Ketone bodies supplementation restores the barrier function, induces a metabolic switch, and elicits beta-hydroxybutyrate diffusion across a monolayer of iPSC-derived brain microvascular endothelial cells

Starvation Induces Upregulation of Monocarboxylate Transport in Glial Cells at the Drosophila Blood-Brain Barrier

Living organisms can sense and adapt to constant changes in food availability. Maintaining a homeostatic supply of energy molecules is crucial for animal survival and normal organ functioning, particularly the brain, due to its high-energy demands. However, the mechanisms underlying brain adaptive responses to food availability have not been completely established. The nervous system is separated from the rest of the body by a physical barrier called the blood-brain barrier (BBB). In addition to its structural role, the BBB regulates the transport of metabolites and nutrients into the nervous system. This regulation is achieved through adaptive mechanisms that control the transport of nutrients, including glucose and monocarboxylates such as lactate, pyruvate, and ketone bodies. In Drosophila melanogaster, carbohydrate transporters increase their expression in glial cells of the BBB in response to starvation. However, changes in the expression or activity of Drosophila monocarboxylate transporters (dMCTs) at the BBB have not yet been reported. Here, we show that neuronal ATP levels remain unaffected despite reduced energy-related metabolites in the hemolymph of Drosophila larvae during starvation. Simultaneously, the transport of lactate and beta-hydroxybutyrate increases in the glial cells of the BBB. Using genetically encoded sensors, we identified Yarqay as a proton-coupled monocarboxylate transporter whose expression is upregulated in the subperineurial glia of the BBB during starvation. Our findings reveal a novel component of the adaptive response of the brain to starvation: the increase in the transport of monocarboxylates across the BBB, mediated by Yarqay, a novel dMCT enriched in the BBB.

DAG-MAG-ΒHB: A Novel Ketone Diester Modulates NLRP3 Inflammasome Activation in Microglial Cells in Response to Beta-Amyloid and Low Glucose AD-like Conditions

BACKGROUND

A neuroinflammatory disease such as Alzheimer's disease, presents a significant challenge in neurotherapeutics, particularly due to the complex etiology and allostatic factors, referred to as CNS stressors, that accelerate the development and progression of the disease. These CNS stressors include cerebral hypo-glucose metabolism, hyperinsulinemia, mitochondrial dysfunction, oxidative stress, impairment of neuronal autophagy, hypoxic insults and neuroinflammation. This study aims to explore the efficacy and safety of DAG-MAG-ΒHB, a novel ketone diester, in mitigating these risk factors by sustaining therapeutic ketosis, independent of conventional metabolic pathways.

METHODS

We evaluated the intestinal absorption of DAG-MAG-ΒHB and the metabolic impact in human microglial cells. Utilizing the HMC3 human microglia cell line, we examined the compound's effect on cellular viability, Acetyl-CoA and ATP levels, and key metabolic enzymes under hypoglycemia. Additionally, we assessed the impact of DAG-AG-ΒHB on inflammasome activation, mitochondrial activity, ROS levels, inflammation and phagocytic rates.

RESULTS

DAG-MAG-ΒHB showed a high rate of intestinal absorption and no cytotoxic effect. In vitro, DAG-MAG-ΒHB enhanced cell viability, preserved morphological integrity, and maintained elevated Acetyl-CoA and ATP levels under hypoglycemic conditions. DAG-MAG-ΒHB increased the activity of BDH1 and SCOT, indicating ATP production via a ketolytic pathway. DAG-MAG-ΒHB showed remarkable resilience against low glucose condition by inhibiting NLRP3 inflammasome activation.

CONCLUSIONS

In summary, DAG-MAG-ΒHB emerges as a promising treatment for neuroinflammatory conditions. It enhances cellular health under varying metabolic states and exhibits neuroprotective properties against low glucose conditions. These attributes indicate its potential as an effective component in managing neuroinflammatory diseases, addressing their complex progression.

The toxic effect of lead exposure on the physiological homeostasis of grouper: Insight from gut-liver axis

The heavy metal lead (Pb) pollution in marine environment has been widely concerned. The liver and intestine are important for the health of fish. In this study, the grouper were exposed to 1 μg/L Pb for 14 days, and the physiological homeostasis changes were explored via gut-liver axis. The results showed that Pb stress caused liver morphological changes, oxidative stress, and the accumulation and peroxidation of the lipids. The liver metabolism were disturbed, especially amino acid metabolism and the synthesis and degradation of ketone bodies. Pb stress also caused intestinal mucosal ablation, tight junction dysfunction and inflammatory response. Additionally, intestinal microbial diversity was decreased, and the community composition was altered especially several bacteria genera (Ruminococcus UCG-005, Ruminococcus UCG-014, Oscillibacter, and Streptococcus) were significantly correlated with the physiological indexes and metabolites of the liver. These results reveal that Pb stress negatively affect the physiological homeostasis of the grouper via gut-liver axis.

β-hydroxybutyrate and ischemic stroke: roles and mechanisms

Stroke is a significant global burden, causing extensive morbidity and mortality. In metabolic states where glucose is limited, ketone bodies, predominantly β-hydroxybutyrate (BHB), act as alternative fuel sources. Elevated levels of BHB have been found in the ischemic hemispheres of animal models of stroke, supporting its role in the pathophysiology of cerebral ischemia. Clinically, higher serum and urinary BHB concentrations have been associated with adverse outcomes in ischemic stroke, highlighting its potential utility as a prognostic biomarker. In both animal and cellular models, exogenous BHB administration has exhibited neuroprotective effects, reduction of infarct size, and improvement of neurological outcomes. In this review, we focus on the role of BHB before and after ischemic stroke, with an emphasis on the therapeutic potential and mechanisms of ketone administration after ischemic stroke.

Brain microvascular endothelial cell metabolism and its ties to barrier function

Brain microvascular endothelial cells, which lie at the interface between blood and brain, are critical to brain energetics. These cells must precisely balance metabolizing nutrients for their own demands with transporting nutrients into the brain to sustain parenchymal cells. It is essential to understand this integrated metabolism and transport so that we can develop better diagnostics and therapeutics for neurodegenerative diseases such as Alzheimer's disease, multiple sclerosis, and traumatic brain injury. In this chapter, we first describe brain microvascular endothelial cell metabolism and how these cells regulate both blood flow and nutrient transport. We then explain the impact of brain microvascular endothelial cell metabolism on the integrity of the blood-brain barrier, as well as how metabolites produced by the endothelial cells impact other brain cells. We detail some ways that cell metabolism is typically measured experimentally and modeled computationally. Finally, we describe changes in brain microvascular endothelial cell metabolism in aging and neurodegenerative diseases. At the end of the chapter, we highlight areas for future research in brain microvascular endothelial cell metabolism. The goal of this chapter is to underscore the importance of nutrient metabolism and transport at the brain endothelium for cerebral health and neurovascular disease treatment.