Diurnal blood pressure profile, autonomic neuropathy and nephropathy in diabetes

Abstract

Given the crucial role of elevated blood pressure (BP) in the progression of diabetic nephropathy, the study of the diurnal variation in BP in diabetes is a surprisingly late phenomenon. It is well documented that the normal night-time drop in BP is reduced in patients with increased urinary albumin excretion (UAE) and in patients with autonomic neuropathy (1). Several recent studies have demonstrated an association between autonomic neuropathy, reduced night-time fall in BP and elevated UAE (2, 3).The question of a possible causative role of autonomic neuropathy in the development of diabetic nephropathy has naturally arisen (2, 3) and was actually coined 10 years ago (4, 5). The proposed pathogenic link is a higher BP burden at night which is more readily transmitted to glomeruli because of renal vasodilation. If true, ambulatory BP monitoring could identify normoalbuminuric patients at risk of progressing to microalbuminuria as those with a disturbed diurnal BP variation. In support of the theory it has been reported that even in normoalbuminuric patients a proportion present abnormal regulation of BP (6). However, we do not know how many of these patients ultimately develop microalbuminuria. The night/day ratio of BP in patients who progress during a 3-year follow-up study overlaps with the values for the non-progressors (7). Diabetes duration is an important confounder, since the night/ day ratio of BP is elevated in very long-term normo¬ albuminuric patients, who a priori are expected to have a favourable prognosis (1, 7). Against the theory is the fact that a substantial number of patients with micro¬ albuminuria show a night/day ratio which is considered normal. Thus a disturbed diurnal BP regulation cannot be decisive for progression to microalbuminuria (8).Furthermore, it should be recognized that the night/day ratio of BP is not a very reproducible parameter and this problem cannot be overcome by remeasurement as easily as for UAE. Therefore it is not plausible that ambulatory BP monitoring will become a sensitive instrument for detecting normoalbuminuric patients at risk of progressing.Alternatively, autonomie neuropathy and blunted diurnal variation of BP could merely be cofactors. According to this view autonomie neuropathy has no independent role in the development of diabetic renal disease (but may promote progression of nephropathy when established). The coexistence of autonomie neuro¬ pathy and nephropathy might be explained by the effects of poor metabolic control on a background of unknown genetic factors. Obviously there is a need for longitudinal studies in normoalbuminuric patients; this should combine information about the evolution of UAE, ambulatory BP and autonomie neuropathy.The discussion of the role of very early autonomie neuropathy in insulin-dependent diabetes mellitus (IDDM) patients closely mimics the classical controversy about the temporal relationship between UAE and BP in incipient diabetic nephropathy (i.e. which is the first to rise?). Our understanding of this relationshi...

Renal functional changes in relation to hemodynamic parameters during exercise test in normoalbuminuric insulin‐dependent children

“…The lack of correlation between RPF and glycemic control, suggests other independent variables involved in renal microvascular changes. Autonomic neuropathy has been thought to be one reason for the increase in intraglomerular pressure (FF) (13). However, the finding of normal resting heart rates and the normal response of HR to exercise together with the results of the 24‐h AMBP suggests a normal parasympathetic activity, hereby excluding an autonomic dysfunction.…”

Ambulatory blood pressure and heart rate in relation to kidney structure and metabolic control in adolescents with Type I diabetes

“…The relation between nephropathy and autonomic neuropathy has been discussed by several authors [29,31,54,55], and could be due to the coexistence of two diabetic complications with a common background, i. e., poor metabolic control or genetic susceptibility. On the other hand, autonomic neuropathy could have a pathophysiological effect of its own and cause renal lesions through higher BP, renal vascular dilation and higher intraglomerular pressure [55±57].…”

Non-dipping in diabetic patients: insights from the siesta

“…link was a higher blood pressure load during the night, which is transmitted to the glomeruli because of renal afferent arteriole vasodilatation. 15,19 An association between non-dipping, autonomic neuropathy and diabetic nephropathy was also described. 20 However, autonomic neuropathy and blunted nocturnal blood pressure decline could merely be cofactors, with no causative role in diabetic nephropathy, representing, for instance, complications of poor glycaemic control.…”

“…20 However, autonomic neuropathy and blunted nocturnal blood pressure decline could merely be cofactors, with no causative role in diabetic nephropathy, representing, for instance, complications of poor glycaemic control. 17,19 The association of non-dipping and diabetes has also been proposed to be related to the more pronounced cardiovascular morbidity in diabetic patients. Hypertensive diabetic patients have higher degree of left ventricular hypertrophy as compared with nondiabetic matched hypertensives.…”