Peroxisome proliferator-activated receptors (PPARs) and their implications in diseases:

Radioiodination and biological evaluation of mesalamine as a tracer for ulcerative colitis imaging

This study aims to evaluate newly radioiodinated mesalamine (Mes) as a tracer for ulcerative colitis imaging. Mes was labeled with [125I] with chloramine-T (Ch-T) as the oxidizing agent. Labeling factors such as pH, reaction temperature, reaction time, substrate amount and oxidizing agent amount were investigated to optimize the radiochemical yield (98.5%). The labeled compound was separated and purified using thin layer chromatography (TLC), paper electrophoreses and high performance liquid chromatography (HPLC). The biological distribution indicated that the radioiodinated mesalamine localization was highest (72.28%) in microbial model compared to normal mice (29.25%) at 120 min post injection. So, 125I-Mes could be considered as a new radiotracer for ulcerative colitis.

Pro12Ala PPAR γ2 gene polymorphism in PCOS women: the role of compounds regulating satiety

Five to ten percent of women of reproductive age suffer from polycystic ovary syndrome (PCOS). Leptin, NPY, galanin, cholecystokinin (CCK) are involved in the regulation of eating behavior. PPARγ are receptors that are probably involved in hyperandrogenism. This study was designed to assess associations between the Pro12Ala PPARγ2 gene polymorphism and satiety factors in PCOS. Fifty-four PCOS women and 51 healthy women were studied. Leptin, NPY, galanin, CCK levels, and genetic studies to detect Pro12Ala PPARγ2 gene polymorphism were assessed. The leptin levels in the PCOS women carrying Pro12Ala genotype were higher than in those with Pro12Pro and Ala12Ala. The PCOS women had higher leptin and NPY levels and lower galanin levels. Obese PCOS patients had lower CCK levels.

CONCLUSIONS

In the PCOS women, a single Ala allele may have a protective role as far as hyperleptinemia is concerned. The PCOS women may reveal a disrupted central leptin/NPY feedback loop with some shifts in food intake.

Thiazolidinediones for the treatment of type 2 diabetes

Thiazolidinediones (TZD), or glitazones, represent a new generation of antidiabetic drugs that have recently been introduced in Europe. They improve insulin resistance, one of the key anomalies involved in the pathogenesis of type 2 diabetes mellitus, by activating the nuclear peroxoxisome proliferator activated receptor-gamma (PPAR-gamma), leading to crucial metabolic alterations in adipose tissue. Rosiglitazone and pioglitazone have been shown to be active as monotherapy, in combination therapy with metformin or sulfonylureas, and even in triple therapy. They are generally well tolerated but can induce fluid retention. Cardiac failure is a contraindication for the use of TZDs, as is the concomitant administration of insulin. Aside from their effect on glycemic control, TZDs act on several cardiovascular risk factors and may protect pancreatic beta cells from apoptosis. The cardiovascular protective effect of TZDs has recently been demonstrated with the results of the PROactive study, and long-term preservation of beta-cell function is currently under further investigation.

Biochemical and morphological effects of K-111, a peroxisome proliferator-activated receptor (PPAR)alpha activator, in non-human primates

K-111 has been characterized as a potent peroxisome proliferator-activated receptor (PPAR)alpha activator. Antidiabetic potency and amelioration of disturbed lipid metabolism were demonstrated in rodents, which were accompanied by elevations of peroxisomal enzymes and liver weight. To examine the possible therapeutic application of K-111 we have now assessed its efficacy in non-human primates with high transferability to humans. For this purpose obese, hypertriglyceridaemic, hyperinsulinaemic prediabetic rhesus monkeys were dosed sequentially with 0, 1, 3 and 10mg/kg per day orally over a period of 4 weeks each. In addition, the effect of K-111 on the peroxisome compartment was analyzed in cynomolgus monkeys using liver samples obtained following a 13-week oral toxicity study. In prediabetic monkeys, the reduction of hyperinsulinaemia and improvement of insulin-stimulated glucose uptake rate indicated amelioration of insulin resistance. These effects were nearly maximal at a dose of 3mg/kg per day, while triglycerides and body weight were lowered significantly in a dose-dependent manner. This reduction of body weight contrasts sharply with the adipogenic response observed with thiazolidinediones, another family of insulin-sensitizing agents. In young cynomolgus monkeys at a dosage of 5mg/kg per day and more, K-111 induced an up to three-fold increase in lipid beta-oxidation enzymes with an 1.5- to 2-fold increase in peroxisome volume density. This moderate increase in peroxisomal activity by K-111 in monkeys is consistent with its role as an PPARalpha activator and corresponds to the observations with fibrates in other low responder mammalian species. The increase in beta-oxidation may explain, at least in part, the lipid modulating effect as well as the antidiabetic potency of K-111. This pharmacological profile makes K-111 a highly promising drug candidate for clinical applications in the treatment of type 2 diabetes, dyslipidaemia, obesity and the metabolic syndrome.

Management of co-existing diabetes mellitus and dyslipidemia: defining the role of thiazolidinediones

The observed reduction in macrovascular outcomes in the United Kingdom Progressive Diabetes Study (UKPDS) trial in patients with type 2 diabetes mellitus (DM), treated intensively with insulin or sulfonylureas, was of borderline significance (p = 0.052). This may be because of the role of factors other than glycemic control in the etiology of macrovascular disease. The UKPDS and other studies have suggested that lipid parameters are potent predictors of adverse outcomes in patients with type 2 DM. In patients with DM, dyslipidemia is characterized by elevated serum triglycerides and low high density lipoprotein-cholesterol (HDL-C) with normal total serum cholesterol levels and usually accompanied by an elevation of atherogenic, small, dense low density lipoprotein-cholesterol (LDL-C) particles. Dyslipidemia is only partly corrected by dietary and lifestyle modifications and pharmacological glycemic control in patients with DM. Several guidelines, including those published by the New Zealand Heart Foundation, suggest that lipid-modifying therapies are appropriate in patients considered to be at high or very high risk of a cardiac event. This includes patients with established vascular disease. Some recent studies suggest that patients with type 2 DM have risk comparable to patients without DM, but have experienced previous myocardial infarction (MI). Subgroup analysis of trials including the Scandinavian Simvastatin Survival Study (4S) and Cholesterol and Recurrent Events (CARE), which included patients with DM, have shown a significant reduction in adverse outcomes, although many patients with DM and dyslipidemia were excluded. Of lipid-lowering drugs, fibric acid derivatives are probably the most appropriate for patients with DM and dyslipidemia and their role is being evaluated in large, long-term outcome studies such as Fenofibrate Intervention and Event Lowering in Diabetes (FIELD). Thiazolidinediones, a new class of compound for treating patients with type 2 DM, primarily exert their glucose-lowering effect by increasing insulin sensitivity at the level of skeletal muscle, and to a lesser extent, at the liver by decreasing hepatic glucose output. Some of their actions are mediated through binding and activation of the peroxisome proliferator-activated receptor-gamma, a nuclear receptor that has a regulatory role in differentiation of cells, especially adipocytes. The nonhypoglycemic effects of thiazolidinediones, therefore, offer additional potential mechanisms for benefit in patients with type 2 DM and insulin resistance. Thiazolidinediones increase serum HDL-C levels. Troglitazone and pioglitazone have been shown to decrease serum triglyceride levels. Rosiglitazone, conversely has no significant effect on serum triglyceride levels. All of the thiazolidinediones increase serum LDL-C levels (pioglitazone to a lesser extent), although changes in the size of the LDL fraction may render it less susceptible to oxidation and, therefore, less atherogenic. A randomized comparative trial needs to be undertaken to determine whether true differences exist between the thiazolidinediones. Longer studies need to be undertaken to assess their effect on cardiovascular outcomes.

Downregulation of PPARγ expression in peripheral blood monocytes correlated with adhesion molecules in acute coronary syndrome

BACKGROUND

Peroxisome proliferator-activated receptor-gamma (PPARgamma) is a nuclear hormone receptor and may regulate the metabolism of lipids, inhibit monocytes/macrophages function and reduce the production of cell adhesion molecules and some inflammatory factors. Thus, it may affect the occurrence and progression of atherosclerosis.

METHODS

Forty-three patients with acute coronary syndrome and 34 control subjects were studied for PPARgamma expression in peripheral blood monocytes by reverse transcription-polymerase chain reaction (RT-PCR), and adhesion molecules were measured by enzyme-linked immunosorbent assay (ELISA).

RESULTS

Expression of PPARgamma in peripheral blood monocytes was significantly reduced in acute coronary syndrome, which was inversely associated with intercellular adhesion molecule 1 (r=-0.339, P<0.05), vascular cell adhesion molecule 1 (r=-0.331, P<0.05) and body mass index (r=-0.334, P<0.05), respectively, and positively correlated with apoA1 (r=0.289, P<0.05).

CONCLUSIONS

The reduced expression of PPARgamma in peripheral blood monocytes of patients with acute coronary syndrome is inversely associated with plasma soluble adhesion molecules, suggesting that PPARgamma may be involved in acute coronary syndrome.