Increased prevalence of salt sensitivity of blood pressure in IDDM with and without microalbuminuria

Abstract

In insulin-dependent diabetes mellitus (IDDM) elevated exchangeable sodium (Na) levels are found even in the absence of hypertension, but it is not known whether this is associated with increased sensitivity of blood pressure to sodium level. To clarify this issue we compared 30 patients with IDDM (19 without and 11 with microalbuminuria, i.e. more than 30 mg albumin/day) and 30 control subjects matched for age, gender and body mass index. The subjects were studied on the 4th day of a low-salt diet (20 mmol/day) under in-patient conditions and were subsequently changed to the same diet with a high-salt supplement, yielding a total daily intake of 220 mmol Na/day. Circadian blood pressure, plasma renin activity (PRA), plasma atrial natriuretic factor (p-ANF), plasma cyclic guanosine 5'-phosphate (p-cGMP) and urinary albumin were measured. The proportion of salt-sensitive subjects, i.e. showing increment of mean arterial pressure > or = 3 mmHg on high-salt diet, was 43% in diabetic patients (50% of diabetic patients with and 37% without microalbuminuria) and 17% in control subjects (p < 0.05). Lying and standing PRA levels on low- or high-salt diet were significantly lower in diabetic patients than in control subjects. Salt-sensitive diabetic patients had significantly higher lying ANF on high-salt (38.7 +/- 4.2 pmol/l vs 20.1 +/- 2.3 pmol/l, p < 0.005) than on low-salt diet. The results suggest that (i) the prevalence of sodium sensitivity is high in IDDM (ii) sodium sensitivity is found even in the absence of nephropathy as indicated by albuminuria.

Salt Sensitivity of Blood Pressure

“…76 In contrast, other investigators have failed to detect differences in the ANP responses to high-salt intake between SS and SR subjects, 77 and some actually detected significantly higher levels of ANP in SS than SR, 78 whether on high-(220 mEq/d) or low-(20 mEq/d) salt diets. 79 Finally, opposite to the observations on N-terminal ANP in the Framingham cohort, increased levels of plasma pro-ANP have been shown to be predictors of SSBP in normal volunteers 80 and prehypertensive subjects. 81 This controversial information in humans can be reconciled only if ANP plays a pathogenic role in the BP response to salt in some SS subjects, whereas it is stimulated as a compensatory response to hypertension in others, analogous to the observations in different genetic SS strains of rats.…”

Salt supplementation blunts the blood pressure response to telmisartan with or without hydrochlorothiazide in hypertensive patients with type 2 diabetes

“…Blood pressure levels in patients with diabetes have been observed to be more salt-sensitive than in those without diabetes [20,21]. This may in part be related to the fact that exchangeable sodium is significantly increased in patients with diabetes [8,9].…”

Blood Pressure Does Not Rise Before the Onset of Microalbuminuria in Children Followed From Diagnosis of Type 1 Diabetes

“…Sodium retention could also increase BP by increasing fluid retention and increasing vasoconstriction in response to angiotensin II (27); these are mechanisms that could be enhanced by insulin resistance (27). Sensitivity of BP to sodium is more prevalent in subjects with type 1 diabetes with or without MA (28). Interestingly, a higher diastolic BP SDS was also reported in another group of diabetic children from the U.K., who were compared with European nondiabetic children; however, no difference in systolic BP SDS was detected (29).…”