Basal insulin-level oscillations in normotensive individuals with genetic predisposition to essential hypertension exhibit an irregular pattern

BACKGROUNDInsulin is secreted in regular pulses at intervals of 12–14 min in normal fasting subjects. An abnormal pattern has been found in subjects with non-insulin-dependent diabetes mellitus (NIDDM) and in young individuals predisposed to NIDDM. It has been suggested that there might be a causal relationship between insulin-secretion abnormalities and insulin resistance. OBJECTIVETo examine whether insulin-secretion abnormalities are also present in offspring of patients with essential hypertension. METHODSEleven young (aged 18–35 years) normotensive individuals each of whom had two parents with essential hypertension were compared with 10 age- and sex- matched controls each of whom had two normotensive parents. We verified that diabetes and morbid obesity were absent among the subjects and their parents. We studied basal insulin-secretion patterns during a 60 min period, glucose tolerance by administering an oral glucose-tolerance test, insulin resistance by using an isoglycaemic hyperinsulinaemic clamp and basal plasma catecholamine levels. RESULTSAutocorrelation analysis of insulin concentrations showed that the hypertension-prone subjects had a significantly reduced or irregular oscillatory pattern compared with the regular insulin-level oscillations with a period of 12–14 min in control subjects. The hypertension-prone subjects had significantly higher systolic blood pressures and tended to be insulinresistant. CONCLUSIONThis is the first evidence of early insulin-secretion abnormalities in young normotensive individuals with a genetic predisposition to essential hypertension, but with a normal glucose tolerance and without a genetic predisposition to NIDDM. Early insulin-secretion abnormalities may be the very first step towards the development of insulin resistance and an important factor initiating the hypertension in hypertension-prone individuals.