Cell Kinetics in the Adult Neurogenic Niche and Impact of Diet-Induced Accelerated Aging

Aqueous Extract of Psiloxylon mauritianum, Rich in Gallic Acid, Prevents Obesity and Associated Deleterious Effects in Zebrafish

Obesity has reached epidemic proportions, and its prevalence tripled worldwide between 1975 and 2016, especially in Reunion Island, a French overseas region. Psiloxylon mauritianum, an endemic medicinal plant from Reunion Island registered in the French pharmacopeia, has recently gained interest in combating metabolic disorders because of its traditional lipid-lowering and “anti-diabetic” use. However, scientific data are lacking regarding its toxicity and its real benefits on metabolic diseases. In this study, we aim to determine the toxicity of an aqueous extract of P. mauritianum on zebrafish eleutheroembryos following the OECD toxicity assay (Organization for Economic Cooperation and Development, guidelines 36). After defining a non-toxic dose, we determined by liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS) that this extract is rich in gallic acid but contains also caffeoylquinic acid, kaempferol and quercetin, as well as their respective derivatives. We also showed that the non-toxic dose exhibits lipid-lowering effects in a high-fat-diet zebrafish larvae model. In a next step, we demonstrated its preventive effects on body weight gain, hyperglycemia and liver steatosis in a diet-induced obesity model (DIO) performed in adults. It also limited the deleterious effects of overfeeding on the central nervous system (i.e., cerebral oxidative stress, blood-brain barrier breakdown, neuro-inflammation and blunted neurogenesis). Interestingly, adult DIO fish treated with P. mauritianum display normal feeding behavior but higher feces production. This indicates that the “anti-weight-gain” effect is probably due to the action of P. mauritianum on the intestinal lipid absorption and/or on the microbiota, leading to the increase in feces production. Therefore, in our experimental conditions, the aqueous extract of P. mauritianum exhibited “anti-weight-gain” properties, which prevented the development of obesity and its deleterious effects at the peripheral and central levels. These effects should be further investigated in preclinical models of obese/diabetic mice, as well as the impact of P. mauritianum on the gut microbiota.

Acute and long-term metabolic consequences of early developmental Bisphenol A exposure in zebrafish (Danio rerio)

Bisphenol A (BPA) is an estrogenic contaminant linked to metabolic disruption. Developmental BPA exposure is of particular concern, as organizational effects may irreversibly disrupt metabolism at later life-stages. While BPA exposures in adult fish elicit metabolic perturbations similar to effects described in rodents, the metabolic effects of developmental BPA exposure in juvenile fish remain largely unknown. Following embryonic zebrafish exposure to BPA (0.1, 1 and 4 mg/L) and EE₂ (10 ng/L) from 2 to 5 dpf, we assessed the metabolic phenotype in larvae (4-6 dpf) and juveniles (43-49 dpf) which had been divided into regular-fed and overfed groups at 29 dpf. Developmental BPA exposure in larvae dose-dependently reduced food-intake and locomotion and increased energy expenditure. Juveniles (29 dpf) exhibited a transient increase in body weight after developmental BPA exposure and persistent diet-dependent locomotion changes (43-49 dpf). At the molecular level, glucose and lipid metabolism-related transcript abundance clearly separated BPA exposed fish from controls and EE₂ exposed fish at the larval stage, in juveniles on a regular diet and, to a lesser extent, in overfed juveniles. In general, the metabolic endpoints affected by BPA exposure were not mimicked by EE₂ treatment. We conclude that developmental BPA exposure elicits acute metabolic effects in zebrafish larvae and fewer transient and persistent effects in juveniles and that these metabolic effects are largely independent of BPA's estrogenicity.

Effects of nutraceutical intervention on serum proteins in aged rats

Aging is associated with many pathophysiological changes that could lead to the onset of degenerative disease. Some of the physiological changes that occur with aging include increased inflammation and decreased stem cell proliferation, leading to decreased capacity for tissue regeneration and loss of function. In previous studies, we and others have found nutraceutical intervention to ameliorate some of the deleterious effects associated with aging. In particular, we have previously shown that NT-020, a supplement composed of a proprietary blend of blueberries, green tea, vitamin D3, and carnosine, is able to rescue age-related cognitive deficits, impaired neurogenesis, and inflammation in rats. We have also previously demonstrated that stem cells cultured with old serum showed decreased proliferation; however, when stem cells were cultured in serum from old rats given a diet supplemented with NT-020, proliferation did not differ from that of cells cultured with serum from young rats. While it is clear that NT-020 is exerting a therapeutic, anti-aging effect, the mechanisms of action were yet to be fully elucidated.To that end, in the present study, we conducted a bioinformatics experiment to examine the rat proteome of serum from young and old control rats and young and old rats given a diet supplemented with NT-020. Serum from old rats showed an increase in some inflammatory and pro-aging factors while serum from old rats given a diet supplemented with NT-020 showed an increase in some anti-aging factors, most notably proteins associated with the complement system and autophagy. A number of immune functions that increase with age were shown to be downregulated with NT-020 treatment.

Looking through Brains with Fast Passive CLARITY: Zebrafish, Rodents, Non-human Primates and Humans

Recently developed CLARITY (Clear Lipid-exchanged Acrylamide-hybridized Rigid Imaging/Immunostaining/In situ-hybridization-compatible Tis-sue-hYdrogel) technique renders the tissue transparent by removing lipids in the tissue, while preserving and stabilizing the cellular and subcellular structures. This provides effective penetration of diverse labeling probes, from primary and secondary antibodies to complementary DNA and RNA strands. Followed by high-resolution 3D imaging of neuronal cells and their projections in thick sections, tissue blocks, whole brains, or whole animals, CLARITY allows for superior quantitative analysis of neuronal tissue. Here, we provide our detailed protocol for PACT (Passive Clarity Technique) in brain tissue of diverse species, including human, non-human primate, rodents, and zebrafish. We describe the six principal steps: (1) Tissue fixation and preparation, (2) Passive lipid removal, (3) Immuno-labeling, (4) Optical clearing, (5) Imaging, (6) 3D visualization and quantification.