1,610 research outputs found
The C-peptide Signaling
For years an assumption was made that C-peptide, a
byproduct of insulin biosynthesis, possessed no appreciable
physiologic role. As other contributions in this volume
amply testify, the time has come to re-evaluate that notion.
C-peptide either directly through interaction with its specific
cell-surface receptor or indirectly through an interaction
with a related membrane entity, exerts a unique effect
on several intracellular processes.We review here results of
studies attempting to elucidate such molecular effects of
C-peptide in different cell systems and tissues. Lacking a
purified C-peptide receptor, we also demonstrate C-peptide
effects on distinct elements of the insulin signal transduction
pathways
Structure-function interactions in the therapeutic response of diabetic neuropathy
Conventional electrophysiologic measurements such as nerve conduction velocity, compound action potential, and neuropathic symptom scores have been used to assess the severity of diabetic neuropathy and have been the major efficacy end points following pharmacologic intervention trials. Unfortunately, these measurements are not particularly sensitive and their reproducibility is, at best, good. Detailed morphometric analysis of sural nerve biopsies has evolved as a sensitive and highly reproducible method for assessing the severity and progression of diabetic peripheral neuropathy. In this study we demonstrate highly significant correlations between morphometric parameters of diabetic sural nerves and electrophysiologic and sensory score measurements of the same sural nerve. These data suggest that detailed morphometric examination is a more sensitive and reproducible method for assessing the severity of diabetic neuropathy, and that quantitative morphometric parameters provide sensitive indicators of electrophysiologic and clinically meaningful nerve damage. Morphometric analysis of sural nerve biopsies therefore constitutes a rational basis for sensitive efficacy end points in the design of future therapeutic clinical trials.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/30284/1/0000686.pd
The Insulin-Like Growth Factor System and Neurological Complications in Diabetes
The IGF system plays vital roles in neuronal development,
metabolism, regeneration and survival. It consists of
IGF-I, IGF-II, insulin, IGF-I-receptor, and those of IGF-II
and insulin as well as IGF-binding proteins. In the last
decades it has become clear that perturbations of the IGF
system play important roles in the pathogenesis of diabetic
neurological complications. In the peripheral nervous system
IGF-I, insulin, and C-peptide particularly in type 1 diabetes
participate in the development of axonal degenerative
changes and contributes to impaired regenerative capacities.
These abnormalities of the IGF system appear to be
less pronounced in type 2 diabetes, which may in part account
for the relatively milder neurological complications
in this type of diabetes. The members of the IGF system
also provide anti-apoptotic effects on both peripheral and
central nervous system neurons. Furthermore, both insulin
and C-peptide and probably IGF-I possess gene regulatory
capacities on myelin constituents and axonal cytoskeletal
proteins. Therefore, replenishment of various members of
the IGF system provides a reasonable rational for prevention
and treatment of diabetic neurological complications
C-Peptide Prevents Hippocampal Apoptosis in Type 1 Diabetes
To explore mechanisms underlying central nervous system
(CNS) complications in diabetes, we examined hippocampal neuronal
apoptosis and loss, and the effect of C-peptide replacement
in type 1 diabetic BB/W rats. Apoptosis was demonstrated after
8 months of diabetes, by DNA fragmentation, increased number of
apoptotic cells, and an elevated ratio of Bax/Bcl-xL, accompanied
by reduced neuronal density in the hippocampus. No apoptotic activity
was detected and neuronal density was unchanged in 2-month
diabetic hippocampus, whereas insulin-like growth factor (IGF) activities
were impaired. In type 1 diabetic BB/W rats replaced with
C-peptide, no TdT-mediated dUTP nick-end labeling (TUNEL)-
positive cells were shown and DNA laddering was not evident in
hippocampus at either 2 or 8 months. C-peptide administration prevented
the preceding perturbation of IGF expression and reduced
the elevated ratio of Bax/Bcl-xL. Our data suggest that type 1 diabetes
causes a duration-dependent programmed cell death of the
hippocampus, which is partially prevented by C-peptide
Avaliação por multicritérios de apoio à decisão da inovação no arranjo produtivo local de pêssego indústria.
Projeto/Plano de Ação: 11.11.11.111
Human C-peptide Dose Dependently Prevents Early Neuropathy in the BB/Wor-rat
In order to explore the neuroprotective and crossspecies
activities of.C-peptide on type 1 diabetic
neuropathy, spontaneously diabetic BB/W-rats were
given increasing doses of human recombinant Cpeptide
(hrC-peptide). Diabetic rats received 10, 100,
500, or 1000 μg of hrC-peptide/kg body weight/
day from onset of diabetes. After 2 months of hrC-peptide
administration, 100 μg and greater doses
completely prevented the nerve conduction defect,
which was associated with a significant but incomplete
prevention of neural Na+/K+-ATPase activity
in diabetic rats with 500 μg or greater C-peptide replacement.
Increasing doses of hrC-peptide showed
increasing prevention of early structural abnormalities
such as paranodal swelling and axonal degeneration
and an increasing frequency of regenerating
sural nerve fibers. We conclude that hrC-peptide exerts
a dose dependent protection on type 1 diabetic
neuropathy in rats and that this effect is probably
mediated by the partially conserved sequence of the
active C-terminal pentapeptid
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