Circulating Interleukin-6 Is Associated with Skeletal Muscle Strength, Quality, and Functional Adaptation with Exercise Training in Mobility-Limited Older Adults

BACKGROUND

Human aging is characterized by a chronic, low-grade inflammation suspected to contribute to reductions in skeletal muscle size, strength, and function. Inflammatory cytokines, such as interleukin-6 (IL-6), may play a role in the reduced skeletal muscle adaptive response seen in older individuals.

OBJECTIVES

To investigate relationships between circulating IL-6, skeletal muscle health and exercise adaptation in mobility-limited older adults.

DESIGN

Randomized controlled trial.

SETTING

Exercise laboratory on the Health Sciences campus of an urban university.

PARTICIPANTS

99 mobility-limited (Short Physical Performance Battery (SPPB) ≤9) older adults.

INTERVENTION

6-month structured physical activity with or without a protein and vitamin D nutritional supplement.

MEASUREMENTS

Circulating IL-6, skeletal muscle size, composition (percent normal density muscle tissue), strength, power, and specific force (strength/CSA) as well as physical function (gait speed, stair climb time, SPPB-score) were measured pre- and post-intervention.

RESULTS

At baseline, Spearman's correlations demonstrated an inverse relationship (P<0.05) between circulating IL-6 and thigh muscle composition (r = -0.201), strength (r = -0.311), power (r = -0.210), and specific force (r = -0.248), and positive association between IL-6 and stair climb time (r = 0.256; P<0.05). Although the training program did not affect circulating IL-6 levels (P=0.69), reductions in IL-6 were associated with gait speed improvements (r = -0.487; P<0.05) in "higher" IL-6 individuals (>1.36 pg/ml). Moreover, baseline IL-6 was inversely associated (P<0.05) with gains in appendicular lean mass and improvements in SPPB score (r = -0.211 and -0.237, respectively).

CONCLUSIONS

These findings implicate age-related increases in circulating IL-6 as an important contributor to declines in skeletal muscle strength, quality, function, and training-mediated adaptation. Given the pervasive nature of inflammation among older adults, novel therapeutic strategies to reduce IL-6 as a means of preserving skeletal muscle health are enticing.

Accuracy of respiratory rate monitoring using a non-invasive acoustic method after general anaesthesia

BACKGROUND

Respiratory rate should be monitored continuously in the post-anaesthesia care unit (PACU) to avoid any delay in the detection of respiratory depression. Capnometry is the standard of care but in extubated patients requires a nasal cannula or a face mask that may be poorly tolerated or can be dislodged, leading to errors in data acquisition and false alarms. The value of a new non-invasive acoustic monitor in this setting has not been fully investigated.

METHODS

Adult patients admitted to the PACU after general anaesthesia were included. After tracheal extubation, an adhesive sensor with an integrated acoustic transducer (RRa™) was placed on the patient's throat and connected to its monitor while the patient breathed through a face mask with a carbon dioxide sampling port (Capnomask™) connected to a capnometer. Both the acoustic monitor and the capnometer were connected to a computer to record one pair of data per second for up to 60 min.

RESULTS

Fifty-two patients, mean (range) age 54 (22-84) yr and BMI 26 (19-39) kg m(-2), were studied. Compared with capnometry, the bias and limits of agreement of the acoustic method were 0 (-1.4-1.4) bpm. The acoustic sensor was well tolerated while the face mask was removed by eight patients, leading to study discontinuation in two patients.

CONCLUSIONS

In extubated patients, continuous assessment of respiration rate with an acoustic monitor correlated well with capnometry.

[Right atrioventricular metastasis of a myxoid liposarcoma. Case report and al review of the literature]

Malignant tumours of the heart and pericardium are rare. Secondary tumours are 20 to 40 times more common than primary tumours. The authors report the case of a cardiac metastasis of a myxoid liposarcoma of the inguinal region. Surgical ablation with chemotherapy significantly improved the patient' clinical and haemodynamic status. A review of the literature shows that postoperative survival does not exceed 2 years, but the prognosis is better when chemotherapy is associated with surgery. Transoesophageal echocardiography is an excellent diagnostic imaging method. It provides a better evaluation of the tumour and its location, compared to thoracic CT scan and transthoracic echocardiography.

Temporal and spatial rhythmicity of jejunal wall motion in rats

Isolated segments of jejunum of fasted rats exhibit regular rhythmic contractions at the same frequency as slow-waves. The aim of the present study was to search for a possible spatial rhythmicity of this activity. Using a video imaging technique, jejunal segments of 50 rats were studied. Only experiments (n=76) with no propagated contractions at visual inspection were included in the study. After the measurement, a spectral analysis of the diameter variations was performed. The bands were characterized by four parameters: level, main frequency, amplitude and phase. At each level, the phase varied, suggesting that the same rhythmic phenomenon occurred, but with a delay as a function of the spatial position. In 58 measurements, the rhythmic activity had a frequency near 0.50 Hz and in 18, near 0.25 Hz. Phase difference was found in 32 segments (42%). The variation with distance was linear as a function of time and its length was greater for the low-frequency group than for the high-frequency group (25.6 +/- 9.4 vs. 33.3 +/- 5.2 mm, P=0.015). By contrast, the speed of propagation was not significantly different. The wavelength lambda of the spatial rhythmicity was 27.7 +/- 23.2 and 9.8 +/- 4.2 mm (P=NS) in the high- and low-frequency groups, respectively. This corresponds to a speed of propagation of v=lambda*f, where f is the frequency of the wall motion (7.0 +/- 5.2 vs. 5.2 +/- 2.2 mm sec-1, P=NS).

In vitro analysis of rat intestinal wall movements at rest and during propagated contraction: a new method

Intestinal wall motions are not easily studied and are frequently deduced from manometric and electromyographic measurements. This study aimed to establish a method of wall movement analysis based on an automatic technique of image processing. Segments of rat jejunum were fixed in an organ bath under isometric conditions. A real-time edge-detection algorithm was used to find the contours of the intestine using video imaging. After the measurement, a mapping of intestinal wall movements was performed based on diameter variations. In the 260 experiments without stimulation, intestinal wall activity was always detected. Propagated activity was found in 40% of the experiments and periodic wall motion in 60%, with 0.5-Hz activity found more frequently (41%) than 0.24-Hz activity (19%). These cyclic activities, related to intestinal slow waves, had their amplitude decreased by acetylcholine and were modified by vapreotide. Analysis of a propagated wave after cholinergic stimulation showed that it is characterized by an increase of the diameter of the intestine followed by a decrease. Moreover, this methodology allows analysis of the initiation of a propagated wave.