Targeting ER Stress in Vascular Dysfunction

Study Overview
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Brief Summary
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Aging and obesity are both risk factors for cardiovascular disease (CVD). One process that links both of these conditions to CVD is vascular dysfunction. Data from animal studies indicate that endoplasmic reticulum (ER) stress may play an important role in the development of endothelial dysfunction in aging and obesity. Therefore, the goal of this study is to investigate the relative contributions of aging and obesity on vascular dysfunction and ER stress. Additionally, this study will determine if taking an oral supplement for 8 weeks will improve vascular dysfunction and ER stress. Results from this study have the potential to identify a safe treatment option for improving vascular function in aging and obese populations.

Detailed Description
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Aging is the primary risk factor for cardiovascular disease (CVD). One critical process that links aging to CVD is the development of vascular dysfunction, characterized by endothelial dysfunction and arterial stiffness. Both endothelial dysfunction and arterial stiffness predict cardiovascular events in older individuals. Aging often coincides with obesity, another independent risk factor for CVD. Although vascular function is well characterized in both aging and obesity, it's unclear how these two conditions interact to modulate vascular function, and whether the combination of aging and obesity has additive or compounding effects on endothelial dysfunction and arterial stiffness. Currently, it is unknown whether vascular dysfunction is driven by the same underlying cellular mechanisms in aging and obesity. Accumulating data in experimental animals suggest that ER stress may be an important factor in aging- and obesity-related vascular dysfunction. Additionally, middle-aged and older obese adults with endothelial dysfunction display evidence of ER stress within biopsied endothelial cells. In light of these data, the overall goal of this proposal is to test the hypothesis that ER stress is associated with human vascular dysfunction in the settings of aging and obesity, and to determine the efficacy of the chemical chaperone tauroursodeoxycholic acid (TUDCA), an established inhibitor of ER stress, to reduce endothelial cell ER stress and improve vascular function in these at-risk individuals. Results from this study have the potential to identify a novel, safe, and clinically relevant intervention strategy for the treatment of vascular dysfunction in an aging population at high-risk for the development of CVD.

Official Title
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Targeting Endoplasmic Reticulum Stress in Aging- and Obesity-Induced Vascular Dysfunction

Conditions
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Vasodilation, Arterial Stiffness

Intervention / Treatment
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* Drug: Acetylcholine
* Drug: Sodium Nitroprusside
* Drug: Ascorbic Acid


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: Young, healthy weight adults (age: 18-35; BMI 18.5-24.9 kg/m2) Young, obese adults (age: 18-35; BMI 30- 39.9 kg/m2) Older, healthy weight adults (age: 60-80; 18.5-24.9 kg/m2) Older, obese adults (age: 60-80; 30-39.9 kg/m2) Exclusion Criteria: blood pressure >140/90 mmHg triglycerides >500 mg/dL or LDL cholesterol >190 mg/dL current smoking or history of smoking in the last 12 months diagnosed chronic disease including cancer, cardiovascular, diabetes, kidney, liver, and pancreatic disease weight change >3 kg in the past 3 months or actively trying to lose weight >12 alcoholic drinks/week hormone replacement therapy

Ages Eligible for Study
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Minimum Age: 18 Years
Maximum Age: 80 Years

Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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Accepts Healthy Volunteers

Study Plan
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How is the study designed?
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Design Details

Primary Purpose: Basic Science
Allocation: Randomized
Intervention Model: Parallel Assignment
Interventional Model Description: Participants from each group (young healthy weight, young obese, older healthy weight, older obese) will be studied before and after 8 weeks of tauroursodeoxycholic acid (TUDCA) treatment. Additional older obese participants will be studied before and after 8 weeks of a placebo treatment.
Masking: Double


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Experimental: TUDCA<br>Young and older healthy weight and obese participants will visit the lab for assessment of vascular function prior to the intervention. Aortic stiffness will be evaluated non-invasively using carotid-femoral pulse-wave velocity. A physician will place a catheter in the brachial artery for endothelial cell biopsies and local vasodilator infusions. A venous catheter will also be placed for the systemic ascorbic acid infusion. Aortic stiffness measures and vascular responses to vasodilator infusions will be performed before and after the ascorbic acid infusion. Following the completion of the vascular assessments, participants will receive 1750 mg/day of the dietary supplement tauroursodeoxycholic acid (TUDCA) for 8 weeks. Participants will return to the lab after the 8 week intervention and the vascular assessments described above will be repeated. | Drug: Acetylcholine<br>* Endothelium-dependent vasodilation will be determined via graded intra-arterial infusions of acetylcholine (ACh). Doses of 1, 4, 8, and 16 μg/100ml forearm volume/min will be infused in the brachial artery for 3 minutes each.<br>* Other names: ACh;Drug: Sodium Nitroprusside<br>* Endothelium-independent vasodilation will be determined via graded intra-arterial infusions of sodium nitroprusside (SNP). Doses of 0.25, 0.5, 1, and 2 μg/100ml forearm volume/min will be infused in the brachial artery for 3 minutes each.<br>* Other names: SNP;Drug: Ascorbic Acid<br>* The influence of oxidative stress on arterial stiffness and vasodilation will be assessed by using intravenous ascorbic acid (AA). A single supra-physiological dose of 0.06 g/kg fat-free mass (FFM) will be infused over 20 min followed by a drip infusion of 0.02 g/kg FFM administered over 60 min.<br>* Other names: Vitamin C;|
| Placebo Comparator: Placebo<br>Older obese participants will visit the lab for assessment of vascular function prior to the intervention. Aortic stiffness will be evaluated non-invasively using carotid-femoral pulse-wave velocity. A physician will place a catheter in the brachial artery for endothelial cell biopsies and local vasodilator infusions. A venous catheter will also be placed for the systemic ascorbic acid infusion. Aortic stiffness measures and vascular responses to vasodilator infusions will be performed before and after the ascorbic acid infusion. Following the completion of the vascular assessments, participants will receive oral capsules containing a placebo treatment for 8 weeks. Participants will return to the lab after the 8 week intervention and the vascular assessments described above will be repeated. | Drug: Acetylcholine<br>* Endothelium-dependent vasodilation will be determined via graded intra-arterial infusions of acetylcholine (ACh). Doses of 1, 4, 8, and 16 μg/100ml forearm volume/min will be infused in the brachial artery for 3 minutes each.<br>* Other names: ACh;Drug: Sodium Nitroprusside<br>* Endothelium-independent vasodilation will be determined via graded intra-arterial infusions of sodium nitroprusside (SNP). Doses of 0.25, 0.5, 1, and 2 μg/100ml forearm volume/min will be infused in the brachial artery for 3 minutes each.<br>* Other names: SNP;Drug: Ascorbic Acid<br>* The influence of oxidative stress on arterial stiffness and vasodilation will be assessed by using intravenous ascorbic acid (AA). A single supra-physiological dose of 0.06 g/kg fat-free mass (FFM) will be infused over 20 min followed by a drip infusion of 0.02 g/kg FFM administered over 60 min.<br>* Other names: Vitamin C;|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Endothelium-dependent vasodilation | Blood flow response to increasing doses of acetycholine | Change in baseline vasodilation at 8 weeks | 
| Endothelium-independent vasodilation | Blood flow response to increasing doses of sodium nitroprusside | Change in baseline vasodilation at 8 weeks | 
| Aortic stiffness | Carotid-femoral pulse-wave velocity | Change in baseline pulse-wave velocity at 8 weeks | 
| Endothelial cell ER stress marker ATF6 | Protein expression of activating transcription factor 6 (ATF6) | Change in baseline endothelial ATF6 at 8 weeks | 
| Endothelial cell ER stress marker PERK | Protein expression of RNA-dependent protein kinase- like ER eukaryotic initiation factor-2α kinase (PERK) | Change in baseline endothelial PERK at 8 weeks | 
| Endothelial cell ER stress marker IRE1α | Protein expression of inositol-requiring ER-to-nucleus signaling protein 1(IRE1α) | Change in baseline endothelial IRE1α at 8 weeks | 
| Endothelial cell ER stress marker CHOP | Protein expression of CCAAT-enhancer-binding protein homologous protein (CHOP) | Change in baseline endothelial CHOP at 8 weeks | 
| Endothelial cell ER stress marker GRP78 | Protein expression of glucose-regulated protein 78 (GRP78) | Change in baseline endothelial GRP78 at 8 weeks | 
| Endothelial cell ER stress marker GADD34 | Protein expression of growth arrest and DNA damage-inducible 34 (GADD34) | Change in baseline endothelial GADD34 at 8 weeks | 
| Endothelial cell oxidative stress marker p47phox | Protein expression of nicotinamide adenine dinucleotide phosphate (NADPH) oxidase subunit p47phox | Change in baseline endothelial p47phox at 8 weeks | 
| Endothelial cell oxidative stress marker NT | Protein expression of nitrotyrosine (NT) | Change in baseline endothelial NT at 8 weeks | 
| Endothelial cell oxidative stress marker MnSOD | Protein expression of manganese superoxide dismutase (MnSOD) | Change in baseline endothelial MnSOD at 8 weeks | 
| Endothelial cell oxidative stress marker CuZnSOD | Protein expression of copper-zinc SOD (CuZnSOD) | Change in baseline endothelial CuZnSOD at 8 weeks | 
| Endothelial cell inflammatory marker p65 | Protein expression of nuclear factor kappa B phosphorylated p65 subunit | Change in baseline endothelial p65 at 8 weeks | 
| Endothelial cell inflammatory marker IκBα | Protein expression of phosphorylated inhibitor of kappa B (IκBα) | Change in baseline endothelial IκBα at 8 weeks | 
| Endothelial cell inflammatory marker TNFα | Protein expression of tumor necrosis factor-alpha (TNFα) | Change in baseline endothelial TNFα at 8 weeks | 
| Endothelial cell inflammatory marker IL-6 | Protein expression of interleukin-6 (IL-6) | Change in baseline endothelial IL-6 at 8 weeks | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Circulating glucose | Blood glucose | Change in baseline blood glucose at 8 weeks | 
| Circulating insulin | Blood levels of insulin | Change in baseline insulin at 8 weeks | 
| Circulating cholesterol | Blood levels of total cholesterol, LDL cholesterol, and HDL cholesterol | Change in baseline total cholesterol, LDL cholesterol, and HDL cholesterol at 8 weeks | 
| Circulating triglycerides | Blood levels of triglycerides | Change in baseline triglycerides at 8 weeks | 
| Circulating CRP | Blood levels of C-reactive protein (CRP) | Change in baseline CRP at 8 weeks | 
| Circulating IL-6 | Blood levels of interleukin (IL)-6 | Change in baseline IL-6 at 8 weeks | 
| Circulating IL-18 | Blood levels of interleukin (IL)-18 | Change in baseline IL-18 at 8 weeks | 
| Circulating IL-10 | Blood levels of interleukin (IL)-10 | Change in baseline IL-10 at 8 weeks | 
| Circulating IL-1β | Blood levels of interleukin (IL)-1 beta (β) | Change in baseline IL-1β at 8 weeks | 
| Circulating TNFα | Blood levels of tumor necrosis factor-alpha (TNFα) | Change in baseline TNFα at 8 weeks | 

 Terms related to the study
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Keywords Provided by Centre Hospitalier Valida
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ER stress, Unfolded protein response, Vascular function, Aging, Obesity, TUDCA