Explaining the link between adiposity and colorectal cancer risk in men and postmenopausal women in the UK Biobank: A sequential causal mediation analysis

Association of the systemic inflammation and anthropometric measurements with cancer risk: a prospective study in MJ cohort

Objective

To investigate the specific role of inflammation in the connection between obesity and the overall incidence of cancer.

Methods

A total of 356,554 participants in MJ cohort study were included. Systemic inflammation markers from blood samples and anthropometric measurements were determined using professional instruments. The Cox model was adopted to evaluate the association.

Results

Over a median follow-up of 8.2 years, 9,048 cancer cases were identified. For individual systemic inflammation biomarkers, the overall cancer risk significantly escalated as blood C-reactive protein (CRP) (hazard ratio (HR)=1.036 (1.017-1.054)) and globulin (GLO) (HR=1.128 (1.105-1.152)) levels increased, and as hemoglobin (HEMO) (HR=0.863 (0.842-0.884)), albumin (ALB) (HR=0.846 (0.829-0.863)) and platelets (PLA) (HR=0.842 (0.827-0.858)) levels decreased. For composite indicators, most of them existed a significant relationship to the overall cancer risk. Most indicators were correlated with the overall cancer and obesity-related cancer risk, but there was a reduction of association with non-obesity related cancer risk. Most of indicators mediated the association between anthropometric measurements and overall cancer risk.

Conclusions

Systemic inflammatory state was significantly associated with increased risks of cancer risk. Inflammation biomarkers were found to partly mediate the association between obesity and cancer risk.

Mediation analysis of chronic kidney disease risk factors using kidney biomarkers in women living with HIV

OBJECTIVE

Novel urinary biomarkers reflecting kidney tubule health are associated with chronic kidney disease (CKD) risk in persons living with HIV. However, it is unknown whether these biomarkers provide mechanistic insight into the associations between clinical risk factors for CKD and subsequent CKD risk.

METHODS

Among 636 women living with HIV in the Women's Interagency HIV Study with estimated glomerular filtration rate (eGFR) >60 ml/min/1.73 m 2 , we used a counterfactual approach to causal mediation analysis to evaluate the extent to which systolic blood pressure (SBP), diastolic blood pressure (DBP), hemoglobin a1c (Hba1c) and serum albumin associations with incident CKD were mediated by eight urine proteins. These biomarkers reflect proximal tubular reabsorptive dysfunction (α1-microglobulin [a1m], β2-microglobulin, trefoil factor 3); tubular injury (interleukin 18 [IL-18], kidney injury molecule 1 [KIM-1]); kidney repair (epidermal growth factor); tubular reserve (uromodulin); and glomerular injury (urinary albumin). Incident CKD was defined as eGFR <60 ml/min/1.73 m 2 measured at two consecutive 6-month visits with an average annual eGFR decline ≥3% per year.

RESULTS

During a median follow-up of 7 years, 11% developed CKD. Urinary albumin and KIM-1 mediated 32% (95% CI: 13.4%, 76.6%) and 23% (6.9%, 60.7%) of the association between SBP and incident CKD, respectively; and 19% (5.1%, 42.3%) and 22% (8.1%, 45.7%) of the association between DBP and incident CKD, respectively. Urinary albumin, α1m, and IL-18 were significant mediators of the association between Hba1c and incident CKD. None of the eight biomarkers mediated the association between serum albumin and incident CKD.

CONCLUSIONS

Among women living with HIV, several urinary biomarkers reflecting distinct dimensions of kidney health may partially explain the associations between SBP, DBP, and Hba1c and subsequent CKD risk.

Identification of potential mediators of the relationship between body mass index and colorectal cancer: a Mendelian randomization analysis

BACKGROUND

Colorectal cancer (CRC) is the third-most-common cancer worldwide and its rates are increasing. Elevated body mass index (BMI) is an established risk factor for CRC, although the molecular mechanisms behind this association remain unclear. Using the Mendelian randomization (MR) framework, we aimed to investigate the mediating effects of putative biomarkers and other CRC risk factors in the association between BMI and CRC.

METHODS

We selected as mediators biomarkers of established cancer-related mechanisms and other CRC risk factors for which a plausible association with obesity exists, such as inflammatory biomarkers, glucose homeostasis traits, lipids, adipokines, insulin-like growth factor 1 (IGF1), sex hormones, 25-hydroxy-vitamin D, smoking, physical activity (PA) and alcohol consumption. We used inverse-variance weighted MR in the main univariable analyses and performed sensitivity analyses (weighted-median, MR-Egger, Contamination Mixture). We used multivariable MR for the mediation analyses.

RESULTS

Genetically predicted BMI was positively associated with CRC risk [odds ratio per SD (5 kg/m2) = 1.17, 95% CI: 1.08-1.24, P-value = 1.4 × 10-5] and robustly associated with nearly all potential mediators. Genetically predicted IGF1, fasting insulin, low-density lipoprotein cholesterol, smoking, PA and alcohol were associated with CRC risk. Evidence for attenuation was found for IGF1 [explained 7% (95% CI: 2-13%) of the association], smoking (31%, 4-57%) and PA (7%, 2-11%). There was little evidence for pleiotropy, although smoking was bidirectionally associated with BMI and instruments were weak for PA.

CONCLUSIONS

The effect of BMI on CRC risk is possibly partly mediated through plasma IGF1, whereas the attenuation of the BMI-CRC association by smoking and PA may reflect confounding and shared underlying mechanisms rather than mediation.

Sex differences in colorectal cancer: with a focus on sex hormone-gut microbiome axis

Sexual dimorphism has been observed in the incidence and prognosis of colorectal cancer (CRC), with men generally exhibiting a slightly higher incidence than women. Research suggests that this difference may be attributed to variations in sex steroid hormone levels and the gut microbiome. The gut microbiome in CRC shows variations in composition and function between the sexes, leading to the concept of 'microgenderome' and 'sex hormone-gut microbiome axis.' Conventional research indicates that estrogens, by promoting a more favorable gut microbiota, may reduce the risk of CRC. Conversely, androgens may have a direct pro-tumorigenic effect by increasing the proportion of opportunistic pathogens. The gut microbiota may also influence sex hormone levels by expressing specific enzymes or directly affecting gonadal function. However, this area remains controversial. This review aims to explore the differences in sex hormone in CRC incidence, the phenomenon of sexual dimorphism within the gut microbiome, and the intricate interplay of the sex hormone-gut microbiome axis in CRC. The objective is to gain a better understanding of these interactions and their potential clinical implications, as well as to introduce innovative approaches to CRC treatment.

UK Biobank: a globally important resource for cancer research

UK Biobank is a large-scale prospective study with deep phenotyping and genomic data. Its open-access policy allows researchers worldwide, from academia or industry, to perform health research in the public interest. Between 2006 and 2010, the study recruited 502,000 adults aged 40-69 years from the general population of the United Kingdom. At enrolment, participants provided information on a wide range of factors, physical measurements were taken, and biological samples (blood, urine and saliva) were collected for long-term storage. Participants have now been followed up for over a decade with more than 52,000 incident cancer cases recorded. The study continues to be enhanced with repeat assessments, web-based questionnaires, multi-modal imaging, and conversion of the stored biological samples to genomic and other '-omic' data. The study has already demonstrated its value in enabling research into the determinants of cancer, and future planned enhancements will make the resource even more valuable to cancer researchers. Over 26,000 researchers worldwide are currently using the data, performing a wide range of cancer research. UK Biobank is uniquely placed to transform our understanding of the causes of cancer development and progression, and drive improvements in cancer treatment and prevention over the coming decades.

Associations Between Glycemic Traits and Colorectal Cancer: A Mendelian Randomization Analysis

BACKGROUND

Glycemic traits-such as hyperinsulinemia, hyperglycemia, and type 2 diabetes-have been associated with higher colorectal cancer risk in observational studies; however, causality of these associations is uncertain. We used Mendelian randomization (MR) to estimate the causal effects of fasting insulin, 2-hour glucose, fasting glucose, glycated hemoglobin (HbA1c), and type 2 diabetes with colorectal cancer.

METHODS

Genome-wide association study summary data were used to identify genetic variants associated with circulating levels of fasting insulin (n = 34), 2-hour glucose (n = 13), fasting glucose (n = 70), HbA1c (n = 221), and type 2 diabetes (n = 268). Using 2-sample MR, we examined these variants in relation to colorectal cancer risk (48 214 case patient and 64 159 control patients).

RESULTS

In inverse-variance models, higher fasting insulin levels increased colorectal cancer risk (odds ratio [OR] per 1-SD = 1.65, 95% confidence interval [CI] = 1.15 to 2.36). We found no evidence of any effect of 2-hour glucose (OR per 1-SD = 1.02, 95% CI = 0.86 to 1.21) or fasting glucose (OR per 1-SD = 1.04, 95% CI = 0.88 to 1.23) concentrations on colorectal cancer risk. Genetic liability to type 2 diabetes (OR per 1-unit increase in log odds = 1.04, 95% CI = 1.01 to 1.07) and higher HbA1c levels (OR per 1-SD = 1.09, 95% CI = 1.00 to 1.19) increased colorectal cancer risk, although these findings may have been biased by pleiotropy. Higher HbA1c concentrations increased rectal cancer risk in men (OR per 1-SD = 1.21, 95% CI = 1.05 to 1.40), but not in women.

CONCLUSIONS

Our results support a causal effect of higher fasting insulin, but not glucose traits or type 2 diabetes, on increased colorectal cancer risk. This suggests that pharmacological or lifestyle interventions that lower circulating insulin levels may be beneficial in preventing colorectal tumorigenesis.

Circulating Sex Hormone Levels and Colon Cancer Risk in Men: A Nested Case-Control Study and Meta-Analysis

BACKGROUND

Endogenous sex hormones may contribute to higher colorectal cancer incidence rates in men compared with women, but despite an increased number of studies, clear evidence is lacking.

METHODS

We conducted a comprehensive nested case-control study of circulating concentrations of sex hormones, sex hormone precursors, and sex hormone binding globulin (SHBG) in relation to subsequent colon cancer risk in European men. Concentrations were measured using liquid LC/MS-MS in prospectively collected plasma samples from 690 cases and 690 matched controls from the European Prospective Investigation into Cancer and Nutrition (EPIC) and the Northern Sweden Health and Disease Study (NSHDS) cohorts. Multivariable conditional logistic regression was used to estimate odds ratios (OR) and 95% confidence intervals (CI). In addition, we conducted a meta-analysis of previous studies on men.

RESULTS

Circulating levels of testosterone (OR, 0.68; 95% CI, 0.51-0.89) and SHBG (OR, 0.77; 95% CI, 0.62-0.96) were inversely associated with colon cancer risk. For free testosterone, there was a nonsignificant inverse association (OR, 0.83; 95% CI, 0.58-1.18). In a dose-response meta-analysis of endogenous sex hormone levels, inverse associations with colorectal/colon cancer risk were found for testosterone [relative risks (RR) per 100 ng/dL = 0.98; 95% CI, 0.96-1.00; I2 = 22%] and free testosterone (RR per 1 ng/dL = 0.98; 95% CI, 0.95-1.00; I2 = 0%).

CONCLUSIONS

Our results provide suggestive evidence for the association between testosterone, SHBG, and male colon cancer development.

IMPACT

Additional support for the involvement of sex hormones in male colon cancer.

Insulin resistance and inflammation mediate the association of abdominal obesity with colorectal cancer risk

BACKGROUND

The close association of abdominal obesity rather than general obesity with colorectal cancer (CRC) risk might be mediated by IR and inflammation, which has never been systematically explored in large-scale prospective studies.

METHODS

We prospectively examined the mediation effects of the fasting triglyceride-glucose (TyG) index and C-reactive protein (CRP) on the associations of obesity (general and abdominal) with CRC risk among 93,659 participants. We used the Cox proportional hazards regression models and subgroup analyses to evaluate the hazard ratios (HRs) and 95% confidence intervals (95% CIs) of CRC. The CAUSALMED procedure was used to perform the mediation analyses.

RESULTS

During 13.02 years of follow-up, a total of 586 CRC cases were verified. Male participants with general obesity and abdominal obesity had a 1.29-fold and a 1.28-fold increased risk of CRC. However, a significant association was only observed among female individuals with abdominal obesity. Both TyG index and CRP were associated with an elevated risk of CRC, and A significant interaction between the TyG index and CRP was found for the risk of CRC (P for interaction<0.05). CRP and the TyG index significantly mediated the positive association between abdominal obesity and CRC risk.

CONCLUSION

CRP and TyG index increased the risk of CRC independently and synergistically. Mediation effects of CRP and the TyG index were found for the association between abdominal obesity and CRC risk.

The association of prediagnostic circulating levels of cardiometabolic markers, testosterone and sex hormone-binding globulin with risk of breast cancer among normal weight postmenopausal women in the UK Biobank

Emerging evidence suggests that normal weight postmenopausal women with a relative excess of body fat are at increased breast cancer risk. However, little is known about the associations between obesity-related blood markers and risk of breast cancer among these individuals. In this prospective study comprising 58 629 normal weight postmenopausal women (body mass index between 18.5 kg/m² and 24.9 kg/m² ) who were enrolled in the UK Biobank cohort between 2006 and 2010, we examined the associations of glycated hemoglobin, triglycerides, high-density lipoprotein cholesterol, C-reactive protein (CRP), testosterone and sex hormone-binding globulin (SHBG) with risk of breast cancer. A total of 1268 postmenopausal breast cancer cases were ascertained during a median follow-up period of 7 years. Women with CRP, total testosterone and free testosterone (FT) levels in the highest quintile had increased risk of breast cancer compared to those in the lowest quintile (HR_{Q5 vs Q1} : 1.35, 95% confidence interval [CI]: 1.12-1.63, HR _{Q5 vs Q1} : 1.47, 95% CI: 1.20-1.80 and HR _{Q5 vs Q1} : 1.53, 95% CI: 1.23-1.90, respectively), whereas those with SHBG in the highest quintile had reduced risk (HR _{Q5 vs Q1} : 0.70, 95% CI: 0.56-0.88). These associations were attenuated but persisted after additional adjustment for BMI, fat mass index (whole body fat mass [kg]/height [m² ]) or waist circumference and after mutual adjustment for testosterone, CRP and/or SHBG. Our study suggests that the risk of postmenopausal breast cancer among normal weight women is increased in association with relatively high levels of CRP and testosterone and with relatively low levels of SHBG.

Plasma sex hormones and risk of conventional and serrated precursors of colorectal cancer in postmenopausal women

BACKGROUND

Sex hormones have been suggested to play a role in colorectal cancer (CRC), but their influence on early initiation of CRC remains unknown.

METHODS

We retrospectively examined the associations with risk of CRC precursors, including conventional adenomas and serrated polyps, for plasma estrone, estradiol, free estradiol, testosterone, free testosterone, sex hormone-binding globulin (SHBG), and the ratio of estradiol to testosterone among 5404 postmenopausal women from the Nurses' Health Study I and II. Multivariable logistic regression was used to calculate the odds ratio (OR) and 95% confidence intervals (CI). Given multiple testing, P < 0.005 was considered statistically significant.

RESULTS

During 20 years of follow-up, we documented 535 conventional adenoma cases and 402 serrated polyp cases. Higher concentrations of SHBG were associated with lower risk of conventional adenomas, particularly advanced adenomas (multivariable OR comparing the highest to the lowest quartile, 0.40, 95% CI 0.24-0.67, P for trend < 0.0001). A nominally significant association was found for SHBG with lower risk of large serrated polyps (≥ 10 mm) (OR, 0.47, 95% CI 0.17-1.35, P for trend = 0.02) as well as free estradiol and free testosterone with higher risk of conventional adenomas (OR, 1.54, 95% CI 1.02-2.31, P for trend = 0.03 and OR, 1.33, 95% CI 0.99-1.78, P for trend = 0.03, respectively).

CONCLUSIONS

The findings suggest a potential role of sex hormones, particularly SHBG, in early colorectal carcinogenesis.

Sexual Dimorphism in Colon Cancer

A higher incidence of colorectal cancer (CRC) is found in males compared to females. Young women (18-44 years) with CRC have a better survival outcome compared to men of the same age or compared to older women (over 50 years), indicating a global incidence of sexual dimorphism in CRC rates and survival. This suggests a protective role for the sex steroid hormone estrogen in CRC development. Key proliferative pathways in CRC tumorigenesis exhibit sexual dimorphism, which confer better survival in females through estrogen regulated genes and cell signaling. Estrogen regulates the activity of a class of Kv channels (KCNQ1:KCNE3), which control fundamental ion transport functions of the colon and epithelial mesenchymal transition through bi-directional interactions with the Wnt/β-catenin signalling pathway. Estrogen also modulates CRC proliferative responses in hypoxia via the novel membrane estrogen receptor GPER and HIF1A and VEGF signaling. Here we critically review recent clinical and molecular insights into sexual dimorphism of CRC biology modulated by the tumor microenvironment, estrogen, Wnt/β-catenin signalling, ion channels, and X-linked genes.