The Effect of Glucagon on Rates of Hepatic Mitochondrial Oxidation in Man Assessed by PINTA

The Effect of Glucagon on Rates of Hepatic Mitochondrial Oxidation and Pyruvate Carboxylase Flux in Man Assessed by Positional Isotopomer NMR Tracer Analysis (PINTA)

It is well established that alterations in the portal vein insulin:glucagon ratio play a major role in the dysregulated hepatic glucose metabolism in type 2 diabetes but the molecular mechanism by which glucagon promotes alterations in hepatic glucose production and mitochondrial oxidation remain poorly understood. This is borne out of the fact that both glucagon agonists and antagonists are being developed to treat type 2 diabetes with unclear mechanisms of action.

This study will directly assess rates of mitochondrial oxidation and pyruvate carboxylase flux for the first time in humans using PINTA analysis as well as the effects of glucagon. The results will have important implications for the possibility of intervening in the pathogenesis of non alcoholic fatty liver and type 2 diabetes via chronic dual GLP-1/glucagon receptor antagonism and provide an important rationale for why a dual agonist may be more efficacious for treatment of non alcoholic fatty liver and T2D than GLP-1 alone.

Study Overview

• Status: Completed
• Conditions: Healthy Participants
• Intervention / Treatment: Biological: Glucagon; Other: Control Study

Detailed Description

Objectives:

To examine rates of hepatic mitochondrial oxidation in healthy volunteers with liver lipid less than 2%.

To examine the effects of glucagon on hepatic glucose and fat metabolism in vivo, this study will apply a novel Positional Isotopomer NMR Tracer Analysis (PINTA) method to quantify rates of hepatic mitochondrial oxidation and pyruvate carboxylase flux, which has been cross-validated in awake rodents and humans (Perry et al. Nature Communications 2017). Preliminary rodent studies have found that glucagon stimulates intrahepatic lipolysis through an InsP3R-I-dependent process, leading to increases in hepatic acetyl-CoA content, which allosterically activates pyruvate carboxylase activity and flux, and that this phenomenon explains its acute, transcription-independent effect to acutely stimulate hepatic gluconeogenesis in vivo (unpublished results). In addition, using PINTA analysis it has been shown that glucagon stimulates hepatic mitochondrial oxidation through calcium signaling in awake mice, and that this process can be exploited by short-term continuous glucagon treatment leading to two-fold increases in hepatic mitochondrial fat oxidation, which in turn results in large reductions in hepatic steatosis and marked improvements in glucose tolerance through reversal of hepatic insulin resistance in a high fat fed rat model of non alcoholic fatty liver.

Hypothesis:

1. A physiological increase in plasma glucagon concentrations will promote a significant increase in rates of hepatic mitochondrial oxidation in healthy humans.

3. A physiological increase in plasma glucagon concentrations will promote a significant increase in rates of hepatic pyruvate carboxylase flux in healthy humans.

4. A physiological increase in plasma glucagon concentrations will promote a significant increase in rates of 13C4 β-hydroxybutyrate turnover (hepatic ketogenesis) in healthy humans.

Study Design - Clinical Plan:

The effects of a physiological increase in plasma glucagon on rates of hepatic mitochondrial oxidation and pyruvate carboxylase flux will be examined in a group of up to 12 healthy participants (ages 21-65) using Positional Isotopomer NMR Tracer Analysis (PINTA) (Perry et al. Nature Communication 2017). Briefly rates of hepatic mitochondrial oxidation and hepatic pyruvate carboxylase flux will be assessed in 12 healthy overnight fasted participants by PINTA after a three-hour infusion of glucagon or saline. The glucagon infusion will be designed to increase peripheral and portal vein plasma glucagon concentrations 3-4 fold. The effects of a physiological increase in plasma glucagon on rates of hepatic ketogenesis will also be assessed using an infusion of 13C4 β-betahydroxybutyrate (Perry et al. Cell Metabolism 2017).

Rates of hepatic pyruvate carboxylase flux /citrate synthase flux by PINTA: Participants (n=12) will be studied by PINTA under 2 conditions: 1) following an overnight fast and a 3 hour saline infusion (Control), 2) following an overnight fast and a 3 hour glucagon infusion. Briefly, after collection of baseline blood samples a 3 hour infusion of tracers as described below will be started. Relative rates of pyruvate carboxylase to citrate synthesis flux will be assessed using a constant infusion of [3-13C] lactate and rates of glucose production will be measured using an infusion of [2H7]glucose (Perry et al. Nature Communication 2017). Rates of hepatic ketogenesis will be measured using a constant infusion of [3C β-hydroxybutyrate as previously described (Perry et al. Cell Metabolism 2017).

Whole body energy expenditure and the respiratory quotient will be assessed by indirect calorimetry.

• Study Type: Interventional
• Enrollment (Actual): 10
• Phase: Phase 1

Contacts and Locations

Study Locations

• United States
  • Connecticut
    • New Haven, Connecticut, United States, 06520
      • Yale Hospital reserach Unit / YCCI

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: 21 years to 75 years (Adult, Older Adult)
• Accepts Healthy Volunteers: Yes

Description

Inclusion Criteria:

• Healthy
• Non smoking
• Taking no medications except birth control

Exclusion Criteria:

• Any systemic or organ disease
• Smoking
• Taking any drug or medications other than birth control (women)

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Basic Science
• Allocation: Randomized
• Interventional Model: Crossover Assignment
• Masking: None (Open Label)

Number of Arms

2

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Experimental: Glucagon; Participants will receive glucagon during the PINTA study	Biological: Glucagon; PINTA study with glucagon; Other Names: hormone study
Experimental: Control; The same participants will not receive glucagon during the PINTA study	Other: Control Study; The same participants will not receive glucagon during the PINTA study; Other Names: No glucagon

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Rates of Hepatic Mitochondrial Oxidation	Rates of pyruvate carboxylase flux and citrate synthesis flux will be assessed using GC/MS and NMR analyses of plasma glucose 13C enrichments after the [3-13C]lactate infusion	5 hours

Collaborators and Investigators

• Sponsor: Yale University
• Collaborators: Merck Sharp & Dohme LLC
• Investigators: Principal Investigator: Kitt F Petersen, MD, Professor

Study record dates

Study Major Dates

• Study Start (Actual): June 5, 2019
• Primary Completion (Actual): July 7, 2022
• Study Completion (Actual): July 6, 2023

Study Registration Dates

• First Submitted: May 23, 2019
• First Submitted That Met QC Criteria: May 24, 2019
• First Posted (Actual): May 28, 2019

Study Record Updates

• Last Update Posted (Estimated): November 26, 2024
• Last Update Submitted That Met QC Criteria: November 18, 2024
• Last Verified: November 1, 2024

More Information

Terms related to this study

• Keywords: Glucagon; Hepatic Glucose Metabolism; Hepatic Mitochondrial Oxidation; PINTA
• Additional Relevant MeSH Terms: Infections; Skin Diseases; Bacterial Infections; Bacterial Infections and Mycoses; Gram-Negative Bacterial Infections; Spirochaetales Infections; Skin Diseases, Bacterial; Skin Diseases, Infectious; Treponemal Infections; Pinta; Physiological Effects of Drugs; Gastrointestinal Agents; Hormones; Hormones, Hormone Substitutes, and Hormone Antagonists; Incretins; Glucagon; Glucagon-Like Peptide 1
• Other Study ID Numbers: 0209020997_a; MISP58340 (Other Grant/Funding Number: Merck)

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: NO
• IPD Plan Description: Final data to be shared with study sponsor

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: Yes
• Studies a U.S. FDA-regulated device product: No
• product manufactured in and exported from the U.S.: No