الفهرس 
Pathogenesis of Type 1 DM (T1DMOnly 14 pages are availabe for public view
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Abstract
Diabetes mellitus (DM) is a metabolic disease characterized
by hyperglycemia and insulin dysregulation, mostly accompanied by
severe chronic complications. Currently, DM affects more than 425
million people worldwide and this number is progressively
increasing.
Diabetic peripheral neuropathy (DPN) is one of the most
common disabling complications of DM with an estimated
prevalence ranging from 13% to 58% among uncontrolled diabetic
patients.
DPN can affect both sensorimotor and autonomic peripheral
nervous systems. The most common clinically recognized form is
diabetic sensorimotor polyneuropathy (DSPN).
The pathogenesis of DSPN is multifactorial & the exact
mechanism of this disease remains poorly understood. It has been
suggested that hyperglycemia is responsible for multiple
biochemical changes in the nerve tissue.
The pathophysiological mechanisms involved in diabetic
neuropathy include microvascular damage, metabolic disorders,
inflammatory changes, oxidative stress, advanced glycation end
products & growth factor deficiency.
Streptozotocin (STZ) is an antimicrobial agent and
chemotherapeutic alkylating agent. It is used to induce diabetes
mellitus in experimental animals because it causes specific necrosis
of the pancreatic beta cells leading to pathological changes that
mimic human type I DM. It became an attractive model for DM due to its low cost and needs only single injection. It causes β-cell
damage through oxidative stress & liberation of nitric oxide (NO).
Atorvastatin is an antihyperlipidemic drug that acts by
inhibition of 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA)
reductase enzyme. Lately, it has been shown to have neuroprotective
effect in Alzheimer disease through antioxidant mechanism. It also
has anti-inflammatory effect in experimental autoimmune
encephalomyelitis & relapsing-remitting multiple sclerosis.
Vitamin D is an essential fat soluble vitamin; it is formed
under the skin during exposure to ultra violet rays or obtained from
diet. Recently, it has been shown to play a role as anti-inflammatory,
antioxidant and immunomodulator in primary immune mediated
peripheral neuropathies, multiple sclerosis, Alzheimer &
Parkinsonism disease.
Therefore, the aim of the study is to evaluate the possible
role of vitamin D3 and atorvastatin in prevention of DSPN.
This study was carried out on 50 male albino rats weighing
(150-200gm). The animals were housed in wire mesh cages and fed
standard animal diet and water. Animals were divided into 5 groups
(10 rats each) as following:
▪ group 1: normal control group received single i.p.
injection of citrate buffer.
▪ group 2: diabetic group that was induced by single
i.p. injection of 60 mg/kg STZ & received vehicle
(distilled water) orally and served as untreated
diabetic group.▪ group 3: received daily dose of 0.03 μg/kg/day of
water soluble form of vitamin D3 dissolved in
distilled water orally before and after induction of
DM by single i.p. 60 mg/kg STZ and served as
vitamin D3 treated diabetic group.
▪ group 4: received daily dose of 10 mg/kg/day
atorvastatin dissolved in distilled water orally before
and after induction of DM by single i.p. 60 mg/kg
STZ and served as atorvastatin treated diabetic
group.
▪ group 5: received both vitamin D3 & atorvastatin
orally before and after induction of DM by single
i.p. 60 mg/kg STZ and served as combined treated
diabetic group till the end of the experiment.
At the end of experimental time (4 weeks):
A. Hot tail immersion test was done.
B. Then, the rats were anesthetized using ether inhalation then
blood samples were collected through cardiac puncture,
centrifuged and serum was separated and stored to be used in
detection of:
• Serum glucose (spectrophotometry).
• Creatine phosphokinase (CPK-MM) (ELISA).
C. After that, the rats were sacrificed, and sciatic nerves were
dissected. The right one was kept in buffered formalin for
histopathological examination , Immunohistochemical assay
of caspase-3 and the left one was homogenized and
centrifuged, then the supernatant was stored and used for
detection of:• Malondialdehyde (MDA) (spectrophotometry).
• Catalase activity (spectrophotometry).
• Nerve growth factor (NGF) (ELISA).
• Interleukin-6 (IL-6) (ELISA).
Results of the present study revealed the following:
The untreated STZ-induced DSPN group (group 2) showed
histopathological changes in sciatic nerve similar to DSPN. Also, it
showed significant decrease in withdrawal latency in hot tail
immersion test, tissue catalase activity and NGF, but showed
significant increase in serum glucose level, tissue MDA & IL-6 and
increased expression of caspase-3 in immunohistochemical
examination in comparison to the control group (group 1). However,
it showed non-significant difference in serum CPK-MM in
comparison to the control group.
The vitamin D3 treated group (group 3) showed very minimal
histopathological changes in sciatic nerve that resemble DSPN.
Also, it showed significant decrease of tissue MDA & IL-6 levels
and decreased expression of caspase-3 in immunohistochemical
examination, but it showed significant increase in withdrawal
latency in hot tail immersion test, tissue catalase activity and NGF in
comparison to the untreated group (group 2). Nevertheless, it
showed non-significant difference in serum glucose and CPK-MM
in comparison to the untreated group.
The atorvastatin treated group (group 4) showed very
minimal histopathological changes in sciatic nerve that resemble
DSPN. Moreover, it showed significant decrease of tissue MDA &
IL-6 levels and decrease expression of caspase-3 in mmunohistochemical examination, but it showed significant
increase in withdrawal latency in hot tail immersion test, serum
CPK-MM, tissue catalase activity & NGF in comparison to the
untreated group (group 2). However, it showed non-significant
difference in serum glucose level in comparison to the untreated
group.
The combined vitamin D3 & atorvastatin treated group
(group 5) showed histopathological findings in sciatic nerve similar
to the control group. In addition to that, it showed significant
decrease of tissue MDA in comparison the untreated group (group
2). Also, it showed significant decrease in tissue IL-6 levels in
comparison to the untreated group and monotherapy by either
vitamin D3 (group 3) or atorvastatin (group 4). Moreover, it showed
decrease expression of caspase-3 in immunohistochemical
examination, but it showed significant increase in withdrawal
latency in hot tail immersion test in comparison to the untreated
group and monotherapy by either vitamin D3 or atorvastatin. It also
showed significant increase in tissue catalase activity & NGF in
comparison to the untreated group and monotherapy by either
vitamin D3 or atorvastatin. Nevertheless, it showed non-significant
difference in serum glucose and CPK-MM in comparison to the
untreated group, but there was significant decrease in serum CPKMM
in comparison to the atorvastatin treated group.