Nobuyuki Miyatake

Increased Expression of Intercellular Adhesion Molecule-1 (ICAM-1) in Diabetic Rat Glomeruli: Glomerular Hyperfiltration Is a Potential Mechanism of ICAM-1 Upregulation

Mononuclear cells, including monocytes/macrophages and T-cells, are considered to be involved in the progression of diabetic nephropathy, although the mechanism of their recruitment into diabetic glomeruli is unclear. The intercellular adhesion molecule-1 (ICAM-1) promotes the infiltration of leukocytes into atherosclerotic lesions as well as inflammatory tissues. In the present study, we investigated the expression of ICAM-1 in the glomeruli of streptozotocin-induced diabetic rats. The expression of ICAM-1 was increased significantly during the early stage of diabetes. The number of mononuclear cells, primarily monocytes/macrophages and lymphocytes, was significantly increased in diabetic glomeruli. Mononuclear cell infiltration into diabetic glomeruli was prevented by anti-ICAM-1 monoclonal antibody. Insulin treatment decreased ICAM-1 expression and mononuclear cell infiltration. The ICAM-1 expression on cultured human umbilical vein endothelial cells was not induced under high glucose culture conditions. Glomerular hyperfiltration is a characteristic change in the early stage of diabetic nephropathy. Treatment with aldose reductase inhibitor, which prevented glomerular hyperfiltration without changes in blood glucose levels, decreased ICAM-1 expression and mononuclear cell infiltration. Moreover, we examined the ICAM-1 expression in the glomeruli of the 5/6 nephrectomized rat, which is a model for glomerular hyperfiltration without hyperglycemia. The ICAM-1 expression and infiltration of mononuclear cells was significantly increased in the glomeruli of 5/6 nephrectomized rats. We conclude that ICAM-1 is upregulated and promotes the recruitment of mononuclear cells in diabetic glomeruli. Moreover, glomerular hyperfiltration that occurs in the early stage of diabetic glomeruli may be one of the potential mechanisms of ICAM-1 upregulation in diabetic nephropathy.

Nitric oxide system is involved in glomerular hyperfiltration in Japanese normo- and micro-albuminuric patients with type 2 diabetes.

Glomerular hyperfiltration plays a pathogenic role in the early stages of diabetic nephropathy. Experimental studies in laboratory animals suggest that nitric oxide (NO) might be involved in the pathogenesis of glomerular hyperfiltration. We performed a cross-sectional study to determine the relationship between diabetic glomerular hyperfiltration and the NO system. Normoalbuminuric (n=41), microalbuminuric (n=25), and macroalbuminuric (n=16) patients with type 2 diabetes were recruited in this study and compared with age-matched 84 non-diabetic control subjects. Creatinine clearance and urinary NO(2)(-)/NO(3)(-) excretion (urinary NOx) were measured, and the expression of endothelial cell nitric oxide synthase (ecNOS) was evaluated in human renal tissues. Glomerular hyperfiltration was present in 19 (37.5%) and nine (36.6%) of normoalbuminuric and microalbuminuric type 2 diabetic patients, respectively. The urinary NOx was significantly higher in normoalbuminuric patients compared with normal subjects. Creatinine clearance correlated significantly with urinary NOx in normoalbuminuric and microalbuminuric patients. Immunohistochemical staining intensities for ecNOS were significantly increased in glomerular endothelial cells of microalbuminuric type 2 diabetic patients as compared with the control subjects. These results suggest that NO may contribute to the pathogenesis of glomerular hyperfiltration in Japanese type 2 diabetic patients.

Re-evaluation of exercise prescription for Japanese type 2 diabetic patients by ventilatory threshold

Prescription of aerobic exercise for Type 2 diabetes mellitus (Type 2 DM) in clinical practice is frequently based on exercise intensity at maximum heart rate (60<HR(max)<79%), heart rate reserve (50<HR(reserve)<74%), and rating of perceived exertion (12<RPE<13). We examined these parameters in Japanese males with Type 2 DM at ventilatory threshold (VT) to investigate the exercise capacity of Type 2 DM patients and re-evaluate the exercise prescription. Fifty-six Japanese Type 2 DM males without autonomic neuropathy [age, 53.5+/-7.7 years; body mass index (BMI), 23.7+/-3.6 kg/m(2)] were enrolled and compared with 56 age- and BMI-matched healthy Japanese males. VT was determined breath by breath during exercise test using a ramp protocol and rates of oxygen consumption (VO(2)), work rate (WR), HR, DeltaHR, %HR(max), %HR(reserve), and RPE were measured at VT. Type 2 DM patients had significantly lower VO(2) (3.6+/-0.4 metabolic equivalents (METs)) and WR (62+/-14 W) than controls (VO(2), 3.9+/-0.6 METs; WR, 74+/-13 W). %HR(reserve), (32.6+/-7.7%) was also significantly lower compared with controls (37.6+/-8.3%), while %HR(max), was not different. RPE was also similar in diabetics (12.4+/-1.5) and controls (12.9+/-1.2), however, it was significantly lower in diabetic patients aged 60-69 years (11.8+/-2.0) and those with distal symmetric sensory neuropathy (12.2+/-1.0). Our results indicate reduced exercise capacity in Japanese Type 2 DM males and the exercise intensity of 60%HR(max), 30%HR(reserve), and RPE 12 is recommended in elderly diabetics and those with diabetic sensory neuropathy.

Relationship between reduced serum IGF-I levels and accumulation of visceral fat in Japanese men.

OBJECTIVE: To investigate whether the changes in IGF-I concentrations after weight reduction in Japanese overweight men are associated with changes in visceral and subcutaneous fat.DESIGN: Cross-sectional and longitudinal clinical intervention study with exercise education.SUBJECTS: One-hundred and twelve Japanese overweight men aged 30–59u2005y (body mass index (BMI) 28.4±2.5u2005kg/m2) and 33 normal-weight men aged 30–39u2005y (BMI 22.1±1.5u2005kg/m2) at baseline. From the participants, 56 randomly selected overweight men (BMI 28.8±2.8) were further enrolled into a 1u2005y exercise program.MEASUREMENTS: Fat distribution was evaluated by visceral fat (V) and subcutaneous fat (S) areas measured with computed tomography scanning at umbilical levels, metabolic parameters and hormones including insulin, leptin and IGF-I at baseline and after 1u2005y.RESULTS: In 112 overweight subjects at baseline, insulin (10.5±5.0u2005µU/ml) and leptin (6.4±3.7u2005ng/ml) significantly correlated with both V (r=0.260, P=0.0073; r=0.410, P<0.0001) and S areas (r=0.377, P<0.0001; r=0.613, P<0.0001), respectively. IGF-I (156.8±48.7u2005µU/ml) significantly and negatively correlated with V area (r=−0.242, P=0.0125) and age (r=−0.192, P=0.0480). In normal-weight men aged 30–39u2005y (n=33) and age-matched subjects (n=30) selected from the 112 overweight men, the serum IGF-I further tightly correlated with V area (r=−0.467, P<0.0001). Visceral fat area and age were independently related to serum IGF-I levels by multiple regression analysis. By intervention with exercise education, 56 overweight subjects showed an increase in daily steps (6224±2781 to 7898±4141 steps/day) and reduction of BMI (28.8±2.8 to 27.7±2.9). ΔIGF-I significantly correlated with ΔV area (r=−0.432, P=0.0009) but not with ΔS area or ΔBMI.CONCLUSION: The present study indicated a negative correlation between IGF-I levels and visceral fat at baseline as well as an association between the reduction in visceral fat and increase in IGF-I levels after an exercise intervention.

Intercellular Adhesion Molecule 1 Mediates Mononuclear Cell Infiltration into Rat Glomeruli after Renal Ablation

Mononuclear cells, primarily macrophages and lymphocytes, infiltrate the renal glomeruli and are involved in the progression of various glomerular diseases. Intercellular adhesion molecule 1 (ICAM-1) is expressed on the vascular endothelium and mediates the infiltration of leukocytes into the site of inflammation. Although the expression of ICAM-1 can be induced by the stimulation of inflammatory cytokine, ICAM-1 expression can also be induced by such nonimmune mechanisms as shear stress. Glomerular hyperfiltration is a major mechanism that contributes to the progression of the glomerular sclerosis that results from the loss of functioning nephrons. In the present study, we examined the role of ICAM-1 for mononuclear cell infiltration in the glomeruli of the five-sixth nephrectomized rat as a model of glomerular hyperfiltration. The fluorescence intensity score of the staining for ICAM-1 in the glomeruli of the five-sixth nephrectomized rats was significantly increased as compared with that in the control (sham-operated) rats at 1 week (1.51 ± 0.15 vs. 0.61 ± 0.13; p < 0.01) and 2 weeks (1.31 ± 0.17 vs. 0.51 ± 0.09; p < 0.01). The number of leukocytes present in the glomeruli was significantly increased in the five-sixth nephrectomized rats compared with control (sham-operated) rats at 1 week (3.44 ± 0.16 vs. 0.99 ± 0.08; p < 0.01) and 2 weeks (3.14 ± 0.14 vs. 0.89 ± 0.07; p < 0.01). Leukocytes mainly consisted of macrophages in the five-sixth nephrectomized rats at 1 week (2.39 ± 0.19) and 2 weeks (1.46 ± 0.11). Anti-ICAM-1 monoclonal antibody effectively prevented the infiltration of macrophages into the glomeruli following nephrectomy. These results indicate that glomerular hyperfiltration may be involved in the induction of the expression of ICAM-1 and the infiltration of macrophages into the renal glomeruli following glomerular injury.

High-Resolution Ultrastructural Comparison of Renal Glomerular and Tubular Basement Membranes

Background/Aims: Glomerular basement membranes (GBM) and tubular basement membranes (TBM) consist of a fine meshwork composed mainly of type IV collagen. Each segment of tubules has specialized physiologic functions, and thus we investigated the ultrastructure of various basement membranes in rat kidneys. Methods: Since purifying basement membranes from different tubule segments is technically challenging, we employed tissue negative staining rather than conventional negative staining to compare the ultrastructures of proximal and distal TBM and GBM in normal rats. We also assessed the distribution of extracellular matrix components including type IV collagen, laminin, heparan sulfate proteoglycan, and fibronectin in the basement membranes by immunohistochemistry. Results: TBM and GBM of normal rats showed a fine meshwork structure consisting of fibrils forming small round to oval pores. Short- and long-pore diameters in proximal tubules were 3.3 ± 0.5 and 3.9 ± 0.6 nm, respectively, and in distal tubules 3.5 ± 0.7 and 4.3 ± 0.8 nm, respectively. For GBM the respective diameters were 2.5 ± 0.5 and 3.0 ± 0.5 nm. Immunohistochemical analysis showed no significant difference in distribution of extracellular matrix components between proximal and distal TBM. However, immunofluorescence scores of α1 chain of type IV collagen, fibronectin, and laminin were higher in the TBM than in the GBM. On the other hand, heparan sulfate proteoglycan was higher in the GBM. Conclusion: Ultrastructural differences in renal basement membranes may be related to differences in physiologic function in each segment.

Serum bFGF levels are reduced in Japanese overweight men and restored by a 6-month exercise education.

OBJECTIVE: To investigate whether the changes in vascular endothelial growth factor (VEGF) and basic fibroblast growth factor (bFGF) concentrations before and after weight reduction in Japanese overweight men are associated with changes in body mass index (BMI), visceral, subcutaneous fat, VO2 and work rate (WR) at ventilatory threshold (VT).DESIGN: Cross-sectional and longitudinal clinical intervention study with exercise education.SUBJECTS: In total, 30 Japanese overweight men (BMI, 29.0±2.2u2009kg/m2) and 31 normal-weight men (BMI, 22.5±1.6u2009kg/m2) at baseline were enrolled: 30 overweight men (BMI, 29.0±2.2u2009kg/m2) were further enrolled into a 6-month exercise program.MEASUREMENTS: Fat distribution evaluated by visceral fat (V) and subcutaneous fat (S) areas measured with computed tomography scanning at umbilical levels, angiogenic peptides including VEGF and bFGF, exercise tests at baseline and after 6 months.RESULTS: In normal-weight and overweight subjects at baseline, VEGF positively correlated with S area (r=0.350, P=0.007) but not with V area. In contrast, bFGF negatively correlated with BMI (r=−0.619, P<0.001), S (r=−0.457, P<0.001) and V areas (r=−0.466, P<0.001). By intervention with exercise education, 30 overweight subjects showed reduction in BMI (29.0±2.2 to 28.0±2.0, P<0.001), V and S areas, increase in VO2 and WR at VT, increase in bFGF (9.21±5.82–21.2±7.04u2009ng/ml, P<0.001), and no change in VEGF (1.45±0.72–1.88±0.52u2009ng/ml, P=0.016). The stepwise multiple regression analysis revealed that ΔBMI (β=−6.052) and ΔVO2 (β=2.806) were independently related to ΔbFGF (P<0.001) and all other variables including ΔS area, and ΔV area, and ΔWR did not enter the equation at significant levels.CONCLUSION: The present study indicated a negative correlation between serum bFGF levels and BMI at baseline as well as an association of ΔBMI and ΔVO2 with ΔbFGF after exercise intervention. The exercise-induced elevation of bFGF may be beneficial in the prevention of the atherosclerosis in overweight subjects.

Ultrasound assessment of tibial cortical bone acquisition in Japanese children and adolescents

Abstract. The purpose of the present study was to evaluate the normal process of cortical bone acquisition during childhood and adolescence, and the relationship between speed of sound (SOS), measured by the Sound Scan 2000 system, and linear growth. A total of 1689 healthy Japanese children and adolescents (862 males and 827 females, aged 7–19 years) were enrolled in the study. SOS (m/s) was measured at the right tibial midshaft and the standard SOS values in the children and adolescents were generated. Various growth parameters were also measured. SOS of tibia increased significantly with age in both males and females (P < 0.001 each). In both sexes, a spurt in SOS was noted 1 year after the standard age at which Japanese peak height velocity (PHV; cm/year) occurs, and SOS increased markedly after the age at which the length of tibia reached a maximum. Multiple regression equations for SOS were generated as a function of various growth parameters; for males, SOS = 3047 + 6.2 × height (cm) + 2.1 × weight (kg) − 9.8 × length of tibia (cm) (R2 = 0.50; P < 0.001) and for females, SOS = 2713 + 10.3 × height (cm) + 1.8 × weight (kg) − 15.5 × length of tibia (cm) (R2 = 0.49; P < 0.001). In both sexes, SOS correlated positively with body height and weight, but negatively with length of tibia. Our results indicate that SOS is quite useful for evaluating cortical bone status in children and adolescents; the results of these measurements may provide an explanation for the relative weakness of the mechanical properties of the bone during childhood and adolescence.

Differential Distribution of Insulin-Like Growth Factor-1 and Insulin-Like Growth Factor Binding Proteins in Experimental Diabetic Rat Kidney

Insulin-like growth factor-1 (IGF-1) is a peptide growth factor, and its activity is modulated by interaction with the family of IGF binding proteins (IGFBP-1 to 6). IGF-1 is detected in rat kidney and has metabolic and growth effects. To explore the possible involvement of IGFBPs in glomerular hypertrophy in streptozotocin (STZ)-induced diabetic rat, the immunolocalization of IGF-1 and IGFBPs were investigated. IGF-1 was gradually increased in the glomeruli of diabetic rats and correlated with glomerular hypertrophy. IGFBP-1 was transiently increased at 1 week after the STZ injection and declined to control level during the following period. In contrast, IGFBP-4 was increased in the diabetic glomeruli throughout the observation period. With insulin treatment, the levels of IGF-1, IGFBP-1 and 4 were normalized and glomerular hypertrophy was prevented. Initial glomerular hypertrophy of diabetic nephropathy is a related IGF-1 action, which may be modulated by IGFBP-1 and 4.

Relationships of Serum Levels of Insulinlike Growth Factors with Indices of Bone Metabolism and Nutritional Conditions in Hemodialysis Patients

Insulinlike growth factor (IGF) I and IGF-II are synthesized in osteoblasts and stimulate proliferation, differentiation, and matrix synthesis in these cells. There is some evidence that IGFs act on bone cells not only by paracrine but also by endocrine pathways, suggesting that circulating IGFs may be of importance for the regulation of bone metabolism. On the other hand, the serum IGF-I level is also thought to be a good indicator of the nutritional conditions in hemodialysis patients. The present study was performed to analyze the correlations of circulating levels of IGF-I, IGF-II, IGF-binding protein (IGFBP) 1 and IGFBP-3 with biochemical markers of bone metabolism and parameters of the urea kinetic model which reflect nutritional conditions in hemodialysis patients. We also examined the differences between these relationships in male and female patients on hemodialysis. Sixty-two hemodialysis patients, 36 men (male group) and 26 women (female group), were included in this study. We measured the serum levels of IGF-I, IGF-II, IGFBP-1, and IGFBP-3. The bone mineral content (BMC) of the radius was measured by dual-energy X-ray absorptiometry. We calculated Kt/V, protein catabolic rate, and percent creatinine generation rate (%CGR). We also examined the relationships between serum levels of IGFs and BMC and the parameters of the urea kinetic model. It was found that the serum levels of IGF-I in the hemodialysis patients were almost the same as those in the control group. However, the serum levels of IGF-II, IGFBP-1, and IGFBP-3 in the hemodialysis patients were significantly higher than those in the control group. In the male group, the serum IGF-I levels showed a significant correlation with both serum intact parathyroid hormone levels and BMC, but no significant correlations between these indices were found in the female group. The serum levels of both IGF-I and IGF-II showed significant correlations with %CGR in the male group, but not in the female group. Stepwise multiple regression analysis was performed to clarify the relationship between serum levels of IGFs and BMC or %CGR. It was found that age, hemodialysis duration, serum intact parathyroid hormone levels, and sex were independent factors associated with BMC. The %CGR was associated independently with serum levels of IGF-I, and IGF-II and with the presence of diabetes mellitus. In conclusion, it is thought that serum levels of IGF-I and IGF-II can be used as indices of nutritional conditions in hemodialysis patients. However, the serum IGF-I level cannot be used as a marker of bone metabolism in hemodialysis patients.