Regulation of Postprandial Nitric Oxide Bioavailability and Vascular Function By Dairy Fat

Cardiovascular disease (CVD) is the leading cause of death in the United States. Short-term increases in blood sugar, or postprandial hyperglycemia (PPH), affect blood vessel function and increase the risk of CVD. Greater intakes of dairy foods have been associated with a lower risk of CVD, but whether these effects occur directly or indirectly by displacing foods in the diet that might increase CVD risk is unclear. Further controversial is the extent to which dietary fat derived from dairy foods regulate the risk of CVD. The health benefits of dairy on CVD risk are at least partly attributed to its ability to limit PPH and resulting PPH-mediated responses leading to vascular dysfunction. This provides rationale to investigate full-fat containing dairy as a dietary strategy to reduce PPH and risk for heart disease. The objective of this project is to define the extent to which full-fat dairy milk compared to non-fat dairy milk protects against PPH-induced vascular dysfunction by reducing oxidative stress responses that limit nitric oxide bioavailability to the vascular endothelium in adults with prediabetes.

This study consists of three, 3-hour postprandial trials in response to consuming the following dietary treatments: 1. oral glucose challenge, 2. oral glucose challenge in combination with non-fat milk, and 3. oral glucose challenge in combination with whole milk. For three days preceding each trial, participants will be provided all meals to standardize physiologic responses to test meals. On each trial day, vascular function will be assessed and blood samples collected prior to and at 30 minute intervals for 3 hours following test meal ingestion.

Dairy, Milk, Glucose, Postprandial, Hyperglycemia, Prediabetes, Blood glucose, Oxidative stress, Vascular health, Vascular function

This study day will last approximately three hours and will be separated from the other arms by four days for men and one month for women.

This study day will last approximately three hours and will be separated from the other arms by four days for men and one month for women.

This study day will last approximately three hours and will be separated from the other arms by four days for men and one month for women.

Following baseline measurements, participants will consume a 75 g glucose solution within five minutes.

Following baseline measurements, participants will consume 75 g glucose dissolved in two cups of whole fat milk within five minutes.

Following baseline measurements, participants will consume 75 g glucose dissolved in two cups of non-fat milk within five minutes.

Flow mediated dilation (FMD) evaluated on the basis as change from baseline to calculate FMD area under the curve from 0-180 min, i.e. i.e. Area Under the Curve (AUC) of change from baseline in FMD from 0 min to 180 min (i.e., AUC (FMD 0 min- 0 min, FMD 30 min-0 min, FMD 60 min-0 min, etc)

Biomarker of nitric oxide homeostasis is based on the assessment of total nitrite and nitrate concentrations. Changes relative to baseline were used to calculate area under the curve of total nitric oxide metabolites from 0-180 min, i.e. Area Under the Curve (AUC) of change from baseline in nitric oxide homeostasis from 0 min to 180 min (i.e., AUC (NOx 0 min- 0 min, NOx 30 min-0 min, NOx 60 min-0 min, etc)

Glucose concentrations evaluated on the basis as change from baseline to calculate glucose area under the curve from 0-180 min, i.e. Area Under the Curve (AUC) of change from baseline in glucose from 0 min to 180 min (i.e., AUC (glucose 0 min- 0 min, glucose 30 min-0 min, glucose 60 min-0 min, etc)

MDA concentrations evaluated on the basis as change from baseline to calculate MDAarea under the curve from 0-180 min, i.e. Area Under the Curve (AUC) of change from baseline in MDA from 0 min to 180 min (i.e., AUC (MDA 0 min- 0 min, MDA 30 min-0 min, MDA 60 min-0 min, etc)

Inclusion Criteria: hemoglobin A1c 5.7-6.4% non-dietary supplement user no medications affecting vasodilation, inflammation, or energy metabolism no CVD nonsmokers individuals having blood pressure <140/90 mmHg and total cholesterol <240 mg/dL Exclusion Criteria: unstable weight (±2 kg) vegetarian or dairy allergy alcohol intake >3 drinks/day or >10 drinks/week ≥ 7 hours/week of aerobic activity

Mozaffarian D, Benjamin EJ, Go AS, Arnett DK, Blaha MJ, Cushman M, de Ferranti S, Despres JP, Fullerton HJ, Howard VJ, Huffman MD, Judd SE, Kissela BM, Lackland DT, Lichtman JH, Lisabeth LD, Liu S, Mackey RH, Matchar DB, McGuire DK, Mohler ER 3rd, Moy CS, Muntner P, Mussolino ME, Nasir K, Neumar RW, Nichol G, Palaniappan L, Pandey DK, Reeves MJ, Rodriguez CJ, Sorlie PD, Stein J, Towfighi A, Turan TN, Virani SS, Willey JZ, Woo D, Yeh RW, Turner MB; American Heart Association Statistics Committee and Stroke Statistics Subcommittee. Heart disease and stroke statistics--2015 update: a report from the American Heart Association. Circulation. 2015 Jan 27;131(4):e29-322. doi: 10.1161/CIR.0000000000000152. Epub 2014 Dec 17. No abstract available. Erratum In: Circulation. 2015 Jun 16;131(24):e535. Circulation. 2016 Feb 23;133(8):e417.

DECODE Study Group, the European Diabetes Epidemiology Group.. Glucose tolerance and cardiovascular mortality: comparison of fasting and 2-hour diagnostic criteria. Arch Intern Med. 2001 Feb 12;161(3):397-405. doi: 10.1001/archinte.161.3.397.

Ballard KD, Bruno RS. Protective role of dairy and its constituents on vascular function independent of blood pressure-lowering activities. Nutr Rev. 2015 Jan;73(1):36-50. doi: 10.1093/nutrit/nuu013.

Ballard KD, Mah E, Guo Y, Pei R, Volek JS, Bruno RS. Low-fat milk ingestion prevents postprandial hyperglycemia-mediated impairments in vascular endothelial function in obese individuals with metabolic syndrome. J Nutr. 2013 Oct;143(10):1602-10. doi: 10.3945/jn.113.179465. Epub 2013 Aug 21.

McDonald JD, Mah E, Chitchumroonchokchai C, Dey P, Labyk AN, Villamena FA, Volek JS, Bruno RS. Dairy milk proteins attenuate hyperglycemia-induced impairments in vascular endothelial function in adults with prediabetes by limiting increases in glycemia and oxidative stress that reduce nitric oxide bioavailability. J Nutr Biochem. 2019 Jan;63:165-176. doi: 10.1016/j.jnutbio.2018.09.018. Epub 2018 Sep 25.