Human patatin-like phospholipase domain-containing 3 (PNPLA3) is associated with increased liver fat content and liver injury. Here, we show that nutritional status regulates PNPLA3 gene expression in the mouse liver. Sterol response element binding protein-1 (SREBP-1) activated PNPLA3 gene transcription via sterol regulatory elements (SREs) mapped to the promoter region. Chromatin immunoprecipitation and electrophoretic mobility shift assays confirmed that SREBP-1 proteins bound to the identified SREs. Furthermore, SREBP-1c mediated the insulin and liver X receptor agonist TO901317-dependent induction of PNPLA3 gene expression in hepatocytes. Adenovirus-mediated overexpression of mouse PNPLA3 increased intracellular triglyceride content in primary hepatocytes, and knockdown of PNPLA3 suppressed the ability of SREBP-1c to stimulate lipid accumulation in hepatocytes. Finally, the overexpression of PNPLA3 in mouse liver increased the serum triglyceride level and impaired glucose tolerance; in contrast, the knockdown of PNPLA3 in db/db mouse liver improved glucose tolerance. Conclusion: Our data suggest that mouse PNPLA3, which is a lipogenic gene directly targeted by SREBP-1, promotes lipogenesis in primary hepatocytes and influences systemic lipid and glucose metabolism. (HEPATOLOGY 2011;54:509-521)

Edited by Robert BaroukiKeywords: SREBP-1c promoter FoxO1 LXRa Insulin a b s t r a c t Recent studies have demonstrated that FoxO1 modulates the expression of SREBP-1c, but the exact mechanism remains unknown. Our results demonstrate that FoxO1 suppresses the SREBP-1c promoter transcriptional activity in HepG2 cells. This repression was independent of FoxO1 binding to the SREBP-1c promoter, but LXR responsive elements (LXREs) were crucial to this phenomenon. Moreover, FoxO1 also strongly inhibited the LXRa-mediated elevated transcription by SREBP-1c promoter. Electrophoretic mobility shift assay and chromatin immuno-precipitation further suggested the ability of FoxO1 to inhibit LXRa binding with the LXRE in the SREBP-c promoter. FoxO1-mediated suppression of SREBP-1c promoter activity could be partially alleviated by insulin.

The orphan nuclear receptor SF-1 (steroidogenic factor 1) is highly expressed in the pituitary, gonad and adrenal glands and plays key roles at all levels of the hypothalamic-pituitary-steroidogenic tissue axis. In the present study, we show that PGC-1α [PPARγ (peroxisome-proliferator-activated receptor γ) co-activator 1α] interacts with and co-activates SF-1 to induce LHβ (luteinizing hormone β) and αGSU (α-glycoprotein subunit) gene expression, subsequently leading to the increased secretion of LH in pituitary gonadotrope-derived αT3-1 cells. PGC-1α co-activation of LHβ expression requires an SF-1-binding element [GSE (gonadotrope-specific element)] mapped to the promoter region of LHβ. Mammalian two-hybrid and co-immunoprecipitation assays, as well as GST (glutathione transferase) pull-down experiments demonstrated that PGC-1α interacts with SF-1 in vivo and in vitro. Additionally, PGC-1α stimulates the expression of Cyp11b2 (aldosterone synthase gene), Cyp11b1 (steroid 11β-hydroxylase gene) and P450scc (cholesterol side-chain cleavage enzyme), and the synthesis of aldosterone in adrenal-cortex-derived Y-1 cells. Chromatin immunoprecipitation assays confirmed that endogenous PGC-1α co-localizes with SF-1 in the LHβ and Cyp11b2 promoter region. Knockdown of endogenous SF-1 by siRNA (small interfering RNA) abolished the PGC-1α induction of LHβ and Cyp11b2 gene expression in αT3-1 and Y-1 cells respectively. Finally, we demonstrated that PGC-1α induces SF-1 gene expression in both αT3-1 and Y-1 cells. Taken together, our findings reveal the potential role of PGC-1α and suggest that it may play important roles in steroidogenesis, gonad development and sex differentiation through SF-1.

Articles about in vivo brain tumor 1 HMRS have been widely reported at home and abroad, reflected some of the characteristics of brain tumors [1] . But in vivo 1 HMRS by low field strength, partial volume effect and other constraints has limited value on the metabolism of information and diagnosis of diseases. In vitro specimens can be applied to the higher field strength spectrometer and 1 HMRS can detect some compounds for in vivo spectroscopy difficult detection. But former extraction method of HR-1 HMRS destructed histological characteristics of the sample, separated the spectral results and disease state, its application in clinic remains limited. However, recently developed and perfected a new technique that HRMAS-1 HMRS did not suffer greatly destruction in the sample and improved resolution, maintaining a state of the disease and the results of spectral consistency. This study explored water soluble metabolite features of brain tumor (meningiomas and gliomas) specimens with HRMAS-1 HMRS and its potential clinical value. Materials and methodsCollected surgical resection 30 cases of brain tumor by pathologically confirmed, according to the WHO criteria, 6 cases were I-II grade astrocytomas, 7 cases were III grade anaplastic astrocytomas, 10 cases were IV glioblastomas and 7 patients were meningiomas. Thirteen cases were males and seventeen cases were females, aged 13 to 70 years, with an average age of 48 years old. Normal brain tissue HRMAS-1 HMRS referred to the No. 2 referAbstract Objective: To explore water soluble metabolite features of brain tumor specimens with HRMAS-1 HMRS and its potential clinical value. Methods: There were thirty cases of pathologically proven brain tumor, including 6 I-II grade astrocytomas, 7 III grade anaplastic astrocytomas, 10 IV grade glioblastomas and 7 meningiomas. Used Varian Company 600 MHz spectrometer with the Nano-probe for acquisition HRMAS-1 HMRS, which was postprocessed with jMRUI 3.2 version software. These metabolic probability and their ratios to Cr were summed. Results: (1) HRMAS-1 HMRS could resolve NAA, PCr/Cr, GPC + PCho + Cho, Glu/Gln, Gly, Tau, Ala, Lac, mI and so on. All samples showed Lac, 6 samples showed unknown single peak at 3.72 ppm or 3.90 ppm. (2) The mean Cho/Cr of 6 I-II grade astrocytomas was 2.42 ± 1.01 (P = 0.003, compared with glioblastoma). The mean Cho/Cr of 7 anaplastic astrocytomas was 3.48 ± 0.59 (P = 0.01, compared with glioblastoma). The Cho/Cr of 10 glioblastomas broadly ranged from 0.9 to 11.3 (mean 5.40 ± 1.23). From I-II grade astrocytoma to glioblastoma, Ala/Cr, Tau/Cr and Gly/Cr trends were increased; the mean Ala/Cr of glioma was 0.31 ± 0.13. (3) Meningiomas showed higher Ala and Cho. Their Cr was lower than that of gliomas. 4/7 cases had no NAA, 3/7 patients had lower NAA. Mean Cho/Cr was 3.56 ± 1.01, Ala/Cr was 0.53 ± 0.28 (P = 0.006, compared with glioma). Conclusion: HRMAS-1 HMRS can show further details in vivo MRS, resolve in vivo spectroscopic metabolite of Cho compound and differentiate the extent of benign and malign...