SREBPs: the crossroads of physiological and pathological lipid homeostasis

Anti-b diminishes hyperlipidaemia and hepatic steatosis in hamsters and mice by suppressing the mTOR/PPARγ and mTOR/SREBP1 signalling pathways

BACKGROUND AND PURPOSE

As a chronic metabolic syndrome, hyperlipidaemia is manifested as aberrantly elevated cholesterol and triglyceride (TG) levels, primarily attributed to disorders in lipid metabolism. Despite the promising outlook for hyperlipidaemia treatment, the need persists for the development of lipid-lowering agents with heightened efficiency and minimal toxicity. This investigation aims to elucidate the lipid-lowering effects and potential pharmacodynamic mechanisms of Anti-b, a novel low MW compound.

EXPERIMENTAL APPROACH

We employed high-fat diet (HFD) in hamsters and mice or oleic acid (OA) in cultures of HepG2 cells and LO2 cells to induce hyperlipidaemia models. We administered Anti-b to assess its therapeutic effects on dyslipidaemia and hepatic steatosis. We used western blotting, RNA sequencing, GO and KEGG analysis, oil red O staining, along with molecular docking and molecular dynamics simulation to elucidate the mechanisms underlying the effects of Anti-b.

KEY RESULTS

Anti-b exhibited a substantial reduction in HFD-induced elevation of blood lipids, liver weight to body weight ratio, liver diameter and hepatic fat accumulation. Moreover, Anti-b demonstrated therapeutic effects in alleviating total cholesterol (TC), TG levels, and lipid accumulation derived from OA in HepG2 cells and LO2 cells. Mechanistically, Anti-b selectively bound to the mTOR kinase protein and increased mTOR thermal stability, resulting in downregulation of phosphorylation level. Notably, Anti-b exerted anti-hyperlipidaemia effects by modulating PPARγ and SREBP1 signalling pathways and reducing the expression level of mSREBP1 and PPARγ proteins.

CONCLUSION AND IMPLICATIONS

In conclusion, our study has provided initial data of a novel low MW compound, Anti-b, designed and synthesised to target mTOR protein directly. Our results indicate that Anti-b may represent a novel class of drugs for the treatment of hyperlipidemia and hepatic steatosis.

Growth Hormone Excess Drives Liver Aging via increased Glycation stress

Growth hormone (GH) plays a crucial role in various physiological functions, with its secretion tightly regulated by complex endocrine mechanisms. Pathological conditions such as acromegaly or pituitary tumors result in elevated circulating GH levels, which have been implicated in a spectrum of metabolic disorders, potentially by regulating liver metabolism. In this study, we focused on the liver, a key organ in metabolic regulation and a primary target of GH, to investigate the impact of high circulating GH on liver metabolism. We used bovine GH overexpressing transgenic (bGH-Tg) mice to conduct a comprehensive transcriptomic analysis of hepatic tissues. The bGH-Tg mouse livers exhibit dysregulated fatty acid metabolism and heightened inflammatory responses. Notably, the transcriptomic profile of young bGH-Tg mouse livers resembled that of aged livers and displayed markers of increased cellular senescence. Furthermore, these mice exhibited a significant accumulation of advanced glycation end products (AGEs). Intervention with glycation-lowering compounds effectively reversed the insulin resistance and aberrant transcriptomic signatures in the liver that are associated with elevated GH levels. These findings underscore the potential therapeutic value of glycation-lowering agents in mitigating the deleterious effects of chronic GH overexpression.

Highlights

Overexpression of bovine growth hormone impacts transcriptional changes in liver fat metabolism and inflammatory response in mice.High circulating growth hormone leads to transcriptional changes that suggest enhanced liver aging and induce cellular senescence.Detoxification pathways in bGH-Tg mice are inhibited, leading to the accumulation of Advanced Glycation End (AGE) products.Glycation-lowering compounds can mitigate pathologies associated with high GH levels.

10-Hydroxy-2-decenoic acid attenuates nonalcoholic fatty liver disease by activating AMPK-α signaling pathway

Nonalcoholic fatty liver disease (NAFLD) originates from metabolic dysfunctions, is one of the most commonly encountered liver disorders worldwide, characterized by ectopic lipid deposition within hepatocytes, accompanied by hepatocellular injury and necroinflammation. Currently, NAFLD has very few treatment options. Purified from royal jelly, 10-hydroxy-2-decenoic acid (10-HDA) is the primary bioactive ingredient with a series of beneficial effects against various metabolic diseases. Herein, we investigated the effects of 10-HDA in methionine and choline deficiency (MCD) diet induced NAFLD model and free fatty acids (FFAs) induced lipid-laden hepatocyte model and explored the underlying mechanisms. In the mice fed with MCD diet, 10-HDA treatment significantly reduced hepatic steatosis, hepatocellular injury, apoptosis, inflammatory response and fibrosis. In vitro, 10-HDA treatment reduced lipid accumulation and apoptosis in hepatocytes induced by FFAs. Mechanistically, 10-HDA therapy restored AMPK-α phosphorylation, leading to the phosphorylation and inactivation acetyl-CoA carboxylase (ACC). Consequently, this increased the expression of carnitine palmitoyl transferase 1α(CPT1α), and peroxisome proliferators-activated receptors α (PPARα), and lowered the expression of cleavage forms of sterol regulatory element binding protein-1 (SREBP-1) and fatty acid synthetase (FASN). Furthermore, pretreating the cells with the AMPK-α inhibitor, compound C, greatly eliminated these beneficial effects of 10-HDA. Additionally, molecular docking analysis indicated that 10-HDA bound the domain of AMPK-α1 subunit. Based on these findings, 10-HDA suppresses hepatic lipogenesis via AMPK-α-dependent suppression of the ACC pathway, thus inhibiting hepatocellular injury, apoptosis, inflammatory response and fibrosis. 10-HDA may represent a promising candidate drug for the treatment of NAFLD.

MetAP2 as a Therapeutic Target for Obesity and Type 2 Diabetes: Structural Insights, Mechanistic Roles, and Inhibitor Development

Type 2 Diabetes Mellitus (T2DM) and obesity are globally prevalent metabolic disorders characterized by insulin resistance, impaired glucose metabolism, and excessive adiposity. Methionine aminopeptidase 2 (MetAP2), an intracellular metalloprotease, has emerged as a promising therapeutic target due to its critical role in regulating lipid metabolism, energy balance, and protein synthesis. This review provides a comprehensive analysis of MetAP2, including its structural characteristics, catalytic mechanism, and functional roles in the pathophysiology of T2DM and obesity. The unique architecture of MetAP2's active site and its interactions with substrates are examined to elucidate its enzymatic function. The review also explores the development of MetAP2 inhibitors, focusing on their mechanisms of action, preclinical and clinical findings, and therapeutic potential. Special emphasis is placed on docking studies to analyze the binding interactions of six key inhibitors (fumagillin, TNP-470, beloranib, ZGN-1061, indazole, and pyrazolo[4,3-b]indole) with MetAP2, revealing their structural determinants for efficacy and specificity. These findings underscore the potential of MetAP2 as a therapeutic target and provide valuable insights for the rational design of next-generation inhibitors to address obesity and T2DM.

Zhimu-Huangbai herb-pair ameliorates hepatic steatosis in mice by regulating IRE1α/XBP1s pathway to inhibit SREBP-1c

BACKGROUND

Currently, there is a lack of validated pharmacological interventions for non-alcoholic fatty liver disease (NAFLD), which is characterized by the accumulation of hepatic triglyceride. Zhimu-Huangbai (ZH) herb-pair is a traditional Chinese medicine that regulates glucose and lipid metabolism disorders. However, the precise mechanisms underlying the preventive effects of hepatic triglyceride induced by high-fat diet (HFD) remain elusive.

PURPOSE

The study aimed to examine the impact of ZH herb-pair on NAFLD in mice and explore the underlying mechanisms, particularly its effects on endoplasmic reticulum (ER) stress and lipid metabolism.

METHODS

NAFLD was induced in mice using HFD, and the treated mice were orally administered ZH, metformin (Glucophage) or lovastatin. The lipid metabolism factors, ER stress markers, and the unfolded protein response (UPR) branch factors were measured using immunohistochemistry, western blotting or qRT-PCR. Co-Immunoprecipitation (CoIP) was performed to reveal the connection between SCAP and SREBP-1c. Tunicamycin (TM) and plasmid delivery were used to induce acute ER stress or crease XBP1 gain function models. The main compounds in ZH binding to IRE1α protein were studied by molecular docking and cellular thermal shift assay (CETSA).

RESULTS

Treatment with ZH significantly ameliorated hepatic steatosis and reduced lipid synthesis process mainly inhibiting the expression of mature active form of SREBP-1c through relieving ER stress. The expression of IRE1α and XBP1s was inhibited after treatment with ZH. In addition, ZH improved the fatty liver phenotype caused by XBP1 overexpression via decreasing srebp1c transcription. In vitro experimental results suggested that the main compounds in ZH decreased cellular TG contents. Mechanistically, ZH targeted IRE1α and inhibited XBP1s mRNA expression to relieve ER stress and inhibit SREBP-1c production.

CONCLUSIONS

ZH herb-pair can protect against NAFLD by reducing the expression of SREBP-1c, in part, via regulating IRE1α/XBP1s pathway.

Life cycle assessment of hepatotoxicity induced by cyhalofop-butyl in environmental concentrations on zebrafish in light of gut-liver axis

Cyhalofop-butyl (CB) poses a significant threat to aquatic organisms, but there is a discrepancy in evidence about hepatotoxicity after prolonged exposure to environmental levels. The aim of this study was to investigate long-term hepatotoxicity and its effects on the gut-liver axis through the exposure of zebrafish to environmental concentrations of CB (0.1,1,10 μg/L) throughout their life cycle. Zebrafish experienced abnormal obesity symptoms and organ index after a prolonged exposure of 120 days. The gut-liver axis was found to be damaged both morphologically and functionally through an analysis of histology, electron microscopy subcellular structure, and liver function. The disruption of the gut-liver axis inflammatory process by CB is suggested by the rise in inflammatory factors and the alteration of inflammatory genes. Furthermore, there was a noticeable alteration in the blood and gut-liver axis biochemical parameters as well as gene expression linked to lipid metabolism, which may led to an imbalance in the gut flora. In conclusion, the connection between the gut-liver axis, intestinal microbiota, and liver leads to the metabolic dysfunction of zebrafish exposed to long-term ambient concentrations of CB, and damaged immune system and liver lipid metabolism. This study gives another knowledge into the hepatotoxicity component of long haul openness to ecological centralization of CB, and might be useful to assess the potential natural and wellbeing dangers of aryloxyphenoxypropionate herbicides.

Evolutionary analysis of buffalo sterol regulatory element-binding factor (SREBF) family genes and their affection on milk traits

The sterol regulatory element-binding factor (SREBF) genes are a vital group of proteins binding to the sterol regulatory element 1 (SRE-1) regulating the synthesis of fatty acid. Two potential candidate genes (SREBF1 and SREBF2) have been identified as affecting milk traits. This study aims to identify the SREBF family of genes and find candidate markers or SREBF genes influencing lactation production in buffalo. A genome-wide study was performed and identified seven SREBF genes randomly distributed on 7 chromosomes and 24 protein isoforms in buffalos. The SREBF family of genes were also characterized in cattle, goat, sheep and horse, and using these all-protein sequences, a phylogenetic tree was built. The SREBF family genes were homologous between each other in the five livestock. Eight single nucleotide polymorphisms (SNPs) within or near the SREBF genes in the buffalo genome were identified and at least one milk production trait was associated with three of the SNP. The expression of SREBF genes at different lactation stages in buffalo and cattle from published data were compared and the SREBF genes retained a high expression throughout lactation with the trend being the same for buffalo and cattle. These results provide valuable information for clarifying the evolutionary relationship of the SREBF family genes and determining the role of SREBF genes in the regulation of milk production in buffalo.

Mild Intermittent Cold Stimulation Affects Cardiac Substance Metabolism via the Neuroendocrine Pathway in Broilers

This study aimed to investigate the impact of cold adaptation on the neuroendocrine and cardiac substance metabolism pathways in broilers. The broilers were divided into the control group (CC), cold adaptation group (C3), and cold-stressed group (C9), and experimental period was divided into the training period (d 1-35), recovery period (d 36-43), and cold stress period (d 43-44). During the training period, the CC group was reared at ambient temperature, while C3 and C9 groups were reared at 3 °C and 9 °C lower than the ambient temperature, respectively, for 5 h/d at 1 d intervals. During the recovery period, all the groups were maintained at 20 °C. Lastly, during the cold stress period, the groups were divided into two sub-groups, and each sub-group was placed at 10 °C for 12 h (Y12) or 24 h (Y24) for acute cold stimulation. The blood, hypothalamic, and cardiac tissues samples were obtained from all the groups during the training, recovery, and acute stress periods. The results revealed that the transcription of calcium voltage-gated channel subunit alpha 1 C (CACNAIC) was increased in the hypothalamic tissues of the C3 group (p < 0.05). Moreover, compared to the CC group, the serum norepinephrine (NE) was increased in the C9 group (p < 0.05), but insulin (INS) was decreased in the C9 group (p < 0.05). In addition, the transcription of the phosphoinositide-3 kinase (PI3K), protein kinase B (Akt), mammalian target of rapamycin (mTOR), SREBP1c, FASN, ACC1, and SCD genes was down-regulated in the C3 and C9 groups (p < 0.05); however, their expression increased in the C3 and C9 groups after acute cold stimulation (p < 0.05). Compared to the CC group, the transcription of forkhead box O1 (FoxO1), PEPCK, G6Pase, GLUT1, HK1, PFK, and LDHB genes was up-regulated in the C3 and C9 groups (p < 0.05. Furthermore, compared to the CC and C9 groups, the protein and mRNA expressions of heat shock protein (HSP) 70 and HSP90 were significantly increased in the C3 group (p < 0.05). These results indicate that intermittent cold training can enhance cold stress tolerance in broilers by regulating their neuroendocrine and cardiac substance metabolism pathways.

Effect of diet and genotype on the miRNome of mice with altered lipoprotein metabolism

The molecular mechanism by which lipid/lipoprotein biosynthesis is regulated in mammals involves a very large number of genes that are subject to multiple levels of regulation. miRNAs are recognized contributors to lipid homeostasis at the post-transcriptional level, although the elucidation of their role is made difficult by the multiplicity of their targets and the ability of more miRNAs to affect the same mRNAs. In this study, an evaluation of how miRNA expression varies in organs playing a key role in lipid/lipoprotein metabolism was conducted in control mice and in two mouse models carrying genetic ablations which differently affect low-density lipoprotein metabolism. Mice were fed a lipid-poor standard diet and a diet enriched in cholesterol and saturated fat. The results obtained showed that there are no miRNAs whose expression constantly vary with dietary or genetic changes. Furthermore, it appears that diet, more than genotype, impacts on organ-specific miRNA expression profiles.

Effects of epigallocatechin gallate, caffeine, and their combination on fat accumulation in high-glucose diet-fed Caenorhabditis elegans

Epigallocatechin gallate (EGCG) and caffeine are inevitable to be ingested together in the process of drinking green tea. This study used Caenorhabditis elegans as an organism model to examine whether the binding of EGCG and caffeine could influence the fat-reduction effect. The results revealed that EGCG significantly reduced the Nile Red fluorescence intensity and the triglyceride/protein ratio of the C. elegans obesity model by 14.7% and 16.5%, respectively, while the effect of caffeine was not significant. Moreover, the degree of reduction in fluorescence intensity and triglyceride/protein ratio by EGCG + caffeine was comparable to that of EGCG. In the exploration of underlying mechanism, we found that EGCG and EGCG + caffeine treatments had no influence on food intake and energy expenditure of C. elegans. Their fat-reduction effects were dependent on the regulation of lipogenesis, as shown by the decreased expression of the sbp-1, fat-7, and daf-16 genes.

Oxygen-induced pathological angiogenesis promotes intense lipid synthesis and remodeling in the retina

The retina is a notable tissue with high metabolic needs which relies on specialized vascular networks to protect the neural retina while maintaining constant supplies of oxygen, nutrients, and dietary essential fatty acids. Here we analyzed the lipidome of the mouse retina under healthy and pathological angiogenesis using the oxygen-induced retinopathy model. By matching lipid profiles to changes in mRNA transcriptome, we identified a lipid signature showing that pathological angiogenesis leads to intense lipid remodeling favoring pathways for neutral lipid synthesis, cholesterol import/export, and lipid droplet formation. Noteworthy, it also shows profound changes in pathways for long-chain fatty acid production, vital for retina homeostasis. The net result is accumulation of large quantities of mead acid, a marker of essential fatty acid deficiency, and a potential marker for retinopathy severity. Thus, our lipid signature might contribute to better understand diseases of the retina that lead to vision impairment or blindness.

Dynamic chromatin architecture of the porcine adipose tissues with weight gain and loss

Using an adult female miniature pig model with diet-induced weight gain/weight loss, we investigated the regulatory mechanisms of three-dimensional (3D) genome architecture in adipose tissues (ATs) associated with obesity. We generated 249 high-resolution in situ Hi-C chromatin contact maps of subcutaneous AT and three visceral ATs, analyzing transcriptomic and chromatin architectural changes under different nutritional treatments. We find that chromatin architecture remodeling underpins transcriptomic divergence in ATs, potentially linked to metabolic risks in obesity development. Analysis of chromatin architecture among subcutaneous ATs of different mammals suggests the presence of transcriptional regulatory divergence that could explain phenotypic, physiological, and functional differences in ATs. Regulatory element conservation analysis in pigs and humans reveals similarities in the regulatory circuitry of genes responsible for the obesity phenotype and identified non-conserved elements in species-specific gene sets that underpin AT specialization. This work provides a data-rich tool for discovering obesity-related regulatory elements in humans and pigs.

Lipidomic Analysis of Hand Skin Surface Lipids Reveals Smoking-Related Skin Changes

Smoking contributes to the formation of skin wrinkles and reduces skin function, but the mechanism is not yet fully proven. This study aims to compare and analyze the effects of smoking on skin lipids and to further investigate the harmful effects of smoking on the skin. A total of 40 subjects (20 male smokers and 20 healthy control males) were recruited for this study. Measurement of hand skin-surface lipids (SSLs) in smoking and healthy control groups was undertaken using ultra-performance liquid chromatography quadrupole time-of-flight mass spectrometry (UPLC-Q-TOF-MS). Multivariate data analysis was used to investigate the differences in SSLs between the two groups. There were 1230 lipids detected in the two groups and significant differences in SSLs' composition were observed between them. Under selected conditions, 26 types of lipid with significant differences were observed between the two groups (p < 0.05). Sphingolipids (SP) and glycerolipids (GL) were significantly increased, and sterol lipids (ST) were significantly reduced. Smoking causes changes in skin lipids that disrupt skin homeostasis, making the skin more fragile and more susceptible to skin aging and diseases.

Insulin-induced gene 2 expression is associated with cervical adenocarcinoma malignant behavior

BACKGROUND

The incidence of cervical adenocarcinoma (CA) as a malignant tumor has increased over the past few decades due to its low detection rate and malignant biological behaviors. Insulin-induced gene 2 (INSIG2), a membrane protein of the endoplasmic reticulum (ER), plays a crucial role in cancer progression. However, there is little known about the connection between INSIG2 and CA.

METHODS

The Human Protein Atlas (HPA) and the Cancer Genome Atlas (TCGA) Cervical Cancer (CESC) data were applied to study the alteration in INSIG2 expression. Biological functions were performed to test the change of malignant behavior. Bioinformatics analysis was conducted to explore the potential affection of INSIG2 in CA progression.

RESULTS

Our study confirmed that the high INSIG2 expression levels had a poor prognosis. INSIG2-knockdown inhibited the CA cell proliferation, migration, and invasion of CA cells while downregulating the epithelial-mesenchymal transition (EMT)-associated gene expression levels. Moreover, the enrichment analysis of DEGs showed more potential functions of INSIG2 in the CA progression.

CONCLUSION

We found that INSIG2 knockdown may play a suppressor role in the CA progression, and may provide the potential functional influence in inhibiting of CA development.

Application of Caenorhabditis elegans in Lipid Metabolism Research

Over the last decade, the development and prevalence of obesity have posed a serious public health risk, which has prompted studies on the regulation of adiposity. With the ease of genetic manipulation, the diversity of the methods for characterizing body fat levels, and the observability of feeding behavior, Caenorhabditis elegans (C. elegans) is considered an excellent model for exploring energy homeostasis and the regulation of the cellular fat storage. In addition, the homology with mammals in the genes related to the lipid metabolism allows many aspects of lipid modulation by the regulators of the central nervous system to be conserved in this ideal model organism. In recent years, as the complex network of genes that maintain an energy balance has been gradually expanded and refined, the regulatory mechanisms of lipid storage have become clearer. Furthermore, the development of methods and devices to assess the lipid levels has become a powerful tool for studies in lipid droplet biology and the regulation of the nematode lipid metabolism. Herein, based on the rapid progress of C. elegans lipid metabolism-related studies, this review outlined the lipid metabolic processes, the major signaling pathways of fat storage regulation, and the primary experimental methods to assess the lipid content in nematodes. Therefore, this model system holds great promise for facilitating the understanding, management, and therapies of human obesity and other metabolism-related diseases.

Effects of Six Weeks of Hypoxia Exposure on Hepatic Fatty Acid Metabolism in ApoE Knockout Mice Fed a High-Fat Diet

Nonalcoholic fatty liver disease (NAFLD) is the most common liver disease with a characteristic of abnormal lipid metabolism. In the present study, we employed apolipoprotein E knockout (ApoE KO) mice to investigate the effects of hypoxia exposure on hepatic fatty acid metabolism and to test whether a high-fat diet (HFD) would suppress the beneficial effect caused by hypoxia treatment. ApoE KO mice were fed a HFD for 12 weeks, and then were forwarded into a six-week experiment with four groups: HFD + normoxia, normal diet (ND) + normoxia, HFD + hypoxia exposure (HE), and ND + HE. The C57BL/6J wild type (WT) mice were fed a ND for 18 weeks as the baseline control. The hypoxia exposure was performed in daytime with normobaric hypoxia (11.2% oxygen, 1 h per time, three times per week). Body weight, food and energy intake, plasma lipid profiles, hepatic lipid contents, plasma alanine aminotransferase (ALT) and aspartate aminotransferase (AST), and molecular/biochemical makers and regulators of the fatty acid synthesis and oxidation in the liver were measured at the end of interventions. Six weeks of hypoxia exposure decreased plasma triglycerides (TG), total cholesterol (TC), and low-density lipoprotein cholesterol (LDL-C) contents but did not change hepatic TG and non-esterified fatty acid (NEFA) levels in ApoE KO mice fed a HFD or ND. Furthermore, hypoxia exposure decreased the mRNA expression of Fasn, Scd1, and Srebp-1c significantly in the HFD + HE group compared with those in the HFD + normoxia group; after replacing a HFD with a ND, hypoxia treatment achieved more significant changes in the measured variables. In addition, the protein expression of HIF-1α was increased only in the ND + HE group but not in the HFD + HE group. Even though hypoxia exposure did not affect hepatic TG and NEFA levels, at the genetic level, the intervention had significant effects on hepatic metabolic indices of fatty acid synthesis, especially in the ND + HE group, while HFD suppressed the beneficial effect of hypoxia on hepatic lipid metabolism in male ApoE KO mice. The dietary intervention of shifting HFD to ND could be more effective in reducing hepatic lipid accumulation than hypoxia intervention.

Lipidomic analysis reveals the effect of passive smoking on facial skin surface lipid in females

BACKGROUND

Smoking has toxic effects on the skin and can damage it. However, few studies have focused on the lipid profile changes of facial skin surface lipids (SSL) by passive smoking.

METHOD

A cross-sectional analytical study was conducted on middle-aged females volunteered from Henan, China to participate in the study. A total of 20 passive smoking females and 20 non-passive smoking females were recruited for this study. The components of skin surface lipids were measured by ultra-performance liquid chromatography quadrupole time of flight mass spectrometry (UPLC-QTOF-MS). Multivariate data analysis and enrichment analysis were used to investigate the differences in facial SSL between passive and non-passive smoking females.

RESULT

There were 1247 lipid entities identified in facial SSL between passive and non-passive smoking females. Significant differences in composition of facial SSL were observed between the two groups. After multivariate data analysis suggested, 28 significantly different lipids were identified and classified into four classes in SSL of the female cheeks. As well as 32 significantly different lipids were obtained in SSL of the female foreheads, which included three classes of lipids. Subsequent analysis revealed that the content of fatty acids (FA) in passive smoking females was significantly reduced and the content of glycerolipids (GL) and sphingolipids (SP) increased, compared with the control group.

CONCLUSION

These results indicated that an increase in GLs and SPs of facial lipids and a decrease in FAs in passive smoking females. These changes in lipids might be associated with oxidative stress and interference with signaling pathways by substances in smoke. And passive smoking affected facial SSL and changed the content and metabolism of skin lipids.

Reducing VEGFB accelerates NAFLD and insulin resistance in mice via inhibiting AMPK signaling pathway

Objective

Vascular endothelial growth factor B (VEGFB) was regarded to improve lipid metabolism and reduce obesity-related hyperlipidemia. Whether VEGFB participates in lipid metabolism in nonalcoholic fatty liver disease (NAFLD) has not been clear yet. This study investigated the involvement of VEGFB in lipid metabolism and insulin resistance via the AMPK signaling pathway in NAFLD.

Methods

We constructed the animal and cell model of NAFLD after VEGFB gene knockout to detect liver damage and metabolism in NAFLD. Bioinformatics analysis of VEGFB and the AMPK signaling pathway relative genes to verify the differential proteins. And mRNA levels of NAFLD fatty acid metabolism-related genes were detected.

Results

After the systemic VEGFB knockout mice were fed with high fat, the body fat, serum lipoprotein, NAFLD score, and insulin resistance were increased. Animal and cell experiments showed that the expression levels of phosphorylated proteins of CaMKK2 and AMPK decreased, the expression of proteins related to AMPK/ACC/CPT1 signaling pathway decreased, and the target genes CPT1α and Lcad decreased accordingly, reducing fatty acid oxidation in hepatocyte mitochondria; The expression of AMPK/SREBP1/Scd1 signaling pathway relative proteins increased, ACC1 and FAS increased correspondingly, which increased lipid synthesis in the endoplasmic reticulum.

Conclusion

VEGFB can participate in lipid metabolism and insulin resistance of NAFLD through the AMPK signaling pathway.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12967-022-03540-2.

Sterol carrier protein 2 in lipid metabolism and non-alcoholic fatty liver disease: Pathophysiology, molecular biology, and potential clinical implications

Non-alcoholic fatty liver disease (NAFLD) is considered as the most common chronic liver disease and has become a rapidly global public health problem. Sterol carrier protein 2 (SCP-2), also called non-specific lipid-transfer protein, is predominantly expressed by the liver. SCP-2 plays a key role in intracellular lipid transport and metabolism. SCP-2 has been closely implicated in the development of NAFLD-related metabolic disorders, such as obesity, atherosclerosis, Type 2 diabetes mellitus (T2DM), and gallstones. Recent studies indicate that SCP-2 plays a beneficial role in NAFLD by regulating cholesterol-, endocannabinoid-, and fatty acid-related aspects of lipid metabolism. Hence, in this paper, we summarize the latest findings about the roles of SCP-2 in hepatic steatosis and further describe its molecular function in the pathogenesis of NAFLD.

Dietary fibers with different viscosity regulate lipid metabolism via ampk pathway: roles of gut microbiota and short-chain fatty acid

Dietary fiber (DF) improves gastrointestinal health and has important associations with the alleviation of intestinal diseases and metabolic syndrome. However, due to DFs complex characteristics, such as solubility, viscosity, and fermentability, the mechanism in these was not consistent. As an herbivore, the goose has a prominent digestive ability to DF.

Therefore, we choose low, medium, and high viscosity DFs (respectively resistant starch-3 []RS], inulin [INU], and β–glucan [GLU]) as Magang goose diet treatment for 4 wk, to investigate the effect and potential mechanism of different viscosities DFs on the growth and development process of goose.

In summary, three degrees of viscous DFs could decrease the mechanismic lipid level of geese by promoting acid-producing bacteria and short-chain fatty acid (SCFA) production, therefore, activating AMPK pathway-related genes through the gut-liver axis. High viscous DF has a greater lipid-lowering effect on geese, while medium viscous DF has preferable intestinal mucosal protection.

A mutation in transmembrane protein 135 impairs lipid metabolism in mouse eyecups

Aging is a significant factor in the development of age-related diseases but how aging disrupts cellular homeostasis to cause age-related retinal disease is unknown. Here, we further our studies on transmembrane protein 135 (Tmem135), a gene involved in retinal aging, by examining the transcriptomic profiles of wild-type, heterozygous and homozygous Tmem135 mutant posterior eyecup samples through RNA sequencing (RNA-Seq). We found significant gene expression changes in both heterozygous and homozygous Tmem135 mutant mouse eyecups that correlate with visual function deficits. Further analysis revealed that expression of many genes involved in lipid metabolism are changed due to the Tmem135 mutation. Consistent with these changes, we found increased lipid accumulation in mutant Tmem135 eyecup samples. Since mutant Tmem135 mice have similar ocular pathologies as human age-related macular degeneration (AMD) eyes, we compared our homozygous Tmem135 mutant eyecup RNA-Seq dataset with transcriptomic datasets of human AMD donor eyes. We found similar changes in genes involved in lipid metabolism between the homozygous Tmem135 mutant eyecups and AMD donor eyes. Our study suggests that the Tmem135 mutation affects lipid metabolism as similarly observed in human AMD eyes, thus Tmem135 mutant mice can serve as a good model for the role of dysregulated lipid metabolism in AMD.

Pathophysiological Integration of Metabolic Reprogramming in Breast Cancer

Simple Summary

Tumors exhibit metabolic changes that differentiate them from the normal tissues from which they derive. These metabolic changes favor tumor growth, are primarily induced by cancer cells, and produce metabolic and functional changes in the surrounding stromal cells. There is a close functional connection between the metabolic changes in tumor cells and those that appear in the surrounding stroma. A better understanding of intratumoral metabolic interactions may help identify new vulnerabilities that will facilitate new, more individualized treatment strategies against cancer. We review the metabolic changes described in tumor and stromal cells and their functional changes and then consider, in depth, the metabolic interactions between the cells of the two compartments. Although these changes are generic, we illustrate them mainly with reference to examples in breast cancer.

Abstract

Metabolic changes that facilitate tumor growth are one of the hallmarks of cancer. The triggers of these metabolic changes are located in the tumor parenchymal cells, where oncogenic mutations induce an imperative need to proliferate and cause tumor initiation and progression. Cancer cells undergo significant metabolic reorganization during disease progression that is tailored to their energy demands and fluctuating environmental conditions. Oxidative stress plays an essential role as a trigger under such conditions. These metabolic changes are the consequence of the interaction between tumor cells and stromal myofibroblasts. The metabolic changes in tumor cells include protein anabolism and the synthesis of cell membranes and nucleic acids, which all facilitate cell proliferation. They are linked to catabolism and autophagy in stromal myofibroblasts, causing the release of nutrients for the cells of the tumor parenchyma. Metabolic changes lead to an interstitium deficient in nutrients, such as glucose and amino acids, and acidification by lactic acid. Together with hypoxia, they produce functional changes in other cells of the tumor stroma, such as many immune subpopulations and endothelial cells, which lead to tumor growth. Thus, immune cells favor tissue growth through changes in immunosuppression. This review considers some of the metabolic changes described in breast cancer.

Targeting Lipid Metabolism for the Treatment of Age-Related Macular Degeneration: Insights from Preclinical Mouse Models

Age-related macular degeneration (AMD) is a major leading cause of irreversible visual impairment in the world with limited therapeutic interventions. Histological, biochemical, genetic, and epidemiological studies strongly implicate dysregulated lipid metabolism in the retinal pigmented epithelium (RPE) in AMD pathobiology. However, effective therapies targeting lipid metabolism still need to be identified and developed for this blinding disease. To test lipid metabolism-targeting therapies, preclinical AMD mouse models are needed to establish therapeutic efficacy and the role of lipid metabolism in the development of AMD-like pathology. In this review, we provide a comprehensive overview of current AMD mouse models available to researchers that could be used to provide preclinical evidence supporting therapies targeting lipid metabolism for AMD. Based on previous studies of AMD mouse models, we discuss strategies to modulate lipid metabolism as well as examples of studies evaluating lipid-targeting therapeutics to restore lipid processing in the RPE. The use of AMD mouse models may lead to worthy lipid-targeting candidate therapies for clinical trials to prevent the blindness caused by AMD.

Hypoglycemic mechanism of intestinal bypass surgery in type 2 diabetic rats

To investigate the effect of duodenal-jejunal bypass (DJB) surgery on postoperative blood glucose in type 2 diabetic rats, and further explore possible mechanisms for the effect of surgical treatment of type 2 diabetes. Forty rats with type 2 diabetes were randomly assigned to 4 groups (n = 10 rats per group), which subsequently underwent DJB, new biliopancreatic diversion (NBPD) or duodenal-jejunal exclusion (DJE) surgery or a sham operation (SHAM). Fasting glucose, 2-h postprandial glucose and blood lipids were measured, and the mRNA in liver and intestinal tissue for bile acid receptor (FXR), as well as the FXR protein expression in the liver tissues were determined. Postprandial blood glucose and fasting TG and FFA in the DJB and NBPD groups were significantly lower than those in the SHAM group and preoperative (p < 0.05) at 8 weeks postoperation. Liver FXR protein was expressed at significantly higher in the DJB and NBPD groups than in the other two (p < 0.05), and the intestinal FXR mRNA in the DJE group were highest. DJB up-regulates the expression of bile acid receptors in the liver and down-regulates those receptors in the intestinal tract via biliopancreatic diversion. This process reduces TG levels, and subsequently any lipotoxicity to islet cells to produce a hypoglycemic effect.

Policosanol alleviates hepatic lipid accumulation by regulating bile acids metabolism in C57BL6/mice through AMPK-FXR-TGR5 cross-talk

Policosanol exhibits a lipid accumulation alleviating effect, but the underlying mechanisms remains unclear. Bile acids are a significant factor in regulating cholesterol and lipid metabolism homeostasis in mammals. This study was aimed to elucidate the alleviating effect and underlying mechanisms of policosanol on hepatic lipid accumulation through bile acid (BA) metabolism. Policosanol supplementation significantly reduced hepatic triglycerides (19.29%), cholesterol (30.38%) in high fat diet (HFD) induced obese mice (P < 0.05). Furthermore, compared with the control group, HFD decreased the levels of total BAs (TBAs, 37.67%) and cholic acid (CA, 62.74%) in the serum of mice (P < 0.05). Meanwhile, compared to HFD group, policosanol also increased the level of secondary BAs (SBAs) and muricholic acids (MCAs, P < 0.05). qRT-PCR combined with protein level analysis revealed that policosanol significantly decreased sterol regulatory element-binding protein (SREBP-1c) and CD36, and increased the expression level of cytochrome P450 family 7 subfamily A member 1 (CYP7A1) and cytochrome P450 Family 27 Subfamily A Member 1 (CYP27A1, P < 0.05). Additionally, in the liver, policosanol was found downregulated the expression of farnesoid X receptor (FXR)-small heterodimer partner (SHP), and activate the Takeda G-coupled protein receptor 5 (TGR5)-adenosine-monophosphate-activated protein kinase (APMK) signaling pathway (P < 0.05). Peroxisome proliferator activated receptor (PPAR)-α, hormone sensitive lipase (HSL), and carnitine palmitoyltransferase (CPT)-1α also significantly increased in HP group (P < 0.05). The aforementioned results reveal that the potential mechanism of policosanol in alleviating liver lipid accumulation is to promote BA synthesis and lipolysis through regulating the cross-talk of the AMPK-FXR-TGR5. New insight for the application of policosanol as an anti-fatty liver functional food ingredient or supplement is also provided. PRACTICAL APPLICATION: Policosanol is an important active component of cereals and insect waxes (15-80%). However, almost no policosanol in refined foods such as clear corn germ oil and wheat flour. This study showed that oral administration of policosanol can significantly reduce triglyceride and cholesterol levels in the liver through affecting AMPK-TGR5-FXR cross-talk, whereas no significant toxicological effect is reported in human and mouse models. This study may provide theoretical support for the theory of dietary structure and the development of dietary supplements to improve lipid metabolism targeting the "bile acid-AMPK-TGR5" pathway.

Lily bulbs' polyphenols extract ameliorates oxidative stress and lipid accumulation in vitro and in vivo

BACKGROUND

Polyphenols have the potential to reduce the risk of many metabolic disorders. Lily bulbs are rich in polyphenols; however, their effects on lipid metabolism remain unclear. This study aimed to explore the effects of lily bulbs' polyphenols (LBPs) on oxidative stress and lipid metabolism.

RESULTS

A total of 14 polyphenolic compounds in LBPs were identified by high-performance liquid chromatography equipped with diode-array detection mass spectrometry. Total phenolic compound in LBPs was 53.76 ± 1.12 g kg^-1 dry weight. In cellular experiments, LBPs attenuated the disruption of mitochondrial membrane potential, impeded reactive oxygen species production, alleviated oxidative stress, and reduced lipid accumulation in oleic acid induced HepG2 cells. In in vivo studies, LBPs significantly inhibited body weight gain, reduced lipid levels in serum and liver, and improved oxidative damage in a dose-dependent manner in mice fed a high-fat diet. Moreover, LBPs ameliorated hepatic steatosis and suppressed the expression of hepatic-lipogenesis-related genes (SREBP-1c, FAS, ACC1, and SCD-1) and promoted lipolysis genes (SRB1 and HL) and lipid oxidation genes (PPARα and CPT-1) in mice fed a high-fat diet.

CONCLUSION

It was concluded that LBPs are a potential complementary therapeutic alternative in the development of functional foods to curb obesity and obesity-related diseases, such as metabolic syndrome. © 2021 Society of Chemical Industry.

Lipocalin-type Prostaglandin D2 Synthase appears to function as a Novel Adipokine Preventing Adipose Dysfunction in response to a High Fat Diet

Adipose dysfunction is the primary defect in obesity that contributes to the development of dyslipidemia, insulin resistance, cardiovascular diseases, type 2 diabetes, non-alcoholic fatty liver disease (NAFLD) and some cancers. Previously, we demonstrated the development of NAFLD in lipocalin-type prostaglandin D₂ synthase (L-PGDS) knockout mice regardless of diet. In the present study, we examined the role of L-PGDS in adipose in response to a high fat diet. We observed decreased expression of L-PGDS in adipose tissue and concomitant lower plasma levels in a dietary model of obesity as well as in insulin resistant 3T3-L1 adipocytes. We show reduced adiponectin expression and phosphorylation of AMPK in white adipose tissue of L-PGDS KO mice after 14 weeks on a high fat diet as compared to control C57BL/6 mice. We also observe an increased fat content in L-PGDS KO mice as demonstrated by adipocyte hypertrophy and increased expression of lipogenenic genes. We confirmed our in vivo findings in in vitro 3T3-L1 adipocytes, using an enzymatic inhibitor of L-PGDS (AT56). Rosiglitazone treatment drastically increased L-PGDS expression in insulin resistant 3T3-L1 adipocytes and increased adiponectin expression and AMPK phosphorylation in AT56 treated 3T3-L1 adipocytes. We conclude that the absence of L-PGDS has a deleterious effect on adipose tissue functioning, which further reduces insulin sensitivity in adipose tissue. Consequently, we propose L-PGDS appears to function as a potential member of the adipokine secretome involved in the regulation of the obesity-associated metabolic syndrome.

Intestinal Transcriptome Analysis Reveals Enrichment of Genes Associated with Immune and Lipid Mechanisms, Favoring Soybean Meal Tolerance in High-Growth Zebrafish (Danio Rerio)

The molecular mechanisms underlying fish tolerance to soybean meal (SBM) remain unclear. Identifying these mechanisms would be beneficial, as this trait favors growth. Two fish replicates from 19 experimental families were fed fishmeal-(100FM) or SBM-based diets supplemented with saponin (50SBM + 2SPN) from juvenile to adult stages. Individuals were selected from families with a genotype-by-environment interaction higher (HG-50SBM + 2SPN, 170 ± 18 mg) or lower (LG-50SBM + 2SPN, 76 ± 10 mg) weight gain on 50SBM + 2SPN for intestinal transcriptomic analysis. A histological evaluation confirmed middle intestinal inflammation in the LG- vs. HG-50SBM + 2SPN group. Enrichment analysis of 665 differentially expressed genes (DEGs) identified pathways associated with immunity and lipid metabolism. Genes linked to intestinal immunity were downregulated in HG fish (mpx, cxcr3.2, cftr, irg1l, itln2, sgk1, nup61l, il22), likely dampening inflammatory responses. Conversely, genes involved in retinol signaling were upregulated (rbp4, stra6, nr2f5), potentially favoring growth by suppressing insulin responses. Genes associated with lipid metabolism were upregulated, including key components of the SREBP (mbtps1, elov5l, elov6l) and cholesterol catabolism (cyp46a1), as well as the downregulation of cyp7a1. These results strongly suggest that transcriptomic changes in lipid metabolism mediate SBM tolerance. Genotypic variations in DEGs may become biomarkers for improving early selection of fish tolerant to SMB or others plant-based diets.

Feprazone Displays Antiadipogenesis and Antiobesity Capacities in in Vitro 3 T3-L1 Cells and in Vivo Mice

BACKGROUND AND PURPOSE

Excessive lipid accumulation in adipose tissues and deregulation of adipogenesis-induced obesity affect millions of people worldwide. Feprazone, a nonsteroidal anti-inflammatory drug, has a wide clinical use. However, it is unknown whether Feprazone possesses an antiadipogenic ability. The aim of this study is to investigate whether Feprazone possesses an antiadipogenic ability in 3 T3-L1 cells and an antiobesity capacity in mouse models.

METHODS

An MTT assay was used to determine the optimized incubation concentrations of Feprazone in 3 T3-L1 cells. The lipid accumulation was evaluated using Oil Red O staining. The concentrations of triglyceride and glycerol release were detected to check the lipolysis during 3 T3-L1 adipogenesis. A quantitative real-time polymerase chain reaction (qRT-PCR) was used to determine the expressions of sterol regulatory element-binding protein-1C (SREBP-1C) and fatty acid binding protein 4 (FABP4) in treated cells. The expressions of peroxisome proliferator-activated receptor-γ (PPAR-γ), CCAAT/enhancer-binding protein α (C/EBP-α), adipose triglyceride lipase (ATGL), and aquaporin-7 (AQP-7) were detected using qRT-PCR and Western blot analysis. After the high-fat diet (HFD) mice were treated with Feprazone, the pathological state of adipocyte tissues was evaluated using HE staining. The adipocyte size, visceral adipocyte tissue weight, and bodyweights were recorded.

RESULTS

According to the proliferation result, 30 and 60 μM Feprazone were used as the optimized concentrations of Feprazone. In the in vitro study, lipid accumulation, elevated production of triglycerides, the release of glycerol, upregulated SREBP-1C, FABP4, PPAR-γ, and C/EBP-α and downregulated ATGL and AQP-7 in the 3 T3-L1 adipocytes induced by the adipocyte differentiation cocktail medium were significantly reversed by treatment with Feprazone. In the in vivo experiment, we found that the increased adipocyte size, visceral adipocyte tissue weight, and body weights induced by HFD feeding in mice were significantly suppressed by the administration of Feprazone.

CONCLUSION

Feprazone might display anti-adipogenic and antiobesity capacities in in vitro 3 T3-L1 cells and in vivo mice.

Prenatal dexamethasone exposure induces nonalcoholic fatty liver disease in male rat offspring via the miR-122/YY1/ACE2-MAS1 pathway

Epidemiological studies have shown that nonalcoholic fatty liver disease (NAFLD) has an intrauterine developmental origin. We aimed to demonstrate that NAFLD is caused by prenatal dexamethasone exposure (PDE) in adult male rat offspring and to investigate the intrauterine programming mechanism. Liver samples were obtained on gestational day (GD) 21 and postnatal week (PW) 28. The effects and epigenetic mechanism of dexamethasone were studied with bone marrow mesenchymal stem cells (BMSCs) hepatoid differentiated cells and other cell models. In the PDE group, lipid accumulation increased, triglyceride synthesis-related gene expression increased, and oxidation-related gene expression decreased in livers of adult male rat offspring. In utero, hepatic triglyceride synthesis increased and oxidative function decreased in PDE fetal male rats. Moreover, low hepatic miR-122 expression, high Yin Yang-1 (YY1) expression and angiotensin-converting enzyme 2 (ACE2)-Mas receptor (MAS1) signaling pathway inhibition were observed before and after birth. At the cellular level, dexamethasone (100-2500 nM) elevated the intracellular triglyceride content, increased triglyceride synthesis-related gene expression and decreased oxidation-related gene expression. Dexamethasone treatment also decreased miR-122 expression, increased YY1 expression and inhibited the ACE2-MAS1 signaling pathway. Interference or overexpression of glucocorticoid receptor (GR), miR-122, YY1 and ACE2 could reverse the changes in downstream gene expression. In summary, PDE could induce NAFLD in adult male rat offspring. The programming mechanism included inhibition of miR-122 expression after GR activation, and dexamethasone increased hepatocyte YY1 expression; these effects resulted in ACE2-MAS1 signaling pathway inhibition, which led to increased hepatic triglyceride synthesis and decreased oxidative function. The increased triglyceride synthesis and decreased oxidative function of hepatocytes caused by low miR-122 expression due to dexamethasone could continue postnatally, eventually leading to NAFLD in adult rat offspring.

The Metabolic Mechanisms of Breast Cancer Metastasis

Breast cancer is one of the most common malignancy among women worldwide. Metastasis is mainly responsible for treatment failure and is the cause of most breast cancer deaths. The role of metabolism in the progression and metastasis of breast cancer is gradually being emphasized. However, the regulatory mechanisms that conduce to cancer metastasis by metabolic reprogramming in breast cancer have not been expounded. Breast cancer cells exhibit different metabolic phenotypes depending on their molecular subtypes and metastatic sites. Both intrinsic factors, such as MYC amplification, PIK3CA, and TP53 mutations, and extrinsic factors, such as hypoxia, oxidative stress, and acidosis, contribute to different metabolic reprogramming phenotypes in metastatic breast cancers. Understanding the metabolic mechanisms underlying breast cancer metastasis will provide important clues to develop novel therapeutic approaches for treatment of metastatic breast cancer.

Physicochemical Properties and Effects of Honeys on Key Biomarkers of Oxidative Stress and Cholesterol Homeostasis in HepG2 Cells

Manuka honey and newly developed honeys (arjuna, guggul, jiaogulan and olive) were examined for their physicochemical, biochemical properties and effects on oxidative stress and cholesterol homeostasis in fatty acid-induced HepG2 cells. The honeys exhibited standard moisture content (<20%), electrical conductivity (<0.8 mS/cm), acidic pH, and monosaccharides (>60%), except olive honey (<60% total monosaccharides). They all expressed non-Newtonian behavior and 05 typical regions of the FTIR spectra as those of natural ones. Guggul and arjuna, manuka honeys showed the highest phenolic contents, correlating with their significant antioxidant activities. Arjuna, guggul and manuka honeys demonstrated the agreement of total cholesterol reduction and the transcriptional levels of AMPK, SREBP2, HCMGR, LDLR, LXRα. Jiaogulan honey showed the least antioxidant content and activity, but it was the most cytotoxic. Both jiaogulan and olive honeys modulated the tested gene in the pattern that should lead to a lower TC content, but this reduction did not occur after 24 h. All 2% concentrations of tested honeys elicited a clearer effect on NQO1 gene expression. In conclusion, the new honeys complied with international norms for natural honeys and we provide partial evidence for the protective effects of manuka, arjuna and guggul honeys amongst the tested ones on key biomarkers of oxidative stress and cholesterol homeostasis, pending further studies to better understand their modes of action.

Why Hepatic CYP2E1-Elevation by Itself Is Insufficient for Inciting NAFLD/NASH: Inferences from Two Genetic Knockout Mouse Models

Hepatic cytochrome P450 CYP2E1 is an enzyme engaged in the metabolic biotransformation of various xenobiotics and endobiotics, resulting in both detoxification and/or metabolic activation of its substrates to more therapeutic or toxic products. Elevated hepatic CYP2E1 content is implicated in various metabolic diseases including alcoholic liver disease, nonalcoholic fatty liver disease (NAFLD)/nonalcoholic steatohepatitis (NASH), diabetes and obesity. While hepatic CYP2E1 elevation is considered essential to the pathogenesis of these liver diseases, our findings in two mouse models of E3 ubiquitin ligase genetic ablation fed a regular lab chow diet, argue that it is not sufficient for triggering NAFLD/NASH. Thus, albeit comparable hepatic CYP2E1 elevation and functional stabilization in these two models upon E3 ubiquitin ligase genetic ablation and consequent disruption of its ubiquitin-dependent proteasomal degradation, NAFLD/NASH was only observed in the mouse livers that exhibited concurrent SREBP1c-transcriptional upregulation of hepatic lipogenesis. These findings reinforce the critical complicity of an associated prolipogenic scenario induced by either an inherently upregulated hepatic lipogenesis or a high fat/high carbohydrate diet in CYP2E1-mediated NAFLD/NASH.

FoxO1 Knockdown Promotes Fatty Acid Synthesis via Modulating SREBP1 Activities in the Dairy Goat Mammary Epithelial Cells

FoxO1 is a crucial transcription factor involved in lipid metabolism in mouse liver through repressing a key regulator of lipogenesis, sterol regulatory element binding protein 1 (SREBP1). However, it remains elusive whether FoxO1 plays roles in the regulation of fatty acid metabolism during lactation in dairy goats. In this study, we aim to investigate the function of FoxO1 in goat mammary epithelial cells (GMECs). We found that the expression of FoxO1 is significantly upregulated during lactation compared with the dry period. FoxO1 knockdown enhanced the expression of genes related to de novo fatty acid synthesis (e.g., FASN, ELOVL6 and SCD1) and triacylglycerol (TAG) synthesis (e.g., DGAT2 and GPAM). Consistently, intracellular TAG was significantly increased in FoxO1 knockdown cells and reduced in FoxO1 overexpression cells. Immunofluorescence staining revealed that insulin suppresses FoxO1 transcription by promoting its nuclear export. Further, we found that FoxO1 inhibits insulin-induced SREBP1 promoter activities in GMECs. Moreover, FoxO1 suppresses SREBP1 transcription via the LXR response element (LXRE) and SREBP response element (SRE) located in the SREBP1 promoter. Our data reveal that FoxO1 plays critical roles in regulating the synthesis of the fatty acid and triacylglycerol (TAG) in GMECs.

Phospholipase Cε Regulates Prostate Cancer Lipid Metabolism and Proliferation by Targeting AMP-Activated Protein Kinase (AMPK)/Sterol Regulatory Element-Binding Protein 1 (SREBP-1) Signaling Pathway

BACKGROUND Metabolic reprogramming is a common characteristic of numerous kinds of tumors, including prostate cancer (PCa). Tumor metabolism such as lipid metabolism provides sufficient lipids for tumor cell division and rapid growing as well as a vital source for formation of new cellular membranes. Phospholipase Cε (PLCε) is an oncogene that can drive proliferation, progression, and lipid metabolism of tumors, but its effect in lipid metabolism of PCa is not clear. MATERIAL AND METHODS Benign prostatic hyperplasia (BPH) and PCa tissue specimens were assessed for SREBP-1, FASN, and PLCε by immunohistochemistry, and PLCε was knocked-down by a lentiviral short hairpin RNA. The mRNA and protein level expression of related factors were tested by qPCR and Western blot analyses. Cell proliferation was assessed by clone formation, CCK-8, and Ki-67 assays. Nile red and oil red O staining were performed to detect endogenous lipid levels. Immunofluorescence was used to localize the protein of SREBP-1. Finally, a tumor xenograft assay of nude mice was performed to assess the role of PLCε in prostate tumor generation. RESULTS We found that overexpression of PLCε indicates low PFS in PCa and is involved in metastasis of PCa, and that the PLCε/AMPK/SREBP-1 signaling network promotes the progression of PCa through lipid metabolism in vivo and in vitro. CONCLUSIONS This study is the first to discover the lethal role of PLCε in lipid metabolism and malignant behavior of PCa, elucidation PCa occurrence and progression.

Dominant gut Prevotella copri in gastrectomised non-obese diabetic Goto-Kakizaki rats improves glucose homeostasis through enhanced FXR signalling

AIMS/HYPOTHESIS

Drug and surgical-based therapies in type 2 diabetes are associated with altered gut microbiota architecture. Here we investigated the role of the gut microbiome in improved glucose homeostasis following bariatric surgery.

METHODS

We carried out gut microbiome analyses in gastrectomised (by vertical sleeve gastrectomy [VSG]) rats of the Goto-Kakizaki (GK) non-obese model of spontaneously occurring type 2 diabetes, followed by physiological studies in the GK rat.

RESULTS

VSG in the GK rat led to permanent improvement of glucose tolerance associated with minor changes in the gut microbiome, mostly characterised by significant enrichment of caecal Prevotella copri. Gut microbiota enrichment with P. copri in GK rats through permissive antibiotic treatment, inoculation of gut microbiota isolated from gastrectomised GK rats, and direct inoculation of P. copri, resulted in significant improvement of glucose tolerance, independent of changes in body weight. Plasma bile acids were increased in GK rats following inoculation with P. copri and P. copri-enriched microbiota from VSG-treated rats; the inoculated GK rats then showed increased liver glycogen and upregulated expression of Fxr (also known as Nr1h4), Srebf1c, Chrebp (also known as Mlxipl) and Il10 and downregulated expression of Cyp7a1.

CONCLUSIONS

Our data underline the impact of intestinal P. copri on improved glucose homeostasis through enhanced bile acid metabolism and farnesoid X receptor (FXR) signalling, which may represent a promising opportunity for novel type 2 diabetes therapeutics.

Lipidomic and biophysical homeostasis of mammalian membranes counteracts dietary lipid perturbations to maintain cellular fitness

Proper membrane physiology requires maintenance of biophysical properties, which must be buffered from external perturbations. While homeostatic adaptation of membrane fluidity to temperature variation is a ubiquitous feature of ectothermic organisms, such responsive membrane adaptation to external inputs has not been directly observed in mammals. Here, we report that challenging mammalian membranes by dietary lipids leads to robust lipidomic remodeling to preserve membrane physical properties. Specifically, exogenous polyunsaturated fatty acids are rapidly incorporated into membrane lipids, inducing a reduction in membrane packing. These effects are rapidly compensated both in culture and in vivo by lipidome-wide remodeling, most notably upregulation of saturated lipids and cholesterol, resulting in recovery of membrane packing and permeability. Abrogation of this response results in cytotoxicity when membrane homeostasis is challenged by dietary lipids. These results reveal an essential mammalian mechanism for membrane homeostasis wherein lipidome remodeling in response to dietary lipid inputs preserves functional membrane phenotypes.

Proper membrane physiology requires maintenance of a narrow range of physicochemical properties, which must be buffered from external perturbations. Here, authors report lipidomic remodeling to preserve membrane physical properties upon exogenous polyunsaturated fatty acids exposure.

Pathophysiologic mechanisms of obesity- and chronic inflammation-related genes in etiology of polycystic ovary syndrome

OBJECTIVES

One of the common heterogeneous reproductive disorders in women of childbearing age is polycystic ovary syndrome (PCOS). It is characterized by lack of fertility due to anovulatory cycles, hyperandrogenemia, polycystic ovaries, hyperinsulinemia, and obesity. Both reproductive anomalies and metabolic disorders are involved in PCOS pathology. Although the role of increased levels of androgens in initiation of PCOS is almost proven, mechanisms of PCOS pathophysiology are not clear. Here we discuss roles of altered metabolic conditions, obesity, and chronic inflammation in PCOS pathophysiology.

MATERIALS AND METHODS

In this review, we attempted to identify genes related to obesity and chronic inflammation aspects of PCOS and their physiological functions to explain the pathways that are regulated by these genes and can be a prominent function in PCOS predisposition. For this purpose, published articles and reviews dealing with genetic evaluation of PCOS in women in peer-reviewed journals in PubMed and Google Scholar databases were included in this review.

RESULTS

Obesity and chronic inflammation are not prominent diagnostic features of PCOS, but they play an important role in exacerbating metabolic and hyperandrogenic states. ADIPOQ, FTO TGFβ, and DENND1A as the main obesity- and chronic inflammation-related genes have roles in PCOS pathophysiology.

CONCLUSION

It seems that genes related to obesity pathology in genomic research association, are related to metabolic aspects and body mass index in PCOS patients. Genomes have roles in chronic inflammation, followed by obesity, in the pathogenesis of PCOS.

Sp1 is Involved in Vertebrate LC-PUFA Biosynthesis by Upregulating the Expression of Liver Desaturase and Elongase Genes

The rabbitfish Siganus canaliculatus was the first marine teleost demonstrated to have the ability for the biosynthesis of long-chain (≥C20) polyunsaturated fatty acids (LC-PUFA) from C18 PUFA precursors, and all the catalytic enzymes including two fatty acyl desaturase 2 (Δ4 Fads2 and Δ6/Δ5 Fads2) and two elongases (Elovl4 and Elovl5) have been identified, providing a good model for studying the regulatory mechanisms of LC-PUFA biosynthesis in fish. Stimulatory protein 1 (Sp1) has been speculated to be a vital transcription factor in determining the promoter activity of Fads-like genes in fish, however its regulatory effects on gene expression and LC-PUFA biosynthesis have not been demonstrated. Bioinformatic analysis predicted potential Sp1 binding sites in the promoters of the rabbitfish Δ6/Δ5 fads2 and elovl5, but not in Δ4 fads2 promoter. Here we cloned full-length cDNA of the rabbitfish sp1 gene, which encoded a putative protein of 701 amino acids, and was expressed in all tissues studied with highest levels in gill and eyes. The dual luciferase reporter assay in HepG2 line cells demonstrated the importance of the Sp1 binding site for the promoter activities of both Δ6/Δ5 fads2 and elovl5. Moreover, the electrophoretic mobility shift assay confirmed the direct interaction of Sp1 with the two promoters. Insertion of the Sp1 binding site of Δ6/Δ5 fads2 promoter into the corresponding region of the Δ4 fads2 promoter significantly increased activity of the latter. In the Siganus canaliculatus hepatocyte line (SCHL) cells, mRNA levels of Δ6/Δ5 fads2 and elovl5 were positively correlated with the expression of sp1 when sp1 was overexpressed or knocked-down by RNAi or antagonist (mithramycin) treatment. Moreover, overexpression of sp1 also led to a higher conversion of 18:2n−6 to 18:3n−6, 18:2n−6 to 20:2n−6, and 18:3n−3 to 20:3n−3, which related to the functions of Δ6/Δ5 Fads2 and Elovl5, respectively. These results indicated that Sp1 is involved in the transcriptional regulation of LC-PUFA biosynthesis by directly targeting Δ6/Δ5 fads2 and elovl5 in rabbitfish, which is the first report of Sp1 involvement in the regulation of LC-PUFA biosynthesis in vertebrates.

Effects of in ovo injection of vitamin C on heat shock protein and metabolic genes expression

Some studies have shown that the excessive metabolic heat production is the primary cause for dead chicken embryos during late embryonic development. Increasing heat shock protein (HSP) expression and adjusting metabolism are important ways to maintain body homeostasis under heat stress. This study was conducted to investigate the effects of in ovo injection (IOI) of vitamin C (VC) at embryonic age 11th day (E11) on HSP and metabolic genes expression. A total of 320 breeder eggs were randomly divided into normal saline and VC injection groups. We detected plasma VC content and rectal temperature at chick's age 1st day, and the mRNA levels of HSP and metabolic genes in embryonic livers at E14, 16 and 18, analysed the promoter methylation levels of differentially expressed genes and predicted transcription factors at the promoter regions. The results showed that IOI of VC significantly increased plasma VC content and decreased rectal temperature (P < 0.05). In ovo injection of VC significantly increased heat shock protein 60 (HSP60) and pyruvate dehydrogenase kinase 4 (PDK4) genes expression at E16 and PDK4 and secreted frizzled related protein 1 (SFRP1) at E18 (P < 0.05). At E16, IOI of VC significantly decreased the methylation levels of total CpG sites and -336 CpG site in HSP60 promoter and -1137 CpG site in PDK4 promoter (P < 0.05). Potential binding sites for nuclear factor-1 were found around -389 and -336 CpG sites in HSP60 promoter and potential binding site for specificity protein 1 was found around -1137 CpG site in PDK4 promoter. Our results suggested that IOI of VC increased HSP60, PDK4 and SFRP1 genes expression at E16 and 18, which may be associated with the demethylation in gene promoters. Whether IOI of VC could improve hatchability needs to be further verified by setting uninjection group.

Postprandial changes in gene expression of cholesterol influx and efflux mediators after intake of SFA compared with n-6 PUFA in subjects with and without familial hypercholesterolaemia: secondary outcomes of a randomised controlled trial

The long-term cholesterol-lowering effect of replacing intake of SFA with PUFA is well established, but has not been fully explained mechanistically. We examined the postprandial response of meals with different fat quality on expression of lipid genes in peripheral blood mononuclear cells (PBMC) in subjects with and without familial hypercholesterolaemia (FH). Thirteen subjects with FH (who had discontinued lipid-lowering treatment ≥4 weeks prior to both test days) and fourteen normolipidaemic controls were included in a randomised controlled double-blind crossover study with two meals, each with 60 g of fat either mainly SFA (about 40% energy) or n-6 PUFA (about 40% energy). PBMC were isolated in fasting, and 4 and 6 h postprandial blood samples. Expression of thirty-three lipid genes was analysed by reverse transcription quantitative PCR. A linear mixed model was used to assess postprandial effects between meals and groups. There was a significant interaction between meal and group for MSR1 (P = 0·03), where intake of SFA compared with n-6 PUFA induced a larger reduction in gene expression in controls only (P = 0·01). Intake of SFA compared with n-6 PUFA induced larger reductions in gene expression levels of LDLR and FADS1/2, smaller increases of INSIG1 and FASN, and larger increases of ABCA1 and ABCG1 (P = 0·01 for all, no group interaction). Intake of SFA compared with n-6 PUFA induced changes in gene expression of cholesterol influx and efflux mediators in PBMC including lower LDLR and higher ABCA1/G1, potentially explaining the long-term cholesterol-raising effect of a high SFA intake.

Mono-2-ethylhexyl phthalate induces the expression of genes involved in fatty acid synthesis in HepG2 cells

Mono-2-ethylhexyl phthalate (MEHP) is a major bioactive metabolite in the widely used industrial plasticizer diethylhexyl phthalate (DEHP) that has been found to be toxic to the liver. The aim of this study is to determine whether MEHP exposure can change the expression of fatty acid metabolism-related genes in HepG2 cells, which might be related to non-alcoholic fatty liver disease (NAFLD). The results revealed that exposure to MEHP promoted lipid accumulation in HepG2 cells. The levels of intracellular triglycerides in the hepatocytes increased after exposure to 0.8-100 μM MEHP for 24 h and 48 h. The genetic expressions of SREBP-1c, ChREBP, ACC1, FASN, and SCD significantly increased at 6 h after exposure to MEHP. At 24 h, the expression of the SREBP-1c and ChREBP genes remained increased, while the expression of the FASN and SCD genes decreased. At 48 h, the expression of SREBP-1c, ChREBP, ACC1, FASN, and SCD decreased. Furthermore, the levels of proteins including ACC1, FASN, SCD, and ChREBP (except SREBP-1c) increased at 24 h. These findings suggest that MEHP exposure can promote fatty acid synthesis in hepatocytes by regulating the expression of relevant genes and proteins, contributing to NAFLD.

Mitochondrial fusion regulates lipid homeostasis and stem cell maintenance in the Drosophila testis

The capacity of stem cells to self-renew or differentiate has been attributed to distinct metabolic states. A genetic screen targeting regulators of mitochondrial dynamics revealed that mitochondrial fusion is required for the maintenance of male germline stem cells (GSCs) in Drosophila melanogaster. Depletion of Mitofusin (dMfn) or Opa1 led to dysfunctional mitochondria, activation of Target of rapamycin (TOR) and a marked accumulation of lipid droplets. Enhancement of lipid utilization by the mitochondria attenuated TOR activation and rescued the loss of GSCs that was caused by inhibition of mitochondrial fusion. Moreover, constitutive activation of the TOR-pathway target and lipogenesis factor Sterol regulatory element binding protein (SREBP) also resulted in GSC loss, whereas inhibition of SREBP rescued GSC loss triggered by depletion of dMfn. Our findings highlight a critical role for mitochondrial fusion and lipid homeostasis in GSC maintenance, providing insight into the potential impact of mitochondrial and metabolic diseases on the function of stem and/or germ cells.

Obstructive Sleep Apnea and the Liver

Nonalcoholic fatty liver disease (NAFLD), a disorder of altered metabolic pathways, is increasing worldwide. Recent studies established obstructive sleep apnea (OSA) and chronic intermittent hypoxia (CIH) as NAFLD risk factors. Studies have ascertained that CIH is independently related to NAFLD. Continuous positive airway pressure (CPAP) shows inconsistent results regarding its efficacy in improving NAFLD. Observational, longer duration CPAP therapy studies have shown positive outcomes, whereas shorter duration, randomized controlled trials have shown no benefit. A multifaceted approach to NAFLD management with sufficiently longer duration of CPAP therapy may be beneficial in patients with moderate to severe OSA.