High fat diet reveals sex-specific fecal and liver metabolic alterations in C57BL/6J obese mice.

Obesity is a major health concern that poses significant risks for many other diseases, including diabetes, cardiovascular disease, and cancer. Prevalence of these diseases varies by biological sex. This study utilizes a mouse (C57BL/6J) model of obesity to analyze liver and fecal metabolic profiles at various time points of dietary exposure: 5, 9, and 12 months in control or high fat diet (HFD)-exposed mice. Our study discovered that the female HFD group has a more discernable perturbation and set of significant changes in metabolic profiles than the male HFD group. In the female mice, HFD fecal metabolites including pyruvate, aspartate, and glutamate were lower than control diet-exposed mice after both 9th and 12th month exposure time points, while lactate and alanine were significantly downregulated only at the 12th month. Perturbations of liver metabolic profiles were observed in both male and female HFD groups, compared to controls at the 12th month. Overall, the female HFD group showed higher lactate and glutathione levels compared to controls, while the male HFD group showed higher levels of glutamine and taurine compared to controls. These metabolite-based findings in both fecal and liver samples for a diet-induced effect of obesity may help guide future pioneering discoveries relating to the analysis and prevention of obesity in people, especially for females.

Syngap1 Disruption Induced by Recombination between Inverted loxP Sites Is Associated with Hippocampal Interneuron Dysfunction.

SYNGAP1 haploinsufficiency in humans causes intellectual disability (ID). SYNGAP1 is highly expressed in cortical excitatory neurons and, reducing its expression in mice accelerates the maturation of excitatory synapses during sensitive developmental periods, restricts the critical period window for plasticity, and impairs cognition. However, its specific role in interneurons remains largely undetermined. In this study, we investigated the effects of conditional Syngap1 disruption in medial ganglionic eminence (MGE)-derived interneurons on hippocampal interneuron firing properties and excitatory synaptic inputs, as well as on pyramidal cell synaptic inhibition and synaptic integration. We show that conditional Syngap1 disruption in MGE-derived interneurons results in cell-specific impairment of firing properties of hippocampal Nkx2.1 fast-spiking interneurons, with enhancement of their AMPA receptor (AMPAR)-mediated excitatory synaptic inputs but compromised short-term plasticity. In contrast, regular-spiking Nkx2.1 interneurons are largely unaffected. These changes are associated with impaired pyramidal cell synaptic inhibition and enhanced summation of excitatory responses. Unexpectedly, we found that the Syngap1flox allele used in this study contains inverted loxP sites and that its targeted recombination in MGE-derived interneurons induces some cell loss during embryonic development and the reversible inversion of the sequence flanked by the loxP sites in postmitotic cells. Together, these results suggest that Syngap1 plays a role in cell-specific regulation of hippocampal interneuron function and inhibition of pyramidal cells in mice. However, because of our finding that the Syngap1flox allele used in this study contains inverted loxP sites, it will be important to further investigate interneuron function using a different Syngap1 conditional allele.

Connecting gut microbiomes and short chain fatty acids with the serotonergic system and behavior in Gallus gallus and other avian species.

The chicken gastrointestinal tract has a diverse microbial community. There is increasing evidence for how this gut microbiome affects specific molecular pathways and the overall physiology, nervous system and behavior of the chicken host organism due to a growing number of studies investigating conditions such as host diet, antibiotics, probiotics, and germ-free and germ-reduced models. Systems-level investigations have revealed a network of microbiome-related interactions between the gut and state of health and behavior in chickens and other animals. While some microbial symbionts are crucial for maintaining stability and normal host physiology, there can also be dysbiosis, disruptions to nutrient flow, and other outcomes of dysregulation and disease. Likewise, alteration of the gut microbiome is found for chickens exhibiting differences in feather pecking (FP) behavior and this alteration is suspected to be responsible for behavioral change. In chickens and other organisms, serotonin is a chief neuromodulator that links gut microbes to the host brain as microbes modulate the serotonin secreted by the host's own intestinal enterochromaffin cells which can stimulate the central nervous system via the vagus nerve. A substantial part of the serotonergic network is conserved across birds and mammals. Broader investigations of multiple species and subsequent cross-comparisons may help to explore general functionality of this ancient system and its increasingly apparent central role in the gut-brain axis of vertebrates. Dysfunctional behavioral phenotypes from the serotonergic system moreover occur in both birds and mammals with, for example, FP in chickens and depression in humans. Recent studies of the intestine as a major site of serotonin synthesis have been identifying routes by which gut microbial metabolites regulate the chicken serotonergic system. This review in particular highlights the influence of gut microbial metabolite short chain fatty acids (SCFAs) on the serotonergic system. The role of SCFAs in physiological and brain disorders may be considerable because of their ability to cross intestinal as well as the blood-brain barriers, leading to influences on the serotonergic system via binding to receptors and epigenetic modulations. Examinations of these mechanisms may translate into a more general understanding of serotonergic system development within chickens and other avians.

Sensitive period for rescuing parvalbumin interneurons connectivity and social behavior deficits caused by TSC1 loss.

The Mechanistic Target Of Rapamycin Complex 1 (mTORC1) pathway controls several aspects of neuronal development. Mutations in regulators of mTORC1, such as Tsc1 and Tsc2, lead to neurodevelopmental disorders associated with autism, intellectual disabilities and epilepsy. The correct development of inhibitory interneurons is crucial for functional circuits. In particular, the axonal arborisation and synapse density of parvalbumin (PV)-positive GABAergic interneurons change in the postnatal brain. How and whether mTORC1 signaling affects PV cell development is unknown. Here, we show that Tsc1 haploinsufficiency causes a premature increase in terminal axonal branching and bouton density formed by mutant PV cells, followed by a loss of perisomatic innervation in adult mice. PV cell-restricted Tsc1 haploinsufficient and knockout mice show deficits in social behavior. Finally, we identify a sensitive period during the third postnatal week during which treatment with the mTOR inhibitor Rapamycin rescues deficits in both PV cell innervation and social behavior in adult conditional haploinsufficient mice. Our findings reveal a role of mTORC1 signaling in the regulation of the developmental time course and maintenance of cortical PV cell connectivity and support a mechanistic basis for the targeted rescue of autism-related behaviors in disorders associated with deregulated mTORC1 signaling.

Restriction of intracellular Salmonella replication by restoring TFEB-mediated xenophagy.

Macroautophagy/autophagy functions as a part of the innate immune system in clearing intracellular pathogens. Although this process is well known, the mechanisms that control antibacterial autophagy are not clear. In this study we show that during intracellular Salmonella typhimurium infection, the activity of TFEB (transcription factor EB), a master regulator of autophagy and lysosome biogenesis, is suppressed by maintaining it in a phosphorylated state on the lysosomes. Furthermore, we have identified a novel, antibacterial small molecule autophagy (xenophagy) modulator, acacetin. The xenophagy effect exerted by acacetin occurs in an MTOR (mechanistic target of rapamycin kinase)-independent, TFEB-dependent manner. Acacetin treatment results in persistently maintaining active TFEB in the nucleus and also in TFEB mediated induction of functional lysosomes that target Salmonella-containing vacuoles (SCVs). The enhanced proteolytic activity due to deployment of lysosomes results in clamping down Salmonella replication in SCVs. Acacetin is effective as a xenophagy compound in an in vivo mouse model of infection and reduces intracellular Salmonella burden. ABBREVIATIONS: 3-MA: 3-methyladenine; BafA1: bafilomycin A1; CFU: colony-forming units; DQ-BSA: dye quenched-bovine serum albumin; EEA1: early endosome antigen 1; FITC: fluorescein isothiocyanate; FM 4-64: pyridinium,4-(6-[4-{diethylamino}phenyl]-1,3,5-hexatrienyl)-1-(3[triethylammonio] propyl)-dibromide; GFP: green fluorescent protein; LAMP1: lysosomal associated membrane protein 1; MAPILC3/LC3: microtubule associated protein 1 light chain 3; MOI: multiplicity of infection; MTOR: mechanistic target of rapamycin kinase; RFP: red fluorescent protein; SCVs: Salmonella-containing vacuoles; SD: standard deviation; SDS: sodium dodecyl sulfate; SEM: standard mean error; SQSTM1: sequestosome 1; TBK1: TANK binding kinase 1; TFEB: transcription factor EB.