Influence of surgical stress and parenteral nutrition on serum leptin concentration

Body Fat Distribution Contributes to Defining the Relationship between Insulin Resistance and Obesity in Human Diseases

The risk for metabolic and cardiovascular complications of obesity is defined by body fat distribution rather than global adiposity. Unlike subcutaneous fat, visceral fat (including hepatic steatosis) reflects insulin resistance and predicts type 2 diabetes and cardiovascular disease. In humans, available evidence indicates that the ability to store triglycerides in the subcutaneous adipose tissue reflects enhanced insulin sensitivity. Prospective studies document an association between larger subcutaneous fat mass at baseline and reduced incidence of impaired glucose tolerance. Case-control studies reveal an association between genetic predisposition to insulin resistance and a lower amount of subcutaneous adipose tissue. Human peroxisome proliferator-activated receptorgamma (PPAR-γ) promotes subcutaneous adipocyte differentiation and subcutaneous fat deposition, improving insulin resistance and reducing visceral fat. Thiazolidinediones reproduce the effects of PPAR-γ activation and therefore increase the amount of subcutaneous fat while enhancing insulin sensitivity and reducing visceral fat. Partial or virtually complete lack of adipose tissue (lipodystrophy) is associated with insulin resistance and its clinical manifestations, including essential hypertension, hypertriglyceridemia, reduced HDL-c, type 2 diabetes, cardiovascular disease, and kidney disease. Patients with Prader Willi syndrome manifest severe subcutaneous obesity without insulin resistance. The impaired ability to accumulate fat in the subcutaneous adipose tissue may be due to deficient triglyceride synthesis, inadequate formation of lipid droplets, or defective adipocyte differentiation. Lean and obese humans develop insulin resistance when the capacity to store fat in the subcutaneous adipose tissue is exhausted and deposition of triglycerides is no longer attainable at that location. Existing adipocytes become large and reflect the presence of insulin resistance.

Genetics of Cholesterol-Related Genes in Metabolic Syndrome: A Review of Current Evidence

Metabolic syndrome (MetS) refers to a cluster of metabolic dysregulations, which include insulin resistance, obesity, atherogenic dyslipidemia and hypertension. The complex pathogenesis of MetS encompasses the interplay between environmental and genetic factors. Environmental factors such as excessive nutrients and sedentary lifestyle are modifiable and could be improved by lifestyle modification. However, genetic susceptibility to MetS, a non-modifiable factor, has attracted the attention of researchers, which could act as the basis for future diagnosis, prognosis, and therapy for MetS. Several cholesterol-related genes associated with each characteristic of MetS have been identified, such as apolipoprotein, lipoprotein lipase (LPL), cholesteryl ester transfer protein (CETP) and adiponectin. This review aims to summarize the genetic information of cholesterol-related genes in MetS, which may potentially serve as biomarkers for early prevention and management of MetS.

Leptin and Obesity: Role and Clinical Implication

The peptide hormone leptin regulates food intake, body mass, and reproductive function and plays a role in fetal growth, proinflammatory immune responses, angiogenesis and lipolysis. Leptin is a product of the obese (ob) gene and, following synthesis and secretion from fat cells in white adipose tissue, binds to and activates its cognate receptor, the leptin receptor (LEP-R). LEP-R distribution facilitates leptin's pleiotropic effects, playing a crucial role in regulating body mass via a negative feedback mechanism between adipose tissue and the hypothalamus. Leptin resistance is characterized by reduced satiety, over-consumption of nutrients, and increased total body mass. Often this leads to obesity, which reduces the effectiveness of using exogenous leptin as a therapeutic agent. Thus, combining leptin therapies with leptin sensitizers may help overcome such resistance and, consequently, obesity. This review examines recent data obtained from human and animal studies related to leptin, its role in obesity, and its usefulness in obesity treatment.

Increased intestinal mucosal leptin levels in patients with diarrhea-predominant irritable bowel syndrome

AIM

To measure the leptin levels in patients with diarrhea-predominant irritable bowel syndrome (IBS-D) and analyze the relationship of leptin with clinical features, visceral sensitivity, mast cells, and nerve fibers.

METHODS

Forty-two patients with IBS-D fulfilling the Rome III criteria and 20 age- and sex-matched healthy controls underwent clinical and psychological evaluations using validated questionnaires (including IBS Symptom Severity Scale, IBS-specific Quality of Life, Hamilton Anxiety Scale, and Hamilton Depression Scale), along with colonoscopy, colonic mucosal biopsy, and visceral sensitivity testing. Serum leptin levels were assayed using enzyme-linked immunosorbent assay. Mucosal leptin expression and localization were evaluated using immunohistochemistry and immunofluorescence. Mucosal leptin mRNA levels were quantified using quantitative real-time reverse transcription polymerase chain reaction. Mast cell counts and activation rates were investigated by toluidine blue staining. Correlation analyses between these parameters were performed.

RESULTS

There were no statistically significant differences in age, gender, or body mass index between the IBS-D group and the control group. The median IBS Symptom Severity Scale score in the IBS-D group was 225.0 (range, 100-475). IBS-D patients had significantly increased anxiety [IBS-D: median, 6.5; interquartile range (IQR), 3.3; control: median, 2.0; IQR, 2.0; P < 0.001] and depression (IBS-D: median, 7.0; IQR, 3.0; control: median, 3.0; IQR, 2.0; P < 0.001) scores. IBS-D patients had significantly lower first sensation threshold (IBS-D: median, 50.6; IQR, 25.9; control: median, 80.5; IQR, 18.6; P < 0.001), defecation sensation threshold (IBS-D: median, 91.5; IQR, 29.3; control: median, 155.0; IQR, 21.1; P < 0.001) and maximum tolerable threshold (IBS-D: median, 163.2; IQR, 71.2; control: median, 226.2; IQR, 39.3; P < 0.001). Mucosal leptin expression, as reflected by integrated optical density (IBS-D: median, 4424.71; IQR, 4533.63; control: median, 933.65; IQR, 888.10; P < 0.001), leptin mRNA expression (IBS-D: median, 1.1226; IQR, 1.6351; control: median, 0.8947; IQR, 0.4595; P = 0.009), and mast cell activation rate (IBS-D: median, 71.2%; IQR, 12.9%; control group: median, 59.4%; IQR, 18.88%; P < 0.001) were significantly increased in IBS-D patients. The colocalization of leptin and leptin receptors was observed on mast cells and PGP9.5-positive nerve fibers in the intestinal mucosa. Also, leptin expression was positively correlated with anxiety, depression, and the mast cell activation rate, but negatively correlated with the defecation sensation threshold and the maximum tolerance threshold during visceral sensitivity testing (adjusted P < 0.0038).

CONCLUSION

Increased levels of mucosal leptin may interact with mast cells and the nervous system to contribute to the pathogenesis of IBS-D.

The Effect of Neonatal Maternal Stress on Plasma Levels of Adrenocorticotropic Hormone, Corticosterone, Leptin, and Ghrelin in Adult Male Rats Exposed to Acute Heterotypic Stressor

Activation of the hypothalamic-pituitary-adrenal (HPA) axis is important for maintenance of homeostasis during stress. Recent studies have shown a connection between the HPA axis and adipose tissue. The present study investigated the effect of acute heterotypic stress on plasma levels of adrenocorticotropic hormone (ACTH), corticosterone (CORT), leptin, and ghrelin in adult male rats with respect to neonatal maternal social and physical stressors. Thirty rat mothers and sixty of their male progeny were used. Pups were divided into three groups: unstressed control (C), stressed by maternal social stressor (S), stressed by maternal social and physical stressors (SW). Levels of hormones were measured in adult male progeny following an acute swimming stress (10 min) or no stress. ELISA immunoassay was used to measured hormones. The ACTH and CORT levels were significantly increased in all groups of adult progeny after acute stress; however, CORT levels were significantly lower in both neonatally stressed groups compared to controls. After acute stress, plasma leptin levels were decreased in the C and SW groups but increased in the S group. The data suggest that long-term neonatal stressors lead to lower sensitivity of ACTH receptors in the adrenal cortex, which could be a sign of stress adaptation in adulthood. Acute stress in adult male rats changes plasma levels of leptin differently relative to social or physical neonatal stressors.

Cytokine expression in the visceral adipose tissue after laparoscopic and conventional surgery in a rodent model

Background

Laparoscopic Surgery has become a worldwide standard procedure for a variety of indications. This has been attributed to a milder postoperative inflammatory response by the innate immune system potentially mediated through immune mediators released by the visceral adipose tissue (VAT). However, an in vivo experimental evidence is lacking and is the issue of our present study.

Methods

Male Wistar rats (N = 24) underwent standardized surgical procedures of conventional cecum resection (CCR), conventional sham operation, laparoscopic cecum resection (LCR), or laparoscopic sham operation. Cytokine expression of leptin, resistin, and IL-6 was analyzed in VAT before and after resection by quantitative RT-PCR.

Results

Postoperative leptin gene expression was reduced in the CCR and LCR groups, while expression was not significantly affected in both sham groups compared to the preoperative levels. In contrast, IL-6 expression was not affected in the LCR group, but was significantly elevated in the CCR cohort. The IL-6 expression was significantly higher in CCR compared to LCR. Resistin expression levels did not differ between all groups.

Conclusions

Our study underlines the role of immunological involvement of VAT in the postoperative phase. Low leptin levels seem to act as a stimulator for energy uptake in order to cope with postoperative stress. A lower IL-6 expression in the LCR compared to the CCR group may indicate a weaker inflammatory activity potentially adding to the clinical benefits observed in patients undergoing LS.

Leptin and adiponectin during the first week after kidney transplantation: biomarkers of graft dysfunction?

CONTEXT AND OBJECTIVE

Based on evidence that leptin and adiponectin are removed from circulation primarily by the kidney, we designed a study to examine the longitudinal changes of these adipokines during the first week after kidney transplantation (KTx) and to test the hypothesis that higher levels of leptin and/or adiponectin could be early biomarkers of delayed graft function (DGF=dialysis requirement during the first post-transplant week) and acute rejection.

STUDY DESIGN

Repeated-measures prospective study.

MATERIAL AND METHODS

Forty consecutive adult patients with end-stage renal disease who were undergoing KTx. Leptin and adiponectin were measured in blood samples that were collected before (day-0) and after KTx (days-1, 2, 4 and 7). Linear mixed-models, receiver operating characteristic and area under curve (AUC-ROC) were used.

RESULTS

At post-transplant day-1, leptinemia and adiponectinemia declined 43% and 47%, respectively. At all times studied after KTx, the median leptin levels were significantly higher in patients developing DGF (n=18), but not adiponectin levels. Shortly after KTx (day-1), leptin values were significantly higher in DGF recipients in contrast to patients with promptly functioning kidneys, approximately two times higher when controlling for gender and BMI. The leptin reduction rate between pre-tranplant and one-day after KTx moderately predicted DGF (AUC=0.73). On day-1, serum leptin predicted DGF (AUC-ROC=0.76) with a performance slightly better than serum creatinine (AUC-ROC=0.72), even after correcting for BMI (AUC-ROC=0.73). Separating this analysis by gender showed that the performance of leptin in predicting DGF for male gender (AUC-ROC=0.86) improved.

CONCLUSIONS

Kidney graft function is an independent determinant of leptin levels, but not of adiponectin. Leptin levels at day-1 slightly outperformed serum creatinine in predicting the occurrence of DGF, and more accurately in male gender. No significant association was detected with acute rejection.

Stimulation of leptin secretion by insulin

Leptin has a crucial role in regulating food intake and maintaining metabolic homeostasis. Although little is known about the process of leptin secretion, insulin, which has an important role in the metabolism of glucose and lipids, is believed to regulate leptin secretion through a posttranscriptional mechanism in the short term, and via glucose metabolism in the long term. The gastric mucosa secretes leptin, but this mechanism has not been completely elucidated. Understanding the mechanism of insulin-regulated leptin secretion could lead to the development of new treatment methods for obesity and its comorbidities, which are serious public health concerns.

Dexamethasone reduces food intake, weight gain and the hypothalamic 5-HT concentration and increases plasma leptin in rats

This study was conducted to define the regulatory mechanisms underlying stress-induced decreases in food intake and weight gain. Rats received a single or 4 daily injections of dexamethasone (0.1 or 1 mg/kg). Food intake and weight gain were recorded, and plasma leptin, brain contents of serotonin (5-hydroxytryptamine; 5-HT), 5-hydroxy-indole-acetic acid (5-HIAA) and the raphe expression of tryptophan hydroxylase (TPH), monoamine oxidase A (MAO-A) and 5-HT reuptake transporter (5-HTT) genes were examined. A single injection of dexamethasone did not acutely affect food intake, but cumulative food intake and weight gain were suppressed dose-dependently by daily injections of dexamethasone. Both a single and repeated injections of dexamethasone elevated plasma leptin in a dose dependent manner. 5-HT contents in the hypothalamus was decreased, but 5-HIAA increased, both by a single and repeated dexamethasone. A single injection of dexamethasone did not affect mRNA expressions of TPH, MAO-A and 5-HTT genes, but repeated dexamethasone increased them in the dorsal raphe nucleus. These results suggest that plasma leptin may play a role in dexamethasone-induced anorexia. Additionally, increased expression of MAO-A and 5-HTT genes by repeated dexamethasone appears to be implicated in decreases of the brain 5-HT contents.

Use of serum leptin levels for determination of nutritional status and the effects of different enteral nutrients on intestinal mucosa after minor surgery: an experimental study

BACKGROUND

We planned to evaluate the effects of different enteral nutrients on the levels of serum leptin, protein and albumin changes and also to compare their effects on mucosal morphology of small intestine.

METHODS

Rats were randomly divided into 5 groups each including 10 animals. Group I rats were given rat chow and water. Group II rats were fed with standard enteral nutrient. Group III rats were fed with calorie enriched enteral nutrient. Group IV rats were given enteral nutrition supplemented with fiber. Group V rats were fed with immunonutrient. Serum albumin, protein, leptin levels were measured. Terminal ileum of each rat was scored.

RESULTS

We found no difference in serum leptin, protein and albumin levels. The average mucosal atrophy of rats fed with standard chow was significantly different than that of rats fed with standard and calorie enriched nutrients. Feeding with nutrients supplemented with fiber and immunonutrient did not cause significant distortion in mucosal integrity when compared with feeding with standard chow.

CONCLUSION

Low levels of leptin may show malnutrition but for determination of nutritional status of a patient receiving enteral nutrition, studies with long duration are required.

Similar effects of general and spinal anaesthesia on perioperative stress response in patients undergoing haemorrhoidectomy

Surgery induces release of neuroendocrine hormones (cortisol), cytokines (interleukin-6: IL-6, tumour necrosis factor-α: TNF-α), acute phase proteins (C-reactive protein: CRP, leptin). We studied the effects of general and spinal anaesthesia on stress response to haemorrhoidectomy. Patients were assigned to general and spinal anaesthesia groups (n = 7). Blood samples were drawn before induction and 24 hours after surgery. Perioperative levels of IL-6, TNF-α, CRP, cortisol, and leptin were comparable among the groups. Twenty four hours after surgery, TNF-α and cortisol did not change; IL-6 and CRP increased significantly in all patients. Significant increase in leptin levels was found in patients undergoing spinal anaesthesia. Except for the increase in leptin levels, there was no significant difference related to the effects of general and spinal anaesthesia.

Systemic stress increases serum leptin level

BACKGROUND AND AIM

Leptin, the product of the obese (ob) gene, is a circulating peptide mainly synthesized by adipocytes. Leptin inhibits food intake and decreases body weight. A recent report has suggested that the gastric mucosa is also the source of leptin, and that the stomach leptin also contributes to the regulation of the serum leptin level. The aim of the present study was to investigate the effect of water-immersion stress on serum, stomach and adipose tissue leptin levels to understand the relationship between stress and eating behavior.

METHODS

Male Sprague-Dawley rats were used in this experiment. The leptin level in the serum, gastric mucosa and adipose tissue was measured using ELISA system before and after the initiation of water-immersion stress.

RESULTS

The serum leptin level was significantly increased by water-immersion stress. The peak was observed 9 h after the initiation of the stress (P < 0.01). However, the gastric leptin level significantly decreased 6 and 9 h after the stress. The adipose tissue leptin level significantly increased 3 h after the stress.

CONCLUSIONS

The results suggest that changes in serum leptin levels could be associated with stimulation of leptin secretion from the gastric mucosa and leptin production in the adipose tissue by systemic stress and that leptin might be regulated by stress-related events.

Leptin and insulin response to long-term total parenteral nutrition depends on body fat mass

BACKGROUND & AIMS

Circulating leptin and insulin concentrations are physiologically representing energy homeostasis. However, the artificial situation of long-term total parenteral nutrition (TPN) and its effects on serum leptin and insulin is not fully understood.

METHODS

We studied 42 gastroenterological patients who received TPN for 19+/-11 days. Serum leptin and insulin levels as well as body composition assessed by bioelectrical impedance analysis were evaluated on days 0, 7 and 14. Insulin sensitivity was estimated by calculating the QUICKI.

RESULTS

Before the start of TPN, leptin correlated positively with female gender (P<0.03), BMI (P<0.02), fat mass (P<0.02), insulin levels (P<0.001) and QUICKI (P<0.001). Within the first week of TPN, an increase of leptin levels was found only in patients with a body fat mass of >30% (P<0.02). As these were predominantly women, their leptin levels increased likewise (P<0.003). In regression analysis, fat mass (P<0.001), female gender (P<0.04), insulin levels (P<0.03), and i.v. glucose supply rates (P<0.05) were independently associated to leptin levels.

CONCLUSIONS

TPN-especially glucose-induces a neurohumoral response as shown here for leptin and insulin that is mainly depending on the fat mass. Better understanding of this regulatory mechanism during artificial nutrition could offer a new approach to improve its therapeutic effects.

Ghrelin and leptin elevation in postoperative intra-abdominal sepsis

BACKGROUND

Both ghrelin and leptin are important signals in the regulation of food intake and energy balance. Leptin concentrations are elevated in the majority of obese individuals, and its levels usually correlate with adiposity and body mass index. Ghrelin as a new growth hormone (GH)-releasing peptide was discovered in 1999. Ghrelin stimulates food intake and exhibits gastroprotective properties. Many other regulatory effects of both ghrelin and leptin involving cardiovascular, gastrointestinal, renal, and endocrine systems were revealed. New experimental studies show both hormones as new acute phase reactants in animal models of inflammatory reaction. The aim of this study was to characterize the levels of circulating ghrelin and leptin in relation to systemic inflammatory response. We used a postoperative bacterial sepsis after large abdominal surgery as a model of cytokine network hyperstimulation.

PATIENTS AND METHODS

The prospective study was performed on 25 surgical patients with proven postoperative intra-abdominal sepsis after large abdominal surgery. Plasma levels of ghrelin (RIA), leptin, TNF-alpha, IL-1beta, sIL-2R, IL-6 (ELISA analysis), CRP and alpha1-antitrypsin (nephelometric analysis) were analyzed.

RESULTS

Authors demonstrate statistically significant elevation of plasma ghrelin (492.3+/-70.6 ng/l) and leptin (31.6+/-12.2 microg/l) compared with the control group (336.5+/-46,1, p<0.01 for ghrelin, 3.5+/-1.2 microg/l, p<0.001 for leptin). The regression coefficient was the highest for ghrelin and IL-6 (r=0,44, p<0.05), and for ghrelin and TNF (r=0.43, p<0.05) in the sepsis group. In regard to leptin, the regression coefficient was the highest for IL-6 and leptin (r=0.53, p<0.05) and for leptin and CRP (r=0.51, p<0.05). There was no significant correlation between ghrelin and IL-1beta, ghrelin and sIL-2R, and leptin and IL-1beta.

CONCLUSIONS

During postoperative intra-abdominal sepsis, both ghrelin and leptin plasma levels are elevated and positively correlate with both inflammatory cytokines (TNF-alpha, IL-6) and main APP member (CRP). It supports experimental finding that TNF-alpha and IL-6 can be important regulatory factors of their synthesis. This hormonal reaction is not specific to sepsis--the significant increase of both ghrelin and leptin occurs during an uncomplicated postoperative response, although in a lesser extent than was shown in sepsis.

Evaluation of serum leptin concentration in Behçet's disease with ocular involvement

PURPOSE

To assess the correlation between the serum leptin concentration and ocular involvement in patients with Behçet's disease.

METHODS

The study included 28 male consecutive patients with Behçet's disease ( group A, aged 19-59, median 35.5 years) and 15 male healthy control subjects ( group B, aged 25-45, median 35 years). The body mass index (BMI) was calculated for each subject at the study enrollment stage. We measured serum leptin, neutrophil count and erythrocyte sedimentation rate (ESR). Kruskal-Wallis variance analysis and the Mann-Whitney U-test were used for statistical analysis.

RESULTS

The age and BMI between the patients with ocular Behçet's disease and the control group were not different. White cell count and ESR values were found to be significantly higher among patients with Behçet's disease and ocular involvement (p<0.001). The median serum leptin concentrations were as follows: group A: 2.66 (0.57-7.02 ng/ml) and in group B: 2.55 (1.55-7.82 ng/ml). There was no statistically significant difference between the groups.

CONCLUSION

Serum leptin level does not correlate with ocular involvement in patients with Behçet's disease.

Augmentation of leptin and hypoxia-inducible factor 1alpha mRNAs in the pre-eclamptic placenta

The placenta is a major source of leptin in the fetomaternal circulation, although its physiological role remains to be clarified. Leptin in the fetomaternal circulation is proposed to be a marker of acute stress in the fetus, and the fetus suffering from pre-eclampsia would be under chronic stress. In 16 pre-eclamptic placentas, the expressions of leptin, hypoxia-inducible factor 1alpha (HIF1alpha) and leptin receptor mRNAs were analyzed by semi-quantitative reverse-transcriptase-polymerase chain reaction and compared with clinical data. The co-expressions of leptin and the isoforms of the leptin receptor were observed in all the pre-eclamptic placentas. Leptin mRNA was significantly augmented in the pre-eclamptic placentas, although the level in fetal plasma was not high. The level of the expression of leptin mRNA was correlated with the placental HIF1alpha mRNA level and fetal body weight, but not with the levels of the leptin receptor isoforms in the pre-eclamptic placentas. This observation may suggest that autocrine/paracrine regulation of leptin exists in the human placenta and is upregulated in the pre-eclamptic placenta.

Simultaneous measurements of serum insulin-like growth factor-I and leptin reflect the postoperative nutrition status of oral tumor patients

OBJECTIVE

Recent evidence has shown that circulating levels of insulin-like growth factor-I (IGF-I) and leptin are regulated by nutrition support. Our objective was to investigate the reliability of IGF-I and leptin in monitoring the efficacy of nutrition support and nutrition status in oral tumor patients.

METHODS

Fifty-one male patients scheduled to receive resection operation for oral tumor were recruited. Fasted blood samples were collected before surgery (d0), on the first postoperative day before feeding (d1), and on the seventh postoperative day (d7) with nasogastric tube feeding (35 kcal x kg(-1) x d(-1)). Fifty male healthy volunteers were recruited as controls.

RESULTS

After adjustment for age, patients had significantly greater serum concentrations of transferrin and significantly lower serum concentrations of prealbumin and tumor-necrosis factor-alpha than did healthy volunteers on d0. In oral tumor patients, resection with prolonged fasting significantly increased levels of growth hormone and interleukin-6 and significantly decreased levels prealbumin, retinol-binding protein, IGF-I, and leptin, and these alterations were reversed by nutrition support for 6 d in oral tumor patients. Serum IGF-I was further increased on d7 compared with d0. In addition, leptin was the only nutrition-related serum protein showing significantly positive correlation with body mass index in healthy volunteers and patients.

CONCLUSIONS

Our results suggested that simultaneous measurements of serum IGF-I and leptin may provide information with regard to the efficacy of nutrition support and nutrition status in oral tumor patients undergoing surgery.