Effects of Mango on Insulin Sensitivity in Prediabetes

The proposed project is based on the hypothesis that mango enhances whole-body insulin sensitivity through increased antioxidant-mediated mechanisms. Accordingly, the primary objective is to explore whole-body insulin sensitivity, as measured by the Matsuda index, in individuals with Pre-DM following 6 weeks of mango consumption. The secondary objective is to clarify the underlying mechanism of action through enhanced antioxidant status. The tertiary object will be to monitor glucose concentration using CGM before and during (the last 10 days of the interventions) to understand the real-time dynamic glucose changes with the mango interventions compared to the control intervention.

This study will last for about six weeks and involves a total of six visits to our Clinical Nutrition Research Center at Illinois Tech (CNRC). These visits include one screening visit to see if they are eligible to participate in this study, followed by Visits 1, 2, 3, 4, and 5. During the study, participant will be asked to drink a mango drink or a simple controlled drink every day for 42 days. Also, they will wear a small device called a continuous glucose monitor (CGM) for a period of 7 days at two different times in the study. This device remains on their skin and tracks their blood sugar level day and night, so the investigators can see how it changes in real time.

Screening Visit:

Participant's eligibility for the study is based on the inclusion and exclusion criteria listed above. To assess this, they will need to arrive at the CNRC fasting for 10-12 hours, meaning no food or drink other than plain water during this period.

During the screening visit, the following assessments will be conducted:

• The participant will complete a screening questionnaire about their health, dietary habits, and physical activity history.
• The participant's height, weight, waist circumference, and body composition will be measured. Their Body Mass Index (BMI) will be calculated based on their height and weight. BMI is an estimate of body fat that applies to both adult men and women.
• The participant's forehead temperature, blood pressure, and heart rate will be measured. They will be seated in a comfortable chair with their feet flat on the ground and uncrossed. They will be asked to relax for five minutes before their blood pressure and heart rate are recorded.
• A finger prick test will be performed to check their blood sugar levels.
• A licensed healthcare practitioner (LHCP) and/or a certified phlebotomist will assess their arm veins using a vein access scale test. A butterfly needle will then be used to draw 3 milliliters (mL) of blood from their arm to measure their plasma blood glucose levels.
• If the participant is a woman under the age of 60 year, they will be required to take a pregnancy test.

Also, participants will complete a Food Frequency Log to evaluate their typical consumption patterns for specified food products. For each listed food item, participants will report their intake frequency by selecting one of five response options: more than once per day, once per day, 2-3 times per week, once per week, or not at all.

Based on the results of the questionnaire, blood glucose levels, physical measurements, and overall health evaluation, the participant may meet the eligibility criteria and be invited to participate in the study.

Procedures for Each Study Day Visit (Visits 1, 2, 3, 4 and 5):

VISIT 1: (which may take place on the same day as the screening visit or on a different day)

If participant qualify based on your screening results, visit 1 can take place immediately after your screening or on a later date. This visit lasts approximately 30-45 minutes, during which participant will meet with one of our investigators who will provide detailed instructions on the study procedures and how to prepare for each study day. Participant will also receive training on study procedures, including dietary restrictions, medications, and supplements to avoid, food and GI-tract diary recording, and overnight fasting requirements. Study dates will be scheduled, and participant will receive a study booklet containing the study calendar and all the instructions covered during visit 1.

CGM Placement: During this visit, the study staff will prepare the participant for glucose monitoring. A Continuous Glucose Monitor (CGM) will be placed on participant's arm. This is a small sensor that remains on skin to monitor the blood glucose levels.

Diet restrictions ("Foods to Avoid"): Participant will be asked to continue their usual dietary habits throughout study. However, certain foods and beverages must be avoided, as they may interfere with our ability to assess the effects of mango consumption.

They will be asked to limit their intake of mango, dark chocolate, chestnut, cloves and red wine throughout the study. Additionally, participants will be provided a specific list of foods to avoid for three days prior to each longer study visit (Visits 2 and 5), along with a separate 24-hour avoidance list before those visits.

ASA24 Food Recall: To help track diet, participant will use an online tool called the ASA24 to report all food and beverages consumed during the previous day. They will complete this questionnaire during every single study visit, including Visits 1, 2, 3, 4, and 5. In addition to these visits, they will complete the ASA24 weekly at home to document what they ate the day before. Each questionnaire takes about 45 minutes to finish. To make this easier, they will get regular reminders, so they know exactly when to complete their weekly records.

GI-tract Diary: To help us understand gut, participant will simply answer a few questions about your stomach and digestion by ticking the boxes that best describe how they feel.

Visit 2 and 5: LMTT (Liquid Meal Test)

Participant will be asked to fast for at least 10 hours (no food or drink except plain water). Investigators will collect their initial fasting blood. They will be asked to consume a liquid meal consisting of two bottles of Ensure Original Nutrition Shake. This meal provides 440 kcal, 20 g of sugar, 12 g of fat, and 10 g of protein. To see how their body processes the meal, additional blood samples will be and collected at specific times: one fasting blood draw before the LMTT followed by 15mins, 30mins, 60mins, 90mins, 120mins, 180mins and 240mins after they finish the drink.

At the end of Visit 2, they will be given a 16-day supply of study beverages to take home and consume daily until their next visit.

Before each of the study day visit:

The day before your Study Day Visit, they will review the instructions on "How to Prepare for Your Study Day". This will include guidelines for eating a standardized dinner meal, fasting overnight for at least 10 hours (which aligns with typical overnight fasting). They will also be asked to avoid vigorous physical activity and alcoholic beverages for the 24 hours preceding their study day, aim for their usual night's sleep, and maintain their normal diet except for the specified restrictions under "Foods and Beverages to AVOID or Limit."

3-Day food record: Three days before their Study Days, they will avoid mango, dark chocolate, red wine, almonds, walnuts and pecans. Additionally, they must refrain from consuming caffeinated beverages and alcohol for 24 hours before the Study Day. During this period, they will complete a three-day consecutive food record, documenting everything they eat and drink, including the portion size, from the time they wake up until they go to sleep.

Standardized Meal: The night before Visit 2 and 5, they will eat a repeatable dinner of either a homemade meal or a frozen meal provided to participants by CNRC, similar as Visit 1.

ASA24 and GI-tract diary: During your visits, participants will use the online links to fill out your ASA24 food record and answer the GI-Track questionnaire about their gut health.

At the end of the Study Days: They will be evaluated for safety and any discomfort or symptoms before leaving and will be given a 16-days supply of study beverages to take home and consume daily until their next visit. They will receive a take-home snack, and compensation will be issued after all study procedures are completed. Additionally, they will be given instructions on how to prepare for their next visit.

How much blood will be collected during the study visit? Blood will be collected a total of eight times on each visit (Visits 2 and 5), for approximately 91 mL of blood collected per visit. Throughout the entire study, a total of approximately 190 mL of blood will be collected.

Visit 3: Pickup Day This is a shorter visit designed to keep the participant supplied for the study. Staff will briefly meet with them to see how they are doing. They will pick up their next 19-days supply of study beverages to last until Visit 4.

ASA24 and GI-tract diary: During visit, they will use the online links to fill out their ASA24 food record and answer the GI-Track questionnaire about gut health.

Visit 4: Pickup visit and Second CGM Placement A new Continuous Glucose Monitor (CGM) sensor will be placed on participant's arm to monitor their glucose levels leading up to their final visit. They will pick up their next 7-days supply of study beverages to last until Visit 5.

ASA24 and GI-tract diary: During their visit, they will use the online links to fill out your ASA24 food record and answer the GI-Track questionnaire about their gut health.