Serum levels of autoantibodies against the angiotensin II type I receptor are not associated with serum dicarbonyl or AGE levels in patients with an aldosterone-producing adenoma.

Patients with an aldosterone-producing adenoma (APA) carry a higher risk of cardiovascular disease and commonly have high levels of autoantibodies (AT1AA) that may activate the angiotensin II type 1 receptor (AT1R). AT1R activation is linked to an increase of the glucose metabolite methylglyoxal (MGO), a potential precursor of advanced glycation endproducts (AGEs) and driver of vascular inflammation. We investigated whether serum AT1AA levels are associated with serum MGO and AGE levels in APA patients. In a case series of 26 patients with APA we measured levels of dicarbonyls MGO, glyoxal (GO) and 3-deoxyglucosone (3-DG), and dicarbonyl-derived AGEs 5-hydro-5-methylimidazolone (MG-H1), Nε-(carboxyethyl)lysine (CEL) and Nε-(carboxymethyl)lysine (CML) with UPLC-MS/MS. We also measured AT1AA by ELISA. These measurements were repeated 1-month after adrenalectomy in a subset of 14 patients. Panels of inflammation and endothelial function were also measured by immunoassays. Although baseline higher AT1AA levels tended to be correlated with higher baseline serum MGO, GO and 3-DG levels (r = 0.18, p = 0.38; r = 0.20, p = 0.33; r = 0.23, p = 0.26; respectively), these correlations were not statistically significant. We observed no obvious correlations between higher AT1AA levels and protein-bound and free MG-H1, CEL and CML levels, and markers of inflammation and endothelial function. No decrease was observed in any of the dicarbonyls, protein-bound AGE levels and markers of inflammation and endothelial function after adrenalectomy. In patients with APA the serum levels of AT1AA were not significantly correlated with serum dicarbonyls, protein-bound and free AGE levels. Increased signalling of the AT1AA receptor may therefore be unlikely to overtly increase systemic dicarbonyl levels.

Irbesartan treatment does not influence plasma levels of the dicarbonyls methylglyoxal, glyoxal and 3-deoxyglucosone in participants with type 2 diabetes and microalbuminuria: An IRMA2 sub-study.

AIM: Angiotensin receptor blockers (ARBs) reduce vascular complications in diabetes independently of blood pressure. Experimental studies suggested that ARBs may restore the detoxifying enzyme glyoxalase 1, thereby lowering dicarbonyls such as methylglyoxal. Human data on the effects of ARBs on plasma dicarbonyl levels are lacking. We investigated, in individuals with type 2 diabetes, whether irbesartan lowered plasma levels of the dicarbonyls methylglyoxal, glyoxal, 3-deoxyglucosone and their derived advanced glycation end products (AGEs), and increased d-lactate, reflecting greater methylglyoxal flux. METHODS: We analysed a subset of the Irbesartan in Patients with T2D and Microalbuminuria (IRMA2) study. We measured plasma dicarbonyls methylglyoxal, glyoxal and 3-deoxyglucosone, free AGEs and d-lactate using ultra-performance liquid chromatography tandem mass-spectrometry (UPLC-MS/MS) in the treatment arm receiving 300 mg irbesartan (n = 121) and a placebo group (n = 101) at baseline and after 1 and 2 years. Effect of treatment was analysed with repeated measurements ANOVA. RESULTS: There was a slight, but significant difference in baseline median methylglyoxal levels [placebo 1119 (907-1509) nmol/l vs. irbesartan 300 mg 1053 (820-1427) nmol/l], but no significant changes were observed in any of the plasma dicarbonyls over time in either group and there was no effect of irbesartan treatment on plasma free AGEs or d-lactate levels at either 1 or 2 years. CONCLUSION: Irbesartan treatment does not change plasma levels of the dicarbonyls methylglyoxal, glyoxal and 3-deoxyglucosone, free AGEs or d-lactate in type 2 diabetes. This indicates that increased dicarbonyls in type 2 diabetes are not targetable by ARBs, and other approaches to lower systemic dicarbonyls are needed in type 2 diabetes. (Clinical Trial Registry No: #NCT00317915).

Fasting and post-oral-glucose-load levels of methylglyoxal are associated with microvascular, but not macrovascular, disease in individuals with and without (pre)diabetes: The Maastricht Study.

AIMS: Reactive dicarbonyl compounds, such as methylglyoxal (MGO), rise during an oral glucose tolerance test (OGTT), particularly in (pre)diabetes. Fasting MGO levels are associated with chronic kidney disease (CKD) and cardiovascular disease (CVD) in patients with poorly controlled type 2 diabetes mellitus (T2DM). Yet, whether fasting or post-OGTT plasma MGO levels are associated with vascular disease in people with (pre)diabetes is unknown. METHODS: Subjects with normal glucose metabolism (n=1796; age: 57.9±8.2 years; 43.3% men), prediabetes (n=478; age: 61.6±7.6 years; 54.0% men) and T2DM (n=669; age: 63.0±7.5 years; 67.0% men) from the Maastricht Study underwent OGTTs. Plasma MGO levels were measured at baseline and 2h after OGTT by mass spectrometry. Prior CVD was established via questionnaire. CKD was reflected by estimated glomerular filtration rate (eGFR) and albuminuria; retinopathy was assessed using retinal photographs. Data were analyzed using logistic regression adjusted for gender, age, smoking, systolic blood pressure, total-to-HDL cholesterol ratio, triglycerides, HbA1c, BMI and medication use. Odd ratios (ORs) were expressed per standard deviation of LN-transformed MGO. RESULTS: Fasting and post-OGTT MGO levels were associated with higher ORs for albuminuria ≥30mg/24h [fasting: 1.12 (95% CI: 0.97-1.29); post-OGTT: 1.19 (1.01-1.41)], eGFR<60mL/min/1.73 m2 [fasting: 1.58 (95% CI: 1.38-1.82), post-OGTT: 1.57 (1.34-1.83)] and retinopathy [fasting: 1.59 (95% CI: 1.01-2.53), post-OGTT: 1.38 (0.77-2.48)]. No associations with prior CVD were found. CONCLUSION: Fasting and post-OGTT MGO levels were associated with microvascular disease, but not prior CVD. Thus, therapeutic strategies directed at lowering MGO levels may prevent microvascular disease.

Systemic stiffening of mouse tail tendon is related to dietary advanced glycation end products but not high-fat diet or cholesterol.

Tendon pathology is related to metabolic disease and mechanical overloading, but the effect of metabolic disease on tendon mechanics is unknown. This study investigated the effect of diet and apolipoprotein E deficiency (ApoE(-/-)) on mechanical properties and advanced glycation end product (AGE) cross-linking of non-weight-bearing mouse tail tendons. Twenty ApoE(-/-) male mice were used as a model for hypercholesterolemia along with 26 wild-type (WT) mice. One-half of the mice from each group was fed a normal diet (ND) and the other half was fed a high-fat diet (HFD) to induce obesity. All were killed at 40 wk, and tail tendon fascicles were mechanically tested to failure and analyzed for AGEs. Diets were also analyzed for AGEs. ApoE(-/-) mice displayed a 14% increase in plateau modulus compared with WT mice (P < 0.05), whereas HFD mice displayed a 13% decrease in plateau modulus (P < 0.05) and a 12% decrease in total modulus (P < 0.05) compared with ND mice. Tail tendons of HFD mice had significantly lower concentrations of AGEs [carboxymethyllysine (CML): 26%, P < 0.0001; methylglyoxal-derived hydroimidazolone 1 (MG-H1): 15%, P < 0.005; pentosidine: 13%, P < 0.0005]. The HFD had ∼44-fold lower content of CML (P < 0.01), ∼29-fold lower content of carboxyethyllysine (P < 0.005), and ∼16-fold lower content of MG-H1 (P < 0.05) compared with ND. ApoE(-/-) increased, whereas HFD decreased mouse tail tendon stiffness. Dietary AGE content may be a crucial determinant for accumulation of AGE cross-links in tendons and for tissue compliance. The results demonstrate how systemic metabolic factors may influence tendon health.