Prostaglandin F2α Facilitates Hepatic Glucose Production Through CaMKIIγ/p38/FOXO1 Signaling Pathway in Fasting and Obesity

Thromboxane A2 Modulates de novo Synthesis of Adrenal Corticosterone in Mice via p38/14-3-3γ/StAR Signaling

Prostanoids are endogenous lipid bioactive mediators that play essential roles in physiological processes such as glucocorticoid secretion. Here, it is found that the thromboxane (Tx)A2 receptor (TP) is highly expressed in the adrenal cortex of mice. Both global and adrenocortical-specific deletion of the TP receptor lead to increased adiposity in mice by elevating corticosterone synthesis. Mechanistically, the TP receptor deletion increases the phosphorylation of steroidogenic acute regulatory protein (StAR) and corticosterone synthesis in adrenal cortical cells by suppressing p-p38-mediated phosphorylation of 14-3-3γ adapter protein at S71. The activation of the p38 in the adrenal cortical cells by forced expression of the MKK6EE gene attenuates hypercortisolism in TP-deficient mice. These observations suggest that the TxA2/TP signaling regulates adrenal corticosterone homeostasis independent of the hypothalamic-pituitary-adrenal axis and the TP receptor may serve as a promising therapeutic target for hypercortisolism.

Thromboxane A2/thromboxane A2 receptor axis facilitates hepatic insulin resistance and steatosis through endoplasmic reticulum stress in non-alcoholic fatty liver disease

BACKGROUND AND PURPOSE

Defective insulin signalling and dysfunction of the endoplasmic reticulum (ER), driven by excessive lipid accumulation in the liver, is a characteristic feature in the pathogenesis of non-alcoholic fatty liver disease (NAFLD). Thromboxane A2 (TXA2 ), an arachidonic acid metabolite, is significantly elevated in obesity and plays a crucial role in hepatic gluconeogenesis and adipose tissue macrophage polarization. However, the role of liver TXA2 /TP receptors in insulin resistance and lipid metabolism is largely unknown.

EXPERIMENTAL APPROACH

TP receptor knockout (TP-/- ) mice were generated and fed a high-fat diet for 16 weeks. Insulin sensitivity, ER stress responses and hepatic lipid accumulation were assessed. Furthermore, we used primary hepatocytes to dissect the mechanisms by which the TXA2 /TP receptor axis regulates insulin signalling and hepatocyte lipogenesis.

KEY RESULTS

TXA2 was increased in diet-induced obese mice, and depletion of TP receptors in adult mice improved systemic insulin resistance and hepatic steatosis. Mechanistically, we found that the TXA2 /TP receptor axis disrupts insulin signalling by activating the Ca2+ /calcium calmodulin-dependent kinase II γ (CaMKIIγ)-protein kinase RNA-like endoplasmic reticulum kinase (PERK)-C/EBP homologous protein (Chop)-tribbles-like protein 3 (TRB3) axis in hepatocytes. In addition, our results revealed that the TXA2 /TP receptor axis directly promoted lipogenesis in primary hepatocytes and contributed to Kupffer cell inflammation.

CONCLUSIONS AND IMPLICATIONS

The TXA2 /TP receptor axis facilitates insulin resistance through Ca2+ /CaMKIIγ to activate PERK-Chop-TRB3 signalling. Inhibition of hepatocyte TP receptors improved hepatic steatosis and inflammation. The TP receptor is a new therapeutic target for NAFLD and metabolic syndrome.

Transcriptomics and metabolomics analysis reveal the dietary copper deficiency and supplementation effects of liver gene expression and metabolite change in grazing sheep

BACKGROUND

The appropriate mineral nutrients are essential for sheep growth and reproduction. However, traditional grazing sheep often experience mineral nutrient deficiencies, especially copper (Cu), due to inadequate mineral nutrients from natural pastures.

RESULTS

The results indicated that dietary Cu deficiency and supplementation significantly reduced and elevated liver concentration of Cu, respectively (p < 0.05). FOXO3, PLIN1, ACTN2, and GHRHR were identified as critical genes using the weighted gene co-expression network analysis (WGCNA), quantitative real-time polymerase chain reaction (qRT-PCR), and receiver operating characteristic curve (ROC) validation as potential biomarkers for evaluating Cu status in grazing sheep. Combining these critical genes with gene functional enrichment analysis, it was observed that dietary Cu deficiency may impair liver regeneration and compromise ribosomal function. Conversely, dietary Cu supplementation may enhance ribosomal function, promote lipid accumulation, and stimulate growth and metabolism in grazing sheep. Metabolomics analysis indicated that dietary Cu deficiency significantly decreased the abundance of metabolites such as cholic acid (p < 0.05). On the other hand, dietary Cu supplementation significantly increased the abundance of metabolites such as palmitic acid (p < 0.05). Integrative analysis of the transcriptome and metabolome revealed that dietary Cu deficiency may reduce liver lipid metabolism while Cu supplementation may elevate it in grazing sheep.

CONCLUSIONS

The Cu content in diets may have an impact on hepatic lipid metabolism in grazing sheep. These findings provide new insights into the consequences of dietary Cu deficiency and supplementation on sheep liver and can provide valuable guidance for herders to rationalize the use of mineral supplements.

Prostaglandin F2α Affects the Cycle of Clock Gene Expression and Mouse Behavior

Prostaglandins are bioactive compounds, and the activation of their receptors affects the expression of clock genes. However, the prostaglandin F receptor (Ptgfr) has no known relationship with biological rhythms. Here, we first measured the locomotor period lengths of Ptgfr-KO (B6.129-Ptgfrtm1Sna) mice and found that they were longer under constant dark conditions (DD) than those of wild-type (C57BL/6J) mice. We then investigated the clock gene patterns within the suprachiasmatic nucleus in Ptgfr-KO mice under DD and observed a decrease in the expression of the clock gene cryptochrome 1 (Cry1), which is related to the circadian cycle. Moreover, the expression of Cry1, Cry2, and Period2 (Per2) mRNA were significantly altered in the mouse liver in Ptgfr-KO mice under DD. In the wild-type mouse, the plasma prostaglandin F2α (PGF2α) levels showed a circadian rhythm under a 12 h cycle of light-dark conditions. In addition, in vitro experiments showed that the addition of PTGFR agonists altered the amplitude of Per2::luc activity, and this alteration differed with the timing of the agonist addition. These results lead us to hypothesize that the plasma rhythm of PGF2α is important for driving clock genes, thus suggesting the involvement of PGF2α- and Ptgfr-targeting drugs in the biological clock cycle.

Arachidonic acid metabolism in health and disease

Arachidonic acid (AA), an n-6 essential fatty acid, is a major component of mammalian cells and can be released by phospholipase A2. Accumulating evidence indicates that AA plays essential biochemical roles, as it is the direct precursor of bioactive lipid metabolites of eicosanoids such as prostaglandins, leukotrienes, and epoxyeicosatrienoic acid obtained from three distinct enzymatic metabolic pathways: the cyclooxygenase pathway, lipoxygenase pathway, and cytochrome P450 pathway. AA metabolism is involved not only in cell differentiation, tissue development, and organ function but also in the progression of diseases, such as hepatic fibrosis, neurodegeneration, obesity, diabetes, and cancers. These eicosanoids are generally considered proinflammatory molecules, as they can trigger oxidative stress and stimulate the immune response. Therefore, interventions in AA metabolic pathways are effective ways to manage inflammatory-related diseases in the clinic. Currently, inhibitors targeting enzymes related to AA metabolic pathways are an important area of drug discovery. Moreover, many advances have also been made in clinical studies of AA metabolic inhibitors in combination with chemotherapy and immunotherapy. Herein, we review the discovery of AA and focus on AA metabolism in relation to health and diseases. Furthermore, inhibitors targeting AA metabolism are summarized, and potential clinical applications are discussed.

Chlorogenic Acid Inhibits Ceramide Accumulation to Restrain Hepatic Glucagon Response

Chlorogenic acid (CGA), a dietary natural phenolic acid, has been widely reported to regulate glucose and lipid metabolism. However, the protective effects and the underlying mechanisms of CGA on glucagon-induced hepatic glucose production remain largely uncharacterized. Herein, we investigated the efficacy of CGA on hepatic gluconeogenesis both in vivo and in vitro. The elevated levels of endogenous glucose production induced by infusion of glucagon or pyruvate were lowered in mice administered with CGA. Furthermore, chronic CGA treatment ameliorated the accumulation of glucose and ceramide in high-fat diet (HFD)-fed mice. CGA also attenuated HFD-fed-induced inflammation response. The protective effect of CGA on glucose production was further confirmed in primary mouse hepatocytes by inhibiting accumulation of ceramide and expression of p38 MAPK. Moreover, CGA administration in HFD-fed mice preserved the decreased phosphorylation of Akt in the liver, resulting in the inhibition of FoxO1 activation and, ultimately, hepatic gluconeogenesis. However, these protective effects were significantly attenuated by the addition of C2 ceramide. These results suggest that CGA inhibits ceramide accumulation to restrain hepatic glucagon response.

Prostaglandin F2α regulates mitochondrial dynamics and mitophagy in the bovine corpus luteum

Prostaglandins are arachidonic acid-derived lipid mediators involved in numerous physiological and pathological processes. PGF2α analogues are therapeutically used for regulating mammalian reproductive cycles and blood pressure, inducing term labor, and treating ocular disorders. PGF2α exerts effects via activation of calcium and PKC signaling, however, little is known about the cellular events imposed by PGF2α signaling. Here, we explored the early effects of PGF2α on mitochondrial dynamics and mitophagy in the bovine corpus luteum employing relevant and well characterized in vivo and in vitro approaches. We identified PKC/ERK and AMPK as critical protein kinases essential for activation of mitochondrial fission proteins, DRP1 and MFF. Furthermore, we report that PGF2α elicits increased intracellular reactive oxygen species and promotes receptor-mediated activation of PINK-Parkin mitophagy. These findings place the mitochondrium as a novel target in response to luteolytic mediator, PGF2α. Understanding intracellular processes occurring during early luteolysis may serve as a target for improving fertility.

A Liquid Biopsy-Based Approach to Isolate and Characterize Adipose Tissue-Derived Extracellular Vesicles from Blood

Obesity is a major risk factor for multiple chronic diseases. Anthropometric and imaging approaches are primarily used to assess adiposity, and there is a dearth of techniques to determine the changes in adipose tissue (AT) at the molecular level. Extracellular vesicles (EVs) have emerged as a novel and less invasive source of biomarkers for various pathologies. Furthermore, the possibility of enriching cell or tissue-specific EVs from the biofluids based on their unique surface markers has led to classifying these vesicles as "liquid biopsies", offering valuable molecular information on hard-to-access tissues. Here, we isolated small EVs from AT (sEVAT) of lean and diet-induced obese (DIO) mice, identified unique surface proteins on sEVAT by surface shaving followed by mass spectrometry, and developed a signature of five unique proteins. Using this signature, we pulled out sEVAT from the blood of mice and validated the specificity of isolated sEVAT by measuring the expression of adiponectin, 38 adipokines on an array, and several adipose tissue-related miRNAs. Furthermore, we provided evidence of sEV applicability in disease prediction by characterizing sEVAT from the blood of lean and DIO mice. Interestingly, sEVAT-DIO cargo showed a stronger pro-inflammatory effect on THP1 monocytes compared to sEVAT-Lean and a significant increase in obesity-associated miRNA expression. Equally important, sEVAT cargo revealed an obesity-associated aberrant amino acid metabolism that was subsequently validated in the corresponding AT. Lastly, we show a significant increase in inflammation-related molecules in sEVAT isolated from the blood of nondiabetic obese (>30 kg/m2) individuals. Overall, the present study offers a less-invasive approach to characterize AT.

A hepatokine derived from the ER protein CREBH promotes triglyceride metabolism by stimulating lipoprotein lipase activity

The endoplasmic reticulum (ER)-tethered, liver-enriched stress sensor CREBH is processed in response to increased energy demands or hepatic stress to release an amino-terminal fragment that functions as a transcription factor for hepatic genes encoding lipid and glucose metabolic factors. Here, we discovered that the carboxyl-terminal fragment of CREBH (CREBH-C) derived from membrane-bound, full-length CREBH was secreted as a hepatokine in response to fasting or hepatic stress. Phosphorylation of CREBH-C mediated by the kinase CaMKII was required for efficient secretion of CREBH-C through exocytosis. Lipoprotein lipase (LPL) mediates the lipolysis of circulating triglycerides for tissue uptake and is inhibited by a complex consisting of angiopoietin-like (ANGPTL) 3 and ANGPTL8. Secreted CREBH-C blocked the formation of ANGPTL3-ANGPTL8 complexes, leading to increased LPL activity in plasma and metabolic tissues in mice. CREBH-C administration promoted plasma triglyceride clearance and partitioning into peripheral tissues and mitigated hypertriglyceridemia and hepatic steatosis in mice fed a high-fat diet. Individuals with obesity had higher circulating amounts of CREBH-C than control individuals, and human CREBH loss-of-function variants were associated with dysregulated plasma triglycerides. These results identify a stress-induced, secreted protein fragment derived from CREBH that functions as a hepatokine to stimulate LPL activity and triglyceride homeostasis.

Aspirin Suppresses Hepatic Glucagon Signaling Through Decreasing Production of Thromboxane A2

Excessive hepatic glucose production (HGP) is a major cause of fasting hyperglycemia in diabetes, and antihyperglycemic therapy takes center stage. Nonsteroidal anti-inflammatory drugs, such as acetylsalicylic acid (aspirin), reduce hyperglycemia caused by unrestrained gluconeogenesis in diabetes, but its mechanism is incompletely understood. Here, we reported that aspirin lowers fasting blood glucose and hepatic gluconeogenesis, corresponds with lower thromboxane A2 (TXA2) levels, and the hypoglycemic effect of aspirin could be rescued by TP agonist treatment. On fasting and diabetes stress, the cyclooxygenase (COX)/TXA2/thromboxane A2 receptor (TP) axis was increased in the livers. TP deficiency suppressed starvation-induced hepatic glucose output, thus inhibiting the progression of diabetes, whereas TP activation promoted gluconeogenesis. Aspirin restrains glucagon signaling and gluconeogenic gene expression (phosphoenolpyruvate carboxykinase [PCK1] and glucose-6-phosphatase [G6Pase]) through the TXA2/TP axis. TP mediates hepatic gluconeogenesis by activating PLC/IP3/IP3R signaling, which subsequently enhances CREB phosphorylation via facilitating CRTC2 nuclear translocation. Thus, our findings demonstrate that TXA2/TP plays a crucial role in aspirin's inhibition of hepatic glucose metabolism, and TP may represent a therapeutic target for diabetes.

PGF2α facilitates pathological retinal angiogenesis by modulating endothelial FOS-driven ELR+ CXC chemokine expression

The pathological retinal angiogenesis often causes blindness. Current anti-angiogenic therapy for proliferative retinopathy targets the vascular endothelial growth factor (VEGF), but many patients do not radically benefit from this therapy. Herein, we report that circulating prostaglandin (PG) F_2α metabolites were increased in type 2 diabetic patients with proliferative retinopathy, and the PGF_2α receptor (Ptgfr) was upregulated in retinal endothelial cells (ECs) from a mouse model of oxygen-induced retinopathy (OIR). Further, disruption of the PTGFR receptor in ECs attenuated OIR in mice. PGF_2α promoted the proliferation and tube formation of human retinal microvascular endothelial cells (HRMECs) via the release of ELR⁺ CXC chemokines, such as CXCL8 and CXCL2. Mechanistically, the PGF_2α /PTGFR axis potentiated ELR⁺ CXC chemokine expression in HRMECs through the G_q /CAMK2G/p38/ELK-1/FOS pathway. Upregulated FOS-mediated ELR⁺ CXC chemokine expression was observed in retinal ECs from PDR patients. Moreover, treatment with PTGFR inhibitor lessened the development of OIR in mice in a CXCR2-dependent manner. Therefore, inhibition of PTGFR may represent a new avenue for the treatment of retinal neovascularization, particularly in PDR.

FOXO1 is downregulated in obese mice subjected to short-term strength training

Obesity is a worldwide health problem and is directly associated with insulin resistance and type 2 diabetes. The liver is an important organ for the control of healthy glycemic levels, since insulin resistance in this organ reduces phosphorylation of forkhead box protein 1 (FOXO1) protein, leading to higher hepatic glucose production (HGP) and fasting hyperglycemia. Aerobic physical training is known as an important strategy in increasing the insulin action in the liver by increasing FOXO1 phosphorylation and reducing gluconeogenesis. However, little is known about the effects of strength training in this context. This study aimed to investigate the effects of short-term strength training on hepatic insulin sensitivity and glycogen synthase kinase-3β (GSK3β) and FOXO1 phosphorylation in obese (OB) mice. To achieve this goal, OB Swiss mice performed the strength training protocol (one daily session for 15 days). Short-term strength training increased the phosphorylation of protein kinase B and GSK3β in the liver after insulin stimulus and improved the control of HGP during the pyruvate tolerance test. On the other hand, sedentary OB animals reduced FOXO1 phosphorylation and increased the levels of nuclear FOXO1 in the liver, increasing the phosphoenolpyruvate carboxykinase (PEPCK) and glucose-6-phosphatase (G6Pase) content. The bioinformatics analysis also showed positive correlations between hepatic FOXO1 levels and gluconeogenic genes, reinforcing our findings. However, strength-trained animals reverted to this scenario, regardless of body adiposity changes. In conclusion, short-term strength training is an efficient strategy to enhance the insulin action in the liver of OB mice, contributing to glycemic control by reducing the activity of hepatic FOXO1 and lowering PEPCK and G6Pase contents.

Modeling microRNA-driven post-transcriptional regulation using exon-intron split analysis in pigs

The contribution of microRNAs (miRNAs) to mRNA post-transcriptional regulation has often been explored by the post hoc selection of downregulated genes and determining whether they harbor binding sites for miRNAs of interest. This approach, however, does not discriminate whether these mRNAs are also downregulated at the transcriptional level. Here, we have characterized the transcriptional and post-transcriptional changes in mRNA expression in two porcine tissues: gluteus medius muscle of fasted and fed Duroc gilts and adipose tissue of lean and obese Duroc-Göttingen minipigs. Exon-intron split analysis of RNA-seq data allowed us to identify downregulated mRNAs with high post-transcriptional signals in fed or obese states, and we assessed whether they harbor binding sites for upregulated miRNAs in any of these two physiological states. We found 26 downregulated mRNAs with high post-transcriptional signals in the muscle of fed gilts and 21 of these were predicted targets of miRNAs upregulated in fed pigs. For adipose tissue, 44 downregulated mRNAs in obese minipigs displayed high post-transcriptional signals, and 25 of these were predicted targets of miRNAs upregulated in the obese state. These results suggest that the contribution of miRNAs to mRNA repression is more prominent in the skeletal muscle system. Finally, we identified several genes that may play relevant roles in the energy homeostasis of the pig skeletal muscle (DKK2 and PDK4) and adipose (SESN3 and ESRRG) tissues. By differentiating transcriptional from post-transcriptional changes in mRNA expression, exon-intron split analysis provides a valuable view of the regulation of gene expression, complementary to canonical differential expression analyses.

Pharmacological analysis of Empagliflozin: Acting through the CaMKII pathway in type 2 diabetes and acute cardiovascular events

Background

Type 2 diabetes mellitus is a high-risk factor for acute cardiovascular events. Some reports show that Empagliflozin has a protective effect on cardiovascular events and diabetes mellitus, and Empagliflozin can act on the CaMKII pathway. However, the specific gene of action is not precise. Therefore, this study investigated the target genes of Empagliflozin by integrated gene analysis and molecular docking method to provide a theoretical basis for further elucidating the mechanism of action of Empagliflozin.

Method

In this study, we obtained 12 datasets from GEO, divided into experimental and validation groups, with a total of 376 samples. We then integrated CaMKII pathway-related genes from OMIM, NCBI, and genecards databases. We then intersected them with the differential genes we obtained to obtain 5 common genes and performed functional enrichment analysis. We then performed group comparisons in the validation set, and we obtained 2 clinically significant genes. Then we performed group comparison in the validation set, and we obtained 2 clinically significant genes, followed by molecular docking analysis with pymol, autodock software. We obtained molecular docking models for the 2 genes.

Conclusion

In this study, we obtained CaMK2G and PPP1CA, genes associated with the CaMKII pathway and type 2 diabetes and acute cardiovascular events, by integrative gene analysis and validated their expression in the relevant dataset. We also derived that Empagliflozin acts on amino acid TRP-125 of CaMK2G gene and GLN-249 ASP-210 ASP-208 of PPP1CA through CaMKII pathway, thus acting on type 2 diabetes and acute cardiovascular events by molecular docking technique.

Prostaglandin F2α evokes vasoconstrictor and vasodepressor activities that are both independent of the F prostanoid receptor

The F prostanoid receptor (FP), which accounts for the therapeutic effect of PGF_2α in uterine atony that leads to postpartum hemorrhage and maternal morbidity, could possibly mediate vasoconstrictor effect in small or resistance arteries to elevate blood pressure that limits the clinical use of the agent in patients with cardiovascular disorders. This study aimed to test the above hypothesis with genetically altered mice. Ex vivo and in vivo experiments were performed on control wild-type (WT) mice and mice with deficiencies in FP (FP^-/- ) or thromboxane (Tx)-prostanoid receptor (the original receptor of TxA₂ ; TP^-/- ), and/or those with an additional deficiency in E prostanoid receptor-3 (one of the vasoconstrictor receptors of PGE₂ ; EP3^-/- ). Here, we show that PGF_2α indeed evoked vasoconstrictor responses in the above-mentioned tissues of WT mice, which were however unaltered by FP^-/- . Interestingly, such contractile responses were reversed into dilations by TP^-/- /EP3^-/- . A similar pattern of results was observed with the pressor effect of PGF_2α under in vivo conditions. However, TP^-/- alone (which could largely remove the contractile responses) did not result in relaxation to PGF_2α . Also, either the ex vivo vasodilator effect or the in vivo depressor response of PGF_2α obtained after the removal of TP and EP3-mediated actions was unaltered by FP^-/- . Therefore, both the ex vivo vasoconstrictor action in small or resistance arteries and the systemic pressor effect of PGF_2α can reflect vasoconstrictor activities derived from the non-FP receptors TP and EP3 outweighing a concurrently activated dilator effect, which is again independent of FP.

Platelet-Activating Factor Promotes the Development of Non-Alcoholic Fatty Liver Disease

Non-alcoholic fatty liver disease (NAFLD) is a multifaceted clinicopathological syndrome characterised by excessive hepatic lipid accumulation that causes steatosis, excluding alcoholic factors. Platelet-activating factor (PAF), a biologically active lipid transmitter, induces platelet activation upon binding to the PAF receptor. Recent studies have found that PAF is associated with gamma-glutamyl transferase, which is an indicator of liver disease. Moreover, PAF can stimulate hepatic lipid synthesis and cause hypertriglyceridaemia. Furthermore, the knockdown of the PAF receptor gene in the animal models of NAFLD helped reduce the inflammatory response, improve glucose homeostasis and delay the development of NAFLD. These findings suggest that PAF is associated with NAFLD development. According to reports, patients with NAFLD or animal models have marked platelet activation abnormalities, mainly manifested as enhanced platelet adhesion and aggregation and altered blood rheology. Pharmacological interventions were accompanied by remission of abnormal platelet activation and significant improvement in liver function and lipids in the animal model of NAFLD. These confirm that platelet activation may accompany a critical importance in NAFLD development and progression. However, how PAFs are involved in the NAFLD signalling pathway needs further investigation. In this paper, we review the relevant literature in recent years and discuss the role played by PAF in NAFLD development. It is important to elucidate the pathogenesis of NAFLD and to find effective interventions for treatment.

Biochemical and Structural Characteristics, Gene Regulation, Physiological, Pathological and Clinical Features of Lipocalin-Type Prostaglandin D2 Synthase as a Multifunctional Lipocalin

Lipocalin-type prostaglandin (PG) D₂ synthase (L-PGDS) catalyzes the isomerization of PGH₂, a common precursor of the two series of PGs, to produce PGD₂. PGD₂ stimulates three distinct types of G protein-coupled receptors: (1) D type of prostanoid (DP) receptors involved in the regulation of sleep, pain, food intake, and others; (2) chemoattractant receptor-homologous molecule expressed on T helper type 2 cells (CRTH2) receptors, in myelination of peripheral nervous system, adipocyte differentiation, inhibition of hair follicle neogenesis, and others; and (3) F type of prostanoid (FP) receptors, in dexamethasone-induced cardioprotection. L-PGDS is the same protein as β-trace, a major protein in human cerebrospinal fluid (CSF). L-PGDS exists in the central nervous system and male genital organs of various mammals, and human heart; and is secreted into the CSF, seminal plasma, and plasma, respectively. L-PGDS binds retinoic acids and retinal with high affinities (Kd < 100 nM) and diverse small lipophilic substances, such as thyroids, gangliosides, bilirubin and biliverdin, heme, NAD(P)H, and PGD₂, acting as an extracellular carrier of these substances. L-PGDS also binds amyloid β peptides, prevents their fibril formation, and disaggregates amyloid β fibrils, acting as a major amyloid β chaperone in human CSF. Here, I summarize the recent progress of the research on PGD₂ and L-PGDS, in terms of its “molecular properties,” “cell culture studies,” “animal experiments,” and “clinical studies,” all of which should help to understand the pathophysiological role of L-PGDS and inspire the future research of this multifunctional lipocalin.

Adipocyte CAMK2 deficiency improves obesity-associated glucose intolerance

OBJECTIVE

Obesity-related adipose tissue dysfunction has been linked to the development of insulin resistance, type 2 diabetes, and cardiovascular disease. Impaired calcium homeostasis is associated with altered adipose tissue metabolism; however, the molecular mechanisms that link disrupted calcium signaling to metabolic regulation are largely unknown. Here, we investigated the contribution of a calcium-sensing enzyme, calcium/calmodulin-dependent protein kinase II (CAMK2), to adipocyte function, obesity-associated insulin resistance, and glucose intolerance.

METHODS

To determine the impact of adipocyte CAMK2 deficiency on metabolic regulation, we generated a conditional knockout mouse model and acutely deleted CAMK2 in mature adipocytes. We further used in vitro differentiated adipocytes to dissect the mechanisms by which CAMK2 regulates adipocyte function.

RESULTS

CAMK2 activity was increased in obese adipose tissue, and depletion of adipocyte CAMK2 in adult mice improved glucose intolerance and insulin resistance without an effect on body weight. Mechanistically, we found that activation of CAMK2 disrupted adipocyte insulin signaling and lowered the amount of insulin receptor. Further, our results revealed that CAMK2 contributed to adipocyte lipolysis, tumor necrosis factor alpha (TNFα)-induced inflammation, and insulin resistance.

CONCLUSIONS

These results identify a new link between adipocyte CAMK2 activity, metabolic regulation, and whole-body glucose homeostasis.

Suppressor of cytokine signalling-2 controls hepatic gluconeogenesis and hyperglycemia by modulating JAK2/STAT5 signalling pathway

Hepatic gluconeogenesis plays a crucial role in maintaining blood glucose homeostasis in mammals. Globe knockout of suppressor of cytokine signalling-2 (SOCS2), a feedback inhibitor of cytokine signalling, has been shown resistant to high-fat-diet (HFD)-induced hepatic steatosis with impaired glucose tolerance in mice. However, the underlying mechanism of SOCS2 regulates hepatic glucose homeostasis still undefined. In the present study, we demonstrated that the hepatic SOCS2 expression is markedly reduced in fasted C57BL/6 J mice or db/db mice. Moreover, hepatic SOCS2 expression levels are induced by metformin treatment. Ablation of SOCS2 attenuates suppressing effects of metformin on gluconeogenesis in hepatocytes. Gain- and loss-of-function studies indicated that SOCS2 regulates hepatic gluconeogenic genes expression and glucose output by mediating JAK2/STAT5 signalling pathway in db/db mice. Mechanistically, we observed that SOCS2 inactivates STAT5 by attenuating the interaction between JAK2 and STAT5, which in turn reduces hepatic gluconeogenesis. The present study reveals a critical role of SOCS2 in regulating hepatic gluconeogenesis. The inhibitory effect of metformin on gluconeogenesis is mediated, at least in part, by upregulating SOCS2 and therefore reducing hepatic gluconeogenic genes expression. SOCS2 may represent a new therapeutic target for the treatment of diabetes.

Oxylipin Responses to Fasting and Insulin Infusion in a Large Mammalian Model of Fasting-Induced Insulin Resistance, the Northern Elephant Seal

The prolonged, post-weaning fast of northern elephant seal (Mirounga angustirostris) pups is characterized by a reliance on lipid metabolism and reversible, fasting-induced insulin resistance providing a unique model to examine the effects of insulin on lipid metabolism. We have previously shown that acute insulin infusion induced a shift in fatty acid metabolism dependent on fasting duration. This study complements the previous study by examining the effects of fasting duration and insulin infusion on circulating levels of oxylipins, bioactive metabolites derived from the oxygenation of polyunsaturated fatty acids. Northern elephant seal pups were studied at two post-weaning periods (n = 5/period): early fasting (1-2 weeks post-weaning; 127 ± 1 kg) and late fasting (6-7 weeks post-weaning; 93 ± 4 kg). Different cohorts of pups were weighed, sedated, and infused with 65 mU/kg of insulin. Plasma was collected prior to infusion (T0), and at 10, 30, 60, and 120 min post-infusion. A profile of ~80 oxylipins were analyzed by UPLC-ESI-MS/MS. Nine oxylipins changed between early and late fasting and eight were altered in response to insulin infusion. Fasting decreased PGF2a and increased 14,15-DiHETrE, 20-HETE, and 4-HDoHE (p<0.03) in T0 samples, while insulin infusion resulted in an inverse change in area under the curve (AUC) levels in these same metabolites (p<0.05). In addition, 12-HpETE and 12-HETE decreased with fasting and insulin infusion, respectively (p<0.04). The oxylipins altered during fasting and in response to insulin infusion may contribute to the manifestation of insulin resistance and participate in the metabolic regulation of associated cellular processes.

Low-level lead exposure promotes hepatic gluconeogenesis and contributes to the elevation of fasting glucose level

BACKGROUND

Lead (Pb) is considered an endocrine-disrupting chemical. However, few studies have investigated the effects of low-level Pb exposure on plasma glucose levels. Herein, we aimed to investigate whether low-level Pb exposure causes elevated plasma glucose levels and the possible mechanisms involved.

METHODS

We conducted a cross-sectional study of 5747 participants from 16 sites in China. The participants underwent measurements of anthropometric factors, blood lead level (BLL) and fasting plasma glucose (FPG). Wistar rats were exposed to 0.05% Pb through drinking water or fed with a high-fat diet (HFD) for 28 weeks. The relevant parameters of glucose homeostasis, hepatic glucose production (HGP) and gene expression levels of hepatic gluconeogenesis enzymes, including phosphoenolpyruvate carboxy kinase (PEPCK), glucose-6-phosphatase (G6PC) and fructose-1,6-bisphosphatase (FBP1), were measured. In addition, gene expression levels of gluconeogenesis enzymes were also measured in HepG2 cells administered with different concentrations of lead acetate for 24 h.

RESULTS

In humans, after adjusting for confounders, the odds of having High_FPG (≥5.6 mmol/L) were significantly increased by 25% in the participants in the fourth BLL quartile (OR 1.25, 95% CI 1.05, 1.49). In the animals exposed to 0.05% Pb, FPG, HGP and hepatic gene expression levels of PEPCK, G6PC and FBP1 were increased. In addition, the mRNA expression levels of PEPCK, G6PC and FBP1 in HepG2 cells were also increased in response to Pb exposure.

CONCLUSIONS

These findings support the possibility that low-level Pb exposure may increase HGP by affecting key enzymes of hepatic gluconeogenesis, eventually resulting in impaired FPG and hyperglycemia.

Impact of Different Durations of Fasting on Intestinal Autophagy and Serum Metabolome in Broiler Chicken

Simple Summary

Fasting is usually used before metabolizable energy assessment in poultry. Recently, fasting-induced autophagy has been of concern because of the beneficial function of autophagy. In this study, we found that the intestinal autophagy gene Atg7 has a good quadratic fitting with fasting duration. We found that the serum metabolism pathways involved in glycerophospholipid, phenylalanine, GnRH signaling pathways, glycosylphosphatidylinositol anchor biosynthesis, autophagy, and ferroptosis changed with fasting. Furthermore, we found a correlation between intestinal autophagy and serum metabolite PE (18:3(9Z,12Z,15Z)/P-18:0).

Abstract

Fasting-induced autophagy in the intestine is beneficial for body health. This study was designed to explore the relationship between the host metabolism and intestinal autophagy. Broilers were randomly assigned into 48 cages. At 0 (CT), 12 (FH12), 24 (FH24), 36 (FH36), 48(FH48), and 72 h (FH72) before 09:00 a.m. on day 25, eight cages of birds were randomly allotted to each fasting time point using completely random design, and their food was removed. At 09:00 a.m. on day 25, the blood and jejunum were sampled for serum metabolome and autophagy gene analyses, respectively. The results showed that the autophagy gene Atg7 has a good quadratic fit with fasting duration (R² = 0.432, p < 0.001). Serum phosphatidylethanolamine (PE) and lyso-PE were decreased in the birds that were fasted for 24 h or longer. Conversely, the serum phosphatidylcholine (PC) and lyso-PC were increased in the birds that were fasted for 36 h or longer. Metabolism pathway analysis showed that the serum glycerophospholipid, phenylalanine, and GnRH signaling pathways were downregulated with the extended fasting duration. The serum metabolites involved in glycosylphosphatidylinositol anchor biosynthesis, autophagy, and ferroptosis were upregulated in all of the fasted groups. Correlation analysis showed that serum PE (18:3(9Z,12Z,15Z)/P-18:0) was a potential biomarker for intestinal autophagy. Our findings provide a potential biomarker related to intestinal autophagy.

Effect of n-3 long-chain polyunsaturated fatty acid intake on the eicosanoid profile in individuals with obesity and overweight: a systematic review and meta-analysis of clinical trials

Dietary n-3 polyunsaturated fatty acids (PUFAs) present beneficial effects on counteracting inflammation status, displaying a critical anti-inflammatory role and maintaining physiological homeostasis in obesity. The primary objective of this systematic review was to evaluate the effect of n-3 PUFAs intake on the eicosanoid profile of people with obesity and overweight. The search strategy on Embase, Scopus, PubMed, Web of Science, Cochrane Library, Google Scholar and ProQuest was undertaken until November 2019 and updated January 2021. The effect size of n-3 PUFAs on prostaglandins was estimated by Glass's, type 1 in a random-effect model for the meta-analysis. Seven clinical trials met the eligible criteria and a total of 610 subjects were included in this systematic review, and four of seven studies were included in meta-analysis. The intake of n-3 PUFAs promoted an overall reduction in serum pro-inflammatory eicosanoids. Additionally, n-3 PUFAs intake significantly decreased the arachidonic acid COX-derived PG eicosanoid group levels (Glass's Δ -0⋅35; CI -0⋅62, -0⋅07, I ² 31⋅48). Subgroup analyses showed a higher effect on periods up to 8 weeks (Glass's Δ -0⋅51; CI -0⋅76, -0⋅27) and doses higher than 0⋅5 g of n-3 PUFAs (Glass's Δ -0⋅46; CI -0⋅72, -0⋅27). Dietary n-3 PUFAs intake contributes to reduce pro-inflammatory eicosanoids of people with obesity and overweight. Subgroup's analysis showed that n-3 PUFAs can reduce the overall arachidonic acid COX-derived PG when adequate dose and period are matched.

Role of 2‑series prostaglandins in the pathogenesis of type 2 diabetes mellitus and non‑alcoholic fatty liver disease (Review)

Nowadays, metabolic syndromes are emerging as global epidemics, whose incidence are increasing annually. However, the efficacy of therapy does not increase proportionately with the increased morbidity. Type 2 diabetes mellitus (T2DM) and non-alcoholic fatty liver disease (NAFLD) are two common metabolic syndromes that are closely associated. The pathogenic mechanisms of T2DM and NAFLD have been studied, and it was revealed that insulin resistance, hyperglycemia, hepatic lipid accumulation and inflammation markedly contribute to the development of these two diseases. The 2-series prostaglandins (PGs), a subgroup of eicosanoids, including PGD₂, PGE₂, PGF_2α and PGI₂, are converted from arachidonic acid catalyzed by the rate-limiting enzymes cyclooxygenases (COXs). Considering their wide distribution in almost every tissue, 2-series PG pathways exert complex and interlinked effects in mediating pancreatic β-cell function and proliferation, insulin sensitivity, fat accumulation and lipolysis, as well as inflammatory processes. Previous studies have revealed that metabolic disturbances, such as hyperglycemia and hyperlipidemia, can be improved by treatment with COX inhibitors. At present, an accumulating number of studies have focused on the roles of 2-series PGs and their metabolites in the pathogenesis of metabolic syndromes, particularly T2DM and NAFLD. In the present review, the role of 2-series PGs in the highly intertwined pathogenic mechanisms of T2DM and NAFLD was discussed, and important therapeutic strategies based on targeting 2-series PG pathways in T2DM and NAFLD treatment were provided.

Time-restricted feeding attenuates gluconeogenic activity through inhibition of PGC-1α expression and activity

BACKGROUND

Time-restricted feeding (TRF), a key component of intermittent fasting regimens, has gained considerable attention in recent years due to reversing obesity and insulin resistance. To the best of our knowledge, here, we reported for the first time the underlying mechanistic therapeutic efficacy of TRF against hepatic gluconeogenic activity in obese mice.

METHODS

The obese mice were subjected to either ad lib or TRF of a high fat diet for 8 h per day for 4 weeks. Western blotting, qRT-PCR, and plasma biochemical analyses were applied.

RESULTS

The present findings showed that TRF regimen reduced food intake, and reversed high fat diet-induced glucose intolerance, hyperglycemia and insulin resistance in mice of high fat diet-induced obesity. Mechanistically, we confirmed that TRF regimen protected against hyperglycemia and ameliorated hepatic gluconeogenic activity through inhibition of p38 MAPK/SIRT1/PGC-1α signal pathway.

CONCLUSION

Our findings suggest that TRF regimen might be a potential novel nonpharmacological strategy against obesity/diabetes-induced hyperglycemia and insulin resistance.

Metabolism pathways of arachidonic acids: mechanisms and potential therapeutic targets

The arachidonic acid (AA) pathway plays a key role in cardiovascular biology, carcinogenesis, and many inflammatory diseases, such as asthma, arthritis, etc. Esterified AA on the inner surface of the cell membrane is hydrolyzed to its free form by phospholipase A2 (PLA2), which is in turn further metabolized by cyclooxygenases (COXs) and lipoxygenases (LOXs) and cytochrome P450 (CYP) enzymes to a spectrum of bioactive mediators that includes prostanoids, leukotrienes (LTs), epoxyeicosatrienoic acids (EETs), dihydroxyeicosatetraenoic acid (diHETEs), eicosatetraenoic acids (ETEs), and lipoxins (LXs). Many of the latter mediators are considered to be novel preventive and therapeutic targets for cardiovascular diseases (CVD), cancers, and inflammatory diseases. This review sets out to summarize the physiological and pathophysiological importance of the AA metabolizing pathways and outline the molecular mechanisms underlying the actions of AA related to its three main metabolic pathways in CVD and cancer progression will provide valuable insight for developing new therapeutic drugs for CVD and anti-cancer agents such as inhibitors of EETs or 2J2. Thus, we herein present a synopsis of AA metabolism in human health, cardiovascular and cancer biology, and the signaling pathways involved in these processes. To explore the role of the AA metabolism and potential therapies, we also introduce the current newly clinical studies targeting AA metabolisms in the different disease conditions.

Resolvin D1 Enhances Necroptotic Cell Clearance Through Promoting Macrophage Fatty Acid Oxidation and Oxidative Phosphorylation

OBJECTIVE

Plaque necrosis is a key feature of defective resolution in atherosclerosis. Recent evidence suggests that necroptosis promotes plaque necrosis; therefore, we sought to determine how necroptotic cells (NCs) impact resolution programs in plaques. Approach and Results: To investigate the role(s) of necroptosis in advanced atherosclerosis, we used mice deficient of Mlkl, an effector of necroptosis. Mlkl^-/- mice that were injected with a gain-of-function mutant PCSK9 (AAV8-gof-PCSK9) and fed a Western diet for 16 weeks, showed significantly less plaque necrosis, increased fibrous caps and improved efferocytosis compared with AAV8-gof-PCSK9 injected wt controls. Additionally, hypercholesterolemic Mlkl^-/- mice had a significant increase in proresolving mediators including resolvin D1 (RvD1) and a decrease in prostanoids including thromboxane in plaques and in vitro. We found that exuberant thromboxane released by NCs impaired the clearance of both apoptotic cells and NCs through disruption of oxidative phosphorylation in macrophages. Moreover, we found that NCs did not readily synthesize RvD1 and that exogenous administration of RvD1 to macrophages rescued NC-induced defective efferocytosis. RvD1 also enhanced the uptake of NCs via the activation of p-AMPK (AMP-activated protein kinase), increased fatty acid oxidation, and enhanced oxidative phosphorylation in macrophages.

CONCLUSIONS

These results suggest that NCs derange resolution by limiting key SPMs and impairing the efferocytic repertoire of macrophages. Moreover, these findings provide a molecular mechanism for RvD1 in directing proresolving metabolic programs in macrophages and further suggests RvD1 as a potential therapeutic strategy to limit NCs in tissues. Graphic Abstract: A graphic abstract is available for this article.

Prostaglandin F2α in vitro can affect basic inflammatory parameters of mesenchymal stem cells and slight modulating some of their immunomodulatory properties

In the last decade, mesenchymal stem cells (MSCs) have been gaining attention due their ability to influence the function of other cells as well as modulate the inflammatory response. This occurs via their immunomodulatory functions,  acting through direct cell-cell interaction or by releasing a broad spectrum of bioactive factors such as cytokines and growth factors. In addition, prostaglandins are arachidonic acid metabolites that play a key role in the generation and modulation of the inflammatory response. Among the bioactive prostaglandins, PGF_2α is able to stimulate cell proliferation as well as act to inhibit progenitor cell differentiation, but no information about this prostaglandin's action on the immunoregulatory function of MSCs has been reported. In this study we evaluate important aspects of the influence of PGF_2α analog (17-phenyl-trinor PGF_2α), which is a potent prostaglandin FP receptor agonist, on some mechanisms that control the main functions of MSCs. C3H10T1/2, a mesenchymal stem cell linage, was stimulated with PGF_2α under inflammatory conditions trigged by LPS in order to investigate PGF_2α inflammatory parameters as well as its ability to immunoregulate macrophages and lymphocytes. PGF_2α has the ability to increase proliferation tax without altering the cell viability of LPS-stimulated MSCs, while also diminishing the phosphorylation of NFκB transcription factor leading to attenuation of IL-1β and GM-CSF production. Additionally, MSC-s conditioned media from cells stimulated with PGF_2α was able to increase the lymphocytes' IL-10 production. Overall, this study implied that PGF_2α are able to modify some properties of MSCs.

Inhibition of α1-adrenoceptor reduces TGF-β1-induced epithelial-to-mesenchymal transition and attenuates UUO-induced renal fibrosis in mice

Renal fibrosis is a common pathological hallmark of chronic kidney disease (CKD). Renal sympathetic nerve activity is elevated in patients and experimental animals with CKD and contributes to renal interstitial fibrosis in obstructive nephropathy. However, the mechanisms underlying sympathetic overactivation in renal fibrosis remain unknown. Norepinephrine (NE), the main sympathetic neurotransmitter, was found to promote TGF-β1-induced epithelial-mesenchymal transition (EMT) and fibrotic gene expression in the human renal proximal epithelial cell line HK-2. Using both genetic and pharmacological approaches, we identified that NE binds Gαq-coupled α1-adrenoceptor (α1-AR) to enhance EMT of HK-2 cells by activating p38/Smad3 signaling. Inhibition of p38 diminished the NE-exaggerated EMT process and increased the fibrotic gene expression in TGF-β1-treated HK-2 cells. Moreover, the pharmacological blockade of α1-AR reduced the kidney injury and renal fibrosis in a unilateral ureteral obstruction mouse model by suppressing EMT in the kidneys. Thus, sympathetic overactivation facilitates EMT of renal epithelial cells and fibrosis via the α1-AR/p38/Smad3 signaling pathway, and α1-AR inhibition may be a promising approach toward treating renal fibrosis.

Impact of Conventional and Atypical MAPKs on the Development of Metabolic Diseases

The family of mitogen-activated protein kinases (MAPKs) consists of fourteen members and has been implicated in regulation of virtually all cellular processes. MAPKs are divided into two groups, conventional and atypical MAPKs. Conventional MAPKs are further classified into four sub-families: extracellular signal-regulated kinases 1/2 (ERK1/2), c-Jun N-terminal kinase (JNK1, 2 and 3), p38 (α, β, γ, δ), and extracellular signal-regulated kinase 5 (ERK5). Four kinases, extracellular signal-regulated kinase 3, 4, and 7 (ERK3, 4 and 7) as well as Nemo-like kinase (NLK) build a group of atypical MAPKs, which are activated by different upstream mechanisms than conventional MAPKs. Early studies identified JNK1/2 and ERK1/2 as well as p38α as a central mediators of inflammation-evoked insulin resistance. These kinases have been also implicated in the development of obesity and diabetes. Recently, other members of conventional MAPKs emerged as important mediators of liver, skeletal muscle, adipose tissue, and pancreatic β-cell metabolism. Moreover, latest studies indicate that atypical members of MAPK family play a central role in the regulation of adipose tissue function. In this review, we summarize early studies on conventional MAPKs as well as recent findings implicating previously ignored members of the MAPK family. Finally, we discuss the therapeutic potential of drugs targeting specific members of the MAPK family.

Stanniocalcin-1 (STC-1), a downstream effector molecule in latanoprost signaling, acts independent of the FP receptor for intraocular pressure reduction

Prostaglandin F2 alpha (PGF2α) analogues such as latanoprost are common first-line intraocular pressure (IOP) lowering medications. However, their clinical use is limited in some patient populations due to minimal or no IOP lowering response or side effects. In searching for a more targeted approach for IOP reduction, our lab recently identified Stanniocalcin-1 (STC-1) as a molecule that was required for latanoprost-mediated IOP reduction and also acted as a stand-alone IOP lowering agent. In order to determine whether latanoprost and STC-1 were equivalent and/or additive for IOP reduction, we treated C57BL/6J mice with one or a combination of these agents and measured IOP. Importance of the FP receptor for latanoprost- and STC-1-mediated IOP reduction was examined in C57BL/6J mice utilizing the pharmacologic FP receptor inhibitor AL-8810 as well as FP receptor knockout mice generated in our laboratory. Latanoprost-free acid (LFA) and STC-1 reduced IOP to a similar degree and were non-additive in C57BL/6J mice. As expected, the IOP lowering effects of LFA were abrogated by pharmacologic inhibition of the FP receptor with AL-8810 and in FP receptor knockout mice. In contrast, STC-1 maintained IOP-lowering effects in the presence of AL-8810 and also in FP receptor knockout mice. These results suggest that LFA and STC-1 show equivalent and non-additive IOP reduction in C57BL/6J mice and that unlike LFA, STC-1-mediated IOP reduction occurs independent of the FP receptor.

Obesity-induced overexpression of miR-802 impairs insulin transcription and secretion

B cell dysfunction due to obesity can be associated with alterations in the levels of micro-RNAs (miRNAs). However, the role of miRNAs in these processes remains elusive. Here, we show that miR-802 is increased in the pancreatic islets of obese mouse models and demonstrate that inducible transgenic overexpression of miR-802 in mice causes impaired insulin transcription and secretion. We identify Foxo1 as a transcription factor of miR-802 promoting its transcription, and NeuroD1 and Fzd5 as targets of miR-802-dependent silencing. Repression of NeuroD1 in β cell and primary islets impairs insulin transcription and reduction of Fzd5 in β cell, which, in turn, impairs Ca²⁺ signaling, thereby repressing calcium influx and decreasing insulin secretion. We functionally create a novel network between obesity and β cell dysfunction via miR-802 regulation. Elucidation of the impact of obesity on microRNA expression can broaden our understanding of pathophysiological development of diabetes.

Obesity predisposes to type 2 diabetes, but the mechanisms of obesity-associated β cell dysfunction are incompletely understood. Here the authors report that obesity increases the levels of miR-802, which impairs insulin transcription and secretion by targeting NeuroD1 and Fzd5.

San-Huang-Tang protects obesity/diabetes induced NAFLD by upregulating PGC-1α/PEPCK signaling in obese and galr1 knockout mice models

ETHNOPHARMACOLOGICAL RELEVANCE

San-Huang-Tang (ST), a classic prescription, has been clinically used to cure diabetes and diabetes-associated metabolic disorders. Established studies have reported that ST can alleviate inflammation, obesity, hyperglycemia and insulin resistance.

AIM OF THE STUDY

To the best of our knowledge, here, we reported for the first time the underlying mechanistic therapeutic efficacy of the ST against nonalcoholic fatty liver disease (NAFLD) in high-fat induced obese and galr1-deficient diabetic mice.

MATERIALS AND METHODS

The obese and galr1-deficient mice were treated with ST at a dose of 10 g/kg every day for three weeks. Then food intake, body weight and insulin resistance indexes were measured. Western blotting, qRT-PCR, and plasma biochemical analyses were applied.

RESULTS

ST reduced food intake, body weight, blood glucose level and insulin resistance, improved glucose tolerance in obese and galr1-deficient mice. Mechanistically, we confirmed that ST protected against NAFLD through activation of PGC-1α and its downstream signaling pathways as shown by the attenuated hepatic adipogenesis and lipid accumulation, increased hepatic fatty acid oxidation, regulated plasma lipid parameters, and increased energy expenditure and metabolic function in fat and muscle.

CONCLUSIONS

Reduction in food intake produced by ST may contribute to the observed metabolic effects. Our findings strongly suggest that ST might be a potential novel therapeutic drug against obesity/diabetes-induced NAFLD and other metabolic disorders.

Baicalin ameliorates hepatic insulin resistance and gluconeogenic activity through inhibition of p38 MAPK/PGC-1α pathway

BACKGROUND

Although the results of our and other studies show that baicalin can enhance glucose uptake and insulin sensitivity in skeletal muscle and adipocytes of mice, the specific metabolic contribution of baicalin on hepatic insulin resistance and gluconeogenic activity is still unclear.

PURPOSE

The aim of this study is to investigate whether baicalin is involved in regulation of hepatic insulin resistance and gluconeogenic activity and its underlying mechanisms.

STUDY DESIGN/METHODS

In the present study, high-fat diet-induced obese mice were given 50 mg/kg baicalin intraperitoneally (i.p.) once a day for 21 consecutive days, and hepatocytes were treated with baicalin (100 μM) or metformin (100 μM) in the presence of glucagon (200 nM) for 12 h. Then insulin resistance indexes and genes related to gluconeogenesis were examined in liver tissues.

RESULTS

The present findings showed that baicalin decreased body weight, HOMA-IR, and alleviated high fat diet-induced glucose intolerance, hyperglycemia and insulin resistance in diet-induced obese mice. Furthermore, baicalin markedly suppressed p-p38 MAPK, p-CREB, FoxO1, PGC-1α, PEPCK and G6Pase expression in liver of obese mice and hepatocytes. Moreover, inhibition of gluconeogenic genes by baicalin was also strengthened by p38MAPK inhibitor in hepatocytes.

CONCLUSION

Baicalin suppressed expression of PGC-1α and gluconeogenic genes, and reduced glucose production in high-fat diet-induced obese mice. Baicalin ameliorated hepatic insulin resistance and gluconeogenic activity mainly through inhibition of p38 MAPK/PGC-1α signal pathway. This study provides a possibility of using baicalin to treat hyperglycemia and hepatic insulin resistance in clinic.

Control strategies in systemic metabolism

Metabolic control systems coordinate myriad processes across the cellular, tissue and organismal levels to optimize the allocation of limited supplies across multiple, often competing, metabolic demands. As such, the regulation of metabolism can be analysed from the perspective of the economic theory of supply and demand. Here, we discuss how such analyses can provide new insights into the logic of metabolic control. In particular, we suggest that, in addition to being subject to well-appreciated homeostatic control, metabolism is subject to supply-driven and demand-driven controls, each operated by a dedicated set of signals throughout various physiological states, including inflammation. Furthermore, we argue that systemic homeostasis is a derived feature that evolved from the control systems that monitor metabolic supply and demand.

The FoxO-Autophagy Axis in Health and Disease

Autophagy controls cellular remodeling and quality control. Dysregulated autophagy has been implicated in several human diseases including obesity, diabetes, cardiovascular disease, neurodegenerative diseases, and cancer. Current evidence has revealed that FoxO (forkhead box class O) transcription factors have a multifaceted role in autophagy regulation and dysregulation. Nuclear FoxOs transactivate genes that control the formation of autophagosomes and their fusion with lysosomes. Independently of transactivation, cytosolic FoxO proteins induce autophagy by directly interacting with autophagy proteins. Autophagy is also controlled by FoxOs through epigenetic mechanisms. Moreover, FoxO proteins can be degraded directly or indirectly by autophagy. Cutting-edge evidence is reviewed that the FoxO-autophagy axis plays a crucial role in health and disease.

Arachidonic Acid Metabolites in Cardiovascular and Metabolic Diseases

Lipid and immune pathways are crucial in the pathophysiology of metabolic and cardiovascular disease. Arachidonic acid (AA) and its derivatives link nutrient metabolism to immunity and inflammation, thus holding a key role in the emergence and progression of frequent diseases such as obesity, diabetes, non-alcoholic fatty liver disease, and cardiovascular disease. We herein present a synopsis of AA metabolism in human health, tissue homeostasis, and immunity, and explore the role of the AA metabolome in diverse pathophysiological conditions and diseases.