The balance between leptin and adiponectin in the control of carcinogenesis - focus on mammary tumorigenesis. Biochimie. 2012;94:2164-2171. [PMID: 22728769 DOI: 10.1016/j.biochi.2012.06.013]

WISER Survivor Trial: Combined Effect of Exercise and Weight Loss Interventions on Adiponectin and Leptin Levels in Breast Cancer Survivors with Overweight or Obesity

Adipocyte dysregulation is one mechanism linking overweight and breast cancer recurrence. Exercise and weight loss are associated with a decreased risk of breast cancer recurrence in breast cancer survivors with overweight or obesity, which may be mediated through reduced leptin levels, increased adiponectin levels, and an elevated adiponectin to leptin (A:L) ratio. The four-arm randomized controlled WISER Survivor trial examined the 12-month intervention effects of exercise, weight loss, and the combination of exercise and weight loss on adipokine levels among breast cancer survivors (n = 339) with overweight or obesity. Compared with Control, the Combination of Exercise and Weight Loss decreased leptin levels (-35.9%; 95% CI: -46.8%, -25.0%) and increased A:L ratio (11.6%; 95% CI: 5.6%, 17.6%) but did not change adiponectin levels (4.1%; 95% CI: -3.1%, 11.2%). Compared with Control, Weight Loss Alone decreased leptin levels (-35.6%; 95% CI: -46.6%, -24.5%) and increased A:L ratio (10.6%; 95% CI: 4.7%, 16.5%) but did not change adiponectin levels (0.9%; 95% CI: -6.0%, 7.9%). Compared with Control, Exercise Alone did not change leptin levels, adiponectin levels, or A:L ratio. In analyses that consolidated intervention groups, compared with Control, weight loss of ≥5% decreased leptin levels (p trend < 0.01) and increased A:L ratio (p trend < 0.01) but did not alter adiponectin levels (p trend = 0.53). Weight loss, with or without exercise, was associated with decreased leptin levels in breast cancer survivors with overweight or obesity. Improvements in the adipokine secretion profile (A:L ratio) were primarily driven by a weight loss-induced change in leptin levels.

Assessment of the Role of Leptin and Adiponectinas Biomarkers in Pancreatic Neuroendocrine Neoplasms

Data on the possible connection between circulating adipokines and PanNENs are limited. This novel study aimed to assess the serum levels of leptin and adiponectin and their ratio in patients with PanNENs and to evaluate the possible relationship between them and PanNEN's grade or stage, including the presence of metastases. The study group consisted of PanNENs (n = 83), and healthy controls (n = 39). Leptin and adiponectin measurement by an ELISA assay was undertaken in the entire cohort. The serum concentration of adiponectin was significantly higher in the control group compared to the study group (p < 0.001). The concentration of leptin and adiponectin was significantly higher in females than in males (p < 0.01). Anincreased leptin-adiponectin ratio was observed in well-differentiated PanNENs (G1) vs. moderatelydifferentiated PanNENs (G2) (p < 0.05). An increased leptin-adiponectin ratio was found in PanNENs with Ki-67 < 3% vs. Ki-67 ≥ 3% (p < 0.05). PanNENs with distal disease presented lower leptin levels (p < 0.001) and a decreased leptin-adiponectin ratio (p < 0.01) compared with the localized disease group. Leptin, adiponectin, and the leptin-adiponectin ratio may serve as potential diagnostic, prognostic, and predictive biomarkers for PanNENs. Leptin levels and the leptin-adiponectin ratio may play an important role as predictors of malignancy and metastasis in PanNENs.

Genetic alterations in LEP and ADIPOQ genes and risk for breast cancer: a meta-analysis

Introduction

Breast cancer has a strong genetic predisposition, and its genetic architecture is not fully understood thus far. In this study, we aimed to perform a meta-analysis to evaluate the association of genetic alterations in LEP and ADIPOQ genes, as well as their receptor-encoded genes with risk for breast cancer.

Methods

Only published studies conducted in humans and written in English were identified by searching PubMed, SCOPUS, CINAHIL and Embase from their inception to October 2022. Eligibility assessment and data collection were completed independently by two researchers. Statistical analyses were done using the STATA software.

Results

After literature search, 33 publications were eligible for inclusion. Overall, LEP gene rs7799039-G allele (odds ratio [OR]: 0.78, 95% confidence interval [CI]: 0.62 to 0.98) and ADIPOQ gene rs1501299-T allele (OR: 1.41, 95% CI: 1.06 to 1.88) were associated with the significant risk of breast cancer. In subgroup analyses, differences in menopausal status, obesity, race, study design, diagnosis of breast cancer, genotyping method and sample size might account for the divergent observations of individual studies. Circulating leptin levels were comparable across genotypes of LEP gene rs7799039, as well as that of LEPR gene rs1137101 (P>0.05). Begg's funnel plots seemed symmetrical, with the exception of LEPR gene rs1137100 and ADIPOQ gene rs1501299.

Discussion

Taken together, we found, in this meta-analysis, that LEP gene rs7799039 and ADIPOQ gene rs1501299 were two promising candidate loci in predisposition to breast cancer risk.

The altered levels of adiponectin - leptin as predictive biomarkers to estimate the severity of prostate cancer

Introduction and Aim: Prostate is one of the commonest sites of malignancy affecting elderly male population & is increasingly becoming a significant public health issue especially in countries having aging population. We hypothesized that altered levels of adiponectin-leptins may be an underlying connection between incidence of prostate cancer (PCa) and aged matched males.   Materials and Methods: This study was designed to comparatively corelate circulating serum levels of adiponectin & leptin in 160 elderly patients with PCa to their serum levels in 160 healthy controls. The age and body mass index in all groups were dissimilar in case and control. Based on the Gleason score of 7, =7 >7, patients were further subdivided into low, intermediate, high grades of PCa, respectively.    Results: No significant statistical variance was identified in terms of age, Body mass index (BMI), Radom blood glucose, HDL, LDL, triglycerides, total cholesterol, creatinine, and BUN levels within the compared groups. In PCa patients’ group, concentration levels of serum adiponectin were significantly lower, and levels of serum leptin was significantly greater compared to healthy controls (P<0.001). Statistical analysis revealed a significant positive inverse association between PSA and adiponectin levels (r=0.285, P<0.001) and significant association between serum levels of PSA and leptin (r=0.285, P<0.001). Significant statistical correlation was also evident between BMI, PSA, TG, and leptin were whole group. However, there was no significant association observed between adiponectin or leptin level and grade of the disease.   Conclusion: Evaluation of data in our study suggests that patients of PCa exhibit low concentration of serum adiponectin levels and high concentration of leptin levels. Further, this association was independent of histological grading of disease of disease/disease progression as well as other biochemical parameters.

A new finding for the obesity paradox? Evaluation of the relationship between muscle and adipose tissue in nuclear grade prediction in patients with clear cell renal cell carcinoma

Background

Obesity is associated with an increased risk of developing clear cell renal cell carcinoma (ccRCC), but paradoxically there is a positive association between obesity and surveillance.

Purpose

To investigate the relationship between nucleus grade classification and body composition in patients with matched co-morbid conditions with non-metastatic ccRCC.

Materials and Methods

A total of 253 patients with non-metastatic ccRCC were included in the study. Body composition was assessed with abdominal computed tomography (CT) using an automated artificial intelligence software. Both adipose and muscle tissue parameters of the patients were calculated. In order to investigate the net effect of body composition, propensity score matching (PSM) procedure was applied over age, sex, and T stage parameters. In this way, selection bias and imbalance between groups were minimized. Univariate and multivariate logistic regression analyses were performed to identify the association between body composition and WHO/ISUP grade (I–IV).

Result

When the body composition of the patients was examined without matching the conditions, it was found that the subcutaneous adipose tissue (SAT) values were higher in patients with low grades ( P = 0.001). Normal attenuation muscle area (NAMA) was higher in high-grade patients than low-grade patients ( P < 0.05). In the post-matching evaluation, only SAT/NAMA was found to be associated with high-grade ccRCC (univariate analysis: odds ratio [OR]=0.899, 95% confidence interval [CI]=0.817−0.988, P = 0.028; multivariate analysis: OR=0.922, 95% CI=0.901−0.974, P = 0.042).

Conclusion

CT-based body composition parameters can be used as a prognostic marker in predicting nuclear grade when age, sex, and T stage match conditions. This finding offers a new perspective on the obesity paradox.

Neuroendocrine Tumors: A Comprehensive Review on Nutritional Approaches

Neuroendocrine neoplasms are a heterogeneous group of neoplasms with increasing incidence, high prevalence, and survival worldwide. About 90% of cases are well differentiated forms, the so-called neuroendocrine tumors (NETs), with slow proliferation rates and prolonged survival but frequent development of liver metastases and endocrine syndromes. Both the tumor itself and systemic therapy may have an impact on patient nutrition. Malnutrition has a negative impact on outcome in patients with NETs, as well as obesity. In addition, obesity and metabolic syndrome have been shown to be risk factors for both the development and prognosis of NET. Therefore, dietary assessment based on body composition and lifestyle modifications should be an integral part of the treatment of NET patients. Nutrition plans, properly formulated by a dietician, are an integral part of the multidisciplinary treatment team for patients with NETs because they allow an improvement in quality of life, providing a tailored approach based on nutritional needs and nutritional manageable signs and/or symptoms related to pharmacological treatment. The aim of this review is to condense the latest evidence on the role of the most used dietary models, the Mediterranean diet, the ketogenic diet, and intermittent fasting, in the context of NETs, while considering the clinical and molecular mechanisms by which these dietary models act.

Obesity and Breast Cancer Risk: The Oncogenic Implications of Metabolic Dysregulation

CONTEXT

Breast cancer is increasing in prevalence in parallel with rising rates of obesity worldwide. Obesity is recognized as a leading modifiable risk factor for the development of breast cancer; however, this association varies considerably by clinicopathologic features, and the underlying mechanisms are complex.

EVIDENCE ACQUISITION

Pubmed literature search using combinations of "obesity," "breast cancer risk," "diet," "exercise," "weight gain," "weight loss," "adipose tissue inflammation," "crown-like structure," "immune markers," "metformin," "gliflozins," "SGLT-2i," "GLP1-RA," and related terms.

EVIDENCE SYNTHESIS

Elevated body mass index and weight gain are associated with increased risk of postmenopausal, hormone receptor-positive breast cancer. Emerging evidence suggests that adverse measures of body composition in individuals of any weight can also confer increased breast cancer risk. Mechanistically, various factors including altered adipokine balance, dysfunctional adipose tissue, dysregulated insulin signaling, and chronic inflammation contribute to tumorigenesis. Weight loss and more specifically fat mass loss through lifestyle and pharmacologic interventions improve serum metabolic and inflammatory markers, sex hormone levels, and measures of breast density, suggesting a link to decreased breast cancer risk.

CONCLUSION

Incorporating markers of metabolic health and body composition measures with body mass index can capture breast cancer risk more comprehensively. Further studies of interventions targeting body fat levels are needed to curb the growing prevalence of obesity-related cancer.

Renal Cell Cancer and Obesity

Cancers are a frequent cause of morbidity and mortality. There are many risk factors for tumours, including advanced age, personal or family history of cancer, some types of viral infections, exposure to radiation and some chemicals, smoking and alcohol consumption, as well as obesity. Increasing evidence suggest the role of obesity in the initiation and progression of various cancers, including renal cell carcinoma. Since tumours require energy for their uncontrollable growth, it appears plausible that their initiation and development is associated with the dysregulation of cells metabolism. Thus, any state characterised by an intake of excessive energy and nutrients may favour the development of various cancers. There are many factors that promote the development of renal cell carcinoma, including hypoxia, inflammation, insulin resistance, excessive adipose tissue and adipokines and others. There are also many obesity-related alterations in genes expression, including DNA methylation, single nucleotide polymorphisms, histone modification and miRNAs that can promote renal carcinogenesis. This review focuses on the impact of obesity on the risk of renal cancers development, their aggressiveness and patients’ survival.

Intermittent fasting in the prevention and treatment of cancer

Chronic caloric restriction (CR) has powerful anticarcinogenic actions in both preclinical and clinical studies but may be difficult to sustain. As an alternative to CR, there has been growing interest in intermittent fasting (IF) in both the scientific and lay community as a result of promising study results, mainly in experimental animal models. According to a survey by the International Food Information Council Foundation, IF has become the most popular diet in the last year, and patients with cancer are seeking advice from oncologists about its beneficial effects for cancer prevention and treatment. However, as discussed in this review, results from IF studies in rodents are controversial and suggest potential detrimental effects in certain oncologic conditions. The effects of IF on human cancer incidence and prognosis remain unknown because of a lack of high-quality randomized clinical trials. Preliminary studies suggest that prolonged fasting in some patients who have cancer is safe and potentially capable of decreasing chemotherapy-related toxicity and tumor growth. However, because additional trials are needed to elucidate the risks and benefits of fasting for patients with cancer, the authors would not currently recommend patients undergoing active cancer treatment partake in IF outside the context of a clinical trial. IF may be considered in adults seeking cancer-prevention benefits through means of weight management, but whether IF itself affects cancer-related metabolic and molecular pathways remains unanswered.

Rapid Escalation of High-Volume Exercise during Caloric Restriction; Change in Visceral Adipose Tissue and Adipocytokines in Obese Sedentary Breast Cancer Survivors

Simple Summary

Aerobic exercise reduces risk for developing breast cancer or for breast cancer recurrence. In obese women exercise can significantly augment the effects of caloric restriction on visceral fat, reducing metabolic abnormalities and cancer. Women who are older, obese, and sedentary, especially those who have been treated for breast cancer, find it difficult to initiate and achieve the minimum or optimum levels of exercise. In a two-part pilot we found that by providing older, obese, sedentary breast cancer survivors 12 weeks of twice weekly personal training sessions, they could safely increase exercise to ≥200 min/week by 9 weeks during caloric restriction. At 24 weeks, high levels of exercise were still observed with continued behavioral support and study-provided exercise facility. Substantial improvement in visceral fat and breast cancer risk biomarkers were observed with this affordable intervention that is readily exportable to the community.

Abstract

Aerobic exercise reduces risk for breast cancer and recurrence and promotes visceral adipose tissue (VAT) loss in obesity. However, few breast cancer survivors achieve recommended levels of moderate to vigorous physical activity (MVPA) without supervision. In a two-cohort study, feasibility of 12 weeks of partially supervised exercise was started concomitantly with caloric restriction and effects on body composition and systemic risk biomarkers were explored. In total, 22 obese postmenopausal sedentary women (including 18 breast cancer survivors) with median age of 60 and BMI of 37 kg/m² were enrolled. Using personal trainers twice weekly at area YMCAs, MVPA was escalated to ≥200 min/week over 9 weeks. For cohort 2, maintenance of effect was assessed when study provided trainer services were stopped but monitoring, group counseling sessions, and access to the exercise facility were continued. Median post-escalation MVPA was 219 min/week with median 12-week mass and VAT loss of 8 and 19%. MVPA was associated with VAT loss which was associated with improved adiponectin:leptin ratio. In total, 9/11 of cohort-2 women continued the behavioral intervention for another 12 weeks without trainers. High MVPA continued with median 24-week mass and VAT loss of 12 and 29%. This intervention should be further studied in obese sedentary women.

Leptin, Both Bad and Good Actor in Cancer

Leptin is an important regulator of basal metabolism and food intake, with a pivotal role in obesity. Leptin exerts many different actions on various tissues and systems, including cancer, and is considered as a linkage between metabolism and the immune system. During the last decades, obesity and leptin have been associated with the initiation, proliferation and progression of many types of cancer. Obesity is also linked with complications and mortality, irrespective of the therapy used, affecting clinical outcomes. However, some evidence has suggested its beneficial role, called the "obesity paradox", and the possible antitumoral role of leptin. Recent data regarding the immunotherapy of cancer have revealed that overweight leads to a more effective response and leptin may probably be involved in this beneficial process. Since leptin is a positive modulator of both the innate and the adaptive immune system, it may contribute to the increased immune response stimulated by immunotherapy in cancer patients and may be proposed as a good actor in cancer. Our purpose is to review this dual role of leptin in cancer, as well as trying to clarify the future perspectives of this adipokine, which further highlights its importance as a cornerstone of the immunometabolism in oncology.

Fatty Acids and Membrane Lipidomics in Oncology: A Cross-Road of Nutritional, Signaling and Metabolic Pathways

Fatty acids are closely involved in lipid synthesis and metabolism in cancer. Their amount and composition are dependent on dietary supply and tumor microenviroment. Research in this subject highlighted the crucial event of membrane formation, which is regulated by the fatty acids' molecular properties. The growing understanding of the pathways that create the fatty acid pool needed for cell replication is the result of lipidomics studies, also envisaging novel fatty acid biosynthesis and fatty acid-mediated signaling. Fatty acid-driven mechanisms and biological effects in cancer onset, growth and metastasis have been elucidated, recognizing the importance of polyunsaturated molecules and the balance between omega-6 and omega-3 families. Saturated and monounsaturated fatty acids are biomarkers in several types of cancer, and their characterization in cell membranes and exosomes is under development for diagnostic purposes. Desaturase enzymatic activity with unprecedented de novo polyunsaturated fatty acid (PUFA) synthesis is considered the recent breakthrough in this scenario. Together with the link between obesity and cancer, fatty acids open interesting perspectives for biomarker discovery and nutritional strategies to control cancer, also in combination with therapies. All these subjects are described using an integrated approach taking into account biochemical, biological and analytical aspects, delineating innovations in cancer prevention, diagnostics and treatments.

Biological Support to Obesity Paradox in Renal Cell Carcinoma: A Review

Obesity is a proven risk factor and a debated prognostic factor in renal cell carcinoma (RCC). Termed as an "obesity paradox," the topic has churned controversies, with a few arguing of no true biological association. Suggesting otherwise, a few studies revealed adiposity-induced altered molecular and transcriptomic signatures, at both the systemic and local (tumor and peritumoral adipose tissue) levels, in RCC patients, favoring the paradox. Summarizing such studies suggests of a considerable biological support to adiposity as a promising prognostic factor in RCC patients, although much needs to be clarified before adopting it as a valuable addition to the existing prognostic model.

Hyperinsulinemia and Hypoadiponectinemia are Associated with Increased Risk for Occurrence of Ovarian Cancer in Non-diabetic Women of North Indian Population

Ovarian cancer has been emerged as a most common and lethal gynecological malignancy in India. High serum insulin and low adiponectin have been associated with increased risk of ovarian cancer. But their role in development of ovarian cancer is conflicting and little evidence is available. We aimed to evaluate blood levels of insulin and adiponectin in epithelial ovarian cancer (EOC) patients and their association with the risk to develop EOC. The study included following three groups; Group 1: fifty cases of cytohistopathologically confirmed cases of EOC, Group 2: fifty age matched cases of benign ovarian conditions and Group 3: fifty ages matched healthy controls with no evidence of any benign or malignant ovarian pathology as ruled out by clinical examination and relevant investigations. Cytohistopathologically confirmed and newly diagnosed cases of EOC and benign ovarian cancer were included in this study. The median value of fasting serum insulin was significantly high (15.0 µlU/ml, P = 0.02) and adiponectin were significantly low (5.1 µg/ml, P < 0.001) in ovarian cancer patients compared to benign ovarian tumors and healthy controls group. A significant increase risk of ovarian cancer was found in high tertile (≥ 18.7 µlU/ml) of serum insulin level (OR = 2.7; 95% CI = 1.00-6.67, P = 0.04) and lower tertile (≤ 5.45 µg/ml) of adiponectin level (OR = 3.2; 95% CI = 1.10-9.71, P = 0.03). High serum insulin level and low adiponectin levels were significantly associated with increased risk for development of ovarian cancer.

Genetic and epigenetic modifications of adiponectin gene: Potential association with breast cancer risk

BACKGROUND

Adipokines produced by adipose tissue are directly linked to obesity and may contribute to the pathogenesis of cancer. We hypothesized that genetic and epigenetic modifications in the adiponectin (ADIPOQ) gene and their impact on serum ADIPOQ levels may participate in increasing breast cancer (BC) risk. The present study aimed to investigate ADIPOQ +45 T/G gene polymorphism, methylation status at CpG sites -74 nucleotides (nt) and -283 nt of the ADIPOQ gene, and ADIPOQ serum levels in BC obese women.

METHODS

Serum ADIPOQ was measured by an enzyme-linked immunosorbent assay. ADIPOQ +45 T/G gene polymorphism and ADIPOQ promoter methylation status were determined using a polymerase chain reaction (PCR) and a methylation-specific PCR, respectively, in 120 obese women with BC and 120 age-matched controls.

RESULTS

ADIPOQ +45 GG genotype carriers had a significant increased risk of developing BC (odds ratio = 6.2, 95% confidence interval = 1.3-29.6, p = 0.02). ADIPOQ gene methylation at site -74 nt resulted in a 1.7-fold increased BC risk. Methylation at site -283 nt resulted in a 1.9-fold increased BC risk. Moreover serum levels of ADIPOQ were significantly decreased in BC patients and down-regulated in the presence of methylation in both examined sites. By contrast, no association between ADIPOQ gene polymorphism and serum ADIPOQ level was detected. Using both methylated sites in one panel detected cancer breast with 76.67% sensitivity and 62.18% accuracy.

CONCLUSIONS

ADIPOQ +45 T/G polymorphism and ADIPOQ promoter methylation were found to be associated with BC risk in obese Egyptian women.

Obesity and Breast Cancer: Role of Leptin

Obesity-related breast cancer is an important threat that affects especially post-menopausal women. The link between obesity and breast cancer seems to be relying on the microenvironment generated at adipose tissue level, which includes inflammatory cytokines. In addition, its association with systemic endocrine changes, including hyperinsulinemia, increased estrogens levels, and hyperleptinemia may be key factors for tumor development. These factors may promote tumor initiation, tumor primary growth, tissue invasion, and metastatic progression. Although the relationship between obesity and breast cancer is already established, the different pathophysiological mechanisms involved are not clear. Obesity-related insulin resistance is a well-known risk factor for breast cancer development in post-menopausal women. However, the role of inflammation and other adipokines, especially leptin, is less studied. Leptin, like insulin, appears to be a growth factor for breast cancer cells. There exists a link between leptin and metabolism of estrogens and between leptin and other factors in a more complex network. As a result, obesity-associated hyperleptinemia has been suggested as an important mediator in the pathophysiology of breast cancer. On the other hand, recent data on the paradoxical effect of obesity on cancer immunotherapy efficacy has brought some controversy, since the proinflammatory effect of leptin may help the effect of immune checkpoint inhibitors. Therefore, a better knowledge of the molecular mechanisms that mediate leptin action may be helpful to understand the underlying processes which link obesity to breast cancer in post-menopausal women, as well as the possible role of leptin in the response to immunotherapy in obese patients.

Do estrogens regulate lipid status in testicular steroidogenic Leydig cell?

In this study mouse Leydig cell (MA-10) were treated with G-protein coupled membrane estrogen receptor antagonist (G-15; 10 nM). Cells were analyzed by Western blotting for expression of estrogen-related receptors (ERRα, β and γ), steroidogenic markers (lutropin receptor; LHR and 3β-hydroxysteroid dehydrogenase; 3β-HSD) and lipid droplet markers (perilipin; PLIN and microtubule-associated protein 1 A/1B-light chain 3; LC3). Concomitantly, microscopic analyses by light microscope (immunofluorescent staining for lipid droplets, PLIN and LC3) as well as by electron microscope (for lipid droplet ultrastructure) were utilized. For analysis of cholesterol content, cAMP level and progesterone secretion, G-15, estrogen receptor (ER) antagonist (ICI 182,780; 10 μM), 17β-estradiol (10 mM) and, bisphenol A (BPA; 10 nM) were used alone or in combinations. We revealed no changes in ERRs expression but alterations in ERRβ and γ localization in G-15-treated cells when compared to control. Partial translocation of ERRβ and γ from the cell nucleus to cytoplasm was observed. Decreased expression of LHR, 3β-HSD, PLIN and LC3 was detected. Moreover, in treated cells large lipid droplets and differences in their distribution were found. Very strong signal of co-localization for PLIN and LC3 was found in treated cells when compared to control. In ultrastructure of treated cells, degenerating lipid droplets and double membrane indicating on presence of lipophagosome were observed. We found, that only (i) BPA and G-15 did not effect on cholesterol content, (ii) BPA, G-15 and ICI did not effect on cAMP level and (iii) BPA, ICI alone and in combination, and BPA with G-15 did not modulate progesterone secretion. These findings showed complex and diverse estrogen effects on mouse Leydig cells at various steps of steroid hormone production (cholesterol storage, release and processing). Lipid homeostasis and metabolism in these cells were affected by endogenous and exogenous estrogen, interactions of receptors (GPER, ER and ERR) and GPER and ER antagonists.

Elevated leptin disrupts epithelial polarity and promotes premalignant alterations in the mammary gland

Obesity is a highly prevalent and modifiable breast cancer risk factor. While the role of obesity in fueling breast cancer progression is well established, the mechanisms linking obesity to breast cancer initiation are poorly understood. A hallmark of breast cancer initiation is the disruption of apical polarity in mammary glands. Here we show that mice with diet-induced obesity display mislocalization of Par3, a regulator of cellular junctional complexes defining mammary epithelial polarity. We found that epithelial polarity loss also occurs in a 3D coculture system that combines acini with human mammary adipose tissue, and establish that a paracrine effect of the tissue adipokine leptin causes loss of polarity by overactivation of the PI3K/Akt pathway. Leptin sensitizes non-neoplastic cells to proliferative stimuli, causes mitotic spindle misalignment, and expands the pool of cells with stem/progenitor characteristics, which are early steps for cancer initiation. We also found that normal breast tissue samples with high leptin/adiponectin transcript ratio characteristic of obesity have an altered distribution of apical polarity markers. This effect is associated with increased epithelial cell layers. Our results provide a molecular basis for early alterations in epithelial architecture during obesity-mediated cancer initiation.

LEP rs7799039, LEPR rs1137101, and ADIPOQ rs2241766 and 1501299 Polymorphisms Are Associated With Obesity and Chemotherapy Response in Mexican Women With Breast Cancer

BACKGROUND

Obesity plays a major role in the pathogenesis of breast cancer. Leptin (LEP) and adiponectin (ADIPOQ) are important in the regulation of adipose tissue. The response to cancer treatment depends on the histological and molecular tumor type, clinical stage, and genetic variability that might promote carcinogenic development. The aim of this study was to investigate the association between overweight/obesity and polymorphisms in the LEP (rs7799039), LEP receptor (LEPR; rs1137101), and ADIPOQ genes (rs2241766, rs1501299) with the response to breast cancer treatment in Mexican women.

PATIENTS AND METHODS

A sample of 177 patients with primary breast cancer (stage I-III) and who received neoadjuvant therapy were included. Polymorphisms were genotyped and their serum LEP concentrations (n = 59) were quantified.

RESULTS

The patients' median age was 53.1 years, the frequency of overweight and obesity was 57 and 84 patients, respectively, 117 were postmenopausal, and 64 of the patients did not respond to chemotherapy. An association of the LEP rs7799039, LEPR rs1137101, and ADIPOQ rs1501299 polymorphisms with overweight/obesity was found. The patients who did not respond to treatment were more frequently obese, at clinical stage III, had metastases, and high levels of glucose. Moreover, in samples that were positive for estrogen receptor, higher levels of LEP were found, and in wild type genotypes for LEP rs7799039 and LEPR rs1137101.

CONCLUSION

There was a direct association between the polymorphisms in LEP rs7799039 and ADIPOQ rs1501299 with overweight/obesity, and these genotypes affected the response to chemotherapeutic treatment, suggesting that an obesogenic microenvironment is more favorable for tumoral progression.

Analysis of circulating adipokines in patients newly diagnosed with solid cancer: Associations with measures of adiposity and tumor characteristics

The development and progression of cancer is a complex and multifactorial process and the global prevalence of obesity is markedly increasing. A number of studies have made an association between obesity and increased rates of epithelial tumors. Obesity is associated with altered adipokine levels, potentially contributing to the process of tumor development and metastasis. In the current study, the associations between circulating adipokines and measures of adiposity and tumor characteristics among patients diagnosed with solid malignancies were examined at the time of presentation, and following the administration of chemotherapy. A total of 30 patients with cancer and matched healthy controls were enrolled in the present study. Plasma adipokine levels of hepatocyte growth factor (HGF), adiponectin and leptin were determined using commercially available ELISA kits. At baseline, plasma HGF, adiponectin and leptin levels were not significantly different between patients with cancer and the healthy controls. Circulating HGF levels were significantly associated with the stage of cancer at diagnosis (P=0.044), but lacked a significant association with lymph node status (P=0.194). Plasma adiponectin and leptin levels were not significantly associated with tumor characteristics at the time of diagnosis. Only leptin was positively correlated with the body mass index of patients with cancer (P<0.001). No significant correlations were detected between the evaluated adipokines and measures of visceral obesity, as determined by waist circumference and the waist-hip ratio at presentation. Following administration of chemotherapy, adiponectin was the only adipokine evaluated in the current study that exhibited a significant difference, when compared with baseline plasma levels (P=0.013), and a significant positive correlation between baseline and follow-up circulating levels (P=0.002) among patients with cancer. In addition, there were no significant inter-correlations between circulating adipokines at baseline level and during follow-up in patients with cancer. Collectively, the findings of the current study suggest a lack of diagnostic roles for the adipokines investigated and no significant association with measures of adiposity. Adiponectin may be a potential adipokine to measure in patients with cancer, in order to further assess its prognostic and predictive potential.

Effect of Intermittent versus Chronic Calorie Restriction on Tumor Incidence: A Systematic Review and Meta-Analysis of Animal Studies

Both chronic calorie restriction (CCR) and intermittent calorie restriction (ICR) have shown anticancer effects. However, the direct evidence comparing ICR to CCR with respect to cancer prevention is controversial and inconclusive. PubMed and Web of Science were searched on November 25, 2015. The relative risk (RR) [95% confidence interval (CI)] was calculated for tumor incidence, and the standardised mean difference (95% CI) was computed for levels of serum insulin-like growth factor-1 (IGF-1), leptin, and adiponectin using a random-effects meta-analysis. Sixteen studies were identified, including 11 using genetically engineered mouse models (908 animals with 38-76 weeks of follow-up) and 5 using chemically induced rat models (379 animals with 7-18 weeks of follow-up). Compared to CCR, ICR decreased tumor incidence in genetically engineered models (RR = 0.57; 95% CI: 0.37, 0.88) but increased the risk in chemically induced models (RR = 1.53, 95% CI: 1.13, 2.06). It appears that ICR decreases IGF-1 and leptin and increases adiponectin in genetically engineered models. Thus, the evidence suggests that ICR exerts greater anticancer effect in genetically engineered mouse models but weaker cancer prevention benefit in chemically induced rat models as compared to CCR. Further studies are warranted to confirm our findings and elucidate the mechanisms responsible for these effects.

The Obesity-Breast Cancer Conundrum: An Analysis of the Issues

Breast cancer develops over a timeframe of 2-3 decades prior to clinical detection. Given this prolonged latency, it is somewhat unexpected from a biological perspective that obesity has no effect or reduces the risk for breast cancer in premenopausal women yet increases the risk for breast cancer in postmenopausal women. This conundrum is particularly striking in light of the generally negative effects of obesity on breast cancer outcomes, including larger tumor size at diagnosis and poorer prognosis in both pre- and postmenopausal women. This review and analysis identifies factors that may contribute to this apparent conundrum, issues that merit further investigation, and characteristics of preclinical models for breast cancer and obesity that should be considered if animal models are used to deconstruct the conundrum.

A weighty problem: metabolic perturbations and the obesity-cancer link

Obesity is an established risk factor for several cancers, including breast, colon, endometrial, ovarian, gastric, pancreatic and liver, and is increasingly a public health concern. Obese cancer patients often have poorer prognoses, reduced response to standard treatments, and are more likely to develop metastatic disease than normo-weight individuals. Many of the pathologic features of obesity promote tumor growth, such as metabolic perturbations, hormonal and growth factor imbalances, and chronic inflammation. Although obesity exacerbates tumor development, the interconnected relationship between the two conditions presents opportunities for new treatment approaches, some of which may be more successful in obese cohorts. Here, we discuss the many ways in which excess adiposity can impact cancer development and progression and address potential preventive and therapeutic strategies to reduce the burden of obesity-related cancers.

Leptin Modulates Mitochondrial Function, Dynamics and Biogenesis in MCF-7 Cells

The adipokine leptin, known for its key role in the control of energy metabolism, has been shown to be involved in both normal and tumoral mammary growth. One of the hallmarks of cancer is an alteration of tumor metabolism since cancerous cells must rewire metabolism to satisfy the demands of growth and proliferation. Considering the sensibility of breast cancer cells to leptin, the objective of this study was to explore the effects of this adipokine on their metabolism. To this aim, we treated the MCF-7 breast cancer cell line with 50 ng/mL leptin and analyzed several features related to cellular and mitochondrial metabolism. As a result, leptin increased cell proliferation, shifted ATP production from glycolysis to mitochondria and decreased the levels of the glycolytic end-product lactate. We observed an improvement in ADP-dependent oxygen consumption and an amelioration of oxidative stress without changes in total mitochondrial mass or specific oxidative phosphorylation (OXPHOS) complexes. Furthermore, RT-PCR and western blot showed an up-regulation for genes and proteins related to biogenesis and mitochondrial dynamics. This expression signature, together with an increased mitophagy observed by confocal microscopy suggests that leptin may improve mitochondrial quality and function. Taken together, our results propose that leptin may improve bioenergetic efficiency by avoiding the production of reactive oxygen species (ROS) and conferring benefits for growth and survival of MCF-7 breast cancer cells.

Modulation of Cell Death and Survival by Adipokines in the Liver

Adipokines, hormones predominantly produced from adipose tissue, have been shown to impart dynamic functions in the liver. Emerging evidence has shown that adipokines are also involved in modulating liver cell survival and/or death. Among the various adipokines, adiponectin and leptin directly regulate proliferation of hepatocytes, Kupffer cells, and hepatic stellate cells. Moreover, these adipokines control apoptosis and cell cycle of hepatic cancer cells in a complex manner. Adiponectin possesses both pro- and anti-proliferative properties, whereas leptin appears to play roles as a pro-survival hormone. Recent studies have revealed that regulation of cell death and proliferation is one of the critical factors regulating liver physiology by adipokines. In this review, we summarize the effects of adipokines on apoptosis and survival of liver cells and also demonstrate their implications in regulating various liver functions and decipher the underlying molecular mechanisms.

Metabolic Syndrome, Type 2 Diabetes, and Cancer: Epidemiology and Potential Mechanisms

Obesity is associated with multiple metabolic disorders that drive cardiovascular disease, T2D and cancer. The doubling in the number of obese adults over the past 3 decades led to the recognition of obesity as a "disease". With over 42 million children obese or overweight, this epidemic is rapidly growing worldwide. Obesity and T2D are both associated together and independently with an increased risk for cancer and a worse prognosis. Accumulating evidence from epidemiological studies revealed potential factors that may explain the association between obesity-linked metabolic disorders and cancer risk. Studies based on the insulin resistance MKR mice, highlighted the roe of the insulin receptor and its downstream signaling proteins in mediating hyperinsulinemia's mitogenic effects. Hypercholesterolemia was also shown to promote the formation of larger tumors and enhancement in metastasis. Furthermore, the conversion of cholesterol into 27-Hydroxycholesterol was found to link high fat diet-induced hypercholesterolemia with cancer pathophysiology. Alteration in circulating adipokines and cytokines are commonly found in obesity and T2D. Adipokines are involved in tumor growth through multiple mechanisms including mTOR, VEGF and cyclins. In addition, adipose tissues are known to recruit and alter macrophage phenotype; these macrophages can promote cancer progression by secreting inflammatory cytokines such as TNF-α and IL-6. Better characterization on the above factors and their downstream effects is required in order to translate the current knowledge into the clinic, but more importantly is to understand which are the key factors that drive cancer in each patient. Until we reach this point, policies and activities toward healthy diets and physical activities remain the best medicine.

The Effects of Adjuvant Endocrine Treatment on Serum Leptin, Serum Adiponectin and Body Composition in Patients with Breast Cancer: The Izmir Oncology Group (IZOG) Study

Background: A limited number of studies have been conducted on the effects of hormonal therapy with tamoxifen (TMX) or aromatase inhibitors (AIs) on plasma levels of leptin and adiponectin, as well as body composition in breast cancer (BC) patients. Therefore, we aimed to analyze the relationship between adipocytokines and body composition as well as the effects of TMX and AIs on plasma adiponectin, leptin, leptin/adiponectin ratio (LAR) and body composition. Methods: Patients were treated with either TMX or AI according to their menopausal status after adjuvant radiotherapy. Changes in body composition and serum leptin and adiponectin levels were evaluated. We recorded the type of hormonal therapy, BMI, waist/hip ratio (WHR), leptin and adiponectin levels at study entry, and after 6 and 12 months. Results: From baseline to the 6- and 12-month follow-ups, there were statistically significant increases in WHR (p = 0.003), fat mass (p = 0.041), and serum leptin (p < 0.001) and adiponectin levels (p < 0.001). The changes in body composition and serum leptin and adiponectin levels were similar in TMX and AI groups. A statistically significant decrease was found in total body water and LAR (p < 0.001). Although weight and body fat percentage increased, such increases were not statistically significant. A positive correlation was found between baseline BMI and serum leptin levels. This correlation was maintained at 6 and 12 months. The negative correlation found between serum adiponectin levels at baseline and baseline BMI did not last throughout the study. Conclusion: In this study, increased leptin and adiponectin levels and a decreased LAR were found in both AI and TMX groups. These changes might have occurred through both mechanisms of hormonal therapy and body composition changes. Therefore, AIs and TMX may exert their protective effects for BC patients by decreasing LAR rather than affecting leptin or adiponectin alone.

Energy homeostasis genes and breast cancer risk: The influence of ancestry, body size, and menopausal status, the breast cancer health disparities study

BACKGROUND

Obesity and breast cancer risk is multifaceted and genes associated with energy homeostasis may modify this relationship.

METHODS

We evaluated 10 genes that have been associated with obesity and energy homeostasis to determine their association with breast cancer risk in Hispanic/Native American (2111 cases, 2597 controls) and non-Hispanic white (1481 cases, 1585 controls) women.

RESULTS

Cholecystokinin (CCK) rs747455 and proopiomelanocortin (POMC) rs6713532 and rs7565877 (for low Indigenous American (IA) ancestry); CCK rs8192472 and neuropeptide Y (NYP) rs16141 and rs14129 (intermediate IA ancestry); and leptin receptor (LEPR) rs11585329 (high IA ancestry) were strongly associated with multiple indicators of body size. There were no significant associations with breast cancer risk between genes and SNPs overall. However, LEPR was significantly associated with breast cancer risk among women with low IA ancestry (PARTP=0.024); POMC was significantly associated with breast cancer risk among women with intermediate (PARTP=0.015) and high (PARTP=0.012) IA ancestry. The overall pathway was statistically significant for pre-menopausal women with low IA ancestry (PARTP=0.05), as was cocaine and amphetamine regulated transcript protein (CARTPT) (PARTP=0.014) and ghrelin (GHRL) (PARTP=0.007). POMC was significantly associated with breast cancer risk among post-menopausal women with higher IA ancestry (PARTP=0.005). Three SNPs in LEPR (rs6704167, rs17412175, and rs7626141), and adiponectin (ADIPOQ); rs822391) showed significant 4-way interactions (GxExMenopausexAncestry) for multiple indicators of body size among pre-menopausal women.

CONCLUSIONS

Energy homeostasis genes were associated with breast cancer risk; menopausal status, body size, and genetic ancestry influenced this relationship.

Aromatase overexpression in dysfunctional adipose tissue links obesity to postmenopausal breast cancer

The number of breast cancer cases has increased in the last a few decades and this is believed to be associated with the increased prevalence of obesity worldwide. The risk of breast cancer increases with age beyond menopause and the relationship between obesity and the risk of breast cancer in postmenopausal women is well established. The majority of postmenopausal breast cancers are estrogen receptor (ER) positive and estrogens produced in the adipose tissue promotes tumor formation. Obesity results in the secretion of inflammatory factors that stimulate the expression of the aromatase enzyme, which converts androgens into estrogens in the adipose tissue. Evidence demonstrating a link between obesity and breast cancer has led to the investigation of metabolic pathways as novel regulators of estrogen production, including pathways that can be targeted to inhibit aromatase specifically within the breast. This review aims to present some of the key findings in this regard.

Impact of Weight Loss on Plasma Leptin and Adiponectin in Overweight-to-Obese Post Menopausal Breast Cancer Survivors

Women who are obese at the time of breast cancer diagnosis have higher overall mortality than normal weight women and some evidence implicates adiponectin and leptin as contributing to prognostic disadvantage. While intentional weight loss is thought to improve prognosis, its impact on these adipokines is unclear. This study compared the pattern of change in plasma leptin and adiponectin in overweight-to-obese post-menopausal breast cancer survivors during weight loss. Given the controversies about what dietary pattern is most appropriate for breast cancer control and regulation of adipokine metabolism, the effect of a low fat versus a low carbohydrate pattern was evaluated using a non-randomized, controlled study design. Anthropometric data and fasted plasma were obtained monthly during the six-month weight loss intervention. While leptin was associated with fat mass, adiponectin was not, and the lack of correlation between leptin and adiponectin concentrations throughout weight loss implies independent mechanisms of regulation. The temporal pattern of change in leptin but not adiponectin was affected by magnitude of weight loss. Dietary pattern was without effect on either adipokine. Mechanisms not directly related to dietary pattern, weight loss, or fat mass appear to play dominant roles in the regulation of circulating levels of these adipokines.

Leptin-STAT3-G9a Signaling Promotes Obesity-Mediated Breast Cancer Progression

Obesity has been linked to breast cancer progression but the underlying mechanisms remain obscure. Here we report how leptin, an obesity-associated adipokine, regulates a transcriptional pathway to silence a genetic program of epithelial homeostasis in breast cancer stem-like cells (CSC) that promotes malignant progression. Using genome-wide ChIP-seq and RNA expression profiling, we defined a role for activated STAT3 and G9a histone methyltransferase in epigenetic silencing of miR-200c, which promotes the formation of breast CSCs defined by elevated cell surface levels of the leptin receptor (OBR(hi)). Inhibiting the STAT3/G9a pathway restored expression of miR-200c, which in turn reversed the CSC phenotype to a more differentiated epithelial phenotype. In a rat model of breast cancer driven by diet-induced obesity, STAT3 blockade suppressed the CSC-like OBR(hi) population and abrogated tumor progression. Together, our results show how targeting STAT3-G9a signaling regulates CSC plasticity during obesity-related breast cancer progression, suggesting a novel therapeutic paradigm to suppress CSC pools and limit breast malignancy.

The integrative role of leptin, oestrogen and the insulin family in obesity-associated breast cancer: potential effects of exercise

Obesity is an established risk factor for postmenopausal breast cancer. The mechanisms through which obesity influences the development and progression of breast cancer are not fully elucidated; however, several factors such as increased oestrogen, concentrations of various members of the insulin family and inflammation that are associated with adiposity are purported to be important factors in this relationship. Emerging research has also begun to focus on the role of adipokines, (i.e. adipocyte secreted factors), in breast cancer. Leptin secretion is directly related to adiposity and is believed to promote breast cancer directly and independently, as well as through involvement with the oestrogen and insulin signalling pathways. As leptin is secreted from white adipose tissue, any intervention that reduces adiposity may be favourable. However, it is also important to consider that energy expenditure through exercise, independent of fat loss, may improve leptin regulation. The purpose of this narrative review was to explore the role of leptin in breast cancer development and progression, identify key interactions with oestrogen and the insulin family, and distinguish the potential effects of exercise on these interactions.

n-3 polyunsaturated fatty acids and mechanisms to mitigate inflammatory paracrine signaling in obesity-associated breast cancer

Globally, the prevalence of obesity is increasing which subsequently increases the risk of the development of obesity-related chronic diseases. Low-grade chronic inflammation and dysregulated adipose tissue inflammatory mediator/adipokine secretion are well-established in obesity, and these factors increase the risk of developing inflammation-associated cancer. Breast cancer is of particular interest given that increased inflammation within the subcutaneous mammary adipose tissue depot can alter the local tissue inflammatory microenvironment such that it resembles that of obese visceral adipose tissue. Therefore, in obese women with breast cancer, increased inflammatory mediators both locally and systemically can perpetuate inflammation-associated pro-carcinogenic signaling pathways, thereby increasing disease severity. Herein, we discuss some of these inflammation-associated pro-carcinogenic mechanisms of the combined obese breast cancer phenotype and offer evidence that dietary long chain n-3 polyunsaturated fatty acids (PUFA) may have utility in mitigating the severity of obesity-associated inflammation and breast cancer.

Equol producers can have low leptin levels among prediabetic and diabetic females

OBJECTIVES

Soy isoflavones have received great attention for their beneficial effects on health and disease, i.e., in patients with diabetes. Equol is a biologically active isoflavone-related metabolite with interindividual differences in its production. The current study investigated the relationship between an equol-producing state and the levels of adipocytokine markers in a prediabetic and diabetic population.

SUBJECTS AND METHODS

A total of 79 subjects (34 males/45 females) in a prediabetic or diabetic state recruited from the general population were examined regarding their ability to produce equol using urine samples. Clinical data, such as age, smoking as well as anthropometric and biochemical variables, including body mass index (BMI), lipids, insulin, glucose, hemoglobin A1c, leptin and adiponectin, were recorded.

RESULTS

Equol producers exhibited lower leptin and leptin/BMI than non-producers among females. Simple correlation tests and stepwise multiple regression analyses revealed a significant inverse correlation between the leptin/BMI and equol-production. This relationship was not found in males.

CONCLUSIONS

Female equol producers can have favorable metabolic traits in relation to leptin metabolism in this population. Further studies are needed to confirm these results.

Excess weight gain accelerates 1-methyl-1-nitrosourea-induced mammary carcinogenesis in a rat model of premenopausal breast cancer

In contrast to the null effects generally reported, high-risk premenopausal women (Gail score ≥1.66) enrolled in the Breast Cancer Prevention P-1 Trial were recently reported to be at increased risk for breast cancer when overweight (HR = 1.59) or obese (HR = 1.70). To investigate this clinical observation in a preclinical setting, ovary-intact female rats were intraperitoneally injected with 50 mg/kg 1-methyl-1-nitrosourea at 21 days of age to simulate premenopausal women with increased risk. Two commercially available strains of Sprague-Dawley rat (Taconic Farms) were used, which are dietary resistant (DR) or dietary susceptible (DS) to excess weight gain when fed a purified diet containing 32% kcal from fat, similar to levels consumed by the typical American woman. DS rats were approximately 15.5% heavier than DR rats at study termination and plasma leptin indicated a marked difference in adiposity. DS rats had higher incidence (26% increase), multiplicity (2.5-fold increase), and burden (5.4-fold increase) of mammary carcinomas with a concomitant reduction in cancer latency (16% earlier detection) compared with DR rats (P < 0.001 for all analyses), and displayed a higher proportion of hormone receptor negative tumors compared with DR rats [OR = 1.78; 95% confidence interval (CI), 0.83-3.81]. Circulating levels of several breast cancer-risk factors, including leptin, adiponectin:leptin ratio, insulin, insulin-like growth factor (IGF)-1, IGF-1:IGF-1 binding protein-3 ratio, and calculated insulin resistance (HOMA-IR) were negatively impacted in DS rats (P < 0.05 for all analyses). These findings support further investigation of the effects of excess weight in high-risk premenopausal women and demonstrate a useful preclinical model for rapid evaluation of mechanistic hypotheses.

Multifaceted roles of adiponectin in cancer

Obesity is linked to increased cancer risk. Pathological expansion of adipose tissue impacts adipocyte function and secretion of hormonal factors regulating tissue homeostasis and metabolism. Adiponectin is an adipocyte-secreted, circulating hormone with pleiotropic functions in lipid and glucose metabolism, and beneficial roles in cardiovascular functions and inflammation. In obesity, decreased Adiponectin plasma levels correlate with tumor development and progression. The association of Adiponectin with potential tumor-limiting functions has raised significant interest in exploring this adipokine as a target for cancer-diagnostic and therapeutic applications. Recent studies, however, also implicate Adiponectin in supporting malignancy. This review highlights the evidence that links Adiponectin signaling to either cancer-protective or cancer-supporting functions. In this context, we discuss Adiponectin interactions with its receptors and associated signaling pathways. Despite significant advances in understanding Adiponectin functions and signaling mechanisms, its role in cancer remains multifaceted and subject to controversy.

Leptin and adiponectin: emerging therapeutic targets in breast cancer

Obesity is a recognized risk factor for breast cancer development and poorer response to therapy. Two major fat tissue-derived adipokines, leptin and adiponectin have been implicated in mammary carcinogenesis. Leptin appears to promote breast cancer progression through activation of mitogenic, antiapoptotic, and metastatic pathways, while adiponectin may restrict tumorigenic processes primarily by inhibiting cell metabolism. Furthermore, adiponectin is known to counteract detrimental leptin effects in breast cancer models. Thus, therapeutic inhibition of pro-neoplastic leptin pathways and reactivation of anti-neoplastic adiponectin signaling may benefit breast cancer patients, especially the obese subpopulation. This review focuses on current experimental strategies aiming at leptin and adiponectin pathways in breast cancer models. Novel leptin receptor antagonists and adiponectin receptor agonists as well as other compounds for therapeutic modulation of adipokine pathways are discussed in detail, including potential pharmacological advantages and limitations of these approaches.

Deficiency of metabolic regulator FGFR4 delays breast cancer progression through systemic and microenvironmental metabolic alterations

BACKGROUND

Endocrine FGF21 and FGF19 target adipocytes and hepatocytes through betaKlotho (KLB) and FGFR tyrosine kinases effecting glucose, lipid and energy metabolism. Both factors alleviate obesity and metabolic abnormalities which are contributing factors to breast tumor progression. Genomic manipulation of hepatic FGFR4 has uncovered roles of endocrine FGF signaling in both metabolic and cellular homeostasis. Here we determined whether systemic and microenvironmental metabolic alterations caused by the FGFR4 deficiency affect tumorigenesis in breast where FGFR4 is negligible. Breast tumors were induced in the bigenic mice with ablation of FGFR4 and overexpression of TGFα that activates Her2 in the ductal and lobular epithelium surrounded by adipocytes. Mammary tumorigenesis and alterations in systemic and breast microenvironmental metabolic parameters and regulatory pathways were analyzed.

RESULTS

Ablation of FGFR4 had no effect on cellular homeostasis and Her2 activity of normal breast tissue. However, the absence of FGFR4 reduced TGFα-driven breast tumor incidence and progression and improved host survival. Notable increases in hepatic and serum FGF21, ileal FGF15/19, adiponectin and adipsin, and decreases in systemic Fetuin A, IGF-1, IGFBP-1, RBP4 and TIMP1 were observed. The ablation affected adipogenesis and secretory function of adipocytes as well as lipogenesis, glycolysis and energy homeostasis associated with the functions of mitochondria, ER and peroxisomes in the breast and tumor foci. Treatment with a chemical inhibitor of NAMPT involved in the pathways inhibited the growth and survival of breast tumor cells and tumor-initiating cell-containing spheres. The FGFR4 ablation also caused elevation of inflammatory factors in the breast.

CONCLUSIONS

Although the primary role of FGFR4 in metabolism occurs in hepatocytes, its ablation results in a net inhibitory effect on mammary tumor progression. We suggest that the tumor-delaying effect of FGFR4 deficiency may be in large part due to elevated anti-obesogenic FGF21 that triggers tumor-suppressing signals from both peripheral and breast adipocytes. The predominant changes in metabolic pathways suggested roles of metabolic effects from both peripheral and breast adipocytes on metabolic reprogramming in breast epithelial cells that contribute to the suppression of tumor progression. These results provide new insights into the contribution of systemic and microenvironmental metabolic effects controlled by endocrine FGF signaling to breast carcinogenesis.

Obesity, metabolism and the microenvironment: Links to cancer

Historically, cancer research has focused on identifying mutations or amplification of genes within the tumor, which informed the development of targeted therapies against affected pathways. This work often considers tumor cells in isolation; however, it is becoming increasingly apparent that the microenvironment surrounding tumor cells strongly influences tumor onset and progression. This is the so-called “seed and soil” hypothesis wherein the seed (cancer cell) is fed and molded by the metabolites, growth factors, modifications of the extracellular matrix or angiogenic factors provided by the soil (or stroma). Currently, 65% of the US population is obese or overweight; similarly staggering figures are reported in US children and globally. Obesity mediates and can exacerbate, both normal and tumor microenvironment dysfunction. Many obesity-associated endocrine, metabolic and inflammatory mediators are suspected to play a role in oncogenesis by modifying systemic nutrient metabolism and the nutrient substrates available locally in the stroma. It is vitally important to understand the biological processes linking obesity and cancer to develop better intervention strategies aimed at curbing the carcinogenic events associated with obesity. In this review, obesity-driven changes in both the normal and tumor microenvironment, alterations in metabolism, and release of signaling molecules such as endocrine, growth, and inflammatory mediators will be highlighted. In addition, we will discuss the effects of the timing of obesity onset or particular “windows of susceptibility,” with a focus on breast cancer etiology.

Circulatory estrogen level protects against breast cancer in obese women

Literary data suggest apparently ambiguous interaction between menopausal status and obesity-associated breast cancer risk based on the principle of the carcinogenic capacity of estrogen. Before menopause, breast cancer incidence is relatively low and adiposity is erroneously regarded as a protective factor against this tumor conferred by the obesity associated defective estrogen-synthesis. By contrast, in postmenopausal cases, obesity presents a strong risk factor for breast cancer being mistakenly attributed to the presumed excessive estrogen-production of their adipose-tissue mass. Obesity is associated with dysmetabolism and endangers the healthy equilibrium of sexual hormone-production and regular menstrual cycles in women, which are the prerequisites not only for reproductive capacity but also for somatic health. At the same time, literary data support that anovulatory infertility is a very strong risk for breast cancer in young women either with or without obesity. In the majority of premenopausal women, obesity associated insulin resistance is moderate and may be counteracted by their preserved circulatory estrogen level. Consequently, it is not obesity but rather the still sufficient estrogen-level, which may be protective against breast cancer in young adult females. In obese older women, never using hormone replacement therapy (HRT) the breast cancer risk is high, which is associated with their continuous estrogen loss and increasing insulin-resistance. By contrast, obese postmenopausal women using HRT, have a decreased risk for breast cancer as the protective effect of estrogen-substitution may counteract to their obesity associated systemic alterations. The revealed inverse correlation between circulatory estrogen-level and breast cancer risk in obese women should advance our understanding of breast cancer etiology and promotes primary prevention measures. New patents recommend various methods for the prevention and treatment of obesity-related systemic disorders and the associated breast cancer.

Leptin's Pro-Angiogenic Signature in Breast Cancer

Obesity is linked to increased incidence of breast cancer. The precise causes and mechanisms of these morbid relationships are unknown. Contradictory data on leptin angiogenic actions have been published. However, accumulating evidence would suggest that leptin’s pro-angiogenic effects in cancer play an essential role in the disease. Leptin, the main adipokine secreted by adipose tissue, is also abnormally expressed together with its receptor (OB-R) by breast cancer cells. Leptin induces proliferation and angiogenic differentiation of endothelial cells upregulates VEGF/VEGFR2 and transactivates VEGFR2 independent of VEGF. Leptin induces two angiogenic factors: IL-1 and Notch that can increase VEGF expression. Additionally, leptin induces the secretion and synthesis of proteases and adhesion molecules needed for the development of angiogenesis. Leptin’s paracrine actions can further affect stromal cells and tumor associated macrophages, which express OB-R and secrete VEGF and IL-1, respectively. A complex crosstalk between leptin, Notch and IL-1 (NILCO) that induces VEGF/VEGFR2 is found in breast cancer. Leptin actions in tumor angiogenesis could amplify, be redundant and/or compensatory to VEGF signaling. Current failure of breast cancer anti-angiogenic therapies emphasizes the necessity of targeting the contribution of other pro-angiogenic factors in breast cancer. Leptin’s impact on tumor angiogenesis could be a novel target for breast cancer, especially in obese patients. However, more research is needed to establish the importance of leptin in tumor angiogenesis. This review is focused on updated information on how leptin could contribute to tumor angiogenesis.

Obesity, insulin resistance, adipocytokines and breast cancer: New biomarkers and attractive therapeutic targets

Worldwide, breast cancer (BC) represents the most common type of non-skin human malignancy and the second leading cause of cancer-related deaths amid women in Western countries. Obesity and its metabolic complications have rapidly become major global health issues and are associated with increased risk for cancer, especially BC in postmenopausal women. Adipose tissue is considered as a genuine endocrine organ secreting a variety of bioactive adipokines, such as leptin, adiponectin, resistin and nicotinamide phosphoribosyl-transferase/visfatin. Recent evidence has indicated that the constellation of obesity, insulin resistance and adipokines is associated with the risk and prognosis of postmenopausal BC. Direct evidence is growing rapidly supporting the stimulating and/or inhibiting role of adipokines in the process of development and progression of BC. Adipokines could exert their effects on the normal and neoplastic mammary tissue by endocrine, paracrine and autocrine mechanisms. Recent studies support a role of adipokines as novel risk factors and potential diagnostic and prognostic biomarkers in BC. This editorial aims at providing important insights into the potential pathophysiological mechanisms linking adipokines to the etiopathogenesis of BC in the context of a dysfunctional adipose tissue and insulin resistance in obesity. A better understanding of these mechanisms may be important for the development of attractive preventive and therapeutic strategies against obesity-related breast malignancy.

Interplay of adipokines and myokines in cancer pathophysiology: Emerging therapeutic implications

Excess body weight constitutes a worldwide health problem with epidemic proportions impacting on the risk and prognosis of several disease states including malignancies. It is believed that the metabolic changes associated with weight gain, particularly visceral obesity, and physical inactivity could lead to dysfunctional adipose and muscle tissues causing insulin resistance, low-grade chronic inflammation and abnormal secretion of adipokines and myokines. The complex paracrine and endocrine interconnection between adipokines and myokines reflects a yin-yang balance with important implications in processes such as lipolysis control, insulin sensitivity and prevention from obesity-driven chronic low-grade inflammation and cancer promotion through anti-inflammatory adipokines and myokines. Furthermore, the complex pathophysiology of cancer cachexia is based on the interplay between muscle and adipose tissue mediated by free fatty acids, various adipokines and myokines. The purpose of this editorial is to explore the role of the adipose and muscle tissue interplay in carcinogenesis, cancer progression and cachexia, and to examine the mechanisms underpinning their association with malignancy. Understanding of the mechanisms connecting the interplay of adipokines and myokines with cancer pathophysiology is expected to be of importance in the development of therapeutic strategies against cancer cachexia. Advances in the field of translational investigation may lead to tangible benefits to obese and inactive persons who are at increased risk of cancer as well as to cancer patients with cachexia.

Leptin's role in lipodystrophic and nonlipodystrophic insulin-resistant and diabetic individuals

Leptin is an adipocyte-secreted hormone that has been proposed to regulate energy homeostasis as well as metabolic, reproductive, neuroendocrine, and immune functions. In the context of open-label uncontrolled studies, leptin administration has demonstrated insulin-sensitizing effects in patients with congenital lipodystrophy associated with relative leptin deficiency. Leptin administration has also been shown to decrease central fat mass and improve insulin sensitivity and fasting insulin and glucose levels in HIV-infected patients with highly active antiretroviral therapy (HAART)-induced lipodystrophy, insulin resistance, and leptin deficiency. On the contrary, the effects of leptin treatment in leptin-replete or hyperleptinemic obese individuals with glucose intolerance and diabetes mellitus have been minimal or null, presumably due to leptin tolerance or resistance that impairs leptin action. Similarly, experimental evidence suggests a null or a possibly adverse role of leptin treatment in nonlipodystrophic patients with nonalcoholic fatty liver disease. In this review, we present a description of leptin biology and signaling; we summarize leptin's contribution to glucose metabolism in animals and humans in vitro, ex vivo, and in vivo; and we provide insights into the emerging clinical applications and therapeutic uses of leptin in humans with lipodystrophy and/or diabetes.

Oxidative stress associated to dysfunctional adipose tissue: a potential link between obesity, type 2 diabetes mellitus and breast cancer

Diabetes mellitus and breast cancer are two important health problems. Type 2 diabetes (T2DM) and obesity are closely linked with both being associated with breast cancer. Despite abundant epidemiological data, there is no definitive evidence regarding the mechanisms responsible for this association. The proposed mechanisms by which diabetes affects breast cancer risk and prognosis are the same as the mechanisms hypothesised for the contribution of obesity to breast cancer risk. The obesity-induced inflammation promoted by adipose tissue dysfunction is a key feature, which is thought to be an important link between obesity and cancer. Inflammation induces an increase in free radicals and subsequently promotes oxidative stress, which may create a microenvironment favourable to the tumor development in obese persons. Oxidative stress is also proposed as the link between obesity and diabetes mellitus. Therefore, obesity-related oxidative stress could be a direct cause of neoplastic transformation associated with obesity and T2DM in breast cancer cells. This review is focused on the role of obesity-related oxidative stress in the context of chronic inflammation, on the time of breast cancer onset and progression, which provide targets for preventive and therapeutic strategies in the fields of diabetes and obesity-related breast cancer.

Obesity-associated adipokines correlate with survival in epithelial ovarian cancer

OBJECTIVES

Obesity impacts outcome in women with epithelial ovarian cancer (EOC), although its exact role and the molecular mechanisms remain poorly defined. Adipocytes secrete leptin and adiponectin, and the leptin to adiponectin (L:A) ratio is correlated with poor survival in other malignancies. We hypothesized that the L:A ratio is associated with survival in women with EOC.

METHODS

We queried the institutional tumor registry for patients with advanced stage EOC and identified a cohort of 161 women with banked fasting prediagnostic serum samples. Patients underwent cytoredutive surgery followed by platinum-based chemotherapy. Sera were assayed for leptin and adiponectin, and clinico-pathologic data were abstracted. Standard statistical tests were performed.

RESULTS

161 patients met inclusion criteria. We identified a significant correlation between BMI and leptin and the L:A ratio, but not adiponectin, in this cohort (r=0.46, 0.46, and -0.13, respectively; p=0.001, 0.001, and 0.106). Women with low L:A ratios demonstrated statistically longer disease-specific survival (57 months) compared to those with median or high levels (49 and 37 months, respectively; p=0.02). On multivariate analysis, we determined that BMI and age, but not L:A ratio, retained significance as independent prognostic factors for survival (p=0.04, 0.004, and 0.895, respectively).

CONCLUSIONS

In this cohort, the L:A ratio correlated statistically with clinical outcome, but did not independently predict survival. Obesity remains a modifiable risk factor in women with EOC. Further studies are needed to determine if leptin and/or adiponectin may be potential therapeutic targets in obese women with EOC.