Long-term effects of a PPAR-gamma agonist, pioglitazone, on neointimal hyperplasia and endothelial regrowth in insulin resistant rats

Different Effects of Thiazolidinediones on In-Stent Restenosis and Target Lesion Revascularization after PCI: A Meta-Analysis of Randomized Controlled Trials

In-stent restenosis (ISR) remains the leading problem encountered after percutaneous coronary intervention (PCI). Thiazolidinediones (TZDs) has been shown to be associated with reduced ISR and target lesion revascularization (TLR); however, the results are inconsistent, especially between rosiglitazone and pioglitazone. In this study, fourteen RCTs with a total of 1350 patients were finally included through a systematical literature search of Embase, Pubmed, the Cochrane Library, and ClinicalTrials.gov from inception to January 31, 2017. The follow-up duration of the included trials ranged from 6 months to 18 months. The results demonstrated that TZDs treatment is associated with significantly reduced risk of TLR (RR:0.45, 95%CI 0.30 to 0.67 for pioglitazone, RR:0.68, 95%CI 0.46 to 1.00 for rosiglitazone). Pioglitazone is associated with significantly reduced risks of ISR (RR:0.47, 95%CI 0.27 to 0.81), major adverse cardiac events (MACE) (RR:0.44, 95%CI 0.30 to 0.64) and neointimal area (SMD: −0.585, 95%CI −0.910 to −0.261). No significant relationship was observed between rosiglitazone and ISR (RR:0.91, 95%CI 0.39 to 2.12), MACE (RR:0.73, 95%CI 0.53 to 1.00) and neointimal area (SMD: −0.164, 95%CI −1.146 to 0.818). This meta-analysis demonstrated that TZDs treatment is associated with significant reduction in ISR, TLR and MACE for patients after PCI. Pioglitazone treatment seems to have more beneficial effects than rosiglitazone and no significantly increased cardiovascular risk was detected for both agents.

Effects of MHY908, a New Synthetic PPARα/γ Dual Agonist, on Inflammatory Responses and Insulin Resistance in Aged Rats

Insulin resistance is common with aging and is associated with the inflammatory response in both humans and rodents. A number of peroxisome proliferator-activated receptor (PPAR) α/γ dual agonists have been tested for their abilities to attenuate insulin resistance and type 2 diabetes. However, there is no study on the effects of PPARα/γ dual agonists on inflammation and insulin resistance during aging. In the present study, we investigated the ability of 2-[4-(5-chlorobenzothiazothiazol-2-yl)phenoxy]-2-methyl-propionic acid (MHY908), a newly synthesized novel PPARα/γ dual agonist, to suppress the inflammatory response and attenuate insulin resistance in aged rats. Twenty-month-old rats were divided into four groups: ad libitum fed, ad libitum fed supplemented with MHY908 (1 mg and 3 mg/kg/day for 4 weeks), and 40% calorie restricted. Six-month-old ad libitum fed rats were used as an age control. The aged rats supplemented with MHY908 showed reduced serum glucose, triglyceride, and insulin levels, as well as reduced liver triglyceride levels. MHY908 brought about a reduction in endoplasmic reticulum stress and activation of the c-Jun N-terminal kinase in the livers of aged rats, which consequently improved insulin signaling. In the kidneys of aged rats, the efficacy of MHY908 as a potent anti-inflammatory agent was shown by its suppression of NF-κB activation through inhibition of the Akt/IκB kinase signaling pathway. Therefore, the major finding of this study is that MHY908 acts as a therapeutic agent against age-related inflammation associated with insulin resistance by activating PPARα and PPARγ, thus attenuating endoplasmic reticulum stress.

Reno-protection of G004, a novel anti-diabetic sulfonylurea in db/db mice

1-[4-[2-(4-Bromobenzene-sulfonamino)ethyl]phenylsulfonyl]-3-(trans-4-methylcyclohexyl) urea (G004, CAS865483-06-3) is a synthetic sulfonylurea, incorporating the hypoglycemic active structure of glimepiride (CAS 93479-97-1) and anti-TXA2 receptor (TP) active structure of BM-531(CAS 284464-46-6). In this study, we evaluated the effect of G004 on hyperglycemia and dyslipidemia as well as diabetic nephropathy (DN) in db/db mice by gavage over 90 consecutive days of treatment. The fasting blood glucose (FBG), glucose, and insulin tolerance as well as dyslipidemia were effectively ameliorated in db/db mice treated with G004. Interestingly, renal histological results of db/db mice revealed that G004 markedly reversed the expansion of mesangial extracellular matrix (ECM), the early hallmark of DN. Indeed, G004 treatment downregulated the renal expressions of type 4 collagen (Col IV) and transforming growth factor-β1 (TGF-β1) in db/db mice. In addition, imbalance in expressions of matrix metalloproteinase-9 (MMP-9) and its tissue inhibitor-1 (TIMP-1) in db/db mice kidneys was observed. However, G004 increased and decreased the expressions of MMP-9 and TIMP-1, respectively. It is well known that TGF-β pathway signaling plays an essential role in hyperglycemia-induced cell protein synthesis. On the other hand, MMP/TIMP system is responsible for the breakdown and turnover of ECM. Thus, we speculate that G004 possibly attenuated ECM accumulation via remodeling the synthesis and degradation of ECM component Col IV through modulation in TGF-β1 and MMP-9/TIMP-1 expressions in kidneys of db/db mice. Results from this study provide a strong rationale for G004 to be an efficient glucose-controlling agent with significant reno-protective properties.

Pioglitazone in the treatment of type 2 diabetes: safety and efficacy review

The increase in obesity and the aging of the population has lead to an increase in the incidence of type 2 diabetes. This has led to the development of new drugs such as thiazolidinediones (TZDs) which are Peroxisome Proliferator-Activated Receptor (PPARgamma) agonists, to treat type 2 diabetes. TZDs have recently been at the center of a controversy with regards to their cardiovascular safety. Pioglitazone is a TZD which has been shown to be effective in glycemic control by lowering insulin resistance. Pioglitazone also has beneficial effects on lipid metabolism and cardiovascular risk. The safety and efficacy of pioglitazone including its pleotropic effects are discussed at length in this article.

Peroxisome proliferator-activated receptors as stimulants of angiogenesis in cardiovascular disease and diabetes

The incidence of diabetes is directly related to the incidence of obesity, which is at epidemic proportions in the US. Cardiovascular disease is a common complication of diabetes, which results in high morbidity and mortality. Peroxisome proliferator-activated receptors (PPARs) are a group of nuclear hormone receptors that regulate lipid and glucose metabolism. PPAR-α agonists such as fenofibrate and PPAR-γ agonists such as the thiozolidinediones have been used to treat dyslipidemia and insulin resistance in diabetes. Over the past few years research has discovered the role of PPARs in the regulation of inflammation, proliferation, and angiogenesis. Clinical trials looking at the effect of PPAR agonists on cardiovascular outcomes have produced controversial results. Studies looking at angiogenesis and proliferation in various animal models and cell lines have shown a wide variation in results. This may be due to the differential effects of PPARs on proliferation and angiogenesis in various tissues and pathologic states. This review discusses the role of PPARs in stimulating angiogenesis. It also reviews the settings in which stimulation of angiogenesis may be either beneficial or harmful.

Peroxisome proliferator-activated receptor agonists: do they increase cardiovascular risk?

Cardiovascular disease is a major cause of morbidity and mortality among people with type 2 diabetes mellitus. The peroxisome proliferator-activated receptor (PPAR) agonists have a significant role on glucose and fat metabolism. Thiazolidinediones (TZDs) are predominantly PPARγ agonists, and their primary benefit appears to be the prevention of diabetic complications by improving glycemic control and lipid profile. Recently, the cardiovascular safety of rosiglitazone was brought to center stage following meta analyses and the interim analysis of the RECORD trial. Current evidence points to rosiglitazone having a greater risk of myocardial ischemic events than placebo, metformin, or sulfonylureas. This review article discusses the mechanism of action of PPAR agonists and correlates it with clinical and laboratory outcomes in the published literature. In addition, this review article attempts to discuss some of the molecular mechanisms regarding the association between TZDs therapy and the nontraditional cardiovascular risks.

Effects of a PPAR-gamma agonist, on growth factor and insulin stimulated endothelial cells

OBJECTIVE

PPAR-gamma agonists such as thiazolidinediones, used in patients with insulin resistance have been shown to reduce neointimal hyperplasia in the short term. However recent studies suggest increased cardiovascular risk for some thiazolidinediones. Longer-term animal studies show inhibition of endothelial regrowth post endothelial injury which may account for some of the increased risk. We studied the effect of pioglitazone on VEGF, FGF and insulin stimulated endothelial cells to determine if this was a mechanism of inhibition of endothelial regrowth.

METHODS AND RESULTS

FGF/VEGF stimulated human umbilical vein endothelial cell (HUVEC) proliferation and apoptosis was measured, in vitro, in the presence and absence of hyperinsulinemia, with and without treatment with the PPAR-gamma agonist pioglitazone. Activation of ERK 1/2 and p38MAPK was measured under the same conditions. There was 40% decrease in proliferation with pioglitazone in VEGF stimulated cells, which was reversed by insulin. ERK 1/2 activation was decreased by pioglitazone in VEGF stimulated cells and was partially reversed by insulin. p38MAPK activation was increased by pioglitazone and was unaffected by insulin or VEGF. Pioglitazone also increased endothelial cell apoptosis.

CONCLUSION

PPAR-gamma agonists may have detrimental cardiovascular effects post angioplasty especially in patients with insulin resistance. We have shown that one of the mechanisms may be inhibition of endothelial regrowth and re-endothelialization by inhibition of VEGF/FGF stimulation of the ERK 1/2 pathways in endothelial cells.