Effect of salinity on the synthesis and concentration of glycine betaine in osmoregulatory tissues from juvenile shrimps Litopenaeus vannamei

Cloning and expression profile of the alanine aminotransferase gene from kuruma shrimp Penaeus japonicus exposed to different salinities

Several crustaceans including shrimps change the amount of specific free amino acids to regulate the osmotic pressure in their bodies. Kuruma shrimp Penaeus japonicus also increases the concentration of alanine (Ala) in the abdominal muscle following the increase of environmental salinity. In the present study, to elucidate the mechanisms of changes in Ala accumulation of kuruma shrimp depending on salinity, we cloned the gene encoding alanine aminotransferase (ALT), an enzyme involved in Ala biosynthesis, and examined its expression profile. It was found that the full-length kuruma shrimp ALT1 cDNA consisted of 3,301 bp, encoding 514 amino acids, and that all amino acid residues important for ALT activity were conserved. Phylogenetic analysis also indicated that the ALT gene cloned in this study was classified as ALT1. Moreover, we examined the expression levels of the ALT1 gene in the abdominal muscle and the hepatopancreas of kuruma shrimp acclimated at 17‰, 34‰, and 40‰ salinities, resulting that the mRNA levels of the ALT1 genes in both tissues of the shrimp acclimated at 40‰ were significantly higher than those at 17‰ for 12 h (p < 0.05). The mRNA levels of the ALT1 gene in the abdominal muscle of the shrimp acclimated for more than 24 h tended to increase following the increase of environmental salinity. These results indicate that ALT1 is responsible for the increase of free Ala concentration in the abdominal muscle of kuruma shrimp to regulate osmotic pressure at high salinity.

Metabolic profiling of Mytilus coruscus mantle in response of shell repairing under acute acidification

Mytilus coruscus is an economically important marine bivalve mollusk found in the Yangtze River estuary, which experiences dramatic pH fluctuations due to seasonal freshwater input and suffer from shell fracture or injury in the natural environment. In this study, we used intact-shell and damaged-shell M. coruscus and performed metabolomic analysis, free amino acids analysis, calcium-positive staining, and intracellular calcium level tests in the mantle to investigate whether the mantle-specific metabolites can be induced by acute sea-water acidification and understand how the mantle responds to acute acidification during the shell repair process. We observed that both shell damage and acute acidification induced alterations in phospholipids, amino acids, nucleotides, organic acids, benzenoids, and their analogs and derivatives. Glycylproline, spicamycin, and 2-aminoheptanoic acid (2-AHA) are explicitly induced by shell damage. Betaine, aspartate, and oxidized glutathione are specifically induced by acute acidification. Our results show different metabolic patterns in the mussel mantle in response to different stressors, which can help elucidate the shell repair process under ocean acidification. furthermore, metabolic processes related to energy supply, cell function, signal transduction, and amino acid synthesis are disturbed by shell damage and/or acute acidification, indicating that both shell damage and acute acidification increased energy consumption, and disturb phospholipid synthesis, osmotic regulation, and redox balance. Free amino acid analysis and enzymatic activity assays partially confirmed our findings, highlighting the adaptation of M. coruscus to dramatic pH fluctuations in the Yangtze River estuary.

Osmotic Contribution of Synthesized Betaine by Choline Dehydrogenase Using In Vivo and In Vitro Models of Post-traumatic Syringomyelia

Introduction

Syringomyelia (SM) is a debilitating spinal cord disorder in which a cyst, or syrinx, forms in the spinal cord parenchyma due to congenital and acquired causes. Over time syrinxes expand and elongate, which leads to compressing the neural tissues and a mild to severe range of symptoms. In prior omics studies, significant upregulation of betaine and its synthesis enzyme choline dehydrogenase (CHDH) were reported during syrinx formation/expansion in SM injured spinal cords, but the role of betaine regulation in SM etiology remains unclear. Considering betaine's known osmoprotectant role in biological systems, along with antioxidant and methyl donor activities, this study aimed to better understand osmotic contributions of synthesized betaine by CHDH in response to SM injuries in the spinal cord.

Methods

A post-traumatic SM (PTSM) rat model and in vitro cellular models using rat astrocytes and HepG2 liver cells were utilized to investigate the role of betaine synthesis by CHDH. Additionally, the osmotic contributions of betaine were evaluated using a combination of experimental as well as simulation approaches.

Results

In the PTSM injured spinal cord CHDH expression was observed in cells surrounding syrinxes. We next found that rat astrocytes and HepG2 cells were capable of synthesizing betaine via CHDH under osmotic stress in vitro to maintain osmoregulation. Finally, our experimental and simulation approaches showed that betaine was capable of directly increasing meaningful osmotic pressure.

Conclusions

The findings from this study demonstrate new evidence that CHDH activity in the spinal cord provides locally synthesized betaine for osmoregulation in SM pathophysiology.

Supplementary Information

The online version of this article contains supplementary material available 10.1007/s12195-022-00749-5.