Effects Of Insulin-like Growth Factor-1 (IGF-1) And Insulin On Modulating Glucose Metabolism And Functions Of Lung Fibroblast

PrefaceInterstitial lung diseases (ILDs) are characterized by pulmonary fibrosis and are one of the focuses in respiratory medicine internationally because of its unknown etiology, complicated pathogenesis and refractory to any current therapeutic approaches. It is now recognized that lung fibroblast ( LF) acts as an " common pathway" in the development of fibrosis from alveolitis of whatever etiology. It is understandable that a therapeutic approach which is targeted on LF metabolism and function modulation could be a reasonable one in intervening pulmonary fibrosis. Insulin - like growth factor - 1 (IGF - 1) is a cytokine with similarities in structure with insulin and can play a more important role in modulating glucose metabolism in LF. The present study is undertaken to investigate the modulating effects of IGF - 1 and insulin or combined with insulin on LF glucose metabolism and its functions producing extracellular matrix to shed light on possible therapeutic target through modulating LF in intervening pulmonary fibrosis.MethodologyHuman embryonic lung( HEL) diploid fibroblast cell line were cultured respectively for 24hrs with blank control,100ng/ml IGF -1,200ng/ml IGF - 1, 100ng/ml IGF - 1 + 100ng/ml Insulin,100ng/mlIGF - 1 + 200ng/ml Insulin,lOOng/ml Insulin ,200ng/ml Insulin. ,200ng/ml InsulinThen the culture supernatant and cell pellet were collected in centrifuge tubes and preserved in - 20 for future use. The cell pellet was lysed with Trizol to extract its intracellular mRNA and protein. After quantitation with ultraviolet spectrometer, RT - PCR and Northern - blotting were employed to determine the content of GLUT - 4 , HK -2 mRNA compared to 28sRNA,GAPDH, which are in a stable level during cell multiplication. Western - blotting were used to determine GLUT -4/HK -II expression and extracellular matrix secretion, eg. elastin and collagens IV.Results1. Compared with control group, IGF - 1 significantly enhances LF glucose metabolism signified by the increased expression of GLUT - 4 and HK - II mRNA expressions, leading to increased elastin and collagen mRNA transcription. The aboved mentioned enhancing effect of IGF - 1 is in a concentration - dependent manner.2. Enhancing effect of IGF - Ion LF glucose metabolism is weak compared with that of insulin itself.3. Insulin also exerts a enhancing effect of LF to express elastin and collagen , which is weak compared with IGF -1. Moreover, insulin can decrease the enhancing effect of IGF - 1 on elastin and collagen expressions01.DiscussionInsulin - like growth factor - 1 (IGF - 1) protein has a length of 70 amino acids (7.6 kDa) with highly homologous to human pro - insulin in structure. IGF -1 is synthesized in many tissues. Normal serum levels in healthy human subjects are 150 - 250 microgram/L. Its activitiy can be modulated by IGF binding proteins in interstitial fluid. In fact,it is IGF - 1 derived from interstitial macrophage plays an important role in pulmonary fibrosis.Elevated IGF -1 levels in rat lung homogenate have been found in fibrosis developed by hyperoxia. Respondingly, IGFs binding proteins and glucose transporter - IV ( GLUT - IV ) ,hexokinase - H ( HK - II ) were expressed excessively. As a result, the synthesize and secretion of collagen and elastin were en-...