Effects of High Protein Diet on the Large Intestine in Overweight Humans
Condition: Overweight; Healthy
MeSH terms: Overweight
Study type: Interventional

Summary: 
      This study aims at evaluating the consequences of a 3 weeks high protein diet on the large
      intestine ecosystem (microbiota, metabolites and gene expression in rectal mucosa). Those
      parameters will be analysed with technics including OMICs methods. After a run-in period, 42
      volunteers will receive either soy or milk protein or maltodextrin as a placebo control. This
      trial is double blind randomized placebo-controlled paralleled design (3 arms). Longitudinal
      sampling will allow the comparison of parameters during the study.
    

Detailed description: 
      High protein diets are widely used for their slimming effect. Those diets increase the
      quantity of undigested protein and peptides reaching the large intestine. Microbiota utilizes
      protein and peptides as substrates and produces amino-acid derived metabolites such as short
      chain fatty acids, branched chain fatty acids, lactate, formate, succinate, ammonium,
      hydrogen sulfide and phenolic compounds. Some of those metabolites have been shown to be
      beneficial to the host whereas other could be deleterious. High protein diets may have
      different effects whether based on animal or plant proteins since those two kinds of protein
      have different amino acids composition and slightly different digestibility. The objective of
      this study is to evaluate in overweight volunteers the consequences of high protein diets
      (animal vs vegetal) vs isocaloric-normoproteic diet at the level of the large intestine and
      metabolism. Firstly, composition and activity of the microbiota and the metabolites produced
      in the large intestine lumen will be determined. Then, to evaluate the consequences of the
      tested diets on mucosal physiology, gene expression will be analyzed in rectal biopsies and
      fecal water will be tested on colonocytes cell lines. Lastly, the consequences of the diets
      on host metabolism will be evaluated.

      Dietary intervention

      Before the study, volunteers (n=42) will provide a 3 day food record that will be utilized by
      a dietician to calculate their usual energy intake. The study will start with a 2 weeks
      normalization period during which the volunteers will have to eat according to menus (Fig.
      1). The diet will provide to the volunteer their usual individual energy intake; and protein,
      carbohydrates and fat will respectively provide 15, 50 and 35 % of the energy intake.

      At the end of this standardization period, volunteers will be randomly assigned into 3 groups
      (n=14) for 3 weeks (intervention period) (Fig. 1). Volunteers of the 3 groups will follow a
      diet with a reduced digestible carbohydrates intake (15% of energy intake) while undigestible
      carbohydrate intake will remain unchanged. The volunteers will consume 3 times per day a
      dietary supplement powder that they will dissolve in water and then drink. This supplement
      will provide them 15% of their energy intake. The first group will receive a casein (animal
      protein) supplement so that they will have a high protein diet (protein, carbohydrates and
      fat will respectively provide 30, 35 and 35 % of the energy intake). The second group will
      receive a soy protein(vegetal) supplement so that they will also consume a high protein diet
      (protein, carbohydrates and fat will respectively provide 30, 35 and 35 % of the energy
      intake). The third group will receive a maltodextrin (digestible carbohydrate, placebo
      control) supplement so that they will ingest a normoproteic diet, similar in macronutrient
      composition to the standardization diet (protein, carbohydrates and fat will respectively
      provide 15, 50 and 35 % of the energy intake). The dietary supplement will be given in a
      double-blinded protocol. There will be no energy restriction between the standaridization and
      intervention periods.

      Clinical protocol

      Daily, the volunteers will measure their body weight and record their food consumption and
      physical activity. Once a week, they will have a phone call with a dietician to ensure
      dietary compliance (Fig. 2).

      At the end of the normalization period, 13 days after the beginning of the study (D13),
      volunteers will collect 24h urine samples. Stool samples will be collected from the evening
      of D13 to the morning of D14 . A cooler will be provided to the volunteer for storage and
      transport of samples. After one night fasting, in the morning of D14, the volunteers will
      come to the hospital and will bring their samples that will be immediately conditioned for
      storage. Blood samples will be collected. Then, rectal biopsies will be recovered. Every week
      during the intervention period, urine stool and blood will be sampled (D21, D28, D35). At the
      end of the intervention period, rectal biopsies will be recovered (D35). Body weight and
      blood pressure will be measured at each visit.

      Analyses All measured parameters will be expressed relatively to baseline.

      Dietary intake will be evaluated by dietician based on food records.

      Stool samples

        -  Microbiota composition and functions

        -  Luminal metabolites composition

        -  pH, osmolarity, water content

        -  Fecal water test on HT-29 cells (colonocytes) for mitochondrial respiration,
           proliferation, genotoxicity, cytotoxicity, gene expression

      Urines

        -  Urea and creatinine assay (protein consumption marker to verify dietary compliance)

        -  Metabolomics

      Blood

        -  Clinical parameters (total cholesterol, LDL and HDL cholesterol, non-esterified fatty
           acids, triglycerides, glycemia, insulinemia)

        -  Metabolomics

      Rectal biopsies

      • Transcriptomic analyses
    

Intervention name(s): casein supplementation; soy protein supplementation; maltodextrin supplementation
Intervention type(s): Dietary Supplement; Dietary Supplement; Dietary Supplement
Intervention description(s): After the run-in period, volunteers will receive casein supplementation (15 % of energy intake) for 3 weeks.; After the run-in period, volunteers will receive soy protein supplementation (15 % of energy intake) for 3 weeks.; After the run-in period, volunteers will receive maltodextrin supplementation (15 % of energy intake) for 3 weeks.
Intervention MeSH terms: Caseins
Allocation: Randomized
Intervention model: Parallel Assignment
Masking: Double (Participant, Investigator)
Primary purpose: Basic Science
Keywords: High protein diet; Microbiota; Rectal biopsies; Metabolomics; Bacterial metabolites; volunteers