Lower expression of advanced glycation endproduts receptor-1 (AGER1) in peripheral blood mononuclear cells is associated with renal disease in type 1 diabetes patients

Author(s)

Daniele Pereira dos Santos

• Document type: Master's Dissertation
• Press: São Paulo.
• Institution: Universidade de São Paulo (USP). Faculdade de Medicina (FM/SBD)
• Defense date: 2015-07-03

Examining board members

Maria Lucia Cardillo Correa Giannella; Ubiratan Fabres Machado; Márcia Silva Queiroz

• Advisor: Maria Lucia Cardillo Correa Giannella

Abstract

The role of hyperglycemia in the pathogenesis of chronic complications of type 1 diabetes (T1D) is well established; one of the mechanisms proposed to explain its deleterious effects is the increased formation of advanced glycation end products (AGEs). AGEs irreversibly alter macromolecule structure, compromising its biological function. In addition, AGEs interact with its specific receptor RAGE (encoded by AGER) leading to the generation of reactive oxygen species (ROS). The AGER1 receptor (encoded by DDOST) counteracts RAGE signaling by stimulating cellular antioxidants and reducing inflammatory stress. An enzyme of potential interest is sirtuin 1, a deacetylase that plays an important role in the response to stress and to toxic compounds that may have their activity decreased in diabetes, being negatively modulated by AGEs. The Thioredoxin (TXN) system is a major endogenous antioxidant system; TXN is able to interact with several proteins, such as TXN interacting protein (TXNIP), implicated in the pathogenesis of diabetes and its complications. There are few studies addressing the expression of AGEs receptor and its association with microvascular chronic complications in T1D. The objectives of this study were to evaluate mRNA expression of the genes encoding RAGE (AGER), AGER1 (DDOST), sirtuin 1 (SIRT1) and TXNIP (TXNIP) (quantitative RT-PCR with the use of TaqMan probes) in peripheral blood mononuclear cells (PBMC) of T1D patients with diferent degrees of microvascular complications (retinopathy [DR], cardiovascular autonomic neuropathy [CAN] and nephropathy [DN]). The results of the target genes were normalized by the mean expression of two housekeeping genes (beta 2-microglobulin and beta actin). A total of 130 patients with T1D was sorted into two groups: Group A: patients without microvascular chronic complications or presenting mild non-proliferative DR (n = 68; 61.7% female; age 33; age at diagnostic 12; DM1 duration of 19 years, HbA1c 8.1%, data expressed as median), and Group B: patients with at least one of microvascular complication (moderate/severe non-proliferative DR or proliferative DR or CAN or ND; n = 82; 66% female; age 33 years; age at diagnosis of 11 years; duration of T1D of 21 years, HbA1c 8.2%; data expressed as median). Smokers were excluded from the study. Differences between groups were analyzed by Mann-Whitney test and correlations between continuous variables were assessed using Spearman\'s test. T1D patients presented, respectively, higher and lower relative expression of TXNIP (p<0.001) and DDOST (p=0.01) in comparison to the control group. In the analyses considering diabetes complications, TXNIP expression was higher in Groups A and B (p=0.01 and p=0.04, respectively) versus the control group. Patients with proliferative or moderate/severe non-proliferative DR (n=44) and also patients with mild non-proliferative DR or without DR (n=86) presented higher TXNIP expression versus the control group (p=0.0012 and p=0.01, respectively). Patients without (n=104) and with (n=46) CAN presented higher TXNIP expression than the control group (p=0.03 and p=0.04, respectively); finally, concerning estimated glomerular filtration rate (eGFR), both the group of patients with values <60 mL/min and < 60 ml/min presented higher TXNIP expression versus the control group (p=0.01 and p=0.005, respectivamente). Patients presenting DN (n=44) had a lower DDOST expression in comparison to patients without DN (n=107) (p=0.031) and to the control group (p=0.011); patients with eGFR <60 mL/min also presented a lower expression of DDOST in comparison to the control group (p=0.03). A positive correlation was observed between expression of SIRT1 and AGER (? Spearman=0=51; p < 0.0001) and between expression of SIRT1 and DDOST (? Spearman=0,51; p < 0.0001). The expression of TXN positively correlated with the expression of TXNIP (p Spearman=0.65; p < 0.0001), SIRT1 (p Spearman=0.41; p < 0.0001) and DDOST (p Spearman=0.23; p 0.004). In a subgroup of 30 T1D patients, a higher expression of the gene encoding RAGE was observed in those patients consuming a diet enriched in AGEs (p=0.03). Expression of TXNIP in PBMC is affected by the metabolic abnormalities of T1D but does not reflect the presence of microvascular complications while expression of the gene encoding AGER1 seems to reflect diabetic kidney impairment since it is decreased in patients with DN and in patients with an eGFR < 60 mL/min/1.73m2 (AU)

• FAPESP's process: 12/25490-8 - Lower expression of advanced glycation endproduts receptor-1 (AGER1) in peripheral blood mononuclear cells is associated with renal disease in type 1 diabetes patients
• Grantee: Daniele Pereira dos Santos Bezerra
• Support Opportunities: Scholarships in Brazil - Master