Association of circulating leptin and adiponectin levels with colorectal cancer risk: A systematic review and meta-analysis of case-control studies

The role of Adiponectin and Leptin in Colorectal Cancer and Adenoma: a systematic review and meta-analysis

BACKGROUND

Colorectal cancer ranks as the third most frequently diagnosed cancer globally. Adipokines, including adiponectin and leptin, are believed to play a vital role in the development and progression of tumors. This study aimed to clarify the association between circulating adiponectin and leptin concentrations and the risk of colorectal cancer and adenoma.

METHODS

A detailed literature review was conducted in different databases, including Google Scholar, Web of Science, Scopus, and PubMed. Articles measuring serum concentrations of adiponectin and leptin in colorectal adenoma or cancer patients were analyzed. Pooled odds ratios (ORs) and their related 95% confidence intervals (CIs) were estimated through a random-effects meta-analysis.

RESULTS

In total, 30 articles were analyzed. According to the meta-analysis, higher adiponectin concentrations were inversely linked to a reduced CRC risk (OR: 0.85, 95% CI: 0.74-0.96), particularly in men. However, no notable connection was detected between higher leptin concentrations and risk of CRC (OR: 1.12, 95% CI: 0.96-1.31). In subgroup analyses, BMI adjustment reinforced the negative association between higher adiponectin levels and risk of CRC, while insulin adjustment yielded non-significant results. Additionally, higher leptin levels revealed a meaningful relationship with colorectal adenoma risk (OR: 1.39, 95% CI: 1.06-1.84), whereas higher levels of adiponectin were not significantly linked to adenoma (OR: 0.79, 95% CI: 0.46-1.36).

CONCLUSION

According to this meta-analysis, elevated adiponectin concentrations may play a protective role against CRC, while leptin could potentially contribute to an elevated colorectal adenoma risk. Further studies are required to explore the potential mechanisms underlying adipokine-mediated colorectal carcinogenesis.

Biomarkers of inflammation and colorectal cancer risk

Globally, colorectal malignancy ranks among the most prevalent forms of cancer and stands as the third principal cause of cancer-associated mortality. Recent studies indicate that inflammatory processes play a significant role in the initiation and advancement of various malignancies, colorectal cancer included. It explores inflammatory biomarkers, with C-reactive protein (CRP) being a key focus. While CRP's elevation during inflammation is linked to tumorigenesis, studies on its association with CRC risk are inconsistent, showing gender and methodological differences. Interleukin-6 (IL-6), TNF - α, and their receptors also play roles in CRC development, yet research findings vary. Adiponectin and leptin, secreted by adipocytes, have complex associations with CRC, with gender disparities noted. In terms of screening, non-invasive methods like fecal occult blood tests (FOBTs) are widely used, and combining biomarkers with iFOBT shows potential. Multi-omics techniques, including genomics and microbiomics, offer new avenues for CRC diagnosis. Overall, while evidence highlights the significance of inflammatory biomarkers in CRC risk prediction, larger prospective studies are urgently needed to clarify their roles due to existing inconsistencies and methodological limitations.

Deciphering endocrine function of adipose tissue and its significant influences in obesity-related diseases caused by its dysfunction

Current research has found that adipose tissue is not only involved in energy metabolism, but also a highly active endocrine organ that secretes various adipokines, including adiponectin, leptin, resistin and apelin, which are involved in the regulation of physiology and pathology of tissues and organs throughout the body. With the yearly increasing incidence, obesity has become a risk factor for a variety of pathological changes, including inflammation and metabolic syndrome in various system (endocrine, circulatory, locomotor and central nervous system). Thus these symptoms lead to multi-organ dysfunctions, including the heart, liver, kidneys, brain and joints. An in-depth summary of the roles of adipokines in the regulation of other tissues and organs can help to provide more effective therapeutic strategies for obesity-related diseases and explore potential therapeutic targets. Therefore, this review has retrospected the endocrine function of adipose tissue under obesity and the role of dysregulated adipokine secretion in related diseases and the underlying mechanisms, in order to provide a theoretical basis for targeting adipokine-mediated systemic dysregulation.

Systemic adiponectin levels in colorectal cancer and adenoma: a systematic review and meta-analysis

BACKGROUND

Obesity is a well-established risk factor in the development of colorectal cancer; however, the mechanism mediating this relationship is not well understood. The adipokine, adiponectin, has an inverse relationship with obesity. Experimental studies have shown adiponectin to have dichotomous inflammatory and tumorigenic roles. Its role in the development of colorectal cancer, including the potential effect of its increase following bariatric surgery, is not yet clear. There are conflicting results from studies evaluating this relationship. This study sought to provide a systematic review and meta-analysis to examine the association between systemic adiponectin levels in patients with colorectal cancer and adenoma.

METHODS

An electronic literature search was performed using PubMed, EMBASE, Web of Science as well as gray literature. Articles were screened for inclusion criteria and assessed for quality using the Newcastle-Ottawa Scale. Pooled mean differences were calculated using a random effects model. Subgroup and meta-regression analyses were performed to identify potential sources of heterogeneity.

RESULTS

Thirty-two observational studies comparing systemic adiponectin in colorectal cancer vs healthy controls were included. Colorectal cancer cases had lower systemic adiponectin levels (overall pooled mean difference = -1.05 μg/ml [95% CI: -1.99; -0.12] p = 0.03); however, significant heterogeneity was present (I2 = 95% p < 0.01). Subgroup and meta- regression analyses results could not identify a source of the significant heterogeneity across the studies.

CONCLUSIONS

Studies suggest a trend towards lower systemic adiponectin levels in colorectal cancer patients, but the heterogeneity observed showed current evidence is not sufficient to definitively draw any conclusions. These data, however, suggest rising adiponectin is unlikely to account for the reported observation of increased CRC following bariatric surgery. Further studies with prospective age, race, and BMI-matched cohorts, and standardized adiponectin measurements may provide a better understanding of this relationship.

Fecal and Urinary Adipokines as Disease Biomarkers

The use of biomarkers is of great clinical value for the diagnosis and prognosis of disease and the assessment of treatment efficacy. In this context, adipokines secreted from adipose tissue are of interest, as their elevated circulating levels are associated with a range of metabolic dysfunctions, inflammation, renal and hepatic diseases and cancers. In addition to serum, adipokines can also be detected in the urine and feces, and current experimental evidence on the analysis of fecal and urinary adipokine levels points to their potential as disease biomarkers. This includes increased urinary adiponectin, lipocalin-2, leptin and interleukin-6 (IL-6) levels in renal diseases and an association of elevated urinary chemerin as well as urinary and fecal lipocalin-2 levels with active inflammatory bowel diseases. Urinary IL-6 levels are also upregulated in rheumatoid arthritis and may become an early marker for kidney transplant rejection, while fecal IL-6 levels are increased in decompensated liver cirrhosis and acute gastroenteritis. In addition, galectin-3 levels in urine and stool may emerge as a biomarker for several cancers. With the analysis of urine and feces from patients being cost-efficient and non-invasive, the identification and utilization of adipokine levels as urinary and fecal biomarkers could become a great advantage for disease diagnosis and predicting treatment outcomes. This review article highlights data on the abundance of selected adipokines in urine and feces, underscoring their potential to serve as diagnostic and prognostic biomarkers.

Adipocytokine imbalance and breast cancer in obese women

CONTEXT

Breast cancer is the most common diagnosis established in women with malignant tumors.

AIMS

The purpose is to investigate the blood contents of adiponectin and leptin in women with breast cancer and obesity.

SETTINGS AND DESIGN

A total of 140 women aged 40-50 were examined.

MATERIALS AND METHODS

Group 1 included 70 women from classes 1 or 2 obesity. Group 2 included 70 women with stage 1 or 2 breast cancer and classes 1 or 2 obesity. The control group included 30 apparently healthy women, with mean age of 42.5 ± 2.5 years.

STATISTICAL ANALYSIS USED

Statistical processing of the results obtained was performed using Statistica.

RESULTS

Groups 1 and 2 were statistically significantly different from each other across all parameters, except for leptin resistance. In group 2, the course of breast cancer with concomitant obesity is characterized by disrupted adipocytokine homeostasis, which manifests as a 1.94-fold decrease in the blood content of adiponectin (P < 0.05), a 4.14-fold increase in the blood content of leptin (P < 0.05), and an 8.00-fold increase in the leptin/adiponectin ratio (P < 0.05). Poorly differentiated breast tumors exhibit a more pronounced imbalance in the blood levels of adipocytokines. Thus, the serum content of leptin in women with poorly differentiated tumors (G3) was 1.79 times (P < 0.05) higher than in women with moderately differentiated tumors (G2).

CONCLUSIONS

The course of breast cancer with concomitant obesity is characterized by disrupted adipocytokine homeostasis and decreased adiponectin concentration in the blood.

Sex-Dependent Differences in Colorectal Cancer: With a Focus on Obesity

Colorectal cancer (CRC) is the third most common cancer and has the second highest cancer-related mortality in the world. The incident rates of CRC vary country-wise; however, population studies and data from different countries show a general increase in the CRC rate in young adults, males, and females ≥65 years. CRC incidence is affected by age, sex, environmental, dietary, hormonal, and lifestyle factors. Obesity is a known disease that is spreading rapidly throughout the world. A large body of literature indicates that, among many conditions, obesity is the increasing cause of CRC. Even though obesity is one of the known factors for CRC development, limited studies are available that explain the mechanistic link between obesity, sex hormones, and CRC development. Thus, this review summarizes the literature and aims to understand sex-dependent differences in CRC, especially in the context of obesity.

Associations between potential causal factors and colorectal cancer risk: A systematic review and meta-analysis of Mendelian randomization studies

OBJECTIVE

To summarize the associations between potential causal factors and colorectal cancer (CRC) risk based on existing Mendelian randomization studies.

METHODS

This systematic review and meta-analysis involved a literature search in Embase and Medline. All published articles using Mendelian randomization to explore potential causal factors of CRC were included. Studies that reported Mendelian randomization estimates of standard deviation changes in exposures were included in the meta-analysis. Subgroup analyses based on sex and anatomical sites were performed.

RESULTS

One hundred and ninety studies presented in 51 articles were included in systematic review, and 114 studies conducted in 32 articles were included in the meta-analysis. Adult body mass index, waist circumference, waist hip ratio, body height, body fat percentage, arm fat ratio, childhood obesity, lifetime cigarette consumption, short sleep, coffee consumption, and blood levels of vitamin B₁₂ , arachidonic acid, stearic acid, and insulin-like growth factor binding protein 3 were positively associated with CRC risk. Conversely, acceleration-vector-magnitude physical activity, milk consumption, and blood levels of adiponectin, linoleic acid, α-linolenic acid, oleic acid, palmitoleic acid, interleukin-6 receptor subunit-α, and tumor necrosis factor were inversely associated with CRC risk.

CONCLUSIONS

Most obesity-related anthropometric characteristics, several unhealthy lifestyles, and blood levels of some micronutrients, fatty acids, and diabetes-related biomarkers were positively associated with CRC risk. In contrast, some lifestyles and blood levels of some fatty acids and inflammatory biomarkers were inversely associated with CRC risk. Future studies with more valid genetic variants are needed for factors with discrepancies between Mendelian randomization and epidemiological studies.

Epidemiology and biology of early onset colorectal cancer

Colorectal cancer (CRC) is the third leading cause of cancer-related mortality in men or women in the United States. Average-risk screening that begins at age 50 years has reduced incidence and mortality of CRC in those over 50 years of age, whereas CRC incidence in those under age 50 years (early onset colorectal cancer (eoCRC)) has recently and dramatically increased. In this review, we summarize the recent literature including risk factors for eoCRC, differences in clinicopathologic presentation and outcomes in eoCRC, and emerging evidence regarding the molecular pathways that are altered in eoCRC compared to later onset CRC (loCRC). Epidemiologic studies of eoCRC show predominance in distal colon and rectum, and association with several modifiable risk factors, including diabetes, obesity, diet, sedentary time, alcohol consumption and smoking. Data regarding potential risk factors of prior antibiotic exposure and microbiome alterations or direct carcinogen exposure are still emerging. Aggressive clinicopathologic features of eoCRC at presentation may be due to delay in diagnosis or more aggressive tumor biology. EoCRC outcomes are similar to loCRC when matched for stage, but overall mortality is greater due to higher frequency of advanced disease at a younger presentation, with more life-years lost. There are only few molecular evaluations of eoCRC to date, with findings of potential increase in TP53 and CTNNB1 somatic mutation and decrease in APC, KRAS and BRAF somatic mutation, compared to loCRC. Other findings include LINE-1 hypomethylation, absence of microsatellite instability (MSI-H), presence of chromosomal instability (CIN) or microsatellite and chromosomal stability (MACS). These studies are only now emerging and have not yet identified a specific molecular signature defining eoCRC. Further research evaluating genetic and molecular differences as well as environmental triggers for eoCRCs should provide a clearer understanding to inform targeted screening for pre-symptomatic at-risk younger individuals.

Association of IGF-1 and IGFBP-3 levels with gastric cancer: A systematic review and meta-analysis

PURPOSE

Many studies have investigated the association between serum IGF-1 and IGFBP levels with gastric cancer (GC), but the results remained inconclusive. In this work, we performed a systematic review and meta-analysis to examine the precise association of serum levels of IGF-1 and IGFBP with GC.

METHODS

A comprehensive systematic search was carried out in PubMed/MEDLINE, SCOPUS, Web of Science, and EMBASE databases for (nested) case-control studies that reported the levels of IGF-1 and IGFBP in GC cases and healthy controls, from inception until October 2020. Weighted mean difference (WMD) was calculated for estimating combined effect size. Subgroup analysis was performed to identify the source of heterogeneity among studies.

RESULTS

We found eight and five eligible studies (with 1541 participants) which provided data for IGF-1 and IGFBP, respectively. All studies on IGFBP reported the IGFBP-3 isoform. The pooled results indicate that GC patients had significantly lower serum IGF-1 [WMD = -26.21 ng/mL (95% CI, -45.58 to -6.85; P = .008)] and IGFBP-3 [WMD = -0.41 ng/mL (95% CI, -0.80 to -0.01; P = .04; I²  = 89.9%; P < .001)] levels than those in healthy subjects. Significant heterogeneity was observed in the association, which could be attributed to the sample size of the studies.

CONCLUSIONS

In conclusion, our study reveals a significantly lower level of IGF-1 and IGFBP-3 in GC patients compared with healthy control subjects.

'Energy-Dense, High-SFA and Low-Fiber' Dietary Pattern Lowered Adiponectin but Not Leptin Concentration of Breast Cancer Survivors

Dietary pattern (DP) and its relationship with disease biomarkers have received recognition in nutritional epidemiology investigations. However, DP relationships with adipokines (i.e., adiponectin and leptin) among breast cancer survivors remain unclear. Therefore, we assessed relationships between DP and high-molecular weight (HMW) adiponectin and leptin concentration among breast cancer survivors. This cross-sectional study involved 128 breast cancer survivors who attended the oncology outpatient clinic at two main government hospitals in the East Coast of Peninsular Malaysia. The serum concentration of HMW adiponectin and leptin were measured using enzyme-linked immunosorbent assay (ELISA) kits. A reduced rank regression method was used to analyze DP. Relationships between DP with HMW adiponectin and leptin were examined using regression models. The findings show that with every 1-unit increase in the ‘energy-dense, high-SFA, low-fiber’ DP z-score, there was a reduction by 0.41 μg/mL in HMW adiponectin which was independent of age, BMI, education level, occupation status, cancer stage, and duration since diagnosis. A similar relationship with leptin concentration was not observed. In conclusion, the ‘energy-dense, high-saturated fat and low-fiber’ DP, which is characterized by high intake levels of sugar-sweetened drinks and fat-based spreads but low intake of fruits and vegetables, is an unhealthy dietary pattern and unfavorable for HMW adiponectin concentration, but not for leptin. These findings could serve as a basis in developing specific preventive strategies that are tailored to the growing population of breast cancer survivors.

Highly Sensitive and Single-Use Biosensing System Based on a GP Electrode for Analysis of Adiponectin, an Obesity Biomarker

This study presents a disposable, novel, and sensitive biosensing system to determine adiponectin, an obesity biomarker, in real human serum. The graphite paper (GP) working electrode is a new material for impedimetric biosensors. In the literature, there is no study in which this electrode is used in impedance-based biosensors for adiponectin detection. Sensitive and useful techniques, such as electrochemical impedance spectroscopy and cyclic voltammetry, were utilized for investigation of the modification of the GP electrode surface and optimization and characterization of the constructed biosensor. The single frequency impedance technique was used to study the interactions between antiadiponectin and adiponectin. The morphology of the electrode surface for each immobilization step was examined with scanning electron microscopy. All experimental parameters were optimized to fabricate a rapid and sensitive biosensing system. The designed biosensor presents excellent performance with a wide detection range (0.05-25 pg mL^-1) and a low limit of detection (0.0033 pg mL^-1) for adiponectin determination. Also, it has been demonstrated that the biosensor sensitively allows for the detection of adiponectin in human serum. The affinity of the designed immunosensor toward other proteins and components was examined in the presence of the target protein (adiponectin), leptin (100 pg mL^-1), creatine kinase (50 pg mL^-1), parathyroid hormone (50 pg mL^-1), and d-glucose (0.5 M). The selectivity of the adiponectin biosensor resulted in high capacity to neglect the interference effect. The constructed biosensor showed good linearity, long-term storage life (10 weeks), high reusability (18 times regenerability), and high ability to detect adiponectin concentrations at picogram levels.