Attenuation of intestinal ischemia-reperfusion-injury by β-alanine: a potentially glycine-receptor mediated effect

Lonicerin alleviates intestinal myenteric neuron injury induced by hypoxia/reoxygenation treated macrophages by downregulating EZH2

Intestinal ischemia-reperfusion (IR) injury is a common gastrointestinal disease that induces severe intestinal dysfunction. Intestinal myenteric neurons participate in maintaining the intestinal function, which will be severely injured by IR. Macrophages are widely reported to be involved in the pathogenesis of organ IR injury, including intestine, which is activated by NLRP3 signaling. Lonicerin (LCR) is a natural extracted monomer with inhibitory efficacy against the NLRP3 pathway in macrophages. The present study aims to explore the potential protective function of LCR in intestinal IR injury. Myenteric neurons were extracted from mice. RAW 264.7 cells were stimulated by H/R with or without 10 μM and 30 μM LCR. Remarkable increased release of IL-6, MCP-1, and TNF-α were observed in H/R treated RAW 264.7 cells, along with an upregulation of NLRP3, cleaved-caspase-1, IL-1β, and EZH2, which were sharply repressed by LCR. Myenteric neurons were cultured with the supernatant collected from each group. Markedly decreased neuron number and shortened length of neuron axon were observed in the H/R group, which were signally reversed by LCR. RAW 264.7 cells were stimulated by H/R, followed by incubated with 30 μM LCR with or without pcDNA3.1-EZH2. The inhibition of LCR on NLRP3 signaling in H/R treated RAW 264.7 cells was abolished by EZH2 overexpression. Furthermore, the impact of LCR on neuron number and neuron axon length in myenteric neurons in the H/R group was abated by EZH2 overexpression. Collectively, LCR alleviated intestinal myenteric neuron injury induced by H/R treated macrophages via downregulating EZH2.

Effect of carnosine synthesis precursors in the diet on jejunal metabolomic profiling and biochemical compounds in slow-growing Korat chicken

The slow-growing Korat chicken (KR) has been developed to provide an alternative breed for smallholder farmers in Thailand. Carnosine enrichment in the meat can distinguish KR from other chicken breeds. Therefore, our aim was to investigate the effect of enriched carnosine synthesis, obtained by the β-alanine and L-histidine precursor supplementation in the diet, on changes to metabolomic profiles and biochemical compounds in slow-growing KR jejunum tissue. Four hundred 21-day-old female KR chickens were divided into 4 experimental groups: a group with a basal diet, a group with a basal diet supplemented with 1.0% β-alanine, 0.5% L-histidine, and a mix of 1.0% β-alanine and 0.5% L-histidine. The feeding trial lasted 70 d. Ten randomly selected chickens from each group were slaughtered. Metabolic profiles were analyzed using proton nuclear magnetic resonance spectroscopy. In total, 28 metabolites were identified. Significant changes in the concentrations of these metabolites were detected between the groups. Partial least squares discriminant analysis was used to distinguish the metabolites between the experimental groups. Based on the discovered metabolites, 34 potential metabolic pathways showed differentiation between groups, and 8 pathways (with impact values higher than 0.05, P < 0.05, and FDR < 0.05) were affected by metabolite content. In addition, biochemical changes were monitored using synchrotron radiation-based Fourier transform infrared microspectroscopy. Supplementation of β-alanine alone in the diet increased the β-sheets and decreased the α-helix content in the amide I region, and supplementation of L-histidine alone in the diet also increased the β-sheets. Furthermore, the relationship between metabolite contents and biochemical compounds were confirmed using principal component analysis (PCA). Results from the PCA indicated that β-alanine and L-histidine precursor group was highly positively correlated with amide I, amide II, creatine, tyrosine, valine, isoleucine, and aspartate. These findings can help to understand the relationships and patterns between the spectral and metabolic processes related to carnosine synthesis.

A High-Specific-Activity L-aspartate-α-Decarboxylase from Bacillus aryabhattai Gel-09 and Site-Directed Mutation to Improve Its Substrate Tolerance

L-aspartate-α-decarboxylase (ADC) can recognize L-aspartic acid specifically and catalyze the decarboxylation of L-aspartic acid to β-alanine. In this study, a novel L-aspartate-α-decarboxylase (BaADC) with high specific activity from Bacillus aryabhattai Gel-09 was heterologously expressed and characterized. It exhibited optimal enzyme activity at pH 5.5 and 75 °C, and its specific activity was 33.9 U/mg. To improve the substrate tolerance of BaADC, site-directed mutation was used to construct variants. The optimal variant BaADC_I88M exhibited higher pH stability and thermostability, with 1.2-fold increase in catalytic efficiency. Moreover, through the fed-batch method, the conversion of L-aspartic acid to β-alanine catalyzed by BaADC_I88M reached 98.6% (128.67 g/L) at 12 h, which was 1.42-fold that of the wild-type enzyme. The mechanism of improved substrate tolerance was interpreted by molecular dynamics simulation and structural analysis, which revealed that the local conformational change in the active pocket could promote correct protonation. These results suggested that BaADC and its variant are potential candidates for use in the industrial production of β-alanine.

Different Approaches to Ergogenic, Pre-, and Probiotic Supplementation in Sports with Different Metabolism Characteristics: A Mini Review

Sport disciplines with different metabolic characteristics require different dietary approaches. Bodybuilders or sprinters ("anaerobic" athletes) need a high-protein diet (HPD) in order to activate muscle protein synthesis after exercise-induced muscle damage and use nitric oxide enhancers (such as citrulline and nitrates) to increase vasodilatation, whereas endurance athletes, such as runners or cyclists ("aerobic" athletes), prefer a high-carbohydrate diet (HCHD), which aims to restore the intramuscular glycogen, and supplements containing buffering agents (such as sodium bicarbonate and beta-alanine). In both cases, nutrient absorption, neurotransmitter and immune cell production and muscle recovery depend on gut bacteria and their metabolites. However, there is still insufficient data on the impact of an HPD or HCHD in addition to supplements on "anaerobic" and "aerobic" athletes' gut microbiota and how this impact could be affected by nutritional interventions such as pre- and probiotic therapy. Additionally, little is known about the role of probiotics in the ergogenic effects of supplements. Based on the results of our previous research on an HPD in amateur bodybuilders and an HCHD in amateur cyclists, we reviewed human and animal studies on the effects of popular supplements on gut homeostasis and sport performance.

Plasma β-Alanine is Positively Associated With Risk of Ischemic Stroke: a Nested Case-Control Study

BACKGROUND

Previous studies suggested that β-alanine as a neurotransmitter could affect the pathogenesis of ischemic damage. However, the association between circulating β-alanine and risk of ischemic stroke (IS) has not been evaluated in populations.

OBJECTIVES

We aimed to examine the association between β-alanine and IS risk in a nested case-control study.

METHODS

We performed a case-control study nested within a prospective community-based cohort (n = 16457; median follow-up time: 5.3 y), which included 321 incident IS cases and 321 controls matched by age and sex. Β-alanine and other metabolites were measured in plasma after overnight fasting by LC-MS/MS. The association of β-alanine with risk of IS was evaluated by conditional logistic regression. BMI, current smoking, educational attainment, physical activity, total energy intake, family history of stroke, hypertension, diabetes, hyperlipidemia, and estimated GFR were adjusted in multivariable models.

RESULTS

There was a significant Spearman partial correlation between β-alanine and 4-pyridoxic acid (ρ = 0.239; P < 0.001). Participants with elevated β-alanine levels were more likely to develop IS with an adjusted OR of 1.26 (95% CI: 1.06-1.51; P = 0.011) (per standard deviation increment). This association remained significant after excluding the first 2 y of follow-up, and after further adjustment for red meat intake, total protein intake, medication use, or vitamin B6 indicators.

CONCLUSIONS

Our novel findings revealed that plasma β-alanine at baseline were positively associated with risk of IS and may function as an early biomarker of IS risk.

Multi-target action of β-alanine protects cerebellar tissue from ischemic damage

Brain ischemic stroke is among the leading causes of death and long-term disability. New treatments that alleviate brain cell damage until blood supply is restored are urgently required. The emerging focus of anti-stroke strategies has been on blood-brain-barrier permeable drugs that exhibit multiple sites of action. Here, we combine single-cell electrophysiology with live-cell imaging to find that β-Alanine (β-Ala) protects key physiological functions of brain cells that are exposed to acute stroke-mimicking conditions in ex vivo brain preparations. β-Ala exerts its neuroprotective action through several distinct pharmacological mechanisms, none of which alone could reproduce the neuroprotective effect. Since β-Ala crosses the blood-brain barrier and is part of a normal human diet, we suggest that it has a strong potential for acute stroke treatment and facilitation of recovery.

Synergistic Effect of β-alanine and Aprotinin on Mesenteric Ischemia

BACKGROUND

Acute mesenteric ischemia arises through sudden interruption of mesenteric blood flow, mostly due to an occlusion of the superior mesenteric artery and is associated with a high mortality of approximately 50% to 90%. In previous studies, the single application of β-alanine or aprotinin caused an ameliorated intestinal damage but without any systemic effects.

METHODS

To analyze the combined effect of β-alanine and aprotinin on acute ischemia and reperfusion of the small intestine, a model with anesthetized rats was used. Ischemia and reperfusion were initiated by occluding and reopening the superior mesenteric artery. After 120 min of ischemia and 180 min of reperfusion, the intestine was analyzed for tissue damage, the activity of the saccharase, and accumulation of granulocytes. In addition, systemic and metabolic as well as inflammatory parameters were measured in blood at certain points in time.

RESULTS

The combination of β-alanine and aprotinin resulted in a clearly stabilized mean arterial blood pressure and blood glucose level during the reperfusion period. Furthermore, the combined administration resulted in significantly reduced tissue damage parameters, cytokine and cell-free hemoglobin concentrations in blood plasma. In addition, the damage to the small intestine was significantly attenuated, so that the animals ultimately survived the entire test period because of the administration of both substances.

CONCLUSIONS

Overall, the simultaneous application of both substances leads to a synergistic protection without the occurrence of undesirable side effects. The combined usage of β-alanine and aprotinin can be seen as a promising approach to inhibit the onset of acute mesenteric ischemia.

Incidence, Characteristics, Laboratory Findings and Outcomes in Acro-Ischemia in COVID-19 Patients

Aim

In addition to its respiratory impact of SARS-CoV2, skin lesions of probable vascular origin have been described. This study intends to quantify the incidence of acro-ischemic lesions in COVID-19 infected adult subjects in our population, describing clinical patterns and associated findings.

Methods

All adult confirmed cases of COVID-19 infection who presented with acro-ischemic lesions and received care in our institution were prospectively enrolled up to May 15th, 2020. The variables included demographics, comorbidities, analytical parameters, clinical presentations and COVID-19 treatment.

Results

We enrolled 24 patients. The overall rate of acro-ischemic findings in COVID-19 patients was 1.2% [0.6% for outpatients and 2.9% for hospitalized (ICU and non-ICU patients)], but the observed incidence for acro-ischemia in ICU patients was remarkably higher (23.0%, p<0.001). We have described four different clinical patterns of acroischemia: atypical Raynaud´s phenomenon (ARP), (4); pseudo-pernio (PP), (5); severe microcirculatory ischemia with preserved pulse (SMI), (6); and dry gangrene with arteriosclerosis obliterans (AO), (9). Kendall´s τ correlation with lung disease severity was 0.877 (95% CI, 0.756 to 0.968); p<0.01). ARP individuals were predominantly female, while SMI appeared lately in elderly hospitalized subjects with better prognosis. AO occurred in patients with more comorbidity and younger than those with SMI. We observed other associated lesions of suggestive ischemic nature in other organs in all groups (15 patients of total sample). Plasma procalcitonin was significantly higher in patients who developed SMI (median and interquartile range: 9.99 (4.2, 12.3) mg/mL vs 0.26 (0.11, 0.89) mg/mL; p<0.001), and D-dimer level at hospital admission was significantly higher in AO patients (median and interquartile range: 1166 (1050, 2111) mg/L vs 502 (448, 777) mg/L; p<0.001).

Conclusion

The observed risk for acroischemia in COVID-19 is high in ICU patients (23%). We have described four different clinical patterns of acroischemia (ARP, PP, SMI and AO) associated with lung disease severity. Authors have communicated various lesions of suggestive ischemic nature in other organs. Raynaud-like pattern is reported as a "novelty".

[Endovascular surgery for acute mesenteric ischemia]

OBJECTIVE

To demonstrate the results of endovascular treatment of 15 patients with acute mesenteric ischemia.

MATERIAL AND METHODS

There were 15 patients with acute mesenteric ischemia who underwent surgery (9 men and 6 women). Mean age was 77±11 years. Acute intestinal ischemia was caused by thromboembolism of superior mesenteric artery (9 patients), thrombosis of superior mesenteric artery (5 patients) and critical stenosis of the ostia of superior mesenteric artery and celiac trunk (1 patient). Mean time from clinical manifestation of disease to admission to the hospital was 13 hours (range 2-72 hours). In-hospital development of acute mesenteric ischemia was noted in 2 patients. Indications for endovascular intervention and techniques of endovascular revascularization of superior mesenteric artery are described in the article.

RESULTS

Blood flow restoration in superior mesenteric artery was achieved in 14 (93%) out of 15 patients. Laparotomy was required in 4 (27%) patients for extensive resection of necrotic intestine (n=1, 6.7%), local resection of small bowel (n=2, 13%). In another (6.7%) patient, intestine was recognized as viable after laparotomy. A bulk of intestine was preserved in most patients (n=14, 93%). In-hospital mortality rate was 47% (7 patients died). The main cause of nosocomial death (6 cases) was reperfusion syndrome followed by respiratory distress syndrome and multiple organ failure.

CONCLUSION

New methods of prevention and treatment of reperfusion syndrome can improve the results of treatment of acute mesenteric ischemia.

Pathway construction and metabolic engineering for fermentative production of β-alanine in Escherichia coli

β-Alanine is a naturally occurring β-amino acid that has been widely applied in the life and health field. Although microbial fermentation is a promising method for industrial production of β-alanine, an efficient microbial cell factory is still lacking. In this study, a new metabolically engineered Escherichia coli strain for β-alanine production was developed through a series of introduction, deletion, and overexpression of genes involved in its biosynthesis pathway. First, the L-aspartate a-decarboxylase gene, BtADC, from Bacillus tequilensis, with higher catalytic activity to produce β-alanine from aspartate, was constitutively expressed in E. coli, leading to an increased production of β-alanine up to 2.76 g/L. Second, three native aspartate kinase genes, akI, akII, and akIII, were knocked out to promote the production of β-alanine to a higher concentration of 4.43 g/L by preventing from bypass loss of aspartate. To increase the amount of aspartate, the native AspC gene was replaced with PaeAspDH, a L-aspartate dehydrogenase gene from Pseudomonas aeruginosa, accompanied with the overexpression of the native AspA gene, to further improve the production level of β-alanine to 9.27 g/L. Last, increased biosynthesis of oxaloacetic acid (OAA) was achieved by a combination of overexpression of the native PPC, introduction of CgPC, a pyruvate decarboxylase from Corynebacterium glutamicum, and deletion of ldhA, pflB, pta, and adhE in E. coli, to further enhance the production of β-alanine. Finally, the engineered E. coli strain produced 43.12 g/L β-alanine in fed-batch fermentation. Our study will lay a solid foundation for the promising application of β-alanine in the life and health field. KEY POINTS: • Overexpression of BtADC resulted in substantial accumulation of β-alanine. • The native AspC was replaced with PaeAspDH to catalyze the transamination of OAA. • Deletion of gluDH prevented from losing carbon flux in TCA recycle. • A 43.12-g/L β-alanine production in fed-batch fermentation was achieved. Graphical abstract.

Glycine receptors are involved in hippocampal neuronal damage caused by oxygen-glucose deficiency

Glycine receptors (GlyRs) belong to the family of ligand-gated cys-loop receptors and effectuate fast inhibitory neurotransmission in central nervous system (CNS). They are involved in numerous physiological processes, such as movement, respiration, and processing of sensory information, as well as in regulation of neuronal excitability in different brain regions. GlyRs play important role in the maintenance of excitatory/inhibitory balance in the hippocampus and participate in the development of various brain pathologies. In the present study, we have examined a surface expression of GlyRs by pyramidal neurons and astrocytes in control and after 30 min of oxygen-glucose deprivation (OGD) in the organotypic culture of hippocampal slices. Our investigation has demonstrated a decrease in GlyR-positive staining associated with pyramidal neurons and relative stability of GlyRs expression at the surface of astrocytes 4 hs after OGD. These data indicate that GlyRs dysfunction may represent a significant additional factor leading to enhanced neuronal damage induced by OGD. Pharmacological modulation of GlyRs is a promising venue of research for the correction of negative consequences of oxygen-glucose deficiency.

Evaluation of small intestinal damage in a rat model of 6 Minutes cardiac arrest

BACKGROUND

Contribution of the small intestine to systemic inflammation after cardiac arrest (CA) is poorly understood. The objective was to evaluate whether an in vivo rat model of 6 min CA is suitable to initiate intestinal ischaemia-reperfusion-injury and to evaluate histomorphological changes and inflammatory processes in the small intestinal mucosa resp. in sera.

METHODS

Adult male Wistar rats were subjected to CA followed by cardio-pulmonary resuscitation. Proximal jejunum and serum was collected at 6 h, 24 h, 72 h and 7 d post return of spontaneous circulation (ROSC) and from a control group. The small intestine was evaluated histomorphologically. Cytokine concentrations were measured in jejunum lysates and sera.

RESULTS

Histomorphological evaluation revealed a significant increase in mucosal damage in the jejunum at all timepoints compared to controls (p < 0.0001). In jejunal tissues, concentrations of IL-1α, IL-1β, IL-10, and TNF-α showed significant peaks at 24 h and were 1.5- to 5.7-fold higher than concentrations at 6 h and in the controls (p < 0.05). In serum, a significant higher amount of cytokine was detected only for IL-1β at 24 h post-ROSC compared to controls (15.78 vs. 9.76 pg/ml).

CONCLUSION

CA resulted in mild small intestinal tissue damage but not in systemic inflammation. A rat model of 6 min CA is not capable to comprehensively mimic a post cardiac arrest syndrome (PCAS). Whether there is a vital influence of the intestine on the PCAS still remains unclear.

Effect of Glycine, Pyruvate, and Resveratrol on the Regeneration Process of Postischemic Intestinal Mucosa

Background

Intestinal ischemia is often caused by a malperfusion of the upper mesenteric artery. Since the intestinal mucosa is one of the most rapidly proliferating organs in human body, this tissue can partly regenerate itself after the onset of ischemia and reperfusion (I/R). Therefore, we investigated whether glycine, sodium pyruvate, and resveratrol can either support or potentially harm regeneration when applied therapeutically after reperfusion injury.

Methods

I/R of the small intestine was initiated by occluding and reopening the upper mesenteric artery in rats. After 60 min of ischemia and 300 min of reperfusion, glycine, sodium pyruvate, or resveratrol was administered intravenously. Small intestine regeneration was analyzed regarding tissue damage, activity of saccharase, and Ki-67 positive cells. Additionally, systemic parameters and metabolic ones were obtained at selected periods.

Results

Resveratrol failed in improving the outcome after I/R, while glycine showed a partial beneficial effect. Sodium pyruvate ameliorated metabolic acidosis, diminished histopathologic tissue injury, and increased cell proliferation in the small intestine.

Conclusion

While glycine could improve in part regeneration but not proliferation, sodium pyruvate seems to be a possible therapeutic agent to facilitate proliferation and to support mucosal regeneration after I/R injury to the small intestine.