Gut Microbiota Dependent and Independent Impacts of Dietary Pulses on Pre- and Postprandial Metabolism and Inflammation in Overweight/Obese Humans

Investigators will utilize a parallel intervention of lentil versus macronutrient-matched (not including fiber) control treatment for 12 weeks in OW/OB adults with demonstrated risk for T2D and CVD. Experimental diets will be provided to participants in the form of pre-made midday meals to exploit the second meal effect and lower caloric intake at the evening meal. Pre- and post-intervention assessments will be made for the following variables: makeup of the gut microbiome (microbial species and relative abundance), gut metabolome, postprandial response of TG, inflammatory cytokines, and serum metabolome to a high-fat meal challenge (established inflammation stimulus), fasting serum glucose, lipid, insulin, inflammation markers and metabolome, blood pressure, and anthropometric measures including weight, body composition, waist circumference, and quantity of visceral adipose tissue. Habitual diet will be measured so that these variables can be used to aid in our characterization of participants and aid in analysis and interpretation of data.

Procedures:

Postprandial lipidemic and inflammation responses: High-fat meal challenges with 40 to 100 g of dietary fat are an established laboratory test to measure both postprandial triglyceridemic and inflammation responses. Investigators have used a 50 g dose of fat delivered in the form of butter on toast on > 50 individuals because this particular dose is effective at discriminating between low versus high TG and inflammation responders. In brief, participants will report to the laboratory after an overnight fast, an indwelling venous catheter will be placed in an antecubital vein, and blood samples will be collected before, and 1, 2, 3, 4, and 5 hours following ingestion of the high-fat meal. Samples will be analyzed in real time for TG (and full lipid panel plus glucose) using a clinical chemistry analyzer (Piccolo xpress), while serum samples will be aliquoted and stored at -80 C until analysis for inflammatory cytokines, metabolomics, and insulin. Investigators will measure inflammatory cytokines (TNF-α, IFN-y, interleukin (IL)-1β, IL-6 IL-17, IL-23, IL-10, and granulocyte macrophage colony stimulating factor (GM-CSF)) using high-sensitivity Luminex multiplexing technology (Bio-Rad Bio-Plex® 200 HTS) prepared by Millipore.

Dietary intervention: Using methods established for an ongoing CRT with lentils, investigators will prepare 7 meals per participant per week to deliver a dose of 4.6 or 0 cups of lentils per week for the experimental and control groups. Meals are matched for macronutrient content (except for fiber), and ground turkey or chicken replaces lentils in the control meals. Dietary intervention will be 12 weeks in length with a possible extension to 13 weeks if participants either 1) miss 3 or more meals in a row at any point during the intervention or 2) miss any meals at all in the last week of the intervention prior to their final visit. To keep the meal intervention period between 12 and 13 weeks, participants will be dropped from the study if meal adherence failures result in more than a one week intervention extension.

Participants will be instructed to consume food provided for their midday meal, and then to proactively reduce portion sizes and to not eat beyond fullness at the evening meal. This strategy exploits the satiety effect of pulses at the midday meal and the 'second meal effect' in which volitional consumption is reduced at the next meal, the evening meal. Each participant will be surveyed once weekly to determine whether they consumed the experimental meal that day, their perceptions of hunger, fullness, satiety, and satisfaction with that day's meal (at 4:00 pm), and their gastrointestinal comfort (level of bloating, flatulence, cramping, and comfort) throughout the day (at 8:00 pm). This methodology has been successfully implemented in our ongoing study to demonstrate that lentil meals are equally pleasing, produce greater satiety, and are well-tolerated.