Prediagnostic circulating adipokine concentrations and risk of renal cell carcinoma in male smokers

Research progress on the correlation between obesity and the occurrence and development of kidney cancer: a narrative review

Background and Objective

Obesity is an important risk factor for the onset of kidney cancer, and the mechanism of obesity leading to the occurrence and development of kidney cancer has been further studied and confirmed in the past decade. The emergence of the "obesity paradox" phenomenon has made the correlation between obesity and the prognosis of kidney cancer survival controversial. This review summarizes the association between obesity and the occurrence and development of kidney cancer based on newly discovered evidence in the past 10 years, in order to provide reference for follow-up research.

Methods

A comprehensive, non-systematic review of the latest literature was carried out in order to investigate the progress of the correlation between obesity and kidney cancer. PubMed, Web of Science and Embase were being examined and the last run was on July 15, 2024.

Key Content and Findings

The correlation between obesity and the occurrence and development of kidney cancer was discussed in this review, and the newly discovered evidence of epidemiology and related mechanisms in the past 10 years was summarized. The latest evidence suggests that obesity is an important risk factor for the development of kidney cancer. Perirenal fat plays an important role in promoting kidney cancer progression and prognosis.

Conclusions

Epidemiology shows that the high rates of kidney cancer and obesity coincide in terms of region and ethnicity. The underlying mechanisms associated with obesity in promoting the occurrence and development of kidney cancer mainly include: abnormal expression of adipocytokines, abnormal lipid metabolism, abnormalities in the insulin-like growth factor-I (IGF-I) axis and hyperinsulinemia/insulin resistance, hypoxia and inflammation. As adipose tissue is adjacent to the kidney, the effect of perirenal adipose tissue on the prognosis of kidney cancer is controversial, and some evidence supports the idea of the "obesity paradox".

Fatty acid metabolism reprogramming in ccRCC: mechanisms and potential targets

Lipid droplet formation is a defining histological feature in clear-cell renal cell carcinoma (ccRCC) but the underlying mechanisms and importance of this biological behaviour have remained enigmatic. De novo fatty acid (FA) synthesis, uptake and suppression of FA oxidation have all been shown to contribute to lipid storage, which is a necessary tumour adaptation rather than a bystander effect. Clinical studies and mechanistic investigations into the roles of different enzymes in FA metabolism pathways have revealed new metabolic vulnerabilities that hold promise for clinical effect. Several metabolic alterations are associated with worse clinical outcomes in patients with ccRCC, as lipogenic genes drive tumorigenesis. Enzymes involved in the intrinsic FA metabolism pathway include FA synthase, acetyl-CoA carboxylase, ATP citrate lyase, stearoyl-CoA desaturase 1, cluster of differentiation 36, carnitine palmitoyltransferase 1A and the perilipin family, and each might be potential therapeutic targets in ccRCC owing to the link between lipid deposition and ccRCC risk. Adipokines and lipid species are potential biomarkers for diagnosis and treatment monitoring in patients with ccRCC. FA metabolism could potentially be targeted for therapeutic intervention in ccRCC as small-molecule inhibitors targeting the pathway have shown promising results in preclinical models.

Potential Value of Visfatin, Omentin-1, Nesfatin-1 and Apelin in Renal Cell Carcinoma (RCC): A Systematic Review and Meta-Analysis

Renal cell carcinoma (RCC) is the most lethal genitourinary malignancy. Obesity is a risk factor for RCC development. The role of adipokines in the relationship between obesity and RCC requires confirmatory evidence in the form of a systematic review and meta-analysis, specifically for visfatin, omentin-1, nesfatin-1 and apelin. A search of databases up to July 2022 (PubMed, Web of Science and Scopus) for studies reporting the association of these selected adipokines with RCC was conducted. A total of 13 studies fulfilled the selection criteria. Only visfatin (p < 0.05) and nesfatin-1 (p < 0.05) had a significant association with RCC. Meanwhile, apelin and omentin-1 showed no association with RCC. The meta-analysis results of nesfatin-1 showed no association with early-stage (OR = 0.09, 95% CI = −0.12−0.29, p = 0.41), late-stage (OR = 0.36, 95% CI = 0.07−1.89, p = 0.23) and low-grade (OR = 1.75, 95% CI = 0.37−8.27, p = 0.48) RCC. However, nesfatin-1 showed an association with a high grade of the disease (OR = 0.29, 95% CI = 0.13−0.61, p = 0.001) and poorer overall survival (OS) (HR = 3.86, 95% CI = 2.18−6.85; p < 0.01). Apelin showed no association with the risk of RCC development (mean difference = 21.15, 95% CI = −23.69−65.99, p = 0.36) and OS (HR = 1.04, 95% Cl = 0.45−2.41; p = 0.92). Although the number of studies evaluated was limited, analysis from this systematic review and meta-analysis indicate that visfatin and nesfatin-1 were elevated. In summary, these adipokines may play a role in the development and progression of RCC and hence may have potential diagnostic and prognostic capabilities for RCC.

Metabolomic Analysis of Renal Cell Carcinoma in the Prostate, Lung, Colorectal, and Ovarian Cancer Screening Trial

Background: In the US in 2021, 76,080 kidney cancers are expected and >80% are renal cell carcinomas (RCCs). Along with excess fat, metabolic dysfunction is implicated in RCC etiology. To identify RCC-associated metabolites, we conducted a 1:1 matched case−control study nested within the Prostate, Lung, Colorectal, and Ovarian (PLCO) Cancer Screening Trial. Methods: We measured 522 serum metabolites in 267 cases/control pairs. Cases were followed for a median 7.1 years from blood draw to diagnosis. Using conditional logistic regression, we computed adjusted odds ratios (ORs) and 95% confidence intervals (CIs) comparing risk between 90th and 10th percentiles of log metabolite intensity, with the significance threshold at a false discovery rate <0.20. Results: Four metabolites were inversely associated with risk of RCC during follow-up—C38:4 PI, C34:0 PC, C14:0 SM, and C16:1 SM (ORs ranging from 0.33−0.44). Two were positively associated with RCC risk—C3-DC-CH3 carnitine and C5 carnitine (ORs = 2.84 and 2.83, respectively). These results were robust when further adjusted for metabolic risk factors (body mass index (BMI), physical activity, diabetes/hypertension history). Metabolites associated with RCC had weak correlations (|r| < 0.2) with risk factors of BMI, physical activity, smoking, alcohol, and diabetes/hypertension history. In mutually adjusted models, three metabolites (C38:4 PI, C14:0 SM, and C3-DC-CH3 carnitine) were independently associated with RCC risk. Conclusions: Serum concentrations of six metabolites were associated with RCC risk, and three of these had independent associations from the mutually adjusted model. These metabolites may point toward new biological pathways of relevance to this malignancy.

Renal Lipid Metabolism Abnormalities in Obesity and Clear Cell Renal Cell Carcinoma

Clear cell renal cell carcinoma is the most common and deadly type of cancer affecting the kidney, and is characterized histologically by large intracellular lipid deposits. These deposits are thought to result from lipid metabolic reprogramming occurring in tumor cells, but the exact mechanisms and implications of these metabolic alterations are incompletely understood. Obesity is an independent risk factor for clear cell renal cell carcinoma, and is also associated with lipid accumulation in noncancerous epithelial cells of the proximal tubule, where clear cell renal cell carcinoma originates. This article explores the potential link between obesity-associated renal lipid metabolic disturbances and lipid metabolic reprogramming in clear cell renal cell carcinoma, and discusses potential implications for future research.

Circulating adipokine concentrations and risk of five obesity-related cancers: A Mendelian randomization study

Obesity is considered a chronic inflammatory state characterized by continued secretion of adipokines and cytokines. Experimental and epidemiological evidence indicates that circulating adipokines may be associated with the development of obesity-related cancers, but it is unclear if these associations are causal or confounded. We examined potential causal associations of specific adipokines (adiponectin, leptin, soluble leptin receptor [sOB-R] and plasminogen activator inhibitor-1 [PAI-1]) with five obesity-related cancers (colorectal, pancreatic, renal cell carcinoma [RCC], ovarian and endometrial) using Mendelian randomization (MR) methods. We used summary-level data from large genetic consortia for 114 530 cancer cases and 245 284 controls. We constructed genetic instruments using 18 genetic variants for adiponectin, 2 for leptin and 4 for both sOB-R and PAI-1 (P value for inclusion<5 × 10-8 ). Causal estimates were obtained using two-sample MR methods. In the inverse-variance weighted models, we found an inverse association between adiponectin and risk of colorectal cancer (odds ratio per 1 μg/mL increment in adiponectin concentration: 0.90 [95% confidence interval = 0.84-0.97]; P = .01); but, evidence of horizontal pleiotropy was detected and the association was not present when this was taken into consideration. No association was found for adiponectin and risks of pancreatic cancer, RCC, ovarian cancer and endometrial cancer. Leptin, sOB-R and PAI-1 were also similarly unrelated to risk of obesity-related cancers. Despite the large sample size, our MR analyses do not support causal effects of circulating adiponectin, leptin, sOB-R and PAI-1 concentrations on the development of five obesity-related cancers.

Obesity-Dependent Adipokine Chemerin Suppresses Fatty Acid Oxidation to Confer Ferroptosis Resistance

Clear cell renal cell carcinoma (ccRCC) is characterized by accumulation of neutral lipids and adipogenic transdifferentiation. We assessed adipokine expression in ccRCC and found that tumor tissues and patient plasma exhibit obesity-dependent elevations of the adipokine chemerin. Attenuation of chemerin by several approaches led to significant reduction in lipid deposition and impairment of tumor cell growth in vitro and in vivo. A multi-omics approach revealed that chemerin suppresses fatty acid oxidation, preventing ferroptosis, and maintains fatty acid levels that activate hypoxia-inducible factor 2α expression. The lipid coenzyme Q and mitochondrial complex IV, whose biogeneses are lipid-dependent, were found to be decreased after chemerin inhibition, contributing to lipid reactive oxygen species production. Monoclonal antibody targeting chemerin led to reduced lipid storage and diminished tumor growth, demonstrating translational potential of chemerin inhibition. Collectively, the results suggest that obesity and tumor cells contribute to ccRCC through the expression of chemerin, which is indispensable in ccRCC biology. SIGNIFICANCE: Identification of a hypoxia-inducible factor-dependent adipokine that prevents fatty acid oxidation and causes escape from ferroptosis highlights a critical metabolic dependency unique in the clear cell subtype of kidney cancer. Targeting lipid metabolism via inhibition of a soluble factor is a promising pharmacologic approach to expand therapeutic strategies for patients with ccRCC.See related commentary by Reznik et al., p. 1879.This article is highlighted in the In This Issue feature, p. 1861.

Identification of genes that correlate clear cell renal cell carcinoma and obesity and exhibit potential prognostic value

Background

Renal cell carcinoma (RCC) is a common urologic malignancy. Although the relationship between clear cell RCC (ccRCC) and obesity has been well-established by several large-scale retrospective studies, the molecular mechanisms and genetic characteristics behind this correlation remains unclear. In the current study, several bioinformatics tools were used to identify the key genes in ccRCC related to obesity.

Methods

Microarray data comparing ccRCC with normal renal tissues in patients with and without obesity were downloaded from the GEO database for screening of differentially expressed genes (DEGs). The DEGs were verified with expression level and survival analysis using several online bioinformatics tools.

Results

In the current study, the differential expression of five genes correlated with both ccRCC and obesity; IGHA1 and IGKC as oncogenes, and MAOA, MUC20 and TRPM3 as tumor suppressor genes. These genes were verified by comparing the relationship between the expression levels and survival outcomes from open-source data in The Cancer Genome Atlas (TCGA) dataset.

Conclusions

In conclusion, the five genes differentially expressed in ccRCC and obesity are related to disease progression and prognosis, and therefore could provide prognostic value for patients with ccRCC.

Lower circulating adiponectin is associated with higher risk of renal cell carcinoma: A meta-analysis

BACKGROUND

Changes in circulating adiponectin have been related to the risks of various cancers. However, the association between circulating adiponectin and the risk of renal cell carcinoma has not been fully determined. A meta-analysis was performed to evaluate the relationship between circulating adiponectin and renal cell carcinoma risk.

METHODS

Observational studies that evaluated the association between circulating adiponectin and renal cell carcinoma risk were identified via a systematic search of PubMed and Embase databases. The difference between circulating adiponectin in renal cell carcinoma cases and healthy controls, and the multivariable adjusted association between circulating adiponectin and renal cell carcinoma risk were evaluated. A random effects model was used if significant heterogeneity existed; otherwise a fixed effects model was applied.

RESULTS

Eight case-control studies with 2624 renal cell carcinoma cases and 2904 healthy controls were included. Pooled results showed that circulating adiponectin was significantly lower in renal cell carcinoma cases than in healthy controls (mean difference = -1.08 ug/mL; 95% confidence interval (CI) -1.62, -0.54; P < 0.001). Higher circulating adiponectin was independently associated with a significantly lowered risk of renal cell carcinoma (adjusted odds ratio for 1 SD increment of adiponectin = 0.78; 95% CI: 0.63, 0.96; P = 0.02). Subgroup analyses according to characteristics including study design, ethnics of participants, blood samples, numbers of participants, mean ages of participants, and study quality showed consistent results.

CONCLUSIONS

Lower circulating adiponectin is associated with increased risk of renal cell carcinoma. The potential pathophysiological mechanisms underlying the role of circulating adiponectin in the pathogenesis of renal cell carcinoma deserve further investigation.

Circulating obesity-driven biomarkers are associated with risk of clear cell renal cell carcinoma: a two-stage, case-control study

Obesity is one of modifiable risk factors for clear cell renal cell cancer (ccRCC). We aim to identify the association between obesity-driven biomarkers and ccRCC risk. This is a retrospective, two-phase, case-control study involving 682 cases and 733 controls. Obesity-driven biomarkers [gastric inhibitory polypeptide (GIP), C-peptide, insulin, resistin, adipsin, peptide YY, pancreatic polypeptide, interleukin-6 (IL-6), tumor necrosis factor-α (TNF-α), plasminogen activator inhibitor-1, monocyte chemoattractant protein 1, lipocalin2, leptin, adiponectin] were measured using the Milliplex method. Multivariate logistic regression was used to assess the associations between biomarkers and ccRCC risk. Results revealed that GIP, C-peptide, IL-6 and TNF-α levels were consistently distinct between cases and controls. These markers were significantly associated with ccRCC risk in both phases (except C-peptide). In the combined population, compared with individuals with low levels of the biomarkers, individuals with high level of GIP [odds ratio (OR) = 0.52, 95% confidence interval (CI): 0.40-0.67] had lower risk, whereas individuals with high levels of C-peptide (OR = 1.46, 95% CI: 1.15-1.87), IL-6 (OR = 2.20, 95% CI: 1.50-3.22), TNF-α (OR = 1.90, 95% CI: 1.49-2.43) had significantly higher risk. Stratified analysis showed consistent associations with ccRCC risk in most subgroups (P < 0.05). The risk score based on the IL-6, TNF-α and GIP was positively associated with ccRCC risk in a dose-response manner (P for trend = 2.18E-13). Data from The Cancer Genome Atlas indicate that insulin signaling, IL-6 signaling and TNF-α signaling were enhanced in tumors. Collectively, our study demonstrates the integrative effect of insulin resistance and inflammation in ccRCC development, which may elucidate the basis of association between obesity and carcinogenesis. Further confirmation in prospective cohort studies are warranted for clinical applications in prevention and precision medicine of ccRCC.

Increased UCP1 expression in the perirenal adipose tissue of patients with renal cell carcinoma

Perirenal adipose tissue (PAT) has been implicated in renal cell carcinoma (RCC). The expression of uncoupling protein 1 (UCP1) is higher in PAT compared with that in back subcutaneous adipose tissue (bSAT). The aim of the present study was to determine UCP1 expression in different parts of PAT and to analyze the correlation between UCP1 expression in PAT and RCC. PAT from the upper and lower renal poles and bSAT samples were collected from 50 patients with RCC (RCC group) and 54 patients with renal cysts (control group) who had undergone renal surgery. Both UCP1 mRNA and protein levels were found to be significantly higher and adipocytes appeared to be smaller in the PAT of the RCC group. Furthermore, the RCC group had more multilocular UCP1-positive adipocytes. UCP1 staining in the PAT was significantly stronger in the RCC group, but there was no significant difference in UCP1 staining in the bSAT between the two groups. Furthermore, Fuhrman grade and T stage were higher in the high UCP1 expression group of RCC patients. In conclusion, high UCP1 expression in the PAT may serve as an indicator of poor prognosis in RCC.

Circulating adiponectin as a biomarker in renal cell carcinoma: a systematic review and meta-analysis

Context: Metabolic imbalance in renal cell carcinoma (RCC) can lead to abnormal adiponectin levels. Objective: To evaluate circulating adiponectin as a detection or predictive marker for RCC. Methods: A comprehensive literature search and meta-analysis was performed on studies reporting circulating adiponectin levels and RCC. The meta-analysis was performed using RevMan. Results: Seven studies compared the circulating adiponection levels between RCC cases and controls. Adiponectin level was significantly lower in RCC cases compared to controls at pre-diagnosis and pre-operative time-points. RCC stage, grade and subtype did not affect adiponectin levels. Conclusion: Low circulating adiponectin could be a predictive or risk factor for RCC.

Prognostic biomarkers in renal cell carcinoma: is there a relationship with obesity?

Obesity is a recognized risk factor for renal cell carcinoma (RCC) the commonest form of kidney cancer. Both obesity and RCC are serious diseases with increasing incidence yearly. This review examined certain obesity associated measurements and adipokines as detection/prognostic indicators for RCC. The obesity related measurements such as body mass index (BMI), waist circumstance (WC), waist-hip ratio (WHR) in predicting RCC are valid when used in conjunction with other risk factors such as age and sex or with histological findings. The adipokine adiponectin holds promising outcomes as a predictive marker in assessing the risk of developing RCC. In addition, tissue leptin/leptin receptor may be a distinguishing marker for RCC subtypes. However, circulating leptin may not be a suitable detection or prognostic biomarker for RCC. The other less investigated adipokines; omentin, visfatin, apelin and resistin are also expressed in RCC but their prognostic capabilities are still inconclusive. BMI, WC and adipokines may be useful additions in a nomogram which includes TNM staging and pathological grading system to detect, confirm and follow-up RCC cases.

Global patterns in excess body weight and the associated cancer burden

The prevalence of excess body weight and the associated cancer burden have been rising over the past several decades globally. Between 1975 and 2016, the prevalence of excess body weight in adults-defined as a body mass index (BMI) ≥ 25 kg/m² -increased from nearly 21% in men and 24% in women to approximately 40% in both sexes. Notably, the prevalence of obesity (BMI ≥ 30 kg/m² ) quadrupled in men, from 3% to 12%, and more than doubled in women, from 7% to 16%. This change, combined with population growth, resulted in a more than 6-fold increase in the number of obese adults, from 100 to 671 million. The largest absolute increase in obesity occurred among men and boys in high-income Western countries and among women and girls in Central Asia, the Middle East, and North Africa. The simultaneous rise in excess body weight in almost all countries is thought to be driven largely by changes in the global food system, which promotes energy-dense, nutrient-poor foods, alongside reduced opportunities for physical activity. In 2012, excess body weight accounted for approximately 3.9% of all cancers (544,300 cases) with proportion varying from less than 1% in low-income countries to 7% or 8% in some high-income Western countries and in Middle Eastern and Northern African countries. The attributable burden by sex was higher for women (368,500 cases) than for men (175,800 cases). Given the pandemic proportion of excess body weight in high-income countries and the increasing prevalence in low- and middle-income countries, the global cancer burden attributable to this condition is likely to increase in the future. There is emerging consensus on opportunities for obesity control through the multisectoral coordinated implementation of core policy actions to promote an environment conducive to a healthy diet and active living. The rapid increase in both the prevalence of excess body weight and the associated cancer burden highlights the need for a rejuvenated focus on identifying, implementing, and evaluating interventions to prevent and control excess body weight.

Modifiable risk factors to reduce renal cell carcinoma incidence: Insight from the PLCO trial

INTRODUCTION

Identify modifiable factors contributing to renal cell carcinoma in the PCLO to target disease prevention and reduce health care costs.

METHODS

The prostate, lung, colorectal, and ovarian database were queried for the primary outcome of kidney cancer. Demographics were investigated, specifically focusing on modifiable risk factors. Statistical analysis includes the Student t-test for continuous variables, chi-squared or Fisher's exact tests for dichotomous and categorical variables for bivariate analysis. The Cox proportional hazards model was used in a multivariate time-to-event analysis.

RESULTS

We investigate existing data relating specifically to renal cancer. After missing data were excluded, we analyzed 149,683 subjects enrolled in the prostate, lung, colorectal, and ovarian trial and noted 0.5% (n = 748) subjects developed renal cancer. Age, male gender, body mass index, diabetes, and hypertension were all significant associated with renal cancer in bivariate analysis (P<0.05). Men have a significant increased risk of kidney cancer over women (hazard ratio [HR] = 1.85; 95% CI: 1.58-2.16; P<0.0001). Nonmodifiable risk factors that are associated with kidney cancer include age (HR = 1.05; 95% CI: 1.01; 1.05, P = 0.001). Modifiable risk factors include obesity measured by body mass index (HR = 1.05; 95% CI: 1.02-1.07; P<0.0001), hypertension (HR = 1.32; 95% CI: 1.13-1.54; P = 0.0004), and smoking in pack-years (HR = 1.04; 95% CI: 1.02-1.07; P = 0.0002).

CONCLUSIONS

Obesity, hypertension, and smoking are the 3 modifiable risk factors that could aggressively be targeted to reduce renal cell carcinoma.

Circulating adiponectin levels in various malignancies: an updated meta-analysis of 107 studies

Early detection of cancers is challenging for lack of specific biomarkers. Adiponectin is an adipokine predominantly derived from adipocytes and hypoadiponectinemia has been reported to associate with risk of many types of cancers. However, available evidence is controversial. Some studies show that increased adiponectin levels correlate with cancer risk. Therefore, we performed a meta-analysis of the association between circulating adiponectin levels and cancer development. A systematic search of PubMed, EMBASE, Wiley Online Library and Cochrane Library was conducted for eligible studies involving circulating adiponectin and malignancies from inception to August 8, 2015. Standard mean differences (SMDs) with 95% confidence intervals (95% CIs) were calculated by use of a random-effect model. Funnel plot and Egger's linear regression test were conducted to examine the risk of publication bias. 107 studies were included with 19,319 cases and 25,675 controls. The pooled analysis indicated that circulating adiponectin levels were lower in patients with various cancers than in controls, with a pooled SMD of −0.334 μg/ml (95% CI, −0.465 to −0.203, P = 0.000). No evidence of publication bias was observed. Circulating high molecular weight adiponectin levels were also lower in cancer patients than in controls, with a pooled SMD of −0.502 μg/ml (95% CI, −0.957 to −0.047, P = 0.000). This meta-analysis provides further evidence that decreased adiponectin levels is associated with risk of various cancers. Hypoadiponectinemia may represent a useful biomarker for early detection of cancers.

Circulating levels of obesity-related markers and risk of renal cell carcinoma in the PLCO cancer screening trial

PURPOSE

Obesity is an established risk factor for renal cell carcinoma (RCC). It is unclear what biologic mechanisms underlie this association, although recent evidence suggests that the effects of circulating hormones such as insulin-like growth factors (IGF) and adipokines may play a role.

METHODS

To address this question, we conducted a nested case-control study of RCC (252 cases, 252 controls) within the Prostate, Lung, Colorectal, and Ovarian Cancer Screening Trial investigating associations with pre-diagnostic serum levels of total adiponectin, high-molecular-weight (HMW) adiponectin, IGF-1, IGF-binding protein-3 (IGFBP-3), and C-peptide. Odds ratios (ORs) and 95% confidence intervals (95% CIs) were estimated using conditional logistic regression.

RESULTS

After adjustment for potential confounders, non-significant associations with RCC were observed for total adiponectin (OR for highest vs. lowest quartile = 0.65, 95% CI 0.37-1.14; p trend = 0.35), HMW adiponectin (0.67, 0.38-1.17; p trend = 0.36), IGF-1 (1.35, 0.77-2.39; p trend = 0.17), IGFBP-3 (1.47, 0.83-2.62; p trend = 0.53), and C-peptide (1.52, 0.86-2.70; p trend = 0.15). In a joint analysis with body mass index (BMI, kg/m2), obese individuals (BMI ≥30) with above-median levels of IGFBP-3 had a significantly higher risk versus those with BMI <25 and below-median IGFBP-3 (OR 2.42, 1.11-5.26), whereas obese individuals with low IGFBP-3 did not (1.18, 0.53-2.64) (p interaction = 0.35).

CONCLUSIONS

The results of this study, while not clearly supporting associations with these obesity-related hormones, suggest that the association between obesity and RCC may be partially modified through mechanisms related to elevated IGFBP-3.

Association of leptin, visfatin, apelin, resistin and adiponectin with clear cell renal cell carcinoma

Although an association between obesity and the occurrence of renal cell carcinoma (RCC) has been identified, the mechanism by which obesity functions to increase this risk of cancer remains unclear. Leptin, visfatin, apelin, resistin and adiponectin are peptide hormones secreted by adipocytes; it is considered that these may affect RCC development by exerting effects on proliferation, cell growth and inflammation. The aim of the present study was to investigate the association between the aforementioned adipokine genes and clear cell RCC (CC-RCC). The GSE6344 dataset was downloaded from the Gene Expression Omnibus database, and the relative expression levels of the adipokine genes were analyzed. To verify the results of the mRNA microarray, 77 paired samples of CC-RCC and corresponding adjacent normal tissue were allocated into two groups. The extraction of total RNA was conducted, and the mRNA expression of adipokine genes was analyzed using reverse transcription-quantitative polymerase chain reaction (RT-qPCR). The data from the GSE6344 dataset indicated that the expression of visfatin and apelin was upregulated (P<0.0001 and P<0.01, respectively), and adiponectin was downregulated (P<0.001) in the CC-RCC tissues compared with the adjacent normal tissues. The data from RT-qPCR demonstrated that visfatin and resistin gene expression was increased (P<0.01 and P<0.05, respectively) in the CC-RCC tissues. Furthermore, the mRNA expression level of leptin and adiponectin in the adjacent normal tissue was higher than those in the cancer tissue (P<0.01). The current study verifies that visfatin and adiponectin are associated with an increased risk of CC-RCC, which presents further insights into the molecular mechanisms of CC-RCC tumorigenesis.

Circulating resistin levels and obesity-related cancer risk: A meta-analysis

Resistin levels have been reported to be abnormal in obesity-related cancer patients with epidemiological studies yielding inconsistent results. Therefore, a meta-analysis was performed to assess the association between blood resistin levels and obesity-related cancer risk. A total of 13 studies were included for pooling ORs analysis. High resistin levels were found in cancer patients (OR= 1.20, 95% CI= 1.10-1.30). After excluding one study primarily contributing to between-study heterogeneity, the association between resistin levels and cancer risk was still significant (OR=1.18, 95% CI = 1.09-1.28). Stratification analysis found resistin levels were not associated with cancer risk in prospective studies. Meta-regression analysis identified factors such as geographic area, detection assay, or study design as confounders to between-study variance. The result of 18 studies of pooling measures on SMD analysis was that high resistin levels were associated with increased cancer risk (SMD = 0.94, 95% CI = 0.63-1.25), but not in the pooling SMD analysis of prospective studies. Except for the studies identified as major contributors to heterogeneity by Galbraith plot, resistin levels were still higher in cancer patients (SMD = 0.75, 95% CI = 0.63-0.87) in retrospective studies. Meta-regression analysis found factors, such as geographic area, BMI-match, size, and quality score, could account for 66.7% between-study variance in pooling SMD analysis of retrospective studies. Publication bias was not found in pooling ORs analysis. Our findings indicated high resistin levels were associated with increased obesity-related cancer risk. However, it may not be a predictor.

A Prospective Analysis of Plasma Adiponectin and Risk of Incident Cancer: The Dallas Heart Study

BACKGROUND

Adiponectin dysregulation is postulated to affect cancer risk via modulation of insulin resistance and inflammation. Epidemiologic studies evaluating this relationship have conflicting results and data from non-white cohorts are lacking. We examined the association between adiponectin and risk of cancer incidence in the multiethnic Dallas Heart Study (DHS).

METHODS

Participants enrolled in the DHS and known adiponectin values were included. Incident cancer cases were identified through a systematic linkage of the DHS and the Texas Cancer Registry. Univariate/multivariate analysis were performed to test the association between adiponectin and incident cancer after adjusting for age, diabetes status, gender, ethnicity, C-reactive protein level, smoking status, and body mass index. Adiponectin level was evaluated both as a continuous variable and in race/ethnicity specific quartiles.

RESULTS

Of 3444 individuals, there were 152 incident cancers. The study population was comprised of 44.4% men, and 51.05% were black. Baseline median adiponectin levels were 6.43 mcg/mL (interquartile range [IQR], 4.37-9.45 mcg/mL) in the incident cancer group versus 6.33 mcg/mL (IQR, 4.57-9.97 mcg/mL) in those without cancer. In multivariable analysis, adiponectin level was not associated with cancer incidence after adjusting for covariates. In analyses stratified by race/ethnic group, no association was observed in white, Hispanic, or African American subgroups.

CONCLUSIONS

In this study of a predominant ethnic minority population, no association between adiponectin and cancer incidence was demonstrated. Despite preclinical rationale and confirmatory findings in other studies, this association may not replicate across all ethnic populations. Additional studies with strong minority representation are warranted to further examine this association.

Identifying the emerging role of adipokine as a diagnostic and prognostic biomarker of renal cell carcinoma

OBJECTIVE

To assess the association and prognostic value of adipokines (adipocyte-secreted peptide hormones) in renal cell carcinoma (RCC).

MATERIALS AND METHODS

Plasma samples from 54 RCC patients and 25 age-matched healthy controls were analyzed for levels of adipokines (adiponectin, leptin, retinol-binding protein 4 [RBP4], and nicotinamide phosphoribosyltransferase [NAMPT]). Baseline characteristics and adipokine levels were compared between patients and controls. The effect of adipokine levels on RCC severity was also investigated.

RESULTS

Medians (patients/controls) were body mass index: 24.6/23.5kg/m(2), serum glucose: 111/93mg/dl, and high-density lipoprotein: 43/53mg/dl, and significantly differed between the 2 groups. Median levels (patients/controls) of adipokines were adiponectin: 4.36/8.84ug/ml, leptin: 2.91/2.92ng/ml, RBP4: 30.27/16.17ug/ml and NAMPT: 2.26/2.06ng/ml; adiponectin, RBP4 and NAMPT (but not leptin) were independently associated with RCC in logistic regression models, and only serum NAMPT was significantly associated with RCC severity (T stage).

CONCLUSIONS

Lower plasma levels of adiponectin, and higher levels of RBP4 and NAMPT, are strongly correlated with RCC, indicating that these adipokines could be used as biomarkers for RCC.

Obesity and Kidney Cancer

Renal cell cancer (RCC) is the major type of kidney cancer with increasing incidence. Obesity is one of the well-established risk factors for RCC. Meta-analyses including multiple cohort and case-control studies have found a consistent positive association between obesity and RCC. The association appeared to be independent of other RCC risk factors including hypertension and has been often stronger in women, although a positive association has also been observed in men. Obesity has been largely measured as body mass index (BMI). Studies which evaluated other measures of obesity including waist circumference (WC), waist-to-hip ratio (WHR) as well as increase in weight have reported similar positive associations with RCC. Although the mechanisms by which obesity influences renal carcinogenesis have been under-explored, insulin resistance and certain growth factors including insulin-like growth factor (IGF-1), sex steroid hormones, and biochemical markers such as adiponectin may be involved. The positive association with obesity has been observed with the clear cell type of RCC, which is the major histological subtype. On the other hand, the association between obesity and RCC survival appears to be much more complex. An apparent inverse association between obesity at time of diagnosis and RCC survival has been observed in some studies' generating speculation of an "obesity paradox" hypothesis. However, this "paradox" may be due to reverse causation, selection bias, or other forms of bias rather than a true biological association.

Obesity Biomarkers, Metabolism and Risk of Cancer: An Epidemiological Perspective

Obesity is associated with metabolic alterations that may pose a biological link between body fatness and risk of cancer. Elucidating the role of obesity-related biomarkers in cancer development is essential for developing targeted strategies aiming at obesity-associated cancer prevention. Molecular epidemiological studies of the past decades have provided evidence that major hormonal pathways linking obesity and cancer risk include the insulin and insulin-like growth factor-1 (IGF-1) axis, sex-steroid hormones, adipokines and chronic low-grade inflammation. These pathways are interrelated with each other, and their importance varies by obesity-related cancer type. The insulin/IGF-1 axis has been implicated to play an important mediating role in the association between obesity and risk of pancreatic, colorectal and prostate cancer. Endogenous sex-steroid hormone concentrations, in particular obesity-associated pre-diagnostic elevations of estrogens and androgens, play an important role in postmenopausal breast cancer and endometrial cancer development. The adipokines adiponectin and leptin and adipocyte-mediated chronic low-grade inflammation represented by the acute-phase C-reactive protein may explain a substantial part of the association between obesity and risk of colorectal cancer. There is less evidence on whether these hormonal pathways play a mediating role in other obesity-associated types of cancer. In this chapter, the molecular epidemiologic evidence from prospective studies relating circulating obesity-related biomarkers to cancer risk is summarized, taking into account available evidence from Mendelian Randomization investigations aiming at improving causal inference.

Serum leptin, C-reactive protein, and cancer mortality in the NHANES III

Adipokines, such as leptin, may affect cancer through its link with inflammation and obesity. We investigated the association between leptin, C‐reactive protein, and risk of cancer death while accounting general and abdominal obesity. From the Third National Health and Examination Survey (NHANES III), we selected 5957 adult men and women with baseline measurements of serum leptin and CRP. Multivariable Cox regression was used to assess leptin and CRP levels (low, moderate, high) in relation to risk of cancer death. Stratification analyses were performed for obesity as defined by body mass index (BMI) and waist circumference. Fine and Gray regression was performed to account for death from cardiovascular disease and other causes as competing events. A total of 385 participants died of cancer during a mean follow‐up of 18 years. After adjusting for BMI and waist circumference, an inverse association with log‐transformed leptin was found for women, with a hazard ratio (HR) of 0.81 (95% confidence interval [CI]: 0.51–1.30) and 0.40 (95% CI: 0.24–0.68) for moderate and high compared to low levels of leptin, respectively; P_trend = 0.0007). No association for leptin was observed in men, but higher CRP corresponded to increased risk of dying from cancer (HR: 2.98; 95% CI: 1.57–5.64 for the highest vs. lowest categories of CRP). Similar associations were observed with competing risk analysis also adjusted for BMI and waist circumference. Contrasting associations of serum leptin and CRP with cancer mortality may indicate sex‐specific biological or environmental pathways linking obesity and cancer in men and women which warrant mechanistic investigations.

Serum Adiponectin Predicts Cancer-specific Survival of Patients with Renal Cell Carcinoma

BACKGROUND

Prediction of outcomes in patients with renal cell carcinoma (RCC) is crucial for clinical decision-making. The limited accuracy of conventional prognostic factors such as stage and grade may be increased by the use of biomarkers.

OBJECTIVE

To evaluate the association of serum adiponectin and leptin and polymorphisms in the leptin and leptin receptor genes with RCC histopathology and prognosis.

DESIGN, SETTING, AND PARTICIPANTS

Adiponectin and leptin levels were measured in preoperative serum samples from 131 consecutive patients with sporadic unilateral RCC. The polymorphisms G-2548A (rs7799039) in the leptin gene (LEP) and Gln223Arg (Q223R, A668G, rs1137101) in the leptin receptor gene (LEPR) were genotyped in 233 patients.

OUTCOME MEASUREMENTS AND STATISTICAL ANALYSIS

Multivariable associations with RCC-specific survival were analyzed using Cox models.

RESULTS AND LIMITATIONS

Median preoperative serum adiponectin was 15.8μg/ml (interquartile range 10.0-23.1). Adiponectin was lower in patients with distant metastases (p=0.017) or histologic tumor necrosis (p=0.015). On multivariable analysis adjusted for the effects of variables in the Karakiewicz nomogram, each 1-μg/ml increase in adiponectin was associated with a 8% decrease in the hazard of death from RCC (hazard ratio 0.92, 95% confidence interval 0.86-0.98; p=0.007). The discrimination of the Karakiewicz nomogram increased by 0.6% on inclusion of adiponectin. Leptin levels, LEP G-2548A and LEPR Q223R were not associated with either RCC pathology or outcomes. Limitations include the retrospective study design, the low numbers of patients, and a lack of standardized follow-up.

CONCLUSIONS

This study suggests that lower preoperative serum adiponectin is associated with features of biologically aggressive RCC, metastasis, and survival.

PATIENT SUMMARY

We assessed the relationship between outcomes and blood levels of adiponectin and leptin and genetic changes in leptin and leptin receptor genes. We found that patients with lower adiponectin levels have more aggressive tumors and poorer survival.

Losartan reduces oxidative damage to renal DNA and conserves plasma antioxidant capacity in diabetic rats

Increased reactive oxygen species (ROS) levels produced by hyperglycemia and angiotensin-II (AT-II) are considered among the pathogenic factors in the malignant transformation of diabetic renal cells. We aimed to investigate the potential role of AT-II in the increased cancer risk seen in diabetes; measuring oxidative damage to renal DNA and protective antioxidant defenses, including adiponectin (Adp) and plasma antioxidant capacity by the Ferric Reducing Ability of Plasma (FRAP) method. In the kidney of streptozotocin (STZ)-induced (55 mg/kg) diabetic rats either treated or not treated for 3 weeks with losartan, an AT-II type 1 receptor antagonist (20 mg/kg/day); we measured 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxodGuo) levels, as an index of oxidative DNA damage, circulating Adp and FRAP. Diabetic rats showed significantly higher 8-oxodGuo levels in renal DNA (8.48 ± 0.98 × 10(-6) dG, mean ± SEM n = 11) than normoglycemic ones (1.18 ± 0.04 × 10(-6) dG, mean ± SEM, n=7) and lower plasma Adp and FRAP levels in comparison to normoglycemics. The treatment of diabetic rats with losartan significantly (P < 0.01) reduced 8-oxodGuo levels (5.4 ± 0.58 × 10(-6) dG, mean ± SEM n=9) in renal DNA and conserved FRAP values. Moreover, an inverse correlation was found between 8-oxodGuo in kidney DNA and circulating Adp levels in normoglycemic and diabetic rats. Losartan treatment preserves FRAP levels, reduces DNA oxidative injury and thus the carcinogenesis risk. Furthermore, our results indicate that Adp plasma levels are a further marker of oxidative injury to the kidney and confirm that it is an important part of the plasma antioxidant defense.

Visceral fat accumulation is associated with different pathological subtypes of renal cell carcinoma (RCC): a multicentre study in China

OBJECTIVE

To investigate whether visceral obesity is associated with certain histological subtypes of renal cell carcinoma (RCC) ina multicentre Chinese cohort.

PATIENTS AND METHODS

A kidney tumour database was created using three tertiary centres in China; 487 patients were enrolled presenting with localised RCC and complete computer tomography(CT)/magnetic resonance imaging (MRI) information. A single-slice CT image was used to measure the area of visceral and subcutaneous adipose tissues in each patient. Statistical methods were used to analyse clear-cell RCC (ccRCC) and non-clear-cell RCC (non-ccRCC) as they relate to visceral fat area (VFA) and other risk factors, such as age, gender, tumour size, diabetes, hypertension, total fat area (TFA) and body mass index (BMI).

RESULTS

In all, 418 patients had a ccRCC subtype and 69 had a non-ccRCC subtype. For all the patients with RCC, the mean VFA was 102 cm2, while mean BMI was 24 kg/m2. The mean VFA was greater in ccRCC than non-ccRCC patients by 25 cm2. There were significant differences in the mean VFA and TFA between patients with ccRCC and those with non-ccRCC.Multivariate analysis showed that the presence ofVFA was more important than the effects of BMI and Type 2 diabetes on pathology prediction. In patients with a normal BMI, those with a higher quartile of VFA were more likely to develop ccRCC than those with a low VFA.

CONCLUSIONS

Increased visceral fat was found to be associated with ccRCC and the significance of VFA outweighed the effects of BMI and Type 2 diabetes for the prediction of RCC pathology in multivariate analyses. As a result, VFA could constitute a primary explanation for the link between obesity and ccRCC.

Resistin as a biomarker linking obesity and inflammation to cancer: potential clinical perspectives

Excess body weight is associated with various types of malignancies. Resistin, originally described as an adipocyte-specific hormone modulating insulin resistance in rodents, may exhibit proliferative, antiapoptotic, proinflammatory, proangiogenic and metastatic properties. Accumulating evidence supports a role of resistin as a risk factor and potential diagnostic and prognostic biomarker in cancer. In this report, the current knowledge about resistin's properties and pathophysiological implications in cancer in the context of dysregulated adipose tissue in obesity is summarized; clinical translations, preventive and therapeutic considerations, and future perspectives in the field of resistin research are discussed. At the same time, several enigmatic issues involving resistin receptor and signaling pathways remain to be clarified in order to unmask its ontological role in cancer pathophysiology.