Differential metabolite levels in response to spawning-induced inappetence in Atlantic salmon Salmo salar

Untargeted plasma metabolomic analysis of wild bottlenose dolphins (Tursiops truncatus) indicate protein degradation when in poorer health

Cumulative exposure to sub-lethal anthropogenic stressors can affect the health and reproduction of coastal cetaceans and hence their population viability. To date, we do not have a clear understanding of the notion of health for cetaceans in an ecological context; that is, how health status affects the ability of individuals to survive and reproduce. Here, we make use of a unique health-monitoring programme of estuarine bottlenose dolphins in South Carolina and Florida to determine de novo changes in biological pathways, using untargeted plasma metabolomics, depending on the health status of individuals obtained from veterinary screening. We found that individuals that were in a poor health state had lower circulating amino acids pointing towards increased involvement of gluconeogenesis (i.e., new formation of glucose). More mechanistic work is needed to disentangle the interconnection between health and energy metabolism in cetaceans to mediate potential metabolic constraints they may face during periods of stress.

Antimicrobial Peptides of Salmonid Fish: From Form to Function

Antimicrobial peptides (AMPs) are small, usually cationic, and amphiphilic molecules that play a crucial role in molecular and cellular host defense against pathogens, tissue damage, and infection. AMPs are present in all metazoans and several have been discovered in teleosts. Some teleosts, such as salmonids, have undergone whole genome duplication events and retained a diverse AMP repertoire. Salmonid AMPs have also been shown to possess diverse and potent antibacterial, antiviral, and antiparasitic activity and are induced by a variety of factors, including dietary components and specific molecules also known as pathogen-associated molecular patterns (PAMPs), which may activate downstream signals to initiate transcription of AMP genes. Moreover, a multitude of cell lines have been established from various salmonid species, making it possible to study host-pathogen interactions in vitro, and several of these cell lines have been shown to express various AMPs. In this review, the structure, function, transcriptional regulation, and immunomodulatory role of salmonid AMPs are highlighted in health and disease. It is important to characterize and understand how salmonid AMPs function as this may lead to a better understanding of host-pathogen interactions with implications for aquaculture and medicine.

Metabolomics Provide Sensitive Insights into the Impacts of Low Level Environmental Contamination on Fish Health-A Pilot Study

This exploratory study aims to investigate the health of sand flathead (Platycephalus bassensis) sampled from five sites in Port Phillip Bay, Australia using gas chromatography-mass spectrometry (GC-MS) metabolomics approaches. Three of the sites were the recipients of industrial, agricultural, and urban run-off and were considered urban sites, while the remaining two sites were remote from contaminant inputs, and hence classed as rural sites. Morphological parameters as well as polar and free fatty acid metabolites were used to investigate inter-site differences in fish health. Significant differences in liver somatic index (LSI) and metabolite abundance were observed between the urban and rural sites. Differences included higher LSI, an increased abundance of amino acids and energy metabolites, and reduced abundance of free fatty acids at the urban sites compared to the rural sites. These differences might be related to the additional energy requirements needed to cope with low-level contaminant exposure through energy demanding processes such as detoxification and antioxidant responses as well as differences in diet between the sites. In this study, we demonstrate that metabolomics approaches can offer a greater level of sensitivity compared to traditional parameters such as physiological parameters or biochemical markers of fish health, most of which showed no or little inter-site differences in the present study. Moreover, the metabolite responses are more informative than traditional biomarkers in terms of biological significance as disturbances in specific metabolic pathways can be identified.

Gas Chromatography-Mass Spectrometry Microbial Metabolomics for Applications in Strain Optimization

Metabolomics is the systems-scale measurement of biochemical intermediates in biological systems; by virtue of its deep and broad study of metabolism, it has great potential for applications in metabolic engineering. While a number of the analytical techniques used widely in metabolomics are familiar to metabolic engineers performing post hoc analyses of product titers, the requirements for accurately capturing metabolism at a systems scale rather than just measuring a single secreted product are much more complicated. Nonetheless, metabolomics (which is still not widely available as an affordable consumer service like many molecular biology services) is within reach of many properly equipped metabolic engineering groups. To this end, we present a detailed metabolomics protocol with application to strain optimization. Specifically, we focus on characterizing metabolism in the yeast Saccharomyces cerevisiae using gas chromatography coupled to mass spectrometry. The measurement of metabolic intermediates that results from such approaches has the potential to enable more informed and rational efforts towards pathway engineering and strain optimization.

Metabolomics Responses of Pearl Oysters (Pinctada fucata martensii) Fed a Formulated Diet Indoors and Cultured With Natural Diet Outdoors

Natural disasters and environmental pollution are the main problems in traditional offshore cultivation. While culturing pearl oysters through industrial farming can avoid these problems, food availability in this case is limited. This study compares the metabolomics responses of pearl oysters, Pinctada fucata martensii, fed a formulated diet indoors with those of oysters cultured with natural diet outdoors by using a gas chromatography time-of-flight mass spectrometry (GC-TOF/MS)-based metabolomics approach. The animals were divided into two groups as follows: the experimental group (EG) was fed a formulated diet indoors and the control group (CG) was cultured with natural diet outdoors. After 45 days of feeding, the survival rate of EG was significantly higher than that of CG. The absolute growth rate (AGR) of the total weight of EG did not significantly differ from that of CG, but the AGRs of the shell length, shell height, and shell width of CG were significantly higher than those of EG. EG showed significantly higher amylase activities than CG, and the hexokinase and glucose-6-phosphate isomerase concentrations of the former were significantly lower than those of the latter. Metabolomics revealed 125 metabolites via mass spectrum matching with a spectral similarity value > 700 in the hepatopancreas, and 48 metabolites were considered to be significantly different between groups (VIP > 1 and P < 0.05). Pathway analysis results indicated that these significantly different metabolites were involved in 34 pathways. Further integrated key metabolic pathway analysis showed that, compared with CG, EG had lower capabilities for cysteine and methionine metabolism, sulfur metabolism, and starch and sucrose metabolism. This study demonstrated that the formulated diet could be an excellent substitute for natural diet; however, its nutrients were insufficient. Effective strategies should be developed to enhance the utilization of formulated diets.