Alterations of lung structure in experimental diabetes, and diabetes associated with hyperlipidaemia in hamsters

Since hyperglycaemia is known to affect normal pulmonary physiology and biochemistry and few structure-function correlations have been reported, we designed experiments on hamsters subjected to streptozotocin-induced diabetes or diabetes associated with hyperlipidaemia, and investigated the impact of these conditions on the lung structure. At time intervals ranging 2-24 weeks from the inception of disease (without correcting blood glucose with insulin), the animals were sacrificed, and plasma glucose and cholesterol assayed. The lung was processed for electron microscopy, and the structural changes of the capillary and venular endothelium, of epithelial cells, and interstitium were examined. In diabetic animals, especially after 6 weeks of disease, a gradual narrowing of approximately 35% of the capillaries and approximately 30% of the alveoli, and hyperplasia of the extracellular matrix, rich in collagen bundles, were observed. Frequently, capillaries contained adherent intravascular macrophages suggestive of an inflammatory process. The capillary endothelium was characterized by numerous plasmalemmal vesicles, often fused, well-developed synthesizing apparatus (endoplasmic reticulum and Golgi complex) and cytoskeleton, and an uneven distribution of the anionic sites on the luminal plasmalemma. The venular endothelium was particularly rich in Weibel-Palade bodies. The alveolar epithelium was often collapsed, compressing surfactant within the airspace. The lung interstitium was apparently enlarged, and the fibroblasts and contractile interstitial cells frequently contained lipid droplets. These alterations were more pronounced and occurred at a faster rate (4 weeks) in diabetes associated with hyperlipidaemia. The structural modifications reported in this study support the functional disturbances observed in association with hyperglycaemia, sustaining the conclusion that the lung is an organ affected by diabetes.