Diet-induced inflammation in the anterior paraventricular thalamus induces compulsive sucrose-seeking

Neuronal activity in the anterior paraventricular nucleus of thalamus positively correlated with sweetener consumption in mice

Although the brain can discriminate between various sweet substances, the underlying neural mechanisms of this complex behavior remain elusive. This study examines the role of the anterior paraventricular nucleus of the thalamus (aPVT) in governing sweet preference in mice. We fed the mice six different diets with equal sweetness for six weeks: control diet (CD), high sucrose diet (HSD), high stevioside diet (HSSD), high xylitol diet (HXD), high glycyrrhizin diet (HGD), and high mogroside diet (HMD). The mice exhibited a marked preference specifically for the HSD and HSSD. Following consumption of these diets, c-Fos expression levels in the aPVT were significantly higher in these two groups compared to the others. Utilizing fiber photometry calcium imaging, we observed rapid activation of aPVT neurons in response to sucrose and stevioside intake, but not to xylitol or water. Our findings suggest that aPVT activity aligns with sweet preference in mice, and notably, stevioside is the sole plant-based sweetener that elicits an aPVT response comparable to that of sucrose.

Vagus Nerve and Gut-Brain Communication

The vagus nerve, as an important component of the gut-brain axis, plays a crucial role in the communication between the gut and brain. It influences food intake, fat metabolism, and emotion by regulating the gut-brain axis, which is closely associated with the development of gastrointestinal, psychiatric, and metabolism-related disorders. In recent years, significant progress has been made in understanding the vagus-mediated regulatory pathway, highlighting its profound implications in the development of many diseases. Here, we summarize the latest advancements in vagus-mediated gut-brain pathways and the novel interventions targeting the vagus nerve. This will provide valuable insights for future research on treatment of obesity and gastrointestinal and depressive disorders based on vagus nerve stimulation.

Effects of KGM and Degradation Products on Appetite Regulation and Energy Expenditure in High-Fat-Diet Mice via the Adipocyte-Hypothalamus Axis

Konjac glucomannan (KGM), high-viscosity dietary fiber, is utilized in weight management. Previous investigations on the appetite-suppressing effects of KGM have centered on intestinal responses to nutrients and gastric emptying rates, with less focus on downstream hypothalamic neurons of satiety hormones. In our studies, the molecular mechanisms through which KGM and its degradation products influence energy homeostasis via the adipocyte-hypothalamic axis have been examined. It was found that high-viscosity KGM more effectively stimulates enteroendocrine cells to release glucagon-like peptide-1 (GLP-1) and reduces ghrelin production, thereby activating hypothalamic neurons and moderating short-term satiety. Conversely, low-viscosity DKGM has been shown to exhibit stronger anti-inflammatory properties in the hypothalamus, enhancing hormone sensitivity and lowering the satiety threshold. Notably, both KGM and DKGM significantly reduced leptin signaling and fatty acid signaling in adipose tissue and activated brown adipose tissue thermogenesis to suppress pro-opiomelanocortin (POMC) expression and activate agouti-related protein (AgRP) expression, thereby reducing food intake and increasing energy expenditure. Additionally, high-viscosity KGM has been found to activate the adipocyte-hypothalamus axis more effectively than DKGM, thereby promoting greater daily energy expenditure. These findings provide novel insights into the adipocyte-hypothalamic axis for KGM to suppress appetite and reduce weight.

Saturated fatty acids stimulate cytokine production in tanycytes via the PP2Ac-dependent signaling pathway

The hypothalamic tanycytes are crucial for free fatty acids (FFAs) detection, storage, and transport within the central nervous system. They have been shown to effectively respond to fluctuations in circulating FFAs, thereby regulating energy homeostasis. However, the precise molecular mechanisms by which tanycytes modulate lipid utilization remain unclear. Here, we report that the catalytic subunit of protein phosphatase 2 A (PP2Ac), a serine/threonine phosphatase, is expressed in tanycytes and its accumulation and activation occur in response to high-fat diet consumption. In vitro, tanycytic PP2Ac responds to palmitic acid (PA) exposure and accumulates and is activated at an early stage in an AMPK-dependent manner. Furthermore, activated PP2Ac boosts hypoxia-inducible factor-1α (HIF-1α) accumulation, resulting in upregulation of an array of cytokines. Pretreatment with a PP2Ac inhibitor, LB100, prevented the PA-induced elevation of vascular endothelial growth factor (VEGF), fibroblast growth factor 1 (FGF1), hepatocyte growth factor (HGF), and dipeptidyl peptidase IV (DPPIV or CD26). Our results disclose a mechanism of lipid metabolism in tanycytes that involves the activation of PP2Ac and highlight the physiological significance of PP2Ac in hypothalamic tanycytes in response to overnutrition and efficacious treatment of obesity.

Long-term intake of thermo-induced oxidized oil results in anxiety-like and depression-like behaviors: involvement of microglia and astrocytes

Frequent consumption of fried foods has been strongly associated with a higher risk of anxiety and depression, particularly among young individuals. The existing evidence has indicated that acrylamide produced from starchy foods at high temperatures can induce anxious behavior. However, there is limited research on the nerve damage caused by thermo-induced oxidized oil (TIOO). In this study, we conducted behavioral tests on mice and found that prolonged consumption of TIOO led to significant anxiety behavior and a tendency toward depression. TIOO primarily induced these two emotional disorders by affecting the differentiation of microglia, the level of inflammatory factors, the activation of astrocytes, and glutamate circulation in brain tissue. By promoting the over-differentiation of microglia into M1 microglia, TIOO disrupted their differentiation balance, resulting in an up-regulation of inflammatory factors (IL-1β, IL-6, TNF-α, NOS2) in M1 microglia and a down-regulation of neuroprotective factors IL-4/IL-10 in M2 microglia, leading to nerve damage. Moreover, TIOO activated astrocytes, accelerating their proliferation and causing GFAP precipitation, which damaged astrocytes. Meanwhile, TIOO stimulates the secretion of the BDNF and reduces the level of the glutamate receptor GLT-1 in astrocytes, leading to a disorder in the glutamate-glutamine cycle, further exacerbating nerve damage. In conclusion, this study suggests that long-term intake of thermo-induced oxidized oil can trigger symptoms of anxiety and depression.

Presentation and Management of Acute Mania in Fanconi-Bickel Syndrome, A Metabolic Genetic Disorder

Fanconi-Bickel syndrome (FBS) is a rare metabolic disorder caused by decreased glucose transporter 2 (GLUT2) function due to several known mutations in the SLC2A2 gene. As of 2020, 144 cases of FBS have been described in the literature. Metabolic and somatic sequelae include dysglycemia and accumulation of glycogen in the kidney and liver. However, there are no descriptions in the literature of possible neuropsychiatric manifestations of FBS. This case report is to our knowledge the first in this regard, describing a patient with FBS who was admitted to our psychiatric inpatient unit while experiencing acute mania. We conceptualize the case as a novel psychiatric presentation of acute mania in FBS, which may inform our understanding of bipolar disorder pathophysiology because of the hypothesized functional changes in neural pathways involving the paraventricular thalamus induced by decreased GLUT2 activity in FBS.

Association between dietary inflammatory index with all-cause and cardiovascular disease mortality among older US adults: A longitudinal cohort study among a nationally representative sample

OBJECTIVE

To investigate the association between DII with all-cause and cardiovascular disease (CVD) mortality among older adults in the U.

S METHODS

This prospective cohort study included older adults with complete DII data and mortality data from the National Health and Nutrition Examination Survey (NHANES) 2001-2018. Mortality outcomes were linked to National Death Index records through 31 December 2019. The multivariate Cox proportional hazards models were performed to evaluate the association between DII and mortality. Restricted cubic spline analyses were used to examine the nonlinear association of DII with all-cause and CVD mortality.

RESULTS

During the median follow-up date of 6.7 years, 4446 all-cause deaths were documented among 10,827 representative older adults, including 1230 CVD deaths. After multivariate adjustment, linear relationships between DII with all-cause mortality (P non-linear = 0.17) and non-linear relationship between DII with CVD mortality (P non-linear = 0.04) were observed. Compared to participants with the lowest quartile of DII scores (-5.28 to≤0.43), the multivariate-adjusted HRs and 95 %CI for participants with higher DII scores were 1.19 (Q2, 95 %CI: 1.08-1.31), 1.28 (Q3, 95 %CI: 1.14-1.44), 1.30 (Q4, 95 %CI: 1.17-1.44) for all-cause mortality (P trend <0.001) and 1.19 (Q2, 95 %CI: 0.99-1.43), 1.34 (Q3, 95 %CI: 1.10-1.62), 1.30 (Q4, 95 %CI: 1.06-1.58) for CVD mortality (P trend < 0.01), respectively.

CONCLUSIONS

In the representative sample of older adults in the U.S, higher DII scores were associated with increased risks of all-cause and CVD mortality.

Microglia trigger the structural plasticity of GABAergic neurons in the hippocampal CA1 region of a lipopolysaccharide-induced neuroinflammation model

It is well-established that microglia-mediated neuroinflammatory response involves numerous neuropsychiatric and neurodegenerative diseases. While the role of microglia in excitatory synaptic transmission has been widely investigated, the impact of innate immunity on the structural plasticity of GABAergic inhibitory synapses is not well understood. To investigate this, we established an inflammation model using lipopolysaccharide (LPS) and observed a prolonged microglial response in the hippocampal CA1 region of mice, which was associated with cognitive deficits in the open field test, Y-maze test, and novel object recognition test. Furthermore, we found an increased abundance of GABAergic interneurons and GABAergic synapse formation in the hippocampal CA1 region. The cognitive impairment caused by LPS injection could be reversed by blocking GABA receptor activity with (-)-Bicuculline methiodide. These findings suggest that the upregulation of GABAergic synapses induced by LPS-mediated microglial activation leads to cognitive dysfunction. Additionally, the depletion of microglia by PLX3397 resulted in a decrease in GABAergic interneurons and GABAergic inhibitory synapses, which blocked the cognitive decline induced by LPS. In conclusion, our findings indicate that excessive reinforcement of GABAergic inhibitory synapse formation via microglial activation contributes to LPS-induced cognitive impairment.

Noteworthy perspectives on microglia in neuropsychiatric disorders

Microglia are so versatile that they not only provide immune surveillance for central nervous system, but participate in neural circuitry development, brain blood vessels formation, blood-brain barrier architecture, and intriguingly, the regulation of emotions and behaviors. Microglia have a profound impact on neuronal survival, brain wiring and synaptic plasticity. As professional phagocytic cells in the brain, they remove dead cell debris and neurotoxic agents via an elaborate mechanism. The functional profile of microglia varies considerately depending on age, gender, disease context and other internal or external environmental factors. Numerous studies have demonstrated a pivotal involvement of microglia in neuropsychiatric disorders, including negative affection, social deficit, compulsive behavior, fear memory, pain and other symptoms associated with major depression disorder, anxiety disorder, autism spectrum disorder and schizophrenia. In this review, we summarized the latest discoveries regarding microglial ontogeny, cell subtypes or state spectrum, biological functions and mechanistic underpinnings of emotional and behavioral disorders. Furthermore, we highlight the potential of microglia-targeted therapies of neuropsychiatric disorders, and propose outstanding questions to be addressed in future research of human microglia.

Perinatal metabolic inflammation in the hypothalamus impairs the development of homeostatic feeding circuitry

Over the past few decades, there has been a global increase in childhood obesity. This rise in childhood obesity contributes to the susceptibility of impaired metabolism during both childhood and adulthood. The hypothalamus, specifically the arcuate nucleus (ARC), houses crucial neurons involved in regulating homeostatic feeding. These neurons include proopiomelanocortin (POMC) and agouti-related peptide (AGRP) secreting neurons. They play a vital role in sensing nutrients and metabolic hormones like insulin, leptin, and ghrelin. The neurogenesis of AGRP and POMC neurons completes at birth; however, axon development and synapse formation occur during the postnatal stages in rodents. Insulin, leptin, and ghrelin are the essential regulators of POMC and AGRP neurons. Maternal obesity and postnatal overfeeding or a high-fat diet (HFD) feeding cause metabolic inflammation, disrupted signaling of metabolic hormones, netrin-1, and neurogenic factors, neonatal obesity, and defective neuronal development in animal models; however, the mechanism is unclear. Within the hypothalamus and other brain areas, there exists a wide range of interconnected neuronal populations that regulate various aspects of feeding. However, this review aims to discuss how perinatal metabolic inflammation influences the development of POMC and AGRP neurons within the hypothalamus.

Short-wavelength artificial light affects visual neural pathway development in mice

Nearly all modern life depends on artificial light; however, it does cause health problems. With certain restrictions of artificial light emitting technology, the influence of the light spectrum is inevitable. The most remarkable problem is its overload in the short wavelength component. Short wavelength artificial light has a wide range of influences from ocular development to mental problems. The visual neuronal pathway, as the primary light-sensing structure, may contain the fundamental mechanism of all light-induced abnormalities. However, how the artificial light spectrum shapes the visual neuronal pathway during development in mammals is poorly understood. We placed C57BL/6 mice in three different spectrum environments (full-spectrum white light: 400-750 nm; violet light: 400 ± 20 nm; green light: 510 ± 20 nm) beginning at eye opening, with a fixed light time of 7:00-19:00. During development, we assessed the ocular axial dimension, visual function and retinal neurons. After two weeks under short wavelength conditions, the ocular axial length (AL), anterior chamber depth (ACD) and length of lens thickness, real vitreous chamber depth and retinal thickness (LLVR) were shorter, visual acuity (VA) decreased, and retinal electrical activity was impaired. The density of S-cones in the dorsal and ventral retinas both decreased after one week under short wavelength conditions. In the ventral retina, it increased after three weeks. Retinal ganglion cell (RGC) density and axon thickness were not influenced; however, the axonal terminals in the lateral geniculate nucleus (LGN) were less clustered and sparse. Amacrine cells (ACs) were significantly more activated. Green light has few effects. The KEGG and GO enrichment analyses showed that many genes related to neural circuitry, synaptic formation and neurotransmitter function were differentially expressed in the short wavelength light group. In conclusion, exposure to short wavelength artificial light in the early stage of vision-dependent development in mice delayed the development of the visual pathway. The axon terminus structure and neurotransmitter function may be the major suffering.