Propionic Acid Administration Research Articles

Could the Propionic Acid Treatment in Combination with Metformin be Safe for the Small Intestine of Diabetic Rats?

Effects of propionic acid (PA) on the cellular and molecular processes in the small intestine under type 2 diabetes mellitus (T2DM)-induced endoplasmic reticulum (ER) stress remain incompletely studied. The aim of the study was to assess the state of unfolded protein response (UPR) system in the small intestine of diabetic rats and to explore PA's influence on metformin treatment. Male Wistar rats were divided into 1) control and 2) T2DM groups, and groups receiving (14 days, orally) 3) metformin (60 mg/kg), 4) PA (60 mg/kg), and 5) PA+metformin. Western blotting, RT-PCR, and transmission electron microscopy were performed. We found that T2DM induced elevation of ER intermembrane space and UPR overactivation based on increased GRP78, ATF6 and PERK levels in small intestine. Metformin treatment led to a further UPR activation. PA supplementation partially restored enterocytes functioning via normalization of ATF6 and PERK content, while IRE1 level reached the maximum value, compared to all groups. The most pronounced effect of adaptation to the T2DMinduced ER stress was observed after combined metformin and PA action. In particular, decreased ER intermembrane space in enterocytes was detected compared to separate metformin and PA administration, which was accompanied by restored GRP78, PERK and IRE1 levels. Our study proves the safety of additional therapy with propionic acid in combination with metformin for the functional state of small intestine. Due to its ability to modulate UPR signaling, PA may be considered a safe and perspective candidate for supportive therapy in T2DM, especially for neuroprotection.

Protective properties of Ophiopogonin D in DSS-induced colitis: insights into microbiota modulation.

Ulcerative colitis (UC), a chronic inflammatory gastrointestinal disorder, is becoming increasingly prevalent worldwide. Ophiopogonin D, which is derived from Ophiopogon japonicus, exhibits anti-inflammatory and antioxidant properties, yet its therapeutic potential in UC remains unclear. In this study, we employed a mouse model of DSS-induced colitis to assess the impact of Ophiopogonin D on various parameters, including weight loss, bloody stools, and inflammation in the colon. Ophiopogonin-D treatment significantly mitigated these DSS-induced effects, improved colon permeability, and modulated inflammatory markers like ZO-1, MUC-2, TNF-α, and IL-1β in mice compared with the control. Furthermore, compared to the DSS-treatment group, Ophiopogonin-D treatment improved the α- and β-diversity indices of the mouse intestinal microbiota, along with an increase in the abundance of genera such as Akkermansia (AKK) and a decrease in the abundance of genera such as Enterobacter. Notably, propionic acid, a metabolite of AKK, demonstrated significant improvement in the symptoms of DSS-induced colitis in mice compared to the control. Moreover, propionic-acid administration also resulted in alterations in the levels of inflammatory factors and calreticulin within the intestinal tissues. Overall, Ophiopogonin D significantly affects intestinal microbiota composition, thereby improving symptoms of DSS-induced colitis in mice. These findings present promising therapeutic strategies and potential pharmaceutical candidates for the treatment of ulcerative colitis.

Progesterone attenuate autism-like-phenotype through modulation of cerebral inflammation and oxidative stress

Objectives: Autism spectrum disorder (ASD) is a neurodevelopmental disorder that characterises repetitive behaviour and impairment in social communication as well as interaction. The complex aetiology of ASD involves multiple genes, epigenetic mechanisms and environmental factors. Propionic acid (PPA) is observed to be well associated with behavioural and biochemical phenotypes akin to ASD. This study evaluates the potential effect of progesterone in PPA-induced ASD phenotype. Materials and Methods: PPA (250 mg/kg, po) was administered to induce ASD-like behavioural and neurobiochemical alterations in Albino Wistar rats from post-natal day 21st to 23rd. Rats were observed for locomotor activity (open filed apparatus), exploratory behaviour (hole board apparatus- no. of rearing, latency to first poke and hole poking), stereotypy behaviour (self-grooming) and biochemical parameters (interleukin-6, tumour necrosis factor-alpha, glutathione and thiobarbituric acid reactive substance). Results: Post-natal PPA administration resulted in hyperlocomotion, repetitive behaviour and a decrease in exploratory activity. Furthermore, an increase in inflammation and oxidative stress markers was observed in the brain regions of PPA-administered rats. Progesterone (4 mg/kg and 8 mg/kg) administration was observed to attenuate postnatal PPA-induced impairments in experimental animals. Conclusion: Progesterone (4 mg/kg and 8 mg/kg) administration may protect against behavioural and biochemical alterations that are associated with ASD.

The enteric metabolite, propionic acid, impairs social behavior and increases anxiety in a rodent ASD model: Examining sex differences and the influence of the estrous cycle

Research suggests that certain gut and dietary factors may worsen behavioral features of autism spectrum disorder (ASD). Treatment with propionic acid (PPA) has been found to create both brain and behavioral responses in rats that are characteristic of ASD in humans. A consistent male bias in human ASD prevalence has been observed, and several sex-differential genetic and hormonal factors have been suggested to contribute to this bias. The majority of PPA studies in relation to ASD focus on male subjects; research examining the effects of PPA in females is scarce. The present study includes two experiments. Experiment 1 explored sex differences in the effects of systemic administration of PPA (500 mg/kg, ip) on adult rodent social behavior and anxiety (light-dark test). Experiment 2 investigated differential effects of systemic administration of PPA (500 mg/kg) on social behavior and anxiety in relation to fluctuating estrogen and progesterone levels during the adult rodent estrous cycle. PPA treatment impaired social behavior and increased anxiety in females to the same degree in comparison to PPA-treated males. As well, females treated with PPA in their diestrus phase did not differ significantly in comparison to females administered PPA in their proestrus phase, in terms of reduced social behavior and increased anxiety.

Regulation of the apoptosis/autophagy switch by propionic acid in ventromedial hypothalamus of rats with type 2 diabetes mellitus

BackgroundHypothalamic dysregulation may cause abnormal glucose metabolism and type 2 diabetes mellitus (T2DM). The balance between autophagy and apoptosis is important for maintaining cellular/tissue homeostasis and may be disrupted in T2DM. ObjectivesSince propionic acid (PA) exerts neuroprotective effects, the aim was to investigate its effects on apoptosis/autophagy switch in the ventromedial hypothalamus (VMH) of T2DM rats. Materials and methodsMale Wistar rats were divided: 1) control; 2) T2DM; groups that received (14 days, orally): 3) metformin (60 mg/kg); 4) sodium salt of PA (60 mg/kg); 5) PA + metformin. Western blotting (Bax, Bcl-xl, LC3, Beclin-1, caspase-3), RT-PCR (Bax, Bcl-xl, LC3, Beclin-1), transmission electron microscopy and immunohistochemical staining (Bax, Bcl-xl) were performed on the VMH samples. ResultsT2DM-induced apoptosis and mitoptosis, enlarged endoplasmic reticulum (ER) tubules/cisterns were observed in VMH, and accompanied by an imbalance of pro- and anti-apoptotic factors: elevation of pro-apoptotic markers Bax and caspase-3, decrease in autophagy protein LC3 and anti-apoptotic Bcl-xl. Metformin and PA administration partially improved VMH ultrastructural changes by reducing mitochondrial swelling and diminishing the number of apoptotic neurons. Metformin inhibited neuronal apoptosis, however, caused reactive astrogliosis and accumulation of lipofuscin granules. Elevated number of autophagosomes was associated with the LC3, Beclin-1 and Bcl-xl increase and decrease in Bax and caspase-3 vs. T2DM. PA switched cell fate from apoptosis to autophagy by elevating LC3 and Beclin-1 levels, increasing Bcl-xl content that altogether may represent adaptive response to T2DM-induced apoptosis. PA + metformin administration lowered relative area of ER membranes/cisterns vs. control, T2DM and metformin, and was optimal considering ratio between the pro-apoptotic, anti-apoptotic and autophagy markers. ConclusionT2DM was associated with apoptosis activation leading to impairments in VMH. PA in combination with metformin may be effective against diabetes-induced cell death by switching apoptosis to autophagy in VMH.

Demonstration of ameliorating effect of vardenafil through its anti-inflammatory and neuroprotective properties in autism spectrum disorder induced by propionic acid on rat model

Introduction Autism spectrum disorder (ASD) is a neurodevelopmental disorder with complex etiology. In this study, we aimed to determine the ameliorating effects of vardenafil in the ASD rat model induced by propionic acid (PPA) in terms of neurobehavioral changes and also support these effects with histopathological changes, brain biochemical analysis and magnetic resonance spectroscopy (MRS) findings. Materials and methods Twenty-one male rats were randomly assigned into three groups. Group 1 (control, 7 rats) did not receive treatment. Rats in groups 2 and 3 were given PPA at the dose of 250 mg/kg/day intraperitoneally for 5 days. After PPA administration, animals in group 2 (PPAS, 7 rats) were given saline and animals in group 3 (PPAV, 7 rats) were given vardenafil. Behavioral tests were performed between the 20th and 24th days of the study. The rats were taken for MRS on the 25th day. At the end of the study, brain levels of interleukin-2 (IL-2), IL-17, tumor necrosis factor-α, nerve growth factor, cGMP and lactate levels were measured. In the cerebellum and the CA1 and CA3 regions of the hippocampus, counts of neurons and Purkinje cells and glial fibrillary acidic protein (associated with gliosis) were evaluated histologically. Results Three chamber sociability and passive avoiding test, histopathological results, lactate levels derived from MRS, and biochemical biomarkers revealed significant differences among the PPAV and PPAS groups. Conclusion We concluded that vardenafil improves memory and social behaviors and prevent loss of neuronal and Purkinje cell through its anti-inflammatory and neuroprotective effect.

Propionic Acid, Induced in Gut by an Inulin Diet, Suppresses Inflammation and Ameliorates Liver Ischemia and Reperfusion Injury in Mice.

Liver ischemia and reperfusion injury (IRI) is one of the obstacles in liver surgery such as liver resection and transplantation. In this study, we investigated the preventive effect on mouse liver IRI by feeding mice with inulin, which is a heterogeneous blend of indigestible fructose polymer. Mice were fed either a control ordinary diet (CD) or an inulin diet (ID) containing 5% inulin in the CD, for 14 days before the ischemia and reperfusion (IR) maneuver. IR induced-liver damages were significantly ameliorated in the ID group, compared with those in the CD group. Feeding mice with an ID, but not a CD, elevated levels of Bacteroidetes among gut microbiota, and especially increased Bacteroides acidifaciens in mouse feces, which resulted in significant elevation of short-chain fatty acids (SCFAs) in the portal vein of mice. Among SCFAs, propionic acid (PA) was most significantly increased. The microbial gene functions related to PA biosynthesis were much higher in the fecal microbiome of the ID group compared to the CD. However, the action of PA on liver IRI has not been yet clarified. Direct intraperitoneal administration of PA alone prior to the ischemia strongly suppressed liver cell damages as well as inflammatory responses caused by liver IR. Furthermore, PA suppressed the secretion of inflammatory cytokines from peritoneal macrophages stimulated in vitro through TLR-4 with high-mobility group box 1 protein (HMGB-1), known to be released from apoptotic liver cells during the IR insult. The present study shows that PA may play a key role in the inulin-induced amelioration of mouse liver IRI.

Propionic acid regulates immune tolerant properties in B Cells.

Interleukin 10 (IL‐10)‐producing B cells (B10 cells) are a canonical cell fraction for regulating other activities of immune cells. Posttranscriptional modification of IL‐10 in B10 cells is not yet fully understood. Short‐chain fatty acids play an important role to regulate the functions of immune cells. This study aims to clarify the role of propionic acid (PA), a short‐chain fatty acid, in regulating the expression of IL‐10 in B10 cells. Blood samples were collected from patients with food allergy (FA) and healthy subjects. Serum and cellular components were prepared with the samples, and analysed by enzyme‐linked immunosorbent assay and flow cytometry, respectively. The results showed that serum PA levels were lower in FA patients. PA concentrations were negatively correlated with serum cytokine Th2 concentrations, specific IgE concentrations in serum and skin prick test results. The peripheral frequency of B10 cells and the production of IL‐10 in B cells were also associated with serum PA concentrations. Activation of B cells by CpG induced the production of IL‐10 and tristetretrprolin (TTP), in which TTP caused the spontaneous decay of IL‐10 mRNA. PA was necessary to stabilize the IL‐10 mRNA in B cells by inducing the production of granzyme B, which resulted in the degradation of the IL‐10 mRNA. Administration of PA attenuated FA response in mice by maintaining homeostasis of B10 cells. In conclusion, PA is needed to stabilize the expression of IL‐10 in B10 cells. PA administration can mitigate experimental FA by maintaining B10 cell functions.

Current Neuropharmacological Interventions in Autism: Potential Drug Targets from Pre-clinical and Clinical Findings

Autism spectrum disorder is the term used in the most recent edition of the diagnostic and statistical manual of neurodevelopmental disorders, which includes conditions such as autism. Etiological factors such as environmental toxins, food, genes, bacterial infections, and viruses are the reasons behind autism. In the lack of diagnostic criteria, early studies of the disorder reported differences in motor and cognitive abilities in persons with autism. Autism neuropathological features are correlated with different brain areas, such as the cerebral cortex, amygdala, and hippocampus. Autism is associated with mitochondrial dysfunction, oxidative stress, neuroinflammatory reactions, neuroexcitation, and abnormal synapse formation. Pre-clinically, the administration of propionic acid in the brains of rats by stereotaxic technique exacerbates autistic behavioral and neurochemical alterations. Prescription drugs to alleviate neurological disorders for autism are risperidone (Blocks D2 and 5HT2A receptors) and aripiprazole (D2 and 5HT1A partial agonist) approved by the US-FDA, which comes with limited therapeutic intervention. Findings suggest that malfunctions of propionic acid-disrupted neuronal mitochondrial coenzyme Q10 (CoQ10) and etc-complexes are the most pathogenic events for autism. As a result, the current review focused on the history of disease, clinical and pre-clinical drugs under investigation and suggested mediating neuroprotective intervention in autism with mitochondrial CoQ10 activation. Additionally, a greater understanding of the mitochondrial signaling pathway is an effort to improve successful treatment not only for Autism but also for other neurological disorders.

Systemic treatment with the enteric bacterial metabolic product propionic acid results in reduction of social behavior in juvenile rats: Contribution to a rodent model of autism spectrum disorder.

The role of the gut microbiome and its enteric metabolites, such as short-chain fatty acids (SCFAs), in the etiology of autism spectrum disorders (ASDs) has recently received increased attention. Of particular interest has been the SCFA, propionic acid (PPA). Several different rodent models have been developed using PPA treatment to examine behaviors of relevance to ASD. The effects of systemic (intraperitoneal, i.p.) administration of PPA on social behavior, anxiety-related behavior, and locomotor activity in juvenile male rats (age 35days) were examined in this study. Rats received seven i.p. injections of buffered PPA (500mg/kg) or phosphate-buffered saline. Behavior was video-recorded during social interaction in a large open field (first four injections) or assessed in an automated activity system (individual animals, last three injections). PPA treatment significantly reduced social interaction, increased anxiety-related behavior, and produced hypoactivity and increased abnormal motor movements. These findings suggest that PPA alters behaviors of relevance to ASD in juvenile rats. These results contribute to the behavioral validity of the rodent model of ASD with systemic PPA treatment.

Comparative study on the independent and combined effects of omega-3 and vitamin B12 on phospholipids and phospholipase A2 as phospholipid hydrolyzing enzymes in PPA-treated rats as a model for autistic traits

BackgroundAbnormal phospholipid metabolism is a major component of many neurodevelopmental disorders including autism. Oral administration of propionic acid (PPA) can produce behavioral abnormalities and biochemical features in rodents similar to those observed in autism and can thus be used as a model to understand impaired brain fatty acid metabolism in autism.MethodsThe present study was designed to understand alterations in phospholipid metabolism in the brain of a rodent model of autism and to explore omega-3 and vitamin B12 as remedies. Five groups of rats were selected: Group 1 was the control. Group 2 was the rodent model of autism treated with a neurotoxic dose of PPA. Group 3 was given vitamin B12 cobalamin (16.7 mg/kg/day) for 30 days after PPA treatment. Group 4 was given pharmaceutical grade Omega-3 (200 mg cholesterol free-DHA/kg body weight/day), a product of Madre lab, Germany, for 30 days after PPA treatment for 3 days. Group 5 was given a combined dose of ω-3 + Vitamin B12 for the same duration post-PPA treatment. Phospholipid levels and Phospholipase A2 were measured in the brain homogenates of all the groups. ELISA and western blotting were used to detect the cPLA2 protein level.ResultsA significant decrease in phospholipid levels and a significant increase in cPLA2 were found in brain tissue of PPA-treated rats; however, both ω-3 and vitamin B12 were efficient in ameliorating the neurotoxic effect of PPA.ConclusionBoth ω-3 and vitamin B12 may play a role in ameliorating impaired phospholipid metabolism in autism; however, proper clinical trials are needed.

Pathophysiological and neurobehavioral characteristics of a propionic acid‐mediated autism‐like rat model

Autism spectrum disorder (ASD) is induced by complex hereditary and environmental factors. However, the mechanisms of ASD development are poorly understood. The purpose of this study was to identify the standard indicators of this condition by comparing clinical, pathophysiological, and neurobehavioral features in an autism‐like animal model. A total of 22 male Sprague‐Dawley (SD) rats were randomly divided into control and 500 mg/kg propionic acid (PPA)‐treated groups. The rats were subjected to behavioral testing, gene expression, and histology were examined to detect pathophysiological and neurobehavioral alterations. Exploratory activity and non‐aggressive behavior were significantly reduced in PPA‐treated rats, whereas we observed enhanced aggressive behavior in terms of adjacent interactions on Day 14 after PPA treatment. To evaluate gene expression after PPA administration, we analyzed tissue from the hippocampus using reverse transcription polymerase chain reaction (RT‐PCR). Glial fibrillary acidic protein (GFAP) was augmented in the PPA‐treated group on Day 14 after ASD induction, whereas octamer‐binding transcription factor 4 (OCT4) expression was significantly decreased in the PPA‐treated group. The histological evaluation revealed significantly reduced granule cells diameter and granule cell layer (GCL) thickness in PPA‐treated rats compared with control rats. We suggest that PPA administration induced abnormal neural cell organization, which may have led to autism‐like neurobehaviors including increased in aggressive behavior, reduced in exploratory activity, and isolative and passive behaviors.Support or Funding InformationFunds: NRF‐2017R1A2A2A01067169, KGM4611714, 2016 Creative Research Program of Inje University, Republic of KoreaThis abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

P.2.039 - Effect of propionic acid on the rat’s behaviour: autism model

Autism spectrum disorder (ASD) is a group of developmental disabilities that cause significant social, communication and behavioral challenges. ASD is characterized by deficits in social interactions, restrictive interests, repetitive behavior, impairments in language development/communication skills and emotional disorders [1]. The current prevalence of ASD is approximately 1 in 68 children [2]. Also, the prevalence is approximately 4- 5 times greater in males than in females [2]. There is a strong genetic component of ASD’s etiology; however, recently it has been shown that ASD can be exacerbated by several environmental factors. In accordance with this, the link between several dietary factors or gastrointestinal disturbances and ASD symptoms was described. Propionic Acid (PPA), a gut-derived compound, is one of such factors. Many studies indicate that PPA administration in experimental animals produces various alterations associated with human ASD; however, many questions related to the PPA model of ASD still need to be elucidated. In the present research, the changes in cognitive functions, social behavior and emotions of male, young adult Wistar rats (P45-60) were evaluated. The animals were treated intraperitoneally with PPA at a dose of 175 mg/kg diluted to 10 times in saline. The experimental groups were compared with control (untreated) ones using following behavioral tests: (i) Multi-branch maze–in order to assess the process of learning. The test was started 24 h after PPA injection. The time needed to cover the distance between starting point and cage and number of errors (numbers of entering the deadlock branches of the maze) was measured. (ii) Novel rat versus novel object-in order to evaluate changes in social behavior. The test was started 3 h after PPA injection. The number of physical contacts and total time spent together by two rats (one of them was held in cage) was measured. (iii) Crossed/T-maze–in order to evaluate the anxiety-related behavior. The experiments were performed 2, 24 and 48 h after PPA injections. The parameters: number/duration of episodes spent in the center of the maze, number of grooming episodes in open/closed branch of the maze, number of vertical standings in open/closed branch were studied. To compare the quantitative data obtained from control and experimental animals the 2-Sample t test was used. The P The Results revealed: (i) Compared to control, experimental rats need a significantly longer time for covering the distance between starting point and cage. There is no significant difference regarding errors. (ii) Compared to control, in the experimental group a significant decrease in the number of physical contacts between two rats was revealed. No significant difference in total time spent between two animals was detected. (iii) There is no significant difference between control and experimental animals in the above-mentioned parameters. Thus, a single injection of 175 mg/kg PPA induces alterations in learning and social behavior of young adult male rats, and produces no effect on some parameters of emotional behavior.

Pathophysiological and neurobehavioral characteristics of a propionic acid-mediated autism-like rat model.

Autism spectrum disorder (ASD) is induced by complex hereditary and environmental factors. However, the mechanisms of ASD development are poorly understood. The purpose of this study was to identify standard indicators of this condition by comparing clinical, pathophysiological, and neurobehavioral features in an autism-like animal model. A total of 22 male Sprague-Dawley rats were randomly divided into control and 500 mg/kg propionic acid (PPA)-treated groups. Rats were subjected to behavioral tests, gene expression analyses, and histological analyses to detect pathophysiological and neurobehavioral alterations. Exploratory activity and non-aggressive behavior were significantly reduced in PPA-treated rats, whereas enhanced aggressive behavior during adjacent interactions was observed on day 14 after PPA administration. To evaluate gene expression after PPA administration, we analyzed hippocampal tissue using reverse transcription PCR. Glial fibrillary acidic protein was augmented in the PPA-treated group on day 14 after appearance of ASD-like behaviors by PPA administration, whereas octamer-binding transcription factor 4 expression was significantly decreased in the PPA-treated group. Histological evaluation revealed significantly reduced diameter and layer thickness of granule cells in PPA-treated rats compared with control rats. We conclude that PPA administration induced abnormal neural cell organization, which may have led to autism-like neurobehaviors, including increased aggressive behavior, reduced exploratory activity, and isolative and passive behaviors.

The role of apitoxin in alleviating propionic acid-induced neurobehavioral impairments in rat pups: The expression pattern of Reelin gene

The efficacy of apitoxin (bee venom; BV) in ameliorating propionic acid (PPA) −induced neurobehavioral impacts was studied. Sixty rat pups were enrolled in a split litter design to six groups: a control group, a PPA-treated group, a BV-treated group, a BV/PPA protective group, a PPA/BV therapeutic group, and a BV/PPA/BV protective and therapeutic group. Exploratory, social, locomotor, and repetitive/stereotype-like activities were assessed and prosocial, empathy, and acquired behavior were evaluated. Levels of neurotransmitter including serotonin, dopamine, and gamma-aminobutyric acid (GABA) were determined and a quantitative analysis of Reelin gene expression was performed. PPA treatment induced several behavioral alterations, as reduced exploratory activity and social behaviors, increased repetitive/stereotypic behaviors, and hyperactivity. In addition, a marked decline of neurotransmitters and down-regulation of Reelin mRNA expression were observed. BV exhibited high efficiency in ameliorating the PPA-induced neurobehavioral alterations, particularly when applied both before and after PPA administration. Overall, the results implied that BV has merit as a candidate therapeutic treatment to alleviate PPA-induced neurobehavioral disorders.

Intracerebroventricular injection of propionic acid, an enteric metabolite implicated in autism, induces social abnormalities that do not differ between seizure-prone (FAST) and seizure-resistant (SLOW) rats

Autism is a complex neurodevelopmental disorder that is characterized by social abnormalities. Genetic, dietary and gut-related factors are implicated in autism, however the causal properties of these factors and how they may interact are unclear. Propionic acid (PPA) is a product of gut microbiota and a food preservative. PPA has been linked to autism, and PPA administration to rats is an animal model of the condition. Seizure-prone (FAST) and seizure-resistant (SLOW) rats were initially developed to investigate differential vulnerability to developing epilepsy. However, FAST rats also display autistic-like features, and have been proposed as a genetic model of autism. Here we examined the effects of PPA on social behavior in FAST and SLOW rats. A single intracerebroventricular injection of PPA, or phosphate-buffered saline (PBS), was administered to young-adult male FAST and SLOW rats. Immediately after treatment, rats were placed in same-treatment and same-strain pairs, and underwent social behavior testing. PPA induced social abnormalities in both FAST and SLOW rat strains. While there was no evidence of social impairment in FAST rats that were not treated with PPA, these rats were hyperactive relative to SLOW rats. Post-mortem immunofluorescence analysis of brain tissue indicated that PPA treatment resulted in increased astrogliosis in the corpus callosum and cortex compared to PBS treatment. FAST rats had increased astrogliosis in the cortex compared to SLOW rats. Together these findings support the use of PPA as a rat model of autism, but indicate there are no interactive effects between the PPA and FAST models.

Disruption of redox homeostasis and brain damage caused in vivo by methylmalonic acid and ammonia in cerebral cortex and striatum of developing rats

Hyperammonemia is a common finding in children with methylmalonic acidemia and propionic acidemia, but its contribution to the development of the neurological symptoms in the affected patients is poorly known. Considering that methylmalonic acid (MMA) and propionic acid (PA) predominantly accumulate in these disorders, we investigated the effects of hyperammonemia induced by urease treatment in 30-day-old rats receiving an intracerebroventricular (ICV) injection of MMA or PA on important parameters of redox homeostasis in cerebral cortex and striatum. We evaluated glutathione (GSH) concentrations, sulfhydryl content, nitrate and nitrite concentrations, 2′,7′-dichlorofluorescein (DCFH) oxidation, and the activity of antioxidant enzymes. MMA decreased GSH concentrations and sulfhydryl content and increased nitrate and nitrite concentrations in cerebral cortex and striatum from hyperammonemic rats, whereas MMA or ammonia per se did not alter these parameters. MMA plus hyperammonemia also decreased glutathione reductase activity in rat cerebral cortex, but did not affect catalase, superoxide dismutase and glutathione peroxidase activities, neither DCFH oxidation. Furthermore, ICV PA administration alone or combined with hyperammonemia did not alter any of the evaluated parameters. We also found that pre-treatment with antioxidants prevented GSH reduction and sulfhydryl oxidation, whereas Nω-nitro-L-arginine methyl ester (L-NAME) prevented the increased nitrate and nitrite concentrations provoked by MMA plus ammonia treatments. Histological alterations, including vacuolization, ischemic neurons, and pericellular edema, were observed in brain of hyperammonemic rats injected with MMA. The data indicate a synergistic effect of MMA and ammonia disturbing redox homeostasis and causing morphological brain abnormalities in rat brain.

Short-chain fatty acid fermentation products of the gut microbiome: implications in autism spectrum disorders

Recent evidence suggests potential, but unproven, links between dietary, metabolic, infective, and gastrointestinal factors and the behavioral exacerbations and remissions of autism spectrum disorders (ASDs). Propionic acid (PPA) and its related short-chain fatty acids (SCFAs) are fermentation products of ASD-associated bacteria (Clostridia, Bacteriodetes, Desulfovibrio). SCFAs represent a group of compounds derived from the host microbiome that are plausibly linked to ASDs and can induce widespread effects on gut, brain, and behavior. Intraventricular administration of PPA and SCFAs in rats induces abnormal motor movements, repetitive interests, electrographic changes, cognitive deficits, perseveration, and impaired social interactions. The brain tissue of PPA-treated rats shows a number of ASD-linked neurochemical changes, including innate neuroinflammation, increased oxidative stress, glutathione depletion, and altered phospholipid/acylcarnitine profiles. These directly or indirectly contribute to acquired mitochondrial dysfunction via impairment in carnitine-dependent pathways, consistent with findings in patients with ASDs. Of note, common antibiotics may impair carnitine-dependent processes by altering gut flora favoring PPA-producing bacteria and by directly inhibiting carnitine transport across the gut. Human populations that are partial metabolizers of PPA are more common than previously thought. PPA has further bioactive effects on neurotransmitter systems, intracellular acidification/calcium release, fatty acid metabolism, gap junction gating, immune function, and alteration of gene expression that warrant further exploration. These findings are consistent with the symptoms and proposed underlying mechanisms of ASDs and support the use of PPA infusions in rats as a valid animal model of the condition. Collectively, this offers further support that gut-derived factors, such as dietary or enteric bacterially produced SCFAs, may be plausible environmental agents that can trigger ASDs or ASD-related behaviors and deserve further exploration in basic science, agriculture, and clinical medicine.

Regulation of the body temperature by oxytocin receptor/serotonin pathway

The efficacy of apitoxin (bee venom; BV) in ameliorating propionic acid (PPA) −induced neurobehavioral impacts was studied. Sixty rat pups were enrolled in a split litter design to six groups: a control group, a PPA-treated group, a BV-treated group, a BV/PPA protective group, a PPA/BV therapeutic group, and a BV/PPA/BV protective and therapeutic group. Exploratory, social, locomotor, and repetitive/stereotype-like activities were assessed and prosocial, empathy, and acquired behavior were evaluated. Levels of neurotransmitter including serotonin, dopamine, and gamma-aminobutyric acid (GABA) were determined and a quantitative analysis of Reelin gene expression was performed. PPA treatment induced several behavioral alterations, as reduced exploratory activity and social behaviors, increased repetitive/stereotypic behaviors, and hyperactivity. In addition, a marked decline of neurotransmitters and down-regulation of Reelin mRNA expression were observed. BV exhibited high efficiency in ameliorating the PPA-induced neurobehavioral alterations, particularly when applied both before and after PPA administration. Overall, the results implied that BV has merit as a candidate therapeutic treatment to alleviate PPA-induced neurobehavioral disorders.

A Novel Rodent Model of Autism: Intraventricular Infusions of Propionic Acid Increase Locomotor Activity and Induce Neuroinflammation and Oxidative Stress in Discrete Regions of Adult Rat Brain

Innate neuroinflammatory changes, increased oxidative stress and disorders of glutathione metabolism may be involved in the pathophysiology of autism spectrum disorders (ASD). Propionic acid (PPA) is a dietary and gut bacterial short chain fatty acid which can produce brain and behavioral changes reminiscent of ASD following intraventricular infusion in rats. Adult Long-Evans rats were given intraventricular infusions of either PPA (.26M, 4µl animal -1 ) or phosphate buffered saline (PBS) vehicle, twice daily for 7 days. Immediately following the second daily infusion, the locomotor activity of each rat was assessed in an automated open field (Versamax) for 30 min. PPA-treated rats showed significant increases in locomotor activity compared to PBS vehicle controls. Following the last treatment day, specific brain regions were assessed for neuroinflammatory or oxidative stress markers. Immunohistochemical analyses revealed reactive astrogliosis (GFAP), activated microglia (CD68, Iba1) without apoptotic cell loss (Caspase 3' and NeuN) in hippocampus and white matter (external capsule) of PPA treated rats. Biomarkers of protein and lipid peroxidation, total glutathione (GSH) as well as the activity of the antioxidant enzymes superoxide dismutase (SOD), catalase, glutathione peroxidase (GPx), glutathione reductase (GR) and glutathione S-transferase (GST) were examined in brain homogenates. Some brain regions of PPA treated animals (neocortex, hippocampus, thalamus, striatum) showed increased lipid and protein oxidation accompanied by decreased total GSH in neocortex. Catalase activity was decreased in most brain regions of PPA treated animals suggestive of reduced antioxidant enzymatic activity. GPx and GR activity was relatively unaffected by PPA treatment while GST was increased, perhaps indicating involvement of GSH in the removal of PPA or related catabolites. Impairments in GSH and catalase levels may render CNS cells more susceptible to oxidative stress from a variety of toxic insults. Overall, these findings are consistent with those found in ASD patients and further support intraventricular PPA administration as an animal model of ASD.