Publicação: Effects of diabetes mellitus and antioxidant supplementation in
oxidative stress and expression of myosin in rat brain
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CNPQ::CIENCIAS BIOLOGICAS::GENETICA
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CHAPTER II: Ca+2/calmodulin complex interacts with and regulates various enzymes and target
proteins, known as calmodulin-binding proteins (CaMBPs). This group of proteins
includes molecular motors such as myosins. Non-muscle myosin-IIB was shown in
our study to be overexpressed in diabetic rat brains. In this study, we compared
CaMBPs, purified by immobilized-calmodulin, affinity chromatography, isolated
from non-diabetic and streptozotocin-induced diabetic rat brains. Proteins eluted
with EGTA and urea were separated on a SDS-PAGE gel, digested and submitted
to peptide mass fingerprinting analysis. There were fifteen and sixteen intense
bands for non-diabetic and diabetic brains, respectively. Two proteins were
exclusively in non-diabetic brains, four were found exclusively in diabetic brains
and thirteen were found in both. Protein sequences were then analyzed for the
presence of the calmodulin-binding sites. A large fraction of the eluted proteins
(83%) had putative IQ motifs or calmodulin-binding sites. The myosin-IIB affinity
chromatography elution in association with western blot, immunohistochemistry
and RT-PCR analyses strongly suggest that myosin-IIB protein and mRNA are
highly expressed levels in diabetic rat brains. This is the first study that identified
and showed calmodulin-binding proteins differential expression in non-diabetic and
diabetic rat brains through a comparative proteomic analysis, and it opens up a
new field of study relating myosin-IIB expression in the brain, diabetes mellitus and
intracellular calcium regulation.
CHAPTER III: Diabetes mellitus is a chronic disease characterized by persistent
hyperglycemia, which may lead to brain tissue damage due to oxidative stress.
The enhancement of free radicals during hyperglycemia contributes to
increased neuronal death and changes in synaptic transmission. This study
evaluated the effect of oxidative stress and the use of antioxidants (calcium,
zinc and vitamin E) supplementation on myosins expression levels in brain
tissues of streptozotocin-induced diabetes experimental rat model. Lipid
peroxidation, antioxidant enzymes activities and myosins IIB and Va
expressions at transcriptional and protein levels were examined after 5 and 90
days post streptozotocin induction. The chronic effect of the streptozotocininduced
diabetes led to upregulation of glutathione peroxidase (GPx) and
malondialdehyde (MDA) levels, and downregulation of superoxide dismutase
(SOD) and catalase (CAT) activities. These alterations were accompanied by
increased myosin-IIB and decreased myosin-Va expressions in diabetic rat
brains. The antioxidant supplementation protected against hyperglycemia
damage by reducing CAT activity and increasing GPx and SOD activities,
although it had no influence on MDA levels. Interestingly, only diabetic rats
restored myosin-IIB expression at both transcriptional and protein levels in brain
tissues after supplementation, and no differences were observed in myosin-Va
expression in comparison to non-diabetic rat brains. The functional alterations
of antioxidant enzymes and myosins IIB and Va in rat brains of experimentallyinduced
diabetes were strongly associated with the disease and aging during
acute and chronic stages, but only myosin-IIB expression could be reversed by
antioxidants. These data highlight the supplementation (calcium, zinc and
vitamin E) antioxidants effects on the oxidative stress and the involvement of
myosins IIB and Va in the diabetes stages; however, their mechanisms of action
on enzymes activities, lipid peroxidation and myosins expression remain to be
elucidated.
Abstract
Palavras-chave
Antioxidantes, Miosina, Diabetes mellitus, Brain, Calcium, Calmodulin, Myosin-IIB
Citação
CALÁBRIA, Luciana Karen. Efeitos do diabetes mellitus e da suplementação com antioxidantes no estresse ocidativo e na expressão de miosinas no cérebro de ratos. 2010. 108 f. Tese (Doutorado em Ciências Biológicas) - Universidade Federal de Uberlândia, Uberlândia, 2010.