DI-5-Cuffs: Bone Remodelling and Associated Metabolism Markers in Humans After Five Days of Dry Immersion to Simulate Microgravity

Abstract

Background: The dry immersion (DI) model closely reproduces factors of spaceflight environment such as supportlessness, mechanical and axial unloading, physical inactivity, and induces early increased bone resorption activity and metabolic responses as well as fluid centralization. The main goal of this experiment was to assess the efficacity of venoconstrictive thigh cuffs, as countermeasure to limit cephalad fluidshift, on DI-induced deconditioning, in particular for body fluids and related ophthalmological disorders. Our specific goal was to deepen our knowledge on the DI effects on the musculoskeletal events and to test whether intermittent counteracting fluid transfer would affect DI-induced bone modifications.Methods: Eighteen males divided into Control (DI) or Cuffs (DI-TC) group underwent an unloading condition for 5 days. DI-TC group wore thigh cuffs 8–10 h/day during DI period. Key markers of bone turnover, phospho-calcic metabolism and associated metabolic factors were measured.Results: In the DI group, bone resorption increased as shown by higher level in Tartrate-resistant acid phosphatase isoform 5b at DI24h. C-terminal telopeptide levels were unchanged. Bone formation and mineralization were also affected at DI24h with a decreased in collagen type I synthesis and an increased bone-specific alkaline phosphatase. In addition, osteocalcin and periostin levels decreased at DI120h. Calcemia increased up to a peak at DI48h, inducing a trend to decrease in parathyroid hormone levels at DI120h. Phosphatemia remained unchanged. Insulin-like growth factor 1 and visfatin were very sensitive to DI conditions as evidenced by higher levels by 120% vs. baseline for visfatin at DI48h. Lipocalin-2, a potential regulator of bone homeostasis, and irisin were unchanged. The changes in bone turnover markers were similar in the two groups. Only periostin and visfatin changes were, at least partially, prevented by thigh cuffs.Conclusion: This study confirmed the rapid dissociation between bone formation and resorption under DI conditions. It revealed an adaptation peak at DI48h, then the maintenance of this new metabolic state during all DI. Notably, collagen synthesis and mineralisation markers evolved asynchronously. Thigh cuffs did not prevent significantly the DI-induced deleterious effects on bone cellular activities and/or energy metabolism.

The State of the Organs of the Female Reproductive System after a 5-Day “Dry” Immersion

“…Another generally accepted ground-based model is “dry” immersion [ 12 , 13 , 14 ]. However, similar to the bed-rest model, studies during “dry” immersion are most often aimed at the musculoskeletal, nervous, and cardiovascular systems [ 15 , 16 , 17 , 18 ]. Moreover, the first “dry” immersion study with women as the subjects that lasted 3 days was conducted in 2020 [ 19 ].…”

Comprehensive assessment of physiological responses in women during the ESA dry immersion VIVALDI microgravity simulation

“…These results confirm that short-term DI as a model of microgravity challenges bone remodeling activity in females. In men, in 5-day DI ( n = 9 men controls), variations in total Ca (+5%), PTH (−18%), and bone formation markers (−15% for P1NP and −15% for intact OC) were similar 76 . As for CTx (resorption marker), it was 13% increased in 3-day DI (12 men) 77 , but unmodified in 5-day DI 76 , compared to 17% increase trend in women.…”

“…In men, in 5-day DI ( n = 9 men controls), variations in total Ca (+5%), PTH (−18%), and bone formation markers (−15% for P1NP and −15% for intact OC) were similar 76 . As for CTx (resorption marker), it was 13% increased in 3-day DI (12 men) 77 , but unmodified in 5-day DI 76 , compared to 17% increase trend in women. Finally, the increased calcium excretion secondary to bone loss during spaceflight is associated with an increased risk of renal oxalate stone formation in men and women, without sex differences 77 .…”

“…The skeletal unloading negatively impacts astronauts’ musculoskeletal system when exposed to microgravity. Serum levels of CTx have been shown to increase as early as the 8th day of spaceflight 74 followed by a drop in bone formation markers (P1NP, OC) after the first week of spaceflight 73 – 76 . The decrease in bone mineral density is particularly pronounced at the femoral neck and proximal femur (around −8%) after 4.5–7 months of spaceflight, as shown by DXA 73 .…”

The Effect of Microgravity on Parathyroid Hormone Secretion: A Meta-Analysis

“…Table 2 [27,28,[37][38][39][40][41][42][43][44][45][46] shows the characteristics and data extracted from the 12 studies.…”