[Components and lipid-lowering effect of total saponins from underground part of Gynostemma pentaphyllum].

The saponins in different parts of Gynostemma pentaphyllum were analyzed via UPLC-Q-TOF-MS~E. A total of 46 saponins were identified, and the underground part had 26 saponins more than the aboveground part, most of which were trisaccharide saponins. The rat model of hyperlipidemia was established with high-fat diet. This study explored the lipid-lowering activity of total saponins in the underground part of G. pentaphyllum, so as to provide a theoretical basis for the comprehensive utilization of the underground part of G. pentaphyllum. A total of 99 healthy SD rats were randomly assigned into a blank group, a model group, a positive drug group, an aboveground total saponins group, and low-, medium-, and high-dose underground total saponins groups. Except the blank group, the other groups were fed with high-fat diet for 6 weeks. Then, the blood was collected from the orbital cavity to determine whether the modeling was successful according to the serum levels of total cholesterol(TC) and triglyceride(TG). After intragastric administration of the corresponding agents for 30 continuous days, the physical state of the rats were observed, and the body weight and liver specific gravity were measured. Furthermore, the levels of TC, TG, low-density lipoprotein cholesterol(LDL-C), high-density lipoprotein cholesterol(HDL-C), alanine transaminase(ALT), aspartate transaminase(AST), bilirubin, and total bile acids in serum, as well as the levels of superoxide dismutase(SOD), malondialdehyde(MDA), peroxidase proliferator-activated receptor(PPAR-γ) in the liver tissue, were determined. The pathological changes of liver was observed via HE staining. The results showed that the aboveground total saponins and medium-and high-dose underground total saponins can treat hepatocyte steatosis, lower TC, TG, LDL-C, ALT, AST, total bilirubin, MDA, and PPAR-γ levels, and increase HDL-C and SOD levels in the model rats. The effect tended to be more obvious with the increase in dosage. Therefore, the total saponins in the underground part of G. pentaphyllum have good pharmacological effect of reducing blood lipid, which provides a theoretical basis for the comprehensive utilization of the underground part of G. pentaphyllum.

Acute Exercise Stimulates Carnitine Biosynthesis and OCTN2 Expression in Mouse Kidney.

BACKGROUND/AIMS: Carnitine is essential for the transport of long-chain FAs (FA) into the mitochondria for energy production. During acute exercise, the increased demand for FAs results in a state of free carnitine deficiency in plasma. The role of kidney in carnitine homeostasis after exercise is not known. METHODS: Swiss Webster mice were sacrificed immediately after a 1-hour moderate intensity treadmill run, and at 4-hours and 8-hours into recovery. Non-exercising mice served as controls. Plasma was analyzed for carnitine using acetyltransferase and [14C] acetyl-CoA. Kidney was removed for gene and protein expression of butyrobetaine hydroxylase (γ-BBH), organic cation transporter (OCTN2), and peroxisome proliferator-activated receptor (PPARα), a regulator of fatty acid oxidation activated by FAs. RESULTS: Acute exercise caused a decrease in plasma free carnitine levels. Rapid return of free carnitine to control levels during recovery was associated with increased γ-BBH expression. Both mRNA and protein levels of OCTN2 were detected in kidney after exercise and during recovery, suggesting renal transport mechanisms were stimulated. These changes were accompanied with a reciprocal increase in PPARα protein expression. CONCLUSIONS: Our results show that the decrease in free carnitine after exercise rapidly activates carnitine biosynthesis and renal transport mechanism in kidney to establish carnitine homeostasis.

Peroxisome proliferator-activated receptor (PPAR) isoforms are differentially expressed in peri-implantation porcine conceptuses.

Peroxisome proliferator-activated receptors (PPARs) are members of the nuclear receptor family of ligand-dependent transcription factors. PPARs are critical regulators of glucose homeostasis and lipid metabolism, and affect cell proliferation and differentiation. In the current study, we examined (1) the profiles of PPARA, PPARD, and PPARG mRNA expression and DNA binding activity in porcine conceptuses collected on Days 10-11 (spherical and tubular conceptuses), 11-12 (filamentous conceptuses), 13-14, and 15-16 (elongated conceptuses) of pregnancy, (2) the presence of PPARA, PPARD, and PPARG proteins in Days 10, 12, and 15 conceptuses. Moreover, we analyzed the abundance of retinoid X receptor (RXR; PPARs heterodimer partner) transcripts as well as the correlation between PPARs mRNA expression and the expression of genes important for and/or associated with elongation of porcine conceptuses: aromatase (CYP19A1), prostaglandin endoperoxide synthase 2 (PTGS2), glucose transporter 1 (SLC2A1), and interleukin 1B (IL1B). PPARA mRNA expression in conceptuses did not change during Days 10-14 of gestation, but was greater on Days 15-16 compared to Days 10-11 (P < 0.05). A considerable increase in PPARD and PPARG mRNA expression was observed in filamentous conceptuses from Days 11-12 compared to spherical and tubular conceptuses from Days 10-11 (P < 0.01), followed by a decrease on Days 13-14 and 15-16 (P < 0.05). PPARA, PPARD, and PPARG proteins were present in conceptus tissue demonstrating nuclear localization clearly visible on Days 12 and 15 of pregnancy. DNA binding activity of the PPARD isoform was greater in filamentous conceptuses from Days 11-12 than in spherical and tubular conceptuses from Days 10-11 (P < 0.01). Moreover, concentrations of active PPARD and PPARG proteins in nuclear fractions of conceptus tissue were greater on Days 11-12 compared to Days 13-14 and 15-16 of pregnancy (P < 0.05). RXRA, RXRD, and RXRG mRNA expression in conceptuses increased on Days 11-12 compared to Days 10-11 (P < 0.05). PPARD and PPARG mRNA expression showed strong positive correlations with PTGS2 mRNA expression (P < 0.0001). Additionally, PPARD gene expression correlated with SLC2A1 and IL1B mRNA expression (P < 0.01). Collectively, these results indicate that among all three PPARs expressed in peri-implantation porcine conceptuses, PPARD and PPARG may be involved in conceptus elongation before implantation.

Features of an altered AMPK metabolic pathway in Gilbert's Syndrome, and its role in metabolic health.

Energy metabolism, involving the ATP-dependent AMPK-PgC-Ppar pathway impacts metabolic health immensely, in that its impairment can lead to obesity, giving rise to disease. Based on observations that individuals with Gilbert's syndrome (GS; UGT1A1(*)28 promoter mutation) are generally lighter, leaner and healthier than controls, specific inter-group differences in the AMPK pathway regulation were explored. Therefore, a case-control study involving 120 fasted, healthy, age- and gender matched subjects with/without GS, was conducted. By utilising intra-cellular flow cytometry (next to assessing AMPKα1 gene expression), levels of functioning proteins (phospho-AMPK α1/α2, PgC 1 α, Ppar α and γ) were measured in PBMCs (peripheral blood mononucleated cells). In GS individuals, rates of phospho-AMPK α1/α2, -Ppar α/γ and of PgC 1α were significantly higher, attesting to a boosted fasting response in this condition. In line with this finding, AMPKα1 gene expression was equal between the groups, possibly stressing the post-translational importance of boosted fasting effects in GS. In reflection of an apparently improved health status, GS individuals had significantly lower BMI, glucose, insulin, C-peptide and triglyceride levels. Herewith, we propose a new theory to explain why individuals having GS are leaner and healthier, and are therefore less likely to contract metabolic diseases or die prematurely thereof.

Expression of peroxisome proliferator activation receptors (PPARs) and TNFα in placenta tissues in unexplained recurrent pregnancy loss: an immunohistochemical study.

INTRODUCTION: PPAR expression in placenta tissues regulates proinflammatory cytokine production and preserves the quiescence of the uterus during pregnancy. PPAR-γ regulates inflammatory response during gestation while PPAR-δ and TNFα play a central role at implantation, decidualization and placentation. However, their expression levels affect normal pregnancy and may cause gestational complications and miscarriage. The aim of this report is to investigate the relationship of these molecules with unexplained recurrent miscarriage. MATERIALS-METHODS: The miscarriage group was obtained from 12 women, between the ages of 35 to 42 years, who miscarried during the 1st trimester of gestation and controls consisted of 12 healthy women, between the ages of 27 to 39 years, who had electively terminated their pregnancies, during the 1st trimester of gestation. The abortion material was processed and specimens taken were studied using immunohisto-chemical methods. Specimens were taken from decidua basalis and decidua parietalis. Monoclonal antibodies were used against PPAR-γ (Peroxisome Proliferator Activation Receptor γ), PPAR-δ and TNFα (Tumor Necrosis Factor alpha). The results were statistically analyzed with Mann-Whitney test. RESULTS: Our research identified PPAR-γ expression in decidua basalis and decidua parietalis from control group and decidua basalis from miscarriage group. PPAR-δ expression was also identified in both deciduas from both groups. Statistically, no significant change in PPAR-γ and PPAR-δ expression was observed between recurrent miscarriage group and controls. On the contrary, a statistically significant upregulation of TNFα was identified in both deciduas between miscarriage group and controls (p<0.05). CONCLUSIONS: Our evidence did not support a possible role of PPARs expression in recurrent pregnancy loss. However, a potential involvement of TNFα in the syndrome was reported. Further research should be performed due to insufficient bibliographic data.

Changes in ghrelin, CCK, GLP-1, and peroxisome proliferator-activated receptors in a hypoxia-induced anorexia rat model.

INTRODUCTION: A high-altitude environment causes appetite loss in unacclimatised humans, leading to weight reduction. Ghrelin, cholecystokinin (CCK), and glucagon like peptide-1 (GLP-1), are gut hormones involved in the regulation of food intake and energy metabolism. The liver is an important site of metabolic regulation, and together with the gut it plays a role in food intake regulation. This study intends to study the time-dependent changes occurring in plasma gut hormones, PPARα, PPARδ, and PGC1α, in the stomach and liver during hypoxia. MATERIAL AND METHODS: Male Sprague Dawley rats were exposed to hypobaric hypoxia in a decompression chamber at 7620 m for different durations up to seven days. RESULTS: Hypoxia increased circulating ghrelin from the third day onwards while CCK and GLP-1 decreased immediately. An increase in ghrelin, ghrelin receptor protein levels, and GOAT mRNA levels in the stomach was observed. Stomach cholecystokinin receptor (CCKAR), PPARα, and PPARδ decreased. Liver CCKAR decreased during the first day of hypoxia and returned to normal levels from the third day onwards. PPARα and PGC1α expression increased while PPARδ protein levels reduced in the liver on third day. CONCLUSION: Hypoxia alters the expression of ghrelin and ghrelin receptor in the stomach, CCKAR in the liver, and PPAR and its cofactors, which might be possible role players in the contribution of gut and liver to anorexia at high altitude.

Triptolide disrupts fatty acids and peroxisome proliferator-activated receptor (PPAR) levels in male mice testes followed by testicular injury: A GC-MS based metabolomics study.

Triptolide is the major active ingredient of Tripterygium Glycosides (TG), a traditional Chinese medicine with very potent anti-inflammatory effects and has been used in China for the treatment of rheumatoid arthritis and many other inflammatory diseases. However, clinical application of triptolide is restricted due to its multiple side effects, especially male infertility. The mechanism of triptolide on reproduction toxicity remains unclear. In the present study, a GC-MS based metabolomic approach was employed to evaluate the mechanism of triptolide-induced reproductive toxicity as well as identify potential novel biomarkers for the early detection of spermatogenesis dysfunction. In brief, male mice were divided into two groups with or without triptolide intraperitoneal injection at 60 µg/kg/day for 2 weeks and toxic effect of triptolide on testicular tissues were examined by biochemical indicator analysis, testis histopathologic analysis, and sperm quantity analysis. Metabolomics technology was then performed to evaluate systematically the endogenous metabolites profiling. Our results demonstrated that triptolide suppressed the marker-enzymes of spermatogenesis and testosterone levels, decreased sperm counts, reduced the gonad index and destroyed the microstructure of testis. Multivariate data analysis revealed that mice with triptolide induced testicular toxicity could be distinctively differentiated from normal animals and 35 and 39 small molecule metabolites were changed significantly in testis and serum, respectively (Fold-changes >1.5, P<0.05), in triptolide-treated mice. Abnormal level of fatty acids, an important energy source of sertoli cells with critical role in maintaining normal function of the testis tissue, was observed in triptolide-treated mice. Additionally, the protein expressions of PPAR, a transcription factor known to play a pivotal role in lipid and energy metabolism was significantly decreased in the testis tissue of triptolide-treated mice. In summary, our study represents the first comprehensive GC-MS based metabolomics analysis of triptolide-induced testicular toxicity. We reported for the first time that exposure to triptolide led to marked changes of a panel of endogenous metabolites in both testis and serum. The impairment of spermatogenesis may be caused by abnormal lipid and energy metabolism in testis via the down-regulation of PPARs mediated by triptolide. The presence of research suggested that PPARs and its related fatty acids metabolism may serve as potential targets for intervention or treatment of male infertility induced by triptolide.

EZH2, a potential regulator of dental pulp inflammation and regeneration.

INTRODUCTION: Dental pulp has limited capability to regenerate, which happens in the early stage of pulpitis. An ambiguous relationship exists; inflammation may impair or support pulp regeneration. Epigenetics, which is involved in cell proliferation and inflammation, could regulate human dental pulp cell (HDPCs) regeneration. The aim of this study was to determine the role of the epigenetic mark, enhancer of zeste homolog 2 (EZH2), in the inflammation, proliferation, and regeneration of dental pulp. We used trimethylated histone H3 lysine 27(H3K27me3) and its lysine demethylase 6B (KDM6B) to monitor functional effects of altered EZH2 levels. METHODS: We detected epigenetic marks (EZH2, H3K27me3, and KDM6B) in pulp tissue by immunohistochemistry and immunofluorescence. EZH2 levels in HDPCs in inflammatory responses or differentiation were analyzed by quantitative polymerase chain reaction and Western blot. Quantitative polymerase chain reaction was used to assess the effects of EZH2 inhibition on interleukins in HDPCs upon tumor necrosis factor alpha stimulation. Cell proliferation was tested by cell counting kit-8, cell cycle, and apoptosis analysis. HDPC differentiation was investigated by quantitative polymerase chain reaction, alkaline phosphatase activity, and oil red O staining. RESULTS: EZH2 and H3K27me3 were decreased, whereas KDM6B was increased in infected pulp tissue and cells, which were similar to HDPC differentiation. EZH2 inhibition suppressed IL-1b, IL-6, and IL-8 messenger RNA (mRNA) in HDPCs upon inflammatory stimuli and impeded HDPC proliferation by decreasing cell number, arresting cell cycle, and increasing apoptosis. Suppressed EZH2 impaired adipogenesis, peroxisome proliferator-activated receptor r (PPAR-r), and CCAAT-enhancer binding protein a (CEBP/a) mRNA in adipogenic induction while enhancing alkaline phosphatase activity, Osx, and bone sialoprotein (BSP) mRNA in mineralization induction of HDPCs. CONCLUSIONS: EZH2 inhibited HDPC osteogenic differentiation while enhancing inflammatory response and proliferation, suggesting its role in pulp inflammation, proliferation, and regeneration.

Immunohistochemical characterization of peroxisome proliferator-activated receptors in canine normal testis and testicular tumours.

Peroxisome proliferator-activated receptors (PPARs) are ligand-activated transcription factors belonging to the nuclear hormone receptor superfamily. Recent studies have demonstrated that PPARs regulate lipid metabolism and are expressed in various cancers. The aim of the present study was to investigate the expression of PPAR-α, -ß and -γ in normal canine testicular tissue and canine testicular tumours (CTTs). Expression of PPAR-α, -ß and -γ was greater (P <0.05) than in normal testicular tissue. PPARs were therefore induced in CTTs and they may play a role in the biology of these tumours.

Assessment of chitosan-affected metabolic response by peroxisome proliferator-activated receptor bioluminescent imaging-guided transcriptomic analysis.

Chitosan has been widely used in food industry as a weight-loss aid and a cholesterol-lowering agent. Previous studies have shown that chitosan affects metabolic responses and contributes to anti-diabetic, hypocholesteremic, and blood glucose-lowering effects; however, the in vivo targeting sites and mechanisms of chitosan remain to be clarified. In this study, we constructed transgenic mice, which carried the luciferase genes driven by peroxisome proliferator-activated receptor (PPAR), a key regulator of fatty acid and glucose metabolism. Bioluminescent imaging of PPAR transgenic mice was applied to report the organs that chitosan acted on, and gene expression profiles of chitosan-targeted organs were further analyzed to elucidate the mechanisms of chitosan. Bioluminescent imaging showed that constitutive PPAR activities were detected in brain and gastrointestinal tract. Administration of chitosan significantly activated the PPAR activities in brain and stomach. Microarray analysis of brain and stomach showed that several pathways involved in lipid and glucose metabolism were regulated by chitosan. Moreover, the expression levels of metabolism-associated genes like apolipoprotein B (apoB) and ghrelin genes were down-regulated by chitosan. In conclusion, these findings suggested the feasibility of PPAR bioluminescent imaging-guided transcriptomic analysis on the evaluation of chitosan-affected metabolic responses in vivo. Moreover, we newly identified that downregulated expression of apoB and ghrelin genes were novel mechanisms for chitosan-affected metabolic responses in vivo.

Potential characteristics of stem cells from human exfoliated deciduous teeth compared with bone marrow-derived mesenchymal stem cells for mineralized tissue-forming cell biology.

INTRODUCTION: Tissue engineering and regenerative medicine using stem cell biology has been a promising field for treatment of local and systemic intractable diseases. Recently, stem cells from human exfoliated deciduous teeth (SHED) have been identified as a novel population of stem cells. This study focused on the characterization of SHED as compared with bone marrow-derived mesenchymal stem cells (BMMSCs). METHODS: We investigated potential characteristics of SHED by using DNA microarray, real-time reverse transcriptase polymerase chain reaction, and immunofluorescence analysis. RESULTS: Multiple gene expression profiles indicated that the expression of 2753 genes in SHED had changed by ≥2.0-fold as compared with that in BMMSCs. One of the most significant pathways that accelerated in SHED was that of bone morphogenetic protein (BMP) receptor signaling, which contains several cascades such as PKA, JNK, and ASK1. When the BMP signaling pathway was stimulated by BMP-2, the expression of BMP-2, BMP-4, Runx2, and DSPP was up-regulated significantly in SHED than that in BMMSCs. Furthermore, the BMP-4 protein was expressed much higher in SHED but not in BMMSCs, as confirmed by immunofluorescence. CONCLUSIONS: By using the gene expression profiles, this study indicates that SHED is involved in the BMP signaling pathway and suggests that BMP-4 might play a crucial role in this. These results might be useful for effective cell-based tissue regeneration, including that of bone, pulp, and dentin, by applying the characteristics of SHED.

Chronic alcohol intake upregulates hepatic expression of carotenoid cleavage enzymes and PPAR in rats.

Excessive and chronic alcohol intake leads to a lower hepatic vitamin A status by interfering with vitamin A metabolism. Dietary provitamin A carotenoids can be converted into vitamin A mainly by carotenoid 15,15'-monooxygenase 1 (CMO1) and, to a lesser degree, carotenoid 9'10'-monooxygenase 2 (CMO2). CMO1 has been shown to be regulated by several transcription factors, such as the PPAR, retinoid X receptor, and thyroid receptor (TR). The regulation of CMO2 has yet to be identified. The impact of chronic alcohol intake on hepatic expressions of CMO1 and CMO2 and their related transcription factors are unknown. In this study, Fischer 344 rats were pair-fed either a liquid ethanol Lieber-DeCarli diet (n = 10) or a control diet (n = 10) for 11 wk. Hepatic retinoid concentration and expressions of CMO1, CMO2, PPARγ, PPARα, and TRß as well as plasma thyroid hormones levels were analyzed. We observed that administering alcohol decreased hepatic retinoid levels but increased mRNA concentrations of CMO1, CMO2, PPARγ, PPARα, and TRß and upregulated protein levels of CMO2, PPARγ, and PPARα. There was a positive correlation of PPARγ with CMO1 (r = 0.89; P < 0.0001) and both PPARγ and PPARα with CMO2 (r = 0.72, P < 0.001 and r = 0.62, P < 0.01, respectively). Plasma thyroid hormone concentrations did not differ between the control rats and alcohol-fed rats. This study suggests that chronic alcohol intake significantly upregulates hepatic expression of CMO1 and, to a much lesser extent, CMO2. This process may be due to alcohol-induced PPARγ expression and lower vitamin A status in the liver.

Peroxisome proliferator-activated receptors in reproductive tissues: from gametogenesis to parturition.

Peroxisome proliferator-activated receptors (PPARalpha, PPARbeta/delta and PPARgamma) are a family of nuclear receptors that are activated by binding of natural ligands, such as polyunsaturated fatty acids or by synthetic ligands. Synthetic molecules of the glitazone family, which bind to PPARgamma, are currently used to treat type II diabetes and also to attenuate the secondary clinical symptoms frequently associated with insulin resistance, including polycystic ovary syndrome (PCOS). PPARs are expressed in different compartments of the reproductive system (hypothalamus, pituitary, ovary, uterus and testis). Conservative functions of PPARs in mammalian species could be suggested through several in vivo and in vitro studies, especially in the ovary and during placental development. Several groups have described a strong expression of PPARgamma in ovarian granulosa cells, and glitazones modulate granulosa cell proliferation and steroidogenesis in vitro. All these recent data raise new questions about the biologic actions of PPARs in reproduction and their use in therapeutic treatments of fertility troubles such as PCOS or endometriosis. In this review, we first describe the roles of PPARs in different compartments of the reproductive axis (from male and female gametogenesis to parturition), with a focus on PPARgamma. Secondly, we discuss the possible molecular mechanisms underlying the effect of glitazones on PCOS. Like other 'insulin sensitizer' molecules, such as metformin, glitazones may in fact act directly on ovarian cells. Finally, we discuss the eventual actions of PPARs as mediators of environmental toxic substances for reproductive function.

Developmental regulation of prostacyclin synthase and prostacyclin receptors in the ovine uterus and conceptus during the peri-implantation period.

This study documents the expression of prostacyclin (PGI2) synthase (PTGIS) and PGI2 receptors in the trophoblast and uterus of the ewe at the time of maternal recognition of pregnancy (i.e. days 7, 9, 12, 14 and 17). The membrane receptor for PGI2 (PTGIR) and the nuclear receptors, i.e. peroxisome proliferator-activated receptors (PPAR) and their heterodimer partners the retinoid X receptors (RXR), were analysed. In the endometrium, PTGIS transcript and protein were expressed at day 9 of pregnancy and levels declined from days 12 to 17. Immunohistochemistry and in situ hybridization indicated that PTGIS was mainly located in the luminal epithelium of the endometrium. Endometrial PTGIR, PPARA, PPARG and RXRG expression was regulated during the peri-implantation period whereas PPARD, RXRA and RXRB were consistently expressed. In the trophoblast, PTGIS transcript levels rose as development progressed and peaked at day 17. PTGIR and PPARA transcripts peaked before day 12 and then declined and became nearly undetectable by day 17, whereas PPARD and PPARG transcript levels rose steadily from days 12 to 17. Because the PPARs and the RXRs display different expression profiles, we suggest that different heterodimers may form and support distinct functions as development proceeds. Our results also underline the importance of PTGIS and PPARD in the trophoblast and PTGIR in the uterus, suggesting that PGI2 is of both uterine and trophoblastic origin and is involved in a complex signalling pathway at around the time of implantation in the ewe.

Ageing introduces a complex pattern of changes in several rat brain transcription factors depending on gender and anatomical localization.

As ageing changes the activity of several transcription factors in the rat cortex, we were interested in determining whether similar changes also appear in the hippocampus of old rats. We determined by electrophoretic gel shift assays the binding activity of nuclear factor kappa B (NFkappaB), activator protein-1 (AP-1), peroxisome proliferator-activated receptor (PPAR), and liver X receptor (LXR) in cortex and hippocampus samples from young (3-month-old), and old (18-month-old) male and female Sprague-Dawley rats. NFkappaB activity increased in old male and female rats, though only in cortex samples, while AP-1 activity decreased only in the cortex and hippocampus of old female animals. LXR activity decreased in all conditions, except in old male cortexes; whereas PPAR activity only decreased in the hippocampus of old female rats. Decreases in AP-1 and PPAR activities restricted to old female rats did not result from an age-related decline in plasma 17beta-estradiol concentration, as their activities did not change in samples obtained from ovariectomized young female rats. Our results indicate that ageing induces a complex pattern of changes in the brain-binding activity of NFkappaB, AP-1, PPAR and LXR, depending on the anatomical origin of the samples (cortex or hippocampus), and the sex of the animals studied.

Up-regulation of peroxidase proliferator-activated receptor gamma in cholesteatoma.

OBJECTIVE: To evaluate the localization and expression of peroxidase proliferator-activated receptor (PPAR)gamma in cholesteatoma epithelium. STUDY DESIGN: Experimental study. METHODS: Reverse-transcription polymerase chain reaction was performed on cholesteatoma tissues from 10 adult patients undergoing tympanomastoid surgery for middle ear cholesteatoma and on 10 samples of normal external auditory canal skin tissue. The expression levels of PPARgamma to glyceraldehyde-3-phosphate dehydrogenase transcripts were semiquantified by densitometry. We also characterized the cellular localization of the PPARgamma protein immunohistochemically. Ki-67 was also localized to compare the proliferative activity of cells in cholesteatoma epithelium and in normal external auditory canal skin. RESULTS: PPARgamma mRNA and protein were detected in normal external auditory canal skin and in cholesteatoma epithelium. The expression level of PPARgamma mRNA in cholesteatoma was significantly increased compared with that in normal external auditory canal skin. PPARgamma protein was expressed in cells mainly in the granular and prickle cell layers. However, the intensity of its expression was generally decreased in the parabasal layer of the cholesteatoma epithelium. Ki-67 was expressed in the nuclei of cells in the basal and parabasal layers, and a greater number of cells were Ki-67 immunopositive in cholesteatoma epithelium. CONCLUSION: PPARgamma is up-regulated in the cholesteatoma epithelium compared with normal external auditory canal skin. These results suggest that PPARgamma may play an important role in the pathogenesis of cholesteatoma.

Caloric restriction results in decreased expression of peroxisome proliferator-activated receptor superfamily in muscle of normal and long-lived growth hormone receptor/binding protein knockout mice.

Resistance to growth hormone, reduced insulin-like growth factor 1 (IGF1) action, and enhanced insulin sensitivity are likely mediators of extended life span and delayed aging process in growth hormone receptor/binding protein knockout (GHR-KO) mice. Fat metabolism and genes involved in fatty acid oxidation are strongly involved in insulin action. Using real-time polymerase chain reaction and western blot we have examined expression of peroxisome proliferator-activated receptors (PPARs) and retinoid X receptor (RXR) genes in the skeletal muscle of normal and GHR-KO mice subjected to 30% caloric restriction. The results indicate that caloric restriction decreased the expression of PPARgamma, PPARalpha, and PPARbeta/delta which would lead to down-regulation of fat metabolism. This suggested metabolic change clearly does not affect whole-body insulin action. These findings suggest that whole-animal insulin sensitivity is not regulated through skeletal muscle insulin action.

Immunohistochemical distribution of activated nuclear factor kappaB and peroxisome proliferator-activated receptors in carbon tetrachloride-induced chronic liver injury in rats.

We investigated the immunohistochemical distribution of active NF-kappaB p65 and peroxisome proliferator-activated receptor (PPAR) subtypes alpha and gamma in the different phases of liver steatonecrosis and cirrhosis induced in rats after 3 and 9 weeks of carbon tetrachloride (CCl4) intoxication. CCl4 treatment can induce changes in the expression of NF-kappaB and PPARs. Immunohistochemical analysis of liver tissue sections from rats with steatonecrosis or cirrhosis demonstrated a significant increase in the number of NF-kappaB-positive and TNF-alpha-positive hepatocytes and Kupffer cells. In healthy controls, no expression of active NF-kappaB was detected. In previous studies, we have demonstrated that Kupffer cells isolated from rats with CCl4-induced steatonecrosis produced more reactive oxygen intermediates than cells isolated from normal rats. These oxidants could activate NF-kappaB and lead to an overexpression of TNF-alpha, observed in liver tissue sections. After CCl4 ingestion, the rat livers demonstrated a significantly decreased number of hepatocytes expressing PPARalpha and PPARgamma and a significantly increased number of ED2-positive Kupffer cells expressing these transcription factors, compared to normal. The activation of the p65 isoform of NF-kappaB correlates negatively with transcription of the alpha and gamma isoforms of PPAR in hepatocytes, and positively in Kupffer cells. These results suggest that the regulation and the role of these two transcription factors differ in the two cell types studied.

Immune-enhancing enteral nutrients differentially modulate the early proinflammatory transcription factors mediating gut ischemia/reperfusion.

BACKGROUND: Recent reports suggest that enteral diets enriched with arginine may be harmful by enhancing inflammation. This is consistent with our gut ischemia/reperfusion (I/R) model in which arginine induced the proinflammatory mediator inducible nitric oxide synthase and resulted in injury and inflammation whereas glutamine was protective. We now hypothesize that arginine and glutamine differentially modulate the early proinflammatory transcription factors activated by gut I/R. METHODS: At laparotomy, jejunal sacs were filled with either 60 mmol/L glutamine, arginine, or an iso-osmotic control followed by 60 minutes of superior mesenteric artery occlusion and 6 hours of reperfusion and compared with shams. Jejunum was harvested for nuclear factor (NF)-kappaB and activator protein-1 (AP-1) measured by electrophoretic mobility shift assay and c-jun and c-fos (AP-1 family) by supershift. RESULTS: Both NF-kappaB and AP-1 were activated by gut I/R. Arginine and glutamine had no differential effect on NF-kappaB, whereas AP-1 expression (c-jun but not c-fos) was markedly enhanced by arginine and significantly lessened by glutamine. CONCLUSION: Arginine enhanced expression of the early proinflammatory transcription factor AP-1 but not NF-kappaB. This represents a novel mechanism by which arginine may be harmful when administered to critically ill patients.

Fluorescence imaging reveals the nuclear behavior of peroxisome proliferator-activated receptor/retinoid X receptor heterodimers in the absence and presence of ligand.

In a global approach combining fluorescence recovery after photobleaching (FRAP), fluorescence correlation spectroscopy (FCS), and fluorescence resonance energy transfer (FRET), we address the behavior in living cells of the peroxisome proliferator-activated receptors (PPARs), a family of nuclear receptors involved in lipid and glucose metabolism, inflammation control, and wound healing. We first demonstrate that unlike several other nuclear receptors, PPARs do not form speckles upon ligand activation. The subnuclear structures that may be observed under some experimental conditions result from overexpression of the protein and our immunolabeling experiments suggest that these structures are subjected to degradation by the proteasome. Interestingly and in contrast to a general assumption, PPARs readily heterodimerize with retinoid X receptor (RXR) in the absence of ligand in living cells. PPAR diffusion coefficients indicate that all the receptors are engaged in complexes of very high molecular masses and/or interact with relatively immobile nuclear components. PPARs are not immobilized by ligand binding. However, they exhibit a ligand-induced reduction of mobility, probably due to enhanced interactions with cofactors and/or chromatin. Our study draws attention to the limitations and pitfalls of fluorescent chimera imaging and demonstrates the usefulness of the combination of FCS, FRAP, and FRET to assess the behavior of nuclear receptors and their mode of action in living cells.