Obesity is a risk factor for atherosclerosis and is a major cause of morbidity and mortality in the United States. Endothelium derived nitric oxide (NO) a key regulator of arterial homeostasis is lost in the early stages of atherosclerosis. Reduced NO bioavailability during obesity involves increased generation of reactive oxygen species (ROS) that scavenge NO. Most studies indicate that diet induced weight loss, the cornerstone of weight management strategies, improves endothelial function. The benefits of the recently popularized low carbohydrate (LC), Atkins'diet, on endothelial health are controversial since they require strict reductions of carbohydrate intake at the expense of high dietary fat content. For instance, a recent study in our laboratory showed divergent effects of isocaloric LC and low fat (LF) diets on NO- mediated endothelium- dependent flow mediated dilation (FMD). While FMD was improved on a LF diet, it was impaired on a LC diet suggesting that the potential benefits of weight loss on NO are negated on LC. The overall hypothesis of this study is that low carbohydrate diets reduce the benefits of weight loss on endothelial function by lowering the protective effect of adiponectin against endothelial reactive oxygen species generation compared to isocaloric low fat diets. Thus, LC diets impair NO- mediated endothelium-dependent dilation of isolated peripheral resistance arteries. This hypothesis is supported by preliminary data indicating adiponectin is reduced and resistance artery endothelial function is impaired on LC diets. This will be tested with a prospective, randomized, 6 week feeding trial in obese (BMI: 30- 39) subjects ages 18-40. Low fat or Low carbohydrate diets will be administered at caloric thresholds designed to either lose or maintain weight in each group. Endothelial- dependent vasodilation will be determined in isolated resistance arteries obtained from subcutaneous fat biopsies before and after 6 weeks of dietary intervention.
In aim 1 we will determine the contribution of endothelial oxidant systems on reduced NO- mediated endothelial function in resistance arteries during low carbohydrate diets compared to isocaloric low fat diets.
In aim 2 we will determine whether low carbohydrate diets increase pro-atherogenic adipokines, decrease anti-atherogenic adipokines, or both.
In aim 3 we will test whether adiponectin improves endothelial function in resistance arteries of subjects on low carbohydrate diets and whether the mechanism involves eNOS regulation (phosphorylation) or superoxide dismutase expression. Pharmacologic inhibitors, fluorescent probes for ROS and NO, HPLC, and molecular approaches of measuring enzyme expression will determine the site and source of ROS and NO production in vascular tissue. Adipokine mediated endothelial dysfunction has been linked to high fat intake and if confirmed on a low carbohydrate diet will provide clinically important information regarding the mechanisms whereby diets differing in macronutrient contents can be optimized to improve vascular function during weight loss. These results will begin to address how lifestyle interventions that optimize adiponectin may be used to prevent the vascular risks associated with diets high in fat.

Public Health Relevance

Obesity is a risk factor for heart disease and a major cause of death and disability in the United States. A variety of weight loss strategies have gained attention including traditional Low Fat (LF) and the recently popularized Low Carbohydrate (LC) diets. The proposed feeding trial will examine the impact of 6 weeks of LF and LC diets designed for body weight loss and maintenance on vascular endothelial function (an early prognostic indicator of the propensity for heart disease) in young men and women.

Agency
National Institute of Health (NIH)
Institute
National Heart, Lung, and Blood Institute (NHLBI)
Type
Research Project (R01)
Project #
3R01HL095701-01A2S1
Application #
8260442
Study Section
Clinical and Integrative Cardiovascular Sciences Study Section (CICS)
Program Officer
Arteaga, Sonia M
Project Start
2010-08-13
Project End
2015-07-31
Budget Start
2011-05-01
Budget End
2011-07-31
Support Year
1
Fiscal Year
2011
Total Cost
$16,495
Indirect Cost
Name
University of Illinois at Chicago
Department
Other Health Professions
Type
Schools of Allied Health Profes
DUNS #
098987217
City
Chicago
State
IL
Country
United States
Zip Code
60612
Sudhahar, Varadarajan; Okur, Mustafa Nazir; Bagi, Zsolt et al. (2018) Akt2 (Protein Kinase B Beta) Stabilizes ATP7A, a Copper Transporter for Extracellular Superoxide Dismutase, in Vascular Smooth Muscle: Novel Mechanism to Limit Endothelial Dysfunction in Type 2 Diabetes Mellitus. Arterioscler Thromb Vasc Biol 38:529-541
Robinson, Austin T; Fancher, Ibra S; Mahmoud, Abeer M et al. (2018) Microvascular Vasodilator Plasticity After Acute Exercise. Exerc Sport Sci Rev 46:48-55
Das, Emon K; Lai, Pui Y; Robinson, Austin T et al. (2018) Regular Aerobic, Resistance, and Cross-Training Exercise Prevents Reduced Vascular Function Following a High Sugar or High Fat Mixed Meal in Young Healthy Adults. Front Physiol 9:183
Mahmoud, Abeer M; Ali, Mohamed M; Miranda, Edwin R et al. (2017) Nox2 contributes to hyperinsulinemia-induced redox imbalance and impaired vascular function. Redox Biol 13:288-300
Zinkevich, Natalya S; Fancher, Ibra S; Gutterman, David D et al. (2017) Roles of NADPH oxidase and mitochondria in flow-induced vasodilation of human adipose arterioles: ROS-induced ROS release in coronary artery disease. Microcirculation 24:
Mahmoud, Abeer M; Szczurek, Mary R; Blackburn, Brian K et al. (2016) Hyperinsulinemia augments endothelin-1 protein expression and impairs vasodilation of human skeletal muscle arterioles. Physiol Rep 4:
Cavka, Ana; Jukic, Ivana; Ali, Mohamed et al. (2016) Short-term high salt intake reduces brachial artery and microvascular function in the absence of changes in blood pressure. J Hypertens 34:676-84
Robinson, Austin T; Franklin, Nina C; Norkeviciute, Edita et al. (2016) Improved arterial flow-mediated dilation after exertion involves hydrogen peroxide in overweight and obese adults following aerobic exercise training. J Hypertens 34:1309-16
Grizelj, Ivana; Cavka, Ana; Bian, Jing-Tan et al. (2015) Reduced flow-and acetylcholine-induced dilations in visceral compared to subcutaneous adipose arterioles in human morbid obesity. Microcirculation 22:44-53
Durand, Matthew J; Dharmashankar, Kodlipet; Bian, Jing-Tan et al. (2015) Acute exertion elicits a H2O2-dependent vasodilator mechanism in the microvasculature of exercise-trained but not sedentary adults. Hypertension 65:140-5

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