A systematic review and meta-analysis of bone loss in space travelers

Abstract

Bone loss in space travelers is a major challenge for long-duration space exploration. To quantify microgravity-induced bone loss in humans, we performed a meta-analysis of studies systematically identified from searching Medline, Embase, Web of Science, BIOSIS, NASA Technical reports, and HathiTrust, with the last update in November 2019. From 25 articles selected to minimize the overlap between reported populations, we extracted post-flight bone density values for 148 individuals, and in-flight and postflight biochemical bone marker values for 124 individuals. A percentage difference in bone density relative to pre-flight was positive in the skull, +2.2% [95% confidence interval: +1.1, +3.3]; neutral in the thorax/upper limbs, −0.7% [−1.3, −0.2]; and negative in the lumbar spine/pelvis, −6.2 [−6.7, −5.6], and lower limbs, −5.4% [−6.0, −4.9]. In the lower limb region, the rate of bone loss was −0.8% [−1.1, −0.5] per month. Bone resorption markers increased hyperbolically with a time to half-max of 11 days [9, 13] and plateaued at 113% [108, 117] above pre-flight levels. Bone formation markers remained unchanged during the first 30 days and increased thereafter at 7% [5, 10] per month. Upon landing, resorption markers decreased to pre-flight levels at an exponential rate that was faster after longer flights, while formation markers increased linearly at 84% [39, 129] per month for 3-5 months post-flight. Microgravity-induced bone changes depend on the skeletal-site position relative to the gravitational vector. Post-flight recovery depends on spaceflight duration and is limited to a short post-flight period during which bone formation exceeds resorption.

Targeting myostatin/activin A protects against skeletal muscle and bone loss during spaceflight

“…2 B ). Interestingly, BMD in the humerus was not reduced in flight mice during this 22 d period, consistent with the differential effects of microgravity on the femur and humerus reported in rats ( 26 ) and humans ( 27 ). Surprisingly, BMD in the humerus was even higher in flight mice compared to ground mice by the time of the first in-flight DXA scan on day L+6, with BMD of the left humerus being 14% higher in flight mice ( Fig.…”

Spaceflight Induced Disorders: Potential Nutritional Countermeasures

“…Arteriosclerosis (Hughson et al, 2016: Garrett-Bakelman et al, 2019 Aggregates of endolhelial cells (Krüger et al, 2019) Heart change in shape (May et al, 2014) Arrhythmias (Respress et al, 2014) change in structure-function of pluripotent stem cell-derived cardiomyocytes Ca handling (Wnorowski et al, 2019) Bone Increased activity of osteoclasts and the decreased activity of osteoblasts (Stavnichuk et al, 2020) fractures and osteoporosis (Grimm et al, 2016) muscle loss of muscle mass (Stein and Blanc, 2011) Muscle fatigue and pain, weakness and lack of movement coordination (Fitts et al, 2000).…”

“…Bones play different roles, from supporting body weight to mineral reserves, acid-base homeostasis and bone marrow containment and protection. These functions are all affected by microgravity (Stavnichuk et al, 2020). In physiological conditions on Earth, the osteoclast activity with consequent bone resorption and the osteoblast activity with consequent bone tissue production are balanced.…”

“…In physiological conditions on Earth, the osteoclast activity with consequent bone resorption and the osteoblast activity with consequent bone tissue production are balanced. Bone loss occurs during spaceflight, due to the combined effect of the increased activity of osteoclasts and the decreased activity of osteoblasts, resulting in negative calcium balance and consequent bone loss (Stavnichuk et al, 2020). Calcium is thus released into the bloodstream and urine, increasing the risk of kidney stone formation (Stavnichuk et al, 2020).…”

“…Bone loss occurs during spaceflight, due to the combined effect of the increased activity of osteoclasts and the decreased activity of osteoblasts, resulting in negative calcium balance and consequent bone loss (Stavnichuk et al, 2020). Calcium is thus released into the bloodstream and urine, increasing the risk of kidney stone formation (Stavnichuk et al, 2020). The calcium release from the bone suppresses the parathyroid hormone (PTH) with consequent reduction of vitamin D3 activation in the kidney.…”