Xiaojun Ma

Activation of FoxO1/ PGC-1α prevents mitochondrial dysfunction and ameliorates mesangial cell injury in diabetic rats.

The generation of hyperglycemia-induced mitochondrial reactive oxygen species (ROS) is a key event in diabetic nephropathy development. The forkhead-box class O1 (FoxO1) and peroxisome proliferator-activated receptor γ co-activator 1α (PGC-1α) proteins are implicated in oxidative stress. We investigated the in vivo association of FoxO1 and PGC-1α in renal cortices from streptozotocin-induced diabetic rats and in rat kidney mesangial cells (MCs) treated with high glucose, in vitro. High-glucose induced FoxO1 inhibition was associated with decreased PGC-1α expression in MCs. These changes were accompanied by mitochondrial dysfunction and increased ROS generation. However, constitutive FoxO1 activation increased PGC-1α expression and partially reversed these changes, which were significantly decreased by the treatment of PGC-1α-small interfering RNA. We identified PGC-1α as a direct FoxO1 transcriptional target by chromatin immunoprecipitation. In addition, lentiviral-mediated FoxO1 overexpression in diabetic-rat kidneys significantly increased PGC-1α, NRF-1, and Mfn2 expression, and decreased malondialdehyde production and proteinuria. These data suggest that FoxO1/PGC-1α activation protected rats against high-glucose-induced MC injury by attenuating mitochondrial dysfunction and cellular ROS production.

SIRT1 attenuates high glucose-induced insulin resistance via reducing mitochondrial dysfunction in skeletal muscle cells.

Insulin resistance is often characterized as the most critical factor contributing to the development of type 2 diabetes mellitus (T2DM). Sustained high glucose is an important extracellular environment that induces insulin resistance. Acquired insulin resistance is associated with reduced insulin-stimulated mitochondrial activity as a result of increased mitochondrial dysfunction. Silent information regulator 1 (SIRT1) is one member of the SIRT2 (Sir2)-like family of proteins involved in glucose homeostasis and insulin secretion in mammals. Although SIRT1 has a therapeutic effect on metabolic deterioration in insulin resistance, it is still not clear how SIRT1 is involved in the development of insulin resistance. Here, we demonstrate that pcDNA3.1 vector-mediated overexpression of SIRT1 attenuates insulin resistance in the high glucose-induced insulin-resistant skeleton muscle cells. These beneficial effects were associated with ameliorated mitochondrial dysfunction. Further studies have demonstrated that SIRT1 restores mitochondrial complex I activity leading to decreased oxidative stress and mitochondrial dysfunction. Furthermore, SIRT1 significantly elevated the level of another SIRT which is named SIRT3, and SIRT3 siRNA-suppressed SIRT1-induced mitochondria complex activity increments. Taken together, these results showed that SIRT1 improves insulin sensitivity via the amelioration of mitochondrial dysfunction, and this is achieved through the SIRT1–SIRT3–mitochondrial complex I pathway.

The effect of FoxO1 on the proliferation of rat mesangial cells under high glucose conditions

BACKGROUND Hyperproliferation of glomerular mesangial cells (MCs) is a major pathological characteristic in the early stage of diabetic nephropathy (DN). We have previously confirmed that forkhead transcription factor O1 (FoxO1) was significantly downregulated in both the renal cortex of DN rats and MCs cultured under high-glucose (HG) conditions, but the effects and mechanisms of FoxO1 involved in the hyperproliferation of MCs are still unclear. This study aims to investigate whether FoxO1 regulates the hyperproliferation of MCs induced under high-glucose conditions, through modulating the cyclin-dependent kinase inhibitor (CKI), p27. METHODS Lentiviral vectors of LV-constitutively active FoxO1 (CA-FoxO1) and LV-small interfering RNA (siRNA)-FoxO1 were constructed to up- and downregulate FoxO1. Similarly, LV-NC-FoxO1 was used as negative control (NC). Rat MCs were cultured in normal glucose (5.6 mM) medium, HG (30 mM) medium, HG with LV-NC-FoxO1, HG with LV-CA-FoxO1 and HG with LV-siRNA-FoxO1 for 72 h. Cell proliferation, cell cycle progression, messenger RNA and protein expression of FoxO1, p27, cyclin D1 and CDK4 were detected by methyl thiazolyl tetrazolium assay, flow cytometry, quantitative real-time polymerase chain reaction and western blotting, respectively. RESULTS MCs exposed to HG medium triggered hyperproliferation of MCs. Nevertheless, overexpression of FoxO1 caused by LV-CA-FoxO1 promoted cell cycle arrest at the G0/G1 phase and attenuated proliferation, which was associated with upregulation of p27 and downregulation of cyclin D1 and CDK4. Moreover, specific degradation of FoxO1 by LV-siRNA-FoxO1 caused a decrease of p27, increase of cyclin D1 and CDK4, overrode the limited cell cycle and stimulated proliferation of MCs. CONCLUSIONS Overexpression of FoxO1 caused upregulation of p27, which promoted cell cycle arrest and inhibited hyperproliferation of MCs induced by HG. Degradation of FoxO1 caused an increase in p27 and stimulated MC proliferation. These findings unveil part of the molecular mechanism of FoxO1 regulation of MC hyperproliferation induced by HG.

Vitamin D supplement improved testicular function in diabetic rats

This study was designed to investigate the role that 1,25(OH)2D3 plays against testicular lesion in diabetic rats and try to find its possible mechanism of the steroidogenesis and the spermatogenesis. In diabetic rats, prolonged hyperglycemia evaluated inflammatory cytokines, damaged sperm production function and redox balance, diminished serum testosterone. After treated with 1,25(OH)2D3 at two different doses respectively for 12 months, all the alternations were effectively normalized. 1,25(OH)2D3 showed inhibitory effect on excessive inflammatory biomarkers and adjusted the expression reproductive genes and testicular androgen synthesis. It also upregulated Bcl-2 expression, decreased Bax and COX-2 expression and inhibited active caspase cascade (caspase 8 and caspase 3), which may preserved the testicular cells under diabetic condition. It revealed that vitamin D supplement may protect the cells through suppressing inflammation factors and alleviating cell apoptotic death, as well as upregulating the expression of genes related to reproductive and testosterone synthesis.

MicroRNA-27a Induces Mesangial Cell Injury by Targeting of PPARγ, and its In Vivo Knockdown Prevents Progression of Diabetic Nephropathy

MicroRNAs play important roles in the pathogenesis of diabetic nephropathy (DN). In this study, we found that high glucose upregulated miR-27a expression in cultured glomerular mesangial cells and in the kidney glomeruli of streptozotocin (STZ)-induced diabetic rats. miR-27a knockdown prevented high glucose-induced mesangial cell proliferation and also blocked the upregulation of extracellular matrix (ECM)-associated profibrotic genes. Reduction of cell proliferation and profibrotic gene expression by a miR-27a inhibitor depended upon the expression of peroxisome proliferator-activated receptor γ (PPARγ). Further studies showed that miR-27a negatively regulated PPARγ expression by binding to the 3′-untranslated region of rat PPARγ. An antisense oligonucleotide specific to miR-27a (antagomir-27a) significantly reduced renal miR-27a expression in STZ-induced diabetic rats and significantly increased PPARγ levels. Antagomir-27a also reduced kidney ECM accumulation and proteinuria in STZ-induced diabetic rats. These findings suggest that specific reduction of renal miR-27a decreases renal fibrosis, which may be explained in part by its regulation of PPARγ, and that targeting miR-27a may represent a novel therapeutic approach for DN.

LDOC1 inhibits proliferation and promotes apoptosis by repressing NF-κB activation in papillary thyroid carcinoma

BackgroundThe incidence of thyroid cancer has progressively increased over the past few decades, and the most frequent types of this cancer are papillary thyroid carcinoma (PTC) and small primary tumors. In PTC, oncogene activation is known to occur at a high frequency. However, the potential roles of tumor suppressor genes in thyroid carcinogenesis remain unclear. LDOC1 was first identified as a gene encoding a leucine zipper protein whose expression was decreased in a series of pancreatic and gastric cancer cell lines. In this study, we aimed to determine the status of LDOC1 in PTC and identify its mechanistic role in PTC pathogenesis.MethodsLDOC1 expression was evaluated in fresh samples and stored specimens of human PTC and contralateral normal tissues by performing quantitative reverse transcription-PCR and immunohistochemical staining. The correlation to nuclear p65 content in the stored specimens was analyzed. Moreover, the basal level of LDOC1 in two human PTC-derived cell lines (BCPAP and TPC-1) compared with normal thyroid tissue was determined. Human LDOC1 cDNA was inserted into a lentiviral vector and transduced into TPC-1 cells. TPC-1 cells overexpressing LDOC1/GFP (Lv-LDOC1) or negative control GFP (Lv-NC) were stimulated with TNFα or recombinant TGF-β1, and then cell proliferation, cell cycle distribution, and apoptosis were assessed. Western blotting was used to examine the expression of p65, IκBα, c-Myc, Bax, and Bcl-xL, and a luciferase reporter assay was used to measure NF-κB activity stimulated by TNFα. Statistical significance was determined using Student’s t tests or ANOVA and Newman-Keuls multiple comparison tests. Pearson chi-square test was used to analyze possible associations.ResultsLDOC1 expression was significantly downregulated in PTC specimens as compared with the expression in normal thyroid tissues, and this downregulation was associated with an increase in tumor size (P < 0.05). There is a correlation between LDOC1 and nuclear P65 expression in human PTC tissues (P < 0.01). Lentivirus-mediated restoration of LDOC1 expression in TPC-1 cells characterized by low level of LDOC1 expression suppressed proliferation and induced apoptosis by inhibiting NF-κB activation, and LDOC1-overexpressing TPC-1 cells recovered responsiveness to TGF-β1 antiproliferative signaling.ConclusionsLDOC1 might function as a tumor suppressor gene in PTC by inhibiting NF-κΒ signaling, and thus might represent a promising therapeutic target in patients with PTC.

Nesfatin-1 correlates with hypertension in overweight or obese Han Chinese population

Abstract We investigated blood nesfatin-1 levels in hypertension patients. We found that fasting plasma nesfatin-1 levels were significantly higher in hypertension patients than in control groups, especially in overweight/obese hypertension patients (4.5 ± 2.1 versus 3.3 ± 1.1 ng/ml, p < 0.01). Body mass index, systolic blood pressure and diastolic blood pressure were indeed positively correlated with fasting plasma nesfatin-1 levels (r = 0.234, p < 0.05; r = 0.304, p < 0.01; r = 0.251, p < 0.05; r = 0.461, p < 0.01; respectively). Logistic regression analysis revealed that the plasma level of nesfatin-1 could be independent of risk prediction over standard measures (OR = 1.547, 95% CI: 1.153–6.273, p = 0.026). Nesfatin-1 has the incremental contribution to hypertension risk prediction (IDI: 0.014, p = 0.018; NRI: 0.050, p = 0.043). The plasma nesfatin-1 level in hypertension patients with microalbuminuria are significantly higher than those without microalbuminuria patients (6.4 ± 2.1 ng/ml versus 3.9 ± 1.8 ng/ml, p < 0.01). Nesfatin-1 might play an important role in obesity hypertension, and its increase could be a risk factor for obesity-associated hypertension.

FoxO1 Promotes Mitophagy in the Podocytes of Diabetic Male Mice via the PINK1/Parkin Pathway

We recently showed that forkhead-box class O1 (FoxO1) activation protects against high glucose-induced injury by preventing mitochondrial dysfunction in the rat kidney cortex. In addition, FoxO1 has been reported to mediate putative kinase 1 (PINK1) transcription and promote autophagy in response to mitochondrial oxidative stress in murine cardiomyocytes. In this study, we ascertained whether overexpressing FoxO1 in the kidney cortex reverses preestablished diabetic nephropathy in animal models. The effect of FoxO1 on mitophagy signaling pathways was evaluated in mouse podocytes. In vivo experiments were performed in male KM mice. A mouse model of streptozotocin (STZ)-induced type 1 diabetes (T1D) was used, and lentiviral vectors were injected into the kidney cortex to overexpress FoxO1. A mouse podocyte cell line was treated with high concentrations of glucose and genetically modified using lentiviral vectors. We found aberrant mitochondrial morphology and reduced adenosine triphosphate production. These mitochondrial abnormalities were due to decreased mitophagy via reduced phosphatase/tensin homolog on chromosome 10-induced PINK1/Parkin-dependent signaling. FoxO1 upregulation and PINK1/Parkin pathway activation can individually restore injured podocytes in STZ-induced T1D mice. Our results link the antioxidative activity of FoxO1 with PINK1/Parkin-induced mitophagy, indicating a novel role of FoxO1 in diabetic nephropathy.

FoxP3 in papillary thyroid carcinoma induces NIS repression through activation of the TGF-β1/Smad signaling pathway

Forkhead box P3 (FoxP3) expression in papillary thyroid carcinoma (PTC) is associated with resistance to radioiodine treatment. The sodium iodine symporter (NIS) is a plasma membrane glycoprotein, the repression of which may render the tumor refractive to radioiodine therapy. In this study, samples from 90 PTCs as well as 40 normal thyroid tissues were examined for FoxP3 and NIS by immunohistochemistry and real-time PCR. We found that FoxP3 was associated with decreased NIS expression. Lentiviral-mediated FoxP3-overexpressing cells were constructed and real-time PCR and western blotting were performed to evaluate the expression of NIS. Meanwhile, key members of the transforming growth factor-β1 (TGF-β1) pathway were explored by ELISA and immunofluorescence and a neutralizing TGF-β1 antibody was used to block activity. In vitro, FoxP3 overexpression significantly reduced NIS transcript and protein levels and the TGF-β1 pathway was activated. However, treatment with neutralizing TGF-β1 antibody partially abrogated FoxP3-induced NIS repression. These findings suggest that FoxP3 could compromise NIS expression by inducing TGF-β1.

Plasma Ghrelin Concentrations Are Negatively Correlated With Urine Albumin-to-Creatinine Ratio in Newly Diagnosed Type 2 Diabetes

Background:Aging is associated with a decrease in appetite, energy intake and glucose tolerance. Experimental studies have suggested that ghrelin and obestatin play a role in glucose homeostasis and in the regulation of energy metabolism. However, few studies have been performed on the role of ghrelin and obestatin in middle-aged and old adults. Methods:In the present study, we investigated the plasma concentrations of ghrelin and obestatin in middle-aged (41–64 years) and old (65–76 years) subjects with newly diagnosed type 2 diabetes mellitus (NDD) and normal glucose tolerance (NGT). We also characterized the relationship among plasma ghrelin and obestatin levels and glucose/lipid metabolism. The fasting plasma ghrelin and obestatin concentrations were analyzed using enzyme immunoassay method. Results:Plasma obestatin concentrations in diabetic subjects were significantly lower than those in NGT subjects. Plasma ghrelin were negatively associated with fasting glucose, hemoglobin A1c, urine albumin-to-creatinine ratio (UACR) and positively correlated with high-density lipoprotein cholesterol. In addition, plasma obestatin level was correlated negatively with systolic blood pressure, triglycerides and total cholesterol. Furthermore, multiple regression analysis indicated that UACR was a significantly independent predictor of fasting plasma ghrelin levels. Conclusions:Collectively, ghrelin and obestatin levels may be markers reflecting glucose and lipid conditions in NDD. The lower ghrelin levels may be a potential indicator for renal dysfunction in patients with type 2 diabetes mellitus.