Curcumin Ameliorates the Experimental Diabetic Peripheral Neuropathy through Promotion of NGF Expression in Rats

Abstract

Increasing evidence suggested that inhibiting the apoptosis of Schwann cells (SCs) and promoting nerve growth factor (NGF) expression in sciatic nerves play key roles in preventing the onset of diabetic peripheral neuropathy (DPN). Curcumin, a primary bioactive substance in turmeric with multiple characteristics, has been shown to have many therapeutic effects in a variety of diseases. However, curcumin is poorly studied in the DPN models. We aimed to explore the therapeutic benefits and underlying mechanism of curcumin in high fat/sugar diets joint streptozotocin (STZ)‐induced DPN rat models. Sprague‐Dawley (SD) rats were divided into five groups (6 rats per group), control group, DPN group, Curcumin groups (50, 100, and 150 mg/kg). Curcumin was administered intragastrically once per day for 4 continuous weeks. Body weight (BW) and fasting blood glucose (FBG) were monitored in all groups. The mechanical withdraw threshold (MWT) was measured. We also assessed neuropathic change by testing nerve conductance velocity (NCV) in sciatic nerves. TEM was applied to observe the sciatic nerves ultrastructure. The SCs apoptosis in sciatic nerves was stained using TUNEL kit. NGF contents in sciatic nerves and serum were detected using western blotting and ELISA analysis. The results showed curcumin had no obvious effect on the BW and FBG change. Curcumin (100 and 150 mg/kg) attenuated the MWT, NCV, and sciatic nerves ultrastructure in DPN rats. Curcumin (50, 100 and 150 mg/kg) reduced SCs apoptosis in sciatic nerves. In addition, curcumin at 150 mg/kg had the best efficacy in increasing protein expression of NGF in sciatic nerves and serum NGF level. Our work demonstrated that curcumin has neuroprotective effects for the treatment of DPN.

Suppression of neuronal apoptosis and glial activation with modulation of Nrf2/HO-1 and NF-kB signaling by curcumin in streptozotocin-induced diabetic spinal cord central neuropathy

“…This pathway can counteract oxidative stress, regulate apoptosis, modulate inflammation, and contribute to angiogenesis. The present study reports down-regulation of Nrf2 with up-regulation in the expression of HO-1, consistent with the findings of Pouso-Vazquez et al (2022) with the induction of NF-kB pro-inflammatory pathway similar to the results of Mandour et al (2022). However, Castany et al (2016) reported no change in HO-1 in diabetes.…”

“…The current study found that Curcumin could exert an antihyperglycemic effect on Diabetic rats, another mechanism that helps the neuroprotective role of Curcumin, however, it did not normalize serum glucose, similar to previous reports by Daugherty et al (2018) and Zhang et al (2022) .…”

“…Curcumin (Turmeric), a primary bioactive substance, derived from Curcuma Longa, has shown neuroprotective effects in many diseases. Many studies reported the beneficial effect of Curcumin on diabetic peripheral neuropathy ( Zhang et al, 2022 ) and spinal cord traumatic injury models ( Kahuripour et al, 2022 ). However, the role of curcumin in the management of diabetes-induced spinal cord impairment requires clarification.…”

“…In the present study, Curcumin was found to protect the spinal cord against diabetes-induced injury. Many studies reported the beneficial effect of Curcumin on diabetic peripheral neuropathy through antioxidant activity ( Zhao et al, 2014 ), activation of the opioid system ( Banafshe et al, 2014 ), suppression of TNF alpha expression ( Daugherty et al, 2018 ), reduction of depression and anxiety ( Asadi et al, 2020 ), modulation of the activity of DRG astrocytes and neurons ( Park et al, 2021 ), inhibition of Schwann cell apoptosis and promoting nerve growth factor (NGF) ( Zhang et al, 2022 ). On the other hand, many studies reported the beneficial role of curcumin in the treatment of injury, induced by spinal cord trauma models (SCI) ( Kahuripour et al, 2022 ).…”

“…Furthermore, the action of curcumin in neuropathic pain may involve the pJNK pathway in the astrocytes and neurons of the dorsal root ganglia (DRG) ( Park et al, 2021 ). Moreover, Curcumin could inhibit the apoptosis of Schwann cells (SCs) and could promote nerve growth factor (NGF) expression in sciatic nerves of diabetic peripheral neuropathy (DPN) rat model ( Zhang et al, 2022 ). All the previous studies explored the role of Curcumin in diabetic peripheral neuropathy; however, few of these studies explored its role in diabetic central neuropathy.…”