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Rezulin was launched in Japan, the UK (subseqently withdrawn) and the US
for treatment of type Ⅱ diabetes. Two approaches, four steps and six steps, converge
on 6-acetoxy-2-(4-aminophenoxymethyl)-2,5,7,8-tetramethylchroman which can be
elaborated in two steps to Rezulin. It is the first of a new class of thiazolidenediones
for NIDDM that reduces glucose concentrations without effecting insulin secretion. It
binds to peroxisome proliferator-activated receptor gamma (PPARγ) thus activating
this nuclear receptor which then influences carbohydrate metabolism. This is
accomplished by increasing insulin sensitivity by upregulating glucose transporter
(Glut1 and/or Glut4) expression without affecting the number or affinity of insulin
receptors. There is also an increase in hepatic glycogen synthase activity which
enhances glucose utilization and a reduction in hepatic gluconeogenesis by inhibiting
fructose-1 ,&bisphosphatase. Pancreatic islet cell destruction is prevented. It reduces
serum triglycerides because PPARγ causes fibroblasts to differentiate into adipocytes
and does not activate RARα. It has a half-life of 9 h and is metabolized into three
compounds having no activity.
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Crystalline Solid
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Troglitazone (Sankyo) was firstly approved 1995 in Japan and 1997 in USA and UK. It was launched in these countries in 1997. The recommended starting dose was 400 mg/d and the highest dose 600 mg. After being marketed, the daily practice revealed adverse events in the liver with cases of fatal liver failure. This lead to withdrawal of troglitazone from the market in the UK already after two months, in USA and Japan in the year 2000.
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Troglitazone is an an oral hypoglycemic agent which improves insulin sensitivity and decreases hepatic glucose production. Antidiabetic.
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A α-tocopherol (vitamin E) moiety containing thiazolidinedione class of insulin-sensitizer that acts as an activator of peroxisome proliferator-activated receptors γ (PPARγ). Also exhibits anti-proliferative and anti-inflammatory properties. Shown to induce cell cycle arrest and apoptosis in human hepatoma cells. Inhibits vascular smooth muscle cell (VSMC) migration by rapidly activating MEK/ERK pathway leading to the induction of
c-fos and
Ets-1 expression. Blocks PDGF-induced cell proliferation of pancreatic stellate and accelerates p21
Cip1 turnover by inhibiting PKC
δ signaling in VSMCs. Exerts positive inotropic effect via Ca
2+ sensitization in the sarcoplasmic reticulum and inhibits Na
+/H
+ exchange activity and proliferation of macrovascular endothelial cells.
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Selective PPAR γ receptor agonist (EC 50 values are 780 and 555 nM at murine and human PPAR γ receptors respectively). Displays no activity at PPAR α or PPAR δ receptors. Antidiabetic agent; exerts potent glucose-lowering effects in insulin-resistant diabetic mice. Displays anti-invasive effect on human breast cancer cells; reduces migration, adhesion and spreading on fibronectin-coated plates. Also inhibits lamellipodia formation and actin polymerization.
Pharmacology
Depending on the animal model, after repeated dosing troglitazone lowered hyperglycemia as well as levels of free fatty acids, triglycerides, and insulin at daily doses of 50 mg/kg p.o. or slightly lower.
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