BES2005 Poster Presentations Endocrine tumours and neoplasia (46 abstracts)
Leptin and the diurnal rhythm of blood pressure
F Joseph 1 , M Ul-Haq 1 , AM Ahmad 1 , P Whittingham 1 , HD White 1 , AM Wallace 2 , WD Fraser 3 & JP Vora 1
1Department of Diabetes and Endocrinology, Royal Liverpool University Hospital, Liverpool, UK; 2University Department of Pathological Biochemistry, Glasgow Royal Infirmary, Glasgow, UK, 3Department of Clinical Biochemistry, Royal Liverpool University Hospital, UK
Background: Untreated adult growth hormone deficiency (AGHD) is associated with hypertension, obesity and hyperleptinemia. Leptin is linked to obesity related hypertension, is secreted in a circadian rhythm and may contribute to the regulation of BP circadian rhythmicity.
Methods: We studied the relationship between plasma leptin (half hourly samples), ambulatory systolic BP (SBP), diastolic BP (DBP) and mean arterial pressure (MAP) over a 24-h period in 10 AGHD patients (5 women) prior to and following 12 months of (GHR) using cosinor and cross-correlation analysis.
Results: Significant circadian rhythms were observed for SBP, DBP, MAP and leptin (p < 0.001). Secretory pattern of leptin was inversely related to the circadian pattern of SBP, DBP and MAP. Maximal negative correlation prior to and following 12 months of GHR (leptin/SBP, r = -0.9; leptin/DBP, r = -0.9; leptin/MAP, r = -0.9) was observed at 0 lags and 2 lag points (1 hour) respectively. GHR was associated with significant decreases in 24-h mean leptin (1.72±0.03 vs. 1.64±0.03 nmol/liter; P<0.001), SBP (124±1 vs. 121±1 mm of Hg, P<0.001), DBP (78±1 vs. 75±1 mm of Hg; P<0.001) and MAP (93±1 vs. 89±1 mm of Hg; P<0.001). The day time increase in SBP, DBP and MAP (0600-1800) decreased significantly (p < 0.001) and the day time decrease in leptin concentration increased significantly following GHR (p < 0.001).
Conclusions: Leptin secretion and arterial BP appear to be under the control of common rhythm generating factors. Leptin may, in part, negatively regulate the circadian rhythm of BP via peripheral vasodilatory effects. Decrease in mean leptin concentrations following GHR may contribute to the decrease in the mean SBP, DBP and MAP due to a decrease in the centrally mediated pressor effect of leptin. Changes in leptin may partly explain the changes in mean BP and BP circadian rhythm following GHR.
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Endocrine Abstracts
ISSN 1470-3947 (print) | ISSN 1479-6848 (online)
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