In Type 2 Diabetes Mellitus Glycated Albumin Alters Macrophage Gene Expression Impairing ABCA1‐Mediated Cholesterol Efflux

Abstract

Advanced glycation end products (AGE) are elevated in diabetes mellitus (DM) and predict the development of atherosclerosis. AGE-albumin induces oxidative stress, which is linked to a reduction in ABCA-1 and cholesterol efflux. We characterized the glycation level of human serum albumin (HSA) isolated from poorly controlled DM2 (n = 11) patients compared with that of control (C, n = 12) individuals and determined the mechanism by which DM2-HSA can interfere in macrophage lipid accumulation. The HSA glycation level was analyzed by MALDI/MS. Macrophages were treated for 18 h with C- or DM2-HSA to measure the (14) C-cholesterol efflux, the intracellular lipid accumulation and the cellular ABCA-1 protein content. Agilent arrays (44000 probes) were used to analyze gene expression, and the differentially expressed genes were validated by real-time RT-PCR. An increased mean mass was observed in DM2-HSA compared with C-HSA, reflecting the condensation of at least 5 units of glucose. The cholesterol efflux mediated by apo AI, HDL3 , and HDL2 was impaired in DM2-HSA-treated cells, which was related to greater intracellular lipid accumulation. DM2-HSA decreased Abcg1 mRNA expression by 26%. Abca1 mRNA was unchanged, although the final ABCA-1 protein content decreased. Compared with C-HAS-treated cells, NADPH oxidase 4 mRNA expression increased in cells after DM2-HSA treatment. Stearoyl-Coenzyme A desaturase 1, janus kinase 2, and low density lipoprotein receptor mRNAs were reduced by DM2-HSA. The level of glycation that occurs in vivo in DM2-HSA-treated cells selectively alters macrophage gene expression, impairing cholesterol efflux and eliciting intracellular lipid accumulation, which contribute to atherogenesis, in individuals with DM2.

Combination Therapy with a Sodium-Glucose Cotransporter 2 Inhibitor and a Dipeptidyl Peptidase-4 Inhibitor Additively Suppresses Macrophage Foam Cell Formation and Atherosclerosis in Diabetic Mice

“…Cholesterol efflux to apolipoprotein A-1 or HDL requires ABCA1 and ABCG1, respectively [8]. Accumulating experimental evidence suggest that ABCA1 or ABCG1 expression in macrophages is suppressed by high-glucose concentrations in vitro and by hyperglycemia ex vivo [16–18]. Thus, our data may provide support for the association of glycemia with ABCA1 and ABCG1 expressions.…”

RAGE Mediates Cholesterol Efflux Impairment in Macrophages Caused by Human Advanced Glycated Albumin

“…Gene expression was assessed in BMDM isolated from WT and Ager null mice ( Figure 3 ) or in AGER -silenced THP-1 cells ( Figure 4 ) treated with albumin samples. Genes were chosen based on our previous findings, which demonstrated their involvement in the ABC-mediated cholesterol efflux in macrophages [ 15 , 16 ]. Ager expression was increased in WT BMDMs after treatment with DM 1 or AGE albumin in comparison to, respectively, C and non-glycated albumin ( Figure 3 A).…”

“…Glycated albumin is an important clinical marker of glycemic control and independently predicts long-term outcomes in DM [ 17 ]. AGE albumin plays a potential atherogenic role, particularly via its deleterious effects in macrophage reverse cholesterol transport [ 16 ]. Considering the involvement of the AGE/RAGE axis in the development of inflammation and vascular damage in DM, we addressed how RAGE is involved in the impairment of apo A-I and HDL-mediated cholesterol efflux elicited by human AGE albumin in macrophages.…”

“…We demonstrated that AGE albumin, isolated from both type 1 and 2 DM subjects’ serum, alters the transcription of genes involved in ABCA1 expression and activity in macrophages, such as Scd1 (Stearoyl-Coenzyme A desaturase 1), Jak2 (Janus kinase 2) and Nox4 (NADPH oxidase 4) [ 15 , 16 ], leading to intracellular lipid accumulation. Here, we tested the hypothesis that AGER silencing suppresses the reduction in macrophage cholesterol efflux induced by AGE albumin and rescues the gene expression profile.…”

Advanced Glycated apoA-IV Loses Its Ability to Prevent the LPS-Induced Reduction in Cholesterol Efflux-Related Gene Expression in Macrophages

“…Advanced glycation is independently related to cardiovascular disease, by inducing oxidative and inflammatory stress and disturbing the flux of cholesterol from the artery wall to the liver in the reverse cholesterol transport pathway. This may contribute to atherogenesis in diabetes mellitus (DM), chronic kidney disease, and inflammatory diseases [49][50][51][52].…”