BACKGROUND: Muscle quantity at intensive care unit (ICU) admission has been independently associated with mortality. In addition to quantity, muscle quality may be important for survival. Muscle quality is influenced by fatty infiltration or myosteatosis, which can be assessed on computed tomography (CT) scans by analysing skeletal muscle density (SMD) and the amount of intermuscular adipose tissue (IMAT). We investigated whether CT-derived low skeletal muscle quality at ICU admission is independently associated with 6-month mortality and other clinical outcomes.METHODS: This retrospective study included 491 mechanically ventilated critically ill adult patients with a CT scan of the abdomen made 1 day before to 4 days after ICU admission. Cox regression analysis was used to determine the association between SMD or IMAT and 6-month mortality, with adjustments for Acute Physiological, Age, and Chronic Health Evaluation (APACHE) II score, body mass index (BMI), and skeletal muscle area. Logistic and linear regression analyses were used for other clinical outcomes.RESULTS: Mean APACHE II score was 24 ± 8 and 6-month mortality was 35.6%. Non-survivors had a lower SMD (25.1 vs. 31.4 Hounsfield Units (HU); p < 0.001), and more IMAT (17.1 vs. 13.3 cm(2); p = 0.004). Higher SMD was associated with a lower 6-month mortality (hazard ratio (HR) per 10 HU, 0.640; 95% confidence interval (CI), 0.552-0.742; p < 0.001), and also after correction for APACHE II score, BMI, and skeletal muscle area (HR, 0.774; 95% CI, 0.643-0.931; p = 0.006). Higher IMAT was not significantly associated with higher 6-month mortality after adjustment for confounders. A 10 HU increase in SMD was associated with a 14% shorter hospital length of stay.CONCLUSIONS: Low skeletal muscle quality at ICU admission, as assessed by CT-derived skeletal muscle density, is independently associated with higher 6-month mortality in mechanically ventilated patients. Thus, muscle quality as well as muscle quantity are prognostic factors in the ICU.TRIAL REGISTRATION: Retrospectively registered (initial release on 06/23/2016) at ClinicalTrials.gov: NCT02817646 .
Background: Lipoedema is a chronic disorder of adipose tissue typically involving an abnormal build-up of fat cells in the legs, thighs and buttocks. Occurring almost exclusively in women, it often co-exists with obesity. Due to an absence of clear objective diagnostic criteria, lipoedema is frequently misdiagnosed as obesity, lymphoedema or a combination of both. The purpose of this observational study was to compare muscle strength and exercise capacity in patients with lipoedema and obesity, and to use the findings to help distinguish between lipoedema and obesity. Design: This cross-sectional, comparative pilot study performed in the Dutch Expertise Centre of Lymphovascular Medicine, Drachten, a secondary-care facility, included 44 women aged 18 years or older with lipoedema and obesity. Twenty-two women with lipoedema (diagnosed according the criteria of Wold et al, 1951) and 22 women with body mass index ≥30kg/m2 (obesity) were include in the study. No interventions were undertaken as part of the study. Results: Muscle strength of the quadriceps was measured with the MicroFET™, and functional exercise capacity was measured with the 6-minute walk test. The group with lipoedema had, for both legs, significantly lower muscle strength (left: 259.9 Newtons [N]; right: 269.7 N; p < 0.001) than the group with obesity. The group with lipoedema had a non-significant, but clinically relevant lower exercise-endurance capacity (494.1±116.0 metres) than the group with obesity (523.9±62.9 metres; p=0.296). Conclusions: Patients with lipoedema exhibit muscle weakness in the quadriceps. This finding provides a potential new criterion for differentiating lipoedema from obesity. We recommend adding measuring of muscle strength and physical endurance to create an extra diagnostic parameter when assessing for lipoedema.
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Insulin sensitivity and metabolic flexibility decrease in response to bed rest, but the temporal and causal adaptations in human skeletal muscle metabolism are not fully defined. Here, we use an integrative approach to assess human skeletal muscle metabolism during bed rest and provide a multi-system analysis of how skeletal muscle and the circulatory system adapt to short- and long-term bed rest (German Clinical Trials: DRKS00015677). We uncover that intracellular glycogen accumulation after short-term bed rest accompanies a rapid reduction in systemic insulin sensitivity and less GLUT4 localization at the muscle cell membrane, preventing further intracellular glycogen deposition after long-term bed rest. We provide evidence of a temporal link between the accumulation of intracellular triglycerides, lipotoxic ceramides, and sphingomyelins and an altered skeletal muscle mitochondrial structure and function after long-term bed rest. An intracellular nutrient overload therefore represents a crucial determinant for rapid skeletal muscle insulin insensitivity and mitochondrial alterations after prolonged bed rest.
