**5.2 In vivo studies of diet-induced intestinal permeability**

The cafeteria (CAF) diet is a self-selected high-saturated fat/high-refined sugar diet that stimulates hyperphagia and a rapid weight gain in experimental animals [97, 98]. In this feeding regime, highly palatable and energy dense foods commercially available, such as muffins, biscuits, bacon, sausages, and sugared milk, are offered *ad libitum* [15, 99]. A long-term CAF diet (62% carbohydrate (mostly sugar), 23% lipid, and 13% protein) has negative effects on intestinal function in rodents, increasing intestinal permeability, and inducing mucosal inflammation [43]. We have described the beneficial effects of administering GSPE against the intestinal dysfunction induced by a long-term CAF diet (17–18 weeks) in Wistar rats [8, 14, 15]. The composition of the GSPE used in these studies has been analyzed in detail [100]. Both nutritional (5–50 mg kg<sup>1</sup> [14]) and pharmacological (100–500 mg kg<sup>1</sup> [8, 15]) doses of GSPE administered orally as a preventive [8] or counteractive treatment [14, 15], tended to reduce intestinal inflammatory markers such as TNF-α release or myeloperoxidase (MPO) activity (an indicator of neutrophil infiltration in tissues). The reduction of plasma ovalbumin (OVA), an in vivo marker of intestinal permeability, was supported by (1) the increase in TEER in small and large intestine segments. This parameter is determined *ex vivo* by UChbased protocols [8, 15]; and (2) by the upregulation of TJ proteins such as ZO-1 [14] and claudin-1 [8, 15]. Notably, the protective effect of GSPE in the intestinal barrier function was linked to the amelioration of metabolic endotoxemia (reduction of plasma LPS) and systemic inflammation (reduction of plasma TNF-α) in obese rats [15, 101]. Other authors have also reported the upregulation of ZO-1 and claudin-1 TJ proteins in high-fat fed rats supplemented with other PAC-rich extracts [81].
