Dietary protein quality differentially regulates trypsin enzymes at the secretion and transcription level in Panulirus argus by distinct signaling pathways

Abstract

with the results of previous digestibility studies (Ward et al., 2003; Irving and Williams, 2007;Perera et al., 2010b). Poor protein use could be related to some impairment in digestive progression when lobsters are fed on pelleted diets (Simon and Jeffs, 2008;Simon, 2009).The aim of the present work was to assess the effect of feeding P. argus with different protein sources on trypsin expression and secretion. Our results demonstrate that trypsin enzymes are differentially regulated at the transcription and secretion level by ingested proteins. Additionally, we provide evidence that intact proteins, rather than small peptides or free amino acids, are the major signal eliciting the prandial secretory response in lobster, whereas SUMMARYThe effects of pelleted diets with different protein composition (fish, squid or soybean meals as main protein sources) on trypsin secretion and expression were studied in the lobster Panulirus argus. Trypsin secretion was shown to be maximal 4h after ingestion. At this time, fish-and squid-based diets induced trypsin secretion, as well as up-regulation of the major trypsin isoform at the transcription level. While fish-and squid-based diets elicited a prandial response, soybean-based diet failed to stimulate the digestive gland to secrete trypsin into the gastric fluid or induce trypsin expression above the levels observed in fasting lobsters. In vitro assays showed that intact proteins rather than protein hydrolysates stimulate trypsin secretion in the lobster. However, the signal for trypsin transcription appears to be different to that for secretion and is probably mediated by the appearance of free amino acids in the digestive gland, suggesting a stepwise regulation of trypsin enzymes during digestion. We conclude that trypsin enzymes in P. argus are regulated at the transcription and secretion level by the quality of dietary proteins through two distinct signaling pathways. Our results indicate that protein digestion efficiency in spiny lobsters can be improved by selecting appropriated protein sources. However, other factors like the poor solubility of dietary proteins in dry diets could hamper further enhancement of digestion efficiency.

Effect of dietary cornstarch levels on growth performance, enzyme activity and hepatopancreas histology of juvenile red swamp crayfish, Procambarus clarkii (Girard)

“…Studies on enzymes regulating the digestion of carbohydrates and proteins can provide useful insight into the utilization of dietary components because various crustaceans have demonstrated the ability to adjust the activity of digestive enzymes to adapt to long-term changes in dietary composition (Guzman et al, 2001;Hoyle, 1973;Lee et al, 1984;Perera et al, 2012;Simon and Jeffs, 2013). Once starch is absorbed, a system located in hepatopancreas with α-amylase performs hydrolysis (Al-Mohanna and Nott, 1987;Wigglesworth and Griffith, 1994).…”

The effects of pre-digested protein sources on the performance of early–mid stage Panulirus ornatus phyllosoma

“…The rudimentary digestive system of phyllosoma and resultant short gut retention time has been identified as a major cause of poor digestibility of formulated feeds (Johnston, 2006;Lipcius and Eggleston, 2000), as slowly digested proteins and other nutrients may be lost in the faeces (Green and Hardy, 2002;Rønnestad and Conceição, 2012). This is concordant with the significantly shorter retention times observed in both the hepatopancreas and hindgut of phyllosoma fed the IFM treatment, indicating that the larger protein particles have been partially rejected (Perera et al, 2012), causing comparatively poor growth and slower development. Conversely, the significantly longer retention times of the HFM diet in both the hepatopancreas and hindgut, coupled with high growth rates and superior development, suggests that the retention time allowed for optimal absorption, and that this diet was better absorbed by the phyllosoma digestive system.…”

“…The increased solubility of protein Table 5 Protein-bound amino acid composition of Panulirus ornatus phyllosoma receiving the IFM, DFM and HFM experimental diets for 35 days (mg g sample wet weight −1 ). following acid-denaturation has been suggested to alleviate the inherently low digestive capabilities of fish larvae (Nankervis and Southgate, 2009;Perera et al, 2012), and this treatment has been used successfully in stomach-less bone fish (Carassius auratus gibelio) (Jany, 1976) and barramundi larvae (Lates calcarifer) (Nankervis and Southgate, 2009). The inferior performance of the denatured protein compared to the hydrolysed protein in this study suggests that the change in conformational state of the protein by the denaturation process may not have sufficiently decreased its structural complexity (Fink et al, 1994;Nankervis and Southgate, 2009), resulting in only a relatively minor increase in assimilation compared to the intact fishmeal.…”

Effect of environmental salinity and dopamine injections on key digestive enzymes in hepatopancreas of the euryhaline crab <i>Cyrtograpsus angulatus</i> (Decapoda: Brachyura: Varunidae)

“…In the American crayfish Orconectes limosus, in vitro experiments showed a differential release of digestive enzyme activity from the hepatopancreas stimulated by several vertebrate gastrointestinal hormones (Resch-Sedlmeir and Sedlmeir 1999). In the lobster Panulirus argus trypsin enzymes are regulated at the transcription and secretion level by distinct pandrial signals related to the quality of dietary proteins (Perera et al 2012).…”