Cholic and deoxycholic acids induce mitochondrial dysfunction, impaired biogenesis and autophagic flux in skeletal muscle cells

BACKGROUND: Skeletal muscle is sensitive to bile acids (BA) because it expresses the TGR5 receptor for BA. Cholic (CA) and deoxycholic (DCA) acids induce a sarcopenia-like phenotype through TGR5-dependent mechanisms. Besides, a mouse model of cholestasis-induced sarcopenia was characterised by increased levels of serum BA and muscle weakness, alterations that are dependent on TGR5 expression. Mitochondrial alterations, such as decreased mitochondrial potential and oxygen consumption rate (OCR), increased mitochondrial reactive oxygen species (mtROS) and unbalanced biogenesis and mitophagy, have not been studied in BA-induced sarcopenia.METHODS: We evaluated the effects of DCA and CA on mitochondrial alterations in C2C12 myotubes and a mouse model of cholestasis-induced sarcopenia. We measured mitochondrial mass by TOM20 levels and mitochondrial DNA; ultrastructural alterations by transmission electronic microscopy; mitochondrial biogenesis by PGC-1α plasmid reporter activity and protein levels by western blot analysis; mitophagy by the co-localisation of the MitoTracker and LysoTracker fluorescent probes; mitochondrial potential by detecting the TMRE probe signal; protein levels of OXPHOS complexes and LC3B by western blot analysis; OCR by Seahorse measures; and mtROS by MitoSOX probe signals. RESULTS: DCA and CA caused a reduction in mitochondrial mass and decreased mitochondrial biogenesis. Interestingly, DCA and CA increased LC3II/LC3I ratio and decreased autophagic flux concordant with raised mitophagosome-like structures. In addition, DCA and CA decreased mitochondrial potential and reduced protein levels in OXPHOS complexes I and II. The results also demonstrated that DCA and CA decreased basal, ATP-linked, FCCP-induced maximal respiration and spare OCR. DCA and CA also reduced the number of cristae. In addition, DCA and CA increased the mtROS. In mice with cholestasis-induced sarcopenia, TOM20, OXPHOS complexes I, II and III, and OCR were diminished. Interestingly, the OCR and OXPHOS complexes were correlated with muscle strength and bile acid levels. CONCLUSION: Our results showed that DCA and CA decreased mitochondrial mass, possibly by reducing mitochondrial biogenesis, which affects mitochondrial function, thereby altering potential OCR and mtROS generation. Some mitochondrial alterations were also observed in a mouse model of cholestasis-induced sarcopenia characterised by increased levels of BA, such as DCA and CA.

Ursodeoxycholic acid induces sarcopenia associated with decreased protein synthesis and autophagic flux

BACKGROUND: Skeletal muscle generates force and movements and maintains posture. Under pathological conditions, muscle fibers suffer an imbalance in protein synthesis/degradation. This event causes muscle mass loss and decreased strength and muscle function, a syndrome known as sarcopenia. Recently, our laboratory described secondary sarcopenia in a chronic cholestatic liver disease (CCLD) mouse model. Interestingly, the administration of ursodeoxycholic acid (UDCA), a hydrophilic bile acid, is an effective therapy for cholestatic hepatic alterations. However, the effect of UDCA on skeletal muscle mass and functionality has never been evaluated, nor the possible involved mechanisms. METHODS: We assessed the ability of UDCA to generate sarcopenia in C57BL6 mice and develop a sarcopenic-like phenotype in C2C12 myotubes and isolated muscle fibers. In mice, we measured muscle strength by a grip strength test, muscle mass by bioimpedance and mass for specific muscles, and physical function by a treadmill test. We also detected the fiber's diameter and content of sarcomeric proteins. In C2C12 myotubes and/or isolated muscle fibers, we determined the diameter and troponin I level to validate the cellular effect. Moreover, to evaluate possible mechanisms, we detected puromycin incorporation, p70S6K, and 4EBP1 to evaluate protein synthesis and ULK1, LC3 I, and II protein levels to determine autophagic flux. The mitophagosome-like structures were detected by transmission electron microscopy. RESULTS: UDCA induced sarcopenia in healthy mice, evidenced by decreased strength, muscle mass, and physical function, with a decline in the fiber's diameter and the troponin I protein levels. In the C2C12 myotubes, we observed that UDCA caused a reduction in the diameter and content of MHC, troponin I, puromycin incorporation, and phosphorylated forms of p70S6K and 4EBP1. Further, we detected increased levels of phosphorylated ULK1, the LC3II/LC3I ratio, and the number of mitophagosome-like structures. These data suggest that UDCA induces a sarcopenic-like phenotype with decreased protein synthesis and autophagic flux. CONCLUSIONS: Our results indicate that UDCA induces sarcopenia in mice and sarcopenic-like features in C2C12 myotubes and/or isolated muscle fibers concomitantly with decreased protein synthesis and alterations in autophagic flux.

Associations of Sarcopenia, Handgrip Strength and Calf Circumference with Cognitive Impairment among Chinese Older Adults / 生物医学与环境科学（英文）

Objective@#To evaluate the associations of sarcopenia, handgrip strength and calf circumference with cognitive impairment among Chinese older adults.@*Methods@#Totally 2,525 older adults were recruited from the Healthy Aging and Biomarkers Cohort Study. Cognitive impairment was assessed by the Chinese Mini-Mental State Examination. Handgrip strength was calculated from the means of the right and left hand values. Calf circumference was measured at the site of maximum circumference of the non-dominant leg. The formula developed by Ishii was used to define sarcopenia. Multiple logistic regression was performed to evaluate the associations of sarcopenia, handgrip strength, and calf circumference with cognitive impairment.@*Results@#The prevalence of cognitive impairment was 34.36%. The adjusted odds ratio ( @*Conclusion@#Sarcopenia, identified by low handgrip strength and low calf circumference, was positively associated with cognitive impairment.

Effect of summer holidays on anthropometric measures and body composition of older adults, inadequacy of body mass index to detect changes during a critical period: a pilot study / Efecto de las vacaciones de verano en la composición corporal de adultos mayores, insuficiencia del índice de masa corporal para detectar cambios durante un período crítico: un estudio piloto

Obesity is a major health problem worldwide. Obesity prevalence in Chilean older adults (OA) is increasing, associated with several negative health outcomes. Therefore, determining critical periods of adiposity increase is relevant in OA. The aim of the study was to assess body composition changes in OA during summer holidays. This observational study involved two test visits, without a control group. Twelve OA (9 females) with an average age of 71.92±6.97 years participated in an initial evaluation (E1) and final evaluation (E2) at the beginning and at the end of the summer in 2015. Weight, height, and body mass index (BMI) were assessed; fat-free mass (FFM), fat mass (FM), and muscular mass (MM) data were collected through foot-to-foot bioimpedance analysis. No significant variations were reported in weight and BMI between E1 and E2. This prevalence was maintained between E1 and E2. The FM significantly increased between E1 (27.63±10.91) and E2 (28.64±11.39) (p= 0.007), while the FFM significantly decreased between E1 (45.38±5.89) and E2 (44.33±5.36) (P= 0.006), also the MM between E1 (43.08±5.62) and E2 (42.07±5.10). Both, weight and BMI are insufficient measures for detecting changes during this critical summer holiday period. However, the body composition measures identified significant changes in the OA during the study.

La obesidad es el principal problema de salud en todo el mundo. La prevalencia de obesidad en adultos mayores (AM) chilenos es cada vez mayor, lo que se ha asociado con varios efectos negativos para la salud. Por lo tanto, la determinación de períodos críticos de aumento de la adiposidad es relevante en AM. El objetivo fue evaluar los cambios de la composición corporal en adultos mayores AM durante las vacaciones de verano. Doce AM participaron en una evaluación inicial (E1) y final (E2) del verano 2015. Se evaluó: peso, talla, índice de masa corporal (IMC), masa libre de grasa (MLG), masa grasa (MG) y masa muscular (MM). No hubo diferencias significativas en peso e IMC. La MG aumentó entre E1 (27,63±10,91) y E2 (28,64±11,39) (p= 0,007), la MLG disminuyó significativamente entre E1 (45,38±5,89) y E2 (44,33±5,36), como también la MM entre E1 (43,08±5,62) y E2 (42,07±5,10). Tanto el peso como el IMC son medidas insuficientes para detectar cambios durante este período crítico de vacaciones de verano. Sin embargo, las medidas de la composición corporal identificaron cambios significativos en AM durante el estudio.

Sarcopenia in COPD: relationship with COPD severity and prognosis / Sarcopenia na DPOC: relação com a gravidade e o prognóstico da DPOC

Objective: To evaluate the prevalence of sarcopenia in COPD patients, as well as to determine whether sarcopenia correlates with the severity and prognosis of COPD.Methods: A cross-sectional study with COPD patients followed at the pulmonary outpatient clinic of our institution. The patients underwent dual-energy X-ray absorptiometry. The diagnosis of sarcopenia was made on the basis of the skeletal muscle index, defined as appendicular lean mass/height2 only for low-weight subjects and adjusted for fat mass in normal/overweight subjects. Disease severity (COPD stage) was evaluated with the Global Initiative for Chronic Obstructive Lung Disease (GOLD) criteria. The degree of obstruction and prognosis were determined by the Body mass index, airflow Obstruction, Dyspnea, and Exercise capacity (BODE) index.Results: We recruited 91 patients (50 females), with a mean age of 67.4 ± 8.7 years and a mean BMI of 25.8 ± 6.1 kg/m2. Sarcopenia was observed in 36 (39.6%) of the patients, with no differences related to gender, age, or smoking status. Sarcopenia was not associated with the GOLD stage or with FEV1 (used as an indicator of the degree of obstruction). The BMI, percentage of body fat, and total lean mass were lower in the patients with sarcopenia than in those without (p < 0.001). Sarcopenia was more prevalent among the patients in BODE quartile 3 or 4 than among those in BODE quartile 1 or 2 (p = 0.009). The multivariate analysis showed that the BODE quartile was significantly associated with sarcopenia, regardless of age, gender, smoking status, and GOLD stage.Conclusions: In COPD patients, sarcopenia appears to be associated with unfavorable changes in body composition and with a poor prognosis.

Objetivo: Avaliar a prevalência de sarcopenia em pacientes com DPOC e determinar se sarcopenia está correlacionada com a gravidade e o prognóstico de DPOC.Métodos: Estudo retrospectivo em pacientes com DPOC atendidos no ambulatório de pneumologia de nossa instituição. Os pacientes realizaram absorciometria de dupla energia por raios X. O diagnóstico de sarcopenia foi baseado no índice de massa muscular esquelética, definido como massa magra apendicular/altura2 somente para indivíduos com baixo peso, sendo ajustado pela massa gorda para aqueles com peso normal/sobrepeso. A gravidade da doença (estádio da DPOC) foi avaliada com os critérios da Global Initiative for Chronic Obstructive Lung Disease (GOLD). O grau de obstrução e o prognóstico foram determinados pelo índice Body mass index, airflow Obstruction, Dyspnea, and Exercise capacity (BODE).Resultados: Foram incluídos 91 pacientes (50 mulheres), com média de idade de 67,4 ± 8,7 anos e média de IMC de 25,8 ± 6,1 kg/m2. Sarcopenia foi diagnosticada em 36 (39,6%) dos pacientes, sem diferenças relacionadas a sexo, idade ou status tabágico. Não houve associação de sarcopenia com estádios GOLD ou VEF1 (utilizado como indicador do grau de obstrução). O IMC, a porcentagem de gordura corporal e a massa magra total foram menores nos pacientes com sarcopenia do que naqueles sem a doença (p < 0,001). A prevalência de sarcopenia foi maior nos pacientes com BODE nos quartis 3 ou 4 que naqueles com BODE nos quartis 1 ou 2 (p = 0,009). A análise multivariada mostrou que os quartis do BODE estavam significativamente associados à sarcopenia, independentemente de idade, gênero, status tabágico e estádio GOLD.Conclusões: Em pacientes com DPOC, sarcopenia parece estar associada a alterações desfavoráveis na composição corporal e pior prognóstico.

Área muscular abdominal determinada por tomografía computada como predictor de mortalidad en pacientes oncológicos / Abdominal muscle area determined by computed tomography as a predictor of mortality in oncology patients

Objective. To demonstrate that the current lumbar skeletal muscle index (LSMI) cutoff points overestimate sarcopenia in oncology patients. New cutoff points are proposed as predictors of mortality in oncology patients. Materials and methods: LSMI was estimated in a group of oncology and healthy patients on whom computed tomography was performed for oncological and non-oncological reasons, respectively. The prevalence of sarcopenia in the oncology group was determined using international cutoff points and cutoff points estimated from -1 SD and -2 SD below the average for healthy patients, recommending intermediate values to facilitate its use. A survival study was performed to demonstrate whether the cutoff points differ between mortality curves of sarcopenic and non-sarcopenic patients. Results: 131 healthy patients and 64 oncology patients were selected. The prevalence of sarcopenia in oncology patients was 80.8 percent and 42.1 percentwith international cutoff points, 57.5 percent and 39.5 percent tusing -1 SD and 15.4 percent and 13.2 percent using -2 SD, in men and women respectively. During the follow-up, 17 patients died and the best predictor of mortality was LSMI of 45 cm²/m² for men and 34 cm²/m² for women. Conclusion: LSMI using cutoff points of 45 cm²/m² for men and 34 cm²/m² for women, is a good predictor of mortality.

Objetivo: Demostrar que los actuales puntos de corte del índice muscular esquelético lumbar (IMEL) sobreestiman sarcopenia en pacientes oncológicos. Se proponen nuevos puntos de corte como predictores de mortalidad en pacientes oncológicos. Materiales y métodos: Se estimó el IMEL en un grupo de pacientes oncológicos y sanos que se realizaron tomografía computada por motivos oncológicos y no oncológicos, respectivamente. Se determinó la prevalencia de sarcopenia del grupo oncológico utilizando los puntos de corte internacionales y puntos de corte estimados a partir de -1DS y -2DS bajo el promedio de pacientes sanos, proponiendo valores intermedios para poder facilitar su utilización. Se realizó un estudio de sobrevida para demostrar si los puntos de corte diferencian entre curvas de mortalidad de pacientes sarcopénicos y no sarcopénicos. Resultados: Se seleccionaron 131 pacientes sanos y 64 pacientes oncológicos. La prevalencia de sarcopenia en pacientes oncológicos fue de 80.8 por ciento y 42.1 por ciento con puntos de corte internacionales, 57.5 porciento y 39.5 por ciento utilizando -1 DS y 15.4 por ciento y 13.2 por ciento utilizando -2 DS, en hombres y mujeres respectivamente. Durante el seguimiento,17 pacientes fallecieron y el mejor predictor de mortalidad fue el IMEL de 45 cm2/m2 para hombres y 34 cm²/m² para mujeres. Conclusión: El IMEL utilizando puntos de corte de 45 cm²/m² para hombres y 34 cm²/m² para mujeres, es un buen predictor de mortalidad.

Identification of sarcopenic obesity in postmenopausal women: a cutoff proposal

Sarcopenic obesity is the combination of reduced fat-free mass (FFM) and increased fat mass (FM) with advancing age but there is lack of clear criteria for its identification. The purposes of the present investigation were: 1) to determine the prevalence of postmenopausal women with reduced FFM relative to their FM and height, and 2) to examine whether there are associations between the proposed classification and health-related variables. A total of 607 women were included in this cross-sectional study and were separated into two subsets: 258 older women with a mean age of 66.8 ± 5.6 years and 349 young women aged 18-40 years (mean age, 29.0 ± 7.5 years). All volunteers underwent body composition assessment by dual-energy X-ray absorptiometry. The FFM index relative to FM and height was calculated and the cutoff value corresponded to two standard deviations below the mean of the young reference group. To examine the clinical significance of the classification, all older participants underwent measurements of quadriceps strength and cardiorespiratory fitness. Values were compared between those who were classified as low FFM or not, using an independent samples t-test and correlations were examined. The cutoff corresponded to a residual of -3.4 and generated a sarcopenic obesity prevalence of 19.8 percent that was associated with reduced muscle strength and aerobic fitness among the older participants. Also, the index correlated significantly with the health-related fitness variables. The results demonstrated reduced functional capacity for those below the proposed cutoff and suggested applicability of the approach as a definition for sarcopenic obesity.