|
The relative roles of advanced glycation, oxidation
and aldose reductase inhibition in the development of
experimental diabetic nephropathy in the Sprague-Dawley
rat.
Soulis-Liparota T, Cooper ME, Dunlop M, Jerums G
Department of Medicine, University of Melbourne, Austin
Hospital, Victoria, Australia.
Diabetologia (Germany) Apr 1995, 38 (4) p387-94
Advanced glycation is an important pathogenic mechanism in
the development of diabetic complications. However, other
biochemical processes, such as the polyol pathway or lipid and
protein oxidation which can interact with advanced glycation
can also yield tissue fluorescence and may also be implicated
in the genesis of diabetic microangiopathy. Aminoguanidine is
an inhibitor of advanced glycation, but it is not known if all
of its effects are mediated by this mechanism. The present
study explores the relative contributions of aldose reductase,
oxidative stress and advanced glycation on the development of
aortic and renal fluorescence and urinary albumin excretion in
streptozotocin diabetic rats. The study groups included
non-diabetic (control), streptozotocin diabetic rats and
diabetic rats receiving aminoguanidine, the anti-oxidants
butylated hydroxytoluene and probucol and the aldose reductase
inhibitor, ponalrestat. Serial measurements of glycaemic
control and urinary albumin excretion were performed every 8
weeks. At 32 weeks, animals were killed, tissues removed and
collagen extracted for measurement of fluorescence. Diabetic
rats had increased fluorescence in aorta, glomeruli and renal
tubules. Aminoguanidine prevented an increase in fluorescence
at all three sites suggesting that diabetes-related tissue
fluorescence is predominantly due to advanced glycation.
Ponalrestat retarded fluorescence in aorta only and butylated
hydroxytoluene attenuated fluorescence at the renal sites but
not in the aorta. Diabetic rats had increased renal cortical
sorbitol levels. Ponalrestat normalized renal cortical
sorbitol levels but aminoguanidine did not affect this
parameter. The only agent to decrease plasma thiobarbituric
acid reactive substances was butylatedhydroxytoluene. Diabetic
rats developed albuminuria over the 32-week period.
Cloning and expression of cytokine-inducible nitric
oxide synthase cDNA from rat islets of Langerhans.
Karlsen AE, Andersen HU, Vissing H, Larsen PM, Fey SJ,
Cuartero BG, Madsen OD, Petersen JS, Mortensen SB,
Mandrup-Poulsen T, et al
Steno Diabetes Center, Gentofte, Denmark.
Diabetes 1995 Jul;44(7):753-8
An inducible nitric oxide (NO) synthase isoform (iNOS) is
specifically induced in the beta-cells of interleukin (IL)-1
beta-exposed rat islets, suggesting a role for NO in the
pathogenesis of type I diabetes. The aim of this study was to
clone and characterize iNOS cDNA from cytokine-exposed islets.
Neither NO production nor iNOS transcription could be detected
in rat islets or in rat insulinoma RIN-5AH beta-cells cultured
in the absence of cytokines. Addition of IL-1 beta alone or in
combination with tumor necrosis factor-alpha induced a
concentration- and time-dependent expression of the iNOS gene
and associated NO production (measured asnitrite) from both
islets and RIN cells. iNOS transcripts were cloned by reverse
transcriptase-polymerase chain reaction from the
cytokine-exposed rat islets and RIN cells, and DNA sequence
analysis revealed a near 100% identity to the recently
published iNOS cDNA cloned from cytokine-exposed rat
hepatocytes and smooth muscle cells. Recombinant rat islet
iNOS was transiently and stably expressed in human kidney 293
fibroblasts, and the high enzymatic activity was inhibited by
addition of the L-arginine analogs, N omega-nitro-L-arginine
methyl ester and aminoguanidine. Two-dimensional gel
electrophoresis revealed the recombinant iNOS as aseries of
spots with the expected molecular mass of 131 kDa and pI
values in the range of 6.8 to 7.0. In conclusion, the IL-1
beta-induced iNOS cloned and expressed from rat islets and RIN
cells is encoded by the same transcript as the iNOS induced in
other cell types.
Aminoguanidine does not inhibit the initial phase
of experimental diabetic retinopathy in rats.
Hammes HP, Ali SS, Uhlmann M, Weiss A, Federlin K, Geisen K,
Brownlee M
Third Medical Department, Justus-Liebig-University of
Giessen, Germany.
Diabetologia (Germany) Mar 1995, 38 (3) p269-73
We have previously shown that long-term administration of
aminoguanidine, an inhibitor of advanced glycosylation product
formation, reduces the extent of experimental diabetic
retinopathy in the rat by 85%. In order to determine whether
the residual retinopathy that developed despite aminoguanidine
was attributable to advanced glycation endproduct formation, a
time-course study was performed in three different groups of
male Wistar rats: non-diabetic controls (NC),
streptozotocin-diabetic controls (DC) and
streptozotocin-diabetic rats treated with aminoguanidine HCL,
50 mg/100 ml drinking water (D-AG). Eyes were obtained at 24,
32, 44 and 56 weeks of diabetes/treatment duration and
morphologic evaluation was done on retinal digest
preparations. At 56 weeks, retinal basement membrane thickness
was additionally measured. After 24 weeks of diabetes, the
number of acellular capillaries was significantly elevated in
DC (44.6 +/- 5.7/mm2 of retinal area, NC 19.6 +/- 4.9; p <
0.001) and increased continuously over time (DC56 weeks 87.4
+/- 15.1; p < 0.001 vs DC24 weeks). In contrast, acellular
capillaries in D-AG increased over the first 24 weeks and then
remained constant for the rest of the study (D-AG 24 weeks
35.7 +/- 5.18; p < 0.01 vs NC 24 weeks and NS vs DC 24
weeks; D-AG 56 weeks 42.0 +/- 6.20; p NS vsD-AG 24 weeks).
(ABSTRACT TRUNCATED AT 250 WORDS)
Neurotoxicity of advanced glycation endproducts
during focal stroke and neuroprotective effects of
aminoguanidine.
Zimmerman GA, Meistrell M 3rd, Bloom O, Cockroft KM, Bianchi
M, Risucci D, Broome J, Farmer P, Cerami A, Vlassara H, et
al
Department of Surgery, North Shore University Hospital,
Manhasset, NY 11030, USA.
Proc Natl Acad Sci U S A (United States) Apr 25 1995, 92 (9)
p3744-8
Cerebral infarction (stroke) is a potentially disastrous
complication of diabetes mellitus, principally because the
extent of cortical loss is greater in diabetic patients than
in nondiabetic patients. The etiology of this enhanced
neurotoxicity is poorly understood. We hypothesized that
advanced glycation endproducts (AGEs), which have previously
been implicated in the development of other diabetic
complications, might contribute to neurotoxicity and brain
damage during ischemic stroke. Using a rat model of focal
cerebral ischemia, we show that systemically administered
AGE-modified bovine serum albumin (AGE-BSA) significantly
increased cerebral infarct size. The neurotoxic effects of
AGE-BSA administration were dose- and time-related and
associated with a paradoxical increase in cerebral blood flow.
Aminoguanidine, an inhibitor of AGE cross-linking, attenuated
infarct volume in AGE-treated animals. We conclude that AGEs
may contribute to the increased severity of stroke associated
with diabetes and other conditions characterized by AGE
accumulation.
Agmatine and spermidine reduce collagen
accumulation in kidneys of diabetic db/db mice.
Marx M, Trittenwein G, Aufricht C, Hoeger H, Lubec B
Department of Pediatrics, University of Vienna,
Austria.
Nephron (Switzerland) 1995, 69 (2) p155-8
In the present study, we tested the hypothesis whether
agmatine and spermidine, metabolites of arginine metabolism,
share the pharmacological activities of arginine reducing
collagen accumulation in the diabetic kidney. Eleven db/db
mice were administered agmatine and 12 db/db mice spermidine
(50 mg/kg body weight). Ten db/db mice received no treatment
as negative controls and 10 db/db mice were treated with
aminoguanidine (50mg/kg body weight) as positive controls.
Mean kidney OH-proline content reflecting kidney collagen
content and mean CML concentration were significantly higher
but acid solubility of collagen significantly lower in the
untreated group than in the treated groups. Agmatine, although
missing the alpha-amino group and the carboxyl group, and
spermidine, although missing the guanidino group, thus still
revealed the arginine activity. We hypothesize that the
strongly nucleophilic structure of polyamines common to all
active compounds is able to block reactive carbonyls.
Mechanism of autoxidative glycosylation:
identification of glyoxal and arabinose as intermediates in
the autoxidative modification of proteins by glucose.
Wells-Knecht KJ, Zyzak DV, Litchfield JE, Thorpe SR, Baynes
JW
Department of Chemistry and Biochemistry, University of South
Carolina, Columbia 29208.
Biochemistry (United States) Mar 21 1995, 34 (11)
p3702-9
Glycation and oxidation reactions contribute to protein
modification in aging and diabetes. Formation of dicarbonyl
sugars during autoxidation of glucose is the hypothetical
first step in the autoxidative glycosylation and subsequent
browning of proteins by glucose [Wolff, S. P., & Dean, R.
T. (1987) Biochem. J. 245, 243-250]. In order to identify the
dicarbonyl sugar(s) formed during autoxidation of glucose
under physiological conditions, glucose was incubated in
phosphate buffer (pH 7.4) at 37 degrees C under air (oxidative
conditions) or nitrogen with transition metal chelators
(antioxidative conditions). Dicarbonyl compounds were analyzed
spectrophotometrically and by HPLC after reaction with
Girard-T reagent. Carbohydrates were analyzed by gas
chromatography-mass spectrometry. Both dicarbonyl sugar and
arabinose concentrations increased with time and glucose
concentration in incubations conducted under oxidative
conditions; only trace amounts of these products were detected
in glucose incubated under antioxidative conditions. HPLC
analysis of adducts formed with Girard-T reagent indicated
that glyoxal was the only alpha-dicarbonyl sugar formed on
autoxidation of glucose. Glyoxal and arabinose accounted for
> or = 50% of the glucose lost during a 21 day incubation.
Neither glucosone nor its degradation product, ribulose, was
detectable. Reaction of glyoxal with RNase yielded the
glycoxidation product, N epsilon-(carboxymethyl)lysine, while
arabinose is a source of pentosidine. Our results implicate
glyoxal and arabinose as intermediates in the browning and
crosslinking of proteins by glucose under oxidative
conditions. They also provide a mechanism by which
antioxidants and dicarbonyl trapping reagents, such as
aminoguanidine, limit glycoxidation reactions and support
further evaluation of these types of compounds for inhibition
of chemical modification and crosslinking of proteins during
aging and diabetes.
Nitric oxide synthesis and the effect of
aminoguanidine and NG-monomethyl-L-arginine on the onset of
diabetes in the spontaneously diabetic BB rat.
Wu G
Department of Animal Science, Texas A&M University,
College Station TX 77843-2471
Diabetes (United States) Mar 1995, 44 (3) p360-4
Nitric oxide (NO) synthesis and the effect of
aminoguanidine (AG) and NG-monomethyl-L-arginine (NMMA)
(inhibitors of NO synthase) on the onset of diabetes were
studied in the spontaneously diabetic BB rat. To measure in
vivo NO production, 20 male 50-day-old diabetes-prone BB
(BBdp) rats and age-matched non-diabetes-prone BB (BBn) rats
were individually placed in metabolism cages. The animals had
free access to a casein-based semipurified diet and deionized
and double-distilled water. Urine excretion was collected
every other day for 70 days, and urinary excretion of nitrate
was measured as an index of in vivo NO synthesis. The urinary
excretion of nitrate was enhanced by 150-200% in BBdp rats 4-6
days before the onset of diabetes, compared with aged-matched
BBn rats. There was no difference in urinary excretion of
nitrate between BBn rats and those BBdp rats that did not
develop diabetes by the age of up to 120 days. To determine a
role of NO in the development of spontaneous diabetes,
40-day-old male BBdp rats (30 rats per group) received daily
subcutaneous injections of NMMA (acetate salt) (5 mg/kg body
wt) or equal amounts of acetate (control) or oral
administration of AG (0 or 3 g/l of drinking water) for 80
days. Both NMMA and AG delayed the onset of diabetes in BBdp
rats by 13-15 days without altering the rate of incidence of
diabetes.
The pharmacokinetics of aminoguanidine in end-stage
renal disease patients on hemodialysis.
Foote EF, Look ZM, Giles P, Keane WF, Halstenson CE
Department of Medicine, Hennepin County Medical Center,
Minneapolis, MN 55404.
Am J Kidney Dis (United States) Mar 1995, 25 (3)
p420-5
Aminoguanidine is an investigational agent that may slow or
prevent many diabetes-related complications. Since the
elimination of aminoguanidine is dependent on renal function,
its pharmacokinetics was investigated in eight chronic renal
failure patients maintained on hemodialysis. Each patient
received 300 mg of aminoguanidine hydrochloride during both an
interdialytic and an intradialytic period. During the
interdialytic period, the maximum aminoguanidine concentration
(Cmax) and time to reach Cmax was 4.5 micrograms/mL and 1.5
hours, respectively. The terminal elimination hallife in these
patients was prolonged (37.9 hours). The renal clearance was
2.1 mL/min. Only 8.7% of the administered dose was recovered
unchanged in the urine, which is markedly reduced from what is
recovered in urine in subjects with normal renal function.
There was a positive correlation between the renal clearance
of aminoguanidine and the patients' residual renal function (P
< 0.05). During hemodialysis, the hallife of aminoguanidine
was shortened to 3.9 hours. The hemodialysis clearance of
aminoguanidine was 203.6 mL/min. After cessation of
hemodialysis, a significant rebound in plasma aminoguanidine
concentrations (mean, 39%) was observed. Thus, the dose of
aminoguanidine hydrochloride will need to be significantly
reduced in patients with end-stage renal disease. Given the
interdialytic and intradialytic pharmacokinetics of
aminoguanidine, three times weekly dosing after each
hemodialysis session is suggested.
Effect of aminoguanidine on the impaired nitric
oxide-mediated neurotransmission in anococcygeus muscle from
diabetic rats.
Way KJ, Reid JJ
Department of Pharmacology, University of Melbourne,
Parkville, Victoria, Australia.
Neuropharmacology (England) Nov 1994, 33 (11)
p1315-22
The contribution of advanced glycation end-product (AGE)
formation to alterations in nitrergic neurotransmission caused
by 8-week streptozotocin-induced diabetes has been examined in
the rat anococcygeus muscle. Relaxant responses to nitrergic
nerve stimulation (0.5-5 Hz, 10-sectrain), to nitric oxide
(NO; 0.1-3 microM), to the NO donor, sodium nitroprusside
(SNP; 5-500 nM), and to the cell-permeable analogue of cyclic
guanosine monophosphate (cGMP), 8-bromo-cGMP (15 and 30
microM), were significantly smaller in muscles from diabetic
rats than from control rats.Pretreatment with aminoguanidine
hemisulphate (1 milligram drinking water) to inhibit AGE
formation, did not alter the relaxant responses to nitrergic
nerve stimulation, NO or SNP in tissues from control rats, or
responses to NO or SNP in tissues from diabetic rats, however
relaxations to nitrergic nerve stimulation were further
reduced in tissues from diabetic rats. In anococcygeus muscles
from untreated animals, a 20-min exposure to aminoguanidine (1
mM) in vitro had no effect on relaxations to nitrergic nerve
stimulation. The results suggest that diabetes impairs
nitrergic transmission in the rat anococcygeus at least partly
through alterations in the cGMP-relaxation pathway. The
impaired neurotransmission does not appear to be related to
the formation of AGEs.
Interleukin 1 beta induces diabetes and fever in
normal rats by nitric oxide via induction of different nitric
oxide synthases.
Reimers JI, Bjerre U, Mandrup-Poulsen T, Nerup J
Steno Diabetes Center, Gentofte, Denmark.
Cytokine (United States) Sep 1994, 6 (5) p512-20
Substantial in vitro evidence suggests that nitric oxide
may be a major mediator of interleukin 1 (IL-1) induced
pancreatic beta-cell inhibition and destruction in the initial
events leading to insulin-dependent diabetes mellitus. Using
NG-nitro-L-arginine methyl ester, an inhibitor of both the
constitutive and the cytokine inducible forms of nitric oxide
synthase, andaminoguanidine, a preferential inhibitor of the
inducible form of nitric oxide synthase, we investigated the
impact of inhibiting nitric oxide production on food-intake,
body weight and temperature, blood glucose,plasma insulin,
glucagon, corticosterone and leukocyte- and
differential-counts in normal rats injected once daily for 5
days with interleukin 1 beta (IL-1 beta) (0.8 microgram/rat =
4.0 micrograms/kg). Inhibition of both the constitutive and
the inducible forms of nitric oxide synthase prevented IL-1
beta-induced fever, hyperglycaemia, hypoinsulinemia, and
hyperglucagonemia, and partially prevented lymphopenia and
neutrophilia, but had no effect on IL-1 beta-induced anorexia
and changes in plasma corticosterone. Preferential inhibition
of the inducible form of nitric oxide synthase using two daily
injections of 5 mg/rat of aminoguanidine prevented IL-1
beta-induced hyperglycaemia and hypoinsulinaemia, and slightly
reduced the pyrogenicity of IL-1 on 3 out of 5 days. Higher
doses of aminoguanidine (100 mg/rat) prevented lymphopenia and
neutrophilia. We conclude that nitric oxide produced by the
inducible form of nitric oxide synthase, mediates the IL-1
beta-induced inhibition of insulin release and that the effect
of IL-1 beta on temperature, pancreatic alpha-cells, and
leukocyte differential counts seems to be mediated by nitric
oxide produced by the constitutive form of nitric oxide
synthase.
Reversal of diabetes by intrapancreatic injection
of aminoguanidine liposomes.
Ricordi C, Behboo R, Klibanov A, Singal A, Huang L
University of Pittsburgh Transplantation Institute,
Pennsylvania.
Transplant Proc (United States) Dec 1994, 26 (6)
p3479
No abstract.
The reaction of methylglyoxal with aminoguanidine
under physiological conditions and prevention of methylglyoxal
binding to plasma proteins.
Lo TW, Selwood T, Thornalley PJ
Department of Chemistry and Biological Chemistry, University
of Essex, Colchester, UK
Biochem Pharmacol (England) Nov 16 1994, 48 (10)
p1865-70
Increased formation of methylglyoxal in clinical diabetes
mellitus and metabolism by the glyoxalase system has been
linked to the development of clinical complications of
diabetes: retinopathy, neuropathy and nephropathy.
Aminoguanidine has been proposed as a prophylactic agent for
preventive therapy of diabetic complications. Methylglyoxal
reacted with aminoguanidine under physiological conditions to
form two isomerictriazines, 3-amino-5-methyl-1,2,4-triazine
and 3-amino-6-methyl-1,2,4-triazine. The mean second order
rate constant for the reaction of methylglyoxal with
aminoguanidine, kMG.AG = 0.39 +/- 0.06 M-1 sec-1 at pH 7.4 and
37degrees. Under these conditions, no methylglyoxal
bisguanylhydrazone was detected. Aminoguanidine prevented the
irreversible modification of human plasma protein by a
physiological concentration of methylglyoxal (1microM); the
median inhibitory concentration IC50 value of aminoguanidine
was 203 +/- 16 microM (N = 28). The scavenging of
methylglyoxal by aminoguanidine may contribute to the
beneficial effects of aminoguanidine in the prevention of
vascular pathogenesis in diabetes.
Advanced glycation end products induce glomerular
sclerosis and albuminuria in normal rats.
Vlassara H, Striker LJ, Teichberg S, Fuh H, Li YM, Steffes
M
Picower Institute for Medical Research, Manhasset, NY
11030.
Proc Natl Acad Sci U S A (United States) Nov 22 1994, 91 (24)
p11704-8
High levels of tissue advanced glycation end products
(AGEs) that result from the spontaneous modification of
proteins by glucose occur in diabetes and aging. To address
the potential pathogenic role of AGEs in the
glomerulosclerosis of diabetes or nephrosclerosis of aging,
doses of AGE-modified rat albumin (25 mg per kg per day, i.v.)
sufficient to elevate circulating AGE levels to the range of
diabetic serum were administered daily to healthy rats alone
or in combination with the AGE inhibit oraminoguanidine. After
5 months, the AGE content of renal tissues in AGE-treated rats
rose to 50% above controls (P < 0.025), whereas serum
contained 2.8-fold greater AGE levels (P < 0.025). Light
and electronmicroscopy of kidneys from AGE-treated rats
revealed a more than 50% increase in glomerular volume
compared to controls (P < 0.001), significant periodic
acid/Schiff reagent-positive deposits, basement membrane
widening, and mesangial extracellular matrix increase and
indicated significant glomerulosclerosis compared to untreated
(P < 0.002) or albumin-treated controls (P < 0.002).
These changes were associated with significant loss of protein
(P < 0.005) and albumin (P < 0.002) in the urine of
AGE-treated rats compared to controls. Cotreatment with
aminoguanidine markedly limited both the structural and
functional defects. These in vivo data demonstrate that AGEs
influence glomerular structure and function in a manner
leading to glomerulosclerosis. The effects are AGE-specific,
as they are ameliorated by a pharmacological AGE inhibitor,
aminoguanidine.
Active and passive mechanical properties of
isolated arterioles from STZ-induced diabetic rats. Effect of
aminoguanidine treatment.
Hill MA, Ege EA
Department of Physiology, Eastern Virginia Medical School,
Norfolk 23501.
Diabetes (United States) Dec 1994, 43 (12)
p1450-6
Studies were performed to examine the effect of
experimental diabetes (4-6 weeks duration) on both the passive
elastic and active myogenic properties of isolated skeletal
muscle arterioles. Studies were conducted on untreated
streptozotocin (60 mg/kg)-induced diabetic rats and in similar
rats treated daily with either amino-guanidine (25 mg/kg)
ormethylguanidine (25 mg/kg). First-order cremaster muscle
arterioles were isolated, cannulated, and pressurized in the
absence of intraluminal flow.Video microscopy was used to
determine relationships between arteriolar diameter and
intraluminal pressure both in the active and passive (o
mmol/lCa(2+)-2 mmol/l EGTA superfusated) tes. The measurements
were used to calculate active myogenic responses, arteriolar
distensibility, and stress-strain relationships. Under passive
conditions, arterioles from untreated diabetic animals
appeared to be stiffer and less distensible compared with
similar arterioles from control animals. Under active
conditions, i.e., in the presence of extracellular Ca2+,
arterioles from the untreated diabetic group showed impaired
myogenic reactivity as evidenced by a significant (P <
0.001) reduction in the negative slope of the
pressure-diameter relationship over a physiological range of
intraluminal pressures. Chronic treatment with aminoguanidine
prevented the diabetes-induced changes in the active and
passive properties of the isolated arterioles while treatment
with methylguanidine appeared ineffective. Vasodilator
responses to topically applied acetylcholine (10(-8) to 5 x
10(-6) mol/l) were significantly impaired in diabetic animals
irrespective of treatment with aminoguanidine. The data
indicate that experimental diabetes is associated with a
decreased passive distensibility, or stiffening, of skeletal
muscle arterioles that, in addition, may contribute to
impaired active myogenic responses.
Effects of aminoguanidine on insulin release from
pancreatic islets.
Tasaka Y, Nakaya F, Matsumoto H, Omori Y
Tokyo Women's Medical College, Diabetes Center, Japan.
Endocr J (England) Jun 1994, 41 (3) p309-13
Aminoguanidine (AG) is a potential therapeutic agent for
preventing the generation of advanced glycation end products
in diabetes mellitus. In this study, the effect of AG on
insulin secretion was investigated in in vitro rat pancreatic
islets. The islets were aseptically isolated and cultured in
tissue culture medium 199 for 48 h with or without AG. After
the culture, batches of 10 islets were incubated in
Krebs-Ringer bicarbonate buffer containing 3.3 mM or 16.7 mM
glucose. Islets previously exposed to 0.18 mM AG or 0.45 mM AG
showed similar insulin release to control islets at a 16.7 mM
glucose concentration, but high glucose-stimulated insulin
release was inhibited in the islets exposed to 1.8 mM. In the
perifusion experiment, insulin release caused by 16.7 mM
glucose from the islets previously exposed to 1.8 mM AG was
not significantly different from that of the control islets.
However, culture of the islets with higher AG concentrations,
4.55 mM and 9.1 mM, significantly inhibited glucose-stimulated
insulin release (< 0.02 and 0.002, respectively). These
results suggest that AG at high concentrations impairs
pancreatic B-cell response to a high concentration of
glucose.
TNF-alpha and IFN-gamma potentiate the deleterious
effects of IL-1 beta on mouse pancreatic islets mainly via
generation of nitric oxide.
Cetkovic-Cvrlje M, Eizirik DL
Department of Medical Cell Biology, Uppsala University,
Sweden.
Cytokine (United States) Jul 1994, 6 (4)
p399-406
Cytokines may be important mediators of beta-cell damage in
early insulin-dependent diabetes mellitus. In order to further
characterize the mechanism(s) of action of cytokines on
insulin-producing cells, mouse pancreatic islets were exposed
for 48 h to IL-1 beta, IFN-gamma or TNF-alpha, alone or in
combinations. The three cytokines induced islet nitric oxide
(NO) production, an effect most marked when islets were
exposed to the three cytokines together. In parallel with NO
production, IL-1 beta+IFN-gamma+TNF-alpha impaired islet
function, as judged by decreased islet DNA and insulin
content, decreased glucose metabolism and decreased
glucose-induced insulin release. Aminoguanidine, an inhibitor
of NO production, prevented all the above described
suppressive effects of the cytokines, with exception of
depletion in islet insulin content. In parallel experiments,
insulin-producing RIN cells were exposed for 6 h to the same
cytokines. Both IL-1 beta and TNF-alpha, but not IFN-gamma,
induced NO production and expression of the mRNA encoding for
the inducible form of the enzyme NO synthase (iNOS). These
effects were most pronounced when combinations of IL-1
beta+IFN-gamma or IL-1 beta+IFN-gamma+TNF-alpha were used. As
a whole, the data suggest that combinations of cytokines
induce higher amounts of NO generation by mouse pancreatic
islets than each of the cytokines isolated. An important
source of islet NO production are probably the beta-cells, as
pointed by data obtained with an insulinoma cell line. Most of
the deleterious effects of the cytokines of mouse islets are
prevented by blocking NO production, suggesting that NO is the
main mediator of cytokine-induced beta-cell damage.
Modification of low density lipoprotein by advanced
glycation end products contributes to the dyslipidemia of
diabetes and renal insufficiency.
Bucala R, Makita Z, Vega G, Grundy S, Koschinsky T, Cerami A,
Vlassara H
Picower Institute for Medical Research, Manhasset, NY
11030.
Proc Natl Acad Sci U S A (United States) Sep 27 1994, 91 (20)
p9441-5
Atherosclerosis develops rapidly in patients with diabetes
or renal insufficiency. Plasma lipoprotein profiles are
frequently abnormal in these conditions and reflect an
elevation in the level of the apoprotein B (ApoB)-containing
components very low density lipoprotein (VLDL) and low density
lipoprotein (LDL). High levels of circulating advanced
glycation end products (AGEs) also occur in diabetes and
end-stage renal disease (ESRD). These products arise from
glucose-derived Amadori products and include AGE-modified
peptides (AGE-peptides) which result from the catabolism of
AGE-modified tissue proteins. AGE-peptides have been shown to
crosslink protein amino groups and to accumulate in plasma as
a consequence of renal insufficiency. To address potential
mechanisms for the dyslipidemia of diabetes and ESRD, we
investigated the possibility that circulating AGEs react
directly with plasma lipoproteins to prevent their recognition
by tissue LDL receptors. AGE-specific ELISA showed a
significantly increased level of AGE-modified LDL in the
plasma of diabetic or ESRD patients compared with normal
controls. AGE-LDL formed readily in vitro when native LDL was
incubated with either synthetic AGE-peptides or AGE-peptides
isolated directly from patient plasma. LDL which had been
modified by AGE-peptides in vitro to the same level of
modification as that present in the plasma of diabetics with
renal insufficiency exhibited markedly impaired clearance
kinetics when injected into transgenic mice expressing the
human LDL receptor. These data indicate that AGE modification
significantly impairs LDL-receptor-mediated clearance
mechanisms and may contribute to elevated LDL levels in
patients with diabetes or renal insufficiency. This hypothesis
was further supported by the observation that the
administration of the advanced glycation inhibitor
aminoguanidine to diabetic patients decreased circulating LDL
levels by 28%.
Chemistry of the fructosamine assay: D-glucosone is
the product of oxidation of Amadori compounds.
Baker JR, Zyzak DV, Thorpe SR, Baynes JW
Department of Clinical Biochemistry, Green Lane Hospital,
Auckland, New Zealand.
Clin Chem (United States) Oct 1994, 40 (10)
p1950-5
The chemistry of the fructosamine assay was studied by
using the Amadori compound, N alpha-formyl-N
epsilon-fructose-lysine (fFL), an analog of glycated lysine
residues in protein. Previously (Clin Chem 1993;39:2460-5), we
reported that free lysine was formed from fFL at 70% yield
during incubation with alkaline nitroblue tetrazolium (NBT)
under the conditions routinely used for the fructosamine assay
(sodium carbonate buffer, pH10. 35 at 37 degrees C). Here, we
show that D-glucosone is the primary carbohydrate oxidation
product formed from Amadori compounds in the fructosamine
assay. Glucosone, which decomposes under alkaline assay
conditions with a hallife of < 30 min, reaches a maximum
concentration of approximately 50% of the initial fFL
concentration after 10 min of incubation. Like fFL, glucosone
reduces NBT to the purple monoformazan dye, but its
decomposition is not accelerated by the presence of NBT. The
dicarbonyl-trapping reagent, aminoguanidine, inhibits the
fructosamine assay by approximately 25% when fFL is the
substrate, but by nearly 100% with glucosone as substrate.
Studies with serum samples from diabetics and nondiabetics
indicate that glucosone formation does not have a significant
effect on the clinical usefulness of the fructosamine assay;
however, corrections for glucosone formation may be required
when the assay is used for estimating the extent of glycation
of proteins.
Creatine reduces collagen accumulation in the
kidneys of diabetic db/db mice.
Lubec B, Aufricht C, Herkner K, Hoeger H, Adamiker D,
Gialamas H, Fang-Kircher S, Lubec G
Department of Paediatrics, University of Vienna,
Austria.
Nephron (Switzerland) 1994, 67 (2) p214-7
In the present study, we tested the hypothesis whether
creatine, a metabolite of arginine metabolism, shares the
pharmacological activities of arginine reducing collagen
accumulation in the diabetic kidney. Ten db/db mice were
given, for 3 months, a solution containing a daily dosage of
creatine of 50 mg/kg body weight. Eleven db/db mice served as
controls. At the end of the 3-month study period, the mean
N-carboxymethyllysine concentration in the untreated group was
significantly higher than in the treated group (0.163 +/- 0.18
versus 0.096 +/- 0.017 nmol/mumol hydroxyproline, p <
0.001). Collagen accumulation was also significantly higher in
the untreated than in the treated group (2.21 +/- 0.24 versus
1.68 +/- 0.22 mumol hydroxyproline/100 mg kidney weight, p
< 0.001). We conclude that creatine led to a significant
reduction in collagen type IV accumulation resembling arginine
or aminoguanidine action. We do suggest that the guanidino
group common to both compounds is able to block reactive
carbonyls.
Increase in 3-deoxyglucosone levels in diabetic rat
plasma. Specific in vivo determination of intermediate in
advanced Maillard reaction.
Yamada H, Miyata S, Igaki N, Yatabe H, Miyauchi Y, Ohara T,
Sakai M, Shoda H, Oimomi M, Kasuga M
Second Department of Internal Medicine, Kobe University
School of Medicine, Japan.
J Biol Chem (United States) Aug 12 1994, 269 (32)
p20275-80
A specific assay of 3-deoxyglucosone (3-DG) was developed
in our laboratory to help elucidate the relationship between
advanced Maillard reaction and diabetic complications. 3-DG is
known as a highly reactive intermediate of the reaction in
vitro and a precursor of advanced glycosylation end products
such as pyrraline and pentosidine, which have been previously
detected in vivo. 3-DG was converted to a stable compound,
2-(2,3,4-trihydroxybutyl)-benzo[g]quinoxaline, by reacting
with 2,3-diaminonaphthalene. Since the derivative had a
characteristic UV spectrum, it was determined at 268 nm by
high performance liquid chromatography. This method was
sensitive enough to detect 10 ng/ml (61.7nM) of 3-DG in vitro.
A slight modification to this method allowed in vivodetection
of small amounts of 3-DG. Plasma free 3-DG levels were
significantly higher in streptozotocin-induced diabetic rats
compared with controls (918 +/- 134 nM versus 379 +/- 69 nM, p
< 0.001) and were suppressed with the administration of
aminoguanidine, an inhibitor of Maillard reaction. Plasma
pyrraline levels in diabetic rats also increased in parallel
with elevated 3-DG levels but were only marginally suppressed
by administration of aminoguanidine. Our results indicate that
3-DG ispresent in vivo under normal conditions and that its
level increases indiabetic subjects. Determination of 3-DG
represents a good tool to predict development and progression
of diabetic complications and to assess the efficiency of
inhibitors to Maillard reaction.
L-arginine reduces heart collagen accumulation in
the diabetic db/db mouse.
Khaidar A, Marx M, Lubec B, Lubec G
Department of Paediatrics, University of Vienna,
Austria.
Circulation (United States) Jul 1994, 90 (1)
p479-83
BACKGROUND: Diabetic cardiomyopathy presents with
significant collagen accumulation; decreased solubility,
increased glucose-mediated abnormal cross-linking, free
radical cross-linking, or glucose-induced increased
transcription of collagen is incriminated. In a previous
study, we reducedcollagen accumulation in the kidneys of
diabetic mice by treatment with oral arginine. This
observation led us to examine the effect of arginine oncardial
fibrosis.
METHODS AND RESULTS: Twenty-nine db/db
spontaneouslydiabetic mice were used in the experiments.
Sixteen were given L-arginine(free base, in tap water, 50
mg/kg body wt per day) for 4 months. At theend of the
experiment, we determined total collagen content of total
ventricular tissue, acid solubility, carboxymethyllysine,
O-tyrosine, glutathione, blood glucose, and fructosamine as
parameters for glycemic control. Heart collagen level was
significantly (P = .0001) reduced in the experimental group
(mean, 0.24 +/- 0.05) compared with the control group (mean,
0.49 +/- 0.10 mumol hydroxyproline per 100 mg heart tissue).
Significantly more collagen could be eluted from heart samples
of the experimental group (P = .02). Carboxymethyllysine and
O-tyrosine did not differ when related to heart weight.
Glutathione level was significantly higher in the untreated
group (P = .003). Parameters of glycemic control did not
differ between the groups.
CONCLUSIONS: Our findings clearly indicate that L-arginine
reduced total heart collagen and increased acid solubility of
heart collagen. Both findings are compatible with the
cross-linking hypothesis. The data for carboxymethyllysine,
O-tyrosine, and glutathione would rule out the glycoxidation
hypothesis and, therefore, free radical cross-linking. The
postulated mechanism of action is most likely the blocking of
reactive carbonyl functions by L-arginine in analogyto amino
guanidine activity. Correlations of collagen with glycemic
control, however, point to an association of glucose with
collagen metabolism, a phenomenon documented in cell cultures
at the transcriptional level.
Reactive glycosylation endproducts in diabetic
uraemia and treatment of renal failure.
Makita Z, Bucala R, Rayfield EJ, Friedman EA, Kaufman AM,
Korbet SM, Barth RH, Winston JA, Fuh H, Manogue KR, et
al
Picower Institute for Medical Research, Manhasset, NY
11030.
Lancet (England) Jun 18 1994, 343 (8912)
p1519-22
In diabetes and ageing, glucose-derived advanced
glycosylationend products (AGEs) cross-link proteins and cause
vascular tissue damage. Elimination of circulating
low-molecular weight AGE-modified molecules (LMW-AGEs) by the
kidney is impaired in diabetic patients with end-stage renal
disease, a group subject to accelerated atherosclerosis. We
determined the effectiveness of current renal replacement
treatments on elimination of serum LMW-AGEs in diabetic and
non-diabetic patients with end-stage renal disease. Although
diabetic patients receiving high-flux haemodialysis achieved
33% lower steady-state serum LMW-AGE than did those in
conventional haemodialysis (p < 0.005), LMW-AGE
concentrations remained 3.5-6 fold above normal, whether
high-flux dialysis, conventional haemodialysis, or chronic
ambulatory peritoneal dialysis were used. High-flux
haemodialysis markedly reduced AGE during each treatment
session (47.9% in the diabetic, p < 0.001 and 60.6% in the
non-diabetic group, p <0.001) but concentrations returned
to pre-treatment range within 3 hours. In contrast, normal
LMW-AGE concentrations were maintained in patients with
functioning renal transplants. We found that LMW-AGEs with an
apparent molecular weight of 2000-6000 circulate and retain
strong inherent chemical reactivity--when exposed to collagen
in vitro, up to 77% attached covalently to form AGE-collagen,
and the AGE-crosslink inhibitor aminoguanidine completely
inhibited this reaction. The results suggest that LMW-AGEs
comprise a set of chemically-reactive molecules that are
refractory to removal by current dialysis treatments. Through
covalent reattachment onto vascular matrix or serum
components, LMW-AGEs may exacerbate vascular pathology
associated with end-stage renal disease.
Cytokines suppress human islet function
irrespective of their effects on nitric oxide
generation.
Eizirik DL, Sandler S, Welsh N, Cetkovic-Cvrlje M, Nieman A,
Geller DA, Pipeleers DG, Bendtzen K, Hellerstrom C
Department of Medical Cell Biology, Uppsala University,
Sweden.
J Clin Invest (United States) May 1994, 93 (5)
p1968-74
Cytokines have been proposed as inducers of beta-cell
damage in human insulin-dependent diabetes mellitus via the
generation of nitric oxide (NO). This concept is mostly based
on data obtained in rodent pancreatic islets using
heterologous cytokine preparations. The present study examined
whether exposure of human pancreatic islets to different
cytokines induces NO and impairs beta-cell function. Islets
from 30 human pancreata were exposed for 6-144 h to the
following human recombinant cytokines, alone or in
combination: IFN-gamma (1,000 U/ml), TNF-alpha (1,000 U/ml),
IL-6 (25U/ml), and IL-1 beta (50 U/ml). After 48 h, none of
the cytokines alone increased islet nitrite production, but
IFN-gamma induced a 20% decrease in glucose-induced insulin
release. Combinations of cytokines, notably IL-1beta plus
IFN-gamma plus TNF-alpha, induced increased expression of
inducible NO synthase mRNA after 6 h and resulted in a
fivefold increase in medium nitrite accumulation after 48 h.
These cytokines did not impair glucose metabolism or insulin
release in response to 16.7 mM glucose, but there was an 80%
decrease in islet insulin content. An exposure of 144 h toIL-1
beta plus IFN-gamma plus TNF-alpha increased NO production and
decreased both glucose-induced insulin release and insulin
content. Inhibitors of NO generation, aminoguanidine or
NG-nitro-L-arginine, blocked this cytokine-induced NO
generation, but did not prevent the suppressive effect of IL-1
beta plus IFN-gamma plus TNF-alpha on insulin release
andcontent. In conclusion, isolated human islets are more
resistant to thesuppressive effects of cytokines and NO than
isolated rodent islets. Moreover, the present study suggests
that NO is not the major mediator of cytokine effects on human
islets.
Amelioration of dermal lesions in
streptozotocin-induced diabetic rats by aminoguanidine.
Bannai C, Yamazaki M, Matsushima Y, Kunika K, Itakura M,
Okuda Y, Yamashita K
Department of Endocrinology and Metabolism, University of
Tsukuba, Ibaraki, Japan
Diabetes Res (Scotland) 1992, 20 (4) p87-95
As aminoguanidine (AG) is known to prevent non-enzymatic
glycosylation in various tissues, we have histologically and
biochemically evaluated AG effects on the skin in control,
SZ-diabetic and AG-treated (25 mg/kgbw/day, 10w) diabetic
rats. HbA1c and plasma glucose levels in diabetic
andAG-treated diabetic rats were maintained about two times
higher than those in control rats during the 10 weeks of the
experiment. Histological findings revealed that the dermis in
diabetic rats was thin and edematous, associated with swelling
and degeneration of collagen fibers. Necrobiotic changes were
seen in the lower dermis. These changes were greatly improved
in AG-treated diabetic rats. Skin glucose contents in diabetic
andAG-treated diabetic rats were about 10 times higher than
those in the controls, whereas there was no difference in the
sorbitol contents between three groups. Dry weight of the skin
and collagen content was wellcorrelated (r = 0.9044) and
collagen represented 78.0 +/- 2.3% of the dryweight. By
SDS-PAGE analysis of cyanogen bromide digests it was shown
that high molecular weight peptides were increased in diabetic
rats, but were decreased in AG-treated diabetic rats. The mean
of glycosaminoglycan (GAG) contents of diabetic skin was 54%
of that in the controls (1.58 +/- 0.09vs. 2.94 +/- 0.39
micrograms/mg dry weight, P < 0.0025), which increased
significantly in AG-treated diabetic rats (1.75 +/- 0.07
microgram/mg dryweight, P < 0.01 vs. diabetic).
Glycation, glycoxidation, and cross-linking of
collagen by glucose. Kinetics, mechanisms, and inhibition of
late stages of the Maillard reaction.
Fu MX, Wells-Knecht KJ, Blackledge JA, Lyons TJ, Thorpe SR,
Baynes JW
Department of Chemistry and Biochemistry, University of South
Carolina, Columbia SC 29208
Diabetes (United States) May 1994, 43 (5)
p676-83
The Maillard or browning reaction between sugar and protein
contributes to the increased chemical modification and
cross-linking of long-lived tissue proteins in diabetes. To
evaluate the role of glycation and oxidation in these
reactions, we have studied the effects of oxidative and
antioxidative conditions and various types of inhibitors on
the reaction of glucose with rat tail tendon collagen in
phosphate buffer at physiological pH and temperature. The
chemical modifications of collagen that were measured included
fructoselysine, the glycoxidation products
Nepsilon-(carboxymethyl) lysine and pentosidine and
fluorescence. Collagen cross-linking was evaluated by analysis
of cyanogen bromide peptides using sodium dodecyl
sulfate-polyacrylamide gel electrophoresis and by changes in
collagen solubilization on treatment with pepsin or sodium
dodecylsulfate. Although glycation was unaffected, formation
of glycoxidation products and cross-linking of collagen were
inhibited by antioxidative conditions. The kinetics of
formation of glycoxidation products proceeded with a short lag
phase and were independent of the amount of Amadori adduct on
the protein, suggesting that autoxidative degradation of
glucose was a major contributor to glycoxidation and
cross-linking reactions. Chelators, sulfhydryl compounds,
antioxidants, and aminoguanidine also inhibited formation of
glycoxidation products, generation of fluorescence, and
cross-linking of collagen without significant effect on the
extent of glycation of the protein. We conclude that
autoxidation of glucose or Amadori compounds on protein plays
a major role in the formation of glycoxidation products and
cross-liking of collagen by glucose in vitro and that
chelators, sulfhydryl compounds, antioxidants, and
aminoguanidine act as uncouplers of glycation from subsequent
glycoxidation and cross-linking reactions.
Aminoguanidine inhibits the development of
accelerated diabetic retinopathy in the spontaneous
hypertensive rat.
Hammes HP, Brownlee M, Edelstein D, Saleck M, Martin S,
Federlin K
Third Medical Department, of Justus-Liebig-University of
Giessen, Germany.
Diabetologia (Germany) Jan 1994, 37 (1) p32-5
Arterial hypertension has been identified as a major
secondary risk factor for diabetic retinopathy. However, the
mechanisms by which hypertension worsens retinopathy are
unknown. Inhibition of advanced glycation product formation
prevents the development of experimental diabetic retinopathy
in normotensive diabetic rats. In this study the effect of
hypertension on the rate of diabetic retinopathy development
and the formation of arteriolar thrombosis was evaluated. We
also evaluated the effect of aminoguanidine, an inhibitor of
advanced glycation and product formation on retinal pathology
of diabetic hypertensive rats. After 26 weeks of diabetes,
hypertension accelerated the development of retinopathy
despite a lower mean blood glucose level than in the
non-hypertensive group (diabetic spontaneous hypertensive rats
(SHR) 16.00 +/- 6.83 mmol/l; diabetic normotensive Wistar
Kyoto rats (WKY) 34.9 +/- 3.64 mmol/l; p <0.0001). Diabetic
SHR had nearly twice as many acellular capillaries as diabetic
WKY (SHR diabetic: 91.9 +/- 7.5 acellular capillaries per mm2
of retinal area vs WKY diabetic: 53.7 +/- 8.5 acellular
capillaries per mm2 of retinal area), and a 3.8-fold increase
in the number of arteriolar microthromboses (SHR diabetic
23,504 +/- 5523 microns2 vs SHR non-diabetic 6228 +/- 2707
microns2). Aminoguanidine treatment of SHR diabetic rats
reduced the number of acellular capillaries by 50%, and
completely prevented both arteriolar deposition of
PAS-positive material and abnormal microthrombus formation.
These data suggest that hypertension-induced deposition of
glycated proteins in the retinal vasculature plays a central
role in the acceleration of diabetic retinopathy by
hypertension.
Aminoguanidine reduces regional albumin clearance
but not urinary albumin excretion in streptozotocin-diabetic
rats.
Huijberts MS, Wolffenbuttel BH, Crijns FR, Nieuwenhuijzen
Kruseman AC, Bemelmans MH, Struijker Boudier HA
Department of Internal Medicine, University Hospital
Maastricht, The Netherlands.
Diabetologia (Germany) Jan 1994, 37 (1) p10-4
Advanced glycation end-product-formation is thought to play
a role in the development of diabetic angiopathy. By altering
the structure of different extracellular matrix components
advanced glycation end-products might affect vascular and
glomerular permeability. In this study we investigated the
effect of treatment with an inhibitor of advanced glycation
end-product-formation, aminoguanidine, on vascular
permeability and the development of albuminuria in
streptozotocin-induced diabetic rats. Male Wistar Rp rats were
randomized into a control group, a diabetic group, and an
aminoguanidine-treated diabetic group. After 8 weeks, 24-h
urine collections were taken and rats were implanted with an
arterial and avenous catheter. mean arterial blood pressure
was determined by intra-arterial measurement. Regional albumin
clearances were assessed in the eye, ileum, lung, skeletal
muscle and skin using an isotope technique. Mean arterial
pressure in the diabetic group was significantly lower in the
control and aminoguanidine-treated groups (p < 0.02).
Regional albumin clearances were significantly increased in
all tissues of diabetic rats compared to control rats (p <
0.05). Aminoguanidine treatment of diabetic rats resulted in a
significant decrease of regional albumin clearance in all
tissues except the lung (p < 0.05, lung p = 0.07). The
development of albuminuria in diabetic rats however, was not
affected by aminoguanidine.
Aminoguanidine, an inhibitor of nitric oxide
formation, fails to protect against insulitis and
hyperglycemia induced by multiple low dose streptozotocin
injections in mice.
Holstad M, Sandler S
Department of Medical Cell Biology, Uppsala University,
Sweden.
Autoimmunity (Switzerland) 1993, 15 (4) p311-4
It has been suggested that pancreatic beta-cell destruction
occurring during the process leading to insulin-dependent
diabetes mellitus (IDDM) involves formation of nitric oxide
(NO). We have presently studied the effect of aminoguanidine
(AG), which has recently been reported to inhibit generation
of NO induced by the cytokine interleukin-1 beta. AG currently
counteracted IL-1 beta induced impairment of the glucose
oxidation rate in rat pancreatic islets. Then we studied the
effect of AG on the development of hyperglycemia and
pancreatic insulitis in mice treated with multiple low dose
injections of streptozotocin (40 mg/kg body-weight for five
consecutive days). It was found that one daily intraperitoneal
injection of AG (50 mg/kg body-weight) for 14 days failed to
prevent the development of diabetes as well as insulitis
following the streptozotocin injections. Furthermore, the mice
treated with streptozotocin plus AG showed an increased
mortality compared to mice treated with streptozotocin plus
saline. Although the present data do not exclude a role for NO
in IDDM, it raises concerns about the use of testing AG as
therapeutic agent in IDDM.
Aminoguanidine: a drug proposed for prophylaxis in
diabetes inhibits catalase and generates hydrogen peroxide in
vitro.
Ou P, Wolff SP
Department of Medicine, University College London Medical
School, Rayne Institute, U.K
Biochem Pharmacol (England) Oct 5 1993, 46 (7)
p1139-44
Aminoguanidine (AG) has been proposed as a drug of
potential benefit in prophylaxis of the complications of
diabetes. We show here that AG irreversibly inhibits catalase
with an efficacy similar to aminotriazole. AG also produces
hydrogen peroxide, in a transition metal-catalysed process
which may be partially dependent upon prior hydrolysis of AG
to semicarbazide and hydrazine. These observations may be of
importance in proposals for the long term administration of AG
in diabetes.
Nitric oxide production in islets from nonobese
diabetic mice: aminoguanidine-sensitive and -resistant stages
in the immunological diabetic process.
Corbett JA, Mikhael A, Shimizu J, Frederick K, Misko TP,
McDaniel ML, Kanagawa O, Unanue ER
Department of Pathology, Washington University School of
Medicine, St. Louis, MO 63110.
Proc Natl Acad Sci U S A (United States) Oct 1 1993, 90 (19)
p8992-5
The role of nitric oxide (NO.) in the development of
immunologically induced diabetes was examined. Transfer of
spleen cells obtained from diabetic female nonobese diabetic
(NOD) mice to nondiabetic irradiated males induced diabetes
11-13 days after transfer. Islets isolated from recipient male
mice produced NO. in a time-dependent fashion. The production
of nitrite was initially detected at day 6 after transfer,
with increasing levels by days 9 and 13. Under similar
conditions glucose-induced insulin secretion by isolated NOD
mouse islets was irreversibly reduced by approximately 40% at
days 6, 9, and 13 after transfer of spleen cells. The number
of islets harvested per pancreas by the 9th and 13th day after
transfer was decreased by 20-25% as compared to controls.
Treatment of male NOD mice with aminoguanidine, an inhibitor
of the inducible form of NO. synthase, reduced the production
of NO. in islets and delayed the development of diabetes by
3-8 days. The temporary inhibition by aminoguanidine was
dependent on both inhibitor concentration and number of spleen
cells transferred. These results indicate that NO. is produced
in NOD islets as a result of an immunological diabetogenic
process and suggests a role of this compound in the
immunological diabetic process.
Inhibition of matrix-induced bone differentiation
by advanced glycation end-products in rats.
Fong Y, Edelstein D, Wang EA, Brownlee M
Department of Surgery, Memorial Sloan-Kettering Cancer
Center, New York, New York.
Diabetologia (Germany) Sep 1993, 36 (9) p802-7
Glycation of long-lived proteins is an inevitable
consequence of aging that is accelerated in patients with
diabetes mellitus. Treatment of demineralized bone matrix
particles from 35-week-old normal Long-Evans rats with
glycoaldehyde, a precursor of advanced glycation end-products,
was used to assess the effects of bone-matrix glycation on the
process of bone differentiation. Matrix was incubated in
phosphate buffered saline alone, phosphate buffered saline
containing glycolaldehyde, glycolaldehyde plus the advanced
glycation product-inhibitor aminoguanidine, or glycolaldehyde
plus the advanced glycation product-inhibitor sodium
cyanoborohydride. Glycolaldehyde increased the matrix advanced
glycation product content as measured by specific fluorescence
more than two-fold, while inhibiting bone differentiation more
than 90% as measured by in vivo 45CaCl2 uptake, alkaline
phosphatase levels, and histology. In contrast, simultaneous
incubation with the advanced glycation product-inhibitor
aminoguanidine or sodium cyanoborohydride not only reduced
fluorescence to normal, but also restored bone
differentiation. Furthermore, the inhibition of bone
differentiation by glycolaldehyde was not reversed by
subsequent application of recombinant bone morphogenetic
protein-2. These observations suggest that formation of
advanced glycation products on bone matrix alters its ability
to induce bone formation, and probably involves alterations of
binding sites for extractable proteins with direct bone
inductive properties such as bone morphogenetic protein-2.
Decreased bone formation associated with aging and diabetes
may result, in part, from advancedglycation product formation
on matrix proteins.
|