# Analyses of astrocyte-neuron lactate shuttle transporter levels in brain tissues from people with HIV-associated neurocognitive impairment and Alzheimer’s disease

## TL;DR

This study compares metabolic changes in brain tissues of people with HIV and Alzheimer’s disease, focusing on energy transport systems linked to cognitive decline.

## Contribution

The study identifies distinct patterns of astrocyte–neuron lactate shuttle transporter alterations in Alzheimer’s disease and HIV-associated neurocognitive impairment.

## Key findings

- Alzheimer’s disease shows reduced glucose and lactate transporters, indicating widespread metabolic impairment.
- Non-suppressed HIV patients exhibit downregulated transporters, suggesting inflammation-driven uncoupling of energy systems.
- Virally suppressed HIV patients maintain transporter expression, highlighting the role of viral control in metabolic preservation.

## Abstract

With the success of antiretroviral therapy (ART), people with HIV (PWH) are living longer. As they age, they increasingly face age-related comorbidities, including neurodegenerative conditions. The astrocyte–neuron lactate shuttle (ANLS) is a key mechanism that couples astrocytic glycolysis to neuronal oxidative metabolism, ensuring an adequate energy supply for synaptic activity. Disruption of this system has been implicated in both Alzheimer’s disease (AD) and HIV-associated neurocognitive impairment (HIV-NCI), conditions characterized by some overlapping cognitive deficits yet distinct pathological drivers.

We investigated the expression of major ANLS transporters, including glucose transporters (GLUT1, GLUT3) and monocarboxylate transporters (MCT1, MCT2, MCT4), in postmortem frontal cortex from individuals with AD and PWH. There were two HIV cohorts based on viral suppression (suppressed/non-suppressed), and both were stratified by neurocognitive status (neurocognitively normal/neurocognitively impaired), while AD participants were compared to cognitively healthy participants. Quantitative immunoblotting and immunofluorescence imaging characterized disease-specific alterations.

In AD, both endothelial (GLUT155 kDa) and astrocytic (GLUT145 kDa) isoforms were significantly reduced, along with MCT1, indicating widespread impairment of glucose and lactate transport. GLUT3, the neuronal glucose transporter, also showed a marked reduction. In contrast, in virally non-suppressed (VNS) PWH, GLUT145 kDa and MCT4 were downregulated, while virally suppressed (VS) PWH maintained preserved expression. Correlation analyses revealed strong GLUT3–MCT1 coupling in AD, suggestive of coordinated neuronal–astrocytic adaptation, but disrupted GLUT1–MCT4 relationships in VNS PWH, reflecting ANLS uncoupling under viremia.

These findings identify shared and distinct patterns of metabolic disruption: degeneration-driven ANLS failure in AD versus inflammation-driven uncoupling in HIV-NCI.