Amino acid supplementation for reversing bed rest and steroid myopathies

Use of plasma-free amino acids as biomarkers for detecting and predicting disease risk

This paper reviews developments regarding the use of plasma-free amino acid (PFAA) profiles as biomarkers for detecting and predicting disease risk. This work was initiated and first published in 2006 and was subsequently developed by Ajinomoto Co., Inc. After commercialization in 2011, PFAA-based tests were adopted in over 1500 clinics and hospitals in Japan, and numerous clinician-led studies have been performed to validate these tests. Evidence is accumulating that PFAA profiles can be used for diabetes prediction and evaluation of frailty; in particular, decreased plasma essential amino acids could contribute to the pathophysiology of severe frailty. Integration of PFAA evaluation as a biomarker and effective essential amino acid supplementation, which improves physical and mental functions in the elderly, could facilitate the development of precision nutrition, including personalized solutions. This present review provides the background for the technology as well as more recent clinical findings, and offers future possibilities regarding the implementation of precision nutrition.

Nutritional interventions during bed rest and spaceflight: prevention of muscle mass and strength loss, bone resorption, glucose intolerance, and cardiovascular problems

Bed rest is necessary for many medical conditions but also used as a ground-based model for space flight (along with head-down tilt to simulate fluid shifts in microgravity). The purpose of this review is to examine nutritional interventions during bed rest and spaceflight for prevention of muscle and strength loss, glucose intolerance, bone resorption, and cardiovascular problems. Increased dietary protein intake and supplementation with amino acids, β-hydroxy-β-methylbutyrate, or cofactors with antioxidant properties are effective for ameliorating bed rest-induced loss of muscle mass and strength. Previous literature involving bed rest with dietary protein/amino acid supplementation had mixed findings, likely due to differences in dosage. Although high protein intake in some studies prevents bed rest-induced muscle loss, it also increases bone resorption. High calcium intake and vitamin D supplementation are not beneficial for preventing bone degradation during bed rest or spaceflight. Very few studies investigated countermeasures to prevent glucose intolerance and cardiovascular risks during bed rest/spaceflight. Low-glycemic index diets might be beneficial for the prevention of bed rest-induced glucose intolerance and cardiovascular problems. The present evidence warrants additional studies on the exact threshold of protein/amino acid intake to prevent the loss of muscle mass and strength during bed rest/spaceflight specifically to maintain the beneficial effects of proteins on muscle mass and function without increasing bone resorption. Furthermore, it is suggested to study the effects of vitamin K supplementation on bone health during bed rest/spaceflight and determine the role of long-term low-glycemic index diets on glucose regulation and cardiovascular health during extended bed rest.

A Novel Amino Acid Composition Ameliorates Short-Term Muscle Disuse Atrophy in Healthy Young Men

Skeletal muscle disuse leads to atrophy, declines in muscle function, and metabolic dysfunction that are often slow to recover. Strategies to mitigate these effects would be clinically relevant. In a double-blind randomized-controlled pilot trial, we examined the safety and tolerability as well as the atrophy mitigating effect of a novel amino acid composition (AXA2678), during single limb immobilization. Twenty healthy young men were randomly assigned (10 per group) to receive AXA2678 or an excipient- and energy-matched non-amino acid containing placebo (PL) for 28d: days 1–7, pre-immobilization; days 8–15, immobilization; and days 16–28 post-immobilization recovery. Muscle biopsies were taken on d1, d8 (immobilization start), d15 (immobilization end), and d28 (post-immobilization recovery). Magnetic resonance imaging (MRI) was utilized to assess quadriceps muscle volume (Mvol), muscle cross-sectional area (CSA), and muscle fat-fraction (FF: the fraction of muscle occupied by fat). Maximal voluntary leg isometric torque was assessed by dynamometry. Administration of AXA2678 attenuated muscle disuse atrophy compared to PL (p < 0.05) with changes from d8 to d15 in PL: ΔMvol = −2.4 ± 2.3% and ΔCSA = −3.1% ± 2.1%, both p < 0.001 vs. zero; against AXA2678: ΔMvol: −0.7 ± 1.8% and ΔCSA: −0.7 ± 2.1%, both p > 0.3 vs. zero; and p < 0.05 between treatment conditions for CSA. During immobilization, muscle FF increased in PL but not in AXA2678 (PL: 12.8 ± 6.1%, AXA2678: 0.4 ± 3.1%; p < 0.05). Immobilization resulted in similar reductions in peak leg isometric torque and change in time-to-peak (TTP) torque in both groups. Recovery (d15–d28) of peak torque and TTP torque was also not different between groups, but showed a trend for better recovery in the AXA2678 group. Thrice daily consumption of AXA2678 for 28d was found to be safe and well-tolerated. Additionally, AXA2678 attenuated atrophy, and attenuated accumulation of fat during short-term disuse. Further investigations on the administration of AXA2678 in conditions of muscle disuse are warranted.

Clinical Trial Registration:https://clinicaltrials.gov, identifier: NCT03267745.

Interventional strategies to combat muscle disuse atrophy in humans: focus on neuromuscular electrical stimulation and dietary protein

Numerous situations, such as the recovery from illness or rehabilitation after injury, necessitate a period of muscle disuse in otherwise healthy individuals. Even a few days of immobilization or bed rest can lead to substantial loss of skeletal muscle tissue and compromise metabolic health. The decline in muscle mass is attributed largely to a decline in postabsorptive and postprandial muscle protein synthesis rates. Reintroduction of some level of muscle contraction by the application of neuromuscular electrical stimulation (NMES) can augment both postabsorptive and postprandial muscle protein synthesis rates and, as such, prevent or attenuate muscle loss during short-term disuse in various clinical populations. Whereas maintenance of habitual dietary protein consumption is a prerequisite for muscle mass maintenance, supplementing dietary protein above habitual intake levels does not prevent muscle loss during disuse in otherwise healthy humans. Combining the anabolic properties of physical activity (or surrogates) with appropriate nutritional support likely further increases the capacity to preserve skeletal muscle mass during a period of disuse. Therefore, effective interventional strategies to prevent or alleviate muscle disuse atrophy should include both exercise (mimetics) and appropriate nutritional support.

Despite Inflammation, Supplemented Essential Amino Acids May Improve Circulating Levels of Albumin and Haemoglobin in Patients after Hip Fractures

Essential amino acids (EAAs) are nutritional substrates that promote body protein synthesis; thus we hypothesised that their supplementation may improve circulating albumin (Alb) and haemoglobin (Hb) in rehabilitative elderly patients following hip fractures (HF). Out of the 145 HF patients originally enrolled in our study, 112 completed the protocol. These subjects were divided into two randomised groups, each containing 56 patients. For a period of two months, one group (age 81.4 ± 8.1 years; male/female 27/29) received a placebo, and the other (age 83.1 ± 7.5 years; male/female 25/31) received 4 + 4 g/day oral EAAs. At admission, the prevalence of both hypoAlb (<3.5 g/dL) and hypoHb (<13 g/dL male, <12 g/dL female) was similar in the placebo group (64.3% hypoAlb, 66% hypoHb) and the treated group of patients (73.2% hypoAlb, 67.8% hypoHb). At discharge, however, the prevalence of hypoAlb had reduced more in EAAs than in placebo subjects (31.7% in EAAs vs. 77.8% in placebo; p < 0.001). There was a 34.2% reduction of anaemia in hypoHb in EAA subjects and 18.9% in placebo subjects, but the difference was not statistically significant. Oral supplementation of EAAs improves hypoAlb and, to a lesser extent, Hb in elderly rehabilitative subjects with hip fractures. Anaemia was reduced in more than one third of patients, which, despite not being statistically significant, may be clinically relevant.

Protein: A nutrient in focus

Protein is an essential component of a healthy diet and is a focus of research programs seeking to optimize health at all stages of life. The focus on protein as a nutrient often centers on its thermogenic and satiating effect, and when included as part of a healthy diet, its potential to preserve lean body mass. A growing body of literature, including stable isotope based studies and longer term dietary interventions, suggests that current dietary protein recommendations may not be sufficient to promote optimal muscle health in all populations. A protein intake moderately higher than current recommendations has been widely endorsed by many experts and working groups and may provide health benefits for aging populations. Further, consuming moderate amounts of high-quality protein at each meal may optimally stimulate 24-h muscle protein synthesis and may provide a dietary platform that favors the maintenance of muscle mass and function while promoting successful weight management in overweight and obese individuals. Dietary protein has the potential to serve as a key nutrient for many health outcomes and benefits might be increased when combined with adequate physical activity. Future studies should focus on confirming these health benefits from dietary protein with long-term randomized controlled studies.

Unaffected arm muscle hypercatabolism in dysphagic subacute stroke patients: the effects of essential amino acid supplementation

Alterations in muscle protein turnover of the unaffected side of stroke patients could contribute to physical disability. We investigated whether hypercatabolic activity occurred in unaffected arm muscle and whether supplemented essential amino acids (EAAs) could limit muscle hypercatabolism (MH). Thirty-eight dysphagic subacute stroke subjects (<3 months after acute event) (29 males+9 females; 69.7±11.4 yrs) were enrolled and randomized to receive 8 g/day EAAs (n=19; EAA group) or isocaloric placebo (maltodextrin; n=19, Plac group). Before randomization, all patients had their arterial (A) and venous (V) amino acids measured and muscle (A-V) differences calculated in the unaffected arm. Eight matched and healthy subjects served as controls. When compared to healthy controls, the entire stroke population showed significant muscle release (=negative value A-V) of the amino acid phenylalanine (phenyl-) indicating a prevalence of MH. Moreover, randomized EAA and Plac groups had similar rates of MH. After 38 days from the start of the protocol, the EAA group but not the Plac group had MH converted to balanced protein turnover or anabolic activity. We concluded that muscle protein metabolism of the unaffected arm of dysphagic subacute stroke individuals could be characterized by MH which can be corrected by supplemented EAAs.

Interventions for preventing critical illness polyneuropathy and critical illness myopathy

BACKGROUND

Critical illness polyneuropathy or myopathy (CIP/CIM) is a frequent complication in the intensive care unit (ICU) and is associated with prolonged mechanical ventilation, longer ICU stay and increased mortality. This is an interim update of a review first published in 2009 (Hermans 2009). It has been updated to October 2011, with further potentially eligible studies from a December 2013 search characterised as awaiting assessment.

OBJECTIVES

To systematically review the evidence from RCTs concerning the ability of any intervention to reduce the incidence of CIP or CIM in critically ill individuals.

SEARCH METHODS

On 4 October 2011, we searched the Cochrane Neuromuscular Disease Group Specialized Register, CENTRAL, MEDLINE, and EMBASE. We checked the bibliographies of identified trials and contacted trial authors and experts in the field. We carried out an additional search of these databases on 6 December 2013 to identify recent studies.

SELECTION CRITERIA

All randomised controlled trials (RCTs), examining the effect of any intervention on the incidence of CIP/CIM in people admitted to adult medical or surgical ICUs. The primary outcome was the incidence of CIP/CIM in ICU, based on electrophysiological or clinical examination. Secondary outcomes included duration of mechanical ventilation, duration of ICU stay, death at 30 and 180 days after ICU admission and serious adverse events from the treatment regimens.

DATA COLLECTION AND ANALYSIS

Two authors independently extracted the data and assessed the risk of bias in included studies.

MAIN RESULTS

We identified five trials that met our inclusion criteria. Two trials compared intensive insulin therapy (IIT) to conventional insulin therapy (CIT). IIT significantly reduced CIP/CIM in the screened (n = 825; risk ratio (RR) 0.65, 95% confidence interval (CI) 0.55 to 0.77) and total (n = 2748; RR 0.70, 95% CI 0.60 to 0.82) population randomised. IIT reduced duration of mechanical ventilation, ICU stay and 180-day mortality, but not 30-day mortality compared with CIT. Hypoglycaemia increased with IIT but did not cause early deaths.One trial compared corticosteroids with placebo (n = 180). The trial found no effect of treatment on CIP/CIM (RR 1.27, 95% CI 0.77 to 2.08), 180-day mortality, new infections, glycaemia at day seven, or episodes of pneumonia, but did show a reduction of new shock events.In the fourth trial, early physical therapy reduced CIP/CIM in 82/104 evaluable participants in ICU (RR 0.62. 95% CI 0.39 to 0.96). Statistical significance was lost when we performed a full intention-to-treat analysis (RR 0.81, 95% CI 0.60 to 1.08). Duration of mechanical ventilation but not ICU stay was significantly shorter in the intervention group. Hospital mortality was not affected but 30- and 180-day mortality results were not available. No adverse effects were noticed.The last trial found a reduced incidence of CIP/CIM in 52 evaluable participants out of a total of 140 who were randomised to electrical muscle stimulation (EMS) versus no stimulation (RR 0.32, 95% CI 0.10 to 1.01). These data were prone to bias due to imbalances between treatment groups in this subgroup of participants. After we imputed missing data and performed an intention-to-treat analysis, there was still no significant effect (RR 0.94, 95% CI 0.78 to 1.15). The investigators found no effect on duration of mechanical ventilation and noted no difference in ICU mortality, but did not report 30- and 180-day mortality.We updated the searches in December 2013 and identified nine potentially eligible studies that will be assessed for inclusion in the next update of the review.

AUTHORS' CONCLUSIONS

There is moderate quality evidence from two large trials that intensive insulin therapy reduces CIP/CIM, and high quality evidence that it reduces duration of mechanical ventilation, ICU stay and 180-day mortality, at the expense of hypoglycaemia. Consequences and prevention of hypoglycaemia need further study. There is moderate quality evidence which suggests no effect of corticosteroids on CIP/CIM and high quality evidence that steroids do not affect secondary outcomes, except for fewer new shock episodes. Moderate quality evidence suggests a potential benefit of early rehabilitation on CIP/CIM which is accompanied by a shorter duration of mechanical ventilation but without an effect on ICU stay. Very low quality evidence suggests no effect of EMS, although data are prone to bias. Strict diagnostic criteria for CIP/CIM are urgently needed for research purposes. Large RCTs need to be conducted to further explore the role of early rehabilitation and EMS and to develop new preventive strategies.

Interventions for preventing critical illness polyneuropathy and critical illness myopathy

BACKGROUND

Critical illness polyneuropathy or myopathy (CIP/CIM) is a frequent complication in the intensive care unit (ICU) and is associated with prolonged mechanical ventilation, longer ICU stay and increased mortality. This is an interim update of a review first published in 2009 (Hermans 2009). It has been updated to October 2011, with further potentially eligible studies from a December 2013 search characterised as awaiting assessment.

OBJECTIVES

To systematically review the evidence from RCTs concerning the ability of any intervention to reduce the incidence of CIP or CIM in critically ill individuals.

SEARCH METHODS

On 4 October 2011, we searched the Cochrane Neuromuscular Disease Group Specialized Register, CENTRAL, MEDLINE, and EMBASE. We checked the bibliographies of identified trials and contacted trial authors and experts in the field. We carried out an additional search of these databases on 6 December 2013 to identify recent studies.

SELECTION CRITERIA

All randomised controlled trials (RCTs), examining the effect of any intervention on the incidence of CIP/CIM in people admitted to adult medical or surgical ICUs. The primary outcome was the incidence of CIP/CIM in ICU, based on electrophysiological or clinical examination. Secondary outcomes included duration of mechanical ventilation, duration of ICU stay, death at 30 and 180 days after ICU admission and serious adverse events from the treatment regimens.

DATA COLLECTION AND ANALYSIS

Two authors independently extracted the data and assessed the risk of bias in included studies.

MAIN RESULTS

We identified five trials that met our inclusion criteria. Two trials compared intensive insulin therapy (IIT) to conventional insulin therapy (CIT). IIT significantly reduced CIP/CIM in the screened (n = 825; risk ratio (RR) 0.65, 95% confidence interval (CI) 0.55 to 0.77) and total (n = 2748; RR 0.70, 95% CI 0.60 to 0.82) population randomised. IIT reduced duration of mechanical ventilation, ICU stay and 180-day mortality, but not 30-day mortality compared with CIT. Hypoglycaemia increased with IIT but did not cause early deaths.One trial compared corticosteroids with placebo (n = 180). The trial found no effect of treatment on CIP/CIM (RR 1.27, 95% CI 0.77 to 2.08), 180-day mortality, new infections, glycaemia at day seven, or episodes of pneumonia, but did show a reduction of new shock events.In the fourth trial, early physical therapy reduced CIP/CIM in 82/104 evaluable participants in ICU (RR 0.62. 95% CI 0.39 to 0.96). Statistical significance was lost when we performed a full intention-to-treat analysis (RR 0.81, 95% CI 0.60 to 1.08). Duration of mechanical ventilation but not ICU stay was significantly shorter in the intervention group. Hospital mortality was not affected but 30- and 180-day mortality results were not available. No adverse effects were noticed.The last trial found a reduced incidence of CIP/CIM in 52 evaluable participants out of a total of 140 who were randomised to electrical muscle stimulation (EMS) versus no stimulation (RR 0.32, 95% CI 0.10 to 1.01). These data were prone to bias due to imbalances between treatment groups in this subgroup of participants. After we imputed missing data and performed an intention-to-treat analysis, there was still no significant effect (RR 0.94, 95% CI 0.78 to 1.15). The investigators found no effect on duration of mechanical ventilation and noted no difference in ICU mortality, but did not report 30- and 180-day mortality.We updated the searches in December 2013 and identified nine potentially eligible studies that will be assessed for inclusion in the next update of the review.

AUTHORS' CONCLUSIONS

There is moderate quality evidence from two large trials that intensive insulin therapy reduces CIP/CIM, and high quality evidence that it reduces duration of mechanical ventilation, ICU stay and 180-day mortality, at the expense of hypoglycaemia. Consequences and prevention of hypoglycaemia need further study. There is moderate quality evidence which suggests no effect of corticosteroids on CIP/CIM and high quality evidence that steroids do not affect secondary outcomes, except for fewer new shock episodes. Moderate quality evidence suggests a potential benefit of early rehabilitation on CIP/CIM which is accompanied by a shorter duration of mechanical ventilation but without an effect on ICU stay. Very low quality evidence suggests no effect of EMS, although data are prone to bias. Strict diagnostic criteria for CIP/CIM are urgently needed for research purposes. Large RCTs need to be conducted to further explore the role of early rehabilitation and EMS and to develop new preventive strategies.

WISE-2005: Countermeasures to prevent muscle deconditioning during bed rest in women

The objectives of this study were to evaluate the efficacy of two separate countermeasures, exercise and protein supplementation, to prevent muscle strength and lean tissue mass losses during 60 days of bed rest (BR) in women and whether countermeasure efficacy was influenced by pre-BR muscular fitness (strength, endurance, tissue mass). Twenty-four women were assigned to an exercise (EX, n = 8), a no-exercise control (CON, n = 8), or a no-exercise protein supplementation group (PROT, n = 8). EX performed supine treadmill exercise within lower body negative pressure 3-4 days/wk and maximal concentric and eccentric supine leg- and calf-press exercises 2-4 days/wk. PROT consumed a diet with elevated protein content compared with CON and EX (1.6 vs. 1.0 g·kg(-1)·day(-1)). Knee and calf isokinetic strength and endurance, isotonic leg-press strength, and leg lean mass were measured before and after BR. Post-BR knee extensor strength and endurance, ankle strength, and leg lean mass were significantly greater and leg-press strength tended to be higher in EX than in CON and PROT. Post-BR measures in PROT were not different than those in CON. Exercise countermeasure efficacy was less, and strength, endurance, and leg lean mass losses in CON and PROT were greater, in subjects who were more fit pre-BR. An exercise protocol combining resistive and aerobic exercise training protects against losses in strength, endurance, and leg lean mass in women during BR, while a nutritional countermeasure without exercise was not effective. Exercise countermeasures may require individualization to protect higher levels of strength and endurance.

A dietary supplementation with leucine and antioxidants is capable to accelerate muscle mass recovery after immobilization in adult rats

Prolonged inactivity induces muscle loss due to an activation of proteolysis and decreased protein synthesis; the latter is also involved in the recovery of muscle mass. The aim of the present work was to explore the evolution of muscle mass and protein metabolism during immobilization and recovery and assess the effect of a nutritional strategy for counteracting muscle loss and facilitating recovery. Adult rats (6–8 months) were subjected to unilateral hindlimb casting for 8 days (I0–I8) and then permitted to recover for 10 to 40 days (R10–R40). They were fed a Control or Experimental diet supplemented with antioxidants/polyphenols (AOX) (I0 to I8), AOX and leucine (AOX + LEU) (I8 to R15) and LEU alone (R15 to R40). Muscle mass, absolute protein synthesis rate and proteasome activities were measured in gastrocnemius muscle in casted and non-casted legs in post prandial (PP) and post absorptive (PA) states at each time point. Immobilized gastrocnemius protein content was similarly reduced (-37%) in both diets compared to the non-casted leg. Muscle mass recovery was accelerated by the AOX and LEU supplementation (+6% AOX+LEU vs. Control, P<0.05 at R40) due to a higher protein synthesis both in PA and PP states (+23% and 31% respectively, Experimental vs. Control diets, P<0.05, R40) without difference in trypsin- and chymotrypsin-like activities between diets. Thus, this nutritional supplementation accelerated the recovery of muscle mass via a stimulation of protein synthesis throughout the entire day (in the PP and PA states) and could be a promising strategy to be tested during recovery from bed rest in humans.

Diurnal cortisol patterns are associated with physical performance in the Caerphilly Prospective Study

Background Cross-sectional studies have suggested that elevated cortisol is associated with worse physical performance, a surrogate of ageing. We examined the relationship between repeat cortisol measures over 20 years and physical performance in later life.

Methods Middle-aged men (45–59 years) were recruited between 1979 and 1983 (Phase 1) from the Caerphilly Prospective Study (CaPS) and re-examined 20 years later at 65–83 years of age (Phase 5). Participants included 750 and 898 subjects with either Phase 1 and/or Phase 5 data on exposure and outcomes. Outcome measures were walking speed and balance time and exposures included morning fasting serum cortisol (Phase 1) and four salivary samples on 2 consecutive days (Phase 5).

Results Faster walking speed was associated with higher morning cortisol at Phase 1 [coefficient per standard deviation (SD) increase 0.68, 95% confidence interval (95% CI) 0.09–1.27; P = 0.02] though this was attenuated after adjustment for covariates (coefficient per SD increase 0.45; 95% CI –0.16 to 1.07; P = 0.15). Higher night-time cortisol at Phase 5 was associated with slower speed (coefficient per SD increase –1.06; 95% CI –1.60 to –0.52; P < 0.001) and poorer balance (odds ratio of top tertile vs bottom 2.49; 95% CI 1.63–3.81; P < 0.001). Worst performance was seen for men with a poor morning response (Phase 1) and less nocturnal decline (Phase 5).

Conclusions Dysregulation of the hypothalamic pituitary adrenal (HPA) axis is associated with worse physical performance in later life. This may reflect a causal effect of the HPA axis on ageing or that ageing itself is associated with reduced HPA reactivity.

Effects of inflammation and/or inactivity on the need for dietary protein

PURPOSE OF REVIEW

Protein requirement in healthy young and old individuals is traditionally defined as the lowest protein intake sufficient to achieve neutral body protein balance. This concept, however, cannot be applied to those conditions characterized by unavoidable protein catabolism despite optimal nutrition, such as inactivity and diseases associated with systemic inflammation.

RECENT FINDINGS

The ability of dietary proteins to promote protein anabolism is reduced by inactivity and inflammatory mediators, whereas physical exercise ameliorates the efficiency in using dietary proteins. Consequently, the protein intake level associated with the lowest rate of catabolism in inactivity and/or inflammation is greater than the minimum protein intake required to achieve neutral protein balance in healthy, physically active individuals. A protein intake of 1.2 g.kg.day is currently recommended for inactive healthy individuals, whereas guidelines recommend up to 1.5 g.kg.day in patients with severe systemic inflammation, such as those affected by critical illness or cancer. High protein intake accelerates progression of renal insufficiency but does not affect renal function in healthy individuals.

SUMMARY

In inflammation and/or inactivity a relatively high protein intake may be required to promote synthesis of specific proteins, prevent depletion of selected amino acids (e.g., glutamine or arginine), modulate immune functions, counteract insulin resistance and redox unbalance. Thus, an optimal protein/amino acid intake may be greater than that required to decrease whole body protein wasting.

Interventions for preventing critical illness polyneuropathy and critical illness myopathy

BACKGROUND

Critical illness polyneuro-and/or myopathy (CIP/CIM) is an important and frequent complication in the intensive care unit (ICU), causing delayed weaning from mechanical ventilation. It may increase ICU stay and mortality.

OBJECTIVES

To examine the ability of any intervention to prevent the occurrence of CIP/CIM.

SEARCH STRATEGY

We searched the Cochrane Neuromuscular Disease Group Trials Register (October 2007), MEDLINE (January 1950 to April 2008), EMBASE (January 1980 to October 2007), checked bibliographies and contacted trial authors and experts in the field.

SELECTION CRITERIA

All randomised controlled trials (RCTs), examining the effect of any intervention on the incidence of CIP/CIM in adult medical or surgical ICU patients. The primary outcome measure was the incidence of CIP/CIM after at least seven days in ICU, based on electrophysiological or clinical examination.

DATA COLLECTION AND ANALYSIS

Two authors independently extracted the data.

MAIN RESULTS

Three out of nine identified trials, provided data on our primary outcome measure. Two trials examined the effects of intensive insulin therapy versus conventional insulin therapy. Eight hundred and twenty-five out of 2748 patients randomised, were included in the analysis. The incidence of CIP/CIM was significantly reduced with intensive insulin therapy in the population screened for CIP/CIM (relative risk (RR) 0.65, 95% confidence interval (CI) 0.55 to 0.78) and in the total population randomised (RR 0.60, 95% CI 0.49 to 0.74). Duration of mechanical ventilation, duration of ICU stay and 180-day mortality but not 30-day mortality, were significantly reduced with intensive insulin therapy, in both the total and the screened population. Intensive insulin therapy significantly increased hypoglycaemic events and recurrent hypoglycaemia. Death within 24 hours of the hypoglycaemic event was not different between groups. The third trial examined the effects of corticosteroids versus placebo in 180 patients with prolonged acute respiratory distress syndrome. No significant effect of corticosteroids on CIP/CIM was found (RR 1.09, 95% CI 0.53 to 2.26). No effect on 180-day mortality, new serious infections and glycaemia at day seven was found. A trend towards fewer episodes of pneumonia and reduction of new events of shock was shown.

AUTHORS' CONCLUSIONS

Substantial evidence shows that intensive insulin therapy reduces the incidence of CIP/CIM, the duration of mechanical ventilation, duration of ICU stay and 180-day mortality. There was a significant associated increase in hypoglycaemia. Further research needs to identify the clinical impact of this and strategies need to be developed to reduce the risk of hypoglycaemia. Limited evidence shows no significant effect of corticosteroids on the incidence of CIP/CIM, or on any of the other secondary outcome measures, except for a significant reduction of new episodes of shock. Strict diagnostic criteria for the purpose of research should be defined. Other interventions should be investigated in randomised controlled trials.

Dietary protein recommendations and the prevention of sarcopenia

PURPOSE OF REVIEW

To draw attention to recent work on the role of protein and the amount of protein needed with each meal to preserve skeletal muscle mass in ageing.

RECENT FINDINGS

Ageing does not inevitably reduce the anabolic response to a high-quality protein meal. Ingestion of approximately 25-30 g of protein per meal maximally stimulates muscle protein synthesis in both young and older individuals. However, muscle protein synthesis is blunted in elderly when protein and carbohydrate are coingested or when the quantity of protein is less than approximately 20 g per meal. Supplementing regular mixed-nutrient meals with leucine may also enhance the muscle protein synthetic response in elders.

SUMMARY

On the basis of recent work, we propose a novel and specific dietary approach to prevent or slow down muscle loss with ageing. Rather than recommending a large, global increase in the recommended dietary allowance (RDA) for protein for all elderly individuals, clinicians should stress the importance of ingesting a sufficient amount of protein with each meal. To maximize muscle protein synthesis while being cognizant of total energy intake, we propose a dietary plan that includes 25-30 g of high quality protein per meal.

Avaliação do volume de fluxo venoso da bomba sural por ultra-sonografia Doppler durante cinesioterapia ativa e passiva: um estudo piloto

CONTEXTO: O fisioterapeuta na unidade hospitalar atua sobre os efeitos da hipoatividade ou inatividade do paciente acamado. Na prática diária, a contração do músculo da panturrilha é difundida entre os profissionais de saúde no ambiente hospitalar, principalmente nos períodos de pré e pós-operatório, como forma de diminuir a estase venosa e os riscos de trombose venosa profunda nos membros inferiores. OBJETIVO: Avaliar o volume de fluxo venoso na bomba sural, através de ultra-sonografia doppler, durante cinesioterapia ativa e passiva (flexão plantar do tornozelo). MÉTODOS: A amostra foi constituída por 30 indivíduos escolhidos aleatoriamente e submetidos a ultra-sonografia doppler da veia poplítea direita, visando mensurar o volume de fluxo sanguíneo em quatro momentos: repouso, compressão manual da panturrilha, movimentação passiva e ativa do tornozelo em flexão plantar. Na análise dos resultados, utilizou-se o teste t, sendo utilizado um valor de p < 0,05 como índice de significância estatística. RESULTADOS: Na amostra constituída, 16 eram do sexo feminino e 14 do sexo masculino, apresentando as seguintes médias: idade (31,57 anos), altura (1,68 m), peso (68,25 kg) e índice de massa corporal (24,16). Na análise estatística, a flexão plantar do tornozelo realizada de forma passiva, quando comparada ao valor basal, é significante (p < 0,000056) em relação à ativação da bomba sural, embora não tanto quanto o exercício ativo (p < 0,0000016). Também mostrou significância a compressão manual do músculo tríceps sural em relação ao exercício passivo (p < 0,000000081). CONCLUSÃO: Neste estudo, a flexão plantar do tornozelo de forma ativa mostrou-se estatisticamente mais eficaz do que a passiva na ativação da bomba sural, aumentando o volume do fluxo de sangue na veia poplítea e diminuindo a estase venosa nos membros inferiores.

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.

Role of dietary protein in the sarcopenia of aging

Sarcopenia is a complex, multifactorial process facilitated by a combination of factors including the adoption of a more sedentary lifestyle and a less than optimal diet. Increasing evidence points to a blunted anabolic response after a mixed nutrient meal as a likely explanation for chronic age-related muscle loss. There is currently insufficient longer-term research with defined health outcomes to specify an optimal value for protein ingestion in elderly individuals. However, there is general agreement that moderately increasing daily protein intake beyond 0.8 g x kg(-1) x d(-1) may enhance muscle protein anabolism and provide a means of reducing the progressive loss of muscle mass with age. The beneficial effects of resistance exercise in aging populations are unequivocal. However, research has not identified a synergistic effect of protein supplementation and resistance exercise in aging populations. There is little evidence that links high protein intakes to increased risk for impaired kidney function in healthy individuals. However, renal function decreases with age, and high protein intake is contraindicated in individuals with renal disease. Assessment of renal function is recommended for older individuals before they adopt a higher-protein diet.

Bed rest and myopathies

PURPOSE OF REVIEW

The loss of skeletal muscle with injury or critical illness can be dramatic. This review emphasizes the importance of skeletal muscle as a metabolic reserve. Changes in protein metabolism with bed rest alone and during physiological stress are discussed. Nutritional and hormonal interventions that ameliorate the loss of skeletal muscle are highlighted.

RECENT FINDINGS

The loss of skeletal muscle that occurs with inactivity alone can be prevented by nutritional supplementation with an essential amino acid formula. Bed rest with accompanying hypercortisolemia produces a threefold greater loss of skeletal muscle than bed rest alone. Essential amino acids stimulate muscle anabolism during acute hypercortisolemia; however, their effects during chronic hypercortisolemia must be explored.

SUMMARY

Skeletal muscle loss with trauma or critical illness is due in great part to the interaction of bed rest (muscular inactivity) and stress (hypercortisolemia). Younger individuals respond to nutritional and pharmacological interventions during bed rest alone. Given a lower relative lean mass in the elderly and the importance of skeletal muscle as a metabolic reserve during stress, it is understandable that clinical outcomes are worse in older patients. Countermeasures to the loss of skeletal muscle, especially in the stressed patient, must be developed.