prostaglandins and specialized pro-resolving mediators (SPMs) that are synthesized from polyunsaturated fatty acids. Notably, SPM biosynthesis is impaired in obesity and contributes toward impaired antibody production. Future directions for research, including avenues for therapeutic intervention, are included.