Satiating potential and anti-obesogenic effect of mediterranean foodstuffs. In vitro and in vivo assessments.

Abstract

Obesity has increased dramatically, and it has now reached epidemic proportions around the world. The global importance of overweight and obesity is worrying, in part, due to their public health significance because they are associated with a higher risk of type 2 diabetes, coronary heart disease, etc. Regulation of food intake by enhancing satiety and the promotion of a healthy life style shape the key to mitigate this epidemic. The adherence to a Mediterranean diet together with the inclusion into the diet of ingredients capable to promote satiety are key strategies to prevent and treat overweight and obesity. Based on this background, this manuscript has been developed with the objective to identify and to evaluate the satiety potential of several ingredients consumed usually in the Mediterranean diet. In chapter 1 has been described the satiety potential of macronutrients and different Mediterranean foodstuffs, being proteins the most satiating macronutrient. Interesting anti-obesogenic and satiating features of Mediterranean active compounds or ingredients (whey, egg white, hesperetin, capsicum, pistachio, carob pulp, nopal, tiger nut) were revealed. In chapter 2 was performed an initial characterisation of several types of whey through an in vitro digestion and colonic fermentation. Results demonstrated that sheep whey was the richest one in protein content, meanwhile goat milk whey yielded the highest concentration of lactose. Biopeptides derived from digestion showed biological effects such as antihypertensive, satiating, antidiabetic and antioxidant/anti-inflammatory. Obesity is closely linked to gut health and immune system and a low-grade of systemic inflammation has been found in this situation. To assay the anti-inflammatory capacity of several types of whey, chapter 3 was developed by means of in vitro co-culture model of gut inflammation (Caco-2 and RAW 264.7) after an in vitro digestion and fermentation. The potential of digested and fermented whey from cow, sheep, goat and mixture to minimize the in vitro inflammation was demonstrated by reducing the secretion of IL-8 and TNF-? of inflamed cells. Chapter 4 was developed to know the role as secretagogue of several types of raw whey and after a whole digestion and fermentation on two satiating peptides (CCK and GLP-1) releasing by using the intestinal tumour cell line STC-1. Digested whey showed the highest satiating potential due to its protein degradation, followed by fermented samples, which caused the satiating effect through the synergistic effect of short chain fatty acids (SCFA) and protein breakdown products. The least satiating effect was found in undigested whey, suggesting that intact whey protein is not a good satiating candidate. Follow on with healthy effect of milk whey, in chapter 5 was studied the qualitative and quantitative differences of the gut microbiota and SCFA from normal-weigh and obese human donors in response to different types of whey milk, by simulating an in vitro digestion and colonic fermentation. Gut microbiota has been related to obesity and diabetes, inflammatory bowel diseases and colon cancer. Microbiota related to obesity is characterised by a low diversity of bacteria population with increases of Firmicutes and decreases in Bacteroidetes, meanwhile normal-whey microbiota profile is rather than linked to increases in Bifidobacterium animalis, Methanobrevibacter smithii and phylum Bacteroidetes. SCFA derived from bacterial fermentation has been associated to regulation of energy intake and energy metabolism. We found that whey milk from cow, sheep and mixture had a prebiotic effect on the gut microbiota of normal-weight and obese donors during batch culture fermentation stimulating the growth of probiotic bacteria. Chapter 6 had the objective of optimising the ultrafiltration technology (varying pressure, lactose concentration and ultrafiltration membranes) to separate lactose and protein in sheep whey. For this purpose, 3 ultrafiltration membranes with different composition and molecular weight cut-off were used (GR60PP, GR80PP and GR90PP). Main results revealed that lactose separation was not affected by pressure in GR60PP and GR90PP and remaining lactose removal stable in 3 membranes when feeding concentration increased. Finally, chapter 7 had the main objective of evaluating the satiating and anti-obesogenic effect of several ingredients from Mediterranean regions: goat whey protein, egg white protein, tiger nut and nopal by using obese C57BL/6J mice for 11 weeks of dietary intervention. Feeding pattern, cumulative food and energy intake, circulating satiating peptides, organs morphology and body composition were determined. Results demonstrated the satiating potential and the ability to revert an obese condition of several Mediterranean ingredients. Obese mice fed with high-protein diets (goat whey and egg white) and nopal exhibited decreases in food and energy intake over 11 weeks of treatment, obtaining a reduction of body weight and total fat storage. Although all Mediterranean ingredients tested in obese mice over 11 weeks have demonstrated beneficial effect on satiety and body weight management, whey, egg white and nopal proved promising effect on regulating markers related to obesity and satiety signals.