Functional abnormalities of the extrathoracic airway (EA) may produce symptoms mimicking bronchial asthma. We assessed the bronchial (B) and EA responsiveness to inhaled histamine in 40 patients with asthmatic symptoms and in nine asymptomatic controls. FEV1 and maximal mid-inspiratory flow (MIF50) were used as index of bronchial and EA narrowing. Hyperresponsiveness of the intra-(BHR) or extra-(EA-HR) thoracic airway was diagnosed when the provocative concentrations of histamine (PC20FEV1 or PC25MIF50) were less than 8 mg/ml. Fiberoptic laryngoscopy was performed in nine patients and three controls. The glottal region was measured at mid-volume of maximal inspiration (AgMI) and expiration (AgME) before and after histamine. Predominant EA-HR was found in 13 patients, predominant BHR in 12, equivalent BHR and EA-HR in another 12; no significant airway narrowing was observed in three patients and in the nine controls. EA-HR was significantly associated with female sex, sinusitis, post-nasal drip, dysphonia; BHR with atopy, wheezing and lower MEF50. The percent change in AgMI after histamine was closely related to the PC25MIF50 (r = 0.87, P less than 0.001), that of AgME to the PC20FEV1 (r = 0.78, P less than 0.01). These findings suggest that the assessment of EA responsiveness may be useful in the evaluation of asthmatic symptoms, especially in patients with no BHR.
Dysregulation of skeletal muscle metabolism influences whole body insulin sensitivity and glucose homeostasis. We hypothesized that type 2 diabetes-associated alterations in the plasma metabolome directly contributes to skeletal muscle immunometabolism and the subsequent development of insulin resistance. To this end, we analyzed the plasma and skeletal muscle metabolite profile and identified glutamine as a key amino acid that was inversely correlating with body mass index (BMI) and HOMA-IR index in people with normal glucose tolerance or type 2 diabetes. Using an in vitro model of human myotubes and an in vivo model of diet-induced obesity and insulin resistance in mice, we provide evidence that glutamine levels directly influence the inflammatory response of skeletal muscle and regulates the expression of the adaptor protein GRB10, an inhibitor of insulin signaling. Moreover, we demonstrate that a systemic increase of glutamine levels in a mouse model of obesity improves insulin sensitivity and restores glucose homeostasis. We conclude that glutamine supplementation may represent a potential therapeutic strategy to prevent or delay the onset of insulin resistance in obesity by reducing inflammatory markers and promoting skeletal muscle insulin sensitivity.
We investigated the acute effect of ascorbic acid on histamine bronchial responsiveness (PC20: concentration causing a 20% fall in FEV,) in 9 hospital staff members with upper respiratory tract infection (URI) and cough. Subjects were examined within 5 days from the start of illness and 6 weeks after. On day 1, the reproducibility of PC20 was assessed by 2 consecutive inhalation challenges 1 h apart; the two values were closely related (r = 0.96, p < 0.001). Five subjects had bronchial hyperresponsiveness (PC20 < 8 mg/ml histamine). On the following day, PC20 was measured before and 1 h after oral intake of 2 g ascorbic acid. Vitamin C produced a significant increase in average PC20 (p < 0.01) from 7.8 ± (SE) 1.2 to 25.1 ± (SE) 1.2 mg/ml. None had airway hyperresponsiveness after treatment. Six weeks after the onset of URI, bronchial responsiveness was normal in all the subjects but one. The mean PC20 was 15.5 ± (SE) 1.25 mg/ml, significantly higher than during URI (p < 0.05); after ascorbic acid it increased nonsignificantly to 25.7 ± (SE) 1.35 mg/ml. Our results indicate that vitamin C inhibits the transient increase in bronchial responsiveness occurring in otherwise normal subjects during URI.
Bronchial responsiveness has been evaluated in patients with chronic lung congestion secondary to mitral valve disease. Methacholine bronchial challenge was performed by intermittent aerosol generation in 31 patients with mitral valve disease, 18 in New York Heart Association (NYHA) Class II and 13 in NYHA Class III, non-atopic and with baseline forced expiratory volume in one second/vital capacity (FEV1/VC) greater than 85% of predicted and in 30 normal controls. Haemodynamic data were available in 17 patients. The methacholine bronchial provocation dose causing a 35% fall of airway conductance (PD35sGaw) was significantly lower in patients (507 +/- C.I. 205 micrograms) than in normals (2779 +/- C.I. 358 micrograms), (p less than 0.001). In patients log PD35sGaw was significantly correlated with mean pulmonary artery pressure (r = 0.53, p less than 0.05), mean pulmonary capillary wedge pressure (r = 0.67, p less than 0.01), but not with any spirometric parameters. Bronchial hyperresponsiveness seems to be common in patients with mitral valve disease and evidence of lung congestion.
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