Could lipid content in shellfish diet impact immune signaling?

Posted in Publication

Most people might only associate ceramide with a key ingredient in hand lotion, however Emma Timmins-Schiffman’s recent paper “Characterization of genes involved in ceramide metabolism in the Pacific oyster (Crassostrea gigas)” sheds light on a role for ceramide in responding to stress.

Specifically, Emma examined the role of ceramide in adult oysters’ physiological response to being experimentally challenged with the pathogenic bacteria, Vibrio vulnificus. Two genes demonstrated increased expression during the bacterial challenge: a gene involved in hydrolytic breakdown of ceramide (acid ceramidase) and a gene involved in de novo generation of ceramide (3-ketodihydrosphingosine reductase), suggesting a possible role of ceramide in the invertebrate stress and immune responses.

 

From the Conclusions section of the manuscript:

Here we report the identification of numerous genes in Crassostrea gigas that are homologous to genes involved in vertebrate metabolism of ceramide, an important lipid signaling molecule. Gene expression analysis suggests that ceramide is involved in the immune response of oysters exposed to microbial pathogens. It should be noted that a limited number of genes were examined here and targeted studies would be required to further elucidate the functional role of ceramide metabolism in bivalves. For instance future efforts might directly quantify sphingolipid levels and correlate levels with specific cellular function or use of fluorescence in situ hybridization to show cellular gene expression. Assays of gene expression are sometimes merely suggestive of a true, functional organismal response effected by changes in protein expression. Changes in global gene expression, however, are indicative of a significant physiological response, at least at the cellular level, and frequently these changes are correlated with changes in protein expression. It is not known if lipid content in bivalve diets impacts stress physiology by influencing ceramide levels. Le Grand et al. discovered that ceramide-based phosphophingolipids are an important component of Pacific oyster hemocyte membranes. Characterizing how diet and other conditions affect ceramide metabolism could offer a framework for better understanding mechanisms associated environmental effects on immune function.