SGLT2 Inhibitor Promotes Ketogenesis to Improve MASH by Suppressing CD8+ T Cell Activation

Hepatobiliary System Life Sciences Immunology Medicine Biochemistry
SGLT2 inhibitor ketogenesis CD8+ T cells MASH inflammation liver injury

The Effects of SGLT2 Inhibitors on MASH

Research on SGLT2 Inhibitors Alleviating MASH by Enhancing Ketogenesis to Inhibit CD8+ T Cell Activation

Research Background and Problem Positioning

Metabolic Dysfunction-Associated Steatotic Liver Disease (MASLD) has become a global health concern. Its severe stage, Metabolic Dysfunction-Associated Steatohepatitis (MASH), leads to hepatocyte damage, inflammation, fat deposition, and fibrosis, which can progress to cirrhosis, liver failure, or even hepatocellular carcinoma. Despite ongoing research, there is still no definitive treatment for MASH. Studies indicate that dysregulation in the liver’s immune system plays a crucial role in MASH’s pathogenesis. CD8+ T cells, capable of releasing cytotoxic substances and cytokines (such as granzyme B and interferon-γ), are viewed as significant pro-inflammatory cells driving MASH progression. Research suggests that CD8+ T cells preferentially use non-glucose carbon sources for metabolism under dysglycemic conditions, indicating that modulating their metabolic pathways might be an effective treatment strategy.

Sodium-Glucose Co-Transporter 2 Inhibitors (SGLT2i), selective inhibitors of SGLT2, have been shown to enhance ketogenesis, providing cardiac and renal protection. Studies suggest that SGLT2i can improve liver enzyme levels in patients with Non-Alcoholic Fatty Liver Disease (NAFLD), hinting at potential benefits in MASH treatment. This study hypothesizes that SGLT2i can alleviate MASH progression by modulating ketone metabolism in CD8+ T cells to inhibit their activation.

Research Methods and Process

Conducted by a research team from Southern Medical University and other institutions, this study was published in the October 1, 2024, issue of “Cell Metabolism”. Through animal experiments and clinical research, the team systematically investigated SGLT2i’s mechanism in MASH treatment, involving the following steps:

  1. Animal Model Experiments: MASH mouse models induced by Methionine-Choline-Deficient (MCD) and High-Fructose, High-Fat, and High-Cholesterol (HFHC) diets were grouped into control and SGLT2i groups, administered Empagliflozin (EMPA, a representative SGLT2i) at 10 and 30 mg/kg. Liver pathology examinations, serum transaminase levels, liver triglycerides (TG), and hydroxyproline (Hyp) contents were measured to evaluate changes in fat deposition, inflammation, and fibrosis.

  2. Gene Expression Analysis: RNA sequencing (RNA-seq) revealed significant downregulation of immune-related pathways in the SGLT2i group, with notable reduction of CD8a, a CD8+ T cell biomarker. Single-cell RNA sequencing (scRNA-seq) analysis showed a significant reduction in CD8+ T cell proportions in MASH mouse livers.

  3. Cell Transfer Experiments: To explore CD8+ T cells’ role in SGLT2i efficacy, Rag2-/- mice underwent CD8+ T cell transfer experiments, inducing MCD diet after transferring untreated and EMPA-treated CD8+ T cells. Results showed significant liver damage improvement in the EMPA-treated CD8+ T cell transfer group.

  4. Ketogenesis Mechanism Study: The study confirmed EMPA significantly increased β-hydroxybutyrate (B-OHB) levels in CD8+ T cells by analyzing the key enzyme 3-hydroxybutyrate dehydrogenase 1 (BDH1) in ketogenesis. BDH1 deficiency aggravated MASH phenotype, underscoring BDH1’s crucial role in EMPA-mediated ketogenesis and CD8+ T cell function inhibition.

  5. Clinical Case-Control Study: A study on 5 MASH patients and 4 healthy controls showed significant liver damage and CD8+ T cell infiltration improvement after 12 months of oral SGLT2i drug Dapagliflozin treatment.

Research Results

  1. Inhibition of CD8+ T Cell Infiltration and Function: SGLT2i significantly reduced CD8+ T cell infiltration and Granzyme B expression in both MASH mice and patients’ livers. In vivo experiments indicated that SGLT2i’s efficacy disappeared upon CD8+ T cell removal, indicating CD8+ T cells’ decisive role in EMPA’s therapeutic effect.

  2. Ketogenesis and BDH1’s Key Role: SGLT2i enhanced ketogenesis in CD8+ T cells by upregulating BDH1 expression, with β-hydroxybutyrate in CD8+ T cells significantly inhibiting activation. Further experiments showed BDH1 deficiency exacerbated MASH pathology, with EMPA unable to improve outcomes under BDH1-deficient conditions.

  3. Regulation of Ketone Metabolism and IRF4 Inhibition: Mechanistic studies found that β-hydroxybutyrate from the ketogenesis pathway significantly inhibited transcription factor IRF4 expression and nuclear localization in CD8+ T cells. IRF4 inhibition decreased CD8+ T cells’ effector function, alleviating liver inflammation.

Research Conclusion and Significance

This study first revealed SGLT2i’s mechanism of inhibiting CD8+ T cell activation through enhanced ketogenesis, confirming CD8+ T cells as direct targets for EMPA in MASH treatment. The study demonstrated that SGLT2i, by upregulating BDH1 and increasing β-hydroxybutyrate production, inhibited CD8+ T cells’ effector functions and pro-inflammatory actions, effectively reducing MASH progression. This discovery extends SGLT2i’s indications, highlighting it as a potential MASH therapy and providing new insights for MASH immunometabolic treatment.

Research Highlights and Innovations

  1. Innovative CD8+ T Cell Ketogenesis Regulation Mechanism: Unfolded the mechanism by which SGLT2i modulates ketone metabolism to inhibit CD8+ T cell activation, thereby reducing MASH, providing a theoretical basis for SGLT2i’s application in immunometabolism.

  2. BDH1’s Crucial Role: Demonstrated BDH1’s role in SGLT2i-induced CD8+ T cell inhibition and its therapeutic effect in MASH, proposing regulation of BDH1 and ketogenesis pathways as potential MASH intervention strategies.

  3. IRF4 Inhibition and Anti-inflammatory Effects of β-Hydroxybutyrate: Found β-hydroxybutyrate can downregulate CD8+ T cell pro-inflammatory responses by inhibiting IRF4 expression and localization, offering new directions to explore β-hydroxybutyrate in other immune diseases.

Prospects and Study Limitations

While this study unveils SGLT2i’s immunoregulatory potential in MASH treatment, some limitations should be noted:

  1. Potential Epigenetic Mechanisms: The study hasn’t deeply explored the effects of SGLT2i-induced ketone metabolism on epigenetic modifications (like histone deacetylation), which future research could verify.

  2. Larger-scale Clinical Validation: The clinical sample size is small; future large-scale randomized controlled trials are needed to validate SGLT2i’s efficacy in MASH treatment.

  3. Further Study on Cell Types and Molecular Mechanisms: In MASH’s complex inflammatory environment, NK cells, macrophages, etc., may also be involved. Further exploration of their roles and interactions with CD8+ T cells is necessary.

This study provides new perspectives and theoretical support for MASH immunometabolic therapy, suggesting that by modulating ketone metabolism to inhibit CD8+ T cell activation, SGLT2i may develop into an innovative MASH therapy in the future.