Glycolysis-derived alanine from glia fuels neuronal mitochondria for memory in Drosophila.

Glucose is the primary source of energy for the brain; however, it remains controversial whether, upon neuronal activation, glucose is primarily used by neurons for ATP production or if it is partially oxidized in astrocytes, as proposed by the astrocyte-neuron lactate shuttle model for glutamatergic neurons. Thus, an in vivo picture of glucose metabolism during cognitive processes is missing. Here, we uncover in Drosophila melanogaster a glia-to-neuron alanine transfer involving alanine aminotransferase that sustains memory formation. Following associative conditioning, glycolysis in glial cells produces alanine, which is back-converted into pyruvate in cholinergic neurons of the olfactory memory center to uphold their increased mitochondrial needs. Alanine, as a mediator of glia-neuron coupling, could be an alternative to lactate in cholinergic systems. In parallel, a dedicated glial glucose transporter imports glucose specifically for long-term memory, by directly transferring it to neurons for use by the pentose phosphate pathway. Our results demonstrate in vivo the compartmentalization of glucose metabolism between neurons and glial cells during memory formation.

Identification of Epigenetic Interactions between MicroRNA-30c-5p and DNA Methyltransferases in Neuropathic Pain.

Neuropathic pain is a prevalent and severe chronic syndrome, often refractory to treatment, whose development and maintenance may involve epigenetic mechanisms. We previously demonstrated a causal relationship between miR-30c-5p upregulation in nociception-related neural structures and neuropathic pain in rats subjected to sciatic nerve injury. Furthermore, a short course of an miR-30c-5p inhibitor administered into the cisterna magna exerts long-lasting antiallodynic effects via a TGF-ß1-mediated mechanism. Herein, we show that miR-30c-5p inhibition leads to global DNA hyper-methylation of neurons in the lumbar dorsal root ganglia and spinal dorsal horn in rats subjected to sciatic nerve injury. Specifically, the inhibition of miR-30-5p significantly increased the expression of the novo DNA methyltransferases DNMT3a and DNMT3b in those structures. Furthermore, we identified the mechanism and found that miR-30c-5p targets the mRNAs of DNMT3a and DNMT3b. Quantitative methylation analysis revealed that the promoter region of the antiallodynic cytokine TGF-ß1 was hypomethylated in the spinal dorsal horn of nerve-injured rats treated with the miR-30c-5p inhibitor, while the promoter of Nfyc, the host gene of miR-30c-5p, was hypermethylated. These results are consistent with long-term protection against neuropathic pain development after nerve injury. Altogether, our results highlight the key role of miR-30c-5p in the epigenetic mechanisms' underlying neuropathic pain and provide the basis for miR-30c-5p as a therapeutic target.

Potential Development of Vitrified Immature Human Oocytes: Influence of the Culture Medium and the Timing of Vitrification.

How does the in vitro maturation (IVM) medium and the vitrification procedure affect the survival of germinal vesicle (GV) oocytes obtained from stimulated cycles and their development to the blastocyst stage? In total, 1085 GV human oocytes were obtained after women underwent a cycle of controlled ovarian stimulation, and these oocytes were subjected to IVM before or after their vitrification. IVM was carried out in two commercial culture media not specifically designed for maturation. MII oocytes were then activated and embryo development until day 6 was evaluated. According to the results, a higher percentage of oocytes reach the MII stage if they are vitrified before they undergo IVM. Nevertheless, the medium used and the sample size determine whether these differences become significant or not. Similar survival rates and development to blastocysts were observed in all the conditions studied.

Impact of Maturation and Vitrification Time of Human GV Oocytes on the Metaphase Plate Configuration.

The combination of in vitro maturation (IVM) techniques and oocyte vitrification (OV) could increase the number of useful oocytes in different types of patients. IVM and subsequent OV is the most widely used clinical strategy. Would the results improve if we reverse the order of the techniques? Here, we evaluated survival, in vitro maturation, time to extrude the first polar body (PB), and the metaphase plate configuration of human prophase I (GV) oocytes before or after their vitrification. Specific, 195 GV oocytes from 104 patients subjected to controlled ovarian stimulation cycles were included. We stablished three experimental groups: GV oocytes vitrified and IVM (Group GV-Vit), GV oocytes IVM and vitrified at MII stage (Group MII-Vit), and GV oocytes IVM (Group not-Vit). All of them were in vitro matured for a maximum of 48 h and fixed to study the metaphase plate by confocal microscopy. According to our results, the vitrification of immature oocytes and their subsequent maturation presented similar survival, maturation, and metaphase plate conformation rates, but a significantly higher percentage of normal spindle than the standard strategy. Additionally, the extension of IVM time to 48 h did not seem to negatively affect the oocyte metaphase plate configuration.

BMP-7 protects male and female rodents against neuropathic pain induced by nerve injury through a mechanism mediated by endogenous opioids.

Neuropathic pain is highly prevalent in pathological conditions such as diabetes, herpes zoster, trauma, etc. The severity and refractoriness to treatments make neuropathic pain a significant health concern. The transforming growth factor (TGF-ß) family of cytokines is involved in pain modulation. Bone morphogenetic proteins (BMPs) constitute the largest subgroup within the TGF-ß family. BMP-7 induces the transcription of genes coding endogenous opioid precursors in vitro. However, a nociception modulatory function for this cytokine remains unexplored in vivo. Herein, we show that BMP-7 and its type I receptors were detected in regions of the nervous system involved in pain transmission, processing, and modulation. BMP-7 haploinsufficiency confers to male and female mice a tactile hyperalgesia phenotype to mechanical stimuli, both at baseline and after sciatic nerve injury (SNI). The administration of recombinant BMP-7 (rBMP-7) reduced the severity of the allodynia after SNI in rodents without sexual dimorphism. Central administration of rBMP-7 delayed allodynia development after SNI and reduced the severity of allodynia. The opioid antagonist naloxone antagonized the antinociceptive effect of rBMP-7 in rats. The analgesic effect of morphine was significantly attenuated in BMP-7+/- mice. The antiallodynic effect of voluntary exercise after SNI, whose mechanism involves the endogenous opioid system, was hampered by BMP-7 deficiency while potentiated by rBMP-7. Our results suggest that BMP-7 may constitute a novel therapeutic target for the treatment of neuropathic pain, which improves the function of the endogenous pain-resolution mechanisms to alleviate chronic pain.

MicroRNA-30c-5p modulates neuropathic pain in rodents.

Neuropathic pain is a debilitating chronic syndrome that is often refractory to currently available analgesics. Aberrant expression of several microRNAs (miRNAs) in nociception-related neural structures is associated with neuropathic pain in rodent models. We have exploited the antiallodynic phenotype of mice lacking the bone morphogenetic protein and activin membrane-bound inhibitor (BAMBI), a transforming growth factor-ß (TGF-ß) pseudoreceptor. We used these mice to identify new miRNAs that might be useful for diagnosing, treating, or predicting neuropathic pain. We show that, after sciatic nerve injury in rats, miR-30c-5p was up-regulated in the spinal cord, dorsal root ganglia, cerebrospinal fluid (CSF) and plasma and that the expression of miR-30c-5p positively correlated with the severity of allodynia. The administration of a miR-30c-5p inhibitor into the cisterna magna of the brain delayed neuropathic pain development and reversed fully established allodynia in rodents. The mechanism was mediated by TGF-ß and involved the endogenous opioid system. In patients with neuropathic pain associated with leg ischemia, the expression of miR-30c-5p was increased in plasma and CSF compared to control patients without pain. Logistic regression analysis in our cohort of patients showed that the expression of miR-30c-5p in plasma and CSF, in combination with other clinical variables, might be useful to help to predict neuropathic pain occurrence in patients with chronic peripheral ischemia.