Martina Heer

IU International University of Applied Sciences | IU

Background and objective Long-term sodium balance studies have revealed a phenomenon of temporary storage of sodium in tissues. Consequently, relying on an individual's single 24-hour urine collections may lead to an unreliable estimation of sodium intake. Our recent research has shown that the accuracy of repeated spot urine collections is equal t...

Background Spaceflight poses a unique set of challenges to humans and the hostile spaceflight environment can induce a wide range of increased health risks, including dermatological issues. The biology driving the frequency of skin issues in astronauts is currently not well understood. Methods To address this issue, we used a systems biology appro...

Pre-proenkephalin 1 (Penk1) is a pro-neuropeptide that belongs to the typical opioid peptide’s family, having analgesic properties. We previously found Penk1 to be the most downregulated gene in a whole gene profiling analysis performed in osteoblasts subjected to microgravity as a model of mechanical unloading. In this work, Penk1 downregulation w...

Intracellular levels of glutathione, the major mammalian antioxidant, are reported to decline with age in several species. To understand whether ageing affects circulating glutathione levels in cats, blood was sampled from two age groups, < 3 years and > 9 years. Further, to determine whether dietary supplementation with glutathione precursor glyci...

In recent decades of spaceflight, inadequate caloric intake has posed significant nutritional challenges, contributing to muscle degradation, weakened immune and cardiovascular systems during and after space missions. This challenge becomes more acute on longer exploration missions, where transporting all food for the entire mission becomes a logis...

Dietary countermeasures to mitigate detrimental spaceflight-induced effects on bone health would alleviate the requirements and the consequences imposed by other types of countermeasures for this risk. We hypothesised that antioxidant supplementation during 60 days of 6° head-down tilt bed rest (HDBR), an analogue of spaceflight, would have a prote...

Although we have sent humans into space for more than 50 years crucial questions regarding kidney physiology, volume regulation and osmoregulation remain unanswered. The complex interactions between the renin-angiotensin-aldosterone system, the sympathetic nervous system, osmoregulatory responses, glomerular function, tubular function, and environm...

Astronauts on the International Space Station are exposed to levels of atmospheric carbon dioxide (CO 2 ) above typical terrestrial levels. We explored the possibility that increased levels of ambient CO 2 further stimulate bone resorption during bed rest. We report here data from 2 ground-based spaceflight analog studies in which 12 male and 7 fem...

Long-duration spaceflight impacts human physiology, including well documented immune system dysregulation. The space food system has the potential to serve as a countermeasure to maladaptive physiological changes during spaceflight. However, the relationship between dietary requirements, the food system, and spaceflight adaptation requires further...

Spaceflight poses a unique set of challenges to humans and the hostile spaceflight environment can induce a wide range of increased health risks, including dermatological issues. The biology driving the frequency of skin issues in astronauts is currently not well understood. To address this issue, we used a systems biology approach utilizing NASA’s...

Spaceflight entails a variety of environmental and psychological stressors that may have long-term physiological and genomic consequences. Metabolomics, an approach that investigates the terminal metabolic outputs of complex physiological alterations, considers the dynamic state of the human body and allows the identification and quantification of...

Reduced-caloric intake lowers blood pressure through sympathetic inhibition, and worsens orthostatic tolerance within days. Conversely, hypercaloric nutrition augments sympathetic activity and blood pressure. Because dietary interventions could be applied in patients with syncope, we tested the hypothesis that short-term hypercaloric dieting improv...

Space travelers are exposed to microgravity (µg), which induces enhanced bone loss compared to the age-related bone loss on Earth. Microgravity promotes an increased bone turnover, and this obstructs space exploration. This bone loss can be slowed down by exercise on treadmills or resistive apparatus. The objective of this systematic review is to p...

The availability of safe food with high quality attributes is essential for crew during their space flights as an adequate and balanced energy and nutrients intake is essential to avoid weight loss and to minimize negative effects on the immune system, physiological functions as well as the metabolic and health status that, in turn, could impair th...

Determining the extent of bone recovery after prolonged spaceflight is important for understanding risks to astronaut long-term skeletal health. We examined bone strength, density, and microarchitecture in seventeen astronauts (14 males; mean 47 years) using high-resolution peripheral quantitative computed tomography (HR-pQCT; 61 μm). We imaged the...

Objectives Carbon dioxide (CO2) levels on board the International Space Station reach 10× those of outdoor terrestrial levels. We report here studies assessing whether increased levels of ambient CO2 contribute to elevated bone resorption characteristically observed with bed rest as an analog for skeletal unloading during spaceflight. Methods Data...

Spaceflight entails a variety of environmental and psychological stressors that may have long-term physiological and genomic consequences. Metabolomics, an approach that investigates the terminal metabolites of complex physiological alterations, takes into account the dynamic state of the human body and allows the identification and quantification...

Background: A venous thromboembolism (VTE) event occurred in a female astronaut during long-duration spaceflight. Multiple factors may have contributed to this risk, including the use of combined (progestin + estrogen) oral contraceptives (cOC). Methods: Biochemistry data from 65 astronauts were evaluated for associations with cOC use and with s...

Introduction: Hypothalamic neural circuits, which adjust efferent autonomic activity in the face of altered nutrient supply, have been implicated in the pathogenesis of obesity, obesity-associated hypertension, and type 2 diabetes mellitus. Recent advances in functional magnetic resonance imaging (fMRI) permit to capture hypothalamic activity chang...

Hypothalamic and brainstem pathways, particularly the leptin melanocortin system, regulate energy balance through adjustments in autonomic efferent activity. Disordered regulation of the system predisposes to obesity and obesity-associated arterial hypertension. We applied high-resolution subcortical functional magnetic resonance imaging (fMRI) to...

Objectives 2020 marked the 20th anniversary of a continuous human presence off the planet. Space flight is challenging, with environmental stressors, a closed food system, and adaptations affecting virtually all body systems. Our objective was to evaluate the time course of biochemical changes during flight, the effects of countermeasures, and the...

Background and Aims In daily clinical practice, individual-level sodium (Na) intake is often estimated by measuring Na excretion in a single 24h urine collection, but long-term Na balance studies indicate that 7 consecutive 24h urine collections are needed. However, this approach is not feasible in clinical settings. In this study, we investigate w...

Background: Immobilization and related oxidative stress are associated with bone loss. Antioxidants like polyphenols, omega-3 fatty acids, vitamins, and micronutrients may mitigate these negative effects on bone metabolism through scavenging of free radicals. Objectives: We hypothesized that antioxidant supplementation during 60 days of 6° head-...

Objective In clinical practice, individual sodium (Na+) intake is estimated by measuring Na+ excretion in one 24-h urine collection (UC), whereas long-term Na+ balance studies indicate that 7 consecutive 24-h UCs may be needed. In this study, we investigate whether the use of repeated spot UCs is an appropriate alternative for multiple 24-h UCs to...

Objectives Bone loss remains a primary health concern for astronauts, despite in-flight exercise. We examined changes in bone microarchitecture, density and strength before and after long-duration spaceflight in relation to biochemical markers of bone turnover and exercise. Methods Seventeen astronauts had their distal tibiae and radii imaged befo...

The intention to send a crewed mission to Mars involves a huge amount of planning to ensure a safe and successful mission. Providing adequate amounts of food for the crew is a major task, but 20 years of feeding astronauts on the International Space Station (ISS) have resulted in a good knowledge base. A crucial observation from the ISS is that ast...

The upcoming exploration missions will imply a much longer duration than any of the missions flown so far. In these missions, physiological adaptation to the new environment leads to changes in different body systems, such as the cardiovascular and musculoskeletal systems, metabolic and neurobehavioral health and immune function. To keep space trav...

Muscle atrophy is a deleterious consequence of physical inactivity and is associated with increased morbidity and mortality. The aim of this study was to decipher the mechanisms involved in disuse muscle atrophy in 8 healthy men using 21-day bed rest with a cross-over design (control, with resistive vibration exercise (RVE) or RVE combined with whe...

Objectives 2020 marks the 20th anniversary of a continuous human presence off the planet. Space flight is physically and physiologically challenging, with environmental stressors, a closed food system, and adaptations affecting virtually all body systems. Key objectives for this effort included evaluating the time course of biochemical changes that...

When astronauts enter weightlessness, cephalad fluid shifts increase left ventricular dimensions, whereas central venous pressure is surprisingly reduced. More chronically, counterregulatory adjustments attenuate total blood volume; however, the internal jugular vein remains grossly dilated.1 This finding would raise suspicion for central volume ov...

Biomarkers of cartilage metabolism are sensitive to changes in the biological and mechanical environment and can indicate early changes in cartilage homeostasis. The purpose of this study was to determine if a daily locomotion replacement program can serve as a countermeasure for changes in cartilage biomarker serum concentration caused by immobili...

Optimal function of the immune system requires nominal, if not optimal, nutritional status. This fact led to the concept of “Immunonutrition” which describes diets that are specifically designed to enhance immune system function. Without adequate nutrition, the immune system is deprived of critical components needed to generate an effective immune...

Previous chapters have provided some insight into the regulation of immune responses under spaceflight conditions which correspond to a unique combination of psychosocial and physical stressors. This multitude of factors affect almost all components of the immune system, potentially leading to compromised host defense against infections, and could...

For the prevention and treatment of bone loss related diseases, focus has been put on naturally derived substances such as polyphenols. Based on human intervention studies, this review gives an overview of the effects of dietary significant polyphenols (flavonoids, hydroxycinnamic acids, and stilbenes) on bone turnover. Literature research was cond...

To understand the health impact of long-duration spaceflight, one identical twin astronaut was monitored before, during, and after a 1-year mission onboard the International Space Station; his twin served as a genetically matched ground control. Longitudinal assessments identified spaceflight-specific changes, including decreased body mass, telomer...

Andrew Taylor, Jonathan Beauchamp, Loic Briand, Victor Demaria Pesce, Martina Heer, Thomas Hummel, Scott McGrane, Christian Margot, Serge Pieters, Paola Pittia and Charles Spence consider the role of food flavour in combatting under-consumption of nutrients by astronauts on the Mars expedition.

Context: Physical inactivity and sedentary behaviours are independent risks factors for numerous diseases. Objective: We examined the capacity of a nutrient cocktail composed of polyphenols, omega-3 fatty acids, vitamin E and selenium to prevent the expected metabolic alterations induced physical activity and sedentary behaviors. Design/setting...

Potassium bicarbonate was administrated to an already alkaline diet in seven male subjects during a 21-day bed rest study and was able to decrease bed rest induced increased calcium excretion but failed to prevent bed rest-induced bone resorption. Introduction Supplementation with alkali salts appears to positively influence calcium and bone metab...

Human studies in space provide unique and often unexpected findings regarding the role of terrestrial gravity for human cardiovascular and renal regulation. While vascular volume is shifted towards the head, which would be expected to increase natriuretic peptide (NP) release, preliminary observations suggested the opposite. Therefore, we assessed...

Recent studies have established that dysregulation of the human immune system and the reactivation of latent herpesviruses persists for the duration of a 6-month orbital spaceflight. It appears certain aspects of adaptive immunity are dysregulated during flight, yet some aspects of innate immunity are heightened. Interaction between adaptive and in...

Background: Bed rest studies document that a lower dietary acid load is associated with lower bone resorption. Objective: We tested the effect of dietary acid load on bone metabolism during spaceflight. Design: Controlled 4-d diets with a high or low animal protein-to-potassium (APro:K) ratio (High and Low diets, respectively) were given to 17...

Background & aims Physical inactivity is associated with lean body mass wasting, oxidative stress and pro-inflammatory changes of cell membrane lipids. Alkalinization may potentially counteract these alterations. We evaluated the effects of potassium bicarbonate supplementation on protein kinetics, glutathione status and pro- and anti-inflammatory...

Context The effects of energy balanced bed-rest on metabolic flexibility has not been thoroughly examined. Objective We investigated the effects of 21-days bed-rest, with and without whey protein supplementation, on metabolic flexibility while maintaining energy balance. We further hypothesized protein supplementation mitigates metabolic inflexibi...

The objective of the study was to test the hypothesis that serum levels of cartilage oligomeric matrix protein (COMP) would decrease and serum levels of tumor-necrosis factor alpha (TNF-α) and selected matrix metalloproteinases (MMPs) would increase in response to bed rest (BR) and that these changes are unaffected by the intake of potassium bicarb...

PURPOSE: Physical inactivity and sedentary behaviours are recognized as major independent risks factors for numerous diseases. We examined the capacity of a nutrient cocktail composed of polyphenols, omega-3 fatty acids, vitamin E and selenium to prevent the metabolic deteriorations induced by 20 days of step reduction, including fructose overfeedi...

Aims/hypothesis: Physical inactivity has broad implications for human disease including insulin resistance, sarcopenia and obesity. The present study tested the hypothesis that (1) impaired mitochondrial respiration is linked with blunted insulin sensitivity and loss of muscle mass in healthy young men, and (2) resistive vibration exercise (RVE) w...

Inhibition of sodium glucose cotransporter 2 with empagliflozin results in caloric loss by increasing urinary glucose excretion and has a mild diuretic effect. Diuretic effects are usually associated with reflex-mediated increases in sympathetic tone, whereas caloric loss is associated with decreased sympathetic tone. In an open-label trial, muscle...

Bed rest (BR) causes bone loss, even in otherwise healthy subjects. Several studies suggest that ambulatory subjects may benefit from high-protein intake to stimulate protein synthesis and to maintain muscle mass. However, increasing protein intake above the recommended daily intake without adequate calcium and potassium intake may increase bone re...

Background: Astronauts in space consume fewer calories and return to earth predisposed to orthostatic intolerance. The role that caloric deficit plays in the modulation of autonomic control of the cardiovascular system is unknown. Therefore, the purpose of this study was to determine the effects of 6° head-down bedrest (an analog of spaceflight) w...

Purpose: The goal of this study was to investigate the pharmacodynamic effects of co-administration of empagliflozin, a sodium glucose cotransporter 2 inhibitor, with diuretic agents. Methods: In a randomized, open-label cross-over study, 22 patients with type 2 diabetes mellitus received empagliflozin 25 mg for 5 days and either hydrochlorothia...

Purpose: Our aim was to investigate the effects of the sodium glucose cotransporter 2 inhibitor empagliflozin on urinary and serum glucose and electrolytes, urinary volume, osmolality, and the renin-angiotensin system in patients with type 2 diabetes. Methods: In an open-label study, 22 patients receiving metformin (median age 56 years; range 40...

The effect of weightlessness on the human skeletal system is one of the greatest concerns in safely extending space missions. The ability to understand and counteract weightlessness-induced bone mineral loss will be vital to crew health and safety during and after extended-duration space station and exploration missions. Research on bone mineral lo...

Bone loss and renal stone risk are longstanding concerns for astronauts. Bone resorption brought on by spaceflight elevates urinary calcium and the risk of renal stone formation. Loss of bone calcium leads to concerns about fracture risk and increased long-term risk of osteoporosis. Bone metabolism involves many factors and is interconnected with m...

Low-grade metabolic acidosis (LGMA), as induced by high dietary acid load or sodium chloride (NaCl) intake, has been shown to increase bone and protein catabolism. Underlying mechanisms are not fully understood, but from clinical metabolic acidosis interactions of acid-base balance with glucocorticoid (GC) metabolism are known. We aimed to investig...

Ophthalmic changes have occurred in a subset of astronauts on International Space Station missions. Visual deterioration is considered the greatest human health risk of space flight. Affected astronauts exhibit higher concentrations of 1-carbon metabolites (e.g., homocysteine) before flight. We hypothesized that genetic variations in 1-carbon metab...

The impact of effective exercise against bone loss during experimental bed rest appears to be associated with increases in bone formation rather than reductions of bone resorption. Sclerostin and dickkopf-1 are important inhibitors of osteoblast activity. We hypothesized that exercise in bed rest would prevent increases in sclerostin and dickkopf-1...

Astronauts consume fewer calories during spaceflight and return to earth with an increased risk of orthostatic intolerance. Whether a caloric deficiency modifies orthostatic responses is not understood. Thus, we determined the effects of a hypocaloric diet (25% caloric restriction) during 6° head down bedrest (an analog of spaceflight) on autonomic...

Mitigating bone loss is critical for space exploration, and diet can play a major role in this effort. Previous studies showed that dietary composition could influence bone resorption during bed rest. In this study we examined the role of dietary intake patterns in bone mineral loss in astronauts during space flight. Crewmembers were asked to consu...

Besides carbohydrates, other nutrients, such as dietary protein and amino acids; the supply of fat, vitamin D, and vitamin K; and sodium intake seem to affect glucose homeostasis. Although their impact is less pronounced than that of the amount and composition of carbohydrates, it seems reasonable to consider how nutrient intake habits may be modif...

Minerals are inorganic elements, such as calcium, iron, or magnesium, which are essential to the functioning of the human body and are obtained from foods.

Our body needs energy to keep up all the major functions of the body such as heartbeat, breathing, metabolism, organ function, and much more. The energy needed for maintaining these functions is called basal metabolism and is the amount of energy needed by the body when it is not performing any physical exercise. The rate at which this energy is us...

The popular perception is that space food is liquid and consists of a formula of easily digested macronutrients such as amino acids, fatty acids, and di- or oligosaccharides, which also contains the micronutrients required to keep a person healthy. A formula diet is different from food for astronauts in space, which sometimes in layman’s terms is c...

Nutrients are required for the structure and function of every cell and each body system, regardless of the environment. However, changes in environment can have significant effects on nutrient metabolism and requirements. Thus, defining the nutrient requirements for spaceflight and ensuring the provision and intake of those nutrients are primary i...

Sodium is the major cation of extracellular fluid (Oh 2015). Together with chloride, sodium is utilized by the body to maintain normal water distribution, osmotic pressure, and anion–cation balance in the extracellular fluid compartment (Tietz et al. 1994). Electrolyte concentrations in the body are essential for proper cardiovascular function and...

The vitamin B-complex group and vitamin C are the so-called water-soluble vitamins, which dissolve in water and are not stored by the body (IOM (Institute of Medicine) Standing Committee on the Scientific Evaluation of Dietary Reference Intakes 1998). As they are eliminated in urine, a continuous daily supply in the diet is required. Eight of the w...

Oxidative damage has been implicated in the etiology of chronic diseases and acute pathologic states (Stein 2002). Spaceflight (Markin et al. 1997; Stein and Leskiw 2000) and long-term bed rest (Smith et al. 2005a; Zwart et al. 2009b) lead to an increase in oxidative stress. Several in-flight studies have shown changes in cell-mediated immunity (Ta...

For a compound to be considered a vitamin, it has to be an essential component of the diet, a dietary essential. The elimination of a vitamin from the diet must result in a more or less clearly defined deficiency disease (Bender 2009). Vitamins are classified as either fat soluble or water soluble. In light of the astronauts’ inadequate dietary int...

This book provides an overview of microgravity-induced changes in human metabolism, muscle, bone and the cardio-vascular system, and discusses in detail the nutrient uptake required during spaceflight to counteract these adaptive mechanisms and ensure an improved physical constitution upon returning to Earth. It addresses the needs of professors, r...

To investigate the effect of whey protein plus potassium bicarbonate supplement on disused skeletal muscle structure and proteolysis after bed rest (BR). Soleus (SOL) and vastus lateralis (VL) biopsies were sampled from ten (n=10) healthy male subjects (aged 31±6 years) who did BR once with and once without protein supplement as a dietary counterme...

The purpose of this study was to directly assess sex differences in bone loss, bone biochemistry, and renal stone risk in bed rest. Bed rest simulates some spaceflight effects on human physiology and can be used to address the potential existence of sex-specific effects on bone metabolism and renal stone risk in space. We combined data from the con...

Mechanical loading represents a crucial factor in the regulation of skeletal homeostasis. Its reduction causes loss of bone mass, eventually leading to osteoporosis. In a previous global transcriptome analysis performed in mouse calvarial osteoblasts subjected to simulated microgravity, the most upregulated gene compared to unit gravity condition w...

Bone loss, a key concern for long-duration space travelers, is typically considered a female issue. The number of women who have flown long-duration space missions is now great enough to allow a quantitative comparison of changes in bone and renal stone risk by sex. Participants were 42 astronauts on long-duration missions to the International Spac...