Contribution of mitochondria to pain in diabetic neuropathy

Molecular Functions of Ceruloplasmin in Metabolic Disease Pathology

Ceruloplasmin (CP) is a multicopper oxidase and antioxidant that is mainly produced in the liver. CP not only plays a crucial role in the metabolic balance of copper and iron through its oxidase function but also exhibits antioxidant activity. In addition, CP is an acute-phase protein. In addition to being associated with aceruloplasminemia and neurodegenerative diseases such as Wilson's disease, Alzheimer's disease, and Parkinson's disease, CP also plays an important role in metabolic diseases, which are caused by metabolic disorders and vigorous metabolism, mainly including diabetes, obesity, hyperlipidemia, etc. Based on the physiological functions of CP, we provide an overview of the association of type 2 diabetes, obesity, hyperlipidemia, coronary heart disease, CP oxidative stress, inflammation, and metabolism of copper and iron. Studies have shown that metabolic diseases are closely related to systemic inflammation, oxidative stress, and disorders of copper and iron metabolism. Therefore, we conclude that CP, which can reduce the formation of free radicals in tissues, can be induced during inflammation and infection, and can correct the metabolic disorder of copper and iron, has protective and diagnostic effects on metabolic diseases.

Soluble Epoxide Hydrolase Regulation of Lipid Mediators Limits Pain

The role of lipids in pain signaling is well established and built on decades of knowledge about the pain and inflammation produced by prostaglandin and leukotriene metabolites of cyclooxygenase and lipoxygenase metabolism, respectively. The analgesic properties of other lipid metabolites are more recently coming to light. Lipid metabolites have been observed to act directly at ion channels and G protein-coupled receptors on nociceptive neurons as well as act indirectly at cellular membranes. Cytochrome P450 metabolism of specifically long-chain fatty acids forms epoxide metabolites, the epoxy-fatty acids (EpFA). The biological role of these metabolites has been found to mediate analgesia in several types of pain pathology. EpFA act through a variety of direct and indirect mechanisms to limit pain and inflammation including nuclear receptor agonism, limiting endoplasmic reticulum stress and blocking mitochondrial dysfunction. Small molecule inhibitors of the soluble epoxide hydrolase can stabilize the EpFA in vivo, and this approach has demonstrated relief in preclinical modeled pain pathology. Moreover, the ability to block neuroinflammation extends the potential benefit of targeting soluble epoxide hydrolase to maintain EpFA for neuroprotection in neurodegenerative disease.

Curcumin inhibits alloxan-induced pancreatic islet cell damage via antioxidation and antiapoptosis

The present study elucidates the possible protective effects of curcumin on β-cells damaged by oxidative stress and its significance in controlling diabetes mellitus in in vitro experiments. Pancreatic islet (RIN-m5F) cells were treated with 25 mmol/L alloxan (AXN) to induce cell damage and the protective effects of curcumin were observed. The results showed that curcumin significantly promoted the cellular activity of AXN-treated RIN-m5F cells, decreased the ratio of apoptosis, downregulated the level of malondialdehyde, upregulated the levels of superoxide dismutase and reactive oxygen species, increased the expression of Bcl-2, cleaved caspase-3, and cleaved PARP1, and decreased the expression of Bax in AXN-treated cells. These results suggest that curcumin inhibits AXN-induced damage in RIN-m5F cells via antioxidative and antiapoptotic mechanisms.

Endoplasmic reticulum-mitochondria interplay in chronic pain: The calcium connection

Chronic pain is a debilitating condition that affects roughly a third to a half of the world's population. Despite its substantial effect on society, treatment for chronic pain is modest, at best, notwithstanding its side effects. Hence, novel therapeutics are direly needed. Emerging evidence suggests that calcium plays an integral role in mediating neuronal plasticity that underlies sensitization observed in chronic pain states. The endoplasmic reticulum and the mitochondria are the largest calcium repositories in a cell. Here, we review how stressors, like accumulation of misfolded proteins and oxidative stress, influence endoplasmic reticulum and mitochondria function and contribute to chronic pain. We further examine the shuttling of calcium across the mitochondrial-associated membrane as a mechanism of cross-talk between the endoplasmic reticulum and the mitochondria. In addition, we discuss how endoplasmic reticulum stress, mitochondrial impairment, and calcium dyshomeostasis are implicated in various models of neuropathic pain. We propose a novel framework of endoplasmic reticulum-mitochondria signaling in mediating pain hypersensitivity. These observations require further investigation in order to develop novel therapies for chronic pain.

Ameliorative Effects Of N-Acetylcysteine As Adjunct Therapy On Symptoms Of Painful Diabetic Neuropathy

Purpose

Painful diabetic neuropathy (PDN) is a variant of diabetic peripheral neuropathy which is highly prevalent and distressing in diabetic patients. Despite its high burden, the optimal treatment of PDN has remained a clinical challenge. To explain the emergence and maintenance of PDN, increasing attention has been focused on dimensions of inflammation and oxidative toxic stress (OTS). Accordingly, the aim of this study was to investigate the effects of oral N-acetylcysteine (NAC), an agent with known anti-oxidant and anti-inflammatory effects, as an adjunct therapy in patients suffering from PDN.

Patients and methods

113 eligible patients with type 2 diabetes suffering from PDN were randomly assigned to either the pregabalin + placebo or pregabalin + NAC group for 8 weeks (pregabalin at a dose of 150 mg per day, NAC and matched placebo at doses of 600 mg twice a day). Mean pain score was evaluated at baseline, week 1, 2, 4, 6, and 8 of the study based on the mean 24 hr average pain score, using an 11-point numeric rating scale (NRS). As secondary efficacy measures, mean sleep interference score (SIS) resulting from PDN, responder rates, Patient Global Impression of Change (PGIC), Clinical Global Impression of Change (CGIC), and safety were also assessed. Additionally, serum levels of total antioxidant capacity (TAC), total thiol groups (TTG), catalase activity (CAT), glutathione peroxidase (GPx), superoxide dismutase (SOD), nitric oxide (NO), and malondialdehyde (MDA) were assessed at baseline and at the end of the study.

Results

Ninety patients completed the eight-week course of the study. The decrease in mean pain scores and mean sleep interference score in pregabalin + NAC group was greater in comparison with pregabalin + placebo group (p value<0.001 in both conditions). Moreover, more responders (defined as ≥50% reduction in mean pain score from baseline to end-point) were observed in the pregabalin + NAC group, in comparison with pregabalin + placebo group (72.1% vs 46.8%). More improvement in PGIC and CGIC from baseline to the end of the study was reported in pregabalin + NAC group. Oral NAC had minimal adverse effects and was well tolerated in almost all patients. Furthermore, in respect to OTS biomarkers, adjuvant NAC significantly decreased serum level of MDA and significantly increased serum levels of SOD, GPx, TAC, and TTG.

Conclusion

The pattern of results suggests that compared to placebo and over a time period of 8 weeks, adjuvant NAC is more efficacious in improving neuropathic pain associated with diabetic neuropathy than placebo. Ameliorative effects of NAC on OTS biomarkers demonstrated that NAC may alleviate painful symptoms of diabetic neuropathy, at least in part by its antioxidant effects.

Mechanism of TangGanJian on nonalcoholic fatty liver disease with type 2 diabetes mellitus

CONTEXT

TangGanJian (TGJ) has a curative effect in the clinical treatment of nonalcoholic fatty liver disease (NAFLD) with type 2 diabetes mellitus (T2DM), while the mechanism involved in the treatment process remains unclear.

OBJECTIVE

This study details the mechanism of TGJ on the treatment of NAFLD with T2DM.

MATERIALS AND METHODS

NAFLD was induced in T2DM rat model. Male Wistar rats were assigned into six groups: Group I (control), Group II (model), Group III (pioglitazone, 0.5 mg/kg), Group IV (high dose of TGJ, 24.8 g/kg), Group V (middle dose of TGJ, 12.4 g/kg) and Group VI (low dose of TGJ, 6.2 g/kg). All rats in each group were treated with the corresponding drugs by gavage for 8 weeks. Haematoxylin and eosin analysis was conducted. The indicators of inflammatory and oxidative stress were analysed utilizing one-way ANOVA.

RESULTS

The contents of TNF-α (15.794 ± 3.302 pg/mL), IL-6 (76.801 ± 8.491 pg/mL), IL-1β (100.101 ± 13.150 pg/mL), CRP (1.052 ± 0.079 pg/mL) and MDA (3.972 ± 0.159 pg/mL) were obviously elevated in NAFLD with T2DM rats compared to controls. Except for the IL-6, the levels of other markers declined in a dose-dependent manner after treatment with TGJ. The SOD (14.139 ± 1.479 U/mgprot) and GSH-PX (81.511 ± 5.276 U/mgprot) levels significantly decreased in NAFLD with T2DM rats, while the levels of these indicators increased after treatment with TGJ.

CONCLUSIONS

TGJ may be a therapy for the NAFLD with T2DM rats by modulating the inflammatory response and the oxidative stress capacity.

The Expanded Bead Size of Corneal C-Nerve Fibers Visualized by Corneal Confocal Microscopy Is Associated with Slow Conduction Velocity of the Peripheral Nerves in Patients with Type 2 Diabetes Mellitus

This study aims to establish the corneal nerve fiber (CNF) morphological alterations in a large cohort of type 2 diabetic patients and to investigate the association between the bead size, a novel parameter representing composite of accumulated mitochondria, glycogen particles, and vesicles in CNF, and the neurophysiological dysfunctions of the peripheral nerves. 162 type 2 diabetic patients and 45 healthy control subjects were studied in detail with a battery of clinical and neurological examinations and corneal confocal microscopy. Compared with controls, patients had abnormal CNF parameters. In particular the patients had reduced density and length of CNF and beading frequency and increased bead size. Alterations in CNF parameters were significant even in patients without neuropathy. The HbA1c levels were tightly associated with the bead size, which was inversely related to the motor and sensory nerve conduction velocity (NCV) and to the distal latency period of the median nerve positively. The CNF density and length positively correlated with the NCV and amplitude. The hyperglycemia-induced expansion of beads in CNF might be a predictor of slow NCV in peripheral nerves in type 2 diabetic patients.

Jinmaitong decreases sciatic nerve DNA oxidative damage and apoptosis in a streptozotocin-induced diabetic rat model

Diabetic peripheral neuropathy (DPN) is a common chronic complication of diabetes. Jinmaitong (JMT), a Traditional Chinese Medicine, improves certain symptoms of DPN, such as limb pain and numbness. The aim of the present study was to investigate the effects of JMT on DNA oxidative damage and apoptosis in the sciatic nerve of diabetic rats. The rats were divided into a normal and a diabetic group. Diabetes was induced using streptozotocin (60 mg/kg). The diabetic model (DM) rats received vitamin C (0.05 g/kg/day) or JMT [low-dosage (L), 0.44 g/kg/day; medium-dosage (M), 0.88 g/kg/day or high-dosage (H), 1.75 g/kg/day]. After 16 weeks, the mechanical pain threshold of the rats was evaluated. The expression of 8-hydroxy-deoxyguanosine (8-OHdG), nicotinamide adenine dinucleotide phosphate (NADPH) oxidase p22^phox, B-cell lymphoma 2 (Bcl-2), caspase 3 and cleaved-poly(ADP-ribose) polymerase 1 (PARP-1) in the sciatic nerve tissues was measured using the reverse transcription-quantitative polymerase chain reaction, immunohistochemistry and western blotting. JMT had no effect on body weight and fasting blood glucose levels. Following treatment, the rats in the JMT groups had an improved pain threshold compared with the DM controls (JMT-L, 52.9±6.5 g; JMT-M, 74.7±9.3 g; and JMT-H, 61.7±2.0 g vs. DM control, 35.32±12.06 g; all P<0.01), while the threshold in the JMT-M rats was similar to that of normal controls (P>0.05). 8-OHdG and NADPH oxidase p22^phox expression was significantly decreased in the three JMT groups compared with that in the DM controls (all P<0.05). Following JMT treatment, Bcl-2 levels were increased, while caspase 3 and cleaved-PARP-1 levels were decreased compared with those in the DM controls (all P<0.01). In conclusion, JMT may reduce DNA oxidative damage to the sciatic nerve in diabetic rats, as well as regulate genes involved in peripheral neuronal cell apoptosis, suggesting that JMT could be used to prevent or treat DPN in diabetic patients.