Insulin hypersensitivity induced by hepatic PTEN gene ablation protects from murine endotoxemia

Malic Enzyme 1 as a Novel Anti-Ferroptotic Regulator in Hepatic Ischemia/Reperfusion Injury

Ferroptosis has been linked to the pathogenesis of hepatic injury induced by ischemia/reperfusion (I/R). However, the mechanistic basis remains unclear. In this study, by using a mouse model of hepatic I/R injury, it is observed that glutathione (GSH) and cysteine depletion are associated with deficiency of the reducing power of nicotinamide adenine dinucleotide phosphate (NADPH). Genes involved in maintaining NADPH homeostasis are screened, and it is identified that I/R-induced hepatic ferroptosis is significantly associated with reduced expression and activity of NADP+ -dependent malic enzyme 1 (Me1). Mice with hepatocyte-specific Me1 gene deletion exhibit aggravated ferroptosis and liver injury under I/R treatment; while supplementation with L-malate, the substrate of ME1, restores NADPH and GSH levels and eventually inhibits I/R-induced hepatic ferroptosis and injury. A mechanistic study further reveals that downregulation of hepatic Me1 expression is largely mediated by the phosphatase and tensin homologue (PTEN)-dependent suppression of the mechanistic target of rapamycin/sterol regulatory element-binding protein 1 (mTOR/SREBP1) signaling pathway in hepatic I/R model. Finally, PTEN inhibitor, mTOR activator, or SREBP1 over-expression all increase hepatic NADPH, block ferroptosis, and protect liver against I/R injury. Taken together, the findings suggest that targeting ME1 may provide new therapeutic opportunities for I/R injury and other ferroptosis-related hepatic conditions.

Enhancer of Zeste 2 Polycomb Repressive Complex 2 Subunit Is Required for Uterine Epithelial Integrity

Normal proliferation and differentiation of uterine epithelial cells are critical for uterine development and function. Enhancer of zeste 2 polycomb repressive complex 2 subunit (EZH2), a core component of polycomb repressive complexes 2, possesses histone methyltransferase activity that catalyzes the trimethylation of lysine 27 of histone H3. EZH2 has been involved in epithelial-mesenchymal transition, a key event in development and carcinogenesis. However, its role in uterine epithelial cell function remains unknown. To determine the role of uterine EZH2, Ezh2 was conditionally deleted using progesterone receptor Cre recombinase, which is expressed in both epithelial and mesenchymal compartments of the uterus. Loss of EZH2 promoted stratification of uterine epithelium, an uncommon and detrimental event in the uterus. The abnormal epithelium expressed basal cell markers, including tumor protein 63, cytokeratin 5 (KRT5), KRT6A, and KRT14. These results suggest that EZH2 serves as a guardian of uterine epithelial integrity, partially via inhibiting the differentiation of basal-like cells and preventing epithelial stratification. The observed epithelial abnormality was accompanied by fertility defects, altered uterine growth and function, and the development of endometrial hyperplasia. Thus, the Ezh2 conditional knockout mouse model may be useful to explore mechanisms that regulate endometrial homeostasis and uterine function.

Short-term insulin intensive therapy decreases MCP-1 and NF-κB expression of peripheral blood monocyte and the serum MCP-1 concentration in newlydiagnosed type 2 diabetics

OBJECTIVE

To observe the effect of short-term insulin intensive treatment on the monocyte chemoattractant protein-1 (MCP-1) as well as on the nuclear factor-kappa B (NF-κB) expression of peripheral blood monocyte. This is also in addition to observing the serum MCP-1 level in newlydiagnosed type 2 diabetic patients and probing its anti-inflammation effects.

SUBJECTS AND METHODS

Twenty newly-diagnosed type 2 diabetic patients were treated with an insulin intensive treatment for 2 weeks. MCP-1 and NF-κB expression on the monocyte surface were measured with flow cytometry, the serum MCP-1 level was measured by enzyme linked immunosorbent assay (ELISA) during pretreatment and post-treatment.

RESULTS

After 2 weeks of the treatment, MCP-1 and NF-κB protein expression of peripheral blood monocyte and serum MCP-1 levels decreased significantly compared with those of pre-treatment, which were (0.50 ± 0.18)% vs (0.89 ± 0.26)% (12.22 ± 2.80)% vs (15.53 ± 2.49)% and (44.53 ± 3.97) pg/mL vs (49.53 ± 3.47) pg/mL, respectively (P < 0.01). The MCP-1 expression on monocyte surface had a significant positive relationship with serum MCP-1 levels (r = 0.47, P < 0.01).

CONCLUSIONS

Short-term insulin intensive therapy plays a role in alleviating the increased inflammation reaction in type 2 diabetics.

MiR-19a mediates gluconeogenesis by targeting PTEN in hepatocytes

As a member of miR-17-92 miRNA clusters, miR‑19a has been considered to regulate hepatic glycogenesis by mediating the PI3K/AKT signaling pathway. However, whether miR‑19a serves an important role in gluconeogenesis in hepatocytes remains unknown. In the present study, the impact of miR‑19a on gluconeogenesis in HEP1‑6 cells and its mechanisms of action were investigated. It was observed that overexpression of miR‑19a led to decreased glucose production, accompanied by increased activation of the AKT/FOXO1 signaling pathway and downregulated expression of gluconeogenesis‑associated genes, including peroxisome proliferator‑activated receptor γ coactivator 1α, phosphoenolpyruvate carboxykinase and glucose 6‑phosphatase in the HEP1‑6 cells transfected with the miR‑19a mimic. In contrast, suppression of miR‑19a impaired the activation of the AKT/FOXO1 signaling pathway and increased the expression of gluconeogenesis‑associated genes, accompanied by an elevated glucose production. Additionally, phosphatase and tensin homolog (PTEN) was identified as a target of miR‑19a and participated in the miR‑19a‑mediated gluconeogenesis in hepatocytes. These findings provide mechanistic insight into the effects of miR‑19a on the regulation of the AKT/FOXO1 signaling pathway and the expression of gluconeogenesis‑associated genes. MiR‑19a may mediate gluconeogenesis in hepatocytes by downregulating PTEN expression.

Liver-Specific Deletion of Phosphatase and Tensin Homolog Deleted on Chromosome 10 Significantly Ameliorates Chronic EtOH-Induced Increases in Hepatocellular Damage

Alcoholic liver disease is a significant contributor to global liver failure. In murine models, chronic ethanol consumption dysregulates PTEN/Akt signaling. Hepatospecific deletion of phosphatase and tensin homolog deleted on chromosome 10 (PTEN^LKO) mice possess constitutive activation of Akt(s) and increased de novo lipogenesis resulting in increased hepatocellular steatosis. This makes PTEN^LKO a viable model to examine the effects of ethanol in an environment of preexisting steatosis. The aim of this study was to determine the impact of chronic ethanol consumption and the absence of PTEN (PTEN^LKO) compared to Alb-Cre control mice (PTEN^f/f) on hepatocellular damage as evidenced by changes in lipid accumulation, protein carbonylation and alanine amino transferase (ALT). In the control PTEN^f/f animals, ethanol significantly increased ALT, liver triglycerides and steatosis. In contrast, chronic ethanol consumption in PTEN^LKO mice decreased hepatocellular damage when compared to PTEN^LKO pair-fed controls. Consumption of ethanol elevated protein carbonylation in PTEN^f/f animals but had no effect in PTEN^LKO animals. In PTEN^LKO mice, overall hepatic mRNA expression of genes that contribute to GSH homeostasis as well as reduced glutathione (GSH) and oxidized glutathione (GSSG) concentrations were significantly elevated compared to respective PTEN^f/f counterparts. These data indicate that during conditions of constitutive Akt activation and steatosis, increased GSH homeostasis assists in mitigation of ethanol-dependent induction of oxidative stress and hepatocellular damage. Furthermore, data herein suggest a divergence in EtOH-induced hepatocellular damage and increases in steatosis due to polyunsaturated fatty acids downstream of PTEN.

MicroRNA 152 regulates hepatic glycogenesis by targeting PTEN

Hepatic insulin resistance, defined as a diminished ability of hepatocytes to respond to the action of insulin, plays an important role in the development of type 2 diabetes and metabolic syndrome. Aberrant expression of mmu-miR-152-3p (miR-152) is related to the pathogenesis of tumors such as hepatitis B virus related hepatocellular carcinoma. However, the role of miR-152 in hepatic insulin resistance remains unknown. In the present study, we identified the potential role of miR-152 in regulating hepatic glycogenesis. The expression of miR-152 and the level of glycogen were significantly downregulated in the liver of db/db mice and mice fed a high fat diet. In vivo and in vitro results suggest that inhibition of miR-152 expression induced impaired glycogenesis in hepatocytes. Interestingly, miR-152 expression, glycogen synthesis and protein kinase B/glycogen synthase kinase (AKT/GSK) pathway activation were significantly decreased in the liver of mice injected with 16 μg·mL(-1) interleukin 6 (IL-6) by pumps for 7 days and in NCTC 1469 cells treated with 10 ng·mL(-1) IL-6 for 24 h. Moreover, hepatic overexpression of miR-152 rescued IL-6-induced impaired glycogenesis. Finally, phosphatase and tensin homolog (PTEN) was identified as a direct target of miR-152 to mediate hepatic glycogen synthesis. Our findings provide mechanistic insight into the effects of miR-152 on the regulation of the AKT/GSK pathway and the synthesis of glycogen in hepatocytes. Downregulated miR-152 induced impaired hepatic glycogenesis by targeting PTEN. PTEN participated in miR-152-mediated glycogenesis in hepatocytes via regulation of the AKT/GSK pathway.

MiR-19a regulates PTEN expression to mediate glycogen synthesis in hepatocytes

MiR-19a, a member of mir-17-92 microRNA clusters, has been demonstrated to promote cell proliferation and angiogenesis via regulating the PI3K/AKT pathway, the major insulin signaling pathway. However, whether miR-19a plays an important role in glycogen synthesis in hepatocytes remains unknown. Here, we define the impact of miR-19a on glycogen synthesis and IL-6-induced reduced glycogenesis in hepatocytes and its underlying mechanisms. Our studies indicate that miR-19a was down-regulated in the livers of db/db mice and mice injected with IL-6, as well as mouse NCTC 1469 hepatocytes and HEP 1–6 hepatocytes treated by IL-6. We found that over-expression of miR-19a in NCTC 1469 cells and HEP 1–6 cells led to increased activation of the AKT/GSK pathway and synthesis of glycogen, whereas down-regulation of miR-19a impaired AKT/GSK phosphorylation and glycogenesis. Over-expression of miR-19a ameliorated IL-6-induced reduced glycogen synthesis in hepatocytes. Moreover, we identified PTEN as the target of miR-19a by a luciferase assay. Down-regulation of PTEN rescued the effects of miR-19a suppression on the activation of the AKT/GSK pathway and improved glycogenesis in NTC 1469 cells. These findings show for the first time that miR-19a might activate the AKT/GSK pathway and glycogenesis via down-regulation of PTEN expression.