Constitutive activation of AMPK α1 in vascular endothelium promotes high-fat diet-induced fatty liver injury: role of COX-2 induction

Taste receptor type 1 member 3 regulates Western diet-induced male infertility

Western diet (WD), characterized by a high intake of fats and sugary drinks, is a risk factor for male reproductive impairment. However, the molecular mechanisms underlying this remain unclear. Taste receptor type 1 member 3 (TAS1R3), activated by ligands of WD, is highly expressed in extra-oral tissues, particularly in the testes. Here, we investigated to determine the effects of WD intake on male reproduction and whether TAS1R3 mediates WD-induced impairment in male reproduction. Male C57BL/6 J wild-type (WT) and Tas1r3 knockout (KO) mice were fed either a normal diet and plain water (ND) or a 60 % high-fat-diet and 30 % (w/v) sucrose water (WD) for 18 weeks (n = 7-9/group). Long-term WD consumption significantly impaired sperm count, motility and testicular morphology in WT mice with marked Tas1r3 overexpression, whereas Tas1r3 KO mice were protected from WD-induced reproductive impairment. Testicular transcriptome analysis revealed downregulated AMP-activated protein kinase (AMPK) signaling and significantly elevated AMPK-targeted nuclear receptor 4A1 (Nr4a1) expression in WD-fed Tas1r3 KO mice. In vitro studies further validated that Tas1r3 knockdown in Leydig cells prevented the suppression of Nr4a1 and downstream steroidogenic genes (Star, Cyp11a1, Cyp17a1, and Hsd3b1) caused by high glucose, fructose, and palmitic acid levels, and maintained the levels of testosterone. Additionally, we analyzed the public human dataset to assess the clinical implications of our findings and confirmed a significant association between TAS1R3 and male-infertility-related diseases. Our findings suggest that TAS1R3 regulates WD-induced male reproductive impairment via the AMPK/NR4A1 signaling and can be a novel therapeutic target for male infertility.

Endothelial AMPKα1/PRKAA1 exacerbates inflammation in HFD-fed mice

BACKGROUND AND PURPOSE

Excess nutrient-induced endothelial cell inflammation is a hallmark in high fat diet (HFD)-induced metabolic syndrome. Pharmacological activation of protein kinase AMP-activated alpha 1(PRKAA1)/5'-Adenosine monophosphate-activated protein kinase alpha1 (AMPKα1) shows its beneficial effects in many studies of cardiometabolic disorders. However, AMPKα1, as a major cellular sensor of energy and nutrients in endothelial cells, has not been studied for its physiological role in excess nutrient-induced endothelial cell (EC) inflammation.

EXPERIMENTAL APPROACH

Wild-type and EC-specific Prkaa1 knockout mice were fed with an HFD. Body weight, fat mass composition, glucose and lipid levels were monitored regularly. Insulin sensitivity was analyzed systemically and in major metabolic organs/tissues. Inflammation status in metabolic organs/tissues were examined with quantitative RT-PCR and flow cytometry. Additionally, metabolic status, inflammation severity and signaling in cultured ECs were assayed with multiple approaches at the molecular level.

KEY RESULTS

EC Prkaa1 deficiency unexpectedly alleviated HFD-induced metabolic syndromes including decreased body weight and fat mass, enhanced glucose clearance and insulin sensitivity, and relieved adipose inflammation and hepatic steatosis. Mechanistically, PRKAA1 knockdown in cultured ECs reduced endothelial glycolysis and fatty acid oxidation, decreased the levels of acetyl-coA, and suppressed transcription of inflammatory molecules mediated by ATP citrate lyase (ACLY) and histone acetyltransferase p300.

CONCLUSIONS AND IMPLICATIONS

This unexpected pro-inflammatory effect of endothelial AMPKα1/PRKAA1 in metabolic context provides additional insight in AMPKα1/PRKAA1 activities, warranting that in-depth study and thoughtful consideration should be applied when AMPKα1/PRKAA1 is used as a therapeutic target in the treatment of metabolic syndrome.

Phosphatidylinositol 3-kinase gamma participates in nimesulide-induced hepatic damage

OBJECTIVE

To evaluate the participation of the phosphatidylinositol 3-kinase pathway in the liver damage caused by nimesulide.

METHODS

Liver damage been induced by nimesulide. Mice were treated with either 2% dimethyl sulfoxide or AS605240, a phosphatidylinositol 3-kinase gamma pathway antagonist. Blood samples were collected for function assays of liver. The liver was removed for analysis of liver weight/animal weight ratio, histopathological parameters, oxidative and nitrous stress, cytokine levels, and the immunostaining for cyclooxygenase 2 and nuclear factor kappa B.

KEY FINDINGS

Liver injured by nimesulide and treated with phosphatidylinositol 3-kinase gamma inhibitor significantly reversed (P < 0.05) the damage; it decreased the liver weight/animal weight ratio, histopathological scores, and neutrophil infiltration, consequently reducing oxidative stress. In addition, we show that phosphatidylinositol 3-kinase gamma is associated with hepatic damage induced by nimesulide, because it altered liver function and increased the protein immunostaining of cyclooxygenase 2 and nuclear factor kappa B in the liver tissue of nimesulide-treated animals.

CONCLUSIONS

The findings from the present study allows us to infer that nimesulide causes liver damage through the phosphatidylinositol 3-kinase gamma pathway.

Vascular adenosine monophosphate-activated protein kinase: Enhancer, brake or both?

Adenosine monophosphate-activated protein kinase (AMPK), expressed/present ubiquitously in the body, contributes to metabolic regulation. In the vasculature, activation of AMPK is associated with several beneficial biological effects including enhancement of vasodilatation, reduction of oxidative stress and inhibition of inflammatory reactions. The vascular protective effects of certain anti-diabetic (metformin and sitagliptin) or lipid-lowering (simvastatin and fenofibrate) therapeutic agents, of active components of Chinese medicinal herbs (resveratrol and berberine) and of pharmacological agents (AICAR, A769662 and PT1) have been attributed to the activation of AMPK (in endothelial cells, vascular smooth muscle cells and/or perivascular adipocytes), independently of changes in the metabolic profile (eg glucose tolerance and/or plasma lipoprotein levels), leading to improved endothelium-derived nitric oxide-mediated vasodilatation and attenuated endothelium-derived cyclooxygenase-dependent vasoconstriction. By contrast, endothelial AMPK activation with pharmacological agents or by genetic modification is associated with reduced endothelium-dependent relaxations in small blood vessels and elevated systolic blood pressure. Indeed, AMPK activators inhibit endothelium-dependent hyperpolarization (EDH)-type relaxations in superior mesenteric arteries, partly by inhibiting endothelial calcium-activated potassium channel signalling. Therefore, AMPK activation is not necessarily beneficial in terms of endothelial function. The contribution of endothelial AMPK in the regulation of vascular tone, in particular in the microvasculature where EDH plays a more important role, remains to be characterized.

HBx combined with AFB1 triggers hepatic steatosis via COX-2-mediated necrosome formation and mitochondrial dynamics disorder

Hepatitis B virus (HBV) infection and aflatoxin B1 (AFB1) exposure have been recognized as independent risk factors for the occurrence and exacerbation of hepatic steatosis but their combined impacts and the potential mechanisms remain to be further elucidated. Here, we showed that exposure to AFB1 impaired mitochondrial dynamics and increased intracellular lipid droplets (LDs) in the liver of HBV-transgenic mice in vivo and the hepatitis B virus X protein (HBx)-expressing human hepatocytes both ex vivo and in vitro. HBx combined with AFB1 exposure also up-regulated receptor interaction protein 1 (RIP1), receptor interaction protein 3 (RIP3) and activated mixed lineage kinase domain like protein (MLKL), providing evidence of necrosome formation in the hepatocytes. The shift of the mitochondrial dynamics towards imbalance of fission and fusion was rescued when MLKL was inhibited in the HBx and AFB1 co-treated hepatocytes. Most importantly, based on siRNA or CRISPR/Cas9 system, we found that the combination of HBx and AFB1 exposure increased cyclooxygenase-2 (COX-2) to mediate up-regulation of RIP3 and dynamin-related protein 1 (Drp1), which in turn promoted location of RIP3-MLKL necrosome on mitochondria, subsequently exacerbated steatosis in hepatocytes. Taken together, these findings advance the understanding of mechanism associated with HBx and AFB1-induced hepatic necrosome formation, mitochondrial dysfunction and steatosis and make COX-2 a good candidate for treatment.

The Biological Efficacy of Natural Products against Acute and Chronic Inflammatory Diseases in the Oral Region

The oral inflammatory diseases are divided into two types: acute and chronic inflammatory diseases. In this review, we summarize the biological efficacy of herbal medicine, natural products, and their active ingredients against acute and chronic inflammatory diseases in the oral region, especially stomatitis and periodontitis. We review the effects of herbal medicines and a biscoclaurin alkaloid preparation, cepharamthin, as a therapy against stomatitis, an acute inflammatory disease. We also summarize the effects of herbal medicines and natural products against periodontitis, a chronic inflammatory disease, and one of its clinical conditions, alveolar bone resorption. Recent studies show that several herbal medicines such as kakkonto and ninjinto reduce LPS-induced PGE2 production by human gingival fibroblasts. Among herbs constituting these herbal medicines, shokyo (Zingiberis Rhizoma) and kankyo (Zingiberis Processum Rhizoma) strongly reduce PGE2 production. Moreover, anti-osteoclast activity has been observed in some natural products with anti-inflammatory effects used against rheumatoid arthritis such as carotenoids, flavonoids, limonoids, and polyphenols. These herbal medicines and natural products could be useful for treating oral inflammatory diseases.

Linkage of Metabolic Defects to Activated PIK3CA Alleles in Endothelial Cells Derived from Lymphatic Malformation

BACKGROUND

Lymphatic endothelial cells (LECs) derived from lymphatic malformations (LMs) bear activated PIK3CA alleles yet display an inflammatory gene expression profile. A basis for the inflammatory phenotype was sought by screening for coexisting somatic mutations.

METHODS AND RESULTS

Fourteen independent LEC populations bearing activated PIK3CA alleles were isolated from LM. These were characterized by the expression of growth and inflammatory genes (VEGFC, IL-6, COX-2, IL-8, HO-1, E-SEL) by qRT-PCR. Most commonly upregulated gene products were VEGFC, COX2, HO-1, and ANGPTL4. The specific inhibition of PI3K reduced VEGFC expression without resolving inflammation. Whole exome sequencing of six LM-LEC populations identified five novel somatically acquired alleles coexisting with activated PIK3CA alleles. Two affected genes regulate lipid droplet metabolism (FITM2 and ATG2A), two are gene regulators (MTA1 and TAF1L), and the fifth is an isoform of ANK3 (an endosomal/lysosomal protein). Inhibition of AMPK implicated its involvement in regulating COX-2 and HO-1 overexpression. ANGPTL4 expression was independent of AMPK and PI3K activity and reflected lipid stress demonstrated in normal LECs. AMPK activation with AICAR had a selective growth-limiting effect in a subset of LM-LEC isolates.

CONCLUSIONS

Inflammatory stress displayed by LM-LECs is consistent with errors in lipid metabolism that may be linked to acquired mutations. The acquisition of PIK3CA alleles may be a permissive event that antagonizes inflammation and metabolic defect.

Caffeoylquinic Acid-Rich Extract of Aster glehni F. Schmidt Ameliorates Nonalcoholic Fatty Liver through the Regulation of PPARδ and Adiponectin in ApoE KO Mice

Aster glehni is well known for its therapeutic properties. This study was performed to investigate the effects of A. glehni on nonalcoholic fatty liver disease (NAFLD) in atherosclerotic condition, by determining the levels of biomarkers related to lipid metabolism and inflammation in serum, liver, and adipose tissue. Body and abdominal adipose tissue weights and serum triglyceride level decreased in all groups treated with A. glehni. Serum adiponectin concentration and protein levels of peroxisome proliferator-activated receptor δ, 5′ adenosine monophosphate-activated protein kinase, acetyl-CoA carboxylase, superoxide dismutase, and PPARγ coactivator 1-alpha in liver tissues increased in the groups treated with A. glehni. Conversely, protein levels of ATP citrate lyase, fatty acid synthase, tumor necrosis factor α, and 3-hydroxy-3-methylglutaryl-CoA reductase and the concentrations of interleukin 6 and reactive oxygen species decreased upon A. glehni. Triglyceride concentration in the liver was lower in mice treated with A. glehni than in control mice. Lipid accumulation in HepG2 and 3T3-L1 cells decreased upon A. glehni treatment; this effect was suppressed in the presence of the PPARδ antagonist, GSK0660. Our findings suggest that A. glehni extracts may ameliorate NAFLD through regulation of PPARδ, adiponectin, and the related subgenes.

High-Fat and Fat-Enriched Diets Impair the Benefits of Moderate Physical Training in the Aorta and the Heart in Rats

AIM

Millions of people die each year due to cardiovascular disease (CVD). A Western lifestyle not only fuses a significant intake of fat with physical inactivity and obesity but also promotes CVD. Recent evidence suggests that dietary fat intake impairs the benefits of physical training. We investigated whether aerobic training could reverse the adverse effects of a high-fat diet (HFD) on the aorta. Then, we explored whether this type of exercise could reverse the damage to the heart that is imposed by fat-enriched diet (FED).

METHODS

Rats were randomly assigned to two experiments, which lasted 8 weeks each. First, rats swam for 60 min and were fed either a regular diet [standard diet (STD)] or an HFD. After aortic samples had been collected, the rats underwent a histopathological analysis for different biomarkers. Another experiment subjected rats that were fed either an STD or an FED to swimming for 20 or 90 min.

RESULTS

The first experiment revealed that rats that were subjected to an HFD-endured increased oxidative damage in the aorta that exercises could not counteract. Together with increased cyclooxygenase 2 expression, an HFD in combination with physical training increased the number of macrophages. A reduction in collagen fibers with an increased number of positive α-actin cells and expression of matrix metalloproteinase-2 occurred concomitantly. Upon analyzing the second experiment, we found that physically training rats that were given an FED for 90 min/day decreased the cardiac adipose tissue density, although it did not protect the heart from fat-induced oxidative damage. Even though the physical training lowered cholesterol levels that were promoted by the FED, the levels were still higher than those in the animals that were given an STD. Feeding rats an FED impaired the swimming protocol's effects on lowering triglyceride concentration. Additionally, exercise was unable to reverse the fat-induced deregulation in hepatic antioxidant and lipid peroxidation activities.

CONCLUSION

Our findings reveal that an increased intake of fat undermines the potential benefits of physical exercise on the heart and the aorta.

AMPK and HIF signaling pathways regulate both longevity and cancer growth: the good news and the bad news about survival mechanisms

The AMP-activated protein kinase (AMPK) and hypoxia-inducible factor (HIF) signaling pathways are evolutionarily-conserved survival mechanisms responding to two fundamental stresses, energy deficiency and/or oxygen deprivation. The AMPK and HIF pathways regulate the function of a survival network with several transcription factors, e.g. FOXO, NF-κB, NRF2, and p53, as well as with protein kinases and other factors, such as mTOR, ULK1, HDAC5, and SIRT1. Given that AMPK and HIF activation can enhance not only healthspan and lifespan but also cancer growth in a context-dependent manner; it seems that cancer cells can hijack certain survival factors to maintain their growth in harsh conditions. AMPK activation improves energy metabolism, stimulates autophagy, and inhibits inflammation, whereas HIF-1α increases angiogenesis and helps cells to adapt to severe conditions. First we will review how AMPK and HIF signaling mechanisms control the function of an integrated survival network which is able not only to improve the regulation of longevity but also support the progression of tumorigenesis. We will also describe distinct crossroads between the regulation of longevity and cancer, e.g. specific regulation through the AMPKα and HIF-α isoforms, the Warburg effect, mitochondrial dynamics, and cellular senescence.

Impact of AMP-Activated Protein Kinase α1 Deficiency on Tissue Injury following Unilateral Ureteral Obstruction

Background

AMP-activated protein kinase (Ampk) is a sensor of the cellular energy status and a powerful regulator of metabolism. Activation of Ampk was previously shown to participate in monocyte-to-fibroblast transition and matrix protein production in renal tissue. Thus, the present study explored whether the catalytic Ampkα1 isoform participates in the regulation of the renal fibrotic response following unilateral ureteral obstruction (UUO).

Methods

UUO was induced in gene-targeted mice lacking functional Ampkα1 (Ampkα1^-/-) and in corresponding wild-type mice (Ampkα1^+/+). In the obstructed kidney and, for comparison, in the non-obstructed control kidney, quantitative RT-PCR, Western blotting and immunostaining were employed to determine transcript levels and protein abundance, respectively.

Results

In Ampkα1^+/+ mice, UUO significantly up-regulated the protein abundance of the Ampkα1 isoform, but significantly down-regulated the Ampkα2 isoform in renal tissue. Phosphorylated Ampkα protein levels were significantly increased in obstructed kidney tissue of Ampkα1^+/+ mice but not of Ampkα1^-/- mice. Renal expression of α-smooth muscle actin was increased following UUO, an effect again less pronounced in Ampkα1^-/- mice than in Ampkα1^+/+ mice. Histological analysis did not reveal a profound effect of Ampkα1 deficiency on collagen 1 protein deposition. UUO significantly increased phosphorylated and total Tgf-ß-activated kinase 1 (Tak1) protein, as well as transcript levels of Tak1-downstream targets c-Fos, Il6, Pai1 and Snai1 in Ampkα1^+/+ mice, effects again significantly ameliorated in Ampkα1^-/- mice. Moreover, Ampkα1 deficiency inhibited the UUO-induced mRNA expression of Cd206, a marker of M2 macrophages and of Cxcl16, a pro-fibrotic chemokine associated with myeloid fibroblast formation. The effects of Ampkα1 deficiency during UUO were, however, paralleled by increased tubular injury and apoptosis.

Conclusions

Renal obstruction induces an isoform shift from Ampkα2 towards Ampkα1, which contributes to the signaling involved in cell survival and fibrosis.