The association between circulating endostatin and a disturbed circadian blood pressure pattern in patients with type 2 diabetes

Background: Endostatin, cleaved from collagen XVIII in the extracellular matrix, is a promising circulating biomarker for cardiovascular damage. It possesses anti-angiogenic and anti-fibrotic functions and has even been suggested to be involved in blood pressure regulation. Less is known if endostatin levels relate to circadian blood pressure patterns. In the present paper we studied the association between circulating levels of endostatin and nocturnal dipping in blood pressure.Methods: We used the CARDIPP-study, a cohort of middle aged, type 2 diabetics (n=593, 32% women), with data on both 24-hour and office blood pressure, serum-endostatin, cardiovascular risk factors, and incident major cardiovascular events. Nocturnal dipping was defined as a >10% difference between day- and night-time blood pressures.Results: Two-hundred four participants (34%) were classified as non-dippers. The mean endostatin levels were significantly higher in non-dippers compared to dippers (meanstandard deviation: 62.6 +/- 1.8 mu g/l vs. 58.7 +/- 1.6 mu g/l, respectively, p=.007). Higher serum levels of endostatin were associated with a diminished decline in nocturnal blood pressure adjusted for age, sex, HbA1c, mean systolic day blood pressure, hypertension treatment, glomerular filtration rate, and prevalent cardiovascular disease (regression coefficient per SD increase of endostatin -0.01, 95% CI, -0.02-(-0.001), p=.03). Structural equation modelling analyses suggest that endostatin mediates 7% of the association between non-dipping and major cardiovascular events.Conclusion: We found an independent association between higher circulating levels of endostatin and a reduced difference between day- and night-time systolic blood pressure in patients with type 2 diabetes. Yet endostatin mediated only a small portion of the association between non-dipping and cardiovascular events arguing against a clinical utility of our findings.