Association of the DD genotype and development of Japanese type 2 diabetic nephropathy

We determined the insertion/deletion (I/D) polymorphism of the angiotensin-coverting enzyme (ACE) gene in a multicenter trial of ethnically homogeneous Japanese type 2 diabetes mellitus (DM) patients. All patients (n = 748) were divided into 5 groups as follows: group I (normoalbuminuric patients), group II (microalbuminuric patients), group III (overt albuminuric patients with serum creatinine (s-Cr) levels of less than 1.2 mg/dl), group IV (overt albuminuric patients with s-Cr levels of more than 1.3 mg/dl but excluding hemodialysis patients), and group V (hemodialysis patients). We selected patients with a diabetic duration of more than 15 years in the mild stage (groups I and II), but placed no limits on those in the advanced and end-stages (groups III, IV and V). The frequency of the DD genotype was slightly higher in the advanced and end stages. The frequency of the DD genotype in the mild stage differed from that in the end stage (II/ID/DD 47.8%/41.0%/11.2% vs. 37.0 %/43.3%/19.7% p = 0.07, II + ID/DD 88.8%/11.2% vs. 80.3%/19.7%, p < 0.05). D allele frequency in the mild stage also differed from that in the end stage (I/D 68.3%/31.7% vs. 58.7%/41.3%, p < 0.02). The presence of the DD genotype increased the risk of end-stage renal disease (ESRD) more than that of the other genotypes (odds ratio ID/II = 1.37, 95% CI 0.82-2.27; DD/II = 2.27, 95% CI 1.12-4.61). It appears that the DD genotype is associated with progression of Japanese type 2 diabetic nephropathy.

Dinucleotide repeat polymorphism of matrix metalloproteinase-9 gene is associated with diabetic nephropathy

BACKGROUND

Although genetic susceptibility has been proposed as an important factor for the development and progression of diabetic nephropathy, the definitive gene has not been identified. To identify the genetic marker for diabetic nephropathy, we examined the association between the (A-C)n dinucleotide repeat polymorphism upstream of the matrix metalloproteinase-9 (MMP-9) gene and diabetic nephropathy in a group of Japanese patients with type 2 diabetes.

METHODS

Patients were divided into three groups based on their urinary albumin excretion rate (AER) and the stage of diabetic retinopathy as follows: uncomplicated group (U), normal albuminuria (AER <20 microg/min) without proliferative retinopathy and with the duration of diabetes more than 20 years (N = 32); microalbuminuria group (M), 20 < or = AER < 200 microg/min (N = 155); overt nephropathy group (O), AER > or = 200 microg/min (N = 63). The region containing the dinucleotide repeat upstream of MMP-9 gene was amplified by polymerase chain reaction (PCR). The amplified products were analyzed with 7% formamide/urea acrylamide gel electrophoresis. The promoter constructs of the MMP-9 gene were transfected with the CMV-beta-galactosidase construct into 293 cells using the liposome method. Twenty-four hours after transfection, cells were harvested, and luciferase and beta-galactosidase activities were measured.

RESULTS

Nine alleles of the dinucleotide repeat polymorphism (17 to 25 repeats) were identified, and the frequency of each allele in diabetic subjects was not different from that in nondiabetic controls. The frequency of the allele containing 21 repeats (A21) was most abundant (42.4% in control and 45.6% in diabetic subjects), followed by the allele with 23 repeats (A23; 35.4% in control and 27.6% in diabetic subjects). The A21 allele was less frequent in M and O than U (O, 38.9%; M, 45.5%; U, 59.3%, chi2 = 7.18; P < 0.05, O vs. U), while the frequency of the alleles other than A21 was not different among each group. The calculated odds ratio for nephropathy in the noncarrier, heterozygote, or homozygote of A21 allele was 3.38, 1.97, and 0.2, respectively. Furthermore, the promoter assay for the MMP-9 gene revealed that the A21 allele had a higher promoter activity compared with other alleles. No significant correlation was observed between serum MMP-9 concentrations and the MMP-9 gene polymorphism.

CONCLUSION

These results indicate that the patients with A21 allele of the MMP-9 gene may be protected from the development and progression of diabetic nephropathy. Thus, the microsatellite polymorphism upstream of the MMP-9 gene could be a useful genetic marker for diabetic nephropathy.

Cellular mechanisms in the development and progression of diabetic nephropathy: activation of the DAG-PKC-ERK pathway

Diabetic nephropathy is characterized functionally by glomerular hyperfiltration and albuminuria and histologically by the expansion of glomerular mesangium. We and others have found that protein kinase C (PKC) is activated through an increase in de novo synthesis of diacylglycerol (DAG) from glucose in glomerular mesangial cells cultured under high glucose conditions and in glomeruli of diabetic rats. The activation of PKC could activate further various intracellular signal transduction systems, such as extracellular regulated kinase (ERK). The activation of the DAG-PKC-ERK pathway is considered to be one of the important molecular mechanisms of the development and progression of diabetic nephropathy. To prove this hypothesis, we examined whether the inhibition of the DAG-PKC-ERK pathway could prevent the development of glomerular dysfunction in diabetic animals. First, we found that thiazolidinedione compounds could inhibit PKC activation by activating DAG kinase. Thiazolidinedione compounds were able to prevent glomerular hyperfiltration, albuminuria, and excessive production of extracellular matrix proteins in glomeruli in streptozotocin-induced diabetic rats, a model for type 1 diabetes. Second, we tried to inhibit PKC directly by oral administration of PKC beta inhibitor. PKC beta inhibitor could prevent albuminuria and mesangial expansion in db/db mice, a model for type 2 diabetes. These results confirmed the importance of the activation of the DAG-PKC-ERK pathway in the development of glomerular dysfunction in diabetes.

Expression of Rho-family GTPases (Rac, cdc42, RhoA) and their association with p-21 activated kinase in adult rat peripheral nerve

To clarify the presence of the Rho family of small GTPases p21-activated kinase (pak) signaling pathway in the PNS, we have examined their expression, the association between the small GTPases and pak and the pak kinase activity in the PNS using immunoblot analysis, immunohistochemistry, co-immunoprecipitation study, and in vitro kinase assay. Immunoblot analysis showed the expression of Rac, cdc42, RhoA and pak in the dorsal root ganglion (DRG) and sciatic nerve. The localization of these proteins in the DRG neurons and axons and Schwann cells of the sciatic nerve was confirmed by immunohistochemistry. Co-immunoprecipitation studies indicated the in vivo associations of pak with Rac and cdc42, but not with RhoA, in both the DRG and sciatic nerve. The autophosphorylation of pak and phosphorylation of histone H4 by pak were also found in the DRG and sciatic nerve as well as in the CNS. These results suggest that the Rac/cdc42-pak signaling pathway exists and functions in the PNS and may mediate some intracellular signals.

Aluminum-induced apoptosis in PC12D cells

The addition of aluminum-maltol complex to PC12D cells induced a time-dependent and concentration-dependent growth inhibition as well as cell death, whereas aluminum chloride or maltol alone did not affect the viability of PC12D cells. Apoptosis of differentiated PC12D cells was assessed by using terminal deoxynucleotidyltransferase-mediated 2'-deoxyuridine-5'-triphosphate nick end labeling (TUNEL) technique to detect DNA strand breaks in situ. The number of TUNEL-positive cells treated with aluminum-maltol increased with time in the treatment cultures. The ability of aluminum ion to elevate intracellular reactive oxygen species was determined by fluorescence in PC12D cells loaded with the oxidant-sensitive dye 2',7'-dichlorofluorescin diacetate. Aluminum ion incorporated to PC 12D cells causes apoptotic cell death by enhancing the generation of reactive oxygen species.

Enhancement of glomerular heme oxygenase-1 expression in diabetic rats

An increase in oxidative stress in diabetic subjects is implicated to play a pivotal role in diabetic vascular complications. In response to oxidative stress, antioxidant enzymes are considered to be induced and protect cellular functions to keep in vivo homeostasis. However, it remains to be clarified whether antioxidant enzymes are induced against oxidative stress especially in renal glomeruli at an early stage of diabetes. To answer this question, we examined the gene expression of a variety of antioxidant enzymes in glomeruli isolated from streptozotocin-induced diabetic rats. The mRNA expression of antioxidant enzymes such as catalase, glutathione peroxidase, and CuZn-superoxide dismutase, was unaltered in glomeruli of diabetic rats and was comparable to control rats. In contrast, the mRNA expression of heme oxygenase-1 (HO-1) was enhanced in glomeruli of diabetic rats as compared with control rats. A treatment with insulin as well as with vitamin E (40 mg/kg body weight every other day, intra-peritoneal injection) normalized the mRNA expression of HO-1 in the glomeruli of diabetic rats. Immunohistochemical analysis revealed that the up-regulated expression of HO-1 protein was localized in glomerular cells of diabetic rats. In conclusion, these results provide the first evidence that among antioxidant enzymes HO-1 expression is preferentially increased in diabetic glomeruli.

Purification, molecular cloning, and immunohistochemical localization of dipeptidyl peptidase II from the rat kidney and its identity with quiescent cell proline dipeptidase

We purified dipeptidyl peptidase II (DPP II) to homogeneity from rat kidney and determined its physicochemical properties, including its molecular weight, substrate specificity, and partial amino acid sequence. Furthermore, we screened a rat kidney cDNA library, isolated the DPP II cDNA and determined its structure. The cDNA was composed of 1,720 base pairs of nucleotides, and 500 amino acid residues were predicted from the coding region of cDNA. Human quiescent cell proline dipeptidase (QPP) cloned from T-cells is a 58-kDa glycoprotein existing as a homodimer formed with a leucine zipper motif. The levels of amino acid homology were 92.8% (rat DPP II vs. mouse QPP) and 78.9% (rat DPP II vs. human QPP), while those of nucleotide homology were 93.5% (rat DPP II vs. mouse QPP) and 79.4% (rat DPP II vs. human QPP). The predicted amino acid sequences of rat DPP II and human and mouse QPP possess eight cysteine residues and a leucine zipper motif at the same positions. The purified DPP II showed similar substrate specificity and optimal pH to those of QPP. Consequently, it was thought that DPP II is identical to QPP. Northern blot analysis with rat DPP II cDNA revealed prominent expression of DPP II mRNA in the kidney, and the order for expression was kidney >> testis > or = heart > brain > or = lung > spleen > skeletal muscle > or = liver. In parallel with Northern blot analysis, the DPP II antigen was detected by immunohistochemical staining in the cytosol of epithelial cells in the kidney, testis, uterus, and cerebrum.

Evaluation of a new care system provided to diabetic patients in the outpatient clinic

OBJECTIVE

Evaluation of metabolic states and chronic complications is essential for maintaining a high quality of care for diabetic patients. We have assessed the quality of care in routine outpatient clinics for diabetic subjects in our university hospital, and compared with those in a newly introduced standardized clinic to evaluate the new care system.

METHODS

The quality of care was assessed by the chart review in 1995, and compared with those from 1996-1997 in the "Diabetes Follow-up Clinic" which is systematically designed for the standardized care.

PATIENTS

The subjects were recruited among 860 patients who visited the outpatient clinic in July and August of 1995 with a diagnosis of diabetes or glucose intolerance. Six hundred seventy-two patients whose follow-up period had been more than 6 months with clinically diagnosed diabetes were used for the analysis.

RESULTS

Laboratory tests such as determination of HbA1c, and serum levels of lipids and creatinine were performed in more than 90% of the patients in the routine outpatient clinics. However, ophthalmology referral, 24-hour urine collection for the determination of creatinine clearance and albumin excretion, and electrocardiograms were not well performed and were incompletely documented (40-60% of the patients within a previous year and 70-80% in the last 2 years). In the standardized "Diabetes Follow-up Clinic", only four out of 555 diabetic patients failed to collect their 24-hour urine, and all participants had ankle blood pressure measurements, nerve conduction study, and nylon monofilament tests, etc. Furthermore, more than 95% of the patients had funduscopic examinations by ophthalmologists as well as records of electrocardiogram.

CONCLUSION

Introduction of the standardized "Diabetes Follow-up Clinic" may be one of the choices for increasing the quality of outpatient care and for the prevention of chronic diabetic complications.

Role of mitogen-activated protein kinases as downstream effectors of transforming growth factor-beta in mesangial cells

Transforming growth factor-beta (TGF-beta) is a multifunctional cytokine that regulates cell proliferation, differentiation, and production of extracellular matrix proteins in various types of cells including mesangial cells. Although TGF-beta has been also known as an important player in the pathogenesis of various fibrotic diseases including glomerulosclerosis, signal-transduction cascades of TGF-beta have remained to be clarified. However, emerging evidence indicates that TGF-beta can activate various signal transduction cascades such as Smad proteins and mitogen-activated protein kinases (MAPKs) in many types of cells. Here, we examine the role of MAPKs in TGF-beta-induced gene expression of extracellular matrix proteins in mesangial cells. TGF-beta increases extracellular signal-regulated kinase (ERK) activity, one of the MAPKs, and the expression of fibronectin mRNA and protein in rat mesangial cells. Furthermore, PD98059, a specific inhibitor of MAPK/ERK kinase (MEK), can inhibit this TGF-beta-induced fibronectin expression. These data suggest that MAPKs play an important role in TGF-beta-mediated extracellular matrix production in mesangial cells.

Increases in K+ conductance and Ca2+ influx under high glucose with suppressed Na+/K+-pump activity in rat myelinated nerve fibers

To test the combined effect of high glucose and decreased Na+/K+-pump activity, a condition which closely mimics the diabetic state, on nerve ionic currents, changes in action potential and membrane current induced by high glucose in the presence of ouabain were investigated using voltage clamp analysis in rat single myelinated nerve fibers. In the presence of 0.1 mM ouabain, 30 mM glucose caused a progressive increase in the delayed K+ current as well as persistent decreases in action potential and Na+ current, suggesting that Na+/K+ pump plays an important role in preventing the increase in the K+ current. The latter increase was suppressed by a blocker of Ca2+-activated K+ channels. Two types of voltage-dependent Ca2+ channel blockers (L and N-type) as well as a Na+/Ca2+-exchange blocker diminished the ouabain-induced increase in K+ conductance. These results suggest that high glucose with suppressed Na+/K+ pump activity might induce an increase of Ca2+ influx through either Ca2+ channels or reverse Na+/Ca2+-exchange, possibly leading to the elevation of Ca2+-activated voltage-dependent K+ channels. Both a decrease in inward Na+ current and an increase in K+ conductance may result in decreased nerve conduction. In addition, a possible increase of axoplasmic Ca2+ concentration may lead to axonal degeneration. These results provide a clue for understanding the pathophysiologic mechanism of diabetic neuropathy.

Usefulness of waveform analysis of popliteal artery in type II diabetic patients using gated magnetic resonance 2D-cine-PC imaging and 31P spectroscopy

AIMS/HYPOTHESIS

We studied 76 patients with Type II (non-insulin-dependent) diabetes mellitus and 16 age-matched non-diabetic subjects (control group) to clarify qualitative and quantitative abnormalities of waveform and flow volume of the popliteal artery.

METHODS

The 76 diabetic patients comprised 16 patients with occlusive arterial disease in the lower extremities [arteriosclerosis obliterans (ASO) group] and 60 patients free from this disease (non-ASO group). We flow analysed the popliteal artery and measured the phosphocreatine to inorganic phosphate ratio of resting plantar muscles to identify risk factors for foot lesions using gated magnetic resonance two-dimensional cine-mode phase-contrast imaging and 31P spectroscopy.

RESULTS

The control and non-ASO groups had a triphasic waveform with systolic, early and late diastolic components. All ASO patients had an abnormal monophasic waveform and a lower ankle brachial index than that of the control and non-ASO groups. To clarify the mechanism of reduced flow volume of lower extremities, we assigned the 60 patients of the non-ASO group to the three subgroups based on their levels of total flow volume of the popliteal artery. The lowest group showed an abnormal triphasic waveform with lower amplitudes of systolic and late diastolic components and flow velocities in foot arteries than those of the highest group although ABI was similar. From stepwise multiple regression analysis, late diastolic flow volume was identified as an independent determinant for the phosphocreatine to inorganic phosphate ratio (r2 = 0.484, p < 0.001).

CONCLUSION/INTERPRETATION

Waveform analysis of popliteal artery provides a powerful tool for identifying impaired peripheral circulation caused by either occlusive arterial disease or increased arterial resistance in diabetic patients.

Thiazolidinedione compounds ameliorate glomerular dysfunction independent of their insulin-sensitizing action in diabetic rats

Thiazolidinedione (TZD) compounds are widely used as oral hypoglycemic agents. Herein, we provide evidence showing that troglitazone, one of the TZD compounds, is able to prevent glomerular dysfunction in diabetic rats through a novel mechanism independent of its insulin-sensitizing action. We examined the effect of troglitazone on functional and biochemical parameters of glomeruli in streptozotocin-induced diabetic rats. Troglitazone was able to prevent not only diabetic glomerular hyperfiltration and albuminuria, but an increase in mRNA expression of extracellular matrix proteins and transforming growth factor-beta1 in glomeruli of diabetic rats, without changing blood glucose levels. Biochemically, an increase in diacylglycerol (DAG) contents and the activation of the protein kinase C (PKC)-extracellular signal-regulated kinase (ERK) pathway in glomeruli of diabetic rats were abrogated by troglitazone. The activation of DAG-PKC-ERK pathways in vitro in mesangial cells cultured under high glucose conditions was also inhibited by troglitazone. Troglitazone enhanced the activities of DAG kinase, which could metabolize DAG to phosphatidic acid, in both glomeruli of diabetic rats and mesangial cells cultured under high glucose conditions. Surprisingly, pioglitazone, another TZD compound without alpha-tocopherol moiety in its structure, also prevented the activation of the DAG-PKC pathway and activated DAG kinase in mesangial cells cultured under high glucose conditions. These results may identify the TZDs as possible new therapeutic agents for diabetic nephropathy that prevent glomerular dysfunction through the inhibition of the DAG-PKC-ERK pathway.

Immunohistochemical characterization of glomerular PDGF B-chain and PDGF beta-receptor expression in diabetic rats

Platelet-derived growth factor (PDGF) was found to contribute to the pathophysiological process in the development and progression of glomerulosclerosis characterized by mesangial cell proliferation and accumulation of extracellular matrix. To examine the role of PDGF in the development of diabetic nephropathy, we conducted immunohistochemical analysis for PDGF B-chain (PDGF-B) and PDGF beta-receptor (PDGFR-beta) in the glomeruli of streptozotocin-induced diabetic rats. At 2, 4, and 12 weeks after the onset of diabetes, the expression of PDGF-B in glomeruli of diabetic rats was increased significantly as compared to control or diabetic rats treated with insulin. Similar changes were observed on PDGFR-beta immunostaining. The immunostaining of mirror sections revealed the existence of PDGF-B or PDGFR-beta not only in mesangial cells but also in visceral epithelial cells. Glomerular volume was significantly increased in diabetes. This early glomerular abnormality was prevented by an inhibition of PDGF system with trapidil as well as by the treatment of insulin. Our results suggest that the activation of the PDGF system in glomerular cells might play an important role in the development of early glomerular lesion in diabetes.

Significance of glomerular deposition of C3c and C3d in IgA nephropathy

BACKGROUND

Complement activation plays an important role in the pathogenesis of IgA nephropathy. The clinico-pathological significance of the glomerular deposition of complement breakdown products, C3c and C3d in IgA nephropathy remains to be clarified.

METHODS

We examined the relationship between glomerular staining patterns of C3c and C3d and clinico-pathological findings with 163 patients with IgA nephropathy. Renal biopsy specimens were stained with C3c and C3d by immunofluorescence, and patients were divided into the following two groups: the intensity of C3c deposition stronger than C3d deposition, or equal to it (group A); the intensity of C3d deposition stronger than C3c deposition (group B).

RESULTS

In group A, the incidence of severe hematuria (over 20 urinary red blood cells in high-power field microscope (x400)) or of higher urinary fibrinogen degenerated products (over 0.1 microg/ml) was significantly higher than that in group B. In addition, group A showed a significant decrease in the glomerular filtration rate. Group A also showed a significantly higher incidence of glomerular endocapillary proliferation than in group B.

CONCLUSION

These findings suggest that the glomerular deposition of C3c is associated with the inflammatory active phase of glomeruli in IgA nephropathy.

Amelioration of accelerated diabetic mesangial expansion by treatment with a PKC beta inhibitor in diabetic db/db mice, a rodent model for type 2 diabetes

Activation of protein kinase C (PKC) is implicated as an important mechanism by which diabetes causes vascular complications. We have recently shown that a PKC beta inhibitor ameliorates not only early diabetes-induced glomerular dysfunction such as glomerular hyperfiltration and albuminuria, but also overexpression of glomerular mRNA for transforming growth factor beta1 (TGF-beta1) and extracellular matrix (ECM) proteins in streptozotocin-induced diabetic rats, a model for type 1 diabetes. In this study, we examined the long-term effects of a PKC beta inhibitor on glomerular histology as well as on biochemical and functional abnormalities in glomeruli of db/db mice, a model for type 2 diabetes. Administration of a PKC beta inhibitor reduced urinary albumin excretion rates and inhibited glomerular PKC activation in diabetic db/db mice. Administration of a PKC beta inhibitor also prevented the mesangial expansion observed in diabetic db/db mice, possibly through attenuation of glomerular expression of TGF-beta and ECM proteins such as fibronectin and type IV collagen. These findings provide the first in vivo evidence that the long-term inhibition of PKC activation in the renal glomeruli can ameliorate glomerular pathologies in diabetic state, and thus suggest that a PKC beta inhibitor might be an useful therapeutic strategy for the treatment of diabetic nephropathy.

1H- and 31P-magnetic resonance spectroscopy and imaging as a new diagnostic tool to evaluate neuropathic foot ulcers in Type II diabetic patients

AIMS/HYPOTHESIS

We studied 36 Type II (non-insulin-dependent) diabetic patients without occlusive arterial diseases in the lower extremities and 12 age-matched and sex-matched non-diabetic subjects to clarify the association between diabetic polyneuropathy and foot ulcers using 1H- and 31P-magnetic resonance spectroscopy and imaging.

METHODS

The 36 diabetic patients consisted of 12 patients with superficial foot ulcers and 24 patients free from this disease. We measured fat to water and phosphocreatine to inorganic phosphate (PCr:Pi) ratios and calculated the intracellular pH of resting plantar muscles by depth-resolved surface-coil spectroscopy using an 1H-31P double tuned coil. Furthermore, foot vasculature, fat and PCr contents of plantar muscles were visualised by phase-contrast angiography, T1-weighted spin-echo imaging and 31P-chemical shift imaging.

RESULTS

The 12 foot ulcer patients showed a reduced PCr to Pi ratio (p < 0.001) and peripheral nerve functions (p < 0.01-0.001) but an increased fat to water ratio (p < 0.001) and intracellular pH (p < 0.001) compared with the 24 patients without ulcers. From stepwise multiple regression analyses, motor nerve function as well as severity of nephropathy was associated with both fat to water and PCr to Pi ratios. When these patients were categorised into three groups based on their level of motor nerve function, the frequency of foot ulcers of the lowest group was higher than that of the highest group.

CONCLUSION/INTERPRETATION

Our findings indicated that motor nerve dysfunction in diabetic patients was closely associated with impaired energy metabolism, fatty infiltration and increased intracellular pH of plantar muscles and high frequency of foot ulcers. These new techniques could contribute to help clarify the predisposing factors for foot ulcers.

[Kidney disease and insulin resistance--clinical impact of thiazolidinedione compounds for kidney disease]

The thiazolidinedione compounds are well known hypoglycemic agents via increasing insulin-sensitivity. Herein, we provide the possibility that thiazolidinedione compounds could be useful for renal dysfunction through mechanism dependent or independent of its insulin-sensitizing action. In type 2 diabetes, troglitazone could reduce urinary albumin-creatinine ratio compared to metformin. Furthermore, we have shown that troglitazone was able to prevent diabetic glomerular dysfunction through inhibition of diacylglycerol-protein kinase C-extracellular signal-regulated kinase pathway in type 1 diabetic rats. Thus, thiazolidinediones might be effective agents for treating insulin-resistant diabetes as well as diabetes-induced kidney disease.

The sera from GM1 ganglioside antibody positive patients with Guillain-Barré syndrome or chronic inflammatory demyelinating polyneuropathy blocks Na+ currents in rat single myelinated nerve fibers

OBJECTIVE

To determine the possible role of anti-GM1 ganglioside antisera from patients with Gullain-Barr*e syndrome (GBS) or chronic inflammatory demyelinating polyneuropathy (CIDP) in the development of nerve dysfunction.

METHODS

The effect of the anti-GM1 antibody positive antisera obtained from 4 GBS patients and 1 CIDP patient on membrane potential and ionic currents in rat single myelinated nerve fibers was investigated using the voltage clamp technique and compared with that of the anti-GM1 negative antisera obtained from 3 healthy controls and 2 GBS patients.

RESULTS

In the presence of active complement, anti-GM1 positive antisera from 5 patients including 4 GBS patients and 1 CIDP patient significantly suppressed Na+ current more than anti-GM1 negative antisera.

CONCLUSION

This study supports the notion that anti-GM1 antibody is one of the causative factors of conduction abnormality in GBS patients.

Endothelium-specific activation of NAD(P)H oxidase in aortas of exogenously hyperinsulinemic rats

To examine the effects of chronic hyperinsulinemia on vascular tissues, we examined the production of superoxide anion (O(-2)) in the aortic tissues of control and exogenously hyperinsulinemic rats performed by the implantation of an insulin pellet for 4 wk. O(-2) production by aortic segments from hyperinsulinemic rats was 2. 4-fold (lucigenin chemiluminescence method) and 1.7-fold (cytochrome c method) of that of control rats without any differences in O(-2) degrading activities in aortic tissues, respectively (P < 0.025). The increment was completely abolished in the presence of either 100 micromol/l apocynin (an inhibitor of NADPH oxidase) or 10 micromol/l diphenyleneiodonium (an inhibitor of flavin-containing enzyme) and was exclusively endothelium dependent. Consistently, NAD(P)H oxidase activities in endothelial homogenate in hyperinsulinemic rats were dose dependently stimulated above the values of control rats, although these activities in nonendothelial homogenate were not significantly stimulated by insulin. Furthermore, an insulin effect was also demonstrated 1 h after exposing aortic tissues to insulin. These results indicate that O(-2) production specifically increases in endothelium of aortic tissues in chronic hyperinsulinemic rats through the activation of NAD(P)H oxidase.

Prooxidant activity of flavonoids: copper-dependent strand breaks and the formation of 8-hydroxy-2'-deoxyguanosine in DNA

The naturally occurring flavonoids caused strand scission of DNA in the presence of copper ion. Flavonoids such as myricetin, baicalein, and quercetin as well as ascorbic acid cleaved plasmid pBR322 DNA and calf thymus DNA potently. Addition of catalase protected DNA from the strand breaks caused by flavonoids. Treatment of calf thymus DNA with these flavonoids or ascorbate plus copper produced 8-hydroxy-2'-deoxyguanosine. Cuprous ion reduced by flavonoids and ascorbic acid may play a key role in the oxidative cleavage of DNA and the formation of base adduct. Mutagenic and carcinogenic action of flavonoids may be explained by the prooxidant effects of the compounds.