Reduced LRP6 expression and increase in the interaction of GSK3ß with p53 contribute to podocyte apoptosis in diabetes mellitus and are prevented by green tea.

In diabetes mellitus (DM), podocyte apoptosis leads to albuminuria and nephropathy progression. Low-density lipoprotein receptor-related protein 6 (LRP6) is WNT pathway receptor that is involved in podocyte death, adhesion and motility. Glycogen synthase kinase 3 (GSK3) interaction with p53 (GSK3-p53) promotes apoptosis in carcinoma cells. It is unknown if GSK3-p53 contributes to podocyte apoptosis in DM. In experimental DM, green tea (GT) reduces albuminuria by an unknown mechanism. In the present study, we assessed the role of the GSK3ß-p53 in podocyte apoptosis and the effects of GT on these abnormalities. In diabetic spontaneously hypertensive rats (SHRs), GT prevents podocyte's p-LRP6 expression reduction, increased GSK3ß-p53 and high p53 levels. In diabetic SHR rats, GT reduces podocyte apoptosis, foot process effacement and albuminuria. In immortalized mouse podocytes (iMPs), high glucose (HG), silencing RNA (siRNA) or blocking LRP6 (DKK-1) reduced p-LRP6 expression, leading to high GSK3ß-p53, p53 expression, apoptosis and increased albumin influx. GSK3ß blockade by BIO reduced GSK3ß-p53 and podocyte apoptosis. In iMPs under HG, GT reduced apoptosis and the albumin influx by blocking GSK3ß-p53 following the rise in p-LRP6 expression. These effects of GT were prevented by LRP6 siRNA or DKK-1. In conclusion, in DM, WNT inhibition, via LRP6, increases GSK3ß-p53 and podocyte apoptosis. Maneuvers that inactivate GSK3ß-p53, such as GT, may be renoprotective in DM.

Retinal nerve fibre layer loss in patients with type 1 diabetes mellitus without retinopathy.

BACKGROUND/AIM: There is evidence suggesting the occurrence of neurovisual abnormalities in patients with diabetes without retinopathy. However, the determination of abnormalities in the neural and glial elements in vivo is difficult. The aim of this study was to investigate whether a retinal nerve fibre layer (RNFL) defect (as determined by scanning laser polarimetry, SLP) is present in patients without clinical manifestations of diabetic retinopathy. METHODS: 12 patients with type 1 diabetes mellitus (DM) without retinopathy or other diabetes induced microvascular complications, underwent a complete ophthalmological examination, including automated perimetry and RNFL measurements with a nerve fibre layer analyser GDx. The data were compared with a normal control group matched for age and sex. RESULTS: The superior segment retardation in patients with diabetes was lower than in the control group, based on the superior integral (0.19 (SD 0.06) v 0.23 (0.04) mm(2), p=0.03) and the superior average (71.0 (11.05) v 84.27 (10.56) microm, p=0.007) parameters. CONCLUSION: This finding may be indicative of significant nerve fibre loss in the superior segment of the retina in patients with type 1 diabetes mellitus but without retinopathy. The meaning of intraretinal differences in RNFL retardation, indicating asymmetric NFL loss, in patients with diabetes is yet not understood.

Neurovisual abnormalities preceding the retinopathy in patients with long-term type 1 diabetes mellitus.

BACKGROUND: Changes in the retina caused by diabetes may lead to visual impairment in dim light, even with good visual acuity and visual fields. To evaluate the visual abnormalities preceding the retinopathy in patients with type 1 diabetes mellitus (DM), we applied electrophysiological methods. METHODS: The visual evoked responses were recorded with sinusoidally modulated vertical gratings at 10 spatial frequencies presented sequentially on a high-resolution monitor in patients with type 1 DM and in normal volunteers. Similarly, the contrast visual evoked responses of 10 contrast levels were recorded at five spatial frequencies. Both amplitudes at the second harmonic were calculated by discrete Fourier transform. The visual acuity and contrast thresholds were determined objectively. RESULTS: There was dissociation between the Snellen and the estimated visual evoked response acuity measurements in patients with diabetes (r2=0.077, P=0.44). The saturation phenomena were observed at lower levels of contrast stimuli than in normal individuals at. 1.0, 2.0, 4.0 and 8.0 cycles per degree (P=0.0001). The contrast sensitivity function was deeply abnormal in all tested patients despite the metabolic control. The values of the area under the curve of the visual evoked response amplitude-contrast level function at five spatial frequencies were smaller in patients with DM than in the control group (P<0.05) at all spatial frequencies tested. CONCLUSIONS: Patients with type 1 DM without retinopathy showed significant lower amplitude of the visual evoked responses at all spatial frequencies tested, with the saturation phenomena observed at lower level of contrast stimuli. In addition, there was a dissociation between the sweep visual evoked responses and the Snellen acuity measurements. A significant and nonselective neuronal visual loss involving the visual pathway precedes the ophthalmoscopically detectable retinopathy in patients with type 1 DM.

Erythrocyte sodium-lithium countertransport and proliferative diabetic retinopathy.

PURPOSE: To investigate whether elevated erythrocyte Na+/Li+ countertransport (Na+/Li+ CT) activity is present in patients with proliferative diabetic retinopathy (PDR). METHODS: The rate of Na+/Li+ CT activity assayed in 21 patients with type 1 diabetes mellitus (DM) presenting PDR was compared with 10 patients with nonproliferative retinopathy (NPDR) and with 11 patients with normal fundi. Twelve normal volunteers with no family history of hypertension were used as a control group. The albumin excretion rate was determined by nephelometry, and the glomerular filtration rate was measured by the plasma clearance of eidetic acid labeled with chromium-51. RESULTS: Patients with PDR showed higher diastolic blood pressure levels (mean +/- SD) compared with those with NPDR or normal fundi (95 +/- 13 versus 90 +/- 09 and 82 +/- 19 mm Hg, P = 0.02, respectively). The albumin excretion rate was higher [geometric mean (range)], and the glomerular filtration rate was lower (mean +/- SD) in patients with PDR than in those with NPDR or normal fundi [333 (2 to 5140) versus 32 (5.9 to 2200) and 6 (1.5 to 306) microg/min, P = 0.01, and 63 +/- 33 versus 99 +/- 37 and 93 +/- 43 ml/min, P = 0.02, respectively]. The mean Na+/Li+ CT in patients with PDR was significantly higher than in patients with NPDR or normal fundi and control group (0.46 +/-0.20 versus 0.32 +/- 0.12, 0.32 +/- 11, and 0.21 +/- 0.07 mM/L red blood cells (RBC)/h, respectively, P = 0.0001). In a multiple logistic regression analysis, with PDR as the dependent variable, Na+/Li+ CT (odds ratio [OR]: 4.7, confidence interval [CI]: 1.2-17.6, P = 0.02), diastolic blood pressure (OR, 3.4; CI, 1.3 to 9.6; P = 0.018), and glomerular filtration rate (OR, 5.1; CI, 1.6-17.7; P = 0.007) were the only variables that were maintained in the equation, indicating that they were the main determinants of PDR. CONCLUSIONS: Patients with type 1 DM and proliferative retinopathy have elevated erythrocyte Na+/Li+ CT.

Diabetic macular edema: risk factors and concomitants.

PURPOSE: To investigate the systemic and ocular factors associated with diffuse macular edema in patients with diabetic retinopathy (DR) and compare with patients with focal or no macular edema. METHODS: From 160 consecutive patients with DR, we obtained medical and ocular histories, blood pressure and visual acuity. Macular edema was determined by biomicroscopy and stereoscopic fundus photography. Fluorescein angiography was used in the characterization of its leakage, and the vitreoretinal relationship was performed by preset lens biomicroscopy. RESULTS: Among adult-onset diabetes mellitus (DM) patients, 55% had diffuse, 23.5% had focal and 21.5% had no macular edema (p=0.01). The risk of developing diffuse macular edema was 3.2 times greater in patients with high blood pressure (HBP) (95% confidence interval (CI), 1.5 to 6.9). Patients with cardiovascular disease (CVD) had a higher prevalence of diffuse (58.0%) than focal (26.0%) or no maculopathy (16.0%) (p=0.01). The odds for development of diffuse macular edema was 3.4 times greater in patients with vitreomacular adhesion (95% CI, 1.15 to 13.30) than in those with complete posterior vitreoretinal attachment or vitreoretinal separation. The odds for development of diffuse macular edema were 6.2 (95% CI, 1.83 to 21.04) and 7.7 times greater (95% CI, 3.12 to 19.12) in patients with PPDR and PDR, respectively, in comparison with those with NPDR. CONCLUSIONS: In this study, adult-onset DM, HBP, CVD, vitreomacular adhesion and advanced retinopathy were associated with increased risk of development of diffuse diabetic macular edema.

Effects of stimulus blocking, light scattering, and distortion on multifocal electroretinogram.

PURPOSE: To investigate how the multifocal electroretinogram (ERG) is altered in conditions of blocking, light scattering, or distortion of the stimulus that are seen in ocular pathologies. METHODS: A central 40 degree-diameter stimulus pattern consisting of 61 hexagons was presented on a cathode ray tube monitor at a rate of 75 Hz according to the pseudo-random binary M sequence by the Veris computer program. Localized responses corresponding to each hexagon and ERG topographies were displayed on the computer screen. Central scotoma was simulated by blocking the central area of the stimulus, visual field constriction by blocking the outer area of the stimulus, mild cataract by using acrylic filters that caused light scatter, and epiretinal membrane by using a wavy plastic plate that produced metamorphopsia. RESULTS: The responses from the blocked area were nonrecordable whether blockage was central or peripheral; responses from the adjacent unblocked area had a larger amplitude when large areas of the stimulus were blocked. The light scatter that decreased vision from 20/20 to 20/70 did not significantly decrease response amplitudes. Responses from areas in which the stimulus pattern was distorted were minimally affected. CONCLUSIONS: The results show that the system records local ERGs from the macula and outside the macula. It can detect the area where the stimulus is blocked. Moderate light scattering and distortion do not cause loss of local ERG characteristics.

Objective measurement of contrast sensitivity function using contrast sweep visual evoked responses.

AIM/BACKGROUND: The contrast sensitivity function (CSF) measurement provides information that is not accessible by standard visual acuity determinations. The contrast sweep pattern reversal visual evoked responses (CSVER) technique was used to objectively measure the CSF in clinical practice. METHODS: The contrast thresholds were measured at five spatial frequencies in 10 normal subjects. The CSVER were recorded with sinusoidally modulated vertical gratings at 10 contrast levels (96, 64, 48, 32, 16, 8, 4, 2, 1, and 0.5%) presented in five spatial frequencies (0.5, 1.0, 2.0, 4.0, and 8.0 cycles per degree). Each of 10 contrast levels was displayed for 2 seconds at the desired spatial frequency. The CSVER amplitudes at the second harmonic were calculated by discrete Fourier transform. The results were compared with those obtained using a psychophysical method. RESULTS: An inverted U-shaped CSF which peaked at 2.0 cycles per degree with a contrast sensitivity of 34.5 (contrast, 2.9%) was observed. The CSF assessed electrophysiologically was 0.62 to 0.79 log units lower than the sensitivity measured using the psychophysical method. However, the overall shapes were highly correlated. CONCLUSION: One can objectively measure CSF with CSVER and this may be useful in patients in whom the psychophysical method is limited.

Comparison of Snellen acuity and objective assessment using the spatial frequency sweep PVER.

BACKGROUND: We compared the vision objectively assessed by spatial frequency sweep pattern-reversal visual-evoked response (SPVER) with the Snellen acuity in patients. METHODS: SPVER acuity and Snellen acuity were measured in 100 patients with various ocular pathologies, including macular diseases, diffuse retinal degeneration, optic nerve diseases, glaucoma, and high myopia. For SPVER, 10 sinusoidally modulated vertical gratings were presented as stimuli. The responses were averaged and displayed through the discrete Fourier transform on the monitor display. The PVER acuity was determined by extrapolating the SPVER amplitude-spatial frequency function to baseline. RESULTS: Vision ranged from 20/15 to 20/400 with Snellen acuity, and from 20/25 to 20/190 with SPVER. The overall correlation between the two acuities was r = 0.666. The correlation varied from r = 0.895 in eyes with glaucoma to r = 0.436 in eyes with optic nerve disease. Seventy-seven eyes (77%) had a visual acuity agreement of within 1.0 octave between the two measurements. CONCLUSION: The SPVER acuity and the Snellen acuity correlated to a certain degree. Discrepancies were found in certain diseases, with the highest disparity in patients with optic nerve disease. We conclude that the SPVER is effective in estimating vision objectively, particularly in patients in whom the standard Snellen test is impossible to perform or yields unreliable results.