Magnesium supplementation, metabolic and inflammatory markers, and global genomic and proteomic profiling: a randomized, double-blind, controlled, crossover trial in overweight individuals

Abstract

Background: Dietary magnesium intake has been favorably associated with reduced risk of metabolic outcomes in observational studies; however, few randomized trials have introduced a systems-biology approach to explore molecular mechanisms of pleiotropic metabolic actions of magnesium supplementation.

Objective: We examined the effects of oral magnesium supplementation on metabolic biomarkers and global genomic and proteomic profiling in overweight individuals.

Design: We undertook this randomized, crossover, pilot trial in 14 healthy, overweight volunteers [body mass index (in kg/m(2)) ≥25] who were randomly assigned to receive magnesium citrate (500 mg elemental Mg/d) or a placebo for 4 wk with a 1-mo washout period. Fasting blood and urine specimens were collected according to standardized protocols. Biochemical assays were conducted on blood specimens. RNA was extracted and subsequently hybridized with the Human Gene ST 1.0 array (Affymetrix, Santa Clara, CA). Urine proteomic profiling was analyzed with the CM10 ProteinChip array (Bio-Rad Laboratories, Hercules, CA).

Results: We observed that magnesium treatment significantly decreased fasting C-peptide concentrations (change: -0.4 ng/mL after magnesium treatment compared with +0.05 ng/mL after placebo treatment; P = 0.004) and appeared to decrease fasting insulin concentrations (change: -2.2 μU/mL after magnesium treatment compared with 0.0 μU/mL after placebo treatment; P = 0.25). No consistent patterns were observed across inflammatory biomarkers. Gene expression profiling revealed up-regulation of 24 genes and down-regulation of 36 genes including genes related to metabolic and inflammatory pathways such as C1q and tumor necrosis factor-related protein 9 (C1QTNF9) and pro-platelet basic protein (PPBP). Urine proteomic profiling showed significant differences in the expression amounts of several peptides and proteins after treatment.

Conclusion: Magnesium supplementation for 4 wk in overweight individuals led to distinct changes in gene expression and proteomic profiling consistent with favorable effects on several metabolic pathways. This trial was registered at clinicaltrials.gov as NCT00737815.

Figures

FIGURE 1.

Flow chart of magnesium-trial enrollment and design.

FIGURE 2.

A: Gene expression patterns for 58 genes differentially regulated after magnesium (n = 13) and placebo (n = 13) treatments with the Affymetrix microarray (Affymetrix, Santa Clara, CA). Each row represents one study participant, and differentially expressed genes are shown in columns. B: Principal components (PC) analysis, which revealed similar gene expression profiles within each treatment of 58 differentially expressed genes. Cluster and PC analyses were performed on the list of differentially expressed genes generated by using ANOVA.

FIGURE 3.

Real-time polymerase chain reaction confirmation of microarray results for TRPM6 and TRPM7 (n = 9). Mean (±SD) fold changes were calculated by comparing the differences in expression across magnesium (MG) and placebo treatments.

FIGURE 4.

Surface-enhanced laser-desorption/ionization time-of-flight mass spectrometry protein expression profiles from fasting urine samples collected after 4 wk of magnesium supplementation (n = 7–9) compared with after 4 wk of placebo treatment (n = 4–7). Values shown are the relative intensity of expression of proteins at varying molecular weights. P values were calculated by using one-factor ANOVA. AUC, area under the receiver operating characteristic curve.