Dietary Oxysterols and β-Cell Function Among African Americans

African Americans (AAs) have a higher risk of developing type 2 diabetes than the general population. AAs are also more likely to eat foods that contain cholesterol oxides/oxysterols.

Dietary oxysterols can harm the cells that produce insulin and decrease insulin production.

This pilot study seeks to determine if removing dietary oxysterols with a plant-based diet will improve insulin production and decrease the risk of type 2 diabetes among AAs.

African Americans (AAs) have almost twice the incidence and prevalence of Type 2 diabetes (T2D) compared to the general population. T2D occurs when pancreatic β-cell dysfunction prevents secretion of sufficient insulin to overcome insulin resistance. While the causes of β-cell dysfunction are not fully understood, the role of cytotoxic oxidative stress is well documented. Serum oxysterols are biomarkers of oxidative stress. Oxysterols form endogenously or exogenously when cholesterol in food is exposed to light, heat, and processing. Dietary oxysterols are cytotoxic, they are absorbed and carried in the blood by lipoprotein carriers or circulate freely in serum. 7-Ketocholesterol (7-KC), the most common oxysterol in food and serum is a biomarker of cholesterol oxidation. High serum levels of 7-KC are associated with an increased risk of T2D. AAs who consume Southern dietary pattern foods such as fried and processed meats have a higher consumption of dietary oxysterols than the general population. Our central hypothesis is that the higher consumption of dietary oxysterols among AAs contributes to β-cell dysfunction and higher rates of T2D. The aim of this pilot study is to determine the effect of lowering dietary oxysterols on serum 7-KC and β-cell function among AAs with prediabetes and early T2D (HbA1c 5.7% - 7.0%). The expected outcome is that decreased exposure to dietary oxysterols will decrease serum oxysterols and β-cells oxidative stress which will improve β-cell function and glycemic control. The knowledge gained from this study may lead to improved T2D prevention and treatment strategies that may decrease the burden of T2D in all communities and eliminate the racial disparity among AAs.

Eligibility Criteria:
Inclusion Criteria: Participants must be:

1. HbA1c: 5.7% - 7.0%: This HbA1c range reflects mild to moderate β-cell dysfunction.
2. Self-identified AA: This group has higher rates of T2D than the general population.
3. Adults over18 years old: This age group is at higher risk of T2D.
4. Ability to read, understand and communicate effectively in English: All information about the study and instructions for the study protocol will be in English.
5. Committed to eating the allocated study diet for 12 weeks: This is important to ensure that the study protocol is followed, and the data collected from participants is meaningful/valid.
6. On stable medication dosages for the three months prior to recruitment: This is to avoid bias or confounding with new medications or dosages changes.
7. Able to safely store a week's supply of prepared meals: Participants will receive packages of prepared food that has to stored and last them for the following week.
8. Mentally competent and able to follow the study protocol and provide informed consent
9. Currently eating the Standard American diet: The baseline diet of the participants will be assessed and correlated their baseline serum 7-KC levels and HOMA2 Index of β-cell function.

Exclusion Criteria: Participants cannot:

1. Be pregnant or lactating: Fetuses and breast-feeding infants are a protected vulnerable group. The risk of involving them in research must outweigh the benefits, Hormonal levels and other factors in pregnant and lactating woman may confound study results.
2. Be taking statin medications or any other cholesterol lowering drugs or supplements: These medications may artificially lower serum cholesterol and oxysterol levels.
3. Be currently on a vegan, vegetarian, or any type of plant-based diet for the 3 months prior to recruitment: Participants currently on these diets may not see significant changes on the dietary interventions of the study protocol.
4. Be a current smoker: Smoking is a risk factor for oxidative stress - this could be an effect modifier or a confounding faction for this study.
5. Be on medications or supplements to lower blood glucose or treat diabetes: This will be an effect modifier or confounding factor. We will not know the effect of the dietary intervention if the participants are also on medications for diabetes.
6. Be status post blood transfusion in the previous 3 months: This will interfere with the test for HbA1c levels. This is one of our primary outcomes:
7. Have a hemoglobin or any other blood disorder: This will interfere with the test for HBA1c which measures glycation of hemoglobin in red blood cells.:
8. Be taking biotin supplements: This interferes with the test for fasting C-Peptide.
9. Be on dialysis or have any stage of renal failure: Dialysis patients need special diets and more intense monitoring than is planned for the participants in this study.
10. Have food allergies: Participants will be screened for food allergies. This is to prevent food sensitivities or adverse reactions to the prepared meals in the study.