Adult Hippocampal Neurogenesis: One Lactate to Rule Them All

Adult hippocampal neurogenesis is a dynamic process involved in cognitive functions, like learning and memory. Numerous intrinsic and extrinsic factors regulate and affect hippocampal neurogenesis. An exceptionally beneficial external factor is physical exercise due to the impact of the lactate accumulated during physical effort on neural plasticity. Lactate has recently emerged as one of the most interesting and potent factors in health and disease due to its involvement in the metabolism and signaling of most, if not all, of the cells in the CNS. Herein, we illustrate the effects induced by lactate on the different cell types within the neurogenic niche, in light of their described roles in regulating adult hippocampal neurogenesis.

Maternal antibodies facilitate Amyloid-β clearance by activating Fc-receptor-Syk-mediated phagocytosis

Maternal antibodies (MAbs) protect against infections in immunologically-immature neonates. Maternally transferred immunity may also be harnessed to target diseases associated with endogenous protein misfolding and aggregation, such as Alzheimer's disease (AD) and AD-pathology in Down syndrome (DS). While familial early-onset AD (fEOAD) is associated with autosomal dominant mutations in the APP, PSEN1,2 genes, promoting cerebral Amyloid-β (Aβ) deposition, DS features a life-long overexpression of the APP and DYRK1A genes, leading to a cognitive decline mediated by Aβ overproduction and tau hyperphosphorylation. Although no prenatal screening for fEOAD-related mutations is in clinical practice, DS can be diagnosed in utero. We hypothesized that anti-Aβ MAbs might promote the removal of early Aβ accumulation in the central nervous system of human APP-expressing mice. To this end, a DNA-vaccine expressing Aβ1-11 was delivered to wild-type female mice, followed by mating with 5xFAD males, which exhibit early Aβ plaque formation. MAbs reduce the offspring's cortical Aβ levels 4 months after antibodies were undetectable, along with alleviating short-term memory deficits. MAbs elicit a long-term shift in microglial phenotype in a mechanism involving activation of the FcγR1/Syk/Cofilin pathway. These data suggest that maternal immunization can alleviate cognitive decline mediated by early Aβ deposition, as occurs in EOAD and DS.

L-Lactate Promotes Adult Hippocampal Neurogenesis

Neurogenesis, the formation of new neurons in the adult brain, is important for memory formation and extinction. One of the most studied external interventions that affect the rate of adult neurogenesis is physical exercise. Physical exercise promotes adult neurogenesis via several factors including brain-derived neurotrophic factor (BDNF) and vascular endothelial growth factor (VEGF). Here, we identified L-lactate, a physical exercise-induced metabolite, as a factor that promotes adult hippocampal neurogenesis. While prolonged exposure to L-lactate promoted neurogenesis, no beneficial effect was exerted on cognitive learning and memory. Systemic pharmacological blocking of monocarboxylate transporter 2 (MCT2), which transports L-lactate to the brain, prevented lactate-induced neurogenesis, while 3,5-dihydroxybenzoic acid (3,5-DHBA), an agonist for the lactate-receptor hydroxycarboxylic acid receptor 1 (HCAR1), did not affect adult neurogenesis. These data suggest that L-lactate partially mediates the effect of physical exercise on adult neurogenesis, but not cognition, in a MCT2-dependent manner.

The Behavior of Heterolepidoderma sp. (Gastrotricha)

The behavior of Heterolepidoderma sp. was studied with the same approach as those already used for many species of ciliates. The ethogram we drew comprehends both helicoidal swimming (n = 20, r = 52.5 +/-12.2 mum, pitch = 512 +/- 101 mum, v--> = 215 +/- 43 mum/sec), periodically interrupted by irregular patterns changing the direction of the swimming of random angles and creeping on the substrate. The latter behavioral state, very common for the species we studied, occurs along tracks formed by successive elements (circular, C, vs linear segments, S) joined to each other by two kinds of reactions, which change their trajectory. The surprising similarities and the unexpected differences between the behavior of this gastrotrich and those of the ciliates already studied from this point of view are discussed, on the basis of the dimensional ranges and ecological niches shared by these two, definitely unrelated groups of organisms.

Ursodeoxycholic acid administration in patients with cholestasis of pregnancy: effects on primary bile acids in babies and mothers

Little is known about the effects on the fetus of ursodeoxycholic acid (UDCA) treatment for intrahepatic cholestasis of pregnancy (ICP). Twenty ICP patients were given UDCA at 1.5 to 2 g/d, to our knowledge the highest dosage yet reported. Effects were evaluated on conjugated bile acids (BA) in amniotic fluid (15 of 20 patients) and umbilical cord serum obtained at delivery (20 of 22 newborns), as compared with 10 untreated patients (amniotic fluid, 9 of 10 patients; cord serum, 9 of 10 newborns). Liver function tests, serum BA and UDCA were evaluated on enrollment and then weekly until 1 week after delivery. Maternal serum conjugated cholic (CCA) and chenodeoxycholic (CCDCA) acids levels fell (18.5 +/- 1.9 to 10.5 +/- 1.9 micromol/L, and 5.8 +/- 0.8 to 2.97 +/- 0.7 micromol/L, respectively [P <.01]) in treated patients, and remained unaffected (20.0 +/- 3.1 vs. 20.3 +/- 2.3, and 5.6 +/- 0.6 vs. 5.4 +/- 0.5, respectively [P = not significant]) in untreated ones. Serum conjugated UDCA levels rose to 16.5 +/- 1.8 micromol/L (P<.001). Median values of CCA and CCDCA in amniotic fluid around delivery were 4.9 +/- 12.4 and 4.8 +/- 7.7 micromol/L, respectively, in treated patients, as against 17.9 +/- 27.5 and 18.5 +/- 20.9 micromol/L in untreated ones. In treated mothers, CCA and CCDCA concentrations in cord blood were 6.0 +/- 0.9 and 5.2 +/- 0.95 micromol/L, respectively, as against 21.9 +/- 5.6 and 18.9 +/- 2.1 micromol/L in untreated ones. In treated patients, median UDCA values in amniotic fluid and cord blood were 0.8 +/- 2.4 and 0.9 +/- 0.14 micromol/L, respectively. We conclude that increasing the dose of UDCA more effectively controls ICP and improves maternal clinical outcome after delivery.