Elsevier

Canadian Journal of Diabetes

Volume 42, Issue 5, October 2018, Pages 525-532.e4
Canadian Journal of Diabetes

Original Research
Accumulation of Advanced Glycation Endproducts and Subclinical Inflammation in Deep Tissues of Adult Patients With and Without Diabetes

https://doi.org/10.1016/j.jcjd.2018.01.003Get rights and content

Abstract

Objectives

Advanced glycation endproducts (AGEs) play a key role in the development of foot complications in people with diabetes. Skin autofluorescence (AF) might noninvasively determine tissue accumulation of AGEs. This study evaluated the association between skin AF and AGE contents in the deep tissues of those with diabetes and the further consequences of such contents.

Methods

Between September 2014 and September 2015, we studied 33 patients, with and without diabetes, who had received lower-limb amputations. Skin AF was measured. Artery, nerve and skin were harvested during surgery. AGE contents were quantified using high-performance liquid chromatography mass spectrometry and were located by immunohistochemistry staining. Inflammatory cells were also located by immunohistochemistry, immunofluorescence and scanning electron microscopy.

Results

Values of skin AF and AGE contents in artery, nerve and skin in patients with diabetes were higher than those in healthy patients. Skin AF was strongly affected by AGE contents in these tissues. AGE contents in various tissues were strongly correlated with each other. Differing AGEs were deposited in similar manners in the same tissues and were accompanied by inflammatory cells.

Conclusions

AGE contents were strongly correlated with each other and were accompanied by inflammatory cells. Skin AF measurement could provide information about the systemic accumulation of AGEs.

Résumé

Objectifs

Les produits terminaux de la glycation avancée (PTGA) jouent un rôle essentiel dans le développement des complications du pied chez les personnes diabétiques. L'autofluorescence (AF) cutanée déterminerait de manière non effractive l'accumulation tissulaire des PTGA. La présente étude a permis d'évaluer l'association entre l'AF cutanée et les PTGA contenus dans les tissus profonds des personnes diabétiques et ses conséquences futures.

Méthodes

Entre septembre 2014 et septembre 2015, notre étude a porté sur 33 patients, diabétiques ou non, qui avaient subi des amputations des membres inférieurs. Nous avons mesuré l'AF cutanée. Nous avons effectué des prélèvements sur les artères, les nerfs et la peau durant la chirurgie. Nous avons quantifié les teneurs en PTGA au moyen de la chromatographie en phase liquide à haute performance couplée à la spectrométrie de masse et l'avons mise en évidence par la coloration immunohistochimique. Nous avons également mis en évidence les cellules inflammatoires par immunohistochimie, immunofluorescence et microscopie électronique à balayage.

Résultats

Les valeurs de l'AF cutanée et des PTGA contenus dans les artères, les nerfs et la peau des patients diabétiques étaient plus élevées que celles des patients en bonne santé. L'AF cutanée était fortement affectée par les PTGA contenus dans ces tissus. Les PTGA contenus dans les divers tissus montraient une forte corrélation entre eux. Différents PTGA formaient des dépôts similaires dans les mêmes tissus et étaient accompagnés de cellules inflammatoires.

Conclusions

Les PTGA montraient une forte corrélation entre eux et étaient accompagnés de cellules inflammatoires. La mesure de l'AF cutanée pourrait offrir de l'information sur l'accumulation systémique des PTGA.

Introduction

Advanced glycation endproducts (AGEs) are ubiquitous, irreversible endproducts of protein glycation that are formed from Amadori protein products (1). These cross-linked and highly stable complexes are resistant to enzymatic degradation (2). AGEs can be formed de novo in all tissues when proteins meet glucose (3), and oxidant activities might increase this process (4). Lowered clearance and absorption from food and smoking can also aggravate the accumulation of AGEs in tissue 5, 6, 7.

Nonenzymatic glycation leading to AGE formation is 1 of the important biochemical pathways involved in the progression of chronic, age-related degenerative diseases (8), such as atherosclerosis, chronic renal failure (9) and Alzheimer disease (10), and in the development of the long-term complications of diabetes (11).

High-performance liquid chromatography (HPLC) with tandem mass spectrometry (MS) has evolved as the gold standard for quantitative analysis of AGEs, but the complexity, cost and lack of reproducibility of this technique limit its broad use. Immunohistochemistry (IHC) staining can provide the specific location of AGE deposition in human tissues (12). However, IHC is invasive, requiring tissue for examination, which limits its clinical use. Moreover, blood and urine sampling for AGEs does not necessarily reflect AGE levels in tissue. In 2004, Meerwaldt et al proposed the assessment of skin autofluorescence (AF) as a new method for measuring AGEs in humans. This simple, noninvasive method was based on the fluorescent properties of AGEs 13, 14. The first clinical trial showed a positive correlation between collagen-linked fluorescence and AGE content in skin biopsies (14). The assessment of skin AF has advantages over traditional measurements of plasma AGEs (15), including being inexpensive, easy to conduct and noninvasive, and having higher reproducibility and higher correlation with the tissue content of AGEs (16). Several studies of patients with diabetes who have various complications have shown that higher skin AF was associated with diabetic nephropathy and cardiovascular complications and could predict their long-term risks 17, 18, 19. Skin AF provided additional information to the United Kingdom Prospective Diabetes Study risk engine, and that resulted in the reclassification of risk in a substantial number of patients (20). More recently, we have found that in Chinese patients with diabetes, skin AF has a significant and independent association with foot ulcerations resulting from diabetes (21).

However, studies regarding the quantitative relationship between skin AF and AGE accumulation within deep key tissues are insufficient. Furthermore, although several mechanisms by which AGEs cause chronic tissue damage, including aseptic inflammation, have been proposed and partially verified through in vitro testing or animal models, directive evidence of a correlation between chronic AGE deposition and chronic inflammation within deep tissues is absent.

In the present study, we evaluated skin AF in patients who received lower-limb amputations and determined the amount and distribution of AGEs in artery, nerve and skin tissue samples, and we explored the relationship between AGE distribution and chronic inflammation in these tissues.

Section snippets

Criteria for inclusion

We enrolled in the study 33 patients who had received lower-limb amputations between September 2014 and September 2015. Criteria for inclusion were a lower limb with severe damage and/or necrosis for which there was no chance of limb salvage, as determined by more than 3 attending surgeons who agreed that amputation was the only option. After being fully informed, patients and their families provided written consent for amputation. Patients who refused amputation, had malignancy in a lower limb

Statistical results

A total of 25 males and 8 females were included in the study. Among them, 5 had diabetic foot complications, 11 had arteriosclerosis obliterans and 17 were healthy traffic-accident victims. Patients' basic characteristics are shown in Table 2. The levels of each AGE measured by HPLC are listed in Table 3. The distributions of all AGEs and fasting plasma glucose levels were not normal.

The correlations between skin AF and normally distributed variables were tested by using the Pearson

Discussion

This study showed that skin AF was significantly affected by the quantitative AGE content deposition in both deep tissues (artery and nerve) and superficial tissue (skin). Moreover, different AGEs in different tissues were significantly associated with each other. IHC results indicated that in the tissues of patients with arteriosclerosis obliterans and foot problems related to diabetes, all AGEs were uniformly distributed, with the most significant distribution around structural destruction.

Conclusions

Skin AF was significantly affected by the quantity of AGE deposition in both deep tissues (artery and nerve) and superficial tissue (skin). Moreover, different AGEs in different tissues were significantly associated with each other. Skin AF measurement could provide information about the systemic accumulation of AGEs. In the tissues of patient with arteriosclerosis obliterans and foot problems related to diabetes, all AGEs were uniformly distributed, with the most significant distribution found

Author Disclosures

Conflicts of interest: None. The authors alone are responsible for the content and writing of the article.

Acknowledgments

The authors acknowledge the financial support of the National Science Foundation of China (#81601687).

References (29)

  • P.J. Thornalley et al.

    Formation of glyoxal, methylglyoxal and 3-deoxyglucosone in the glycation of proteins by glucose

    Biochem J

    (1999)
  • S.R. Thorpe et al.

    Maillard reaction products in tissue proteins: New products and new perspectives

    Amino Acids

    (2003)
  • T. Koschinsky et al.

    Orally absorbed reactive glycation products (glycotoxins): An environmental risk factor in diabetic nephropathy

    Proc Natl Acad Sci USA

    (1997)
  • C. Cerami et al.

    Tobacco smoke is a source of toxic reactive glycation products

    Proc Natl Acad Sci USA

    (1997)
  • Cited by (0)

    The Canadian Diabetes Association is the registered owner of the name Diabetes Canada.

    View full text