Causes of death in Japanese diabetics: A questionnaire survey of 18,385 diabetics over a 10-year period

We collated and analysed data from hospital records regarding the cause of death of 18,385 patients with diabetes who died in 282 medical institutions throughout Japan over the 10‐year period between 1991 and 2000. Autopsy was carried out in 1750 cases. The most frequent cause of death in all 18,385 cases was malignant neoplasia, accounting for 34.1% of cases, followed by vascular diseases (including diabetic nephropathy, ischemic heart diseases and cerebrovascular diseases) in 26.8%, infections in 14.3%, and then diabetic coma in 1.2%. The most common malignancy was liver cancer, accounting for 8.6% of all the deaths. Of the deaths from vascular diseases, diabetic nephropathy was the cause of death in 6.8% of cases, and the frequency as cause of death for ischemic heart diseases and cerebrovascular diseases were similar at 10.2% and 9.8%, respectively. Myocardial infarction accounted for almost all the deaths from ischemic heart diseases, whereas deaths from cerebral infarction were 2.2‐fold as common as those from cerebral hemorrhage. In the analyses of the relationship between age and causes of death in diabetic patients who underwent autopsy, the overall mortality rate as a result of vascular diseases increased with age, although the mortality rates from diabetic nephropathy and cerebrovascular diseases increased little from the fifth decade of life. The mortality rate from ischemic heart diseases increased with age, however, and was higher than the other forms of vascular diseases from the sixth decade of life, accounting for approximately 50% of vascular deaths in the eighth decade. Malignant neoplasia was the most frequent cause of death from the fifth decade of life, and was extremely common in the seventh decade, accounting for 46.3% of all the deaths. The mortality rate from infections varied little between age groups from the fifth decade of life. In the analyses of glycemic control and the age at the time of death, lifespans were 2.5 years shorter in males, and 1.6 years shorter in female diabetics with poor glycemic control than in those with good or fair glycemic control. This difference was greater for deaths as a result of infections and vascular diseases, particularly diabetic nephropathy, than for malignant neoplasia. Analysis of the relationship between glycemic control and the duration of diabetes and deaths as a result of vascular diseases showed no correlation between the level of glycemic control and death from diabetic nephropathy, ischemic heart diseases or cerebrovascular diseases. In diabetics with disease durations of less than 10 years, the mortality rate from macroangiopathy was higher than that as a result of diabetic nephropathy, a form of microangiopathy. Treatment for diabetes comprised of diet alone in 21.5%, oral hypoglycemic agents in 29.5%, and insulin with or without oral hypoglycemic agents in 44.2%, which was the most common. In particular, 683/1170 (58.4%) diabetics who died from diabetic nephropathy were on insulin therapy, a higher proportion than the 661/1687 (39.2%) who died from ischemic heart diseases, or the 659/1622 (40.6%) who died from cerebrovascular diseases. The average age at the time of death in the survey population was, 68 years for males and 71.6 years for females. These were 9.6 and 13 years, respectively, short of the average life expectancy for the Japanese general population. In comparison with the previous survey (1981–1990), the average age at the time of death had increased 1.5 years for males, and 3.2 years for females. The average life expectancy for the Japanese general population had also increased 1.7 and 2.7 years, respectively, over that period, showing that advances in the management and treatment of diabetes have not led to any improvement in patients’ life expectancies. (J Diabetes Invest, doi: 10.1111/j.2040‐1124.2010.00019.x, 2010)

Non-high-density lipoprotein cholesterol: an important predictor of stroke and diabetes-related mortality in Japanese elderly diabetic patients

AIMS

To evaluate the association of low-density lipoprotein, high-density lipoprotein and non-high-density lipoprotein cholesterol with the risk of stroke, diabetes-related vascular events and mortality in elderly diabetes patients.

METHODS

This study was carried out as a post-hoc landmark analysis of a randomized, controlled, multicenter, prospective intervention trial. We included 1173 elderly type 2 diabetes patients (aged ≥ 65 years) from 39 Japanese institutions who were enrolled in the Japanese elderly diabetes intervention trial study and who could be followed up for 1 year. A landmark survival analysis was carried out in which follow up was set to start 1 year after the initial time of entry.

RESULTS

During 6 years of follow up, there were 38 cardiovascular events, 50 strokes, 21 diabetes-related deaths and 113 diabetes-related events. High low-density lipoprotein cholesterol was associated with incident cardiovascular events, and high glycated hemoglobin was associated with strokes. After adjustment for possible covariables, non-high-density lipoprotein cholesterol showed a significant association with increased risk of stroke, diabetes-related mortality and total events. The adjusted hazard ratios (95% confidence intervals) of non-high-density lipoprotein cholesterol were 1.010 (1.001-1.018, P = 0.029) for stroke, 1.019 (1.007-1.031, P < 0.001) for diabetes-related death and 1.008 (1.002-1.014; P < 0.001) for total diabetes-related events.

CONCLUSIONS

Higher non-high-density lipoprotein cholesterol was associated with an increased risk of stroke, diabetes-related mortality and total events in elderly diabetes patients.

Long-term multiple risk factor interventions in Japanese elderly diabetic patients: the Japanese Elderly Diabetes Intervention Trial--study design, baseline characteristics and effects of intervention

AIM

To evaluate long-term, multiple risk factor intervention on physical, psychological and mental prognosis, and development of complications and cardiovascular disease in elderly type 2 diabetes patients.

METHODS

Our randomized, controlled, multicenter, prospective intervention trial included 1173 elderly type 2 diabetes patients who were enrolled from 39 Japanese institutions and randomized to an intensive or conservative treatment group. Glycemic control, dyslipidemia, hypertension, obesity, diabetic complications and atherosclerotic disease were measured annually. Instrumental activity of daily living, cognitive impairment, depressive symptoms and diabetes burden were assessed at baseline and 3 years.

RESULTS

There was no significant difference in clinical or cognitive parameters at baseline between the two groups. The prevalence of low activities of daily living, depressive symptoms and cognitive impairment was 13%, 28% and 4%, respectively, and was similar in the two groups. A small, but significant difference in HbA1c between the two groups was observed at 1 year after the start of intervention (7.9% vs 8.1%, P < 0.05), although this significant difference was not observed after the second year. With the exception of coronary revascularization, there was no significant difference in fatal or non-fatal events between the two groups. Composite events were also similar in the two groups.

CONCLUSIONS

This study showed no significant differences in fatal or non-fatal events between intensive and conventional treatment. The present study might clarify whether treatment of risk factors influences function and quality of life in elderly diabetic patients.

Cerebral microvascular disease predicts renal failure in type 2 diabetes

Abnormalities in small renal vessels may increase the risk of developing impaired renal function, but methods to assess these vessels are extremely limited. We hypothesized that the presence of small vessel disease in the brain, which manifests as silent cerebral infarction (SCI), may predict the progression of kidney disease in patients with type 2 diabetes. We recruited 608 patients with type 2 diabetes without apparent cerebrovascular or cardiovascular disease or overt nephropathy and followed them for a mean of 7.5 years. At baseline, 177 of 608 patients had SCI, diagnosed by cerebral magnetic resonance imaging. The risk for the primary outcome of ESRD or death was significantly higher for patients with SCI than for patients without SCI [hazard ratio, 2.44; 95% confidence interval (CI) 1.36 to 4.38]. The risk for the secondary renal end point of any dialysis or doubling of the serum creatinine concentration was also significantly higher for patients with SCI (hazard ratio, 4.79; 95% CI 2.72 to 8.46). The estimated GFR declined more in patients with SCI than in those without SCI; however, the presence of SCI did not increase the risk for progression of albuminuria. In conclusion, independent of microalbuminuria, cerebral microvascular disease predicted renal morbidity among patients with type 2 diabetes.

Long-term effect of modification of dietary protein intake on the progression of diabetic nephropathy: a randomised controlled trial

AIMS/HYPOTHESIS

There is currently insufficient evidence to recommend a low-protein diet for type 2 diabetic patients with diabetic nephropathy. We assessed whether a low-protein diet could prevent the progression of diabetic nephropathy.

METHODS

This was a multi-site parallel randomised controlled trial for prevention of diabetic nephropathy progression among 112 Japanese type 2 diabetic patients with overt nephropathy. It was conducted in Japan from 1 December 1997 to 30 April 2006. The participants were randomly assigned using a central computer-generated schedule to either low-protein diet (0.8 g kg(-1) day(-1)) and normal-protein diet (1.2 g kg(-1) day(-1)), and were followed for 5 years. The participants and investigators were not blinded to the assignment. The primary outcomes were the annual change in estimated GFR and creatinine clearance, the incidence of doubling of serum creatinine and the time to doubling of baseline serum creatinine.

RESULTS

The study was completed by 47 (84%) of 56 participants in the low-protein diet group and 41 (73%) of 56 participants in the normal-diet group. During the study period, the difference in mean annual change in estimated GFR between the low-protein diet and the normal-protein diet groups was -0.3 ml min(-1) 1.73 m(-2) (95% CI -3.9, 4.4; p = 0.93). The difference in mean annual change in creatinine clearance between the low-protein diet and the normal-protein diet groups was -0.006 ml s(-1) 1.73 m(-2) (95% CI -0.089, 0.112; p = 0.80). A doubling of serum creatinine was reached in 16 patients of the low-protein group (34.0%), compared with 15 in the normal-protein group (36.6%), the difference between groups being -2.6% (95% CI -22.6, 17.5; p = 0.80). The time to doubling of serum creatinine was similar in both groups (p = 0.66).

CONCLUSIONS/INTERPRETATION

It is extremely difficult to get patients to follow a long-term low-protein diet. Although in the low-protein group overall protein intake was slightly (but not significantly) lower, it did not confer renoprotection.

CLINICAL TRIAL REGISTRATION

ClinicalTrials.gov NCT00448526.

FUNDING

Research grant from the Ministry of Health, Labour and Welfare of Japan.

Clinical impact of reducing microalbuminuria in patients with type 2 diabetes mellitus

Diabetic nephropathy in type 2 diabetes is a leading cause of end-stage renal disease worldwide. Its early clinical sign is microalbuminuria, which is not only a predictor for progression of nephropathy but also an independent risk factor for cardiovascular disease. A few decades ago, diabetic nephropathy was believed to be progressive and irreversible. Thus, the main therapeutic objective for type 2 diabetic patients with microalbuminuria was to prevent progression to overt proteinuria. However, there is now growing evidence regarding remission/regression of diabetic nephropathy. In recent clinical trials using the renin-angiotensin system blockade drugs, a reduction in microalbuminuria by the use of these drugs has been noted. We also reported that a reduction in microalbuminuria was more frequent than progression to overt proteinuria and that multifactorial control approach was important to the reduction of microalbuminuria. These results for type 2 diabetes are similar to those previously reported for type 1 diabetes. Furthermore, our recent study showed that the 8-year cumulative incidence rate of renal and cardiovascular events was significantly lower in patients with remission than in those without it. The annual decline rate of estimated glomerular filtration rate in patients with remission was also significantly slower. These studies provide clinical evidence implying that the reduction of microalbuminuria in type 2 diabetic patients occurs frequently and brings about renal and cardiovascular risk reduction. Reducing microalbuminuria is therefore considered to be an important therapeutic objective and may be a biomeasure of therapeutic success in type 2 diabetic patients.

Genetic variations associated with diabetic nephropathy and type II diabetes in a Japanese population

Genetic susceptibility plays an important role in the pathogenesis of diabetic nephropathy and type II diabetes. To identify the genetic polymorphisms associated with diabetic nephropathy and type II diabetes, we performed a genome-wide association study using single-nucleotide polymorphisms as genetic markers. We also analyzed polymorphisms within the genes encoding for the renin-angiotensin system that were considered as candidate genes for diabetic nephropathy susceptibility and the transcription factor 7-like 2 (TCF7L2) as a candidate for type II diabetes, in a large cohort of a Japanese population. A genome-wide association study identified SLC12A3 and engulfment and cell motility 1 gene as the new candidates for diabetic nephropathy and transcription factor-activating protein 2beta as a novel susceptibility gene for type II diabetes; this observation was based on the significant association between the polymorphisms within the genes and the corresponding diseases (P<0.0001). Further, we discovered that the genes encoding the angiotensin-converting enzyme, angiotensinogen, and angiotensin II type I receptor have a significant combinational effect on conferring susceptibility to diabetic nephropathy. Furthermore, TCF7L2 that has been reported as a convincing susceptibility gene for type II diabetes in Caucasian populations was also shown to be associated with type II diabetes in a Japanese population. These genes could be considered as strong susceptibility genes for diabetic nephropathy and type II diabetes in the Japanese, although the new candidates that have been identified by genome-wide screening need to be examined in greater detail by several replication studies.

MAPK/AP-1-dependent regulation of PAI-1 gene expression by TGF-beta in rat mesangial cells

BACKGROUND

Receptor-regulated Smads and/or mitogen-activated protein kinases (MAPKs) are involved in transforming growth factor-beta (TGF-beta)-induced expression of various genes, including plasminogen activator inhibitor-1 (PAI-1). Because the sequence of the promoter region in rat PAI-1 gene differs from that in the human gene, we examined the mechanisms of TGF-beta-induced rat PAI-1 expression in rat mesangial cells.

METHODS

TGF-beta1-induced PAI-1 and c-fos mRNA expressions were determined by Northern blot analysis. Activation of MAPKs and Smad proteins was evaluated by an immunoblot analysis. DNA binding activities of nuclear protein were examined by using an electrophoretic mobility shift assay (EMSA). The activities of PAI-1 promoter were measured by a luciferase reporter assay.

RESULTS

Extracellular-regulated kinase (ERK) and c-Jun NH-terminal kinase (JNK) phosphorylation, c-fos mRNA expression, and activator protein-1 (AP-1) DNA binding activity stimulated by TGF-beta1 were completely suppressed by the ERK kinase (MEK) inhibitors. EMSA and reporter analysis revealed that an AP-1-like sequence located in the proximal region of the rat PAI-1 promoter was the target for TGF-beta1, and the disruption of this AP-1-like sequence suppressed basal and TGF-beta1-induced promoter activation. TGF-beta1 also stimulated nuclear translocation of Smads and binding to palindromic Smad binding element (SBE) located in the rat PAI-1 promoter, without being affected by MEK inhibitor. Point mutation and deletion of palindromic SBE did not affect TGF-beta1-induced rat PAI-1 promoter activity. Moreover, interferon-gamma (IFN-gamma) inhibited TGF-beta1-induced PAI-1 expression through selectively suppressing the ERK-AP-1 pathway.

CONCLUSION

These results suggest that the essential requirement of MAPK/AP-1 activation for TGF-beta1-induced PAI-1 expression is unique to rat mesangial cells.

Single nucleotide polymorphisms in the gene encoding Krüppel-like factor 7 are associated with type 2 diabetes

AIMS/HYPOTHESIS

Although genetic susceptibility plays an important role in the pathogenesis of type 2 diabetes, most of the genes that influence susceptibility to type 2 diabetes have yet to be identified. Krüppel-like transcription factors are known to play important roles in development and cell differentiation, and have recently been implicated in the pathogenesis of type 2 diabetes. The present study aimed to examine the associations of single nucleotide polymorphisms (SNPs) in genes encoding members of the Krüppel-like-factor (KLF) family with type 2 diabetes in a large cohort of Japanese subjects.

METHODS

We genotyped 33 SNP loci found in 12 KLF genes in subjects with type 2 diabetes and in subjects from the general population using the PCR-Invader assay. We also examined the effects of the overexpression of KLF7 on adipogenesis in 3T3-L1 cells.

RESULTS

We identified a significant association between an SNP in KLF7 and type 2 diabetes (A vs C: p=0.004 after Bonferroni's correction, odds ratio=1.59, 95% CI 1.27-2.00). The expression of Klf7 decreased in response to the differentiation of 3T3-L1 adipocytes, and the overexpression of KLF7 resulted in significant inhibition of adipogenesis in 3T3-L1 cells.

CONCLUSIONS/INTERPRETATION

These results indicate that the gene encoding KLF7 is a novel candidate for conferring genetic susceptibility to type 2 diabetes.

Genetic variations in the gene encoding TFAP2B are associated with type 2 diabetes mellitus

To search a gene(s) conferring susceptibility to type 2 diabetes mellitus, we genotyped nearly 60,000 gene-based SNPs for Japanese patients and found evidence that the gene at chromosome 6p12 encoding transcription-factor-activating protein 2beta (TFAP2B) was a likely candidate in view of significant association of polymorphism in this gene with type 2 diabetes. Extensive analysis of this region identified that several variations within TFAP2B were significantly associated with type 2 diabetes [a variable number of tandem repeat locus: chi(2)=10.9, P=0.0009; odds ratio=1.57, 95% CI 1.20-2.06, intron 1+774 (G/T); chi(2)=11.6, P=0.0006; odds ratio=1.60, 95% CI 1.22-2.09, intron 1+2093 (A/C); chi(2)=12.2, P=0.0004; odds ratio=1.61, 95% CI 1.23-2.11]. The association of TFAP2B with type 2 diabetes was also observed in the UK population. These results suggest that TFAP2B might be a new candidate for conferring susceptibility to type 2 diabetes and contribute to the pathogenesis of type 2 diabetes.

Genetic variations in the gene encoding ELMO1 are associated with susceptibility to diabetic nephropathy

To search for a gene(s) conferring susceptibility to diabetic nephropathy (DN), we genotyped over 80,000 gene-based single nucleotide polymorphisms (SNPs) in Japanese patients and identified that the engulfment and cell motility 1 gene (ELMO1) was a likely candidate for conferring susceptibility to DN, in view of the significant association of an SNP in this gene with the disease (intron 18+9170, GG vs. GA+AA, chi(2) = 19.9, P = 0.000008; odds ratio 2.67, 95% CI 1.71-4.16). In situ hybridization (ISH) using the kidney of normal and diabetic mice revealed that ELMO1 expression was weakly detectable mainly in tubular and glomerular epithelial cells in normal mouse kidney and was clearly elevated in the kidney of diabetic mice. Subsequent in vitro analysis revealed that ELMO1 expression was elevated in cells cultured under high glucose conditions (25 mmol/l) compared with cells cultured under normal glucose conditions (5.5 mmol/l). Furthermore, we identified that the expression of extracellular matrix protein genes, such as type 1 collagen and fibronectin, were increased in cells that overexpress ELMO1, whereas the expression of matrix metalloproteinases was decreased. These results indicate that ELMO1 is a novel candidate gene that both confers susceptibility to DN and plays an important role in the development and progression of this disease.

A simple and sensitive method for glutamine:fructose-6-phosphate amidotransferase assay

For measuring glutamine:fructose-6-phosphate amidotransferase (GFAT) activity in cultured cells, an enzyme method -GDH method- was set up with high-efficiency, high-sensitivity and simple operation by determining the formed glutamate. During the process of making samples, reduced glutathione (GSH, 5 mM) and glucose-6-phosphate Na2 (5 mM) were added to the buffer for scraping the cells. The range of protein content in the samples was 80-150 microg. In the GFAT activity assay, the end product reduced acetylpyridine adenine dinucleotide (APADH) was determined at 370 nm directly. The suitable concentrations of the reactants fructose-6-phosphate (F-6-P), glutamine, acetylpyridine adenine dinucleotide (APAD) and glutamate dehydrogenase (GDH) were 0.8, 6 and 0.3 mM and 6 U, respectively. However, the excess of APAD may interfere with the APADH measurement. The reaction time course was 90 min. The GFAT activity in 3T3-L1, L6, HepG2 and HIRc cells were 1.84-8.51 nmol glutamate/mg protein.min.

Successful recovery of infective endocarditis-induced rapidly progressive glomerulonephritis by steroid therapy combined with antibiotics: a case report

Background

The mortality rate among patients with infective endocarditis, especially associated with the presence of complications or coexisting conditions such as renal failure and the use of combined medical and surgical therapy remains still high. Prolonged parenteral administration of a bactericidal antimicrobial agent or combination of agents is usually recommended, however, the optimal therapy for infective endocarditis associated with renal injury is not adequately defined.

Case presentation

Patient was a 24-years old man who presented to our hospital with fever, fatigue, and rapidly progressive glomerulonephritis. He had a history of ventricular septum defect (VSD). A renal biopsy specimen revealed crescentic glomerulonephritis and echocardiogram revealed VSD with vegetation on the tricuspid valve. Specimens of blood demonstrated Propionibacterium Acnes. The intensive antibiotic therapy with penicillin G was started without clinical improvement of renal function or resolution of fever over the next 7 days. After the short-term treatment of low dose of corticosteroid combined with continuous antibiotics, high fever and renal insufficiency were dramatically improved.

Conclusion

Although renal function in our case worsened despite therapy with antibiotics, a short-term and low dose of corticosteroid therapy with antibiotics was able to recover renal function and the patient finally underwent tricuspid valve-plasty and VSD closure. We suggest that the patients with rapidly progressive glomerulonephritis associated with infective endocarditis might be treated with a short-term and low dose of corticosteroid successfully.

Association of the gene encoding wingless-type mammary tumor virus integration-site family member 5B (WNT5B) with type 2 diabetes

Recent reports have suggested that WNT signaling is an important regulator for adipogenesis or insulin secretion and might be involved in the pathogenesis of type 2 diabetes. To investigate possible roles of the WNT genes in conferring susceptibility to type 2 diabetes, we examined the association of the genes that encode members of the WNT family with type 2 diabetes in the Japanese population. First, 40 single-nucleotide polymorphism (SNP) loci within 11 WNT genes were analyzed in 188 subjects with type 2 diabetes (case-1) and 564 controls (control-1). Among them, six SNP loci exhibited a significant difference (P<.05) in the allele and/or genotype distributions between case and control subjects. These SNP loci were further analyzed in another set of case (case-2; n=733) and control (control-2; n=375) subjects to confirm their statistical significance. As a result, one SNP locus in the WNT5B gene was strongly associated with type 2 diabetes ( chi 2=15.6; P=.00008; odds ratio=1.74; 95% confidence interval 1.32-2.29). Expression of the WNT5B gene was detectable in several tissues, including adipose, pancreas, and liver. Subsequent in vitro experiments identified the fact that expression of the Wnt5b gene was increased at an early phase of adipocyte differentiation in mouse 3T3-L1 cells. Furthermore, overexpression of the Wnt5b gene in preadipocytes resulted in the promotion of adipogenesis and the enhancement of adipocytokine-gene expression. These results indicate that the WNT5B gene may contribute to conferring susceptibility to type 2 diabetes and may be involved in the pathogenesis of this disease through the regulation of adipocyte function.

Antiproteinuric effect of candesartan cilexetil in Japanese subjects with type 2 diabetes and nephropathy

The effect of the angiotensin II receptor blocker, candesartan cilexetil, on proteinuria was examined in a prospective, multicenter, randomized, double-blind study in Japanese subjects with type 2 diabetes. This study enrolled diabetic subjects with confirmed proteinuria into four groups for 12 weeks of treatment with placebo or candesartan cilexetil 2, 4, or 8 mg. The contribution of the angiotensin converting enzyme (ACE) gene polymorphism to the effect of candesartan cilexetil was also examined. In 127 subjects, candesartan cilexetil showed a dose-related reduction in proteinuria after 12 weeks of treatment (F = 9.45, P = 0.0013), with a 18.1% reduction in the 4-mg group, and a 5.8% reduction in the 8-mg group, in contrast to a 32.2% increase in the placebo group, and a 0.8% increase in the 2-mg group. These results indicate that candesartan cilexetil is useful in reducing proteinuria in diabetic subjects when compared with placebo. In addition, candesartan cilexetil seems to be effective in subjects with both the II and DD genotypes of the ACE gene.

Characteristics of pancreas transplantation currently performed in japan

The Pancreas Transplantation (tx) Program under the Japanese Organ Transplant Act was started in 2000. PTx is indicated for type 1 diabetic patients on hemodialysis therapy. As of April 2003 93 patients are listed as candidates. Ten cases of PTx with enteric or bladder-drained technique were performed during the last 3 years as well as nine SPK and one PAK. Of 10 cases, nine recipients are insulin-free with HbA1c values ranging from 4.4% to 5.7%, although exogenous insulin was required in six cases temporarily, namely for a median 63 days (12 to 225 days). One case was lost due to pancreatic graft thrombosis. All 10 kidney grafts are functioning. Based on the experiences with 14 cases of pancreas tx using non-heart-beating (NHB) donors, we defined the criteria of NHB donor as: age younger than 40 years and cessation of respiratory support. One case of SPK with graft of NHB donor was done, and the recipient is off insulin. Pancreas and kidney are allocated for SPK if the recipient shares at least one HLA-DR antigen. Marginal donors were defined as higher mean donor age, median 37 (range 18 to 58 years); mean 38 +/- 12 years), and no death cause of by trauma. The revascularization of gastroduodenal artery to the pancreatic graft was performed in eight cases to minimize the risk of ischemic injury to the pancreatic graft and technical failure in cases of marginal donor.

Association of solute carrier family 12 (sodium/chloride) member 3 with diabetic nephropathy, identified by genome-wide analyses of single nucleotide polymorphisms

To identify genetic elements that might confer susceptibility to diabetic nephropathy, we performed a genome-wide analysis of gene-based single nucleotide polymorphisms (SNPs) in a large cohort of Japanese patients with diabetes. In case-control association studies, patients with type 2 diabetes were divided into two groups, one having retinopathy as well as overt nephropathy and the other (the control group) having diabetic retinopathy but with no signs of renal involvement. Genotyping of these patients at >55,000 SNP loci indicated a gene encoding solute carrier family 12 member 3 (SLC12A3) to be a good candidate for the susceptibility to diabetic nephropathy, in view of a significant association of one landmark SNP located in the 24th intron (chi(2) = 15.4, P = 0.000087, odds ratio = 2.53 [95% CI 1.57-4.09]). Subsequent analysis of additional genetic variations in this gene identified several SNPs that were significantly associated with nephropathy, especially one in exon 23 (+78 G to A: Arg913Gln, chi(2) = 18.5, P = 0.00002, odds ratio = 2.53 [95% CI 1.64-3.90]). The results implicated that substitution of Arg913 to Gln in the SLC12A3 gene might reduce the risk to develop diabetic nephropathy and suggested that the gene product might be a potential target for the prevention or treatment of this disease.

Effects of antioxidants in diabetes-induced oxidative stress in the glomeruli of diabetic rats

Numerous reports have demonstrated that oxidative stress induced by diabetes plays an important role in the development and progression of diabetic vascular complications including nephropathy. Indeed, there is emerging evidence that the formation of reactive oxygen species (ROS) is a direct consequence of hyperglycemia. Biomarkers for oxidative damage to DNA, lipids, and proteins are also supporting the concept of increased oxidative stress in diabetes and diabetic nephropathy. However, there is an unanswered question: When does oxidative stress as a pathogenetic event occur in the process of diabetic nephropathy? To answer this question, glomerular ROS was imaged with the use of 2', 7'-dichlorofluorescein diacetate (DCFH-DA). The image of DCF fluorescence was strong in glomeruli from diabetic rats as compared with that of glomeruli from nondiabetic control rats. mRNA expression of antioxidant enzymes such as catalase, glutathione peroxidase, Cu/Zn superoxide dismutase, and heme oxygenase-1 (HO-1) was also determined because oxidative stress definitely refers to the situation of an imbalance between the production of ROS and antioxidant defense. The mRNA expression of catalase, glutathione peroxidase, and Cu/Zn superoxide dismutase 2 wk after the induction of diabetes was not significantly different from that in control rats. Alternatively, mRNA and protein expression of HO-1 was strongly induced by 16-fold in diabetic glomeruli after the induction of diabetes. Antioxidant treatment with either vitamin E or probucol almost completely normalized HO-1 overexpression in diabetic glomeruli, supporting the existence of oxidative stress in the glomeruli of early diabetes. Furthermore, It has reported that antioxidant treatment with vitamin E, probucol, alpha-lipoic acid, or taurine normalized diabetes-induced not only renal dysfunction such as albuminuria and glomerular hypertension but also glomerular pathologies. In summary, oxidative stress by diabetes could play a crucial role in the development and progression of diabetic nephropathy, and antioxidant treatment could be a potential therapeutic procedure for diabetic nephropathy.

APOE polymorphism and the progression of diabetic nephropathy in Japanese subjects with type 2 diabetes: results of a prospective observational follow-up study

OBJECTIVE

The aim of this study is to clarify the conflicting results of the epsilon2/epsilon3/epsilon4 APOE polymorphism as a risk factor on diabetic nephropathy by a cohort study.

RESEARCH DESIGN AND METHODS

A total of 429 Japanese subjects with type 2 diabetes and with normoalbuminuria (n = 299) or with microalbuminuria (n = 130) were enrolled in a prospective observational follow-up study during 1995-1998 and followed until 2001 (for at least 3 years). The endpoint was the occurrence of a renal event defined as the progression to a higher stage of diabetic nephropathy.

RESULTS

During the study (the mean follow-up period: 4.4 +/- 1.0 years), 31 of 429 subjects progressed: 21 from normoalbuminuria to microalbuminuria and 10 from microalbuminuria to overt proteinuria. The allele frequency of the APOE polymorphism was significantly different between the progressors and the nonprogressors. Eight of 42 epsilon2 carriers (19%) progressed, whereas 23 of 387 noncarriers (6%) progressed with a relative risk of 3.2 (95% CI 1.5-6.7). When subjects were stratified by renal status at baseline, each relative risk for the progression in the epsilon2 carriers was 2.7 (0.99-7.4) in those with normoalbuminuria and 4.2 (1.3-13.3) in those with microalbuminuria. Furthermore, when analyzed only in subjects with normoalbuminuria and short duration of diabetes (<15 years) at baseline, the risk in the epsilon2 carriers became higher to 3.2 (1.2-8.8).

CONCLUSIONS

Our follow-up study indicates that the epsilon2 allele of the APOE polymorphism is a prognostic risk factor for both the onset and the progression of diabetic nephropathy in Japanese type 2 diabetes.

Activation of Src kinase in platelet-derived growth factor-B-dependent tubular regeneration after acute ischemic renal injury

We previously reported that the platelet-derived growth factor B-chain (PDGF-B)/PDGF receptor (PDGFR) axis is involved in tubular regeneration after ischemia/reperfusion injury of the kidney. In the present study, we examined the activation of Src tyrosine kinase, a crucially important signaling molecule for PDGFR, and assessed the role of Src in PDGF-B-dependent renal tubular regeneration afterischemia/reperfusion injury. Immunoblot using clone 28, a monoclonal antibody specific for the active form of Src kinases, demonstrated increased active Src expression in the injured rat kidney 6 hours after reperfusion with peak activation at 12 hours. In vitro kinase assay confirmed increased Src activity that concurred with PDGFR-beta activation as detected by the increment of receptor-phosphorylated tyrosine. Immunohistochemistry using clone 28 demonstrated that active Src was preferentially expressed in the S3 segment of the proximal tubule in reperfused kidney, where it is not normally expressed. This enhanced expression of active Src was co-localized with the increased PDGFR expression in the tubular cells that were undergoing cell proliferation cycle. Trapidil administration suppressed Src and PDGFR-beta activation in the reperfused kidney and resulted in deteriorated renal function. These findings suggest that active Src participates in PDGF-B-dependent regeneration of tubular cells from acute ischemic injury.

Diabetic neuropathy and nerve regeneration

Diabetic neuropathy is the most common peripheral neuropathy in western countries. Although every effort has been made to clarify the pathogenic mechanism of diabetic neuropathy, thereby devising its ideal therapeutic drugs, neither convinced hypotheses nor unequivocally effective drugs have been established. In view of the pathologic basis for the treatment of diabetic neuropathy, it is important to enhance nerve regeneration as well as prevent nerve degeneration. Nerve regeneration or sprouting in diabetes may occur not only in the nerve trunk but also in the dermis and around dorsal root ganglion neurons, thereby being implicated in the generation of pain sensation. Thus, inadequate nerve regeneration unequivocally contributes to the pathophysiologic mechanism of diabetic neuropathy. In this context, the research on nerve regeneration in diabetes should be more accelerated. Indeed, nerve regenerative capacity has been shown to be decreased in diabetic patients as well as in diabetic animals. Disturbed nerve regeneration in diabetes has been ascribed at least in part to all or some of decreased levels of neurotrophic factors, decreased expression of their receptors, altered cellular signal pathways and/or abnormal expression of cell adhesion molecules, although the mechanisms of their changes remain almost unclear. In addition to their steady-state changes in diabetes, nerve injury induces injury-specific changes in individual neurotrophic factors, their receptors and their intracellular signal pathways, which are closely linked with altered neuronal function, varying from neuronal survival and neurite extension/nerve regeneration to apoptosis. Although it is essential to clarify those changes for understanding the mechanism of disturbed nerve regeneration in diabetes, very few data are now available. Rationally accepted replacement therapy with neurotrophic factors has not provided any success in treating diabetic neuropathy. Aside from adverse effects of those factors, more rigorous consideration for their delivery system may be needed for any possible success. Although conventional therapeutic drugs like aldose reductase (AR) inhibitors and vasodilators have been shown to enhance nerve regeneration, their efficacy should be strictly evaluated with respect to nerve regenerative capacity. For this purpose, especially clinically, skin biopsy, by which cutaneous nerve pathology including nerve regeneration can be morphometrically evaluated, might be a safe and useful examination.

Progression of diabetic nephropathy

BACKGROUND

Diabetic nephropathy, a kidney disease caused by diabetes, is the most devastating and money-consuming complication in patients with diabetes throughout the world. The cardinal lesion of diabetic nephropathy resides in renal glomeruli and is called diabetic glomerulosclerosis. Hyperglycemia is responsible for the development and progression of diabetic nephropathy through metabolic derangements, including increased oxidative stress, renal polyol formation, activation of protein kinase C (PKC)-mitogen-activated protein kinases (MAPKs), and accumulation of advanced glycation end products, as well as such hemodynamic factors as systemic hypertension and increased intraglomerular pressure.

METHODS

We examined whether inhibition of the PKC-MAPK pathway could inhibit functional and pathological abnormalities in glomeruli from diabetic animal models and cultured mesangial cells exposed to high glucose condition and/or mechanical stretch.

RESULTS

Direct inhibition of PKC by PKC beta inhibitor prevented albuminuria and mesangial expansion in db/db mice, a model of type 2 diabetes. We also found that inhibition of MAPK by PD98059, an inhibitor of MAPK, or mitogen-activated extracellular regulated protein kinase kinase prevented enhancement of activated protein-1 (AP-1) DNA binding activity and fibronectin expression in cultured mesangial cells exposed to mechanical stretch in an in vivo model of glomerular hypertension.

CONCLUSION

These findings highlight the important role of PKC-MAPK pathway activation in mediating the development and progression of diabetic nephropathy.

Antiproteinuric effect of candesartan cilexetil in patients with chronic glomerulonephritis

A prospective, randomised, double-blind, parallel-group, dose-response trial was conducted to investigate the antiproteinuric effect of candesartan cilexetil, the angiotensin II type 1 receptor blocker, in patients with chronic glomerulonephritis. Patients (n=280) were treated for 12 weeks with candesartan cilexetil 2, 4, or 8 mg given orally once-daily (o.d.). The improvement in urinary protein excretion observed at the end of the treatment period was 15.9% in the 2 mg group, 25.6% in the 4 mg group, and 34.6% in the 8 mg group, respectively, showing a clear dose-response (2 mg <4 mg <8 mg; p=0.003). The mean reduction in urinary protein excretion was 11.3% in the 2 mg group, 26.3% in the 4 mg group, and 26.0% in the 8 mg group, showing a dose-response pattern, in that the effect of 4 mg and 8 mg was greater than that of 2 mg (2 mg <4 mg asymptotically equal to 8 mg; p=0.010). As the observed reduction in urinary protein excretion failed to correlate with changes in mean blood pressure, it could not be attributed to the antihypertensive effect of the study drug alone. This suggests that candesartan cilexetil, 4 8 mg o.d., has antiproteinuric effects in patients with chronic glomerulonephritis.

Increase in intracellular Ca(2+) and calcitonin gene-related peptide release through metabotropic P2Y receptors in rat dorsal root ganglion neurons

We examined the effects of the activation of metabotropic P2Y receptors on the intracellular Ca(2+) concentration and the release of neuropeptide calcitonin gene-related peptide (CGRP) in isolated adult rat dorsal root ganglion neurons. In small-sized dorsal root ganglion neurons (soma diameter<30 microm) loaded with fura-2, a bath application of ATP (100 microM) evoked an increase in intracellular Ca(2+) concentration, while the removal of extracellular Ca(2+) partly depressed the response to ATP, thus suggesting that the ATP-induced increase in intracellular Ca(2+) concentration is due to both the release of Ca(2+) from intracellular stores and the influx of extracellular Ca(2+). Bath application of uridine 5'-triphosphate (UTP; 100 microM) also caused an increase in intracellular Ca(2+) concentration in small-sized dorsal root ganglion neurons and the P2 receptor antagonists suramin (100 microM) and pyridoxalphosphate-6-azophenyl-2',4'-disulfonic acid (PPADS; 10 microM) virtually abolished the response, indicating that the intracellular Ca(2+) elevation in response to UTP is mediated through metabotropic P2Y receptors. This intracellular Ca(2+) increase was abolished by pretreating the neurons with thapsigargin (100 nM), suggesting that the UTP-induced increase in intracellular Ca(2+) is primarily due to the release of Ca(2+) from endoplasmic reticulum Ca(2+) stores. An enzyme-linked immunosorbent assay showed that an application of UTP (100 microM) significantly stimulated the release of CGRP and that suramin (100 microM) totally abolished the response, suggesting that P2Y receptor-mediated increase in intracellular Ca(2+) is accompanied by CGRP release from dorsal root ganglion neurons. These results suggest that metabotropic P2Y receptors contribute to extracellular ATP-induced increase in intracellular Ca(2+) concentration and subsequent release of neuropeptide CGRP in rat dorsal root ganglion neurons.

15-Deoxy-Delta12,14-prostaglandin J2 inhibits IL-1beta-induced cyclooxygenase-2 expression in mesangial cells

BACKGROUND

Cyclooxygenase-2 (COX-2), a key enzyme in the synthesis of prostaglandins, is induced in mesangial cells in response to proinflammatory cytokines. Recently, 15-deoxy-Delta12,14-prostaglandin J2 (15d-PGJ2), one of the natural ligands of peroxisome proliferator-activated receptor gamma (PPARgamma), has been reported to have an anti-inflammatory effect. Therefore, we examined the effect of 15d-PGJ2 on COX-2 expression in cultured rat mesangial cells.

METHODS

Mesangial cells were incubated with 15d-PGJ2 for 30 minutes and then exposed to interleukin-1beta (IL-1beta). The expression of COX-2 mRNA and proteins was determined by Northern blot and immunoblot analyses, respectively. Accumulation of prostaglandin E2 (PGE2) was measured by an enzyme-linked immunosorbent assay (ELISA). Activities of mitogen-activated protein kinases (MAPKs) were evaluated by an immunoblot analysis. DNA binding activities of activator protein-1 (AP-1) or nuclear factor-kappaB (NF-kappaB) were examined by an electrophoretic mobility shift assay (EMSA). The activities of PPAR responsive elements (PPRE) and COX-2 promoter were measured by a luciferase reporter assay.

RESULTS

15D-PGJ2 significantly suppressed IL-1beta-induced COX-2 expression and PGE2 production, but thiazolidinediones, synthetic PPARgamma ligands, did not affect COX-2 expression. Moreover, the cells transfected with a PPRE luciferase reporter did not respond to 15d-PGJ2. IL-1beta rapidly activated extracellular signal-regulated kinase (ERK) and c-Jun NH2-terminal kinase (JNK), which were involved in the up-regulation of COX-2 induction, but 15d-PGJ2 inhibited the activation of these kinases. 15d-PGJ2 inhibited the IL-1beta-induced increase in binding activities of nuclear proteins to consensus AP-1 site and AP-1-like site of COX-2 promoter but not of NF-kappaB. IL-1beta was unable to activate the COX-2 promoter when the AP-1-like site was mutated.

CONCLUSIONS

These data suggest that 15d-PGJ2 inhibits IL-1beta-induced COX-2 expression, independent of PPARgamma activation, by suppression of ERK and JNK pathways and AP-1 activation in mesangial cells. Thus, 15d-PGJ2 may play an important role in the negative feedback mechanism of COX-2 expression in renal inflammation and may be useful as an anti-inflammatory agent.

Amelioration of high fructose-induced metabolic derangements by activation of PPARalpha

To elucidate molecular mechanisms of high fructose-induced metabolic derangements and the influence of peroxisome proliferator-activated receptor-alpha (PPARalpha) activation on them, we examined the expression of sterol regulatory element binding protein-1 (SREBP-1) and PPARalpha as well as its nuclear activation and target gene expressions in the liver of high fructose-fed rats with or without treatment of fenofibrate. After 8-wk feeding of a diet high in fructose, the mRNA contents of PPARalpha protein and its activity and gene expressions of fatty acid oxidation enzymes were reduced. In contrast, the gene expressions of SREBP-1 and lipogenic enzymes in the liver were increased by high fructose feeding. Similar high fructose effects were also found in isolated hepatocytes exposed to 20 mM fructose in the media. The treatment of fenofibrate (30 mg.kg(-1).day(-1)) significantly improved high fructose-induced metabolic derangements such as insulin resistance, hypertension, hyperlipidemia, and fat accumulation in the liver. Consistently, the decreased PPARalpha protein content, its activity, and its target gene expressions found in high fructose-fed rats were all improved by fenofibrate treatment. Furthermore, we also found that the copy number of mitochondrial DNA, the expressions of mitochondrial transcription factor A, ATPase-6 subunit, and uncoupling protein-3 were increased by fenofibrate treatment. These findings suggest that the metabolic syndrome in high fructose-fed rats is reversed by fenofibrate treatment, which is associated with the induction of enzyme expression related to beta-oxidation and the enhancement of mitochondrial gene expression.

Combined expression of pancreatic duodenal homeobox 1 and islet factor 1 induces immature enterocytes to produce insulin

Immature rat intestinal stem cells (IEC-6) given the ability to express the transcription factor, pancreatic duodenal homeobox 1 (Pdx-1), yielded YK cells. Although these cells produced multiple enteroendocrine hormones, they did not produce insulin. Exposure of YK cells to 2 nmol/l betacellulin yielded BYK cells that showed the presence of insulin expression in cytoplasm and that secreted insulin into culture media. By examining the mechanism of differentiation in BYK cells, we found that another transcription factor, islet factor 1 (Isl-1) was newly expressed with the disappearance of Pax-6 expression in those cells after exposure to betacellulin. These results indicated that combined expression of Pdx-1 and Isl-1 in IEC-6 cells was required for the production of insulin. In fact, overexpression of both Pdx-1 and Isl-1 in IEC-6 cells (Isl-YK-12, -14, and -15 cells) gave them the ability to express insulin without exposure to betacellulin. Furthermore, implantation of the Isl-YK-14 cells into diabetic rats reduced the animals' plasma glucose levels; glucose levels dropped from 19.4 to 16.9 mmol/l 1 day after the injection of cells. As expected, the plasma insulin concentrations were 2.7 times higher in the diabetic rats injected with Isl-YK-14 cells compared to in controls. In summary, our results indicated that immature intestinal stem cells can differentiate into insulin-producing cells given the ability to express the transcription factors Pdx-1 and Isl-1.

Reduced activity of mtTFA decreases the transcription in mitochondria isolated from diabetic rat heart

To evaluate abnormalities in the mitochondrial transcription factor A (mtTFA) function as a cause of mitochondrial dysfunction in diabetes, we measured the mRNA contents of the proteins consisting of the mitochondrial respiratory chain as well as transcriptional and translational activities in the mitochondria isolated from controls and streptozotocin-induced diabetic rat hearts. Using Northern blot analysis, we found 40% reduced mRNA contents of mitochondrial-encoded cytochrome b and ATP synthase subunit 6 in diabetic rat hearts compared with control rats (P < 0.05). These abnormalities were completely recovered by insulin treatment. Furthermore, the mitochondrial activities of transcription and translation were decreased significantly in mitochondria isolated from diabetic rats by 60% (P < 0.01) and 71% (P < 0.01), respectively, compared with control rats. The insulin treatment also completely normalized these abnormalities in diabetic rats. Consistently, gel retardation assay showed a reduced binding of mtTFA to the D-loop of mitochondrial DNA in diabetic rats, although there was no difference in the mtTFA mRNA and protein content between the two groups. On the basis of these findings, a reduced binding activity of mtTFA to the D-loop region in the hearts of diabetic rats may contribute to the decreased mitochondrial protein synthesis.

Cyclic AMP inhibits stretch-induced overexpression of fibronectin in glomerular mesangial cells

Glomerular hypertension is proposed to play an important role in the progression of various glomerular diseases. Glomerular mesangial cells are considered to be exposed to the stretch stress due to glomerular hypertension and are found to produce the excess amount of extracellular matrix (ECM) proteins including fibronectin when exposed to the mechanical stretch. Herein, we provide the evidence that cAMP-generating agents inhibit the stretch-induced overexpression of fibronectin through the inhibition of the stretch-induced activation of mitogen-activated protein kinases (MAPKs) in protein kinase-A-dependent manner. We also found that the mechanical stretch enhanced the binding of nuclear extracts to activator protein-1 (AP-1)-like sequences in the promoter region of rat fibronectin gene and this enhancement was also prevented by the cAMP-generating agent. These results indicate that the agents, which activate cAMP/protein kinase-A axis, may work protectively against the injury from glomerular hypertension in mesangial cells.

Effect of captopril or imidapril on the progression of diabetic nephropathy in Japanese with type 1 diabetes mellitus: a randomized controlled study (JAPAN-IDDM)

OBJECTIVE

to clarify and confirm the renoprotective effects of ACEIs in Japanese type 1 diabetics.

RESEARCH DESIGN AND METHODS

a double-blind randomized study using two ACEIs, imidapril (a prodrug of imdaprilat without an SH-residue) and captopril as well as placebo was performed. Seventy-nine eligible cases were randomized to receive captopril 37.5 mg (n=26), imidapril 5 mg (n=26) or their placebos (n=27) daily in a double-blind manner.

RESULTS

urinary albumin excretion (UAE), determined every half year, was significantly decreased by the ACEIs (placebo vs. ACEIs F=11.316, P=0.001, placebo vs. captopril F=4.260, P=0.043, placebo vs. imidapril F=14.341, P<0.001) during the study period (the mean; 1.48 years). Although the HbA(1C) levels and systolic blood pressure (BP) between the three groups were not different, glycemic and BP control significantly affected UAE. Systolic BP in the placebo group tended to be higher by 7-10 mmHg throughout the study.

CONCLUSIONS

these results suggest that the ACE inhibitors, imidapril and captopril, prevent the increase in UAE in micro and macroalbuminuric patients with type 1 diabetes mellitus and that the target BP might be less than 130/80 mmHg.

Coronary endothelial dysfunction in the insulin-resistant state is linked to abnormal pteridine metabolism and vascular oxidative stress

OBJECTIVES

We investigated whether abnormal pteridine metabolism is related to coronary endothelial dysfunction in insulin-resistant subjects.

BACKGROUND

Depletion of tetrahydrobiopterin (BH(4)) and elevation of the 7,8-dihydrobiopterin (BH(2)) (activating and inactivating cofactors of nitric oxide synthase [NOS], respectively) contribute to impairment of NO-dependent vasodilation through reduction of NOS activity as well as increased superoxide anion generation in insulin-resistant rats.

METHODS

Thirty-six consecutive nondiabetic, normotensive and nonobese subjects with angiographically normal coronary vessels were studied. Traditional coronary risk factors, plasma pteridine levels, activities of erythrocyte dihydropteridine reductase (DHPR), the recycling enzyme that converts BH(2) to BH(4) and lipid peroxide (LPO) levels were measured and coronary endothelial function was assessed with graded infusions of acetylcholine (ACh).

RESULTS

When we divided patients into tertiles based on insulin sensitivity, we observed stepwise decreases in the maximal ACh-induced vasodilation and plasma BH(4)/7,8-BH(2) ratio, and increases in coronary LPO production as insulin sensitivity decreased. The ACh-induced vasodilation was positively correlated with insulin sensitivity, BH(4)/7,8-BH(2) ratio and DHPR activity. Furthermore, BH(4)/7,8-BH(2) was inversely correlated with DHPR activity and insulin sensitivity. In multiple stepwise regression analysis, BH(4)/BH(2) was independently related to ACh-induced vasodilation and accounted for 39% of the variance. However, no significant correlation existed between other traditional risk factors and BH(4)/7,8-BH(2).

CONCLUSIONS

These results indicate that both abnormal pteridine metabolism and vascular oxidative stress are linked to coronary endothelial dysfunction in the insulin-resistant subjects.

Increased arterial wall stiffness limits flow volume in the lower extremities in type 2 diabetic patients

OBJECTIVE

To document an association between arterial wall stiffness and reduced flow volume in the lower-extremity arteries of diabetic patients.

RESEARCH DESIGN AND METHODS

We recruited 60 consecutive type 2 diabetic patients who had no history or symptoms of peripheral arterial disease (PAD) in the lower extremities and normal ankle/brachial systolic blood pressure index at the time of the study (non-PAD group) and 20 age-matched nondiabetic subjects (control group). We used an automatic device to measure pulse wave velocity (PWV) in the lower extremities as an index of arterial wall stiffness. At the popliteal artery, we evaluated flow volume and the resistive index as an index of arterial resistance to blood flow using gated two-dimensional cine-mode phase-contrast magnetic resonance imaging.

RESULTS

Consistent with previous reports, we confirmed that the non-PAD group had an abnormally higher PWV compared with that of the control group (P < 0.001). To further demonstrate decreased flow volume and abnormal flow pattern at the popliteal artery in patients with a higher degree of arterial wall stiffness, we assigned the 60 non-PAD patients to tertiles based on their levels of PWV. In the highest group, magnetic resonance angiograms of the calf and foot arteries showed decreased intravascular signal intensity, indicating the decreased arterial inflow in those arteries. The highest group was also characterized by the lowest late diastolic and total flow volumes as well as the highest resistive index among the groups. From stepwise multiple regression analysis, PWV and autonomic function were identified as independent determinants for late diastolic flow volume (r(2) = 0.300; P < 0.001).

CONCLUSIONS

Arterial wall stiffness was associated with reduced arterial flow volume in the lower extremities of diabetic patients.

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.

Clinical efficacy of fidarestat, a novel aldose reductase inhibitor, for diabetic peripheral neuropathy: a 52-week multicenter placebo-controlled double-blind parallel group study

OBJECTIVE

The purpose of this study was to evaluate the efficacy of fidarestat, a novel aldose reductase (AR) inhibitor, in a double-blind placebo controlled study in patients with type 1 and type 2 diabetes and associated peripheral neuropathy.

RESEARCH DESIGN AND METHODS

A total of 279 patients with diabetic neuropathy were treated with placebo or fidarestat at a daily dose of 1 mg for 52 weeks. The efficacy evaluation was based on change in electrophysiological measurements of median and tibial motor nerve conduction velocity, F-wave minimum latency, F-wave conduction velocity (FCV), and median sensory nerve conduction velocity (forearm and distal), as well as an assessment of subjective symptoms.

RESULTS

Over the course of the study, five of the eight electrophysiological measures assessed showed significant improvement from baseline in the fidarestat-treated group, whereas no measure showed significant deterioration. In contrast, in the placebo group, no electrophysiological measure was improved, and one measure significantly deteriorated (i.e., median nerve FCV). At the study conclusion, the fidarestat-treated group was significantly improved compared with the placebo group in two electrophysiological measures (i.e., median nerve FCV and minimal latency). Subjective symptoms (including numbness, spontaneous pain, sensation of rigidity, paresthesia in the sole upon walking, heaviness in the foot, and hypesthesia) benefited from fidarestat treatment, and all were significantly improved in the treated versus placebo group at the study conclusion. At the dose used, fidarestat was well tolerated, with an adverse event profile that did not significantly differ from that seen in the placebo group.

CONCLUSIONS

The effects of fidarestat-treatment on nerve conduction and the subjective symptoms of diabetic neuropathy provide evidence that this treatment alters the progression of diabetic neuropathy.

Differentiation of immature enterocytes into enteroendocrine cells by Pdx1 overexpression

The development of a variety of enteroendocrine cells of the gut is poorly understood. We tested whether immature intestinal stem cells were switched to multiple enteroendocrine hormone-producing cells by in vitro transfer of a homeobox gene. We transfected the pancreatic-duodenal homeobox 1 gene (Pdx1) into IEC-6 cells, an embryonic intestinal epithelial cell line derived from a normal rat, and selected the cells that overexpressed Pdx1 by 150-fold compared with control. The cells were examined for differentiation into enteroendocrine cells by immunocytochemical and electron microscopic analyses. Transfected cells cultured on micropore filters formed a trabecular network piled up on monolayer cells. These trabecular cells showed nuclear localization of Pdx1 protein and contained well-developed rough endoplasmic reticulum as well as many secretory granules of pleomorphic shape in the cytoplasm. Antibodies against chromogranin A, serotonin, cholecystokinin, gastrin, and somatostatin stained these secretory granules in the cytoplasm. Furthermore, immunofluorescence double staining analysis showed that different hormones were produced within a cell. These results provide the evidence that immature intestinal epithelial cells can differentiate into multiple hormone-producing enteroendocrine cells in response to overexpression of Pdx1.

Endothelin-1 induces cyclooxygenase-2 expression via nuclear factor of activated T-cell transcription factor in glomerular mesangial cells

Nuclear factor of activated T cells (NFAT) originally was identified as a T-cell-specific transcription factor whose activity is regulated by calcineurin, one of the serine-threonine phosphatases. Recent studies have shown that NFAT also is expressed in nonlymphoid cells and plays an important role in various cell functions. It is widely known that treatment with cyclosporin A (CsA), which can inhibit calcineurin/NFAT signaling, results in glomerular dysfunction characterized by a decrease of GFR or glomerulosclerosis, suggesting that NFAT might regulate the glomerular function. However, the precise function of NFAT in glomerular cells remains to be clarified. Herein, evidence has been produced that NFAT2/NFATc, one of five known NFAT isoforms, is expressed in glomerular mesangial cells. Stimulation of mesangial cells with endothelin-1 caused translocation of NFAT2 into the nucleus with a concomitant increase in NFAT2 DNA-binding activity, both of which were inhibited by CsA. Furthermore, CsA inhibited endothelin-1-induced cyclooxygenase-2 (COX-2) expression in mesangial cells. NFAT2 bound directly to the GGAAA sequence, which is the minimal consensus sequence for NFAT binding, in a promoter region of rat COX-2 gene, and it enhanced the reporter activity of rat COX-2 promoter in mesangial cells. These findings provide the first evidence that NFAT2 is expressed and regulates COX-2 gene expression in mesangial cells. These results will contribute to evaluation of the precise roles of NFAT in glomerular functions and the CsA-induced nephrotoxicity.

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.

Insulin-induced c-Jun N-terminal kinase activation is negatively regulated by protein kinase C delta

We investigated the role of protein kinase C (PKC) in insulin-induced c-Jun N-terminal kinase (JNK) activation in rat 1 fibroblasts expressing human insulin receptors. Insulin treatment led to increased SAPK/ERK kinase 1 (SEK1) phosphorylation, and then stimulated JNK activity in a dose- and time-dependent manner, as measured either by a solid-phase kinase assay using glutathione S-transferase (GST)-c-Jun fusion protein as a substrate, or by quantitation of the levels of phosphorylated JNK by Western blotting using anti-phospho-JNK antibody. Insulin-induced JNK activation was potentiated by either preincubating cells with 2 nM GF109203X (PKC inhibitor) or down-regulation of PKC by overnight treatment with 100 nM tetradecanoyl phorbol acetate. In contrast, brief preincubation with 100 nM tetradecanoyl phorbol acetate inhibited the insulin- induced JNK activation. Furthermore, we found that 5 microM rottlerin, a PKCdelta inhibitor, enhanced insulin-induced JNK activation, but a PKCbeta inhibitor, LY333531, had no effect. Consistent with these findings, overexpression of PKCdelta led to decreased insulin-induced JNK activation, whereas overexpression of PKCbeta had no effect. Although overexpression of wild-type PKCdelta attenuated insulin-induced JNK activation, a kinase-dead PKCdelta mutant did not cause such attenuation. Finally, we found that the magnitude of insulin-induced JNK activation was inversely correlated with the expression level of PKCdelta among different cell lines. In conclusion, the expression of PKCdelta may negatively regulate insulin-induced JNK activation.

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.