Gut, Immune, and Vascular Health in Metabolically Healthy Obesity

This study consists of two parts (part 1 and part 2) that are approved under the same IRB approval code. As a result, there is only one unique identifier for the entirety of this project. As a results, the investigators have included both parts in this registration.

Part 1 of project:

The investigators will recruit individuals with a BMI in the normal (18.5-24.9 kg/m2) or obesity (>30.0 kg/m2) ranges from the Ball State University campus and surrounding communities. At a screening visit, the investigators will measure metabolic syndrome risk (blood pressure, triglycerides, glucose, HDL-C) to see if individuals meet criteria for "metabolically healthy obesity" and "metabolically healthy normal-weight" - our two groups of interest.

Each participant will complete one meal trial. At the meal trial, an intravenous catheter will be inserted and baseline blood sample collected. Next, vascular assessments (i.e., flow mediated dilation [FMD], pulse wave analysis [PWA], pulse wave velocity [PWV]) will be completed. Then, participants will consume the high-fat meal consisting of heavy cream, chocolate syrup, and protein powder. The meal will contain ~700 calories (55g fat).

Following completion of the meal, blood samples will also be collected at 1-, 2-, 3-, 4-, 5-, and 6-hours. At each time point the investigators will collect serum to assess biomarkers of intestinal permeability and inflammation. Serum will also be used in mechanistic experiments where the investigators will treat endothelial cells in culture with serum from participants pre/post high-fat meal and examine differences in gene and protein expression, as well as nitric oxide production. Additional blood will be collected for peripheral blood mononuclear cell isolation at baseline and 3 hours. Vascular assessments listed above will be repeated at 2-, 4-, and 6-hours.

Participants will provide a stool sample collected at home for microbiome analyses.

Part 2 of project:

The investigators will recruit individuals with a BMI in the obesity (>30.0 kg/m2) range from the Ball State University campus and surrounding communities. At a screening visit, the investigators will measure metabolic syndrome risk (blood pressure, triglycerides, glucose, HDL-C) to see if individuals meet criteria for "metabolically healthy obesity" - our sole group of interest.

Qualifying participants will report for a baseline assessment. At the baseline assessment, the investigators will collect fasting blood samples to assess biomarkers related to gut, immune, and vascular health. Serum will also be used in mechanistic experiments where the investigators will treat endothelial cells in culture with serum from participants pre/post intervention and examine differences in gene and protein expression, as well as nitric oxide production. Next, vascular assessments (i.e., flow mediated dilation [FMD], pulse wave analysis [PWA], pulse wave velocity [PWV]) will be completed. This will conclude data collection and participants will be randomized to receive 6 weeks of supplemental inulin (a soluble fiber) or a placebo (maltodextrin). At 2-, 4-, and 6-weeks of the intervention, the same samples and measurements will be collected at in-lab visits. Stool samples will be collected at baseline and 6 weeks.

Inclusion criteria

• 18-55 years old.
• BMI is 18.5-24.9 kg/m2 or >30kg/m2 (part 1). BMI > 30 kg/m2 (part 2)
• Not pregnant or expecting to become pregnant (females only).
• Not postmenopausal (females only).
• Have 0-1 risk factors based on blood pressure, blood sugar, triglycerides, and HDL-cholesterol ("good cholesterol").
• Have not been diagnosed with an advanced cardiometabolic condition (e.g., cardiovascular disease, type 2 diabetes).
• Have not been diagnosed with a chronic inflammatory or gastrointestinal condition (e.g., rheumatoid arthritis, inflammatory bowel disease).
• Do not regularly take anti-inflammatory drugs (more than 2x week) or are able to temporarily suspend use of anti-inflammatory drugs three days prior to the study visit.
• Have not taken antibiotics or probiotics in the last month.
• Do not use lipid-lowering drugs (e.g., statins), glucose-lowering drugs (e.g., metformin), or anti-hypertensive drugs.
• Do not use weight-loss drugs (e.g., Ozempic, Wegovy).
• Have not had any surgery that alters the stomach/gastrointestinal tract (e.g., gastric sleeve, gastric bypass).
• Do not use tobacco products or any illicit drugs.
• Do not have a pacemaker.
• Do not have dietary restrictions prohibiting consumption of the provided meal (e.g., vegan/vegetarian diets, gluten-free diet, relevant food allergies).
• Able to stay in the supine position in the dark for at least 10 minutes (related to vascular measurements)

Exclusion criteria

• Not 18-55 years old.
• BMI is not 18.5-24.9 kg/m2 or >30kg/m2 (part 1). BMI is not > 30 kg/m2 (part 2)
• Pregnant or expecting to become pregnant (females only).
• Postmenopausal (females only).
• Do not have 0-1 risk factors based on blood pressure, blood sugar, triglycerides, and HDL-cholesterol ("good cholesterol").
• Have been diagnosed with an advanced cardiometabolic condition (e.g., cardiovascular disease, type 2 diabetes).
• Have been diagnosed with a chronic inflammatory or gastrointestinal condition (e.g., rheumatoid arthritis, inflammatory bowel disease).
• Regularly take anti-inflammatory drugs (more than 2x week) or are unable to temporarily suspend use of anti-inflammatory drugs three days prior to the study visit.
• Have taken antibiotics or probiotics in the last month.
• Use lipid-lowering drugs (e.g., statins), glucose-lowering drugs (e.g., metformin), or anti-hypertensive drugs.
• Use weight-loss drugs (e.g., Ozempic, Wegovy).
• Have had any surgery that alters the stomach/gastrointestinal tract (e.g., gastric sleeve, gastric bypass).
• Use tobacco products or any illicit drugs.
• Have a pacemaker.
• Have dietary restrictions prohibiting consumption of the provided meal (e.g., vegan/vegetarian diets, gluten-free diet, relevant food allergies).
• Not able to stay in the supine position in the dark for at least 10 minutes (related to vascular measurements)