Investigating the beneficial effect of aliskiren in attenuating neuropathic pain in diabetic Sprague-Dawley rats

Objectives

Worldwide, diabetic neuropathy (DN) is a major complication of diabetes mellitus. The direct renin inhibitor aliskiren is recognized as a treatment for cardiovascular disease in diabetic patients, but little is known about its potential benefits in cases of diabetic neuropathy. Accordingly, we investigated the effects of aliskiren (ALIS) and gliclazide (GLZ) and their combination therapy on peripheral neuropathy in streptozotocin-induced diabetic rats.

Methods

In total, 112 adult Sprague-Dawley rats were used for this study. Diabetes was induced using streptozotocin (STZ), whereas the control group was treated with an equal volume of citrate buffer. The diabetic rats were divided randomly into six groups according to the proposed treatment regime: diabetic control (DC), gliclazide (GLZ), aliskiren (ALIS), ramipril (RAM), (GLZ + ALIS) and (GLZ + RAM). Behavioural responses to thermal (hot-plate) and mechanical (tail-pinch) pain were evaluated. After eight weeks of daily treatments, the animals were fasted and sacrificed. The blood samples were collected, with the serum separated and subjected to various biochemical and enzyme analyses so as to assess the effect of the treatments on diabetic peripheral neuropathy.

Results

After 8 weeks, aliskiren alone and in combination with gliclazide therapy had a significant effect (P < .001) in reducing blood glucose levels and showed increased hot-plate and tail-flick latencies compared with the diabetic control group. The threshold of mechanical hyperalgesia was also significantly elevated (P < .001).

Conclusions/Interpretations

These data suggest that either aliskerin alone or in combination with gliclazide can protect against the development and progression of diabetic neuropathy.

Antioxidant treatment ameliorates diabetes-induced dysfunction of the vas deferens in a rat model

Diabetes mellitus (DM) affects the male ejaculatory function. This study was designed to evaluate the role of oxidative stress in the development of diabetes-induced dysfunction of vas deferens (VD) in the rat. DM was induced by streptozotocin in 40 male Wistar rats. Subsequently, the diabetic animals were divided into three groups: DM group, DM + Eda group and DM + Tau group. These groups were administered saline, edaravone and taurine, respectively, daily for 4 weeks. Another group of ten rats served as a control group. DM was diagnosed in the 40 streptozotocin-injected rats. DM significantly reduced the VD weight. Additionally, DM induced in vitro VD hypercontractility, VD histological abnormalities and increased the serum and VD tissue concentration of malondialdehyde. VD immunohistochemistry revealed overexpression of three markers of oxidative stress. DM significantly reduced serum testosterone levels. No live birth was documented in all DM rats in mating experiments. Antioxidants significantly improved all the aforementioned parameters, except the testosterone levels. This study indicates a deleterious impact of DM-induced oxidative stress on VD histological and functional features. Antioxidant treatment may provide an adjunct tool to alleviate ejaculatory disorders for male patients with type 1 diabetes.

[The evoked activity of the dorsal root afferent fibres of the spinal cord of white rats in experimental diabetes mellitus]

We analyzed the functional status of the dorsal root of spinal cord in experimental diabetes mellitus (DM), for instance the parameters of the action potential (AP): threshold, chronaxy and the dynamics of the dorsal root excitability. It was revealed the 1,5 times increase in threshold of excitation when compared to the control animals (P<0,001), the amplitude of AP decreased by 21,7% (P<0,05). It was also revealed a significant increase in response to the 2nd stimulus under applying the paired stimuli on the sciatic nerve in animals with experimental DM. Under applying the stimuli of increasing intensity there was found significant decrease in the amplitude of the AP in animals of the experimental group. It was concluded that hyperglycemia made changes to the processes of excitability and refractoriness in the afferent fibers of the spinal cord.

PDE5 inhibitors in diabetic peripheral neuropathy

Peripheral neuropathy is the most common complication of diabetes. This paper reviews the case histories of five patients with diabetic peripheral neuropathy or severe peripheral vascular disease who reported improvement in their symptoms when treated with regular or daily dosing with phosphodiesterase type 5 inhibitors (PDE5Is). These patients had been previously treated with PDE5Is for erectile dysfunction (ED) and not responded to on-demand therapy with a PDE5I at maximal recommended dose. This improvement is likely to be due to the known benefit of these drugs on endothelial dysfunction via an improvement of blood supply to the vasa nervorum. These cases suggest that further research is indicated to evaluate the potential use of PDE5Is in the treatment and prevention of diabetic peripheral neuropathy, particularly as these drugs are already licensed to treat ED, which occurs in around 50% of male diabetics.