Glucocorticoids affect metabolic but not muscle microvascular insulin sensitivity following high versus low salt intake.
Level 2 - randomized trial
Randomized, double-blind, crossover clinical trial.
PubMed 32107343 · doi:10.1172/jci.insight.127530
What was done
In 20 lean and 20 abdominally obese individuals, researchers compared the effects of 7-day low-salt versus high-salt diets using a randomized, double-blind, crossover design. They measured 24-hour mean arterial pressure (MAP via ambulatory monitoring), insulin-mediated whole-body glucose disposal (M/I value via hyperinsulinemic-euglycemic clamp), insulin-mediated muscle microvascular recruitment (IMMR via contrast-enhanced ultrasound), osmolyte/water balance, and urinary excretion of glucocorticoids, mineralocorticoids, and amino and organic acids.
What was found
Compared with high-salt intake, low-salt intake resulted in lower MAP, lower M/I values (lower whole-body glucose disposal), and greater IMMR across both lean and abdominally obese participants (exact quantitative values are not reported in the abstract). Log IMMR was inversely associated with MAP only in lean participants on the low-salt diet. High-salt intake decreased free water clearance and increased urinary excretion of glucocorticoids and amino acids involved in the urea cycle.
Why it matters
These findings suggest that salt-induced changes in hemodynamics and insulin sensitivity are uncoupled, supporting the model that high salt intake stimulates glucocorticoid-driven muscle catabolism and glucose uptake to support urea generation for renal water conservation.
Limits
The study is limited by a small sample size (n = 40 total) and a short intervention window (7 days per phase), precluding assessment of long-term metabolic or cardiovascular outcomes. The abstract provides directional findings but lacks exact numerical values, effect sizes, confidence intervals, or statistical p-values.
Cited by
- contradicts Placing a human subject on a high-salt diet can induce insulin resistance within one week.