Meta-analysis: circulating adiponectin levels and risk of colorectal cancer and adenoma

Visceral Fat Thickness, Serum Adiponectin, and Metabolic Syndrome in Patients with Colorectal Adenomas

BACKGROUND/OBJECTIVES

Most cases of colorectal cancer (CRC) arise from adenomatous polyps. Identifying risk factors for colorectal adenoma (CRA) is critical for CRC prevention. Emerging evidence suggests a link between metabolic syndrome (MetS) and an elevated risk of CRA and CRC, potentially mediated by visceral obesity and adiponectin (APN). We aimed to evaluate the association between different markers of visceral obesity, serum APN, MetS, and the presence of CRA.

METHODS

A cross-sectional study was conducted at the University Clinical Center of Vojvodina, involving 120 patients, aged 40-75 years, who underwent colonoscopy between January 2022 and January 2023. Sixty patients with CRA were compared to 60 controls with normal colonoscopy findings. Visceral fat thickness (VFT) was measured using ultrasound (US), and bioelectrical impedance analysis (BIA) was used to assess visceral fat area (VFA). Serum APN levels, anthropometric measures, and MetS components were also evaluated.

RESULTS

Patients with CRA had significantly higher VFT measured by US (p < 0.05), but no significant differences were found in VFA measured by BIA, waist circumference (WC), or waist-to-hip ratio (WHR). MetS was significantly more prevalent in the CRA group (55% vs. 31.6%, p < 0.05), and logistic regression confirmed MetS as a significant predictor of CRA presence (OR = 2.6). Serum APN levels were inversely correlated with visceral fat measurements and MetS (p < 0.01), but no significant difference in APN levels was observed between patients with and without CRA.

CONCLUSIONS

This study highlights the importance of VFT measured by US and the presence of MetS as significant factors associated with CRA.

An Updated Review of Resistin and Colorectal Cancer

Resistin is one of the most important adipokines, and its role lies mainly in controlling insulin sensitivity and inflammation. However, over the last years, the study of resistin gained increased popularity since it was proved that there is a considerable relationship between high levels of resistin and obesity as well as obesity-induced diseases, including diabetes, cardiovascular disorders, and cancer. Regarding cancer risk, circulating resistin levels have been correlated with several types of cancer, including colorectal, breast, lung, endometrial, gastroesophageal, prostate, renal, and pancreatic cancer. Colorectal cancer is regarded as a multi-pathway disease. Several pathophysiological features seem to promote colorectal cancer (CRC) such as chronic inflammation, insulin resistance, and obesity. Even though the molecular mechanisms involved in CRC development remain rather vague, it is widely accepted that several biochemical factors promote CRC by releasing augmented pro-inflammatory cytokines, like IGF-I, insulin, sex-steroid hormones, and adipokines. A wide range of research studies has focused on evaluating the impact of circulating resistin levels on CRC risk and determining the efficacy of chemotherapy in CRC patients by measuring resistin levels. Moreover, significant outcomes have emerged regarding the association of specific single nucleotide polymorphisms (SNPs) in the resistin gene and CRC risk. The present study reviewed the role of circulating resistin levels in CRC development and shed light on specific resistin gene SNPs implicated in the disease's development. Finally, we analyzed the impact of resistin levels on the effectiveness of chemotherapy and further discussed whether resistin can be regarded as a valuable biomarker for CRC prognosis and treatment. Resistin is one of the most important adipokines, and its role lies mainly in controlling insulin sensitivity and inflammation. However, over the last years, the study of resistin gained increased popularity since it was proved that there is a considerable relationship between high levels of resistin and obesity as well as obesity-induced diseases, including diabetes, cardiovascular disorders, and cancer. This review discusses the aberrant expression of resistin and its receptors, its diverse downstream signaling, and its impact on tumor growth, metastasis, angiogenesis, and therapy resistance to support its clinical exploitation in biomarker and therapeutic development.

The role of bidirectional communication between the adipokines and the endogenous opioid system in an experimental mouse model of colitis-associated colorectal cancer

BACKGROUND

Colorectal cancer (CRC) is one of the leading causes of death globally. Multiple factors may contribute to the pathogenesis of CRC, including the abnormalities in the functioning of the endogenous opioid system (EOS) or adiponectin-related signaling. The aim of our study was to evaluate if differences in the expression of opioid receptors (ORs) influence the development of CRC and if modulation of adiponectin receptors using AdipoRon, a selective AdipoR1 receptor agonist, affects colorectal carcinogenesis.

METHODS

Naltrexone, an opioid receptor antagonist, was injected intraperitoneally every second day for 2 weeks, at the dose of 1 mg/kg in healthy Balb/C mice to induce changes in ORs expression. CRC was induced by a single intraperitoneal injection of azoxymethane (AOM) and the addition of dextran sodium sulfate (DSS) into drinking water in three-week cycles. The development of CRC was assessed using macro- and microscopic scoring and molecular analysis (RT qPCR, ELISA) after 14 weeks.

RESULTS

Naltrexone significantly increased the mRNA expression of Oprm1, Oprd1, and Oprk1 in the mouse colon and in the brain (non-significantly). The pretreatment of mice with naltrexone aggravated the course of CRC (as indicated by tumor area, colon thickness, and spleen weight). The level of circulatory adiponectin was lowered in mice with CRC and increased in the colon as compared with healthy mice. The β-endorphin level was increased in the plasma of mice with CRC and decreased in the colon as compared to healthy mice. AdipoRon, AdipoR1 agonist, worsened the CRC development, and pretreatment with naltrexone enhanced this negative effect in mice. CRC did not affect the expression of the Adipor1 gene, but the Adipor1 level was increased in mice pretreated with naltrexone (AOM/DSS and healthy mice). AdipoRon did not influence the expression of opioid receptors at the mRNA level in the colon of mice with CRC. The mRNA expression of Ptgs2, Il6, Nos2, Il1b, Il18, Gsdmd, and Rela was increased in mice with CRC as compared to the healthy colon. AdipoRon significantly decreased mRNA expression of Ptgs2, Il6, Il1b, and Il18 as compared to CRC mice.

CONCLUSION

EOS and adiponectin-related signaling may play a role in the pathogenesis of CRC and these systems may present some additivity during carcinogenesis.

Novel Adiponectin Receptor Agonist Inhibits Cholangiocarcinoma via Adenosine Monophosphate-activated Protein Kinase

BACKGROUND

Cholangiocarcinoma (CCA) has a poor prognosis and only limited palliative treatment options. The deficiency of adiponectin and adenosine monophosphate-activated protein kinase (AMPK) signaling was reported in several malignancies, but the alteration of these proteins in CCA is still unclear.

OBJECTIVES

This study aimed to assess the role of adiponectin and AMPK signaling in CCA. Furthermore, AdipoRon, a novel adiponectin receptor (AdipoR) agonist, was evaluated in vitro and in vivo as a new anti-tumor therapy for CCA.

METHODS

The expression of AdipoR1 and p-AMPKα in human tissue microarrays (TMAs) was evaluated by immunohistochemistry staining (IHC). The effect of 2-(4-Benzoylphenoxy)-N-[1-(phenylmethyl)-4-piperidinyl]-acetamide (AdipoRon) was investigated in vitro with proliferation, crystal violet, migration, invasion, colony formation, senescence, cell cycle and apoptosis assays and in vivo using a CCA engineered mouse model (AlbCre/LSL-KRASG12D/p53L/L). RT-qPCR and western blot methods were applied to study molecular alterations in murine tissues.

RESULTS

AdipoR1 and p-AMPKα were impaired in human CCA tissues, compared to adjacent non-tumor tissue. There was a positive correlation between the AdipoR1 and p-AMPKα levels in CCA tissues. Treatment with AdipoRon inhibited proliferation, migration, invasion and colony formation and induced apoptosis in a time- and dose-dependent manner in vitro (p<0.05). In addition, AdipoRon reduced the number of CCA and tumor volume, prolonged survival, and decreased metastasis and ascites in the treated group compared to the control group (p<0.05).

CONCLUSIONS

AdipoR1 and p-AMPKα are impaired in CCA tissues, and AdipoRon effectively inhibits CCA in vitro and in vivo. Thus, AdipoRon may be considered as a potential anti-tumor therapy in CCA.

Association between post-treatment circulating biomarkers of inflammation and survival among stage II-III colorectal cancer patients

BACKGROUND

Biomarker studies on colorectal cancer (CRC) prognosis are limited to pre-diagnostic or pre-operative measures. Post-treatment biomarkers are not well understood for their associations with CRC survival.

METHODS

We included 306 eligible incident stage II-III CRC cases from the population-based Seattle Colon Cancer Family Registry. Concentrations of C-reactive protein (CRP), interleukin-6 (IL-6), monocyte chemoattractant protein-1 (MCP-1), adiponectin, and leptin were measured using post-treatment plasma samples. Adjusted hazard ratios (HRs) and 95% confidence intervals (CIs) for all-cause and CRC-specific mortality were calculated using Cox proportional hazard models.

RESULTS

Elevated levels of CRP, IL-6, MCP-1, and adiponectin were significantly associated with a higher risk of all-cause mortality within 10 years post blood draw with HRs (95% CI) of 1.32 (1.10-2.59), 2.72 (2.07-3.56), 1.97 (1.18-3.28) and 1.71 (1.14-2.58), respectively. IL-6 and adiponectin had a dose-response effect (P_trend < 0.0001). For CRC-specific mortality, we observed positive associations for CRP (HR = 1.75, 95% CI: 1.2-2.56), IL-6 (HR = 5.02, 95% CI: 2.92-8.59), MCP-1 (HR = 3.78, 95% CI: 1.41-10.08), and adiponectin (HR = 3.16, 95% CI: 1.27-7.86), and inverse association for leptin (HR = 0.44, 95% CI: 0.29-0.68) within the first year of blood draw, whereas the association for IL-6 remained statistically significant over 10 years.

CONCLUSION

Our results support the role of chronic inflammation in CRC progression and suggested several post-treatment inflammatory biomarkers, particularly IL-6, are promising prognostic markers for stage II-III CRC patients.

Cancer Risk in Normal Weight Individuals with Metabolic Obesity: A Narrative Review

Obesity represents one of the most significant public health challenges worldwide. Current clinical practice relies on body mass index (BMI) to define the obesity status of an individual, even though the index has long been recognized for its limitations as a measure of body fat. In normal BMI individuals, increased central adiposity has been associated with worse health outcomes, including increased risks of cardiovascular disease and metabolic disorders. The condition leading to these outcomes has been described as metabolic obesity in the normal weight (MONW). More recent evidence suggests that MONW is associated with increased risk of several obesity-related malignancies, including postmenopausal breast, endometrial, colorectal, and liver cancers. In MONW patients, the false reassurance of a normal range BMI can lead to lost opportunities for implementing preventive interventions that may benefit a substantial number of people. A growing body of literature has documented the increased risk profile of MONW individuals and demonstrated practical uses for body composition and biochemical analyses to identify this at-risk population. In this review, we survey the current literature on MONW and cancer, summarize pathophysiology and oncogenic mechanisms, highlight potential strategies for diagnosis and treatment, and suggest directions for future research.

Growth hormone-releasing hormone (GHRH) deficiency promotes inflammation-associated carcinogenesis

The somatotropic axis, in addition to its well-known metabolic and endocrine effects, plays a pivotal role in modulation of inflammation. Moreover, growth hormone (GH)-releasing hormone (GHRH) has been involved in the development of various human tumors. In this work we aimed to investigate the consequences of GHRH deficiency on the development of inflammation-associated colon carcinogenesis in a mouse model of isolated GH deficiency due to generalized ablation of the GHRH gene [GHRH knock out (GHRHKO)]. Homozygous GHRHKO (-/-) male mice and wild type (C57/BL6, +/+) male mice as control group, were used. After azoxymetane (AOM)/dextran sodium sulfate (DSS) treatment -/- mice displayed higher Disease Activity Index (DAI) score, and more marked weight loss compared to +/+ animals. Additionally, -/- mice showed a significant increase in total tumors, in particular of large size predominantly localized in distal colon. In colonic tissue of AOM/DSS-treated -/- mice we found the presence of invasive adenocarcinomas, dysplasia and colitis with mucosal ulceration. Conversely, AOM/DSS-treated +/+ mice showed only presence of adenomas, without invasion of sub-mucosa. Treatment with AOM/DSS significantly increased prostaglandin (PG)E₂ and 8-iso-PGF_2α levels along with cyclooxygenase-2 (COX-2), tumor necrosis factor (TNF)-α, nuclear factor kappa B (NF-kB) and inducible nitric oxide synthase (iNOS) gene expression, in colon specimens. The degree of increase of all these parameters was more markedly in -/- than +/+ mice. In conclusion, generalized GHRH ablation increases colon carcinogenesis responsiveness in male mice. Whether this results from lack of GH or GHRH remains to be established.

Low bone turnover levels predict increased risk of cancer

BACKGROUND

Several epidemiological studies have shown an association between bone mineral density (BMD) and risk of breast cancer in postmenopausal women, but it remains unknown whether bone turnover is associated with increased risk of cancer. The aim of this study was to investigate if markers of bone formation and resorption are associated with increased risk of cancer.

MATERIAL AND METHODS

The study population included 5855 postmenopausal Danish women enrolled in the Prospective Epidemiologic Risk Factor (PERF) study. Cancer diagnosis was obtained from the Danish Cancer Registry. Baseline spine, femur, and whole-body BMD were evaluated by DXA-scanners. Baseline bone turnover (CTX-1 and osteocalcin) were measured in serum. Multivariate Cox analysis was performed with 3, 6 and 12 years of follow-up. All continuous variables were transformed into z-score for the cox analyses.

RESULTS

252 developed cancer after 3 years, 462 developed cancer after 6 years, and 881 developed cancer with 12 years of follow-up. CTX-1, osteocalcin and spine BMD were all predictors of cancer at all time points (3 years of follow-up: Spine BMD, HR = 1.20, p = 0.003; CTX-1, HR = 0.82, p = 0.005; osteocalcin, HR = 0.75, p < 0.001). After adjusting for cancer risk factors and other bone measures CTX-1 and osteocalcin remained independent predictors of cancer (3 years of follow-up: CTX-1, HR = 0.82, p = 0.02; osteocalcin, HR = 0.75, p = 0.002).

CONCLUSIONS

We found that levels of the bone turnover markers CTX-1 and osteocalcin were inversely associated with risk of cancer independent of BMD and other known cancer risk factors in postmenopausal women.

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.

Mendelian randomization analysis of C-reactive protein on colorectal cancer risk

BACKGROUND

Chronic inflammation is a risk factor for colorectal cancer (CRC). Circulating C-reactive protein (CRP) is also moderately associated with CRC risk. However, observational studies are susceptible to unmeasured confounding or reverse causality. Using genetic risk variants as instrumental variables, we investigated the causal relationship between genetically elevated CRP concentration and CRC risk, using a Mendelian randomization approach.

METHODS

Individual-level data from 30 480 CRC cases and 22 844 controls from 33 participating studies in three international consortia were used: the Genetics and Epidemiology of Colorectal Cancer Consortium (GECCO), the Colorectal Transdisciplinary Study (CORECT) and the Colon Cancer Family Registry (CCFR). As instrumental variables, we included 19 single nucleotide polymorphisms (SNPs) previously associated with CRP concentration. The SNP-CRC associations were estimated using a logistic regression model adjusted for age, sex, principal components and genotyping phases. An inverse-variance weighted method was applied to estimate the causal effect of CRP on CRC risk.

RESULTS

Among the 19 CRP-associated SNPs, rs1260326 and rs6734238 were significantly associated with CRC risk (P = 7.5 × 10-4, and P = 0.003, respectively). A genetically predicted one-unit increase in the log-transformed CRP concentrations (mg/l) was not associated with increased risk of CRC [odds ratio (OR) = 1.04; 95% confidence interval (CI): 0.97, 1.12; P = 0.256). No evidence of association was observed in subgroup analyses stratified by other risk factors.

CONCLUSIONS

In spite of adequate statistical power to detect moderate association, we found genetically elevated CRP concentration was not associated with increased risk of CRC among individuals of European ancestry. Our findings suggested that circulating CRP is unlikely to be a causal factor in CRC development.

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.

Diagnosis of obesity and use of obesity biomarkers in science and clinical medicine

The global epidemic of obesity is a major public health problem today. Obesity increases the risk of many chronic diseases, such as type 2 diabetes, coronary heart disease, and certain types of cancer, and is associated with lower life expectancy. The body mass index (BMI), which is currently used to classify obesity, is only an imperfect measure of abnormal or excessive body fat accumulation. Studies have shown that waist circumference as a measure of fat distribution may improve disease prediction. More elaborate techniques such as magnetic resonance imaging are increasingly available to assess body fat distribution, but these measures are not readily available in routine clinical practice, and health-relevant cut-offs not yet been established. The measurement of biomarkers that reflect the underlying biological mechanisms for the increased disease risk may be an alternative approach to characterize the relevant obesity phenotype. The insulin/insulin-like growth factor (IGF) axis and chronic low-grade inflammation have been identified as major pathways. In addition, specific adipokines such as leptin, adiponectin and resistin have been related to obesity-associated health outcomes. This biomarker research, which is currently further developed with the application of high throughput methods, gives important insights in obesity-related disease etiology and pathophysiological pathways and may be used to better characterize obese persons at high risk of disease development and target disease-causing biomarkers in personalized prevention strategies.

Adiponectin as Link Factor between Adipose Tissue and Cancer

Adipose tissue is a key regulator of energy balance playing an active role in lipid storage as well as in synthesizing several hormones directly involved in the pathogenesis of obesity. Obesity represents a peculiar risk factor for a growing list of cancers and is frequently associated to poor clinical outcome. The mechanism linking obesity and cancer is not completely understood, but, amongst the major players, there are both chronic low-grade inflammation and deregulation of adipokines secretion. In obesity, the adipose tissue is pervaded by an abnormal number of immune cells that create an inflammatory environment supporting tumor cell proliferation and invasion. Adiponectin (APN), the most abundant adipokine, shows anti-inflammatory, anti-proliferative and pro-apoptotic properties. Circulating levels of APN are drastically decreased in obesity, suggesting that APN may represent the link factor between obesity and cancer risk. The present review describes the recent advances on the involvement of APN and its receptors in the etiology of different types of cancer.

Leptin gene variants and colorectal cancer risk: Sex-specific associations

BACKGROUND

High levels of serum leptin and low levels of serum adiponectin are strongly correlated with obesity, a well-established risk factor for colorectal cancer (CRC). Growing evidence suggests that dysregulation of leptin and adiponectin levels may play an etiological role in colorectal carcinogenesis. We evaluated 20 candidate variants in 4 genes previously shown to alter serum leptin and adiponectin levels for associations with obesity (BMI>30 kg/m2) and CRC risk.

METHODS

We analyzed 6,246 CRC cases and 7,714 population-based controls from 11 studies within the Genetics and Epidemiology of Colorectal Cancer Consortium (GECCO). Associations of each variant with obesity or CRC were evaluated using multivariate logistic regression models stratified by sex and adjusted for age, a study variable, and the first three principal components of genetic ancestry. Gene-specific False Discovery Rate (FDR)-adjusted p-values <0.05 denoted statistical significance.

RESULTS

Two variants in the leptin gene showed statistically significant associations with CRC among women: LEP rs2167270 (OR = 1.13, 95% CI: 1.06-1.21) and LEP rs4731426 (OR = 1.09, 95% CI: 1.02-1.17). These associations remained significant after adjustment for obesity, suggesting that leptin SNPs may influence CRC risk independent of obesity. We observed statistically significant interactions of the leptin variants with hormone replacement therapy (HRT) for CRC risk; these variant associations were strengthened when analyses were restricted to post-menopausal women with low estrogen exposure, as estimated by 'never use' of HRT and/or non-obese BMI. No variants were associated with CRC among men.

CONCLUSIONS

Leptin gene variants may exhibit sex-specific associations with CRC risk. Endogenous and exogenous estrogen exposure may modify the association between these variants, leptin levels, and CRC risk.

Sex differences in associations among metabolic syndrome, obesity, related biomarkers, and colorectal adenomatous polyp risk in a Japanese population

To investigate sex differences in the associations among metabolic syndrome, obesity, adipose tissue-related biomarkers, and colorectal adenomatous polyps, a cross-sectional, multicenter study was conducted on 489 consecutive individuals who underwent their first colonoscopy at 3 hospitals. Plasma concentrations of adiponectin and leptin, as well as homeostatic model assessment of insulin resistance were also evaluated. The presence and number of adenomatous polyps, including advanced adenoma, were higher in men than in women. Metabolic syndrome was a risk factor for adenomatous polyps in both sexes. Large waist circumference was an independent risk factor for adenomatous polyps in men, and high BMI and large waist circumference were risk factors for adenomatous polyps in women. Interestingly, low BMI was associated with large adenomatous polyps (≥10 mm) and advanced adenoma, and waist-hip ratio was involved in proximal adenomatous polyp development only in women. In contrast, the highest quartile of leptin concentration had a 3.67-fold increased adenomatous polyp risk compared with the lowest quartile only in men. These results indicate that regarding colorectal pathogenesis, sex differences were identified in obesity but not in metabolic syndrome. Visceral obesity and a high serum leptin level may be risk factors for colorectal adenomatous polyp development in Japanese men.

Polymorphisms in genes related to inflammation and obesity and colorectal adenoma risk

We previously investigated the association between single nucleotide polymorphisms (SNPs) in genes related to obesity and inflammation and colorectal cancer in the CLUE II cohort. However, the relationships between these SNPs and colorectal adenomas have not been well evaluated. In a nested case-control study of 135 incident adenoma cases and 269 matched controls in the CLUE II cohort (1989-2000), we genotyped 17 candidate SNPs in 12 genes (PPARG, TCF7L2, ADIPOQ, LEP, IL10, CRP, TLR4, IL6, IL1B, IL8, TNF, RNASEL) and 19 tagSNPs in three genes (IL10, CRP, and TLR4). Conditional logistic regression was used to calculate odds ratios (OR) for adenomas (overall and by size, histology, location, number). Polymorphisms in the inflammatory-related genes CRP, ADIPOQ, IL6, and TLR4 were observed to be associated with adenoma risk. At rs1205 in CRP, T (minor allele) carriers had a higher risk (OR 1.67, 95%CI 1.07-2.60; reference: CC) of adenomas overall and adenomas with aggressive characteristics. At rs1201299 in ADIPOQ, the AC genotype had a higher risk (OR 1.58, 95%CI 1.00-2.49) of adenomas, while the minor AA genotype had a borderline inverse association (OR 0.44, 95%CI 0.18-1.08; reference: CC). At rs1800797 in IL6, the AA genotype had a borderline inverse association (OR 0.53, 95%CI 0.27-1.05; reference: GG). Three TLR4 tagSNPs (rs10116253, rs1927911, rs7873784) were associated with adenomas among obese participants. None of these SNPs were associated with colorectal cancer in our prior study in CLUE II, possibly suggesting a different genetic etiology for early colorectal neoplasia.

Low circulating total adiponectin, especially its non-high-molecular weight fraction, represents a promising risk factor for colorectal cancer: a meta-analysis

Aim

The principal goal of this meta-analysis is to test the hypothesis that circulating total adiponectin or certain fractions may represent a promising biological candidate in modulating the risk of colorectal cancer.

Methods

The processes of paper identification, paper selection and data extraction were accomplished independently by two authors. Effect-size estimates were expressed as weighted mean difference (WMD) and 95% confidence interval (95% CI). A total of 31 papers including 48 qualified studies (7,554 patients with colorectal cancer and 9,798 controls) were meta-analyzed.

Results

Pooling all studies found that circulating total adiponectin was significantly lower in patients with colorectal cancer than in controls (WMD: −0.76 µg/mL, 95% CI: −1.20 to −0.32, p=0.001), with significant heterogeneity (I²: 94.2%) and low publication bias (Egger’s p=0.336). By adiponectin fractions, the difference in high-molecular weight (HMW) adiponectin was comparable between the two groups (WMD: −0.22 µg/mL, 95% CI: −0.70 to 0.25, p=0.350), while non-HMW adiponectin was significantly lower in patients with colorectal cancer than in controls (WMD: −0.27 µg/mL, 95% CI: −0.35 to −0.19, p<0.001), with marginal heterogeneity (I²: 52.3%). Subgroup analysis revealed that effect-size estimates were heterogeneous when grouping studies by cancer subtype, region, study design, matching status, gender and obesity. Further meta-regression analysis indicated that age and gender were significant potential sources of heterogeneity. The results showed the studied subgroups were not subject to publication bias (Egger’s p<0.1).

Conclusion

Our data collectively indicate that low circulating total adiponectin, especially its non-HMW fraction, represents a promising risk factor for colorectal cancer. Further studies are needed to explore underlying mechanisms.

Sex differences in associations among metabolic syndrome, obesity, related biomarkers, and colorectal adenomatous polyp risk in a Japanese population

To investigate sex differences in the associations among metabolic syndrome, obesity, adipose tissue-related biomarkers, and colorectal adenomatous polyps, a cross-sectional, multicenter study was conducted on 489 consecutive individuals who underwent their first colonoscopy at 3 hospitals. Plasma concentrations of adiponectin and leptin, as well as homeostatic model assessment of insulin resistance were also evaluated. The presence and number of adenomatous polyps, including advanced adenoma, were higher in men than in women. Metabolic syndrome was a risk factor for adenomatous polyps in both sexes. Large waist circumference was an independent risk factor for adenomatous polyps in men, and high BMI and large waist circumference were risk factors for adenomatous polyps in women. Interestingly, low BMI was associated with large adenomatous polyps (≥10 mm) and advanced adenoma, and waist-hip ratio was involved in proximal adenomatous polyp development only in women. In contrast, the highest quartile of leptin concentration had a 3.67-fold increased adenomatous polyp risk compared with the lowest quartile only in men. These results indicate that regarding colorectal pathogenesis, sex differences were identified in obesity but not in metabolic syndrome. Visceral obesity and a high serum leptin level may be risk factors for colorectal adenomatous polyp development in Japanese men.

Pre-diagnostic biomarkers of metabolic dysregulation and cancer mortality

INTRODUCTION

The obesogenic milieu is a pro-tumorigenic environment that promotes tumor initiation, angiogenesis and metastasis. In this prospective cohort, we examined the association between pre-diagnostic metabolic biomarkers, plasma adiponectin, resistin, leptin and lipoprotein (a), and the risk of cancer mortality.

METHODS

Prospective data was obtained from the REasons for Geographic and Racial Differences in Stroke (REGARDS) cohort of Blacks and Whites followed from 2003 through 2012 for cancer mortality. We determined the association between metabolism biomarkers (log-transformed and tertiles) and risk of cancer mortality using Cox Proportional Hazards models with robust sandwich estimators to calculate the 95% confidence intervals (CIs), and adjusted for baseline covariates, including age, gender, income, education, physical activity, BMI, smoking status, alcohol use, and comorbidity score.

RESULTS

Among 1764 participants with available biomarker data, each SD higher log-leptin was associated with a 54% reduced risk of total cancer mortality (HR: 0.46, 95% CI: 0.23 – 0.92) and obesity-related cancer mortality (HR: 0.55, 95% CI: 0.39-0.79). Among Blacks only, each SD higher log-resistin was associated with a nearly 7-fold increased risk of cancer mortality (adjusted HR: 6.68, 95% CI: 2.10 – 21.21). There were no significant associations of adiponectin or Lp(a) and cancer mortality.

CONCLUSIONS

Leptin is involved in long-term regulation of energy balance, while resistin is involved in chronic inflammation and LDL production. These findings highlight the biological mechanisms linking metabolic dysregulation with cancer mortality, and the influence of resistin on cancer mortality only among Blacks suggests that this hormone may be a useful biomarker of racial differences in cancer mortality that deserves further study.

IMPACT

Our observed increased risk of cancer mortality associated with higher serum resistin levels among Blacks suggests that if validated in larger cohorts, clinical strategies focused on resistin control may be a promising cancer prevention strategy.

Adult weight gain and colorectal adenomas-a systematic review and meta-analysis

Background

Colorectal adenomas are known as precursors for the majority of colorectal carcinomas. While weight gain during adulthood has been identified as a risk factor for colorectal cancer, the association is less clear for colorectal adenomas. We conducted a systematic review and meta-analysis to quantify the evidence on this association.

Methods

We searched Medline up to September 2016 to identify observational (prospective, cross-sectional and retrospective) studies on weight gain during adulthood and colorectal adenoma occurrence and recurrence. We conducted meta-analysis on high weight gain versus stable weight, linear and non-linear dose-response meta-analyses to analyze the association. Summary odds ratios (OR) and 95% confidence intervals (95% CI) were estimated using a random effects model.

Results

For colorectal adenoma occurrence, the summary OR was 1.39 (95% CI: 1.17-1.65; I2: 43%, N = 9 studies, cases = 5507) comparing high (midpoint: 17.4 kg) versus stable weight gain during adulthood and with each 5 kg weight gain the odds increased by 7% (2%-11%; I2: 65%, N = 7 studies). Although there was indication of non-linearity (Pnon-linearity < 0.001) there was an increased odds of colorectal adenoma throughout the whole range of weight gain. Three studies were identified investigating the association between weight gain and colorectal adenoma recurrence and data were limited to draw firm conclusions.

Conclusions

Even a small amount of adult weight gain was related to a higher odds of colorectal adenoma occurrence. Our findings add to the benefits of weight control in adulthood regarding colorectal adenoma occurrence, which might be relevant for early prevention of colorectal cancer.

Higher body mass index is associated with an increased risk of multiplicity in surveillance colonoscopy within 5 years

We aimed to evaluate whether obesity was associated with a certain clinicopathologic characteristics of metachronous CRA. This retrospective longitudinal cohort study included 2,904 subjects who had at least one resected CRA at index colonoscopy and who subsequently underwent one or more surveillance colonoscopies within 5 years. Of the 2,904 subjects, 60.9% (n = 1,769) were normal, 35.8% (n = 1,040) were overweight, and 3.3% (n = 95) were obese. Patients with any metachronous CRA were 53.7% (n = 1,559). In multivariate analyses, higher BMI at index colonoscopy was significantly associated with any metachronous CRA (overweight, OR = 1.07; obese, OR = 1.82; p for trend = 0.049). Regarding the multiplicity, the ORs of ≥ 3, ≥ 4 and ≥ 5 metachronous CRAs significantly increased as index BMI increased (p for trend < 0.001, = 0.007 and = 0.004, respectively). In negative binomial regression regarding the incidence for total number of metachronous CRA, the higher BMI the subject has at the time of index colonoscopy, the more metachronous CRAs the subject will have at the surveillance colonoscopy (p for trend = 0.016). Higher index BMI was significantly associated with the risk of multiple metachronous CRAs on surveillance colonoscopy within 5 years.

A Functional Interplay between IGF-1 and Adiponectin

A functional relationship is suggested between two well-known protein hormones, insulin-like growth factor 1 (IGF-1) and adiponectin. In the last two decades in fact, different experimental evidence has indicated a non-random link between them. Here, we describe briefly the IGF-1 and adiponectin systems, and we then focus on their putative interplay in relation to several pathological conditions, including obesity, diabetes, insulin resistance, cardiovascular disease, and cancer. Although the existing studies are hardly comparable, they definitely indicate a functional connection between these two protein hormones. In conclusion, the current knowledge strongly encourages further research into the common, as well as novel, mechanisms through which IGF-1 and adiponectin exert their concerted action.

BMI Is a Risk Factor for Colorectal Cancer Mortality

BACKGROUND

The relationship between dietary and lifestyle risk factors and long-term mortality from colorectal cancer is poorly understood. Several factors, such as obesity, intakes of red meat, and use of aspirin, have been reported to be associated with risk of colorectal cancer mortality, though these findings have not been replicated in all studies to date.

METHODS

In the Minnesota Colon Cancer Control Study, 46,551 participants 50-80 years old were randomly assigned to usual care (control) or annual or biennial screening by fecal occult blood testing. Colon cancer mortality was assessed after 30 years of follow-up. Dietary intake and lifestyle risk factors were assessed by questionnaire at baseline.

RESULTS

Age [hazard ratio (HR) 1.09; 95% CI 1.07, -1.11], male sex (HR 1.25; 95% CI 1.01, 1.57), and higher body mass index (BMI) (HR 1.03; 95% CI 1.00-1.05) increased the risk of CRC mortality, while undergoing screening for CRC was associated with a reduced risk of colorectal cancer mortality (HR 0.76; 95% CI 0.61-0.94 and 0.67; 95% CI 0.53-0.83 for biennial and annual screening, respectively). Intakes of grains, meats, proteins, coffee, alcohol, aspirin, fiber, fruits, and vegetables were not associated with colorectal cancer mortality.

CONCLUSIONS

Our study confirms the relationship between BMI and long-term colorectal cancer mortality. Modulation of BMI may reduce risk of CRC mortality.

Risk of Colorectal Cancer and Associated Mortality in HIV: A Systematic Review and Meta-Analysis

BACKGROUND

As people with HIV live longer, the numbers of colorectal cancer cases are expected to increase. We sought to compare the colorectal cancer incidence and cause-specific mortality among people living with and without HIV.

DESIGN

Systematic review and meta-analysis.

METHODS

We searched 5 electronic databases up to June 28, 2016, for primary studies reporting standardized incidence ratios (SIRs), standardized mortality ratios (SMRs)/hazard ratios or data sufficient for estimating these summary measures. We performed a random effects pooled analysis to estimate SIR and SMR of colorectal cancer in HIV.

RESULTS

Of 8110 articles, we included 27 studies from North America (n = 18), Europe (n = 7), the Pacific region (n = 4), and South America (n = 1). Overall, 1660 cases of colorectal cancer and colon cancer (excluding rectal cancer) occurred among 1,696,070 persons with HIV. In pooled analysis, we found no summary risk of malignancy among those with HIV relative to an uninfected population (SIR 1.00; 95% confidence interval 0.82 to 1.22; I = 89.2%). Colorectal cancer-specific mortality was higher among people with HIV but did not reach statistical significance (SMR 2.09; 95% confidence interval: 1.00 to 4.40; I = 85.0%).

CONCLUSIONS

Rates of colorectal cancer are similar between people with and without HIV. Existing screening guidelines are likely adequate for people with HIV.

Genetic variation in the ADIPOQ gene, adiponectin concentrations and risk of colorectal cancer: a Mendelian Randomization analysis using data from three large cohort studies

Higher levels of circulating adiponectin have been related to lower risk of colorectal cancer in several prospective cohort studies, but it remains unclear whether this association may be causal. We aimed to improve causal inference in a Mendelian Randomization meta-analysis using nested case-control studies of the European Prospective Investigation into Cancer and Nutrition (EPIC, 623 cases, 623 matched controls), the Health Professionals Follow-up Study (HPFS, 231 cases, 230 controls) and the Nurses' Health Study (NHS, 399 cases, 774 controls) with available data on pre-diagnostic adiponectin concentrations and selected single nucleotide polymorphisms in the ADIPOQ gene. We created an ADIPOQ allele score that explained approximately 3% of the interindividual variation in adiponectin concentrations. The ADIPOQ allele score was not associated with risk of colorectal cancer in logistic regression analyses (pooled OR per score-unit unit 0.97, 95% CI 0.91, 1.04). Genetically determined twofold higher adiponectin was not significantly associated with risk of colorectal cancer using the ADIPOQ allele score as instrumental variable (pooled OR 0.73, 95% CI 0.40, 1.34). In a summary instrumental variable analysis (based on previously published data) with higher statistical power, no association between genetically determined twofold higher adiponectin and risk of colorectal cancer was observed (0.99, 95% CI 0.93, 1.06 in women and 0.94, 95% CI 0.88, 1.01 in men). Thus, our study does not support a causal effect of circulating adiponectin on colorectal cancer risk. Due to the limited genetic determination of adiponectin, larger Mendelian Randomization studies are necessary to clarify whether adiponectin is causally related to lower risk of colorectal cancer.

Diets link metabolic syndrome and colorectal cancer development (Review)

Diets have been believed to be an important factor in the development of metabolic syndrome and colorectal cancer (CRC). In recent years, many studies have shown an intimate relationship between mucosal immunity, metabolism and diets, which has led to a greater understanding of the pathophysiology of metabolic syndrome and CRC development. Although the precise effects of diets on oncogenesis have not been compl-etely elucidated, microbiota changes and inflammation are believed to be important factors that influence the development of CRC. Moreover, increased release of pro-inflammatory cytokines and alteration of adipokine levels have been observed in patients with colorectal adenoma and/or CRC, and these all have been considered as the important mechanisms that link diets to the development of metabolic syndrome and CRC. Importantly, a high-fat, low-fiber diet is associated with dysbiosis, and as the gut signature becomes more important in metabolic syndrome and CRC, an increased understanding of diets on bacterial activity in the pathogenesis of metabolic syndrome and CRC will lead to new preventive and therapeutic strategies.

Circulating Resistin Levels and Risk of Colorectal Cancer: A Meta-Analysis

Objectives. Published data on resistin levels in patients with colorectal cancer (CRC) were conflicting and heterogeneous. We conducted a meta-analysis of observational studies to examine the association of circulating resistin levels with carcinogenesis of the CRC. Methods. Potentially eligible studies published up to November 2015 were searched through MEDLINE, EMBASE, Science Citation Index Expanded database, CNKI, and WanFang database. The pooled weighted mean differences (WMDs) with 95% confidence intervals (CIs) calculated by fixed- or random-effect model were used to estimate the effects. Results. A total of 11 studies involving 965 patients were admitted in our meta-analysis. The pooled effects indicated that resistin levels were higher in CRC patients compared to healthy controls (WMD: 1.47 ng/mL; 95% CI: 0.78 to 2.16), with significant heterogeneity across the studies (I² = 72%, p < 0.0001). Subgroup analyses and sensitivity analyses revealed that study quality, design, sample type, and resistin assays may account for this heterogeneity. No publication bias was observed. Conclusions. Our meta-analysis suggests that increased circulating resistin levels are associated with greater risk of colorectal cancer. Given the limited number of available studies and significant heterogeneity, larger well-designed randomized studies are warranted.

Body mass index and risk of colorectal cancer according to tumor lymphocytic infiltrate

Higher body mass index (BMI), higher body adiposity and obesity have been associated with increased risk of colorectal cancer. Evidence suggests that excess energy balance may influence systemic immune and inflammatory status. Thus, we hypothesized that the positive association between BMI and colorectal cancer risk might differ according to colorectal carcinoma subtypes according to levels of histopathological lymphocytic reaction to tumor. We collected biennial questionnaire data on weight and baseline height information in two prospective cohort studies, the Nurses' Health Study (1980-2010) and the Health Professionals Follow-up Study (1986-2010). Utilizing duplication-method Cox proportional hazards regression models, we prospectively assessed the association between BMI and risk of colorectal cancer subtypes according to the degree of Crohn's-like lymphoid reaction, peritumoral lymphocytic reaction, intratumoral periglandular reaction, tumor-infiltrating lymphocytes, the overall lymphocytic reaction score, or T-cell [CD3(+) , CD8(+) , CD45RO (PTPRC)(+) or FOXP3(+) ] density in tumor tissue. Statistical significance level was adjusted for multiple hypotheses testing by Bonferroni correction. During follow up of 1,708,029 men and women (over 3,346,752 person-years), we documented 1,436 incident rectal and colon cancer cases with available formalin-fixed paraffin-embedded tumor tissue materials and pathological immunity data. BMI was significantly associated with higher risk of overall colorectal cancer (Ptrend  < 0.001); however, the association of BMI with colorectal carcinoma risk did not significantly differ by the level of lymphocytic reaction or T-cell infiltration in tumor tissue status (Pheterogeneity  > 0.10). BMI may be associated with risk of colorectal cancer regardless of levels of lymphocytic response to tumor.

Evolving role of adiponectin in cancer-controversies and update

Adiponectin (APN), an adipokine produced by adipocytes, has been shown to have a critical role in the pathogenesis of obesity-associated malignancies. Through its receptor interactions, APN may exert its anti-carcinogenic effects including regulating cell survival, apoptosis and metastasis via a plethora of signalling pathways. Despite the strong evidence supporting this notion, some work may indicate otherwise. Our review addresses all controversies critically. On the whole, hypoadiponectinaemia is associated with increased risk of several malignancies and poor prognosis. In addition, various genetic polymorphisms may predispose individuals to increased risk of obesity-associated malignancies. We also provide an updated summary on therapeutic interventions to increase APN levels that are of key interest in this field. To date efforts to manipulate APN levels have been promising, but much work remains to be done.

Circulating adiponectin levels and risk of endometrial cancer: Systematic review and meta-analysis

Previous epidemiological studies have presented conflicting results regarding associations between circulating adiponectin (APN) levels and the risk of endometrial cancer. Thus a meta-analysis was performed to investigate the association between these factors. Multiple electronic sources, including PubMed, SpringerLink and Google Scholar databases were searched to identify relevant studies for the present meta-analysis. All of the selected studies examined the correlation between circulating APN levels and endometrial cancer. The standardized mean difference (SMD) and 95% confidence intervals (CIs) were estimated and pooled using meta-analysis methods. Overall, 18 case-control studies met the inclusion criteria. A total of 5,692 participants and 2,337 cases of endometrial cancer were included in this meta-analysis. The SMD of the pooled analysis (95% CI) were −1.96 (−2.60, −1.31), P=0.000. When the cancer grades were compared, the APN values were not significantly different between the grades of endometrial cancer [G1 vs. G3, 1.02 (−0.68, 2.72), P>0.05; G1 vs. G2, 0.34 (−0.86, 1.54), P>0.05]. However, there was a significant association between high APN levels and postmenopausal endometrial cancer cases with an SMD (95% CI) of −2.27 (−4.36, −0.18) and P<0.05, however, no association was observed in premenopausal endometrial cancer cases with an SMD (95% CI) of −1.52 (−3.49, 0.45) and P>0.05. The low circulating APN level increases the risk of endometrial cancer, whereas the high APN level decreases this risk in postmenopausal women. Circulating APN as simple biomarkers may be a promising tool for the prevention, early diagnosis and disease monitoring of endometrial cancer.

Adiponectin and colorectal cancer

Colorectal cancer is an obesity-related malignancy. Adiponectin is an adipokine produced exclusively by adipose tissue, and its concentration in the serum is reduced in obesity. A low serum level of adiponectin is associated with an increased risk of various types of malignancies including colorectal cancer. These facts suggest that the epidemiological link between obesity and cancer may have a significant association with adiponectin. Although numerous studies of colorectal cancer have been reported, the results are conflicting about the anti-cancer effect of adiponectin, and how adiponectin affects carcinogenesis or cancer development remains controversial. Because adiponectin has multiple systemic effects and exists as a high serum concentration protein, the main role of adiponectin should be regulation of homeostasis, and it would not likely act as an anti-cancerous hormone. However, as epidemiological evidence shows, a low adiponectin level may be a basic risk factor for colorectal cancer. We speculate that when the colonic epithelium is stimulated or damaged by another carcinogen under the condition of a low adiponectin level, carcinogenesis is promoted and cancer development is facilitated. In this report, we summarize recent findings of the correlation between adiponectin and colorectal cancer and investigate the effect of adiponectin on colorectal cancer.

Obesity and Colorectal Cancer

There is strong evidence that modifiable lifestyle factors such as obesity play a key role in colorectal carcinogenesis. Epidemiologic data have consistently reported a positive association between obesity and colorectal cancer. The relative risk associated with general obesity (as assessed by BMI) is higher in men than in women and for cancer of the colon than for cancer of the rectum. Abdominal obesity (as assessed by waist circumference (WC) or waist-to-hip ratio) is associated with an increased risk of colorectal cancer in both sexes, with stronger associations for cancer of the colon than for cancer of the rectum. Plausible biological mechanisms include insulin resistance, hyperinsulinemia, chronic inflammation, altered levels of growth factors, adipocytokines and steroid hormones. In addition to its effect on colorectal cancer incidence, obesity may play a role in colorectal cancer recurrence, treatment outcomes and survival. Understanding the effects of childhood and adolescent obesity and weight change over the life course in relation to future risk of colorectal cancer is incomplete but essential for targeted preventive recommendations. This chapter summarizes the current evidence on the relationship between obesity and colorectal cancer and colorectal adenoma, a common precursor lesion.

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.

Adiponectin: A biomarker for chronic hepatitis C?

Adiponectin, a hormone primarily synthesized and secreted by adipose tissue, plays a pivotal role in lipid metabolism. Chronic hepatitis C (CHC) infection is characterized by disordered lipid metabolism, which may potentially evolve into steatosis over a period of time. A growing body of evidence appears to link decreased adiponectin plasma levels with severe CHC-related steatosis, which suggests a potential role of this adipokine as a diagnostic and therapeutic target for clinical application. In this review, we have attempted to summarize the current status of adiponectin research in the context of CHC, concentrating predominantly on its roles in CHC, and its potential relevance as a biomarker for CHC.

Prediagnosis Plasma Adiponectin in Relation to Colorectal Cancer Risk According to KRAS Mutation Status

BACKGROUND

Low levels of adiponectin (ADIPOQ; HGNC ID; HGNC:13633), an adipokine, are associated with obesity, adiposity, excess energy balance, and increased risk of colorectal neoplasia. Given the reported association of increased body mass index (BMI) and low-level physical activity with KRAS-mutated colorectal tumor, we hypothesized that low-level plasma adiponectin might be associated with increased risk of KRAS-mutant colorectal carcinoma but not with risk of KRAS wild-type carcinoma.

METHODS

We conducted molecular pathological epidemiology research using a nested case-control study design (307 incident rectal and colon cancer case patients and 593 matched control individuals) within prospective cohort studies, the Nurses' Health Study (152 case patients and 297 control individuals, with blood collection in 1989-1990) and the Health Professionals Follow-up Study (155 case patients and 296 control individuals, with blood collection in 1993-1995). Multivariable conditional logistic regression models and two-sided likelihood ratio tests were used to assess etiologic heterogeneity of the associations.

RESULTS

The association of low-level plasma adiponectin with colorectal cancer risk statistically significantly differed by KRAS mutation status (P heterogeneity = .004). Low levels of plasma adiponectin were associated with KRAS-mutant colorectal cancer (for the lowest vs highest tertile: multivariable odds ratio [OR] = 2.83, 95% confidence interval [CI] = 1.50 to 5.34, P trend = .002) but not with KRAS wild-type cancer (for the lowest vs highest tertile: multivariable OR = 0.83, 95% CI = 0.49 to 1.43, P trend = .48). In secondary analyses, the association between plasma adiponectin and colorectal cancer did not appreciably differ by BRAF or PIK3CA oncogene mutation status.

CONCLUSIONS

Low-level plasma adiponectin is associated with KRAS-mutant colorectal cancer risk but not with KRAS wild-type cancer risk.

Factors Determining Colorectal Cancer: The Role of the Intestinal Microbiota

The gastrointestinal tract, in particular the colon, holds a complex community of microorganisms, which are essential for maintaining homeostasis. However, in recent years, many studies have implicated microbiota in the development of colorectal cancer (CRC), with this disease considered a major cause of death in the western world. The mechanisms underlying bacterial contribution in its development are complex and are not yet fully understood. However, there is increasing evidence showing a connection between intestinal microbiota and CRC. Intestinal microorganisms cause the onset and progression of CRC using different mechanisms, such as the induction of a chronic inflammation state, the biosynthesis of genotoxins that interfere with cell cycle regulation, the production of toxic metabolites, or heterocyclic amine activation of pro-diet carcinogenic compounds. Despite these advances, additional studies in humans and animal models will further decipher the relationship between microbiota and CRC, and aid in developing alternate therapies based on microbiota manipulation.

Prediagnostic Plasma Adiponectin and Survival among Patients with Colorectal Cancer

Circulating adiponectin is inversely related to the risk of colorectal cancer. However, its influence on colorectal cancer survival is unclear. We conducted a prospective study to evaluate the association between prediagnostic plasma levels of adiponectin and mortality in patients with colorectal cancer. We identified 621 incident colorectal cancer cases who provided blood specimens prior to diagnosis within the Nurses' Health Study (NHS) and Health Professionals Follow-up Study (HPFS). Cox proportional hazards models were used to calculate HRs and 95% confidence intervals (CI). After a median follow-up of 9 years, there were 269 (43%) total deaths, of which 181 (67%) were due to colorectal cancer. Compared with participants in the lowest quartile of adiponectin, those in the highest quartile had multivariate HRs of 1.89 (95% CI, 1.21-2.97; P(trend) = 0.01) for colorectal cancer-specific mortality and 1.66 (95% CI, 1.15-2.39; P(trend) = 0.009) for overall mortality. The apparent increased risk in colorectal cancer-specific mortality was more pronounced in patients with metastatic disease (HR, 3.02: 95% CI, 1.50-6.08). Among patients with colorectal cancer, prediagnostic plasma adiponectin is associated with an increased risk of colorectal cancer-specific and overall mortality and is more apparent in patients with metastatic disease. Adiponectin may be a marker for cancers which develop through specific pathways that may be associated with worsened prognosis. Further studies are needed to validate these findings.

Obesity and cancer: local and systemic mechanisms

Obesity is a leading modifiable risk factor for the development of several epithelial malignancies. In addition to increasing risk, obesity also confers worse prognosis for many cancers. Obesity represents an overall state of energy imbalance frequently associated with systemic effects including insulin resistance, altered hormone signaling, and high circulating levels of proinflammatory mediators. In addition to its systemic effects, obesity causes subclinical white adipose inflammation including increased tissue levels of proinflammatory mediators. Both local and systemic effects are likely to contribute to the development and progression of cancer. An understanding of the interplay between local and systemic alterations involved in the obesity-cancer link provides the basis for developing interventions aimed at mitigating the protumorigenic effects.

Targeting obesity-related adipose tissue dysfunction to prevent cancer development and progression

The incidence of obesity, a leading modifiable risk factor for common solid tumors, is increasing. Effective interventions are needed to minimize the public health implications of obesity. Although the mechanisms linking increased adiposity to malignancy are incompletely understood, growing evidence points to complex interactions among multiple systemic and tissue-specific pathways including inflamed white adipose tissue. The metabolic and inflammatory consequences of white adipose tissue dysfunction collectively provide a plausible explanation for the link between overweight/obesity and carcinogenesis. Gaining a better understanding of these underlying molecular pathways and developing risk assessment tools that identify at-risk populations will be critical in implementing effective and novel cancer prevention and management strategies.

Association between plasma adiponectin levels and colorectal cancer risk in women

BACKGROUND

Adiponectin, an adipocyte-secreted hormone, has insulin-sensitizing characteristics. It remains unclear whether adiponectin may influence colorectal cancer development.

METHODS

To determine whether prediagnostic levels of adiponectin were associated with risk of incident colorectal cancer in the Women's Health Study, we conducted a nested case-control study of 275 colorectal cancer cases and 275 matched controls. Each case was matched to a control by age, ethnicity, fasting status at the time of blood collection, time of day when blood was drawn, and month of blood draw. Multivariable logistic regression with adjustment for colorectal cancer risk factors was used to estimate the odds ratio (OR) and 95 % confidence interval (CI) for risk of colorectal cancer incidence and mortality by adiponectin quartiles based on the control distribution.

RESULTS

Median plasma adiponectin level was similar in cases versus controls (6.00 vs. 6.24 μg/mL). In multivariable-adjusted logistic regression models, high plasma adiponectin levels were not significantly associated with risk of colorectal cancer [quartile 4 (Q4) vs. quartile 1 (Q1): OR (95 % CI) 0.86 (0.48-1.56), p trend = 0.63].

CONCLUSIONS

These results suggest no appreciable association between plasma adiponectin and risk of colorectal cancer in women. Confirmation of these observations in larger studies is needed.

Obesity related adipokines and colorectal cancer: a review and meta-analysis

Obesity has been considered as an important risk factor for the development of colorectal cancer (CRC), but the association has not been fully elucidated. Obesity is linked significantly to adipose tissue dysfunction and to alteration of adipokines in blood; in particular, obesity-induced inflammation is thought to be an important link between obesity and colorectal cancer. Based on epidemiological studies, we undertook a systematic review to understand the association of circulating levels of selected adipokines, including adiponectin, leptin, resistin, IL-6 and TNF-α, with the level of CRC risk. Most prospective studies suggested protective effects of adiponectin, but these were attenuated by body mass index (BMI) and waist circumference (WC) data in our meta-analysis. On the other hand, meta-analyses for leptin and CRC did not demonstrate any association, similar to the results of systematic review. Although it proved difficult to determine whether other selected adipokines (resistin, IL-6 and TNF-α) were related to CRC risk due to small number of reports, the present systematic review suggested a positive association with elevated resistin levels but null associations with IL-6 and TNF-α.

Involvement of adiponectin in early stage of colorectal carcinogenesis

Background

Although altered levels of adiponectin have been reported as a potential risk factor in colorectal cancer (CRC), the importance of the role played by adiponectin in colorectal carcinogenesis has not been established. We sought to examine the expression pattern of adiponectin and adiponectin receptors (AdipoRs) in the normal-adenoma-carcinoma sequence and to assess the implications of adiponectin in colorectal carcinogenesis.

Methods

Serum adiponectin concentrations, and the mRNA and protein expression of adiponectin and AdipoRs were examined using serum and tissues from patients with CRC, advanced adenoma, and a normal colon. mRNA expression of AdipoRs and epithelial-mesenchymal transition regulators including E-cadherin, cyclooxygenase-2 (COX-2) and T-cadherin were examined in HCT116 cells treated with adiponectin.

Results

Serum adiponectin concentrations in patients with advanced adenoma and CRC were lower than those in controls. Adiponectin mRNA was not detected in colonic tissue, whereas AdipoRs mRNA was lower in advanced adenoma and CRC than that in normal colon tissues. Immunohistochemical staining demonstrated that adiponectin was expressed in spindle-shaped cells of the subepithelial layer in normal colon tissues, whereas ill-defined overexpression of adiponectin was seen in the stroma of advanced adenoma and CRC tissues. AdipoRs expression was strong in normal epithelium, but weak to negative in the epithelia of CRC tissues. Adiponectin downregulated COX-2 mRNA expression in vitro, but upregulated T-cadherin in HCT116 cells.

Conclusions

Systemic adiponectin and local AdipoRs expression in the colon may be associated with anti-tumorigenesis during the early stages of CRC. These findings offer new insight into understanding the relationship between adiponectin and colorectal carcinogenesis.

Electronic supplementary material

The online version of this article (doi:10.1186/1471-2407-14-811) contains supplementary material, which is available to authorized users.

Adipokines do not mediate the association of obesity and colorectal adenoma

Purpose. The association between obesity and colon neoplasia is well established but the underlying biological mechanisms are not fully understood. Rates of both obesity and colon cancer differ by race. Adipokines have been postulated as contributors to the observed association; however, few studies have examined the mediating effect of adipokines on the obesity-colon adenoma association with consideration of racial differences. Methods. We determined prediagnostic levels of adiponectin and leptin in Caucasians (217 cases and 650 controls) and African Americans (175 cases and 378 controls) participating in the Case Transdisciplinary Research on Energetics and Cancer Colon Adenoma Study. We evaluated mediating effects of adiponectin and leptin on the association of abdominal adiposity and colon adenoma separately according to race using mediational pathway analysis. Results. We observed differences in circulating adipokine concentrations by race; African Americans had higher levels of leptin and lower levels of adiponectin than Caucasians for both adenoma cases and controls (P values <0.001). Leptin and adiponectin did not mediate the waist-to-hip ratio (WHR) adenoma association in either group (all Sobel P values >0.27). Conclusions. We found no evidence that leptin or adiponectin mediates the abdominal obesity-colorectal adenoma pathway. Larger studies on how these associations vary by race, sex, and obesity are needed.

Specific metabolic biomarkers as risk and prognostic factors in colorectal cancer

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

Republished: obesity and colorectal cancer

Excess body weight, as defined by the body mass index (BMI), has been associated with several diseases and includes subjects who are overweight (BMI≥25-29.9 kg/m(2)) or obese (BMI≥30 kg/m(2)). Overweight and obesity constitute the fifth leading risk for overall mortality, accounting for at least 2.8 million adult deaths each year. In addition around 11% of colorectal cancer (CRC) cases have been attributed to overweight and obesity in Europe. Epidemiological data suggest that obesity is associated with a 30-70% increased risk of colon cancer in men, whereas the association is less consistent in women. Similar trends exist for colorectal adenoma, although the risk appears lower. Visceral fat, or abdominal obesity, seems to be of greater concern than subcutaneous fat obesity, and any 1 kg/m(2) increase in BMI confers additional risk (HR 1.03). Obesity might be associated with worse cancer outcomes, such as recurrence of the primary cancer or mortality. Several factors, including reduced sensitivity to antiangiogenic-therapeutic regimens, might explain these differences. Except for wound infection, obesity has no significant impact on surgical procedures. The underlying mechanisms linking obesity to CRC are still a matter of debate, but metabolic syndrome, insulin resistance and modifications in levels of adipocytokines seem to be of great importance. Other biological factors such as the gut microbita or bile acids are emerging. Many questions still remain unanswered: should preventive strategies specifically target obese patients? Is the risk of cancer great enough to propose prophylactic bariatric surgery in certain patients with obesity?

Epidemiological transition of colorectal cancer in developing countries: Environmental factors, molecular pathways, and opportunities for prevention

Colorectal cancer (CRC) is one of the leading causes of cancer and cancer-related mortality worldwide. The disease has been traditionally a major health problem in industrial countries, however the CRC rates are increasing in the developing countries that are undergoing economic growth. Several environmental risk factors, mainly changes in diet and life style, have been suggested to underlie the rise of CRC in these populations. Diet and lifestyle impinge on nuclear receptors, on the intestinal microbiota and on crucial molecular pathways that are implicated in intestinal carcinogenesis. In this respect, the epidemiological transition in several regions of the world offers a unique opportunity to better understand CRC carcinogenesis by studying the disease phenotypes and their environmental and molecular associations in different populations. The data from these studies may have important implications for the global prevention and treatment of CRC.