Is skin autofluorescence a novel non-invasive marker in diabetes? A systematic review and meta-analysis of case-control studies

Background

The advanced glycation end product (AGE) is produced from the nonenzymatic reaction between glucose and macromolecules by aging. Accumulation of AGE causes functional and structural changes in body proteins that lead to impairment of tissue protein functions. We aimed to validate AGE measurement by skin autofluorescence (SAF) in diabetes mellitus (DM) compared to the nondiabetes population.

Materials and Methods

We searched the PubMed, Cochrane, and Scopus databases from their inception till September 18, 2022, for casecontrol studies measuring AGE by SAF. Nonhuman studies, as well as review articles, study proposals, editorials, case reports, or congress posters, were excluded. We used a random effects model to assess the standard mean difference (MD) of age, body mass index (BMI), HbA1c, and SAF between diabetes and nondiabetes individuals.

Results

Higher SAF in DM patients indicated more accumulation of AGE compared with the nondiabetic population. Furthermore, HbA1c was considerably higher in DM patients. The MD of age, male gender, and BMI were significantly different between the DM individuals, compared with nondiabetic subjects, which can lead to altered SAF level and AGE production. There was a remarkable heterogeneity between diabetes and nondiabetes when measuring age, gender, and BMI, as well as HbA1c and SAF level.

Conclusion

This study could not confirm the validity of SAF as a surrogate marker in diabetes patients. Interestingly, metabolic load and high BMI can increase SAF, considerably. Altogether, SAF could be helpful in the future as a marker for metabolic syndrome or diabetes.

Advanced Glycation End Products and Their Effect on Vascular Complications in Type 2 Diabetes Mellitus

Diabetes is well established as a chronic disease with a high health burden due to mortality or morbidity from the final outcomes of vascular complications. An increased duration of hyperglycemia is associated with abnormal metabolism. Advanced glycation end products (AGEs) are nonenzymatic glycated forms of free amino acids that lead to abnormal crosslinking of extra-cellular and intracellular proteins by disrupting the normal structure. Furthermore, the interaction of AGEs and their receptors induces several pathways by promoting oxidative stress and inflammation. In this review, we discuss the role of AGEs in diabetic vascular complications, especially type 2 DM, based on recent clinical studies.

The effect of 1,25-dihydroxyvitamin D3 on liver damage, oxidative stress, and advanced glycation end products in experimental nonalcoholic- and alcoholic- fatty liver disease

Background/aim

Oxidative stress and advanced glycation end products (AGEs) formation are proposed as effective mechanisms in the pathogenesis of nonalcoholic fatty liver disease (NAFLD) and alcoholic liver disease (ALD). 1,25(OH)2D3 was proposed to have antioxidant, antiinflammatory and antiglycation properties. In this study, the effect of 1,25(OH)2D3 treatment on oxidative stress parameters and AGEs levels together with hepatic histopathology was investigated in high fructose (HFr) or ethanol (EtOH)-treated rats.

Materials and methods

Rats were treated with fructose (30%) or ethanol (5-20%) in drinking water with and without 1,25(OH)2D3 treatment (5 µg/kg two times a week) for 8 weeks. Insulin resistance (IR), oxidative stress parameters, AGEs, triglyceride (TG), and hydroxyproline (Hyp) levels together with histopathology were investigated in the liver.

Results

1,25(OH)2D3 decreased hepatic reactive oxygen species, lipid and protein oxidation products together with histopathological improvements in HFr- and EtOH-treated rats. 1,25(OH)2D3 treatment was observed to decrease significantly serum and hepatic AGEs in HFr group, and hepatic AGEs in EtOH group.

Conclusion

Our results clearly show that 1,25(OH)2 D3 treatment may be useful in the alleviation of hepatic lesions by decreasing glycooxidant stress in both NAFLD and ALD models created by HFr- and EtOH-treated rats, respectively.

Sex May Modulate the Effects of Combined Polyphenol Extract and L-citrulline Supplementation on Ambulatory Blood Pressure in Adults with Prehypertension: A Randomized Controlled Trial

Increased blood pressure (BP), vascular dysfunction and inflammation are involved in the etiology of cardiovascular disease (CVD). Although several dietary components such as polyphenols and L-citrulline may help to control BP, their combined impact on ambulatory BP in individuals at risk of CVD remains unknown. The objective of this research was to investigate the short-term impact of supplementation with a combination of polyphenol extract and L-citrulline on ambulatory BP, endothelial function and inflammation. In a randomized double-blind parallel trial, 73 men and women with prehypertension were supplemented with a placebo (cellulose, n = 34, Plac) or 548 mg/day of polyphenols and 2 g/day of L-citrulline (n = 35, Suppl) for 6 weeks. The primary outcome of this study was the difference between groups in 24-h ambulatory diastolic BP (DBP) at week six. Secondary outcomes were a difference between groups at week six in ambulatory systolic BP (SBP), casual BP, serum lipids and high-sensitivity C-reactive protein (hs-CRP) concentrations and skin advanced glycation end products (AGEs). Potential interaction of treatment with sex was examined. Suppl had no impact on mean ambulatory SBP and DBP (p > 0.10 vs. placebo). Daytime and 24-h SBP were reduced with Suppl in women (p ≤ 0.01), but not in men (p ≥ 0.27). A non-significant reduction in AGEs was observed after Suppl compared to Plac among all participants (p = 0.07) and there was no difference in the concentrations of blood lipids (p > 0.20) or CRP (p = 0.36) between treatments at week six. Therefore, supplementation with polyphenol extract and L-citrulline for 6 weeks has no impact on ambulatory BP, blood lipids and CRP in adults with prehypertension. However, the polyphenol extract/L-citrulline supplement may reduce ambulatory SBP in women, but not in men. These preliminary results need further research efforts towards further documenting this sex-dependent BP response to supplementation with polyphenols and L-citrulline.

The effectiveness of resveratrol in treatment of PCOS on the basis of experimental model in rats

PURPOSE OF THE STUDY

Polycystic ovary syndrome (PCOS) is a widespread endocrine disorder in women of reproductive age. Further research is required to justify new directions of effective targeted therapy of this condition. Resveratrol possesses anti-inflammatory, antioxidant and antidiabetic properties. The purpose of this study was to evaluate the potential effectiveness of resveratrol in PCOS based on the created model of this disease in Wistar rats.

MATERIALS AND METHODS

The PCOS model was created by oral administration of letrozole to female Wistar rats.. The animals received resveratrol at a dosage of 20 mg/kg and 30 mg/kg for the next 30 days. Then ovariectomy was performed for histological confirmation of the effectiveness of resveratrol in the treatment of PCOS. Regularity of estrous cycle, animal's body mass and the level of soluble receptors for advanced glycation end products (sRAGE) in the blood of rats were also evaluated in dynamics.

RESULTS

The study revealed that administration of resveratrol leads to dose-dependent restoration of normal morphology of ovarian tissue, normalizes regularity of estrous cycle and decreases body weight of rats with PCOS.

CONCLUSION

The results obtained in rats suggest that resveratrol may be a promising agent for the treatment of PCOS in women.

Fructosamine-3-Kinase as a Potential Treatment Option for Age-Related Macular Degeneration

Age-related macular degeneration is the leading cause of blindness in the developed world. Since advanced glycation end products (AGEs) are implicated in the pathogenesis of AMD through various lines of evidence, we investigated the potential of fructosamine-3-kinase (FN3K) in the disruption of retinal AGEs, drusenoid material and drusenoid lesions in patients with AMD. AGE-type autofluorescence was measured to evaluate the effects of FN3K on glycolaldehyde-induced AGE-modified neural porcine retinas and unmodified human neural retinas. Eye pairs from cigarette-smoke- and air-exposed mice were treated and evaluated histologically. Automated optical image analysis of human tissue sections was performed to compare control- and FN3K-treated drusen and near-infrared (NIR) microspectroscopy was performed to examine biochemical differences. Optical coherence tomography (OCT) was used to evaluate the effect of FN3K on drusenoid deposits after treatment of post-mortem human eyes. FN3K treatment provoked a significant decrease (41%) of AGE-related autofluorescence in the AGE-modified porcine retinas. Furthermore, treatment of human neural retinas resulted in significant decreases of autofluorescence (−24%). FN3K-treated murine eyes showed less drusenoid material. Pairwise comparison of drusen on tissue sections revealed significant changes in color intensity after FN3K treatment. NIR microspectroscopy uncovered clear spectral differences in drusenoid material (Bruch’s membrane) and drusen after FN3K treatment. Ex vivo treatment strongly reduced size of subretinal drusenoid lesions on OCT imaging (up to 83%). In conclusion, our study demonstrated for the first time a potential role of FN3K in the disruption of AGE-related retinal autofluorescence, drusenoid material and drusenoid lesions in patients with AMD.

High BAL sRAGE is Associated with Low Serum Eosinophils and IgE in Children with Asthma

Asthma remains the most common chronic lung disease in childhood in the United States. The receptor for advanced glycation end products (RAGE) has been recognized as both a marker of and participant in pulmonary pathophysiology. While membrane-bound RAGE (mRAGE) perpetuates the type 2 immune response, the soluble form (sRAGE) may act as a decoy receptor for pro-inflammatory ligands. Bronchoalveolar samples from 45 pediatric patients with asthma were obtained. Patients were divided into high and low BAL sRAGE groups using median sRAGE. Descriptive statistical analysis and non-parametric testing were applied. Children in the "high" sRAGE group had a lower median serum eosinophil (0.27 [SE ± 0.04] vs. 0.57 [± 0.06] K/mcl, adjusted p = 0.003) and lower serum IgE level (194.4 [± 60.7] vs. 676.2 ± 140.5) IU/mL, adjusted p = 0.004) as compared to the "low" sRAGE group. When controlling for age and body mass index percentile, absolute eosinophil count (p = 0.03) and serum IgE (p = 0.043) remained significantly lower in the "high" sRAGE group. Children with asthma and high levels of BAL sRAGE have lower serum eosinophil and IgE levels. These findings are consistent with the hypothesis that sRAGE may act as a decoy receptor by binding ligands that normally interact with mRAGE.

Advanced glycation end products and adipocytokines and oxidative stress in placental tissues of pregnant women with gestational diabetes mellitus

Correlation between expression levels of advanced glycation end products (AGEs) and adipocytokines and oxidative stress index malondialdehyde (MDA) in placental tissues of pregnant women with gestational diabetes mellitus (GDM) was investigated. Seventy-two cases of GDM pregnant women who received routine prenatal examination and gave birth in the Department of Obstetrics, Binzhou City Center Hospital from March 2016 to May 2017 were collected as the observation group. Another 80 cases of normal pregnant women who gave birth at the same time were selected as the control group. Enzyme linked immunosorbent assay (ELISA) was used to detect the expression levels of AGEs, visfatin, APN and IL-6 in the lysate of placental tissues. MDA levels were measured by thiobarbituric acid method. Correlation of expression levels of AGEs, visfatin, APN, IL-6 and MDA were analyzed. The expression level of MDA in placental tissues of the observation group was significantly higher than that of the control group (t=16.44, P<0.001). The correlation of expression levels between AGEs, adipocytokines and MDA in placental tissues of the two groups was analyzed, and it was found that the expression levels of AGEs, visfatin and IL-6 in the two groups were positively correlated with MDA. There was a significantly negative correlation between APN and MDA in the two groups. The incidence of cesarean section, neonatal hypoglycemia, fetal distress and macrosomia in the observation group was significantly higher than that in the control group (P<0.05). There was no significant difference in the incidence of membrane rupture and premature birth between the two groups (P>0.05). In conclusion, the expression levels of AGEs, visfatin and IL-6 in placental tissues of GDM pregnant women are positively correlated with MDA. There is a significant negative correlation between APN and MDA, and they play an important role in the pathogenesis of GDM.

Dialysis Procedures Alter Metabolic Conditions

A progressive chronic kidney disease results in retention of various substances that more or less contribute to dysfunction of various metabolic systems. The accumulated substances are denominated uremic toxins. Although many toxins remain undetected, numerous newly defined toxins participate in the disturbance of food breakdown. In addition, toxic effects may downregulate other pathways, resulting in a reduced ability of free fatty acid breakdown by lipoprotein lipase (LPL) and hepatic lipase (HL). Dialysis may even worsen metabolic functions. For LPL and HL, the use of heparin and low molecular weight heparin as anticoagulation during hemodialysis (HD) initiate a loss of these enzymes from their binding sites and degradation, causing a temporary dysregulation in triglyceride breakdown. This lack of function will cause retention of the triglyceride containing lipids for at least 8 h. In parallel, the breakdown into free fatty acids is limited, as is the energy supply by them. This is repeated thrice a week for a normal HD patient. In addition, dialysis will cause a loss of amino acids and disturb glucose metabolism depending on the dialysates used. The addition of glucose in the dialysate may support oxidation of carbohydrate and the retention of Amadori products and subsequent tissue alterations. To avoid these effects, it seems necessary to further study the effects of anticoagulation in HD, the extent of use of glucose in the dialysate, and the supplementation of amino acids.