Blood lipid and lipoprotein levels and the risk of cancer of the colon and rectum. A prospective study of 62,173 Norwegian men and women

Relationship between serum lipid level and colorectal cancer: a systemic review and meta-analysis

OBJECTIVE

Investigative studies report contradictory results of the relationship between serum lipid levels and the risk of colorectal cancer (CRC). We conducted a meta-analysis of prospective published studies to clarify the relationship between serum lipid and CRC risk.

DESIGN

Systematic review and meta-analysis.

DATA SOURCES

PubMed and Embase from inception until December 2020.

ELIGIBILITY CRITERIA

We considered prospective cohort and case-control studies that evaluated differences in serum lipid levels with the risk of developing CRC.

DATA EXTRACTION AND SYNTHESIS

Two independent reviewers screened and included the studies using standardised electronic data extraction forms. The relative risks of the studies were combined with random-effect and fixed-effect models and were analysed for heterogeneity, publication bias and sensitivity.

RESULTS

Twenty-four prospective studies, including 4 224 317 individuals with 29 499 CRC cases, were included in the meta-analysis. The total pooled risk ratio (RR) for high vs low concentrations of triglyceride (TG) concentrations was reported at 1.21 (95% CI 1.09 to 1.34; I²=46.8%), total cholesterol (TC) was at 1.15 (95% CI 1.08 to 1.22; I²=36.8%), high-density lipoprotein cholesterol (HDL-C) was 0.86 (95% CI 0.77 to 0.97; I²=28.8%) and low-density lipoprotein cholesterol (LDL-C) was observed at 1.03 (95% CI 0.75 to 1.41; I²=69.4%).

CONCLUSIONS

This meta-analysis shows that high levels of serum TG and TC are positively correlated with the incidence rate of CRC, while high levels of serum HDL-C are negatively correlated with CRC incidence rate. Furthermore, no association was found between LDL-C and the risk of developing CRC. Nevertheless, the heterogeneity brought about by comparative methods, demographic differences and pathological differences between the research subjects limits the effectiveness of the overall pooled results.

Blood lipids and risk of colon or rectal cancer: a Mendelian randomization study

PURPOSE

Recent Mendelian randomization (MR) studies derived inconsistent results of blood lipids' effect on colorectal cancer, and whether the blood lipids' effect on colon and rectal cancer is different is still unknown. Here, we sought to answer these questions.

METHODS

Primarily, we employed univariable MR to explore the blood lipids' effect on colon and rectal cancer, including high-density lipoprotein (HDL), low-density lipoprotein (LDL), total cholesterol and triglycerides. Then, multivariable MR was also employed to reassess each blood lipid's effect on the two cancers with adjustment of the other lipids. Reverse MR analysis was adopted to determine whether colon or rectal cancer could affect the levels of blood lipids. The Cochrane's Q value was used to evaluate the heterogeneity, and MR-PRESSO was used to appraise the pleiotropy.

RESULTS

Generally, we did not find any significant result between blood lipids and the colon/rectal cancer after Bonferroni correction in the univariable MR analysis. The multivariable MR analysis also obtained the same results. However, it should be noted that higher total cholesterol level might increase the risk of colon cancer (OR = 1.15 [1.01, 1.31], IVW p value = 0.029) but not rectal cancer (OR = 1.02 [0.85, 1.21], IVW p value = 0.853). Such causal relationship turned insignificant in the multivariable MR. The reverse MR analysis suggested that either colon or rectal cancer could increase the levels of blood lipids.

CONCLUSION

We found no association between blood lipids and risk of colon or rectal cancer, except for a positive association between total cholesterol and colon cancer risk.

Association between cardiovascular risk factors and colorectal cancer: A systematic review and meta-analysis of prospective cohort studies

BACKGROUND

Emerging data have suggested colorectal cancer (CRC) often coexists with cardiovascular diseases, but whether cardiovascular risk factors play a role in CRC remains unclear. We performed a systematic review and meta-analysis to better illustrate the associations between cardiovascular risk factors and CRC.

METHODS

We searched EMBASE, MEDLINE and Web of Science databases from inception up to June 14, 2020. Prospective cohort studies were included if they evaluated the association between at least one of cardiovascular risk factors and CRC incidence, containing sufficient data to obtain relative risk (RR) and 95% confidence interval (CI). We performed separate meta-analyses for each cardiovascular risk factor using random-effect model. PROSPERO registration number: CRD42020175537.

FINDINGS

Data from 84 studies, reporting 52, 348, 827 individuals and 384, 973 incident cases were included in the analysis. Overall, the risk of CRC was 1.31(95% CI, 1.21-1.42) for obesity, 1.14 (95% CI, 1.09-1.20) for per 5 kg/m² increase in body mass index, 1.18 (95% CI, 1.14-1.23) for former smoker, 1.20 (95% CI, 1.11-1.30) for current smoker, 1.25 (95% CI, 1.16-1.35) for diabetes, 1.07 (95% CI, 1.02-1.12) for hypertension. The summary RRs of CRC for the highest versus lowest quartiles of total cholesterol, triglyceride, low-density lipoprotein were 1.12 (95% CI, 1.03-1.22), 1.18 (95% CI, 1.04-1.35), 0.85 (95% CI, 0.62-1.17) respectively and the pooled RR for the lowest versus highest quartile of high-density lipoprotein was 1.14 (95% CI, 1.02-1.28).

INTERPRETATION

Unfavorable cardiovascular risk factors are associated with increased risk of CRC, which may provide novel insight into the screening strategies of CRC in patient with these risk factors.

Plasma lipid levels and colorectal adenoma risk

PURPOSE

Abnormalities in lipid levels have been associated with colorectal neoplasm risk; however, few studies have adjusted for use of cholesterol-lowering medications. The objective of this study was to determine the association of plasma lipid levels with adenoma risk while accounting for statin medication use.

METHODS

We included 254 subjects with advanced adenoma, 246 with single small adenoma, 179 with multiple small adenoma cases, and 403 control participants in the Tennessee Colorectal Polyp Study who also had plasma lipid measurements performed. Data on the use of statin medications were available for 83.4% of these participants. The association between plasma lipids and adenoma risk was evaluated using logistic regression models.

RESULTS

Participants in the highest quartile of HDL cholesterol (range 52-106 mg/dl) had an adjusted odds ratio of 0.49 (95% CI 0.23, 1.07), 0.35 (95% CI 0.13, 0.91), and 0.22 (95% CI 0.09, 0.54) for single small, multiple small, and advanced adenomas compared to the lowest quartile (range 12-34 mg/dl), respectively. Participants with the highest quartile of triglyceride levels (range 178-721 mg/dl) had an adjusted odds ratio of 2.40 (95% CI 1.26, 4.55), 1.67 (95% CI 0.66, 4.23), and 2.79 (95% CI 1.25, 6.23) for single small, multiple small, and advanced adenoma, respectively, compared to the lowest quartile (range 40-84 mg/dl). When restricted to individuals with known statin medication use, adjusting for statin use did not appreciably affect these results.

CONCLUSION

We found a direct association between triglyceride plasma levels and an inverse association between plasma HDL cholesterol levels and adenoma risk. Both effects were not appreciably changed when accounting for the regular use of statin medication.

Lipid levels in serum and cancerous tissues of colorectal cancer patients

AIM: To investigate the correlations between lipid metabolism disorder and the occurrence and development of colorectal cancer by monitoring the alterations in lipid levels in cancerous tissue and serum in patients with colorectal cancer.

METHODS: The levels of total and free cholesterol (TCH and FCH), triglycerides (TG), low density lipoprotein-cholesterol (LDL-C), high density lipoprotein- cholesterol (HDL-C), apolipoprotein A1 (ApoA-1) and ApoB in serum of 206 patients with colorectal cancer, 70 patients with benign colorectal disease and 300 healthy participants, and in the cancerous tissue and paracancerous tissue of 152 patients with colorectal cancer were measured with an Olympus 600 auto-biochemical analyzer. The obtained data were statistically analyzed.

RESULTS: Serum FCH level was significantly higher (1.9 ± 0.4 mmol/L vs 1.3 ± 0.3 mmol/L, 1.9 ± 0.4 mmol/L vs 1.2 ± 0.4 mmol/L, P < 0.05), whereas serum levels of TCH, LDL-C, ApoA-I and ApoB were significantly lower in patients with colorectal cancer than in patients with benign colorectal disease and healthy controls. The levels of FCH and TG in cancerous tissue were significantly lower (14.5 ± 9.6 μmol/g vs 19.3 ± 13.9 μmol/g, P < 0.05; 16.3 ± 19.8 μmol/g vs 44.1 ± 38.1 μmol/g, P < 0.05), whereas HDL-C level was significantly higher (7.9 ± 4.5 μmol/g vs 5.7 ± 3.9 μmol/g, P < 0.01) in cancerous tissue than in paracancerous tissue. The levels of TCH and TG in serum and the levels of TCH and HDL-C in cancerous tissue in patients with colorectal cancer were significantly correlated with TNM stage. The levels of TCH and LDL-C in serum were significantly lower, whereas HDL-C level in cancerous tissue was significantly higher in patients with lymph node metastasis than in patients without lymph node metastasis. The levels of TCH, FCH, TG, HDL-C and LDL-C in cancerous tissue were not significantly different from those in paracancerous tissue. The serum levels of FCH and TG were significantly higher, whereas serum HDL-C levels were significantly lower in patients with rectum cancer than in patients with colon cancer.

CONCLUSION: The disordered and abnormally altered levels of lipids in cancerous tissue and serum of patients with colorectal cancer may be correlated with the occurrence and development of colorectal cancer.

Functional polymorphisms to modulate luminal lipid exposure and risk of colorectal cancer

PURPOSE

Fat absorption may play a crucial role in colorectal carcinogenesis by determining intra-colonic exposure to potentially carcinogenic lipid metabolites.

METHODS

We conducted a population-based case-control study that included 1163 cases and 1501 controls to examine whether individuals who carry genetic variants associated with lower lipid absorption have a higher risk of colorectal cancer. Using Taqman assay, we determined FABP2 alanine (A)/threonine (T) polymorphism at codon 54 in exon-2 and APOE isoforms. Multivariable odds ratios (OR) and 95% confidence intervals (CI) were calculated by unconditional logistic regression models, assuming FABP2 A54 and APO non-E4 as high risk alleles.

RESULTS

We found no associations with either of the polymorphisms. The OR associated with FABP2 A54 homozygotes compared with the others was 1.01 (95% CI; 0.86-1.45) and that for non-ApoE4 carriers compared with carries was 0.95 (95% CI; 0.80-1.13). However, there was a statistically significant negative interaction between total fat intake and FABP2 AA genotypes (p=0.025), indicating that the risk of colorectal cancer associated with this polymorphism is higher in the subjects with lower fat intake.

CONCLUSIONS

These results suggest that these SNPs may not be useful in predicting colorectal cancer risk in populations with high fat intake.

Lifestyle factors and colorectal cancer risk (1): systematic review and meta-analysis of associations with body mass index

OBJECTIVE

Excess body weight, defined by body mass index (BMI), may increase the risk of colorectal cancer. As a prerequisite to the determination of lifestyle attributable risks, we undertook a systematic review and meta-analysis of prospective observational studies to quantify colorectal cancer risk associated with increased BMI and explore for differences by gender, sub-site and study characteristics.

METHOD

We searched MEDLINE and EMBASE (to December 2007), and other sources, selecting reports based on strict inclusion criteria. Random-effects meta-analyses and meta-regressions of study-specific incremental estimates were performed to determine the risk ratio (RR) and 95% confidence intervals (CIs) associated with a 5 kg/m(2) increase in BMI.

RESULTS

We analysed 29 datasets from 28 articles, including 67,361 incident cases. Higher BMI was associated with colon (RR 1.24, 95% CIs: 1.20-1.28) and rectal (1.09, 1.05-1.14) cancers in men, and with colon cancer (1.09, 1.04-1.12) in women. Associations were stronger in men than in women for colon (P < 0.001) and rectal (P = 0.005) cancers. Associations were generally consistent across geographic populations. Study characteristics and adjustments accounted for only moderate variations of associations.

CONCLUSION

Increasing BMI is associated with a modest increased risk of developing colon and rectal cancers, but this modest risk may translate to large attributable proportions in high-prevalence obese populations. Inter-gender differences point to potentially important mechanistic differences, which merit further research.

Hypertriglyceridemia is positively correlated with the development of colorectal tubular adenoma in Japanese men

AIM: To determine the real association between serum lipid levels and colonic polyp formation.

METHODS: We performed a large scale retrospective study to analyze the correlation between the incidence of colorectal adenoma or carcinoma and the fasting serum levels of total cholesterol (TC) and triglycerides (TG) in patients who underwent total colonoscopy for screening for colon cancer.

RESULTS: Both levels were significantly elevated in patients with adenomas as compared with patients without any neoplastic lesion (TC 207.6 ± 29.5 vs 199.5±34.3, n= 4883, P< 0.001; TG 135.0 ± 82.2 vs 108.7±71.5, n= 4874, P< 0.001). The difference was significant in patients with tubular adenoma but not in those with villous or serrated adenoma. Multiple logistic regression analysis including age and sex revealed that TG was an independent correlation factor in male (P < 0.01), but not in female patients. The level of TG in patients with invasive carcinoma did not show a significant elevation from that in patients with adenoma. These findings suggest that hypertriglyceridemia is an independent risk factor for colonic adenoma in men.

CONCLUSION: Although a high level of serum triglyceride does not appear to be mechanically involved in the development of carcinoma, reduction of serum TG and intensive surveillance with total colonoscopy may have benefit in men with hypertriglyceridemia.

Increased risk of colorectal cancer due to interactions between meat consumption and the CD36 gene A52C polymorphism among Japanese

A previous study showed expression of CD36, recently reported to play important roles in metabolism of oxidized low-density lipoprotein and long-chain fatty acids and to be positively correlated with colon cancer prognosis. To examine relationships between colorectal cancer and the CD36 gene A52C polymorphism according to meat consumption as a surrogate for saturated fatty acid intake, we conducted the present hospital-based, case-control study of 128 cases and 238 non-cancer controls. Consumption of meat and vegetables/fruit was divided into three (low, moderate, and high) and two (low and high) groups, respectively. Regarding the risk of colorectal cancer on cross-classifying subjects for the CD36 genotype and meat consumption, the odds ratio (OR) for the C/C genotype with moderate meat consumption relative to the A/A genotype with low meat consumption was 8.30 (95% confidence interval, CI=2.15-32.00). None of individuals with the C/C genotype was in the high meat consumption group. In the low vegetables/fruit consumption group, the OR for the C/C genotype relative to the A/A genotype was 3.03 (95% CI=1.12-7.90). Our findings suggest that interactions between moderate-high meat consumption and the CD36 gene A52C polymorphism may increase the risk of colorectal cancer.

Association of low plasma cholesterol with mortality for cancer at various sites in men: 17-y follow-up of the prospective Basel study

BACKGROUND

Low serum cholesterol has been associated with an increased risk of cancer mortality in various studies, which has led to uncertainty regarding the benefit of lower blood cholesterol.

OBJECTIVE

The aim of our study was to evaluate the association between low blood cholesterol (<5.16 mmol/L) and cancer at sites that have rarely been evaluated. We placed special emphasis on the potential confounding effect of antioxidant vitamins.

DESIGN

Plasma concentrations of cholesterol and antioxidant vitamins were measured in 1971-1973 in 2974 men working in Basel, Switzerland. In 1990, the vital status of all participants was assessed.

RESULTS

Two hundred ninety of the participants had died from cancer, 87 from lung, 30 from prostate, 28 from stomach, and 22 from colon cancer. Group means for plasma cholesterol concentrations did not differ significantly between survivors and those who died from cancer at any of the studied sites. With plasma cholesterol, vitamins C and E, retinol, carotene, smoking, and age accounted for in a Cox model, an increase in total cancer mortality in lung, prostate, and colon but not in stomach cancer mortality was observed in men >60 y of age with low plasma cholesterol. When data from the first 2 y of follow-up were excluded from the analysis, the relative risk estimates remained practically unchanged with regard to lung cancer but decreased for colon, prostate, and overall cancer.

CONCLUSIONS

Increased cancer mortality risks associated with low plasma cholesterol were not explained by the confounding effect of antioxidant vitamins, but were attributed in part to the effect of preexisting cancer.

Metabolism of an artificial emulsion resembling chylomicrons in patients with multiple myeloma

Multiple myeloma, as other neoplastic diseases, is accompanied by alterations in lipid metabolism. The metabolism of chylomicrons is unexplored in this condition, despite the importance of these lipoproteins for the energy body supply. Chylomicron metabolism in the bloodstream consists of lipolysis by lipoprotein lipase and uptake of remnants by the liver. Triglyceride-rich emulsions can mimic chylomicron metabolism in man and are a useful tool to evaluate this metabolic pathway. A double-labeled chylomicron-resembling emulsion was injected into 20 patients with multiple myeloma and 30 normolipidemic healthy subjects. The plasma kinetic curves of the emulsion 3H-triglyceride and 14C-cholesteryl ester were determined in plasma samples collected over 60 minutes. The fractional clearance rate (FCR) of triglycerides in multiple myeloma was not changed compared to controls. However, FCR of cholesteryl esters was smaller in multiple myeloma (0.025 +/- 0.003 and 0.061 +/- 0.010 min(-1), respectively). These results indicate that chylomicron lipolysis is not affected in multiple myeloma, whereas remnant removal is diminished.

Biological effects of the superoxide radical

Can the superoxide radical exert deleterious effects independent of participating with H2O2 in the production of the hydroxyl radical? Examination of the superoxide-related literature reveals data suggesting an affirmative answer to this question.