RESUMEN
Objective:To evaluate the role of lactate dehydrogenase in diabetic neuropathic pain (DNP) and the relationship with peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC-1α) in mice.Methods:SPF-grade healthy male C57BL/6J mice, aged 6-8 weeks, weighing 18-22 g, were used to establish diabetes mellitus model by intraperitoneal injection of streptozotocin (STZ) 120 mg/kg. Twenty-four mice with diabetes mellitus were divided into 2 groups ( n=12 each) using a random number table method: DNP group and DNP + oxamate group (OXA group). Another 12 SPF-grade healthy male C57BL/6J mice were selected as control group (C group). In OXA group, oxamate 750 mg/kg was intraperitoneally injected once a day for 28 consecutive days. The equal volume of normal saline was given instead in C group and DNP group. The mechanical paw withdrawal threshold (MWT), blood glucose and body weight were measured at 3 days before STZ injection and at 1, 2, 3 and 4 weeks after STZ injection (T 0-4). After the last behavioural test was completed, blood samples were collected from the posterior orbits of anesthetized mice for determination of serum lactate concentrations. The animals were then sacrificed and the tissues from the prefrontal cortex of the brain were taken for determination of lactate content, mitochondrial membrane potential (by the JC-1), content of reactive oxygen species (ROS) (using dihydroethidium probes), and level of histone lactylation and expression of PGC-1α (by Western blot). Results:Compared with C group, the MWT was significantly decreased at T 2-4, the serum lactate concentrations, contents of lactate and ROS and level of histone lactylation were increased, the mitochondrial membrane potential was decreased, and the expression of PGC-1α was down-regulated in DNP and OXA groups ( P<0.05). Compared with DNP group, no significant change was found in blood glucose and body weight ( P>0.05), the MWT was significantly increased at T 2-4, the serum lactate concentrations, contents of lactate and ROS and level of histone lactylation were decreased, the mitochondrial membrane potential was increased, and the expression of PGC-1α was up-regulated in OXA group ( P<0.05). Conclusions:Lactate dehydrogenase promotes the development of DNP, and the mechanism is related to promotion of increase in histone lactfication and down-regulation of PGC-1α expression in the prefrontal cortex of mice.
RESUMEN
Objective:To evaluate the effect of metformin preconditioning on adenosine monophosphate-activated protein kinase(AMPK)/PTEN-induced putative protein kinase(PINK1) signaling pathway during ischemia-reperfusion (I/R) injury in diabetic rats.Methods:Thirty-six clean-grade healthy male Sprague-Dawley rats, aged 6 weeks, weighing 120-160 g, were divided into 3 groups ( n=12 each) by the random number table method: diabetic sham operation group (DS group), diabetic myocardial I/R group (DI/R group) and diabetic myocardial I/R+ metformin preconditioning group(DI/R+ Met group). After 4 weeks of feeding a high-fat and high-glucose diet, the model of type 2 diabetes mellitus was induced by a single intraperitoneal injection of 1% streptozotocin 40 mg/kg. The myocardial I/R injury was induced by blocking the anterior descending branch of the left coronary artery for 30 min followed by 120-min reperfusion in anesthetized animals. In DI/R+ Met group, metformin 200 mg/kg was given by intragastric gavage once a day within 1 week before myocardial ischemia. Blood samples from the femoral vein were collected at 120 min of reperfusion for determination of the serum creatine kinase isoenzymes (CK-MB) and cardiac troponin I (cTnI) concentrations by enzyme-linked immunosorbent assay. Then the rats were sacrificed and myocardial tissues were obtained for examination of the pathological changes(by HE staining) and for determination of the percentage of myocardial infarct size (by the double staining of Ewan blue and TTC) and expression of myocardial autophagy-related protein Beclin-1, PTEN-induced putative kinase 1 (PINK1), phosphorylated 5′-adenosine monophosphate-activating protein kinase (p-AMPK), and ratio of microtubule-associated protein 1 light chain 3Ⅱ/Ⅰ (LC3Ⅱ/Ⅰ) (by Western blot). Results:Compared with DS group, the percentage of myocardial infarct size and serum CK-MB and cTnI concentrations were significantly increased, the expression of Beclin-1, p-AMPK and PINK1 in myocardial tissues was up-regulated, the ratio of LC3II/I was increased( P<0.05), and the pathological changes were aggravated in DI/R group and DI/R+ Met group. Compared with DI/R group, the percentage of myocardial infarct size and serum CK-MB and cTnI concentrations were significantly decreased, the expression of Beclin-1, p-AMPK and PINK1 in myocardial tissues was up-regulated, the ratio of LC3Ⅱ/Ⅰ was increased ( P<0.05), and the pathological changes were significantly reduced in DI/R+ Met group. Conclusions:The mechanism by which metformin preconditioning reduces myocardial I/R injury is related to activation of AMPK/PINK1 signaling pathway and up-regulation of mitochondrial autophagy in diabetic rats.