Dietary Lactobacillus casei K17 Improves Lipid Metabolism, Antioxidant Response, and Fillet Quality of Micropterus salmoides

Abstract

We previously demonstrated that Lactobacillus casei K17, isolated from Korean kimchi, has high antioxidant levels in vitro and in vivo. However, its effect on Micropterus salmoides is unknown. In this study, we investigated the impact of L. casei K17 supplementation on the lipid metabolism, antioxidant response, liver histology, and fillet quality of M. salmoides. We randomly assigned 450 M. salmoides (33.0 ± 0.5 g) to six diet groups for 69 days. The diets were as follows: 0.85% normal saline; 10% skim milk powder; 1 × 10⁸ CFU/g live L. casei K17 (LB); 1 × 10⁸ live L. casei K17 protected by skim milk powder (MB); 1 × 10⁸ dead L. casei K17 (DB); and L. casei K17 fermentation supernatant. MB significantly improved the crude protein, total collagen, alkaline-insoluble collagen, fiber numbers, hardness, chewiness, and gumminess of M. salmoides fillets (p < 0.05). LB significantly improved crude protein and fiber numbers (p < 0.05). Furthermore, dietary supplementation with LB, MB, and DB maintained normal liver histology, preserved liver function, and increased hepatic and hemal antioxidant status by enhancing antioxidant enzyme activities. Meanwhile, the three diets also promoted lipid metabolism by increasing HDL-C effectiveness and reducing total cholesterol, triglyceride, and low-density lipoprotein cholesterol levels in serum and liver tissues, indicating that dietary supplementation with DB, LB, and MB had hypolipidemic effects on M. salmoides. MB and LB significantly improved fillet quality and LB, MB, and DB improved hemal and hepatic lipid metabolism and antioxidant response and reduced reactive oxygen species production, protecting M. salmoides hepatic cells from injury.

Keywords: Lactobacillus casei; Micropterus salmoides; antioxidant response; lipid metabolism; liver histology; probiotics.

Figure 1

Effects of dietary supplementation with L. casei K17 on M. salmoides fillet composition. (A) Moisture. (B) Ash. (C) Crude protein. (D) Crude lipid. (E) Total collagen. (F) Alkaline-soluble collagen. (G) Alkaline-insoluble collagen. Values (mean ± SE, n = 9), ^a significantly different from SG, p < 0.05.

Figure 1

Effects of dietary supplementation with L. casei K17 on M. salmoides fillet composition. (A) Moisture. (B) Ash. (C) Crude protein. (D) Crude lipid. (E) Total collagen. (F) Alkaline-soluble collagen. (G) Alkaline-insoluble collagen. Values (mean ± SE, n = 9), ^a significantly different from SG, p < 0.05.

Figure 2

Effects of dietary supplementation with L. casei K17 on M. salmoides fillet fibers. (A) Average number value of fillet fiber according to fillet unit area. (B) Microscopic observation of fillet tissue (×40). Values (mean ± SE, n = 9), ^a significantly different from SG, ^b MB significantly different from MG, p < 0.05.

Figure 3

Liver cells of M. salmoides fed with six experimental diets of L. casei K17 (×40).

Figure 4

Effects of dietary supplementation with L. casei K17 on antioxidant capacity in M. salmoides serum and liver. Values (mean ± SE, n = 9), ^a significantly different from SG, ^b MB significantly different from MG, p < 0.05. (A) Serum SOD. (B) Serum MDA. (C) Serum GSH-Px. (D) Serum T-AOC. (E) Liver SOD. (F) Liver MDA. (G) Liver GSH-Px. (H) Liver T-AOC.

Figure 5

Effects of dietary supplementation with L. casei K17 on serum and liver lipids of M. salmoides. Values (mean ± SE, n = 9), ^a significantly different from SG, ^b MB significantly different from MG, p < 0.05. (A) Serum TC. (B) Serum TG. (C) Serum HDL-c. (D) Serum LDL-c. (E) Liver TC. (F) Liver TG. (G) Liver HDL-c. (H) Liver LDL-c.

Figure 6

Effects of dietary supplementation with L. casei K17 on liver TBA of M. salmoides. Values (mean ± SE, n = 9), ^a significantly different from SG, ^b MB significantly different from MG, p < 0.05.