Distinct Pattern of NPY in Gastro-Entero-Pancreatic System of Goat Kids Fed with a New Standardized Red Orange and Lemon Extract (RLE)

Abstract

The use of natural compounds as feed additive is also increasing in farm animals, thanks to the beneficial effect on both animals and consumers health. Here, we questioned whether natural extracts, such as red orange and lemon extract (RLE) rich in flavanones, anthocyanins, and other polyphenols, used as feed additives could display an effect on the neuropeptide Y (NPY) in the gastro-entero-pancreatic tract of goat kids. NPY is one of the most abundant neuropeptides in mammals, known for its orexigenic role although it is involved in many central and peripheral functions. We carried out immunohistochemical analyses on samples of abomasum, duodenum and pancreas collected from two experimental groups: one fed with standard diet and one with standard diet + RLE. For the first time we document NPY distribution in the abomasum, duodenum and pancreas of goats and observe the highest number of NPY positive cells in neuroendocrine cells of duodenum. Remarkably, upon RLE feed supplementation, NPY immunoreactive cells increased significantly in abomasal epithelium and pancreatic islets but not in duodenum, likely due to pH variation of abomasum and duodenum. Our observations represent a baseline for future studies on the interaction between neuropeptides and polyphenols, used as feed additive.

Keywords: feed additive; gastro-intestinal apparatus; goats; natural compound; neuropeptides; polyphenols; small ruminants.

Figure 1

Neuropeptide Y (NPY) immunoreactivity in the abomasum, duodenum and pancreas of control and treated goat kids. Scattered positive cells (arrowheads) in the epithelium of gastric mucosa of control (a) and anthocyanins (ANTs) fed animals (b). Overview of NPY distribution in neuroendocrine cells (c) in the crypt of Lieberkühn and varicose positive fibers (arrowhead) in the muscular layer of duodenum of control (a) and ANTs fed animals (d). Higher magnification of neuroendocrine cells in the crypt of Lieberkühn (c1,d1) and fibers in the muscular layer (d2). Overview of NPY distribution in the pancreatic islets of control (e) and ANTs fed animals (f). Scale bar: (a,b,e,f) = 50 µm; (c,d) = 100 µm; (c1,d1,d2) = 25 µm.

Figure 2

5-HT immunoreactivity in the abomasum, duodenum and pancreas of control and treated goat kids. Numerous positive cells in the glands at the basis of gastric epithelium of control (a) and ANTs fed animals (b). Overview of 5-HT distribution in neuroendocrine cells (c) in the crypt of Lieberkühn of duodenum of control (c) and ANTs fed animals (d). Overview of 5-HT distribution in scattered cells in the pancreatic parenchyma of control (e) and ANTs fed animals (f). Scale bar: (a,b,f) = 50 µm; (c,d) = 100 µm; (e) = 25 µm.

Figure 3

Immunofluorescence of NPY (green) and 5-HT (red) in the abomasum, duodenum and pancreas of goat kids fed with red orange and lemon extract (RLE) supplementation. NPY distributed in sparse cells of abomasal epithelium (a1) and 5-HT in glands at the basis of gastric epithelium (a2). Absence of NPY/5-HT co-localization (a1+a2). NPY (b1) and 5-HT (b2) co-distributed in the neuroendocrine cells of duodenum, with NPY mainly localized in the cytoplasm and 5-HT on the cellular membrane (b1+b2). NPY (c1) and 5-HT (c2) in the pancreatic islet, localized in different cells (c1+c2). Scale bar: (a) = 25 µm; (b,c) = 50 µm.

Figure 4

Number of immunoreactive cells in the gastro–entero–pancreatic system of goat kids. (a) Higher distribution in the duodenum and pancreas in control animals. (b) Statistically increased number of NPY immunoreactive cells in the abomasum and pancreas but not in the duodenum following RLE feed supplementation. **** p > 0.0001; ns non-significant.