Association of serum leptin levels and pulmonary tuberculosis: a meta-analysis

Leptin levels in childhood tuberculosis and its correlation with body mass index, IFN-γ, and TNF-α in an Indonesian population

BACKGROUND

Leptin plays a key role in the regulation of energy and inflammation in tuberculosis (TB). However, its correlation in children with TB remains unclear. Therefore, this study aimed to evaluate the correlations between body mass index, IFN-γ, TNF-α, and leptin levels in children with TB.

METHODS

This was a cross-sectional study of children aged 2-14 years with TB. Sputum examination, chest radiography, and tuberculin skin test findings and clinical symptoms were considered for TB diagnosis. Data on body weight; height; mid-upper arm circumference (MUAC); body mass index (BMI); food intake; and IFN-γ, TNF-α, and leptin levels were collected and analyzed.

RESULTS

Of the 64 diagnosed TB subjects, 2 subjects had positive bacteriological results. The median age was 6 (2-14) years, body weight was 17.7 (9.45-55) kg, height was 114 ± 21.46 cm, and Z score BMI was -0.85 ± 1.14 kg/m2. Malnourished was observed in 17.2% of the subjects. The median calorie intake was 1448.5 (676-4674) kcal, carbohydrate intake was 182.5 (63-558) g, protein intake was 57.9 (15.8-191.0) g, and fat intake was 81.6 (23.6-594.1) g. The median leptin level was 1.2 (0.2-59) ng/mL, IFN-γ was 2.5 (0.9-161) pg/mL, and TNF-α was 13.0 (5.7-356) pg/mL. Correlations were observed between leptin and MUAC (r = 0.251, p = 0.02), Z score (r = 0.453, p = 0.00), and IFN-γ (r = 0.295, p = 0.018).

CONCLUSION

There were positive correlations between BMI and leptin levels, whereas IFN-γ and MUAC showed weak correlations.

Leptin Deficiency May Influence the Divergence of Cell-Mediated Immunity Between Lepromatous and Tuberculoid Leprosy Patients

Leprosy is a disease caused by an intracellular bacillus bacterium called Mycobacterium leprae which lives and multiplies in the hosts' macrophages and Schwann cells. Depending on the degree of the host's cell-mediated immunity (CMI) response to the bacilli, the disease manifests itself in five clinical spectra ranging from polar tuberculoid (TT) to polar lepromatous leprosy (LL). A very high level of T helper 1 (Th1) driven bacilli-specific CMI is seen in the TT form, whereas this response is essentially nonexistent in the LL form. As a result, there is very low or absent bacillary load and localized nodular lesions in TT patients. On the contrary, LL patients presented with high bacillary load and generalized lesions due to low CMI response. The mechanism underlying this divergence of CMI response is not clearly elucidated yet. However, mounting evidence links it to an elevated number of Th1 and Th17 suppressing CD4+ CD25+ FOXP3+ T regulatory cells (Treg cells) which are abundantly found in LL than in TT patients. The predominance of these cells in LL patients is partly attributed to a deficiency of leptin, the cytokine-like peptide hormone, in these patients. Becausea normal level of leptin promotes the proliferation and preferential differentiation of effector T cells (Th1 and Th17) while inhibiting the growth and functional responsiveness of the Treg cells. In contrast, leptin deficiency or neutralization was reported to exert the opposite effect on Treg cells and effector T cells. Other smaller subsets of lymphocytes such as gamma delta (γδ) T cells and B regulatory cells are also modulated by leptin level in the pathogenesis of leprosy. Leptin may therefore regulate the divergence of CMI between TT and LL patients by regulating the homeostasis of effector T cells and Treg cells, and this review will examine the underlying mechanism for this.

Malnutrition is Associated with an Increased Risk of Death in Hospitalized Patients with Active Pulmonary Tuberculosis: A Propensity Score Matched Retrospective Cohort Study

Background

This study aimed to investigate whether nutrition levels in patients with active pulmonary tuberculosis (TB) affect their risk of all-cause mortality during hospitalization and to further evaluate the predictive ability of Geriatric Nutritional Risk Index (GNRI) and Body Mass Index (BMI) for risk of all-cause mortality.

Methods

Patients from January 1, 2020 to December 31, 2021 were retrieved, and a total of 1847 were included. The primary outcome was all-cause mortality. Propensity score matching (PSM) was performed for risk adjustment, and receiver operating characteristic (ROC) curve analysis was performed to assess the predictive ability of GNRI and BMI for all-cause mortality.

Results

Malnourished TB patients were older, had more congestive heart failure, and had more chronic obstructive pulmonary disease or asthma. Under the nutrition level grouping defined by GNRI, the all-cause mortality in the malnourished group did not appear to reach a statistical difference compared with the nonmalnourished group (P = 0.078). When grouped by level of nutrition as defined by BMI, the all-cause mortality was higher in the malnourished group (P = 0.009), and multivariate logistic regression analysis revealed that malnutrition was an independent risk factor for all-cause mortality. After propensity score matching, the results showed that the all-cause mortality was higher in the malnutrition group, regardless of BMI or GNRI defined nutrition level grouping, compared with the control group (both P < 0.001). The ROC curve analysis revealed that the area under the curve (AUC) was 0.811 ([95% confidence interval (CI) 0.701–0.922], P < 0.001) for GNRI and 0.728 ([95% CI 0.588–0.869], P = 0.001) for BMI.

Conclusion

In the clinical treatment of patients with active TB, more attention should be paid to the management of nutritional risk. GNRI may be a highly effective and easy method for predicting short-term outcomes in patients with active pulmonary TB.

Differences in CT imaging signs between patients with tuberculosis and those with tuberculosis and concurrent lung cancer

OBJECTIVE

The purpose of this study was to compare the differences in imaging features between patients with pulmonary tuberculosis (TB) alone and patients with TB complicated with lung cancer (LCA) as well as to investigate the diagnostic value of CT in these two groups.

METHODS

In this retrospective study, 110 patients with confirmed TB admitted to the Second Affiliated Hospital of Hainan Medical University from March 2020 to April 2021 were collected and divided into TB+LCA group (50 cases, diagnosed with TB complicated with lung cancer) and TB group (60 cases, diagnosed with TB alone) according to actual diagnosis. The CT results of both groups were analyzed by the same group of physicians in a double-blind manner. The diagnostic value of CT for TB alone and TB complicated with lung cancer was calculated. The differences in CT imaging characteristics between the two groups were investigated. The differences in the structural characteristics of para-cancerous tissue between the two groups were analyzed.

RESULTS

The diagnostic accuracy of CT was 91.67% in TB patients (55/60) and 92.00% in TB+LCA patients (46/50) without significant difference (X² =0.004, P=0.949). The detection rate of spiculation, lobulation and cavitation in TB+LCA group was significantly higher than that in TB group (P<0.05), and the distribution, size and wall thickness of cavitation varied significantly between the two groups (P<0.05). Patients in TB group had higher percentage of mediastinal lymph node calcification, peripheral satellite lesion, and mediastinal lymph node enlargement around the TB lesions compared with those in TB+LCA group (P<0.05).

CONCLUSION

CT has certain application value in differentiating TB alone from TB complicated with lung cancer, and there are many similarities in the imaging features of the two conditions. CT can be considered as a preliminary means of differential diagnosis of TB complicated with lung cancer, which is helpful to the primary screening diagnosis of lung cancer.

Leptin mutation and mycobacterial infection lead non-synergistically to a similar metabolic syndrome

INTRODUCTION

The leptin signaling pathway plays an important role as a key regulator of glucose homeostasis, metabolism control and systemic inflammatory responses. However, the metabolic effects of leptin on infectious diseases, for example tuberculosis (TB), are still little known.

OBJECTIVES

In this study, we aim to investigate the role of leptin on metabolism in the absence and presence of mycobacterial infection in zebrafish larvae and mice.

METHODS

Metabolites in entire zebrafish larvae and the blood of mice were studied using high-resolution magic-angle-spinning nuclear magnetic resonance (HR-MAS NMR) spectroscopy and mass spectrometry, respectively. For transcriptome studies of zebrafish larvae, deep RNA sequencing was used.

RESULTS

The results show that leptin mutation leads to a similar metabolic syndrome as caused by mycobacterial infection in the two species, characterized by the decrease of 11 amine metabolites. In both species, this metabolic syndrome was not aggravated further when the leptin mutant was infected by mycobacteria. Therefore, we conclude that leptin and mycobacterial infection are both impacting metabolism non-synergistically. In addition, we studied the transcriptomes of lepb^ibl54 mutant zebrafish larvae and wild type (WT) siblings after mycobacterial infection. These studies showed that mycobacteria induced a very distinct transcriptome signature in the lepb^ibl54 mutant zebrafish compared to WT sibling control larvae. Furthermore, lepb^ibl55 Tg (pck1:luc1) zebrafish line was constructed and confirmed this difference in transcriptional responses.

CONCLUSIONS

Leptin mutation and TB lead non-synergistically to a similar metabolic syndrome. Moreover, different transcriptomic responses in the lepb^ibl54  mutant and TB can lead to the similar metabolic end states.

Adipokines and the risk of active TB: a nested case-control study

BACKGROUND: Adipokines are emerging mediators of immune response, and may affect susceptibility to active TB.OBJECTIVE: To examine the associations between adipokines and the risk of active TB.METHODS: In a case-control study nested within a prospective cohort of middle-aged and older adults in Singapore, 280 incident active TB cases who donated blood for research before diagnosis were matched with 280 controls. Serum levels of adiponectin, resistin, leptin and ghrelin were measured. Multivariable logistic regression models were used to compute the adjusted odds ratios (ORs) and 95% confidence intervals (CIs) for the associations between adipokines and the risk of active TB.RESULTS: Higher levels of leptin and resistin were associated with reduced risk of TB in a dose-dependent manner. Compared to those in the lowest quartile of leptin levels, those in the highest quartile had an OR of 0.46 (95%CI 0.26-0.82; P for trend = 0.009). Similarly, compared to those in the lowest quartile of resistin levels, those in the highest quartile had an OR of 0.46 (95%CI 0.24-0.90; P for trend = 0.03). Adiponectin and ghrelin levels were not associated with TB risk.CONCLUSION: Increased serum levels of leptin and resistin may be associated with reduced susceptibility to active TB infection.

The Thousand Faces of Leptin in the Lung

Leptin is a pleotropic hormone known to regulate a wide range of systemic functions, from satiety to inflammation. Increasing evidence has shown that leptin and its receptor (ObR) are not only expressed in adipose tissue but also in several organs, including the lungs. Leptin levels were first believed to be elevated only in the lungs of obese patients, and leptin was suspected to be responsible for obesity-related lung complications. Aside from obesity, leptin displays many faces in the respiratory system, independently of body weight, as this cytokine-like hormone plays important physiological roles, from the embryogenic state to maturation of the lungs and the control of ventilation. The leptin-signaling pathway is also involved in immune modulation and cell proliferation, and its dysregulation can lead to the onset of lung diseases. This review article addresses the thousand faces of leptin and its signaling in the lungs under physiological conditions and in disease.

Poor Vitamin D Status in Active Pulmonary Tuberculosis Patients and Its Correlation with Leptin and TNF-α

Vitamin D deficiency (VDD) is common in tuberculosis (TB) and may be implicated in the etiology of the disease and in its clinical course. The aim of this study was to investigate the association between leptin, inflammatory markers and VD status in TB patients, stratified for presence or absence of diabetes mellitus (DM). Two hundred ninety-nine TB patients were recruited from October 2015 to August 2016. Also, 91 normal controls were included. The information including socio-demographics, dietary intake and living habits was obtained by face-to-face interview. Serum concentrations of leptin and TNF-α, CRP and IL-6 were compared between TB patients with and without severe VDD (SVDD). Pearson's correlation was used to analyze the association between TNF-α, leptin and 25-hydroxyvitamin D (25(OH)D). A significantly higher prevalence of VDD and SVDD was observed in TB patients compared with normal controls (93.0% vs 70.3%, 65.9% vs 3.3% respectively). Concentration of leptin was significantly lower, while TNF-α higher in TB patients with SVDD compared to those without (p<0.05). After adjustment for confounders, leptin was positively associated with 25(OH)D (r=0.210, p=0.002) with similar correlation in TB patients with DM (r=0.240, p=0.020). A negative association between TNF-α and 25(OH)D was observed (r=-0.197, p=0.003), which was significant only in the subgroup without DM (r=-0.304, p=0.001). Our findings indicate that a higher VD status in TB patients may be related to higher immune activity and less serious tissue damage, and that this relation is different according to presence or absence of DM co-morbidity.

Leptin Functions in Infectious Diseases

Leptin, a pleiotropic protein has long been recognized to play an important role in the regulation of energy homeostasis, metabolism, neuroendocrine function, and other physiological functions through its effects on the central nervous system (CNS) and peripheral tissues. Leptin is secreted by adipose tissue and encoded by the obese (ob) gene. Leptin acts as a central mediator which regulates immunity as well as nutrition. Importantly, leptin can modulate both innate and adaptive immune responses. Leptin deficiency/resistance is associated with dysregulation of cytokine production, increased susceptibility toward infectious diseases, autoimmune disorders, malnutrition and inflammatory responses. Malnutrition induces a state of immunodeficiency and an inclination to death from communicable diseases. Infectious diseases are the disease of poor who invariably suffer from malnutrition that could result from reduced serum leptin levels. Thus, leptin has been placed at the center of many interrelated functions in various pathogenic conditions, such as bacterial, viruses and parasitic infections. We review herein, the recent advances on the role of leptin in malnutrition in pathogenesis of infectious diseases with a particular emphasis on parasitic diseases such as Leishmaniasis, Trypanosomiasis, Amoebiasis, and Malaria.