World Aquaculture Society Meetings

AUTOPHAGY AND STARVATION: A MANAGERIAL MINE FOR SUSTAINABLE AQUACULTURE  

Sipra Mohapatra*, Tapas Chakraborty, Sonoko Shimizu, Takahiro Matsubara,
Yoshitaka Nagahama, and Kohei Ohta
 
South Ehime Fisheries Research Center, Ehime University, Japan 798-4206
mohapatra.sipra.aq@ehime-u.ac.jp

In this era of eco-friendly physiological management, starvation is gaining importance as an alternative for drug-applied disease management. Autophagy is highly instrumental in starvation-associated benefits in different disease management. Fish is a major replenishable food source, which needs sustainable eco-management. Insight into starvation-associated autophagy regulation will help us to determine the management strategies for environment-friendly and toxic residue-free aquaculture. The present study was aimed to focus on the starvation-associated energy management strategies and autophagic mechanism in Japanese anchovy (Engraulis japonicus).

Adult Japanese anchovy (avg. wt. 15 ± 0.25) were randomly distributed into two groups (one group was fed with commercial feed while the other group was starved continuously) with two replicates, and reared for an experimental period of 20 days. The fish were periodically sampled at 2, 6, 12, and 20 dat (days after treatment) to analyze the enzymatic, transcriptional (Realtime PCR) and histological (Hematoxylin & Eosin (HE) and Fluorescent in situ hybridisation (FISH)) changes in the liver at different time points.

In the present study, as expected, increased liver SOD, CAT and glycolytic enzymes (hexokinase and pyruvate kinase) activity was observed in the starved group in comparison to the fed groups. Histological analysis depicted vacuole formation and cell shrinkage, but not severe cell damage. Higher incidence of autophagic marker genes (AMPK, Beclin1, LC3, etc.) was also noticed in the starved fish liver than the apoptosis genes (p53, etc.). Literature suggests that hexokinase is an important factor for autophagic induction in several cell lines. Interestingly, upon hexokinase over-expression (HKOV) in excess (5mg/ml) or no glucose condition, we found that HKOV in excess glucose condition did not enhance autophagy. However, autophagy was significantly elevated in the glucose-starved groups than their non-HKOV counterparts. This highlights that the occurrence of autophagy is a method to preserve energy for a longer period of time under stressful condition, thereby resulting in the higher survivability.  




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