Acute Cheese Consumption Ameliorates Sodium-Induced Cutaneous Microvascular Dysfunction by Reducing Ascorbate-Sensitive Oxidants

Abstract

In epidemiological studies, chronic dairy intake is associated with improved cardiovascular outcomes; conversely, high dietary sodium (Na) consumption impairs endothelial function through increased oxidative stress and reduced nitric oxide (NO)-dependent mechanisms. PURPOSE: To examine if the high Na in cheese has a less negative effect on microvascular dysfunction relative to equivalent Na from non-dairy sources due to the actions of milk-based macronutrients and proteins. We hypothesized that 1) acute dairy based cheese ingestion augments NO-dependent vasodilation (VD) compared to an equal amount of Na from non-dairy sources, and 2) the Na-induced decrease in NO-dependent VD is mediated by oxidant stress mechanisms. METHODS: On 5 separate visits, 14 subjects (61±2 yrs) consumed either 85 g cheddar cheese (560 mg Na), 85 g soy cheese (560 mg Na), 65 g pretzels (560 mg Na), 170 g cheddar cheese (1120 mg Na), or 130 g pretzels (1120 mg Na). Two intradermal microdialysis fibers were inserted in the forearm skin for local delivery of 1) lactated Ringer’s solution (control site) and 2) ascorbate (antioxidant site). Red blood cell flux was measured by laser-Doppler flowmetry (LDF) during local skin heating (42°C) to induce endothelial NO synthase-dependent VD. Once a plateau in cutaneous vascular conductance (CVC = LDF/MAP) occurred, 20 mM L-NAME was perfused at both sites to directly quantify NO-dependent VD. Data were expressed as a percentage of maximum (%CVCmax; 28mM SNP). RESULTS: The total vasodilatory response was not different among the five dietary treatments. NO-dependent VD was higher following dairy cheese consumption compared to a Na-equivalent in soy cheese (59±5 vs. 44±6%; p=0.03) or pretzels (560 mg Na: 59±5 vs. 45±4%; p=0.03, 1120 mg Na: 57±4 vs. 46±5%; p=0.02). Local ascorbate administration abolished these differences (no main dietary treatment effect). CONCLUSION: Na ingestion in cheese was associated with a higher NO-dependent VD compared to an equal amount of non-dairy Na, a difference that was abolished with a local non-specific antioxidant. These data suggest that macronutrients in dairy based cheese may protect against acute Na-induced microvascular dysfunction through antioxidant mechanisms. Supported by Dairy Management Inc.