Leptin: structure, function and biology

Elevated Serum Leptin Levels are Associated With an Increased Risk of Sentinel Lymph Node Metastasis in Cutaneous Melanoma

The metabolic hormone leptin has been implicated in the pathogenesis of various malignancies and may contribute to the high rate of cancer in obese individuals. We reported that leptin and its receptor are expressed by melanoma tumors and cell lines, and that leptin stimulates proliferation of cultured melanoma cells. Here, we tested the hypothesis that leptin contributes to early melanoma progression by assessing its association with sentinel node positivity in cutaneous melanoma patients. The study enrolled 72 patients who were scheduled to undergo lymphatic mapping and sentinel node biopsy. Fasting blood was obtained before surgery, and serum leptin levels were measured by enzyme-linked immunosorbent assay (ELISA) with a "raw" (assay value) and an "adjusted" value (raw value divided by body mass index). Leptin levels and other clinicopathologic parameters were compared between sentinel node positive and negative groups. Logistic regression models were used to predict sentinel node status using leptin and other relevant clinical parameters. The raw and adjusted leptin levels were significantly higher in the 15 patients with positive sentinel nodes. These findings could not be attributed to differences in body mass indices. Univariate models revealed raw leptin, adjusted leptin, Breslow thickness, and mitotic rate as significant predictors of sentinel node status. Leptin levels and Breslow thickness remained significant in multivariate models. Survival and follow-up analysis revealed more aggressive disease in diabetic patients. Elevated serum leptin levels predict sentinel node metastasis in melanoma. Validation of this finding in larger cohorts should enable better stratification of early stage melanoma patients.

Are leptin levels increased among people with schizophrenia versus controls? A systematic review and comparative meta-analysis

OBJECTIVE

Leptin may play a role in the pathophysiology of schizophrenia and it remains unclear if levels are raised compared to controls. Therefore, we performed a systematic review and meta-analysis comparing leptin levels among people with schizophrenia and controls.

METHOD

Two authors independently searched major electronic databases from inception until June 2015 for studies measuring blood leptin levels among people with schizophrenia and controls. Random effects meta-analysis calculating hedges g and 95% confidence intervals (CI) and meta-regression analyses were conducted.

RESULTS

Twenty-seven articles representing 1674 individuals with schizophrenia (34.6 ± 6.8 years, 55% male (0-100%), BMI 25.2 ± 3.1) and 2033 controls (33.9 ± 7.0 years, 51% male (0-100%), BMI=24.1 ± 2.1) were included. Across all studies, leptin levels may be marginally higher in schizophrenia (g=0.164, 95% CI -0.014-0.341, p=0.07, Q=217, p<0.01), particularly when one outlier was removed (g=0.196, 95% CI 0.210-0.370, p=0.02) and when we included the smallest effect size from studies with multiple comparisons (g=0.318, 95% CI 0.125-0.510, p=0.001). Leptin levels were higher in multi-episode schizophrenia (g=0.245, 95% CI 0.058-0.433, p=0.01) and females (g=0.557 95% CI 0.16-0.954, p=0.006). Subgroup analyses revealed leptin levels may be higher in participants taking second-generation antipsychotics compared to controls. Multivariate meta-regression demonstrated a lower percentage of males (β=-0.0064, 95% CI -0.0129 to -0.0002, p=0.05), but not BMI, moderated the results.

CONCLUSION

Our results suggest that schizophrenia is associated with increased blood leptin levels compared to controls, which may not be entirely attributable to antipsychotic medication or BMI. Other illness related and lifestyle choices may play a pivotal role.

Adipocyte and leptin accumulation in tumor-induced thymic involution

Cell-mediated immunity is an important defense mechanism against pathogens and developing tumor cells. The thymus is the main lymphoid organ involved in the formation of the cell-mediated immune response by the maturation and differentiation of lymphocytes that travel from the bone marrow, through the lymphatic ducts, to become T lymphocytes. Thymic involution has been associated with aging; however, other factors such as obesity, viral infection and tumor development have been shown to increase the rate of shrinkage of this organ. The heavy infiltration of adipocyte fat cells has been reported in the involuted thymuses of aged mice. In the present study, the possible accumulation of such cells in the thymus during tumorigenesis was examined by immunohistochemistry. A significant number of adipocytes around and infiltrating the thymuses of tumor-bearing mice was observed. Leptin is a pro-inflammatory adipocytokine that enhances thymopoiesis and modulates T cell immune responses. The levels of leptin and adiponectin, another adipocytokine that has anti-inflammatory properties, were examined by western blot analysis. While no changes were observed in the amounts of adiponectin present in the thymuses of the normal and tumor-bearing mice, significantly higher levels of leptin were detected in the thymocytes of the tumor-bearing mice. This correlated with an increase in the expression of certain cytokines, such as interleukin (IL)-2, interferon (IFN)-γ and granulocyte-macrophage colony-stimulating factor (GM-CSF). The co-culture of thymocytes isolated from normal mice with ex vivo isolated adipocytes from tumor-bearing mice yielded similar results. Our findings suggest that the infiltration and accumulation of adipocytes in the thymuses of tumor-bearing mice play an important role in their altered morphology and functions.

A Comparative Study of Serum and Follicular Fluid Leptin Concentrations among Explained Infertile, Unexplained Infertile and Fertile Women

Background

The relationship between metabolism and reproduction has been always considered as an important topic in female endocrinology. It seems that leptin is one of the involved factors in infertility. Leptin, in addition to regulating body weight plays an important role in regulation of endocrine, reproductive and immune systems. The aim of this stduy is to compare serum and follicular fluid leptin concentrations in order to find the role of leptin level in infertility.

Materials and Methods

This case-control study was performed from September 2010 to March 2013. A total of 90 women referred to the Infertility Center of Afzalipour Hos- pital, Kerman, Iran, and divided into three equal groups (n=30/per group) of explained infertile (including 4 subgroups), unexplained infertile and normal fertile (control group). The three groups were matched in regard to demographic features [age: 20-40 years and body mass index (BMI): 20-25]. In order to determine leptin level, blood sample and fol- licular fluid were taken one hour prior and at the time of follicular puncture, respectively. Serum and follicular fluid leptin levels were measured using enzyme-linked immune sorbent assay (ELISA). Data were analyzed using descriptive-analytic tests, like Mann- Whitney and Kruskal Wallis tests, through Statistical Package for the Social Sciences (SPSS) version 16.

Results

In explained infertile and fertile groups, as opposed to unexplained infertile group, mean leptin level was lower in follicular fluid than in serum. Mean follicular fluid leptin concentration in women with unexplained infertility was higher com- pared to the other two groups. Women with unexplained infertility had lower level of serum leptin in comparison to the other two groups. Follicular fluid leptin level in all subgroups of explained infertile group was lower as compared to unexplained and fertile women.

Conclusion

The results suggested that high leptin level of follicular fluid is one of the main factors involved in infertility.

Anti-obesity effect of total phenylpropanoid glycosides from Ligustrum robustum Blume in fatty diet-fed mice via up-regulating leptin

ETHNOPHARMACOLOGICAL RELEVANCE

In Chinese folk medicine, the leaves of Ligustrum robustum Blume (LR) were commonly used in the treatment of obesity and hyperlipidemia. This study aimed to evaluate the anti-obesity effect and mechanisms of total phenylpropanoid glycosides from Ligustrum robustum Blume (LRTPG) in fatty diet-fed C57BL/6J mice.

MATERIALS AND METHODS

C57BL/6J mice were divided randomly into 6 groups, i.e., control, model, positive (Orlistat 0.12g/kg), and LRTPG at three dosages (0.3, 0.6 or 1.2g/kg), respectively. Control mice were fed with standard diet; the others were fed with fatty diet. After 4 weeks׳ modeling, therapy mice were intragastrically administrated with positive drug or LRTPG for 5 weeks, respectively. Pharmacodynamic effects including body weight, fat weight, Lee׳s index, serum lipid levels, morphological changes and adipocyte area ratio were evaluated. The mechanisms were explored as the factors related to lipids metabolism in gene expressions by real-time PCR, and assured as the protein level of differential gene by Western blotting.

RESULTS

The anti-obesity effects of LRTPG in all treated mice were shown as decreased body weight, fat mass, Lee׳s index, total cholesterol (TC) level, and adipocyte area. The mechanisms were demonstrated as elevated mRNA and protein levels of adipose leptin, and consequently decreasing mRNA of adipose acyl coenzyme A: diacylglycerol acyltransferase (DGAT) with increasing mRNA of hepatic cholesterol 7α-hydroxylase (CYP7A1), which led to inhibition of triglyceride (TG) synthesis and promotion of cholesterol catabolism.

CONCLUSIONS

The anti-obesity effect of LRTPG in fatty diet-fed mice was related to the up-regulation of leptin, which may provide scientific evidence supporting the traditional usage of LR on obesity in China.

Synergy of leptin/STAT3 with HER2 receptor induces tamoxifen resistance in breast cancer cells through regulation of apoptosis-related genes

PURPOSE

Tamoxifen is a major treatment modality for estrogen receptor positive breast cancer, but the occurrence of resistance remains a problem. Recently, obesity-related leptin has been found to interfere with tamoxifen in breast cancer MCF-7 cells. In the present study we investigated the effect of leptin on three tamoxifen-treated breast cancer cell types (i.e., MDA-MB-231, MCF-7 and MCF-7/HER2).

METHODS

The effect of tamoxifen/leptin treatment was evaluated using a MTT cell viability assay. mRNA expression was assessed by real time PCR and protein expression by Western blotting. WWOX, Survivin and BCL2 gene promoter activities were evaluated by chromatin immunoprecipitation.

RESULTS

Cell viability assays revealed that estrogen receptor negative MDA-MB-231 cells were resistant, that estrogen receptor positive MCF-7 cells were sensitive and that MCF-7/HER2 cells were relatively resistant to tamoxifen, while leptin co-administration 'rescued' MCF-7 and, especially, MCF-7/HER2 cells from the anti-proliferative effect of tamoxifen. The cell lines also exhibited a different phosphorylation status of STAT3, a transcription factor that is activated by the obesity related leptin receptor b (Ob-Rb). Most importantly, chromatin immunoprecipitation assays revealed differential STAT3 binding to the anti-apoptotic BCL2 and pro-apoptotic WWOX gene promoters in MCF-7 and MCF-7/HER2 cells, leading to concomitant modifications of its mRNA/protein expression levels, thus providing a selective advantage to HER2 over-expressing MCF-7/HER2 cells after treatment with tamoxifen and tamoxifen plus leptin.

CONCLUSIONS

Our study provides novel evidence indicating that synergy between the leptin/Ob-Rb/STAT3 signalling pathway and the HER2 receptor protects tamoxifen-treated HER2 over-expressing cells from the inhibitory effect of tamoxifen through differential regulation of apoptosis-related genes.

Specific metabolic biomarkers as risk and prognostic factors in colorectal cancer

Advances in genomics, molecular pathology and metabolism have generated many candidate biomarkers of colorectal cancer with potential clinical value. Epidemiological and biological studies suggest a role for adiposity, dyslipidaemia, hyperinsulinemia, altered glucose homeostasis, and elevated expression of insulin-like growth factor (IGF) axis members in the risk and prognosis of cancer. This review discusses some recent past and current approaches being taken by researches in obesity and metabolic disorders. The authors describe three main systems as the most studied metabolic candidates of carcinogenesis: dyslipidemias, adipokines and insulin/IGF axis. However, each of these components is unsuccessful in defining the diseases risk and progression, while their co-occurrence increases cancer incidence and mortality in both men and women.

Leptin and cholecystokinin in Schizothorax prenanti: molecular cloning, tissue expression, and mRNA expression responses to periprandial changes and fasting

In the present study, full-length cDNA sequences of leptin and cholecystokinin (CCK) were cloned from Schizothorax prenanti (S. prenanti), and applied real-time quantitative PCR to characterize the tissue distribution, and appetite regulatory effects of leptin and CCK in S. prenanti. The S. prenanti leptin and CCK full-length cDNA sequences were 1121 bp and 776 bp in length, encoding the peptide of 171 and 123 amino acid residues, respectively. Tissue distribution analysis showed that leptin mRNA was mainly expressed in the liver of S. prenanti. CCK was widely expressed, with the highest levels of expression in the hypothalamus, myelencephalon, telencephalon and foregut of S. prenanti. The CCK mRNA expression was highly elevated after feeding, whereas the leptin mRNA expression was not affected by single meal. These results suggested that CCK is a postprandial satiety signal in S. prenanti, but leptin might not be. In present study, leptin and CCK gene expression were both decreased after fasting and increased after refeeding, which suggested leptin and CCK might be involved in regulation of appetite in S. prenanti. This study provides an essential groundwork to further elucidate the appetite regulatory systems of leptin and CCK in S. prenanti as well as in other teleosts.

Polymorphisms of leptin-b gene associated with growth traits in orange-spotted grouper (Epinephelus coioides)

In mammals, leptin has been demonstrated to perform important roles in many physiological activities and to influence development, growth, metabolism and reproduction. However, in fish, its function is still unclear. Duplicate leptin genes, leptin-a and leptin-b, have been identified in the orange-spotted grouper. In the present study, the polymorphisms in the leptin-b gene of the orange-spotted grouper were detected, and the relation between these polymorphisms and 12 growth traits were analyzed. Six polymorphisms (including 3 single nucleotide polymorphisms (c.14G>A, c.93A>G, c.149G>A) in exon 1, 2 SNPs (c.181A>G, c.193G>A) in intron 1, and 1 SNP (c.360C>T) in exon 2) were identified and genotyped from 200 different individuals. The results revealed that the SNP c.149G>A was significantly associated with growth traits, that the heterozygous mutation genotype GA having negative effects on growth traits. However, the other five SNPs (c.14G>A, c.93A>G, c.181A>G, c.193G>A, c.360C>T) did not show significant associations with all the growth traits. Compared with our findings in leptin-a gene, the results suggested that the leptin-a hormone has more important physiological effects in fish bodies than the leptin-b type. Moreover, leptin genes were supposed to be one class of major candidate genes of regulating growth traits in the orange-spotted grouper.

Leptin as an uremic toxin: Deleterious role of leptin in chronic kidney disease

White adipose tissue secretes a large variety of compounds named adipokines amongst which, leptin exhibits pleiotropic metabolic actions. Leptin is an anorexigenic hormone, secreted in proportion of fat mass, with additional effects on the regulation of inflammation, cardiovascular system, immunity, hematopoiesis and bone metabolism. Chronic kidney disease (CKD) is characterized by an increase of plasma leptin concentration that may be explained by a lack of renal clearance. Hyperleptinemia plays a key role in the pathogenesis of complications associated with CKD such as cachexia, protein energy wasting, chronic inflammation, insulin resistance, cardiovascular damages and bone complications. Leptin is also involved in the progression of renal disease through its pro-fibrotic and pro-hypertensive actions. Most of the adverse effects of leptin have been documented both experimentally and clinically. Leptin may therefore be considered as an uremic toxin in CKD. The aim of this review is to summarize the pathophysiological and clinical role of leptin in in vitro studies, experimental models, as well as in patients suffering from CKD.

Influence of age on leptin induced skeletal muscle signalling

AIM

Age associated fat mass accumulation could be because of dysregulation of leptin signalling in skeletal muscle. Thus, we investigated total protein expression and phosphorylation levels of the long isoform of the leptin receptor (OB-Rb), and leptin signalling through janus kinase 2 (JAK2)/signal transducer and activator of transcription 3 (STAT3), insulin receptor substrate 1 (IRS-1), AMP-activated protein kinase (AMPK) and acetyl-coenzyme A carboxylase (ACC), combined with the leptin signalling inhibitors suppressor of cytokine signalling 3 (SOCS3) and protein tyrosine phosphatase 1B (PTP1B) in human skeletal muscle of different age.

METHODS

Vastus lateralis muscle biopsies were obtained from 39 men matched for BMI < 30 kg m(-2) and separated into three groups: 13 young (Y, 24 ± 4 years); 14 middle aged (MA, 44 ± 5 years) and 12 aged (A, 58 ± 8 years) subjects.

RESULTS

Whole body fat percentage and plasma leptin were higher (P < 0.05), whereas lean mass, plasma free testosterone and total testosterone were lower (P < 0.05) in A compared to Y. Skeletal muscle OB-Rb (170 KDa) protein expression and pTyr(1141) -OB-R170 were comparable between groups, whereas pTyr(985) -OB-R170 was lower in A compared to Y (P < 0.05). pSTAT3 levels tended (P = 0.09) to be lower (50%) in A compared to Y. In A, muscle PTP1B was greater and IRS-1 lower than Y and MA respectively (P < 0.05). PTyr(612) -IRS-1 tended to be lower in A than in Y (P = 0.09). Suppressor of cytokine signalling 3 (SOCS3) protein expression, pJAK2, pSer(1101) -IRS-1, pAMPKα and pACCβ were similar between groups.

CONCLUSION

Age is associated with dysregulation of the leptin signalling and increased PTP1B protein expression in skeletal muscle.

Leptin-induced adhesion and invasion in colorectal cancer cell lines

Leptin, which is encoded by the obese gene, is a multifunctional neuroendocrine peptide that regulates appetite, bone formation, reproductive function and angiogenesis. The aims of the present study were to investigate the expression of leptin in 80 patients with colorectal cancer (CRC) and to determine the effects of leptin on the malignant properties of CRC cells. We evaluated the expression of leptin in tissues of 80 patients with CRC. Suspension cultures were used to isolate CRC stem cells following pretreatment with leptin. We analyzed the effects of leptin on the adhesion and invasive capacities of CRC cell lines. The effects of leptin on JAK and ERK activation were examined using western blotting. Leptin expression was associated with CRC progression and increased the number and size of spheroid formation by CRC cell lines. Leptin enhanced cell invasion and adhesion and activated JAK and ERK signaling in the CRC cell lines. The present study demonstrated that leptin influences the growth and survival of CRC stem cells and regulates adhesion and invasion of colorectal carcinoma through activation of the JAK and ERK signaling pathways.

Activation of endocrine-related gene expression in placental choriocarcinoma cell lines following DNA methylation knock-down

Increasingly, placental DNA methylation is assessed as a factor in pregnancy-related complications, yet the transcriptional impact of such findings is not always clear. Using a proliferative in vitro placental model, the effect of DNA methylation loss on gene activation was evaluated at a number of genes selected for being differentially methylated in pre-eclampsia-associated placentae in vivo. We aimed to determine whether reduced DNA methylation at specific loci was associated with transcriptional changes at the corresponding gene, thus providing mechanistic underpinnings for previous clinical findings and to assess the degree of transcriptional response amongst our candidate genes. BeWo and JEG3 choriocarcinoma cells were exposed to 1 μM 5-Aza-2'-deoxycytidine (5-Aza-CdR) or vehicle control for 48 h, and re-plated and cultured for a further 72 h in normal media before cells were harvested for RNA and DNA. Bisulphite pyrosequencing confirmed that DNA methylation was reduced by ∼30-50% points at the selected loci studied in both cell lines. Gene activation, measured by qRT-PCR, was highly variable and transcript specific, indicating differential sensitivity to DNA methylation. Most notably, loss of DNA methylation at the leptin (LEP) promoter corresponded to a 200-fold and 40-fold increase in LEP expression in BeWo and JEG3 cells, respectively (P < 0.01). Transcripts of steroidogenic pathway enzymes CYP11A1 and HSD3B1 were up-regulated ∼40-fold in response to 5-Aza-CdR exposure in BeWo cells (P < 0.01). Other transcripts, including aromatase (CYP19), HSD11B2, inhibin (INHBA) and glucocorticoid receptor (NR3C1) were more moderately, although significantly, affected by loss of associated DNA methylation. These data present a mixed effect of DNA methylation changes at selected loci supporting cautionary interpretation of DNA methylation results in the absence of functional data.

Metabolic regulation by protein tyrosine phosphatases

Obesity and the metabolic syndrome and their associated morbidities are major public health issues, whose prevalence will continue to increase in the foreseeable future. Aberrant signaling by the receptors for leptin and insulin plays a pivotal role in development of the metabolic syndrome. More complete molecular-level understanding of how both of these key signaling pathways are regulated is essential for full characterization of obesity, the metabolic syndrome, and type II diabetes, and for developing novel treatments for these diseases. Phosphorylation of proteins on tyrosine residues plays a key role in mediating the effects of leptin and insulin on their target cells. Here, we discuss the molecular methods by which protein tyrosine phosphatases, which are key physiological regulators of protein phosphorylation in vivo, affect signaling by the leptin and insulin receptors in their major target tissues.

Are volumetric bone mineral density and bone micro-architecture associated with leptin and soluble leptin receptor levels in adolescent idiopathic scoliosis?--A case-control study

BACKGROUND

Adolescent idiopathic scoliosis (AIS) is associated with low bone mineral density (BMD). The underlying etiology and how it may relate to the development of osteopenia remains unknown. Leptin has been postulated as one of the etiologic factors of AIS because of its profound effects on bone metabolism and pubertal growth. Its modulator, soluble leptin receptor (sOB-R), may affect leptin bioavailability and signaling. This study aimed to investigate whether serum leptin and sOB-R levels may be associated with bone quality, and whether these relationships may differ between young adolescent girls with and without AIS.

METHODS

This was a case-control study involving 94 newly diagnosed AIS girls (Cobb angle 12-48°) aged 12 to 14 years old and 87 age and gender-matched normal controls. Subjects with BMI>23.0 Kg/m(2) were excluded. Anthropometric measurements including body weight, height, arm span and sitting height were taken. Serum total leptin and sOB-R were assayed with ELISA. Non-dominant distal radius was scanned with High Resolution pQCT for assessing bone quality in terms of bone morphometry, volumetric BMD (vBMD) and trabecular bone micro-architecture.

RESULTS

Compared with normal controls, AIS girls had numerically higher sOB-R (p = 0.006), lower average vBMD (p = 0.048), lower cortical vBMD (p = 0.029), higher cortical bone perimeter (p = 0.014) and higher trabecular area (p = 0.027), but none remained statistically significant after the Hochberg-Benjamini procedure. Correlation analysis on serum leptin level indicated that distinctive correlations with trabecular bone parameters occurred only in AIS.

CONCLUSION

This study showed that bone quality in AIS girls was deranged as compared with controls. In addition, the distinct differences in correlation pattern between leptin and trabecular bone parameters indicated possible abnormalities in bone metabolism and dysfunction of the leptin signaling pathway in AIS.

Leptin concentration and nutritional status in the course of treatment in children with brain tumours--preliminary report

PURPOSE

To assess the nutritional status in children with central nervous system (CNS) tumours, including concentration of leptin, the neuropeptide responsible for regulation of energetic homeostasis in an organism.

METHOD

The studied group comprised 44 children with brain tumours, aged (4.02-18.7). In all children during the whole therapy (from the start to the period of 1 year and more after the end of therapy), a number of standard deviations (SDs) for the body mass index (SDS BMI) was derived from anthropometric measurements. Concentrations of leptin were assayed simultaneously.

RESULT

The lowest values of the anthropometric indices were found in children during the maintenance therapy. Concentrations of leptin in patients with malignant CNS tumours and significant undernutrition were slightly greater as compared to patients presenting normal nutritional status; however, without statistical significance.

CONCLUSION

In children with tumours of the central nervous system, there are quantitative disorders of the nutritional status which correlate with the period of the treatment. The most significant disorders in the nutritional status are observed during maintenance chemotherapy. There was no statistically significant correlation between the concentration of leptin and nutritional status in children with malignant brain tumours during the course of treatment and after its completion.

Leptin signaling in skeletal muscle after bed rest in healthy humans

PURPOSE

This study aimed at determining the effects of bed rest on the skeletal muscle leptin signaling system.

METHODS

Deltoid and vastus lateralis muscle biopsies and blood samples were obtained from 12 healthy young men (mean ± SD, BMI 22.8 ± 2.7 kg/m(2)) before and after 7 days of bed rest. Leptin receptor isoforms (OB-Rs), suppressor of cytokine signaling 3 (SOCS3) and protein tyrosine phosphatase 1B (PTP1B) protein expression and signal transducer and activator of transcription 3 (STAT3) phosphorylation were analyzed by Western blot.

RESULTS

After bed rest basal insulin concentration was increased by 53% (P < 0.05), the homeostasis model assessment (HOMA) by 40% (P < 0.05), and serum leptin concentration by 35% (P < 0.05) with no changes in body fat mass. Although the soluble isoform of the leptin receptor (s-OBR) remained unchanged, the molar excess of leptin over sOB-R was increased by 1.4-fold after bed rest (P < 0.05). OB-Rs and SOCS3 protein expression, and STAT3 phosphorylation level remained unaffected in deltoid and vastus lateralis by bed rest, as PTP1B in the deltoid. PTP1B was increased by 90% with bed rest in the vastus lateralis (P < 0.05). There was a linear relationship between the increase in vastus lateralis PTP1B and the increase in both basal insulin concentrations (r = 0.66, P < 0.05) and HOMA (r = 0.68, P < 0.05) with bed rest.

CONCLUSIONS

One week of bed rest is associated with increased leptin levels without augmenting STAT3 phosphorylation indicating some degree of leptin resistance in skeletal muscle, which can be explained, at least in part, by an elevation of PTP1B protein content in the vastus lateralis muscle.

Endurance training increases leptin expression in the retroperitoneal adipose tissue of rats fed with a high-sugar diet

The presence of leptin receptors in white adipose tissue (WAT) suggests a type of peripheral control during the development of obesity and other metabolic disorders. Both diet composition and exercise influence serum leptin; however, the effect of their combination on long-term WAT leptin metabolism is unknown. In this study, rats fed with standard or high-sugar diets (HSD) were simultaneously subjected to running training for 4- and 8-week periods, and the retroperitoneal WAT (rWAT) was evaluated for adipocyte cell size, lipid and catecholamine content, Lep, OB-Rb and Ucp2 mRNA transcription levels, and circulating leptin and non-esterified fatty acids (NEFA). The HSD groups displayed a higher adiposity index and rWAT weight, Lep mRNA and protein upregulation, and a period-dependent effect on OB-Rb mRNA expression. Exercise decreased serum leptin and upregulated the OB-Rb mRNA levels. However, in rats fed with an HSD, the increase in OB-Rb mRNA and reduction in catecholamine levels resulted in a high level of adiposity and hyperleptinemia. The combination of training and an HSD decreases the NEFA levels and upregulating the Ucp2 mRNA expression in the 4-week period, while downregulating the Ucp2 mRNA expression in the 8-week period without changing the NEFA levels. Our results suggest that an HSD induces an increase in leptin expression in rWAT, while reducing adipocytes via leptin-mediated lipolysis after an 8-week period. In exercised rats fed an HSD, TAG synthesis and storage overlaps with lipolysis, promoting fat store development and Lep mRNA and plasma protein upregulation in adult rats.

Exploring leptin antagonism in ophthalmic cell models

Background

Emerging evidence suggests that angiogenic and pro-inflammatory cytokine leptin might be implicated in ocular neovascularization. However, the potential of inhibiting leptin function in ophthalmic cells has never been explored. Here we assessed mitogenic, angiogenic, and signaling leptin activities in retinal and corneal endothelial cells and examined the capability of a specific leptin receptor (ObR) antagonist, Allo-aca, to inhibit these functions.

Methods and Results

The experiments were carried out in monkey retinal (RF/6A) and bovine corneal (BCE) endothelial cells. Leptin at 50-250 ng/mL stimulated the growth of both cell lines in a dose-dependent manner. The maximal mitogenic response (35±7 and 27±3% in RF6A and BCE cells, respectively) was noted at 24 h of 250 ng/mL leptin treatments. Leptin-dependent proliferation was reduced to base levels with 10 and 100 nM Allo-aca in BCE and RF6A cells, respectively. In both cell lines, leptin promoted angiogenic responses, with the maximal increase in tube formation (163±10 and 133±8% in RF6A and BCE cultures, respectively) observed under a 250 ng/mL leptin treatment for 3 h. Furthermore, in both cell lines 250 ng/mL leptin modulated the activity or expression of several signaling molecules involved in proliferation, inflammatory activity and angiogenesis, such as STAT3, Akt, and ERK1/2, COX2, and NFκB. In both cell lines, leptin-induced angiogenic and signaling responses were significantly inhibited with 100 nM Allo-aca. We also found that leptin increased its own mRNA and protein expression in both cell lines, and this autocrine effect was abolished by 100-250 nM Allo-aca.

Conclusions

Our data provide new insights into the role of leptin in ocular endothelial cells and represent the first original report on targeting ObR in ophthalmic cell models.

Insulin and leptin levels in obese patients with and without breast cancer

BACKGROUND

Leptin has been associated with progression and poor survival in BC. Moreover, it is still controversial as to whether the effect of leptin depends only on its correlation with body mass index (BMI), or could be a direct role of adipokine in the development of BC. The aim of this study was to identify if there was a difference between serum leptin levels and insulin in obese patients with and without BC.

PATIENTS AND METHODS

A cross-sectional study was made in 156 women, a group of 78 with obesity and BC and 78 with obesity without BC. When subjects agreed to participate, written informed consent was obtained from all subjects. Biochemical variables such as glucose, triglycerides, high-density and low-density lipoprotein, cholesterol, insulin, and leptin were measured and homeostasis model assessment (HOMA-IR) was calculated.

RESULTS

The age, number of parities, glucose, HOMA-IR, and leptin were significantly different at P < .05.

CONCLUSION

Serum leptin levels and leptin/BMI ratio were statistically significantly increased in patients with BC.

Effect of leptin treatment on mitochondrial function in obese leptin-deficient ob/ob mice

OBJECTIVE

Leptin stimulates peripheral lipid oxidation, but the influence on mitochondrial function is partly unknown. We investigated tissue-specific mitochondrial function in leptin-deficient obese C57BL/6J-ob/ob mice compared to lean littermates following leptin treatment.

MATERIALS AND METHODS

Lean and obese ob/ob mice were treated with saline or leptin for 5 days. At day six, liver, extensor digitorum longus (EDL) and soleus muscle were dissected and mitochondrial respiration analyzed in freshly dissected tissues. Expression of key proteins in the regulation of mitochondrial function was determined.

RESULTS

In liver, mitochondrial respiration was reduced in ob/ob mice compared to lean mice. Expression of mitochondrial transcription factor A (TFAM) was decreased in ob/ob mice, but increased with leptin treatment. In glycolytic EDL muscle, mitochondrial respiration was increased in ob/ob mice. Protein markers of complex II, IV and ATP synthase were increased in EDL muscle from both saline- and leptin-treated ob/ob mice. TFAM protein abundance was decreased, while dynamin-1-like protein was increased in EDL muscle from saline-treated ob/ob mice and restored by leptin treatment. In oxidative soleus muscle, mitochondrial respiration and electron transport system protein abundance were unchanged, while TFAM was reduced in ob/ob mice.

CONCLUSIONS

In conclusion, leptin-deficient ob/ob mice display tissue-specific mitochondrial adaptations under basal conditions and in response to leptin treatment. Mitochondrial respiration was decreased in liver, increased in glycolytic muscle and unaltered in oxidative muscle from ob/ob mice. Insight into the tissue-specific regulation of mitochondrial function in response to energy supply and demand may provide new opportunities for the treatment of insulin resistance.

Designer peptide antagonist of the leptin receptor with peripheral antineoplastic activity

The obesity hormone leptin has been implicated in the development and progression of different cancer types, and preclinical studies suggest that targeting leptin signaling could be a new therapeutic option for the treatment of cancer, especially in obese patients. To inhibit pro-neoplastic leptin activity, we developed leptin receptor (ObR) peptide antagonists capable of blocking leptin effects in vitro and in vivo. Our lead compound (Allo-aca), however, crosses the blood-brain-barrier (BBB), inducing undesirable orexigenic effects and consequent weight gain. Thus, redesigning Allo-aca to uncouple its central and peripheral activities should produce a superior compound for cancer treatment. The aim of this study was to generate novel Allo-aca analogs and test their biodistribution in vivo and anti-neoplastic activity in vitro in breast and colorectal cancer cells. Examination of several Allo-aca analogs resulted in the identification of the peptidomimetic, d-Ser, that distributed only in the periphery of experimental animals. d-Ser inhibited leptin-dependent-proliferation of ObR-positive breast and colorectal cancer cells in vitro at 1nM concentration without exhibiting any partial agonistic activity. d-Ser efficacy was demonstrated in monolayer and three-dimensional cultures, and its antiproliferative action was associated with the inhibition of several leptin-induced pathways, including JAK/STAT3, MAPK/ERK1/2 and PI3K/AKT, cyclin D1, and E-cadherin. In conclusion, d-Ser is the first leptin-based peptidomimetic featuring peripheral ObR antagonistic activity. The novel peptide may serve as a prototype to develop new therapeutics, particularly for the management of obesity-related cancers.

Hypomethylation of the LEP gene in placenta and elevated maternal leptin concentration in early onset pre-eclampsia

In pre-eclampsia, placental leptin is up-regulated and leptin is elevated in maternal plasma. To investigate potential epigenetic regulation of the leptin (LEP) gene in normal and complicated pregnancy, DNA methylation was assessed at multiple reported regulatory regions in placentae from control pregnancies (n=111), and those complicated by early onset pre-eclampsia (EOPET; arising <34 weeks; n=19), late onset pre-eclampsia (LOPET; arising ≥34 weeks; n=18) and normotensive intrauterine growth restriction (nIUGR; n=13). The LEP promoter was hypomethylated in EOPET, but not LOPET or nIUGR placentae, particularly at CpG sites downstream of the transcription start site (-10.1%; P<0.0001). Maternal plasma leptin was elevated in EOPET and LOPET (P<0.05), but not nIUGR, compared with controls. EOPET cases showed a trend towards biallelic LEP expression rather than skewed allelic expression observed in control placentae, suggesting that loss of normal monoallelic expression at the LEP locus is associated with hypomethylation, leading to increased overall LEP expression.

Female heterozygous (+/fa) Zucker rats as a novel leptin-related mammary carcinogenesis model

The homozygous mutant fatty Zucker rat (fa/fa) is the prominent model for the research of obesity, one of the most well-known risk factor of postmenopausal mammary cancer. But the usage as a mammary gland carcinogenesis model is considered to be restricted due to the hypoplasia of mammary gland. In the present study, to find the validity of heterozygous mutant (+/fa) lean Zucker rats as a new leptin-related mammary carcinogenesis model, we examined whether the number of terminal end buds of mammary gland, the serum biochemistry, leptin concentration in serum and adipose tissue are changed in 7-week-old female +/+, +/fa and fa/fa rats, and whether these changes and leptin, TNF-α and VEGF mRNA expression in adipose tissue of +/+ and +/fa rats are influenced by 10% corn oil diet for 5 weeks. We confirmed that mild hyperleptinemia was more pronounced in 7-week-old +/fa as compared with wild type (+/+) and hypoplasia of mammary glands characterized by fewer numbers of terminal end buds in fa/fa was not observed in +/fa. With 10% corn oil diet, leptin mRNA expression in adipose tissue showed increasing tendency both in +/fa and +/+. Comparing with +/+, adipose tissue in +/fa treated with 10% corn oil diet was found to be significantly increased in the concentration of leptin protein and tended to be elevated expression of TNF-α mRNA. These results suggest that +/fa with 10% corn oil diet may be a useful model for investigation of the participation of leptin and TNF-α in mammary gland carcinogenesis.

Topical application of capsaicin reduces visceral adipose fat by affecting adipokine levels in high-fat diet-induced obese mice

OBJECTIVE

Visceral obesity contributes to the development of obesity-related disorders such as diabetes, hyperlipidemia, and fatty liver disease, as well as cardiovascular diseases. In this study, we determined whether topical application of capsaicin can reduce fat accumulation in visceral adipose tissues.

METHODS AND RESULTS

We first observed that topical application of 0.075% capsaicin to male mice fed a high-fat diet significantly reduced weight gain and visceral fat. Fat cells were markedly smaller in the mesenteric and epididymal adipose tissues of mice treated with capsaicin cream. The capsaicin treatment also lowered serum levels of fasting glucose, total cholesterol, and triglycerides. Immunoblot analysis and RT-PCR revealed increased expression of adiponectin and other adipokines including peroxisome proliferator-activated receptor (PPAR) α, PPARγ, visfatin, and adipsin, but reduced expression of tumor necrosis factor-α and IL-6.

CONCLUSIONS

These results indicate that topical application of capsaicin to obese mice limits fat accumulation in adipose tissues and may reduce inflammation and increase insulin sensitivity.

Trajectories of agouti-related protein and leptin levels during antipsychotic-associated weight gain in patients with schizophrenia

OBJECTIVE

Some but not all second-generation antipsychotics can induce considerable weight gain and metabolic syndrome. Although the exact biochemical mechanisms for these adverse effects are unclear, appetite-regulating neuropeptides of the central nervous system are thought to be implicated in this process. The hypothalamic mediator Agouti-related protein (AGRP) is inhibited by leptin and was shown to increase food intake. The aim of the present study was to investigate the trajectory of AGRP levels during antipsychotic-induced weight gain.

METHODS

As part of a controlled prospective clinical study, we determined indicators of body fat mass, plasma AGRP, and leptin levels in 16 patients with schizophrenia treated with ziprasidone and 21 patients with schizophrenia treated with olanzapine. Measurements by enzyme-linked immunosorbent assay were obtained before treatment (T0), after 4 weeks (T1), and after 3 months (T2) of treatment.

RESULTS

Whereas body mass index and leptin levels increased in patients treated with olanzapine compared to patients treated with ziprasidone, plasma AGRP levels did not differ among the treatment groups and did not change over time. Associations between AGRP and fat mass as well as appetite were disrupted in the olanzapine-treated patients but not in the ziprasidone group.

CONCLUSION

Future studies are needed to test whether the lack of a decrease in AGRP levels during weight gain in patients treated with olanzapine could perpetuate adverse metabolic long-term effects.

Effects of laparoscopic adjustable gastric banding on sleep and metabolism: a 12-month follow-up study

Background

Obstructive sleep apnea is commonly associated with metabolic changes and obesity, and changes in body weight by either medical or surgical approaches have been considered to affect the severity of sleep apnea and appetite-controlling hormones. This prospective study evaluated the effect of weight loss induced by laparoscopic adjustable gastric banding (LAGB) surgery on respiratory disturbance during sleep, oxygen saturation levels, sleep architecture, and leptin and ghrelin levels.

Methods

Participants were patients at a university-based medical center surgical weight loss program. All participants with a body mass index > 30 kg/m² undergoing LAGB surgery for weight reduction were offered the opportunity to participate in the study. Procedures included overnight polysomnography followed by fasting hormone levels at baseline and 12 months postoperatively.

Results

Thirty subjects (10 men, 20 women) of mean age 44.0 ± 12.5 years were recruited. At 12 months postoperatively, mean excess weight loss was 44.4% ± 14%. The apnea-hypopnea index decreased from 34.2 ± 35 to 19.0 ± 21.7 events per hour (P < 0.0001), while leptin levels decreased from 24.5 ± 17.42 pg/mL to 11.6 ± 10.6 pg/mL (P = 0.02). Ghrelin levels did not change substantially. Nadir oxygen saturation levels increased from 81% to 84% at 12 months (P = 0.03). Mean oxygen saturation improved and was positively correlated with ghrelin levels at both time points (r = 0.39, P = 0.07, and r = 0.60, P = 0.01).

Conclusion

LAGB surgery was associated with 44.4% excess weight loss at 12 months, accompanied by a 33.7% improvement in apnea-hypopnea index as well as a reduction in leptin levels by 31.7% in this group. An association between ghrelin and mean oxygen saturation was seen and deserves further investigation.

Metformin inhibits leptin-induced growth and migration of glioblastoma cells

Metformin, a derivative of biguanide, is a first-line therapy for type 2 diabetes mellitus. Since the drug has been shown to significantly reduce the risk of various cancers and cancer mortality in diabetic patients, it is being considered as a potential anticancer therapeutic or preventive agent. In cellular models, metformin inhibits the growth of many types of cancer cells; however, its effects on glioblastoma multi-forme (GBM) are not well characterized. Here, we analyzed the effects of metformin on the growth and migration of LN18 and LN229 GBM cells cultured under basal conditions or exposed to leptin, a cytokine that has recently been implicated in GBM development. We found that 2-16 mM metformin reduced basal and leptin-stimulated growth of GBM cells in a dose-dependent manner. Furthermore, the drug significantly inhibited the migration of GBM cells. The action of metformin was mediated through the upregulation of its main signaling molecule, the adenosine monophosphate-activated protein kinase (AMPK), as well as through the downregulation of the signal transducer and activator of transcription 3 (STAT3) and the Akt/PKB serine/threonine protein kinase. In leptin-treated cells, the drug reversed the effects of the cytokine on the AMPK and STAT3 pathways, but modulated Akt activity in a cell-dependent manner. Our results suggest that metformin or similar AMPK-targeting agents with optimized blood-brain-barrier penetrability could be developed as potential treatments of GBM and could be used in conjunction with other target drugs such as leptin receptor antagonists.

Plasma leptin concentrations are greater in type II diabetic patients and stimulate monocyte chemotactic peptide-1 synthesis via the mitogen-activated protein kinase/extracellular signal-regulated kinase pathway

Background

Leptin is an adipokine that is recently reported to be a biomarker of systemic inflammation. Although atherosclerosis causes cardiovascular diseases, it is not clear whether leptin contributes to the acceleration of this process. In this study, we investigated whether alterations of plasma leptin levels were related to diabetic nephropathy and systemic inflammation. In addition, we examined the physiologic action of leptin in cultured vascular smooth muscle cells (VSMCs).

Methods

A total of 126 type 2 diabetic participants and 37 healthy controls were studied. The diabetic participants were divided into three groups according to stage of nephropathy. We investigated whether leptin induced monocyte chemotactic peptide-1 (MCP-1) synthesis through the mitogen-activated protein kinase (MAPK) pathway using cultured VSMCs.

Results

Plasma leptin concentrations were significantly higher in the diabetic group than in the controls. Plasma leptin levels were positively correlated with body mass index, fasting and postprandial blood glucose, hemoglobin A1c, total cholesterol, urinary albumin excretion, high-sensitivity C-reactive protein (hsCRP), and MCP-1 plasma levels, and negatively correlated with creatinine clearance values. In cultured VSMCs, leptin increased MCP-1 production in a dose-dependent manner, and this stimulating effect of leptin on MCP-1 expression was reversed by the MAPK (MEK) inhibitor PD98059. In addition, leptin stimulated the phosphorylation of MEK, extracellular signal–regulated kinase, and E26-like transcription factor, which are components of the MAPK pathway.

Conclusions

Overall, these findings suggest that activation of leptin synthesis may promote MCP-1 activation in a diabetic environment via the MAPK pathway in VSMCs and that it possibly contributes to the acceleration of atherosclerosis.

Smoking, but not malnutrition, influences promoter-specific DNA methylation of the proopiomelanocortin gene in patients with and without anorexia nervosa

OBJECTIVE

Our pilot study evaluates the impact of environmental factors, such as nutrition and smoking status, on epigenetic patterns in a disease-associated gene.

METHOD

We measured the effects of malnutrition and cigarette smoking on proopiomelanocortin (POMC) promoter-specific DNA methylation in female patients with and without anorexia nervosa (AN). POMC and its derived peptides (alpha melanocyte stimulating hormone and adrenocorticotropic hormone) are implicated in stress and feeding response. Promoter-specific DNA methylation of the POMC gene was determined in peripheral blood mononuclear cells of 54 healthy female control subjects, 40 underweight patients with AN, and 21 weight-restored patients with AN using bisulfite sequencing. Malnutrition was characterized by plasma leptin.

RESULTS

POMC promoter-specific DNA methylation was not affected by diagnosis or nutritional status but significantly negatively associated with cigarette smoking.

CONCLUSIONS

Although malnutrition may be expected to reduce DNA methylation through its effects on one-carbon metabolism, our negative results are in line with several in vitro and clinical studies that did not show a direct relation between gene-specific DNA methylation and folate levels. In contrast, smoking has been repeatedly reported to alter DNA methylation of specific genes and should be controlled for in future epigenetic studies.

Differential effects of energy balance on experimentally-induced colitis

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

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

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

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

Genetic polymorphisms in adipokine genes and the risk of obesity: a systematic review and meta-analysis

Polymorphisms in adipokine genes, such as leptin (LEP), leptin receptor (LEPR), resistin (RETN), adiponectin (ADIPOQ), interleukin-1β (IL-1β), IL-6 (IL-6), and tumor necrosis factor-α (TNF-α) may be involved in the development of obesity. We conducted a systematic review of published evidence on the association between different adipokine genes and the risk of obesity. Librarian-designed searches of PubMed and HuGeNet, review of reference lists from published reviews and content expert advice identified potentially eligible studies. The genotyping information and polymorphisms of different adipokine genes, numbers of genotyped cases and controls and frequencies of genotypes were extracted from 48 eligible studies included in this review. Twenty-one polymorphisms each associated with obesity in at least one study were identified. Polymorphisms in the adipokine genes, LEP, LEPR, and RETN were not associated with obesity susceptibility, whereas ADIPOQ G276T (T vs. G: odds ratio (OR), 1.59; 95% confidence interval (CI), 1.39-1.81), IL-1β C3953T (CC vs. CT+TT: OR, 1.61; 95% CI, 1.18-2.20), and TNF-α G308A (GG vs. GA+AA: OR, 1.19; 95% CI, 1.02-1.39) polymorphisms were associated with an increased risk of obesity. The IL-6 G174C polymorphism was also associated obesity when using allelic comparisons, the recessive genetic model and the dominant genetic model with OR (95% CI) of 1.95 (1.37-2.77), 1.44 (1.15-1.80), and 1.36 (1.16-1.59), respectively. No significant evidence of publication bias was present. However, these "null" results were underpowered due to a small pooled sample size, and analysis of additional case-control studies with larger sample sizes should provide further clarifications.

The role of leptin in antipsychotic-induced weight gain: genetic and non-genetic factors

Schizophrenia is a chronic and disabling mental illness affecting millions of people worldwide. A greater proportion of people with schizophrenia tends to be overweight. Antipsychotic medications have been considered the primary risk factor for obesity in schizophrenia, although the mechanisms by which they increase weight and produce metabolic disturbances are unclear. Several lines of research indicate that leptin could be a good candidate involved in pathways linking antipsychotic treatment and weight gain. Leptin is a circulating hormone released by adipocytes in response to increased fat deposition to regulate body weight, acting through receptors in the hypothalamus. In this work, we reviewed preclinical, clinical, and genetic data in order to infer the potential role played by leptin in antipsychotic-induced weight gain considering two main hypotheses: (1) leptin is an epiphenomenon of weight gain; (2) leptin is a consequence of antipsychotic-induced "leptin-resistance status," causing weight gain.

Translational implications of inflammatory biomarkers and cytokine networks in psychoneuroimmunology

Developments in psychoneuroimmunology (PNI) need to be translated into personalized medicine to achieve better clinical outcomes. One of the most critical steps in this translational process is to identify systemic biomarkers for better diagnosis and treatment. Applications of systems biology approaches in PNI would enable the insights into the correlations among various systems and different levels for the identification of the basic elements of the psychophysiological framework. Among the potential PNI biomarkers, inflammatory markers deserve special attention as they play a pivotal role linking various health conditions and disorders. The elucidation of inflammatory markers, cytokine networks, and immune-brain-behavior interactions may help establish PNI profiles for the identification of potential targets for personalized interventions in at risk populations. The understanding of the general systemic pathways among different disorders may contribute to the transition from the disease-centered medicine to patient-centered medicine. Integrative strategies targeting these factors and pathways would be useful for the prevention and treatment of a spectrum of diseases that share the common links. Examples of the translational implications of potential PNI biomarkers and networks in diseases including depression, Alzheimer's disease, obesity, cardiovascular disease, stroke, and HIV are discussed in details.

Pharmacogenetics of leptin in antipsychotic-associated weight gain and obesity-related complications

Second-generation antipsychotics can greatly improve symptoms of psychosis-spectrum disorders. Unfortunately, these drugs are associated with weight gain, which increases a patient's risk for developing chronic diseases including Type 2 diabetes, cardiovascular diseases or other obesity-related complications. There are interindividual differences in weight gain resulting from antipsychotic drug use that may be explained by pharmacodynamic characteristics of these agents as well as clinical factors. In addition, genetic variations in pathways associated with satiety are increasingly recognized as potential contributors to antipsychotic-associated weight gain. Polymorphisms in the leptin gene, as well as the leptin receptor gene, are potential pharmacogenetic markers associated with these outcomes. This article summarizes evidence for the associations of the leptin gene and the leptin receptor gene polymorphisms with antipsychotic-induced weight gain, potential mechanisms underlying these relationships, and discusses areas for future pharmacogenetic investigation.

Cognitive flexibility and Agouti-related protein in adolescent patients with anorexia nervosa

INTRODUCTION

Cognitive flexibility and the flexible learning and relearning of stimulus-reward-associations are important for decision-making and goal-directed behavior. Studies on patients with anorexia nervosa (AN) have shown difficulties in cognitive functions associated with malnutrition and extreme underweight. However, to date we find a lack of neuropsychological studies on cognitive flexibility among adolescent patients with AN. Furthermore, the underlying biological mechanisms remain unclear. Therefore, we aim to examine cognitive functions, especially reward association learning, as a measure of cognitive flexibility in adolescent patients with AN and investigate the relationship between Agouti-related protein (AGRP) and cognitive functions.

METHODS

The study population consists of 30 patients with AN (M(age)=16.2 ± 1.2) and a healthy control group (CG) of 28 female adolescents (M(age)=16.3 ± 1.3). All subjects completed a neuropsychological test battery including the probabilistic Object Reversal Task, the Digit Symbol Test and the Trail Making Test. Patients with AN were explored before and after weight gain, the CG initially and after 3 months.

RESULTS

Subtle deficits in cognitive flexibility were found in patients with AN compared to the CG. After weight gain, the AN group improved relative to their baseline values in most of the variables but did not reach CG values. They still showed slight impairments. Moreover the study revealed a clear association between AGRP levels and cognitive flexibility.

DISCUSSION

Cognitive flexibility plays an important role in AN and may be modulated by abnormal levels of the appetite-regulating peptide AGRP. Even subtle impairments in cognitive flexibility can be relevant for the ability to fully engage in therapy and therefore may hinder a prosperous treatment.

Agouti-related protein in patients with acute and weight-restored anorexia nervosa

BACKGROUND

An imbalance in appetite-regulating neuropeptides of the central nervous system has been associated with anorexia nervosa (AN), but the mechanisms of action are poorly understood. Agouti-related protein (AGRP), an orexigenic mediator of the hypothalamus, increases food intake and decreases energy expenditure in times of negative energy balance. The aim of the present study was to investigate AGRP in acute and fully weight-restored patients with AN, as well as during weight gain.

METHOD

Plasma AGRP and leptin levels were assessed using an enzyme-linked immunosorbent assay kit in a total of 175 female participants, including 75 patients with acute AN, 37 weight-restored AN patients and 63 healthy controls. Of the patients with acute AN, 33 were reassessed after partial weight gain.

RESULTS

In weight-restored AN patients plasma AGRP levels were similar to those in healthy controls, whereas in patients with acute AN, AGRP was elevated. AGRP was inversely correlated with indicators of undernutrition such as body mass index and plasma leptin. In addition, AGRP levels normalized during weight gain of longitudinally assessed AN patients.

CONCLUSIONS

Our results underline the significance of undernutrition and hypoleptinemia for the interpretation of peripheral AGRP concentrations. This provides support for the hypothesis that abnormal AGRP plasma levels in AN patients reflect undernutrition, rather than disease-specific traits.

Glioblastoma-derived leptin induces tube formation and growth of endothelial cells: comparison with VEGF effects

BACKGROUND

Leptin is a pleiotropic hormone whose mitogenic and angiogenic activity has been implicated in the development and progression of several malignancies, including brain tumors. In human brain cancer, especially in glioblastoma multiforme (GBM), leptin and its receptor (ObR) are overexpressed relative to normal tissue. Until present, the potential of intratumoral leptin to exert proangiogenic effects on endothelial cells has not been addressed. Using in vitro models, we investigated if GBM can express leptin, if leptin can affect angiogenic and mitogenic potential of endothelial cells, and if its action can be inhibited with specific ObR antagonists. Leptin effects were compared with that induced by the best-characterized angiogenic regulator, VEGF.

RESULTS

We found that GBM cell lines LN18 and LN229 express leptin mRNA and LN18 cells secrete detectable amounts of leptin protein. Both lines also expressed and secreted VEGF. The conditioned medium (CM) of LN18 and LN 229 cultures as well as 200 ng/mL pure leptin or 50 ng/mL pure VEGF stimulated proliferation of human umbilical vein endothelial cells (HUVEC) at 24 h of treatment. Mitogenic effects of CM were ~2-fold greater than that of pure growth factors. Furthermore, CM treatment of HUVEC for 24 h increased tube formation by ~5.5-fold, while leptin increased tube formation by ~ 80% and VEGF by ~60% at 8 h. The mitogenic and angiogenic effects of both CM were blocked by Aca 1, a peptide ObR antagonist, and by SU1498, which inhibits the VEGF receptor. The best anti-angiogenic and cytostatic effects of Aca1 were obtained with 10 nM and 25 nM, respectively, while for SU1498, the best growth and angiogenic inhibition was observed at 5 μM. The combination of 5 μM SU1498 and Aca1 at 25 nM (growth inhibition) or at 10 nM (reduction of tube formation) produced superior effects compared with single agent treatments.

CONCLUSIONS

Our data provide the first evidence that LN18 and LN 229 human GBM cells express leptin mRNA and might produce biologically active leptin, which can stimulate tube formation and enhance proliferation of endothelial cells. Furthermore, we demonstrate for the first time that a peptide ObR antagonist inhibits proangiogenic and growth effects of leptin on endothelial cells, and that the pharmacological potential of this compound might be combined with drugs targeting the VEGF pathway.

Is sprint exercise a leptin signaling mimetic in human skeletal muscle?

This study was designed to determine whether sprint exercise activates signaling cascades linked to leptin actions in human skeletal muscle and how this pattern of activation may be interfered by glucose ingestion. Muscle biopsies were obtained in 15 young healthy men in response to a 30-s sprint exercise (Wingate test) randomly distributed into two groups: the fasting (n = 7, C) and the glucose group (n = 8, G), who ingested 75 g of glucose 1 h before the Wingate test. Exercise elicited different patterns of JAK2, STAT3, STAT5, ERK1/2, p38 MAPK phosphorylation, and SOCS3 protein expression during the recovery period after glucose ingestion. Thirty minutes after the control sprint, STAT3 and ERK1/2 phosphorylation levels were augmented (both, P < 0.05). SOCS3 protein expression was increased 120 min after the control sprint but PTP1B protein expression was unaffected. Thirty and 120 min after the control sprint, STAT5 phosphorylation was augmented (P < 0.05). Glucose abolished the 30 min STAT3 and ERK1/2 phosphorylation and the 120 min SOCS3 protein expression increase while retarding the STAT5 phosphorylation response to sprint. Activation of these signaling cascades occurred despite a reduction of circulating leptin concentration after the sprint. Basal JAK2 and p38 MAPK phosphorylation levels were reduced and increased (both P < 0.05), respectively, by glucose ingestion prior to exercise. During recovery, JAK2 phosphorylation was unchanged and p38 MAPK phosphorylation was transiently reduced when the exercise was preceded by glucose ingestion. In conclusion, sprint exercise performed under fasting conditions is a leptin signaling mimetic in human skeletal muscle.

Functional variability in corticosteroid receptors is a major component of strain differences in fat deposition and metabolic consequences of enriched diets in rat

We aimed to distinguish mineralocorticoid (MR) from glucocorticoid receptor (GR) actions in the nutritional differences between the Fischer 344 (F344) and LOU/C (LOU) rat strains. The decrease of urinary Na+/K+ ratio induced via MR activation by aldosterone and decrease of circulating lymphocyte counts exerted via GR activation by dexamethasone revealed a higher efficiency of corticosteroid receptor in LOU than in F344 rats. Afterward, we submitted F344 and LOU male rats to adrenalectomy and to substitution treatments with agonists of MR or GR under 3 successive diets--standard, free choice between chow and pork lard, and an imposed high-fat/high-sugar diet--to explore the involvement of the interactions between activation of corticosteroid receptors and diet on food intake, body composition, and metabolic blood parameters in these rats. Lastly, we measured energy expenditure and substrate oxidization in various experimental conditions in LOU and F344 rats by indirect calorimetry. In LOU rats, we showed greater basal and MR-induced energy expenditure, diet-induced thermogenesis, and lipid oxidization. We showed that the F344 rat strain constitutes a relevant model of the unfavorable effects exerted by glucocorticoids via GR on food preference for high-calorie diets, abdominal fat deposition, diabetes, and other deleterious consequences of visceral obesity. Contrary to F344 rats, the LOU rats did not exhibit the expected visceral fat deposition linked to GR activation. This strain is therefore a relevant model of resistance to diet-induced obesity and to the deleterious effects exerted by glucocorticoids on metabolism.

The effect of H. pylori eradication on meal-associated changes in plasma ghrelin and leptin

Background

Appetite and energy expenditure are regulated in part by ghrelin and leptin produced in the gastric mucosa, which may be modified by H. pylori colonization. We prospectively evaluated the effect of H. pylori eradication on meal-associated changes in serum ghrelin and leptin levels, and body weight.

Methods

Veterans referred for upper GI endoscopy were evaluated at baseline and ≥8 weeks after endoscopy, and H. pylori status and body weight were ascertained. During the first visit in all subjects, and during subsequent visits in the initially H. pylori-positive subjects and controls, blood was collected after an overnight fast and 1 h after a standard high protein meal, and levels of eight hormones determined.

Results

Of 92 enrolled subjects, 38 were H. pylori-negative, 44 H. pylori-positive, and 10 were indeterminate. Among 23 H. pylori-positive subjects who completed evaluation after treatment, 21 were eradicated, and 2 failed eradication. After a median of seven months following eradication, six hormones related to energy homeostasis showed no significant differences, but post-prandial acylated ghrelin levels were nearly six-fold higher than pre-eradication (p = 0.005), and median integrated leptin levels also increased (20%) significantly (p < 0.001). BMI significantly increased (5 ± 2%; p = 0.008) over 18 months in the initially H. pylori-positive individuals, but was not significantly changed in those who were H. pylori-negative or indeterminant at baseline.

Conclusions

Circulating meal-associated leptin and ghrelin levels and BMI changed significantly after H. pylori eradication, providing direct evidence that H. pylori colonization is involved in ghrelin and leptin regulation, with consequent effects on body morphometry.

Developmental programming of energy balance and its hypothalamic regulation

Developmental programming is an important physiological process that allows different phenotypes to originate from a single genotype. Through plasticity in early life, the developing organism can adopt a phenotype (within the limits of its genetic background) that is best suited to its expected environment. In humans, together with the relative irreversibility of the phenomenon, the low predictive value of the fetal environment for later conditions in affluent countries makes it a potential contributor to the obesity epidemic of recent decades. Here, we review the current evidence for developmental programming of energy balance. For a proper understanding of the subject, knowledge about energy balance is indispensable. Therefore, we first present an overview of the major hypothalamic routes through which energy balance is regulated and their ontogeny. With this background, we then turn to the available evidence for programming of energy balance by the early nutritional environment, in both man and rodent models. A wealth of studies suggest that energy balance can indeed be permanently affected by the early-life environment. However, the direction of the effects of programming appears to vary considerably, both between and within different animal models. Because of these inconsistencies, a comprehensive picture is still elusive. More standardization between studies seems essential to reach veritable conclusions about the role of developmental programming in adult energy balance and obesity.

Strategies for reducing body fat mass: effects of liposuction and exercise on cardiovascular risk factors and adiposity

Liposuction is the most popular aesthetic surgery performed in Brazil and worldwide. Evidence showing that adipose tissue is a metabolically active tissue has led to the suggestion that liposuction could be a viable method for improving metabolic profile through the immediate loss of adipose tissue. However, the immediate liposuction-induced increase in the proportion of visceral to subcutaneous adipose tissue could be detrimental to metabolism, because a high proportion of visceral to subcutaneous adipose tissue is associated with risk factors for cardiovascular disease. The results of studies investigating the effects of liposuction on the metabolic profile are inconsistent, however, with most studies reporting either no change or improvements in one or more cardiovascular risk factors. In addition, animal studies have demonstrated a compensatory growth of intact adipose tissue in response to lipectomy, although studies with humans have reported inconsistent results. Exercise training improves insulin sensitivity, inflammatory balance, lipid oxidation, and adipose tissue distribution; increases or preserves the fat-free mass; and increases total energy expenditure. Thus, liposuction and exercise appear to directly affect metabolism in similar ways, which suggests a possible interaction between these two strategies. To our knowledge, no studies have reported the associated effects of liposuction and exercise in humans. Nonetheless, one could suggest that exercise training associated with liposuction could attenuate or even block the possible compensatory fat deposition in intact depots or regrowth of the fat mass and exert an additive or even a synergistic effect to liposuction on improving insulin sensitivity and the inflammatory balance, resulting in an improvement of cardiovascular risk factors. Consequently, one could suggest that liposuction and exercise appear to be safe and effective strategies for either the treatment of metabolic disorders or aesthetic purposes.