Dehydroepiandrosterone reduces accumulation of lipid droplets in primary chicken hepatocytes by biotransformation mediated via the cAMP/PKA-ERK1/2 signaling pathway

Genistein upregulates AHR to protect against environmental toxin-induced NASH by inhibiting NLRP3 inflammasome activation and reconstructing antioxidant defense mechanisms

We have previously proven that the environmental toxin could accelerate the development and progression of nonalcoholic steatohepatitis (NASH). However, the underlying mechanism associated with such excessive inflammation hasn't been fully illustrated. Although Genistein has been well accepted for its capability in anti-inflammation and anti-oxidation, its effect in ameliorating contaminants-induced NASH still needs to be identified. In this study, using chickens and primary chicken hepatocytes as models, we found that NOD-like receptor pyrin domain-containing 3 (NLRP3) inflammasome were over-activated in bromoacetic acid (BAA, one of the typical environmental toxins)-induced NASH, characterized by the infiltration of inflammatory cell, and the increase of NLRP3, Caspase-1 p20, and cytokines (IL-1β, IL-18) expressions. Interestingly, genistein treatment could recover these changes, with the signs of restored activities of anti-oxidases, decreased expressions of NLRP3 inflammasome components, and increased levels of elements in phase I metabolic system. The detailed mechanism was that, via up-regulating aryl hydrocarbon receptor (AHR), genistein lifted mRNA levels of Cyp1-related genes to reconstruct cytochrome P450 (CYP450) systems, and the raised AHR negatively regulated NLRP3 inflammasome activity to relieve inflammation. More important, the interaction and co-localization between AHR and NLRP3 was first proved, and genistein could promote the levels of AHR that interacted with NLRP3, which thereafter blocked the activation of NLRP3 inflammasome. Conclusively, in this research, we confirmed the AHR-dependent protective role of genistein in environmental toxin-linked NASH, which shed light on the potential precautions for contaminants-induced NASH.

Dehydroepiandrosterone activates the GPER-mediated AMPK signaling pathway to alleviate the oxidative stress and inflammatory response in laying hens fed with high-energy and low-protein diets

Fatty liver hemorrhagic syndrome (FLHS) seriously threatens the layer industry due to it can cause a sudden decline in egg production and acute death, and dietary supplement with bioactive substance is considered an effective way to prevent the FLHS occurrence. Dehydroepiandrosterone (DHEA) is a popular dietary supplement and it possesses anti-oxidative and anti-inflammatory functions; however, the effect and underlying mechanism about DHEA in protecting against the occurrence and development of FLHS remain elucidated. The current results showed that DHEA relieved HELP-induced decrease of egg productivity and liver injury in laying hens. Meanwhile, DHEA markedly enhanced the antioxidant capacity and then alleviated oxidative stress via activation of nuclear factor (erythroid-derived 2)-like 2 (NRF-2) signal in laying hens fed with HELP diets. In addition, DHEA significantly alleviated HELP-stimulated systemic inflammatory response by suppressing the overproduction of hepatic pro-inflammatory factors in laying hens, and further found this beneficial effect was achieved by blocking the activation of NF-κB pathway. Furthermore, we found that DHEA promoted the AMP-activated protein kinase α (AMPKα) activation and increased the G-protein-coupled estrogen receptor (GPER) expression level in laying hens fed with HELP diets. In summary, our data demonstrated that DHEA attenuates oxidative stress and inflammation through the activation of GPER-AMPK signal axis in laying hens fed with HELP diets. These results might facilitate an understanding of the benefits and mechanism of DHEA on the development of FLHS, and provide sufficient data to support it as a dietary supplement to control the FLHS-related metabolic diseases in chickens.

Genistein accelerates glucose catabolism via activation the GPER-mediated cAMP/PKA-AMPK signaling pathway in broiler chickens

Genistein, the most abundance of phytoestrogens in soybeans, has beneficial effects in regulating metabolism-related disease; however, there is few available literatures about whether genistein regulates glucose metabolism that in turn affects the lipid accumulation in animals or humans. The current study showed that genistein promoted glucose uptake by enhancing glucose transporter-2 (GLUT2) protein level; and it also increased the activity of phosphofructokinase-1 (PFK) and pyruvate dehydrogenase (PDH), and the mRNA level of succinate dehydrogenase (SDH) both in broiler chickens or hepatocytes. Moreover, genistein obviously increased the p-LKB1 and p-AMPKα protein levels both in vivo and in vitro. Furthermore, the enhancement of genistein on glucose uptake and catabolism were reversed in hepatocytes pre-treated with AMPK inhibitor Compound C, and the increasing of genistein on the p-LKB1 and p-AMPKα protein levels were also reversed in hepatocytes pre-treated with PKA inhibitor H89. Importantly, the results showed that genistein simultaneously increased the estrogen receptor β (ERβ) and G protein-coupled estrogen receptor (GPER) protein levels, but the elevation effect of genistein on cAMP content was completely reversed in hepatocytes pre-treated with GPER antagonist G15, rather than ERβ inhibitor PHTPP. Meanwhile, the increasing of p-LKB1 and p-AMPKα protein levels induced by genistein were also reversed in hepatocytes pre-treated with G15. Collectively, our data demonstrated that genistein improves glucose metabolism via activating the GPER-mediated cAMP/PKA-AMPK signaling pathway. These findings provide theoretical basis for genistein as a promising nutritional supplemental to alleviate metabolism disorders and related diseases in animals or even humans.

The sex steroid precursor dehydroepiandrosterone prevents nonalcoholic steatohepatitis by activating the AMPK pathway mediated by GPR30

The prevalence of nonalcoholic steatohepatitis (NASH) caused by estrogen deficiency increased sharply in recent decades and has become a major threat to liver health in postmenopausal women. There is no effective strategy to control the incidence and development of NASH. Dehydroepiandrosterone (DHEA) is the most abundant circulating steroid with immune and metabolic regulatory properties, and its level markedly declines with increasing age in humans. Importantly, DHEA can convert into active sex hormones depending on the local needs of target tissues with little diffusion, which serves to avoid systemic side-effects from other tissues' exposure to estrogen. Here, we found that DHEA prevented the incidence and development of NASH, which is characterized by the reduction of hepatic steatosis, fibrosis, and inflammation in female mice fed with high-fat/high-cholesterol diets and effectively attenuated lipid accumulation, inflammatory response, and oxidative stress in palmitic acid-challenged hepatocytes. Mechanistically, in vitro and in vivo studies showed that the anti-NASH function of DHEA depended on its biotransformation into estrogen rather than androgen, and which up-regulates the expression of G protein-coupled estrogen receptor (GPR30), a non-classical estrogen receptor. The activation of GPR30-mediated AMP-activated protein kinase signaling is a necessary prerequisite for the alleviative effects of DHEA on NASH. Collectively, our data show the mechanisms of DHEA treatment and its effects on NASH that were previously overlooked; the data also show that GPR30 can be used as a target for treating lipid metabolism disorders and related diseases, such as NASH. Furthermore, these findings have the potential to help researchers develop new strategies for preventing NASH in postmenopausal women.

Effect of dehydroepiandrosterone on atherosclerosis in postmenopausal women

In China, cardiovascular disease (CVD) has surpassed malignant tumours to become the disease with the highest mortality rate, and atherosclerosis (AS) is an important pathological cause of CVD. Dehydroepiandrosterone (DHEA) is the most abundant steroid hormone in circulating human blood and is a precursor of estrogen and androgen. DHEA is converted into a series of sex hormones in local peripheral tissues where its acts physiologically. DHEA also acts therapeutically, thereby avoiding the adverse systemic reactions to sex hormones. DHEA inhibits AS, thus inhibiting the development of CVD, and it improves the prognosis for CVD. The incidence of CVD in postmenopausal women is substantially higher than that in premenopausal women, and that incidence is believed to be related to a decrease in ovarian function. The current review analyzes the mechanisms of postmenopausal women's susceptibility to AS. They tend to have dyslipidemia, and their vascular smooth muscle cells (VSMCs) proliferate and migrate more. In addition, oxidative stress and the inflammatory response of endothelial cells (ECs) are more serious in postmenopausal women. This review also discusses how DHEA combats AS by countering these mechanisms, which include regulating the blood lipid status, protecting ECs (including coping with oxidative stress and inflammatory reactions of the vascular endothelium, inhibiting apoptosis of ECs, and inducing NO production) and inhibiting the proliferation and migration of VSMCs. As a result, DHEA has great value in preventing AS and inhibiting its progression in postmenopausal women.

Eif2s3y Promotes the Proliferation of Spermatogonial Stem Cells by Activating ERK Signaling

The future fertility of males with cancer may be irreversibly compromised by chemotherapy and/or radiotherapy. Spermatogonial stem cell transplantation is believed to be a way to restore fertility in men. However, the survival efficiency of transplanted cells is still low. Eukaryotic translation initiation factor 2 subunit 3 and structural gene Y-linked (Eif2s3y) located on the Y chromosome of male animals is a coding gene of eIF2γ which mainly functions in translation initiation. Recently, the emerging role of Eif2s3y in spermatogenesis has been emphasized in several studies. However, the underlying mechanism is still unclear. In addition, how Eif2s3y functions in large animals remains largely unknown. In this study, we obtained the CDS sequence of the Eif2s3y gene from the testis of dairy goats and found that this gene was highly expressed in the testis and was evolutionarily conserved among different species. Interestingly, overexpression of Eif2s3y promoted the proliferation of spermatogonial stem cells of dairy goats by activating the ERK signaling pathway. In animal experiments, overexpressing Eif2s3y promoted transplanted goat spermatogonial stem cells and produced more colonies after microinjection into the seminiferous tubules of infertile mice. In conclusion, our study highlights an undiscovered role of Eif2s3y in dairy goat reproduction. This finding may provide an important basis for future works regarding male spermatogenic cell restoration and represent a major advance toward surrogate sires becoming a tool for disseminating and regenerating germplasm in all mammals.

Dehydroepiandrosterone protects against hepatic glycolipid metabolic disorder and insulin resistance induced by high fat via activation of AMPK-PGC-1α-NRF-1 and IRS1-AKT-GLUT2 signaling pathways

BACKGROUND/OBJECTIVES

Mitochondrial dysfunction, oxidative stress, or fatty liver are the key pathophysiological features for insulin resistance and obesity. Dehydroepiandrosterone (DHEA) can ameliorate obesity and insulin resistance; however, the mechanisms of these actions are poorly understood. The present study aimed to investigate the effect and possible mechanism of DHEA against glycolipid metabolic disorder and insulin resistance.

SUBJECTS/METHODS

Rats fed a high-fat diet (HFD) and palmitic acid (PA)-induced BRL-3A cells were employed to analyze the effect of DHEA on factors related to metabolic disorder and insulin resistance in vivo and in vitro.

RESULTS

DHEA prevented lipid metabolism disorders by enhancing phospho (p)-protein kinase AMP-activated catalytic subunit alpha (AMPKα) (Thr172) protein level and its downstream lipid metabolism-related factors in liver of rats fed an HFD or in PA-induced BRL-3A cells. Meanwhile, DHEA ameliorated mitochondrial dysfunction through activation of the AMPK-peroxisome proliferator-activated receptor gamma coactivator 1 alpha (PGC-1α)-nuclear respiratory factor-1 (NRF-1) pathway, which represented as the enhancing of the mtDNA copy number, ATP level, and membrane potential, and decreasing of reactive oxygen species production. Moreover, DHEA alleviated insulin resistance via increasing the phosphorylated insulin receptor substrate 1 (p-IRS1) (Tyr612) level and decreasing that of p-IRS1 (Ser307) level in liver of rats fed an HFD or in PA-induced BRL-3A cells, which subsequently enhanced p-protein kinase B (AKT) (Ser473) and membrane glucose transporter type 2 (GLUT2) expression levels.

CONCLUSIONS

The protective effect of DHEA on high-fat-induced hepatic glycolipid metabolic disorder and insulin resistance are achieved through activation of the AMPK-PGC-1α-NRF-1 and IRS1-AKT-GLUT2 signaling pathways. The results provide compelling evidence for the mechanism by which DHEA prevents glycolipid metabolic disorder, and suggest its potential applications for controlling diabetes and obesity in animals and humans.

Dietary citrus peel essential oil ameliorates hypercholesterolemia and hepatic steatosis by modulating lipid and cholesterol homeostasis

Integration of lipidomics and gene expression analysis provided new insights into in-depth mechanistic understanding of the effects of dietary CPEO.

Coenzyme Q10 Protects Astrocytes from Ultraviolet B-Induced Damage Through Inhibition of ERK 1/2 Pathway Overexpression

Overexpression of extracellular signal-regulated kinase ½ (ERK ½) signaling pathway leads to overproduction of reactive oxygen species (ROS) which induces oxidative stress. Coenzyme Q10 (CoQ10) scavenges ROS and protects cells against oxidative stress. The present study was designed to examine whether the protection of Coenzyme Q10 against oxidative damage in astrocytes is through regulating ERK 1/2 pathway. Ultraviolet B (UVB) irradiation was chosen as a tool to induce oxidative stress. Murine astrocytes were treated with 10 μg/ml and 25 μg/ml of CoQ10 for 24 h prior to UVB and maintained during UVB and 24 h post-UVB. Cell viability was evaluated by counting viable cells and MTT conversion assay. ROS production was measured using fluorescent probes. Levels of p-ERK 1/2, ERK 1/2, p-PKA, PKA were detected using immunocytochemistry and/or Western blotting. The results showed that UVB irradiation decreased the number of viable cells. This damaging effect was associated with accumulation of ROS and elevations of p-ERK 1/2 and p-PKA. Treatment with CoQ10 at 25 μg/ml significantly increased the number of viable cells and prevented the UVB-induced increases of ROS, p-ERK 1/2, and p-PKA. It is concluded that suppression of the PKA-ERK 1/2 signaling pathway may be one of the important mechanisms by which CoQ10 protects astrocytes from UVB-induced oxidative damage.

Dehydroepiandrosterone Prevents H2O2-Induced BRL-3A Cell Oxidative Damage through Activation of PI3K/Akt Pathways rather than MAPK Pathways

Dehydroepiandrosterone (DHEA) is a popular dietary supplement that has well-known benefits in animals and humans, but there is not enough information about the mechanisms underlying its effects. The present study aimed at investigating these mechanisms through in vitro experiments on the effects of DHEA on rat liver BRL-3A cells exposed to oxidative stress through H₂O₂. The findings showed that DHEA increased the antioxidant enzyme activity, decreased ROS generation, and inhibited apoptosis in H₂O₂-treated cells. These effects of DHEA were not observed when the cells were pretreated with known antagonists of sex hormones (Trilostane, Flutamide, or Fulvestrant). Furthermore, treatment with estradiol and testosterone did not have the same protective effects as DHEA. Thus, the beneficial effects of DHEA were associated with mechanisms that were independent of steroid hormone pathways. With regard to the mechanism underlying the antiapoptotic effect of DHEA, pretreatment with DHEA was found to induce a significant decrease in the protein expression of Bax and caspase-3 and a significant increase in the protein expression of PI3K and p-Akt in H₂O₂-treated BRL-3A cells. These effects of DHEA were abolished when the cells were pretreated with the PI3K inhibitor LY294002. No changes were observed on the p-ERK1/2, p-p38, and p-JNK protein levels in H₂O₂-induced BRL-3A cells pretreated with DHEA. In conclusion, our data demonstrate that DHEA protects BRL-3A cells against H₂O₂-induced oxidative stress and apoptosis through mechanisms that do not involve its biotransformation into steroid hormones or the activation of sex hormone receptors. Importantly, the protective effect of DHEA on BRL-3A cells was mainly associated with PI3K/Akt signaling pathways, rather than MAPK signaling pathways.

(-)-Hydroxycitric Acid Suppresses Lipid Droplet Accumulation and Accelerates Energy Metabolism via Activation of the Adiponectin-AMPK Signaling Pathway in Broiler Chickens

(-)-Hydroxycitric acid (HCA) inhibits the deposition of fat in animals and humans, while the molecular mechanism is still unclear. The present study investigated the effect and mechanism of (-)-HCA's regulation of lipid, glucose, and energy metabolism in broiler chickens. The current results showed that (-)-HCA decreased the accumulation of lipid droplets and triglyceride content by reducing fatty acid synthase protein level and enhancing phosphorylation of acetyl-CoA carboxylase protein level. (-)-HCA accelerated carbohydrate aerobic metabolisms by increasing the activities of phosphofructokinase-1, pyruvate dehydrogenase, succinate dehydrogenase, and malate dehydrogenase. Furthermore, (-)-HCA increased adiponectin receptor 1 mRNA level and enhanced phospho-AMPKα, peroxisome proliferator-activated receptor gamma coactivator-1α, nuclear respiratory factor-1, and mitochondrial transcription factor A protein levels in broiler chickens. These data indicated that (-)-HCA reduced lipid droplet accumulation, improved glucose catabolism, and accelerated energy metabolism in broiler chickens, possibly via activation of adiponectin-AMPK signaling pathway. These results revealed the biochemical mechanism of (-)-HCA-mediated fat accumulation and the prevention of metabolic disorder-related diseases in broiler chickens.

Cascade biotransformation of dehydroepiandrosterone (DHEA) by Beauveria species

Beauveria bassiana is an entomopathogenic fungus used as a biological control agent. It is a well-known biocatalyst for the transformation of steroid compounds. Hydroxylations at the 7α or 11α position and oxidation to D-homo lactones are described in the literature. In our study, we examined the diversity of metabolism of five different B. bassiana strains and compared them to already known pathways. According to the literature, 7α and 11α-hydroxy derivatives as well as 3β,11α-dihydroxy-17a-oxa-D-homo-androst-5-en-17-one have been observed. Here we describe new DHEA metabolic pathways and two products not described before: 3β-hydroxy-17a-oxa-D-homo-androst-5-en-7,17-dione and 3β,11α-dihydroxyandrost-5-en-7,17-dione. We also used for the first time another species from this genus, Beauveria caledonica, for steroid transformation. DHEA was hydroxylated at the 7α, 7β and 11α positions and then reactions of oxidation and reduction leading to 3β,11α-dihydroxyandrost-5-en-7,17-dione were observed. All tested strains from the Beauveria genus effectively transformed the steroid substrate using several different enzymes, resulting in cascade transformation.