Magnesium Status and Stress: The Vicious Circle Concept Revisited

Magnesium deficiency and stress are both common conditions among the general population, which, over time, can increase the risk of health consequences. Numerous studies, both in pre-clinical and clinical settings, have investigated the interaction of magnesium with key mediators of the physiological stress response, and demonstrated that magnesium plays an inhibitory key role in the regulation and neurotransmission of the normal stress response. Furthermore, low magnesium status has been reported in several studies assessing nutritional aspects in subjects suffering from psychological stress or associated symptoms. This overlap in the results suggests that stress could increase magnesium loss, causing a deficiency; and in turn, magnesium deficiency could enhance the body’s susceptibility to stress, resulting in a magnesium and stress vicious circle. This review revisits the magnesium and stress vicious circle concept, first introduced in the early 1990s, in light of recent available data.

A magnesium budget for serpentinisation of abyssal peridotite during the Cenozoic

<p>The marked increase in seawater Mg/Ca during the Cenozoic is poorly understood, due to the limited availability of proxy data and uncertainty in elucidating the respective contributions of Mg sources and sinks through geological time<sup>1</sup>. Though established as a potentially large source of dissolved Mg over twenty years ago, the weathering of abyssal peridotites<sup>2</sup> is a largely unexplored potential source of Mg to oceanic budgets. The release of magnesium from peridotite weathering can occur in high temperature environments, during serpentinisation near the ridge axis<sup>3</sup>, as well as low temperature off-axis environments where peridotite and serpentinite are altered to clays, carbonates and silicates<sup>4</sup>. The relative magnitude of Mg fluxes from these sources are poorly constrained. Recent studies, however, now provide a general method for estimating bulk crustal lithologies of mid-ocean ridges based on spreading rate (i.e. proportion and mass of basalts, gabbros, peridotites and serpentinised peridotite) through time<sup>5</sup>—enabling us to quantitatively assess potential Mg contributions from these different environments.</p><p>We constructed a model for oceanic crustal weathering (proportional to depth below the seafloor) to develop estimates of the mass and isotopic composition of magnesium loss from peridotite during alteration in both high- and low-T environments. As Mg fractionation occurs predominantly in low-T reactions, the primary serpentinisation reaction in near-ridge environments is unlikely to result in isotopic differentiation. Comparably, the secondary low-T alterations, of both remaining peridotites (to clays and iron hydroxides) and serpentinite (e.g. to talc and dolomite) are likely to result in the fractionation of Mg. We extend our analysis to incorporate the fractionation of these systems<sup>4</sup> and their release of Mg into the ocean. We completed our analysis by presenting a compilation of fluid data for magnesium concentrations in ultramafic bodies from hydrothermal systems, in order to evaluate our model.</p><p><strong>References</strong></p><p>(1) Staudigel, H. "Chemical fluxes from hydrothermal alteration of the oceanic crust." (2014): 583-606.</p><p>(2) Snow, J.E. and Dick, H.J., 1995. Pervasive magnesium loss by marine weathering of peridotite. Geochimica et Cosmochimica Acta, 59(20), pp.4219-4235.</p><p>(3) Seyfried Jr, W.E., Pester, N.J., Ding, K. and Rough, M., 2011. Vent fluid chemistry of the Rainbow hydrothermal system (36 N, MAR): Phase equilibria and in situ pH controls on subseafloor alteration processes. Geochimica et Cosmochimica Acta, 75(6), pp.1574-1593.</p><p>(4) Liu, P.P., Teng, F.Z., Dick, H.J., Zhou, M.F. and Chung, S.L., 2017. Magnesium isotopic composition of the oceanic mantle and oceanic Mg cycling. Geochimica et Cosmochimica Acta, 206, pp.151-165.</p><p>(5) Merdith, A.S., Atkins, S.E. and Tetley, M.G., 2019. Tectonic controls on carbon and serpentinite storage in subducted upper oceanic lithosphere for the past 320 Ma. Frontiers in Earth Science, 7, p.332.</p>

Magnesium and Drugs

Several drugs including diuretics and proton-pump inhibitors can cause magnesium loss and hypomagnesemia. Magnesium and drugs use the same transport and metabolism pathways in the body for their intestinal absorption, metabolism, and elimination. This means that when one or more drug is taken, there is always a potential risk of interaction with the magnesium status. Consequently the action of a drug may be adversely affected by magnesium (e.g., magnesium, calcium, and zinc can interfere with the gastrointestinal absorption of tetracycline antibiotics) and simultaneously the physiological function of minerals such as magnesium may be impaired by a drug (e.g., diuretics induce renal magnesium loss). Given the ever-increasing number of drugs on the market and the frequency with which they are used, greater attention must be paid in daily medical and pharmaceutical practice focused in particular on the adverse effects of drug therapy on magnesium status in order to minimize the potential risk to the health of patients.

Magnesium loss in magnesium deficient subjects with and without physical exercise during prolonged hypokinesia

Objective: To show the effect of hypokinesia (HK; diminished movement) on magnesium (Mg2+) loss in Mg2+ deficient subjects and the effect of physical exercise and on Mg2+ deficiency with and without physical exercise: Mg2+ balance, serum Mg2+ concentration and Mg2+ loss were measured. Methods: Studies were conducted on 30 healthy male volunteers during a pre-experimental period of 30 days and an experimental period of 364 days. They were divided equally into three-groups: unrestricted active control subjects (UACS), continuous hypokinetic subjects (CHKS) and periodic hypokinetic subjects (PHKS). The UACS group ran average distances of 9.3 ± 1.2 km.day-l; the CHKS group walked average distances of 0.9 ± 0.2 km.day-l; and the PHKS group walked and ran average distances of 0.9 ± 0.2 km and 9.3 ± 1.2 km.day-l for 5-and 2-days per week, respectively. Results: Mg2+ deficiency, serum Mg2+ level, fecal and urine Mg2+ loss increased (P < 0.05), in the PHKS and CHKS groups compared with their pre-experimental values and the values in the UACS group. However, serum Mg2+ concentration, urine and fecal Mg2+ loss and Mg2+ deficiency increased more (P < 0.05) in the PHKS group than in the CHKS group. Conclusions: Mg2+ deficiency is more evident with than without physical exercise and Mg2+ loss is exacerbated more with higher than lower Mg2+ deficiency. This indicates that Mg2+ deficiency with and without physical exercise and Mg2+ loss with higher and lower Mg2+ deficiency is due to inability of the body to use Mg2+ and more so when physically healthy subjects are submitted to prolonged periodic than continuous hypokinesia.