Nutrigenomic studies on hilsa to evaluate flesh quality attributes and genes associated with fatty acid metabolism from the rivers Hooghly and Padma

Abstract

The Indian shad hilsa (Tenualosa ilisha), a commercially important food fish rich in oils, enjoys high consumer preference in the South Asian countries owing to its unique flavour and culinary properties. The present study was undertaken with the primary objective of determining the flesh quality attributes of hilsa in terms of nutritive value (gross chemical composition, amino acid, fatty acid and mineral composition), pH, water holding capacity (WHC) and expression of genes associated with fatty acid metabolism and flesh quality. Additionally, comparative studies on the flesh quality attributes in hilsa from two distributaries of river Ganga i.e. Hooghly and Padma were also carried out. A high WHC (>80%) suggested juicy and tender nature of hilsa meat. The protein content was 18-21% in hilsa from both the rivers and essential amino acid lysine, valine and functional amino acids leucine and arginine were significantly higher in Hooghly hilsa (P<0.05). The predominance of umami taste amino acids, glutamic acid and aspartic acid and sweet taste amino acids, serine, glycine and alanine in hilsa from both the rivers could be the contributing factors to its unique flavour. The fat content in hilsa from river Hooghly and Padma were found to be 9.94 and 7.84%, respectively. The concentration of flavouring fatty acids like saturated fatty acids (SFA) (myristic acid) and omega (ω)-3 polyunsaturated fatty acids (PUFAs) (linoleic acid, α-linolenic acid, arachidonic acid, eicosapentaenoic acid, EPA and docosahexaenoic acid, DHA) were significantly higher in Hooghly hilsa (P<0.05). Among the genes associated with fatty acid metabolism studied, expression of cluster of differentiation (CD36), acetyl CoA oxidase (ACO), fatty acid synthase (FAS), peroxisome proliferator activated receptor beta (PPARβ), peroxisome proliferator activated receptor gamma (PPARγ) and desaturase were significantly higher in Padma hilsa (P<0.05), and the change was <2 fold. Comparative gene expression profiling of flesh quality genes (actin, GAPDH, LDH, TPI) showed similar levels of expression in hilsa from both the rivers (P<0.05). The nutrigenomic information generated on various flesh quality attributes of hilsa has enriched the knowledgebase. Further, from comparative nutrient analysis on hilsa from river Hooghly and Padma, it was observed that Hooghly hilsa is superior in terms of oil content, ω-3 PUFAs EPA and DHA and essential amino acids; however, the expression profile of genes associated with flesh quality were found to be similar. Thus, within the scope of the present study, Hooghly hilsa (medium size category, 500-700g size) was found to be nutritionally superior.