Gene Doping with Peroxisome-Proliferator-Activated Receptor Beta/Delta Agonists Alters Immunity but Exercise Training Mitigates the Detection of Effects in Blood Samples.

Synthetic ligands of peroxisome-proliferator-activated receptor beta/delta (PPARß/δ) are being used as performance-enhancing drugs by athletes. Since we previously showed that PPARß/δ activation affects T cell biology, we wanted to investigate whether a specific blood T cell signature could be employed as a method to detect the use of PPARß/δ agonists. We analyzed in primary human T cells the in vitro effect of PPARß/δ activation on fatty acid oxidation (FAO) and on their differentiation into regulatory T cells (Tregs). Furthermore, we conducted studies in mice assigned to groups according to an 8-week exercise training program and/or a 6-week treatment with 3 mg/kg/day of GW0742, a PPARß/δ agonist, in order to (1) determine the immune impact of the treatment on secondary lymphoid organs and to (2) validate a blood signature. Our results show that PPARß/δ activation increases FAO potential in human and mouse T cells and mouse secondary lymphoid organs. This was accompanied by increased Treg polarization of human primary T cells. Moreover, Treg prevalence in mouse lymph nodes was increased when PPARß/δ activation was combined with exercise training. Lastly, PPARß/δ activation increased FAO potential in mouse blood T cells. Unfortunately, this signature was masked by training in mice. In conclusion, beyond the fact that it is unlikely that this signature could be used as a doping-control strategy, our results suggest that the use of PPARß/δ agonists could have potential detrimental immune effects that may not be detectable in blood samples.

Pharmacological PPARß/δ activation upregulates VLDLR in hepatocytes / La activación de PPARß/δ aumenta los niveles de VLDLR en hepatocitos

The very low-density lipoprotein receptor (VLDLR) plays an important function in the control of serum triglycerides and in the development of non-alcoholic fatty liver disease (NAFLD). In this study, we investigated the role of peroxisome proliferator-activated receptor (PPAR)ß/δ activation in hepatic VLDLR regulation. Treatment of mice fed a high-fat diet with the PPARß/δ agonist GW501516 increased the hepatic expression of Vldlr. Similarly, exposure of human Huh-7 hepatocytes to GW501516 increased the expression of VLDLR and triglyceride accumulation, the latter being prevented by VLDLR knockdown. Finally, treatment with another PPARß/δ agonist increased VLDLR levels in the liver of wild-type mice, but not PPARß/δ-deficient mice, confirming the regulation of hepatic VLDLR by this nuclear receptor. Our results suggest that upregulation of hepatic VLDLR by PPARß/δ agonists might contribute to the hypolipidemic effect of these drugs by increasing lipoprotein delivery to the liver. Overall, these findings provide new effects by which PPARß/δ regulate VLDLR levels and may influence serum triglyceride levels and NAFLD development

El receptor de las lipoproteínas de muy baja densidad (VLDLR) desempeña una función muy importante en el control de los niveles de triglicéridos séricos y en el desarrollo de la enfermedad del hígado graso no alcohólico (EHGNA). En este estudio hemos investigado el papel de la activación del receptor activado por los proliferadores peroxisómicos (PPAR)ß/δ en la regulación hepática del VLDLR. El tratamiento de ratones alimentados con una dieta rica en grasas con el agonista PPARß/δ GW501516 aumentó la expresión hepática de Vldlr. Asimismo, la exposición de hepatocitos humanos Huh-7 a GW501516 aumentó la expresión de VLDLR y la acumulación de triglicéridos, siendo este ultimo aumento evitado por el knockdown de VLDLR. Finalmente, el tratamiento con otro agonista PPARß/δ incrementó los niveles de VLDLR en el hígado de ratones wild-type, pero no en el de ratones deficientes en PPARß/δ, confirmando la regulación del VLDLR hepático por este receptor. En conjunto, nuestros resultados proporcionan un nuevo efecto por el que PPARß/δ regula los niveles de VLDLR y puede influenciar los niveles de triglicéridos séricos así como el desarrollo de la EHGNA

PPARß/δ attenuates palmitate-induced endoplasmic reticulum stress and induces autophagic markers in human cardiac cells.

BACKGROUND: Chronic endoplasmic reticulum (ER) stress contributes to the apoptotic cell death in the myocardium, thereby playing a critical role in the development of cardiomyopathy. ER stress has been reported to be induced after high-fat diet feeding in mice and also after saturated fatty acid treatment in vitro. Therefore, since several studies have shown that peroxisome proliferator-activated receptor (PPAR)ß/δ inhibits ER stress, the main goal of this study consisted in investigating whether activation of this nuclear receptor was able to prevent lipid-induced ER stress in cardiac cells. METHODS AND RESULTS: Wild-type and transgenic mice with reduced PPARß/δ expression were fed a standard diet or a high-fat diet for two months. For in vitro studies, a cardiomyocyte cell line of human origin, AC16, was treated with palmitate and the PPARß/δ agonist GW501516. Our results demonstrate that palmitate induced ER stress in AC16 cells, a fact which was prevented after PPARß/δ activation with GW501516. Interestingly, the effect of GW501516 on ER stress occurred in an AMPK-independent manner. The most striking result of this study is that GW501516 treatment also upregulated the protein levels of beclin 1 and LC3II, two well-known markers of autophagy. In accordance with this, feeding on a high-fat diet or suppression of PPARß/δ in knockout mice induced ER stress in the heart. Moreover, PPARß/δ knockout mice also displayed a reduction in autophagic markers. CONCLUSION: Our data indicate that PPARß/δ activation might be useful to prevent the harmful effects of ER stress induced by saturated fatty acids in the heart by inducing autophagy.

[PPARs: physiological functions and pharmacological roles of agonists in human diseases. Note II]. / PPARs: functii fiziologice si roluri farmacologice ale agonistilor în bolile umane (Nota II).

Increasing attention paid to the main family of peroxisome proliferator activated receptors--PPARs is generated, on one hand by the multiple functions of its members in numerous metabolically active tissues, and on the other hand by the therapeutic benefits expresed by some specific ligands that are used in certain metabolic diseases treatment plan. PPARalpha stimulates the beta-oxidative degradation of fatty acids and controls plasma lipid transport through the mediated action upon the triglycerides and fatty acids metabolism and by modulation of biosynthesis and catabolism of bile acids in the liver. PPARgamma promotes adipocytes differentiation and fat storage. PPARbeta/delta is involved in control and management of adipogenesis. While PPARalpha mediates the hypolipemiant actions of fibrates, PPARgamma is the receptor for thiazolidinediones (glitazones) reccomended in type 2 diabetes treatment; by binding to PPARgamma, glitazones modulates transcription of genes involved in lipid and carbohydrate metabolism.

Peroxisome proliferator-activated receptor beta stimulation induces rapid cardiac growth and angiogenesis via direct activation of calcineurin.

AIMS: Peroxisome proliferator-activated receptors (PPARs) are ligand-activated transcription factors. PPARbeta agonists were suggested as potential drugs for the treatment of metabolic syndrome, but effects of PPARbeta activation on cardiac growth and vascularization are unknown. Thus, we investigated the consequences of pharmacological PPARbeta activation on the heart and the underlying molecular mechanisms. METHODS AND RESULTS: Male C57/Bl6 mice were injected with the specific PPARbeta agonists GW0742 or GW501516, or vehicle. Cardiomyocyte size and vascularisation were determined at different time points. Expression differences were investigated by quantitative reverse transcriptase-polymerase chain reaction and western blotting. In addition, the effects of PPARbeta stimulation were compared with hearts of mice undergoing long-term voluntary exercise or pharmacological PPARalpha activation. Five hours after GW0742 injection, we detected an enhanced angiogenesis compared with vehicle-injected controls. After 24 h, the heart-to-body weight ratios were higher in mice injected with either GW0742 or GW501516 vs. controls. The increased heart size was due to cardiomyocyte enlargement. No signs of pathological cardiac hypertrophy (i.e. apoptosis, fibrosis, or deteriorated cardiac function) could be detected. The effects are mediated via calcineurin A (CnA) activation as: (i) CnA was upregulated, (ii) GW0742 administration or co-transfection of PPARbeta significantly stimulated the activity of the CnA promoter, (iii) PPARbeta protein bound directly to the CnA promoter, (iv) the CnA target genes NFATc3, Hif-1alpha, and Cdk 9 were upregulated in response to PPARbeta stimulation, and (v) the inhibition of CnA activity by cyclosporine A abolished the hypertrophic and angiogenic responses to PPARbeta stimulation. CONCLUSION: Our data suggest PPARbeta pharmacological activation as a novel approach to increase cardiac vascularization and cardiac muscle mass.

[Study on the antisense oligonucleotide against peroxisome proliferator-activated receptors promoting TNF-alpha mediated apoptosis of HaCat cells].

OBJECTIVE: To investigate the influence of antisense phosphorothioate oligonucleotides on peroxisome proliferator-activated receptors (PPARbeta) in the TNF-alpha mediated apoptosis of HaCat cells. METHODS: HaCat cells were resuscitated and randomly divided into normal control (without transfection), sham (merely with liposome transfection), scrODN (with transfection of 4 micromol/L PPARbeta scrODN), asODN (with transfection of 4 micromol/L PPARbeta asODN), TNF-alpha with transfection of 10 micromol/L TNF-alpha), scrODN + TNF-alpha with 10 micromol/L TNF-alpha stimulation after transfection of 4 micromol/L PPARbeta scrODN), asODN + TNF-alpha with 10 micromol/L TNF-alpha stimulation after transfection of 4 micromol/L PPARbeta asODN) groups. The mRNA and protein levels of PPARbeta were determined with RT-PCR and Western blotting, respectively. The changes in cell morphology were observed with Hoechst 33258 fluorescent staining to quantitate apoptotic rate of nuclei. The effect of PPARbeta asODN on HaCat cell viability was assayed with MTT method. Activation of caspase-3 was evaluated with caspase colorimetric analysis kit. RESULTS: The mRNA and protein expression of PPARbeta in normal control, sham, scrODN groups were similar, but it decreased obviously in asODN group. The nuclear apoptotic rate in normal control, scrODN and asODN groups were rather low, and the caspase-3 activity in these groups was also low. After 24 hours of culture, the nuclear apoptotic rate in TNF-alpha and scrODN + TNF-alpha groups were (33.1 +/- 2.7)% and (32.9 +/- 3.0)%, respectively, while that in asODN + TNF-alpha group was obviously increased (58.8 +/- 4.6)%, with the caspase-3 activity significantly higher, but the number of live cells markedly lower than that in the former 2 groups (P < 0.05). CONCLUSION: PPARbeta expression can promote the apoptosis of HaCat cells mediated by TNF-alpha.