A Theileria annulata parasite with a single mutation, methionine 128 to isoleucine (M128I), in cytochrome B is resistant to buparvaquone

Tropical theileriosis is a fatal leukemic-like disease of cattle caused by the tick-transmitted protozoan parasite Theileria annulata. The economics of cattle meat and milk production is severely affected by theileriosis in endemic areas. The hydroxynaphtoquinone buparvaquone (BPQ) is the only available drug currently used to treat clinical theileriosis, whilst BPQ resistance is emerging and spreading in endemic areas. Here, we chronically exposed T. annulata-transformed macrophages in vitro to BPQ and monitored the emergence of drug-resistant parasites. Surviving parasites revealed a significant increase in BPQ IC50 compared to the wild type parasites. Drug resistant parasites from two independent cloned lines had an identical single mutation, M128I, in the gene coding for T. annulata cytochrome B (Tacytb). This in vitro generated mutation has not been reported in resistant field isolates previously, but is reminiscent of the methionine to isoleucine mutation in atovaquone-resistant Plasmodium and Babesia. The M128I mutation did not appear to exert any deleterious effect on parasite fitness (proliferation and differentiation to merozoites). To gain insight into whether drug-resistance could have resulted from altered drug binding to TaCytB we generated in silico a 3D-model of wild type TaCytB and docked BPQ to the predicted 3D-structure. Potential binding sites cluster in four areas of the protein structure including the Q01 site. The bound drug in the Q01 site is expected to pack against an alpha helix, which included M128, suggesting that the change in amino acid in this position may alter drug-binding. The in vitro generated BPQ resistant T. annulata is a useful tool to determine the contribution of the various predicted docking sites to BPQ resistance and will also allow testing novel drugs against theileriosis for their potential to overcome BPQ resistance.

Interactive effects of dietary leucine and isoleucine affect amino acid profile and metabolism through AKT/TOR signaling pathways in blunt snout bream (Megalobrama amblycephala)

The purpose of this research is to explore the interaction between dietary leucine and isoleucine levels on whole-body composition, plasma and liver biochemical indexes, amino acids deposition in the liver, and amino acid metabolism of blunt snout bream (Megalobrama amblycephala). The test fish (average weight: 56.00 ± 0.55 g) were fed one of six diets at random containing two leucine levels (1.70% and 2.50%) and three isoleucine levels (1.00%, 1.20%, and 1.40%) for 8 weeks. The results showed that the final weight and weight gain rate were the highest in the fish fed low-level leucine and high-level isoleucine diets (P > 0.05). Furthermore, the crude lipid content was significantly adjusted by diets with diverse levels of leucine and isoleucine (P < 0.05). In addition, interactive effects of these two branched-chain amino acids (BCAAs) were found on plasma total protein, blood ammonia, and blood urea nitrogen of test fish (P < 0.05). Additionally, the liver amino acid profiles were significantly influenced by the interactive effects of the two BCAAs (P < 0.05). Moreover, interactive effects of dietary leucine and isoleucine were significantly observed in the expressions of amino acid metabolism-related genes (P < 0.05). These findings suggested that dietary leucine and isoleucine had interaction. Meanwhile, the interaction between them was more conducive to the growth and quality improvement of blunt snout bream when the dietary leucine level was 1.70% and isoleucine level was 1.40%.

Valine improves mitochondrial function and protects against oxidative stress

Among the branched-chain amino acids, leucine and isoleucine have been well studied for their roles in improving mitochondrial function and reducing oxidative stress. However, role of valine in mitochondrial function regulation and oxidative stress management remains elusive. This study investigated valine effect on mitochondrial function and oxidative stress in vitro. Valine increased expression of genes involved in mitochondrial biogenesis and dynamics. It upregulates mitochondrial function at complexes I, II, and IV levels of electron transport chain. Flow cytometry studies revealed, valine reduced oxidative stress by significantly lowering mitochondrial reactive oxygen species and protein expression of 4-hydroxynonenal. Functional role of valine against oxidative stress was analyzed by XFe96 Analyzer. Valine sustained oxidative phosphorylation and improved ATP generation rates during oxidative stress. In conclusion, our findings shed more light on the critical function of valine in protecting mitochondrial function thereby preventing mitochondrial/cellular damage induced by oxidative stress.

Dietary restriction of isoleucine increases healthspan and lifespan of genetically heterogeneous mice

Low-protein diets promote health and longevity in diverse species. Restriction of the branched-chain amino acids (BCAAs) leucine, isoleucine, and valine recapitulates many of these benefits in young C57BL/6J mice. Restriction of dietary isoleucine (IleR) is sufficient to promote metabolic health and is required for many benefits of a low-protein diet in C57BL/6J males. Here, we test the hypothesis that IleR will promote healthy aging in genetically heterogeneous adult UM-HET3 mice. We find that IleR improves metabolic health in young and old HET3 mice, promoting leanness and glycemic control in both sexes, and reprograms hepatic metabolism in a sex-specific manner. IleR reduces frailty and extends the lifespan of male and female mice, but to a greater degree in males. Our results demonstrate that IleR increases healthspan and longevity in genetically diverse mice and suggests that IleR, or pharmaceuticals that mimic this effect, may have potential as a geroprotective intervention.

The Potential Effects of Isoleucine Restricted Diet on Cognitive Impairment in High-Fat-Induced Obese Mice via Gut Microbiota-Brain Axis

SCOPE

Obesity induced by high-fat diet (HFD) can cause lipid metabolism disorders and cognitive impairment. Isoleucine restriction can effectively alleviate lipid metabolism disorders caused by HFD but the underlying mechanisms on cognition are unknown.

METHODS AND RESULTS

Thirty 3-month-old C57BL/6J mice are divided equally into the following groups: the control group, HFD group, and HFD Low Ile group (67% reduction in isoleucine in high fat feeds). Feeding for 11 weeks with behavioral testing, which shows that isoleucine restriction attenuates HFD-induced cognitive dysfunction. As observed by staining, isoleucine restriction inhibits HFD-induced neuronal damage and microglia activation. Furthermore, isoleucine restriction significantly increases the relative abundance of gut microbiota, decreases the proportion of Proteobacteria, and reduces the levels of lipopolysaccharide (LPS) in serum and brain. Isoleucine restriction reduces protein expression of TLR4/MyD88/NF-κB signaling pathway and inhibits upregulation of proinflammatory cytokine genes and protein expression in mice brain. In addition, isoleucine restriction significantly improves insulin resistance in the brain as well as synaptic plasticity impairment.

CONCLUSION

Isoleucine restriction may be a potential intervention to reduce HFD-induced cognitive impairment by altering gut microbiota, reducing neuroinflammation, insulin resistance, and improving synaptic plasticity in mice brain.

Transcranial direct-current stimulation confers neuroprotection by regulating isoleucine-dependent signalling after rat cerebral ischemia-reperfusion injury

Isoleucine is a branched chain amino acid. The role of isoleucine in cerebral ischemia-reperfusion injury remains unclear. Here, we show that the concentration of isoleucine is decreased in cerebrospinal fluid in a rat model of cerebral ischemia-reperfusion injury, the rat middle cerebral artery occlusion (MCAO). To our surprise, the level of intraneuronal isoleucine is increased in an in vitro model of cerebral ischemia injury, the oxygen-glucose deprivation (OGD). We found that the increased activity of LAT1, an L-type amino acid transporter 1, leads to the elevation of intraneuronal isoleucine after OGD insult. Reducing the level of intraneuronal isoleucine promotes cell survival after cerebral ischemia-reperfusion injury, but supplementing isoleucine aggravates the neuronal damage. To understand how isoleucine promotes ischemia-induced neuronal death, we reveal that isoleucine acts upstream to reduce the expression of CBFB (core binding factor β, a transcript factor involved in cell development and growth) and that the phosphatase PTEN acts downstream of CBFB to mediate isoleucine-induced neuronal damage after OGD insult. Interestingly, we demonstrate that direct-current stimulation reduces the level of intraneuronal isoleucine in cortical cultures subjected to OGD and that transcranial direct-current stimulation (tDCS) decreases the cerebral infarct volume of MCAO rat through reducing LAT1-depencent increase of intraneuronal isoleucine. Together, these results lead us to conclude that LAT1 over activation-dependent isoleucine-CBFB-PTEN signal transduction pathway may mediate ischemic neuronal injury and that tDCS exerts its neuroprotective effect by suppressing LAT1 over activation-dependent signalling after cerebral ischemia-reperfusion injury.

Methionine-isoleucine dichotomy at a key position in scorpion toxins inhibiting voltage-gated potassium channels

Previous studies have identified some key amino acid residues in scorpion toxins blocking potassium channels. In particular, the most numerous toxins belonging to the α-KTx family and affecting voltage-gated potassium channels (KV) present a conserved K-C-X-N motif in the C-terminal half of their sequence. Here, we show that the X position of this motif is almost always occupied by either methionine or isoleucine. We compare the activity of three pairs of peptides that differ just by this residue on a panel of KV1 channels and find that toxins bearing methionine affect preferentially KV1.1 and 1.6 isoforms. The refined K-C-M/I-N motif stands out as the principal structural element of α-KTx conferring high affinity and selectivity to KV channels.

Glutamine, proline, and isoleucine support maturation and fertilisation of bovine oocytes

Successful in-vitro production of bovine embryos relies on meiotic maturation of oocytes in vitro (IVM) before they can be fertilised. High levels of IVM are currently achieved using a complex medium that contains all 20 common amino acids, namely TCM199, but can also be achieved using a simple inorganic salt solution containing non-essential amino acids, proline, and glutamine. Further simplification of the amino acid content of medium used for IVM could lead to a more defined medium that provides reproducible IVM. The aim of this study was, therefore, to determine the minimal amino acid requirements for bovine oocyte nuclear maturation, as measured by progression to metaphase II (MII) of meiosis. Supplementation of a simple medium composed of inorganic salts (M1 medium) with multiple amino-acid combinations showed that M1 containing glutamine, proline, and isoleucine resulted in nuclear maturation comparable to that of TCM199 (57.4 ± 3.4% vs 67% ± 1.7%, respectively) but was reduced when cystine (Cys2) to that seen with M1 alone (38.0 ± 2.2%). Viability of oocytes matured in this simplified medium was equal to those matured in TCM199 since the same proportion of zygotes with 2 pronuclei were observed following fertilisation in medium containing no amino acids (33.9 ± 6.5% vs 33.3 ± 3.6%, respectively). Addition of glutamine, proline and isoleucine to fertilisation medium also increased the proportion of zygotes but did not increase blastocyst development rates. Thus, a defined medium containing only glutamine, proline and isoleucine is sufficient for oocyte maturation and successful fertilisation.

Bioefficacy of isolated compound l-isoleucine, N-allyloxycarbonyl-, and dodecyl ester from entomopathogenic actinobacteria Actinokineospora fastidiosa against agricultural insect pests, human vector mosquitoes, and antioxidant activities

Spodoptera litura and Helicoverpa armigera are polyphagous pests of agricultural crops in the Asian tropics since these pests have been responsible for massive crop and carry economic losses and low commodity production. At the same time, mosquitoes are vectors for numerous dreadful diseases, which is the most important group of insect for their public health concern. Using synthetic insecticides to control the pests can lead to contamination of land surface and groundwater and impact beneficial soil organisms and nontarget species. Applications of bioactive compounds are received considerable attention across the world as alternatives to synthetic insecticides. In the current study, actinobacterial secondary metabolite was isolated from Actinokineospora fastidiosa for the first time. The effect of actinobacterial metabolite (l-isoleucine, N-allyloxycarbonyl-, and dodecyl ester) was assessed on agricultural pest S. litura and H. armigera, mosquito vectors larvae Ae. aegypti, An. stephensi, and Cx. quinquefasciatus. The bioactive fraction was characterized through UV, FTIR, and NMR analysis. GC-MS analyses reveal the existence of a bioactive compound with a respective retention time of 19.740 responsible for larvicidal activity. The bioefficacy of the l-isoleucine, N-allyloxycarbonyl-, and dodecyl ester showed high antifeedant activity on S. litura (80.80%) and H. armigera (84.49%); and larvicidal activity on S. litura (82.77%) and H. armigera (88.00%) at 25 μg/mL concentration, respectively. The effective LC₅₀ values were 8.07 μg/mL (F = 2.487, r² = 0.988, P ≤ 0.05) on S. litura and 7.53 μg/mL (F = 123.25, r² = 0.951, P ≤ 0.05) on H. armigera. The mosquito larvicidal effect of isolated compounds l-isoleucine, N-allyloxycarbonyl-, and dodecyl ester treated against Ae. aegypti, An. stephensi, and Cx. quinquefasciatus the obtained percentage mortality was 96.66, 83.24, 64.52, 50.00, and 40.00% against Ae. aegypti; 100.00, 86.22, 73.81, 65.37, and 56.24% against An. stephensi; 100.00, 90.00, 76.24, 68.75, and 56.23% against Cx. quinquefasciatus. The mosquito larvae of Ae. aegypti obtained LC₅₀ value was 13.25 μg/mL, F = 28.50, r² = 0.90; on An. stephensi was 10.19 μg/mL, F = 15.55, r² = 0.83, and Cx. quinquefasciatus was 9.68 μg/mL, F = 20.00, r² = 0.87. Furthermore, l-isoleucine-, N-allyloxycarbonyl-, and dodecyl ester-treated larvae produced significant pupicidal activity on S. litura (62.71%) and H. armigera (66.50%) at 25 μg/mL, along with increased larval and pupal duration as compared to control group. Treated larvae revealed obliteration in the midgut epithelial cells and destruction of microvilli was noticed as compared to the control. The isolated compounds l-isoleucine, N-allyloxycarbonyl-, and dodecyl ester did not produce any significant mortality on zebrafish embryos in all tested concentrations on biosafety observation. The potential microbial isolated molecule may fit well in IPM programs. Since the risk to human health, the environment, etc. is unknown.

Toxicity effects of chlorantraniliprole in zebrafish (Danio rerio) involving in liver function and metabolic phenotype

Chlorantraniliprole (CAP), a representative bisamide insecticide, is widely used in rice fields around the world, posing potential toxicity risks to aquatic organisms. In this study, we examined the effects of exposure to CAP on growth and metabolic phenotype of zebrafish (Danio rerio) and oxidative stress and apoptosis in the liver of zebrafish (Danio rerio). First, we identified that CAP had a low bioaccumulation in zebrafish. Subsequently, growth phenotype analysis revealed that CAP could significantly increase liver weight and liver index in zebrafish. In addition, we found that CAP exposure could cause significant changes in indicators of oxidative stress, resulting in a significant increase in the content of malondialdehyde (MDA), causing oxidative stress in the liver of zebrafish. Meanwhile, the expression levels of apoptosis-related genes were also significantly changed and apoptosis was promoted in the liver of zebrafish with CAP exposure. Importantly, the results of metabolomics analysis shown that CAP exposure could significantly disrupt the metabolic phenotype of zebrafish, interfering with multiple metabolic pathways, mainly including valine, leucine and isoleucine biosynthesis and degradation, alanine, aspartate and glutamate metabolism and d-glutamine and D-glutamate metabolism. Last but not least, correlation analysis identified strong links between changes in liver function involving oxidative stress and apoptosis and changes in metabolic phenotype of zebrafish following CAP exposure. In brief, these results indicate that potential environmental risks of CAP to aquatic organisms should receive more attention.

The effect of standardized ileal digestible isoleucine:lysine in diets containing 20% dried distillers grains with solubles on finishing pig performance and carcass characteristics

In order to determine the standardized ileal digestible (SID) Ile:Lys requirement in finishing diets containing 20% DDGS, a 56-d study was conducted utilizing 2,268 pigs (DNA 600 x Topigs Norsvin 70, initially 82.3 kg). A total of six dietary treatments were fed, including a standard corn-soybean meal (SBM) diet and five diets containing 20% DDGS with SID Ile:Lys ratios of 55%, 60%, 65%, 70%, and 75%. Dietary treatments were assigned to pens, incompletely balancing for previous treatment, with each treatment being replicated 14 times. Pair-wise comparisons were used to evaluate the impact of dietary treatment on performance and carcass traits, whereas single degree of freedom orthogonal polynomials were used to evaluate dose response of SID Ile:Lys in 20% DDGS diets. Increasing the SID Ile:Lys ratio in diets containing 20% DDGS did not impact pig growth performance criteria in a quadratic or linear fashion (P ≥ 0.18). However, increasing the SID Ile:Lys ratio in 20% DDGS diets resulted in decreased back fat (BF; Quadratic, P = 0.01), increased loin depth (Quadratic, P = 0.03), and tended to increase percent lean (Quadratic, P = 0.07) with optimal carcass parameters occurring when 65% SID Ile:Lys was supplied in 20% DDGS diets. Pigs fed the corn-SBM diet had a similar final body weight (BW; P = 0.26) and cumulative average daily gain (ADG; P = 0.12) compared to pigs fed a 20% DDGS diet containing 70% SID Ile:Lys ratio and 3% greater cumulative average daily feed intake (ADFI) compared to pigs receiving diets with SID Ile:Lys ratios of 65% and 75% (P ≤ 0.01). In conclusion, these results suggest that when feeding 20% DDGS in late finishing swine diets, a SID Ile:Lys ratio of 70% should be utilized when attempting to achieve similar overall growth performance relative to a corn-SBM diet.

Immunometabolism – The Role of Branched-Chain Amino Acids

Immunometabolism has been the focus of extensive research over the last years, especially in terms of augmenting anti-tumor immune responses. Regulatory T cells (Tregs) are a subset of CD4⁺ T cells, which have been known for their immunosuppressive roles in various conditions including anti-tumor immune responses. Even though several studies aimed to target Tregs in the tumor microenvironment (TME), such approaches generally result in the inhibition of the Tregs non-specifically, which may cause immunopathologies such as autoimmunity. Therefore, specifically targeting the Tregs in the TME would be vital in terms of achieving a successful and specific treatment. Recently, an association between Tregs and isoleucine, which represents one type of branched-chain amino acids (BCAAs), has been demonstrated. The presence of isoleucine seems to affect majorly Tregs, rather than conventional T cells. Considering the fact that Tregs bear several distinct metabolic features in the TME, targeting their immunometabolic pathways may be a rational approach. In this Review, we provide a general overview on the potential distinct metabolic features of T cells, especially focusing on BCAAs in Tregs as well as in their subtypes.

Post-Stroke Administration of the p75 Neurotrophin Receptor Modulator, LM11A-31, Attenuates Chronic Changes in Brain Metabolism, Increases Neurotransmitter Levels, and Improves Recovery

The aim of this study was to test whether poststroke oral administration of a small molecule p75 neurotrophin receptor (p75NTR) modulator (LM11A-31) can augment neuronal survival and improve recovery in a mouse model of stroke. Mice were administered LM11A-31 for up to 12 weeks, beginning 1 week after stroke. Metabolomic analysis revealed that after 2 weeks of daily treatment, mice that received LM11A-31 were distinct from vehicle-treated mice by principal component analysis and had higher levels of serotonin, acetylcholine, and dopamine in their ipsilateral hemisphere. LM11A-31 treatment also improved redox homeostasis by restoring reduced glutathione. It also offset a stroke-induced reduction in glycolysis by increasing acetyl-CoA. There was no effect on cytokine levels in the infarct. At 13 weeks after stroke, adaptive immune cell infiltration in the infarct was unchanged in LM11A-31-treated mice, indicating that LM11A-31 does not alter the chronic inflammatory response to stroke at the site of the infarct. However, LM11A-31-treated mice had less brain atrophy, neurodegeneration, tau pathology, and microglial activation in other regions of the ipsilateral hemisphere. These findings correlated with improved recovery of motor function on a ladder test, improved sensorimotor and cognitive abilities on a nest construction test, and less impulsivity in an open field test. These data support small molecule modulation of the p75NTR for preserving neuronal health and function during stroke recovery. SIGNIFICANCE STATEMENT: The findings from this study introduce the p75 neurotrophin receptor as a novel small molecule target for promotion of stroke recovery. Given that LM11A-31 is in clinical trials as a potential therapy for Alzheimer's disease, it could be considered as a candidate for assessment in stroke or vascular dementia studies.

Enhanced pro-BDNF-p75NTR pathway activity in denervated skeletal muscle

AIMS

Brain derived neurotrophic factor (BDNF) and the related receptors TrkB and p75NTR are expressed in skeletal muscle, yet their functions remain to be fully understood. Skeletal muscle denervation, which occurs in spinal injury, peripheral neuropathies, and aging, negatively affects muscle mass and function. In this study, we wanted to understand the role of BDNF, TrkB, and p75NTR in denervation-induced adverse effects on skeletal muscle.

MAIN METHODS

Mice with unilateral sciatic denervation were used. Protein levels of pro- and mature BDNF, TrkB, p75NTR, activations of their downstream signaling pathways, and inflammation in the control and denervated muscle were measured with Western blot and tissue staining. Treatment with a p75NTR inhibitor and BDNF skeletal muscle specific knockout in mice were used to examine the role of p75NTR and pro-BDNF.

KEY FINDINGS

In denervated muscle, pro-BDNF and p75NTR were significantly upregulated, and JNK and NF-kB, two major downstream signaling pathways of p75NTR, were activated, along with muscle atrophy and inflammation. Inhibition of p75NTR using LM11A-31 significantly reduced JNK activation and inflammatory cytokines in the denervated muscle. Moreover, skeletal muscle specific knockout of BDNF reduced pro-BDNF level, JNK activation and inflammation in the denervated muscle.

SIGNIFICANCE

These results reveal for the first time that the upregulation of pro-BDNF and activation of p75NTR pathway are involved in denervation-induced inflammation in skeletal muscle. The results suggest that inhibition of pro-BDNF-p75NTR pathway can be a new target to treat skeletal muscle inflammation.

Comparative Effects of the Branched-Chain Amino Acids, Leucine, Isoleucine and Valine, on Gastric Emptying, Plasma Glucose, C-Peptide and Glucagon in Healthy Men

(1) Background: Whey protein lowers postprandial blood glucose in health and type 2 diabetes, by stimulating insulin and incretin hormone secretion and slowing gastric emptying. The branched-chain amino acids, leucine, isoleucine and valine, abundant in whey, may mediate the glucoregulatory effects of whey. We investigated the comparative effects of intragastric administration of leucine, isoleucine and valine on the plasma glucose, C-peptide and glucagon responses to and gastric emptying of a mixed-nutrient drink in healthy men. (2) Methods: 15 healthy men (27 ± 3 y) received, on four separate occasions, in double-blind, randomised fashion, either 10 g of leucine, 10 g of isoleucine, 10 g of valine or control, intragastrically, 30 min before a mixed-nutrient drink. Plasma glucose, C-peptide and glucagon concentrations were measured before, and for 2 h following, the drink. Gastric emptying of the drink was quantified using ¹³C-acetate breath-testing. (3) Results: Amino acids alone did not affect plasma glucose or C-peptide, while isoleucine and valine, but not leucine, stimulated glucagon (p < 0.05), compared with control. After the drink, isoleucine and leucine reduced peak plasma glucose compared with both control and valine (all p < 0.05). Neither amino acid affected early (t = 0–30 min) postprandial C-peptide or glucagon. While there was no effect on overall gastric emptying, plasma glucose at t = 30 min correlated with early gastric emptying (p < 0.05). (4) Conclusion: In healthy individuals, leucine and isoleucine lower postprandial blood glucose, at least in part by slowing gastric emptying, while valine does not appear to have an effect, possibly due to glucagon stimulation.

Neuroimaging, Urinary, and Plasma Biomarkers of Treatment Response in Huntington's Disease: Preclinical Evidence with the p75NTR Ligand LM11A-31

Huntington's disease (HD) is caused by an expansion of the CAG repeat in the huntingtin gene leading to preferential neurodegeneration of the striatum. Disease-modifying treatments are not yet available to HD patients and their development would be facilitated by translatable pharmacodynamic biomarkers. Multi-modal magnetic resonance imaging (MRI) and plasma cytokines have been suggested as disease onset/progression biomarkers, but their ability to detect treatment efficacy is understudied. This study used the R6/2 mouse model of HD to assess if structural neuroimaging and biofluid assays can detect treatment response using as a prototype the small molecule p75NTR ligand LM11A-31, shown previously to reduce HD phenotypes in these mice. LM11A-31 alleviated volume reductions in multiple brain regions, including striatum, of vehicle-treated R6/2 mice relative to wild-types (WTs), as assessed with in vivo MRI. LM11A-31 also normalized changes in diffusion tensor imaging (DTI) metrics and diminished increases in certain plasma cytokine levels, including tumor necrosis factor-alpha and interleukin-6, in R6/2 mice. Finally, R6/2-vehicle mice had increased urinary levels of the p75NTR extracellular domain (ecd), a cleavage product released with pro-apoptotic ligand binding that detects the progression of other neurodegenerative diseases; LM11A-31 reduced this increase. These results are the first to show that urinary p75NTR-ecd levels are elevated in an HD mouse model and can be used to detect therapeutic effects. These data also indicate that multi-modal MRI and plasma cytokine levels may be effective pharmacodynamic biomarkers and that using combinations of these markers would be a viable and powerful option for clinical trials.

Intragastric administration of leucine and isoleucine does not reduce the glycaemic response to, or slow gastric emptying of, a carbohydrate-containing drink in type 2 diabetes

AIMS

In healthy individuals, intragastric administration of the branched-chain amino acids, leucine and isoleucine, diminishes the glycaemic response to a mixed-nutrient drink, apparently by stimulating insulin and slowing gastric emptying, respectively. This study aimed to evaluate the effects of leucine and isoleucine on postprandial glycaemia and gastric emptying in type-2 diabetes mellitus (T2D).

METHODS

14 males with T2D received, on 3 separate occasions, in double-blind, randomised fashion, either 10 g leucine, 10 g isoleucine or control, intragastrically 30 min before a mixed-nutrient drink (500 kcal; 74 g carbohydrates, 18 g protein, 15 g fat). Plasma glucose, insulin and glucagon were measured from 30 min pre- until 120 min post-drink. Gastric emptying of the drink was also measured.

RESULTS

Leucine and isoleucine stimulated insulin, both before and after the drink (all P < 0.05; peak (mU/L): control: 70 ± 15; leucine: 88 ± 17; isoleucine: 74 ± 15). Isoleucine stimulated (P < 0.05), and leucine tended to stimulate (P = 0.078), glucagon before the drink, and isoleucine stimulated glucagon post-drink (P = 0.031; peak (pg/mL): control: 62 ± 5; leucine: 70 ± 9; isoleucine: 69 ± 6). Neither amino acid affected gastric emptying or plasma glucose (peak (mmol/L): control: 12.0 ± 0.5; leucine: 12.5 ± 0.7; isoleucine: 12.0 ± 0.6).

CONCLUSIONS

In contrast to health, in T2D, leucine and isoleucine, administered intragastrically in a dose of 10 g, do not lower the glycaemic response to a mixed-nutrient drink. This finding argues against a role for 'preloads' of either leucine or isoleucine in the management of T2D.

Plant grafting relieves asymmetry of jasmonic acid response induced by wounding between scion and rootstock in tomato hypocotyl

Plant grafting is a sequential wound healing process. However, whether wounding induces a different jasmonic acid (JA) response within half a day (12 h) after grafting or non-grafting remains unclear. Using the tomato hypocotyl grafting method, we show that grafting alleviates the asymmetrical accumulation of JA and jasmonic acid isoleucine conjugate (JA-Ile) in scion and rootstock caused by wounding, and from 2 h after tomato micrografting, grafting obviously restored the level of JA-Ile in the scion and rootstock. Meanwhile, five JA-related genes, SlLOX11, SlAOS, SlCOI1, SlLAPA and SlJA2L, are detected and show significant changes in transcriptional expression patterns within 12 h of grafting, from asymmetrical to symmetrical, when the expression of 30 JA- and defense-related genes were analyzed. The results indicated that grafting alleviates the asymmetrical JA and defense response between scion and rootstock of the tomato hypocotyl within 12 h as induced by wounding. Moreover, we demonstrate that in the very early hours after grafting, JA-related genes may be involved in a molecular mechanism that changes asymmetrical expression as induced by wounding between scion and rootstock, thereby promoting wound healing and grafting success.

Small molecule modulation of the p75 neurotrophin receptor inhibits multiple amyloid beta-induced tau pathologies

Longitudinal preclinical and clinical studies suggest that Aβ drives neurite and synapse degeneration through an array of tau-dependent and independent mechanisms. The intracellular signaling networks regulated by the p75 neurotrophin receptor (p75NTR) substantially overlap with those linked to Aβ and to tau. Here we examine the hypothesis that modulation of p75NTR will suppress the generation of multiple potentially pathogenic tau species and related signaling to protect dendritic spines and processes from Aβ-induced injury. In neurons exposed to oligomeric Aβ in vitro and APP mutant mouse models, modulation of p75NTR signaling using the small-molecule LM11A-31 was found to inhibit Aβ-associated degeneration of neurites and spines; and tau phosphorylation, cleavage, oligomerization and missorting. In line with these effects on tau, LM11A-31 inhibited excess activation of Fyn kinase and its targets, tau and NMDA-NR2B, and decreased Rho kinase signaling changes and downstream aberrant cofilin phosphorylation. In vitro studies with pseudohyperphosphorylated tau and constitutively active RhoA revealed that LM11A-31 likely acts principally upstream of tau phosphorylation, and has effects preventing spine loss both up and downstream of RhoA activation. These findings support the hypothesis that modulation of p75NTR signaling inhibits a broad spectrum of Aβ-triggered, tau-related molecular pathology thereby contributing to synaptic resilience.

Effect of dietary isoleucine on skin mucus barrier and epithelial physical barrier functions of hybrid bagrid catfish Pelteobagrus vachelli × Leiocassis longirostris

The study investigated the effects of dietary isoleucine (Ile) on skin mucus barrier and epithelial physical barrier functions of hybrid bagrid catfish Pelteobagrus vachelli × Leiocassis longirostris. A total of 630 fish (33.11 ± 0.09 g) were fed semi-purified isonitrogenous diets containing 5.0 (control), 7.5, 10.0, 12.5, 15.0, 17.5, and 20.0 g Ile kg ^-1 diet for 8 weeks. The results indicated that dietary Ile increased (P < 0.05) in skin (1) mucus protein content and antimicrobial activity against three gram-negative bacteria (Aeromonas hydrophila, Escherichia coli, and Yersinia ruckeri) and two gram-positive bacteria (Streptococcus agalactiae and Staphylococcus aureus), (2) mucus lysofew information is available about the influencezyme (LZM), acid phosphatase (ACP), and alkaline phosphatase (AKP) activities, and complement 3 and 4 (C3 and C4) and immunoglobulin M (IgM) contents, (3) intelectin 1 (intl1), intelectin 2 (intl2), c-type-lysozyme (c-LZM), g-type-lysozyme (g-LZM), and β-defensin mRNA levels. Dietary Ile decreased (P < 0.05) reactive oxygen species (ROS), malondialdehyde (MDA), and protein carbonyl (PC) contents, and up-regulated (P < 0.05) CuZnSOD, GST, GPX1a, muc5ac, muc5b, zonula occludens-1 (ZO-1), zonula occludens-2 (ZO-2), occludin, and claudin 3 mRNA levels in skin. These results indicated that Ile improved skin mucus barrier function via increasing mucus protein, C3 and C4, and IgM contents and antibacterial factors activities, and promoted epithelial physical barrier function via decreasing skin antioxidant damage and improving tight junction structure in hybrid bagrid catfish.

Small molecule modulation of the p75 neurotrophin receptor suppresses age- and genotype-associated neurodegeneration in HIV gp120 transgenic mice

The persistence of HIV in the central nervous system leads to cognitive deficits in up to 50% of people living with HIV even with systemic suppression by antiretroviral treatment. The interaction of chronic inflammation with age-associated degeneration places these individuals at increased risk of accelerated aging and other neurodegenerative diseases and no treatments are available that effectively halt these processes. The adverse effects of aging and inflammation may be mediated, in part, by an increase in the expression of the p75 neurotrophin receptor (p75^NTR) which shifts the balance of neurotrophin signaling toward less protective pathways. To determine if modulation of p75^NTR could modify the disease process, we treated HIV gp120 transgenic mice with a small molecule ligand designed to engage p75^NTR and downregulate degenerative signaling. Daily treatment with 50 mg/kg LM11A-31 for 4 months suppressed age- and genotype-dependent activation of microglia, increased microtubule associated protein-2 (MAP-2), reduced dendritic varicosities and slowed the loss of parvalbumin immunoreactive neurons in the hippocampus. An age related accumulation of microtubule associated protein Tau was identified in the hippocampus in extracellular clusters that co-expressed p75^NTR suggesting a link between Tau and p75^NTR. Although the significance of the relationship between p75^NTR and Tau is unclear, a decrease in Tau-1 immunoreactivity as gp120 mice entered old age (>16 months) suggests that the Tau may transition to more pathological modifications; a process blocked by LM11A-31. Overall, the effects of LM11A-31 are consistent with strong neuroprotective and anti-inflammatory actions that have significant therapeutic potential.

Small-molecule modulation of the p75 neurotrophin receptor inhibits a wide range of tau molecular pathologies and their sequelae in P301S tauopathy mice

In tauopathies, phosphorylation, acetylation, cleavage and other modifications of tau drive intracellular generation of diverse forms of toxic tau aggregates and associated seeding activity, which have been implicated in subsequent synaptic failure and neurodegeneration. Suppression of this wide range of pathogenic species, seeding and toxicity mechanisms, while preserving the physiological roles of tau, presents a key therapeutic goal. Identification and targeting of signaling networks that influence a broad spectrum of tau pathogenic mechanisms might prevent or reverse synaptic degeneration and modify disease outcomes. The p75 neurotrophin receptor (p75NTR) modulates such networks, including activation of multiple tau kinases, calpain and rhoA-cofilin activity. The orally bioavailable small-molecule p75NTR modulator, LM11A-31, was administered to tauP301S mice for 3 months starting at 6 months of age, when tau pathology was well established. LM11A-31 was found to reduce: excess activation of hippocampal cdk5 and JNK kinases and calpain; excess cofilin phosphorylation, tau phosphorylation, acetylation and cleavage; accumulation of multiple forms of insoluble tau aggregates and filaments; and, microglial activation. Hippocampal extracts from treated mice had substantially reduced tau seeding activity. LM11A-31 treatment also led to a reversal of pyramidal neuron dendritic spine loss, decreased loss of dendritic complexity and improvement in performance of hippocampal behaviors. These studies identify a therapeutically tractable upstream signaling module regulating a wide spectrum of basic mechanisms underlying tauopathies.

Tomato Atypical Receptor Kinase1 Is Involved in the Regulation of Preinvasion Defense

Tomato Atypical Receptor Kinase 1 (TARK1) is a pseudokinase required for postinvasion immunity. TARK1 was originally identified as a target of the Xanthomonas euvesicatoria effector protein Xanthomonas outer protein N (XopN), a suppressor of early defense signaling. How TARK1 participates in immune signal transduction is not well understood. To gain insight into TARK1's role in tomato (Solanum lycopersicum) immunity, we used a proteomics approach to isolate and identify TARK1-associated immune complexes formed during infection. We found that TARK1 interacts with proteins predicted to be associated with stomatal movement. TARK1 CRISPR mutants and overexpression (OE) lines did not display differences in light-induced stomatal opening or abscisic acid-induced stomatal closure; however, they did show altered stomatal movement responses to bacteria and biotic elicitors. Notably, we found that TARK1 CRISPR plants were resistant to Pseudomonas syringae pathovar tomato strain DC3000-induced stomatal reopening, and TARK1 OE plants were insensitive to P syringae pathovar tomato strain DC3118 (coronatine deficit)-induced stomatal closure. We also found that TARK1 OE in leaves resulted in increased susceptibility to bacterial invasion. Collectively, our results indicate that TARK1 functions in stomatal movement only in response to biotic elicitors and support a model in which TARK1 regulates stomatal opening postelicitation.

Effect of curcumin derivatives on hen egg white lysozyme amyloid fibrillation and their interaction study by spectroscopic methods

Two novel Boc-L-isoleucine-functionalized curcumin derivatives have been synthesized and characterized, which exhibited enhanced solubility in water compared with the natural curcumin. The solubility could reach 2.12mg/mL for the monosubstituted compound and 3.05mg/mL for the disubstituted compound, respectively. Their anti-amyloidogenic capacity on the model protein, hen egg white lysozyme (HEWL), was examined in aqueous solution. ThT fluorescence assay showed that the operation concentration was only 0.5mM when the inhibition ratio was above 70%. Meanwhile, the inhibitory capacity of monosubstituted curcumin derivative on the formation of HEWL amyloid fibrils was found to be superior to that of disubstituted derivative, suggesting that the phenolic hydroxyl group might contribute to the anti-amyloidogenic activity. Interaction study showed that both curcumin derivatives could bind with HEWL near tryptophan residues and form new ground-state complex before HEWL self-assemblies into amyloid fibrils and thus inhibits the formation of amyloid fibrils. Both of the two cucumin derivatives have displayed low cytotoxicity with HeLa cell.

The Impact of a Large Bolus Dose of l-leucine and l-isoleucine on Enteroendocrine and Pancreatic Hormones, and Glycemia in Healthy, Inactive Adults

Background: The ingestion of whey protein and amino acids with carbohydrate (CHO) enhances the release of glucagon-like peptide-1 (GLP-1) and glucose-dependent-insulinotropic peptide (GIP) that promote insulin secretion. It is unknown if L-isoleucine (Ile) and L-leucine (Leu) have this same effect. The purpose of this study was to examine how Ile and Leu influence both GLP-1 and GIP, subsequent pancreatic hormones, and glycemia in healthy, inactive adults. Methods: Twelve adults (6F/6M; age 27.4 ± 2 years; BMI 26.3 ± 2 kg/m²; lean body mass 53.2 ± 5 kg; body fat 34.1 ± 3%) completed four conditions in a randomized, cross-over fashion. Treatments standardized (0.3 g/kg·LBM⁻¹) (1) Leu, (2) Ile, (3) Equal (1:1 g) of Leu + Ile, and (4) placebo (Pla, 3.5 g inert stevia) ingested 30 min prior to an oral glucose tolerance test (OGTT). Samples of plasma glucose, insulin, glucagon, GIP_Total, and GLP-1_Active were assessed. Results: A treatment (p = 0.01) effect comparing Ile vs. Leu (p = 0.02) in GIP_Total. Area under the curve showed an increase in GIP_Total from Ile compared to Leu and Pla (p = 0.03). No effect was found on GLP-1. The ingestion of Ile prior to CHO augmented GIP concentration greater than Leu or Pla. No correlation was found between GIP, insulin, and glucose between conditions. Conclusions: Ile impacts GIP concentration, which did not relate to either insulin or glucose concentrations. Neither Ile, nor Leu seem to have an effect on hyperglycemia ingested prior to a CHO drink.

The oriental armyworm ( Mythimna separata) feeding induces systemic defence responses within and between maize leaves

Maize ( Zea mays) is a staple cereal crop cultivated all over the world but that is threatened by various insects. Feeding of the lepidopteran insect Mythimna separata triggers defence signalling and increases anti-herbivore benzoxazinoids (Bxs) in the insect-damaged maize leaves. However, the herbivory-elicited within-leaf and leaf-to-leaf systemic signalling in maize remains largely unexplored. Here, we show that simulated M. separata herbivory and mechanical wounding elicited increased levels of jasmonic acid (JA), JA-Ile (JA-isoleucine conjugate) and Bxs in the damaged areas and in specific systemic regions within a leaf. Importantly, increased contents of Bxs were detected in a systemic leaf, and consistently, this leaf exhibited increased defence against M. separata. Increased JA/JA-Ile and altered transcriptome, including Bx biosynthesis genes, were detected in systemic leaves after wounding or simulated herbivory treatments, although only simulated herbivory induced increase of the contents of Bxs systemically. Promoter and co-expression analysis revealed that transcription factors bHLH57 and WRKY34 may regulate Bx biosynthesis genes in systemic leaves. Moreover, leaf ablation experiment indicated that the systemic signal rapidly exited the local leaves within 30 min after elicitation. This study provides new insight into the temporal and spatial regulation of defence responses of maize against lepidopteran insects. This article is part of the theme issue 'Biotic signalling sheds light on smart pest management'.

Innate and acquired tolerance to bitter stimuli in mice

Tolerance to bitter foods and its potentiation by repetitive exposure are commonly experienced and potentially underlie the consumption of bitter foods, but it remains unknown whether permissive and adaptive responses are general phenomena for bitter-tasting substances or specific to certain substances, and they have not been rigorously studied in mice. Here, we investigated the effects of prolonged exposure to a bitter compound on both recognition and rejection behaviors to the same compound in mice. Paired measurements of rejection (RjT) and apparent recognition (aRcT) thresholds were conducted using brief-access two-bottle choice tests before and after taste aversion conditioning, respectively. First, RjT was much higher than aRcT for the bitter amino acids L-tryptophan and L-isoleucine, which mice taste daily in their food, indicating strong acceptance of those familiar stimuli within the concentration range between RjT and aRcT. Next, we tested five other structurally dissimilar bitter compounds, to which mice were naive at the beginning of experiments: denatonium benzoate, quinine-HCl, caffeine, salicin, and epigallocatechin gallate. RjT was moderately higher than aRcT for all the compounds tested, indicating the presence of innate acceptance to these various, unfamiliar bitter stimuli in mice. Lastly, a 3-week forced exposure increased RjT for all the bitter compounds except salicin, demonstrating that mice acquire tolerance to a broad array of bitter compounds after long-term exposure to them. Although the underlying mechanisms remain to be determined, our studies provide behavioral evidence of innate and acquired tolerance to various bitter stimuli in mice, suggesting its generality among bitterants.

Branched-chain amino acid depletion conditions bone marrow for hematopoietic stem cell transplantation avoiding amino acid imbalance-associated toxicity

Hematopoietic stem cells (HSCs) are used clinically in bone marrow (BM) transplantation due to their unique ability to reform the entire hematopoietic system. Recently, we reported that HSCs are highly sensitive to valine, one of the three branched-chain amino acids (BCAAs) in addition to isoleucine and leucine. Dietary depletion of valine could even be used as a conditioning regimen for HSC transplantation. Here, we report that HSCs are highly sensitive to the balance of BCAAs, with both proliferation and survival reduced by BCAA imbalance. However, low but balanced BCAA levels failed to rescue HSC maintenance. Importantly, in vivo depletion of all three BCAAs was significantly less toxic than depletion of valine only. We demonstrate that BCAA depletion can replace valine depletion as a safer alternative to BM conditioning. In summary, by determining HSC metabolic requirements, we can improve metabolic approaches to BM conditioning.

Which of the branched-chain amino acids increases cerebral blood flow in hepatic encephalopathy? A double-blind randomized trial

Branched-chain amino acids increase the brain perfusion of patients with hepatic encephalopathy (HE), but the amino acid and the mechanisms involved are still unknown. This study compared brain perfusion and clinical improvement during leucine or isoleucine supplementation. After randomization, 27 subjects with cirrhosis and HE received leucine or isoleucine supplements for one year. Brain single Photon Emission Computed Tomography (SPECT) and dynamic brain scintigraphy (DBS) were performed pretreatment and at 1, 8 and 12 months of supplementation. Brain perfusion was increased only in the isoleucine group at 8 months of treatment by both SPECT and DBS (p < 0.001 and p = 0.05, respectively) and by SPECT at the 12th month (p < 0.05). This was associated with hepatic encephalopathy improvement at 8 and 12 months (p = 0.008 and 0.004, respectively), which was not observed in the leucine group (p = 0.313 and 0.055, respectively). Isoleucine supplementation achieved a better impact on brain perfusion restoration in HE.

Interactive effects of dietary leucine and isoleucine on growth, blood parameters, and amino acid profile of Japanese flounder Paralichthys olivaceus

A 60-day feeding trial was conducted to assess the interactions of dietary leucine (Leu) and isoleucine (Ile) on Japanese flounder. Fish of 2.69 ± 0.04 g were fed experimental diets containing two levels of Leu (2.58 and 5.08% of diet) combined with three levels of Ile (1.44, 2.21, and 4.44% of diet), respectively. After the feeding trial, growth, proximate composition, muscle total amino acid profile, blood parameters, mucus lysozyme activity, and stress tolerance to freshwater were measured. Statistically significant (P < 0.05) interactive effects of Leu and Ile were found on growth parameters (final body weight, body weight gain, and special growth rate) of Japanese flounder. Antagonism was discovered in high dietary Leu groups, while stimulatory effects were obtained for increased dietary Ile in low Leu groups. Interactive effects of these two branched-chain amino acids were also found on hepatosomatic index of test fish. In addition, crude lipid content of fish whole body was significantly altered by various diets, with antagonism observed in low dietary Leu groups. Interactive effects also existed in muscle amino acid profiles for low fish meal diets, but no interactive impacts were observed on blood parameters. Furthermore, lysozyme activities and freshwater stress were significantly affected by different diets. And antagonism was found on lysozyme activities in low Leu groups. Moreover, high Leu and high Ile levels of diet significantly altered freshwater stress tolerance of Japanese flounder. These findings suggested that dietary Leu and Ile can effect interactively, and fish fed with diets containing 2.58% Leu with 4.44% Ile and 5.08% Leu with 1.44% Ile showed better growth performance.

Expression and regulation of the neutral amino acid transporter B0AT1 in rat small intestine

Absorption of neutral amino acids across the luminal membrane of intestinal enterocytes is mediated by the broad neutral amino acid transporter B0AT1 (SLC6A19). Its intestinal expression depends on co-expression of the membrane-anchored peptidase angiotensin converting enzyme 2 (ACE2) and is additionally enhanced by aminopeptidase N (CD13). We investigated in this study the expression of B0AT1 and its auxiliary peptidases as well as its transport function along the rat small intestine. Additionally, we tested its possible short- and long-term regulation by dietary proteins and amino acids. We showed by immunofluorescence that B0AT1, ACE2 and CD13 co-localize on the luminal membrane of small intestinal villi and by Western blotting that their protein expression increases in distal direction. Furthermore, we observed an elevated transport activity of the neutral amino acid L-isoleucine during the nocturnal active phase compared to the inactive one. Gastric emptying was delayed by intragastric application of an amino acid cocktail but we observed no acute dietary regulation of B0AT1 protein expression and L-isoleucine transport. Investigation of the chronic dietary regulation of B0AT1, ACE2 and CD13 by different diets revealed an increased B0AT1 protein expression under amino acid-supplemented diet in the proximal section but not in the distal one and for ACE2 protein expression a reverse localization of the effect. Dietary regulation for CD13 protein expression was not as distinct as for the two other proteins. Ring uptake experiments showed a tendency for increased L-isoleucine uptake under amino acid-supplemented diet and in vivo L-isoleucine absorption was more efficient under high protein and amino acid-supplemented diet. Additionally, plasma levels of branched-chain amino acids were elevated under high protein and amino acid diet. Taken together, our experiments did not reveal an acute amino acid-induced regulation of B0AT1 but revealed a chronic dietary adaptation mainly restricted to the proximal segment of the small intestine.

Preventive and reparative effects of isoleucine against copper-induced oxidative damage in primary fish enterocytes

The present study aimed to assess the possible preventive and reparative effects of isoleucine (Ile) against copper (Cu)-induced oxidative stress in fish enterocytes in vitro. In experiment 1, enterocytes were preincubated with increasing concentrations of Ile (0, 50, 120, 190, 260, and 330 mg L^-1) for 72 h followed by exposure to 6 mg L^-1 Cu for 24 h. In experiment 2, the enterocytes were pretreated with 6 mg L^-1 Cu for 24 h and then treated with 0-330 mg L^-1 Ile for 72 h to investigate its potential reparative role. The results of experiment 1 showed that Cu exposure increased lactate dehydrogenase (LDH) activity and malondialdehyde and protein carbonyl (PC) content; these changes were completely suppressed by pretreatment with Ile at optimum concentrations (P < 0.05). Moreover, Ile pretreatment prevented the decrease in superoxide dismutase (SOD) and glutathione peroxidase (GPx) activities in the enterocytes exposed to Cu (P < 0.05). Additionally, cells exposed to Cu exhibited adaptive increases in glutathione-S-transferase (GST) activity. In experiment 2, the LDH activity and protein oxidation induced by Cu were completely reversed by Ile posttreatment. Meanwhile, the Cu-induced decrease in SOD, GPx, and GST activity was completely reversed by subsequent Ile treatment, but the reduced glutathione content was not restored. Collectively, these results indicate that Ile suppresses Cu-induced oxidative damage via preventive and reparative pathways in primary enterocytes and thus protects the structural integrity of enterocytes in fish.

JA-Ile-macrolactones uncouple growth and defense in wild tobacco

Small molecules capable of uncoupling growth-defense in plants are currently not known. In this study, for the first time, semi-synthetic analogues of the phytohormone JA-Ile are employed to uncouple growth and defense responses in wild tobacco. The JA-Ile analogues are easily synthesized from inexpensive substrates via olefin metathesis.

Identification of Jasmonic Acid and Jasmonoyl-Isoleucine, and Characterization of AOS, AOC, OPR and JAR1 in the Model Lycophyte Selaginella moellendorffii

Jasmonic acid (JA) is involved in a variety of physiological responses in seed plants. However, the detection and role of JA in lycophytes, a group of seedless vascular plants, have remained elusive until recently. This study provides the first evidence of 12-oxo-phytodienoic acid (OPDA), JA and jasmonoyl-isoleucine (JA-Ile) in the model lycophyte Selaginella moellendorffii. Mechanical wounding stimulated the accumulation of OPDA, JA and JA-Ile. These data were corroborated by the detection of enzymatically active allene oxide synthase (AOS), allene oxide cyclase (AOC), 12-oxo-phytodienoic acid reductase 3 (OPR3) and JA-Ile synthase (JAR1) in S. moellendorffii. SmAOS2 is involved in the first committed step of JA biosynthesis. SmAOC1 is a crucial enzyme for generating the basic structure of jasmonates and is actively involved in the formation of OPDA. SmOPR5, a functionally active OPR3-like enzyme, is also vital for the reduction of (+)-cis-OPDA, the only isomer of the JA precursor. The conjugation of JA to Ile by SmJAR1 demonstrates that S. moellendorffii produces JA-Ile. Thus, the four active enzymes have characteristics similar to those in seed plants. Wounding and JA treatment induced the expression of SmAOC1 and SmOPR5. Furthermore, JA inhibited the growth of shoots in S. moellendorffii, which suggests that JA functions as a signaling molecule in S. moellendorffii. This study proposes that JA evolved as a plant hormone for stress adaptation, beginning with the emergence of vascular plants.

Unexpected Formation of Low Amounts of (R)-Configurated anteiso-Fatty Acids in Rumen Fluid Experiments

Anteiso-fatty acids (aFA) with odd carbon number are a class of branched-chain fatty acids (BCFA) mainly produced by bacteria. Bacterial sources are also made responsible for their occurrence in the low percent-range in lipids of ruminants (meat and milk) and fish. aFAs are chiral molecules and typically occur predominantly in form of (S)-enantiomers, and their primary precursor has been noted to be isoleucine. Yet, low proportions of (R)-aFAs were also detected in fish and cheese samples. Here we investigated the potential formation of (R)-aFAs by means of incubation experiments with rumen fluid from fistulated cows. Supplementation of rumen fluid with both L- and DL-isoleucine, resulted in a significant (α <0.05) increase of the aFA concentrations but in both cases enantiopure (S)-aFAs were observed. By contrast, incubations without addition of any isoleucine lead to a significant (α <0.05) formation of small proportions of (R)-aFAs similarly to those previously observed in fish and cheese. These results were consistently reproduced in three different years with rumen fluid from different cows fed different diets. All findings point to the existence of a further biosynthesis pathway of aFAs with different stereospecificity than the classic one using isoleucine as primer.

Jasmonates are induced by the PAMP flg22 but not the cell death-inducing elicitor Harpin in Vitis rupestris

Plants employ two layers of defence that differ with respect to cell death: pathogen-associated molecular pattern (PAMP)-triggered immunity (PTI) and effector-triggered immunity (ETI). In our previous work, we have comparatively mapped the molecular events in a cell system derived from the wild American grape Vitis rupestris, where cell death-independent defence can be triggered by PAMP flg22, whereas the elicitor Harpin activates a cell death-related ETI-like response. Both defence responses overlapped with respect to early events, such as calcium influx, apoplastic alkalinisation, oxidative burst, mitogen-activated protein kinase (MAPK) signalling, activation of defence-related genes and accumulation of phytoalexins. However, timing and amplitude of early signals differed. In the current study, we address the role of jasmonates (JAs) as key signalling compounds in hypersensitive cell death. We find, in V. rupestris, that jasmonic acid and its bioactive conjugate jasmonoyl-isoleucine (JA-Ile) rapidly accumulate in response to flg22 but not in response to Harpin. However, Harpin can induce programmed cell death, whereas exogenous methyl jasmonate (MeJA) fails to do so, although both signals induce a similar response of defence genes. Also in a second cell line from V. vinifera cv. 'Pinot Noir', where Harpin cannot activate cell death and where flg22 fails to induce JA and JA-Ile, defence genes are activated in a similar manner. These findings indicate that the signal pathway culminating in cell death must act independently from the events culminating in the accumulation of toxic stilbenes.

A small molecule p75NTR ligand normalizes signalling and reduces Huntington's disease phenotypes in R6/2 and BACHD mice

Decreases in the ratio of neurotrophic versus neurodegenerative signalling play a critical role in Huntington’s disease (HD) pathogenesis and recent evidence suggests that the p75 neurotrophin receptor (NTR) contributes significantly to disease progression. p75NTR signalling intermediates substantially overlap with those promoting neuronal survival and synapse integrity and with those affected by the mutant huntingtin (muHtt) protein. MuHtt increases p75NTR-associated deleterious signalling and decreases survival signalling suggesting that p75NTR could be a valuable therapeutic target. This hypothesis was investigated by examining the effects of an orally bioavailable, small molecule p75NTR ligand, LM11A-31, on HD-related neuropathology in HD mouse models (R6/2, BACHD). LM11A-31 restored striatal AKT and other pro-survival signalling while inhibiting c-Jun kinase (JNK) and other degenerative signalling. Normalizing p75NTR signalling with LM11A-31 was accompanied by reduced Htt aggregates and striatal cholinergic interneuron degeneration as well as extended survival in R6/2 mice. The p75NTR ligand also decreased inflammation, increased striatal and hippocampal dendritic spine density, and improved motor performance and cognition in R6/2 and BACHD mice. These results support small molecule modulation of p75NTR as an effective HD therapeutic strategy. LM11A-31 has successfully completed Phase I safety and pharmacokinetic clinical trials and is therefore a viable candidate for clinical studies in HD.

Stress promotes Arabidopsis - Piriformospora indica interaction

The endophytic fungus Piriformospora indica colonizes Arabidopsis thaliana roots and promotes plant performance, growth and resistance/tolerance against abiotic and biotic stress. Here we demonstrate that the benefits for the plant increase when the two partners are co-cultivated under stress (limited access to nutrient, exposure to heavy metals and salt, light and osmotic stress, pathogen infection). Moreover, physical contact between P. indica and Arabidopsis roots is necessary for optimal growth promotion, and chemical communication cannot replace the physical contact. Lower nutrient availability down-regulates and higher nutrient availability up-regulates the plant defense system including the expression of pathogenesis-related genes in roots. High light, osmotic and salt stresses support the beneficial interaction between the plant and the fungus. P. indica reduces stomata closure and H2O2 production after Alternaria brassicae infection in leaves and suppresses the defense-related accumulation of the phytohormone jasmonic acid. Thus, shifting the growth conditions toward a stress promotes the mutualistic interaction, while optimal supply with nutrients or low stress diminishes the benefits for the plant in the symbiosis.

Allantoin, a stress-related purine metabolite, can activate jasmonate signaling in a MYC2-regulated and abscisic acid-dependent manner

Allantoin is a metabolic intermediate of purine catabolism that often accumulates in stressed plants. Recently, we used Arabidopsis knockout mutants (aln) of ALLANTOINASE to show that this purine metabolite activates abscisic acid (ABA) production, thereby stimulating stress-related gene expression and enhancing seedling tolerance to abiotic stress. A detailed re-examination of the microarray data of an aln mutant (aln-1) confirmed the increased expression of ABA-related genes and also revealed altered expression of genes involved in jasmonic acid (JA) responses, probably under the control of MYC2, a master switch in the JA signaling pathway. Consistent with the transcriptome profiles, the aln-1 mutant displayed increased JA levels and enhanced responses to mechanical wounding and exogenous JA. Moreover, aln mutants demonstrated modestly increased susceptibility to Pseudomonas syringae and Pectobacterium carotovorum, probably reflecting the antagonistic action of MYC2 on the defense against these bacterial phytopathogens. Exogenously administered allantoin elicited the expression of JA-responsive genes, including MYC2, in wild-type plants, supporting the idea that allantoin might be responsible for the observed JA-related phenotypes of aln mutants. However, mutants deficient in bioactive JA (jar1-1), insensitive to JA (myc2-3), or deficient in ABA (aba2-1 and bglu18) suppressed the effect of exogenous allantoin. The suppression was further confirmed in aln-1 jar1-1 and aln-1 bglu18 double mutants. These results indicate that allantoin can activate the MYC2-regulated JA signaling pathway through ABA production. Overall, this study suggests a possible connection of purine catabolism with stress hormone homeostasis and signaling, and highlights the potential importance of allantoin in these interactions.

Recapitulation of metabolic defects in a model of propionic acidemia using patient-derived primary hepatocytes

BACKGROUND

Propionic acidemia (PA) is a disorder of intermediary metabolism with defects in the alpha or beta subunits of propionyl CoA carboxylase (PCCA and PCCB respectively) enzyme. We previously described a liver culture system that uses liver-derived hemodynamic blood flow and transport parameters to restore and maintain primary human hepatocyte biology and metabolism utilizing physiologically relevant milieu concentrations.

METHODS

In this study, primary hepatocytes isolated from the explanted liver of an 8-year-old PA patient were cultured in the liver system for 10 days and evaluated for retention of differentiated polarized morphology. The expression of PCCA and PCCB was assessed at a gene and protein level relative to healthy donor controls. Ammonia and urea levels were measured in the presence and absence of amino acid supplements to assess the metabolic consequences of branched-chain amino acid metabolism in this disease.

RESULTS

Primary hepatocytes from the PA patient maintained a differentiated polarized morphology (peripheral actin staining) over 10 days of culture in the system. We noted lower levels of PCCA and PCCB relative to normal healthy controls at the mRNA and protein level. Supplementation of branched-chain amino acids, isoleucine (5mM) and valine (5mM) in the medium, resulted in increased ammonia and decreased urea in the PA patient hepatocyte system, but no such response was seen in healthy hepatocytes or patient-derived fibroblasts.

CONCLUSIONS

We demonstrate for the first time the successful culture of PA patient-derived primary hepatocytes in a differentiated state, that stably retain the PCCA and PCCB enzyme defects at a gene and protein level. Phenotypic response of the system to an increased load of branched-chain amino acids, not possible with fibroblasts, underscores the utility of this system in the better understanding of the molecular pathophysiology of PA and examining the effectiveness of potential therapeutic agents in the most relevant tissue.

4-Hydroxyisoleucine attenuates the inflammation-mediated insulin resistance by the activation of AMPK and suppression of SOCS-3 coimmunoprecipitation with both the IR-β subunit as well as IRS-1

It is known that 4-hydroxyisoleucine (4-HIL) from seeds of Trigonella foenum-graecum has beneficial effects on low-grade inflammation; therefore, the insulin signaling as well as the anti-inflammatory effects of 4-HIL in TNF-α-induced insulin resistance in C2C12 myotubes was studied with an aim to dissect out the mechanism(s) of the inflammation-mediated insulin resistance. TNF-α suppressed insulin-stimulated glucose transport rate and increased Ser-307 phosphorylation of insulin receptor substrate-1 (IRS-1). However, the treatment of 4-hydroxyisoleucine enhanced insulin-stimulated glucose transport rate via the activation of AMP-activated protein kinase (AMPK) in a dose-dependent manner. 4-HIL also increases the tyrosine phosphorylation of both IR-β and IRS-1. Moreover, coimmunoprecipitation (Co-IP) of insulin receptor-β (IR-β) subunit with IRS-1 was found to be increased by 4-hydroxyisoleucine. Concentration of SOCS-3 protein and coimmunoprecipitation of SOCS-3 protein with both the IR-β subunit as well as IRS-1 was found to be decreased by 4-HIL. We conclude that the 4-hydroxyisoleucine reverses the insulin resistance by the activation of AMPK and suppression of SOCS-3 coimmunoprecipitation with both the IR-β subunit as well as IRS-1.

Novel JAZ co-operativity and unexpected JA dynamics underpin Arabidopsis defence responses to Pseudomonas syringae infection

Pathogens target phytohormone signalling pathways to promote disease. Plants deploy salicylic acid (SA)-mediated defences against biotrophs. Pathogens antagonize SA immunity by activating jasmonate signalling, for example Pseudomonas syringae pv. tomato DC3000 produces coronatine (COR), a jasmonic acid (JA) mimic. This study found unexpected dynamics between SA, JA and COR and co-operation between JAZ jasmonate repressor proteins during DC3000 infection. We used a systems-based approach involving targeted hormone profiling, high-temporal-resolution micro-array analysis, reverse genetics and mRNA-seq. Unexpectedly, foliar JA did not accumulate until late in the infection process and was higher in leaves challenged with COR-deficient P. syringae or in the more resistant JA receptor mutant coi1. JAZ regulation was complex and COR alone was insufficient to sustainably induce JAZs. JAZs contribute to early basal and subsequent secondary plant defence responses. We showed that JAZ5 and JAZ10 specifically co-operate to restrict COR cytotoxicity and pathogen growth through a complex transcriptional reprogramming that does not involve the basic helix-loop-helix transcription factors MYC2 and related MYC3 and MYC4 previously shown to restrict pathogen growth. mRNA-seq predicts compromised SA signalling in a jaz5/10 mutant and rapid suppression of JA-related components on bacterial infection.

4-Hydroxyisoleucine ameliorates an insulin resistant-like state in 3T3-L1 adipocytes by regulating TACE/TIMP3 expression

BACKGROUND

Obesity-associated insulin resistance (IR) is highly correlated with soluble tumor necrosis factor-α (sTNF-α), which is released from transmembranous TNF-α by TNF-α converting enzyme (TACE). In vivo, TACE activity is suppressed by tissue inhibitor of metalloproteinase 3 (TIMP3). Agents that can interact with TACE/TIMP3 to improve obesity-related IR would be highly valuable. In the current study, we assessed whether (2S,3R,4S)-4-hydroxyisoleucine (4-HIL) could modulate TACE/TIMP3 and ameliorate an obesity-induced IR-like state in 3T3-L1 adipocytes.

MATERIALS AND METHODS

3T3-L1 adipocytes were incubated in the presence of 25 mM glucose and 0.6 nM insulin to induce an IR-like state, and were then treated with different concentrations of 4-HIL or 10 µM pioglitazone (positive control). The glucose uptake rate was determined using the 2-deoxy-[(3)H]-D-glucose method, and the levels of sTNF-α in the cell supernatant were determined using ELISA. The protein expression of TACE, TIMP3, and insulin signaling-related molecules was measured using western blotting.

RESULTS

Exposure to high glucose and insulin for 18 hours increased the levels of sTNF-α in the cell supernatant. The phosphorylation of insulin receptor substrate-1 (IRS-1) Ser(307) and Akt Ser(473) was increased, whereas the protein expression of IRS-1, Akt, and glucose transporter-4 was decreased. The insulin-induced glucose uptake was reduced by 67% in 3T3-L1 adipocytes, which indicated the presence of an IR-like state. The above indexes, which demonstrated the successful induction of an IR-like state, were reversed by 4-HIL in a dose-dependent manner by downregulating and upregulating the protein expression of TACE and TIMP3 proteins, respectively.

CONCLUSION

4-HIL improved an obesity-associated IR-like state in 3T3-L1 adipocytes by targeting TACE/TIMP3 and the insulin signaling pathway.

Additional evidence against jasmonate-induced jasmonate induction hypothesis

Jasmonates are phytohormones involved in development and stress reactions. The most prominent jasmonate is jasmonic acid, however, the bioactive jasmonate is (+)-7-iso-jasmonoyl-L-isoleucine (JA-Ile). Biosynthesis of jasmonates is long time known; compartmentalization, enzymes and corresponding genes are well studied. Because all genes encoding these biosynthetic enzymes are jasmonate inducible, a hypothesis of jasmonate-induced-jasmonate-biosynthesis is widely accepted. Here, this hypothesis was revisited by employing the synthetic JA-Ile mimic coronalon to intact and wounded leaves, which excludes structural cross-contamination with endogenous jasmonates. At an effective concentration that induced various jasmonate-responsive genes in Arabidopsis, neither accumulation of endogenous jasmonic acid, JA-Ile, nor of their hydroxylated metabolites was detected. Results indicate that in spite of jasmonate-induced biosynthetic gene expression, no jasmonate biosynthesis/accumulation takes place supporting a post-translational regulation.

CYP94-mediated jasmonoyl-isoleucine hormone oxidation shapes jasmonate profiles and attenuates defence responses to Botrytis cinerea infection

Induced resistance to the necrotrophic pathogen Botrytis cinerea depends on jasmonate metabolism and signalling in Arabidopsis. We have presented here extensive jasmonate profiling in this pathosystem and investigated the impact of the recently reported jasmonoyl-isoleucine (JA-Ile) catabolic pathway mediated by cytochrome P450 (CYP94) enzymes. Using a series of mutant and overexpressing (OE) plant lines, we showed that CYP94B3 and CYP94C1 are integral components of the fungus-induced jasmonate metabolic pathway and control the abundance of oxidized conjugated but also some unconjugated derivatives, such as sulfated 12-HSO4-JA. Despite causing JA-Ile overaccumulation due to impaired oxidation, CYP94 deficiency had negligible impacts on resistance, associated with enhanced JAZ repressor transcript levels. In contrast, plants overexpressing (OE) CYP94B3 or CYP94C1 were enriched in 12-OH-JA-Ile or 12-COOH-JA-Ile respectively. This shift towards oxidized JA-Ile derivatives was concomitant with strongly impaired defence gene induction and reduced disease resistance. CYP94B3-OE, but unexpectedly not CYP94C1-OE, plants displayed reduced JA-Ile levels compared with the wild type, suggesting that increased susceptibility in CYP94C1-OE plants may result from changes in the hormone oxidation ratio rather than absolute changes in JA-Ile levels. Consistently, while feeding JA-Ile to seedlings triggered strong induction of JA pathway genes, induction was largely reduced or abolished after feeding with the CYP94 products 12-OH-JA-Ile and 12-COOH-JA-Ile, respectively. This trend paralleled in vitro pull-down assays where 12-COOH-JA-Ile was unable to promote COI1-JAZ9 co-receptor assembly. Our results highlight the dual function of CYP94B3/C1 in antimicrobial defence: by controlling hormone oxidation status for signal attenuation, these enzymes also define JA-Ile as a metabolic hub directing jasmonate profile complexity.

CYP94-mediated jasmonoyl-isoleucine hormone oxidation shapes jasmonate profiles and attenuates defence responses to Botrytis cinerea infection

Induced resistance to the necrotrophic pathogen Botrytis cinerea depends on jasmonate metabolism and signalling in Arabidopsis. We have presented here extensive jasmonate profiling in this pathosystem and investigated the impact of the recently reported jasmonoyl-isoleucine (JA-Ile) catabolic pathway mediated by cytochrome P450 (CYP94) enzymes. Using a series of mutant and overexpressing (OE) plant lines, we showed that CYP94B3 and CYP94C1 are integral components of the fungus-induced jasmonate metabolic pathway and control the abundance of oxidized conjugated but also some unconjugated derivatives, such as sulfated 12-HSO4-JA. Despite causing JA-Ile overaccumulation due to impaired oxidation, CYP94 deficiency had negligible impacts on resistance, associated with enhanced JAZ repressor transcript levels. In contrast, plants overexpressing (OE) CYP94B3 or CYP94C1 were enriched in 12-OH-JA-Ile or 12-COOH-JA-Ile respectively. This shift towards oxidized JA-Ile derivatives was concomitant with strongly impaired defence gene induction and reduced disease resistance. CYP94B3-OE, but unexpectedly not CYP94C1-OE, plants displayed reduced JA-Ile levels compared with the wild type, suggesting that increased susceptibility in CYP94C1-OE plants may result from changes in the hormone oxidation ratio rather than absolute changes in JA-Ile levels. Consistently, while feeding JA-Ile to seedlings triggered strong induction of JA pathway genes, induction was largely reduced or abolished after feeding with the CYP94 products 12-OH-JA-Ile and 12-COOH-JA-Ile, respectively. This trend paralleled in vitro pull-down assays where 12-COOH-JA-Ile was unable to promote COI1-JAZ9 co-receptor assembly. Our results highlight the dual function of CYP94B3/C1 in antimicrobial defence: by controlling hormone oxidation status for signal attenuation, these enzymes also define JA-Ile as a metabolic hub directing jasmonate profile complexity.

In vitro anti-hyperglycemic activity of 4-hydroxyisoleucine derivatives

The nonproteinogenic amino acid, 4-hydroxyisoleucine (1) has been isolated in large quantities from the fenugreek (T. foenum-graecum) seeds. Few novel derivatives (3-11 and 13-18) were prepared from the naturally occurring 4-hydroxyisoleucine (1) and screened for their in vitro glucose uptake stimulatory effect in L-6 skeletal muscle cells. The derivatives 6, 7, 8, 10 and 11 exhibited better glucose uptake stimulatory activity than parent compound, 4-hydroxyisoleucine at 5 and 10µM concentrations and compounds 7 and 11 enhanced translocation of insulin sensitive glucose transporters-4 in skeletal muscle cells.

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

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.

Amelioration of cisplatin-induced experimental peripheral neuropathy by a small molecule targeting p75 NTR

Cisplatin is an effective and widely used first-line chemotherapeutic drug for treating cancers. However, many patients sustain cisplatin-induced peripheral neuropathy (CIPN), often leading to a reduction in drug dosages or complete cessation of treatment altogether. Therefore, it is important to understand cisplatin mechanisms in peripheral nerve tissue mediating its toxicity and identify signaling pathways for potential intervention. Rho GTPase activation is increased following trauma in several models of neuronal injury. Thus, we investigated whether components of the Rho signaling pathway represent important neuroprotective targets with the potential to ameliorate CIPN and thereby optimize current chemotherapy treatment regimens. We have developed a novel CIPN model in the mouse. Using this model and primary neuronal culture, we determined whether LM11A-31, a small-molecule, orally bioavailable ligand of the p75 neurotrophin receptor (p75(NTR)), can modulate Rho GTPase signaling and reduce CIPN. Von Frey filament analysis of sural nerve function showed that LM11A-31 treatment prevented decreases in peripheral nerve sensation seen with cisplatin treatment. Morphometric analysis of harvested sural nerves revealed that cisplatin-induced abnormal nerve fiber morphology and the decreases in fiber area were alleviated with concurrent LM11A-31 treatment. Cisplatin treatment increased RhoA activity accompanied by the reduced tyrosine phosphorylation of SHP2, which was reversed by LM11A-31. LM11A-31 also countered the effects of calpeptin, which activated RhoA by inhibiting SHP2 tyrosine phosphatase. Therefore, suppression of RhoA signaling by LM11A-31 that modulates p75(NTR) or activates SHP2 tyrosine phosphatase downstream of the NGF receptor enhances neuroprotection in experimental CIPN in mouse model.

Effect of dietary isoleucine on the immunity, antioxidant status, tight junctions and microflora in the intestine of juvenile Jian carp (Cyprinus carpio var. Jian)

This study was conducted to investigate the effects of dietary isoleucine (Ile) on the immune response, antioxidant status, tight junctions, and microbial population in the intestine of juvenile Jian carp (Cyprinus carpio var. Jian). A total of 1200 juvenile Jian carp with average initial weight 6.9 ± 0.03 g were fed semi-purified isonitrogenous diets containing 4.2 (unsupplemented control group), 7.0, 9.5, 11.9, 13.9 and 16.9 g Ile kg(-1) diet for 60 days. Results indicated that Ile supplementation decreased malondialdehyde (MDA) and protein carbonyl content, and the amounts of Escherichia coli and Aeromonas in the intestine (P < 0.05), and increased the activities of superoxide dismutase (SOD), catalase (CAT), and glutathione reductase (GR), glutathione content and the amounts of Lactobacillus and Bacillus in the intestine (P < 0.05). Furthermore, real time polymerase chain reaction revealed that relative mRNA expression of copper/zinc superoxide dismutase (Cu-ZnSOD), manganese superoxide dismutase (MnSOD), CAT, NF-E2-related factor 2 (Nrf2), p38 mitogen-activated protein kinases (p38MAPK) in the intestine were increased with increasing of dietary Ile up to a certain point (P < 0.05). Conversely, the relative mRNA expression of occludin, claudin-3, claudin-7, TNF-α, IL-10, Kelch-like-ECH- associated protein 1 (Keap1), extracellular signal-regulated kinase 1 (ERK1) in the intestine showed a downward trend (P < 0.05). In conclusion, dietary Ile improves intestinal immune function, antioxidant capacity and microbial population, and regulates gene expression of antioxidant enzyme, tight junctions, Nrf2, Keap1, p38 and ERK1 in the intestine of Jian carp.