Circulating microbiota-derived metabolites: a "liquid biopsy?

BACKGROUND/OBJECTIVES: Non-alcoholic fatty liver disease (NAFLD) causes a wide spectrum of liver damage, from simple steatosis (SS) to cirrhosis. SS and non-alcoholic steatohepatitis (NASH) cannot be distinguished by clinical or laboratory features. Dysregulation of the gut microbiota is involved in NASH pathogenesis. The aim of this study was to assess the relationship between microbiota-derived metabolites and the degrees of NAFLD; also, to investigate whether these metabolites could be included in a panel of NASH biomarkers. SUBJECTS/METHODS: We used liquid chromatography coupled to triple-quadrupole-mass spectrometry (LC-QqQ) analysis to quantify choline and its derivatives, betaine, endogenous ethanol, bile acids, short-chain fatty acids and soluble TLR4 in serum from women with normal weight (n = 29) and women with morbid obesity (MO) (n = 82) with or without NAFLD. We used real-time polymerase chain reaction (RT-PCR) analysis to evaluate the hepatic and intestinal expression level of all genes studied (TLR2, TLR4, TLR9, LXRα, SREBP1C, ACC1, FAS, PPARα, CPT1α, CROT, SREBP2, ABCA1, ABCG1 and FXR in the liver; TLR2, TLR4, TLR5, TLR9, GLP-1R, DPP-4, FXR and PPARÉ£ in the jejunum) in 82 women with MO with normal liver histology (NL, n = 29), SS (n = 32), and NASH (n = 21). RESULTS: Hepatic FAS, TLR2, and TLR4 expression were overexpressed in NAFLD patients. TLR2 was overexpressed in NASH patients. In women with MO with NAFLD, we found upregulation of intestinal TLR9 expression and downregulation of intestinal FXR expression in women with NASH. Circulating TMAO, glycocholic acid and deoxycholic acid levels were significantly increased in NAFLD patients. Endogenous circulating ethanol levels were increased in NASH patients in comparison to those in SS patients. CONCLUSIONS: These findings suggest that the intestine participates in the progression of NAFLD. Moreover, levels of certain circulating microbiota-related metabolites are associated with NAFLD severity and could be used as a "liquid biopsy" in the noninvasive diagnosis of NASH.

Proteomic Profile of Unstable Atheroma Plaque: Increased Neutrophil Defensin 1, Clusterin, and Apolipoprotein E Levels in Carotid Secretome.

Because of the clinical significance of carotid atherosclerosis, the search for novel biomarkers has become a priority. The aim of the present study was to compare the protein secretion profile of the carotid atherosclerotic plaque (CAP, n = 12) and nonatherosclerotic mammary artery (MA, n = 10) secretomes. We used a nontargeted proteomic approach that incorporated tandem immunoaffinity depletion, iTRAQ labeling, and nanoflow liquid chromatography coupled to high-resolution mass spectrometry. In total, 162 proteins were quantified, of which 25 showed statistically significant differences in secretome levels between carotid atherosclerotic plaque and nondiseased mammary artery. We found increased levels of neutrophil defensin 1, apolipoprotein E, clusterin, and zinc-alpha-2-glycoprotein in CAP secretomes. Results were validated by ELISA assays. Also, differentially secreted proteins are involved in pathways such as focal adhesion and leukocyte transendothelial migration. In conclusion, this study provides a subset of identified proteins that are differently expressed in secretomes of clinical significance.

New insights into circulating FABP4: Interaction with cytokeratin 1 on endothelial cell membranes.

Fatty acid-binding protein 4 (FABP4) is an adipose tissue-secreted adipokine that is involved in the regulation of energetic metabolism and inflammation. Increased levels of circulating FABP4 have been detected in individuals with cardiovascular risk factors. Recent studies have demonstrated that FABP4 has a direct effect on peripheral tissues, specifically promoting vascular dysfunction; however, its mechanism of action is unknown. The objective of this work was to assess the specific interactions between exogenous FABP4 and the plasma membranes of endothelial cells. Immunofluorescence assays showed that exogenous FABP4 localized along the plasma membranes of human umbilical vein endothelial cells (HUVECs), interacting specifically with plasma membrane proteins. Anti-FABP4 immunoblotting revealed two covalent protein complexes containing FABP4 and its putative receptor; these complexes were approximately 108 kDa and 77 kDa in size. Proteomics and mass spectrometry experiments revealed that cytokeratin 1 (CK1) was the FABP4-binding protein. An anti-CK1 immunoblot confirmed the presence of CK1. FABP4-CK1 complexes were also detected in HAECs, HCASMCs, HepG2 cells and THP-1 cells. Pharmacological FABP4 inhibition by BMS309403 results in a slight decrease in the formation of these complexes, indicating that fatty acids may play a role in FABP4 functionality. In addition, we demonstrated that exogenous FABP4 crosses the plasma membrane to enter the cytoplasm and nucleus in HUVECs. These findings indicate that exogenous FABP4 interacts with plasma membrane proteins, specifically CK1. These data contribute to our current knowledge regarding the mechanism of action of circulating FABP4.

Adipo/cytokines in atherosclerotic secretomes: increased visfatin levels in unstable carotid plaque.

BACKGROUND: Novel pro-inflammatory and anti-inflammatory derivatives from adipose tissue, known as adipokines, act as metabolic factors. The aim of this study was to analyse the secreted expression of different adipo/cytokines in secretomes of unstable carotid atherosclerotic plaque versus non-atherosclerotic mammary artery. METHODS: We evaluated the secretion levels of adiponectin, visfatin, lipocalin-2, resistin, IL-6 and TNFR2 by ELISA in human secretomes from cultured unstable carotid atherosclerotic plaque (n = 18) and non-atherosclerotic mammary artery (n = 13). We also measured visfatin serum levels in patients suffering from atherosclerosis and in a serum cohort of healthy subjects (n = 16). RESULTS: We found that visfatin levels were significantly increased in unstable carotid atherosclerotic plaque secretome than in non-atherosclerotic mammary artery secretome. No differences were found with regard the other adipo/cytokines studied. Regarding visfatin circulating levels, there were no differences between unstable carotid atherosclerotic plaque and non-atherosclerotic mammary artery group. However, these visfatin levels were increased in comparison to serum cohort of healthy subjects. CONCLUSIONS: Of all the adipo/cytokines analysed, only visfatin showed increased levels in secretomes of unstable carotid atherosclerotic plaque. Additional human studies are needed to clarify the possible role of visfatin as prognostic factor of unstable carotid atherosclerotic plaque.

miR33a/miR33b* and miR122 as Possible Contributors to Hepatic Lipid Metabolism in Obese Women with Nonalcoholic Fatty Liver Disease.

Specific miRNA expression profiles have been shown to be associated with nonalcoholic fatty liver disease (NAFLD). We examined the correlation between the circulating levels and hepatic expression of miR122 and miR33a/b*, the key lipid metabolism-related gene expression and the clinicopathological factors of obese women with NAFLD. We measured miR122 and miR33a/b* expression in liver samples from 62 morbidly obese (MO), 30 moderately obese (ModO), and eight normal-weight controls. MiR122 and miR33a/b* expression was analyzed by qRT-PCR. Additionally, miR122 and miR33b* circulating levels were analyzed in 122 women. Hepatic miR33b* expression was increased in MO compared to ModO and controls, whereas miR122 expression was decreased in the MO group compared to ModO. In obese cohorts, miR33b* expression was increased in nonalcoholic steatohepatitis (NASH). Regarding circulating levels, MO patients with NASH showed higher miR122 levels than MO with simple steatosis (SS). These circulating levels are good predictors of histological features associated with disease severity. MO is associated with altered hepatic miRNA expression. In obese women, higher miR33b* liver expression is associated with NASH. Moreover, multiple correlations between miRNAs and the expression of genes related to lipid metabolism were found, that would suggest a miRNA-host gene circuit. Finally, miR122 circulating levels could be included in a panel of different biomarkers to improve accuracy in the non-invasive diagnosis of NASH.

PNPLA3 Expression Is Related to Liver Steatosis in Morbidly Obese Women with Non-Alcoholic Fatty Liver Disease.

Recent reports suggest a role for the Patatin-like phospholipase domain-containing protein 3 (PNPLA3) in the pathology of non-alcoholic fatty liver disease (NAFLD). Lipid deposition in the liver seems to be a critical process in the pathogenesis of NAFLD. The aim of the present work was to evaluate the association between the liver PNPLA3 expression, key genes of lipid metabolism, and the presence of NAFLD in morbidly obese women. We used real-time polymerase chain reaction (PCR) analysis to analyze the hepatic expression of PNPLA3 and lipid metabolism-related genes in 55 morbidly obese subjects with normal liver histology (NL, n = 18), simple steatosis (SS, n = 20), and non-alcoholic steatohepatitis (NASH, n = 17). Liver biopsies were collected during bariatric surgery. We observed that liver PNPLA3 expression was increased in NAFLD than in NL. It was also upregulated in SS than in NL. Interestingly, we found that the expression of PNPLA3 was significantly higher in severe than mild SS group. In addition, the expression of the transcription factors LXRα, PPARα, and SREBP2 was positively correlated with PNPLA3 liver expression. Regarding rs738409 polymorphism, GG genotype was positive correlated with the presence of NASH. In conclusion, our results show that PNPLA3 could be related to lipid accumulation in liver, mainly in the development and progression of simple steatosis.

Downregulation of de Novo Fatty Acid Synthesis in Subcutaneous Adipose Tissue of Moderately Obese Women.

The purpose of this work was to evaluate the expression of fatty acid metabolism-related genes in human adipose tissue from moderately obese women. We used qRT-PCR and Western Blot to analyze visceral (VAT) and subcutaneous (SAT) adipose tissue mRNA expression involved in de novo fatty acid synthesis (ACC1, FAS), fatty acid oxidation (PPARα, PPARδ) and inflammation (IL6, TNFα), in normal weight control women (BMI < 25 kg/m², n = 35) and moderately obese women (BMI 30-38 kg/m², n = 55). In SAT, ACC1, FAS and PPARα mRNA expression were significantly decreased in moderately obese women compared to controls. The downregulation reported in SAT was more pronounced when BMI increased. In VAT, lipogenic-related genes and PPARα were similar in both groups. Only PPARδ gene expression was significantly increased in moderately obese women. As far as inflammation is concerned, TNFα and IL6 were significantly increased in moderate obesity in both tissues. Our results indicate that there is a progressive downregulation in lipogenesis in SAT as BMI increases, which suggests that SAT decreases the synthesis of fatty acid de novo during the development of obesity, whereas in VAT lipogenesis remains active regardless of the degree of obesity.

Interleukin-17A Gene Expression in Morbidly Obese Women.

Data from recent studies conducted in rodent models and humans suggest that interleukin-17A (IL-17A) plays a role in the induction of inflammation in adipose tissue during obesity. The aim of this study was to assess the gene expression of IL-17A in adipose tissue of morbidly obese patients. We used RT-PCR to evaluate the expression of IL-17A and several adipo/cytokines in the visceral adipose tissue (VAT) and subcutaneous adipose tissue (SAT) of 10 normal-weight control women (BMI < 25 kg/m2) and 30 morbidly obese women (MO, BMI > 40 kg/m2). We measured serum levels of IL-17A and adipo/cytokines in MO and normal weight women. IL-17A expression was significantly higher in VAT than in SAT in MO patients (p = 0.0127). It was very low in normal-weight controls in both VAT and SAT tissues. We found positive correlations between IL-17A and IL-6, lipocalin-2 and resistin in VAT of MO patients. The circulating level of IL-17A was higher in the normal-weight group than the MO patients (p = 0.032), and it was significantly related to adiponectin and TNFRII levels. In conclusion, IL-17A expression in VAT is increased in morbidly obese women, which suggests a link between obesity and innate immunity in low-grade chronic inflammation in morbidly obese women.

Altered fatty acid metabolism-related gene expression in liver from morbidly obese women with non-alcoholic fatty liver disease.

Lipid accumulation in the human liver seems to be a crucial mechanism in the pathogenesis and the progression of non-alcoholic fatty liver disease (NAFLD). We aimed to evaluate gene expression of different fatty acid (FA) metabolism-related genes in morbidly obese (MO) women with NAFLD. Liver expression of key genes related to de novo FA synthesis (LXRα, SREBP1c, ACC1, FAS), FA uptake and transport (PPARγ, CD36, FABP4), FA oxidation (PPARα), and inflammation (IL6, TNFα, CRP, PPARδ) were assessed by RT-qPCR in 127 MO women with normal liver histology (NL, n = 13), simple steatosis (SS, n = 47) and non-alcoholic steatohepatitis (NASH, n = 67). Liver FAS mRNA expression was significantly higher in MO NAFLD women with both SS and NASH compared to those with NL (p = 0.003, p = 0.010, respectively). Hepatic IL6 and TNFα mRNA expression was higher in NASH than in SS subjects (p = 0.033, p = 0.050, respectively). Interestingly, LXRα, ACC1 and FAS expression had an inverse relation with the grade of steatosis. These results were confirmed by western blot analysis. In conclusion, our results indicate that lipogenesis seems to be downregulated in advanced stages of SS, suggesting that, in this type of extreme obesity, the deregulation of the lipogenic pathway might be associated with the severity of steatosis.

Huntingtin CAG repeats in neuropathologically confirmed tauopathies: Novel insights.

Previous studies have suggested a relationship between the number of CAG triplet repeats in the HTT gene and neurodegenerative diseases not related to Huntington's disease (HD). This study seeks to investigate whether the number of CAG repeats of HTT is associated with the risk of developing certain tauopathies and its influence as a modulator of the clinical and neuropathological phenotype. Additionally, it aims to evaluate the potential of polyglutamine staining as a neuropathological screening. We genotyped the HTT gene CAG repeat number and APOE-ℰ isoforms in a cohort of patients with neuropathological diagnoses of tauopathies (n=588), including 34 corticobasal degeneration (CBD), 98 progressive supranuclear palsy (PSP) and 456 Alzheimer's disease (AD). Furthermore, we genotyped a control group of 1070 patients, of whom 44 were neuropathologic controls. We identified significant differences in the number of patients with pathological HTT expansions in the CBD group (2.7%) and PSP group (3.2%) compared to control subjects (0.2%). A significant increase in the size of the HTT CAG repeats was found in the AD compared to the control group, influenced by the presence of the Apoliprotein E (APOE)-ℰ4 isoform. Post-mortem assessments uncovered tauopathy pathology with positive polyglutamine aggregates, with a slight predominance in the neostriatum for PSP and CBD cases and somewhat greater limbic involvement in the AD case. Our results indicated a link between HTT CAG repeat expansion with other non-HD pathology, suggesting they could share common neurodegenerative pathways. These findings support that genetic or histological screening for HTT repeat expansions should be considered in tauopathies.

Negative effect of a low-carbohydrate, high-protein, high-fat diet on small peripheral artery reactivity in patients with increased cardiovascular risk.

Low-carbohydrate diets have become increasingly popular for weight loss. Although they may improve some metabolic markers, particularly in type 2 diabetes mellitus (T2D) or the metabolic syndrome (MS), their net effect on arterial wall function remains unclear. The objective was to evaluate the relation between dietary macronutrient composition and the small artery reactive hyperaemia index (saRHI), a marker of small artery endothelial function, in a cohort of patients at increased cardiovascular (CV) risk. The present cross-sectional study included 247 patients. Diet was evaluated by a 3-d food-intake register and reduced to a novel low-carbohydrate diet score (LCDS). Physical examination, demographic, biochemical and anthropometry parameters were recorded, and the saRHI was measured in each patient. Individuals in the lowest LCDS quartile (Q1, 45 % carbohydrate; 20 % protein; 32 % fat) had higher saRHI values than those in the top quartile (Q4, 29 % carbohydrate, 24 % protein, 40 % fat; 1.66 (sd 0.41) v. 1.52 (sd 0.22), P= 0.037). These results were particularly strong in patients with the MS (Q1 = 1.82 (sd 0.32) v. Q4 = 1.61 (sd 027); P= 0.021) and T2D (Q1 = 1.78 (sd 0.31) v. Q4 = 1.62 (sd 0.35); P= 0.011). Multivariate analysis demonstrated that individuals in the highest LCDS quartile had a significantly negative coefficient of saRHI, which was independent of confounders (OR -0.85; 95 % CI 0.19, 0.92; P= 0.031). These findings suggest that a dietary pattern characterised by a low amount of carbohydrate, but high amounts of protein and fat, is associated with a poorer small artery vascular reactivity in patients with increased CV risk.

Fatty acid-binding protein 4 impairs the insulin-dependent nitric oxide pathway in vascular endothelial cells.

BACKGROUND: Recent studies have shown that fatty acid-binding protein 4 (FABP4) plasma levels are associated with impaired endothelial function in type 2 diabetes (T2D). In this work, we analysed the effect of FABP4 on the insulin-mediated nitric oxide (NO) production by endothelial cells in vitro. METHODS: In human umbilical vascular endothelial cells (HUVECs), we measured the effects of FABP4 on the insulin-mediated endothelial nitric oxide synthase (eNOS) expression and activation and on NO production. We also explored the impact of exogenous FABP4 on the insulin-signalling pathway (insulin receptor substrate 1 (IRS1) and Akt). RESULTS: We found that eNOS expression and activation and NO production are significantly inhibited by exogenous FABP4 in HUVECs. FABP4 induced an alteration of the insulin-mediated eNOS pathway by inhibiting IRS1 and Akt activation. These results suggest that FABP4 induces endothelial dysfunction by inhibiting the activation of the insulin-signalling pathway resulting in decreased eNOS activation and NO production. CONCLUSION: These findings provide a mechanistic linkage between FABP4 and impaired endothelial function in diabetes, which leads to an increased cardiovascular risk.

Alpha-tocopherol and BAY 11-7082 reduce vascular cell adhesion molecule in human aortic endothelial cells.

BACKGROUND: In endothelial dysfunction, vascular cell adhesion molecule-1 (VCAM-1), E-selectin and intercellular adhesion molecule-1 (ICAM-1) expression (collectively termed cell adhesion molecules; CAMs) increase at sites of atherosclerosis and are stimulated by proinflammatory cytokines such as tumor necrosis factor-α (TNF-α). METHODS: We evaluated the effect of alpha-tocopherol (AT; 10-150 µM) and BAY 11-7082 (BAY; 0.1 or 1 µM) on CAMs mRNA expression as well as their protein in soluble release form (sCAMs) in human aortic endothelial cells (HAECs) activated by TNF-α (1 or 10 ng/ml). Also, we determined the extent of lymphocyte adhesion to activated HAECs. RESULTS: BAY reduced VCAM-1, E-selectin and ICAM-1 mRNA expression by 30, 30 and 10%, respectively. Furthermore, protein reduction of sVCAM-1 by 70%, sE-selectin by 51% and sICAM-1 by 25% compared to HAECs stimulated by TNF-α was observed (p < 0.05). AT (50, 75 and 150 µM) decreased VCAM-1 mRNA expression by 30% and sVCAM-1 protein by 33% compared to HAECs stimulated by TNF-α (p < 0.05). TNF-α-activated HAEC adhesion to human Jurkat T lymphocytes was higher compared to nonactivated HAECs (p < 0.05). BAY (2 and 5 µM) reduced this lymphocyte adhesion (p < 0.05). CONCLUSION: BAY reduces all the CAMs studied as well as cell adhesion, while AT selectively inhibits VCAM-1; both induce endothelial dysfunction improvement.

Small artery dilation and endothelial markers in cardiovascular risk patients.

BACKGROUND: The use of methods based on reactive hyperaemia of small distal arteries to assess endothelial function (EF) is increasing; however, the mechanisms regulating vascular function in large and small arteries are probably different. We studied the correlations between the hyperaemia reactivity of small peripheral arteries determined by peripheral artery tonometry (PAT) and the levels of serum biomarkers of EF, inflammation and oxidation in patients with cardiovascular (CV) risk factors. METHODS: Four hundred and seven patients with intermediate CV risk were recruited into a cross-sectional study to examine whether soluble endothelial, inflammatory and lipid oxidative biomarkers correlate with small artery reactive hyperaemia index (saRHI) values, which were measured by PAT. RESULTS: A significant correlation was found between saRHI values and the concentrations of soluble E-selectin (sE-selectin) and soluble vascular cell adhesion molecule 1 (sVCAM-1). These correlations were stronger when only non-metabolic syndrome patients (46%) were analysed (r = -0·310, P < 0·0001; r = -0·264, P < 0·0001, respectively). In this subgroup, the oxidised low-density lipoprotein/LDL (oxLDL/LDL) was also correlated with saRHI (r = -0·193, P = 0·009). A stepwise regression study showed that sE-selectin was the only biomarker significantly correlated with saRHI values (P < 0·0001). In multivariate linear regression analysis, this relationship was still strong when the main confounding covariates were taken into consideration. CONCLUSIONS: Elevated levels of sE-selectin and, to a smaller degree, sVCAM-1 and oxLDL/LDL are associated with lower postischemic reactivity in the small distal arteries. sE-selectin is the main determinant biomarker of saRHI as assessed by regression analysis. The presence of multiple risk factors weakens this association.

The Glyoxalase System in Age-Related Diseases: Nutritional Intervention as Anti-Ageing Strategy.

The glyoxalase system is critical for the detoxification of advanced glycation end-products (AGEs). AGEs are toxic compounds resulting from the non-enzymatic modification of biomolecules by sugars or their metabolites through a process called glycation. AGEs have adverse effects on many tissues, playing a pathogenic role in the progression of molecular and cellular aging. Due to the age-related decline in different anti-AGE mechanisms, including detoxifying mechanisms and proteolytic capacities, glycated biomolecules are accumulated during normal aging in our body in a tissue-dependent manner. Viewed in this way, anti-AGE detoxifying systems are proposed as therapeutic targets to fight pathological dysfunction associated with AGE accumulation and cytotoxicity. Here, we summarize the current state of knowledge related to the protective mechanisms against glycative stress, with a special emphasis on the glyoxalase system as the primary mechanism for detoxifying the reactive intermediates of glycation. This review focuses on glyoxalase 1 (GLO1), the first enzyme of the glyoxalase system, and the rate-limiting enzyme of this catalytic process. Although GLO1 is ubiquitously expressed, protein levels and activities are regulated in a tissue-dependent manner. We provide a comparative analysis of GLO1 protein in different tissues. Our findings indicate a role for the glyoxalase system in homeostasis in the eye retina, a highly oxygenated tissue with rapid protein turnover. We also describe modulation of the glyoxalase system as a therapeutic target to delay the development of age-related diseases and summarize the literature that describes the current knowledge about nutritional compounds with properties to modulate the glyoxalase system.

Dietary Patterns, Carbohydrates, and Age-Related Eye Diseases.

Over a third of older adults in the U.S. experience significant vision loss, which decreases independence and is a biomarker of decreased health span. As the global aging population is expanding, it is imperative to uncover strategies to increase health span and reduce the economic burden of this age-related disease. While there are some treatments available for age-related vision loss, such as surgical removal of cataracts, many causes of vision loss, such as dry age-related macular degeneration (AMD), remain poorly understood and no treatments are currently available. Therefore, it is necessary to better understand the factors that contribute to disease progression for age-related vision loss and to uncover methods for disease prevention. One such factor is the effect of diet on ocular diseases. There are many reviews regarding micronutrients and their effect on eye health. Here, we discuss the impact of dietary patterns on the incidence and progression of age-related eye diseases, namely AMD, cataracts, diabetic retinopathy, and glaucoma. Then, we focus on the specific role of dietary carbohydrates, first by outlining the physiological effects of carbohydrates on the body and then how these changes translate into eye and age-related ocular diseases. Finally, we discuss future directions of nutrition research as it relates to aging and vision loss, with a discussion of caloric restriction, intermittent fasting, drug interventions, and emerging randomized clinical trials. This is a rich field with the capacity to improve life quality for millions of people so they may live with clear vision for longer and avoid the high cost of vision-saving surgeries.

Glyoxalase System as a Therapeutic Target against Diabetic Retinopathy.

Hyperglycemia, a defining characteristic of diabetes, combined with oxidative stress, results in the formation of advanced glycation end products (AGEs). AGEs are toxic compounds that have adverse effects on many tissues including the retina and lens. AGEs promote the formation of reactive oxygen species (ROS), which, in turn, boost the production of AGEs, resulting in positive feedback loops, a vicious cycle that compromises tissue fitness. Oxidative stress and the accumulation of AGEs are etiologically associated with the pathogenesis of multiple diseases including diabetic retinopathy (DR). DR is a devastating microvascular complication of diabetes mellitus and the leading cause of blindness in working-age adults. The onset and development of DR is multifactorial. Lowering AGEs accumulation may represent a potential therapeutic approach to slow this sight-threatening diabetic complication. To set DR in a physiological context, in this review we first describe relations between oxidative stress, formation of AGEs, and aging in several tissues of the eye, each of which is associated with a major age-related eye pathology. We summarize mechanisms of AGEs generation and anti-AGEs detoxifying systems. We specifically feature the potential of the glyoxalase system in the retina in the prevention of AGEs-associated damage linked to DR. We provide a comparative analysis of glyoxalase activity in different tissues from wild-type mice, supporting a major role for the glyoxalase system in the detoxification of AGEs in the retina, and present the manipulation of this system as a therapeutic strategy to prevent the onset of DR.

Autophagic receptor p62 protects against glycation-derived toxicity and enhances viability.

Diabetes and metabolic syndrome are associated with the typical American high glycemia diet and result in accumulation of high levels of advanced glycation end products (AGEs), particularly upon aging. AGEs form when sugars or their metabolites react with proteins. Associated with a myriad of age-related diseases, AGEs accumulate in many tissues and are cytotoxic. To date, efforts to limit glycation pharmacologically have failed in human trials. Thus, it is crucial to identify systems that remove AGEs, but such research is scanty. Here, we determined if and how AGEs might be cleared by autophagy. Our in vivo mouse and C. elegans models, in which we altered proteolysis or glycative burden, as well as experiments in five types of cells, revealed more than six criteria indicating that p62-dependent autophagy is a conserved pathway that plays a critical role in the removal of AGEs. Activation of autophagic removal of AGEs requires p62, and blocking this pathway results in accumulation of AGEs and compromised viability. Deficiency of p62 accelerates accumulation of AGEs in soluble and insoluble fractions. p62 itself is subject to glycative inactivation and accumulates as high mass species. Accumulation of p62 in retinal pigment epithelium is reversed by switching to a lower glycemia diet. Since diminution of glycative damage is associated with reduced risk for age-related diseases, including age-related macular degeneration, cardiovascular disease, diabetes, Alzheimer's, and Parkinson's, discovery of methods to limit AGEs or enhance p62-dependent autophagy offers novel potential therapeutic targets to treat AGEs-related pathologies.

Gut Microbiota-Derived Mediators as Potential Markers in Nonalcoholic Fatty Liver Disease.

Nonalcoholic fatty liver disease (NAFLD) is a common, multifactorial, and poorly understood liver disease whose incidence is globally rising. During the past decade, several lines of evidence suggest that dysbiosis of intestinal microbiome represents an important factor contributing to NAFLD occurrence and its progression into NASH. The mechanisms that associate dysbiosis with NAFLD include changes in microbiota-derived mediators, deregulation of the gut endothelial barrier, translocation of mediators of dysbiosis, and hepatic inflammation. Changes in short chain fatty acids, bile acids, bacterial components, choline, and ethanol are the result of altered intestinal microbiota. We perform a narrative review of the previously published evidence and discuss the use of gut microbiota-derived mediators as potential markers in NAFLD.

Targeted metabolomic approach in men with carotid plaque.

BACKGROUND: The aim of the study was to analyse the presence of several metabolites related to atherosclerosis in the plasma of patients with unstable carotid plaque and in the plasma of healthy subjects. MATERIALS AND METHODS: We included 20 patients who had undergone carotid endarterectomy and 20 healthy subjects as a control group. All the subjects recruited were male. We used a metabolomic approach with liquid chromatography coupled to mass spectrometry to evaluate plasma metabolite levels in the metabolic pathway involved in the progression of atherosclerotic plaque. RESULTS: We observed that circulating levels of 20-HETE were significantly higher in patients with atheroma plaque than in healthy subjects (p = 0.018). No differences were found with regard to the other metabolites analysed. We also conducted a random forest analysis and found that 20-HETE was the main differentiator in the list of selected metabolites. In addition, plasma levels of 20-HETE correlated positively with body mass index (r = 0.427, p = 0.007) and diastolic blood pressure (r = 0.365, p = 0.028). CONCLUSION: This study confirms that of all the molecules studied only 20-HETE is related to carotid plaque. Further studies are needed to compare patients with stable carotid plaque vs. patients with unstable carotid plaque in order to confirm that 20-HETE could be a potential factor related to carotid plaque.