Salinity-Dependent Shift in the Localization of Three Peptide Transporters along the Intestine of the Mozambique Tilapia (Oreochromis mossambicus)

Abstract

The peptide transporter (PepT) systems are well-known for their importance to protein absorption in all vertebrate species. These symporters use H+ gradient at the apical membrane of the intestinal epithelial cells to mediate the absorption of small peptides. In fish, the intestine is a multifunctional organ, involved in osmoregulation, acid-base regulation, and nutrient absorption. Therefore, we expected environmental stimuli to affect peptide absorption. We examined the effect of three environmental factors; salinity, pH and feeding, on the expression, activity and localization of three PepT transporters (PepT1a, PepT1b, PepT2) along the intestine of the Mozambique tilapia (Oreochromis mossambicus). Quantitative real time PCR (qPCR) analysis demonstrated that the two PepT1 variants are typical to the proximal intestinal section while PepT2 is typical to the distal intestinal sections. Immunofluorescence analysis with custom-made antibodies supported the qPCR results, localized both transporters on the apical membrane of enterocytes and provided the first evidence for the participation of PepT2 in nutrient absorption. This first description of segment-specific expression and localization points to a complementary role of the different peptide transporters, corresponding to the changes in nutrient availability along the intestine. Both gene expression and absorption activity assays showed that an increase in water salinity shifted the localization of the PepT genes transcription and activity down along the intestinal tract. Additionally, an unexpected pH effect was found on the absorption of small peptides, with increased activity at higher pH levels. This work emphasizes the relationships between different functions of the fish intestine and how they are affected by environmental conditions.

Antioxidant Defence, Oxidative Stress and Oxidative Damage in Saliva, Plasma and Erythrocytes of Dementia Patients. Can Salivary AGE be a Marker of Dementia?

“…Samples were protected from exposure to light. In order to provide protection against oxidation processes, butylated hydroxytoluene antioxidant (BHT, Sigma-Aldrich, Saint Louis, MO, USA; 5 μL 0.5 M BHT in acetonitrile per 0.5 mL plasma/erythrocytes) was added to the obtained supernatants [ 14 ]. The samples were frozen at the temperature of −80 °C in which they were stored until being assayed.…”

“…It has been proven that changes in the quantitative and qualitative composition of saliva in dementia patients may entail significant deterioration in the quality of life of patients, as these changes cause problems with swallowing, impair digestion and cause inflammatory and fungal lesions in the oral cavity [ 11 , 12 , 13 ]. It is very likely that oxidative stress is a key factor causing dysfunction of salivary glands in patients with dementia, in a way that is similar to what is observed in metabolic (insulin resistance [ 14 ], obesity [ 15 ] and diabetes [ 16 , 17 ]) and autoimmune diseases (Sjögren syndrome and rheumatoid arthritis [ 18 ]). However, little is known about the role of oxidative stress in the process of damaging salivary glands in dementia patients, as well as the use of salivary oxidative stress markers in the diagnosis of various types of dementia.…”

Glutamate and glutamine transporter genes in grass carp (Ctenopharyngodon idellus): Molecular cloning, characterization and expression in response to different stocking densities

“…The lowest expression levels of the four genes in Figure 6a,b,c,d were heart, anterior intestine, heart and muscle respectively. Therefore, expression levels in these tissues were set to 1 mossambicus) (Con, Nitzan, & Cnaani, 2017). Our findings indicated that slc1a1, slc1a3 and slc7a7 gene expression levels showed specific adaptations in different intestinal sections.…”

Acquisition of alanyl‐alanine in an Agnathan: Characteristics of dipeptide transport across the hindgut of the Pacific hagfish Eptatretus stoutii

“…Con et al . () suggest that there is a potential role for v‐type H + ATPase (VHA) in Mozambique tilapia Oreochromis mosambicus (Peters 1852) peptide absorption (Con et al ., ). Since protons not only provide the driving force for peptide uptake but also can enhance the affinity of the transporter (Verri et al ., ), VHA could create an optimal pH for peptide absorption (Con et al ., ).…”

“…() suggest that there is a potential role for v‐type H + ATPase (VHA) in Mozambique tilapia Oreochromis mosambicus (Peters 1852) peptide absorption (Con et al ., ). Since protons not only provide the driving force for peptide uptake but also can enhance the affinity of the transporter (Verri et al ., ), VHA could create an optimal pH for peptide absorption (Con et al ., ). While the proton transporters present in hagfishes have yet to be identified, this is a viable option for post‐prandial proton extrusion (Nilson & Fänge, ), particularly because VHA has been localised to certain hagfish tissues (Tresguerres et al ., ) and VHA contributes to gastric acidification of some studied invertebrates (Allman et al ., ).…”