Upregulated IGF‑1 in the lungs of asthmatic mice originates from alveolar macrophages

Circulating insulin-like growth factor-1 and risk of lung diseases: A Mendelian randomization analysis

BACKGROUND

Insulin-like growth factor-1 (IGF-1) display a vital role in in the pathogenesis of lung diseases, however, the relationship between circulating IGF-1 and lung disease remains unclear.

METHODS

Single nucleotide polymorphisms (SNPs) associated with the serum levels of IGF-1 and the outcomes data of lung diseases including asthma, chronic obstructive pulmonary disease (COPD), lung cancer and idiopathic pulmonary fibrosis (IPF) were screened from the public genome-wide association studies (GWAS). Two-sample Mendelian randomization (MR) analysis was then performed to assess the independent impact of IGF-1 exposure on these lung diseases.

RESULTS

Totally, 416 SNPs related to circulating IGF-1 levels among 358,072 participants in UK Biobank. According to a primary casual effects model with MR analyses by the inverse variance weighted (IVW) method, the circulating IGF-1 was demonstrated a significantly related with the risk of asthma (OR, 0.992; 95% CI, 0.985-0.999, P=0.0324), while circulating IGF-1 showed no significant correlation with CODP (OR, 1.000; 95% CI, 0.999-1.001, P=0.758), lung cancer (OR, 0.979, 95% CI, 0.849-1.129, P=0.773), as well as IPIGFF (OR, 1.100, 95% CI, 0.794-1.525, P=0.568).

CONCLUSION

The present study demonstrated that circulating IGF-1 may be causally related to lower risk of asthma.

Novel Aspects of Insulin-like Growth Factor 1/insulin Network in Chronic Inflammatory Airway Disease

At least a proportion of patients suffering from chronic inflammatory airway diseases respond poorly to the bronchodilator and corticosteroid therapies. There is a need for the development of improved anti-inflammatory treatment. Insulin Growth Factor 1 (IGF1) and insulin participate in not only metabolism and glucose homeostasis, but also many other physiological and pathophysiological processes, including growth and inflammation. Recently, it was shown that not only the classical IGF1 and IGF1 Receptor (IGF1R), but also the other molecules in the IGF1/insulin network, including insulin, insulin-like growth factor-binding protein (IGFBP), and IGFBP protease, have roles in chronic inflammatory airway diseases. This review aims to provide a comprehensive insight into recent endeavors devoted to the role of the IGF1/insulin network in chronic inflammatory airway diseases. Its participation in airway inflammation, remodeling, and hyper-responsiveness (AHR), as well as acute exacerbation, has been conclusively demonstrated. Its possible relation to glucocorticoid insensitivity has also been indicated. A better understanding of the IGF1/insulin network by further bench-to-bedside research may provide us with rational clinical therapeutic approaches against chronic inflammatory airway diseases.

Serum insulin-like growth factor-1, asthma, and lung function among British adults

BACKGROUND

Insulin-like growth factor-1 (IGF-1) plays a key role in the pathogenesis of metabolic syndrome, which is in turn associated with asthma. Whether IGF-1 contributes to asthma causation or asthma severity is largely unknown.

OBJECTIVE

To evaluate the relation between serum IGF-1 and asthma, asthma outcomes, and lung function in adults.

METHODS

Cross-sectional study of 297,590 adults (aged 40-69 years) who participated in the United Kingdom Biobank, had no diagnosis of diabetes, and were not on insulin. Multivariable logistic or linear regression was used to analyze serum IGF-1 and physician-diagnosed asthma, current wheezing, asthma hospitalizations, and lung function measures (forced expiratory volume in 1 second [FEV1], forced vital capacity [FVC], and FEV1 to FVC ratio).

RESULTS

Serum IGF-1 levels above the lowest quartile (Q1) were significantly associated with lower odds of asthma (adjusted odds ratio for fourth quartile [Q4] vs Q1 = 0.88; 95% confidence interval [CI], 0.85-0.91). Among the participants with asthma, IGF-1 levels above Q1 were significantly associated with lower odds of current wheezing (adjusted odds ratio for Q4 vs Q1 = 0.89; 95% CI, 0.83-0.96), but not with asthma hospitalizations. Serum IGF-1 was significantly and positively associated with FEV1 (b = 20.9 mL; 95% CI, 19.1-22.7) and FVC (b = 25.6 mL; 95% CI, 23.4-27.7), regardless of an asthma diagnosis; these associations were significant in men and women, with larger estimated effects in men.

CONCLUSION

In a large study of British adults, higher serum IGF-1 levels were associated with lower odds of asthma and current wheezing and higher FEV1 and FVC. Our findings suggest potential beneficial effects of circulating IGF-1 on asthma and asthma outcomes in adults.

Pulmonary involvement in systemic sclerosis: exploring cellular, genetic and epigenetic mechanisms

Systemic sclerosis (SSc) is a chronic progressive autoimmune disease characterized by immune inflammation, vasculopathy, and fibrosis. There are still numerous uncertainties in the understanding of disease initiation and progression. Pulmonary involvement in SSc, and particularly pulmonary fibrosis, is critical for all organ systems affections in this disease. This review is aimed to describe and analyze new findings in the pathophysiology of SSc-associated pulmonary involvement and to explore perspective diagnostic and therapeutic strategies. A myriad of cellular interactions is explored in the dynamics of progressive interstitial lung disease (ILD) and pulmonary hypertension (PH) in SSc. The role of exosomes, microvesicles, and apoptotic bodies is examined and the impact of micro and long non-coding RNAs, DNA methylation, and histone modification in SSc is discussed.

Alveolar Epithelial Cells Promote IGF-1 Production by Alveolar Macrophages Through TGF-β to Suppress Endogenous Inflammatory Signals

To maintain alveolar gas exchange, the alveolar surface has to limit unnecessary inflammatory responses. This involves crosstalk between alveolar epithelial cells (AECs) and alveolar macrophages (AMs) in response to damaging factors. We recently showed that insulin-like growth factor (IGF)-1 regulates the phagocytosis of AECs. AMs secrete IGF-1 into the bronchoalveolar lavage fluid (BALF) in response to inflammatory stimuli. However, whether AECs regulate the production of IGF-1 by AMs in response to inflammatory signals remains unclear, as well as the role of IGF-1 in controlling the alveolar balance in the crosstalk between AMs and AECs under inflammatory conditions. In this study, we demonstrated that IGF-1 was upregulated in BALF and lung tissues of acute lung injury (ALI) mice, and that the increased IGF-1 was mainly derived from AMs. In vitro experiments showed that the production and secretion of IGF-1 by AMs as well as the expression of TGF-β were increased in LPS-stimulated AEC-conditioned medium (AEC-CM). Pharmacological blocking of TGF-β in AECs and addition of TGF-β neutralizing antibody to AEC-CM suggested that this AEC-derived cytokine mediates the increased production and secretion of IGF-1 from AMs. Blocking TGF-β synthesis or treatment with TGF-β neutralizing antibody attenuated the increase of IGF-1 in BALF in ALI mice. TGF-β induced the production of IGF-1 by AMs through the PI3K/Akt signaling pathway. IGF-1 prevented LPS-induced p38 MAPK activation and the expression of the inflammatory factors MCP-1, TNF-α, and IL-1β in AECs. However, IGF-1 upregulated PPARγ to increase the phagocytosis of apoptotic cells by AECs. Intratracheal instillation of IGF-1 decreased the number of polymorphonuclear neutrophils in BALF of ALI model mice, reduced alveolar congestion and edema, and suppressed inflammatory cell infiltration in lung tissues. These results elucidated a mechanism by which AECs used TGF-β to regulate IGF-1 production from AMs to attenuate endogenous inflammatory signals during alveolar inflammation.