Different physical forms of one diet fed to growing pigs induce morphological changes in mandubular glands and local leptin (Ob) production and receptor (ObR) expression

Abstract

The physical form of the diet plays an important role for morphological adaptations of organs in the gastrointestinal tract. It was hypothesized that different physical forms of one diet could exert extra-enteric effects, under local and systemic neuroendocrine regulation. Gross morphology, fresh mass and cytoarchitecture of mandibular glands (MG) were studied in growing pigs fed with one diet processed under four different physical forms. Four dietary treatments were offered for 4 weeks to 32 growing pigs (initial BW: 8.30 ± 0.83 kg) allotted into 4 experimental groups: FP, finely ground pellet (dMean, 0.46 mm); CM, coarsely ground meal (dMean, 0.88 mm); CP, coarsely ground pellet (dMean, 0.84); CE, coarsely ground extruded (dMean, 0.66). Conventional and immuonohistochemical techniques were used to immunolocalize, in particular, leptin (Ob) and its receptor (ObR). A significant effect was observed on the relative mass of the MG, depending on the diet (p < 0.03) and on the BW (p < 0.04), with no interactions (diet*BW). The immunohistochemical reactions for Ob and ObR showed a marked positivity in the MG from the group fed with the CM diet, displaying Ob-positive acinar cells and ObR-positive cells in the striated ducts, together with endocrine-like cells. The intensity of chromogenic reactions positively testing to ObR was used to evaluate the cytoarchitecture of the MG and its possible correlations. Pearson's correlation coefficient resulted to positively link (p < 0.0001) the ObR expression with the absolute mass of MG in the 61.1% of pigs. The physical form of the diet is related to extra-enteral effects, inducing changes in gross and microscopic morphology of the MG in the growing pig. The local production of Ob and the expression of the respective ObR in the striated duct cells shed a new light on the mitogenic activity of Ob in extra-enteral organs, like the MG, in relation to the physical form of the diet.

The presence and distribution of cannabinoid type 1 and 2 receptors in the mandibular gland: The influence of different physical forms of diets on their expression in piglets

“…All animals were housed individually without litter. For the specific dietary treatment, see Cappai et al., . All pigs were fed ad libitum with fresh diet every morning and had free access to water.…”

“…Recently, Cappai et al. () reported morpho‐functional changes in the mandibular gland of growing pigs fed with different physical forms of the same diet. They showed that a coarser diet increased the expression of leptin and its receptor in the epithelial cells of striated ducts (Cappai et al., ).…”

“…Therefore, the aim of this study was to evaluate (i) whether CB1 and CB2 are expressed in the mandibular gland of pigs and (ii) whether different physical types of the same diet modulate their expression in different ways. We chose to investigate the mandibular gland of swine because of our long‐time interest in this salivary gland (Cappai et al., ; Dall'Aglio et al., ) and in consideration of the increasing interest on this animal model due to analogies between the digestive apparatus of swine and that of humans.…”

“…() reported morpho‐functional changes in the mandibular gland of growing pigs fed with different physical forms of the same diet. They showed that a coarser diet increased the expression of leptin and its receptor in the epithelial cells of striated ducts (Cappai et al., ). These findings suggested a link between the type of diet and the functional role of molecules, such as leptin, which are likely involved in the functional regulation of the mandibular gland in human as well in other animal species (Bohlender, Rauh, Zenk, & Gröschl, ; Dall'Aglio, Maranesi, Pascucci, Mercati, & Ceccarelli, ; Leone et al., ).…”

Role of Feed Processing on Gut Health and Function in Pigs and Poultry: Conundrum of Optimal Particle Size and Hydrothermal Regimens

“…Recent data in pigs indicated that molecular and morpho-function of mandibular gland of pigs may be influenced by physical form of diet. A coarser diet was shown to increase the expression of leptin and its receptor in the epithelial cells of striated ducts in growing pigs (93). Further studies in piglets demonstrated differential expression and localization of cannabinoid receptors type 1 (CB1) and cannabinoid receptors type 2 (CB2) in the mandibular glands in response to variable chewing activity due to different diets form (94).…”