Adiposity and cancer: a Mendelian randomization analysis in the UK biobank

• Published in: International Journal of Obesity Vol. 45; no. 12; pp. 2657 - 2665
• Main Authors: Ahmed, Muktar, Mulugeta, Anwar, Lee, S. Hong, Mäkinen, Ville-Petteri, Boyle, Terry, Hyppönen, Elina
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 01.12.2021; Nature Publishing Group
• Subjects: 631/208; 631/67; 692/308/174; 692/499; 692/699/67; Abnormalities; Adipose tissue; Adolescent; Adult; Biobanks; Breast cancer; Cancer; Cohort Studies; Complications and side effects; Confidence intervals; Endometrial cancer; Endometrium; Epidemiology; Female; Genetic aspects; Health Promotion and Disease Prevention; Health risks; Humans; Internal Medicine; Lipids; Male; Medicine; Medicine & Public Health; Mendelian Randomization Analysis - methods; Metabolic Diseases; Metabolism; Middle Aged; Multiple myeloma; Neoplasms - diagnosis; Neoplasms - epidemiology; Obesity; Overweight - diagnosis; Overweight - epidemiology; Prostate cancer; Public Health; Randomization; Retrospective Studies; Risk; Risk factors; Single-nucleotide polymorphism; United Kingdom - epidemiology; Variance analysis; United Kingdom; United Kingdom > UK
• ISSN: 0307-0565; 1476-5497; 1476-5497
• DOI: 10.1038/s41366-021-00942-y

Background Observational and Mendelian randomization (MR) studies link obesity and cancer, but it remains unclear whether these depend upon related metabolic abnormalities. Methods We used information from 321,472 participants in the UK biobank, including 30,561 cases of obesity-related cancer. We constructed three genetic instruments reflecting higher adiposity together with either “unfavourable” (82 SNPs), “favourable” (24 SNPs) or “neutral” metabolic profile (25 SNPs). We looked at associations with 14 types of cancer, previously suggested to be associated with obesity. Results All genetic instruments had a strong association with BMI ( p  < 1 × 10 −300 for all). The instrument reflecting unfavourable adiposity was also associated with higher CRP, HbA1c and adverse lipid profile, while instrument reflecting metabolically favourable adiposity was associated with lower HbA1c and a favourable lipid profile. In MR-inverse-variance weighted analysis unfavourable adiposity was associated with an increased risk of non-hormonal cancers (OR = 1.22, 95% confidence interval [CI]:1.08, 1.38), but a lower risk of hormonal cancers (OR = 0.80, 95%CI: 0.72, 0.89). From individual cancers, MR analyses suggested causal increases in the risk of multiple myeloma (OR = 1.36, 95%CI: 1.09, 1.70) and endometrial cancer (OR = 1.77, 95%CI: 1.16, 2.68) by greater genetically instrumented unfavourable adiposity but lower risks of breast and prostate cancer (OR = 0.72, 95%CI: 0.61, 0.83 and OR = 0.81, 95%CI: 0.68, 0.97, respectively). Favourable or neutral adiposity were not associated with the odds of any individual cancer. Conclusions Higher adiposity associated with a higher risk of non-hormonal cancer but a lower risk of some hormone related cancers. Presence of metabolic abnormalities might aggravate the adverse effects of higher adiposity on cancer. Further studies are warranted to investigate whether interventions on adverse metabolic health may help to alleviate obesity-related cancer risk.