Relationship between advanced glycation end-product accumulation in the skin and pulmonary function

Skin autofluorescence: early sign of lung function deterioration?

Advanced glycation end products (AGEs) comprise a heterogeneous group of stable end-products of the non-enzymatic glycation reactions described by Maillard in 1912, in which reduced sugars irreparably modify proteins, lipids and DNA. This is a slow physiological process and accumulation of AGEs is part of normal ageing. Under conditions of hyperglycaemia and oxidative stress, a much faster and more substantial generation of AGEs is induced. The myriad of pathogenic signals AGEs can induce and the fact that enhanced AGE accumulation accompanies a broad spectrum of age-associated chronic inflammatory diseases [1] form the basis of the Maillard theory of ageing [2].

The relationship between SAF and FEV₁, D_LCO and X₅, independent of COPD or diabetes. Will individuals with raised SAF and subclinical lung function alterations develop disease? What mechanisms underlie parenchymal alterations indicated by SAF?https://bit.ly/2YTtdkL

Measures of lung function and their relationship with advanced glycation end-products

Background

Advanced glycation end-products (AGEs) have been implicated in the pathophysiology of chronic obstructive pulmonary disease (COPD). However, the association between AGE accumulation in the skin measured by skin autofluorescence (SAF) and lung function in healthy subjects has not been explored in detail. We use a population-based study of 50–64-year-olds to assess spirometry, diffusing capacity of the lung for carbon monoxide (D_LCO) and impulse oscillometry (IOS) in relation to SAF.

Methods

Participants with information on SAF, lung function and potential confounding variables were included from the Swedish Cardiopulmonary Bioimage Study (SCAPIS) cohort (spirometry, n=4111; D_LCO, n=3889; IOS, n=3970). Linear regression was used to assess changes in lung function (as measured by spirometry (forced expiratory volume in 1 s (FEV₁), forced vital capacity (FVC) and FEV₁/FVC), D_LCO and IOS (resistance measured at 5 (R₅) and 20 Hz (R₂₀), R₅−R₂₀, area of reactance, reactance measured at 5 Hz (X­₅), and resonant frequency)) by a 1-sd increase in SAF.

Results

FEV₁, FVC and D_LCO were significantly and inversely associated with SAF after adjustment for potential confounding factors (per 1-sd increase in SAF: FEV₁ −0.03 L (95% CI −0.04– −0.02 L), p<0.001; FVC −0.03 L (95% CI −0.05– −0.02 L), p<0.001; D_LCO −0.07 mmol·min⁻¹·kPa⁻¹ (95% CI −0.11– −0.03 mmol·min⁻¹·kPa⁻¹), p<0.001). This association was also found in nonsmokers and in non-COPD subjects. Pulmonary reactance (X₅) but not pulmonary resistance (R₅, R₂₀ and R₅−R₂₀) was significantly associated with SAF (per 1-sd increase in SAF: X₅ −0.001 kPa·L⁻¹·s (95% CI −0.003–0.00 kPa·L⁻¹·s), p=0.042), which was mirrored in non-COPD patients but not in current nonsmokers.

Conclusions

AGE accumulation, as measured by SAF, is significantly associated with lung function decrements indicative of changes in the lung parenchyma

AGEs accumulation as measured by SAF is significantly associated with lung function decrements indicative of changes in the lung parenchymahttp://bit.ly/2IRgSWz

Recent Advances and the Potential for Clinical Use of Autofluorescence Detection of Extra-Ophthalmic Tissues

The autofluorescence (AF) characteristics of endogenous fluorophores allow the label-free assessment and visualization of cells and tissues of the human body. While AF imaging (AFI) is well-established in ophthalmology, its clinical applications are steadily expanding to other disciplines. This review summarizes clinical advances of AF techniques published during the past decade. A systematic search of the MEDLINE database and Cochrane Library databases was performed to identify clinical AF studies in extra-ophthalmic tissues. In total, 1097 articles were identified, of which 113 from internal medicine, surgery, oral medicine, and dermatology were reviewed. While comparable technological standards exist in diabetology and cardiology, in all other disciplines, comparability between studies is limited due to the number of differing AF techniques and non-standardized imaging and data analysis. Clear evidence was found for skin AF as a surrogate for blood glucose homeostasis or cardiovascular risk grading. In thyroid surgery, foremost, less experienced surgeons may benefit from the AF-guided intraoperative separation of parathyroid from thyroid tissue. There is a growing interest in AF techniques in clinical disciplines, and promising advances have been made during the past decade. However, further research and development are mandatory to overcome the existing limitations and to maximize the clinical benefits.