Effects of Dietary Supplementation with Chitosan on the Muscle Composition, Digestion, Lipid Metabolism, and Stress Resistance of Juvenile Tilapia (Oreochromis niloticus) Exposed to Cadmium-Induced Stress

Abstract

The aim of this study was to investigate the effects of dietary chitosan supplementation on the muscle composition, digestion, lipid metabolism, and stress resistance, and their related gene expression, of juvenile tilapia (Oreochromis niloticus) subjected to cadmium (Cd²⁺) stress. Juvenile tilapia with an initial body weight of 21.21 ± 0.24 g were fed with a formulated feed containing five different levels (0%, 0.5%, 1.0%, 1.5%, and 2.0%) of chitosan for 60 days, while the water in all experimental groups contained a Cd²⁺ concentration of 0.2 mg/L. The results showed that, compared with the control group (0% chitosan), the contents of crude fat and crude protein in the muscle, the activities of lipase, trypsin, and amylase in the intestine, as well as the relative expression levels of metallothionein (mt), cytochrome P450 1A (cyp1a), carnitine palmitoyltransferase-1 (cpt-1), peroxisome proliferator-activated receptor alpha (pparα), peroxisome proliferator-activated receptor gamma (pparγ), hormone-sensitive lipase (hsl), lipoprotein lipase (lpl), malate dehydrogenase (mdh), leptin (lep), fatty acid synthase (fas), sterol regulatory element-binding protein 1 (srebp1), and stearoyl-CoA desaturase (scd) genes in the liver of juveniles were significantly increased (p < 0.05). In conclusion, dietary chitosan supplementation could alleviate the effects of Cd²⁺ stress on the muscle composition, digestive enzymes, lipid metabolism, and stress resistance, and their related gene expression, of juvenile tilapia, and to some extent reduce the toxic effect of Cd²⁺ stress on tilapia.

Keywords: cadmium; chitosan; lipid metabolism; stress resistance; tilapia.

Figure 1

Effects of dietary supplementation with chitosan on the relative expression levels of stress-resistance genes in the liver of juvenile GIFT exposed to cadmium-induced stress, where hsp indicates heat shock protein, shh indicates sonic hedgehog, mt indicates metallothionein, and cyp1a indicates cytochrome P450 1A. All above data are mean ± SE (n = 3 × 3 × 3), which means 3 parallel groups for each chitosan level, 3 fish samples for each parallel group, and 3 measured times for each fish sample. Different superscript letters in the same figure indicate significant differences among the data (p < 0.05).

Figure 2

Effects of dietary supplementation with chitosan on the relative expression levels of lipid metabolism genes in the liver of juvenile GIFT exposed to cadmium-induced stress, where hsl indicates hormone-sensitive lipase, pparα indicates peroxisome proliferator-activated receptor alpha, lpl indicates lipoprotein lipase, mdh indicates malate dehydrogenase, cpt-1 indicates carnitine palmitoyltransferase 1, lep indicates leptin, fas indicates fatty acid synthase, scd indicates stearoyl-CoA desaturase, sqle indicates squalene epoxidase, pparγ indicates peroxisome proliferator-activated receptor gamma, and srebp1 indicates sterol regulatory element-binding protein 1. All above data are mean ± SE (n = 3 × 3 × 3), which means 3 parallel groups for each chitosan level, 3 fish samples for each parallel group, and 3 measured times for each fish sample. Different superscript letters in the same figure indicate significant differences among the data (p < 0.05).

Figure 2

Effects of dietary supplementation with chitosan on the relative expression levels of lipid metabolism genes in the liver of juvenile GIFT exposed to cadmium-induced stress, where hsl indicates hormone-sensitive lipase, pparα indicates peroxisome proliferator-activated receptor alpha, lpl indicates lipoprotein lipase, mdh indicates malate dehydrogenase, cpt-1 indicates carnitine palmitoyltransferase 1, lep indicates leptin, fas indicates fatty acid synthase, scd indicates stearoyl-CoA desaturase, sqle indicates squalene epoxidase, pparγ indicates peroxisome proliferator-activated receptor gamma, and srebp1 indicates sterol regulatory element-binding protein 1. All above data are mean ± SE (n = 3 × 3 × 3), which means 3 parallel groups for each chitosan level, 3 fish samples for each parallel group, and 3 measured times for each fish sample. Different superscript letters in the same figure indicate significant differences among the data (p < 0.05).

Figure 2

Effects of dietary supplementation with chitosan on the relative expression levels of lipid metabolism genes in the liver of juvenile GIFT exposed to cadmium-induced stress, where hsl indicates hormone-sensitive lipase, pparα indicates peroxisome proliferator-activated receptor alpha, lpl indicates lipoprotein lipase, mdh indicates malate dehydrogenase, cpt-1 indicates carnitine palmitoyltransferase 1, lep indicates leptin, fas indicates fatty acid synthase, scd indicates stearoyl-CoA desaturase, sqle indicates squalene epoxidase, pparγ indicates peroxisome proliferator-activated receptor gamma, and srebp1 indicates sterol regulatory element-binding protein 1. All above data are mean ± SE (n = 3 × 3 × 3), which means 3 parallel groups for each chitosan level, 3 fish samples for each parallel group, and 3 measured times for each fish sample. Different superscript letters in the same figure indicate significant differences among the data (p < 0.05).