Key Takeaways & Executive Findings
- •• • Apoa4 deletion in DIO mice exacerbated insulin resistance and renal lipid accumulation, with scRNA-seq revealing compromised T, NK, and B cell immune functions despite expanded Gzma+ NK and Derl3+ plasma cell populations. This indicates Apoa4 as a homeostatic regulator; its loss may accelerate CKD progression, highlighting a therapeutic target for obesity-related renal injury. • • Mechanistically, Apoa4 deficiency aggravated metabolic dysregulation and oxidative stress, downregulating Ifng and Il1b expression. This suppression of key effector genes suggests that Apoa4 maintains pro-inflammatory and metabolic signaling necessary for immune competence, and its absence may impair pathogen defense and tissue repair in early CKD. • • Transcription factor network perturbations were observed: Lef1 and Runx3 in Cd8+ T cells; Irf8, T-bet, and Eomes in NK cells; and Tcf4, Lmo2, and Xbp1 in B cells. These disruptions indicate that Apoa4 influences lineage-specific transcriptional programs, potentially altering immune cell differentiation and function, which could serve as biomarkers for early CKD diagnosis. • • CellChat predicted disrupted IFN-II, IL-1, FASLG, ENHO, and ANGPTL signaling, alongside enhanced IL-2-mediated suppression. This signaling rewiring suggests that Apoa4 loss creates an immunosuppressive microenvironment, which may contribute to CKD progression and offers potential targets for immunomodulatory therapies in obesity-related kidney disease.
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Abstract
Obesity-induced metabolic inflammation drives chronic kidney disease (CKD), with lymphocyte dysregulation contributing to early pathology. We established high-fat diet-induced obese (DIO) models in wild-type and Apoa4-knockout (KO) mice to investigate apolipoprotein A4 (Apoa4) in immune-metabolic regulation. KO mice exhibited exacerbated insulin resistance and renal lipid accumulation. Single-cell RNA sequencing (scRNA-seq) of renal immune cells revealed that Apoa4 deletion remodeled the immune-metabolic landscape, compromising T, NK, and B cell functions while expanding cytotoxic Gzma+ NK cells and Derl3+ plasma cells. Mechanistically, Apoa4 deletion aggravated metabolic dysregulation and oxidative stress, downregulating effector genes including Ifng and Il1b. Transcription factor regulatory networks were perturbed: Lef1 and Runx3 in Cd8+ T cells; Irf8, T-bet, and Eomes in NK cells; and Tcf4, Lmo2, and Xbp1 in B cells. CellChat predicted disrupted pro-inflammatory (IFN-II, IL-1), immunoregulatory (FASLG), and metabolic (ENHO, ANGPTL) signaling, with enhanced IL-2-mediated suppression. Flow cytometry, immunofluorescence, and qPCR validated these findings. Sequencing depth averaged 278,276 reads/cell (WT) and 197,768 reads/cell (KO), ensuring robust detection of low-abundance transcripts despite modest cell capture. Apoa4 is a critical regulator of lymphocyte metabolic and immune homeostasis in early obesity-associated CKD.
1. Introduction
Obesity-related chronic kidney disease (CKD) represents a growing global health burden, with metabolic inflammation, insulin resistance, and renal lipid deposition as key drivers. Existing therapeutic approaches targeting single pathways have largely failed to halt disease progression, partly due to the complex interplay between metabolic and immune systems. Immune dysregulation, particularly among lymphocytes, is recognized as a critical contributor to early CKD pathology, yet the molecular regulators coordinating these processes remain poorly defined. Apolipoprotein A4 (Apoa4), traditionally linked to lipid metabolism, has emerged as a potential mediator of immune-metabolic crosstalk, but its specific role in renal immune homeostasis during obesity is unexplored.
To address this gap, we employed single-cell RNA sequencing (scRNA-seq) to dissect the renal immune landscape in high-fat diet-induced obese (DIO) mice with Apoa4 knockout. This approach enabled unbiased profiling of lymphocyte heterogeneity and transcriptional networks at single-cell resolution, overcoming limitations of bulk analyses. By integrating metabolic, functional, and signaling data, we aimed to elucidate how Apoa4 deficiency reprograms immune cell metabolism and function, thereby identifying actionable targets for early intervention in obesity-associated CKD.
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WEI Yang, ZHANG Ting, JIN Yingying, LIU Xiaohuan, ZHOU Jinting, HUANG Na, WANG Yiying (2025). Single-cell transcriptomics reveals apolipoprotein A4-mediated metabolic-immune reprogramming in lymphocytes during early obesity-related chronic kidney disease. Acta Biochimica et Biophysica Sinica. https://doi.org/10.3724/abbs.2025171
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Frequently Asked Questions
What is the quantitative impact of Apoa4 deletion on renal immune cell composition and function, and how does this translate to CKD progression?
Apoa4 deletion expanded cytotoxic Gzma+ NK cells and Derl3+ plasma cells but compromised overall T, NK, and B cell functions, with downregulation of Ifng and Il1b. This dichotomy suggests a shift toward a dysfunctional, pro-inflammatory state that exacerbates renal injury. Clinically, these changes may serve as early biomarkers for CKD, and targeting Apoa4 could restore immune balance.
How does Apoa4 deficiency alter metabolic and signaling pathways in lymphocytes, and what are the therapeutic implications?
Apoa4 deficiency aggravated oxidative stress and metabolic dysregulation, disrupting IFN-II, IL-1, FASLG, ENHO, and ANGPTL signaling while enhancing IL-2-mediated suppression. This rewiring creates an immunosuppressive microenvironment. Therapeutically, modulating these pathways—particularly IL-2 suppression—could reverse immune dysfunction, but requires careful targeting to avoid systemic effects.
What are the technical limitations of the scRNA-seq approach used, and how do they affect data reliability?
The study captured modest cell numbers, but high sequencing depth (278,276 reads/cell in WT, 197,768 in KO) ensured robust detection of low-abundance transcripts. This depth compensates for cell number limitations, providing reliable transcriptomic profiles. However, rare cell populations may be underrepresented, and findings were validated by flow cytometry, immunofluorescence, and qPCR to mitigate false discoveries.
How do the transcription factor network perturbations observed in Apoa4 KO mice inform our understanding of lymphocyte regulation in CKD?
Perturbations in Lef1 and Runx3 (Cd8+ T cells), Irf8, T-bet, and Eomes (NK cells), and Tcf4, Lmo2, and Xbp1 (B cells) indicate that Apoa4 is upstream of lineage-specific transcriptional programs. These factors regulate differentiation, effector function, and survival. Their dysregulation may underlie the functional impairments observed, offering targets for gene therapy or pharmacological intervention to restore immune competence.
What is the translational potential of targeting Apoa4 in obesity-related CKD, and what are the expected challenges?
Apoa4 supplementation or mimetics could potentially restore metabolic-immune homeostasis, but challenges include delivery to renal tissues, potential off-target effects on lipid metabolism, and the need for early intervention before irreversible damage. Preclinical data show exacerbation of insulin resistance and lipid accumulation in KO mice, suggesting that Apoa4 agonism may improve both metabolic and immune outcomes. However, long-term safety and efficacy in humans require further investigation.
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