Mechanisms underlying microbial-mediated changes in social behavior in mouse models of autism spectrum disorder

Shank3B−/− mice show impaired sociability in the three-chamber test.

“By contrast, Shank3B−/− mice showed no preference for the stranger mouse over the empty cup, indicating impaired sociability (Figure 1E).”

Social deficits in Shank3B−/− mice are not due to alterations in olfactory ability.

“The social deficits in Shank3B−/− mice are not due to alterations in their olfactory ability, since olfaction was not impaired in these mice, as determined by the buried food test (Figure S3A).”

The effects of L. reuteri on social behavior are not mediated by restoring the composition of the host's microbiome.

“Interestingly, the effects of L. reuteri on social behavior are not mediated by restoring the composition of the host’s microbiome, which is altered in all of these ASD models.”

• Also stated in: § L. reuteri rescues social deficits independent of other gut microbes. · plain

  “We found that treatment with L. reuteri did not significantly alter the microbial profile of either Shank3B−/− mice (Figure 3A) or BTBR mice (Figure S8).”

• Also stated in: § L. reuteri rescues social deficits independent of other gut microbes. · plain

  “Hence, L. reuteri has no significant impact in the overall microbial composition of the host.”

VPA-treated mice show changes in the composition of the gut microbiota.

“Indeed, we found changes in the composition of the microbiota of VPA-treated mice (Figure S6A-S6E), but L. reuteri levels were not reduced in these mice (Figure S6F).”

L. reuteri rescues social interaction-induced synaptic plasticity in the ventral tegmental area of ASD mice.

“Instead, L. reuteri acts in a vagus nerve-dependent manner and rescues social interaction-induced synaptic plasticity in the ventral tegmental area of ASD mice, but not in oxytocin receptor-deficient mice.”

• Also stated in: § L. reuteri reverses deficits in social behavior via the vagus nerve. · plain

  “More importantly, we found that L. reuteri rescues the deficits in social interaction-induced VTA plasticity in Shank3B−/− mice (Figure 7B).”

Shank3B−/− mice show reduced reciprocal social interaction compared to WT littermates.

“Shank3B−/− mice interacted significantly less than WT littermates and treatment with L. reuteri reversed the social deficits in the mutant mice (Figure 1H).”

Treatment with L. reuteri selectively rescues social deficits in genetic, environmental, and idiopathic mouse models of ASD.

“Here, we found that treatment with L. reuteri selectively rescues social deficits in genetic, environmental, and idiopathic ASD models.”

• Also stated in: § INTRODUCTION · plain

  “Surprisingly, we found that microbial treatment with this single bacterial species rescues the social deficits in genetic, environmental, and idiopathic mouse models of ASD.”

• Also stated in: § BTBR mice show alterations in the composition of the gut microbiota and treatment with L. reuteri rescues their social deficits. · boosted

  “Taken together, our data show that treatment with L. reuteri selectively reverses the ASD-like social deficits in genetic, environmental, and idiopathic models of ASD.”

Treatment with L. reuteri reverses social deficits in BTBR mice.

“treatment with L. reuteri reversed the social deficits in the three chamber and reciprocal social interaction tasks in the BTBR mice (Figure 2C-2E).”

L. reuteri does not rescue social interaction-induced synaptic plasticity in oxytocin receptor-deficient mice.

“but not in oxytocin receptor-deficient mice.”

• Also stated in: § L. reuteri reverses deficits in social behavior via the vagus nerve. · plain

  “Strikingly, treatment with either L. reuteri or oxytocin failed to rescue the deficits in social behaviors (Figure 7C) and related changes in VTA DA synaptic function in DA-Oxtr−/− mice (Figure 7D).”

Shank3B−/− mice exhibit altered gut microbial composition compared to WT littermates.

“By contrast, the bacterial diversity measured by unweighted UniFrac analysis, which assesses community structure by considering only the presence or absence of OTUs, revealed a significant difference in the phylogenetic profile of the microbial communities between genotypes (Figure 1A).”

• Also stated in: § Shank3B−/− mice show alterations in the composition of the gut microbiota and treatment with L. reuteri rescues their social deficits. · plain

  “Thus, Shank3B−/− mice exhibit an altered gut microbial composition, including decreased L. reuteri levels in their gut.”

Treatment with L. reuteri rescues social deficits in Shank3B−/− mice.

“Remarkably, treatment with L. reuteri rescued sociability in Shank3B−/− mice.”

• Also stated in: § Shank3B−/− mice show alterations in the composition of the gut microbiota and treatment with L. reuteri rescues their social deficits. · plain

  “treatment with L. reuteri reversed the social deficits in the mutant mice (Figure 1H).”

• Also stated in: § Shank3B−/− mice show alterations in the composition of the gut microbiota and treatment with L. reuteri rescues their social deficits. · plain

  “Thus, treatment with L. reuteri selectively reverses the ASD-like social deficits in Shank3B−/− mice.”

Shank3B−/− mice have lower levels of L. reuteri compared to WT littermates.

“Moreover, we found that Shank3B−/− mice specifically have lower levels of L. reuteri compared to their WT littermates (Figure 1B).”

• Also stated in: § Shank3B−/− mice show alterations in the composition of the gut microbiota and treatment with L. reuteri rescues their social deficits. · plain

  “including decreased L. reuteri levels in their gut.”

Treatment with L. reuteri ameliorates social deficits in VPA mice.

“treatment with L. reuteri ameliorates the social deficits in VPA mice (Figure S6G-S6H).”

• Also stated in: § The VPA mouse model of ASD shows alterations in the composition of the gut microbiota and treatment with L. reuteri rescues its social deficits. · plain

  “L. reuteri also corrects the social deficits in another environmental model of ASD (VPA) with alterations in the gut microbiome.”

Shank3B−/− mice display normal preference for social novelty.

“In addition, we found that like WT controls, Shank3B−/− mice displayed normal preference for social novelty, as they spent more time interacting with the novel mouse (Mouse 2) than with the familiar one (Mouse 1; Figure 1F).”

L. reuteri rescues social deficits in Shank3B−/− mice in a vagus nerve-dependent manner.

“Instead, L. reuteri acts in a vagus nerve-dependent manner and rescues social interaction-induced synaptic plasticity in the ventral tegmental area of ASD mice, but not in oxytocin receptor-deficient mice.”

• Also stated in: § L. reuteri reverses deficits in social behavior via the vagus nerve. · plain

  “Thus, L. reuteri rescues social deficits in Shank3B−/− mice in a vagus nerve-dependent manner.”

Shank3B−/− mice show no changes in gut permeability compared to control littermates.

“By contrast, compared to control littermates, Shank3B−/− showed no changes in gut permeability (Figure 4A).”

Oxytocin improves social behaviors in VPA mice.

“Moreover, oxytocin improved the social behaviors that are deficient in VPA (Figure S11A and S11B), BTBR mice (Figure S11C-S11E), and partially in GF mice (Figure S11F-S11H)”

Monocolonization with L. reuteri reverses social deficits in germ-free mice.

“Remarkably, monocolonization with L. reuteri reversed the social deficits in GF mice (Figure 3B-3D), supporting the notion that L. reuteri acts solo, rescuing social behavior in the absence of other members of the community.”

Intranasal oxytocin treatment restores social behaviors in vagotomized Shank3B−/− mice.

“Finally, intranasal oxytocin-treatment, which bypasses the gut-microbiota-brain axis, restored social behaviors in vagotomized Shank3B−/− mice (see Figure 6D and 6E), demonstrating that the vagotomy procedure did not prevent the animals’ ability to perform the social task.”

Oxytocin improves social behaviors in BTBR mice.

“Moreover, oxytocin improved the social behaviors that are deficient in VPA (Figure S11A and S11B), BTBR mice (Figure S11C-S11E), and partially in GF mice (Figure S11F-S11H)”

BTBR mice have a specific reduction in L. reuteri levels.

“Moreover, we found a specific reduction in L. reuteri levels in BTBR mice (Figure 2B).”

BTBR mice show markedly altered gut microbiome composition compared to C57BL/6J mice.

“Accordingly, we also found a markedly altered gut microbiome composition in BTBR mice compared to C57BL/6J mice (Figure 2A, Figure S7).”

L. reuteri levels are not reduced in VPA-treated mice.

“but L. reuteri levels were not reduced in these mice (Figure S6F).”

Shank3B−/− mice have a reduction in oxytocin positive neurons in the PVN compared to WT littermates.

“Interestingly, we found a reduction in oxytocin positive neurons in the PVN (Figure 5A) of Shank3B−/−mice compared to WT littermates (Figure 5B and 5C).”

Treatment with L. reuteri does not significantly alter the microbial profile of Shank3B−/− mice or BTBR mice.

“We found that treatment with L. reuteri did not significantly alter the microbial profile of either Shank3B−/− mice (Figure 3A) or BTBR mice (Figure S8).”

The number and fluorescence intensity of NeuN positive neurons do not change in the PVN of Shank3B−/− mice.

“The number and fluorescence intensity of NeuN positive neurons did not change in the PVN of Shank3B−/− mice (Figure 5B, 5D and 5F), indicating that the decrease in oxytocin positive neurons in Shank3B−/− was not due to a decrease in the total number of neurons.”

Expression of key tight junction proteins is not altered in Shank3B−/− mice.

“Accordingly, the expression of key tight junction proteins was not altered in Shank3B−/− mice, as determined by reverse transcription followed by quantitative PCR (RT-qPCR) (Figure 4B).”

Social deficits in BTBR mice are not due to impaired olfaction.

“Similarly to the Shank3B−/− mice, social deficits in BTBR mice were not due to impaired olfaction (see Figure S3B).”

Intranasal oxytocin reverses social deficits in Shank3B−/− mice.

“As predicted, intranasal oxytocin (Figure 6A) reversed the social deficits in Shank3B−/− mice (Figure 6B, 6C and S10A).”

Treatment with L. reuteri fails to rescue social behavior deficits in DA-Oxtr−/− mice.

“Strikingly, treatment with either L. reuteri or oxytocin failed to rescue the deficits in social behaviors (Figure 7C) and related changes in VTA DA synaptic function in DA-Oxtr−/− mice (Figure 7D).”

Mice lacking Oxtr in DA neurons (DA-Oxtr−/−) are socially impaired.

“However, compared to control mice, we found that mice lacking Oxtr in DA neurons (DA-Oxtr−/−) were socially impaired (Figure 7C), consistent with a recent report (Hung et al., 2017).”

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Oxytocin partially improves social behaviors in germ-free mice.

“Moreover, oxytocin improved the social behaviors that are deficient in VPA (Figure S11A and S11B), BTBR mice (Figure S11C-S11E), and partially in GF mice (Figure S11F-S11H)”

Intranasal oxytocin administration rescues impaired LTP in VTA DA neurons from Shank3B−/− mice.

“Consistent with the notion that the effect of L. reuteri on social behavior is mediated by oxytocin, intranasal oxytocin administration also rescued the impaired LTP in VTA DA neurons from Shank3B−/− mice (Figure 7B).”

Treatment with oxytocin fails to rescue social behavior deficits in DA-Oxtr−/− mice.

“Strikingly, treatment with either L. reuteri or oxytocin failed to rescue the deficits in social behaviors (Figure 7C) and related changes in VTA DA synaptic function in DA-Oxtr−/− mice (Figure 7D).”

Baseline AMPAR/NMDAR ratios are similar in Shank3B−/− mice and WT littermates.

“In fact, baseline AMPAR/NMDAR ratios were similar in Shank3B−/−mice and WT littermates (Figure 7B)”

Cocaine evokes LTP in VTA DA neurons of Shank3B−/− mice.

“a single injection of cocaine, which has been shown to increase the AMPAR/NMDAR ratio in VTA DA neurons [(Huang et al., 2016; Ungless et al., 2001) Figure S12D], evoked LTP in VTA DA neurons of Shank3B−/− mice (Figure 7B).”

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• cites Ungless et al., 2001 sourceNot checked yet

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Oxytocin has no effect on hypoactivity in Shank3B−/− mice.

“Interestingly, like L. reuteri treatment, oxytocin had no effect on the hypo-activity behavior in the Shank3B−/− mice (Figure S10B and S10C).”

Administration of the selective oxytocin receptor antagonist L-371,257 to Shank3B−/− mice prevents the prosocial effects associated with L. reuteri treatment.

“Consistently, administration of the selective oxytocin receptor antagonist L-371,257 to Shank3B−/− mice prevented the prosocial effects associated with L. reuteri treatment (Figure S14).”

Social interaction-induced synaptic potentiation is impaired in Shank3B−/− mice.

“By contrast, the same procedure failed to induce synaptic potentiation in Shank3B−/− mice (Figure 7B).”

• Also stated in: § L. reuteri reverses deficits in social behavior via the vagus nerve. · plain

  “Thus, the synaptic potentiation associated specifically with social reward is impaired in Shank3B−/− mice.”

Cocaine induces LTP in VTA DA neurons of DA-Oxtr−/− mice.

“By contrast, cocaine was able to induce LTP in VTA DA neurons of DA-Oxtr−/− mice (Figure 7D), indicating that oxytocin signaling is selectively required for social interaction-induced synaptic plasticity in the reward circuitry.”

Deletion of Oxtr in DA neurons in DA-Oxtr−/− mice has no impact on the levels of L. reuteri in the gut.

“Deletion of Oxtr in DA neurons in DA-Oxtr−/− mice had no impact on the levels of L. reuteri in the gut (Figure S13).”

L. reuteri fails to reverse social deficits in DA-Oxtr−/− mice, which lack oxytocin receptor specifically in dopaminergic neurons.

“it fails to do so in mice lacking oxytocin receptor specifically in dopaminergic neurons (DA-Oxtr−/− mice, Figure 7C)”

Shank3B−/− mice show no significant difference in abundance of Bacteroidetes and Firmicutes compared to control mice.

“Shank3B−/− mice show no significant difference in abundance of the two phyla”

L. reuteri reverses social deficits in genetic, environmental, and idiopathic mouse models of ASD.

“we found that L. reuteri reverses social deficits in genetic, environmental, and idiopathic models of ASD.”

• Also stated in: § DISCUSSION · boosted

  “we have shown that L. reuteri rescues social deficits in several mouse models of ASD, including a genetic (Shank3B−/−), three environmental [VPA, GF, and MHFD (Buffington et al., 2016)] and an idiopathic (BTBR) model of ASD (Figure 1-3 and Figure S6).”

• Also stated in: § DISCUSSION · plain

  “Here, we show that L. reuteri reverses the social deficits in several mouse models of ASD (Figure 1E-H, 2C-E, 3B-D, S6G)”

• AssumptionRests on an assumption: The ASD mouse models used (Shank3B−/−, BTBR, VPA, GF, MHFD) are valid models of human ASD, such that findings in them can inform human ASD therapies.
• AssumptionRests on an assumption: Social deficits in mice, as measured in the behavioral assays, correspond to social deficits in human ASD.

Changes in the gut microbiome can influence long-lasting changes in synaptic efficacy in the mesolimbic dopamine reward system underlying social behaviors.

“we found that changes in the gut microbiome could influence long-lasting changes in synaptic efficacy in the mesolimbic dopamine reward system underlying social behaviors [Fig. 7 and (Buffington et al., 2016)].”

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• AssumptionRests on an assumption: The ASD mouse models used (Shank3B−/−, BTBR, VPA, GF, MHFD) are valid models of human ASD, such that findings in them can inform human ASD therapies.

Genetic models of ASD (Shank3B−/− and DA-Oxtr−/−) exhibit impaired social interaction-induced VTA plasticity.

“genetic models of ASD (Shank3B−/− and DA-Oxtr−/−) exhibit impaired social interaction-induced VTA plasticity and social behavior (Figure 1 and 7)”

BTBR and VPA mouse models show an increased Bacteroidetes/Firmicutes ratio compared to control mice.

“the BTBR and VPA models show an increased Bacteroidetes/Firmicutes ratio compared to control mice (Figure S15)”

In Shank3B−/− mice with pharmacologically blocked oxytocin receptors, L. reuteri does not reverse social deficits.

“in Shank3B−/− mice in which oxytocin receptors were pharmacologically blocked, treatment with L. reuteri was not longer able to reverse the social deficits in these mice (see Figure S14)”

Genetic models of ASD (Shank3B−/− and DA-Oxtr−/−) exhibit impaired social behavior.

“genetic models of ASD (Shank3B−/− and DA-Oxtr−/−) exhibit impaired social interaction-induced VTA plasticity and social behavior (Figure 1 and 7)”

L. reuteri alone is sufficient to reverse social behavioral deficits in GF mice.

“Surprisingly, we found that L. reuteri alone is sufficient to reverse the social behavioral deficits in GF mice”

Oxytocin does not reverse social deficits in DA-Oxtr−/− mice.

“but not in DA-Oxtr−/− mice (Figure 7C)”

Oxytocin reverses social deficits in all other ASD mouse models tested: MHFD, VPA, GF, BTBR, and Shank3B−/−.

“like L. reuteri, oxytocin reverses the social deficits in all of the other ASD mouse models tested [MHFD, VPA, GF, BTBR and Shank3B−/− mice; see Figure 6 and S11 and (Buffington et al., 2016)]”

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L. reuteri modulates social behavior and related changes in synaptic function within the social reward circuits via the oxytocinergic system.

“At the cellular and molecular levels, we provide new causal evidence that L. reuteri modulates social behavior and related changes in synaptic function within the social reward circuits via the oxytocinergic system.”

• Also stated in: § L. reuteri reverses deficits in social behavior via the vagus nerve. · boosted

  “Collectively, these data show that L. reuteri treatment promotes social behaviors and social interaction-mediated synaptic potentiation in an oxytocin-dependent manner.”

Stimulation of the vagus nerve can promote oxytocin release.

“Finally, stimulation of the vagus nerve can promote oxytocin release (Stock and Uvnäs-Moberg, 1988).”

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Social behavior is similar in WT-sham and WT-vagotomized mice.

“Second, social behavior was similar in WT-sham and WT-vagotomized mice (Figure S9B-S9D).”

L. reuteri acts solo, rescuing social behavior in the absence of other members of the microbial community.

“supporting the notion that L. reuteri acts solo, rescuing social behavior in the absence of other members of the community.”

Neuronal activity in the PVN induced by bacterial colonization is blocked by subdiaphragmatic vagotomy.

“and that neuronal activity in the PVN induced by bacterial colonization is blocked by subdiaphragmatic vagotomy (Wang et al., 2002).”

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Preference for social novelty is not affected by vagotomy.

“Moreover, preference for social novelty, which is not impaired in Shank3B−/− mice, was not affected by the vagotomy (Figure 4E), indicating that the vagotomy itself had no effect on social behavior.”

The vagotomy was complete, as determined by food intake analysis based on the satiating effect of CCK-8.

“First, the vagotomy was complete, as determined by a food intake analysis based on the satiating effect of cholecystokinin-octapeptide (CCK-8), which depends on the vagus nerve [(Joyner et al., 1993), Figure S9A].”

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Germ-free mice display social deficits.

“As previously described, unlike conventionally colonized mice, GF mice displayed social deficits (Buffington et al., 2016; Desbonnet et al., 2014).”

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Vagal nerve fibers project to the PVN.

“Additionally, it is known that vagal nerve fibers project to the PVN (Sabatier et al., 2013; Uvnas-Moberg et al., 2014), a brain region where oxytocin is produced”

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L. reuteri increases oxytocin levels.

“We and others have shown that L. reuteri increases oxytocin levels (Buffington et al., 2016; Poutahidis et al., 2013).”

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Vagotomy does not affect motor behavior.

“Third, vagotomy did not affect motor behavior (Figure S9E-S9H).”

Oxytocin reverses social deficits in several mouse models of ASD.

“Treatment with oxytocin reverses social deficits in several mouse models of ASD (Buffington et al., 2016; Hara et al., 2017; Harony-Nicolas et al., 2017; Penagarikano et al., 2015).”

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• cites Hara et al., 2017 sourceNot checked yet

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Brain regions responding to naturally rewarding stimuli, including the VTA and NAc, are crucially involved in social behaviors.

“Brain regions responding to naturally rewarding stimuli, including the ventral tegmental area (VTA) and the nucleus accumbens (NAc), are crucially involved in social behaviors (Dolen et al., 2013; Gunaydin et al., 2014; Huang and Hessler, 2008).”

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• cites Huang and Hessler, 2008Not checked yet

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A large body of preclinical literature supports the notion of a bidirectional communication system linking the gut and the brain, known as the gut-microbiota-brain axis.

“A large body of preclinical literature supports the notion of a bidirectional communication system linking the gut and the brain, known as the gut-microbiota-brain axis (Borre et al., 2014; Sharon et al., 2016; Vuong et al., 2017).”

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BTBR mice harbor a different microbial community in the gut.

“While previous studies have shown that BTBR mice harbor a different microbial community in the gut (Coretti et al., 2017; Golubeva et al., 2017) and cohousing with C57BL/6J mice has been shown to restore their social deficits (Yang et al., 2011), the nature of the bacterial species which may be causally related to the social behavioral deficits in this ASD model remains unknown.”

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• cites Golubeva et al., 2017 sourceNot checked yet

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Germ-free mice or mice treated with broad-spectrum antibiotics show behavioral abnormalities, including endophenotypes associated with ASD.

“Foundational studies have shown that GF mice or mice treated with broad-spectrum of antibiotics show behavioral abnormalities, including endophenotypes associated with ASD (Arentsen et al., 2015; Bercik et al., 2011a; Desbonnet et al., 2014; Heijtz et al., 2011; Leclercq et al., 2017; Neufeld et al., 2011).”

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• cites Desbonnet et al., 2014 sourceNot checked yet

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Selective treatment with L. reuteri reverses social deficits in MHFD offspring.

“More importantly, selective treatment with L. reuteri reverses the social deficits in MHFD offspring (Buffington et al., 2016).”

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No genetic variants in ASD risk genes have been identified in the BTBR genome.

“Given that no genetic variants in ASD risk genes have been identified in the BTBR genome (Jones-Davis et al., 2013), this model is considered an idiopathic model of ASD (Meyza and Blanchard, 2017).”

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Maternal exposure to VPA is associated with increased risk of ASD incidence in offspring.

“More specifically, clinical studies have shown that maternal exposure to VPA, a branched short-chain fatty acid used as an antiepileptic drug, is associated with increased risk of ASD incidence in offspring (Christensen et al., 2013; Ornoy, 2009).”

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VPA administration during gestation leads to ASD-like behaviors, notably social deficits, in offspring.

“Accordingly, in rodents, VPA administration during gestation leads to ASD-like behaviors (notably social deficits) in offspring (Kim et al., 2017).”

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Oxytocinergic signaling is involved in the mechanism by which L. reuteri selectively restores social behavior in several ASD mouse models.

“Together, these data suggest that oxytocinergic signaling is involved in the mechanism of action by which L. reuteri selectively restores social behavior in several ASD mouse models.”

Oxytocin signaling is selectively required for social interaction-induced synaptic plasticity in the reward circuitry.

“indicating that oxytocin signaling is selectively required for social interaction-induced synaptic plasticity in the reward circuitry.”

The effect of L. reuteri on social behavior depends on the oxytocinergic system.

“Thus, our genetic and pharmacological results support the concept that the effect of L. reuteri on social behavior depends on the oxytocinergic systems”

Changes in the Bacteroidetes/Firmicutes ratio may not be a reliable microbial signature associated with ASD-like behaviors, at least in the ASD mouse models studied here.

“Hence, like in humans, changes in the Bacteroidetes/Firmicutes ratio may not be a reliable microbial signature associated with ASD-like behaviors, at least in the ASD mouse models studied here.”

The effect of L. reuteri on social behavior does not depend on other members of the microbial community.

“demonstrating that its effect on social behavior does not depend on other members of the microbial community (Figure 3)”

The vagus nerve is the main communication channel between the gut and the brain through which L. reuteri improves social behaviors in mouse models of ASD.

“our new results identified the vagus nerve as the main communication channel between the gut and the brain through which L. reuteri improves social behaviors in mouse models of ASD (Figure 4D-F).”

• Also stated in: § DISCUSSION · boosted

  “here we provide new evidence that the vagus nerve is a central gut-brain communication pathway by which L. reuteri promote social behavior (Figure 6D-E).”

• AssumptionRests on an assumption: The ASD mouse models used (Shank3B−/−, BTBR, VPA, GF, MHFD) are valid models of human ASD, such that findings in them can inform human ASD therapies.
• AssumptionRests on an assumption: Social deficits in mice, as measured in the behavioral assays, correspond to social deficits in human ASD.

Other patients with ASD show the opposite result, an increased Bacteroidetes/Firmicutes ratio.

“others show the opposite result (De Angelis et al., 2013; Zhang et al., 2018)”

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• cites Zhang et al., 2018 sourceNot checked yet

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The paper's data in mice support the idea that microbial therapies could ameliorate specific endophenotypes associated with ASD.

“Thus, our data (in mice) support the idea that microbial therapies could ameliorate specific endophenotypes associated with ASD.”

• AssumptionRests on an assumption: The ASD mouse models used (Shank3B−/−, BTBR, VPA, GF, MHFD) are valid models of human ASD, such that findings in them can inform human ASD therapies.
• AssumptionRests on an assumption: Social deficits in mice, as measured in the behavioral assays, correspond to social deficits in human ASD.
• AssumptionRests on an assumption: L. reuteri's effects on mouse social behavior can be translated to humans.

L. reuteri increases oxytocin levels, based on prior correlational evidence.

“We and others have previously provided correlational evidence that L. reuteri increases oxytocin levels (Buffington et al., 2016; Poutahidis et al., 2013)”

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Social stimulation triggers synaptic potentiation in VTA DA neurons of birds and mice.

“Social stimulation, which can be particularly rewarding, triggers synaptic potentiation in VTA dopamine (DA) neurons of both birds (Huang and Hessler, 2008) and mice (Buffington et al., 2016).”

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Release of oxytocin from PVN neurons onto VTA DA neurons increases excitability during social interaction.

“the release of oxytocin from PVN neurons onto VTA DA neurons increases excitability during social interaction (Hung et al., 2017)”

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Social behavior and its mechanisms can be studied at the cellular level by measuring changes in synaptic plasticity in VTA dopaminergic neurons upon social interaction.

“Taken together, these data support the notion that social behavior (and its mechanisms) can be studied at the cellular level by measuring changes in synaptic plasticity in VTA dopaminergic neurons upon social interaction.”

Oxytocin-expressing neurons in the PVN project to the VTA.

“In addition, oxytocin-expressing neurons in the PVN project to the VTA (Melis et al., 2007).”

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L. reuteri-mediated increase in oxytocin enhances the salience and rewarding value of social stimuli.

“consistent with the idea that L. reuteri-mediated increase in oxytocin enhances the salience and rewarding value of social stimuli.”

The L. reuteri-mediated rescue of social behavior depends on oxytocinergic and dopaminergic reward systems.

“we found that the L. reuteri-mediated rescue of social behavior depends on oxytocinergic and dopaminergic reward systems.”

In MHFD mice, social interaction-induced LTP in VTA DA neurons is impaired.

“we have previously found that social interaction-induced LTP in VTA DA neurons was impaired in MHFD mice”

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Gut microbes can modulate endophenotypes traditionally associated with brain-centered disorders, including ASD, in mouse models.

“experiments in mouse models have shown that gut microbes can modulate endophenotypes traditionally associated with brain-centered disorders, including ASD (Buffington et al., 2016; Hsiao et al., 2013)”

• cites Buffington et al., 2016 sourceNot checked yet

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• cites Hsiao et al., 2013 sourceNot checked yet

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An independent study by Tabouy and colleagues found that L. reuteri successfully corrects social deficits in Shank3B−/− mice.

“an independent study by Tabouy and colleagues (2018) has recently found that L. reuteri successfully corrects social deficits in Shank3B−/− mice.”

• cites Tabouy and colleagues (2018)Not checked yet

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• AssumptionRests on an assumption: The ASD mouse models used (Shank3B−/−, BTBR, VPA, GF, MHFD) are valid models of human ASD, such that findings in them can inform human ASD therapies.

L. reuteri reverses the long-lasting synaptic changes in MHFD mice that likely underlie social deficits.

“L. reuteri reverses these long-lasting synaptic changes that likely underlie the social deficits (Buffington et al., 2016)”

• cites Buffington et al., 2016 sourceNot checked yet

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An L. reuteri strain used in infants has received a certification of Generally Recognized as Safe (GRAS) for use in humans by the FDA.

“an L. reuteri strain used in infants (Indrio et al., 2014) has received a certification of Generally Recognized as Safe (GRAS) for use in humans by the FDA.”

• cites Indrio et al., 2014 sourceNot checked yet

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There may be a convergent cellular and synaptic mechanism underlying the neuropathology associated with ASD.

“indicating that there may be a convergent cellular and synaptic mechanism underlying the neuropathology associated with ASD.”

PVN-VTA oxytocinergic projections are crucially involved in social behaviors.

“Because PVN-VTA oxytocinergic projections are crucially involved in social behaviors (Hung et al., 2017; Xiao et al., 2017)”

• cites Hung et al., 2017 sourceNot checked yet

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• cites Xiao et al., 2017 sourceNot checked yet

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