The influence of selenium-enriched milk proteins and selenium yeast on plasma selenium levels and rectal selenoprotein gene expression in human subjects

Abstract

Certain forms of dietary Se may have advantages for improving human Se status and regulating the risk for disease, such as cancers, including colorectal cancer (CRC). The present study compared the effects of a Se-enriched milk protein (dairy-Se) with a Se-rich yeast (yeast-Se) on plasma Se levels and rectal selenoprotein gene expression since we reasoned that if these genes were not regulated, there was little potential for regulating the risk for CRC in this organ. A total of twenty-three healthy volunteers with plasma Se in the lower half of the population range were supplemented with dairy-Se (150 mg/d) or yeast-Se (150 mg/d) for 6 weeks, followed by 6 weeks of washout period. Blood was sampled every 2 weeks, and rectal biopsies were obtained before and after Se supplementation and after the washout period. Plasma Se levels and glutathione peroxidase (GPx) activity, and rectal mRNA of selenoprotein P (SeP), cytosolic GPx-1 (GPx-1), gastrointestinal GPx-2 (GPx-2) and thioredoxin reductase-1 (TrxR-1) were measured. Plasma Se levels increased rapidly in both Se groups (P,0·001); plasma GPx activity was not significantly changed. Rectal SeP mRNA increased at 6 weeks compared with baseline in both Se groups (P,0·05); only dairy-Se resulted in a sustained elevation of SeP after the washout period (P,0·05). Rectal GPx-1 and GPx-2 mRNA were higher with dairy-Se (P, 0·05) than with yeast-Se at 6 weeks. In conclusion, three rectal selenoprotein mRNA were differentially regulated by dairy-Se and yeast-Se. Changes in rectal selenoproteins are not predicted by changes in plasma Se; dairy-Se effectively regulates the expression of several rectal selenoproteins of relevance to the risk for CRC.

A Randomized Trial of Selenium Supplementation and Risk of Type-2 Diabetes, as Assessed by Plasma Adiponectin

“…Furthermore, they found no relationship between selenoprotein P and QUICKI (quantitative insulin sensitivity index), a marker of insulin resistance [5]. Evidence from two small interventions also fails to support a diabetogenic effect of Se; one study found no significant disturbances in plasma glucose after six weeks of supplementation with 150 µg/d Se as dairy- or yeast-Se [46] while the other, a randomized, controlled trial, found that 200 µg Se/d as yeast-Se for six weeks significantly lowered fasting serum insulin and HOMA-IR (homeostasis model assessment of insulin resistance) [47].…”

Toward Understanding Success and Failures in the Use of Selenium for Cancer Prevention

“…While increases in plasma Se levels were similar in both Se-supplemented groups, dairy-Se was more effective to stimulate gene expression of selenoproteins. Dairy-Se increased rectal SeP, GPx1, and GPx2 mRNA levels, whereas Se-yeast only increased rectal SeP mRNA levels (33). First attempts have been undertaken to identify suitable biomarkers of Se status in selected tissues.…”

Endoscopic biopsies from gastrointestinal carcinomas and their suitability for molecular analysis: a review of the literature and recommendations for clinical practice and research

“…Eighteen (24%) studies reported the number of EBs used for molecular testing; the median (range) mean number of EBs per patient was 2.1 (1 to 6.6 biopsies) . Only one study reported the location within the tumour from which the biopsy was obtained …”

“…Two studies reported a minimum tumour cell density required in the resection specimen for comparison using cut‐offs of 10% or 50% tumour cells . No association was seen among studies between the mean number of biopsies obtained per patient and the concordance of biomarker testing between biopsy and resection specimen . Results for the different investigative methodologies are detailed below.…”

“…Therefore, simply obtaining more of the same tissue may not reduce the test failure rate. From the current literature review, the ‘required’ amount appeared to be one to two biopsies for gene expression profiling and DNA/RNA‐based assays . However, guidance has also been published; for example, ERBB2 IHC/ISH testing in biopsies that does not refer to a minimum number of biopsies, but the presence of a minimum of five cohesive cells, without providing a rationale for this …”