A cross-sectional study of the peripheral circulation in patients with nephrosis.

Abstract

Background: Lipid abnormalities are a common feature of the nephrotic syndrome that is also characterised by oedema, hypoalbuminaemia, proteinuria, and hypercoagulability. Concern has arisen over the increased incidence of cardiovascular disease that has been reported in individuals with nephrotic syndrome, particularly since the syndrome may occur early in life and become a chronic illness. The presence of proteinuria is a prognostic indicator for the progression of renal disease, but its possible contribution as a cardiovascular risk factor in patients with nephrotic syndrome is not known. In contrast, disordered lipoprotein metabolism, in isolation, is a conventional risk factor for the development of atherosclerosis. An early phase of atherosclerosis, vascular endothelial dysfunction, has been identified. Endothelial function can be measured non-invasively using ultrasonography and plethysmography allowing the impact of risk factors to be assessed in vivo.Aim: To test the hypothesis that endothelial dysfunction occurs in the nephrotic syndrome primarily as a consequence of dyslipidaemia.Methods: A cross-sectional design was used to study vascular function of the peripheral circulation in 45 individuals: fifteen patients with nephrosis (NP), 15 control subjects with primary hyperlipidaemia (HL) and 15 normolipidaernic controls (NC). The groups were matched for age, gender and body mass index. The NP group and the HL group had similar serum lipid and lipoprotein concentrations. High-resolution ultrasonography assessed endothelial function of the brachial artery. This non-invasive technique measured post- ischaemic flow-mediated dilatation (FMD) and endothelium-independent vasodilatation in response to glyceryl trinitrate (GTNMD). Post-ischaemic microcirculatory function was measured using venous occlusion strain gauge plethysmography.Results: Post-ischaemic FMD of the brachial artery was significantly lower in the NP and HL groups, compared with the NC group, with no significant difference found between the former two groups. There were no significant differences in GTNMD of the brachial artery, or in microcirculatory responses. In the patients with nephrosis, non-esterified free fatty acids were inversely associated with FMD, and maximal blood flow with insulin resistance.Conclusion: Dyslipidaemia is associated with endothelial dysfunction in patients with nephrosis and provides a plausible basis for the increased risk of cardiovascular disease observed in individuals with nephrotic syndrome.