Airway inflammatory events in diabetic-antigen sensitized guinea pigs

Lung volume dependence of respiratory function in rodent models of diabetes mellitus

Background

Diabetes mellitus causes the deterioration of smooth muscle cells and interstitial matrix proteins, including collagen. Collagen and smooth muscle cells are abundant in the lungs, but the effect of diabetes on airway function and viscoelastic respiratory tissue mechanics has not been characterized. This study investigated the impact of diabetes on respiratory function, bronchial responsiveness, and gas exchange parameters.

Methods

Rats were allocated randomly to three groups: a model of type 1 diabetes that received a high dose of streptozotocin (DM1, n = 13); a model of type 2 diabetes that received a low dose of streptozotocin with a high-fat diet (DM2, n = 14); and a control group with no treatment (C, n = 14). Forced oscillations were applied to assess airway resistance (Raw), respiratory tissue damping (G), and elastance (H). The arterial partial pressure of oxygen to the inspired oxygen fraction (PaO₂/FiO₂) and intrapulmonary shunt fraction (Qs/Qt) were determined from blood gas samples at positive end-expiratory pressures (PEEPs) of 0, 3, and 6 cmH₂O. Lung responsiveness to methacholine was also assessed. Collagen fibers in lung tissue were quantified by histology.

Results

The rats in groups DM1 and DM2 exhibited elevated Raw, G, H, and Qs/Qt, compromised PaO₂/FiO₂, and diminished airway responsiveness. The severity of adverse tissue mechanical change correlated with excessive lung collagen expression. Increased PEEP normalized the respiratory mechanics, but the gas exchange abnormalities remained.

Conclusions

These findings indicate that diabetes reduces airway and lung tissue viscoelasticity, resulting in alveolar collapsibility that can be compensated by increasing PEEP. Diabetes also induces persistent alveolo-capillary dysfunction and abnormal adaptation ability of the airways to exogenous constrictor stimuli.

Diabetic lung disease: fact or fiction?

Diabetes mellitus is a chronic, progressive, incompletely understood metabolic disorder whose prevalence has been increasing steadily worldwide. Even though little attention has been paid to lung disorders in the context of diabetes, its prevalence has recently been challenged by newer studies of disease development. In this review, we summarize and discuss the role of diabetes mellitus involved in the progression of pulmonary diseases, with the main focus on pulmonary fibrosis, which represents a chronic and progressive disease with high mortality and limited therapeutic options.

Deterioration of epithelium mediated mechanisms in diabetic-antigen sensitized airways of guinea pigs

BACKGROUND

The onset of diabetes causes disruption of respiratory epithelial mediators. The present study investigates whether diabetes modifies the epithelium mediated bronchial responses in hyper-reactive airway smooth muscle (ASM) primarily through nitric oxide (NO), cyclooxygenase (COX), and epithelium derived hyperpolarizing factor (EpDHF) pathways.

METHODS

Experimental model of guinea pigs having hyper-reactive airways with or without diabetes were developed. The responses of tracheal rings to cumulative concentrations of acetylcholine (ACh) and isoproterenol (IP) in the presence and absence of epithelium and before and after incubation with NO, K⁺_ATP and COX inhibitors, N-(ω)-Nitro-L-arginine methyl ester (L-NAME; 100 μM), glybenclamide (10 μM) and indomethacin (100 μM) were assessed.

RESULTS

In diabetic guinea pigs with hyper-reactive airways, a decrease in ACh induced bronchoconstriction was observed after epithelium removal and after incubation with L-NAME/indomethacin, suggesting damage to NO/COX pathways. Hyper-reactivity did not alter the response of trachea to ACh but affected the response to IP which was further reduced in hyper-reactive animals with diabetes. The ASM response to IP after glybenclamide treatment did not alter in hyper-reactive guinea pigs and diabetic guinea pigs with hyper-reactive airways, suggesting damage to the EpDHF pathway. Treatment with indomethacin reduced IP response in the hyper-reactive model, and did not produce any change in diabetic model with hyper-reactive airways, indicating further disruption of the COX pathway.

CONCLUSION

EpDHF pathway is damaged in hyper-reactive guinea pigs and in diabetic guinea pigs with hyper-reactive airways. Diabetes further aggravates the NO and COX mediated pathways in diabetic guinea pigs with hyper-reactive airways.

Onset of diabetes modulates the airway smooth muscle reactivity of guinea pigs: role of epithelial mediators

BACKGROUND

Diabetes induces lung dysfunction, leading to alteration in the pulmonary functions. Our aim was to investigate whether the early stage of diabetes alters the epithelium-dependent bronchial responses and whether nitric oxide (NO), KATP channels and cyclooxygenase (COX) pathways contribute in this effect.

METHODS

Guinea pigs were treated with a single injection of streptozotocin (180 mg/kg, i.p.) for induction of diabetes. Airway conductivity was assessed by inhaled histamine, using a non-invasive body plethysmography. The contractile responses of tracheal rings induced by acetylcholine (ACh) and relaxant responses of precontracted rings, induced by isoproterenol (IP) were compared in the presence and absence of the epithelium. Effects of N(ω)-Nitro-L-arginine methyl ester (L-NAME, a nitric oxide synthase inhibitor), glybenclamide (a KATP channel inhibitor) and indomethacin (a COX inhibitor) were also assessed in diabetic guinea pigs.

RESULTS

Early stage diabetes did not alter the airway conductivity. ACh-induced bronchoconstriction in epithelium intact tracheal rings was not affected by the onset of diabetes, however a reduction in the increased ACh responses due to epithelium removal, to L-NAME or to indomethacin was observed. The relaxation response to IP was impaired in trachea from guinea pigs in which diabetes had just developed. Early diabetes significantly reduced the IP response to glybenclamide and to indomethacin.

CONCLUSION

Our results demonstrate that the early stage of diabetes, modulate the bronchial reactivity to both ACh and IP by disrupting the NO, KATP channels and COX pathways, without affecting the airway conductivity in guinea pigs.

Eosinophil inversely associates with type 2 diabetes and insulin resistance in Chinese adults

CONTEXT

Limited population-based study focused on relationship between eosinophil and type 2 diabetes (T2D).

OBJECTIVES

We aimed to evaluate the relationship between peripheral eosinophil percentage and glucose metabolism and insulin resistance in a large sample size of Chinese population aged 40 and older.

DESIGN AND METHODS

A cross-sectional study was performed among 9,111 Chinese adults including 3,561 men and 5,550 women. The glucose metabolism status was confirmed by 75-g oral glucose tolerance test. Homeostasis model assessment of insulin resistance index and serum insulin levels were used to evaluate insulin resistance. Homeostasis model assessment-B was used to evaluate β cell function.

RESULTS

The average age of participants was 58.5 years. The prevalence of T2D decreased across the tertiles of eosinophil percentage (21.3%, 18.2% and 16.9%, P<0.0001). Each one tertile increase of eosinophil percentage inversely associated with risk of T2D when referred not only to normal glucose tolerance (NGT) (odds ratio (OR) 0.81, 95% CI 0.76-0.87, P< 0.0001), but also to impaired glucose regulation (OR 0.89, 95% CI 0.83-0.97, P = 0.006), respectively, after adjustment for the confounding factors. Compared with the first tertile, the third tertile of eosinophil percentage associated with a 23% decrease of insulin resistance in NGT participants after full adjustments (P = 0.005). Each 1-standard deviation of increment of eosinophil percentage associated with a 37% decrease of insulin resistance (P = 0.005).

CONCLUSIONS

Higher peripheral eosinophil percentage was associated with decreased risk of T2D. The inverse relation to insulin resistance was detected in NGT participants.