Editorial: Body composition measurements in older adults No abstract available

Vitamin D for the older patient: from hype to hope? Purpose of review The review critically appraises the most recent and important meta-analyses that have assessed the effect of vitamin D supplementation on bone health in the older population. Recent findings Vitamin D status is generally lower in study participants with bone wasting. However, studies on the effects of vitamin D supplementation on bone health, summarized in different meta-analyses, have provided conflicting results, likely because of the heterogeneity between studies. Interventional studies performed using more physiological doses of vitamin D (i.e. avoiding very large, nonphysiological doses) or in study participants with low vitamin D status have provided more beneficial effects on bone health. Summary Meta-analyses assessing the impact of vitamin D in the treatment of osteoporosis are heterogeneous in their conception or their results and sometimes have included inappropriate studies to answer the useful research question for the clinician, making the interpretation and the clinical use of these conflicting meta-analyses quite difficult.

Effects of Citrulline alone or combined with exercise on muscle mass, muscle strength, and physical performance among older adults: a systematic review Purpose of review To Establish the potential of Citrulline supplementation (CIT) combined or not with exercise on muscle function and physical performance via a systematic review of randomized controlled trials (RCTs) in human aged 50 years and older. Recent findings Based on Preferred Reporting Items for Systematic Reviews and Meta-analysis guideline, 103 references have been identified. Among this number, only six RCTs (250 participants) matched the inclusion criteria and were included in the present systematic review. Among the included studies, five of six reported beneficial effects of CIT on muscle mass. Then, four of six studies reported CIT effects on muscle strength but also that CIT when combined to exercise results in further improvements in upper muscle strength. Finally, three of six studies reported beneficial CIT effect on physical performance and suggested that CIT with exercise displayed greater improvements in walking speed than exercise alone. Summary CIT supplementation seems to be able to improve muscular and physical factors in frail elderly people (malnourished, hypertensive, obese, dynapenic-obese) compared to placebo. More importantly, CIT combined to exercise is more efficient than exercise or CIT alone. However, because of the small number (six) and heterogeneity (dose, duration, population) of the studies realized in older adults, further studies are needed to confirm its promising potential.

Arginine therapy in mitochondrial myopathy, encephalopathy, lactic acidosis, and stroke-like episodes Purpose of review We would like to inform clinicians that the systematic administration of oral and intravenous L-arginine is therapeutically beneficial and clinically useful for patients with mitochondrial myopathy, encephalopathy, lactic acidosis, and stroke-like episodes (MELAS), when they maintain plasma arginine concentration at least 168 μmol/l. Recent findings MELAS is associated with endothelial dysfunction by decreased plasma L-arginine, nitric oxide (NO), and cyclic guanosine monophosphate. Endothelial dysfunction is also evident using flow-mediated vasodilation measurement by high-resolution Doppler echocardiography in the forearm artery in patients with MELAS. L-arginine is known to be an important precursor of NO to normalize the endothelial function in MELAS. In our clinical trial followed by 7 years follow-up study, the systematic administration of L-arginine to patients with MELAS significantly improved the survival curve of patients compared with natural history. Maintaining plasma arginine concentration at least 168 μmol/l may prevent the ictuses through the putative pathophysiologic mechanism and optimal normalization of endothelial dysfunction. Summary Neither death nor bedriddenness occurred during the 2-year clinical trials, and the latter did not develop during the 7-year follow-up despite the progressively neurodegenerative and eventually life-threatening nature of MELAS. Therapeutic regimen of L-arginine on MELAS may be beneficial and clinically useful for patient care with MELAS.

Formate and its role in amino acid metabolism Purpose of review The aim of this report is to examine critical relationships between amino acid and formate metabolism with particular reference to the production of formate, and to review novel functions of formate. Recent findings In addition to well established mechanisms in one-carbon metabolism, formate may play an important role in early pregnancy by preventing the onset of neural tube defects in sensitive strains of mice, including mice with deficiencies in MTHFD1L, the glycine cleavage system and the mitochondrial folate transporter. Markedly elevated, circulating levels of formate are found in late pregnancy, including in cord blood, as well as elevated levels of amino acid precursors. These are consistent with specific roles for formate in late pregnancy. Serine metabolism may reduce NADP+ to NADPH and permit the use of NADPH in reductive reactions. Novel, noncanonical functions of formate include high rates of formate production from serine in cells and in cancers. Summary Novel, noncanonical functions of formate continue to be discovered. Integrating their functions with well established elements of one-carbon metabolism remains an important future objective.

Arginine supplementation and cardiometabolic risk Purpose of review Because arginine is the substrate for nitric oxide synthesis, which is pivotal to vascular homeostasis and linked to the insulin response, it has long been posited that supplemental arginine could benefit cardiometabolic health. Recent findings Recent data have supported the view that supplemental arginine could alleviate the initiation and development of endothelial dysfunction and also shown that it may reduce the risk of type 2 diabetes. One important finding is that these effects may indeed vary as a function of the amount of arginine, its form and notably the metabolic status of the population. Some studies have shown that low doses of slow-release arginine are better used for nitric oxide synthesis and beneficial in individuals with abnormal arginine metabolism/bioavailability. Pathophysiological data in rodents have emphasized the importance of arginase activation during the development of cardiometabolic risk, which lends credence to a potential benefit for arginine supplements. Likewise, epidemiological evidence suggests that alterations to arginine bioavailability are important regarding the cardiometabolic risk. However, other metabolic mechanisms linked to the multiple pathways of arginine metabolism may also play a role. Summary Further studies are needed to confirm and analyze how and when supplemental arginine is beneficial to cardiometabolic health.

Effect of branched-chain amino acid supplementation, dietary intake and circulating levels in cardiometabolic diseases: an updated review Purpose of review Branched-chain amino acids (BCAAs) are essential amino acids derived from diet. BCAA supplementation has been recommended in elderly and athletes, but recent studies suggest an association between high dietary BCAAs and blood levels of BCAAs with greater risk of cardiometabolic diseases (CMD). This review aims to integrate current epidemiological evidence analyzing the association between BCAAs and related-CMD risk factors. Recent findings Most epidemiological studies consistently show that dietary BCAAs are associated with higher risk of type-2 diabetes (T2D) whereas there is limited evidence related with other cardiovascular risk factors. Evidence also exists showing an association between higher circulating BCAA levels and risk of T2D and cardiovascular disease, and also probably with metabolic syndrome and overweight/obesity. Several clinical trials suggest beneficial cardiometabolic effect of BCAAs supplementation, although with a small sample size and short follow-up. Studies show a weak correlation between dietary BCAAs and circulating BCAA levels. Protein quality sources and whole dietary pattern are key aspects to improve our understanding of the effect of BCAAs as well as factors associated with higher protein needs, such as age or frailty. Summary Dietary and circulating BCAAs exhibit possible detrimental cardiometabolic effects, but BCAA supplementation may have some positive influence on target groups with nutritional deficiencies.

Protein intake and outcome in critically ill patients Purpose of review The objective of this review is to describe the impact of protein intake on the outcomes of critically ill patients in the literature published in the preceding 2 years. Recent findings Observational studies showed inconsistent results regarding the association of higher protein intake and outcomes of critically ill patients. Randomized controlled trials that directly compared higher versus lower protein intake in ICU patients are scarce, varied considerably in their designs and primary outcomes, and generally had relatively small differences in the amount of delivered protein between the study arms. Systematic reviews of existing studies showed no difference in mortality with higher protein intake. In addition, there is uncertainty regarding high protein provision in the early phase of critical illness. Summary The optimal amount of protein intake in critically ill patients remains largely unclear and is considered a high priority for research. Ongoing clinical trials are likely to provide additional evidence on several important questions including the dose, timing, type of protein and the interaction with caloric intake and exercise.

Tackling the question of micronutrients intake as one of the main levers in terms of Inuit food security Purpose of review The Inuit population living in North Canada is facing a drastic change in lifestyle, which has brought about a dramatic nutrition transition characterized by a decrease in the traditional foods consumption and an increasing reliance on processed, store-bought foods. This rapid dietary shift leads to a significant public health concern, as wild-harvested country foods are rich in many micronutrients including vitamins, trace elements and minerals while the most frequently eaten Western foods mainly provide energy, fat, carbohydrates and sodium. This review addresses the emerging strategies to tackle food insecurity in this population. Recent findings Recent studies indicate that diets with a higher fraction of traditional foods (and a lower fraction of ultra-processed foods) exhibit a better Healthy Eating Index. This provides a basis to develop new dietary policies anchored in contemporary food realities. Summary In Northern remote communities, improving food security requires holistic approaches. A mixed strategy that targets the revitalization of traditional foods systems and local food production initiatives seems the most promising strategy, to meet the dietary needs in terms of micronutrients, with respect to the cultural identity of local populations.