gsk0660 and Cardiomegaly

Cardiovascular disease in obese individuals with type 2 diabetes is often associated with hyperleptinemia and leptin resistance, while other studies support that leptin has cardioprotective effects. Besides, the role of leptin in regulating cardiac atrophy or hypertrophy remains to be clearly defined. In fact, in rats with normal leptin sensitivity, the molecular underpinnings of the effects of central leptin regulating cardiac structural pathways remain poorly understood.. Hence, we assessed the effects of intracerebroventricular (icv) leptin infusion on cardiac remodeling analyzing FOXO1/3 and mTORC1 pathways, focusing special attention to PPARβ/δ as mediator of central leptin's effects on cardiac metabolism.. Male 3-months-old Wistar rats, infused with icv leptin (0.2 μg/day) for 7 days, were daily co-treated intraperitoneally with the specific PPARβ/δ antagonist GSK0660, at 1 mg/kg per day along leptin treatment.. Central leptin regulated dynamically, in an opposite manner, the network between FOXOs and mTORC1 and induced an atrophy-related gene program in cardiac tissue. Leptin activated the anti-hypertrophic kinase GSK3β and increased the protein levels of muscle-specific ubiquitin ligases, muscle RING finger 1 (MuRF1) and muscle atrophy F-box (MAFbx)/Atrogin-1 involved in limiting cardiac hypertrophy. FOXO1 activity and the expression of their target genes, Sod2 and Lpl, were also increased in the heart upon central leptin infusion. Besides, Beclin-1 and LC3B-II, gene products of the autophagic pathway response, were upregulated, while the content and expression levels of phenotypic markers of cardiac hypertrophy as ANP and β-myosin heavy chain, gene product of Myh7 were significantly decreased. On the other hand, mTORC1 activity and OXPHOS protein levels were decreased suggesting a key role of central leptin preventing cardiac oxidative stress. In fact, the content of carbonylated proteins, TBARS and ROS/RSN were not increased in cardiac tissue in response to central leptin infusion. Finally, the pharmacological inhibition of PPARβ/δ, via in vivo administration of the selective antagonist GSK0660, blunted the induction of FOXO1/3, Atrogin-1, MuRF1 and GSK3β in the heart mediated by icv leptin infusion.. Our results demonstrate that, in lean rats with normal leptin sensitivity, central leptin regulates nutrient sensing pathways in heart contributing to balance cardiac remodeling through the anti- and pro-hypertrophic programs, and in this process is involved PPARβ/δ.

Topics: Animals; Cardiomegaly; Forkhead Box Protein O1; Forkhead Box Protein O3; Heart; Leptin; Male; Myocardium; PPAR delta; PPAR-beta; Rats; Rats, Wistar; Reactive Nitrogen Species; Reactive Oxygen Species; Signal Transduction; Sulfones; Thiophenes; TOR Serine-Threonine Kinases; Ventricular Remodeling

Peroxisome proliferator-activated receptor δ (PPARδ), the predominant PPAR subtype in the heart, is known to regulate cardiac function. PPARδ activation may inhibit cardiac hypertrophy in H9c2 cells while the potential mechanism has not been elucidated. Then, H9c2 cells incubated with high glucose to induce hypertrophy were used to investigate using GW0742 to activate PPARδ. The fluorescence assays were applied to determine the changes in cell size, cellular calcium levels, and free radicals. Western blot analyses for hypertrophic signals and assays of messenger RNA (mRNA) levels for hypertrophic biomarkers were performed. In H9c2 cells, GW0742 inhibited cardiac hypertrophy. In addition, increases in cellular calcium and hypertrophic signals, including calcineurin and nuclear factor of activated T-cells, were reduced by GW0742. This reduction was parallel to the decrease in the mRNA levels of biomarkers, such as brain/B-type natriuretic peptides and β-myosin heavy chain. These effects of GW0742 were dose-dependently inhibited by GSK0660 indicating an activation of PPARδ by GW0742 to alleviate cardiac hypertrophy. Moreover, free radicals produced by hyperglycemia were also markedly inhibited by GW0742 and were later reversed by GSK0660. GW0742 promoted the expression of thioredoxin, an antioxidant enzyme. Direct inhibition of reactive oxygen species by GW0742 was also identified in the oxidant potassium bromate stimulated H9c2 cells. Taken together, these findings suggest that PPARδ agonists can inhibit free radicals, resulting in lower cellular calcium for reduction of hypertrophic signaling to alleviate cardiac hypertrophy in H9c2 cells. Therefore, PPARδ activation can be used to develop agent(s) for treating cardiac hypertrophy.

Topics: Animals; Blotting, Western; Calcium; Cardiomegaly; Cell Line; Free Radicals; Hyperglycemia; Rats; Reactive Oxygen Species; Sulfones; Thiazoles; Thiophenes