Research background of intestinal brain axis
Parkinson's disease is a neurodegenerative disease and cannot be completely cured. Recent studies show that there are differences in intestinal microbial communities between PD patients and healthy people. Short-chain fatty acids are the main metabolites of intestinal microorganisms, which can transmit the signals of intestinal flora to the host and have a positive effect on regulating the integrity of brain function and blood tissue barrier, but they are also the main regulatory factors for accelerating neuroinflammation and α -nucleoprotein disease in PD model. Therefore, in-depth study of intestinal microorganisms is of great significance for the treatment or improvement of PD.
Osteocalcin (OCN) is a kind of protein secreted by osteoblasts, which has the functions of regulating brain function, crossing the blood-brain barrier, directly combining with neurons in hippocampal CA3 area, and restoring cognitive function in mice. Previous studies have shown that OCN may affect the composition of flora. Therefore, this study assumes that OCN can prevent sports injury and dopaminergic neuron loss by regulating intestinal flora in PD mice, and studies the therapeutic effect and mechanism of OCN and intestinal flora on PD.
Research methods of intestinal brain axis
Sequencing platform: Illumina high-throughput sequencing platform.
Sequencing region: V3-V4 region of microbial group bacteria 16S rRNA gene.
Research achievements of intestinal brain axis
Neuroprotective effect of 1 Effect of OCN on Parkinson's disease mice and its correlation with intestinal flora
The results of animal experiments show that OCN can prevent 6- hydroxydopamine (6-OHDA)-induced motor injury and dopaminergic neuron loss in mice with Parkinson's disease. After antibiotics were used to eliminate intestinal flora four weeks before taking OCN, the protective effect of OCN on motor function and dopamine neuron injury in mice was no longer effective, indicating that the neuroprotective effect of OCN on PD mice was mediated by intestinal flora. The experiment of fecal flora transplantation also reached the same conclusion.
Fig. 1 OCN can prevent motor injury and dopaminergic neuron loss induced by 6-OHDA in mice with Parkinson's disease.
Fig. 2 Antibiotic pretreatment failed to prevent motor injury and dopaminergic neuron loss in mice with Parkinson's disease.
Fig. 3 fecal flora transplantation experiment and dyskinesia experiment
2. Changes of intestinal microbial community in Parkinson's disease mice and mice after OCN treatment.
The results of microbial flora sequencing showed that the intestinal microbial composition of PD mice was significantly different from that of the control group (P
PICRUSt function prediction analysis showed that the propionic acid production ability of intestinal microorganisms in PD mice was obviously reduced, and the relative abundance of KO related to butyric acid production also changed. Notably, OCN government successfully reversed these changes in PD mice. This shows that the intervention of OCN can change the microbial community composition of PD mice and may also enhance the potential of bacteria to produce propionic acid.
Fig. 4 Regulatory effect of OCN on intestinal flora imbalance induced by 6-OHDA in mice with Parkinson's disease.
3. Effect of 3.OCN on fecal propionic acid level in mice with Parkinson's disease.
In order to further study whether the bacterial SCFAs has changed, the author analyzed the content of SCFAs in feces by gas chromatography/mass spectrometry (GC/MS). The results showed that the content of propionic acid in feces of PD mice induced by 6-OHDA was significantly lower than that of the control group, and OCN treatment significantly reversed this change. The results of correlation analysis showed that the level of propionic acid in feces was positively correlated with S24-7 and Rickettsiaceae, but with Lacnosaceae and unclassified? Clostridium was negatively correlated.
More importantly, the propionic acid level in feces is positively correlated with the motor function parameters of open field test, cylinder test and rotating rod test. Therefore, the neuroprotective effect of intestinal microorganisms on OCN may be related to propionic acid.
Fig. 5 OCN administration can increase the fecal propionic acid level of 6-OHDA-induced Parkinson's disease mice.
4.？ Propionic acid and FFAR3 agonists prevent sports injury and dopaminergic neuron loss in PD mice.
In order to further verify the relationship between propionic acid and improving the motor function of PD mice, the author added sodium propionate to the drinking water of PD mice induced by 6-OHDA. The results show that oral propionic acid can effectively improve the motor function of mice in open field test and cylinder test, and prevent the loss of dopaminergic neurons in PD mice injected with 6-OHDA by nearly 40%. This suggests that propionic acid may be a signal from intestinal microbial community, which is related to the development of Parkinson's disease and may be the target of OCN to improve Parkinson's disease.
Subsequently, PD mice were further treated with FFAR3 (the main receptor type mediating the protective effect of propionic acid) agonist, and its neuroprotective effect was similar to that of propionic acid.
Fig. 6 Oral propionic acid prevents 6-OHDA-induced dyskinesia and dopaminergic neuron loss in PD mice.
Fig. 7 In 6-OHDA-induced PD mice, FFAR3 agonist was administered to prevent dyskinesia and dopaminergic neuron loss.
5.？ Correlation between enteric nervous system and propionic acid on neuroprotective effects in mice with Parkinson's disease
After measuring the expression of FFAR3 in different tissues, it was found that the relative expression of FFAR3 in jejunum, ileum and colon was much higher than that in cortex, hippocampus and cerebral striatum. The gastric perfusion experiment of cisplatin (a known enteroneurotoxin) showed that propionic acid had no significant protective effect on the loss of dopaminergic neurons in mice with intestinal cell depletion. This suggests that the neuroprotective effect of propionic acid on PD may be related to enteric nervous system, that is, propionic acid may play a neuroprotective role in PD mice as an FFAR3 agonist against enteric nervous system.
Fig. 8 Neuroprotective effect of propionic acid mediated by enteric nervous system on PD mice induced by 6-OHDA.
To sum up, OCN can promote the microbial production of propionic acid by changing the intestinal microbial community, and propionic acid can activate FFAR3 in intestinal neurons, thus exerting its protective effect on Parkinson's disease.
Research conclusion of intestinal brain axis
In this study, the therapeutic effect and mechanism of OCN and intestinal flora on PD were studied by using the strategy of multi-omics integration and correlation research, combined with experiments such as fecal bacterial transplantation, and the following conclusions were drawn:
①OCN can significantly improve motor dysfunction and dopaminergic neuron loss in PD mice;
②OCN treatment can restore the imbalance of intestinal flora in PD mice, increase the abundance of Bacteroides and decrease the abundance of Firmicutes, and improve the levels of propionic acid-producing bacteria and fecal propionic acid.
③ Antibiotic therapy experiment and fecal bacterial transplantation experiment showed that intestinal flora mediated the neuroprotective effect of OCN.
④ Oral propionate for 2 months can restore the motor function and dopaminergic neurons of PD mice in an intestinal neuron-dependent manner;
⑤FFAR3 agonists have similar neuroprotective effects.
The sequencing and partial data analysis of the research on intestinal brain axis were completed by Shanghai Paisennuo Biotechnology Co., Ltd. ..