Serum leptin in children with asthma treated with inhaled budesonide

Leptin and Asthma: What Are the Interactive Correlations?

Leptin is an adipokine directly correlated with the proinflammatory obese-associated phenotype. Leptin has been demonstrated to inhibit adipogenesis, promote fat demarcation, promote a chronic inflammatory state, increase insulin sensitivity, and promote angiogenesis. Leptin, a regulator of the immune response, is implicated in the pathology of asthma. Studies involved in the key cell reaction and animal models of asthma have provided vital insights into the proinflammatory role of leptin in asthma. Many studies described the immune cell and related cellular pathways activated by leptin, which are beneficial in asthma development and increasing exacerbations. Subsequent studies relating to animal models support the role of leptin in increasing inflammatory cell infiltration, airway hyperresponsiveness, and inflammatory responses. However, the conclusive effects of leptin in asthma are not well elaborated. In the present study, we explored the general functions and the clinical cohort study supporting the association between leptin and asthma. The main objective of our review is to address the knowns and unknowns of leptin on asthma. In this perspective, the arguments about the different faces of leptin in asthma are provided to picture the potential directions, thus yielding a better understanding of asthma development.

Leptin in the Respiratory Tract: Is There a Role in SARS-CoV-2 Infection?

Leptin is a pleiotropic adipocytokine involved in several physiologic functions, with a known role in innate and adaptive immunity as well as in tissue homeostasis. Long- and short-isoforms of leptin receptors are widely expressed in many peripheral tissues and organs, such as the respiratory tract. Similar to leptin, microbiota affects the immune system and may interfere with lung health through the bidirectional crosstalk called the “gut-lung axis.” Obesity leads to impaired protective immunity and altered susceptibility to pulmonary infections, as those by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Although it is known that leptin and microbiota link metabolism and lung health, their role within the SARS-CoV2 coronavirus disease 2019 (COVID-19) deserves further investigations. This review aimed to summarize the available evidence about: (i) the role of leptin in immune modulation; (ii) the role of gut microbiota within the gut-lung axis in modulating leptin sensitivity; and (iii) the role of leptin in the pathophysiology of COVID-19.

Association of asthma diagnosis with leptin and adiponectin: a systematic review and meta-analysis

There is some evidence which shows that higher levels of serum leptin and lower levels of serum adiponectin are associated with the diagnosis of asthma. This meta-analysis evaluated the association of serum leptin and adiponectin levels with the diagnosis of asthma. We searched the MEDLINE, Cochrane, EMBASE and CINAHL Plus databases up to July 2015. Eligible studies were randomized controlled trials, prospective studies, retrospective studies, case-control studies and cohort studies. 13 studies with 3642 patients were included in the study. The meta-analysis found that in the overall study population, the diagnosis of asthma was associated with higher levels of leptin (pooled standardized difference in means=0.867, 95% CI 0.416 to 1.318, p<0.001) and lower levels of adiponectin (pooled standardized difference in means=-0.371, 95% CI -0.728 to -0.014, p=0.042) in patients with asthma compared with controls. Subgroup analysis found that higher leptin levels were associated with asthma both in adults (standardized difference in means=1.374, 95% CI 0.621 to 2.126, p<0.001) and children (standardized difference in means=0.302, 95% CI 0.010 to 0.594, p=0.042). However, borderline association of adiponectin with asthma was seen in adults (p=0.05), but not in children (p=0.509). Sensitivity analysis indicated that the findings for leptin were robust. Our findings are consistent with higher levels of serum leptin being associated with asthma regardless of age, and low adiponectin levels being associated with asthma in adults only.

Adipokine resistin predicts anti-inflammatory effect of glucocorticoids in asthma

Background

Adipokines are protein mediators secreted by adipose tissue. Recently, adipokines have also been involved in the regulation of inflammation and allergic responses, and suggested to affect the risk of asthma especially in obese female patients. We assessed if adipokines predict responsiveness to glucocorticoids and if plasma adipokine levels are associated with lung function or inflammatory activity also in non-obese (body mass index (BMI) ≤ 30 kg/m²) women with newly-diagnosed steroid-naïve asthma.

Methods

Lung function, exhaled NO, plasma levels of adipokines leptin, resistin, adiponectin and adipsin, and inflammatory markers were measured in 35 steroid-naïve female asthmatics and in healthy controls. The measurements were repeated in a subgroup of asthmatics after 8 weeks of treatment with inhaled fluticasone. Adipokine concentrations in plasma were adjusted for BMI.

Results

High baseline resistin concentrations were associated with a more pronounced decrease in serum levels of eosinophil cationic protein (ECP) (r = -0.745, p = 0.013), eosinophil protein X (EPX) (r = -0.733, p = 0.016) and myeloperoxidase (MPO) (r = -0.721, p = 0.019) during fluticasone treatment. In asthmatics, leptin correlated positively with asthma symptom score and negatively with lung function. However, no significant differences in plasma adipokine levels between non-obese asthmatics and healthy controls were found. The effects of resistin were also investigated in human macrophages in cell culture. Interestingly, resistin increased the production of proinflammatory factors IL-6 and TNF-α and that was inhibited by fluticasone.

Conclusions

High resistin levels predicted favourable anti-inflammatory effect of inhaled glucocorticoids suggesting that resistin may be a marker of steroid-sensitive phenotype in asthma. High leptin levels were associated with a more severe disease suggesting that the link between leptin and asthma is not restricted to obesity.

Association between clinical severity of childhood asthma and serum leptin levels

OBJECTIVE

To investigate the association between the clinical severity of childhood asthma and serum leptin levels, to define whether the severity of asthma correlates with body mass index (BMI) or serum leptin levels and to examine the sensitivity of leptin levels in predicting asthma severity.

METHODS

This study was conducted in 65 patients, aged 2 to 14 yrs with newly diagnosed asthma without any chronic co-morbidity. The subjects were distributed into three groups according to the severity of asthma.

RESULTS

Intra-group serum leptin levels before and after treatment did not show significant difference (p>0.05). Inter-group pre-treatment leptin levels were different significantly (p<0.01) and the difference originated from Group I and III as well as Group II and III. No correlation existed between leptin levels and BMI (p>0.05).

CONCLUSIONS

Leptin levels correlated with the clinical severity of asthma and this was suggested to be associated with the severity of inflammation in asthma. More studies are required to evaluate leptin levels in predicting asthma severity.

Does leptin play a role in obesity-asthma relationship?

The increase of asthma has paralleled the rising obesity during the past decades. Obesity is characterized by the increase of leptin in the circulation. Leptin is an obesity gene product, and it can stimulate the production of pro-inflammatory mediators, such as tumor necrosis factor (TNF)-alpha, interleukin (IL)-6 and interferon (IFN)-gamma. There is a link between leptin and asthma, especially in children. It remains unclear however, if leptin is in the pathway of obesity-asthma relationship and if it plays a distinctive role in asthma in obese vs. non-obese subjects. Since leptin is in a positive feedback loop with the pro-inflammatory cytokines such as TNF-alpha, there is a possibility that leptin is involved as a regulatory rather than an etiologic mechanism of asthma development. Weight loss is associated with decreased circulating leptin concentration in children. Weight control program may need to be considered in the treatment of asthma in obese children.

Serum leptin levels and lipid profiles in patients with allergic rhinitis and mild asthma

BACKGROUND

Despite improved understanding of the pathophysiology of allergic rhinitis and asthma, the effect of serum leptin level is still controversial. Only a few studies have been performed to investigate the serum leptin levels in allergic rhinitis and asthma, and contradictory results have been observed.

OBJECTIVE

We aimed to investigate the association between leptin, lipid profiles and allergic rhinitis and mild asthma, and to determine whether inhaled and/or intranasal steroids affect the leptin levels.

PATIENTS AND METHODS

We studied 43 patients with allergic rhinitis (10 of with mild asthma) (mean age 29.81, range 18-45 yr) and 32 volunteers as a control group (mean age 30.53, range 20-45 yr).

RESULTS

Serum leptin levels in patients were 8.49 +/- 10.76 microg/ml, and did not differ from volunteers 5.42 +/- 6.63 microg/ml. (p > 0.05). We found a direct link between increased body mass index (BMI) and serum leptin levels (p = 0.008). No association was seen between leptin and triglyceride, HDL-cholesterol, VLDL-cholesterol, eosinophil, total IgE (p > 0.05); except for total cholesterol and LDL-cholesterol (p < 0.05). Although, no correlation between allergic rhinitis and mild asthma and serum level of leptin was shown, these parameters and age correlations were stronger in female than in male (p = 0.39 for male and p = 0.011 for female), and also found direct link between increased BMI and sex and patients group (p = 0.008 for male and p = 0.0001 for female). We also determined that there was no effect of inhaled and/or intranasal steroids statistically on serum leptin levels.

CONCLUSION

Our data demonstrate that the serum levels of leptin and lipid profiles on allergic rhinitis and mild asthma were not different than those in controls.

Relationship of body mass index with asthma indicators in head start children

OBJECTIVE

To examine the relationship of body mass index (BMI) and asthma indicators on children with asthma in a Head Start (HS) program.

METHODS

In this cross-sectional study (November 18, 2000, to December 12, 2003) of children aged 3 to 5 years with asthma, we compared the BMI data of HS asthmatic patients (n = 213) with the data of peer control subjects from a sample (n = 816) of the National Health and Nutrition Examination Survey aged 3 to 5 years and with children in prekindergarten in Arkansas public schools (n = 1,024). Parental reports of asthma symptoms, health care use, medication use, school days missed, and quality of life were used as indicators of asthma morbidity. Categorical analysis and chi2 tests were performed to examine the relationship between BMI and asthma morbidity.

RESULTS

The prevalence of overweight (> or =95th percentile) was significantly higher in HS children with asthma compared with the National Health and Nutrition Examination Survey children (P < .001) and Arkansas prekindergarten children (P = .05). Compared with HS asthmatic children with a BMI less than the 85th percentile, HS asthmatic patients with a BMI of the 85th percentile or greater reported significantly more school days missed (P = .02), lifetime hospitalizations (P = .04), emergency department visits (P = .02), and activity limitations (P = .03) and fewer oral corticosteroid bursts (P = .04). There was also a trend for more daytime symptoms (P = .05) and lower quality of life (P = .06). No differences were observed in rescue (P = .28) or controller (P = .47) medications, environmental tobacco smoke exposure (P = .47), positive allergy test results (P = .85), and nighttime symptoms (P > .99).

CONCLUSIONS

Having an increased BMI was associated with more asthma morbidity in this group of HS asthmatic patients. Despite the lack of a clear explanation for the link between asthma and BMI, our data suggest that an increased BMI significantly affects the well-being of young asthmatic patients and should be further addressed.

Serum leptin levels in asthmatic children treated with an inhaled corticosteroid

BACKGROUND

Recent observations suggest the presence of an interaction between leptin and the inflammatory system; however, there is no adequate knowledge about the role of leptin in atopic states such as asthma.

OBJECTIVES

To evaluate the potential role of leptin in relation to bronchial asthma and inhaled corticosteroid therapy.

METHODS

Twenty-three children with mild-to-moderate, newly diagnosed asthma enrolled in this 2-period trial. The control group consisted of 20 age- and sex-matched children. Serum leptin levels were measured in patients at initiation and after 4 weeks of budesonide treatment and were compared with control group measurements.

RESULTS

Asthmatic children had higher mean +/- SD serum leptin levels at admission (19.3 +/- 5.1 ng/mL) than after budesonide treatment (10.6 +/- 1.6 ng/mL) and vs control group measurements (9.8 +/- 1.6 ng/mL) (P < .001). There was a significant correlation between serum leptin levels before and after budesonide treatment (r = 0.68; P = .007). Mean +/- SD body mass indices in patients and controls were 16.7 +/- 2.1 and 16.9 +/- 2.6 kg/m2, respectively. Serum leptin levels did not correlate with body mass indices before budesonide treatment in the study group (r = -0.13; P = .65) but correlated well after budesonide treatment (r = 0.58; P = .009) and in the control group (r = 0.65; P = .008).

CONCLUSIONS

The role of leptin elevation in children with asthma might be a regulatory mechanism rather than being etiologic, but a question may be raised whether it is possible that leptin may contribute to poor patient outcomes. Further research, both basic and clinical, is essential to explain the exact mechanism.

Serum leptin level in children with atopic dermatitis-treated topical steroids

Leptin, the obese gene product, is a 16-kDa peptide hormone secreted by adiposities. Systemic administration of exogenous glucocorticoids has been found to increase circulating leptin levels. In this study, we aimed to assess serum leptin in children with atopic dermatitis (AD)-treated with local steroids. Twenty children with AD were included during the 2001-2002 time period. The study was conducted prospectively. Atopy was defined as the presence of at least one aeroallergen-specific immunoglobulin E (IgE) antibody. Serum leptin was determined using a commercially available radioimmunoassay kit with 3.4-8.3% intra-assay and 3.0-6.2% interassay coefficients of variation, and 0.5 ng/ml sensitivity. Fourteen boys and six girls with AD, the mean age of the patients was 3.1 +/- 2.2. Forty-three percentage of the family histories for atopy were positive, 60% of the cases passive smoking histories were positive. In seven patients the aeroallergen-specific IgE were positive. All 20 patients treated clobetasone 17-butirate (0.05%). There was no significant difference in serum leptin between patients (mean +/- s.d.: 4.6 +/- 3.8), and controls (mean +/- s.d.: 6.2 +/- 3.6) (p > 0.05). Local steroid does not influence circulating leptin levels, suggesting that regulation of body weight is unaffected.

Plasma leptin and leptin receptor expression in childhood acute lymphoblastic leukemia

Recently, leptin has been shown to play a regulatory role for differentiation within the myeloid and erythroid cell lineage, whereas results of its regulatory effects on lymphocytes and related tumor cells have been contradictory. To investigate whether leptin plays a role in acute lymphoblastic leukemia (ALL), we investigated the levels of leptin in plasma with enzyme-linked immunosorbent assays and the expression of the leptin receptor on malignant lymphoblasts with reverse transcriptase polymerase chain reaction (RT-PCR). At diagnosis, the leptin levels of bone marrow-derived plasma in children with ALL were found to be significantly lower than the levels of healthy control subjects (0.92 +/- 0.79 ng/mL versus 3.01 +/- 2.27 ng/mL, respectively). Notably, at complete hematologic remission (at day 33 of chemotherapy), leptin levels had normalized to 2.6 +/- 2.4 ng/mL. To elucidate the underlying mechanism of this phenomenon, we analyzed the expression of the leptin receptor on the mononuclear cell populations of the patients. RT-PCR analysis revealed gene expression rates of 33% at diagnosis versus 71% at remission, compared with 100% for healthy control subjects. Results of immunohistochemical staining supported these findings by showing that the tumor clones themselves do not express the leptin receptor. Finally, some hypotheses that might explain the decrease of leptin levels in the presence of the tumor clone are discussed.