Increased amino acid turnover and myofibrillar protein breakdown in advanced cancer are associated with muscle weakness and impaired physical function

Cancer-associated muscle weakness - From triggers to molecular mechanisms

Skeletal muscle weakness is a debilitating consequence of many malignancies. Muscle weakness has a negative impact on both patient wellbeing and outcome in a range of cancer types and can be the result of loss of muscle mass (i.e. muscle atrophy, cachexia) and occur independently of muscle atrophy or cachexia. There are multiple cancer specific triggers that can initiate the progression of muscle weakness, including the malignancy itself and the tumour environment, as well as chemotherapy, radiotherapy and malnutrition. This can induce weakness via different routes: 1) impaired intrinsic capacity (i.e., contractile dysfunction and intramuscular impairments in excitation-contraction coupling or crossbridge cycling), 2) neuromuscular disconnection and/or 3) muscle atrophy. The mechanisms that underlie these pathways are a complex interplay of inflammation, autophagy, disrupted protein synthesis/degradation, and mitochondrial dysfunction. The current lack of therapies to treat cancer-associated muscle weakness highlight the critical need for novel interventions (both pharmacological and non-pharmacological) and mechanistic insight. Moreover, most research in the field has placed emphasis on directly improving muscle mass to improve muscle strength. However, accumulating evidence suggests that loss of muscle function precedes atrophy. This review primarily focuses on cancer-associated muscle weakness, independent of cachexia, and provides a solid background on the underlying mechanisms, methodology, current interventions, gaps in knowledge, and limitations of research in the field. Moreover, we have performed a mini-systematic review of recent research into the mechanisms behind muscle weakness in specific cancer types, along with the main pathways implicated.

Assessing Frailty in Gastrointestinal Cancer: Two Diseases in One?

PURPOSEOF REVIEW

This review examines the challenges of treating gastrointestinal cancer in the aging population, focusing on the importance of frailty assessment. Emphasized are the rise in gastrointestinal cancer incidence in older adults, advances in frailty assessments for patients with gastrointestinal cancer, the development of novel frailty markers, and a summary of recent trials.

RECENT FINDINGS

Increasing evidence suggests that the use of a Comprehensive Geriatric Assessment (CGA) to identify frail older adults and individualize cancer care leads to lower toxicity and improved quality of life outcomes. However, the adoption of a full CGA prior to chemotherapy initiation in older cancer patients remains low. Recently, new frailty screening tools have emerged, including assessments designed to specifically predict chemotherapy-related adverse events. Additionally, frailty biomarkers have been developed, such as blood tests like IL-6 and performance tracking through physical activity monitors. The relevance of nutrition and muscle mass is discussed. Highlights from recent trials suggest the feasibility of successfully identifying patients most at risk of serious adverse events. There have been promising developments in identifying novel frailty markers and methods to screen for frailty in the older adult population. Further prospective trials that focus on and address the needs of the geriatric population for early identification of frailty in cancer care, facilitating a more tailored treatment approach. Practicing oncologists should select a frailty assessment to implement into their routine practice and adjust treatment accordingly.

Sarcopenia and malignancies: epidemiology, clinical classification and implications

Sarcopenia is a progressive systemic skeletal muscle disorder characterized by a pathological decline in muscle strength, quantity, and quality, which frequently affects the elderly population. The majority of cancer patients are of advanced age. Patients may already have sarcopenia prior to cancer development, and those with cancer are prone to developing sarcopenia due to hypercatabolism, inflammation, reduced physical fitness, anorexia, adverse effects, and stress associated with anticancer therapy. Based on the timing, sarcopenia in patients with cancer can be categorized into three: pre-existing sarcopenia before the onset of cancer, sarcopenia related to cancer, and sarcopenia related to cancer treatment. Sarcopenia not only changes the body composition of patients with cancer but also increases the incidence of postoperative complications, reduces therapeutic efficacy, impairs quality of life, and results in shortened survival. Different therapeutic strategies are required to match the cancer status and physical condition of patients with different etiologies and stages of sarcopenia. Here, we present a comprehensive review of the epidemiology and diagnosis of sarcopenia in patients with cancer, elucidate the complex interactions between cancer and sarcopenia, and provide evidence-based strategies for sarcopenia management in these patients.

The importance of protein sources to support muscle anabolism in cancer: An expert group opinion

This opinion paper presents a short review of the potential impact of protein on muscle anabolism in cancer, which is associated with better patient outcomes. Protein source is a topic of interest for patients and clinicians, partly due to recent emphasis on the supposed non-beneficial effect of proteins; therefore, misconceptions involving animal-based (e.g., meat, fish, dairy) and plant-based (e.g., legumes) proteins in cancer are acknowledged and addressed. Although the optimal dietary amino acid composition to support muscle health in cancer is yet to be established, animal-based proteins have a composition that offers superior anabolic potential, compared to plant-derived proteins. Thus, animal-based foods should represent the majority (i.e., ≥65%) of protein intake during active cancer treatment. A diet rich in plant-derived proteins may support muscle anabolism in cancer, albeit requiring a larger quantity of protein to fulfill the optimal amino acid intake. We caution that translating dietary recommendations for cancer prevention to cancer treatment may be inadequate to support the pro-inflammatory and catabolic nature of the disease. We further caution against initiating an exclusively plant-based (i.e., vegan) diet upon a diagnosis of cancer, given the presence of elevated protein requirements and risk of inadequate protein intake to support muscle anabolism. Amino acid combination and the long-term sustainability of a dietary pattern void of animal-based foods requires careful and laborious management of protein intake for patients with cancer. Ultimately, a dietary amino acid composition that promotes muscle anabolism is optimally obtained through combination of animal- and plant-based protein sources.

Impact of β-hydroxy-β-methylbutyrate (HMB) on muscle loss and protein metabolism in critically ill patients: A RCT

PURPOSE

Muscle wasting deteriorates life quality after critical illness and increases mortality. Wasting starts upon admission to intensive care unit (ICU). We aimed to determine whether β-hydroxy-β-methylbutyrate (HMB), a metabolite of leucine, can attenuate this process.

METHODS

Prospective randomized, placebo-controlled double blind trial.

INCLUSION CRITERIA

ICU patients depending on mechanical ventilation on day 3 having a functional gastrointestinal tract. They were randomized to HMB (3 g/day) or placebo (maltodextrin) from day 4 on for 30 days.

PRIMARY OUTCOME

magnitude of loss of skeletal muscle area (SMA) of the quadriceps femoris measured by ultrasound at days 4 and 15.

SECONDARY OUTCOMES

body composition, change in protein metabolism assessed by amino acids tracer pulse, and global health at 60 days. Data are mean [95% CI]. Statistics by ANCOVA with correction for confounders sex, age and/or BMI.

RESULTS

Thirty patients completed the trial, aged 65 [59, 71] years, SAPS2 score 48 [43, 52] and SOFA 8.5 [7.4, 9.7]. The loss of total SMA was 11% between days 4 and 15 (p < 0.001), but not different between the groups (p = 0.86). In the HMB group, net protein breakdown (Δ Estimate HMB-Placebo: -153 [-242, -63]; p = 0.0021) and production of several amino acid was significantly reduced, while phase angle increased more (0.66 [0.09, 1.24]; p = 0.0247), and SF-12 global health improved more (Δ Estimate HMB-Placebo: 27.39 [1.594, 53.19], p = 0.04).

CONCLUSION

HMB treatment did not significantly reduce muscle wasting over 10 days of observation (primary endpoint), but resulted in significantly improved amino acid metabolism, reduced net protein breakdown, a higher phase angle and better global health. CLINICALTRIALS.

GOV IDENTIFIER

NCT03628365.

The Validity of the GLIM Criteria for Malnutrition in Hospitalized Patients with Gastric Cancer

BACKGROUND

The Global Leadership Initiative on Malnutrition (GLIM) has recently proposed a consensus on the criteria to diagnose malnutrition. The validity of the new criteria to detect malnutrition is still being explored. Therefore, this study aimed to verify the validity of the GLIM criteria for malnutrition in hospitalized patients with gastric cancer (GC) using the Patient-Generated Subjective Global Assessment (PG-SGA) as a comparator.

METHODS

This is a cross-sectional study involving 217 GC inpatients. Nutrition assessment was performed during their hospitalization with both the GLIM criteria and the PG-SGA. Consistency of the assessment results and their correlation with the quality of life in patients were evaluated.

RESULTS

A moderate concordance (K = 0.483, P < 0.001) was founded between the two methods for malnutrition diagnosis. Spearman correlation analysis confirmed the significant association (P < 0.05) between most aspects of the quality of life and nutrition status regarding either the GLIM criteria or the PG-SGA. In multivariate linear regression, adjusted for confounding variables, the quality of life was significantly associated with nutrition status by the GLIM criteria (B = 5.63, 95% CI: 0.09-11.16, P = 0.046), and by the PG-SGA (B = 13.53, 95% CI: 7.78-19.27, P < 0.001).

CONCLUSIONS

This study provides a new understanding of the validity of the GLIM criteria in hospitalized GC patients. In the study, we have found that the new GLIM criteria are of concurrent and clinical validity in GC inpatients, suggested by the comparison with the PG-SGA and its correlation with the quality of life.

Hydrolyzed peptides from purple perilla (Perilla frutescens L. Britt.) seeds improve muscle synthesis and exercise performance in mice

The purple perilla (Perilla frutescens L. Britt.) seed peptides (PPSP) were obtained and their improvement of muscle synthesis and exercise performance was investigated in this work. Results showed that the weight-average molecular weight of the PPSP was 869 Dalton. The PPSP were rich in branched-chain amino acids (18.82 g/100 g) and anti-fatigue amino acids, including glutamate (Glu), aspartic acid (Asp), and arginine (Arg). After the administration of PPSP at 1.2 g kg^-1  day^-1 for 4 weeks, the muscle coefficient and muscle fiber thickness in mice displayed a distinct (p < .05) increase via the upregulation of myogenic differentiation (MyoD) and myogenin (MyoG). The improved muscle strength and exercise tolerance were also observed. Simultaneously, the levels of the biochemical blood markers associated with fatigue and the glycogen degradation in liver and muscle were significantly (p < .05) suppressed. These results suggested that PPSP could effectively promote muscle synthesis and ameliorate exercise fatigue. PRACTICAL APPLICATIONS: Purple perilla is an annual herbal plant and widely grown in Asian countries as an important crop and food. It is believed that the protein content of purple perilla seeds can reach 23.7%, and the protein is rich in essential amino acids. However, the information about the beneficial effects of their proteins or peptides on muscle synthesis and anti-exercise fatigue were still limited. The present results discovered that the PPSP can effectively promote the growth of muscle tissue and improve exercise tolerance. It is indicated that PPSP may have a potential application value in partly or completely replacing animal proteins such as whey protein.

Early Signs of Impaired Gut Function Affect Daily Functioning in Patients With Advanced Cancer Undergoing Chemotherapy

BACKGROUND

Gastrointestinal symptoms are common during chemotherapy, but underlying disturbances in gut function and their impact on daily life are unclear. This study investigates gut function in a heterogenous group of cancer patients with gastrointestinal symptoms during chemotherapy and its relation to anabolic response, muscle health, and daily functioning.

METHODS

In 16 patients with solid tumors (mostly stage III+IV) undergoing chemotherapy (T) and 16 healthy (H) matched controls, small-intestinal membrane integrity was measured by urine sugar tests. Protein digestion, absorption, and anabolic response to a conventional protein supplement were analyzed by stable-tracer methods. Muscle mass and strength and daily functioning were assessed.

RESULTS

Eighty-one percent of T patients reported gastrointestinal symptoms. Small-intestinal membrane permeability was similar, but active glucose transport was lower in the T group (T, 35.5% ± 3.4% vs H, 48.4% ± 4.7%; P = .03). Protein digestion and absorption tended to be lower in the T group (0.67 ± 0.02 vs 0.80 ± 0.04; P = .08). Net protein anabolic response to feeding was comparable, although lower in cancer patients with recent weight loss. Gut permeability negatively correlated to hand grip strength, global health, and physical functioning, and active-transport capacity positively correlated to global health in the T group.

CONCLUSION

Advanced cancer patients with gastrointestinal symptoms during chemotherapy, particularly those with recent weight loss, show signs of impaired gut function negatively affecting muscle health, daily functioning, and anabolic response to feeding.

Contemporary stable isotope tracer approaches: Insights into skeletal muscle metabolism in health and disease

NEW FINDINGS

What is the topic of this review? This review discusses the application of new stable isotope tracer techniques in understanding the control of skeletal muscle mass. What advances does it highlight? This review highlights current advances in stable isotope tracer techniques through their combination with high-throughput proteomics technologies.

ABSTRACT

Beyond its primary locomotory and key structural functions, skeletal muscle provides additional vital roles for maintenance of metabolic health, acting as a storage point for glucose and intramuscular lipids for energy production, alongside being the largest reservoir for amino acids in the body. Therefore, maintenance of muscle mass is key to the promotion of health and well-being across the lifespan and in several disease states. As such, when skeletal muscle is lost, in either clinical (cancer, organ failure etc.) or non-clinical (ageing, inactivity) situations, there are potentially devastating consequences attached, with robust links existing between muscle mass loss and mortality. Great efforts are being made to reverse or slow muscle mass declines in health and disease, through combinations of lifestyle changes and nutritional and/or pharmaceutical intervention. However, despite this comprehensive research effort, the underlying metabolic and molecular mechanisms have yet to be defined properly. However, with the rapid acceleration of analytical developments over recent years, the application of stable isotope tracers to the study of human muscle metabolism is providing unique insights into the mechanisms controlling skeletal muscle loss and allowing more targeted therapeutic strategies to be developed. The aim of this review is to highlight the technical breakthroughs in our understanding of muscle wasting in health and disease and how future directions and developments incorporating 'omics' with stable isotope tracers will allow for a more personalized and stratified therapeutic approach.

An update on nutrient modulation in the management of disease-induced muscle wasting: evidence from human studies

PURPOSE OF REVIEW

Skeletal muscle has many essential roles in maintaining human health, not only being crucial for locomotion, but further as a metabolically important organ. Muscle wasting in disease (cachexia) is highly prevalent, associated with poor clinical outcomes and is not fully reversible with nutritional interventions. Understanding proteostasis in diseased states is of great importance to design novel, effective nutritional/nutraceutical strategies aimed at alleviating muscle wasting. In this review, we will provide an update on muscle kinetics in disease and the effects of nutritional interventions.

RECENT FINDINGS

Whole body and skeletal muscle kinetics are commonly shown to be imbalanced in disease, promoting overall catabolism that underlies the development of cachexia. However, recent advancements in defining the effectiveness of nutritional interventions on muscle anabolism are clouded by heterogenous patient populations and a lack of direct incorporation stable isotope techniques. Current recommendations are focused on combating malnutrition, with increased protein intake (high in EAA) demonstrating promise.

SUMMARY

Recent progress in understanding catabolic states in cachexia across disease is minimal. Further, studies investigating muscle-specific protein turnover along with nutritional interventions are scarce. As such, there is a significant requirement for strong RCT's investigating both acute and chronic nutritional interventions and their impact on skeletal muscle in individual disease states.

Whey protein isolate supplementation improves body composition, muscle strength, and treatment tolerance in malnourished advanced cancer patients undergoing chemotherapy

In recent years, whey proteins (WP) have attracted increasing attention in health and disease for their bioactive functions. The aim of this study was to evaluate the benefit of WP isolate (WPI) supplementation in addition to nutritional counseling in malnourished advanced cancer patients undergoing chemotherapy (CT). In a single‐center, randomized, pragmatic, and parallel‐group controlled trial (http://www.ClinicalTrials.gov: NCT02065726), 166 malnourished advanced cancer patients with mixed tumor entities candidate to or undergoing CT were randomly assigned to receive nutritional counseling with (N = 82) or without (N = 84) WPI supplementation (20 g/d) for 3 months. The primary endpoint was the change in phase angle (PhA). Secondary endpoints included changes in standardized PhA (SPA), fat‐free mass index (FFMI), body weight, muscle strength, and CT toxicity (CTCAE 4.0 events). In patients with the primary endpoint assessed (modified intention‐to‐treat population), counseling plus WPI (N = 66) resulted in improved PhA compared to nutritional counseling alone (N = 69): mean difference, 0.48° (95% CI, 0.05 to 0.90) (P = .027). WPI supplementation also resulted in improved SPA (P = .021), FFMI (P = .041), body weight (P = .023), muscle strength (P < .001), and in a reduced risk of CT toxicity (risk difference, −9.8% [95% CI, −16.9 to −2.6]; P = .009), particularly of severe (grade ≥ 3) events (risk difference, −30.4% [95% CI, −44.4 to −16.5]; P = .001). In malnourished advanced cancer patients undergoing CT, receiving nutritional counseling, a 3‐month supplementation with WPI resulted in improved body composition, muscle strength, body weight, and reduced CT toxicity. Further trials, aimed at verifying the efficacy of this nutritional intervention on mid‐ and long‐term primary clinical endpoints in newly diagnosed specific cancer types, are warranted.