# Secreted Phosphoprotein 1 (SPP1) Modulates Intracellular Metabolic Programs in Mature Adipocytes Revealed by Untargeted Metabolomics

## TL;DR

This study shows how different amounts of SPP1 affect metabolism in fat cells, with low doses causing more metabolic changes than high doses.

## Contribution

The study reveals SPP1's novel role in modulating intracellular metabolic programs in mature adipocytes using untargeted metabolomics.

## Key findings

- Low-dose SPP1 (100 ng/mL) caused more pronounced intracellular metabolic remodeling than high-dose SPP1 (500 ng/mL).
- Low-dose SPP1 altered carbohydrate- and amino acid-related metabolic pathways, including the pentose phosphate pathway and alanine metabolism.
- High-dose SPP1 selectively induced matrix metalloproteinase-12 (MMP-12), indicating remodeling-associated responses.

## Abstract

Secreted phosphoprotein 1 (SPP1), also known as osteopontin (OPN), is a multifunctional secreted factor implicated in inflammatory remodeling of adipose tissue. Here, we applied untargeted liquid chromatography–mass spectrometry (LC–MS)-based metabolomics to examine how different concentrations of SPP1 influence metabolism in differentiated 3T3-L1 adipocytes. We found that low-dose SPP1 (100 ng/mL) was associated with more pronounced intracellular metabolic remodeling than higher-dose SPP1 (500 ng/mL). Multivariate analyses, including principal component analysis (PCA), partial least squares–discriminant analysis (PLS-DA), and sparse PLS-DA, revealed a distinct metabolic profile in the low-dose group, whereas the high-dose group showed a comparatively attenuated metabolic response. Pathway enrichment analysis identified alterations in carbohydrate- and amino acid-related metabolic networks, including the pentose phosphate pathway; pentose and glucuronate interconversions; and alanine, aspartate, and glutamate metabolism. In contrast, higher-dose SPP1 was associated with selective induction of matrix metalloproteinase-12 (MMP-12), suggesting the engagement of remodeling-associated responses at elevated SPP1 levels. Together, these findings identify SPP1 as a modulator of metabolic programs in mature adipocytes and highlight its capacity to influence intracellular metabolic remodeling.