# Molecular regulation of gut lipid metabolism by mTOR and autophagy proteins

> **NIH NIH R01** · ALBERT EINSTEIN COLLEGE OF MEDICINE · 2020 · $377,625

## Abstract

Abstract
Dysregulation of absorption of dietary triglycerides (TGs) leads to adiposity or lipodystrophy, each of which can
cause insulin insensitivity. Autophagy degrades unwanted cytoplasmic contents in lysosomes to maintain
quality control. We have shown that autophagy degrades cytosolic lipid droplets (LDs) in multiple tissues via
lipophagy. Whether autophagy in gut contributes to absorption of dietary TGs remains unknown. Dietary
triglycerides (TGs) are absorbed by enterocytes as free fatty acids, which are re-esterified to TGs at the
endoplasmic reticulum (ER) membrane by distinct TG synthesizing enzymes. Nascently produced TGs enter
the ER lumen to form chylomicrons for secretion or are stored transiently as cytosolic LDs. In this application,
using cultured enterocytes and mice as models, we will investigate how interplay between the nutrient sensor
mTORC1, autophagy protein LC3, and TG synthesis enzymes regulates the fate of ingested lipid. We
hypothesize that free fatty acid availability in enterocytes activates and localizes mTOR to ER membranes
where it phosphorylates local pools of LC3. Phosphorylated (P)-LC3 is uncoupled from canonical autophagy
and serves as scaffolds that interact with TG synthesis enzymes to regulate TG biogenesis – a key step
driving chylomicron formation and secretion. We propose further that in the physiological state lipophagy
contributes to clearance of transiently-stored cytosolic LDs, thus limiting the amount of TGs available for
secretion. To test these hypotheses, we propose the following specific aims: S.A. 1: To characterize the
phosphorylations and interactome of LC3 at the ER membrane. In this aim, we will identify the phosphorylation
signature and interacting partners of LC3 at the ER membrane during lipid availability. We will determine the
contribution of mTORC1 or its down-stream target ULK1 to LC3 phosphorylation. We will use site-directed
mutagenesis to study the function of each of the identified phosphorylations towards TG synthesis in the ER,
and TG secretion from the enterocyte. We will determine which of the newly-identified LC3 interacting partners
regulate TG synthesis and secretion. S.A. 2: To dissect the interplay between mTOR, LC3, and lipophagy in
dietary lipid absorption. In S.A. 2, we will use site-directed mutagenesis in cultured Caco2 intestinal cells, and
novel mice models, to dissect the crosstalk between mTOR, LC3 and ER-localized TG synthesis enzymes in
regulation of TG synthesis and TG entry into the ER. S.A. 3: To determine the contribution of gut mTOR
signaling and lipophagy to development of metabolic syndrome during obesity. mTORC1 signaling and
autophagy are each suppressed in obesity, which per se associates with increased absorption of dietary TGs.
Consequently, we will use high fat feeding of mouse models of gain-of-function of mTOR signaling or loss-of-
function of autophagy to explore the contribution of gut-specific mTOR and autophagy to development of
metabolic sy...

## Key facts

- **NIH application ID:** 10079452
- **Project number:** 5R01DK123327-02
- **Recipient organization:** ALBERT EINSTEIN COLLEGE OF MEDICINE
- **Principal Investigator:** Rajat Singh
- **Activity code:** R01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2020
- **Award amount:** $377,625
- **Award type:** 5
- **Project period:** 2019-09-17 → 2024-08-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10079452

## Citation

> US National Institutes of Health, RePORTER application 10079452, Molecular regulation of gut lipid metabolism by mTOR and autophagy proteins (5R01DK123327-02). Retrieved via AI Analytics 2026-05-22 from https://api.ai-analytics.org/grant/nih/10079452. Licensed CC0.

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