Salt intake and insulin sensitivity in healthy human volunteers.
The literature on salt intake and insulin sensitivity presents a mixed picture, as some studies have shown an increase, whereas others have shown a decrease, in insulin action as sodium intake is enhanced. In some cases, this may relate to the study of salt intake in patients with co-morbidities such as hypertension or diabetes. In the present study, we selected healthy normotensive lean volunteers who underwent a euglycaemic clamp following 6 days of a low-salt diet (20 mmol sodium daily) and, subsequently, 6 days of a high-salt diet (200 mmol sodium daily). Our results show an increase in insulin-mediated glucose disposal during euglycaemic clamp conditions that was significantly higher following the high-salt diet compared with the low-salt diet (7.41+/-0.41 compared with 6.11+/-0.40 mg x kg(-1) of body weight x min(-1) respectively; P=0.03). We measured calf blood flow before and during insulin infusion (no significant change after the two dietary salt interventions was detected) and plasma non-esterified fatty acids (also no significant differences were detected). We observed the expected increases in renin concentration and aldosterone activity in subjects on the low-salt diet, and also observed a significantly less increase in plasma noradrenaline concentration during euglycaemic insulin infusion following the high-salt compared with the low-salt diet. We propose that the 4-5-fold increase in serum aldosterone and the greater increase in plasma noradrenaline concentration following the low-salt intervention compared with the high-salt period may have contributed to the differences in insulin sensitivity following the adjustment in dietary sodium intake.
Townsend
Raymond R
RR
Department of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA. townsend@mail.med.upenn.edu
Kapoor
Shiv
S
McFadden
Christopher B
CB
D000328:Adult; D000450:Aldosterone / Q000097:blood; D001786:Blood Glucose / Q000378:metabolism; D001794:Blood Pressure / Q000187:drug effects; D001835:Body Weight / Q000187:drug effects; D002151:Calorimetry / Q000379:methods; D004039:Diet, Sodium-Restricted; D005230:Fatty Acids, Nonesterified / Q000097:blood; D005260:Female; D015309:Glucose Clamp Technique; D006339:Heart Rate / Q000187:drug effects; D006801:Humans; D007333:Insulin Resistance / Q000502:physiology*; D007866:Leg / Q000098:blood supply; D008297:Male; D009638:Norepinephrine / Q000097:blood; D012039:Regional Blood Flow / Q000187:drug effects; D017673:Sodium Chloride, Dietary / Q000008:administration & dosage* / Q000494:pharmacology
D001786:Blood Glucose; D005230:Fatty Acids, Nonesterified; D017673:Sodium Chloride, Dietary; D000450:Aldosterone; D009638:Norepinephrine