Decreased plasma leptin concentrations in tuberculosis patients are associated with wasting and inflammation

Patients with nontuberculous mycobacterial lung disease exhibit unique body and immune phenotypes

RATIONALE

Among patients with nontuberculous mycobacterial lung disease is a subset of previously healthy women with a slender body morphotype, often with scoliosis and/or pectus excavatum. We hypothesize that unidentified factors predispose these individuals to pulmonary nontuberculous mycobacterial disease.

OBJECTIVES

To compare body morphotype, serum adipokine levels, and whole-blood cytokine responses of patients with pulmonary nontuberculous mycobacteria (pNTM) with contemporary control subjects who are well matched demographically.

METHODS

We enrolled 103 patients with pNTM and 101 uninfected control subjects of similar demographics. Body mass index and body fat were quantified. All patients with pNTM and a subset of control subjects were evaluated for scoliosis and pectus excavatum. Serum leptin and adiponectin were measured. Specific cytokines important to host-defense against mycobacteria were measured in whole blood before and after stimulation.

MEASUREMENTS AND MAIN RESULTS

Patients with pNTM and control subjects were well matched for age, gender, and race. Patients with pNTM had significantly lower body mass index and body fat and were significantly taller than control subjects. Scoliosis and pectus excavatum were significantly more prevalent in patients with pNTM. The normal relationships between the adipokines and body fat were lost in the patients with pNTM, a novel finding. IFN-γ and IL-10 levels were significantly suppressed in stimulated whole blood of patients with pNTM.

CONCLUSIONS

This is the first study to comprehensively compare body morphotype, adipokines, and cytokine responses between patients with NTM lung disease and demographically matched controls. Our findings suggest a novel, predisposing immunophenotype that should be mechanistically defined.

Benefits of leptin therapy in HIV patients

Leptin therapy in human recombinant form has recently been used in HIV-associated lipodystrophy syndrome on experimental basis in some small short-term clinical trials. It has shown its beneficial effects only in hypoleptinemic HIV-infected patients by causing definite improvement in their insulin sensitivity, glucose tolerance, lipid status, and truncal obesity. Leptin prevents lipotoxicity and activates insulin signaling pathways through several postulated mechanisms. Central leptin insufficiency with peripheral hyperleptinemia has come out to be a significant contributor to the development of obesity and metabolic syndrome. In this article, we will review the basis of leptin therapy in HIV patients, with its promises. However, further larger clinical trials are needed to prove its long-term efficacy in the control of metabolic complications related to HIV therapy.

Circulating levels of adiponectin, leptin, fetuin-A and retinol-binding protein in patients with tuberculosis: markers of metabolism and inflammation

BACKGROUND

Wasting is known as a prominent feature of tuberculosis (TB). To monitor the disease state, markers of metabolism and inflammation are potentially useful. We thus analyzed two major adipokines, adiponectin and leptin, and two other metabolic markers, fetuin-A and retinol-binding protein 4 (RBP4).

METHODS

The plasma levels of these markers were measured using enzyme-linked immunosorbent assays in 84 apparently healthy individuals (=no-symptom group) and 46 patients with active pulmonary TB around the time of treatment, including at the midpoint evaluation (=active-disease group) and compared them with body mass index (BMI), C-reactive protein (CRP), chest radiographs and TB-antigen specific response by interferon-γ release assay (IGRA).

RESULTS

In the no-symptom group, adiponectin and leptin showed negative and positive correlation with BMI respectively. In the active-disease group, at the time of diagnosis, leptin, fetuin-A and RBP4 levels were lower than in the no-symptom group [adjusted means 2.01 versus 4.50 ng/ml, P<0.0001; 185.58 versus 252.27 µg/ml, P<0.0001; 23.88 versus 43.79 µg/ml, P<0.0001, respectively]. High adiponectin and low leptin levels were associated with large infiltrates on chest radiographs even after adjustment for BMI and other covariates (P=0.0033 and P=0.0020). During treatment, adiponectin levels increased further and then decreased. Leptin levels remained low. Initial low levels of fetuin-A and RBP4 almost returned to the normal reference range in concert with reduced CRP.

CONCLUSIONS

Our data and recent literature suggest that low fat store and underlying inflammation may regulate these metabolic markers in TB in a different way. Decreased leptin, increased adiponectin, or this ratio may be a promising marker for severity of the disease independent of BMI. We should further investigate pathological roles of the balance between these adipokines.

Nutritional status and its response to treatment of children, with and without HIV infection, hospitalized for the management of tuberculosis

BACKGROUND

The association of childhood tuberculosis (TB) and malnutrition is known, but treatment response, the influence of the acute-phase response (APR) and concomitant HIV infection are not well documented.

AIM

To evaluate the nutritional response and APR in HIV-infected and uninfected children hospitalised for the treatment of TB and receiving standard anti-tuberculosis chemotherapy.

METHODS

During a study of the pharmacokinetics of standard anti-tuberculosis agents, anthropometric parameters were measured and blood concentrations of nutrients and C-reactive protein (CRP) determined at 1 and 4 months after initiation of chemotherapy.

RESULTS

24 HIV-infected and 34 HIV-uninfected children were studied. On enrollment, 31.6% of HIV-infected and 2.9% of HIV-uninfected children were underweight, and 31.6% and 14.7%, respectively, were stunted. Mean values of weight, height/length, head circumference and mid-upper-arm circumference on enrollment and at 4-month assessment in HIV-infected and uninfected children did not differ. Mean triceps skinfold (TSF) (8.17 and 9.73 cm) and subscapular skinfold (SSF) thicknesses (5.75 and 7.5 cm) on enrollment differed significantly (P = 0.03 and P = 0.003); by 4 months, TSF had declined to 5.97 cm (P<0.001) and 8.87 cm (P = 0.05), respectively, and SSF to 5.57 cm (P = 0.79) and 6.73 cm (P = 0.04); the arm muscle area (AMA) was low in a majority of children on enrollment and remained so at the second assessment. CRP was raised in 66.6% and 53.3% of HIV-infected and -uninfected children on enrollment, but at 4-month assessment was raised in 63.2% and 15.2%, respectively. Other micronutrient and haematological findings probably reflect an APR, but no children had sub-normal zinc or magnesium values; most selenium and vitamin C and E values were normal. An elevated platelet count (> 420 × 10(9)/L) was significantly more common in HIV-uninfected children, and was still raised in 39% at 4 months.

CONCLUSION

A majority of HIV-infected and uninfected children had an APR but it had resolved by 4 months in most HIV-uninfected children. In both groups, low and declining skinfolds and a persistently low AMA indicate a persistent disturbance of fat and protein metabolism, despite successful chemotherapy.

Frequent detection of anti-tubercular-glycolipid-IgG and -IgA antibodies in healthcare workers with latent tuberculosis infection in the Philippines

Anti-tubercular-glycolipid-IgG (TBGL-IgG) and -IgA (TBGL-IgA) antibodies, and the QuantiFERON-TB Gold test (QFT) were compared in healthcare workers (HCWs, n = 31) and asymptomatic human immunodeficiency virus-carriers (HIV-AC, n = 56) in Manila. In HCWs, 48%, 51%, and 19% were positive in QFT, TBGL-IgG, and -IgA, respectively. The TBGL-IgG positivity was significantly higher (P = 0.02) in QFT-positive than QFT-negative HCWs. Both TBGL-IgG- and -IgA-positive cases were only found in QFT-positive HCWs (27%). The plasma IFN-γ levels positively correlated with TBGL-IgA titers (r = 0.74, P = 0.005), but not TBGL-IgG titers in this group, indicating that mucosal immunity is involved in LTBI in immunocompetent individuals. The QFT positivity in HIV-AC was 31% in those with CD4+ cell counts >350/μL and 12.5% in low CD4 group (<350/μL). 59 % and 29% were positive for TBGL-IgG and -IgA, respectively, in HIV-AC, but no association was found between QFT and TBGL assays. TBGL-IgG-positive rates in QFT-positive and QFT-negative HIV-AC were 61% and 58%, and those of TBGL-IgA were 23% and 30%, respectively. The titers of TBGL-IgA were associated with serum IgA (P = 0.02) in HIV-AC. Elevations of TBGL-IgG and -IgA were related to latent tuberculosis infection in HCWs, but careful interpretation is necessary in HIV-AC.

Differential effects of energy balance on experimentally-induced colitis

AIM: To characterize the influence of diet-induced changes in body fat on colitis severity in SMAD3-/- mice.

METHODS: SMAD3-/- mice (6-8 wk of age) were randomly assigned to receive a calorie restricted (30% of control; CR), control (CON), or high fat (HF) diet for 20 wk and were gavaged with sterile broth or with Helicobacter hepaticus (H. hepaticus) to induce colitis. Four weeks after infection, mice were sacrificed and the cecum and colons were processed for histological evaluation.

RESULTS: Dietary treatment significantly influenced body composition prior to infection (P < 0.05), with CR mice having less (14% ± 2%) and HF-fed mice more body fat (32% ± 7%) compared to controls (22% ± 4%). Differences in body composition were associated with alterations in plasma levels of leptin (HF > CON > CR) and adiponectin (CON > HF ≥ CR) (P < 0.05). There were no significant differences in colitis scores between CON and HF-fed mice 4 wk post-infection. Consistent with this, differences in proliferation and inflammation markers (COX-2, iNOS), and infiltrating cell types (CD3⁺ T lymphocytes, macrophages) were not observed. Unexpectedly, only 40% of CR mice survived infection with H. hepaticus, with mortality observed as early as 1 wk following induction of colitis.

CONCLUSION: Increased adiposity does not influence colitis severity in SMAD3-/- mice. Importantly, caloric restriction negatively impacts survival following pathogen challenge, potentially due to an impaired immune response.

Inflammation and ovarian cancer

Epithelial ovarian cancer (EOC) is a highly lethal gynecological cancer for which overall prognosis has remained poor over the past few decades. A number of theories have been postulated in an effort to explain the etiology of EOC. Noteworthy, these theories likely are not mutually exclusive, as they all converge more or less on the role of inflammation in promoting ovarian tumorigenesis and cancer progression. The tumor milieu in which ovarian carcinoma develops has been described as one enriched with a broad spectrum of pro-inflammatory cytokines and chemokines. In particular, several of these cytokines, such as tumor necrosis factor (TNF)-α, interleukin (IL)-1β and IL-6, produced by tumor itself or/and activated immune cells, besides stimulating cancer cell growth, have been shown to influence clinical disease status and prognosis, by reducing responsiveness to chemotherapy and inducing symptoms such as anorexia, altered energy metabolism, anemia, weight loss, depression and fatigue. Recent data show that cytokine antagonists may have a role to play in the treatment of ovarian cancer. Their action by inhibiting both production and activity of inflammatory cytokines seems to obtain the control of angiogenetic and apoptotic events, the reversal of chemoresistance, the improvement of systemic symptoms and prognosis. In the light of our scientific research and the most recent experimental and clinical advances, our review will discuss the most relevant and recent findings on the role of proinflammatory cytokines in the pathogenesis and prognosis of ovarian cancer and the possible therapeutic implications.

A multifaceted analysis of immune-endocrine-metabolic alterations in patients with pulmonary tuberculosis

Our study investigated the circulating levels of factors involved in immune-inflammatory-endocrine-metabolic responses in patients with tuberculosis with the aim of uncovering a relation between certain immune and hormonal patterns, their clinical status and in vitro immune response. The concentration of leptin, adiponectin, IL-6, IL-1β, ghrelin, C-reactive protein (CRP), cortisol and dehydroepiandrosterone (DHEA), and the in vitro immune response (lymphoproliferation and IFN-γ production) was evaluated in 53 patients with active untreated tuberculosis, 27 household contacts and 25 healthy controls, without significant age- or sex-related differences. Patients had a lower body mass index (BMI), reduced levels of leptin and DHEA, and increased concentrations of CRP, IL-6, cortisol, IL-1β and nearly significant adiponectin values than household contacts and controls. Within tuberculosis patients the BMI and leptin levels were positively correlated and decreased with increasing disease severity, whereas higher concentrations of IL-6, CRP, IL-1β, cortisol, and ghrelin were seen in cases with moderate to severe tuberculosis. Household contacts had lower DHEA and higher IL-6 levels than controls. Group classification by means of discriminant analysis and the k-nearest neighbor method showed that tuberculosis patients were clearly different from the other groups, having higher levels of CRP and lower DHEA concentration and BMI. Furthermore, plasma leptin levels were positively associated with the basal in vitro IFN-γ production and the ConA-driven proliferation of cells from tuberculosis patients. Present alterations in the communication between the neuro-endocrine and immune systems in tuberculosis may contribute to disease worsening.

The role of leptin in the respiratory system: an overview

Since its cloning in 1994, leptin has emerged in the literature as a pleiotropic hormone whose actions extend from immune system homeostasis to reproduction and angiogenesis. Recent investigations have identified the lung as a leptin responsive and producing organ, while extensive research has been published concerning the role of leptin in the respiratory system. Animal studies have provided evidence indicating that leptin is a stimulant of ventilation, whereas researchers have proposed an important role for leptin in lung maturation and development. Studies further suggest a significant impact of leptin on specific respiratory diseases, including obstructive sleep apnoea-hypopnoea syndrome, asthma, COPD and lung cancer. However, as new investigations are under way, the picture is becoming more complex. The scope of this review is to decode the existing data concerning the actions of leptin in the lung and provide a detailed description of leptin's involvement in the most common disorders of the respiratory system.

Association between HIV replication and serum leptin levels: an observational study of a cohort of HIV-1-infected South African women

Background

Advanced HIV infection can result in lipoatrophy and wasting, even in the absence of ongoing opportunistic infections, suggesting that HIV may directly affect adipose tissue amount and distribution.

Methods

We assessed the relationship of fat (measured using anthropometry, DEXA, MRI scans) or markers related to glucose and lipid metabolism with viral load in a cross-sectional sample of 83 antiretroviral-naïve HIV-1-infected South African women. A multivariable linear model was fitted to log₁₀VL to assess the combined effect of these variables.

Results

In addition to higher T cell activation, women with viral load greater than the population median had lower waist circumference, body mass index and subcutaneous abdominal fat, as well as lower serum leptin. We demonstrate that leptin serum levels are inversely associated with viral replication, independent of the amount of adipose tissue. This association is maintained after adjusting for multiple variables associated with disease progression (i.e., cellular activation and innate immunity effector levels).

Conclusions

Our results demonstrate that serum leptin levels are inversely associated with viral replication, independent of disease progression: we postulate that leptin may affect viral replication.

Interleukin-6 and leptin as markers of energy metabolic changes in advanced ovarian cancer patients

The progression of the neoplastic disease is characterized by specific alterations of energy metabolism and by symptoms like fatigue, anorexia, nausea, anaemia, immunodepression and poor performance status (PS). The main cause of these symptoms and metabolic abnormalities is the chronic action of proinflammatory cytokines released both by tumour and immune cells. The present study aimed to assess the relationship between markers of inflammation (C-Reactive Protein, Fibrinogen, proinflammatory cytokines) and energy metabolic status (BMI, leptin, oxidative stress) according to clinical parameters in 104 ovarian cancer patients at different stage and, moreover, to evaluate prospectively the changes of these parameters in accordance to tumour response in a subgroup of 70 advanced stage ovarian cancer patients. Advanced stage and poor PS were associated to high-grade inflammation and impaired energy metabolism. Among inflammatory mediators, interleukin (IL)-6 had a central role as predictive factor of leptin, reactive oxygen species and glutathione peroxidase. In turn, leptin considered the key marker of the nutritional status and energy metabolism, was independently determined from stage and IL-6, not only from BMI. Moreover, the evaluation of the changes of these parameters during the course of the neoplastic disease in the subgroup of advanced ovarian cancer patients clearly unveils the central role of IL-6 and leptin as early markers of the metabolic alterations and symptoms associated to disease progression in advanced stage ovarian cancer. Their assessment should be included in monitoring disease outcome, especially when cancer is no longer curable and quality of life becomes the primary endpoint.

Leptin and Inflammation

The past few years of research on leptin have provided important information on the link between metabolism and immune homeostasis. Adipocytes influence not only the endocrine system but also the immune response through several cytokine-like mediators known as adipokines, which include leptin. It is widely accepted that leptin can directly link nutritional status and pro-inflammatory T helper 1 immune responses, and that a decrease of leptin plasma concentration during food deprivation can lead to an impaired immune function. Additionally, several studies have implicated leptin in the pathogenesis of chronic inflammation, and the elevated circulating leptin levels in obesity appear to contribute to the low-grade inflammatory background which makes obese individuals more susceptible to increased risk of developing cardiovascular diseases, type II diabetes, or degenerative disease including autoimmunity and cancer. Conversely, reduced levels of leptin such as those found in malnourished individuals have been linked to increased risk of infection and reduced cell-mediated immune responses. We discuss here the functional influences of leptin in the physiopathology of inflammation, and the effects of leptin in the modulation of such responses.

An extensive phenotypic characterization of the hTNFalpha transgenic mice

BACKGROUND

Tumor necrosis factor alpha (TNFalpha) is implicated in a wide variety of pathological and physiological processes, including chronic inflammatory conditions, coronary artery disease, diabetes, obesity, and cachexia. Transgenic mice expressing human TNFalpha (hTNFalpha) have previously been described as a model for progressive rheumatoid arthritis. In this report, we describe extensive characterization of an hTNFalpha transgenic mouse line.

RESULTS

In addition to arthritis, these hTNFalpha transgenic mice demonstrated major alterations in body composition, metabolic rate, leptin levels, response to a high-fat diet, bone mineral density and content, impaired fertility and male sexual function. Many phenotypes displayed an earlier onset and a higher degree of severity in males, pointing towards a significant degree of sexual dimorphism in response to deregulated expression of TNFalpha.

CONCLUSION

These results highlight the potential usefulness of this transgenic model as a resource for studying the progressive effects of constitutively expressed low levels of circulating TNFalpha, a condition mimicking that observed in a number of human pathological conditions.

Malnutrition and infection: complex mechanisms and global impacts

The authors discuss current concepts and controversies surrounding the complex influences of malnutrition on infection and immunity, and point to practical consequences of countermeasures in acute malnutrition.

Decreased serum leptin concentration in patients with chronic pancreatitis

OBJECTIVE

Previously reported data suggest that serum leptin concentration changes in some acute and chronic inflammatory diseases. The aim of the present study was to assess serum leptin concentration in patients with chronic pancreatitis.

METHODS

Forty-four male patients with chronic pancreatitis and 16 healthy (male) subjects were examined. Fasting blood samples were collected from patients and healthy controls. Serum leptin and insulin concentrations were determined by radioimmunoassay method.

RESULTS

Significantly lower serum leptin concentration in patients with chronic pancreatitis than in healthy subjects was found. No significant difference in serum leptin concentration between patients without and with exacerbation of chronic pancreatitis on admission was observed. Moreover, patients with chronic pancreatitis had (a) lower serum insulin concentration, (b) higher serum glucose concentration, and (c) lower body mass index than healthy subjects.

CONCLUSION

The results presented in this article indicate that chronic pancreatitis in humans is associated with the decrease in serum leptin concentration. One can suppose that the decrease in serum insulin concentration, maldigestion, and fat loss all contribute to the decrease of serum leptin concentration in chronic pancreatitis.

Autonomic nervous system dysfunction in the course of active pulmonary tuberculosis

BACKGROUND

Functional alterations of the autonomic nervous system have been described in relation to chronic hypoxemia in chronic obstructive pulmonary diseases. Aim of the present study was to investigate the occurrence of neuro-vegetative dysfunction during active tuberculosis in the absence of hypoxemia.

MATERIALS AND METHODS

Fifteen patients affected by pulmonary tuberculosis under standard therapy and 17 matched controls were enrolled. Activation of the sympathetic system was induced by the tilt-up test. Systolic and diastolic arterial pressures and the R-R interval were monitored for 15 min by Finapres and ECG. The baroreflex sensitivity was evaluated by the spontaneous sequences method.

RESULTS

Systolic and diastolic pressures were significantly higher at basal conditions and showed a less increase during the tilt test in tuberculosis patients compared to healthy controls. The basal R-R interval was shorter and its reduction during the tilt test was less evident in patients. The baroreflex sensitivity was decreased in patients at basal conditions and its reduction during the tilt test was less evident than in controls.

CONCLUSIONS

Our preliminary results suggest the presence in tuberculosis patients of an altered autonomic cardiovascular regulation, which is a reduced function of the baroreflex control of the sinus node.

Body composition, insulin, and leptin levels in patients with ankylosing spondylitis

The aim of this study was to compare the effect of chronic inflammation on insulin resistance, serum leptin levels, and body composition (BC) in patients with ankylosing spondylitis (AS) and healthy controls. Twenty-eight AS patients and 17 healthy controls were included in this study. Subjects with hypertension, diabetes, hyperlipidemia, and obesity were excluded. Acute phase reactants and serum levels of glucose, insulin, lipids, and leptin were studied. BC was determined anthropometrically and by foot-to-foot body fat analyzer (BIA, bioelectrical impedance analysis). Quantitative insulin-sensitivity check index, homeostasis model assessment for insulin resistance, and McAuley indices were calculated. Spinal mobility was assessed by the Bath Ankylosing Spondylitis Metrology Index (BASMI). Patients were also evaluated with the Bath Ankylosing Spondylitis Functional Index and the Bath Ankylosing Spondylitis Disease Activity Index. Age, sex distribution, smoking status, serum lipids, insulin concentrations, and insulin resistance indices were comparable between AS patients and controls (p > 0.05). However, acute phase reactants were significantly higher and leptin levels were significantly lower in the AS patients than in controls (p < 0.05). Fat percent assessed by both BIA and anthropometrical methods was lower in the male and female AS patients than in controls, and this reduced fat level reached statistical significance for men (p < 0.05). There were significant correlations between percent body fat, body mass index, leptin, age, and BASMI (p < 0.05; r = 0.6, 0.75, 0.35, -0.41, respectively). On the other hand, body fat percent, waist-to-hip ratio, C-reactive protein, and BASMI were significantly correlated with serum leptin levels (p < 0.05; r = 0.75, -0.42, -0.52, -0.47, respectively). Chronic inflammatory condition in AS may be responsible for the reduced body fat content and lower circulating leptin concentrations. Insulin levels and insulin resistance indices seem similar in patients and controls in the absence of classic vascular risk factors.

Leptin levels in the differential diagnosis between benign and malignant ascites

AIM: To evaluate the role of leptin levels in the differential diagnosis of ascites.

METHODS: Ascitic leptin, TNFα and serum leptin levels were measured in 77 patients with ascites (35 with malignancies, 30 cirrhosis and 12 tuberculosis). Control serum samples were obtained from 20 healthy subjects. Leptin and TNFα levels were measured by ELISA. Body mass index (BMI) and percentage of body fat (BFM) by skin fold measurement were calculated for all patients and control groups. Peritoneal biopsy, ascites cytology and cultures or biochemical values were used for the diagnosis of patients.

RESULTS: In patients with malignancies, the mean serum and ascites leptin levels and their ratios were significantly decreased compared to the other patient groups and controls. In tuberculosis peritonitis, ascitic fluid TNFα levels were significantly higher than malignant ascites and cirrhotic sterile ascites. BMI and BFM values did not distinguish between patients and controls.

CONCLUSION: In patients with malignant ascites, levels of leptin and TNFα were significantly lower than in patients with tuberculous ascites.

Serum leptin is not a diagnostic marker for familial Mediterranean fever attacks

The aim of our study is to determine whether there is a relationship between familial Mediterranean fever (FMF) attacks and serum leptin levels. We enrolled 25 patients (22 males and 3 females) and 25 healthy controls (21 males and 4 females) with a mean age of 24.42 ± 1.22 (Mean ± SEM) years and 24.30 ± 1.19 years (Mean ± SEM), respectively. We investigated serum levels of leptin, interleukin-6 (IL-6), erythrocyte sedimentation rate (ESR), C-reactive protein (CRP), fibrinogen, and leukocyte counts before the attack and 8–12 hours after the attack started. The same parameters have been investigated in the control subjects. The mean serum leptin levels before the attacks were 6.45 ± 1.05 (Mean ± SEM) and during the attacks were 7.59 ± 1.3 (Mean ± SEM) in FMF group, respectively. There was a slight increase in serum leptin levels during the attacks but it was not statistically significant (P > .05). The mean serum leptin levels were 6.12 ± 2.81 in the control group which were not different from the mean serum leptin levels before and during the attack periods in the study group (P > .05). However, there were statistical differences in the serum levels of IL-6, ESR, CRP, fibrinogen, and leukocyte counts before and during the attack periods (P < .05). No correlation was found between serum leptin levels and IL-6, ESR, CRP, fibrinogen, and leukocyte counts (P > .05). Serum leptin levels do not increase during FMF attacks and therefore it is not useful for diagnostic purposes and follow-up during treatment.

Leptin levels in various manifestations of pulmonary tuberculosis

BACKGROUND

Proinflammatory cytokines are prime candidates as causative agents of the metabolic changes that eventually result in tuberculosis-associated weight loss. Microbial products and cytokines such as TNF and IL-1 increase leptin expression dose dependently in adipose tissue. Leptin plays an important role in cellular immunity.

OBJECTIVES

In this study, we investigated serum leptin and TNF-alpha levels before and after antituberculosis therapy in patients with active pulmonary tuberculosis (TB).

METHODS

Twenty five in patients with active pulmonary TB and 18 healthy controls participated in the study. Leptin and TNF-alpha levels were measured before treatment and six months after the treatment and they were compared with the control group. Body mass index (BMI) and chest X-rays before and after the treatment were also evaluated.

RESULTS

The leptin levels before and after the treatment were 1.66+/-1.68 ng/mL and 3.26+/-3.81 ng/mL, respectively. The leptin levels of tuberculous patients were significant than in healthy patients (P < .05). The BMI was 19.36+/-2.55 kg/m2 before the treatment and 22.87+/-3.13 kg/m2 after the treatment. The TNF-alpha level was 23.19+/-12.78 pg/mL before the treatment and 15.95+/-6.58 pg/mL after the treatment. There was no correlation between leptin and TNF-alpha levels. Leptin levels were low in patients who had sequela lesion on chest radiographs.

CONCLUSION

Leptin levels are suppressed in tuberculous patients and low leptin levels may contribute to increased susceptibility to infection and recovery with sequela lesions.

Diagnostic value of leptin in tuberculous pleural effusions

It is suggested that leptin may be involved in inflammation. Although relation between leptin levels and active pulmonary tuberculosis has been studied, there is no information about relation between leptin levels and tuberculous pleural effusions (TPE). We evaluated the diagnostic value of pleural fluid and serum leptin levels in TPE and compared them with adenosine deaminase (ADA). Forty-five patients, 17 tuberculous effusion and 28 nontuberculous effusion, with exudative pleural effusions were included. Leptin and ADA levels were measured from serum and pleural fluid in all patients. There were no statistically significant differences between tuberculous and nontuberculous groups with respect to the serum ADA activity and pleural fluid/serum leptin ratio. On the contrary, pleural fluid leptin level, pleural fluid ADA activity, serum leptin level and pleural fluid/serum ADA activity ratio were statistically different between tuberculous and nontuberculous groups. When leptin levels were corrected for body mass index, serum leptin levels did not reach statistical significance. Cut-off points to predict tuberculosis were calculated as 9.85 ng/ml and 35.55 U/l for pleural fluid leptin level and pleural fluid ADA activity, respectively. Sensitivity, specificity and area under the curve +/- standard error were 82.4%, 82.1%, 0.83 +/- 0.07 for pleural fluid leptin levels and 100%, 100%, 1.00 +/- 0.00 for pleural fluid ADA activity, respectively; the difference between these curves was significant (p = 0.01). Pleural fluid leptin levels were lower in tuberculous effusions than in other exudates. Pleural fluid leptin has a diagnostic value for TPE but not as good as that of ADA.

The role of leptin in innate and adaptive immune responses

Leptin is produced primarily by adipocytes and functions in a feedback loop regulating body weight. Leptin deficiency results in severe obesity and a variety of endocrine abnormalities in animals and humans. Several studies indicated that leptin plays an important role in immune responses. It exerts protective anti-inflammatory effects in models of acute inflammation and during activation of innate immune responses. In contrast, leptin stimulates T lymphocyte responses, thus having rather a proinflammatory role in experimental models of autoimmune diseases. Clinical studies have so far yielded inconsistent results, suggesting a rather complex role for leptin in immune-mediated inflammatory conditions in humans.

Pulmonary Mycobacterium tuberculosis infection in leptin-deficient ob/ob mice

The development of active tuberculosis after infection with Mycobacterium tuberculosis is almost invariably caused by a persistent or transient state of relative immunodeficiency. Leptin, the product of the obese (ob) gene, is a pleiotropic protein produced mainly by adipocytes and is down-regulated during malnutrition and starvation, conditions closely connected with active tuberculosis. To investigate the role of leptin in tuberculosis, we intranasally infected wild-type (Wt) and leptin-deficient ob/ob mice with live virulent M. tuberculosis. Ob/ob mice displayed higher mycobacterial loads in the lungs after 5 and 10 weeks of infection, although the difference with Wt mice remained 1 log of M. tuberculosis colony forming unit. Nevertheless, ob/ob mice were less able to form well-shaped granuloma and lung lymphocyte numbers were reduced compared with Wt mice early during infection. In addition, ob/ob mice had a reduced capacity to produce the protective cytokine IFNgamma at the site of the infection early during infection and upon antigen-specific recall stimulation, and showed reduced delayed-type hypersensitivity reaction to intra-dermal tuberculin purified protein derivative. Leptin replacement restored the reduced IFNgamma response observed in ob/ob mice. Mortality did not differ between ob/ob and Wt mice. These data suggest that leptin plays a role in the early immune response to pulmonary tuberculosis.

Markers of inflammation are negatively correlated with serum leptin in rheumatoid arthritis

BACKGROUND

Leptin regulates food intake and modulates immunity and inflammation. A positive feedback mechanism has been described between tumour necrosis factor (TNF) and leptin, and it has been suggested that leptin potentiates inflammation in patients with rheumatoid arthritis (RA).

OBJECTIVE

To assess whether inflammation correlates with leptin concentrations in patients with RA, and whether anti-TNF treatment modulates leptin concentrations in these patients.

METHODS

Leptin, IL6 and CRP were measured (at baseline and after 2 weeks of treatment) in the blood of 31 patients with RA starting either anti-TNF treatment or placebo, and in 18 healthy controls.

RESULTS

In patients with RA, plasma leptin concentrations at baseline correlated inversely with the degree of inflammation as assessed by C reactive protein (CRP; r(s)(2) = 0.21, p<0.01) or interleukin (IL) 6 concentrations (r(s)(2) = 0.22, p<0.008). Mean (SD) leptin concentrations did not differ between patients with RA and controls (6.0 (4.6) v 4.2 (2.8) ng/ml in men; 15.1 (7.9) v 13.4 (5.2) ng/ml in women). Short course anti-TNF treatment for 2 weeks did not modify leptin concentrations, despite significant reduction of CRP and IL6.

CONCLUSION

A significant inverse correlation between inflammation and leptin concentrations was found in patients with active RA, although plasma leptin concentrations did not significantly differ from those in healthy controls. This suggests that active chronic inflammation may lower plasma leptin concentrations. Two weeks' treatment with anti-TNF did not change plasma leptin concentrations and longer treatment may be needed to see an effect on leptin.

The relation between serum leptin levels and body fat mass in patients with active lung tuberculosis

The relationship of leptin to diminished appetite and weight loss has been investigated in many diseases. Diminished appetite and weight loss are the most apparent characteristics of patients with active lung tuberculosis and in this study the relation of leptin to such diminished appetite and weight loss has been investigated in patients with active lung tuberculosis before and after treatment. Twenty-five patients (7 female, 18 male) with active tuberculosis having an age range of 18-70 years (mean 47.48 +/- 15.36 y) and 25 normal individuals (9 female, 16 male) having an age range of 25-71 years (mean 44.60 +/- 13.80 y) were included in this study. Leptin levels, body mass index (BMI), body fat ratio (BFR), and waist hip ratio (WHR) were measured before and after 6 months of antituberculosis treatment. The same measurements were also made in the control group and the results were compared. While the pretreatment BMI (22.02 +/- 4.31 kg/m2) and BFR (16.60% +/- 9.30%) values in the patient group were significantly lower than in the control group, we found no difference in their pretreatment WHR values. Pretreatment leptin levels (3.49 +/- 3.34 microg/L) were significantly higher in patients with tuberculosis than in the control group (2.33 +/- 1.10 microg/L). Leptin levels were found to be significantly increased at the 6th month of antituberculosis treatment (5.65 +/- 5.41 microg/L) than the pretreatment values (p < 0.05). We observed an evident increase in BMI (24.10 +/- 4.87 kg/m2) and BFR (17.51% +/- 9.25%) due to antituberculosis treatment (p < 0.05). This study suggests that leptin has a role in the diminished appetite and weight loss symptoms in patients with active lung tuberculosis.

Plasma leptin levels in patients with burn injury: a preliminary report

The purpose of this study was to investigate the relationship between the plasma leptin level and clinical parameters in patients with burn injury. Six patients with burn injury were admitted to the Emergency and Critical Care Medicine Center of St. Marianna University Hospital within 1h after injury. Plasma levels were monitored for leptin, proinflammatory cytokines (interleukin (IL)-1 beta, IL-6, tumor necrosis factor alpha (TNF alpha)), stress-related parameters (adrenocorticotropic hormone (ACTH), cortisol, and C-reactive protein (CRP)). The change in individual plasma leptin levels did not show similar pattern in all these patients. However, leptin levels remained within the normal range, except in a patient (Case 1) complicated with severe hypovolemic shock. Plasma ACTH and cortisol levels were also elevated in most of the patients. Examination of relationships among plasma leptin, proinflammatory cytokines, and stress-related parameters revealed a significant positive correlation between the plasma leptin level and IL-1 beta or IL-6. These results suggest that the plasma leptin level may have some relations to plasma proinflammatory cytokines in pathophysiologic responses to critical conditions of burn injury.

Consequences of revised estimates of carotenoid bioefficacy for dietary control of vitamin A deficiency in developing countries

According to existing recommendations of the Food and Agriculture Organization (FAO)/World Health Organization (WHO), the amount of provitamin A in a mixed diet having the same vitamin A activity as 1 microg of retinol is 6 microg of beta-carotene or 12 microg of other provitamin A carotenoids. The efficiency of this conversion is referred to as bioefficacy. Recently, using data from healthy people in developed countries and based on a two-step process, the U.S. Institute of Medicine (IOM) derived new conversion factors. The first step established the bioefficacy of beta-carotene in oil at 2 microg having the same vitamin A activity as 1 microg of retinol; the second step established the bioavailability of beta-carotene in foods relative to that of beta-carotene in oil at 1:6. Thus, 2 microg of beta-carotene in oil or 12 microg of beta-carotene in mixed foods has the same vitamin A activity as 1 microg of retinol. Based on existing FAO food balance sheets and the FAO/WHO conversion rates, all populations should be able to meet their vitamin A requirements from existing dietary sources. However, using the new IOM conversion rates, populations in developing countries could not achieve adequacy. Additionally, field studies suggest that, instead of 12 microg, 21 microg of beta-carotene has the same vitamin A activity as 1 microg of retinol, which implies that effective vitamin A intake is even lower. Therefore, controlling vitamin A deficiency in developing countries requires not only vitamin A supplementation but also food-based approaches, including food fortification, and possibly the introduction of new strains of plants with enhanced vitamin A activity.