POSTNATAL EXPOSURE TO LIPOPOLYSACCHARIDE COMBINED WITH HIGH-FAT DIET CONSUMPTION INDUCES IMMUNE TOLERANCE WITHOUT PREVENTION IN SPATIAL WORKING MEMORY IMPAIRMENT

Early-life malnutrition role in memory, emotional behavior and motor impairments in early brain lesions with potential for neurodevelopmental disorders: a systematic review with meta-analysis

OBJECTIVES

The present study aims to evaluate the impact of early exposure to brain injury and malnutrition on episodic memory and behavior.

METHODS

For this, a systematic review was carried out in the Medline/Pubmed, Web of Science, Scopus, and LILACS databases with no year or language restrictions.

RESULTS

Initially, 1759 studies were detected. After screening, 53 studies remained to be read in full. The meta-analysis demonstrated that exposure to double insults worsens episodic recognition memory but does not affect spatial memory. Early exposure to low-protein diets has been demonstrated to aggravate locomotor and masticatory sequelae. Furthermore, it reduces the weight of the soleus muscle and the muscle fibers of the masseter and digastric muscles. Early exposure to high-fat diets promotes an increase in oxidative stress and inflammation in the brain, increasing anxiety- and depression-like behavior and reducing locomotion.

DISCUSSION

Epigenetic modifications were noted in the hippocampus, hypothalamus, and prefrontal cortex depending on the type of dietetic exposure in early life. These findings demonstrate the impact of the double insult on regions involved in cognitive and behavioral processes. Additional studies are essential to understand the real impact of the double insults in the critical period.

Microglial infiltration mediates cognitive dysfunction in rat models of hypothalamic obesity via a hypothalamic-hippocampal circuit involving the lateral hypothalamic area

This study aimed to explore the mechanism underlying cognitive dysfunction mediated by the lateral hypothalamic area (LHA) in a hypothalamic-hippocampal circuit in rats with lesion-induced hypothalamic obesity (HO). The HO model was established by electrically lesioning the hypothalamic nuclei. The open field (OP) test, Morris water maze (MWM), novel object recognition (NOR), and novel object location memory (NLM) tests were used to evaluate changes in cognition due to alterations in the hypothalamic-hippocampal circuit. Western blotting, immunohistochemical staining, and cholera toxin subunit B conjugated with Alexa Fluor 488 (CTB488) reverse tracer technology were used to determine synaptophysin (SYN), postsynaptic density protein 95 (PSD95), ionized calcium binding adaptor molecule 1 (Iba1), neuronal nuclear protein (NeuN), and Caspase3 expression levels and the hypothalamic-hippocampal circuit. In HO rats, severe obesity was associated with cognitive dysfunction after the lesion of the hypothalamus. Furthermore, neuronal apoptosis and activated microglia in the downstream of the lesion area (the LHA) induced microglial infiltration into the intact hippocampus via the LHA-hippocampal circuit, and the synapses engulfment in the hippocampus may be the underlying mechanism by which the remodeled microglial mediates memory impairments in HO rats. The HO rats exhibited microglial infiltration and synapse loss into the hippocampus from the lesioned LHA via the hypothalamic-hippocampal circuit. The underlying mechanisms of memory function may be related to the circuit.

Prion Disease in the Central Nervous System

Prion diseases such as Creutzfeldt-Jakob disease in humans, bovine spongiform encephalopathy in cattle, and scrapie in sheep, are infectious and chronic neurodegenerative diseases to which there are no cures. Infection with prions in the central nervous system (CNS) ultimately causes extensive neurodegeneration, and this is accompanied by prominent microglial and astrocytic activation in affected regions. The microglia are the CNS macrophages and help maintain neuronal homeostasis, clear dead or dying cells and provide defense against pathogens. The microglia also provide neuroprotection during CNS prion disease, but their pro-inflammatory activation may exacerbate the development of the neuropathology. Innate immune tolerance induced by consecutive systemic bacterial lipopolysaccharide (LPS) treatment can induce long-term epigenetic changes in the microglia in the brain that several months later can dampen their responsiveness to subsequent LPS treatment and impede the development of neuritic damage in a transgenic mouse model of Alzheimer’s disease-like pathology. We therefore reasoned that innate immune tolerance in microglia might similarly impede the subsequent development of CNS prion disease. To test this hypothesis groups of mice were first infected with prions by intracerebral injection, and 35 days later given four consecutive systemic injections with LPS to induce innate immune tolerance. Our data show that consecutive systemic LPS treatment did not affect the subsequent development of CNS prion disease. Our data suggests innate immune tolerance in microglia does not influence the subsequent onset of prion disease-induced neuropathology in mice, despite previously published evidence of this effect in an Alzheimer’s disease mouse model.