Derepression of glomerular filtration, renal blood flow and antioxidant defence in patients with type 2 diabetes at high-risk of cardiorenal disease.

BACKGROUND: The role of antioxidant status on microvascular blood flow and glomerular filtration (eGFR) in patients with type 2 diabetes and hypertension whose risk of progressive renal disease varies by ethnicity is unknown. METHODS: Adult, non-Caucasian (n = 101) and Caucasian (n = 69) patients with type 2 diabetes, hypertension and/or microalbuminuria and an eGFR > 45 mL/min/1.73 m2 were randomised to receive 400 IU vitamin E and/or 20 µg selenium daily or matching placebo. eGFR (CKD-EPI) was measured at baseline, 3,6 and 12 months and renal blood flow by contrast-enhanced ultrasonography in a sub-group (n = 9) at baseline and 3 months by assessing the area under the time intensity curve (TIC). Circulating glutathione peroxidase 3 (GPx-3) activity was measured as a biomarker of oxidative defence status. RESULTS: The time to change in eGFR was shortest with combined vitamin E and selenium than usual care (5.6 [4.0-7.0] vs 8.9 [6.8-10.9 months]; p = 0.006). Area under the TIC was reduced compared to baseline (38.52 [22.41-90.49] vs 123 [86.98-367.03]dB.s; P ≤ 0.05 and 347 [175.88-654.92] vs 928.03 [448.45-1683]dB.s; P ≤ 0.05, respectively] at 3 months suggesting an increase in rate of perfusion. The proportional change in eGFR at 12 months was greater in the group whose GPx-3 activity was above, compared with those below the cohort median (360 U/L) in the non-Caucasian and the Caucasian groups (19.1(12.5-25.7] % vs 6.5[-3.5 to 16.5] % and 12.8 [0.7 to 24] % vs 0.2 [-6.1 to 6.5] %). CONCLUSION: In these patients with type 2 diabetes and early CKD, antioxidant treatment derepresses renal blood flow and a rise in eGFR correlated directly with GPx-3 activity. SIGNIFICANCE: Diabetes mellitus is the world's leading cause of end-stage renal disease which has a predilection for black and minor ethnic groups compared with Caucasians. The differences in risk despite the benefits of conventional care may be related to oxidative stress. We found that glomerular filtration and renal blood flow is suppressed when renal function is preserved in high-risk patients with type 2 diabetes. Conventional care supplemented with selenium - the co-factor for glutathione peroxidase-3 (GPx-3) - improves renal perfusion and increase glomerular filtration according to host antioxidant defence determined by GPx-3 activity. Circulating GPx-3 activity warrants further investigation as a novel biomarker of reversible haemodynamic changes in early diabetic kidney disease to better enable targeting of renoprotective strategies.

Lipopolysaccharide-Induced VEGF Production and Ambient Oxidative Stress in Type 2 Diabetes.

Context: Oxidative stress is implicated in the development of vascular disease and is associated with an upregulation of vascular endothelial growth factor (VEGF), which is pathogenetically linked to the microvascular complications of diabetes. Patients of African origin have an increased susceptibility to microvascular kidney disease compared with white patients; the reasons and mechanisms that contribute to this vulnerability are unclear. Objectives: To investigate whether there are ethnic differences in lipopolysaccharide-induced monocyte VEGF production in whole blood cell cultures. In addition, to assess whether stimulated VEGF production is related to prevailing oxidative stress assessed by plasma lipid hydroperoxides (LOOHs) and α-tocopherol. Design and Setting: Cross-sectional study at a secondary care center in North London, United Kingdom, serving an inner-city community of 154,000 adults. Patients: African-Caribbean and white patients with type 2 diabetes mellitus [(T2DM); n = 52]. Results: Lipopolysaccharide-induced production of VEGF in whole blood cultures [61.8 (31.9) pg/mL to 78.4 (6.0) pg/mL; P < 0.001] correlated positively with LOOH levels (r = 0.3, P = 0.04) and was significantly higher in African-Caribbean than white patients with T2DM [404 (207.5) vs 268.8 (137.0)] pg/mL ×109/L monocytes; P = 0.018]. Plasma α-tocopherol concentration was higher in Caucasian (white) patients [40.3 (18.3) vs 30.0 (9.6)] µmol/L; P = 0.04] compared with African-Caribbean patients. Conclusions: This study suggests that the redox environment influences VEGF production in response to proinflammatory stimuli in T2DM. The differential responsiveness by ethnic origin may be of relevance in the variations in susceptibility to the long-term microvascular complications.

Ethnic differences in the +405 and -460 vascular endothelial growth factor polymorphisms and peripheral neuropathy in patients with diabetes residing in a North London, community in the United Kingdom.

BACKGROUND: There are marked ethnic differences in the susceptibility to the long-term diabetic vascular complications including sensory neuropathy. The vascular endothelial growth factor (VEGF) +405 (C/G) and -460 (T/C) polymorphisms are associated with retinopathy and possibly with nephropathy, however no information is available on their relationship with peripheral neuropathy. Therefore, we examined the prevalence of these VEGF genotypes in a multi-ethnic cohort of patients with diabetes and their relationship with evident peripheral diabetic neuropathy. METHODS: In the current investigation, we studied 313 patients with diabetes mellitus of African-Caribbean, Indo-Asian and Caucasian ethnic origin residing in an inner-city community in London, United Kingdom attending a single secondary care centre. Genotyping was performed for the VEGF +405 and VEGF -460 polymorphisms using a pyrosequencing technique. RESULTS: Forty-nine patients (15.6%) had clinical evidence of peripheral neuropathy. Compared to Caucasian patients, African-Caribbean and Indo-Asian patients had lower incidence of neuropathy (24.6%, 14.28%, 6.7%, respectively; P = 0.04). The frequency of the VEGF +405 GG genotype was more common in Indo-Asian patients compared to African-Caribbean and Caucasian patients (67.5%, 45.3%, 38.4%, respectively; p ≤ 0.02). The G allele was more common in patients with type 2 diabetes of Indo-Asian origin compared to African-Caribbean and Caucasian origin (p ≤ 0.02). There was no difference between the ethnic groups in VEGF -460 genotypes. The distributions of the VEGF +405 and VEGF -460 genotypes were similar between the diabetic patients with and without neuropathy. CONCLUSIONS: In this cohort of patients, VEGF +405 and VEGF -460 polymorphisms were not associated with evident diabetic peripheral neuropathy, however an association was found between VEGF +405 genotypes and Indo-Asian which might have relevance to their lower rates of ulceration and amputation. This finding highlights the need for further investigation of any possible relationship between VEGF genotype, circulating VEGF concentrations and differential vulnerability to peripheral neuropathy amongst diabetic patients of different ethnic backgrounds.

Telemonitoring: use in the management of hypertension.

Hypertension is a major modifiable risk factor for cardiovascular, retinal, and kidney disease. In the past decade, attainment rates of treatment targets for blood pressure control in the UK and US have increased; however, <11% of adult men and women have achieved adequate blood pressure control. Technological advances in blood pressure measurement and data transmission may improve the capture of information but also alter the relationship between the patient and the provider of care. Telemonitoring systems can be used to manage patients with hypertension, and have the ability to enable best-practice decisions more consistently. The improvement in choice for patients as to where and who manages their hypertension, as well as better adherence to treatment, are potential benefits. An evidence base is growing that shows that telemonitoring can be more effective than usual care in improving attainment rates of goal blood pressure in the short-to-medium term. In addition, studies are in progress to assess whether this technology could be a part of the solution to address the health care needs of an aging population and improve access for those suffering health inequalities. The variation in methods and systems used in these studies make generalizability to the general hypertension population difficult. Concerns over the reliability of technology, impact on patient quality of life, longer-term utility and cost-benefit analyses all need to be investigated further if wider adoption is to occur.

Defective nitric oxide production and functional renal reserve in patients with type 2 diabetes who have microalbuminuria of African and Asian compared with white origin.

Diabetic nephropathy is a leading cause of end-stage renal failure. Its incidence is higher and is increasing in persons of Indo-Asian and African-Caribbean (African-Asian) compared with those of white origin. Nitric oxide deficiency is associated with progressive renal disease. It was hypothesized that differences in the capacity to increase glomerular filtration (functional renal reserve) would exist between these racial groups in relation to nitric oxide availability. Patients with type 2 diabetes of African-Asian (n = 9) and white (n = 9) origin with microalbuminuria were studied under euglycemic conditions. Glomerular filtration, renal plasma flow, and clearance of the stable metabolites of nitric oxide, nitrite, and nitrate were measured before and after a renal vasodilatory stimulus of a mixed amino acid intravenous infusion. There were no significant differences in age, duration of diabetes, and baseline glomerular filtration (57.1 [14.1] versus 55.8 [10.1] yr; P = 0.82, 14.5 [10.2] versus 9.1 [7.0] yr; P = 0.19 and 125.9 [30.9] versus 127.2 [44.6] ml/min per 1.73 m(2); P = 0.94) between the African-Asian and white groups. Functional renal reserve, change in renal plasma flow, and percentage change in nitrate and nitrite clearance was significantly higher in the white compared with the African-Asian group (21.9 [45.7] versus -2.5 [28.2] ml/min per 1.73 m(2); P = 0.043, 155.8 [205.9] versus -90.1 [146.0]; P = 0.03 ml/min per 1.73 m(2) and 26.7 [85.1] versus -44.7 [16.9] %; P = 0.013, respectively). The differences in functional reserve were not confounded after adjustment for diabetes duration (P = 0.034). The data suggest that these patients with type 2 diabetes of African and Asian origin lose functional renal reserve earlier in the evolution of nephropathy than whites. The differences appear to be due to defective nitric oxide production or bioavailability and might explain some of the propensity to develop end-stage renal disease.