Methylomic biomarkers for magnesium deficiency and colon neoplasia prevention

Very recently, magnesium (Mg) was selected for new Dietary Reference Intake review. Five US studies using the Mg tolerance test, the “gold standard” test of Mg status, indicated that >50% participants had Mg deficiency. In our ongoing US trial, we have found a similar result. In US and other populations at high risk of Mg deficiency, low Mg intake has been linked to elevated risk of colorectal neoplasia, insulin resistance, dyslipidemia, metabolic syndrome, type 2 diabetes, and cardiovascular disease. Conversely, in populations not at high risk of Mg deficiency, high Mg intake has been related to an increased risk of total mortality, particularly when calcium (Ca) intake is low. These observations suggest that the associations between high Mg intake and risk of diseases may completely differ by the underlying Mg status. Due to major limitations, the Mg tolerance test is not used in conventional clinical practice and rarely used in research. In clinics, serum Mg is used to clinically diagnose Mg deficiency. However, serum Mg performs very poorly at identifying those with Mg deficiency. There is a great need to develop non-invasive, sensitive and specific surrogate biomarkers which can be easily used for identifying people with Mg deficiency which is critical for the development of effective strategies for the prevention of above-mentioned diseases with minimized adverse effects. It is known that DNA methylation changes are inducible by environmental exposures, including nutrients, and reversible when the exposure disappears. There are two major modifications in cytosine, 5-hydroxymethylcytosine (5hmC) and 5-methylcytosine (5mC), which have distinct regulating functions in gene expression. 5-mC is often associated with suppressed gene expression. Recent studies found 5-hmC is specifically enriched in expressed genes and may play a critical role in activating and/or maintaining gene expression . In our pilot studies in human, Mg intake/supplementation was significantly linked to 5-mC biomarkers/pattern, 5-hmC biomarkers, and methylation capacity. Our findings indicate DNA methylation biomarkers may serve as more sensitive biomarkers to identify Mg deficiency than serum Mg. Mg plays a key role in over 300 biological activties. Thus, an epigenome-wide association study (EWAS) may help to identify the most sensitive biomarkers for Mg deficiency. However, current EWAS profiling platforms cannot distinguish 5-hmC from 5-mC. Just recently, our collaborator, Dr. He (HHMI Investigator), established a novel and state of the art technique, TAB-Seq and TAB-Array protocol, which now allows us to separate 5-hmC from 5-mC in the genome. We propose to identify 5-hmC/5-mC biomarkers for Mg deficiency by a 4-phase EWAS study in the “Personalized Prevention of Colorectal Cancer Trial [PPCCT, R01 CA149633; PI, Dai & Yu]” with a total of 240 participants. Mg tolerance test will be used to identify 5-hmC/5-mC biomarkers for Mg deficiency. Using newly identified biomarkers, we will evaluate if the effect of 12-week Mg treatment reduces the expression of TRPM7 (i.e. a gene essential in Mg homeostasis and colorectal carcinogenesis) in rectal tissues only among those with Mg deficiency.