Functional effects of dietary proteins and bioactive peptides on satiety and metabolic response in humans

Gut-brain axis is a crucial hub of the food intake and energy balance regulation. Dichotomy between homeostatic and non-homeostatic/hedonic systems should be replaced by a larger, highly interactive system that unifies homeostasis with reward, cognition, and emotion. Understanding the integrative role of the CNS in energy and reward homeostasis has become increasingly important considering the prevalence of obesity and functional gastrointestinal disorders (FGIDs). The GIT is the largest endocrine organ in the human body and it represents the gateway for communication between the human body and the external environment. Distress (i.e. inflammation) or adaptations in the communication of sensory information may contribute to the development or maintenance of disease. Several diseases such as celiac disease, Crohn’s disease, type 1 diabetes and some food allergies, are known to increase the GIT mucosa permeation of macromolecules. As reported in Chapter 2 FGIDs are classified as morphologic and physiological abnormalities often occurring in combination with motility disturbance, visceral hypersensitivity, as well as altered mucosa, immune function, gut microbiota and CNS processes. The incidence of FGIDs among population is about 11%. Some of the symptoms reported for the functional dyspepsia are similar to those of non-celiac gluten sensitivity such as postprandial fullness, early satiety, epigastric pain, and epigastric burning. These symptoms may appear isolated or combined after consumption of specific foods. The nutritional consequence of this symptomatology is that people arbitrarily exclude from diet the foods which are mainly associated with the symptoms such as spicy foods, high-fat meals, dairy products or cereal-based foods. Life-lasting dietary exclusions may cause nutritional deficiency as well as metabolic adaptation that may be even worst of the previous symptomatology. This is the reason why in the case of a specific food/nutrient-induced disorder the usual dietetic approach is the exclusion from the diet of the specific food/nutrient for a certain period and a slow re-introduction in the follow-up period. The exclusion from the diet of gluten represents the cure only for people with celiac disease but literature was still lacking on the knowledge of the metabolic response to a gluten-free meal in patients with celiac disease compared to healthy subjects. The human study reported in Chapter 3 aimed at filling that gap of knowledge. From a dietetic perspective, the effect of a meal is more relevant in exerting metabolic responses than a single nutrient/food. Celiac subjects (CD) at the diagnosis or on a gluten free diet since 12 months and healthy subjects consumed a standard gluten-free meal and the post-prandial blood glucose and hormone response as well as appetite feelings were monitored. The main results of the study was that CD showed a lower postprandial blood glucose response than healthy subjects with a lower response of GLP-1, GIP and insulin. The different hormonal status was associated with a different evolution of the post-prandial hunger sensation that was higher in CD at diagnosis than in the others. These findings suggested that CD subjects after more than 1 year on a gluten free diet did not recover a complete functionality of the intestine and this might determine an adaptive hormone postprandial response that may influence post-prandial appetite sensations and insulin resistance over long period. From a food science and nutrition perspective, some bioactive compounds are present in foods and may be effective in the control of appetite, intestinal inflammation and glycaemia. In this thesis the potential of food bioactive peptides contained in milk proteins, casein and soy hydrolysates towards appetite, inflammation and glycaemia was tested and described in the human study in Chapter 4, and in in vitro studies of Chapter 5 and 6, respectively. In Chapter 4 two beverages, one enriched with milk proteins and one with carbohydrates (control) were developed and a human study with women consuming the beverage after an exercise session was carried out aiming at evaluating the effect of the beverages on the energy intake at the subsequent dinner. Data showed that the milk protein-enriched beverage was able to influence hunger sensation and reduce energy intake at subsequent meal only in women having a strong cognitive control of eating behaviour. In Chapter 5 casein and soy hydrolysates were tested in Caco-2 cells cultivated in a normal condition and in the presence of TNF-α to induce intestinal inflammation. Data showed that digested casein and soy protein hydrolysates positively influenced cells viability, particularly in inflamed condition. Data about monolayer integrity (TEER) showed an absence of irreversible damage at the normal and inflamed cell monolayer when it was treated with digested samples. In Chapter 6 casein (CH) and soy (SH) protein hydrolysates were tested as functional ingredients for glycaemia control, through inhibition of Dipeptidyl peptidase-IV (DPP-IV) activity. This study showed that when used in a model food CH and SH loosed their inhibitory activity against DPP-IV possibly because of other food components that could hide the bioactivity of CH and SH at the doses used in the model food. This scenario highlights the importance of validation of efficacy of new foods/whole meals both in vitro to assess the potential functionalities before performing human studies as well as in vivo in a well-characterized population. Indeed, growing evidence shows that the effect of food on wellness and dietary behaviour may be also influenced by psychological attitude of people as well as by gut microbiota reactivity to a food/diet. In the context of new foods/diets to tackle obesity and FGIDs the gut-brain interconnection is central and should be better targeted both at the step of the food design and validation

The effects of collagen peptides on exercise-induced gastro-intestinal stress: a randomized, controlled trial

Purpose: We examined the effects of collagen peptides (CP) supplementation on exercise induced-gastro-intestinal (GI) stress. Methods: In a randomized, crossover design, 20 volunteers (16 males: V ̇O2max, 53.4±5.9 ml·kg-1) completed 3 trials: a non-exercise rest trial, with no supplement (REST) and then an exercise trial with CP (10 g·day-1) or placebo control (CON) supplements, which were consumed for 7 days prior to, and 45 min before, a 70 min run at 70-90% of V ̇O2max. Outcome measures included urinary lactulose and rhamnose (L/R), intestinal fatty acid binding protein (I-FABP), lipopolysaccharide (LPS), anti-LPS antibody, monocyte chemoattractant protein-1 (MCP-1), interleukin (IL) 6 and 8, cortisol, alkaline phosphatase (ALP) (measured pre, 10 min post and 2 h post) and subjective GI symptoms. Results: There were no differences in heart rate, perceived exertion, thermal comfort, or core temperature during exercise in the CP and CON trials (all P>0.05). I-FABP was higher in CP (2538±1221pg/ml) and CON (2541±766pg/ml) vs. REST 2 h post (1893±1941pg/ml) (both P0.05), and no differences in L/R or GI symptoms between CON and CP (all P>0.05). Conclusion: Collagen peptides did not modify exercise-induced changes in inflammation, GI integrity or subjective GI symptoms but LPS was higher in CON 2 h post-exercise and thus future studies may be warranted

Collagen peptide supplementation before bedtime reduces sleep fragmentation and improves cognitive function in physically active males with sleep complaints

Purpose: The primary aim of this study was to examine whether a glycine-rich collagen peptides (CP) supplement could enhance sleep quality in physically active men with self-reported sleep complaints. Methods: In a randomized, crossover design, 13 athletic males (age: 24 ± 4 years; training volume; 7 ± 3 h·wk1) with sleep complaints (Athens Insomnia Scale, 9 ± 2) consumed CP (15 g·day1) or a placebo control (CON) 1 h before bedtime for 7 nights. Sleep quality was measured with subjective sleep diaries and actigraphy for 7 nights; polysomnographic sleep and core temperature were recorded on night 7. Cognition, inflammation, and endocrine function were measured on night 7 and the following morning. Subjective sleepiness and fatigue were measured on all 7 nights. The intervention trials were separated by ≥7 days and preceded by a 7-night familiarisation trial. Results: Polysomnography showed less awakenings with CP than CON (21.3±9.7 vs. 29.3±13.8 counts, respectively; P=0.028). The 7-day average for subjective awakenings were less with CP vs. CON (1.3±1.5 vs. 1.9±0.6 counts, respectively; P=0.023). The proportion of correct responses on the baseline Stroop cognitive test were higher with CP than CON (1.0±0.00 vs. 0.97±0.05 AU, respectively; P=0.009) the morning after night 7. There were no trial differences in core temperature, endocrine function, inflammation, subjective sleepiness, fatigue and sleep quality, or other measures of cognitive function or sleep (P>0.05). Conclusion: CP supplementation did not influence sleep quantity, latency, or efficiency, but reduced awakenings and improved cognitive function in physically active males with sleep complaints

Milk protein enriched beverage reduces post-exercise energy intakes in women with higher levels of cognitive dietary restraint

Objective: The aim of this study was to assess the satiating efficacy of milk proteins compared to carbohydrates in twenty women during post-exercise period. Methods: A milk protein-enriched beverage (MPB), and an isocaloric carbohydrate-enriched beverage (CB) containing respectively 9.3. g and 0.3. g of milk proteins per 100. mL beverage, were developed and tested in a satiety study with 20 free-living healthy and normal weight women. The participants drank 250. mL of the two beverages after an aerobic exercise session, filled daily food diaries and rated their appetite on visual analogue scale (VAS), in two days over three consecutive weeks. A psychometric evaluation of eating behaviour was obtained by three-factor eating questionnaire (TFEQ). Results: No differences in appetite feelings and energy intakes between MPB and CB were found in the study population. However, 9 participants were significantly less hungry (-9% vs + 15%, p 0.03) and ate later (208. min vs 127. min, p 0.03) and less (-10% vs + 8% daily energy intake, p 0.01) when they had MPB than CB. These women had a slightly higher BMI and were more restrained than the others. Conclusions: Data showed that MPB compared to CB could modify daily eating habits by enhancing satiety in women with a stronger cognitive control of eating behaviour

The effects of collagen peptides on exercise-induced gastrointestinal stress: a randomized, controlled trial

Purpose  We examined the effects of collagen peptides (CP) supplementation on exercise-induced gastrointestinal (GI) stress.  Methods  In a randomized, crossover design, 20 volunteers (16 males: V˙O2max, 53.4 ± 5.9 ml·kg−1) completed 3 trials: a non-exercise rest trial, with no supplement (REST) and then an exercise trial with CP (10 g·day−1) or placebo control (CON) supplements, which were consumed for 7 days prior to, and 45 min before, a 70 min run at 70–90% of V˙O2max. Outcome measures included urinary lactulose and rhamnose (L/R), intestinal fatty acid binding protein (I-FABP), lipopolysaccharide (LPS), anti-LPS antibody, monocyte-chemoattractant protein-1 (MCP-1), interleukin (IL) 6 and 8, cortisol, alkaline phosphatase (ALP) (measured pre, 10 min post and 2 h post) and subjective GI symptoms.  Results  There were no differences in heart rate, perceived exertion, thermal comfort, or core temperature during exercise in the CP and CON trials (all P > 0.05). I-FABP was higher in CP (2538 ± 1221 pg/ml) and CON (2541 ± 766 pg/ml) vs. REST 2 h post (1893 ± 1941 pg/ml) (both P  0.05), and no differences in L/R or GI symptoms between CON and CP (all P > 0.05).  Conclusion  Collagen peptides did not modify exercise-induced changes in inflammation, GI integrity or subjective GI symptoms but LPS was higher in CON 2 h post-exercise and thus future studies may be warranted.</p

Collagen peptide supplementation before bedtime reduces sleep fragmentation and improves cognitive function in physically active males with sleep complaints

Purpose The primary aim of this study was to examine whether a glycine-rich collagen peptides (CP) supplement could enhance sleep quality in physically active men with self-reported sleep complaints. Methods In a randomized, crossover design, 13 athletic males (age: 24 ± 4 years; training volume; 7 ± 3 h·wk1) with sleep complaints (Athens Insomnia Scale, 9 ± 2) consumed CP (15 g·day1) or a placebo control (CON) 1 h before bedtime for 7 nights. Sleep quality was measured with subjective sleep diaries and actigraphy for 7 nights; polysomnographic sleep and core temperature were recorded on night 7. Cognition, inflammation, and endocrine function were measured on night 7 and the following morning. Subjective sleepiness and fatigue were measured on all 7 nights. The intervention trials were separated by ≥ 7 days and preceded by a 7-night familiarisation trial. Results Polysomnography showed less awakenings with CP than CON (21.3 ± 9.7 vs. 29.3 ± 13.8 counts, respectively; P = 0.028). The 7-day average for subjective awakenings were less with CP vs. CON (1.3 ± 1.5 vs. 1.9 ± 0.6 counts, respectively; P = 0.023). The proportion of correct responses on the baseline Stroop cognitive test were higher with CP than CON (1.00 ± 0.00 vs. 0.97 ± 0.05 AU, respectively; P = 0.009) the morning after night 7. There were no trial differences in core temperature, endocrine function, inflammation, subjective sleepiness, fatigue and sleep quality, or other measures of cognitive function or sleep (P > 0.05). Conclusion CP supplementation did not influence sleep quantity, latency, or efficiency, but reduced awakenings and improved cognitive function in physically active males with sleep complaints.</p

RagD auto-activating mutations impair MiT/TFE activity in kidney tubulopathy and cardiomyopathy syndrome

: Heterozygous mutations in the gene encoding RagD GTPase were shown to cause a novel autosomal dominant condition characterized by kidney tubulopathy and cardiomyopathy. We previously demonstrated that RagD, and its paralogue RagC, mediate a non-canonical mTORC1 signaling pathway that inhibits the activity of TFEB and TFE3, transcription factors of the MiT/TFE family and master regulators of lysosomal biogenesis and autophagy. Here we show that RagD mutations causing kidney tubulopathy and cardiomyopathy are "auto- activating", even in the absence of Folliculin, the GAP responsible for RagC/D activation, and cause constitutive phosphorylation of TFEB and TFE3 by mTORC1, without affecting the phosphorylation of "canonical" mTORC1 substrates, such as S6K. By using HeLa and HK-2 cell lines, human induced pluripotent stem cell-derived cardiomyocytes and patient-derived primary fibroblasts, we show that RRAGD auto-activating mutations lead to inhibition of TFEB and TFE3 nuclear translocation and transcriptional activity, which impairs the response to lysosomal and mitochondrial injury. These data suggest that inhibition of MiT/TFE factors plays a key role in kidney tubulopathy and cardiomyopathy syndrome