Effect of cerivastatin on peripheral capillary permeability to albumin and peripheral nerve function in diabetic rats

The protective role of isorhamnetin on human brain microvascular endothelial cells from cytotoxicity induced by methylglyoxal and oxygen-glucose deprivation

As the first target of stroke, cerebral endothelial cells play a key role in brain vascular repair and maintenance, and their function is impeded in diabetes. Methylglyoxal (MGO), a reactive dicarbonyl produced during glucose metabolism, accumulates in diabetic patients. MGO and MGO-induced advanced glycation end-products (AGEs) could ameliorate stroke-induced brain vascular damage, closely related with ECs dysfunction. Using MGO plus oxygen-glucose deprivation (OGD) to mimic diabetic stroke, we reported the protective effect of isorhamnetin on OGD-induced cytotoxicity after MGO treatment on primary human brain microvascular endothelial cells (HBMEC) and explored the underlying mechanisms. Treatment of MGO for 24 h significantly enhanced 3-h OGD-induced HBMEC toxic effect, which was inhibited by pretreatment of isorhamnetin (100 μmol/L). Moreover, the protective effect of isorhamnetin is multiple function dependent, which includes anti-inflammation, anti-oxidative stress and anti-apoptosis effects. Besides its well-known inhibition on the mitochondria-dependent or intrinsic apoptotic pathway, isorhamnetin also reduced activation of the extrinsic apoptotic pathway, as characterized by the decreased expression and activity of caspase 3 and caspase 8. Furthermore, pretreatment with isorhamnetin specifically inhibited FAS/FASL expression and suppressed nuclear factor-kappa B nuclear translocation. Taken together, our results indicated that isorhamnetin protected against OGD-induced cytotoxicity after MGO treatment in cultured HBMEC due to its multiple protective effects and could inhibit Fas-mediated extrinsic apoptosis. Therefore, isorhamnetin is a promising reagent for the treatment of hyperglycemia and ischemia-induced cerebral vascular degeneration. A proposed model of the potential protective mechanism of isorhamnetin, a metabolite of quercetin, on methylglyoxal (MGO) treatment plus oxygen-glucose deprivation (OGD) exposure-induced cytotoxicity in cultured human brain microvascular endothelial cells. Isorhamnetin inhibits FasL-mediated extrinsic apoptosis and neurotrophic factor κB (NF-κB) nuclear translocation, which can induce the cell DNA damage. Therefore, the protective effect of isorhamnetin occurs through multiple functions, including anti-inflammation, anti-oxidative stress and anti-apoptosis. Therefore, isorhamnetin is a promising reagent for the treatment of hyperglycemia and ischemia-induced cerebral vascular degeneration.

Enhanced permeability responses to inflammation in streptozotocin-induced diabetic rat venules: Rho-mediated alterations of actin cytoskeleton and VE-cadherin

Diabetes is a progressive disease that often leads to microvascular complications. This study investigates the impact of diabetes on microvessel permeability under basal and inflammatory conditions. Streptozotocin-induced diabetic rats were used to mimic type 1 diabetes. Parallel experiments were conducted in intact mesenteric venules in normal rats and diabetic rats experiencing hyperglycemia for 2-3 wk. Microvessel permeability was determined by measuring hydraulic conductivity (Lp). The correlated changes in endothelial intracellular Ca(2+) concentration ([Ca(2+)]i), adherens junctions, and cytoskeleton F-actin were examined with fluorescence imaging. Diabetic vessels showed moderately increased basal Lp, but upon platelet-activating factor (PAF) exposure, these vessels showed an ~10-fold higher Lp increase than the normal vessels. Concomitantly, we observed higher increases in endothelial [Ca(2+)]i, enhanced stress fiber formation, vascular endothelial-cadherin separation, and larger gap formation between endothelial cells than those occurring in normal vessels. PAF receptor staining showed no significant difference between normal and diabetic vessels. The application of Rho kinase inhibitor Y27632 did not affect PAF-induced increases in endothelial [Ca(2+)]i but significantly reduced PAF-induced Lp increases by 90% in diabetic vessels. The application of both Y27632 and nitric oxide (NO) synthase inhibitor attenuated PAF-induced Lp increases more than using one inhibitor alone. Our studies indicate that diabetic conditions prime endothelial cells into a phenotype with increased susceptibility to inflammation without altering receptor expression and that the increased Rho activation and NO production play important roles in exaggerated permeability increases when diabetic vessels were exposed to inflammatory mediators, which may account for the exacerbated vascular dysfunction when diabetic patients are exposed to additional inflammation.

Decreased stroke volume−brachial pulse pressure ratio in patients with type 2 diabetes over 50 years: the role of peripheral neuropathy

BACKGROUND AND AIMS

To document the stroke volume to pulse pressure ratio (SV/PP, an index of total arterial compliance) and its correlates in patients with type 2 diabetes (T2DM) aged over 50 years whose peripheral neuropathy and silent myocardial ischemic (SMI) status were known.

METHODS AND RESULTS

A total of 360 patients with T2DM aged ≥ 50 years, without cardiac history or symptom, left ventricular systolic dysfunction, dilatation and hypokinesia, were retrospectively enrolled. The SV/PP was calculated from echocardiographic left ventricular measurements and brachial blood pressure at rest. Peripheral neuropathy was defined as the presence of any two or more of the following: neuropathic symptoms, decreased distal sensation, or decreased or absent ankle reflexes. SMI was defined as an abnormal stress myocardial scintigraphy and/or stress echocardiography. A low SV/PP ratio (<0.53 ml/m²/mmHg, first tertile) was associated with age, creatinine clearance, 24 h urinary albumin excretion rate, peripheral neuropathy, hypertension, serum total cholesterol and triglycerides levels (p < 0.05-0.0001). In multivariate analysis, age (OR 1.1 [1.0-1.2], p < 0.01), triglycerides (OR 1.5 [1.2-2.0], p = 0.01) and peripheral neuropathy (OR 2.2 [1.2-3.9], p = 0.009) were independently associated with a low SV/PP. The patients with peripheral neuropathy had lower SV (p < 0.01) and higher PP (p < 0.05) than those without, and only lower SV after adjustment for age and nephropathy. Similar results were obtained in the patients with and without SMI.

CONCLUSION

Peripheral neuropathy was independently associated with decreased SV/PP, mainly through decreased SV, in patients with T2DM over 50 years.

Neuroprotective effect of atorvastatin in an experimental model of nerve crush injury

BACKGROUND

Statins have therapeutic benefits for the management of several disorders. A short-term course of a high-dose statin pretreatment has demonstrated neuroprotective effects against neurological diseases. However, the molecular basis underlying the neuroprotective action of statins remains unclear.

OBJECTIVE

We investigated whether a short-term course of high-dose atorvastatin pretreatment has beneficial effects in protecting sciatic nerve from crush injury.

METHODS

Atorvastatin (5 mg/kg) or saline was given orally to Sprague-Dawley rats for 7 days before injury. The rats were subjected to crush injury in the left sciatic nerve with a vessel clamp. Biochemical, functional, electrophysiological, and morphological alterations occurring during injury-induced degeneration/regeneration were examined.

RESULTS

Atorvastatin improved injury-induced neurobehavioral/electrophysiological changes and axonal loss. Damage-associated alterations, including structural disruption, oxidative stress, inflammation, and apoptosis, were attenuated by atorvastatin. After injury, regeneration-associated genes, including growth-associated protein-43, myelin basic protein, ciliary neurotrophic factor, and collagen, were upregulated by atorvastatin. The suppression of extracellular signal-regulated kinase, AKT, signal transducer and activators of transcription-1, and necrosis factor-kappaB and the elevated activation of c-Jun N-terminal kinase, Smad2/3, and activating protein-1 were associated with the neuroprotective action of atorvastatin.

CONCLUSION

These findings suggest that a short-term course of high-dose atorvastatin pretreatment can protect against sciatic nerve crush injury through modifying intracellular or extracellular environments, making it favorable for regeneration.

Diabetic foot ulcer burden may be modified by high-dose atorvastatin: A 6-month randomized controlled pilot trial

BACKGROUND

Diabetic foot ulcers (DFUs) are common complications of diabetes mellitus (DM), with a complex pathogenesis. Treatment is difficult and no single treatment with measurable clinical impact is available. In the present clinical pilot trial, we investigated whether statins could be of use against some of the pathogenic factors in DFUs.

METHODS

Thirteen diabetic patients (10 men; 11 with Type 2 DM; mean age 64 years; mean duration of DM 18 years) with neuropathic DFUs <4 months were randomized to treatment with either 10 mg (six patients; six ulcers) or 80 mg (seven patients; nine ulcers) atorvastatin for 6 months in addition to conventional DFU care (i.e. prompt debridement, DFU pressure relief, and management of any underlying infection).

RESULTS

There were no significant differences in background factors (i.e. HbA1c 8.9%, micro- and macrovascular complications, concomitant medications) or DFU characteristics (duration, surface area, grading) between the two groups. All ulcers in the group receiving 10 mg atorvastatin healed, compared with six of nine ulcers in the group receiving 80 mg atorvastatin (NS). However, two previously healed DFUs recurred and six new DFUs developed in the low-dose group compared with none and one, respectively, in the high-dose group (P = 0.048). There was a significant decrease in C-reactive protein (-1.5 mg/L; P = 0.044) and a non-significant trend towards beneficial effects on lipids and the ankle-arm blood pressure index in the high-dose compared with the low-dose group.

CONCLUSIONS

  We observed a possible beneficial effect of 6-months high-dose atorvastatin on DFUs, which should be tested in appropriately sized prospective studies.

Rosuvastatin positively changes nerve electrophysiology in diabetic rats

OBJECTIVE

To examine the effect of rosuvastatin on peripheral nerve function in diabetic rats using electrophysiological measurements.

BACKGROUND

Diabetes was induced in 5-day-old male Wistar rats by intraperitoneal (i.p.) injection of streptozotocin (STZ). As many as 45 diabetic rats were randomized to three groups: one treated with rosuvastatin (group R), another with rosuvastatin and mevalonate (group MR) and the other was untreated (group U). The data were compared with a group of normal age-matched rats i.e. control rats (group C).

METHODS

Neurophysiological measurements were performed at the age of 3 months (T1) and again at the age of 8 months (T2), after 3 months of treatment.

RESULTS

At T1, there was a trend to lower amplitude of compound motor action potential (CMAP) in the three diabetic groups as compared to controls, and no difference for motor nerve conduction velocity (MNCV), amplitude of sensory nerve action potential (SNAP), sensory nerve conduction velocity (SNCV) between diabetic groups and controls. At T2, the amplitude of CMAP was significantly lower in groups R and MR versus group U and control rats. MNCV was significantly and similarly decreased in the three diabetic groups; the latency of the first sensory peak (fastest sensory fibres) was significantly increased in group U but was normal in groups R and MR.

CONCLUSIONS

This study shows that: 1.rosuvastatin exerts a beneficial effect on the conduction of the fastest sensory fibres;2.these effects are independent of blood pressure and lipid changes.

Effect of rosuvastatin on capillary filtration of albumin and blood pressure in rats with streptozotocin-induced diabetes

An increase in capillary filtration of albumin (CFA) is well demonstrated in diabetes. Statins may exert a protective effect against endothelial dysfunction. The aim of this study was to test whether rosuvastatin may prevent the increase in peripheral CFA in diabetic rats and the role of blood pressure lowering. Rats with streptozotocin-induced diabetes were randomized to receive either rosuvastatin 20mg/kg/d (group R) or both rosuvastatin 20mg/kg/d and mevalonate 20mg/kg/d (group RM) or no treatment (group U). CFA index was measured on a limb by a non-invasive isotopic test using technetium-labelled albumin, at three time points: at mean age of 3 months, before treatment; at 5 and 8 months, i.e. after 2 and 5 months of treatment. At 3 months, interstitial albumin retention (AR) was markedly increased in the 3 groups. From 3 to 5 months, AR increased significantly in group U, decreased in group R and in group RM. At 5 and 8 months, AR was significantly lower in groups R and RM than in group U. Systolic blood pressure (SBP) was measured at 8 months and was significantly lower in group R than in group U and RM. At 8 months, serum cholesterol levels were not different between the three groups whereas triglycerides were significantly lower in groups R and RM than in group U. In conclusion, in diabetic rats rosuvastatin prevents the increase in peripheral CFA and induces a decrease in blood pressure. The beneficial effect of rosuvastatin on endothelial function does not seem to result from blood pressure reduction nor lipid lowering effects.