Heart Failure Results in Inspiratory Muscle Dysfunction Irrespective of Left Ventricular Ejection Fraction.

BACKGROUND: Exercise intolerance in heart failure with reduced ejection fraction (HFrEF) or heart failure with preserved ejection fraction (HFpEF) results from both cardiac dysfunction and skeletal muscle weakness. Respiratory muscle dysfunction with restrictive ventilation disorder may be present irrespective of left ventricular ejection fraction and might be mediated by circulating pro-inflammatory cytokines. OBJECTIVE: To determine lung and respiratory muscle function in patients with HFrEF/HFpEF and to determine its associations with exercise intolerance and markers of systemic inflammation. METHODS: Adult patients with HFrEF (n = 22, 19 male, 61 ± 14 years) and HFpEF (n = 8, 7 male, 68 ± 8 years) and 19 matched healthy control subjects underwent spirometry, measurement of maximum mouth occlusion pressures, diaphragm ultrasound, and recording of transdiaphragmatic and gastric pressures following magnetic stimulation of the phrenic nerves and the lower thoracic nerve roots. New York Heart Association (NYHA) class and 6-min walking distance (6MWD) were used to quantify exercise intolerance. Levels of circulating interleukin 6 (IL-6) and tumor necrosis factor-α (TNF-α) were measured using ELISAs. RESULTS: Compared with controls, both patient groups showed lower forced vital capacity (FVC) (p < 0.05), maximum inspiratory pressure (PImax), maximum expiratory pressure (PEmax) (p < 0.05), diaphragm thickening ratio (p = 0.01), and diaphragm strength (twitch transdiaphragmatic pressure in response to supramaximal cervical magnetic phrenic nerve stimulation) (p = 0.01). In patients with HFrEF, NYHA class and 6MWD were both inversely correlated with FVC, PImax, and PEmax. In those with HFpEF, there was an inverse correlation between amino terminal pro B-type natriuretic peptide levels and FVC (r = -0.77, p = 0.04). In all HF patients, IL-6 and TNF-α were statistically related to FVC. CONCLUSIONS: Irrespective of left ventricular ejection fraction, HF is associated with respiratory muscle dysfunction, which is associated with increased levels of circulating IL-6 and TNF-α.

Inspiratory muscle dysfunction and restrictive lung function impairment in congenital heart disease: Association with immune inflammatory response and exercise intolerance.

BACKGROUND: In adult patients with congenital heart disease (ACHD), both underlying disease and lung restriction contribute to exercise intolerance. In ACHD the yet incompletely understood mechanism underlying restricted ventilation may be inspiratory muscle weakness. Therefore, this study comprehensively evaluated inspiratory muscle function in ACHD and associations with systemic inflammation and the clinical severity of exercise intolerance. METHODS: 30 ACHD patients (21 men, 35 ± 12 years) and 30 healthy controls matched for age, gender and body mass index underwent spirometry, measurement of mouth occlusion pressures, and diaphragm ultrasound. Six-minute walking distance (6MWD) and New York Heart Association functional class were used to quantify exercise intolerance. Interleukin-6 (IL-6) and tumor necrosis factor-alpha (TNF-α) levels were measured using enzyme-linked immunosorbent assays. RESULTS: ACHD patients showed lower forced vital capacity (FVC), and maximum inspiratory (PImax) and expiratory (PEmax) pressures compared with controls (all p < 0.05). On ultrasound, ACHD patients showed a lower diaphragm thickening ratio (2.3 ± 0.5 vs. 2.8 ± 0.9, p < 0.01) and lower diaphragm excursion velocity during a voluntary sniff maneuver (5.7 ± 2.2 vs. 7.6 ± 2.0 cm/s, p < 0.01). Respiratory parameters, such as FVC (r = 0.53; p < 0.01) and PImax (r = 0.43; p = 0.02), correlated with 6MWD. Furthermore, amino terminal pro B-type natriuretic peptide levels were inversely correlated with FVC (r = -0.54; p < 0.01). Circulating pro-inflammatory cytokines were markedly increased, and IL-6 was correlated with 6MWD, dyspnea, and biomarkers of heart, lung and inspiratory muscle function (all p < 0.05). CONCLUSIONS: Our findings show that diaphragm dysfunction is present in ACHD and relates to restrictive ventilation disorder and exercise intolerance, possibly mediated by increased IL-6 levels.

Respiratory Muscle and Lung Function in Lung Allograft Recipients: Association with Exercise Intolerance.

BACKGROUND: In lung transplant recipients (LTRs), restrictive ventilation disorder may be present due to respiratory muscle dysfunction that may reduce exercise capacity. This might be mediated by pro-inflammatory cytokines such as tumor necrosis factor-α (TNF-α) and interleukin-6 (IL-6). OBJECTIVE: We investigated lung respiratory muscle function as well as circulating pro-inflammatory cytokines and exercise capacity in LTRs. METHODS: Fifteen LTRs (6 female, age 56 ± 14 years, 63 ± 45 months post-transplantation) and 15 healthy controls matched for age, sex, and body mass index underwent spirometry, measurement of mouth occlusion pressures, diaphragm ultrasound, and recording of twitch transdiaphragmatic (twPdi) and gastric pressures (twPgas) following magnetic stimulation of the phrenic nerves and the lower thoracic nerve roots. Exercise capacity was quantified using the 6-min walking distance (6MWD). Plasma IL-6 and TNF-α were measured using enzyme-linked immunosorbent assays. RESULTS: Compared with controls, patients had lower values for forced vital capacity (FVC; 81 ± 30 vs.109 ± 18% predicted, p = 0.01), maximum expiratory pressure (100 ± 21 vs.127 ± 17 cm H2O, p = 0.04), diaphragm thickening ratio (2.2 ± 0.4 vs. 3.0 ± 1.1, p = 0.01), and twPdi (10.4 ± 3.5 vs. 17.6 ± 6.7 cm H2O, p = 0.01). In LTRs, elevation of TNF-α was related to lung function (13 ± 3 vs. 11 ± 2 pg/mL in patients with FVC ≤80 vs. >80% predicted; p < 0.05), and lung function (forced expiratory volume after 1 s) was closely associated with diaphragm thickening ratio (r = 0.81; p < 0.01) and 6MWD (r = 0.63; p = 0.02). CONCLUSION: There is marked restrictive ventilation disorder and respiratory muscle weakness in LTRs, especially inspiratory muscle weakness with diaphragm dysfunction. Lung function impairment relates to elevated levels of circulating TNF-α and diaphragm dysfunction and is associated with exercise intolerance.

Prospective exploratory muscle biopsy, imaging, and functional assessment in patients with late-onset Pompe disease treated with alglucosidase alfa: The EMBASSY Study.

BACKGROUND: Late-onset Pompe disease is characterized by progressive skeletal myopathy followed by respiratory muscle weakness, typically leading to loss of ambulation and respiratory failure. In this population, enzyme replacement therapy (ERT) with alglucosidase alfa has been shown to stabilize respiratory function and improve mobility and muscle strength. Muscle pathology and glycogen clearance from skeletal muscle in treatment-naïve adults after ERT have not been extensively examined. METHODS: This exploratory, open-label, multicenter study evaluated glycogen clearance in muscle tissue samples collected pre- and post- alglucosidase alfa treatment in treatment-naïve adults with late-onset Pompe disease. The primary endpoint was the quantitative reduction in percent tissue area occupied by glycogen in muscle biopsies from baseline to 6months. Secondary endpoints included qualitative histologic assessment of tissue glycogen distribution, secondary pathology changes, assessment of magnetic resonance images (MRIs) for intact muscle and fatty replacement, and functional assessments. RESULTS: Sixteen patients completed the study. After 6months of ERT, the percent tissue area occupied by glycogen in quadriceps and deltoid muscles decreased in 10 and 8 patients, respectively. No changes were detected on MRI from baseline to 6months. A majority of patients showed improvements on functional assessments after 6months of treatment. All treatment-related adverse events were mild or moderate. CONCLUSIONS: This exploratory study provides novel insights into the histopathologic effects of ERT in late-onset Pompe disease patients. Ultrastructural examination of muscle biopsies demonstrated reduced lysosomal glycogen after ERT. Findings are consistent with stabilization of disease by ERT in treatment-naïve patients with late-onset Pompe disease.

Role of interleukin-6 in stress, sleep, and fatigue.

Chronic low-grade inflammation, in particular increased concentrations of proinflammatory cytokines such as interleukin (IL)-6 in the circulation, is observed with increasing age, but it is also as a consequence of various medical and psychological conditions, as well as life-style choices. Since molecules such as IL-6 have pleiotropic effects, consequences are wide ranging. This short review summarizes the evidence showing how IL-6 elevations in the context of inflammatory disease affect the organism, with a focus on sleep-related symptoms and fatigue; and conversely, how alterations in sleep duration and quality stimulate increased concentrations of IL-6 in the circulation. Research showing that acute as well as chronic psychological stress also increase concentrations of IL-6 supports the notion of a close link between an organism's response to physiological and psychological perturbations. The findings summarized here further underscore the particular importance of IL-6 as a messenger molecule that connects peripheral regulatory processes with the CNS.

Cell cycle inhibitors p21 and p16 are required for the regulation of Schwann cell proliferation.

Regulated cell proliferation is a crucial prerequisite for Schwann cells to achieve myelination in development and regeneration. In the present study, we have investigated the function of the cell cycle inhibitors p21 and p16 as potential regulators of Schwann cell proliferation, using p21- or p16-deficient mice. We report that both inhibitors are required for proper withdrawal of Schwann cells from the cell cycle during development and following injury. Postnatal Schwann cells express p21 exclusively in the cytoplasm, first detectable at postnatal day 7. This cytoplasmic p21 expression is necessary for proper Schwann cell proliferation control in the late development of peripheral nerves. After axonal damage, p21 is found in Schwann cell nuclei during the initiation of the proliferation period. This stage is critically regulated by p21, since loss of p21 leads to a strong increase in Schwann cell proliferation. Unexpectedly, p21 levels are upregulated in this phase suggesting that the role of p21 may be more complex than purely inhibitory for the Schwann cell cycle. However, inhibition of Schwann cell proliferation is the overriding crucial function of p21 and p16 in peripheral nerves as revealed by the consequences of loss-of-function in development and after injury. Different mechanisms appear to underlie the inhibitory function, depending on whether p21 is cytoplasmic or nuclear.