Peter A. Crawford

Background: Sodium-glucose cotransporter-2 (SGLT2) inhibitors improve outcomes in heart failure, but the mechanisms remain incompletely understood. Metabolic remodeling has been proposed as a key mediator. Methods and Results: Myocardial infarction (MI) was induced in cardiomyocyte-specific BDH1 knockout (BDH1-KO) wild-type (WT) mice and in liver-specific Fibroblast Growth Factor-21 knockout (FGF21-KO) mice. Following confirmation of reduced ejection fraction (EF), mice were randomized to empagliflozin (Empa, 10 mg/kg/day) or saline. After 4 weeks, untreated WT mice demonstrated progressive systolic dysfunction (ΔEF: −11.6 ± 6.3%), whereas Empa-treated WT mice showed significant improvement (ΔEF: 9.9 ± 4.3%). This benefit was completely abolished in BDH1-KO mice (ΔEF: −10.5 ± 2.8%) or FGF21-KO mice, suggesting that FGF21 regulation and cardiomyocyte ketone oxidation are required for Empa cardioprotection. In WT and hepatocyte-specific FGF21-KO mice, 1 week of Empa treatment increased cardiac BDH1 expression in WT but not FGF21-deficient mice. In human iPSC-cardiomyocytes, FGF21 induced BDH1 expression, whereas Empa had no direct effect on BDH1. In HepG2 liver cells, Empa increased both FGF21 and BDH1 expression. Conclusions: Empa activates the liver–heart metabolic axis. Loss of cardiomyocyte BDH1 or FGF21 production by the liver abolishes Empa-mediated improvement in post-MI cardiac function, identifying FGF21/ketone metabolism as a key mechanism of SGLT2 inhibitor cardioprotection.

Ketone body (KB) utilization increases during fasting and exercise due to enhanced hepatic fatty acid oxidation and KB production via the rate-limiting mitochondrial enzyme hydroxymethylglutaryl-CoA synthase (HMGCS2). Since KB metabolism intersects with multiple metabolic pathways and skeletal muscle KB catabolism rises during exercise, we tested the hypothesis that liver-specific HMGCS2 knockouts (KO) would have reduced energy expenditure (EE) and changes in the mitochondrial proteome of skeletal muscle with chronic exercise through voluntary wheel running (VWR), time-restricted feeding (TRF), or both combined to boost hepatic KB production and utilization. Control (CON) and HMGCS2 knockout (KO) mice ( n = 6–8 per group) underwent sedentary ad libitum feeding (SED + AL), SED + TRF, VWR + AL, and VWR + TRF for 16 wk, with whole body EE measured using indirect calorimetry. In CON mice, VWR increased total EE by 19.5% and nonresting EE by 50% under AL conditions, and total EE by 16% and nonresting EE by 47.9% under TRF conditions. However, the EE increases seen with VWR did not occur in KO mice. Proteomic analysis revealed that the loss of liver HMGCS2 significantly impacted proteins involved in metabolic processes within skeletal muscle, including reduced oxidative phosphorylation (OXPHOS) protein expression in SED KO mice compared with sedentary CON. Notably, VWR restored OXPHOS protein expression in the muscle of the liver HMGCS2 KO but did not alter it in the CON. Furthermore, muscle from liver HMGCS2 KO mice had elevated expression of glycolytic pathways in sedentary and VWR conditions. These results indicate that hepatic ketogenic deficiency (HMGCS2 KO) diminishes exercise-induced increases in EE and uniquely impacts baseline and exercise-related adaptations in the metabolic and mitochondrial proteome of skeletal muscle.

Background: Intermittent fasting interventions, such as time-restricted eating (TRE) without calorie restriction, may offer diverse cardiometabolic health benefits, including reductions in inflammation. However, the underlying metabolic mechanisms are poorly understood. Objective: This study is designed to evaluate ketone metabolism and immunoregulation during TRE (6-hour feeding and 18-hour fasting) without caloric restriction compared to a conventional dietary regimen (12-hour feeding and 12-hour fasting) in women. Methods: This is a pilot, prospective, single-arm dietary intervention study in premenopausal women classified as lean and obese, with intraindividual and stratified comparisons. Ketone turnover, immunologic responses, and metabolic profiles will be compared between a conventional dietary regimen (12-hour feeding and 12-hour fasting) at admission and after 3 days of TRE (6-hour feeding and 18-hour fasting). Results: The trial commenced in August 2024. As of February 2026, participant enrollment is ongoing. Complete enrollment is expected in the December 2026. Integrated analyses will be reported once data analysis is completed, which is expected in the winter of 2027. Conclusions: This clinical protocol will evaluate whole-body ketone metabolism and immunoregulatory changes in women during TRE using state-of-the-art stable isotope and immunophenotyping techniques. This study will determine the effects of a time-limited dietary pattern, without caloric restriction, on dynamic measures of immunity and metabolism. Trial Registration: ClinicalTrials.gov NCT06169137; https://clinicaltrials.gov/study/NCT06169137 International Registered Report Identifier (IRRID): DERR1-10.2196/81063

Ketogenesis and ketone body metabolism are linked to brain health benefits, including delaying age-related cognitive decline and neurodegeneration. Exercise, particularly when combined with an overnight fast, stimulates ketogenesis and ketone body turnover as well as improves brain metabolism and cognition. Yet, whether ketone metabolism is obligatory for this response is unknown. Here, we use chronic exercise via voluntary wheel running plus time-restricted feeding (VWR+TRF, fasting from ZT10.5-18.5) to explore whether ketone bodies are a potential mediator of exercise-induced brain health benefits in middle-aged mice. To independently distinguish the roles of neuronal ketone body metabolism vs. hepatic ketone body production, we studied middle-age female neuronal-specific SCOT knockout mice and female hepatocyte-specific HMGCS2 knockout mice, respectively. VWR+TRF was compared to sedentary ad-libitum fed (SED+AL) mice to assess the impact on whole-body metabolism (indirect calorimetry), cognition (Barnes Maze and Y-Maze), and molecular adaptations in the hippocampus (proteomics). VWR+TRF robustly upregulated systemic lipid oxidation in all mice, regardless of genotype, during the first 6.5 hours of the dark period. In female SCOT-Neuron-KO mice, we show impaired responses to VWR+TRF in indices of short- and long-term memory. Proteomic analysis of isolated hippocampi revealed that SCOT-Neuron-KO mice failed to globally upregulate key facilitators of synaptic function, including leucine-rich repeated transmembrane proteins, neurexins, and neuroligins. In female HMGCS2-Liver-KO mice, impaired responses to VWR+TRF in indices of short-term memory were paired with an upregulation in ketogenesis machinery in the hippocampal proteome, suggesting potential in vivo evidence of cerebral ketogenesis, a mechanism mitigating an otherwise more pronounced behavioral phenotype. Together, these findings suggest that neuronal ketone body utilization is essential, and hepatic ketone production is contributory, to the full cognitive and synaptic adaptations to exercise plus time-restricted feeding, supporting ketone metabolism as a key mechanistic link between metabolic state and brain health in midlife.

Despite effective antiretroviral therapy (ART), many people with HIV (PWH) exhibit persistent immune activation (IA) and suffer metabolic comorbidities. We investigated whether residual HIV production in lymphoid tissues drives IA. Among 20 ART-suppressed PWH, HIV RNA ⁺ cells were detected in lymph nodes and correlated directly with markers of pyroptosis, assessed via cleaved gasdermin D positivity, but not with most plasma cytokines or IA markers. Notably, glucagon-like peptide 1 (GLP-1), an enteroendocrine hormone with anti-inflammatory roles, was upregulated in the ileum of PWH and correlated directly with systemic cytokines but inversely with lymph node pyroptosis. These findings suggest that chronic occult inflammation in people with successfully suppressed HIV infection is mediated by persistent virus production in lymph nodes leading to pyroptosis, which may trigger compensatory anti-inflammatory enteroendocrine activation that may dampen pyroptosis. Targeting pyroptosis or enhancing GLP-1 signaling represent potential therapeutic strategies for modulating IA and managing metabolic comorbidities in PWH. Graphical

Reducing calorie intake through dietary restriction (DR) slows tumour growth in mammals, yet the underlying mechanisms are poorly defined. Here, we show that DR enhances anti-tumour immunity by optimizing CD8 ⁺ T cell function within the tumour microenvironment (TME). Using syngeneic xenograft tumour models, we found that DR induces a profound reprogramming of CD8 ⁺ T cell fate in the TME, favouring the expansion of effector T cell subsets with enhanced metabolic capacity and cytotoxic potential, while limiting the accumulation of terminally exhausted T cells. This metabolic reprogramming is driven by enhanced ketone body oxidation, particularly β-hydroxybutyrate (βOHB), which is elevated in both the circulation and tumour tissues of DR-fed mice. βOHB fuels T cell oxidative metabolism under DR, increasing mitochondrial membrane potential and tricarboxylic acid cycle-dependent pathways critical for T cell effector function, including acetyl-CoA production. By contrast, T cells deficient for ketone body oxidation exhibit reduced mitochondrial function, increased exhaustion and fail to control tumour growth under DR conditions. Importantly, DR synergizes with anti-PD1 immunotherapy, further augmenting anti-tumour T cell responses and limiting tumour progression. Our findings reveal that T cell metabolic reprogramming is central to the anti-tumour effects of DR, highlighting nutritional control of CD8 ⁺ T cell fate as a key driver of anti-tumour immunity.

Dietary sulfur amino acid restriction (SAAR) improves whole-body glucose homeostasis, elevates liver insulin action, and lowers liver triglycerides. These adaptations are associated with an increased expression of hepatic de novo serine synthesis enzymes, phosphoglycerate dehydrogenase (PHGDH) and phosphoserine aminotransferase 1 (PSAT1). This study tested the hypothesis that enhanced hepatic serine synthesis is necessary for glucose and lipid adaptations to SAAR. Hepatocyte-specific PSAT1 knockout (KO) mice and wild type (WT) littermates were fed a high-fat control or SAAR diet. In WT mice, SAAR increased liver PSAT1 protein (∼70-fold), serine concentration (∼2-fold), and ¹³ C-serine (∼20-fold) following an intravenous infusion of [U- ¹³ C]glucose. The elevated liver serine and partitioning of circulating glucose to liver serine by SAAR were attenuated in KO mice. This was accompanied by a blunted improvement in glucose tolerance in KO mice fed a SAAR diet. Interestingly, SAAR decreased liver lysine lactoylation, a SAA-supported post-translational modification known to inhibit PHGDH enzymatic activity. This suggests dietary SAAR may increase serine synthesis, in part, by lowering lysine lactoylation. Beyond glucose metabolism, dietary SAAR reduced body weight, adiposity, and liver triglycerides similarly in WT and KO mice. Collectively, these results demonstrate that hepatic PSAT1 is necessary for glucose, but not lipid, adaptations to SAAR. Graphical Schematic representation of liver glucose adaptations to SAAR

Tregs are critical for maintaining immune homeostasis, and their adoptive transfer can treat murine inflammatory disorders. In patients, Treg therapies have been variably efficacious. Therefore, new strategies to enhance Treg therapeutic efficacy are needed. Tregs predominantly depend on oxidative phosphorylation (OXPHOS) for energy and suppressive function. Fatty acid oxidation (FAO) contributes to Treg OXPHOS and can be important for Treg “effector” differentiation, but FAO activity is inhibited by coordinated activity of the isoenzymes acetyl-CoA carboxylase-1 and -2 (ACC1 and ACC2). Here, we show that small-molecule inhibition or Treg-specific genetic deletion of ACC1 significantly increases Treg suppressive function in vitro and in mice with established chronic graft-versus-host disease. ACC1 inhibition skewed Tregs toward an “effector” phenotype and enhanced FAO-mediated OXPHOS, mitochondrial function, and mitochondrial fusion. Inhibiting mitochondrial fusion diminished the effect of ACC1 inhibition. Reciprocally, promoting mitochondrial fusion, even in the absence of ACC1 modulation, resulted in a Treg functional and metabolic phenotype similar to that seen with ACC1 inhibition, indicating a key role for mitochondrial fusion in Treg-suppressive potency. Ex vivo–expanded, ACC1 inhibitor–treated human Tregs similarly augmented suppressor function, as observed with murine Tregs. Together, these data suggest that ACC1 manipulation may be exploited to modulate Treg function in patients.

BACKGROUND Intermittent fasting interventions, such as time-restricted eating (TRE) without calorie restriction, may offer diverse cardiometabolic health benefits, including reductions in inflammation. However, the underlying metabolic mechanisms are poorly understood. OBJECTIVE This study is designed to evaluate ketone metabolism and immunoregulation during TRE (6-hour feeding and 18-hour fasting) without caloric restriction compared to a conventional dietary regimen (12-hour feeding and 12-hour fasting) in women. METHODS This is a pilot, prospective, single-arm dietary intervention study in premenopausal women classified as lean and obese, with intraindividual and stratified comparisons. Ketone turnover, immunologic responses, and metabolic profiles will be compared between a conventional dietary regimen (12-hour feeding and 12-hour fasting) at admission and after 3 days of TRE (6-hour feeding and 18-hour fasting). RESULTS The trial commenced in August 2024. As of February 2026, participant enrollment is ongoing. Complete enrollment is expected in the December 2026. Integrated analyses will be reported once data analysis is completed, which is expected in the winter of 2027. CONCLUSIONS This clinical protocol will evaluate whole-body ketone metabolism and immunoregulatory changes in women during TRE using state-of-the-art stable isotope and immunophenotyping techniques. This study will determine the effects of a time-limited dietary pattern, without caloric restriction, on dynamic measures of immunity and metabolism. CLINICALTRIAL ClinicalTrials.gov NCT06169137; https://clinicaltrials.gov/study/NCT06169137 INTERNATIONAL REGISTERED REPORT DERR1-10.2196/81063