Chemical sensors detect and resolve proteome aggregation in peripheral neuropathy cell model induced by chemotherapeutic agents.

As a consequence of somatosensory nervous system injury or disease, neuropathic pain is commonly associated with chemotherapies, known as chemotherapy-induced peripheral neuropathy (CIPN). However, the mechanisms underlying CIPN-induced proteome aggregation in neuronal cells remain elusive due to limited detection tools. Herein, we present series sensors for fluorescence imaging (AggStain) and proteomics analysis (AggLink) to visualize and capture aggregated proteome in CIPN neuronal cell model. The environment-sensitive AggStain imaging sensor selectively binds and detects protein aggregation with 12.3 fold fluorescence enhancement. Further, the covalent AggLink proteomic sensor captures cellular aggregated proteins and profiles their composition via LC-MS/MS analysis. This integrative sensor platform reveals the presence of proteome aggregation in CIPN cell model and highlights its potential for broader applications in assessing proteome stability under various cellular stress conditions.

Valine promotes milk synthesis by regulating PKM2 nuclear accumulation and histone H3 acetylation through the TAS1R1-mTOR-DDX39B signaling pathway.

Valine, a branched-chain amino acid found in dairy cows, has been recognized for its critical role in milk synthesis. However, the precise effect of valine on lactation in dairy cows remains an area of investigation. In our study, bovine mammary epithelial cells (BMECs) were isolated to explore the mechanism through which valine enhances milk synthesis. The results showed that 100 µM valine significantly boosted the milk synthesis via TAS1R1-mTOR-DDX39B signaling pathway in BMECs. Subsequent investigations revealed that DDX39B governs the accumulation of PKM2 in the nuclei of BMECs. This nuclear buildup of PKM2 weakened the interaction between HDAC3 and histone H3, leading to an increase in the acetylation levels of histone H3. In an vivo context, the 0.25 % valine-enriched drinking water notably elevated in the expression of milk protein and fat in these mice. Further examination showed that 0.25 % valine drinking water considerably augmented the protein expression levels of DDX39B, PKM2, and p-mTOR in the mice mammary glands. In summary, our results suggest that valine, by modulating the TAS1R1-mTOR-DDX39B signaling pathway, directs the accumulation of PKM2 in the nucleus. This, in turn, escalates the acetylation levels of histone H3, promoting the synthesis of both milk protein and fat.

Acylated Ghrelin Activates PI3K/mTOR Signaling Pathway by Promoting ThPOK Acetylation to Promote Milk Fat Synthesis in Bovine Mammary Epithelial Cells.

Ghrelin regulates diverse physiological activities. However, the effects of this hormone on the milk fat synthesis remain unknown. This study aimed to investigate the effect of acylated ghrelin (AG) on milk fat synthesis by modifying the expression (knockdown or overexpression) of growth hormone secretagogue receptor 1a (GHSR1a) and Th-inducing POK (ThPOK) in primary bovine mammary epithelial cells (BMECs). The results showed that AG significantly increased the triglyceride relative content from 260.83 ± 9.87 to 541.67 ± 8.38 in BMECs via GHSR1a. ThPOK functions as a key regulatory target downstream of AG, activating the PI3K and mTOR signaling pathways to promote milk fat synthesis in BMECs. Moreover, AG-regulated ThPOK by increasing the EP300 activity, which promoted ThPOK acetylation to protect it from proteasomal degradation. In conclusion, AG increases ThPOK acetylation and stabilizes ThPOK through GHSR1a, thereby activating the PI3K/mTOR signaling pathway and ultimately promoting the milk fat synthesis in BMECs.

Core fucosylation and its roles in gastrointestinal glycoimmunology.

Glycosylation is a common post-translational modification in eukaryotic cells. It is involved in the production of many biologically active glycoproteins and the regulation of protein structure and function. Core fucosylation plays a vital role in the immune response. Most immune system molecules are core fucosylated glycoproteins such as complements, cluster differentiation antigens, immunoglobulins, cytokines, major histocompatibility complex molecules, adhesion molecules, and immune molecule synthesis-related transcription factors. These core fucosylated glycoproteins play important roles in antigen recognition and clearance, cell adhesion, lymphocyte activation, apoptosis, signal transduction, and endocytosis. Core fucosylation is dominated by fucosyltransferase 8 (Fut8), which catalyzes the addition of α-1,6-fucose to the innermost GlcNAc residue of N-glycans. Fut8 is involved in humoral, cellular, and mucosal immunity. Tumor immunology is associated with aberrant core fucosylation. Here, we summarize the roles and potential modulatory mechanisms of Fut8 in various immune processes of the gastrointestinal system.

Fluorene-based tau fibrillation sensor and inhibitor with fluorogenic and photo-crosslinking properties.

Tau protein aggregation into neurofibrillary tangles often causes tauopathies. Herein, we report fluorene based sensors with fluorogenicity upon binding to tau proteins. Intriguingly, these sensors possess triplet state properties to inhibit tau fibrillation upon photo-induced crosslinking.

Trends of mitochondrial changes in AD: a bibliometric study.

Background: Alzheimer's disease (AD) is a neurodegenerative disease characterized by progressive progress and memory loss, which eventually develops into dementia. It can cause personality disorders and decreased quality of life of patients. Currently, AD patients account for 60-70% of global dementia patients and the incidence rate of AD is increasing annually. AD not only causes pain to patients but also brings a heavy burden to the entire family. Studies have found that there is a connection between mitochondrial dysfunction and other biochemical changes in AD like classical neuropathological hallmarks (ß-amyloid and tau protein), inflammation pathways, oxidative stress, and so on. Evidence shows that early treatment targeted directly to mitochondria could extend the lifespan of model mice and decrease the relevant neuropathological markers. Therefore, research on the mitochondrial dysfunction of AD can be of potential significance for clinical treatment. To date, few bibliometric analysis articles related to mitochondrial dysfunction of AD have been published. Bibliometric analysis refers to quantitatively analyzing certain aspects of articles like publishers, authors, and countries by using statistical and mathematical methods. Combined with statistical software, a large number of papers can be converted to visualization figures and tables, which provide vital information such as keyword hotspots and the names of contributing authors. Through the bibliometric analysis method, our study aimed to provide study trends and keyword hotpots for researchers to conduct further relevant research in this field. Methods: We used the Web of Science core collection database as a literature retrieval tool to obtain data related to mitochondrial changes in Alzheimer's disease during the last 20 years. The retrieval type was [TS = (Alzheimer's disease)] ND [TS = (mitochondrion)], ranging from January 1, 2000 to June 30, 2022. VOSviewer v1.6.18, Arcgis 10.8, and HistCite pro 2.1 were used to conduct data visualization analysis. VOSviewer v1.6.18 made relevant network visualization maps of the cooperative relationship between relevant countries, institutions, and authors (co-authorship), the frequency of different keywords appearing together (co-occurrence), and the frequency of different articles cited together (co-cited). Arcgis 10.8 created the world map of publications distribution in this field and Histcite pro 2.1 was used to count the local citation score (LCS) of references. In addition, Journal Citation Reports were used to consult the latest journal import factor and JCI quartile. Results: As of June 30, 2022, from the Web of Science core collection, we selected 2,474 original articles in English, excluding the document types of the news items, meeting abstracts, and some articles that had little relevance to our theme. The United States acted as the leader and enjoyed a high reputation in this field. The University of California System was the institution that made the greatest contribution (3.64% with 90 papers). Most articles were published in the Journal of Alzheimer's Disease (8.21%, with 203 papers). The most frequently co-cited journal in Q1 was the Journal of Biological Chemistry (8,666 citations, TLS: 1039591). Russel H. Swerdlow (55 publications) was the most productive author and PH Reddy was the most co-cited author with 1,264 citations (TLS: 62971). The hotpots of mitochondrial dysfunction in AD were as follows: "oxidative stress," "amyloid-beta-protein," "tau," "apoptosis," "inflammation," "autophagy," "precursor protein," "endoplasmic-reticulum," "dynamics" and "mitochondrial unfolded protein response." Conclusion: This bibliometric analysis research will help readers rapidly identify current hotpots and milestone studies related to directions of interest in AD research.

Aß Induces Neuroinflammation and Microglial M1 Polarization via cGAS-STING-IFITM3 Signaling Pathway in BV-2 Cells.

Microglia, innate immune cells of the brain, constantly monitor the dynamic changes of the brain microenvironment under physiological conditions and respond in time. Growing evidence suggests that microglia-mediated neuroinflammation plays an important role in the pathogenesis of Alzheimer's disease. In this study, we investigated that the expression of IFITM3 was significantly upregulated in microglia under the Aß treatment, and knockdown of IFITM3 in vitro suppressed the M1-like polarization of microglia. Moreover, IFITM3 was regulated by cGAS-STING signaling in activated microglia, and inhibition of cGAS-STING signaling reduces IFITM3 expression. Taken together, our findings suggested that the cGAS-STING-IFITM3 axis may be involved in Aß-induced neuroinflammation in microglia.

Novel compound heterozygous missense variants in TOE1 gene associated with pontocerebellar hypoplasia type 7.

BACKGROUND: Pontocerebellar hypoplasia type 7(PCH7)is a neurodegenerative disease related to autosomal recessive variants in the target of EGR1 (TOE1)gene. Biallelic mutation in the TOE1 gene causes global developmental delay, cognitive and psychomotor impairment, hypotonia, breathing abnormalities, and gonadal abnormalities. This study examined the clinical and genetic features of a 2-year-old patient carrying novel compound heterozygous variants in the TOE1 gene, mutations of previously reported 14 PCH7 patients were reviewed. METHODS: Clinical data of the 2-year-old patient were captured. Trio- whole exome sequencing (Trio-WES) was performed to identify pathogenic variants. Sanger sequencing was further used to verify the variants. In silico analysis was performed to explain the pathogenicity. RESULTS: Herein, we described the clinical features of the 2-year-old patient diagnosed with PCH7 caused by mutations in the TOE1gene. The kid was presenting with global development delay and gonadal abnormalities. Brain imaging revealed hypoplasia of the cerebellum and pons with ambiguous genitalia. Trio-WES revealed novel compound heterozygous missense variants in TOE1gene (c.911C > T p.S304L, c.161C > T p.A54V). Multiple in silico tools predicted the deleterious effects of the mutations. CONCLUSION: The novel compound heterozygous missense mutation in the TOE1 gene identified in the proband broadened the genotypic and phenotypic spectrum of disorders associated with PCH7. Our findings provide critical information for the differential diagnosis of rare neurodevelopment disorders and genetic counselling.

Assessment of cognitive impairment after acute cerebral infarction with T1 relaxation time measured by MP2RAGE sequence and cerebral hemodynamic by transcranial Doppler.

Objective: This study aimed to investigate early brain microstructural changes discovered using magnetization-prepared two rapid acquisition gradient echo (MP2RAGE) sequence and cerebral hemodynamic using TCD for cognitive impairment after acute cerebral infarction. Methods: We enrolled 43 patients with acute cerebral infarction and 21 healthy people in the study, who were subjected to cognitive assessments, the MP2RAGE sequence, and a cerebral hemodynamic examination. A total of 26 brain regions of interest were investigated. Furthermore, we used cerebral hemodynamics to explain brain microstructural changes, which helped us better understand the pathophysiology of cognitive impairment after acute cerebral infarction and guide treatment. Results: T1 relaxation times in the left frontal lobe, right frontal lobe, right temporal lobe, left precuneus, left thalamus, right hippocampus, right head of caudate nucleus, and splenium of corpus callosum were substantially different across the three groups, which were significantly correlated with neuropsychological test scores. CI group patients had significantly lower cerebral blood flow velocity than those in the N-CI and Normal groups. The receiver operating curve analysis revealed that most T1 relaxation times had high sensitivity and specificity, especially on the right temporal lobe and right frontal lobe. There was a potential correlation between T1 relaxation times and MMSE scores through TCD parameters. Conclusion: The MP2RAGE sequence can detect alterations in whole brain microstructure in patients with cognitive impairment after acute cerebral infarction. Brain microstructural changes could influence cognitive function through cerebral hemodynamics. T1 relaxation times on the right temporal lobe and the right frontal lobe are expected to be a prospective biomarker of cognitive impairment after acute cerebral infarction.

Lysine promotes proliferation and ß-casein synthesis through the SLC6A14-ERK1/2-CDK1-mTOR signaling pathway in bovine primary mammary epithelial cells.

Lysine, as the first limiting amino acid in dairy cows, has been shown to play an important role in milk synthesis and cell proliferation. However, the underlying mechanism remains unclear. In this study, we isolated bovine primary mammary epithelial cells (BMECs) and studied the mechanism in which lysine promotes cell proliferation and ß-casein synthesis through overexpression and knockdown of CDK1 and supplements BCH, U0126, and rapamycin in BMECs. Results show that 0.7 mM lysine can significantly promote cell proliferation and the synthesis of ß-casein in BMECs. In addition, lysine activates the ERK signaling pathway to promote the expression of CDK1. Further studies have shown that CDK1 can promote cell proliferation and the synthesis of ß-casein through the mTOR signaling pathway in BMECs. Lastly, lysine can promote cell proliferation and the synthesis of ß-casein through SLC6A14 in BMECs. The above results indicate that lysine promotes cell proliferation and the synthesis of ß-casein through the SLC6A14-ERK-CDK1-mTOR signaling pathway in BMECs.

CXCL1-CXCR2 signalling mediates hypertensive retinopathy by inducing macrophage infiltration.

Inflammation plays an important role in hypertensive retinal vascular injury and subsequent retinopathy. Monocyte chemotaxis via CXCL1-CXCR2 binding has been implicated in various cardiovascular diseases, but the function of CXCL1-CXCR2 signalling involved in retinopathy, which was investigated as angiotensin II (Ang II)-induced retinopathy, is unclear. In our study, we established a hypertensive retinopathy (HR) model by Ang II infusion (3000 ng/min/kg) for 3 weeks. To determine the involvement of CXCR2 signalling, we used CXCR2 knockout (KO) mice or C57BL/6J wild-type (WT) mice as experimental subjects. The mice were treated with a CXCL1 neutralizing antibody or SB225002 (the specific CXCR2 inhibitor). Our results showed that after Ang II treatment, the mRNA levels of CXCL1 and CXCR2 and the number of CXCR2+ inflammatory cells were significantly elevated. Conversely, unlike in the IgG control group, the CXCL1 neutralizing antibody greatly reduced the increase in central retinal thickness induced by Ang II infusion, arteriolar remodelling, superoxide production, and retinal dysfunction in WT mice. Furthermore, Ang II infusion induced arteriolar remodelling, infiltration of Iba1+ macrophages, the production of oxidative stress, and retinal dysfunction, but the symptoms were ameliorated in CXCR2 KO mice and SB225002-treated mice. These protective effects were related to the reduction in the number of CXCR2+ immune cells, particularly macrophages, and the decrease in proinflammatory cytokine (IL-1ß, IL-6, TNF-ɑ, and MCP-1) expression in Ang II-treated retinas. Notably, serum CXCL1 levels and the number of CXCR2+ monocytes/neutrophils were higher in HR patients than in healthy controls. In conclusion, this study provides new evidence that the CXCL1-CXCR2 axis plays a vital role in the pathogenesis of hypertensive retinopathy, and selective blockade of CXCL1-CXCR2 activation may be a potential treatment for HR.

Comparison of brain microstructure alterations on diffusion kurtosis imaging among Alzheimer's disease, mild cognitive impairment, and cognitively normal individuals.

Objective: Our study aimed to explore the differences in brain microstructure in patients with Alzheimer's disease (AD) and with mild cognitive impairment (MCI) and in individuals with normal cognition using diffusion kurtosis imaging (DKI) to identify a potential non-invasive biomarker of AD. Materials and methods: A total of 61 subjects were included in our study, including 20 subjects diagnosed with AD, 21 patients diagnosed with amnestic MCI, and 20 cognitively normal individuals. We acquired magnetic resonance imaging (MRI) scans, and DKI images were processed. Twelve regions of interest were drawn, and various parameters were measured and analyzed using SPSS version 11.0 software. Results: Comparative analysis showed that differences in brain regions in terms of mean diffusion (MD) and mean kurtosis (MK) between groups were the most marked. Precuneus MD, temporal MK, precuneus MK, and hippocampal MK were significantly correlated with neuropsychological test scores. Hippocampal MK showed the strongest correlation with the medial temporal lobe atrophy score (r = -0.510), and precuneus MD had the strongest correlation with the Koedam score (r = 0.463). The receiver operating curve analysis revealed that hippocampal MK exhibited better diagnostic efficacy than precuneus MD for comparisons between any group pair. Conclusion: DKI is capable of detecting differences in brain microstructure between patients with AD, patients with MCI, and cognitively normal individuals. Moreover, it compensates for the deficiencies of conventional MRI in detecting pathological changes in microstructure before the appearance of macroscopic atrophy. Hippocampus MK was the most sensitive single parameter map for differentiating patients with AD, patients with MCI, and cognitively normal individuals.

L-arginine stimulates the proliferation of mouse mammary epithelial cells and the development of mammary gland in pubertal mice by activating the GPRC6A/PI3K/AKT/mTOR signalling pathway.

Amino acids have been shown to affect the development of mammary gland (MG). However, it is unclear whether L-arginine promotes the development of pubertal MG. Therefore, our study aims to explore the effect of L-arginine on the development of MG in pubertal mice. To investigate its internal mechanism of action, we will use mouse mammary epithelial cells (mMECs) line. Whole-mount staining showed that L-arginine can promote the extension of MG duct. In vitro, 0.4 mM L-arginine could activate the G protein-coupled receptor family C, group 6, subtype A (GPRC6A)/phosphoinositide 3-kinase (PI3K)/protein kinase B (AKT)/mammalian target of rapamycin (mTOR) signalling pathway and increase the phosphorylation of eukaryotic initiation factor 4E binding protein 1 (4EBP1) to promote the synthesis of cell cycle regulatory protein D1 (Cyclin D1), leading to the dissociation of the retinoblastoma tumour suppressor protein (Rb)-E2F1 transcription factor (E2F1) complex in mMECs and releasing E2F1 to promote cell proliferation. Furthermore, GPRC6A was knocked down or inhibition of the PI3K/AKT/mTOR signalling pathway with corresponding inhibitors completely abolished the arginine-induced promotion of mMECs proliferation. In vivo, it was further confirmed that 0.1% L-arginine can activate the PI3K/AKT/mTOR signalling pathway in the MG of pubertal mice. These results were able to indicate that L-arginine stimulates the development of MG in pubertal mice through the GPRC6A/PI3K/AKT/mTOR signalling pathway.

Altered Microstructural Changes Detected by Diffusion Kurtosis Imaging in Patients With Cognitive Impairment After Acute Cerebral Infarction.

Objective: To detect the microstructural changes in patients with cognitive impairment after acute cerebral infarction using diffusion kurtosis imaging (DKI). Materials and Methods: A total of 70 patients with acute cerebral infarction were divided into two groups: 35 patients with cognitive impairment (VCI group), and 35 patients without cognitive impairment (N-VCI group), according to mini-mental state examination (MMSE) score. Healthy individuals (n = 36) were selected as the normal control (NORM) group. DKI parameters from 28 different brain regions of interest (ROIs) were selected, measured, and compared. Results: VCI group patients had significantly higher mean diffusion (MD) and significantly lower mean kurtosis (MK) values in most ROIs than those in the N-VCI and NORM groups. DKI parameters in some ROIs correlated significantly with MMSE score. The splenium of corpus callosum MD was most correlated with MMSE score, the correlation coefficient was -0.652, and this parameter had good ability to distinguish patients with VCI from healthy controls; at the optimal cut-off MD value (0.9915), sensitivity was 91.4%, specificity 100%, and the area under the curve value 0.964. Conclusions: Pathological changes in some brain regions may underlie cognitive impairment after acute cerebral infarction, especially the splenium of corpus callosum. These preliminary results suggest that, in patients with VCI, DKI may be useful for assessing microstructural tissue damage.

Kisspeptin-10 Maintains the Activation of the mTOR Signaling Pathway by Inhibiting SIRT6 to Promote the Synthesis of Milk in Bovine Mammary Epithelial Cells.

Kisspeptin-10 (Kp-10) is a peptide hormone that regulates normal physiological processes. The mechanism of Kp-10 in milk synthesis is still unclear. Therefore, bovine mammary epithelial cells (BMECs) were used to study the mechanism by which Kp-10 affects milk synthesis in BMECs. The GPR54 inhibitor and SIRT6 overexpression plasmid and siRNA were used to study the mechanism of regulating milk protein and milk fat synthesis by Kp-10. The results showed that 100 nM Kp-10 increased milk synthesis in BMECs. SIRT6 overexpression could significantly reduce the milk protein and milk fat synthesis in BMECs. Moreover, overexpression of SIRT6 reversed the activation of the Kp-10-induced mTOR signaling pathway. Further analysis suggested that SIRT6 might regulate the signal transduction of mTOR at the transcriptional level. These results strongly suggested that Kp-10/GPR54 activated the mTOR signaling pathway by inhibiting SIRT6 expression and then increased the milk synthesis in BMECs.

Fasting blood glucose and risk of Stroke: A Dose-Response meta-analysis.

BACKGROUND & PURPOSE: A growing number of studies have shown that fasting blood glucose is related to the risk of stroke, however, the dose-response association between fasting blood glucose and the risk of stroke is still unclear. Accordingly, we conducted a dose-response meta-analysis to evaluate the relationship between fasting blood glucose and the risk of stroke by summarizing cohort studies. METHODS: PubMed and Embase databases were searched for related studies (until October 2020). Cohort studies examining the influence of fasting blood glucose on stroke risk were summarized. A dose-response relationship was determined using a random-effect model. RESULTS: Eighteen cohort studies involving 2,555,666 participants were included. The pooled relative risk for the high-versus-low categories was 1.79 (95% CI: 1.68-1.91) in all people, and 1.16 (95% CI: 1.11-1.21) in non-diabetic people. In addition, there was a non-linear relationship between fasting blood glucose and stroke risk. The incidence of stroke was reduced to its lowest point when fasting blood glucose level was 70-100 mg/dL. CONCLUSION: Fasting blood glucose was positively related to stroke risk, with a non-linear dose-response relationship.

JNK/c-Jun-driven NLRP3 inflammasome activation in microglia contributed to retinal ganglion cells degeneration induced by indirect traumatic optic neuropathy.

BACKGROUND: Indirect traumatic optic neuropathy (ITON) is a major cause of permanent loss of vision after blunt head trauma. Neuroinflammation plays a crucial role in neurodegenerative diseases. The present study concentrated on JNK/c-Jun-driven NLRP3 inflammasome activation in microglia during the degeneration of retinal ganglion cells (RGCs) in ITON. METHODS: An impact acceleration (IA) model was employed to induce ITON, which could produce significant neurodegeneration in the visual system. Pharmacological approaches were employed to disrupt JNK and to explore whether JNK and the microglial response contribute to RGC death and axonal degeneration. RESULTS: Our results indicated that the ITON model induced significant RGC death and axonal degeneration and activated JNK/c-Jun signaling, which could further induce the microglial response and NLRP3 inflammasome activation. Moreover, JNK disruption is sufficient to suppress NLRP3 inflammasome activation in microglia and to prevent RGC death and axonal degeneration. CONCLUSIONS: ITON could promote JNK/c-Jun signaling, which further activates the NLRP3 inflammasome in microglia and contributes to the degeneration of axons and death of RGCs. JNK inhibition is able to suppress the inflammatory reaction and improve RGC survival. Although further work is needed to determine whether pharmacological inhibition of the NLRP3 inflammasome can prevent ITON, our findings indicated that such intervention could be promising for translational work.

Niacin inhibits the synthesis of milk fat in BMECs through the GPR109A-mediated downstream signalling pathway.

AIMS: Previous studies have shown the effect of niacin on dairy cow production, but no study on the role of niacin in milk fat synthesis has been performed. Therefore, the purpose of this study was to examine the effect of niacin on milk fat synthesis and its specific mechanism in BMECs. MAIN METHODS: In this study, 0.5 mM niacin, a GPR109A-inhibiting plasmid, and an AMPK inhibitor were added to BMECs. Milk fat was measured by a triglyceride kit and BODIPY staining. The protein expression of GPR109A, FASN, SREBP1, AMPK, ACC, mTOR and S6K was measured by Western blotting. The gene expression of GPR109A, FASN, and SREBP1 was analysed by RT-PCR. KEY FINDINGS: Our results showed that 0.5 mM niacin could significantly reduce milk fat synthesis in BMECs and activate the AMPK/ACC signalling pathway by stimulating GPR109A, reducing the protein expression of p-mTOR and p-S6K, and reducing the expression of SREBP1 and FASN in BMECs. SIGNIFICANCE: The present study clarified the effect of niacin on milk fat synthesis. The results show that niacin inhibits the synthesis of milk fat in BMECs through the downstream signalling pathway mediated by GPR109A. The function of niacin has been expanded, and knowledge of the new mechanism and signalling pathway will help improve the biosynthesis of milk fat.

Sodium butyrate promotes milk fat synthesis in bovine mammary epithelial cells via GPR41 and its downstream signalling pathways.

OBJECTIVE: Short-chain fatty acids were reported to be the precursors of milk fat and can stimulate the de novo synthesis of fatty acids in bovine mammary epithelial cells (bMECs). However, the mechanism has not been elucidated. The purpose of this study was to investigate the effects of sodium butyrate (NaB) on milk fat synthesis in bMECs and explore its potential mechanism. METHODS: Bovine mammary epithelial cells (bMECs) were isolated for subsequent experimental uses. BODIPY staining and triglyceride kit were used to detect the milk fat synthesis in bMECs. Western blotting and RT-PCR assays were performed to detect the expression of related genes in bMECs. Immunoprecipitation was used to detect the acetylation of SREBP1 in bMECs. RESULTS: The results showed that NaB significantly promoted milk fat synthesis, promoted the activity of mechanistic target of rapamycin (mTOR) and S6 kinase (S6K), inhibited the activity of AMP-activated protein kinase (AMPK), and promoted the gene expression of G protein-coupled receptor 41 (GPR41). Knockdown of GPR41 and sterol regulatory element binding protein 1 (SREBP1) and overexpression of sirtuin1 (SIRT1), mTOR inhibitor (rapamycin), and AMPK activator (AICIR) eliminated these effects. These results indicated that NaB increased the nuclear translocation of SREBP1 via the GPR41/AMPK/mTOR/S6K signalling pathway, promoted the acetylation of mature SREBP1a via GPR41/AMPK/SIRT1, and then promoted milk fat synthesis. CONCLUSION: Taken together, these results demonstrated that NaB increased nuclear translocation and acetylation of SREBP1 to promote milk fat synthesis by activating GPR41 and its downstream signalling pathways.