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Kadambari S. Oswal, Ranjit Gidda, Atul Bansal, Peter Nightingale, Paul M. Stewart, Philip I. Murray, Graham R. Wallace, Saaeha Rauz; Metabolites and Lifestyle - A Link with Primary Open Angle Glaucoma?. Invest. Ophthalmol. Vis. Sci. 2012;53(14):5014.
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Several studies have linked hypertension and primary open angle glaucoma (POAG). A principal determinant of net sodium transport is the epithelial sodium channel (ENaC). A read out for sustained increases in ENaC activity due to mineralocorticoid excess is suppression of plasma renin activity. This is frequently seen in African-Caribbean (Black) populations and might explain their susceptibility to POAG. The aim of this study was to examine the relationship of biochemical, hormonal and metabolite profiles to lifestyle in patients with POAG.
POAG patients were enrolled and where possible, spouses/partners served as robust controls. All participants completed a validated lifestyle questionnaire. Intraocular pressure (IOP) and blood pressure (bp) readings were taken in triplicate, body mass index (BMI) and waist/hip ratio (WHR) were recorded. Plasma renin activity (PRA) and plasma aldosterone along with urinary steroid metabolites (THF, 5αTHF-tetrahydrocortisols; THE-tetrahydrocortisone) and urinary free cortisol and cortisone (UFF, UFE) were measured.
The 137 participants consisted of 105 glaucoma (70 white (WP), 35 black (BP) M:F 60:45)) and 32 controls (25 white (WC), 7 black (BC) M:F 18:14)), of whom 76 had hypertension (patients:controls 61:15). Results are presented for right eye only (as both eyes correlated). There was no statistical difference in the (THF+5αTHF)/THE or UFF/UFE ratios, IOP, systolic bp, diastolic bp, WHR, serum creatinine and plasma aldosterone between groups. However, urinary DHEA was significantly increased in BP as compared to WP (521 ± 782 vs 176 ± 245 µg/24hrs, p=0.004), and in BC vs WC (693 ± 524 vs 148 ± 188, p=0.014). PRA was lower in both in BP and BC (mean ± SD,1.4 ± 4.0 and 0.3 ± 0.3 ng/ml/hr) when compared to WP and WC (mean ± SD,1.7 ± 3.2 and 4.6 ± 11.4, p=0.005 and p=0.044), respectively. In BP only, IOP correlated significantly with total urinary cortisol metabolites (r=0.45, p=0.007) and total urinary cortisone metabolites (r=0.49, p=0.003). BP also had more advanced visual field loss (Mean deviation BP -9.4 ± 8.6 vs WP -6 ± 6.7, p=0.04) and were likely to be on more than 3 glaucoma medications (BP 19/35 (54.3%) vs WP 19/70 (27.1%) eyes, p=0.009). There was a correlation between smoking (pack-years) and alcohol intake (units/week) in all glaucoma patients irrespective of ethnic origin (all patients r=0.32, p=0.001; WP r=0.28, p=0.01; BP r=0.47, p=0.004) but not in controls.
BP with POAG have more advanced visual field loss and are more likely to require multiple topical treatments for glaucoma. WP had lower PRA than WC while all Black participants had a low PRA, independent of POAG status. Raised DHEA may play a role in BP having more severe glaucoma.
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