A difficult lecture to end the nutrient-gene interaction section of the BMS3020 module but hopefully these concise and well-explained notes will surely help! Selenium often appears on the exam so be prepared!
BMS3020 CHRONIC DISEASE
LECTURE 10 – SNPs in the Selenium Metabolism
Learning Outcomes
Do Genetic Factors affect Selenium Metabolism?
MEPLAN - NUTRIENTS 2015, 7(5), 3621-3651/MEPLAN & HESKETH- CANCER TREAT RES 2014-;159:145-66
Selenium (Se): Micronutrient essential for human health, found in many foods e.g. Brazilian nuts,
and bread (flour)
Epidemiological evidence:
- Huge variations between populations intake in the world – depends on soil content of Se
- Sub-optimal Se intake in UK and most European countries – not deficient but not enough
- Low/sub-optimal Se intake associated with increased risk or cancers
- Supplementation trials: Confusing results (Two main studies carried out in the US)
1. NPC – Nutritional Prevention of Cancer Trial
Individuals with low baseline Se (at starting point) received selenium supplement
Dramatic decrease of development of prostate cancer (50%) and colorectal cancer occurrence
2. SELECT – Selenium and Vitamin E Cancer Prevention Trial
Much larger study with 35,000 men
Few mistakes in this study; people recruited had very high baseline Se prior to supplementation,
therefore supplementation
with selenium and vitamin E
showed no effect on
prostate cancer but
increased amount of people
developing type 2 diabetes,
so study had to be stopped
- Ageing: Epidemiological data has shown, something which is commonly observed for
micronutrients, that people who are older have a reduced Se intake and plasma level
Effect on type 2 diabetes shows that
selenium is important in T2D metabolic
regulation
Selenium was originally identified
because of its toxicity in excess
Biological Evidence
- Selenoproteins: Mediates Se biological actions = Se biological actors
- 25 selenoproteins in humans:
o Contain Se in the form of Selenocysteine (Sec) in their structure and function depends on
this being present
o All proteins share Sec availability and the Selenoprotein synthesis machinery
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