Prevalence of pressure injury on the medical wards of public general hospitals in Kuwait: a national cross-sectional study

BACKGROUND

Pressure injury is a severe problem that can significantly impact a patient's health, quality of life, and healthcare expenses. The prevalence of pressure injuries is a widely used clinical indicator of patient safety and quality of care. This study aims to address the research gap that exists on this topic in Kuwait by investigating the prevalence of pressure injuries and preventive measures on the medical wards of the country's public general hospitals.

METHODS

A cross-sectional research design was adopted to measure the point prevalence of pressure injuries on 54 medical wards in the public general hospitals. Data, including variables pertaining to hospitals, patients, pressure injuries and preventive practices, were collected using an online form. The data were processed and analysed using Microsoft Excel and SPSS 23 (α level = 0.05). Analysis provided an overview of patient, pressure injury characteristics and preventive measures, and the relationships between the patient and pressure injury characteristics and the prevalence of pressure injuries. A model for predicting the determinants of pressure injury prevalence was constructed from a linear regression analysis.

RESULTS

The mean national prevalence of pressure injury was 17.6% (95% CI: 11.3-23.8). Purely community-acquired pressure injuries represent the majority of pressure injuries nationally (58.1%). Regarding preventive measures, "pressure injury assessment on admission" has been provided to 65.5% of patients. Correlation analysis revealed that the only statistically significant correlation with the prevalence of hospital-acquired pressure injury was "pressure injury assessment on admission", which was strongly negative (ρ = -0.857). Therefore, this was the only variable included in the regression analysis as a predictor of pressure injury prevalence (Beta = 0.839). The results showed many statistically significant differences between hospitals with respect to the variables studied.

CONCLUSIONS

The national pressure injury prevalence is high compared to the global rate. The higher percentage of purely community-acquired pressure injuries requires particular attention. Many risk factors for the development of pressure injuries are public health concerns, and effective mitigating strategies are needed. Further research is required to assess the knowledge, attitude, and behaviour of nurses with respect to pressure injuries, and to evaluate preventive and management practices.

Protein intake and bone health: an umbrella review of systematic reviews for the evidence-based guideline of the German Nutrition Society

This umbrella review aimed at assessing whether a protein intake exceeding the current recommendation for younger (0.8 g/kg body weight [BW]/day) and older (1.0 g/kg BW/day) adults affects bone mineral density and fracture risk. Moreover, the effect of animal or plant protein was evaluated. A systematic literature search was conducted in PubMed, Embase, and Cochrane Database of Systematic Reviews for systematic reviews (SRs) with or without meta-analysis of prospective studies published between 11/2008 and 08/2021. Methodological quality, outcome-specific certainty of evidence, and overall certainty of evidence of the retrieved SRs were assessed using established tools and predefined criteria. Eleven SRs of randomized controlled trials (RCTs) and/or cohort studies were included. In SRs of cohort studies and RCTs, protein intake/kg BW/day ranged between 0.21-0.95 g (low intake) and > 1.24 g (high intake), respectively, and between 0.67-1.1 g (control groups) and 1.01-1.69 g (intervention groups), respectively. The vast majority of outcome-specific certainty of evidence was rated "low" or "very low." The overall certainty of evidence for an association (cohort studies) or effect (RCTs) of total, animal or plant protein intake on each of the investigated outcomes was rated "insufficient," with the exception of possible evidence for a reduced hip fracture risk by high vs. low protein intake. Since protein intakes in low/control and high/intervention groups were very heterogeneous and with low certainty of evidence, it remains unclear whether a dose above the current recommendation or type of protein intake (animal or plant protein) affects bone health overall. However, there is possible evidence for reduced hip fracture risk with high versus low protein intake.

Health effects of high serum calcium levels: Updated phenome-wide Mendelian randomisation investigation and review of Mendelian randomisation studies

Background

Calcium plays a role in a wide range of biological functions. Here we conducted a phenome-wide Mendelian randomisation (MR-PheWAS) analysis and a systematic review for MR studies to comprehensively investigate the health effects of serum calcium.

Methods

One-hundred and thirty genetic variants strongly associated with serum calcium levels were used as instrumental variables. A phenome-wide association analysis (PheWAS) was conducted to examine the associations of genetically predicted serum calcium with 1473 distinct phenotypes in the UK Biobank including 339,197 individuals. Observed associations in PheWAS were further tested for replication in two-sample MR replication analysis. A systematic review for MR studies on serum calcium was performed to synthesize the published evidence and compare with the current MR-PheWAS findings.

Findings

Higher genetically predicted calcium levels were associated with decreased risk of 5 diseases in dermatologic and musculoskeletal systems and increased risk of 17 diseases in circulatory, digestive, endocrine, genitourinary and immune systems. Eight associations were replicated in two-sample MR analysis. These included decreased risk of osteoarthritis and increased risk of coronary artery disease, myocardial infarction, coronary atherosclerosis, hyperparathyroidism, disorder of parathyroid gland, gout, and calculus of kidney and ureter with increased serum calcium. Systematic review of 25 MR studies provided supporting evidence on five out of the eight disease outcomes, while the increased risk of gout, hyperparathyroidism and disorder of parathyroid gland were novel findings.

Interpretation

This study found wide-ranged health effects of high serum calcium, which suggests that the benefits and adversities of strategies promoting calcium intake should be assessed.

Funding

ET is supported by a CRUK Career Development Fellowship (C31250/A22804). XL is supported by the Natural Science Fund for Distinguished Young Scholars of Zhejiang Province. SCL acknowledges research funding from the Swedish Heart Lung Foundation (Hjärt-Lungfonden, 20210351), the Swedish Research Council (Vetenskapsrådet, 2019-00977), and the Swedish Cancer Society (Cancerfonden).

Serum calcium and 25-hydroxyvitamin D in relation to longevity, cardiovascular disease and cancer: a Mendelian randomization study

Associations of serum calcium (S-Ca) and 25-hydroxyvitamin D (S-25(OH)D) concentrations with longevity, cardiovascular disease, and cancer are not clear. We conducted a Mendelian randomization study to examine the associations of S-Ca and S-25(OH)D with longevity and risk of cardiovascular disease and cancer. The primary genetic instruments for S-Ca and S-25(OH)D were obtained from genome-wide association meta-analyses that included 61,054 individuals for S-Ca and up to 79,366 individuals for S-25(OH)D. Genetic variants associated with S-Ca and S-25(OH)D in the UK Biobank were used as confirmatory instruments. We obtained summary-level data for associations of these instruments with individual survival later than the 90^th versus at most the 60^th percentile of expected age at death from a genome-wide association meta-analysis including 11,262 cases and 25,483 controls, and with parental longevity (both parents in top 10% percentile) from the UK Biobank including 7,182 cases and 79,767 controls. Data for cardiovascular disease (111,108 cases and 107,684 controls) and cancer (38,036 cases and 180,756 controls) were obtained from the FinnGen consortium. A one standard deviation increase in genetically-predicted S-Ca concentration was associated with lower odds of longevity (odds ratio, 0.72; 95% CI, 0.55-0.95) and increased risk of cardiovascular disease (odds ratio, 1.11; 95% CI, 1.03-1.20). The associations were consistent in confirmatory analyses. There was no evidence supporting an association between genetically-predicted S-Ca and cancer, and no associations of genetically-predicted S-25(OH)D with the studied outcomes. Lifelong higher levels of S-Ca but not S-25(OH)D may shorten life expectancy and increase the risk of cardiovascular disease.

Impact of sedentarism due to the COVID-19 home confinement on neuromuscular, cardiovascular and metabolic health: Physiological and pathophysiological implications and recommendations for physical and nutritional countermeasures

The COVID-19 pandemic is an unprecedented health crisis as entire populations have been asked to self-isolate and live in home-confinement for several weeks to months, which in itself represents a physiological challenge with significant health risks. This paper describes the impact of sedentarism on the human body at the level of the muscular, cardiovascular, metabolic, endocrine and nervous systems and is based on evidence from several models of inactivity, including bed rest, unilateral limb suspension, and step-reduction. Data form these studies show that muscle wasting occurs rapidly, being detectable within two days of inactivity. This loss of muscle mass is associated with fibre denervation, neuromuscular junction damage and upregulation of protein breakdown, but is mostly explained by the suppression of muscle protein synthesis. Inactivity also affects glucose homeostasis as just few days of step reduction or bed rest, reduce insulin sensitivity, principally in muscle. Additionally, aerobic capacity is impaired at all levels of the O₂ cascade, from the cardiovascular system, including peripheral circulation, to skeletal muscle oxidative function. Positive energy balance during physical inactivity is associated with fat deposition, associated with systemic inflammation and activation of antioxidant defences, exacerbating muscle loss. Importantly, these deleterious effects of inactivity can be diminished by routine exercise practice, but the exercise dose-response relationship is currently unknown. Nevertheless, low to medium-intensity high volume resistive exercise, easily implementable in home-settings, will have positive effects, particularly if combined with a 15-25% reduction in daily energy intake. This combined regimen seems ideal for preserving neuromuscular, metabolic and cardiovascular health.

Effect of combined parenteral and enteral nutrition for patients with a critical illness: A meta-analysis of randomized controlled trials

BACKGROUND

Whether combined parenteral nutrition (PN) and enteral nutrition (EN) is superior to EN alone remains controversial.

OBJECTIVES

This study aimed to evaluate the efficacy and safety of combined PN and EN versus EN alone for critically ill patients based on published randomized controlled trials (RCTs).

DATA SOURCES

Studies designed as RCTs evaluating the treatment effectiveness of combined PN and EN versus EN alone for critically ill patients were identified from PubMed, Embase, and the Cochrane Library from inception to April 2019.

METHODS

The pooled relative risks and weighted mean differences with corresponding 95% confidence intervals were calculated using the random-effects model. Twelve RCTs recruiting a total of 5609 adults and 1440 children were selected for the final meta-analysis.

RESULTS

The summary relative risks indicated that combined PN and EN was not associated with the risk of all-cause mortality, respiratory infection, urinary tract infection, and nutrition-related complications. Moreover, combined PN and EN was associated with longer hospital stay and higher albumin and prealbumin levels compared with EN alone. No significant differences were, however, found between combined PN and EN and EN alone in terms of ventilatory support, intensive care unit stay, and transferrin and C-reactive protein levels.

CONCLUSIONS

This study showed that combined PN and EN significantly increased hospital stay duration and albumin and prealbumin levels compared with EN alone for critically ill patients. Large-scale RCTs should be conducted to compare the treatment effectiveness of combined PN and EN versus EN alone for critically ill patients due to a specific cause.

Dietary feeding pattern does not modulate the loss of muscle mass or the decline in metabolic health during short-term bed rest

Short periods of bed rest lead to the loss of muscle mass and quality. It has been speculated that dietary feeding pattern may have an impact upon muscle protein synthesis rates and, therefore, modulate the loss of muscle mass and quality. We subjected 20 healthy men (age: 25 ± 1 yr, body mass index: 23.8 ± 0.8 kg/m²) to 1 wk of strict bed rest with intermittent (4 meals/day) or continuous (24 h/day) enteral tube feeding. Participants consumed deuterium oxide for 7 days before bed rest and throughout the 7-day bed rest period. Prior to and immediately after bed rest, lean body mass (dual energy X-ray absorptiometry), quadriceps cross-sectional area (CSA; CT), maximal oxygen uptake capacity (V̇o_2peak), and whole body insulin sensitivity (hyperinsulinemic-euglycemic clamp) were assessed. Muscle biopsies were collected 7 days before, 1 day before, and immediately after bed rest to assess muscle tracer incorporation. Bed rest resulted in 0.3 ± 0.3 vs. 0.7 ± 0.4 kg lean tissue loss and a 1.1 ± 0.6 vs. 0.8 ± 0.5% decline in quadriceps CSA in the intermittent vs. continuous feeding group, respectively (both P < 0.05), with no differences between groups (both P > 0.05). Moreover, feeding pattern did not modulate the bed rest-induced decline in insulin sensitivity (-46 ± 3% vs. 39 ± 3%; P < 0.001) or V̇o_2peak (-2.5 ± 2.2 vs. -8.6 ± 2.2%; P < 0.010) (both P > 0.05). Myofibrillar protein synthesis rates during bed rest did not differ between the intermittent and continuous feeding group (1.33 ± 0.07 vs. 1.50 ± 0.13%/day, respectively; P > 0.05). In conclusion, dietary feeding pattern does not modulate the loss of muscle mass or the decline in metabolic health during 1 wk of bed rest in healthy men.

The Biphasic Effect of Vitamin D on the Musculoskeletal and Cardiovascular System

This narrative review summarizes beneficial and harmful vitamin D effects on the musculoskeletal and cardiovascular system. Special attention is paid to the dose-response relationship of vitamin D with clinical outcomes. In infants and adults, the risk of musculoskeletal diseases is highest at circulating 25-hydroxyvitamin D (25OHD) concentrations below 25 nmol/L and is low if 40-60 nmol/L are achieved. However, evidence is also accumulating that in elderly people the risk of falls and fractures increases again at circulating 25OHD levels > 100 nmol/L. Cohort studies report a progressive increase in cardiovascular disease (CVD) events at 25OHD levels < 50 nmol/L. Nevertheless, meta-analyses of randomized controlled trials suggest only small beneficial effects of vitamin D supplements on surrogate parameters of CVD risk and no reduction in CVD events. Evidence is accumulating for adverse vitamin D effects on CVD outcomes at 25OHD levels > 100 nmol/L, but the threshold may be influenced by the level of physical activity. In conclusion, dose-response relationships indicate deleterious effects on the musculoskeletal system and probably on the cardiovascular system at circulating 25OHD levels < 40-60 nmol/L and >100 nmol/L. Future studies should focus on populations with 25OHD levels < 40 nmol/L and should avoid vitamin D doses achieving 25OHD levels > 100 nmol/L.

Calciotropic and phosphaturic hormones in heart failure

AIMS

Despite adherence to evidence-based guidelines, heart failure [HF] still results in 5-year mortality rates of 50%, indicating a need to implement additional preventive/intervention strategies. This review summarizes data on alterations in the calciotropic and phosphaturic hormones 1,25-dihydroxyvitamin D [1,25(OH)₂D] and fibroblast growth factors-23 [FGF-23] in HF and discusses non-pharmacological measures for targeting these hormones.

DATA SYNTHESIS

The role of 1,25(OH)₂D in the regulation of calcium and phosphate homeostasis is central. 1,25(OH)₂D also plays a pivotal role in cardiac function, but is downregulated by FGF-23. There is accumulating evidence from epidemiological data that HF is associated with decreased circulating 1,25(OH)₂D and elevated FGF-23 levels. In patients with failing hearts, very low 1,25(OH)₂D and extremely high FGF-23 levels have been reported. Experimental data support the assumption that vitamin D deficiency and high serum phosphate/FGF-23 levels increase the risk of HF. This review provides a hypothesis of how vitamin D deficiency, high calcium/phosphorus intake, physical inactivity, and age-related renal impairment may all contribute to HF by adversely affecting calcium- and phosphate-regulating hormones. Several case series in infants and a meta-analysis of randomized controlled trials in adults have already reported successful treatment of or a significant risk reduction in HF by vitamin D supplements. The association of calcium/phosphorus intake, physical activity, or renal function with calciotropic/phosphaturic hormones and HF is however less well documented.

CONCLUSIONS

More attention should be paid in future to the association of circulating 1,25(OH)₂D and FGF-23 levels with HF and to (non-pharmacological) measures for targeting these calciotropic/phosphaturic hormones.

Effect of Vitamin D or Activated Vitamin D on Circulating 1,25-Dihydroxyvitamin D Concentrations: A Systematic Review and Metaanalysis of Randomized Controlled Trials

BACKGROUND

Evidence is accumulating that circulating 1,25-dihydroxyvitamin D [1,25(OH)2D] concentrations are inversely related to overall mortality.

METHODS

We searched PubMed, Embase and ISI Web of Science for randomized controlled trials with a control group receiving a placebo instead of vitamin D/activated vitamin D and performed a metaanalysis to evaluate the effect of oral vitamin D/activated vitamin D on circulating 1,25(OH)2D concentrations using a random effects model.

RESULTS

We included 52 vitamin D intervention groups (4796 individuals) and 14 intervention groups with activated vitamin D (668 individuals). Vitamin D supplements increased circulating 1,25(OH)2D by 12.2 pmol/L (95% CI, 7.8-16.5 pmol/L) and 18.8 pmol/L (95% CI, 9.2-28.4 pmol/L) if only studies with a low risk of bias in study design and reporting were considered (n = 18). There was significant heterogeneity among studies (Cohran's Q P < 0.001, I(2) = 91%). The incremental effect was larger in studies using vitamin D alone compared with coadministration of calcium supplements (18.6 pmol/L; 95% CI, 12.7-24.4 pmol/L vs 4.9 pmol/L; 95% CI, -0.4 to 10.2 pmol/L; P = 0.001), and if quantification was performed with RIA vs other methods (17.1 pmol/L; 95% CI, 11.1-23.1 pmol/L vs 6.9 pmol/L; 95% CI, 1.0-12.8 pmol/L; P = 0.02). Activated vitamin D increased the mean circulating 1,25(OH)2D by 20.5 pmol/L (95% CI, 8.3-32.7 pmol/L; P = 0.04). Again, there was evidence for significant heterogeneity among studies (Cochran Q = 85.4; P < 0.001; I(2) = 87%), but subgroup analysis did not identify parameters significantly influencing the increment in 1,25(OH)2D concentrations.

CONCLUSIONS

Both vitamin D and activated vitamin D significantly increase circulating 1,25(OH)2D concentrations, but in vitamin D users this increase is suppressed by calcium coadministration.

Effects of 60-day head-down bed rest on osteocalcin, glycolipid metabolism and their association with or without resistance training

INTRODUCTION

Bone loss and subclinical diabeteslike are developed during long-term spaceflight. Recently, it was demonstrated that bone was able to regulate energy metabolism and testosterone synthesis via osteocalcin. The aim of this study was to determine whether serum osteocalcin level is associated with glycolipid metabolism or testosterone under the influence of microgravity with or without resistive vibration exercise (RVE).

METHODS

A total of 14 healthy adult male volunteers (25-40 years) were randomly assigned to two groups (n = 7 each): control (CON) group and RVE group. Radioimmunoassay kits and ELISA kits were used for measurement of serum indices.

RESULTS

During 60-day bed rest, serum osteocalcin of both groups increased at day 4 during bed rest. Serum OPG started decreasing and reached its lowest value at day 30 during bed rest. In control group, serum insulin increased at day 4 during bed rest. IGF-I did not change significantly during the entire period of bed rest. The serum glucose decline 10% and 14% in CON and RVE groups at day 4 during bed rest. Relatively, the same results as glucose were found in serum HDL and LDL for both groups. Leptin rose and became highest at day 60 during bed rest in both groups. The level of serum testosterone was declined in control group at day 4 during bed rest. Cortisol kept stable in both group during bed rest. By spearman correlation analysis, serum osteocalcin was significantly associated with serum insulin (P < 0·05), LDL (P < 0·01) and Leptin (P < 0·01).

CONCLUSION

Our findings suggested that the mutual regulation may exist between skeletal and energy metabolism under simulated microgravity.

Hypocaloric vs Normocaloric Nutrition in Critically Ill Patients: A Prospective Randomized Pilot Trial

BACKGROUND

Optimal nutrition of critically ill patients is still a matter of debate. This pilot trial aimed to compare the impact of normocaloric vs hypocaloric feeding in critically ill patients in the first 7 days in the intensive care unit (ICU). The primary end point was the rate of nosocomial infections during the ICU stay.

METHODS

Critically ill patients requiring artificial nutrition for at least 72 hours were included within 24 hours of ICU admission and randomized into a normocaloric group (receiving 100% of their daily energy expenditure) and a hypocaloric group (receiving 50% of their daily energy expenditure).

RESULTS

One hundred patients were included (54 in the normocaloric group and 46 in the hypocaloric group). There were 66 male and 34 female patients with a mean age of 65.8 ± 11.6 years. The mean daily caloric supply was 19.7 ± 5.7 kcal/kg for the normocaloric group and 11.3 ± 3.1 kcal/kg for the hypocaloric group (P = .0001). Insulin demand was significantly higher and gastrointestinal intolerance more frequent in the normocaloric group than in the hypocaloric group. Nosocomial infections were detected more frequently in the hypocaloric group than in the normocaloric group (26.1% vs 11.1%, respectively). The ICU mortality rate was 22.2% in the normocaloric group and 21.7% in the hypocaloric group (not significant). The hospital mortality rate was 31.5% in the normocaloric group and 37.0% in the hypocaloric group (P = .67).

CONCLUSION

Hypocaloric feeding in the first 7 days in critically ill patients was associated with more nosocomial infections but less insulin demand and less gastrointestinal intolerance compared with normocaloric feeding.

TRIAL REGISTRATION NUMBER

DRKS00000104 (German Clinical Trials Register).

Resistive vibration exercise retards bone loss in weight-bearing skeletons during 60 days bed rest

Countermeasures are desirable to retard bone loss during long-term space flight. We evaluated the effect of an intervention protocol on bed rest-induced bone loss.

INTRODUCTION

We developed a resistive vibration exercise (RVE) platform to test if an intervention RVE protocol would be effective to protect bed rest-induced bone loss.

METHODS

Fourteen male subjects were assigned randomly to either the RVE group (n = 7) that performed daily supervised resistive vibration exercise or to the no any exercise control (CON) group (n = 7). Both dual-energy X-ray absorptiometry and peripheral quantitative computed tomography were used to monitor changes in bone mineral density.

RESULTS

RVE significantly prevented bone loss at multiple skeletal sites, including calcaneus, distal tibia, hip, and lumbar spine (L2-L4). The ratio of urinary calcium and creatinine was found higher after starting bed rest in CON group while no significant changes were observed in RVE group. No significant temporal change was found for osteocalcin-N during and after bed rest in CON group. However, a significant increase was shown after bed rest in RVE group. In both groups, the urinary concentration of bone resorption markers, such as C-telopeptide of type I collagen (CTX-I) and deoxypyridinoline (DPD), were significantly elevated after bed rest. In the CON group, no significant temporal effect was found for hydroxyproline (HOP), CTX-I, and DPD during bed rest and the serum concentration of HOP and TGF-β significantly increased about 52.04% and 24.03%, respectively only after bed rest. However, all these markers tended to decrease in the RVE group.

CONCLUSIONS

Our results might imply that the intervention of RVE retarded bone loss induced by simulated microgravity in humans that was mainly attributed to its anabolic effects.

Mechanical loading: bone remodeling and cartilage maintenance

Bone remodeling and cartilage maintenance are strongly influenced by biomechanical signals generated by mechanical loading. Although moderate loading is required to maintain bone mass and cartilage homeostasis, loading can cause deleterious effects such as bone fracture and cartilage degradation. Because a tight coupling exists between cartilage and bone, alterations in one tissue can affect the other. Bone marrow lesions are often associated with an increased risk of developing cartilage defects, and changes in the articular cartilage integrity are linked to remodeling responses in the underlying bone. Although mechanisms regulating the maintenance of these two tissues are different, compelling evidence indicates that the signal pathways crosstalk, particularly with the Wnt pathway. A better understanding of the complex tempero-spatial interplay between bone remodeling and cartilage degeneration will help develop a therapeutic loading strategy that prevents bone loss and cartilage degeneration.

Trabecular and cortical bone density and architecture in women after 60 days of bed rest using high-resolution pQCT: WISE 2005

Prolonged bed rest is used to simulate the effects of spaceflight and causes disuse-related loss of bone. While bone density changes during bed rest have been described, there are no data on changes in bone microstructure. Twenty-four healthy women aged 25 to 40 years participated in 60 days of strict 6-degree head-down tilt bed rest (WISE 2005). Subjects were assigned to either a control group (CON, n = 8), which performed no countermeasures; an exercise group (EXE, n = 8), which undertook a combination of resistive and endurance training; or a nutrition group (NUT, n = 8), which received a high-protein diet. Density and structural parameters of the distal tibia and radius were measured at baseline, during, and up to 1 year after bed rest by high-resolution peripheral quantitative computed tomography (HR-pQCT). Bed rest was associated with reductions in all distal tibial density parameters (p < 0.001), whereas only distal radius trabecular density decreased. Trabecular separation increased at both the distal tibia and distal radius (p < 0.001), but these effects were first significant after bed rest. Reduction in trabecular number was similar in magnitude at the distal radius (p = 0.021) and distal tibia (p < 0.001). Cortical thickness decreased at the distal tibia only (p < 0.001). There were no significant effects on bone structure or density of the countermeasures (p ≥ 0.057). As measured with HR-pQCT, it is concluded that deterioration in bone microstructure and density occur in women during and after prolonged bed rest. The exercise and nutrition countermeasures were ineffective in preventing these changes.

High sodium chloride intake exacerbates immobilization-induced bone resorption and protein losses

We examined, in immobilization, the effect of a diet high in sodium chloride (NaCl) on bone markers, nitrogen balance, and acid-base status. Eight healthy male test subjects participated in a 14-day head-down-tilt bed rest (HDBR) study. During the bed rest period they received, in a randomized crossover design, a high (7.7 meq Na+/kg body wt per day) and a low (0.7 meq Na+/kg body wt per day) NaCl diet. As expected, 24-h excretion of urinary calcium was significantly greater in the high-NaCl-intake HDBR phase than in the low-NaCl-intake HDBR phase ( P < 0.001). High NaCl intake caused a 43–50% greater excretion of the bone resorption markers COOH- (CTX) and NH2- (NTX) terminal telopeptide of type I collagen in HDBR than low NaCl in HDBR (CTX/NTX: P < 0.001). Serum concentrations of the bone formation markers bone-specific alkaline phosphatase (bAP) and NH2-terminal propeptide of type I procollagen (PINP) were identical in both NaCl intake phases. High NaCl intake led to a more negative nitrogen balance in HDBR ( P < 0.001). Changes were accompanied by increased serum chloride concentration ( P = 0.008), reduced blood bicarbonate ( P = 0.017), and base excess ( P = 0.009) whereas net acid excretion was lower during high than during low NaCl intake in immobilization ( P < 0.001). High NaCl intake during immobilization exacerbates disuse-induced bone and muscle loss by causing further protein wasting and an increase in bone resorption. Changes in the acid-base status, mainly caused by disturbances in electrolyte metabolism, seem to determine NaCl-induced degradation processes.

Modeled microgravity and hindlimb unloading sensitize osteoclast precursors to RANKL-mediated osteoclastogenesis

Mechanical forces are essential to maintain skeletal integrity, and microgravity exposure leads to bone loss. The underlying molecular mechanisms leading to the changes in osteoblasts and osteoclast differentiation and function remain to be fully elucidated. Because of the infrequency of spaceflights and payload constraints, establishing in vitro and in vivo systems that mimic microgravity conditions becomes necessary. We have established a simulated microgravity (modeled microgravity, MMG) system to study the changes induced in osteoclast precursors. We observed that MMG, on its own, was unable to induce osteoclastogenesis of osteoclast precursors; however, 24 h of MMG activates osteoclastogenesis-related signaling molecules ERK, p38, PLCγ2, and NFATc1. Receptor activator of NFkB ligand (RANKL) (with or without M-CSF) stimulation for 3-4 days in gravity of cells that had been exposed to MMG for 24 h enhanced the formation of very large tartrate-resistant acid phosphatase (TRAP)-positive multinucleated (>30 nuclei) osteoclasts accompanied by an upregulation of the osteoclast marker genes TRAP and cathepsin K. To validate the in vitro system, we studied the hindlimb unloading (HLU) system using BALB/c mice and observed a decrease in BMD of femurs and a loss of 3D microstructure of both cortical and trabecular bone as determined by micro-CT. There was a marked stimulation of osteoclastogenesis as determined by the total number of TRAP-positive multinucleated osteoclasts formed and also an increase in RANKL-stimulated osteoclastogenesis from precursors removed from the tibias of mice after 28 days of HLU. In contrast to earlier reported findings, we did not observe any histomorphometric changes in the bone formation parameters. Thus, the foregoing observations indicate that microgravity sensitizes osteoclast precursors for increased differentiation. The in vitro model system described here is potentially a valid system for testing drugs for preventing microgravity-induced bone loss by targeting the molecular events occurring in microgravity-induced enhanced osteoclastogenesis.

Vitamin D supplementation enhances the beneficial effects of weight loss on cardiovascular disease risk markers

BACKGROUND

High blood concentrations of parathyroid hormone and low concentrations of the vitamin D metabolites 25-hydroxyvitamin D [25(OH)D] and calcitriol are considered new cardiovascular disease risk markers. However, there is also evidence that calcitriol increases lipogenesis and decreases lipolysis.

OBJECTIVE

We investigated the effect of vitamin D on weight loss and traditional and nontraditional cardiovascular disease risk markers in overweight subjects.

DESIGN

Healthy overweight subjects (n = 200) with mean 25(OH)D concentrations of 30 nmol/L (12 ng/mL) received vitamin D (83 microg/d) or placebo in a double-blind manner for 12 mo while participating in a weight-reduction program.

RESULTS

Weight loss was not affected significantly by vitamin D supplementation (-5.7 +/- 5.8 kg) or placebo (-6.4 +/- 5.6 kg). However, mean 25(OH)D and calcitriol concentrations increased by 55.5 nmol/L and 40.0 pmol/L, respectively, in the vitamin D group but by only 11.8 nmol/L and 9.3 pmol/L, respectively, in the placebo group (P < 0.001), whereas a more pronounced decrease occurred in the vitamin D group than in the placebo group in blood concentrations of parathyroid hormone (-26.5% compared with -18.7%; P = 0.014), triglycerides (-13.5% compared with +3.0%; P < 0.001), and the inflammation marker tumor necrosis factor-alpha (-10.2% compared with -3.2%; P = 0.049). The beneficial biochemical effects were independent of the loss in body weight, fat mass, and sex. However, compared with placebo, vitamin D supplementation also increased LDL-cholesterol concentrations (+5.4% compared with -2.5%; P < 0.001).

CONCLUSIONS

The results indicate that a vitamin D supplement of 83 microg/d does not adversely affect weight loss and is able to significantly improve several cardiovascular disease risk markers in overweight subjects with inadequate vitamin D status participating in a weight-reduction program. This trial was registered at clinicaltrials.gov as NCT00493012.

Circulating calcitriol concentrations and total mortality

BACKGROUND

Evidence is accumulating that vitamin D supplementation of patients with low 25-hydroxyvitamin D concentrations is associated with lower cardiovascular morbidity and total mortality during long-term follow-up. Little is known, however, about the effect of low concentrations of the vitamin D hormone calcitriol on total mortality. We therefore evaluated the predictive value of circulating calcitriol for midterm mortality in patients of a specialized heart center.

METHODS

This prospective cohort study included 510 patients, 67.7% with heart failure (two-thirds in end stage), 64.3% hypertension, 33.7% coronary heart disease, 20.2% diabetes, and 17.3% renal failure. We followed the patients for up to 1 year after blood collection. For data analysis, the study cohort was stratified into quintiles of circulating calcitriol concentrations.

RESULTS

Patients in the lowest calcitriol quintile were more likely to have coronary heart disease, heart failure, hypertension, diabetes, and renal failure compared to other patients. They also had low 25-hydroxyvitamin D concentrations and high concentrations of creatinine, C-reactive protein, and tumor necrosis factor alpha. Eighty-two patients (16.0%) died during follow-up. Probability of 1-year survival was 66.7% in the lowest calcitriol quintile, 82.2% in the second quintile, 86.7% in the intermediate quintile, 88.8% in the fourth quintile, and 96.1% in the highest quintile (P < 0.001). Discrimination between survivors and nonsurvivors was best when a cutoff value of 25 ng/L was applied (area under the ROC curve 0.72; 95% CI 0.66-0.78).

CONCLUSIONS

Decreased calcitriol levels are linked to excess midterm mortality in patients of a specialized heart center.

Triiodothyronine increases calcium loss in a bed rest antigravity model for space flight

Bed rest has been used as a model to simulate the effects of space flight on bone metabolism. Thyroid hormones accelerate bone metabolism. Thus, supraphysiologic doses of this hormone might be used as a model to accelerate bone metabolism during bed rest and potentially simulate space flight. The objective of the study was to quantitate the changes in bone turnover after low doses of triiodothyronine (T(3)) added to short-term bed rest. Nine men and 5 women were restricted to bed rest for 28 days with their heads positioned 6 degrees below their feet. Subjects were randomly assigned to receive either placebo or oral T(3) at doses of 50 to 75 microg/d in a single-blind fashion. Calcium balance was measured over 5-day periods; and T(3), thyroxine, thyroid-stimulating hormone, immunoreactive parathyroid hormone, osteocalcin, bone alkaline phosphatase, and urinary deoxypyridinoline were measured weekly. Triiodothyronine increased 2-fold in the men and 5-fold in the women during treatment, suppressing both thyroxine and thyroid-stimulating hormone. Calcium balance was negative by 300 to 400 mg/d in the T(3)-treated volunteers, primarily because of the increased fecal loss that was not present in the placebo group. Urinary deoxypyridinoline to creatinine ratio, a marker of bone resorption, increased 60% in the placebo group during bed rest, but more than doubled in the T(3)-treated subjects (P < .01), suggesting that bone resorption was enhanced by treatment with T(3). Changes in serum osteocalcin and bone-specific alkaline phosphatase, markers of bone formation, were similar in T(3)- and placebo-treated subjects. Triiodothyronine increases bone resorption and fecal calcium loss in subjects at bed rest.

Nutritional biochemistry of spaceflight

As we approach the end of the first 50 years of human space travel, much has been learned about adaptation to microgravity and the risks associated with extended-duration space exploration. As the frequency and duration of flights grew, nutrition issues became more critical and the questions to be answered became more complex: What are the nutrient requirements for space travelers? Can nutrients be used as tools to mitigate the negative effects of space travel on humans? How does nutrition interrelate with other physiological systems (such as muscle, bone, and cardiovascular system) and their adaptation to microgravity? Much research has been done over the decades in both actual spaceflight and ground-based analogs. We review here much of what is known, and highlight areas of ongoing research and concerns for future exploration of the Moon, Mars, and beyond.

Positive energy balance is associated with accelerated muscle atrophy and increased erythrocyte glutathione turnover during 5 wk of bed rest

BACKGROUND

Physical inactivity is often associated with positive energy balance and fat gain.

OBJECTIVE

We aimed to assess whether energy intake in excess of requirement activates systemic inflammation and antioxidant defenses and accelerates muscle atrophy induced by inactivity.

DESIGN

Nineteen healthy male volunteers were studied before and at the end of 5 wk of bed rest. Subjects were allowed to spontaneously adapt to decreased energy requirement (study A, n = 10) or were provided with an activity-matched diet (study B, n = 9). Groups with higher (HEB) or lower (LEB) energy balance were identified according to median values of inactivity-induced changes in fat mass (DeltaFM, assessed by bioelectrical impedance analysis).

RESULTS

In pooled subjects (n = 19; median DeltaFM: 1.4 kg), bed rest-mediated decreases in fat-free mass (bioelectrical impedance analysis) and vastus lateralis thickness (ultrasound imaging) were significantly greater (P < 0.03) in HEB(AB) (-3.8 +/- 0.4 kg and -0.32 +/- 0.04 cm, respectively) than in LEB(AB) (-2.3 +/- 0.5 kg and -0.09 +/- 0.04 cm, respectively) subjects. In study A (median DeltaFM: 1.8 kg), bed rest-mediated increases in plasma leptin, C-reactive protein, and myeloperoxidase were greater (P < 0.04) in HEB(A) than in LEB(A) subjects. Bed rest-mediated changes of glutathione synthesis rate in eythrocytes (l-[3,3-(2)H(2)]cysteine incorporation) were greater (P = 0.03) in HEB(A) (from 70 +/- 19 to 164 +/- 29%/d) than in LEB(A) (from 103 +/- 23 to 84 +/- 27%/d) subjects.

CONCLUSIONS

Positive energy balance during inactivity is associated with greater muscle atrophy and with activation of systemic inflammation and of antioxidant defenses. Optimizing caloric intake may be a useful strategy for mitigating muscle loss during period of chronic inactivity.

Review of the dietary reference intake for calcium: where do we go from here?

In this article the science relied on to establish the Dietary Reference Intakes (DRI) specifically for calcium was examined. The latest dietary recommendations for the essential nutrients significant with respect to their roles in bone metabolism and health were reported in the Dietary Reference Intakes for Calcium, Phosphorus, Magnesium, Vitamin D, and Fluoride (1997) (NIM, 1997). For calcium an adequate intake was recommended because insufficient data were available at the time to determine specific Recommended Dietary Allowances. Dietary intake data and the controversies regarding the role calcium may play in other chronic diseases have also been discussed. Advances and continued dilemmas regarding these topics reported since the publication of the DRI were also addressed in this review. A recent Dietary Reference Intake Research Synthesis Workshop report identified an extensive range of suggested future research directions needed to improve our understanding of calcium and bone and health.

From space to Earth: advances in human physiology from 20 years of bed rest studies (1986-2006)

Bed rest studies of the past 20 years are reviewed. Head-down bed rest (HDBR) has proved its usefulness as a reliable simulation model for the most physiological effects of spaceflight. As well as continuing to search for better understanding of the physiological changes induced, these studies focused mostly on identifying effective countermeasures with encouraging but limited success. HDBR is characterised by immobilization, inactivity, confinement and elimination of Gz gravitational stimuli, such as posture change and direction, which affect body sensors and responses. These induce upward fluid shift, unloading the body's upright weight, absence of work against gravity, reduced energy requirements and reduction in overall sensory stimulation. The upward fluid shift by acting on central volume receptors induces a 10-15% reduction in plasma volume which leads to a now well-documented set of cardiovascular changes including changes in cardiac performance and baroreflex sensitivity that are identical to those in space. Calcium excretion is increased from the beginning of bed rest leading to a sustained negative calcium balance. Calcium absorption is reduced. Body weight, muscle mass, muscle strength is reduced, as is the resistance of muscle to insulin. Bone density, stiffness of bones of the lower limbs and spinal cord and bone architecture are altered. Circadian rhythms may shift and are dampened. Ways to improve the process of evaluating countermeasures--exercise (aerobic, resistive, vibration), nutritional and pharmacological--are proposed. Artificial gravity requires systematic evaluation. This review points to clinical applications of BR research revealing the crucial role of gravity to health.

Effect of bed rest during pregnancy on bone turnover markers in pregnant and postpartum women

OBJECTIVE

The aims of our study were to evaluate the changes in bone turnover markers during pregnancy and puerperium as a longitudinal study and to elucidate the effect of bed rest during pregnancy on bone turnover markers in pregnant and postpartum women.

METHODS

The study population comprised 27 Japanese pregnant women aged 23-40 years. All women were recruited for the longitudinal study from the outpatients clinic of the Department of Obstetrics and Gynecology, Tokushima University Hospital. Concentrations of serum bone-specific alkaline phosphatase (BAP), urinary cross-linked type I collagen N-telopeptides (NTx), serum NTx and urinary C-terminal telopeptide of type I collagen (CTx) were measured at 10, 26, 30 and 36 weeks of pregnancy and at 4 days and 1 month postpartum. In addition, we recruited 15 pregnant women (aged 25-35 years) who were treated by bed rest before 30 weeks of pregnancy for threatened premature delivery and compared bone turnover markers in these women with those in 22 normal pregnant women (aged 22-39 years). Concentrations of serum BAP, serum NTx, urinary NTx and urinary CTx were measured at 30 and 34 weeks of pregnancy and at 4 days and 1 month postpartum.

RESULTS

In the longitudinal study, serum BAP concentration at 1 month postpartum was significantly higher than that at any stage of pregnancy and that at 4 days postpartum. Urinary concentration of NTx increased gradually during pregnancy and showed a peak at 36 weeks of pregnancy, followed by a decrease in the postpartum period. Serum NTx concentration and urinary CTx concentration showed the same patterns of change as that of urinary NTx concentration. In the comparison study, urinary concentrations of NTx and CTx at 30 and 34 weeks of pregnancy in women with bed rest were significantly (p<0.0001 and p<0.001, respectively) higher than those in normal pregnant women. Serum NTx concentration at 34 weeks of pregnancy in women with bed rest was also significantly (p=0.0029) higher than that in normal pregnant women. Serum BAP concentration at 34 weeks of pregnancy in women with bed rest was significantly (p=0.0038) higher than that in normal pregnant women, and these high levels were maintained during puerperium. Serum BAP concentration at 34 weeks of pregnancy was significantly correlated with duration of bed rest (r=0.767, p=0.0041).

CONCLUSION

Immobilization due to bed rest during pregnancy is associated with increases in bone turnover markers in pregnant and postpartum women. Concentrations of bone resorption markers increased rapidly at the start of bed rest, while the concentration of a bone formation marker gradually increased toward puerperium.

Renal function in space: the link between osteoporosis, hypercalciuria, and aquaporins

This article reviews bone adaptation to microgravity, during manned space missions, in humans undergoing Head Down Tilt (HDT) and in Hind-Limb-Suspended Rats. Under microgravity conditions, bone loss occurs in association with hypercalciuria, which in turn modulates Aquaporin 2 (AQP2) excretion in urine, thus avoiding stone forming in space. This report discloses the need to prevent bone loss in order to prepare for long stays at lunar bases or voyages to Mars.

Markers of bone metabolism in congestive heart failure

Congestive heart failure (CHF) is a chronic disease, whose incidence is especially growing in the subpopulation of elderly people. CHF is characterized by dyspnea and fatigue at rest or with exertion, ankle swelling and pulmonary edema. Cardiac transplantation is the ultimate therapeutic measure in patients with end-stage CHF. Some risk factors associated with CHF such as low mobility, renal failure, and prescription of specific drugs may predispose patients to develop osteoporosis. This review article gives an overview about markers of bone metabolism in CHF patients as well as in heart transplant recipients. At first, the physiology of bone metabolism is summarized. Then, a short description of different bone formation and resorption markers is presented. They can be used to characterize actual bone metabolism and can be helpful to explain possible mechanisms of bone loss. Regarding pre-transplant CHF patients, available data indicate that the disturbances in bone metabolism are only subtle. Heart transplant recipients, however, are at increased risk for osteoporotic bone loss due to the use of immunosuppressive agents such as corticosteroids and calcineurin inhibitors. Preventive strategies are able to normalize bone metabolism and to attenuate the high bone loss during the first year after heart transplantation.

Immobilization decreases duodenal calcium absorption through a 1,25-dihydroxyvitamin D-dependent pathway

Immobilization induces significant and progressive bone loss, with an increase in urinary excretion and a decrease in intestinal absorption of calcium. These actions lead to negative calcium balance and the development of disuse osteoporosis. The aims of this study were to evaluate the molecular mechanisms of decreased intestinal calcium absorption and to determine the effect of dietary 1,25-dihydroxyvitamin D [1,25(OH)2D] and a high-calcium diet on bone loss due to immobilization. The immobilized rat model was developed in the Bollman cage III to induce systemic disuse osteoporosis in the animals. There was a significant decrease in lumbar bone mineral density (BMD) and intestinal calcium absorption in the immobilized group compared with the controls. Serum 25-hydroxyvitamin D concentration did not change, but 1,25(OH)2D concentration decreased significantly. The mRNA levels of renal 25-hydoxyvitamin D 24-hydroxylase (24OHase) increased, whereas those of renal 25-hydroxyvitamin D 1-alpha hydroxylase (1alpha-hydroxylase), duodenal transient receptor potential cation channel, subfamily V, member 6 (TRPV6), TRPV5, and calbindin-D9k were all decreased. A high-calcium diet did not prevent the reduction in lumbar BMD or affect the mRNA expression of proteins related to calcium transport. Dietary administration of 1,25(OH)2D increased the intestinal calcium absorption that had been downregulated by immobilization. TRPV6, TRPV5, and calbindin-D9k mRNA levels were also upregulated, resulting in prevention of the reduction in lumbar BMD. Therefore, it is concluded that dietary 1,25(OH)2D prevented decreases in intestinal calcium absorption and simultaneously prevented bone loss in immobilized rats. However, it remains unclear that calcium absorption and expression of calcium transport proteins are essential for the regulation of lumbar BMD.

Microgravity: the immune response and bone

Exposure to microgravity during space flight affects almost all human physiological systems. The affected systems that are of key importance to human space exploration are the musculoskeletal, neurovestibular, and cardiovascular systems. However, alterations in the immune and endocrine functions have also been described. Bone loss has been shown to be site specific, predominantly in the weight-bearing regions of the legs and lumbar spine. This phenomenon has been attributed to a reduction in bone formation resulting from a decrease in osteoblastic function and an increase in osteoclastic resorption. In order to examine the effects of microgravity on cellular function here on earth, several ground-based studies have been performed using different systems to model microgravity. Our studies have shown that modeled microgravity (MMG) inhibits the osteoblastic differentiation of human mesenchymal stem cells (hMSCs) while increasing their adipogenic differentiation. Here, we discuss the potential molecular mechanisms that could be altered in microgravity. In particular, we examine the role of RhoA kinase in maintaining the formation of actin stress fibers and the expression of nitric oxide synthase under MMG conditions. These proposed mechanisms, although only examined in hMSCs, could be part of a global response to microgravity that ultimately alters human physiology.

Immobilization induces a very rapid increase in osteoclast activity

We studied in a randomized, strictly controlled cross-over design, the effects of 6 days 6 degrees head-down tilt bed rest (HDT) in eight male healthy subjects in our metabolic ward. The study consisted of two periods (phases) of 11 days each in order to allow for the test subjects being their own controls. Both study phases were identical with respect to environmental conditions, study protocol and diet. Two days before arriving in the metabolic ward the subjects started with a diet. The diet was continued in the metabolic ward. The metabolic ward period (1l days) was divided into three parts: 4 ambulatory days, 6 days either HDT or control and 1 recovery day. Continuous urine collection started on the first day in the metabolic ward to analyze calcium excretion and bone resorption markers. On the 2nd ambulatory day in the metabolic ward and on the 5th day in HDT or control blood was drawn to analyze serum calcium, parathyroid hormone, and bone formation markers. Urinary calcium excretion was, as early as the first day in immobilization, increased (p<0.01). CTX- and NTX-excretion stayed unchanged in the first 24 h in HDT compared to the control. But already on the 2nd day of immobilization, both bone resorption markers significantly increased. We conclude from these results--pronounced rise of bone resorption markers--that already 24 h of immobilization induce a significant rise in osteoclast activity in healthy subjects. Thus, it appears possible to use short-term bed rest studies as a first step for the development of countermeasures to immobilization.

A metaanalysis of treatment outcomes of early enteral versus early parenteral nutrition in hospitalized patients

OBJECTIVE

Nutritional support as enteral or parenteral nutrition (PN) is used in hospitalized patients to reduce catabolism. This study compares outcomes of early enteral nutrition (EN) with early PN in hospitalized patients.

DESIGN

The authors conducted a metaanalysis of randomized, controlled trials (RCT) comparing early EN with PN. Studies on immunonutrition were excluded. Studies were categorized as medical, surgical, or trauma.

PATIENTS

RCTs of early EN/PN were identified by search of 1) MEDLINE (1966-2002), 2) published abstracts from scientific meetings, and 3) bibliographies of relevant articles.

MEASUREMENTS AND MAIN RESULTS

Thirty RCTs (ten medical, 11 surgical, and nine trauma) compared early EN with PN. The effect of nutrition type on hospital mortality and complication rates was reported as risk difference (RD%) and hospital length of stay (LOS) as mean weighted difference (MWD days). Missing data, by outcomes, varied from 20% to 63%. As a result of heterogeneity of treatment effects, the DerSimonian-Laird random-effects estimator was reported. There was no differential treatment effect of nutrition type on hospital mortality for all patients (0.6%, p = .4) and subgroups. PN was associated with increases in infective complications (7.9%, p = .001), catheter-related blood stream infections (3.5%, p = .003), noninfective complications (4.9%, p = .04), and hospital LOS (1.2 days, p = .004). There was no effect of nutrition type on technical complications (4.1%, p = .2). EN was associated with a significant increase in diarrheal episodes (8.7%, p = .001). Publication bias was not demonstrated. Metaanalytic regression analysis did not demonstrate any effect of age, time to initiate treatment, and average albumin on mortality estimates. Cumulative metaanalysis showed no change in the mortality estimates with time.

CONCLUSION

There was no mortality effect with the type of nutritional supplementation. Although early EN significantly reduced complication rates, this needs to be interpreted in the light of missing data and heterogeneity. The enthusiasm that early EN, as compared with early PN, would reduce mortality appears misplaced.

Bone turnover during inpatient nutritional therapy and outpatient follow-up in patients with anorexia nervosa compared with that in healthy control subjects

BACKGROUND

Osteopenia and osteoporosis are among the most frequent and severe complications in adolescents with anorexia nervosa.

OBJECTIVE

The aim of this study was to assess the influence of nutritional therapy on bone metabolism during adolescent anorexia nervosa.

DESIGN

We studied 19 anorectic patients aged 14.1 +/- 1.4 y (x +/- SD) with a body mass index (BMI; in kg/m(2)) of 14.2 +/- 1.4 and 19 age-matched control subjects aged 15.1 +/- 2.3 y with a BMI of 20.8 +/- 1.9 for 1 y. Blood samples were taken for the measurement of bone markers, insulin-like growth factor I (IGF-I), and leptin.

RESULTS

BMI rose significantly from 14.2 +/- 1.4 at baseline to 17.4 +/- 0.6 (P < 0.0001) at week 15. Compared with concentrations in the control subjects, concentrations of the bone formation markers procollagen type I propeptide (PICP) and bone alkaline phosphatase (bAP) in the anorectic patients were lower at baseline (PICP: P = 0.0071; bAP: P = 0.0012), increased with nutritional therapy (PICP: P = 0.0060, bAP: P = 0.0147), and were no longer significantly different (P > 0.05) during the follow-up period. Concentrations of IGF-I and leptin were significantly lower (P < 0.0001 for both) in the anorectic patients than in the control subjects at baseline. IGF-I increased with nutritional therapy but was still significantly lower (P = 0.0036) than that in the control group and decreased again during the follow-up period (P = 0.0126). In contrast, serum C-telopeptide decreased with nutritional therapy (P = 0.0446).

CONCLUSION

Nutritional therapy improves concentrations of bone formation markers in adolescent patients with anorexia nervosa.

Body mass index and disease duration are predictors of disturbed bone turnover in anorexia nervosa. A case-control study

OBJECTIVE

To characterize the influence of body mass index (BMI), body composition, hormonal factors and disease duration on bone metabolism markers in anorexia nervosa (AN) patients.

DESIGN

Case-control study with 51 AN patients and 51 controls matched for age, sex and body height. Assessment of anthropometric and bioimpedance data, and of biochemical serum parameters and of oral contraceptives use.

RESULTS

Patients had a lower BMI, lower fat mass, lower fat-free mass and lower muscle mass (MM) compared to the controls (all P values <0.001). Moreover, serum levels of osteocalcin (bone formation marker) were lower while serum C-telopeptide concentrations (CTx; bone resorption marker) and the CTx/osteocalcin ratio (an index reflecting the balance of bone remodeling) were higher in the AN patients compared to the controls (P<0.01-0.001). In addition, patients had enhanced serum calcium and cortisol levels and reduced serum levels of thyroid hormones, insulin, and leptin (P values <0.05-0.001). Mean disease duration was 91+/-13 months. In a multiple regression analysis, BMI (P<0.0001), MM (P<0.005) and duration of the disease (P<0.005) were independent predictors of the CTx/osteocalcin ratio in the AN patients. There was a nonlinear association between BMI and the CTx/osteocalcin ratio of r=-0.72 (P<0.001) in the AN patients, but only a weak relation of r=-0.27 (P<0.05) between these parameters in the control subjects. Use of oral contraceptives had no effect on the CTx/osteocalcin ratio, neither in AN patients nor in controls.

CONCLUSIONS

Data indicate an uncoupling of bone formation and bone resorption in AN, which is primarily the result of a low BMI and influenced by the duration of the disease.

Beyond deficiency: potential benefits of increased intakes of vitamin K for bone and vascular health

Vitamin K is well known for its role in the synthesis of a number of blood coagulation factors. During recent years vitamin K-dependent proteins were discovered to be of vital importance for bone and vascular health. Recommendations for dietary vitamin K intake have been made on the basis of the hepatic requirements for the synthesis of blood coagulation factors. Accumulating evidence suggests that the requirements for other functions than blood coagulation may be higher. This paper is the result of a closed workshop (Paris, November 2002) in which a number of European vitamin K experts reviewed the available data and formulated their standpoint with respect to recommended dietary vitamin K intake and the use of vitamin K-containing supplements.

Carbamazepine does not alter biochemical parameters of bone turnover in healthy male adults

It is still not completely clear whether or not carbamazepine (CBZ) causes alterations in vitamin D status and in bone metabolism. The objective of this study was therefore to investigate prospectively in healthy adults the effects of CBZ on serum levels of 25-hydroxyvitamin D (25OHD) and on biomarkers of bone formation and resorption. Twenty-one free-living male adults were taking 800 mg/day CBZ for 10 weeks. The study was performed from December 1997 until September 1998 at a geographic latitude of 51 degrees N. Blood samples were collected before treatment (t1), 33 days (SE 2.5) after starting treatment (t2), and 70 days (SE 3.6) after starting treatment (t3). In 13 out of the 21 subjects blood samples were also drawn 64 days (SE 9.0) after treatment had been terminated (t4). Serum 25OHD levels remained constant during study periods t1-t3. 25OHD levels were, however, significantly higher at t4 compared to t1-t3. Serum concentrations of intact osteocalcin, a bone formation marker, and C-telopeptide, a bone resorption marker, were similar during all examinations. Moreover, serum levels of parathyroid hormone, calcium, and inorganic phosphate did not change. Data indicate that CBZ per se does not alter bone metabolism and does not lead to decreased circulating 25OHD levels in young males without epilepsy. Variations in 25OHD levels are in line with the seasonal fluctuations in vitamin D status.

Bone resorption is induced on the second day of bed rest: results of a controlled crossover trial

The aim of the study was to analyze the kinetics of short-term changes in bone turnover. We studied in a randomized crossover design the effects of 6 days of bed rest on eight healthy male subjects (mean body wt: 70.1 +/- 5.7 kg; mean age: 25.5 +/- 2.9 yr). The metabolic ward period was divided into three parts: 4 ambulatory days, 6 days of either bed rest or non-bed rest periods, and 1 recovery day. The diet was identical in both bed rest and non-bed rest phases. Continuous urine collection started on the first day in the metabolic ward to analyze excretion of bone resorption markers, namely C-telopeptide (CTX) and N-telopeptide (NTX), creatinine, urea, and 3-methylhistidine. On the second ambulatory day and on the fifth day of bed rest or during the non-bed rest phase, blood was drawn to analyze bone formation markers and amino acid concentrations. Urinary calcium excretion was increased as early as the first day of bed rest (P < 0.01). CTX and NTX excretion stayed unchanged during the first 24 h of bed rest compared with the non-bed rest period. However, already on the second day, both resorption markers had increased significantly. NTX excretion increased by 28.7 +/- 14.0% (P < 0.01), whereas CTX excretion rose by 17.8 +/- 8.3% (P < 0.001). Creatinine, urea, and 3-methylhistidine excretion did not change. We conclude that 24 h of bed rest are sufficient to induce a significant rise in osteoclast activity in healthy subjects.

Microgravity as a model of ageing

PURPOSE OF REVIEW

Longevity with good health and long-term survival in space are two of the many challenges that scientists face in the twenty-first century. Ageing and life in space are both associated with undesirable effects on normal physiological processes. This review will outline how the endocrine, metabolic, immune and musculoskeletal systems are affected by microgravity and ageing, drawing analogies between the observed changes in an attempt to highlight common mechanisms.

RECENT FINDINGS

Mild hypothyroidism, increased stress hormones (mainly catecholamines), decreased sex steroids, insulin resistance, impaired anabolic response to food intake, anorexia, altered mitochondrial function and systemic inflammatory response are common features of both ageing and microgravity. Both conditions lead to progressive bone and muscle atrophy, compromising mobility and the ability to perform essential daily tasks. In skeletal muscle, both ageing and space flight lead to weakness from whole muscle to single fibre level, accompanied by marked alterations in muscle architecture and in tendon mechanical properties.

SUMMARY

What makes microgravity an interesting and unique tool for gerontologists is that many space-related physiological changes resemble those observed during ageing, but are more or less quickly restored after re-entry, thus allowing the biology of ageing to be investigated both ways, not only during its development but also during recovery.