Alterações na homeostase redox e do retículo endoplasmático: mecanismos associados à lipodistrofia generalizada congênita do tipo 2
Congenital generalized lipodystrophy (CGL) type 2 consists of a rare autosomal recessive syndrome characterized by almost complete lack of body fat at birth. CGL, genetically caused by loss-of-function mutations in the two alleles of the BSCL2 gene, was phenotypically characterized by hypertrigly...
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| Formato: | Dissertação |
| Idioma: | pt_BR |
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Brasil
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| Endereço do item: | https://repositorio.ufrn.br/jspui/handle/123456789/27009 |
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| Resumo: | Congenital generalized lipodystrophy (CGL) type 2 consists of a rare autosomal recessive
syndrome characterized by almost complete lack of body fat at birth. CGL, genetically
caused by loss-of-function mutations in the two alleles of the BSCL2 gene, was
phenotypically characterized by hypertriglyceridemia, hyperglycemia, decreased HDL-c,
and hypoadiponectinemia. These laboratory findings are important triggers for changes in
redox and endoplasmic reticulum (ER) homeostasis. Therefore, our aim was to investigate
if these intracellular mechanisms are part of this syndrome. Therefore, we collected the
whole blood from people living in Northeastern Brazil with 0, 1 and 2 mutant alleles for the
c.325dupA mutation (rs786205071) in the BSCL2 gene. Through the qPCR technique, we
evaluated the expression of genes responsible for triggering the antioxidant response, DNA
repair and ER stress in leukocytes. Colorimetric tests were applied to quantify lipid
peroxidation products and to evaluate the redox status of glutathione, as well as to access
plasma energy metabolism panorama. Conventional PCR was also chosen to observe
leukocyte mitochondrial DNA lesions. We also chose the immunoblot technique for the
study of gene expression of chaperone proteins related to ER stress in leukocytes, as well
as plasma adiponectin concentrations. Comparing to the healthy group, subjects with the
rs786205071 mutation in the 2 alleles showed increased transcription of NFE2L2, APEX1,
OGG1 and αOGG1 in leukocytes, as well as the concentrations of malondialdehyde and
the GSSG:GSH ratio in plasma. In addition, we also observed decreased in vitro
polymerization rate of mitochondrial DNA and increased XBP1 splicing in leukocytes. In
silico analyses indicated a high probability of seipin rs786205071 belonging to the ER
membrane, although the aforementioned mutation removes amyloidogenic regions from
that protein. In addition, we observed a decrease in the transcription of BSCL2 in these
leukocytes, associated with the absence of differences in the expression pattern of HSPA5
and P4HB chaperones. In parallel, these cells showed decreased DDIT3 transcripts, but
without differences in the procaspase-3 cleavage pattern. Finally, we also observed a soft
increase of plasmatic triacylglycerol, together with a decrease in plasma concentrations of
adiponectin and HDL-c. Together, results pointed to the presence of lipid lesions due to
changes in redox homeostasis, associated with increased numbers of mitochondrial DNA
damage and transcriptional recruitment of genes that participate of the antioxidant
response and DNA repair. Although there is also evidence of ER stress, the rs786205071
mutation was shown to possibly have a low probability to directly generate this mechanism.
In addition, the data suggest that there was no evidence of increased cell death and that
decreases in adiponectin and HDL-c concentrations may act as potential triggers for
changes in redox and ER homeostasis in CGL type 2. |
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