Contribution of mitochondria to pain in diabetic neuropathy

Alleviation of oxidative stress in pancreatic tissue of hyperglycemic mice by Lactiplantibacillus plantarum SCS4

This study aimed to investigate the effect of Lactiplantibacillus plantarum SCS4 in alleviating oxidative stress in the pancreatic tissue of hyperglycemic mice. A total of 90 six-week-old specific pathogen-free male Kunming mice were randomly divided into six groups [normal group (NG), blank control group (MG), phosphate-buffered saline (PBS) control group (CG), SCS4 first control group (DT1), SCS4 second control group (DT2), and SCS4 third control group (DT3)]. Except the NG group, in the other five groups, streptozotocin (STZ) was intraperitoneally injected for five consecutive days to establish a hyperglycemia model; the concentration of STZ was 50 mg/kg (bw). After successful modeling, DT1, DT2, and DT3 mice were administered 0.2 ml of L. plantarum SCS4 bacterial solution (10¹⁰ colony forming unit/ml), the cellular content of L. plantarum SCS4, and the inactivated cellular content of L. plantarum SCS4, respectively. Furthermore, 0.2 ml of PBS was given to mice in the CG group for control. The levels of insulin (INS), reactive oxygen species (ROS), malondialdehyde (MDA), and antioxidant enzymes such as superoxide dismutase (SOD), glutathione peroxidase (GPx), and catalase (CAT) were measured by enzyme-linked immunosorbent assay, and the morphology of the pancreas was observed. The results showed that after 10 weeks of gavage treatment, the level of INS in the DT3 group significantly increased to 6.36 mIU/L compared with that in the MG group (p < .05). Meanwhile, the levels of ROS and MDA of DT3 returned to normal levels of 291.07 IU/ml and 4.29 mnol/L, respectively. The activities of various antioxidant enzymes increased. The levels of SOD, CAT, and GPx in DT3 were the closest to the levels in NG. In addition, the pathological sections showed that the degree of pancreatic tissue lesions was relatively more severe in the MG group than in the NG group. The degree of pancreatic tissue lesions was relatively less severe in the DT2 group than in the MG group, and no significant lesion was seen in the DT3 group. Our results indicated that the inactivated bacterial content of L. planetarium SCS4 was more effective in improving oxidative stress in the pancreas of hyperglycemic mice. PRACTICAL APPLICATIONS: L. plantarum SCS4 was separated from fermented sausage in Sichuan. This study indicated that inactivated bacterial content of L. planetarium SCS4 was more effective in improving oxidative stress in the pancreas of hyperglycemic mice. The results suggested that lactic acid bacteria from traditional foods with ability of improving oxidative damage, which can be applied in food nutrition and related fields to make people with good dietary habits and prevent the occurrence of chronic diseases such as type II diabetes effectively.

Adjuvant use of melatonin for relieving symptoms of painful diabetic neuropathy: results of a randomized, double-blinded, controlled trial

PURPOSE

The trial aimed to investigate the effectiveness of exogenous melatonin as an adjuvant to pregabalin for relief of pain in patients suffering from painful diabetic neuropathy (PDN).

PATIENTS AND METHODS

This randomized, double-blind, placebo-controlled trial was carried out between October 2019 and December 2020 in an outpatient specialty clinic in Iran. One-hundred-three type 2 diabetic patients suffering from PDN were randomized into either the melatonin group (n = 52) or the placebo group (n = 51). Besides pregabalin at a dose of 150 mg per day, patients started with melatonin or an identical placebo, at a dose of 3 mg/day at bedtime for 1 week, which was augmented to 6 mg/day for further 7 weeks. The primary outcomes were changes in mean NRS (numerical rating scale) pain score from baseline to endpoint and responder rate (patients with a reduction of 50% and higher in average pain score compared with baseline). Secondary endpoints were changes in mean NRS pain-related sleep-interference score, overall improvement evaluated by Patient and Clinical Global Impressions of Change (PGIC, CGIC), and impact of the intervention on patient's Health-related quality of life (QOL). All analyses were conducted on an Intention-to-Treat (ITT) analysis data set.

RESULTS

At the study endpoint, treatment with melatonin resulted in a considerably higher reduction in the mean NRS pain score in comparison with placebo (4.2 ± 1.83 vs. 2.9 ± 1.56; P-value < 0.001). In terms of treatment responders, a greater proportion of melatonin-treated patients satisfied the responder criterion than placebo-treated patients (63.5% vs. 43.1%). Melatonin also reduced pain-related sleep interference scores more than did placebo (3.38 ± 1.49 vs. 2.25 ± 1.26; P-value < 0.001). Further, at the endpoint, more improvement was also seen in terms of PGIC, CGIC, and Health-related QOL in patients treated with melatonin than placebo. Melatonin was also well tolerated.

CONCLUSION

The present results showed that melatonin as an adjunct therapy to pregabalin might be helpful for use in patients with PDN. However, confirmation of these results requires further studies.

Mitoquinone alleviates vincristine-induced neuropathic pain through inhibiting oxidative stress and apoptosis via the improvement of mitochondrial dysfunction

Chemotherapy drugs such as vincristine (Vin) could cause neuropathic pain. However, it is still lack of ideal therapeutic strategy to treat it. Mitochondrial dysfunction has been involved in the pathogenesis of neuropathic pain. The mitochondrial-targeted antioxidant, mitoquinone (MitoQ), is able to modify mitochondrial signaling, showing beneficial effects on various diseases. In the study, we investigated whether MitoQ could regulate Vin-induced neuropathic pain, and the underlying molecular mechanisms. The results showed that MitoQ significantly improved Vin-induced pain hypersensitivity and glial activation in mice. In addition, Vin resulted in severe oxidative stress in spinal cord tissues of mice, which were inhibited by MitoQ treatment through improving Nrf2 (NF-E2-related factor 2) expression in nuclear. Also, MitoQ treatment dose-dependently reduced the expression of pro-inflammatory cytokines, indicating its anti-inflammatory effects. Importantly, Vin stimulation contributed to mitochondrial fission, as evidenced by the increased expression of phosphorylated Drp1 (dynamin related protein 1) and Fis (mitochondrial fission protein 1), whereas mitochondrial fussion was inhibited. However, these effects were notably abrogated by MitoQ, subsequently improving mitochondrial dysfunction. Moreover, neuron death evoked by Vin was significantly rescued by MitoQ treatment. We also observed significantly reduced expression of cleaved Caspase-3 and Bax expression in spinal cord of MitoQ-treated mice with Vin stimulation. In contrast, anti-apoptotic factor Bcl-2 protein levels decreased by Vin were restored by MitoQ. The process of Cyto-c release from mitochondria triggered by Vin was effectively inhibited in mice treated with MitoQ. These in vivo results were further verified in the primary neurons using the in vitro and ex vivo experiments. Furthermore, MitoQ treatment alleviated axonal degeneration and mitochondria dysfunction induced by Vin. Thus, mitoquinone could alleviate vincristine-induced neuropathic pain by inhibiting oxidative stress and apoptosis via the improvement of mitochondrial dysfunction.

Restoration of density of interstitial cells of Cajal in the jejunum of diabetic rats after quercetin supplementation

BACKGROUND

Interstitial cells of Cajal (ICC) are required for normal motility in the gastrointestinal tract. Depletion of ICC has been associated with diabetic gastroenteropathy.

PURPOSE

To determine the effect of quercertin supplementation on anoctamin-1 (Ano1) immunoreactive ICC in the myenteric region (ICC-MY) and deep muscular plexus (ICC-DMP) in the jejunum of diabetic rats.

METHODS

Thirty-two 90-day-old male Wistar rats were distributed into the following groups: normoglycemic (C), normoglycemic supplemented with quercetin (CQ; 40 mg daily), diabetic (D), and diabetic supplemented with quercetin (DQ; 40 mg daily). Diabetes was induced by streptozotocin injection. After 120 days, preparations of the jejunal muscular and submucosal layers were immunostained for Ano1 to visualize ICC. Evaluation of the immunofluorescence intensity as well as density of ICC was performed.

RESULTS

The density of ICC-MY was 46% lower in group D compared to group C (p < 0.01); ICC-DMP were reduced by 37% (p > 0.05). After quercertin treatment, the densities of ICC-MY were significantly higher in the DQ group compared to group D (ICC-MY: 58%, p < 0.05). Supplementation with quercetin in normoglycemic animals (CQ) compared with group C did not significantly change the ICC density (p > 0.05).

CONCLUSIONS

In STZ-treated diabetic rats, diabetes promoted a reduction in the density of jejunal ICC-MY with no significant effect on ICC-DMP. Supplementation with quercetin (DQ) appeared to protect ICC-MY from depletion in diabetes possibly due to its antioxidant action.