Pilot Study of a Dietary Intervention Based Upon Advanced Glycation End Products

Study Overview
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Brief Summary
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The purpose of this pilot study is to determine whether it is feasible to conduct a randomized, controlled dietary intervention trial of high versus low dietary intake of advanced glycation end products (AGEs) in 24 adults; and to gather preliminary data on the impact of high versus low AGE diet health parameters. The investigators hypothesize that it will be feasible to conduct a randomized, parallel arm, controlled dietary intervention in a pilot study involving 24 subjects.

Detailed Description
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Advanced glycation end products (AGEs), bioactive molecules formed by the non-enzymatic glycation of proteins, are emerging as a possible dietary risk factor for many key adverse health outcomes related to obesity and to aging. Major sources of systemic AGEs are endogenous AGEs generated in the body and exogenous AGEs found in foods. When food is heated to high temperatures, the characteristic browning generates Maillard reaction products, known as AGEs. Although AGEs have been implicated in atherosclerosis, insulin resistance, diabetes, cardiovascular disease, aging-related eye disease, Alzheimer's disease, and chronic kidney disease, the possible adverse effects of dietary AGEs have not been well characterized in humans. The objective of the study is to determine whether it is feasible to conduct a randomized, parallel arm, controlled dietary intervention in a pilot study involving 24 subjects; and to compare the effects of a high-AGE and low-AGE diet on (a) serum and urine carboxymethyl-lysine and serum receptor for AGEs (RAGE), (b) endothelial function, (c) interleukin-6, C-reactive protein, (d) lipids, (e) adipokines, (f) glucose metabolism and insulin resistance, (g) renal function, and (h) cognition.

Conditions
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Healthy Adults

Intervention / Treatment
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* Other: Dietary


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: 50 years or older and less than 70 years of age Non-smoker Body mass index of 18.5 to <30 mg/kg2 Exclusion Criteria: Diabetes, thyroid disease, angina, myocardial infarction, heart failure, stroke, peripheral artery disease, chronic obstructive pulmonary disease, inflammatory bowel disease, liver disease, chronic kidney disease, or Raynaud's disease Taking regular vitamin supplements, or if taking regular vitamin supplements, not willing to discontinue taking vitamin supplements while participating in the study Taking vitamin B6 (pyridoxamine) supplements (50 mg or more) Taking aspirin or nonsteroidal anti-inflammatory medications (NSAIDS), or if so, not willing to discontinue taking aspirin or NSAIDS while participating in the study Major food allergies (i.e., dairy, nuts, etc) History of eating disorders or other dietary patterns that are not consistent with the dietary intervention (e.g. vegetarians, very low fat diets, high protein diets) Loss of 10% of body weight within the last 12 months or plan to initiate a weight loss program during the next two months Self-report of alcohol or substance abuse with the past 12 months and/or current acute treatment or rehabilitation program for these problems (long-term participation in Alcoholics Anonymous is not an exclusion) Other medical, psychiatric, or behavioral factors that in the judgment of the study doctor may interfere with study participation or the ability to follow the intervention protocol Not willing to consume the diets being tested by the study Cognitive impairment, indicated by a Mini-Mental State Exam score <23 Triglycerides >300 mg/dL Hemoglobin ≤11 g/dL Creatinine greater or equal to 1.5 mg/dL Fasting plasma glucose >125 mg/dL Proteinuria Long fingernails on the index finger of each hand, or if so, not willing to trim these two fingernails so that peripheral arterial tonometry can be conducted during the study Not willing to give written, informed consent to participate in the study Women who are lactating or pregnant, or plan to become pregnant during the study

Ages Eligible for Study
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Minimum Age: 50 Years
Maximum Age: 69 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

Allocation: Randomized
Intervention Model: Parallel Assignment
Masking: Double


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Experimental: High-AGE Diet<br>The high-AGE diet will be approximately four times higher in AGEs than the low-AGE diet. | Other: Dietary<br>* The diets will each consist of 3 meals/day and 1 snack/day which are either high or low in AGEs.<br>|
| Experimental: Low-AGE Diet<br>The low-AGE diet will be approximately four times lower in AGEs than the high-AGE diet. | Other: Dietary<br>* The diets will each consist of 3 meals/day and 1 snack/day which are either high or low in AGEs.<br>|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Endothelial function | Endothelial function will be measured using peripheral arterial tonometry. | At baseline and following 6-week intervention | 
| Biomarkers | Fasting venous blood samples will be drawn for measurements of CML, IL-6, CRP, leptin, adiponectin, cystatin C, cholesterol, triglycerides, glucose, insulin, sRAGE, and esRAGE. Urinary creatinine and CML also will be measured. | At baseline and following 6-week intervention | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Cognitive function and mood | Five cognitive tests and a test of mood will be used to assess various cognitive parameters including attention, memory, and reasoning. | At baseline and following 6-week intervention |