Enhanced Echo Intensity of Skeletal Muscle Is Associated With Exercise Intolerance in Patients With Heart Failure

Histological changes in skeletal muscle induced by heart failure in human patients and animal models: A scoping review

OBJECTIVE

This scoping review aimed to characterize the histological changes in skeletal muscle after heart failure (HF) and to identify gaps in knowledge.

METHODS

On April 03, 2024, systematic searches were performed for papers in which histological analyses were conducted on skeletal muscle sampled from patients with HF or animal models of HF. Screening and data extraction were conducted by two independent authors.

RESULTS AND CONCLUSION

A total of 118 papers were selected, including 33 human and 85 animal studies. Despite some disagreements among studies, some trends were observed. These trends included a slow-to-fast transition, a decrease in muscle fiber size, capillary to muscle fiber ratio, and mitochondrial activity and content, and an increase in apoptosis. These changes may contribute to the fatigability and decrease in muscle strength observed after HF. Although there were some disagreements between the results of human and animal studies, the results were generally similar. Animal models of HF will therefore be useful in elucidating the histological changes in skeletal muscle that occur in human patients with HF. Because the muscles subjected to histological analysis were mostly thigh muscles in humans and mostly lower leg muscles in animals, it remains uncertain whether changes similar to those seen in lower limb (hindlimb) muscles after HF also occur in upper limb (forelimb) muscles. The results of this review will consolidate the current knowledge on HF-induced histological changes in skeletal muscle and consequently aid in the rehabilitation of patients with HF and future studies.

Ultrasound-measured Quadriceps Muscle Thickness and Mortality in Older Patients With Heart Failure

BACKGROUND

Ultrasound might be helpful for muscle mass assessment in patients with heart failure (HF). We aimed to determine the feasibility and prognostic implications of ultrasound-measured quadriceps muscle thickness (QMT) in older patients with HF.

METHODS

This was a post hoc analysis of a multicentre prospective cohort study including patients hospitalized for HF aged 65 years and older. QMT at rest and during isometric contractions using ultrasound was measured with the patient in the supine position before discharge.

RESULTS

The interobserver agreement for measuring QMT was excellent, with intraclass correlation coefficients of 0.979 (95% confidence interval [CI], 0.963-0.988) at rest and 0.997 (95% CI, 0.994-0.998) during isometric contraction. The intraobserver reproducibility was also excellent (intraclass correlation coefficient > 0.92). Of the 595 patients (median age, 81 years; 56% male), median QMT at rest and during contraction were 18.9 mm and 24.9 mm, respectively. The patients were grouped according to sex-specific tertiles of height-adjusted QMT. During the median follow-up of 735 days, 157 deaths occurred, and Kaplan-Meier curve analysis showed that the lowest tertile of the height-adjusted QMT was associated with a higher mortality. Cox proportional hazard analysis revealed that thinner height-adjusted QMT was independently associated with higher mortality, even after adjusting for conventional risk factors (per 1 mm/m increase: hazard ratio, 0.94; 95% CI, 0.89-0.99; P = 0.030 [at rest] and hazard ratio, 0.94; 95% CI, 0.90-0.99; P = 0.015 [during isometric contraction]).

CONCLUSIONS

Ultrasound-measured QMT in older patients with HF is feasible, and thinner height-adjusted QMT at rest and during isometric contraction was independently associated with higher mortality.

Prognostic impact of muscle ultrasound-guided diagnosis of sarcopenia in older adults with severe aortic stenosis

BACKGROUND

Muscle ultrasound is increasingly popular thanks to its advantages over other techniques. However, its usefulness in the diagnosis of sarcopenia in older adults with aortic stenosis (AS) has not been studied to date.

OBJECTIVES

to analyze the prevalence of sarcopenia using muscle ultrasound and its impact on the health outcomes in older patients with AS.

METHODS

The single-center FRESAS (FRailty-Evaluation-in-Severe-Aortic-Stenosis) registry was used to study patients over 75 years with severe AS susceptible to valve replacement. Sarcopenia was suspected in those individuals with diminished grip strength, and the diagnosis was confirmed in the presence of reduced ultrasound quadriceps muscle thickness, following the recommendations of the EWGSOP2 (European-Working-Group-on-Sarcopenia-in-Older-People). The primary composite endpoint was urgent hospital admission and mortality of cardiac cause 6 months after the diagnosis.

RESULTS

Of the 150 patients studied, 55.3% were females, and only 17.3% were frail; the mean age was 83.4 years. Sarcopenia was diagnosed in 42 patients (28%). The overall survival rate at 6 months was 92%. The primary endpoint was recorded in 23.2% of the cases and was more frequent in the sarcopenic patients (33.3%) than in the non-sarcopenic individuals (17.6%) (p = 0.01). The regression analysis found that sarcopenia was associated with an increased risk of the primary endpoint (HR: 2.25; 95% CI 1.19-4.45; p = 0.02), adjusting for potential confounding factors.

CONCLUSIONS

The incidence of serious cardiac complications in older patients with sarcopenia and severe AS is significant. The present study describes a noninvasive, ultrasound-guided diagnostic technique that may prove efficient in its predictive capacity.

Association between heart failure in asymptomatic stages and skeletal muscle function assessed by ultrasonography in community-dwelling older adults

BACKGROUND

Symptomatic heart failure (HF) negatively affects the quantity and quality of skeletal muscles. However, the association between asymptomatic HF and skeletal muscle function remains unclear. We aimed to use ultrasonography to elucidate the association between asymptomatic HF and skeletal muscle function in community-dwelling older adults.

METHODS

This cross-sectional study comprised community-dwelling older adults aged ≥ 60 years who could perform activities of daily living independently and had never had symptomatic HF (n = 52, 76.3 ± 6.1 years). The participants were classified into three groups namely, non-HF (n = 26), stage A (n = 19), and stage B (n = 7) according to the HF stage criteria of the American Heart Association /American College of Cardiology /Heart Failure Society of America guideline. Skeletal muscle quantity and quality were assessed using ultrasonography (thickness and echo intensity) of the rectus femoris (RF) and vastus intermedius (VI) muscles. The group effects on muscle thickness and echo intensity in each group were assessed using a multivariate analysis.

RESULTS

Both muscles consistently demonstrated significant group effects on the thickness and echo intensity. Thicknesses of the RF (p = 0.020) and VI (p = 0.035) were lower in the stage B group than that in the non-HF group. The echo intensities in the RF (p = 0.006) and VI (p = 0.009) were higher in the stage B group than that in the non-HF group.

CONCLUSION

Asymptomatic HF negatively associated with the characteristics of skeletal muscle function, as assessed by ultrasonography in community-dwelling older adults. The stage B HF contributes to reduced skeletal muscle function as well as symptomatic HF.

Controversies and Conundrums in Cardiac Cachexia: Key Questions About Wasting in Patients With HFrEF

Cardiac cachexia is characterized by unintentional catabolic weight loss, decreased appetite, and inflammation and is common in patients with stage D (advanced) heart failure with reduced ejection fraction (HFrEF). Cardiac cachexia and related muscle-wasting syndromes are markers of, and a consequence of, the heart failure (HF) syndrome. Although many potential modalities for identifying cardiac cachexia exist, the optimal definition, diagnostic tools, and treatment options for cardiac cachexia remain unclear. Furthermore, it remains unclear whether attempts to reverse muscle wasting prior to advanced HF surgeries, such as left ventricular assist devices and heart transplantation, can improve outcomes. It is important that HF clinicians and dietitians are aware of the pathophysiology and mechanisms of muscle-wasting syndromes in patients with HF, to aid in the recognition and risk stratification of advanced HFrEF. Although the opportunities and rationale for attempting to address cardiac cachexia prior to advanced HF surgeries are uncertain, recent publications suggest that control of the neurohumoral syndrome of advanced HF may be important to permit the recovery of skeletal muscle mass.

Skeletal muscle architecture and aging: A comparison of ultrasound techniques and an assessment of intrarater reliability

OBJECTIVE

To assess intrarater reliability of ultrasound-determined measurements of skeletal muscle characteristics across different measurement outcomes, imaging techniques, and age groups.

METHODS

2D ultrasound images (B-mode) of the quadriceps were obtained from young (26 ± 4 year, n = 8 M, 8 F) and older (70 ± 7 year, n = 7 M, 5 F) adults on two occasions, separated by 6 ± 3 days. With participants in both standing and supine postures, images were collected from five anatomical sites along the anterior (two sites) and lateral (three sites) compartments of the thigh corresponding to 56%, 39%, and 22% (lateral only) of femur length. Images were analysed for muscle thickness, pennation angle, and echogenicity. Intraclass correlation coefficients (ICC) were used to assess reliability.

RESULTS

Muscle thickness values were higher (p < 0.05) on images collected in the stand versus supine posture only for muscles of the anterior compartment, independent of age. Echogenicity values were higher (p < 0.05) in the vastus intermedius on images collected in the supine versus stand posture only in older adults. Pennation angle values were not impacted by imaging posture (p > 0.05). ICC values for thickness, echogenicity, and pennation angle were generally higher for analyses conducted on images collected in the supine versus stand posture. Imaging posture generated a greater difference in ICC values in the lateral versus anterior muscles and in older versus younger participants.

CONCLUSION

Our findings suggest that participant posture during imaging impacts the absolute values and intrarater reliability of ultrasound-determined muscle characteristics in a muscle-specific fashion, and this effect is greater in older compared to younger individuals.

Relationship between quadriceps femoris echotexture biomarkers and muscle strength and physical function in older adults with heart failure with preserved ejection fraction

BACKGROUND

Muscle wasting is pronounced in patients with heart failure with preserved ejection fraction (HFpEF). The quadriceps femoris echotexture biomarkers assessed by ultrasound (US) have not been studied in these patients.

OBJECTIVE

To describe echotexture biomarkers assessed by the US and to assess their relationship with sex, age, body mass index (BMI), self-reported outcomes, muscle strength and physical function in older adults with HFpEF.

METHODS

A cross-sectional study was conducted. Patients 70 years and older with HFpEF were included. The sex, age, BMI, and self-reported outcomes were collected. The US assessed muscle and subcutaneous fat tissue contrast, correlation, energy, homogeneity, and entropy at rest and maximal voluntary isometrical contraction (MVIC). The six-minute walk test (6MWT), the short physical performance battery (SPPB), the timed up and go test (TUG), the usual pace gait speed test (UGS), and the fast pace gait speed test (FGS) were used to assess physical function. The five-repetitions sit-to-stand test (5-STS) was performed to assess muscle strength. Bivariant Pearson correlations and subsequent multivariate linear regression analyses were conducted.

RESULTS

Seventy-two older adults with HFpEF [81.06 years, 29.13 BMI, and 55.60% females] were recruited. In women, relaxed and MVIC muscle energy and entropy explained 35.40% of the TUG variance; relaxed muscle entropy and MVIC muscle energy shared 24.00% of the UGS variance; relaxed and MVIC muscle entropy, MVIC muscle contrast and MVIC muscle energy explained 32.60% of the FGS variance, adjusted all the models by age and BMI.

CONCLUSIONS

Echotexture biomarkers are related to women's muscle strength and physical function, especially muscle energy, contrast, and entropy. Echotexture biomarkers assessed by the US could facilitate the management of older adults with HFpEF, monitor its progression and assess the effectiveness of treatments on the musculoskeletal structure.

TRIAL REGISTRATION

NCT03909919. April 10, 2019. Retrospectively registered.

Impact of Changes in Rectus Femoris Cross-Sectional Area Measured by Ultrasound on the Prognosis of Patients With Acute Heart Failure

BACKGROUND

Low muscle mass in patients with acute heart failure (AHF) is associated with poor prognosis; however, this is based on a single baseline measurement, with little information on changes in muscle mass during hospitalization and their clinical implications. This study investigated the relationship between changes in rectus femoris cross-sectional area (RFCSA) on ultrasound and the prognosis of patients with AHF.

METHODS AND RESULTS

This is a retrospective evaluation of 284 AHF patients (mean [±SD] age 79.1±11.9 years; 116 female). RFCSA assessments at admission (pre-RFCSA), ∆RFCSA (i.e., the percentage change in RFCSA from admission to 2 weeks), and composite prognosis (all-cause death and heart failure-related readmission) within 1 year were determined. Patients were divided into 4 groups according to their median pre-RFCSA and ∆RFCSA after sex stratification: Group A, higher pre-RFCSA/better ∆RFCSA; Group B, higher pre-RFCSA/worse ∆RFCSA; Group C, lower pre-RFCSA/better ∆RFCSA; Group D, lower pre-RFCSA/worse ∆RFCSA. In the Cox regression analysis, with Group A as the reference, the cumulative event rate of Group C (hazard ratio [HR] 3.39; 95% confidence interval [CI] 0.71-16.09; P=0.124) did not differ significantly; however, the cumulative event rates of Group B (HR 7.93; 95% CI 1.99-31.60; P=0.003) and Group D (HR 9.24; 95% CI 2.57-33.26; P<0.001) were significantly higher.

CONCLUSIONS

∆RFCSA during hospitalization is useful for risk assessment of prognosis in patients with AHF.

Skeletal Muscle Quality Assessment in Patients With Cardiac Disease Associated With Type 2 Diabetes Mellitus: A Pilot Study

Background Type 2 diabetes mellitus (T2DM) is associated with changes in skeletal muscle quantity and quality, such as increased ectopic fat. Cardiac rehabilitation (CR) aims to improve the exercise capacity and muscle strength. This study aimed to determine the relationship between qualitative changes in the skeletal muscles and exercise function in patients with and without diabetes mellitus. Methods The study included patients with cardiovascular diseases who entered CR. Of 72 CR patients (68.1±9.0 years) who underwent a cardiopulmonary exercise test and skeletal muscle assessment at discharge, 15 patients with T2DM and 15 without DM were selected using propensity score matching by age and gender. Results No significant differences in the skeletal muscle echo intensity (EI) (T2DM: 58.4, Non-DM: 53.4, p=0.32), skeletal muscle index (T2DM: 7.5 kg/m2, Non-DM: 7.2 kg/m2, p=0.36), or the weight-bearing index (WBI)(T2DM: 0.44, Non-DM: 0.50, p=0.35) existed between the two groups. The phase angle (PhA) (T2DM: 3.67°, Non-DM: 4.49°, p<0.05) and peak oxygen uptake (T2DM: 12.3 mL/kg/min, Non-DM: 14.8 mL/kg/min, p<0.05) were significantly lower in the T2DM group. PhA values showed a significant correlation with the WBI, a parameter of lower limb muscle strength (r=0.50, p<0.05). Conclusion The coexistence of cardiovascular disease and T2DM resulted in a decrease in the PhA, indicating a qualitative decrease in skeletal muscle mass. The PhA is also associated with lower limb muscle strength.

Therapeutic application of natural compounds for skeletal muscle-associated metabolic disorders: A review on diabetes perspective

Skeletal muscle (SM) plays a vital role in energy and glucose metabolism by regulating insulin sensitivity, glucose uptake, and blood glucose homeostasis. Impaired SM metabolism is strongly linked to several diseases, particularly type 2 diabetes (T2D). Insulin resistance in SM may result from the impaired activities of insulin receptor tyrosine kinase, insulin receptor substrate 1, phosphoinositide 3-kinase, and AKT pathways. This review briefly discusses SM myogenesis and the critical roles that SM plays in insulin resistance and T2D. The pharmacological targets of T2D which are associated with SM metabolism, such as DPP4, PTB1B, SGLT, PPARγ, and GLP-1R, and their potential modulators/inhibitors, especially natural compounds, are discussed in detail. This review highlights the significance of SM in metabolic disorders and the therapeutic potential of natural compounds in targeting SM-associated T2D targets. It may provide novel insights for the future development of anti-diabetic drug therapies. We believe that scientists working on T2D therapies will benefit from this review by enhancing their knowledge and updating their understanding of the subject.

Relationship between quadriceps femoris muscle architecture and muscle strength and physical function in older adults with heart failure with preserved ejection fraction

Heart failure (HF)-related factors potentially lead to sarcopenia. Ultrasound (US) assessment has all the advantages of being used in clinical practice to assess muscle architecture. This study aimed to assess the relationship between the quadriceps femoris (QF) muscle architecture with the gender, age, body mass index (BMI), muscle strength and physical function in older adults with HF with preserved ejection fraction (HFpEF) as well as to assess the difference in these relationships between the two genders. Patients 70 years and older with HFpEF were included. The gender, age and BMI were collected. The QF muscle thickness, the QF muscle echo-intensity, the subcutaneous fat tissue thickness (FT) and the subcutaneous fat tissue echo-intensity were assessed by the US. The six-minute walk test, the short physical performance battery (SPPB), the timed up and go test (TUG), and the gait speed test (UGS) were used to assess physical function. The five-repetitions sit-to-stand test (5-STS) was performed to assess muscle strength. Bivariant Pearson correlations and subsequent multivariate linear regression analysis were conducted. Seventy older adults with HFpEF [81.00 (5.97) years] were recruited. The FT showed a correlation between poor and moderate muscle strength and physical function in women with HFpEF. The FT explained 24.5% of the 5-STS variance, 32.4% of the SPPB variance, 31.5% of the TUG variance, 28.6% of the UGS variance, and 21.4% of the FGS variance in women. The US assessment could allow clinicians to assess muscle architecture biomarkers related to muscle strength and physical function in older adults with HFpEF.Trial registration NCT03909919. April 10, 2019. Retrospectively registered.

The current use of ultrasound to measure skeletal muscle and its ability to predict clinical outcomes: a systematic review

Quantification and monitoring of lean body mass is an important component of nutrition assessment to determine nutrition status and muscle loss. The negative impact of reduced muscle mass and muscle function is increasingly evident across acute and chronic disease states but is particularly pronounced in patients with cancer. Ultrasound is emerging as a promising tool to directly measure skeletal muscle mass and quality. Unlike other ionizing imaging techniques, ultrasound can be used repeatedly at the bedside and may compliment nutritional risk assessment. This review aims to describe the current use of skeletal muscle ultrasound (SMUS) to measure muscle mass and quality in patients with acute and chronic clinical conditions and its ability to predict functional capacity, severity of malnutrition, hospital admission, and survival. Databases were searched from their inception to August 2021 for full-text articles in English. Relevant articles were included if SMUS was investigated in acute or chronic clinical contexts and correlated with a defined clinical outcome measure. Data were synthesized for narrative review due to heterogeneity between studies. This review analysed 37 studies (3100 patients), which met the inclusion criteria. Most studies (n = 22) were conducted in critical care. The clinical outcomes investigated included functional status at discharge (intensive care unit-acquired weakness), nutritional status, and length of stay. SMUS was also utilized in chronic conditions such as chronic obstructive pulmonary disease, chronic heart failure, and chronic renal failure to predict hospital readmission and disease severity. Only two studies investigated the use of SMUS in patients with cancer. Of the 37 studies, 28 (76%) found that SMUS (cross-sectional area, muscle thickness, and echointensity) showed significant associations with functional capacity, length of stay, readmission, and survival. There was significant heterogeneity in terms of ultrasound technique and outcome measurement across the included studies. This review highlights that SMUS continues to gain momentum as a potential tool for skeletal muscle assessment and predicting clinically important outcomes. Further work is required to standardize the technique in nutritionally vulnerable patients, such as those with cancer, before SMUS can be widely adopted as a bedside prognostic tool.

Biomarkers and the quadriceps femoris muscle architecture assessed by ultrasound in older adults with heart failure with preserved ejection fraction: a cross-sectional study

BACKGROUND

Sarcopenia is an important comorbidity in patients with heart failure with preserved ejection fraction (HFpEF). The ultrasound (US) assessment has all the advantages of being used in primary care to assess muscle quantity and quality. Some biomarkers could be indicative of muscle mass loss.

AIMS

To describe the quantitative and qualitative characteristics of the quadriceps femoris assessed by US in older adults with HFpEF and to assess the relationship of the blood and urinary biomarkers, the polypharmacy and comorbidities with US outcomes in older adults with HFpEF.

METHODS

A cross-sectional study was conducted. 76 older adults with HFpEF were included. The quadriceps femoris muscle thickness (MT, cm), the subcutaneous fat tissue thickness (FT, cm), the muscle echo intensity (MEI) and the subcutaneous fat tissue echo intensity (FEI) were assessed by US in a non-contraction (non-con) and contraction (con) situations. Polypharmacy, comorbidities, blood and urine biomarkers were also collected.

RESULTS

The carbohydrate antigen 125 (CA-125), the folic acid and the urine creatinine shared the 86.6% variance in the non-con MT, adjusted by age, sex and body mass index (BMI). The folic acid shared the 38.5% of the variance in the con MT, adjusted by age, sex and BMI. The glycosylated haemoglobin explained the 39.6% variance in the non-con MEI, adjusted by age, sex and BMI. The chlorine (Cl-) explained the 40.2% of the variance in the non-con FT, adjusted by age, sex and BMI. The polypharmacy and the folic acid explained the 37.9% of variance in the non-con FEI, while the polypharmacy and the thyrotropin (TSH) shared the 44.4% of variance in the con FEI, both adjusted by age, sex and BMI. No comorbidities, polypharmacy, or blood and urinary biomarkers could explain the con MEI and the con FT variance.

CONCLUSIONS

Blood and urinary biomarkers obtained in routine analyses could help clinicians detect US outcome changes in older adults with HFpEF and identify a worsening of sarcopenia.

TRIAL REGISTRATION

NCT03909919. April 10, 2019. Retrospectively registered.

Association of muscle mass and quality with hand grip strength in elderly patients with heart failure

In patients with heart failure, it is unknown whether the extracellular water (ECW)/intracellular water (ICW) ratio is associated with muscle strength, and thus, it is not well understood whether poor muscle quality contributes to muscular weakness. This study examined the relationship among hand grip strength, skeletal muscle mass index (SMI), and upper limb ECW/ICW ratio in patients with heart failure. This study followed a cross-sectional design. Demographic data, medical information, and hand grip strength were collected. The SMI and ECW/ICW ratio were measured using bio-impedance analysis (BIA). Hierarchical multiple regression analysis was conducted to identify factors associated with hand grip strength. 51 patients with heart failure were analyzed for this study (mean age 84.58 ± 7.18). Hierarchical multiple regression analysis identified SMI as well as upper limb ECW/ICW ratio as factors associated with hand grip strength, independent of age, sex, body mass index, and Life Space Assessment scores. Standardized partial regression coefficients representing the magnitude of involvement of each independent variable were 0.33 and - 0.16. The coefficient of determination adjusted for degrees of freedom (R²), representing the contribution rate of the regression equation, was 0.830. We revealed that loss of hand grip strength in patients with heart failure is associated with not only with a decrease in skeletal muscle mass, but also with a decline in muscle quality, characterized by an increased upper limb ECW/ICW ratio. BIA is a simple and useful method to measure the ECW/ICW ratio, and in turn, the muscle quality, in patients with heart failure.

Muscle-Skeletal Abnormalities and Muscle Oxygenation during Isokinetic Strength Exercise in Heart Failure with Preserved Ejection Fraction Phenotype: A Cross-Sectional Study

Exercise intolerance, a hallmark of patients with heart failure (HF), is associated with muscle weakness. However, its causative microcirculatory and muscle characteristics among those with preserved or reduced ejection fraction (HFpEF or HFrEF) phenotype is unclear. The musculoskeletal abnormalities that could result in impaired peripheral microcirculation are sarcopenia and muscle strength reduction in HF, implying lowered oxidative capacity and perfusion affect transport and oxygen utilization during exercise, an essential task from the microvascular muscle function. Besides that, skeletal muscle microcirculatory abnormalities have also been associated with exercise intolerance in HF patients who also present skeletal muscle myopathy. This cross-sectional study aimed to compare the muscle microcirculation dynamics via near-infrared spectroscopy (NIRS) response during an isokinetic muscle strength test and ultrasound-derived parameters (echo intensity was rectus femoris muscle, while the muscle thickness parameter was measured on rectus femoris and quadriceps femoris) in heart failure patients with HFpEF and HFrEF phenotypes and different functional severities (Weber Class A, B, and C). Twenty-eight aged-matched patients with HFpEF (n = 16) and HFrEF (n = 12) were assessed. We found phenotype differences among those with Weber C severity, with HFrEF patients reaching lower oxyhemoglobin (O₂Hb, μM) (−10.9 ± 3.8 vs. −23.7 ± 5.7, p = 0.029) during exercise, while HFpEF reached lower O₂Hb during the recovery period (−3.0 ± 3.4 vs. 5.9 ± 2.8, p = 0.007). HFpEF with Weber Class C also presented a higher echo intensity than HFrEF patients (29.7 ± 8.4 vs. 15.1 ± 6.8, p = 0.017) among the ultrasound-derived variables. Our preliminary study revealed more pronounced impairments in local microcirculatory dynamics in HFpEF vs. HFrEF patients during a muscle strength exercise, combined with muscle-skeletal abnormalities detected via ultrasound imaging, which may help explain the commonly observed exercise intolerance in HFpEF patients.

Longitudinal relationship between intramuscular adipose tissue of the quadriceps and activities of daily living in older inpatients

BACKGROUND

The longitudinal relationship between intramuscular adipose tissue of the quadriceps and activities of daily living (ADL) in older inpatients remains unclear. This study aimed to examine whether decrease of intramuscular adipose tissue of the quadriceps in older inpatients is related to the recovery of ADL than increase of muscle mass.

METHODS

This longitudinal study included 202 inpatients aged ≥65 years [median age: 83.0 (77.0-88.0), 56.4% female]. Recovery of ADL during hospital stay was assessed using the change in Barthel index (BI) score (i.e. BI score at discharge minus BI score at admission) and BI score at discharge. Intramuscular adipose tissue and muscle mass of the quadriceps were assessed using echo intensity and muscle thickness on ultrasound images, respectively. Higher echo intensity indicates greater intramuscular adipose tissue. Multiple regression analysis was performed to identify the factors independently associated with the change in BI score and BI score at discharge. Changes in quadriceps echo intensity and thickness and subcutaneous fat thickness of the thigh, quadriceps echo intensity and thickness, and subcutaneous fat thickness of the thigh at admission, age, sex, days from onset disease, BI score at admission, and disease were set as independent variables.

RESULTS

The means of the change in quadriceps echo intensity and thickness were -2.3 ± 15.7 and 0.1 ± 0.4 cm, respectively. The median of the change in BI score was 15.0 (0.0-30.0). The quadriceps echo intensity at discharge was significantly lower than at admission (P = 0.043). The quadriceps thickness (P = 0.004) and BI score at discharge (P < 0.001) were significantly higher than those at admission. Change in quadriceps echo intensity was independently and significantly associated with the change in BI score (β = -0.25, P = 0.006) and BI score at discharge (β = -0.18, P = 0.006). In contrast, change in quadriceps thickness was not independently and significantly associated with the change in BI score (β = 0.09, P = 0.244) and BI score at discharge (β = 0.06, P = 0.244).

CONCLUSIONS

Our study indicates that a decrease of intramuscular adipose tissue of the quadriceps is related to the recovery of ADL than an increase of muscle mass in older inpatients. Intramuscular adipose tissue of the quadriceps in older inpatients is considered to be a predictor for the recovery of ADL, and intervening for intramuscular adipose tissue may be important for improving ADL in older inpatients.

Abnormalities of Skeletal Muscle, Adipocyte Tissue, and Lipid Metabolism in Heart Failure: Practical Therapeutic Targets

Chronic diseases, including heart failure (HF), are often accompanied with skeletal muscle abnormalities in both quality and quantity, which are the major cause of impairment of the activities of daily living and quality of life. We have shown that skeletal muscle abnormalities are a hallmark of HF, in which metabolic pathways involving phosphocreatine and fatty acids are largely affected. Not only in HF, but the dysfunction of fatty acid metabolism may also occur in many chronic diseases, such as arteriosclerosis, as well as through insufficient physical exercise. Decreased fatty acid catabolism affects adenosine triphosphate (ATP) production in mitochondria, via decreased activity of the tricarboxylic acid cycle; and may cause abnormal accumulation of adipose tissue accompanied with hyperoxidation and ectopic lipid deposition. Such impairments of lipid metabolism are in turn detrimental to skeletal muscle, which is hence a chicken-and-egg problem between skeletal muscle and HF. In this review, we first discuss skeletal muscle abnormalities in HF, including sarcopenia; particularly their association with lipid metabolism and adipose tissue. On the other hand, the precise mechanisms involved in metabolic reprogramming and dysfunction are beginning to be understood, and an imbalance of daily nutritional intake of individuals has been found to be a causative factor for the development and worsening of HF. Physical exercise has long been known to be beneficial for the prevention and even treatment of HF. Again, the molecular mechanisms by which exercise promotes skeletal muscle as well as cardiac muscle functions are being clarified by recent studies. We propose that it is now the time to develop more “natural” methods to prevent and treat HF, rather than merely relying on drugs and medical interventions. Further analysis of the basic design of and molecular mechanisms involved in the human body, particularly the inextricable association between physical exercise and the integrity and functional plasticity of skeletal and cardiac muscles is required.

Angiotensin-converting-enzyme inhibitor prevents skeletal muscle fibrosis in myocardial infarction mice

BACKGROUND

Transforming growth factor beta (TGF-β)-Smad2/3 is the major signaling pathway of fibrosis, which is characterized by the excessive production and accumulation of extracellular matrix (ECM) components, including collagen. Although the ECM is an essential component of skeletal muscle, fibrosis may be harmful to muscle function. On the other hand, our previous studies have shown that levels of angiotensin II, which acts upstream of TGF-β-Smad2/3 signaling, is increased in mice with myocardial infarction (MI). In this study, we found higher skeletal muscle fibrosis in MI mice compared with control mice, and we investigated the mechanisms involved therein. Moreover, we administered an inhibitor based on the above mechanism and investigated its preventive effects on skeletal muscle fibrosis.

METHODS

Male C57BL/6 J mice with MI were created, and sham-operated mice were used as controls. The time course of skeletal muscle fibrosis post-MI was analyzed by picrosirius-red staining (days 1, 3, 7, and 14). Mice were then divided into 3 groups: sham + vehicle (Sham + Veh), MI + Veh, and MI + lisinopril (an angiotensin-converting enzyme [ACE] inhibitor, 20 mg/kg body weight/day in drinking water; MI + Lis). Lis or Veh was administered from immediately after the surgery to 14 days postsurgery.

RESULTS

Skeletal muscle fibrosis was significantly increased in MI mice compared with sham mice from 3 to 14 days postsurgery. Although mortality was lower in the MI + Lis mice than the MI + Veh mice, there was no difference in cardiac function between the 2 groups at 14 days. Skeletal muscle fibrosis and hydroxyproline (a key marker of collagen content) were significantly increased in MI + Veh mice compared with the Sham + Veh mice. Consistent with these results, protein expression of TGF-β and phosphorylated Smad2/3 in the skeletal muscle during the early time points after surgery (days 1-7 postsurgery) and blood angiotensin II at 14 days postsurgery was increased in MI mice compared with sham mice. These impairments were improved in MI + Lis mice, without any effects on spontaneous physical activity, muscle strength, muscle weight, and blood pressure.

CONCLUSIONS

ACE inhibitor administration prevents increased skeletal muscle fibrosis during the early phase after MI. Our findings indicate a new therapeutic target for ameliorating skeletal muscle abnormalities in heart diseases.