Studies of cardiovascular and renal function in subclinical and manifest diabetic nephropathy

Cardiovascular and Renal function were examined in two populations of long-term insulin-dependent diabetics, those with microalbuminuria, a sign of early, subclinical nephropathy and those with clinically manifest diabetic nephropathy. In addition, clinical variables of possible importance for the occurrence and prognosis of diabetic nephropathy were analyzed. Microalbuminuria - a mean of three over-night urinary albumin excretion rates greater than 20 micrograms/min - was found in 16% of Albustix-negative, normotensive, insulin-dependent diabetics. The microalbuminurics had higher supine blood pressures than normoalbuminurics. The albumin excretion rate in microalbuminurics correlated to blood pressure at rest but not to glycosylated haemoglobin. The cardiovascular responses to five different test manoeuvres revealed more evident signs of autonomic nerve dysfunction in microalbuminurics than in normoalbuminurics. The circulatory reactions during mental stress however, were almost identical in the two subgroups. Despite similar glomerular filtration rate and renal plasma flow the albumin excretion during mental stress increased in microalbuminurics, but remained unchanged in normoalbuminurics. It is postulated that a disturbance of glomerular basement membrane permeability is a pre-requisite for the elevated albumin excretion seen in microalbuminurics. Inability to regulate glomerular haemodynamics, due to autonomic nerve dysfunction, may also be a contributing factor. Such dysfunction perhaps even explains why microalbuminurics have higher blood pressures at rest compared with normoalbuminurics. In manifest diabetic nephropathy the rate of renal functional decline correlated to arterial blood pressure, while glycemic control showed no such relation. Patients with rapidly progressive nephropathy showed higher values of growth hormone than slow progressors. In patients with diabetic renal failure, cardiac catheterization revealed reduced stroke work and elevated left ventricular end-distolic pressure during exercise. Autonomic nerve dysfunction and arterial hypertension possibly contributed to the impaired cardiac performance. The existence of a specific diabetic cardiopathy must even be considered. There was a male predominance both in subclinical and manifest diabetic nephropathy. Age at onset of diabetes was lower in micro- as compared to normoalbuminurics. Duration of diabetes had no prognostic implication in subclinical or manifest nephropathy. The mortality rate was high in patients with manifest nephropathy.(ABSTRACT TRUNCATED AT 400 WORDS)