Dietary Sodium Restriction Impairs Insulin Sensitivity in Noninsulin-Dependent Diabetes Mellitus1

Abstract

Dietary sodium restriction has a variety of effects on metabolism, including activation of the renin‐angiotensin system. Angiotensin II has complex metabolic and cardiovascular effects, and these may be relevant to the effects of both nonpharmacological and pharmacological interventions in noninsulin‐dependent diabetes mellitus (NIDDM). We have assessed the effect of dietary sodium restriction on insulin sensitivity and endogenous glucose production in eight normotensive patients with diet‐controlled NIDDM who underwent hyperinsulinemic clamp studies in a randomized, double‐blind, placebo‐controlled cross‐over protocol after two 4‐day periods on sodium replete (160 mmol/day) and sodium deplete (40 mmol/day) diets. Mean +/‐ SD 24‐h urinary sodium was 197 +/‐ 76.0 mmol (replete) and 67 +/‐ 19.5 mmol (deplete), P = 0.03. Insulin sensitivity was 42.0 +/‐ 11.3 mumol/kg.min (replete) and 37.0 +/‐ 11.6 mumol/kg.min (deplete), P = 0.04 (a reduction of 12%). Blood pressure was 130 +/‐ 21/78 +/‐ 11 mmHg (replete) and 128 +/‐ 12/73 +/‐ 10 mmHg (deplete). Dietary sodium restriction may result in a decrease in peripheral insulin sensitivity in normotensive patients with NIDDM, possibly via an elevation in prevailing angiotensin II concentrations.