Biology subjects

Brooks, G. A.

Publications and source records attributed to Brooks, G. A..

3 recordsLinked to original sources

bioRxiv2026

Exercise training improves exercise capacity independent of AMPKa2 T172-mediated adaptations in skeletal muscle

Regular exercise induces adaptations in skeletal muscle and other organ systems to improve physical performance and overall health. Exercise results in phosphorylation of 5 AMP-activated protein kinase (AMPK) at threonine 172 (T172) of the 2 subunit; however, the role of this activation in cellular and functional adaptations has not been elucidated. To this end, we subjected non-activatable Ampk2(T172A) knock-in (KI) adult mice and wild-type (WT) littermates to 4 weeks of voluntary wheel running (VWR). Exercise training led to significant improvements in endurance capacity, maximal oxygen consumption ([Formula]O2max), and glucose tolerance, as well as skeletal muscle IIb-to-IIa fiber type shift in both WT and KI mice. Contrastingly, VWR resulted in increased mitochondrial OxPhos protein expression, mitochondrial volume density, and capillary density in skeletal muscle of WT but not KI mice. Exercise-induced improvements of mitochondrial respiration and conductance revealed by high-resolution respirometry of isolated mitochondria were blunted in KI mice. Therefore, for the first time, we reveal that AMPK2 T172 activation is required for exercise training-induced mitochondrial biogenesis, improvement of mitochondrial respiratory function, and angiogenesis in skeletal muscle, but that these adaptations are not solely responsible for improved [Formula]O2max and exercise endurance capacity. Significance StatementExercise is the most effective lifestyle intervention for promoting health and preventing chronic diseases through adaptive changes in skeletal muscle and many other tissues/organs. AMPK is an energy sensor and signaling regulator for exercise-induced skeletal muscle adaptation, yet its functional role and the impact on exercise capacity have been studied in mouse genetic models wherein protein stoichiometry is disrupted. Using non-activatable Ampk2(T172A) knock-in mice, we ascertained that AMPK2 activation via T172 phosphorylation is required for endurance training-induced mitochondrial and angiogenic adaptations in skeletal muscle. Importantly, these adaptations are not required for improved exercise capacity, challenging the prevailing concept that increased mitochondrial content and function and microvasculature are the sole driving factors for the performance gains with endurance training.

physiology↗

bioRxiv2026

Lactate-Driven Heterogeneity of Immune Checkpoint Expression in Breast and Lung Cancer Cell Lines

Tumor-derived lactate is increasingly recognized as an immunosuppressive metabolite within the tumor microenvironment (TME), with emerging evidence highlighting its role beyond metabolism to include epigenetic and immune regulatory functions. While prior studies have primarily focused on individual immune checkpoints, most prominently PD-L1, it remains unclear whether lactate broadly coordinates the expression of multiple immune regulatory pathways across distinct tumor types, particularly in the context of chronic exposure mimicking glycolytic tumors. Here, we investigated the relationship between lactate-producing metabolism and immune checkpoint gene expression in four human cancer cell lines representing breast and lung cancer: MCF7 (estrogen receptor-positive breast), MDA-MB-231 (triple-negative breast), A549 (non-small cell lung), and H82 (small cell lung). By manipulating glucose availability and exposure duration to model acute (6 h) versus chronic (48 h) lactate production, and by pharmacologically inhibiting lactate dehydrogenase (LDH) with oxamate, we quantified extracellular lactate accumulation and assessed transcriptional responses of a panel of immune checkpoints (PD-L1, CD80, CD73, LGALS9, VISTA, PVR, CD47, FGL1, STING) and lactate-associated genes (MCT1, MCT4, LDHA, HCAR1) via qPCR. Chronic high-glucose conditions produced robust, LDH-dependent lactate accumulation and were associated with coordinated, lineage-specific remodeling of multiple checkpoint transcripts, whereas acute exposure induced minimal changes. MDA-MB-231 and A549 cells displayed striking but distinct checkpoint patterns under chronic lactate-producing conditions: MDA-MB-231 cells showed strong co-induction of PD-L1 and CD80, while A549 cells exhibited dominant CD80 induction with modest PD-L1 upregulation. H82 cells upregulated PD-L1 alongside CD73, LGALS9, CD47, and CD80, whereas MCF7 cells demonstrated more modest yet coordinated increases across several checkpoints. Chronic glucose exposure resulted in sustained, LDH-dependent lactate accumulation and coordinated induction of multiple immune checkpoint genes, with distinct lineage-specific patterns, e.g., robust PD-L1/CD80 upregulation in MDA-MB-231 versus CD80 dominance in A549. Unsupervised clustering and principal component analysis revealed that duration of glucose exposure, rather than acute glucose availability, was the primary axis of variation and that MCT4 and HCAR1 clustered with strongly induced checkpoints, consistent with a transcriptional program linking lactate export and sensing to immune regulation. These findings support a model in which lactate acts as an upstream regulator of a broader immune escape program, potentially via mechanisms like lactylation and HCAR1 signaling. This work highlights the limitations of single-checkpoint blockade strategies in solid tumors and underscores the potential of targeting lactate metabolism to enhance immunotherapy efficacy in breast and lung cancers.

cancer biology↗

bioRxiv2023

Role of Lactate in the Regulation of Transcriptional Activity of Breast Cancer-Related Genes and Epithelial-to-Mesenchymal Transition Proteins: A Comparison of MCF7 and MDA-MB-231 Cancer Cell Lines

The Warburg Effect is characterized by accelerated glycolytic metabolism and lactate production and under fully aerobic conditions is a hallmark of cancer cells. Recently, we have demonstrated the role of endogenous, glucose-derived lactate as an oncometabolite which regulates gene expression in the estrogen receptor positive (ER+) MCF7 cell line cultivated in glucose media. Presently, with the addition of a triple negative breast cancer (TNBC) cell line, MDA-MB-231, we further confirm the effect of lactate on gene expression patterns and extend results to include lactate effects on protein expression. As well, we report effects of lactate on the expression of E-cadherin and vimentin, proteins associated with epithelial-to-mesenchymal transition (EMT). Endogenous lactate regulates the expression of multiple genes involved in carcinogenesis. In MCF7 cells, lactate increased the expression of EGFR, VEGF, HIF-1a, KRAS, MIF, mTOR, PIK3CA, TP53, and CDK4 as well as decreased the expression of ATM, BRCA1, BRCA2, E2F1, MET, MYC, and RAF mainly after 48h of exposure. On the other hand, in the MDA-MB-231 cell line, lactate increased the expressions of PIK3CA, VEGF, EGFR, mTOR, HIF-1, ATM, E2F1, TP53 and decreased the expressions of BRCA1, BRCA2, CDK4, CDK6, MET, MIF, MYC, and RAF after 48h of exposure. In response to endogenous lactate, changes in protein expression of representative genes corroborated changes in mRNA expressions. Finally, lactate exposure decreased E-cadherin protein expression in MCF7 cells and increased vimentin expression in MDA-MB-231 cells. Further-more, by genetically silencing LDHA in MCF7 cells, we show suppression of protein expression of EGFR and HIF-1, while full protein expression occurred under glucose and glucose + exogenous lactate exposure. Hence, endogenous, glucose-derived lactate, and not glucose, elicited changes in gene and protein expression levels. In this study, we demonstrate that endogenous lactate produced under aerobic conditions (Warburg Effect) elicits important changes in gene and protein expression in both ER+ and TNBC cell lines. The widespread regulation of multiple genes by lactate and involves those involved in carcinogenesis including DNA repair, cell growth, proliferation, angiogenesis, and metastasis. Furthermore, lactate affected the expression of two relevant EMT biomarkers, E-cadherin and vimentin, which could contribute to the complex process of EMT and a shift towards a more mesenchymal phenotype in the two cancer cell lines studied.

cancer biology↗