Soluble RAGE Prevents Type 1 Diabetes Expanding Functional Regulatory T Cells

Type 1 diabetes is an autoimmune disease with no cure, where clinical translation of promising therapeutics has been hampered by the reproducibility crisis. Here, short-term administration of an antagonist to the receptor for advanced glycation end products (sRAGE) protected against murine diabetes at two independent research centers. Treatment with sRAGE increased regulatory T cells (Tregs) within the islets, pancreatic lymph nodes, and spleen, increasing islet insulin expression and function. Diabetes protection was abrogated by Treg depletion and shown to be dependent on antagonizing RAGE with use of knockout mice. Human Tregs treated with a RAGE ligand downregulated genes for suppression, migration, and Treg homeostasis (FOXP3, IL7R, TIGIT, JAK1, STAT3, STAT5b, CCR4). Loss of suppressive function was reversed by sRAGE, where Tregs increased proliferation and suppressed conventional T-cell division, confirming that sRAGE expands functional human Tregs. These results highlight sRAGE as an attractive treatment to prevent diabetes, showing efficacy and reproducibility at multiple research centers and in human T cells.

Short Duration Alagebrium Chloride Therapy Prediabetes Does Not Inhibit Progression to Autoimmune Diabetes in an Experimental Model

Mechanisms by which advanced glycation end products (AGEs) contribute to type 1 diabetes (T1D) pathogenesis are poorly understood. Since life-long pharmacotherapy with alagebrium chloride (ALT) slows progression to experimental T1D, we hypothesized that acute ALT therapy delivered prediabetes, may be effective. However, in female, non-obese diabetic (NODShiLt) mice, ALT administered prediabetes (day 50-100) did not protect against experimental T1D. ALT did not decrease circulating AGEs or their precursors. Despite this, pancreatic β-cell function was improved, and insulitis and pancreatic CD45.1+ cell infiltration was reduced. Lymphoid tissues were unaffected. ALT pre-treatment, prior to transfer of primed GC98 CD8+ T cell receptor transgenic T cells, reduced blood glucose concentrations and delayed diabetes, suggesting islet effects rather than immune modulation by ALT. Indeed, ALT did not reduce interferon-γ production by leukocytes from ovalbumin-pre-immunised NODShiLt mice and NODscid recipients given diabetogenic ALT treated NOD splenocytes were not protected against T1D. To elucidate β-cell effects, NOD-derived MIN6N8 β-cell major histocompatibility complex (MHC) Class Ia surface antigens were examined using immunopeptidomics. Overall, no major changes in the immunopeptidome were observed during the various treatments with all peptides exhibiting allele specific consensus binding motifs. As expected, longer MHC Class Ia peptides were captured bound to H-2Db than H-2Kb under all conditions. Moreover, more 10-12 mer peptides were isolated from H-2Db after AGE modified bovine serum albumin (AGE-BSA) treatment, compared with bovine serum albumin (BSA) or AGE-BSA+ALT treatment. Proteomics of MIN6N8 cells showed enrichment of processes associated with catabolism, the immune system, cell cycling and presynaptic endocytosis with AGE-BSA compared with BSA treatments. These data show that short-term ALT intervention, given prediabetes, does not arrest experimental T1D but transiently impacts β-cell function.

Methylglyoxal Scavengers Resensitize KRAS-Mutated Colorectal Tumors to Cetuximab

The use of cetuximab anti-epidermal growth factor receptor (anti-EGFR) antibodies has opened the era of targeted and personalized therapy in colorectal cancer (CRC). Poor response rates have been unequivocally shown in mutant KRAS and are even observed in a majority of wild-type KRAS tumors. Therefore, patient selection based on mutational profiling remains problematic. We previously identified methylglyoxal (MGO), a by-product of glycolysis, as a metabolite promoting tumor growth and metastasis. Mutant KRAS cells under MGO stress show AKT-dependent survival when compared with wild-type KRAS isogenic CRC cells. MGO induces AKT activation through phosphatidylinositol 3-kinase (PI3K)/mammalian target of rapamycin 2 (mTORC2) and Hsp27 regulation. Importantly, the sole induction of MGO stress in sensitive wild-type KRAS cells renders them resistant to cetuximab. MGO scavengers inhibit AKT and resensitize KRAS-mutated CRC cells to cetuximab in vivo. This study establishes a link between MGO and AKT activation and pinpoints this oncometabolite as a potential target to tackle EGFR-targeted therapy resistance in CRC.

Hepatic Fat Content and Liver Enzymes Are Associated with Circulating Free and Protein-Bound Advanced Glycation End Products, Which Are Associated with Low-Grade Inflammation: The CODAM Study

Advanced glycation end products (AGEs) accumulate in fatty livers and may contribute to low-grade inflammation (LGI), potentially via their receptor, RAGE. It is unknown if the AGE accumulation in fatty livers results in elevated circulating AGEs. In a cohort study, we investigated the association of liver fat and hepatocellular damage with circulating AGEs and soluble RAGE (sRAGE) and subsequently the association of circulating AGEs and sRAGE with LGI. Cross-sectional associations of liver fat percentage (eLF%; ln-transformed) and liver enzymes (LE score; standardized) with circulating AGEs (free CML, CEL, and MG-H1 in nM and protein-bound CML, CEL, and pentosidine in nmol/mmol lysine; ln-transformed) and sRAGE (pg/ml, ln-transformed) and additionally of AGEs and sRAGE with LGI (standardized) were determined by multiple linear regression. eLF% was positively associated with circulating free CEL (β = 0.090; 95% CI 0.041; 0.139) but inversely with protein-bound CML (β = -0.071; 95% CI -0.108; -0.034). Similarly, the LE score was positively associated with free CML (β = 0.044; 95% CI 0.012; 0.076) and CEL (β = 0.040; 95% CI 0.009; 0.072) but inversely with protein-bound CML (β = -0.037; 95% CI -0.060; -0.013). Free CML (β = 0.297; 95% CI 0.049; 0.545) was positively associated with LGI, while protein-bound CML (β = -0.547; 95% CI -0.888; -0.207) was inversely associated, although this association was absent after adjustment for BMI. eLF% and LE score were not associated with sRAGE and sRAGE not with LGI after adjustment for BMI. Liver fat and enzymes were positively associated with circulating free AGEs, which were associated with LGI. In contrast, inverse relations were observed of liver fat and enzymes with circulating protein-bound AGEs and of protein-bound AGEs with LGI. These data suggest that hepatic steatosis and inflammation affect the formation and degradation of hepatic protein-bound AGEs resulting in elevated circulating free AGE levels. These alterations in AGE levels might influence LGI, but this is likely independent of RAGE.

Vitreous advanced glycation endproducts and α-dicarbonyls in retinal detachment patients with type 2 diabetes mellitus and non-diabetic controls

Purpose

Advanced glycation endproducts (AGEs) and their precursors α-dicarbonyls are implicated in the progression of diabetic retinopathy. The purpose of this study was to assess AGEs and α-dicarbonyls in the vitreous of patients with type 2 diabetes mellitus (T2DM) with early stages or absence of diabetic retinopathy.

Methods

We examined vitreous samples obtained during vitrectomy from 31 T2DM patients presenting themselves with rhegmatogenous retinal detachment and compared these to 62 non-diabetic rhegmatogenous retinal detachment patients, matched on age, estimated glomerular filtration rate, smoking, intra-ocular lens implantation, and proliferative vitreoretinopathy. AGEs (pentosidine, N^ε-(carboxymethyl)lysine, N^ε-(carboxyethyl)lysine, and 5-hydro-5-methylimidazolone) and α-dicarbonyls (3-deoxyglucosone, methylglyoxal, and glyoxal) were measured by ultra performance liquid chromatography or high performance liquid chromatography. Skin autofluorescence was measured by the AGE Reader.

Results

Mean age was 64 ± 7.6 years for T2DM patients and 63 ± 8.1 years for controls. For T2DM patients, median diabetes duration was 2.2 (0.3–7.4) years. Non-proliferative diabetic retinopathy was present in 1 patient and classified as absent or background retinopathy in 30 patients. Vitreous levels of pentosidine (2.20 vs. 1.59 μmol/mol lysine, p = 0.012) and 3-deoxyglucosone (809 vs. 615 nmol/L, p = 0.001) were significantly elevated in T2DM patients compared to controls. Other AGEs and α-dicarbonyls in the vitreous were not significantly different. There was a trend for increased skin autofluorescence in T2DM patients as compared to controls (p = 0.07).

Conclusions

Pentosidine and 3-deoxyglucosone concentrations were increased in the vitreous of rhegmatogenous retinal detachment patients with a relatively short duration of diabetes compared to non-diabetic rhegmatogenous retinal detachment patients.

Surface Area of Detachment, Proliferative Vitreoretinopathy, and Pulse Pressure, but not AGEs, are Associated With Retinal Redetachment

Purpose

Advanced glycation endproducts (AGEs) have been suggested to play a role in retinal redetachment by promoting proliferative vitreoretinopathy (PVR). The purpose of this study was to investigate whether AGEs, in combination with other clinical characteristics, were able to identify patients at high risk for redetachment after vitrectomy for rhegmatogenous retinal detachment (RRD).

Methods

In this prospective cohort study, 410 RRD patients were included. Skin autofluorescence (SAF), as a reflection of tissue AGE accumulation, was measured by the AGE Reader. In a subgroup of 90 patients, the well characterised AGEs Nε-(carboxymethyl)lysine (CML), Nε-(carboxyethyl)lysine (CEL), 5-hydro-5-methylimidazolone (MG-H1), and pentosidine, and the α-dicarbonyls methylglyoxal, glyoxal, and 3-deoxyglucosone were measured in vitreous biopsies using ultra- or high-performance liquid chromatography. The main outcome was retinal redetachment within 3 months after surgery.

Results

Fifty-three patients developed a redetachment (aged 64 ± 9.6, 64% male) and were compared with 352 patients without a redetachment (aged 61 ± 9.4, 69% male); five patients were excluded for various reasons. Univariable analysis revealed that SAF, vitreous AGEs, and vitreous α-dicarbonyls were not significantly elevated in patients with a redetachment. Multivariable logistic regression analysis showed that surface area of detachment greater than 50% (odds ratio [OR] 2.74, confidence interval [CI] 1.45-5.17), PVR grade C (OR 4.57, CI 1.68-12.42), and pulse pressure (OR 1.37, CI 1.03-1.83 per SD) were independently associated with the occurrence of redetachment.

Conclusions

Skin autofluorescence and vitreous AGEs are not suitable to identify patients at high risk for redetachment after vitrectomy surgery. Surface area of detachment greater than 50%, PVR grade C, and pulse pressure were associated with redetachment.

Methylglyoxal, a glycolysis side-product, induces Hsp90 glycation and YAP-mediated tumor growth and metastasis

Metabolic reprogramming toward aerobic glycolysis unavoidably induces methylglyoxal (MG) formation in cancer cells. MG mediates the glycation of proteins to form advanced glycation end products (AGEs). We have recently demonstrated that MG-induced AGEs are a common feature of breast cancer. Little is known regarding the impact of MG-mediated carbonyl stress on tumor progression. Breast tumors with MG stress presented with high nuclear YAP, a key transcriptional co-activator regulating tumor growth and invasion. Elevated MG levels resulted in sustained YAP nuclear localization/activity that could be reverted using Carnosine, a scavenger for MG. MG treatment affected Hsp90 chaperone activity and decreased its binding to LATS1, a key kinase of the Hippo pathway. Cancer cells with high MG stress showed enhanced growth and metastatic potential in vivo. These findings reinforce the cumulative evidence pointing to hyperglycemia as a risk factor for cancer incidence and bring renewed interest in MG scavengers for cancer treatment.

Energy restriction and Roux-en-Y gastric bypass reduce postprandial α-dicarbonyl stress in obese women with type 2 diabetes

AIMS/HYPOTHESIS

Dicarbonyl compounds are formed as byproducts of glycolysis and are key mediators of diabetic complications. However, evidence of postprandial α-dicarbonyl formation in humans is lacking, and interventions to reduce α-dicarbonyls have not yet been investigated. Therefore, we investigated postprandial α-dicarbonyl levels in obese women without and with type 2 diabetes. Furthermore, we evaluated whether a diet very low in energy (very low calorie diet [VLCD]) or Roux-en-Y gastric bypass (RYGB) reduces α-dicarbonyl stress in obese women with type 2 diabetes.

METHODS

In lean (n = 12) and obese women without (n = 27) or with type 2 diabetes (n = 27), we measured the α-dicarbonyls, methylglyoxal (MGO), glyoxal (GO) and 3-deoxyglucosone (3-DG), and glucose in fasting and postprandial plasma samples obtained during a mixed meal test. Obese women with type 2 diabetes underwent either a VLCD or RYGB. Three weeks after the intervention, individuals underwent a second mixed meal test.

RESULTS

Obese women with type 2 diabetes had higher fasting and particularly higher postprandial plasma α-dicarbonyl levels, compared with those without diabetes. After three weeks of a VLCD, postprandial α-dicarbonyl levels in diabetic women were significantly reduced (AUC MGO -14%, GO -16%, 3-DG -25%), mainly through reduction of fasting plasma α-dicarbonyls (MGO -13%, GO -13%, 3-DG -33%). Similar results were found after RYGB.

CONCLUSIONS/INTERPRETATION

This study shows that type 2 diabetes is characterised by increased fasting and postprandial plasma α-dicarbonyl stress, which can be reduced by improving glucose metabolism through a VLCD or RYGB. These data highlight the potential to reduce reactive α-dicarbonyls in obese individuals with type 2 diabetes.

TRIAL REGISTRATION

ClinicalTrials.gov NCT01167959.

Post-Glucose Load Plasma α-Dicarbonyl Concentrations Are Increased in Individuals With Impaired Glucose Metabolism and Type 2 Diabetes: The CODAM Study

OBJECTIVE

There is increasing evidence that postprandial glucose excursions play an important role in the development of vascular complications. The underlying mechanism is unknown, but glucose-derived formation of reactive α-dicarbonyl compounds may explain why acute hyperglycemia leads to increased risk for diabetes complications. In the current study, we investigated whether α-dicarbonyls are increased after a glucose load in individuals without or with impaired glucose metabolism (IGM) and type 2 diabetes.

RESEARCH DESIGN AND METHODS

Cross-sectional, linear analyses were performed in the Cohort on Diabetes and Atherosclerosis Maastricht (CODAM [n = 574, 61% men, 60 years old]) study. Individuals with normal glucose metabolism (n = 279), IGM (n = 120), and type 2 diabetes (n = 92) who had complete data on an oral glucose tolerance test (OGTT) and were not on insulin treatment were included in the study population. Plasma α-dicarbonyl (methylglyoxal [MGO], glyoxal [GO], and 3-deoxyglucosone [3-DG]) levels were measured in the fasting state and in samples of the OGTT by ultra-performance liquid chromatography-tandem mass spectrometry.

RESULTS

The presence of both IGM and type 2 diabetes was significantly associated with higher α-dicarbonyl incremental areas under the curve (iAUCs), as calculated from the OGTT (for IGM, MGO β = 0.190 [95% CI 0.106-0.274], GO β = 0.287 [95% CI 0.172-0.401], and 3-DG β = 0.285 [95% CI 0.221-0.349]; for type 2 diabetes, MGO β = 0.293 [95% CI 0.180-0.405], GO β = 0.536 [95% CI 0.382-0.689], and 3-DG β = 0.542 [95% CI 0.456-0.628]). Adjustment for glucose iAUC attenuated these associations. iAUCs of the α-dicarbonyls correlated highly with glucose iAUC but not with fasting glucose levels or HbA1c.

CONCLUSIONS

The increased levels of α-dicarbonyls during an OGTT in individuals with IGM and type 2 diabetes underline the potential importance of α-dicarbonyl stress as a candidate to explain the increased risk of diabetes complications in individuals with postprandial hyperglycemia.

Protein-bound uraemic toxins, dicarbonyl stress and advanced glycation end products in conventional and extended haemodialysis and haemodiafiltration

BACKGROUND

Protein-bound uraemic toxins (PBUT), dicarbonyl stress and advanced glycation end products (AGEs) associate with cardiovascular disease in dialysis. Intensive haemodialysis (HD) may have significant clinical benefits. The aim of this study was to evaluate the acute effects of conventional and extended HD and haemodiafiltration (HDF) on reduction ratio (RR) and total solute removal (TSR) of PBUT, dicarbonyl stress compounds and AGEs.

METHODS

Thirteen stable conventional HD patients randomly completed a single study of 4-h HD (HD4), 4-h HDF (HDF4), 8-h HD (HD8) and 8-h HDF (HDF8) with a 2-week interval between the study sessions. RR and TSR of PBUT [indoxyl sulphate (IS), p-cresyl sulphate (PCS), p-cresyl glucuronide, 3-carboxyl-4-methyl-5-propyl-2-furanpropionic acid (CMPF), indole-3-acetic acid (IAA) and hippuric acid] of free and protein-bound AGEs [N(ε)-(carboxymethyl)lysine (CML), N(ε)-(carboxyethyl)lysine (CEL), Nδ-(5-hydro-5-methyl-4-imidazolon-2-yl)-ornithine, pentosidine], as well as of dicarbonyl compounds [glyoxal, methylglyoxal, 3-deoxyglucosone], were determined.

RESULTS

Compared with HD4, HDF4 resulted in increased RR of total and/or free fractions of IAA and IS as well as increased RR of free CML and CEL. HD8 and HDF8 showed a further increase in TSR and RR of PBUT (except CMPF), as well as of dicarbonyl stress and free AGEs compared with HD4 and HDF4. Compared with HD8, HDF8 only significantly increased RR of total and free IAA and free PCS, as well as RR of free CEL.

CONCLUSIONS

Dialysis time extension (HD8 and HDF8) optimized TSR and RR of PBUT, dicarbonyl stress and AGEs, whereas HDF8 was superior to HD8 for only a few compounds.