Browsing by Subject "PPARγ"

Now showing 1 - 5 of 5
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    Adipocytes fail to maintain cellular identity during obesity due to reduced PPARγ activity and elevated TGFβ-SMAD signaling
    (Elsevier, 2020-09-28) Roh, Hyun Cheol; Kumari, Manju; Taleb, Solaema; Tenen, Danielle; Jacobs, Christopher; Lyubetskaya, Anna; Tsai, Linus T. -Y.; Rosen, Evan D.; Biochemistry and Molecular Biology, School of Medicine
    Objective Obesity due to overnutrition causes adipose tissue dysfunction, which is a critical pathological step on the road to type 2 diabetes (T2D) and other metabolic disorders. In this study, we conducted an unbiased investigation into the fundamental molecular mechanisms by which adipocytes transition to an unhealthy state during obesity. Methods We used nuclear tagging and translating ribosome affinity purification (NuTRAP) reporter mice crossed with Adipoq-Cre mice to determine adipocyte-specific 1) transcriptional profiles (RNA-seq), 2) promoter and enhancer activity (H3K27ac ChIP-seq), 3) and PPARγ cistrome (ChIP-seq) profiles in mice fed chow or a high-fat diet (HFD) for 10 weeks. We also assessed the impact of the PPARγ agonist rosiglitazone (Rosi) on gene expression and cellular state of adipocytes from the HFD-fed mice. We integrated these data to determine the transcription factors underlying adipocyte responses to HFD and conducted functional studies using shRNA-mediated loss-of-function approaches in 3T3-L1 adipocytes. Results Adipocytes from the HFD-fed mice exhibited reduced expression of adipocyte markers and metabolic genes and enhanced expression of myofibroblast marker genes involved in cytoskeletal organization, accompanied by the formation of actin filament structures within the cell. PPARγ binding was globally reduced in adipocytes after HFD feeding, and Rosi restored the molecular and cellular phenotypes of adipocytes associated with HFD feeding. We identified the TGFβ1 effector protein SMAD to be enriched at HFD-induced promoters and enhancers and associated with myofibroblast signature genes. TGFβ1 treatment of mature 3T3-L1 adipocytes induced gene expression and cellular changes similar to those seen after HFD in vivo, and knockdown of Smad3 blunted the effects of TGFβ1. Conclusions Our data demonstrate that adipocytes fail to maintain cellular identity after HFD feeding, acquiring characteristics of a myofibroblast-like cell type through reduced PPARγ activity and elevated TGFβ-SMAD signaling. This cellular identity crisis may be a fundamental mechanism that drives functional decline of adipose tissues during obesity.
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    Antagonism of PPARγ signaling expands human hematopoietic stem and progenitor cells by enhancing glycolysis
    (Nature Publishing group, 2018-03) Guo, Bin; Huang, Xinxin; Lee, Man Ryul; Lee, Sang A; Broxmeyer, Hal E.; Microbiology and Immunology, School of Medicine
    Hematopoietic stem cells (HSCs) quiescently reside in bone marrow niches and have the capacity to self-renew or differentiate to form all blood cells throughout the lifespan of an animal–. Allogeneic HSC transplantation is a life-saving treatment for malignant and non-malignant disorders,. HSCs isolated from umbilical cord blood (CB) are used for hematopoietic cell transplantation (HCT)–, but due to limited numbers of HSCs in single units of umbilical CB, a number of methods have been proposed for ex vivo expansion of human HSCs,,. We show here that antagonism of the nuclear hormone receptor PPARγ promotes ex vivo expansion of phenotypically and functionally-defined subsets of human CB HSCs and hematopoietic progenitor cells (HSPCs). PPARγ antagonism in CB HSPCs strongly downregulated expression of several differentiation associated genes, as well as fructose 1, 6-bisphosphatase (FBP1), a negative regulator of glycolysis, and enhanced glycolysis without compromising mitochondrial metabolism. The expansion of CB HSPCs by PPARγ antagonism was completely suppressed by removal of glucose or inhibition of glycolysis. Moreover, knockdown of FBP1 expression promoted glycolysis and ex vivo expansion of long-term repopulating CB HSPCs, whereas overexpression of FBP1 suppressed the expansion of CB HSPCs induced by PPARγ antagonism. Our study suggests the possibility for a new and simple means for metabolic reprogramming of CB HSPCs to improve the efficacy of HCT.
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    Antidiabetic thiazolidinediones induce ductal differentiation but not apoptosis in pancreatic cancer cells
    (Elsevier, 2005-02-28) Ceni, Elisabetta; Mello, Tommaso; Tarocchi, Mirko; Crabb, David W.; Caldini, Anna; Invernizzi, Pietro; Surrenti, Calogero; Milani, Stefano; Galli, Andrea; Department of Biochemistry and Molecular Biology, IU School of Medicine
    AIM: Thiazolidinediones (TZD) are a new class of oral antidiabetic drugs that have been shown to inhibit growth of same epithelial cancer cells. Although TZD were found to be ligands for peroxisome proliferator-activated receptor gamma (PPARgamma), the mechanism by which TZD exert their anticancer effect is presently unclear. In this study, we analyzed the mechanism by which TZD inhibit growth of human pancreatic carcinoma cell lines in order to evaluate the potential therapeutic use of these drugs in pancreatic adenocarcinoma. METHODS: The effects of TZD in pancreatic cancer cells were assessed in anchorage-independent growth assay. Expression of PPARgamma was measured by reverse-transcription polymerase chain reaction and confirmed by Western blot analysis. PPARgamma activity was evaluated by transient reporter gene assay. Flow cytometry and DNA fragmentation assay were used to determine the effect of TZD on cell cycle progression and apoptosis respectively. The effect of TZD on ductal differentiation markers was performed by Western blot. RESULTS: Exposure to TZD inhibited colony formation in a PPARgamma-dependent manner. Growth inhibition was linked to G1 phase cell cycle arrest through induction of the ductal differentiation program without any increase of the apoptotic rate. CONCLUSION: TZD treatment in pancre
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    The peroxisome proliferator-activated receptor γ antagonist, GW9962, alters UVB-induced inflammatory responses, apoptosis, and delayed hyperproliferation
    (2009-01-16T17:25:58Z) Martel, Kellie Clay; Konger, Raymond L.; Travers, Jeffrey B.; Spandau, Dan F, 1957-
    It has recently been shown that the gamma subtype of the peroxisome proliferator-activated receptor (PPARγ) is a target of ultraviolet B (290-320 nm; UVB) irradiation, and that PPARγ activation is necessary for full UVB-induced cyclooxygenase-2 (COX-2) induction. However, the biological significance of PPARγ activation in cutaneous photobiology is unknown. Acute UVB irradiation results in a characteristic series of events in the epidermis which includes: an initial edema response and subsequent inflammation, COX-2 induction, apoptosis, and a delayed hyperproliferative response. Therefore, the regulatory role of PPARγ activation was examined in this acute photoresponse using a topical application of the potent, irreversible PPARγ antagonist, GW9962. GW9662 was applied to the epidermis of SKH1 hairless albino mice at increasing doses (0.01-1.0mM) prior to UVB irradiation. The photobiological responses were examined through RT-PCR, skin thickness measurements, and immunohistochemistry, at 24 and 72 hours after UVB-irradiation. At the highest dose, GW9622 significantly inhibited UVB-induced inflammation, as measured by COX-2 induction at both 24 and 72 hrs. Inflammation assessed by skin thickness measurements indicated that lower doses mildly increased inflammation at 72 hrs, but suppressed inflammation at the highest dose. In contrast, GW9662 treatment dose dependently augmented UVB-induced apoptosis at 24 hours, while affecting the delayed hyperproliferative response at 72 hours in an inverse dose-response manner. The results from this study suggest that PPARγ is a key regulator of these photobiological responses. Because these responses are well known to be involved in tumor development and progression, this study also suggests a potential role for PPARγ in UVB-induced skin cancers.
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    A randomized phase 1b cross-over study of the safety of low-dose pioglitazone for treatment of autosomal dominant polycystic kidney disease
    (Oxford University Press, 2021-07) Blazer-Yost, Bonnie L.; Bacallao, Robert L.; Erickson, Bradley J.; LaPradd, Michelle L.; Edwards, Marie E.; Sheth, Nehal; Swinney, Kim; Ponsler-Sipes, Kristen M.; Moorthi, Ranjani N.; Perkins, Susan M.; Torres, Vicente E.; Moe, Sharon M.; Biology, School of Science
    Background: Autosomal dominant polycystic kidney disease (ADPKD) is one of the most common monogenetic disorders in humans and is characterized by numerous fluid-filled cysts that grow slowly, resulting in end-stage renal disease in the majority of patients. Preclinical studies have indicated that treatment with low-dose thiazolidinediones, such as pioglitazone, decrease cyst growth in rodent models of PKD. Methods: This Phase 1b cross-over study compared the safety of treatment with a low dose (15 mg) of the peroxisome proliferator-activated receptor-γ (PPAR-γ) agonist pioglitazone or placebo in PKD patients, with each treatment given for 1 year. The study monitored known side effects of PPAR-γ agonist treatment, including fluid retention and edema. Liver enzymes and risk of hypoglycemia were assessed throughout the study. As a secondary objective, the efficacy of low-dose pioglitazone was followed using a primary assessment of total kidney volume (TKV), blood pressure (BP) and kidney function. Results: Eighteen patients were randomized and 15 completed both arms. Compared with placebo, allocation to pioglitazone resulted in a significant decrease in total body water as assessed by bioimpedance analysis {mean difference 0.16 Ω [95% confidence interval (CI) 0.24-2.96], P = 0.024} and no differences in episodes of heart failure, clinical edema or change in echocardiography. Allocation to pioglitazone led to no difference in the percent change in TKV of -3.5% (95% CI -8.4-1.4, P = 0.14), diastolic BP and microalbumin:creatinine ratio. Conclusions: In this small pilot trial in people with ADPKD but without diabetes, pioglitazone 15 mg was found to be as safe as placebo. Larger and longer-term randomized trials powered to assess effects on TKV are needed.