VASOPROTECTIVE MECHANISMS OF DAIRY-BASED FOODS: A DIETARY INTERVENTION STRATEGY FOR REDUCING CARDIOVASCULAR DISEASE RISK

Open Access
Author:
Alba, Billie Katherine
Graduate Program:
Kinesiology
Degree:
Doctor of Philosophy
Document Type:
Dissertation
Date of Defense:
May 08, 2018
Committee Members:
  • Lacy M. Alexander, Dissertation Advisor
  • W. Larry Kenney, Committee Chair
  • Sara. B Ferguson, Committee Member
  • Lakshmi Santhanam, Committee Member
  • Kelly J. Karpa, Outside Member
Keywords:
  • dairy
  • microcirculation
  • vasodilation
  • sodium
  • cheese
  • milk
  • oxidative stress
  • endothelial function
Abstract:
Endothelial dysfunction is an early and common pathophysiological pathway in the progression of cardiovascular disease. Endothelial function can be improved with non-pharmacological lifestyle-related interventions, including dietary modifications. Increased total dairy consumption is associated with improved measures of vascular health, which may be attributed to the antioxidant and anti-inflammatory properties of dairy-based proteins. However, some dairy foods, specifically cheese, are also high in sodium. High dietary sodium intake is an independent predictor of cardiovascular mortality and is associated with impaired vascular function. It is unclear whether cheese, despite its high sodium content, has beneficial effects on vascular health. The overarching aim of this dissertation is to examine the acute and short-term effects of dairy milk and cheese on vascular function in middle-aged and older adults. Utilizing skin-sensitive methodologies, this dissertation comprises a series of studies that 1) examine the mechanistic and functional effects of dairy milk and cheese on microvascular endothelium-dependent vasodilation and 2) identify the mechanisms by which dairy cheese may protect against sodium-induced endothelial dysfunction. In the first set of studies, we hypothesized that NO-dependent vasodilation, an index of microvascular endothelial function, would be greater following acute dairy milk consumption compared to a non-dairy beverage (rice milk). Contrary to our hypothesis, NO bioavailability was greater following acute rice milk ingestion compared to dairy milk ingestion, which appeared to be mediated by a greater insulin response following rice milk ingestion. We also hypothesized that 1) acute dairy cheese consumption would improve NO-dependent vasodilation compared to ingestion of an equal amount of dietary sodium from non-dairy sources and 2) this improvement would be mediated by a reduction in oxidative stress. Indeed, we found that acute ingestion of sodium in the form of natural cheddar cheese protected against the impairment in NO bioavailability that followed ingestion of sodium from non-dairy sources (pretzels and soy cheese). Further, this protective effect of dairy on sodium-induced endothelial dysfunction was mediated by a reduction in ascorbate-sensitive oxidants. In a follow-up study, we investigated the effects of short-term controlled feeding of a high-cheese diet on sodium-induced endothelial dysfunction. We hypothesized that a high sodium (5500 mg vs 1500 mg) diet would impair endothelium-dependent vasodilation but that a high cheese diet would preserve endothelium-dependent vasodilation that is otherwise impaired by high dietary sodium. We found that the high cheese diet protected against sodium-induced oxidative stress by reducing the accumulation of superoxide radicals, specifically those derived from NADPH oxidase. Collectively, these findings suggest that antioxidant properties of dairy-based nutrients protect against sodium-induced endothelial dysfunction and that inclusion of cheese into the diet may be an effective dietary intervention to mitigate age-related increases in cardiovascular disease risk.