Titze, now an associate professor of Medicine at Vanderbilt University, wanted to explore long-term sodium balance in humans. He didn’t believe the textbook view – that the salt we eat is rapidly excreted in urine to maintain relatively constant body sodium levels. The “Mars500” simulation gave him the chance to keep salt intake constant and monitor urine sodium levels in humans over a long period of time.
Now, in the Jan. 8 issue of Cell Metabolism, Titze and his colleagues report that – in contrast to the prevailing dogma – sodium levels fluctuate rhythmically with 7-day and monthly cycles. The findings, which demonstrate that sodium is stored in the body, have implications for blood pressure control, hypertension and salt-associated cardiovascular risk.
Titze’s interest in sodium balance was sparked by human space flight simulation studies he conducted in the 1990s that showed rhythmic variations in sodium urine excretion.
“It was so clear to me that sodium must be stored in the body, but no one wanted to hear about that because it was so different from the textbook view,” he said.
He and his team persisted with animal studies and demonstrated that the skin stores sodium and that the immune system regulates sodium release from the skin.
In 2005, planning began for Mars500 – a collaboration between Russia, the European Union and China to prepare for manned spaceflight to Mars. Mars500 was conducted at a research facility in Moscow between 2007 and 2011 in three phases: a 15-day phase to test the equipment, a 105-day phase, and a 520-day phase to simulate a full-length manned mission.
Crews of healthy male cosmonauts volunteered to live and work in an enclosed habitat of sealed interconnecting modules, as if they were on an international space station.
Titze and his colleagues organized the food for the mission and secured commitments from the participants to consume all of the food and to collect all urine each day. They studied twelve men: six for the full 105-day phase of the program, and six for the first 205 days of the 520-day phase.
“It was the participants’ stamina to precisely adhere to the daily menu plans and to accurately collect their urine for months that allowed scientific discovery,” Titze said.
The researchers found that nearly all (95 percent) of the ingested salt was excreted in the urine, but not on a daily basis. Instead, at constant salt intake, sodium excretion fluctuated with a weekly rhythm, resulting in sodium storage. The levels of the hormones aldosterone (a regulator of sodium excretion) and cortisol (no known major role in sodium balance) also fluctuated weekly.
Changes in total body sodium levels fluctuated on monthly and longer cycles, Titze said. Sodium storage on this longer cycle was independent of salt intake and did not include weight gain, supporting the idea that sodium is stored without accompanying increases in water.
The findings suggest that current medical practice and studies that rely on 24-hour urine samples to determine salt intake are not accurate, he said.
“We understand now that there are 7-day and monthly sodium clocks that are ticking, so a one-day snapshot shouldn’t be used to determine salt intake.”
Using newly developed magnetic resonance imaging (MRI) technologies to view sodium, Titze and his colleagues have found that humans store sodium in skin (as they found in their animal studies) and in muscle.
The investigators suspect that genes related to the circadian “clock” genes, which regulate daily rhythms, may be involved in sodium storage and release.
“We find these long rhythms of sodium storage in the body particularly intriguing,” Titze said. “The observations open up entirely new avenues for research.”
The studies were supported by grants from the German Federal Ministry for Economics and Technology/DLR Forschung unter Weltraumbedingungen and the Interdisciplinary Center for Clinical Research at Friedrich-Alexander-University, Erlangen-Nürnberg, Germany. Food products were donated by a number of organizations.
Craig Boerner | Newswise
Indian roadside refuse fires produce toxic rainbow
26.10.2016 | Duke University
Inflammation Triggers Unsustainable Immune Response to Chronic Viral Infection
24.10.2016 | Universität Basel
Ultrafast lasers have introduced new possibilities in engraving ultrafine structures, and scientists are now also investigating how to use them to etch microstructures into thin glass. There are possible applications in analytics (lab on a chip) and especially in electronics and the consumer sector, where great interest has been shown.
This new method was born of a surprising phenomenon: irradiating glass in a particular way with an ultrafast laser has the effect of making the glass up to a...
Terahertz excitation of selected crystal vibrations leads to an effective magnetic field that drives coherent spin motion
Controlling functional properties by light is one of the grand goals in modern condensed matter physics and materials science. A new study now demonstrates how...
Researchers from the Institute for Quantum Computing (IQC) at the University of Waterloo led the development of a new extensible wiring technique capable of controlling superconducting quantum bits, representing a significant step towards to the realization of a scalable quantum computer.
"The quantum socket is a wiring method that uses three-dimensional wires based on spring-loaded pins to address individual qubits," said Jeremy Béjanin, a PhD...
In a paper in Scientific Reports, a research team at Worcester Polytechnic Institute describes a novel light-activated phenomenon that could become the basis for applications as diverse as microscopic robotic grippers and more efficient solar cells.
A research team at Worcester Polytechnic Institute (WPI) has developed a revolutionary, light-activated semiconductor nanocomposite material that can be used...
By forcefully embedding two silicon atoms in a diamond matrix, Sandia researchers have demonstrated for the first time on a single chip all the components needed to create a quantum bridge to link quantum computers together.
"People have already built small quantum computers," says Sandia researcher Ryan Camacho. "Maybe the first useful one won't be a single giant quantum computer...
14.10.2016 | Event News
14.10.2016 | Event News
12.10.2016 | Event News
26.10.2016 | Materials Sciences
26.10.2016 | Health and Medicine
26.10.2016 | Physics and Astronomy