Misato underlies visceral myopathy in Drosophila

Mild Hyperhomocysteinemia Causes Anxiety-like Behavior and Brain Hyperactivity in Rodents: Are ATPase and Excitotoxicity by NMDA Receptor Overstimulation Involved in this Effect?

Mild hyperhomocysteinemia is a risk factor for psychiatric and neurodegenerative diseases, whose mechanisms between them are not well-known. In the present study, we evaluated the emotional behavior and neurochemical pathways (ATPases, glutamate homeostasis, and cell viability) in amygdala and prefrontal cortex rats subjected to mild hyperhomocysteinemia (in vivo studies). The ex vivo effect of homocysteine on ATPases and redox status, as well as on NMDAR antagonism by MK-801 in same structures slices were also performed. Wistar male rats received a subcutaneous injection of 0.03 µmol Homocysteine/g of body weight or saline, twice a day from 30 to 60th-67th days of life. Hyperhomocysteinemia increased anxiety-like behavior and tended to alter locomotion/exploration of rats, whereas sucrose preference and forced swimming tests were not altered. Glutamate uptake was not changed, but the activities of glutamine synthetase and ATPases were increased. Cell viability was not altered. Ex vivo studies (slices) showed that homocysteine altered ATPases and redox status and that MK801, an NMDAR antagonist, protected amygdala (partially) and prefrontal cortex (totally) effects. Taken together, data showed that mild hyperhomocysteinemia impairs the emotional behavior, which may be associated with changes in ATPase and glutamate homeostasis, including glutamine synthetase and NMDAR overstimulation that could lead to excitotoxicity. These findings may be associated with the homocysteine risk factor on psychiatric disorders development and neurodegeneration.

Hyperhomocysteinemia-Induced Oxidative Stress Exacerbates Cortical Traumatic Brain Injury Outcomes in Rats

Traumatic brain injury (TBI) is a leading cause of morbidity and mortality among military service members and civilians in the United States. Despite significant advances in the understanding of TBI pathophysiology, several clinical reports indicate that multiple genetic and epigenetic factors can influence outcome. Homocysteine (HCY) is a non-proteinogenic amino acid, the catabolism of which can be dysregulated by stress, lifestyle, aging, or genetic abnormalities leading to hyperhomocysteinemia (HHCY). HHCY is a neurotoxic condition and a risk factor for multiple neurological and cardiovascular disorders that occurs when HCY levels is clinically > 15 µM. Although the deleterious impact of HHCY has been studied in human and animal models of neurological disorders such as stroke, Alzheimer's disease and Parkinson's disease, it has not been addressed in TBI models. This study tested the hypothesis that HHCY has detrimental effects on TBI pathophysiology. Moderate HHCY was induced in adult male Sprague Dawley rats via daily administration of methionine followed by impact-induced traumatic brain injury. In this model, HHCY increased oxidative stress, upregulated expression of proteins that promote blood coagulation, exacerbated TBI-associated blood-brain barrier dysfunction and promoted the infiltration of inflammatory cells into the cortex. We also observed an increase of brain injury-induced lesion size and aggravated anxiety-like behavior. These findings show that moderate HHCY exacerbates TBI outcomes and suggest that HCY catabolic dysregulation may be a significant biological variable that could contribute to TBI pathophysiology heterogeneity.

The role of glycogen in development and adult fitness in Drosophila

The polysaccharide glycogen is an evolutionarily conserved storage form of glucose. However, the physiological significance of glycogen metabolism on homeostatic control throughout the animal life cycle remains incomplete. Here, we describe Drosophila mutants that have defective glycogen metabolism. Null mutants of glycogen synthase (GlyS) and glycogen phosphorylase (GlyP) displayed growth defects and larval lethality, indicating that glycogen plays a crucial role in larval development. Unexpectedly, however, a certain population of larvae developed into adults with normal morphology. Semi-lethality in glycogen mutants during the larval period can be attributed to the presence of circulating sugar trehalose. Homozygous glycogen mutants produced offspring, indicating that glycogen stored in oocytes is dispensable for embryogenesis. GlyS and GlyP mutants showed distinct metabolic defects in the levels of circulating sugars and triglycerides in a life stage-specific manner. In adults, glycogen as an energy reserve is not crucial for physical fitness and lifespan under nourished conditions, but glycogen becomes important under energy stress conditions. This study provides a fundamental understanding of the stage-specific requirements for glycogen metabolism in the fruit fly.