Modulatory effects of HMG-CoA reductase inhibitors in diabetic microangiopathy

Poly(ADP-ribose) polymerase inhibitors ameliorate nephropathy of type 2 diabetic Leprdb/db mice

The activation of the poly(ADP-ribose) polymerase (PARP) plays an important role in the pathophysiology of various diseases associated with oxidative stress. We found increased amounts of poly(ADP) ribosylated proteins in diabetic kidneys of Lepr(db/db) (BKsJ) mice, suggesting increased PARP activity. Therefore, we examined the effects of two structurally unrelated PARP inhibitors (INO-1001 and PJ-34) on the development of diabetic nephropathy of Lepr(db/db) (BKsJ) mice, an experimental model of type 2 diabetes. INO-1001 and PJ-34 were administered in the drinking water to Lepr(db/db) mice. Both INO-1001 and PJ-34 treatment ameliorated diabetes-induced albumin excretion and mesangial expansion, which are hallmarks of diabetic nephropathy. PARP inhibitors decreased diabetes-induced podocyte depletion in vivo and blocked hyperglycemia-induced podocyte apoptosis in vitro. High glucose treatment of podocytes in vitro led to an early increase of poly(ADP) ribosylated modified protein levels. Reactive oxygen species (ROS) generation appears to be a downstream target of hyperglycemia-induced PARP activation, as PARP inhibitors blocked the hyperglycemia-induced ROS generation in podocytes. INO-1001 and PJ-34 also normalized the hyperglycemia-induced mitochondrial depolarization. PARP blockade by INO-1001 and PJ-34 prevented hyperglycemia-induced nuclear factor-kappaB (NFkappaB) activation of podocytes, and it was made evident by the inhibitor of kappaBalpha phosphorylation and NFkappaB p50 nuclear translocation. Our results indicate that hyperglycemia-induced PARP activation plays an important role in the pathogenesis of glomerulopathy associated with type 2 diabetes and could serve as a novel therapeutic target.

Management of dyslipidemias in patients with diabetes and chronic kidney disease

Cardiovascular disease (CVD) is the leading cause of death in patients with stage 5 chronic kidney disease (CKD), and the mortality rate in stage 5 CKD is even higher in patients with diabetes. CVD risk reduction includes control of hyperglycemia, dyslipidemia, and BP. An LDL cholesterol goal of 70 mg/dl has been suggested for such high-risk patients. Most studies that have showed CVD risk reduction with statins have been in patients without CKD. However, some studies have had sufficient numbers of patients with CKD stages 2 to 3 to permit analysis, and these generally have shown CVD benefits similar to those found in patients without CKD. Studies that have shown benefit in patients who were on dialysis or after transplantation have been mixed, in part because CVD in such patients is far advanced and may not respond as well to intervention. As GFR falls, the dosages of many of the drugs that are used for the treatment of dyslipidemias need to be modified. In general, however, atorvastatin and fluvastatin dosages do not have to be modified. Drug interactions with cyclosporine also occur. In general, combinations of statins and fibrates should be avoided, and fenofibrate should be avoided in all patients with decreased GFR levels. Overall, on the basis of the very high risk for CVD in patients with diabetes and CKD, aggressive management of dyslipidemias is warranted, with an LDL goal of 70 mg/dl.

Preprocedural statin therapy reduces the risk and extent of cardiac biomarker release following percutaneous coronary intervention

This study evaluates the association between statin therapy in patients treated by percutaneous coronary intervention (PCI) for stable angina pectoris and postinterventional myocardial injury with subsequent long-term clinical outcome. Prospectively collected data on 400 consecutive patients with stable angina pectoris or evidence of inducible myocardial ischemia were analyzed. The incidence of myocardial infarction based on postinterventional release of troponin I>1.5 ng/ml was 12% in the statin pretreated patients and 20% in those not pretreated with statin therapy (P=0.04, odds ratio 1.84, 95% confidence interval 1.06-3.21). Of the patients experiencing a post-PCI troponin elevation>1.5 ng/ml, those pretreated with a statin pre-PCI had a lesser troponin elevation compared with those not receiving a statin pre-PCI (median: 2.9 ng/ml [1.9-11.5] vs 5.0 ng/ml [3.1-8.8]; P<0.001). In the multivariate model, preprocedural statin therapy was identified as the only independent negative predictor of procedure-related myocardial necrosis based on postprocedural troponin elevation. In the 21-month follow-up period, statin pretreated patients were observed to have fewer deaths, revascularizations, or myocardial infarction; however, this difference was not statistically significant. These results suggest that pretreatment with statins in patients undergoing PCI for stable angina pectoris reduces the risk and extent of procedure-related myocardial injury measured by troponin release.

Mitochondrial targeting of growth suppressor protein DLC2 through the START domain

Deleted in liver cancer 2 (DLC2) is a candidate tumor suppressor frequently found to be deleted in hepatocellular carcinoma. In this study, we determined the subcellular localization of DLC2. Co-localization and biochemical fractionation studies revealed that DLC2 localized to mitochondria. In addition, the DLC2-containing cytoplasmic speckles were in proximity to lipid droplets. A DLC2 mutant containing the steroidogenic acute regulatory protein-related lipid transfer (START) domain only showed a localization pattern identical to that of DLC2. Taken together, we have provided the first evidence for mitochondrial localization of DLC2 through the START domain. These findings might have implications in liver physiology and carcinogenesis.

HMG CoA reductase inhibition modulates VEGF-induced endothelial cell hyperpermeability by preventing RhoA activation and myosin regulatory light chain phosphorylation

The beneficial effects of statins are usually assumed to stem from their ability to reduce cholesterol biosynthesis. However, because statins are potent inhibitors of the mevalonate, which governs diverse cell signaling pathways, inhibition of 3-hydroxy-3-methylglutaryl-coenzyme-A reductase may also result in pleiotropic effects. The present study describes a novel pleiotropic effect of statins on vascular endothelial growth factor (VEGF)-induced glomerular endothelial cell (GEnC) hyperpermeability. Using live cell imaging with green fluorescent protein-tagged myosin regulatory light chain (MLC) and correlative biochemical analyses, we investigated 1) VEGF signaling pathway leading to GEnC hyperpermeability and 2) the modulatory effects of statins on VEGF signaling. Our findings indicate that VEGF stimulation elicits a robust increase in GEnC permeability. The signaling pathway that mediates VEGF-induced GEnC hyperpermeability involves RhoA activation leading to actin cytoskeletal remodeling, MLC diphosphorylation, and enhanced paracellular gap formation. Remarkably, cotreatment of endothelial cells with simvastatin, a hydrophobic statin, reversed VEGF-induced GEnC hyperpermeability by preventing MLC diphosphorylation, and cytoskeletal remodeling. In summary, this study identifies RhoA and MLC phosphorylation as key mediators of VEGF-induced endothelial cell hyperpermeability and demonstrates the modulatory effects of statins on VEGF signaling pathway.

A review of the efficacy of rosuvastatin in patients with type 2 diabetes

It has been estimated that 92% of individuals with type 2 diabetes, without cardiovascular disease (CVD), have a dyslipidaemic profile. Several guidelines on cardiovascular risk now recommend that patients with diabetes should be considered at high risk of CVD and should thus receive lipid-lowering therapy to reduce low-density lipoprotein cholesterol (LDL-C) to below 2.5 mmol/L. Since their introduction in 1987, statins have revolutionized the management of CVD. The most recent statin to be introduced, rosuvastatin, has been shown to be the most effective at lowering LDL-C, as well as consistently raising HDL-C across the 10-40 mg dose range. This has been confirmed by many studies, including the Measuring Effective Reductions in Cholesterol Using Rosuvastatin Therapy (MERCURY I) study in which rosuvastatin 10 mg was shown to be more effective than commonly used doses of other statins, both for LDL-C reduction and achieving treatment target goals. The effectiveness of rosuvastatin has also been studied in type 2 diabetes patients in three studies: the URANUS (Use of Rosuvastatin vs. Atorvastatin iN type 2 diabetes mellitUS), ANDROMEDA (A raNdomized, Double-blind study to compare Rosuvastatin [10 & 20 mg] and atOrvastatin [10 & 20 Mg] in patiEnts with type II DiAbetes) and CORALL (COmpare Rosuvastatin [10-40 mg] with Atorvastatin [20-80 mg] on apo B/apo A-1 ratio in patients with type 2 diabetes meLLitus and dyslipidaemia) studies. URANUS and ANDROMEDA showed rosuvastatin to be more effective than atorvastatin at reducing LDL-C and achieving treatment target goals. CORALL demonstrated rosuvastatin 10, 20 and 40 mg to be more effective at lowering LDL-C than 20, 40 and 80 mg of atorvastatin, respectively. Ongoing studies will evaluate whether these properties of rosuvastatin translate into beneficial effects on atherosclerosis and significant reductions in cardiovascular events.