Leptin and its receptor in normal human gastric mucosa and in Helicobacter pylori-associated gastritis

The Associations between Helicobacter Pylori immunoglobulin G seropositivity and body mass index in adults

OBJECTIVES

Inconsistent evidence currently exists regarding the associations between Helicobacter Pylori (H. pylori) infection and body mass index (BMI). The goal of the current study was to examine independent associations of H. pylori immunoglobulin G (IgG) seropositivity and BMI in a U.S.-based population sample.

METHODS

The US National Health and Nutrition Examination Survey (NHANES) with 2,576 subjects from 1999 to 2000 were analyzed. Using multivariate logistic regression models, associations between H. pylori IgG seropositivity and BMI were calculated after potential confounders were taken into account. Subgroup analyses were conducted furtherly stratified by sex, age, and race.

RESULTS

H. pylori IgG seropositivity was not associated with BMI in the general population (OR = 0.998; 95% CI = 0.977-1.019; P = 0.842). In the subgroup analyses stratified by race, a negative correction was found between the H. pylori IgG seropositivity and BMI among other races (OR = 0.873; 95% CI = 0.795-0.959; P = 0.004) except non-Hispanic white (OR = 1.006, 95% CI 0.966 to 1.048, P = 0.762), non-Hispanic black (OR = 1.021, 95% CI 0.979 to 1.065, P = 0.335), and Mexican American (OR = 1.010, 95% CI 0.966 to 1.055, P = 0.665).

CONCLUSIONS

In the general population, H. pylori IgG seropositivity is not associated with increased BMI, which provides a new perspective on obesity management.

The Head-to-Toe Hormone: Leptin as an Extensive Modulator of Physiologic Systems

Leptin is a well-known hunger-sensing peptide hormone. The role of leptin in weight gain and metabolic homeostasis has been explored for the past two decades. In this review, we have tried to shed light upon the impact of leptin signaling on health and diseases. At low or moderate levels, this peptide hormone supports physiological roles, but at chronically higher doses exhibits detrimental effects on various systems. The untoward effects we observe with chronically higher levels of leptin are due to their receptor-mediated effect or due to leptin resistance and are not well studied. This review will help us in understanding the non-anorexic roles of leptin, including their contribution to the metabolism of various systems and inflammation. We will be able to get an alternative perspective regarding the physiological and pathological roles of this mysterious peptide hormone.

Increased Glycated Hemoglobin but Decreased Cholesterol after a Loss of Helicobacter pylori Infection: A Community-Based Longitudinal Metabolic Parameters Follow-Up Study

This study aimed to evaluate the impact of Helicobacter pylori (H. pylori) infection on metabolic parameters in a longitudinal follow-up manner. From August 2013 to August 2019, a community-based prospective study of H. pylori and metabolic syndrome (MetS) was performed in the northeastern region of Taiwan. A total of 1865 subjects were divided into four groups according to the serial results of urea breath test (UBT): new H. pylori infection (group 1, n = 41), null H. pylori infection (group 2, n = 897), loss of H. pylori infection (group 3, n = 369), and persistent H. pylori infection (group 4, n = 558). When comparing the subjects between groups 1 and 2, HBA1c was associated with a new H. pylori infection. Body mass index (BMI) was associated with a loss of H. pylori when comparing subjects between groups 3 and 4. Elevated HBA1c and high-density lipoprotein (HDL) levels but lower values of cholesterol and white blood cells (WBCs) were found during serial analyses within group 3. Conclusively, HBA1c was associated with a new H. pylori infection. BMI was associated with H. pylori loss. Increased HBA1c and HDL values but decreased values of cholesterol and WBC were associated with a loss of H. pylori infection.

Differences in glycated hemoglobin levels and cholesterol levels in individuals with diabetes according to Helicobacter pylori infection

This study examined differences in glycated hemoglobin (HbA1c), fasting plasma glucose and cholesterol levels between H. pylori infected and uninfected persons with diabetes. Anonymized data of Maccabi Healthcare Services in Israel were analyzed, of 12,207 individuals (50.0% H. pylori positive) aged 25–95 years who underwent the urea breath test. The data included HbA1c, fasting plasma glucose and cholesterol levels. The inverse probability of treatment weighting approach was used to account for confounders. Differences between individuals who were H. pylori positive and negative, in HbA1c (> or ≤ 7.0%) and in cholesterol levels were assessed using weighted generalized estimating equations. For men, but not women, the likelihood of having HbA1c > 7.0% was increased in those infected than uninfected with H. pylori: prevalence ratio 1.11 (95% CI 1.00, 1.24), P = 0.04. For both sexes, total cholesterol (P = 0.004) and low-density lipoprotein (LDL) levels (P = 0.006) were higher among those infected than uninfected with H. pylori. No significant differences were found in glucose and HDL levels according to H. pylori infection. The results were consistent in unweighted multivariable analyses. In conclusion, H. pylori infection might be related to worse glycemic control in men, and higher total cholesterol and LDL cholesterol levels in both sexes.

Role of Leptin in the Digestive System

Leptin is a pluripotent peptide hormone produced mainly by adipocytes, as well as by other tissues such as the stomach. Leptin primarily acts on the central nervous system, particularly the hypothalamus, where this hormone regulates energy homeostasis and neuroendocrine function. Owing to this, disruption of leptin signaling has been linked with numerous pathological conditions. Recent studies have also highlighted the diverse roles of leptin in the digestive system including immune regulation, cell proliferation, tissue healing, and glucose metabolism. Of note, leptin acts differently under physiological and pathological conditions. Here, we review the current knowledge on the functions of leptin and its downstream signaling in the gastrointestinal tract and accessory digestive organs, with an emphasis on its physiological and pathological implications. We also discuss the current therapeutic uses of recombinant leptin, as well as its limitations.

Expression of leptin and leptin receptors in colorectal cancer-an immunohistochemical study

Obesity is demonstrated to be a risk factor in the development of cancers of various organs, such as colon, prostate, pancreas and so on. Leptine (LEP) is the most renowned of the adipokines. As a hormone, it mediates its effect through leptin receptor (LEPR), which is widely expressed in various tissues including colon mucosa. In this study, we have investigated the degree of expression of LEP and LEPR in colorectal cancer (CRC). We collected 44 surgically resected colon cancer tissues along with normal adjacent colon tissue (NACT) from a sample of CRC patients from the Malaysian population and looked for leptin and leptin receptors using immunohistochemistry (IHC). All the samples showed low presence of both LEP and LEPR in NACT, while both LEP and LEPR were present at high intensity in the cancerous tissues with 100% and 97.7% prevalence, respectively. Both were sparsed in the cytoplasm and were concentrated beneath the cell membrane. However, we did not find any significant correlation between their expression and pathological parameters like grade, tumor size, and lymph node involvement. Our study further emphasizes the possible causal role of LEP and LEPR with CRC, and also the prospect of using LEPR as a possible therapeutic target.

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.

A community-based study on the association between Helicobacter pylori Infection and obesity

Helicobacter pylori (H. pylori) infection can induce chronic inflammation and is associated with insulin resistance, metabolic syndrome and body mass index (BMI, kg/m²) changes. This study aimed to evaluate the association between H. pylori infection and overweight/obesity. This research was a cross-sectional study conducted from March 2014 to November 2016, using data from the three districts in the northeastern region of Taiwan. The inclusion criteria were an age >30 years and the absence of pregnancy. Ultimately, 2686 subjects (1713 women) were included in this study. Among the subjects aged less than 50 years, the subjects with H. pylori infection had higher mean BMI values than those without H. pylori infection (40-49 years: 25.7 ± 4.4 vs. 24.7 ± 3.8, P = 0.025; 30-39 years: 24.9 ± 4.4 vs. 24.0 ± 4.1, P = 0.063). H. pylori infection increased the risk of being obese 2 (BMI ≥30) (odds ratio, OR = 1.836, 95% CI = 1.079-3.125, P = 0.025) with adjustments for demographic factors in subjects aged less than 50 years. In conclusions, subjects with H. pylori infection and age less than 50 years may increase a risk of being obesity (BMI ≥30) compared to those without this type of infection.

Analysis of the associations among Helicobacter pylori infection, adiponectin, leptin, and 10-year fracture risk using the fracture risk assessment tool: A cross-sectional community-based study

Helicobacter pylori (H. pylori) infection may induce inflammatory cytokines or adipokines that influence bone turnover and bone fracture risk. This study aimed to evaluate the association among H. pylori infection, adipokines, and 10-year fracture risk using the Fracture Risk Assessment Tool scale. From August 2013 to February 2016, a community-based cohort was surveyed by Keelung Chang-Gung Memorial Hospital. Subjects were included if they were older than 40 years and not pregnant. All participants underwent a standardized questionnaire survey, physical examination, urea breath test, and blood tests. A total of 2,689 participants (1,792 women) were included in this cross-sectional study. In both sexes, participants with a high fracture risk were older and had higher adiponectin values than participants without a high fracture risk (mean age, female: 72.9 ± 5.6 vs. 55.8 ± 7.3 years, P < 0.0001; male: 78.9 ± 4.7 vs. 58.1 ± 8.9 years, P < 0.001) (adiponectin, female: 10.8 ± 6.3 vs. 8.7 ± 5.2 ng/ml, P < 0.001; male: 9.7 ± 6.1 vs. 5.5 ± 3.8 ng/ml, P < 0.001). Adiponectin was correlated with high fracture risk in both sexes, but H. pylori infection and leptin was not. In logistic regression analysis, adiponectin could not predict high fracture risk when adjusting the factor of body mass index (BMI) in men group. In conclusion, H. pylori infection and leptin could not predict 10-year fracture risk in either sex. Adiponectin was correlated with bone fracture risk in both sexes and the correlation might be from the influence of BMI.

The Associations Between Helicobacter pylori Infection, Serum Vitamin D, and Metabolic Syndrome: A Community-Based Study

The associations between Helicobacter pylori infection, serum vitamin D level, and metabolic syndrome (MS) are controversial. The present community-based study aimed to investigate the effect of H pylori infection and serum vitamin D deficiency on MS development.Individuals from the northeastern region of Taiwan were enrolled in a community-based study from March, 2014 to August, 2015. All participants completed a demographic survey and underwent the urea breath test (UBT) to detect H pylori infection as well as blood tests to determine levels of vitamin D, adiponectin, leptin, and high-sensitivity C-reactive protein. The ATP III criteria for MS were used in this study.A total of 792 men and 1321 women were enrolled. The mean age was 56.4 ± 13.0 years. After adjusting for age and sex, the estimated odds of MS development for a UBT-positive subject were 1.503 (95% confidence interval [CI]: 1.206-1.872, P < 0.001) when compared to a UBT-negative subject. For participants with vitamin D deficiency (<20 ng/mL), the odds of MS development were 1.423 (95% CI: 1.029-1.967, P = 0.033) when compared to those with sufficient vitamin D level (>30 ng/mL). For participants with both H pylori infection and vitamin D deficiency, the odds of MS development were 2.140 (95% CI: 1.348-3.398, P = 0.001) when compared to subjects without H pylori infection and with sufficient vitamin D levels.H pylori infection and vitamin D deficiency could be predictors of MS. For individuals with both H pylori infection and vitamin D deficiency, the odds of MS development were 2.140 when compared to individuals without H pylori infection and with sufficient vitamin D levels.

Helicobacter pylori Infection Increases Insulin Resistance and Metabolic Syndrome in Residents Younger than 50 Years Old: A Community-Based Study

This study aimed to analyze the influence of H. pylori infection on insulin resistance and metabolic syndrome (MS) by multivariate analysis of a community-based cohort study. From January 2013 to February 2014,811 subjects were enrolled in a community-based cohort study from the northeastern region of Taiwan. All subjects received a demographic survey and blood tests, including an H. pylori antibody test, liver biochemistry tests, lipid profiles, sugar/insulin levels for Homeostatic model assessment (HOMA-IR index), and measurements of adipokines and inflammatory cytokines. A total of 264 men and 547 women were included in this study. The mean age was 59.2 ± 12.7 years. Subjects seropositive for H. pylori antibodies exhibited higher rates of hypertension, an increased incidence of a HOMA-IR index > 2.5 and a higher level of tumor necrosis factor-α than those without H. pylori antibodies. We found a significant difference in the presence of H. pylori antibodies between subjects with MS and those without MS (76.7% vs. 53.7%, p = 0.007) among subjects < 50 y/o. A HOMA-IR index >2.5, H. pylori antibody presence and leptin were predictors for MS in subjects < 50 y/o. The estimated odds ratio of MS for a subject with H. pylori antibodies was 3.717 (95% CI = 1.086–12.719) times that of a subject without H. pylori antibodies. In addition, no difference in H. pylori antibody status was detected for MS prediction in subjects that were ≧ 50 y/o (p = 0.861). In conclusion, subjects with H. pylori antibodies had a higher incidence of a HOMA-IR >2.5 than those without H pylori antibodies. For subjects aged < 50 y/o, the H. pylori antibody was a predictor for MS.

Adipocyte versus pituitary leptin in the regulation of pituitary hormones: somatotropes develop normally in the absence of circulating leptin

Leptin is a cytokine produced by white fat cells, skeletal muscle, the placenta, and the pituitary gland among other tissues. Best known for its role in regulating appetite and energy expenditure, leptin is produced largely by and in proportion to white fat cells. Leptin is also important to the maintenance and function of the GH cells of the pituitary. This was shown when the deletion of leptin receptors on somatotropes caused decreased numbers of GH cells, decreased circulating GH, and adult-onset obesity. To determine the source of leptin most vital to GH cells and other pituitary cell types, we compared two different leptin knockout models with Cre-lox technology. The global Lep-null model is like the ob/ob mouse, whereby only the entire exon 3 is deleted. The selective adipocyte-Lep-null model lacks adipocyte leptin but retains pituitary leptin, allowing us to investigate the pituitary as a potential source of circulating leptin. Male and female mice lacking adipocyte leptin (Adipocyte-lep-null) did not produce any detectable circulating leptin and were infertile, suggesting that the pituitary does not contribute to serum levels. In the presence of only pituitary leptin, however, these same mutants were able to maintain somatotrope numbers and GH mRNA levels. Serum GH trended low, but values were not significant. However, hypothalamic GHRH mRNA was significantly reduced in these animals. Other serum hormone and pituitary mRNA differences were observed, some of which varied from previous results reported in ob/ob animals. Whereas pituitary leptin is capable of maintaining somatotrope numbers and GH mRNA production, the decreased hypothalamic GHRH mRNA and low (but not significant) serum GH levels indicate an important role for adipocyte leptin in the regulation of GH secretion in the mouse. Thus, normal GH secretion may require the coordinated actions of both adipocyte and pituitary leptin.

A review on gastric leptin: the exocrine secretion of a gastric hormone

A major advance in the understanding of the regulation of food intake has been the discovery of the adipokine leptin a hormone secreted by the adipose tissue. After crossing the blood-brain barrier, leptin reaches its main site of action at the level of the hypothalamic cells where it plays fundamental roles in the control of appetite and in the regulation of energy expenditure. At first considered as a hormone specific to the white adipose tissue, it was rapidly found to be expressed by other tissues. Among these, the gastric mucosa has been demonstrated to secrete large amounts of leptin. Secretion of leptin by the gastric chief cells was found to be an exocrine secretion. Leptin is secreted towards the gastric lumen into the gastric juice. We found that while secretion of leptin by the white adipose tissue is constitutive, secretion by the gastric cells is a regulated one responding very rapidly to secretory stimuli such as food intake. Exocrine-secreted leptin survives the hydrolytic conditions of the gastric juice by forming a complex with its soluble receptor. This soluble receptor is synthesized by the gastric cells and the leptin-leptin receptor complex gets formed at the level of the gastric chief cell secretory granules before being released into the gastric lumen. The leptin-leptin receptor upon resisting the hydrolytic conditions of the gastric juice is channelled, to the duodenum. Transmembrane leptin receptors expressed at the luminal membrane of the duodenal enterocytes interact with the luminal leptin. Leptin is actively transcytosed by the duodenal enterocytes. From the apical membrane it is transferred to the Golgi apparatus where it binds again its soluble receptor. The newly formed leptin-leptin receptor complex is then secreted baso-laterally into the intestinal mucosa to reach the blood capillaries and circulation thus reaching the hypothalamus where its action regulates food intake. Exocrine-secreted gastric leptin participates in the short term regulation of food intake independently from that secreted by the adipose tissue. Adipose tissue leptin on the other hand, regulates in the long term energy storage. Both tissues work in tandem to ensure management of food intake and energy expenditure.

Cross-talk between adipose and gastric leptins for the control of food intake and energy metabolism

The understanding of the regulation of food intake has become increasingly complex. More than 20 hormones, both orexigenic and anorexigenic, have been identified. After crossing the blood-brain barrier, they reach their main site of action located in several hypothalamic areas and interact to balance satiety and hunger. One of the most significant advances in this matter has been the discovery of leptin. This hormone plays fundamental roles in the control of appetite and in regulating energy expenditure. In accordance with the lipostatic theory stated by Kennedy in 1953, leptin was originally discovered in white adipose tissue. Its expression by other tissues was later established. Among them, the gastric mucosa has been shown to secrete large amounts of leptin. Both the adipose and the gastric tissues share similar characteristics in the synthesis and storage of leptin in granules, in the formation of a complex with the soluble receptor and a secretion modulated by hormones and energy substrates. However while adipose tissue secretes leptin in a slow constitutive endocrine way, the gastric mucosa releases leptin in a rapid regulated exocrine fashion into the gastric juice. Exocrine-secreted leptin survives the extreme hydrolytic conditions of the gastric juice and reach the duodenal lumen in an intact active form. Scrutiny into transport mechanisms revealed that a significant amount of the exocrine leptin crosses the intestinal wall by active transcytosis. Leptin receptors, expressed on the luminal and basal membrane of intestinal epithelial cells, are involved in the control of nutrient absorption by enterocytes, mucus secretion by goblet cells and motility, among other processes, and this control is indeed different depending upon luminal or basal stimulus. Gastric leptin after transcytosis reaches the central nervous system, to control food intake. Studies using the Caco-2, the human intestinal cell line, in vitro allowed analysis of the mechanisms of leptin actions on the intestinal mucosa, identification of the mechanisms of leptin transcytosis and understanding the modulation of leptin receptors by nutrients and hormones. Exocrine-secreted gastric leptin thus participates in a physiological axis independent in terms of time and regulation from that of adipose tissue to rapidly control food intake and nutrient absorption. Adipocytes and gastric epithelial cells are two cell types the metabolism of which is closely linked to food intake and energy storage. The coordinated secretion of adipose and gastric leptins ensures proper management of food processing and energy storage.

Leptin potentiates Prevotella intermedia lipopolysaccharide-induced production of TNF-alpha in monocyte-derived macrophages

PURPOSE

In addition to regulating body weight, leptin is also recognized for its role in the regulation of immune function and inflammation. The purpose of this study was to investigate the effect of leptin on Prevotella (P.) intermedia lipopolysaccharide (LPS)-induced tumor necrosis factor (TNF)-alpha production in differentiated THP-1 cells, a human monocytic cell line.

METHODS

LPS from P. intermedia ATCC 25611 was prepared by the standard hot phenol-water method. THP-1 cells were incubated in the medium supplemented with phorbol myristate acetate to induce differentiation into macrophage-like cells. The amount of TNF-alpha and interleukin-8 secreted into the culture medium was determined by enzyme-linked immunosorbent assay (ELISA). TNF-alpha and Ob-R mRNA expression levels were determined by semi-quantitative reverse transcription-polymerase chain reaction analysis.

RESULTS

Leptin enhanced P. intermedia LPS-induced TNF-alpha production in a dose-dependent manner. Leptin modulated P. intermedia LPS-induced TNF-alpha expression predominantly at the transcriptional level. Effect of leptin on P. intermedia LPS-induced TNF-alpha production was not mediated by the leptin receptor.

CONCLUSIONS

The ability of leptin to enhance P. intermedia LPS-induced TNF-alpha production may be important in the establishment of chronic lesion accompanied by osseous tissue destruction observed in inflammatory periodontal disease.

Helicobacter pylorieradication reduces platelet count in patients without idiopathic thrombocytopenic purpura

Discrepant outcomes of Helicobacter pylori eradication in patients with idiopathic thrombocytopenic purpura have been reported. Here patients with dyspepsia and no other complications underwent gastroendoscopic examination and evaluation for Helicobacter pylori infection. Helicobacter pylori-infected patients with gastritis and gastric ulcer received eradication therapy: lansoprazole (60 mg/day), clarithromycin (400 mg/day), and amoxicillin (1500 mg/day) for 1 week. Lansoprazole 30 mg/day was administrated additional 7 weeks. Peripheral platelets were counted before treatment, 8 weeks after initiation of therapy, and at follow-up periods. Platelet counts in patients with both gastritis and gastric ulcer were evaluated with reference to the presence of Helicobacter pylori infection. Eighty-seven patients with gastritis and 35 of those with gastric ulcer underwent successful eradication therapy. Peripheral platelet counts in patients with gastritis decreased from 235+/-55 to 228+/-58 (10(3)/microL) (p=0.0337), and those with gastric ulcer decreased from 248+/-60 to 232+/-48 (10(3)/microL) (p=0.020) 8 weeks after initiation of therapy. Non-eradicated patients did not show such a tendency. Helicobacter pylori eradication reduced peripheral platelet counts in patients with gastritis and gastric ulcer. Amelioration of thrombocytopenia by eradicating Helicobacter pylori appears to involve mechanisms specific to idiopathic thrombocytopenic purpura.

The relationship between breast milk leptin and neonatal weight gain

AIM

To investigate whether change in leptin content of breast milk during lactation acts on neonatal body weight gain.

METHODS

In total 15 lactating women and their 15 term infants were involved in the study. Breast milk and neonatal serum samples were obtained from the same women and their neonates on the 1st day and any day between the 21st and 30th days after birth. Breast milk and serum leptin concentrations were determined by radioimmunoassay. Anthropometric indexes of the infants were recorded.

RESULTS

The study was completed with 15 multiparious mothers aged 19-37 years and their infants. The mean collection time of the first samples after birth was 6.07 +/- 1.94 h. The leptin level in the mature milk was significantly higher than in the colostrum (p < 0.001). Neonatal weight and height were significantly increased on 21-30 lactation days compared to 1st day of lactation (p < 0.05 and p < 0.001, respectively). The leptin concentration in the mature milk was negatively correlated with delta BMI (r =-0.53; p < 0.05). The delta breast milk leptin concentration was also found to be inversely correlated with delta BMI (r =-0.529; p < 0.05).

CONCLUSION

The results of this study have suggested that change in the leptin content of breast milk during lactation might play a role in the regulation of weight gain in healthy neonates.

Leptin and leptin receptor in pig spermatozoa: evidence of their involvement in sperm capacitation and survival

Several studies have recently investigated the role of leptin, the adipocyte-secreted hormone, in the growth and reproduction of rodents, humans, and domestic animals. The present study was designed to explore the expression of leptin and its receptor in pig spermatozoa. Successful Western blot evidenced a 16 kDa band for leptin and six isoforms, ranging from 120 to 40 kDa, for the leptin receptor. Both leptin and leptin receptor were interestingly located at sperm acrosomal level, suggesting their involvement in the oocyte fertilization events. In fact, both capacitation indexes and acrosin activity were enhanced by leptin, and these effects were reduced by the anti-leptin receptor antibody. Afterwards, we investigated the main transduction pathways regulated by the hormone. Our results showed that, in pig sperm, leptin can trigger the signal transducer and activator of transcription 3, a classical component of cytokine signal transduction pathways, whose expression has not been previously reported in male gamete; in addition it was found constitutively activated. Besides, leptin was able to induce the activation of phosphatidylinositol phosphate kinase 3 and MAP kinase pathways as well as of BCL2, a known antiapoptotic protein. These data address to a role of leptin and its receptor on pig sperm survival. The presence of leptin and its receptor in pig sperm suggests that they, through an autocrine short loop, may induce signal transduction and molecular changes associated with sperm capacitation and survival.

The pathogenesis of Helicobacter pylori-induced gastro-duodenal diseases

Helicobacter pylori is the main cause of peptic ulceration, distal gastric adenocarcinoma, and gastric lymphoma. Only 15% of those colonized develop disease, and pathogenesis depends upon strain virulence, host genetic susceptibility, and environmental cofactors. Virulence factors include the cag pathogenicity island, which induces proinflammatory, pro-proliferative epithelial cell signaling; the cytotoxin VacA, which causes epithelial damage; and an adhesin, BabA. Host genetic polymorphisms that lead to high-level pro-inflammatory cytokine release in response to infection increase cancer risk. Pathogenesis is dependent upon inflammation, a Th-1 acquired immune response and hormonal changes including hypergastrinaemia. Antral-predominant inflammation leads to increased acid production from the uninflamed corpus and predisposes to duodenal ulceration; corpus-predominant gastritis leads to hypochlorhydria and predisposes to gastric ulceration and adenocarcinoma. Falling prevalence of H. pylori in developed countries has led to a falling incidence of associated diseases. However, whether there are disadvantages of an H. pylori-free stomach, for example increased risk of esosphageal adenocarcinoma, remains unclear.

Thyroid and leptin

Leptin, which is produced by adipocytes, is known to be an important regulator of food intake and energy storage. Disturbance of thyroid function is associated with marked changes in both body weight and energy expenditure, and it has therefore been the subject of much research to study the mutual roles of leptin and thyroid hormones in this respect. Despite intensive research in this field, results are still not very clear. The aim of this review has been to update the current state of knowledge of leptin related to thyroid pathophysiology.

The intake of physiological doses of leptin during lactation in rats prevents obesity in later life

BACKGROUND

There is epidemiological evidence that perinatal nutritional factors may have long-term effects on obesity. Which nutrients or food components are involved in this programming mechanism are unknown. Breast milk contains leptin, a hormone that regulates food intake and energy expenditure, and previous studies in rats have shown that leptin orally administered during lactation exerts anorexigenic effects.

OBJECTIVE

To evaluate whether supplementation with physiological doses of oral leptin during lactation has long-term effects on body weight regulation.

DESIGN

A daily oral dose of leptin (equivalent to five times the amount of leptin ingested normally from maternal milk during the suckling period) or the vehicle was given to suckling male rats during lactation. Animals were fed after weaning with a normal fat (NF) or a high-fat (HF) diet. We followed body weight and food intake of animals until the age of 6 months, and measured the size of adipose tissue depots, the thermogenic capacity, the expression of leptin in the stomach and adipose tissues and the expression of two appetite-related peptides (neuropeptide Y (NPY) and proopiomelanocortin (POMC)), leptin receptor (OB-Rb) and suppressor of cytokine signalling 3 (SOCS-3) in the hypothalamus at the age of 6 months.

RESULTS

Leptin-treated animals had, in adulthood, lower body weight and fat content and ate fewer calories than their untreated controls. Unlike adipocitary leptin production, adult animals that were leptin-treated during lactation displayed higher gastric leptin production without changes in OB-Rb mRNA levels. In addition, in response to HF diet, leptin-treated animals (contrary to controls) showed lower hypothalamic NPY/POMC mRNA ratio. Hypothalamic OB-Rb mRNA levels decreased in control animals as an effect of HF diet feeding, but remained unchanged in leptin-treated animals; SOCS-3 mRNA levels were lower in leptin-treated animals than in their controls, both under normal or HF diet.

CONCLUSION

The animals that received leptin during lactation become more protected against fat accumulation in adult life and seem to be more sensitive to the short- and long-term regulation of food intake by leptin. Thus, leptin plays an important role in the earlier stages of neonatal life, as a component of breast milk, in the prevention of later obesity.

Expression and significance of leptin and transforming growth factor-α in gastric mucosa of Helicobacter pylori infected patients with chronic gastritis and gastric ulcer

AIM: To investigate the expression of leptin and trans-forming growth factor-α (TGF-α) in the Helicobacter pylori (H. pylori) infected gastric mucosa, and to explore the correlation between leptin and TGF-α.

METHODS: Immunocytochemistry was used to detect the expression of leptin and TGF-α in the mucosal biopsies from the corpus ventriculi and the gastric antrum of patients with H. pylori ⁺ and H. pylori ^- chronic gastritis and gastric ulcer.

RESULTS: Leptin was weakly positive in the corpus ventriculi mucosa of normal person. The expression of leptin and TGF-α were significantly increased in the corpus ventriculi mucosa of H. pylori + infected patients with gastritis and gastric ulcer as compared with that in the H. pylori - patients (leptin: 73.33% vs 23.08%, P < 0.05; 70.59% vs 25.00%, P < 0.05; TGF-α: 73.33% vs 15.38%, P < 0.05; 76.47% vs 25.00%, P < 0.05). The expression of leptin had no significant difference in the gastric antral mucosa between the four groups (P > 0.05). The expression of TGF-α was markedly higher in the gastric antral mucosa of patients with H. pylori + chronic gastritis than that in patients with H. pylori - gastritis (53.33% vs 7.69%, P < 0.05). The expression of leptin and TGF-α was positively correlated in the corpus ven-triculi mucosa (r = 0.80, P < 0.01).

CONCLUSION: The expression of leptin and TGF-α is positively correlated in the corpus ventriculi mucosa of H. pylori + patients with chronic gastritis and gastric ulcer.

Endothelin-1-dependent leptin induction in gastric mucosal inflammatory responses to Helicobacter pylori lipopolysaccharide

Leptin, a multifunctional hormone that regulates food intake and energy expenditure, has emerged recently as an important modulator of gastric mucosal responses to Helicobacter pylori infection. We applied the animal model of H. pylori LPS-induced gastritis to investigate the role of endothelin-1 (ET-1) in the mucosal leptin production. We show that the histologic pattern of inflammation reached a maximum on the fourth day following the LPS and was reflected in a marked increase in the mucosal level of ET-1 and leptin. Therapeutic administration of phosphoramidon, an inhibitor of ECE-1 activity, led to a 61.2% decline in the mucosal ET-1 level and a 64.1% reduction in leptin, while the severity of mucosal inflammatory involvement increased by 28.6%. A drop in the level of leptin and the increase in severity of the inflammatory involvement elicited by the LPS was also attained in the presence of ET(A) receptor antagonist BQ610, but not the ET(B) receptor antagonist BQ788. Moreover, administration of ERK inhibitor, PD98059, in the presence of ET(B) receptor antagonist, but not the ET(A) receptor antagonist, caused reduction in the mucosal leptin level. Our findings are the first to implicate ET-1 as a key factor in up-regulation of gastric mucosal leptin-associated H. pylori infection. We also show that the effect of ET-1 on leptin production is a consequence of ET(A) receptor activation.

Endothelin-1-dependent up-regulation of leptin production in gastric mucosal injury by indomethacin

Leptin, a multifunctional hormone that regulates food intake and metabolic and endocrine responses, has emerged recently as an important modulatory factor in gastric mucosal resistance to injury. In this study, we applied the animal model of gastric mucosal injury caused by indomethacin to investigate the role of endothelin-1 (ET-1) in the mucosal leptin production. Using groups of rats subjected to intragastric administration of indomethacin (at 0-60 mg/kg), we show that gastric mucosal damage reached a maximum 4 h following the drug, and was accompanied by a marked elevation (up to 3.5-fold) in the mucosal leptin level, up to 4-fold enhancement in the expression of endothelin-converting enzyme-1 (ECE-1) activity and up to 4.5-fold increase in ET-1 generation. Pretreatment with phosphoramidon, an inhibitor of ECE-1 activity, not only led to a decline in ECE-1 and ET-1 generation, but also produced a dose-dependent reduction in the mucosal level of leptin and the extent of mucosal damage caused by indomethacin. This effect of phosphoramidon, however, was subject to suppression by the exogenous ET-1 administration. Moreover, a marked drop in the mucosal level of leptin and the reduction in the severity of mucosal damage was attained following pretreatment with ET(A) receptor antagonist BQ610, but not by ET(B) receptor antagonist BQ788. The results implicate ET-1 as a key factor in the regulation of leptin production associated with gastric mucosal response to injury, and show that the stimulatory effect of ET-1 on leptin production occurs via ET(A) receptor activation.

Role of Leptin in Modulation of Porphyromonas gingivalis Lipopolysaccharide-induced Up-regulation of Endothelin-1 in Salivary Gland Acinar Cells

Leptin, a pleiotropic cytokine that regulates food intake and metabolic and endocrine responses, has emerged recently as an important regulator of mucosal inflammatory responses to bacterial infection. In this study, we report that in sublingual salivary gland acinar cells leptin plays a role in the suppression of up-regulation in endothelin-1 (ET-1), induced by the LPS of a periodontopathic bacterium P. gingivalis. We show that P. gingivalisLPS detrimental effect on salivary mucin synthesis, associated with up-regulation (3.9-fold) in ET-1 generation and the enhancement (3.2-fold) in endothelin-converting enzyme-1 (ECE-1) activity, was subject to a dose-dependent suppression by leptin. The impedance by leptin of the LPS inhibitory effect on mucin synthesis was blocked by wortmannin, an inhibitor of PI3K, as well as by ERK inhibitor, PD98059. However, while the blockade of ERK led also to amplification in the impedance by leptin of the LPS-induced expression of ECE-1 and ET-1, the effect was not observed in the presence of wortmannin. The findings are the first to demonstrate that leptin counters the pathological consequences of P. gingivalisinfection on the synthesis of salivary mucin through the involvement in signaling events of PI3K and ERK pathways. We also show that the ERK cascade represents a critical signaling target for leptin in the LPS-induced up-regulation in ET-1.

Leptin activates STAT and ERK2 pathways and induces gastric cancer cell proliferation

Although leptin is known to induce proliferative response in gastric cancer cells, the mechanism(s) underlying this action remains poorly understood. Here, we provide evidence that leptin-induced gastric cancer cell proliferation involves activation of STAT and ERK2 signaling pathways. Leptin-induced STAT3 phosphorylation is independent of ERK2 activation. Leptin increases SHP2 phosphorylation and enhances binding of Grb2 to SHP2. Inhibition of SHP2 expression with siRNA but not SHP2 phosphatase activity abolished leptin-induced ERK2 activation. While JAK inhibition with AG490 significantly reduced leptin-induced ERK2, STAT3 phosphorylation, and cell proliferation, SHP2 inhibition only partially reduced cancer cell proliferation. Immunostaining of gastric cancer tissues displayed local overexpression of leptin and its receptor indicating that leptin might be produced and act locally in a paracrine or autocrine manner. These findings indicate that leptin promotes cancer growth by activating multiple signaling pathways and therefore blocking its action at the receptor level could be a rational therapeutic strategy.

Leptin orally supplied to neonate rats is directly uptaken by the immature stomach and may regulate short-term feeding

Although leptin is a hormone mainly produced by the adipose tissue, it is also produced by the gastric mucosa and the mammary epithelium and is present in maternal milk. The effects of milk leptin on the neonate are not known. The purpose of the investigation was to evaluate the short-term effects of the administration of a single oral dose of leptin on 4-d-old rats as well as the effects of chronic supplementation during the lactation period with a daily oral dose of leptin (equivalent to 5 times the amount of leptin ingested normally from maternal milk during the suckling period) on body weight, the gastric leptin system, gastric food content, and thermogenic capacity. Our results show that the administration of a single oral dose of 4 ng of leptin to 4-d-old rats produces a short-term increase in leptin levels in the stomach and serum and a decrease in the weight of the gastric contents. Pups treated with a daily oral dose of leptin during the whole lactation period showed, at the end of the suckling period, compared with controls, lower gastric contents, lower leptin production by the stomach and the sc adipose tissue, and lower thermogenic capacity in brown adipose tissue. We conclude that oral leptin is absorbed by the immature gastric epithelium of the neonate, and this leptin exerts clear biological effects, down-regulating endogenous leptin production and playing a potential role in the short-term control on food intake during the lactation period.

Is Helicobacter pylori seropositivity related to body mass index in the United States?

BACKGROUND

Helicobacter pylori infection may decrease serum ghrelin and increase gastric leptin levels, which may, in turn, decrease body mass index.

AIM

To determine whether H. pylori seropositivity is associated with body mass index.

METHODS

Serum H. pylori and cytotoxin-associated gene product A (CagA) antibody levels were measured on 6724 adult participants of the third National Health and Nutrition Examination Survey (1988-91). We evaluated the association between H. pylori/CagA antibody status [both negative (-/-), H. pylori-positive/CagA-negative (+/-), or both positive (+/+)] and body mass index, adjusting for sociodemographic factors. We also investigated whether H. pylori/cytotoxin-associated gene product A antibody status was associated with fasting serum leptin levels.

RESULTS

H. pylori/CagA antibody status was not associated with obesity (body mass index > or = 30 kg/m(2)) [adjusted odds ratio (OR) 1.2, 95% CI: 0.9-1.6 comparing (+/+) to (-/-) and adjusted OR 1.1, 95% CI: 0.8-1.5 comparing (+/-) to (-/-)], overweight (body mass index 25 to <30 kg/m(2)) [adjusted OR 1.0, 95% CI: 0.7-1.2 comparing (+/+) to (-/-) and adjusted OR 1.0, 95% CI: 0.8-1.3 comparing (+/-) to (-/-)], or fasting serum leptin level in the USA population.

CONCLUSIONS

H. pylori seropositivity and CagA antibody status are not associated with body mass index or fasting serum leptin level.

Enhanced production of leptin in gastric fundic mucosa with Helicobacter pylori infection

AIM: To determine the concentrations of leptin in plasma and gastric fundic mucosa in humans, with reference to Helicobacter pylori (H pylori) infection, and their association with gastric mucosal levels of interleukin (IL)-1β, IL-6 and IL-8.

METHODS: Plasma leptin concentrations were determined in 135 outpatients with non-ulcer dyspepsia, consisting of 95 H pylori-infected and 40 uninfected subjects, and 13 patients before and after cure of the infection with anti-H pylori regimen. Using biopsy samples that were endoscopically obtained from the middle corpus along the greater curvature, gastric leptin contents were measured by radioimmunoassay and the mucosal concentrations of IL-1β, IL-6 and IL-8 were measured by enzyme linked immunosorbent assay. We also analysed the expression of leptin in the fundic mucosa by reverse transcriptase-polymerase chain reaction (RT-PCR) and immunohistochemistry.

RESULTS: The mucosal levels of leptin in the fundic mucosa of H pylori-infected patients were significantly higher than those of uninfected patients. The amount of gastric leptin correlated positively with the mucosal levels of IL-1β and IL-6, but not IL-8. Circulating leptin correlated with body mass index, but not with H pylori status, and there was no change in plasma leptin levels following cure of the infection. Leptin immunoreactive cells were noted in the lower half of the fundic glands, and its expression of messenger ribonucleic acid in the oxyntic mucosa was detected by RT-PCR.

CONCLUSION: Leptin production is enhanced in H pylori-infected gastric mucosa. Gastric leptin may be involved in immune and inflammatory response during H pylori infection, through interaction with proinflammatory cytokines.

Eradication of Helicobacter pylori increases the incidence of hyperlipidaemia and obesity in peptic ulcer patients

BACKGROUND

Eradication of Helicobacter pylori improves clinical symptoms and quality of life in patients with peptic ulcer.

AIM

To investigate the effect of eradication of H. pylori on body mass index and incidence of hyperlipidaemia in patients with peptic ulcer.

PATIENTS AND METHODS

The study population comprised 50 patients (42 men, 8 women; mean age, 51 years; 28 gastric ulcer, 22 duodenal ulcer) who underwent physical and blood examination before and 1 year after undergoing eradication therapy and 100 sex- and age-matched control subjects. Body mass index, total cholesterol and triglyceride were measured before and 1 year after therapy.

RESULTS

The eradication therapy group showed a significant increase in body mass index (22.7+/-2.5 kg/m2 before eradication versus 23.6+/-2.6 kg/m2 after eradication, p < 0.01), serum total cholesterol (204.1+/-33.2 mg/dL versus 221.2+/-38.8 mg/dL, p < 0.01), and triglyceride. Additionally, the eradication therapy group showed a significant increase in the incidence of hypercholesterolemia (30% versus 58%, p<0.01), hypertriglyceridaemia (28% versus 44%, p < 0.01) and obesity (12% versus 22%, p <0.05) 12 months after therapy.

CONCLUSION

Our findings show that eradication of H. pylori significantly increases the incidence of hyperlipidaemia and obesity in patients with peptic ulcer.

Serum leptin level in patients with functional dyspepsia

BACKGROUND/GOAL: Previous studies have shown that leptin plays a major role in the amount of food consumption. Recently, leptin and its receptors have been found in the human gastric mucosa. The aim of this study was to seek any possible correlation between serum leptin level and subtypes and pathological findings in functional dyspepsia.

MATERIALS AND METHODS

In a prospective study, we randomly select 44 patients as dysmotility-like and ulcer-like dyspepsia (according to ROME II criteria) in two equivalent groups and compared them with 22 healthy volunteers control group who matched the patients in relation to age, sex and body mass index. From each patient, a fasting blood sample for leptin level and two antral biopsies for evaluating the intensity of gastritis and Helicobacter pylori infection were provided and compared with the control group.

RESULTS

Compared to the control group, serum leptin level was significantly higher in patients with dysmotility-like dyspepsia (P < 0.05). Leptin level were also significantly correlated with the presence of gastritis and H. pylori infection (P < 0.05).

CONCLUSION

Leptin may have a role in the pathogenesis of the dysmotility variety of non-ulcer dyspepsia through mechanisms other than H. pylori infection. Further studies based on gastric leptin immunohistochemistry may need correlation between symptoms of functional dyspepsia and gastric leptin expression.

Expression of leptin in two-layered culture of gastric mucous cells and fibroblasts: effect of Helicobacter pylori attachment

BACKGROUND

Our recent histochemical studies have revealed an increase in myofibroblasts and in leptin and its receptor in endothelial cells, and myofibroblasts in Helicobacter pylori-infected human and Mongolian gerbil fundic mucosa.

AIM

The present study was undertaken to clarify the H. pylori-induced interaction between leptin in cultured gastric surface mucous cells and fibroblasts.

METHODS

GSM06 cells were incubated with an air- liquid interface on a collagen gel layer containing mouse fibroblast cell line L929. Medium containing H. pylori bacilli (ATCC43504) at 10-100 times higher concentration than the GSM06 cells was added from the luminal side and the localization of leptin was observed by immunohistochemistry. The transformation of L929 cells to myofibroblasts was detected by electron microscopy and PR 2D3 immunoreactivity.

RESULTS

L929 cells in the control group showed a spindle shape with scarce cytoplasm. In the H. pylori-treated group, L929 cells showed features characteristic of myofibroblasts, and most GSM06 and L929 cells showed leptin immunoreactivity. In contrast, L929 cells incubated with H. pylori alone did not undergo this differentiation.

CONCLUSIONS

Attachment of H. pylori to surface epithelial cells caused conversion of fibroblasts to myofibroblasts. We suggest that leptin plays a role in this transformation.

Leptin suppresses Porphyromonas gingivalis lipopolysaccharide interference with salivary mucin synthesis

Leptin, a multifunctional hormone produced predominantly by adipocytes but also identified throughout the glandular tissue of alimentary tract, including salivary glands and oral mucosa, has emerged recently as an important regulator of mucosal inflammatory responses to bacterial infection. In this study, we report that leptin prevents (up to 88.4%) the reduction in mucin synthesis evoked in mucous cells of sublingual salivary gland by LPS of periodontopathic bacterium, Porphyromonas gingivalis. The effect of leptin, moreover, was reflected in a marked decrease in the LPS-induced apoptosis, expression of TNF-alpha, caspase-3 activity, and NO generation. The impedance by leptin of the LPS inhibitory effect on mucin synthesis was blocked by wortmannin, an inhibitor of PI3K, which also obviated the inhibitory effect of leptin on the LPS-induced upregulation in apoptosis, caspase-3 activity, and NO generation. A potentiation in the impedance by leptin of the LPS-induced apoptosis, caspase-3 activity, and NO generation was, however, attained with NOS-2 inhibitor, 1400W, that also caused further enhancement in the impedance by leptin of the LPS detrimental effect on mucin synthesis. Taken together, our data are the first to demonstrate the nature of the involvement of leptin in countering the pathological consequences of P. gingivalis infection on the synthesis of salivary mucins.

The effect of gender on Helicobacter felis-mediated gastritis, epithelial cell proliferation, and apoptosis in the mouse model

The murine Helicobacter felis model has been extensively used to investigate the importance of host factors in the development of chronic gastritis. The effect of gender in this murine model is unknown. Male and female C57BL/6J mice were infected with H felis for up to 1 year. At 4, 8, 19, 36, and 52 weeks post-infection, gastric histopathology, epithelial cell proliferation, and apoptosis were examined and compared with age- and gender-matched controls. In female mice, infection with H felis resulted in an earlier onset of chronic gastric inflammation, epithelial hyperplasia, and oxyntic cell loss than males. In females, there was a trend towards increased gastric pathology compared with males, with long-term-infected female mice having significantly greater (p < 0.05) chronic inflammation than male mice. The histopathological differences in male and female mice did not relate to the density of H felis infection. Female mice infected with H felis had significantly increased gastric epithelial cell proliferation in the cardia and corpus at both 8 and 52 weeks post-infection (p < 0.05). Epithelial cell apoptosis in the glandular mucosa of the corpus at 36 and 52 weeks post-infection was significantly increased (p < 0.05) in female mice compared with uninfected gender controls. In contrast, there was no significant increase in epithelial cell proliferation or apoptosis in any area of the stomach at any time point after H felis infection in male mice. These results demonstrate that there are gender differences in the gastric inflammatory and epithelial response to H felis in the murine model. The functional importance of gender should be considered in future murine studies on H felis- and H pylori-induced chronic gastritis.

Increased soluble leptin receptor in children with nephrotic syndrome

In patients with nephrotic syndrome, severe proteinuria is related to significant leptinuria; serum leptin levels remain unchanged. The goal of this study was to elucidate the role of the soluble leptin receptor (sOB-R) in maintaining serum leptin levels in nephrotic patients. Patients with proteinuria were compared with patients in remission of nephrotic syndrome. In this group proteinuria did not exceed 100 mg/m(2) of body surface area per day. The period of remission was at least 6 months and was equal in all patients included. The sOB-R level (mean +/- SD) in serum of patients with nephrotic syndrome was significantly higher during proteinuria (61.0 +/- 17.8 ng/ml) than those in remission or in control patients (36.7 +/- 7.0 ng/ml, 36.6 +/- 12.0 ng/ml, respectively, P < 0.0001). The ratio between serum leptin levels and the sOB-R (free leptin index) was significantly lower in the proteinuric group (0.012 +/- 0.005 vs. 0.06 +/- 0.03 and 0.07 +/- 0.03 in remission and control group, respectively) (P < 0.001). Urinary sOB-R excretion was similar in all groups. Our data suggest that the counteracting pathway in case of leptin loss in parallel to severe proteinuria in nephrotic syndrome is the up-regulation of its soluble binding protein in serum, which can keep total serum leptin levels constant.

Interaction of leptin with gastric myofibroblast transdifferentiation in Helicobacter pylori-infected Mongolian gerbils: the effect of rebamipide

BACKGROUND

Our recent histochemical studies have revealed the marked increase of myofibroblasts in the Helicobacter pylori-infected Mongolian gerbil fundic mucosa, while the mediators, which facilitate the conversion of fibroblasts to the myofibroblasts have remained unknown.

AIM

The present study was undertaken to clarify the alteration of leptin in the control and H. pylori-infected Mongolian gerbil stomach. The effector sites of rebamipide were also investigated in relation to leptin.

METHODS

The localization of leptin was investigated by the indirect immunofluorescence. Plasma leptin levels were determined by ELISA method. The localization of 3H-rebamipide binding sites was investigated by autoradiography.

RESULTS

Serum leptin content in H. pylori-infected Mongolian gerbils was significantly increased. The presence of leptin immunoreactivity was recognized in the endothelial cells of the microcirculatory network and very weakly in the glandular cells in the control group, while in the H. pylori-infected group leptin was markedly recognized in the mesenchymal cells. Rebamipide bound to the fibroblasts and surface mucous cells and decreased the leptin immunoreactivity in the gastric mucosa.

CONCLUSIONS

Leptin was mostly found in the mesenchymal cells. Rebamipide administration brought about the decrease of leptin in the gastric mucosaof the H. pylori-infected gerbils.

Perinatal expression of leptin in rat stomach

It has been reported recently that the stomach can produce and store leptin and release it, both into the blood and into the gastrointestinal lumen, in response to food intake. Here, we have followed the ontogenic pattern of leptin mRNA expression and leptin levels in stomach during the perinatal period, which were compared with adults. Leptin mRNA expression was assessed by reverse transcriptase-polymerase chain reaction, and tissue leptin content by enzyme-linked immunosorbent assay and localised by immunohistochemistry. Leptin mRNA is expressed at low levels in rat stomach in prenatal stages. It increased from 4 to 8 hr of life in suckling rats, an increase not observed in the fasted pups, which were separated from their mothers immediately after birth. Leptin expression rose steadily after birth during the first month of life, with a marked increase from 15-day-old rats, followed by a parallel increase in leptin levels from day 21 of life, which was coincident with the change from suckling to a solid diet. The immunohistochemical analysis showed leptin immunoreactivity at different levels of the stomach mucosa, suggesting that during early development leptin could derive from different sources. During the pre- and neonatal periods, leptin is mainly located at the superficial epithelium (suggesting maternal origin from amniotic cells and mammary glandular cells, respectively). At the beginning of the chow diet, the stomach produces leptin in the glands (main source from 15 days of life), suggesting an endogenous production of the protein after that period. The present work demonstrates the expression of leptin mRNA and leptin protein in the stomach of neonate rats, and shows that the ontogenic profile of leptin appearance in the stomach during the perinatal period is probably related to the onset of suckling and to the change of diet from milk to solid chow.

Antral mucosa expresses functional leptin receptors coupled to STAT-3 signaling, which is involved in the control of gastric secretions in the rat

BACKGROUND & AIMS

Leptin is a circulating hormone that communicates the peripheral nutritional status to the hypothalamus, which controls food intake, energy expenditure, and body weight. This study characterizes leptin receptors and leptin-sensitive STAT proteins in the antrum and investigates the effects of leptin on gastric secretions.

METHODS

The effects of leptin on gastrin messenger RNA (mRNA), plasma gastrin, gastric acid in vivo in the rat, and on somatostatin and gastrin secretions by isolated antral cells were determined in vitro. Leptin receptors were investigated in isolated rat antral cells by reverse transcription-polymerase chain reaction and binding of [(125)I]-leptin studies. The effects of in vivo and in vitro leptin on transduction signal STAT proteins were investigated by immunoblotting antral extracts.

RESULTS

Peripheral injection of leptin inhibited in a dose-dependent manner, basal gastric secretion, gastrinemia, and mucosal gastrin mRNA in vivo. mRNAs encoding the long (Ob-Rb) and short (Ob-Ra) receptor forms were detected in rat antral mucosa, as were STAT-1, -3, and -5b immunoreactive proteins. Isolated antral cells specifically bound [(125)I]-leptin, and addition of leptin to these cells inhibited the release of somatostatin and increased the release of gastrin. These effects were associated with an increase in nuclear STAT-3 proteins in vitro and in vivo.

CONCLUSIONS

This study provides the first molecular evidence for the coexpression of leptin receptors and STAT-3 in antral mucosa. It provides further evidence for the involvement of leptin in the control of gastric secretions.

Identification of leptin in human saliva

Leptin is produced predominantly in adipose tissue but has recently also been found in gastric mucosa. It has been shown that the oral application of leptin induces neuronal activity in the brain stem of rodents. The objective of the present study was to identify this hormone in human saliva and to examine the production and stability of salivary leptin. We have demonstrated production of leptin in salivary glands and oral mucosa by RT-PCR, its storage by immunocytochemistry, and the release of the peptide by RIA. Chromatographic analysis and immunoblotting confirmed the identity of leptin. There is a strong linear correlation (r2 = 0.78) between leptin concentrations from simultaneously collected saliva and plasma samples (n = 61). Stimulation of saliva flow increases total leptin secretion up to 3-fold (P < 0.001). As to the stability of leptin in gastric fluid, we found the peptide was not degraded above pH 3.5. Additionally, salivary leptin remains stable up to 5 d at 4 C. With regard to the presence of leptin receptors in gastric mucosa, we suggest salivary leptin as being a possible ligand for gastric leptin receptors. Furthermore, the determination of leptin in saliva allows for noninvasive sample collection.

Expression of leptin (Ob) and leptin receptor (Ob-R) in human fibroblasts: regulation of leptin secretion by insulin

Leptin, a hormone of the cytokine family, is mainly synthesized by white adipocytes. As fibroblasts and adipocytes share a common stem cell origin, we hypothesized that connective tissue may be another candidate for leptin synthesis. We demonstrated leptin receptors, inclusive of all isoforms, on cultured fibroblasts (n = 13) by RT-PCR and immunohistochemistry. In contrast to its receptor, basal leptin mRNA expression and protein secretion were found in 8 of 13 cultures, reaching 1.4 ng/350,000 cells.24 h. Incubation with physiological insulin concentrations (1 nmol/liter) increased leptin secretion in fibroblast culture supernatants to 152% of basal levels. A maximal stimulation of the basal level up to 192% was found with 10 nmol/liter insulin after 24 h. Actinomycin D and cycloheximide abolished this effect, providing evidence that active RNA and protein synthesis are involved in insulin's action. Completing these in vitro results, we could show protein expression for leptin and leptin receptors in fibroblasts by immunostaining of human skin biopsies in situ. In conclusion, we provide evidence of leptin synthesis and secretion by human fibroblasts that are regulated by insulin. Leptin produced by fibroblasts may thus exert important local autocrine and paracrine actions and contribute to the total plasma pool. Hence it might in part account for variations in body mass index-dependent reference ranges of leptin as well as disruptions in the relationship between fat content and leptin.

The gut and food intake: an update for surgeons

Food intake is the simplest and most obvious measure of gastrointestinal function, yet it rarely receives more than cursory attention from surgeons. In this review we cover recent findings on relationships between gut function and appetite regulation mediated via neuropeptides influenced by afferent and efferent vagal activity. Evidence from the new discipline known as neurogastroenterology elucidates gastric and intestinal signals involved in the elicitation of hunger, satiety, and aversion. Discovery of the adipose-tissue-derived hormone, leptin, has energized the field of metabolism spawning increasing numbers of publications related to interactions between leptin and insulin release and glucose disposal, as well as appetitive behavior. Peptides such as cholecystokinin (CCK), the proglucagon-derived peptides, glucagon-like peptides 1 and 2 (GLP-1 and GLP-2), and the recently identified powerful intake-stimulating molecule, orexin, are examples of potential targets for drug development and studies of surgical pathophysiology. A major conclusion of this work is that the considerable redundancy and overlap between mediators of caloric intake subserving survival of the species, while beneficial after foregut surgery, contribute to the complexity of treating the global epidemic of obesity. Possibly knowledge derived from basic research in neurogastroenterology can translate into advances in surgical treatment of obesity.

Gastric leptin

The recent discovery of gastric leptin has initiated several investigations on the possible role of leptin in digestive physiology. The following clues are currently suggested: leptin might control meal size in cooperation with Cholecystokinin, help cytoprotection of the gastric mucosa, play a role in gut inflammatory processes, regulate secretion of gastric hormones such as gastrin and somatostatin, and modulate intestinal transport of small peptides. The present review is a brief survey of the most significant advances in these issues.

Role of leptin in ulcer healing

Leptin was shown to exhibit similar to cholecystokinin (CCK) cytoprotective activity against acute gastric lesions, but its role in ulcer healing has not been examined. The aims of this study were: (1) to compare the effects of exogenous leptin to those of CCK on the course of healing of chronic gastric ulcers; (2) to study the gene and protein expression of leptin at the ulcer margin during ulcer healing; and (3) to assess the effects of leptin administration on the mucosal gene expression of main growth factor such as transforming growth factor alpha (TGFalpha). Gastric ulcers were produced in rats by the acetic acid method. Rats with ulcers were divided in following treatment groups: (1) vehicle; (2) leptin (10 microg/kg i.p.); (3) CCK (10 microg/kg s.c.); and (4) leptin or CCK with or without tyrphostin A46 (200 microg/kg i.p.), an inhibitor of epidermal growth factor (EGF)-receptor tyrosine kinase or NG-nitro-L-arginine (20 mg/kg i.g.), a blocker of nitric oxide synthase. Animals were euthanized 9 days after ulcer induction. The area of gastric ulcers and the gastric blood flow at the ulcer area were determined. In addition, mucosal biopsy samples were taken from the ulcer area for histological evaluation as well as for the determination of mRNA and protein expression for leptin and constitutive nitric oxide synthase (cNOS) and inducibile nitric oxide synthase (iNOS) by reverse-transcriptase polymerase chain reaction (RT-PCR) and Western blot, respectively. In addition, the gene expression for TGFalpha was analyzed by RT-PCR. Both leptin and CCK reduced significantly the ulcer area as compared to vehicle-treated group by approximately 50%. The treatment with tyrphostin or N(G)-nitro-L-arginine reversed in part the acceleration of ulcer healing by leptin and CCK. The expression of leptin mRNA and protein was significantly increased at the ulcer edge. The leptin-induced acceleration of ulcer healing was associated with increased expression of transcripts for TGFalpha as well as increased mRNA and protein expression for cNOS and iNOS at the ulcer margin. We conclude that leptin accelerates ulcer healing by mechanisms involving the up-regulation of TGFalpha and increased production of nitric oxide due to up-regulation of cNOS and iNOS in the ulcer area.