# Adipose tissue protein profiling: modulation by vitamin D receptor

## TL;DR

This study shows how vitamin D deficiency alters protein patterns in fat tissue, affecting metabolism and disease risk.

## Contribution

The first comprehensive proteomic and succinylomic profile of VDRKO adipose tissue is presented.

## Key findings

- VDR deletion reprograms adipose tissue molecular landscape with 572 differentially expressed proteins.
- Succinylome analysis reveals extensive modifications in energy metabolism pathways beyond mitochondria.
- Collagen proteins are key downregulated regulators in VDRKO mice.

## Abstract

Little is known regarding the expression patterns of adipose tissue proteins in the context of vitamin D deficiency and whether these expression patterns have adverse effects on fat-related diseases.

This study compares vitamin D receptor-knockout (VDRKO) and wild-type (WT) mice to determine whether the VDRKO affects the adipose tissue landscape. High-throughput proteomic technology and parallel reaction monitoring-based targeted proteomics were utilized to determine and verify protein level changes.

Integrated proteomic and succinylomic analyses revealed that VDR deletion profoundly reprograms the adipose tissue molecular landscape. We identified 572 differentially expressed proteins and 313 differentially succinylated proteins. In VDRKO mice, protein levels involved in biological regulation, metabolic processes, ribosome, and endoplasmic reticulum protein processing pathways were upregulated. Conversely, proteins serving as negative regulators were enriched in pathways such as complement and coagulation cascades and protein digestion and absorption. Notably, ribosomal proteins (e.g., pancreatic alpha-amylase: Amy2 and proliferation-associated protein 2G4:Pa2g4) were significantly upregulated, while collagen proteins (e.g., Col24a1, Col6a4) were identified as key downregulated regulators in the protein digestion and absorption pathway. Succinylome analysis further indicated extensive succinylation modifications on proteins associated with energy metabolism pathways, including alanine, aspartate and glutamate metabolism, and arginine biosynthesis. These modifications were prominent not only in mitochondria but also in the cytoplasm, suggesting a broad regulatory role for succinylation beyond mitochondrial metabolism in the VDR-deficient state.

This integrated multi-omics study provides the first comprehensive proteomic and succinylomic profile of VDRKO adipose tissue, revealing succinylation as a novel regulatory layer in energy metabolism. Our findings advance the understanding of vitamin D signaling in adipose biology and highlight potential therapeutic targets for metabolic disorders.

Graphical abstract illustrating a workflow beginning with mouse white adipose tissue protein extraction, tryptic digestion, TMT labeling, HPLC fractionation, LC-MS/MS analysis, bioinformatics using Cytoscape, followed by targeted proteomics quantification and summary of key biological processes analyzed.