# Cellular mechanisms for increased gluconeogenesis in type 2 diabetes mellitus: the role of lipid induced pyruvate carboxylase acetylation in increasing hepatic gluconeogenic capacity.

> **NIH VA I01** · VA CONNECTICUT HEALTHCARE SYSTEM · 2020 · —

## Abstract

Type 2 diabetes (T2D) affects 1 in 6 veterans and is the leading cause of blindness, renal failure and
non-traumatic loss of limb. Increased hepatic gluconeogenesis is the main cause of fasting
hyperglycemia and contributes to postprandial hyperglycemia. Many attribute the increase in
gluconeogenesis to increased transcription of phosphoenolpyruvate carboxykinase and glucose 6-
phosphate. However, previous studies by this lab demonstrated that hyperglycemia develops in
humans with T2D and rodents with hyperglycemia without increases in PEPCK mRNA or protein
expression. Knockdown of PEPCK does not affect fasting glucose concentration or rates of glucose
production. In short, PEPCK expression does not appreciably impact hepatic gluconeogenesis. In
searching for alternate explanations accounting for the increases in gluconeogenesis, hepatic pyruvate
carboxylase (PC) protein was observed to closely relate with HbA1c in humans (R=0.80, P<0.01).
Hepatic PC protein content is also increased in chronically fat-fed rodents. Similar increases in PC
protein expression are seen with prolonged fasting and ketogenic diets, conditions with increased β-
oxidation. These changes occurred without changes in PC mRNA. Moreover, decreasing PC
expression in a variety of rodent models demonstrated that PC expression, unlike PEPCK expression,
regulates glucose production. Decreasing PC expression also improved multiple metabolic insults
associated with overfeeding, including weight gain, hepatic steatosis, insulin resistance and
hyperlipidemia. Preliminary data suggest that this increase in PC protein content is associated with an
increase in lysine acetylation of PC with a reciprocal decrease in PC ubiquitination. The overarching
hypothesis for these studies is that increased acetyl CoA promotes lysine acetylation of PC which
decreases ubiquitination of PC leading to an increase in protein content and increases the
gluconeogenic capacity of the liver. The studies described in this proposal will explore the underlying
mechanisms for, and metabolic impact of, increased hepatic PC protein. The studies in Aim 1 will
establish the mechanism of lysine acetylation of PC. Specifically, whether fatty acids are the source of
the acetyl group attached to PC and whether increasing or decreasing lipid oxidation leads to similar
changes in lysine acetylation and PC protein content using a variety of in vitro, in vivo rodent studies
where we manipulate cellular lipolysis and acetyl CoA concentrations. In Aim 2, experiments will
assess whether lysine acetylation occurs via a non-enzymatic process, identify the specific lysine sites
are acetylated with HFF, determine the impact of specific sites on protein activity and stability using
lysine mutants (using KQ mutants) and determine whether PC ubiquitination occurs within the
mitochondria and impact protein stability. Finally, in Aim 3, we will translate these findings to humans.
We will use human cell culture to establish whether lipol...

## Key facts

- **NIH application ID:** 9859297
- **Project number:** 5I01BX000901-08
- **Recipient organization:** VA CONNECTICUT HEALTHCARE SYSTEM
- **Principal Investigator:** VARMAN T SAMUEL
- **Activity code:** I01 (R01, R21, SBIR, etc.)
- **Funding institute:** VA
- **Fiscal year:** 2020
- **Award amount:** —
- **Award type:** 5
- **Project period:** 2011-10-01 → 2020-12-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/9859297

## Citation

> US National Institutes of Health, RePORTER application 9859297, Cellular mechanisms for increased gluconeogenesis in type 2 diabetes mellitus: the role of lipid induced pyruvate carboxylase acetylation in increasing hepatic gluconeogenic capacity. (5I01BX000901-08). Retrieved via AI Analytics 2026-05-26 from https://api.ai-analytics.org/grant/nih/9859297. Licensed CC0.

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