The Case for a Subcutaneous Magnesium Product and Delivery Device for Space Missions

Abstract

Cardiovascular (CV) complications, associated with space flight (SF), are caused by microgravity, hypokinesia and radiation, particularly beyond earth orbit, with all three conducive to oxidative stress. Except for emergencies, pharmaceuticals appear to be contraindicated, because of unpredictable side effects from malabsorption (M) and potential hepatic and renal impairment. Magnesium (Mg) depletion and elevations of cytokines (interleukin 6) occur during SF, conducive to self-sustaining vascular inflammation mechanisms. There are potential endothelial injuries (EI) and reduced Cyclic GMP (a second messenger of nitric oxide: NO) and elevated urinary excretion of C-peptide (insulin resistance: IR). Recent findings that show reductions in vascular endothelial growth factor (VEGF) suggest that this may result from SF-related thrombocytopenia since platelets (P) are the major source of VEGF, and that NO might play a role. Both VEGF and Mg are vital for angiogenesis, endothelial function and reendothelialization. Insulin is necessary for VEGF expression. To prevent SF-related CV complications in the presence of IR and M and with the potential for renal insufficiency, closely monitored subcutaneous (SC) Mg should be provided. The dosage can be monitored by sublingual intracellular Mg assays. Needed is development of a SC Mg reservoir device, which can be replenished before extra-vehicular activities (EVA) and which must be reliable despite vigorous movements during EVA, that can last up to 8 hours. This could also be protective against decompression sickness and EVA-related 100% oxygen requirements before and during this activity, both of which predispost to EI.

• space flight (SF)
• cardiovascular complications
• endothelial injury
• oxidative stress
• malabsorption
• renal dysfunction
• thrombocytopenia
• Mg-deficiency
• sublingual Mg-assay
• subcutaneous Mg-repletion by subcutaneous device

Key teaching points:

• Space flight (SF) can cause endothelial damage, decreased vascular endothelial growth factor (VEGF), platelet aggregation—related thrombocytopenia and insulin-resistance (IR), leading to cardiovascular complications (CVC).

• Malabsorption and hypokinesia contribute to Mg depletion of SF, and to the CVC and secondary inflammatory processes.

• Need for Mg repletion during SF mandates availability of a Mg salt, that can be administered subcutaneously - preferably by a (to be developed) repletable automatic device, and a means to monitor sublingual Mg levels.

Key teaching points:

• Space flight (SF) can cause endothelial damage, decreased vascular endothelial growth factor (VEGF), platelet aggregation—related thrombocytopenia and insulin-resistance (IR), leading to cardiovascular complications (CVC).

• Malabsorption and hypokinesia contribute to Mg depletion of SF, and to the CVC and secondary inflammatory processes.

• Need for Mg repletion during SF mandates availability of a Mg salt, that can be administered subcutaneously - preferably by a (to be developed) repletable automatic device, and a means to monitor sublingual Mg levels.