Long-Term Efficacy of T3 Analogue Triac in Children and Adults With MCT8 Deficiency: A Real-Life Retrospective Cohort Study

CONTEXT

Patients with mutations in thyroid hormone transporter MCT8 have developmental delay and chronic thyrotoxicosis associated with being underweight and having cardiovascular dysfunction.

OBJECTIVE

Our previous trial showed improvement of key clinical and biochemical features during 1-year treatment with the T3 analogue Triac, but long-term follow-up data are needed.

METHODS

In this real-life retrospective cohort study, we investigated the efficacy of Triac in MCT8-deficient patients in 33 sites. The primary endpoint was change in serum T3 concentrations from baseline to last available measurement. Secondary endpoints were changes in other thyroid parameters, anthropometric parameters, heart rate, and biochemical markers of thyroid hormone action.

RESULTS

From October 15, 2014 to January 1, 2021, 67 patients (median baseline age 4.6 years; range, 0.5-66) were treated up to 6 years (median 2.2 years; range, 0.2-6.2). Mean T3 concentrations decreased from 4.58 (SD 1.11) to 1.66 (0.69) nmol/L (mean decrease 2.92 nmol/L; 95% CI, 2.61-3.23; P < 0.0001; target 1.4-2.5 nmol/L). Body-weight-for-age exceeded that of untreated historical controls (mean difference 0.72 SD; 95% CI, 0.36-1.09; P = 0.0002). Heart-rate-for-age decreased (mean difference 0.64 SD; 95% CI, 0.29-0.98; P = 0.0005). SHBG concentrations decreased from 245 (99) to 209 (92) nmol/L (mean decrease 36 nmol/L; 95% CI, 16-57; P = 0.0008). Mean creatinine concentrations increased from 32 (11) to 39 (13) µmol/L (mean increase 7 µmol/L; 95% CI, 6-9; P < 0.0001). Mean creatine kinase concentrations did not significantly change. No drug-related severe adverse events were reported.

CONCLUSIONS

Key features were sustainably alleviated in patients with MCT8 deficiency across all ages, highlighting the real-life potential of Triac for MCT8 deficiency.

Measurement of Reverse Triiodothyronine Level and the Triiodothyronine to Reverse Triiodothyronine Ratio in Dried Blood Spot Samples at Birth May Facilitate Early Detection of Monocarboxylate Transporter 8 Deficiency

Background: Monocarboxylate transporter 8 (MCT8) deficiency is an X-chromosome-linked neurodevelopmental disorder resulting from impaired thyroid hormone transport across the cell membrane. The diagnosis of MCT8 deficiency is typically delayed owing to the late appearance of signs and symptoms as well as the inability of standard biomarkers of neonatal screening to provide early detection. In this study, we report, for the first time, the ability to detect MCT8 deficiency at birth using dried blood spot (DBS) samples. Methods: We retrospectively measured triiodothyronine (T3), thyroxine (T4), and reverse T3 (rT3) levels in DBS samples obtained at 4-5 days of life from 6 infants with genetically confirmed MCT8 deficiency and from 110 controls. The latter consisted of 58 healthy term neonates obtained at the same time, 16 were stored for more than 1 year before measurement to match samples from the MCT8-deficient infants. Ten DBS samples were collected at day 1 of life and 42 samples were from prematurely born neonates. Measurements were carried out in extract from eight millimeters diameter DBS using liquid chromatography-tandem mass spectrometry. Results: Contrary to characteristic iodothyronine abnormalities of MCT8 deficiency during later life, T3 and T4 values were not discriminatory from those of other study groups. In contrast, rT3 was significantly lower. The T3/rT3 ratio was higher in the DBS samples from the MCT8-deficient infants compared with all other groups with no overlap (p < 0.0001). Conclusions: rT3 and T3/rT3 ratio in DBS samples obtained from neonates can serve as biomarkers to detect MCT8 deficiency at birth.

Sustained Systemic Levels of IL-6 Impinge Early Muscle Growth and Induce Muscle Atrophy and Wasting in Adulthood

IL-6 is a pleiotropic cytokine that can exert different and opposite effects. The muscle-induced and transient expression of IL-6 can act in an autocrine or paracrine manner, stimulating anabolic pathways associated with muscle growth, myogenesis, and with regulation of energy metabolism. In contrast, under pathologic conditions, including muscular dystrophy, cancer associated cachexia, aging, chronic inflammatory diseases, and other pathologies, the plasma levels of IL-6 significantly increase, promoting muscle wasting. Nevertheless, the specific physio-pathological role exerted by IL-6 in the maintenance of differentiated phenotype remains to be addressed. The purpose of this study was to define the role of increased plasma levels of IL-6 on muscle homeostasis and the mechanisms contributing to muscle loss. Here, we reported that increased plasma levels of IL-6 promote alteration in muscle growth at early stage of postnatal life and induce muscle wasting by triggering a shift of the slow-twitch fibers toward a more sensitive fast fiber phenotype. These findings unveil a role for IL-6 as a potential biomarker of stunted growth and skeletal muscle wasting.

MOTS-c reduces myostatin and muscle atrophy signaling

Obesity and type 2 diabetes are metabolic diseases, often associated with sarcopenia and muscle dysfunction. MOTS-c, a mitochondrial-derived peptide, acts as a systemic hormone and has been implicated in metabolic homeostasis. Although MOTS-c improves insulin sensitivity in skeletal muscle, whether MOTS-c impacts muscle atrophy is not known. Myostatin is a negative regulator of skeletal muscle mass and also one of the possible mediators of insulin resistance-induced skeletal muscle wasting. Interestingly, we found that plasma MOTS-c levels are inversely correlated with myostatin levels in human subjects. We further demonstrated that MOTS-c prevents palmitic acid-induced atrophy in differentiated C2C12 myotubes, whereas MOTS-c administration decreased myostatin levels in plasma in diet-induced obese mice. By elevating AKT phosphorylation, MOTS-c inhibits the activity of an upstream transcription factor for myostatin and other muscle wasting genes, FOXO1. MOTS-c increases mTORC2 and inhibits PTEN activity, which modulates AKT phosphorylation. Further upstream, MOTS-c increases CK2 activity, which leads to PTEN inhibition. These results suggest that through inhibition of myostatin, MOTS-c could be a potential therapy for insulin resistance-induced skeletal muscle atrophy as well as other muscle wasting phenotypes including sarcopenia.NEW & NOTEWORTHY MOTS-c, a mitochondrial-derived peptide reduces high-fat-diet-induced muscle atrophy signaling by reducing myostatin expression. The CK2-PTEN-mTORC2-AKT-FOXO1 pathways play key roles in MOTS-c action on myostatin expression.

Distinct determinants of muscle wasting in nonobese heart failure patients with and without type 2 diabetes mellitus

BACKGROUND

Muscle wasting, that is, reduction in muscle mass, is frequently observed in patients with chronic heart failure (CHF) and diabetes mellitus (DM).

METHODS

We retrospectively examined 185 patients with CHF (median age of 71 years [interquartile range, 61-78 years]; 64% male) who received a dual-energy X-ray absorptiometry scan for assessment of appendicular skeletal muscle mass index (ASMI).

RESULTS

Seventy patients with CHF (38%) had DM. Patients with DM had higher prevalences of ischemic heart disease and hypertension, lower levels of estimated glomerular filtration rate (eGFR) and ASMI, and higher levels of plasma renin activity (PRA) than did patients without DM. In simple regression analyses, ASMI was positively correlated with the Mini Nutritional Assessment Short Form (MNA-SF) score and levels of hemoglobin, eGFR, and fasting plasma insulin and was negatively correlated with levels of N-terminal pro B-type natriuretic peptide, PRA, and cortisol. In multiple linear regression analyses, age, MNA-SF score, DM, fasting plasma insulin level, and PRA were independently associated with ASMI. When multiple linear regression analyses were separately performed in a non-DM group and a DM group, MNA-SF score and fasting plasma insulin level were independent variables for ASMI in both groups. PRA was independently associated with ASMI in the DM group but not in the non-DM group, whereas cortisol concentration was independently associated with ASMI only in the non-DM group.

CONCLUSIONS

In addition to malnutrition and reduction in plasma insulin, renin-angiotensin system activation may be responsible for the development of muscle wasting in CHF patients with DM.

Generation of reporter cell lines for factors inducing muscle wasting in cancer cachexia

Rapidly identifying cachexia-inducing factors that directly induce muscle wasting is an existing challenge. We developed two reporter cell lines that allow swift detection of such factors in blood from patients. C2C12 myoblasts were used for the establishment of reporter cells. A luciferase reporter gene, driven by promoters of wasting genes, Muscle RING-finger protein-1 (MuRF1) and Muscle Atrophy F-Box Protein (MAFbx/Atrogin-1) were used for the construction of reporter constructs. Increased expression of these genes in muscle tissue under wasting conditions was shown in vivo and in vitro. We found these reporter cell lines could detect factors associated with cancer cachexia, such as myostatin (Mstn), activin A, and TNF-α. We further investigated the capacity to directly detect a cachectic state using plasma samples from cachectic mice and cancer patients. Activation of the reporter cell lines was observed by the addition of plasma from mice with cancer cachexia and serum samples from patients with pancreatic or colorectal cancer. These results indicate that the reporter cell lines are competent as a tool for screening cachexia-inducing factors and potentially distinguishing a cachectic state induced by cancer.

Sorting Variants of Unknown Significance Identified by Whole Exome Sequencing: Genetic and Laboratory Investigations of Two Novel MCT8 Variants

Mutations in the cell membrane thyroid hormone (TH) transporter monocarboxylate transporter (MCT) 8 produce severe neuropsychomotor defects and characteristic thyroid function test (TFT) abnormalities. Two children with mild neurological phenotypes and normal TFTs were found to harbor MCT8 gene variants of unknown significance (VUS), MCT8-R388Q that occurred de novo, and MCT8-Q212E. Normal TH transport and action in fibroblasts of MCT8-R388Q was demonstrated in a novel nonradioactive functional assay measuring the intracellular TH availability after L-T3 treatment. No genotype-phenotype correlation was found in additional family members carrying MCT8-Q212E. For the field of MCT8 deficiency, it is important to assess the significance of MCT8 gene VUS.

Significance of serum Myostatin in hemodialysis patients

BACKGROUND

Malnutrition and muscle wasting are common in haemodialysis (HD) patients. Their pathogenesis is complex and involves many molecules including Myostatin (Mstn), which acts as a negative regulator of skeletal muscle. The characterisation of Mstn as a biomarker of malnutrition could be useful in the prevention and management of this condition. Previous studies have reported no conclusive results on the actual relationship between serum Mstn and wasting and malnutrition. So, in this study, we evaluated Mstn profile in a cohort of regular HD patients.

METHODS

We performed a cross-sectional study, enrolling 37 patients undergoing bicarbonate-HD (BHD) or haemodiafiltration (HDF) at least for six months. 20 sex-matched healthy subjects comprised the control group. Mstn serum levels were evaluated by ELISA before and after HD. We collected clinical and biochemical data, evaluated insulin resistance, body composition, malnutrition [by Malnutrition Inflammation Score (MIS)] and tested muscle function (by hand-grip strength, six-minute walking test and a questionnaire on fatigue).

RESULTS

Mstn levels were not significantly different between HD patients and controls (4.7 ± 2.8 vs 4.5 ± 1.3 ng/ml). In addition, while a decrease in Mstn was observed after HD treatment, there were no differences between BHD and HDF. In whole group of HD patients Mstn was positively correlated with muscle mass (r = 0.82, p < 0.001) and inversely correlated with age (r = - 0.63, p < 0.01) and MIS (r = - 0.39, p = 0.01). No correlations were found between Mstn and insulin resistance, such as between Mstn levels and parameters of muscle strength and fatigue. In multivariate analysis, Mstn resulted inversely correlated with fat body content (β = - 1.055, p = 0.002).

CONCLUSIONS

Circulating Mstn is related to muscle mass and nutritional status in HD patients, suggesting that it may have a role in the regulation of skeletal muscle and metabolic processes. However, also considering the lack of difference of serum Mstn between healthy controls and HD patients and the absence of correlations with muscle function tests, our findings do not support the use of circulating Mstn as a biomarker of muscle wasting and malnutrition in HD.

Exploration of muscle loss and metabolic state during prolonged critical illness: Implications for intervention?

Background

Muscle wasting in the critically ill is up to 2% per day and delays patient recovery and rehabilitation. It is linked to inflammation, organ failure and severity of illness. The aims of this study were to understand the relationship between muscle depth loss, and nutritional and inflammatory markers during prolonged critical illness. Secondly, to identify when during critical illness catabolism might decrease, such that targeted nutritional strategies may logically be initiated.

Methods

This study was conducted in adult intensive care units in two large teaching hospitals. Patients anticipated to be ventilated for >48 hours were included. Serum C-reactive protein (mg/L), urinary urea (mmol/24h), 3-methylhistidine (μmol/24h) and nitrogen balance (g/24h) were measured on days 1, 3, 7 and 14 of the study. Muscle depth (cm) on ultrasound were measured on the same days over the bicep (bicep and brachialis muscle), forearm (flexor compartment of muscle) and thigh (rectus femoris and vastus intermedius).

Results

Seventy-eight critically ill patients were included with mean age of 59 years (SD: 16) and median Intensive care unit (ICU) length of stay of 10 days (IQR: 6–16). Starting muscle depth, 8.5cm (SD: 3.2) to end muscle depth, 6.8cm (SD: 2.2) were on average significantly different over 14 days, with mean difference -1.67cm (95%CI: -2.3 to -1cm), p<0.0001. Protein breakdown and inflammation continued over 14 days of the study.

Conclusion

Our patients demonstrated a continuous muscle depth loss and negative nitrogen balance over the 14 days of the study. Catabolism remained dominant throughout the study period. No obvious ‘nutritional tipping point” to identify anabolism or recovery could be identified in our cohort. Our ICU patient cohort is one with a moderately prolonged stay. This group showed little consistency in data, reflecting the individuality of both disease and response. The data are consistent with a conclusion that a time based assumption of a tipping point does not exist.

Trial registration

International Standard Randomised Controlled Trial Number: ISRCTN79066838. Registration 25 July 2012.

FoxO Transcription Factors Are Critical Regulators of Diabetes-Related Muscle Atrophy

Insulin deficiency and uncontrolled diabetes lead to a catabolic state with decreased muscle strength, contributing to disease-related morbidity. FoxO transcription factors are suppressed by insulin and thus are key mediators of insulin action. To study their role in diabetic muscle wasting, we created mice with muscle-specific triple knockout of FoxO1/3/4 and induced diabetes in these M-FoxO-TKO mice with streptozotocin (STZ). Muscle mass and myofiber area were decreased 20-30% in STZ-Diabetes mice due to increased ubiquitin-proteasome degradation and autophagy alterations, characterized by increased LC3-containing vesicles, and elevated levels of phosphorylated ULK1 and LC3-II. Both the muscle loss and markers of increased degradation/autophagy were completely prevented in STZ FoxO-TKO mice. Transcriptomic analyses revealed FoxO-dependent increases in ubiquitin-mediated proteolysis pathways in STZ-Diabetes, including regulation of Fbxo32 (Atrogin1), Trim63 (MuRF1), Bnip3L, and Gabarapl. These same genes were increased 1.4- to 3.3-fold in muscle from humans with type 1 diabetes after short-term insulin deprivation. Thus, FoxO-regulated genes play a rate-limiting role in increased protein degradation and muscle atrophy in insulin-deficient diabetes.

Elevated serum Activin A in chronic obstructive pulmonary disease with skeletal muscle wasting

OBJECTIVE

Muscle wasting contributes to the reduced quality of life and increased mortality in chronic obstructive pulmonary disease (COPD). Muscle atrophy in mice with cachexia was caused by Activin A binding to ActRIIB. The role of circulating Activin A leading to muscle atrophy in COPD remains elusive.

METHODS

In the present study, we evaluated the relationship between serum levels of Activin A and skeletal muscle wasting in COPD patients. The expression levels of serum Activin A were measured in 78 stable COPD patients and in 60 healthy controls via ELISA, which was also used to determine the expression of circulating TNF-α levels. Total skeletal muscle mass (SMM) was calculated according to a validated formula by age and anthropometric measurements. The fat-free mass index (FFMI) was determined as the fat-free mass (FFM) corrected for body surface area.

RESULTS

Compared to the healthy controls, COPD patients had upregulated Activin A expression. The elevated levels of Activin A were correlated with TNF-α expression, while total SMM and FFMI were significantly decreased in COPD patients. Furthermore, serum Activin A expression in COPD patients was negatively associated with both FFMI and BMI.

CONCLUSION

The above results showed an association between increased circulating Activin A in COPD patients and the presence of muscle atrophy. Given our previous knowledge, we speculate that Activin A contributes to skeletal muscle wasting in COPD.

Is Iron Accumulation a Possible Risk Factor for Sarcopenia?

Sarcopenia has a high incidence among the elderly, with significant negative effects on the quality of life. The pathogenesis of sarcopenia is complex, and many factors are involved in its development and progression. Sarcopenia might be associated with iron accumulation given that (1) age-related iron accumulation was found in the skeletal muscle, (2) excess iron could cause skeletal muscle damage or atrophy, and (3) patients with sarcopenia showed higher levels of serum ferritin. Understanding the etiology and pathogenesis of sarcopenia would help to develop new treatment and preventive methods, thereby improving the quality of life of the elderly patients.

Poor Vitamin Status is Associated with Skeletal Muscle Loss and Mucositis in Head and Neck Cancer Patients

Mucositis and muscle wasting are two common toxicity effects of cancer treatment in head and neck cancer (HNC). There is limited data evaluating cancer treatment toxicities in relation to vitamin status. This study aimed to assess changes in vitamin status during HNC treatment in relation to body composition, inflammation and mucositis. In this prospective cohort study, dietary intakes (3-day food record), plasma levels of vitamins and C-reactive protein (CRP) were assessed at baseline (at diagnosis) and post-treatment (after 6–8 weeks of radiation therapy with or without chemotherapy). Computed tomography images were used to quantify body composition. Mucositis information was collected from health records of patients. Twenty-eight HNC patients (age 60 ± 10 years) completed both study time points. Patients who developed mucositis had significantly lower dietary intake of vitamins and plasma 25-hydroxy vitamin D (25-OHD) and all-trans retinol levels (p < 0.02). Patients lost a considerable amount of muscle mass (3.4 kg) and fat mass (3.6 kg) over the course of treatment. There was a trend toward greater muscle loss in patients with 25-OHD < 50 nmol/L compared to patients with 25-OHD ≥ 50 nmol/L (p = 0.07). A significant negative correlation was found between plasma all-trans retinol and CRP level at the end of treatment (p = 0.03). Poor vitamin status could be a contributing factor in developing treatment-induced toxicities.

Extracellular polysaccharides purified from Aureobasidium pullulans SM‑2001 (Polycan) inhibit dexamethasone‑induced muscle atrophy in mice

The present study assessed the beneficial skeletal muscle‑preserving effects of extracellular polysaccharides from Aureobasidium pullulans SM‑2001 (Polycan) (EAP) on dexamethasone (DEXA)‑induced catabolic muscle atrophy in mice. To investigate whether EAP prevented catabolic DEXA‑induced muscle atrophy, and to examine its mechanisms of action, EAP (100, 200 and 400 mg/kg) was administered orally, once a day for 24 days. EAP treatment was initiated 2 weeks prior to DEXA treatment (1 mg/kg, once a day for 10 days) in mice. Body weight alterations, serum biochemistry, calf thickness, calf muscle strength, gastrocnemius muscle thickness and weight, gastrocnemius muscle antioxidant defense parameters, gastrocnemius muscle mRNA expression, histology and histomorphometry were subsequently assessed. After 24 days, DEXA control mice exhibited muscle atrophy according to all criteria indices. However, these muscle atrophy symptoms were significantly inhibited by oral treatment with all three doses of EAP. Regarding possible mechanisms of action, EAP exhibited favorable ameliorating effects on DEXA‑induced catabolic muscle atrophy via antioxidant and anti‑inflammatory effects; these effects were mediated by modulation of the expression of genes involved in muscle protein synthesis (AKT serine/threonine kinase 1, phosphatidylinositol 3‑kinase, adenosine A1 receptor and transient receptor potential cation channel subfamily V member 4) and degradation (atrogin‑1, muscle RING‑finger protein‑1, myostatin and sirtuin 1). Therefore, these results indicated that EAP may be helpful in improving muscle atrophies of various etiologies. EAP at 400 mg/kg exhibited favorable muscle protective effects against DEXA‑induced catabolic muscle atrophy, comparable with the effects of oxymetholone (50 mg/kg), which has been used to treat various muscle disorders.

Inhibition of interleukin-6 decreases atrogene expression and ameliorates tail suspension-induced skeletal muscle atrophy

BACKGROUND

Interleukin-6 (IL-6) is an inflammatory cytokine. Whether systemic IL-6 affects atrogene expression and disuse-induced skeletal muscle atrophy is unclear.

METHODS

Tail-suspended mice were used as a disuse-induced muscle atrophy model. We administered anti-mouse IL-6 receptor antibody, beta-hydroxy-beta-methylbutyrate (HMB) and vitamin D to the mice and examined the effects on atrogene expression and muscle atrophy.

RESULTS

Serum IL-6 levels were elevated in the mice. Inhibition of IL-6 receptor suppressed muscle RING finger 1 (MuRF1) expression and prevented muscle atrophy. HMB and vitamin D inhibited the serum IL-6 surge, downregulated the expression of MuRF1 and atrogin-1 in the soleus muscle, and ameliorated atrophy in the mice.

CONCLUSION

Systemic IL-6 affects MuRF1 expression and disuse-induced muscle atrophy.

Melanocortin-4 receptor agonist (RO27-3225) ameliorates soleus but not gastrocnemius atrophy in arthritic rats

Adjuvant-induced arthritis in rats decreases body weight and muscle mass. Melanocyte stimulating hormone administration to arthritic rats decreases inflammation and skeletal muscle wasting. In this study, we investigate whether activation of melanocortin-4 receptor by RO27-3225 administration is able to prevent the effect of arthritis on the expression of muscle-specific E3 ubiquitin ligases and MyoD in two different muscles, gastrocnemius (a mainly fast type muscle) and soleus (slow type). Arthritis was induced in male Wistar rats by intradermal injection of Freund's adjuvant. Control and arthritic rats were injected with RO27-3225 (180 μg/kg i.p. twice a day) or saline, for 8 days. Body weight change, food intake and arthritis index were assessed daily. After sacrifice, serum insulin-like growth factor -1 (IGF-1) and corticosterone, as well as nuclear factor-κB(p65), cyclooxygenase-2 (COX-2), atrogene and MyoD in gastrocnemius and soleus were analysed. Administration of RO27-3225 to arthritic rats decreased arthritis scores, hind paw volume as well as nuclear factor-κB(p65) phosphorylation in gastrocnemius and soleus. However, RO27-3225 was not able to modify the effects of arthritis on serum IGF-1 and corticosterone. RO27-3225 ameliorates arthritis-induced decrease in food intake, body weight gain, epidydimal white adipose tissue and soleus weight, but not in gastrocnemius weight. Arthritis increased COX-2, atrogin-1 and MuRF1 expression in gastrocnemius and soleus, whereas RO27-3225 prevented this increase in soleus but not in gastrocnemius. Arthritis also increased MyoD expression in gastrocnemius and soleus (P < 0.01). RO27-3225 decreased MyoD expression in gastrocnemius but not in soleus of arthritic rats. In control rats RO27-3225 did not modify MyoD expression in gastrocnemius or soleus. In conclusion, our data suggest that in arthritic rats, RO27-3225 treatment decreases inflammation and muscle atrophy, preventing atrogene upregulation in slow type muscle but not in gastrocnemius. The lack of effect in the gastrocnemius can be related to the inability of RO27-3225 to prevent arthritis-induced corticosterone upregulation as well as IGF-1 downregulation.

Baicalin supplementation reduces serum biomarkers of skeletal muscle wasting and may protect against lean body mass reduction in cancer patients: Results from a pilot open-label study

OBJECTIVES

Muscle wasting in patients with cancer has been linked to an increased activity of nuclear factor κB (NF-κB) and higher circulating levels of activin-A (ActA), a negative growth factor for muscle mass. Baicalin is a natural flavonoid that can reduce skeletal muscle atrophy in animal models of cancer cachexia by inhibiting NF-κB. This pilot open-label study assessed the effects of baicalin supplementation (50 mg daily for 3 months) in cancer patients who showed involuntary weight loss >5% over the past 6 months.

METHODS

A total of 20 patients were investigated. Participants were evaluated at baseline and at the end of the 3-month study period for the following endpoints: 1) changes from baseline in serum NF-κB and ActA levels; and 2) change from baseline in lean body mass (LBM).

RESULTS

We observed significant reduction in both NF-κB (p<0.05) and ActA (p<0.05) serum levels from baseline to 3 months. At 3 months, patients also showed a significant mean increase in LBM (+0.8 kg, p<0.05 compared with baseline).

CONCLUSION

Our pilot open-label data suggest that baicalin supplementation is potentially useful for contrasting lean body mass reduction in cancer patients with involuntary weight loss, an effect which is likely mediated by the inhibition of negative growth factors for muscle mass.

Iron-induced skeletal muscle atrophy involves an Akt-forkhead box O3-E3 ubiquitin ligase-dependent pathway

Skeletal muscle wasting or sarcopenia is a critical health problem. Skeletal muscle atrophy is induced by an excess of iron, which is an essential trace metal for all living organisms. Excessive amounts of iron catalyze the formation of highly toxic hydroxyl radicals via the Fenton reaction. However, the molecular mechanism of iron-induced skeletal muscle atrophy has remained unclear. In this study, 8-weeks-old C57BL6/J mice were divided into 2 groups: vehicle-treated group and the iron-injected group (10 mg iron day(-1)mouse(-1)) during 2 weeks. Mice in the iron-injected group showed an increase in the iron content of the skeletal muscle and serum and ferritin levels in the muscle, along with reduced skeletal muscle mass. The skeletal muscle showed elevated mRNA expression of the muscle atrophy-related E3 ubiquitin ligases, atrogin-1 and muscle ring finger-1(MuRF1), on days 7 and 14 of iron treatment. Moreover, iron-treated mice showed reduced phosphorylation of Akt and forkhead box O3 (FOXO3a) in skeletal muscles. Inhibition of FOXO3a using siRNA in vitro in C2C12 myotube cells inhibited iron-induced upregulation of atrogin-1 and MuRF1 and reversed the reduction in myotube diameters. Iron-load caused oxidative stress, and an oxidative stress inhibitor abrogated iron-induced muscle atrophy by reactivating the Akt-FOXO3a pathway. Iron-induced skeletal muscle atrophy is suggested to involve the E3 ubiquitin ligase mediated by the reduction of Akt-FOXO3a signaling by oxidative stress.

Apple Pomace Extract Improves Endurance in Exercise Performance by Increasing Strength and Weight of Skeletal Muscle

Ursolic acid is a lipophilic pentacyclic triterpenoid found in many fruits and herbs and is used in several herbal folk medicines for diabetes. In this study, we evaluated the effects of apple pomace extract (APE; ursolic acid content, 183 mg/g) on skeletal muscle atrophy. To examine APE therapeutic potential in muscle atrophy, we investigated APE effects on the expression of biomarkers associated with muscle atrophy and hypertrophy. We found that APE inhibited atrophy, while inducing hypertrophy in C2C12 myotubes by decreasing the expression of atrophy-related genes and increasing the expression of hypertrophy-associated genes. The in vivo experiments using mice fed a diet with or without APE showed that APE intake increased skeletal muscle mass, as well as grip strength and exercise capacity. In addition, APE significantly improved endurance in the mice, as evidenced by increased exhaustive running time and muscle weight, and reduced the expression of the genes involved in the development of muscle atrophy. APE also decreased the concentration of serum lactate and lactate dehydrogenase, inorganic phosphate, and creatinine, the indicators of accumulated fatigue and exercise-induced stress. These results suggest that APE may be useful as an ergogenic functional food or dietary supplement.

The Thyroid Hormone Analog DITPA Ameliorates Metabolic Parameters of Male Mice With Mct8 Deficiency

Mutations in the gene encoding the thyroid hormone (TH) transporter, monocarboxylate transporter 8 (MCT8), cause mental retardation in humans associated with a specific thyroid hormone phenotype manifesting high serum T3 and low T4 and rT3 levels. Moreover, these patients have failure to thrive, and physiological changes compatible with thyrotoxicosis. Recent studies in Mct8-deficient (Mct8KO) mice revealed that the high serum T3 causes increased energy expenditure. The TH analog, diiodothyropropionic acid (DITPA), enters cells independently of Mct8 transport and shows thyromimetic action but with a lower metabolic activity than TH. In this study DITPA was given daily ip to adult Mct8KO mice to determine its effect on thyroid tests in serum and metabolism (total energy expenditure, respiratory exchange rate, and food and water intake). In addition, we measured the expression of TH-responsive genes in the brain, liver, and muscles to assess the thyromimetic effects of DITPA. Administration of 0.3 mg DITPA per 100 g body weight to Mct8KO mice brought serum T3 levels and the metabolic parameters studied to levels observed in untreated Wt animals. Analysis of TH target genes revealed amelioration of the thyrotoxic state in liver, somewhat in the soleus, but there was no amelioration of the brain hypothyroidism. In conclusion, at the dose used, DITPA mainly ameliorated the hypermetabolism of Mct8KO mice. This thyroid hormone analog is suitable for the treatment of the hypermetabolism in patients with MCT8 deficiency, as suggested in limited preliminary human trials.

Effects of tail suspension on serum testosterone and molecular targets regulating muscle mass

INTRODUCTION

The contribution of reduced testosterone levels to tail suspension (TS)-induced muscle atrophy remains equivocal. The molecular mechanism by which testosterone regulates muscle mass during TS has not been investigated.

METHODS

Effects of TS on serum testosterone levels, muscle mass, and expression of muscle atrophy- and hypertrophy-inducing targets were measured in soleus (SOL) and extensor digitorum longus (EDL) muscles after testosterone administration during 1, 5, and 14 days of TS in male mice.

RESULTS

TS produced an increase followed by a transient drop in testosterone levels. Muscle atrophy was associated with downregulation of Igf1 and upregulation of Mstn, Redd1, Atrogin-1, and MuRF1 mRNA with clear differences in Igf1, Mstn, and MAFbx/Atrogin-1 gene expression between SOL and EDL. Testosterone supplementation did not affect muscle mass or protein expression levels during TS. Conclusions The known anabolic effects of testosterone are not sufficient to ameliorate loss of muscle mass during TS.

Involvement of AMPK in regulating slow-twitch muscle atrophy during hindlimb unloading in mice

AMPK is considered to have a role in regulating skeletal muscle mass. However, there are no studies investigating the function of AMPK in modulating skeletal muscle mass during atrophic conditions. In the present study, we investigated the difference in unloading-associated muscle atrophy and molecular functions in response to 2-wk hindlimb suspension between transgenic mice overexpressing the dominant-negative mutant of AMPK (AMPK-DN) and their wild-type (WT) littermates. Male WT (n = 24) and AMPK-DN (n = 24) mice were randomly divided into two groups: an untreated preexperimental control group (n = 12 in each group) and an unloading (n = 12 in each group) group. The relative soleus muscle weight and fiber cross-sectional area to body weight were decreased by ∼30% in WT mice by hindlimb unloading and by ∼20% in AMPK-DN mice. There were no changes in puromycin-labeled protein or Akt/70-kDa ribosomal S6 kinase signaling, the indicators of protein synthesis. The expressions of ubiquitinated proteins and muscle RING finger 1 mRNA and protein, markers of the ubiquitin-proteasome system, were increased by hindlimb unloading in WT mice but not in AMPK-DN mice. The expressions of molecules related to the protein degradation system, phosphorylated forkhead box class O3a, inhibitor of κBα, microRNA (miR)-1, and miR-23a, were decreased only in WT mice in response to hindlimb unloading, and 72-kDa heat shock protein expression was higher in AMPK-DN mice than in WT mice. These results imply that AMPK partially regulates unloading-induced atrophy of slow-twitch muscle possibly through modulation of the protein degradation system, especially the ubiquitin-proteasome system.

Vitamin D and muscle function in the elderly: the elixir of youth?

PURPOSE OF REVIEW

Circumstantial evidence suggests that vitamin D deficiency may contribute to age-related changes in skeletal muscle. This review discusses recent clinical trials examining effects of vitamin D on muscle function in the elderly, and poses the important question: can vitamin D reverse muscle ageing?

RECENT FINDINGS

Observational studies report an association between vitamin D and muscle atrophy/weakness in elderly subjects. Interventional studies suggest that frail, elderly subjects may benefit from vitamin D supplementation by displaying reduced falls, improved muscle function and increased muscle fibre size. However, meta-analyses do not report convincing effects of vitamin D in the elderly. This may be because of multiple factors including lack of standardized endpoints for muscle function, variable study design and different doses of vitamin D supplementation amongst these studies. The evidence base is therefore inconsistent.

SUMMARY

Vitamin D deficiency may exacerbate ageing of skeletal muscle. However, current evidence that vitamin D supplementation reverses age-related muscle dysfunction is equivocal and does not justify stringent vitamin D targets in the elderly. Until these issues are clarified, the safest option is to aim for conservative vitamin D targets that are sufficient for normal calcium homeostasis.

Muscle atrophy in response to cytotoxic chemotherapy is dependent on intact glucocorticoid signaling in skeletal muscle

Cancer cachexia is a syndrome of weight loss that results from the selective depletion of skeletal muscle mass and contributes significantly to cancer morbidity and mortality. The driver of skeletal muscle atrophy in cancer cachexia is systemic inflammation arising from both the cancer and cancer treatment. While the importance of tumor derived inflammation is well described, the mechanism by which cytotoxic chemotherapy contributes to cancer cachexia is relatively unexplored. We found that the administration of chemotherapy to mice produces a rapid inflammatory response. This drives activation of the hypothalamic-pituitary-adrenal axis, which increases the circulating level of corticosterone, the predominant endogenous glucocorticoid in rodents. Additionally, chemotherapy administration results in a significant loss of skeletal muscle mass 18 hours after administration with a concurrent induction of genes involved with the ubiquitin proteasome and autophagy lysosome systems. However, in mice lacking glucocorticoid receptor expression in skeletal muscle, chemotherapy-induced muscle atrophy is completely blocked. This demonstrates that cytotoxic chemotherapy elicits significant muscle atrophy driven by the production of endogenous glucocorticoids. Further, it argues that pharmacotherapy targeting the glucocorticoid receptor, given in concert with chemotherapy, is a viable therapeutic strategy in the treatment of cancer cachexia.

Measurement of a MMP-2 degraded Titin fragment in serum reflects changes in muscle turnover induced by atrophy

PURPOSE

In this study we sought to determine whether a Titin peptide fragment can serve as a clinical biomarker for changes in muscle mass.

METHODS

Mass spectrometry was used to identify Titin fragment in urine. An antibody against this Titin sequence was raised and used to develop a competitive ELISA assay for measurement in serum. Rat tissue extractions in the presence or absence of a series of proteases of interest were used to identify its enzymatic origin. A rat model of dexamethasone (DEX) induced muscle atrophy and a human 56-day bed rest study with and without vibration therapy were used to assess biological and clinical relevance.

RESULTS

A technically robust ELISA measuring the Titin fragment was developed against a Titin peptide fragment identified in human urine. The fragment was shown to be produced primarily by MMP-2 cleavage of Titin. In the rat muscle DEX induced atrophy model, Titin-MMP2 fragment was decreased in the beginning of DEX treatment, and then significantly increased later on during DEX administration. In the human bed rest study, the Titin-MMP2 fragment was initially decreased 11.9 (±3.7) % after 1day of bed rest, and then gradually increased ending up at a 16.4 (±4.6) % increase at day 47.

CONCLUSIONS

We developed a robust ELISA measuring a muscle derived MMP-2 generated Titin degradation fragment in rat and human serum. Importantly, the fragment can be measured in serum and that these levels are related to induction of skeletal muscle atrophy.

β-Hydroxy β-methylbutyrate improves dexamethasone-induced muscle atrophy by modulating the muscle degradation pathway in SD rat

Skeletal muscle atrophy results from various conditions including high levels of glucocorticoids, and β-hydroxy β-methylbutyrate (HMB; a metabolite of leucine) is a potent therapeutical supplement used to treat various muscle disorders. Recent studies have demonstrated that HMB inhibits dexamethasone-induced atrophy in cultured myotubes, but its effect on dexamethasone-induced muscle atrophy has not been determined in vivo. In the present study, we investigated the effect of HMB on dexamethasone-induced muscle atrophy in rats. Treatment with dexamethasone weakened grip strengths and increased muscle damage as determined by increased serum creatine kinase levels and by histological analysis. Dexamethasone treatment also reduced both soleus and gastrocnemius muscle masses. However, HMB supplementation significantly prevented reductions in grip strengths, reduced muscle damage, and prevented muscle mass and protein concentration decrease in soleus muscle. Biochemical analysis demonstrated that dexamethasone markedly increased levels of MuRF1 protein, which causes the ubiquitination and degradation of MyHC. Indeed, dexamethasone treatment decreased MyHC protein expression and increased the ubiquitinated-MyHC to MyHC ratio. However, HMB supplementation caused the down-regulations of MuRF1 protein and of ubiquitinated-MyHC. Furthermore, additional experiments provided evidence that HMB supplementation inhibited the nuclear translocation of FOXO1 induced by dexamethasone, and showed increased MyoD expression in the nuclear fractions of soleus muscles. These findings suggest that HMB supplementation attenuates dexamethasone-induced muscle wasting by regulating FOXO1 transcription factor and subsequent MuRF1 expression. Accordingly, our results suggest that HMB supplementation could be used to prevent steroid myopathy.

Disuse impairs the muscle protein synthetic response to protein ingestion in healthy men

BACKGROUND

Disuse leads to rapid skeletal muscle atrophy, which brings about numerous negative health consequences. Muscle disuse atrophy is, at least in part, attributed to a decline in basal (postabsorptive) muscle protein synthesis rates. However, it remains to be determined whether muscle disuse also impairs the muscle protein synthetic response to dietary protein ingestion.

PURPOSE

We assessed muscle protein synthesis rates after protein ingestion before and after a period of disuse in humans.

METHODS

Twelve healthy young (24 ± 1 year) men underwent a 14-day period of one-legged knee immobilization by way of a full leg cast. Before and after the immobilization period, quadriceps cross-sectional area, muscle strength, skeletal muscle protein synthesis rates, and associated im (intramuscular) molecular signaling were assessed. Continuous infusions of l-[ring-²H₅]phenylalanine were applied to assess mixed-muscle protein fractional synthetic rates after the ingestion of 20 g dietary protein.

RESULTS

Immobilization led to an 8.4% ± 2.8% (P < .001) and 22.9% ± 2.6% (P < .001) decrease in quadriceps muscle cross-sectional area and strength, respectively. Immobilization resulted in a 31% ± 12% reduction in postprandial muscle protein synthesis rates (from 0.046% ± 0.004% to 0.032% ± 0.006% per hour; P < .05). These findings were observed without any discernible changes in the skeletal muscle phosphorylation status of mammalian target of rapamycin or p70 ribosomal protein S6 kinase.

CONCLUSIONS

A short period of muscle disuse impairs the muscle protein synthetic response to dietary protein intake in vivo in healthy young men. Thus, anabolic resistance to protein ingestion contributes significantly to the loss of muscle mass that is observed during disuse.

Highly specific detection of myostatin prodomain by an immunoradiometric sandwich assay in serum of healthy individuals and patients

Background

Myostatin is a muscle derived factor that functions as a negative regulator of skeletal muscle growth. Induction of myostatin expression was observed in rodent models of muscle wasting and in cachectic patients with cancer or pulmonary disease. Therefore, there is an increasing interest to use serum myostatin as a biomarker.

Methods

We established an immunoradiometric sandwich assay (IRMA), which uses a commercially available chicken polyclonal, affinity purified antibody directed against human myostatin prodomain. We determined the serum concentrations of myostatin prodomain in 249 healthy individuals as well as 169 patients with heart failure, 53 patients with cancer and 44 patients with chronic pulmonary disease.

Results

The IRMA had a detection limit of 0.7ng/ml, an intraassay imprecision of ≤14.1% and an interassay imprecision of ≤ 18.9%. The specificity of our assay was demonstrated by size exclusion chromatography, detection of myostatin by Western-blotting and a SMAD-dependent transcriptional-reporter assay in the signal-rich serum fractions, as well as lack of interference by unspecific substances like albumin, hemoglobin or lipids. Myostatin prodomain was stable at room temperature and resistant to freeze-thaw cycles. Apparently healthy individuals over the age of 55 had a median myostatin prodomain serum concentration of 3.9ng/ml (25^th-75^th percentiles, 2-7ng/ml) and we could not detect increased levels in patients with stable chronic heart failure or cancer related weight loss. In contrast, we found strongly elevated concentrations of myostatin prodomain (median 26.9ng/ml, 25^th-75^th percentiles, 7-100ng/ml) in the serum of underweight patients with chronic pulmonary disease.

Conclusions

We established a highly specific IRMA for the quantification of myostatin prodomain concentration in human serum. Our assay could be useful to study myostatin as a biomarker for example in patients with chronic pulmonary disease, as we detected highly elevated myostatin prodomain serum levels in underweight individuals of this group.

Diiodothyropropionic acid (DITPA) in the treatment of MCT8 deficiency

CONTEXT

Monocarboxylate transporter 8 (MCT8) is a thyroid hormone-specific cell membrane transporter. MCT8 deficiency causes severe psychomotor retardation and abnormal thyroid tests. The great majority of affected children cannot walk or talk, and all have elevated serum T(3) levels, causing peripheral tissue hypermetabolism and inability to maintain weight. Treatment with thyroid hormone is ineffective. In Mct8-deficient mice, the thyroid hormone analog, diiodothyropropionic acid (DITPA), does not require MCT8 to enter tissues and could be an effective alternative to thyroid hormone treatment in humans.

OBJECTIVE

The objective of the study was to evaluate the effect and efficacy of DITPA in children with MCT8 deficiency.

METHODS

This was a multicenter report of four affected children given DITPA on compassionate grounds for 26-40 months. Treatment was initiated at ages 8.5-25 months, beginning with a small dose of 1.8 mg, increasing to a maximal 30 mg/d (2.1-2.4 mg/kg · d), given in three divided doses.

RESULTS

DITPA normalized the elevated serum T(3) and TSH when the dose reached 1 mg/kg · d and T(4) and rT(3) increased to the lower normal range. The following significant changes were also observed: decline in SHBG (in all subjects), heart rate (in three of four), and ferritin (in one of four). Cholesterol increased in two subjects. There was no weight loss and weight gain occurred in two. None of the treated children required a gastric feeding tube or developed seizures. No adverse effects were observed.

CONCLUSION

DITPA (1-2 mg/kg · d) almost completely normalizes thyroid tests and reduces the hypermetabolism and the tendency for weight loss. The effects of earlier commencement and long-term therapy remain to be determined.

Role of IGF-I and the TNFα/NF-κB pathway in the induction of muscle atrogenes by acute inflammation

Several catabolic states (sepsis, cancer, etc.) associated with acute inflammation are characterized by a loss of skeletal muscle due to accelerated proteolysis. The main proteolytic systems involved are the autophagy and the ubiquitin-proteasome (UPS) pathways. Among the signaling pathways that could mediate proteolysis induced by acute inflammation, the transcription factor NF-κB, induced by TNFα, and the transcription factor forkhead box O (FOXO), induced by glucocorticoids (GC) and inhibited by IGF-I, are likely to play a key role. The aim of this study was to identify the nature of the molecular mediators responsible for the induction of these muscle proteolytic systems in response to acute inflammation caused by LPS injection. LPS injection robustly stimulated the expression of several components of the autophagy and the UPS pathways in the skeletal muscle. This induction was associated with a rapid increase of circulating levels of TNFα together with a muscular activation of NF-κB followed by a decrease in circulating and muscle levels of IGF-I. Neither restoration of circulating IGF-I nor restoration of muscle IGF-I levels prevented the activation of autophagy and UPS genes by LPS. The inhibition of TNFα production and muscle NF-κB activation, respectively by using pentoxifilline and a repressor of NF-κB, did not prevent the activation of autophagy and UPS genes by LPS. Finally, inhibition of GC action with RU-486 blunted completely the activation of these atrogenes by LPS. In conclusion, we show that increased GC production plays a more crucial role than decreased IGF-I and increased TNFα/NF-κB pathway for the induction of the proteolytic systems caused by acute inflammation.

Effects of alfacalcidol on circulating cytokines and growth factors in rat skeletal muscle

Supra-physiological levels of vitamin D induce skeletal muscle atrophy, which may be particularly detrimental in already sarcopaenic elderly. Neither the cause nor whether the atrophy is fibre type specific are known. To obtain supraphysiological levels of circulating vitamin D (1,25(OH)(2)D(3)) 27.5-month-old female Fischer(344) × Brown Norway F1 rats were orally treated for 6 weeks with vehicle or the vitamin D analogue alfacalcidol. Alfacalcidol treatment induced a 22% decrease in body mass and 17% muscle atrophy. Fibre atrophy was restricted to type IIb fibres in the low-oxidative part of the gastrocnemius medialis only (-22%; P < 0.05). There was a concomitant 1.6-fold increase in mRNA expression of the ubiquitin ligase MuRF-1 (P < 0.001), whereas those of insulin-like growth factor 1 and myostatin were not affected. Circulating IL-6 was unaltered, but leptin and adiponectin were decreased (-39%) and increased (64%), respectively. The treated rats also exhibited a reduced food intake. In conclusion, supraphysiological levels of circulating 1,25(OH)(2)D(3) cause preferential atrophy of type IIb fibres, which is associated with an increased expression of MuRF-1 without evidence of systemic inflammation. The atrophy and loss of body mass in the presence of supra-physiological levels of vitamin D are primarily due to a reduced food intake.

[Effect of Ligusticum and its two main components on muscle atrophy in a hind limb unloaded rat model]

OBJECTIVE

To study the effects of Ligusticum and its two components (Sodium Ferulate and Ligustrazine as main efficacy components in Ligusticum for invigorating blood circulation) on muscle atrophy in a hind limb unloaded rat model.

METHODS

The tail-suspended rats were subjected to a 14-days disuse, immunohistochemistry and hemorheology were used to study the effects of medicines on soleus muscle.

RESULTS

Compared with HLU+ W: (1) The CSA of soleus type I fibers in HLU + SfH and HLU+ TmpH increased by 37.3% and 39.4% respectively (P < 0.05). (2) Expression level of MHC II were inhibited in all treatment groups (P < 0.01). (3) Expression of MHC II in nuclear bag 2 fiber were altered from positive to negative. (4) The blood viscosity in low shear rates decreased obviously (P < 0.01), even near to control.

CONCLUSION

Ligusticum and its two main efficacy components (Sodium Ferulate and Ligustrazine) can prevent soleus atrophy induced by disuse, and Sodium Ferulate and Ligustrazine in high dose showed most efficacy.

Vitamin E and C supplementation does not ameliorate muscle dysfunction after anterior cruciate ligament surgery

Muscle atrophy and weakness are predominant impairments after anterior cruciate ligament (ACL) surgical repair. We tested the hypothesis that vitamin E and C supplementation will improve recovery from ACL injury. Men undergoing elective ACL surgery were randomly assigned to twice-daily supplements of either antioxidants (AO; vitamins E and C, n=10) or matching placebos (n=10) from 2 weeks before until 3 months after surgery. Each subject provided several fasting blood draws, two muscle biopsies from the thigh muscle of the injured limb, and strength and thigh circumference measurements of the lower limbs. Muscle atrophy was apparent in both groups before and several days after surgery. Compared with baseline measurements, peak isometric force of the injured limb increased significantly (P<0.05) by 3 months postsurgery in both treatment groups; however, AO supplementation did not augment these strength gains. By contrast, baseline plasma ascorbic acid concentrations correlated (r=0.59, P=0.006) with subsequent improvement in the strength of the injured limb. In summary, vitamin E and C supplementation was ineffective in potentiating the improvement in force production by the injured limb; however, baseline vitamin C status was associated with beneficial outcomes in strength, suggesting that long-term dietary habits are more effective than short-term supplements.

Low relative skeletal muscle mass indicative of sarcopenia is associated with elevations in serum uric acid levels: findings from NHANES III

BACKGROUND

Sarcopenia may be related to increases in reactive oxygen species formation and inflammation, both of which are associated with elevations in serum uric acid.

OBJECTIVE

To test the hypothesis that a reduced skeletal muscle mass index, indicative of sarcopenia, is related to elevations in uric acid.

DESIGN

Cross-sectional analysis of nationally representative data.

SETTING

Third National Health and Nutrition Examination Survey, 1988-1994.

PATIENTS

7544 men and women 40 years of age and older who had uric acid, skeletal muscle mass, and select covariate information.

MEASUREMENTS

Skeletal muscle mass assessment was based on a previously published equation including height, BIA-resistance, gender, and age. Absolute skeletal muscle mass was calculated for all study population individuals and compared against the sex-specific mean for younger adults. Serum uric acid data were gathered from the NHANES laboratory file.

RESULTS

A logistic regression analysis revealed that elevations in serum uric acid are significantly related to sarcopenia status. For every unit (mg/dL) increase in uric acid, the odds ratio of manifesting a skeletal muscle mass index at least one standard deviation below the reference mean was 1.12. Participants in the highest grouping (> 8 mg/dL) of serum uric acid concentration had 2.0 times the odds of manifesting sarcopenia compared to the lowest grouping (< 6 mg/dL) (p < 0.01) after adjusting for the additional covariates.

LIMITATIONS

This study design was limited in its cross-sectional nature. Potential selection, measurement, and recall bias may have occurred, and methodology used to classify sarcopenia status based on skeletal muscle mass index is not validated.

CONCLUSION

This observation provides support for the theory that elevations in uric acid may lead to sarcopenia, although the proposed mechanism needs further experimental support.

Skeletal Muscle Atrophy Induced by Intramuscular Repeated Dose of Botulinum Toxin Type A in Rats

Botulinum toxin type A was intramuscularly administered to Sprague-Dawley rats once a day for 28 days at doses of 1, 3, and 9 ng kg-1 day-1 to investigate the possibility of unanticipated toxicity of repeated dose. A dose-related decrease in body weight gain was noted and lasted throughout the 4-week recovery period. Paralytic gait was a common clinical sign observed in the animals dosed at >or=3 ng kg-1 day-1 and muscle atrophy at 9 ng kg-1 day-1. Decreased creatinine was monitored in both males and females treated at 9 ng kg-1 day-1. Microscopic examination of the quadriceps femoris muscle, the test article application site, confirmed the muscle atrophy with a decrease in myofiber diameter and an increase of myofiber nuclei and intermyofiber connective tissue. Although antibody against botulinum toxin type A was detected in the sera from both males and females at 9 ng kg-1 day-1, no immunogenicity-related changes or lesions were noted. In conclusion, no other side effects of the botulinum toxin type A injection except the decrease in body weight gain and the muscle atrophy at the administration site were noted in the 28-day intramuscular repeated dose study.

Hypothyroid myopathy with manifestations of Hoffman's syndrome and myasthenia gravis

Although hypothyroid myopathy is seen frequently and the relationship with autoimmune hypothyroidism and myasthenia gravis is well known, specific forms of hypothyroid myopathy such as Hoffman's syndrome (HS) are rarely described. Here we describe a 40-year-old patient with Hashimoto thyroiditis showing symptoms and signs of two discrete forms of hypothyroid myopathy (HS and myasthenic syndrome) together. To our knowledge this is the first reported case with features of both of these syndromes. We discuss the diagnosis, speculate whether this patient may represent a unique form of hypothyroid myopathy, and report the 6-month follow-up of the patient both clinically and electrophysiologically.

[Reloading of rat soleus after hindlimb unloading and serum insulin-like growth factor 1]

The aim of this study was to elucidate the effects of 14- day hindlimb suspension (HS) and subsqquent reloading (3 or 7 days) on the m. soleus mass, muscle fiber cross-sectional area (CSA), soleus fiber properties and serum IGF-1 in rats. Rats were hindlimb suspended for 14 days or kept as controls (C, n = 7). Soleus muscles were isolated after HS (HS, n = 7) or after reambulation for either three (R3, n = 5) or seven days (R7, n = 6). Frozen serial sections of m. soleus were stained by primary monoclonal antibodies against MHCI. For measurement of concentration IGF-1 in the blood serum, test-system for IFA DSL-10-2800 Non-Extraction IGF-1 ELISA was used. Muscle mass was significantly reduced in HS (-35 %) but subsequently increased with reloading in R3 (-10 % to C) and was recovered to control values in R7 (+5 % to C). Fiber CSA was significantly reduced (-43 %) in HS and was greater in R7 than in HS and slightly greater than in R3. 14 days of HS resulted in a mean maximal tension reduced by 35 %. After 7 days of subsequent reloading the mean maximal specific tension was still low (-33 % to C) and didn't differ from HS level. The level in blood IGF-1 has obviously decreased during 14-day unloading by 48 %, remained at the same level in R3, and increased 10 fold in R7.

Myoglobin plasma level related to muscle mass and fiber composition: a clinical marker of muscle wasting?

Progressive muscle wasting is a central feature of cancer-related cachexia and has been recognized as a determinant of poor prognosis and quality of life. However, until now, no easily assessable clinical marker exists that allows to predict or to track muscle wasting. The present study evaluated the potential of myoglobin (MG) plasma levels to indicate wasting of large locomotor muscles and, moreover, to reflect the loss of MG-rich fiber types, which are most relevant for daily performance. In 17 cancer-cachectic patients (weight loss 22%) and 27 age- and gender-matched healthy controls, we determined plasma levels of MG and creatine kinase (CK), maximal quadriceps muscle cross-sectional area (CSA) by magnetic resonance imaging, muscle morphology and fiber composition in biopsies from the vastus lateralis muscle, body cell mass (BCM) by impedance technique as well as maximal oxygen uptake (VO(2)max). In cachectic patients, plasma MG, muscle CSA, BCM, and VO(2)max were 30-35% below control levels. MG showed a significant positive correlation to total muscle CSA (r = 0.65, p < 0.001) and to the CSA fraction formed by type 1 and 2a fibers (r = 0.80, p < 0.001). However, when adjusted for body height and age by multiple regression, MG yielded a largely improved prediction of total CSA (multiple r = 0.83, p < 0.001) and of fiber type 1 and 2a CSA (multiple r = 0.89, p < 0.001). The correlations between CK and these muscle parameters were weaker, and elevated CK values were observed in 20% of control subjects despite a prior abstinence from exercise for 5 days. In conclusion, plasma MG, when adjusted for anthropometric parameters unaffected by weight, may be considered as a novel marker of muscle mass (CSA) indicating best the mass of MG-rich type 1 and 2a fibers as well as VO(2)max as an important functional readout. CK plasma levels appear to be less reliable because prolonged increases are observed in even subclinical myopathies or after exercise. Notably, cancer-related muscle wasting was not associated with increases in plasma MG or CK in this study.

Sarcopenia is predictive of nosocomial infection in care of the elderly

Protein-energy malnutrition and nosocomial infection (NI) are frequent in elderly patients, and a causal link between the two has often been suggested. The aim of the present study was to identify the nutritional parameters predictive of NI in elderly patients. We assessed on admission 101 patients (sixty-six women, thirty-five men, aged over 65 years) admitted to an acute care of the elderly department. Sarcopenia was detected by dual-energy X-ray absorptiometry, with appendicular skeletal muscle mass expressed with respect to body area. Weight, BMI, albuminaemia, serum transthyretin and C-reactive protein values were also determined on admission, and known risk factors, such as functional dependence and invasive biomedical material, were also evaluated. After up to 3 weeks of hospitalisation, patients were classified according to whether they had developed an NI. After 3 weeks of hospitalisation, we found that twenty-nine patients had suffered an NI, occurring after a mean of 16.1 d. Patients who were sarcopenic on admission had a significantly higher risk of contracting an NI (relative risk 2.1, 95 % CI 1.1, 3.8). None of the other morphometric or biological parameters differed significantly between the two groups of patients on admission. Patients who experienced an NI were also more likely, on admission, to have a medical device (P=0.02 to P=0.001 depending on the device), to have swallowing problems (P=0.002) or to have restricted autonomy (P<0.01). Sarcopenia on admission to an acute care of the elderly unit, as measured by X-ray absorptiometry, was therefore associated with a doubled risk of NI during the first 3 weeks of hospitalisation.

Exercise-induced systemic effects in muscle-wasted patients with COPD

PURPOSE

Physical exercise is known to induce an acute inflammatory response and oxidative stress in healthy subjects and patients with chronic obstructive pulmonary disease (COPD). Increasing evidence associates systemic inflammation and oxidative stress with muscle wasting and muscle dysfunction in COPD. In the present study, it was hypothesized that exercise-induced systemic inflammatory and oxidative responses in muscle-wasted COPD patients are increased compared with non-muscle-wasted patients and healthy subjects.

METHODS

Pulmonary function, body composition, and quadriceps muscle strength were measured in 10 muscle-wasted (fat-free mass index (FFMI) < 16 kg x m(-2) (men), < 15 kg x m(-2) (women)), 10 non-muscle-wasted COPD patients, and 10 healthy subjects. Systemic inflammation (C-reactive protein (CRP), leukocytes, cytokines) and oxidative stress (production of reactive oxygen species (ROS) by neutrophils, plasma antioxidant capacity, protein oxidation, lipid peroxidation, oxidized to reduced glutathione ratio (GSSG/GSH)) were determined before and after maximal and submaximal (50% of maximal work rate) cycle ergometry.

RESULTS

Low-grade systemic inflammation was significantly (P < 0.05) elevated in all COPD patients and tended to be highest in muscle-wasted patients. A decreased antioxidant status (plasma antioxidant capacity, P < 0.05; GSH, P < 0.05) and increased protein oxidation (P < 0.001) reflected increased basal oxidative stress in muscle-wasted COPD patients compared with both other groups. Both maximal and submaximal exercise caused increased inflammatory (IL-6, +1.1 pg. x mL(-1) vs rest, P < 0.05) and oxidative responses (ROS release by neutrophils, + 32%; GSSG/GSH + 29%; lipid peroxidation, + 30% vs rest) in muscle-wasted COPD patients, which were less pronounced or not observed in non-muscle-wasted patients and healthy subjects.

CONCLUSIONS

These data indicate that both maximal and submaximal exercise induce increased systemic inflammatory and oxidative responses in muscle-wasted COPD patients compared with non-muscle-wasted patients and healthy subjects.

Effect of sarcopenia on cardiovascular disease risk factors in obese postmenopausal women

OBJECTIVE

To compare sarcopenic-obese and obese postmenopausal women for risk factors predisposing to cardiovascular disease (CVD) and determine whether there may be a relationship between muscle mass and metabolic risk in obese postmenopausal women.

RESEARCH METHODS AND PROCEDURES

In this cross-sectional study, 22 healthy obese postmenopausal women (mean age, 66 +/- 5 years; mean BMI, 27 +/- 3 kg/m(2)) were divided into two groups matched for age (+/-2 years) and fat mass (FM) (+/-2%). Sarcopenia was defined as a muscle mass index of <14.30 kg fat-free mass (FFM)/m(2) (which corresponds to 1 standard deviation below the values of a young reference population), and obesity was defined as an FM of >35% (which corresponds to the World Health Organization guidelines). FM, FFM (measured by DXA), daily energy expenditure (accelerometry), dietary intake (3-day dietary record), and blood biochemical analyses (lipid profile, insulin, glucose, and C-reactive protein) were obtained. Visceral fat mass (VFM) was calculated by the equation of Bertin, which estimates VFM from DXA measurements.

RESULTS

Obese women had more FFM (p = 0.006), abdominal FM (p = 0.047), and VFM (p = 0.041) and a worse lipid profile [p = 0.040 for triglycerides; p = 0.004 for high-density lipoprotein (HDL); p = 0.026 for total cholesterol/HDL] than sarcopenic-obese postmenopausal women. Obese women also ingested significantly more animal (p = 0.001) and less vegetal proteins (p = 0.013), although both groups had a similar total protein intake (p = 0.967).

DISCUSSION

Sarcopenia seems to be associated with lower risk factors predisposing to CVD in obese postmenopausal women. With the increase in the number of aging people, the health implications of being sarcopenic-obese merit more attention.

Diagnostic usefulness of B-type natriuretic peptide and functional consequences of muscle alterations in COPD and chronic heart failure

COPD affects up to one third of patients with chronic heart failure. The coexistence of COPD and chronic heart failure presents clinicians with diagnostic and therapeutic challenges. Measurement of B-type natriuretic peptide plasma levels facilitates the diagnosis of acute dyspnea in patients known to have both COPD and chronic heart failure. Patients with COPD or chronic heart failure have skeletal muscle abnormalities that limit functional capacity independently from primary organ failure. Exercise training reverses skeletal muscle abnormalities in patients with COPD or chronic heart failure and may be particularly indicated in patients with coexistent COPD and chronic heart failure.

Major pathogenic effects of anti-MuSK antibodies in myasthenia gravis

MG with anti-MuSK antibodies (MuSK+) is often characterized with muscle atrophy and excellent response to plasma exchanges. To elucidate some MuSK+ MG features, we analyzed the functional effects of anti-MuSK Abs in human TE 671 muscle cells. We found that some MuSK+ sera induced a striking inhibition of proliferation, accompanied by: 1) cell cycle arrest, 2) atrogin-1 overexpression, 3) AChR subunits, rapsyn, Rho A and cdc42 downregulation. These effects correlated to disease severity and to anti-MuSK Abs titer and vanished following PE. Altogether, these results indicate that anti-MuSK Abs could be pathogenic by contributing to the muscle atrophy in MuSK+ MG patients.

Loss of class IA PI3K signaling in muscle leads to impaired muscle growth, insulin response, and hyperlipidemia

The evolutionarily conserved phosphoinositide 3-kinase (PI3K) signaling pathway mediates both the metabolic effects of insulin and the growth-promoting effects of insulin-like growth factor-1 (IGF-1). We have generated mice deficient in both the p85alpha/p55alpha/p50alpha and the p85beta regulatory subunits of class I(A) PI3K in skeletal muscles. PI3K signaling in the muscle of these animals is severely impaired, leading to a significant reduction in muscle weight and fiber size. These mice also exhibit muscle insulin resistance and whole-body glucose intolerance. Despite their ability to maintain normal fasting and fed blood glucose levels, these mice show increased body fat content and elevated serum free fatty acid and triglyceride levels. These results demonstrate that in vivo p85 is a critical mediator of class I(A) PI3K signaling in the regulation of muscle growth and metabolism. Our finding also indicates that compromised muscle PI3K signaling could contribute to symptoms of hyperlipidemia associated with human type 2 diabetes.

Are insulin-like growth factor and its binding proteins 1 and 3 clinically useful as markers of malnutrition, sarcopenia and inflammation in end-stage renal disease?

INTRODUCTION

Malnutrition is common in end-stage renal disease (ESRD) and affects both morbidity and mortality. The growth hormone-dependent insulin-like growth factor (IGF)-I may be a good marker of malnutrition because of its short half-life. In the present study, we investigate the influence of decreasing residual renal function as well as of chronic inflammation on the IGF system to assess its usefulness in this patient group.

PATIENTS AND METHODS

Cross-sectional analysis of 220 ESRD patients (140 males) with a mean age of 52+/-1 years. Biochemical analyses of insulin, IGF-I, IGFBP-1, IGFBP-3, IL-6, high sensitivity (hs)-CRP and other routine markers. Malnutrition status was recorded using subjective global assessment (SGA), body mass index, estimated protein intake from nitrogen appearance (nPNA), handgrip strength (HGS) and insulin resistance (HOMA-IR). Dual energy X-ray absorptiometry was used to assess body composition.

RESULTS

Both IGF-I and IGFBP-1 showed significant and opposite correlations with most markers of nutritional status, including SGA (rho=-0.29 and 0.27; P<0.001), nPNA (rho=0.18 and -0.22; P<0.05), S-creatinine (rho=0.19 and -0.19; P<0.01) and HGS (rho=0.21 and -0.25; P<0.01). IFG-I was strongly correlated with IGFBP-3 (rho=0.62; P<0.001) and inversely correlated with IGFBP-1 (rho=0.44; P<0.001). Both IGF-I and IGFBP-3, but not IGFBP-1, were significantly correlated with age (rho=-0.25 for IGF-I and -0.35 for IGFBP-3; P<0.001) and hsCRP (rho=-0.21 and -0.32; P<0.01). In multivariate analysis, SGA and s-albumin were independent predictors of both IGF-I and IGFBP-1.

CONCLUSION

Both IGF-I and IGFBP-1 appear to correlate well with markers of protein-energy malnutrition and sarcopenia. However, IGF-I is also influenced by age, whereas IGFBP-1 is influenced by glucose metabolism. IGFBP-3 does not correlate with nutritional status in ESRD, perhaps because of a strong association with inflammation.

Lower serum albumin concentration and change in muscle mass: the Health, Aging and Body Composition Study

BACKGROUND

Low albumin concentrations in older persons increase the risk of poor health outcomes, including functional decline.

OBJECTIVE

The aim of the study was to investigate the association between serum albumin concentration and skeletal muscle loss (sarcopenia) in old age.

DESIGN

Serum albumin concentration was measured in 1882 black and white men and women aged 70-79 y participating in the Health, Aging and Body Composition Study. Five-year changes in appendicular skeletal muscle mass (ASMM), total-body fat-free mass (FFM), and trunk lean mass (TLM) were measured by using dual-energy X-ray absorptiometry. Confounders included health and lifestyle factors, which are markers of inflammation and protein intake.

RESULTS

A low albumin concentration (< 38 g/L) was observed in 21.2% of the study participants. After adjustment for confounders, the mean (+/-SE) change in ASMM was -82 +/- 26 g per 3-g/L lower albumin concentration (P = 0.002). This association remained after persons with a low albumin concentration (< 38 g/L) were excluded. The decline in ASMM in subjects with low albumin concentrations was almost 30% higher (-930 +/- 56 g) than that in those with albumin concentrations > or = 42 g/L (-718 +/- 38 g; P < 0.01). The association between albumin and change in ASMM remained after additional adjustment for weight change. A weak association was observed for FFM, whereas no association was observed for TLM, which suggests a specific role of albumin in skeletal muscle change.

CONCLUSIONS

Lower albumin concentrations, even above the clinical cutoff of 38 g/L, are associated with future loss of ASMM in older persons. Low albumin concentration may be a risk factor for sarcopenia.

Circulating acute phase mediators and skeletal muscle performance in hospitalized geriatric patients

BACKGROUND

There is growing evidence for the significant involvement of inflammatory processes in the development of muscle wasting in old age. Therefore, any disease accompanied by inflammation can be threatening to the muscle function in geriatric patients.

METHODS

Sixty-three hospitalized geriatric patients (42 female, 21 male; mean age 84.2 +/- 5.7 years) were monitored weekly for muscle function (grip strength, fatigue resistance, shoulder extension strength, and hip extension strength) and for concentration of circulating C-reactive protein (CRP), fibrinogen, interleukin 6 (IL-6), and tumor necrosis factor-alpha alpha (TNF-alpha).

RESULTS

On the basis of circulating CRP and fibrinogen concentrations, 42 patients were categorized on admission as inflammatory and 21 as noninflammatory. Inflammatory patients presented significantly weaker grip strength, shoulder extension strength, and a worse fatigue resistance than did noninflammatory patients. These muscle functions were negatively correlated with the concentrations of circulating CRP and IL-6, but not with fibrinogen or TNF-alpha. In noninflammatory patients, the fatigue resistance improved significantly during the first week of hospitalization. In patients admitted with inflammation, no improvement of muscle function was observed. Patients who remained inflammatory for 2 weeks or more presented a significant worsening of fatigue resistance.

CONCLUSIONS

Geriatric hospitalized patients presenting with inflammation show significantly worse muscle functions, which do not improve during hospitalization despite adequate treatment of the primary disease. Reduced strength and fatigue resistance are significantly related to the concentration of circulating CRP and IL-6. Standard treatment of the underlying illness and classic physical therapy are not sufficient to normalize the skeletal muscle strength and fatigue resistance in these hospitalized patients.

Characteristics of the increase in plasma brain natriuretic peptide level in left ventricular systolic dysfunction, associated with muscular dystrophy in comparison with idiopathic dilated cardiomyopathy

To determine whether the plasma brain natriuretic peptide level increases differentially in muscular dystrophy and idiopathic dilated cardiomyopathy, we investigated the plasma brain natriuretic peptide level and echocardiographic parameters in patients with similarly low left ventricular ejection fraction. The plasma brain natriuretic peptide level was lower, and the left ventricular end-diastolic diameter was shorter in the patients with muscular dystrophy than in those with idiopathic dilated cardiomyopathy. The correlation between the plasma brain natriuretic peptide and left ventricular ejection fraction was shifted downward in the patients with muscular dystrophy compared with those with idiopathic dilated cardiomyopathy. Those between the brain natriuretic peptide and left ventricular end-diastolic diameter were superimposable, although the data from the muscular dystrophy patients were located at the shorter left ventricular end-diastolic diameter side. The plasma brain natriuretic peptide level may differentially increase in the two diseases with similar left ventricular systolic dysfunction. Differences in the left ventricular distension and in the physical activity might explain at least partially the different plasma brain natriuretic peptide levels.

Carotenoid and vitamin E status are associated with indicators of sarcopenia among older women living in the community

BACKGROUND AND AIMS

Oxidative stress may play a role in the pathogenesis of sarcopenia, and the relationship between dietary antioxidants and sarcopenia needs further elucidation. The aim was to determine whether dietary carotenoids and alpha-tocopherol are associated with sarcopenia, as indicated by low grip, hip, and knee strength.

METHODS

Cross-sectional analyses were conducted on 669 non-disabled to severely disabled community-dwelling women aged 70 to 79 who participated in the Women's Health and Aging Studies. Plasma carotenoids and alpha-tocopherol were measured. Grip, hip, and knee strength were measured, and low strength was defined as the lowest tertile of each strength measure.

RESULTS

Higher plasma concentrations of alpha-carotene, beta-carotene, beta-cryptoxanthin, and lutein/zeaxanthin were associated with reduced risk of low grip, hip, and knee strength. After adjusting for potential confounding factors such as age, race, smoking, cardiovascular disease, arthritis, and plasma interleukin-6 concentrations, there was an independent association for women in the highest compared with the lowest quartile of total carotenoids with low grip strength [Odds Ratios (OR) 0.34, 95% Confidence Interval (CI) 0.20-0.59], low hip strength (OR 0.28, 95% CI 0.16-0.48), and low knee strength (OR 0.45, 95% CI 0.27-0.75), and there was an independent association for women in the highest compared with the lowest quartile of alpha-tocopherol with low grip strength (OR 0.44, 95% CI 0.24-0.78) and low knee strength (OR 0.52, 95% CI 0.29-0.95).

CONCLUSIONS

Higher carotenoid and alpha-tocopherol status were independently associated with higher strength measures. These data support the hypothesis that oxidative stress is associated with sarcopenia in older adults, but further longitudinal and interventional studies are needed to establish causality.