Species-specific low plasma glucose in fish is associated with relatively high tissue glucose content and is inversely correlated with cardiac glycogen content

Effects of dietary supplementation with inactivated Lactobacillus plantarum on growth performance, haemato-biochemical parameters, liver fatty acids profile and intestinal microbiome of Nile tilapia

This study investigated the effects of dietary supplementation with inactivated Lactobacillus plantarum for Nile tilapia (Oreochromis niloticus). Three treatments, in quintuplicate, were established: a control group, fish fed a diet without additives; LP group, fish fed a diet supplemented with live probiotic; and IP group, fish fed a diet supplemented with inactivated probiotic. Final weights (49.40 ± 3.15 g) and weight gains (38.20 ± 3.23 g) were increased in tilapia in the IP group. Feed conversion (1.32 ± 0.04) decreased significantly in the IP group. Haemato-biochemical parameters were significantly influenced by dietary supplementation. Erythrocyte count (262.74 ± 69.28 × 106 μL-1) was significantly low, while albumin (1.79 ± 1.12 g dL-1) and cholesterol (254.14 ± 98.49 mg dL-1) were high in the control group. Dietary supplementation modified the tilapia microbiome. Rhodobacter was abundant in fish intestines from the control and IP groups. Phreatobacter was abundant in the IP and LP groups, while Aurantimicrobium and Bosea were abundant in the LP group. Oleic acid (C18:1n9) was significantly increased in the LP (3.25 ± 0.49%) and IP (3.02 ± 0.30%) groups. Hexadecatrienoic acid (C16:3n4) was significantly increased (0.04 ± 0.01%) in the IP group, while Cis 11,14,17-eicosatrienoic acid (C20:3n3) (0.31 ± 0.03%) and adrenic acid (C22:4n6) (0.11 ± 0.02%) were significantly decreased in the LP group. Additionally, monounsaturated fatty acids (MUFA) were significantly increased (4.83 ± 0.35%) in the LP group compared to that in the control group. Collectively, these results indicate the potential of inactivated L. plantarum for use in commercial feed, leading to the conclusion that both inactivated and live L. plantarum can improve the Nile tilapia metabolism, altering haematological and biochemical markers.

Interrelationship Between Contractility, Protein Synthesis and Metabolism in Mantle of Juvenile Cuttlefish (Sepia officinalis)

Young juvenile cuttlefish (Sepia officinalis) can grow at rates as high as 12% body weight per day. How the metabolic demands of such a massive growth rate impacts muscle performance that competes for ATP is unknown. Here, we integrate aspects of contractility, protein synthesis, and energy metabolism in mantle of specimens weighing 1.1 g to lend insight into the processes. Isolated mantle muscle preparations were electrically stimulated and isometric force development monitored. Preparations were forced to contract at 3 Hz for 30 s to simulate a jetting event. We then measured oxygen consumption, glucose uptake and protein synthesis in the hour following the stimulation. Protein synthesis was inhibited with cycloheximide and glycolysis was inhibited with iodoacetic acid in a subset of samples. Inhibition of protein synthesis impaired contractility and decreased oxygen consumption. An intact protein synthesis is required to maintain contractility possibly due to rapidly turning over proteins. At least, 41% of whole animal ṀO₂ is used to support protein synthesis in mantle, while the cost of protein synthesis (50 μmol O₂ mg protein^–1) in mantle was in the range reported for other aquatic ectotherms. A single jetting challenge stimulated protein synthesis by approximately 25% (2.51–3.12% day^–1) over a 1 h post contractile period, a similar response to that which occurs in mammalian skeletal muscle. Aerobic metabolism was not supported by extracellular glucose leading to the contention that at this life stage either glycogen or amino acids are catabolized. Regardless, an intact glycolysis is required to support contractile performance and protein synthesis in resting muscle. It is proposed that glycolysis is needed to maintain intracellular ionic gradients. Intracellular glucose at approximately 3 mmol L^–1 was higher than the 1 mmol L^–1 glucose in the bathing medium suggesting an active glucose transport mechanism. Octopine did not accumulate during a single physiologically relevant jetting challenge; however, octopine accumulation increased following a stress that is sufficient to lower Arg-P and increase free arginine.