Flesh quality loss in response to dietary isoleucine deficiency and excess in fish: a link to impaired Nrf2-dependent antioxidant defense in muscle

PLoS One. 2014 Dec 16;9(12):e115129. doi: 10.1371/journal.pone.0115129. eCollection 2014.

Abstract

The present study explored the impact of dietary isoleucine (Ile) on fish growth and flesh quality and revealed a possible role of muscle antioxidant defense in flesh quality in relation to dietary Ile. Grass carp (weighing 256.8±3.5 g) were fed diets containing six graded levels of Ile (3.8, 6.6, 9.3, 12.5, 15.2 and 18.5 g/kg) for eight weeks. The results indicated that compared with Ile deficiency (3.8 g/kg diets) and excess (18.5 g/kg diets) groups, 9.3-15.2 g Ile/kg diet supplementations promoted fish growth and muscle fat deposition, whereas 6.6-15.2 g Ile/kg diets supplementation enhanced muscle nutrients (protein and total EAAs) deposition. Furthermore, muscle shear force, pH value, and hydroxyproline concentration were improved by 9.3-12.5, 9.3 and 9.3 g Ile/kg diet supplementations, respectively. However, muscle cooking loss, lactate content, and activities of cathepsin B and L were decreased by 6.6-15.2, 9.3-12.5, 9.3-12.5 and 9.3-15.2 g Ile/kg diet supplementations, respectively. Additionally, 6.6-15.2 and 6.6-12.5 g Ile/kg diet supplementations attenuated malondialdehyde and protein carbonyl contents, respectively. The activities of copper/zinc superoxide dismutase (Cu/Zn-SOD) and glutathione peroxidase (GPx), and glutathione content were enhanced by 6.6-9.3, 6.6-12.5 and 6.6-15.2 g Ile/kg diet supplementations, respectively. Moreover, the relative mRNA expressions of antioxidant enzymes, including Cu/Zn-SOD (6.6-12.5 g/kg diets) and GPx (12.5 g/kg diets), as well as antioxidant-related signaling molecules, including NF-E2-related factor 2 (Nrf2) (6.6-12.5 g/kg diets), target of rapamycin (6.6-12.5 g/kg diets), ribosomal S6 protein kinase 1 (9.3-12.5 g/kg diets) and casein kinase 2 (6.6-12.5 g/kg diets), were up-regulated when Ile diet supplementations were administered at these levels, respectively, whereas the relative mRNA expression of Kelch-like ECH-associated protein 1 was down-regulated with 9.3 g Ile/kg diet supplementations. Collectively, the present study indicated that optimum isoleucine improved flesh quality, partly due to the activation of antioxidant defense through the Nrf2 signaling pathway.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Antioxidants / metabolism
  • Body Fat Distribution
  • Carps
  • Casein Kinase II / metabolism
  • Diet
  • Dietary Supplements*
  • Gene Expression Regulation
  • Glutathione / metabolism
  • Glutathione Peroxidase / metabolism
  • Isoleucine / pharmacology*
  • Malondialdehyde / metabolism
  • Meat / analysis*
  • Muscles / metabolism*
  • NF-E2-Related Factor 2 / metabolism
  • Nutritive Value / drug effects*
  • Oxidative Stress / genetics
  • RNA, Messenger / biosynthesis
  • Ribosomal Protein S6 Kinases / metabolism
  • Superoxide Dismutase / metabolism
  • TOR Serine-Threonine Kinases / metabolism

Substances

  • Antioxidants
  • NF-E2-Related Factor 2
  • RNA, Messenger
  • Isoleucine
  • Malondialdehyde
  • Glutathione Peroxidase
  • Superoxide Dismutase
  • Casein Kinase II
  • Ribosomal Protein S6 Kinases
  • TOR Serine-Threonine Kinases
  • Glutathione

Grants and funding

This research was financially supported by the National Department Public Benefit Research Foundation (Agriculture) of China (201003020), Major Scientific and Technological Achievement Transformation Project of Sichuan Province of China (2012NC0007), Science and Technology Support Program of Sichuan Province (2014NZ0003) and National 973 Project (2014CB138600). The authors would like to thank the personnel of these teams for their kind assistance. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.