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The three essential amino acids, valine, leucine and isoleucine, constitute the group of branched-chain amino acids (BCAAs). BCAAs are rapidly taken up into the brain parenchyma, where they serve several distinct functions including that as fuel material in brain energy metabolism. As one function of astrocytes is considered the production of fuel molecules that support the energy metabolism of adjacent neural cells in brain. Astroglia-rich primary cultures (APC) were shown to rapidly dispose of the BCAAs, including valine, contained in the culture medium. While the metabolisms of leucine and isoleucine by APC have already been studied in detail, some aspects of valine metabolism remained to be determined. Therefore, in the present study an NMR analysis was performed to identify the (13)C-labelled metabolites that are generated by APC during catabolism of [U-(13)C]valine and that are subsequently released into the incubation medium. The results presented show that APC (1) are potently disposing of the valine contained in the incubation medium; (2) are capable of degrading valine to the tricarboxylic acid (TCA) cycle member succinyl-CoA; and (3) release into the extracellular milieu valine catabolites and compounds generated from them such as [U-(13)C]2-oxoisovalerate, [U-(13)C]3-hydroxyisobutyrate, [U-(13)C]2-methylmalonate, [U-(13)C]isobutyrate, and [U-(13)C]propionate as well as several TCA cycle-dependent metabolites including lactate.

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Isoleucine, together with leucine and valine, constitutes the group of branched-chain amino acids (BCAAs). BCAAs are transported from the blood into the brain parenchyma, where they can serve several distinct functions. Since brain tissue is known to oxidatively metabolize BCAAs to CO(2), they are considered as fuel material in brain energy metabolism. Also, in the case of leucine, cultured astrocytes have been reported to be able to completely oxidize BCAA. While the metabolism of leucine by astroglia-rich primary culture (APC) has already been studied in detail, the metabolic fates of isoleucine and valine in these cells remained to be identified. Therefore, in the present study an NMR analysis was performed of (13)C-labelled metabolites generated in the catabolism of [U-(13)C]Ile by astrocytes and released by them into the incubation medium. APC potently removed isoleucine from the medium and metabolized it. The major isoleucine metabolites released from APC are 2-oxo-3-methylvalerate, 2-methylbutyrate, 3-hydroxy-2-methylbutyrate and propionate. To a lesser extent, APC generate and release also [2,3-(13)C]glutamine, [4,5-(13)C]glutamine and (13)C-labelled isotopomers of lactate and citrate. These results show that APC can release into the extracellular milieu catabolites and several TCA cycle dependent metabolites resulting from the degradation of isoleucine.

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The present research explored the effects of Bacillus subtilis on water quality, growth, immune responses, endotoxemia and protection against lipopolysaccharide (LPS) damages in Nile tilapia Oreochromis niloticus under biofloc system. B. subtilis was added at 0, 1, 2, 3 and 4 grams (1.19 × 108 CFU/g) per kg of basal diet, named T1 (control), T2, T3, T4 and T5, respectively, and fed to fish (14.82 ± 0.42 g) for 50 days. The concentrations of TAN, NO2 and NO3 were significantly reduced, and fish fed probiotics displayed significantly better growth performances versus the control, concomitantly with significantly enhanced activities of digestive enzymes. They also showed significantly declined serum glucose and cholesterol vice versa significantly improved immune responses (total protein, albumin, globulin, lysozyme, alternative complement, protease, immunoglobulins, alkaline phosphatase and respiratory burst), antioxidant capacity (superoxide dismutase, total antioxidant capacity, malondialdehyde) and skin mucus parameters (total protein, lysozyme, alternative complement, protease, immunoglobulins). Meanwhile, significantly lower endotoxin (LPS) concentrations were detected in the intestines and serum of fish fed probiotics. LPS challenge induced profound oxidative stress and impaired immune responses. Interestingly, probiotic alleviated LPS‐induced damages and restored mentioned parameters. In conclusion, B. subtilis effectively enhanced fish production, immunity and protection against LPS‐induced damages in tilapia under biofloc system.