Intestinal imidazole propioNaTE productioN after histiDinE supplementation in healthy and type 2 Diabetes mellitus subjects:
role of the gut microbiota

Background:
In-vivo and in-vitro studies have suggested that histidine could drive metabolic alterations in obese type 2 DM (T2D) humans via the production of imidazole proprionate (ImP), the production of which might be driven via an altered gut microbiota composition. Since there are currently no data on direct oral histidine supplementation on several markers of cardiometabolism in obese T2D humans nor on its related metabolite production ImP by the gut microbiota in humans, we therefore propopose the following study.

Objective:
Evaluate pharmacokinetic levels of imidazole propionate as a result of orally administrated histidine and assess the role of the gut microbiome in this respect, T2D as compared to healthy controls.

Rationale:
The gut microbiota plays a pivotal role in the pathophysiology of cardio-metabolic diseases (CMD), such as T2D, obesity and atherosclerosis. The diet shapes the gut microbiota, which can further transform dietary food items into circulating metabolites, which acts on the host. Among them, ImP has recently been discovered. In- vitro and animal experiments demonstrated that ImP originate from histidine metabolization by the gut microbiota. Furthermore, ImP is increased in T2D individuals as compared to healthy controls and can induce glucose intolerance in mice. In this study we aim to confirm in humans that ImP indeed derive from gut microbiota processing of oral histidine intake. Furthermore, we aim to evaluate ImP concentrations after an oral challenge and demonstrate that it differs between T2D and controls. We also aim to see if these processes differ by ethnicity, as the gut micorbiota has been shown to also differ per ethnic group.

Study design:
Interventional controlled single centre study

Study Population:
44 subjects: 22 healthy controls, 22 type 2 diabetes mellitus (T2D) on stable metformin use. 11/22 subjects of both groups will be of Caucasian descent and the other 11 of Surinamese descent.

Intervention:
We will orally administrate 4g of the food supplement histidine (Vital Cell Life L-Histidine 500 MG Capsules 100CP) once a day for 7 weeks, after the first 2 weeks, one week of antibiotics will be added to suppress the gut microbiome followed by a four weeks recovery period. Plasma and urinary ImP, histidine, urocanate and glutamate levels will be measured as well as, peripheral blood monocyte cells (PBMC) for inflammatory status will be measured at specific time points.

Outcome measures:
Primary objective will be determination of ImP levels after histidine intake and other degradation products such as urocanate and glutamate before and after oral antibiotics. Secondary objectives will be differences in histidine uptake effect upon oral histidine supplementation on PBMC inflammatory status, influence of gut microbiome on ImP production, continuous (freestyle libre) as well as postprandial (after a mixed meal test) glucose levels between healthy and T2D subjects on stable dose of oral metformin.

Sample Size: 44

Histidine supplementation will lead to higher plasma ImP levels in T2D patients, but not in healthy controls and this effect is mediated by the gut microbiota.

total intervention will be 2 months per subject and the subjects will visit the center for 7 times in total during the 2 months

Histidine supplemenation 4g/day for 7 weeks.