Skeletal Muscle Diacylglycerol and Sphingolipids - Impact of Localization and Species on Insulin Resistance in Humans

The rationale for the proposed research is that elucidating changes in localized diacylglycerol (DAG) and sphingolipid species that predict insulin sensitivity will reveal specific localized lipids to target in therapeutics for type 2 diabetes. To attain the overall objective, the investigators propose three specific aims: 1. Identify the influence of sarcolemmal DAG and sphingolipids on cell signaling and insulin sensitivity before and after insulin sensitizing lifestyle interventions. Strong preliminary data shape the hypothesis that sarcolemmal 1,2-disaturated DAG and C18:0 ceramide species will decrease after insulin sensitizing lifestyle interventions, leading to less Protein kinase C (PKC) and Protein phosphatase 2A (PP2A) activation, and enhanced insulin signaling. Skeletal muscle DAG and sphingolipid isomers, species, localization, and de novo synthesis will be measured before and after diet-induced weight loss or exercise training interventions in obese men and women. Insulin sensitivity will be measured using insulin clamps, and muscle lipids using Liquid Chromatography Mass Spectrometry (LC/MS). 2. Determine the impact of mitochondrial/ER (endoplasmic reticulum) DAG and sphingolipids on mitochondrial function and ER stress in vivo, before and after insulin sensitizing lifestyle interventions. The investigators hypothesize, again based on preliminary data, that mitochondrial/ER sphingolipids will decrease, yet DAG will increase after insulin sensitizing lifestyle interventions, and each will associate with increased insulin sensitivity. Changes in sphingolipids will relate to increased mitochondrial function, less ER stress, reactive oxygen species (ROS), and acyl-carnitine formation, while changes in DAG will relate to increased mitochondrial content and dynamics. 3. Identify the effect of exogenous DAG and sphingolipids on mitochondrial function in vitro, before and after insulin sensitizing lifestyle interventions. The working hypothesis is that DAG and sphingolipids will reduce mitochondrial respiration and increase ROS and acyl-carnitine content, but will be attenuated after endurance exercise training. The proposed research is innovative because it represents a substantive departure from the status quo by addressing cellular compartmentalization of bioactive lipids. The investigators contribution will be significant by identifying key species and locations of DAG and sphingolipids promoting insulin resistance, as well as mechanisms explaining accumulation that could be modified by insulin sensitizing therapeutic interventions.

Study Overview

• Status: Completed
• Conditions: Obesity; Diabetes Mellitus, Type 2; Pre-diabetes
• Intervention / Treatment: Behavioral: Lifestyle

Detailed Description

Accumulation of bioactive lipids such as diacylglycerol (DAG) and sphingolipids are one mechanism proposed to promote muscle insulin resistance. Recent data indicate these lipids are located in membranes, but the distribution and signaling of DAG and sphingolipids in specific cellular organelles which regulate insulin sensitivity is not known. There is a critical need to address these gaps in knowledge to design appropriate interventions to prevent and treat lipid-induced insulin resistance. The overall objective of this project is to determine the impact of changes in subcellular DAG and sphingolipid species, signaling, and metabolic function before and after insulin sensitizing lifestyle interventions. The investigators central hypothesis is that DAG and sphingolipids in muscle promote insulin resistance via mechanisms that are unique to location, type of lipid, and species. The rationale for the proposed research is that elucidating changes in localized DAG and sphingolipid species that predict insulin sensitivity will reveal specific localized lipids to target in therapeutics for type 2 diabetes. To attain the overall objective, the investigators propose three specific aims: 1. Identify the influence of sarcolemmal DAG and sphingolipids on cell signaling and insulin sensitivity before and after insulin sensitizing lifestyle interventions. Strong preliminary data shape the hypothesis that sarcolemmal 1,2-disaturated DAG and C18:0 ceramide species will decrease after insulin sensitizing lifestyle interventions, leading to less Protein kinase C (PKC) and Protein phosphatase 2A (PP2A) activation, and enhanced insulin signaling. Skeletal muscle DAG and sphingolipid isomers, species, localization, and de novo synthesis will be measured before and after diet-induced weight loss or exercise training interventions in obese men and women. Insulin sensitivity will be measured using insulin clamps, and muscle lipids using Liquid Chromatography Mass Spectrometry (LC/MS). 2. Determine the impact of mitochondrial/ER (endoplasmic reticulum) DAG and sphingolipids on mitochondrial function and ER stress in vivo, before and after insulin sensitizing lifestyle interventions. The investigators hypothesize, again based on preliminary data, that mitochondrial/ER sphingolipids will decrease, yet DAG will increase after insulin sensitizing lifestyle interventions, and each will associate with increased insulin sensitivity. Changes in sphingolipids will relate to increased mitochondrial function, less ER stress, reactive oxygen species (ROS), and acyl-carnitine formation, while changes in DAG will relate to increased mitochondrial content and dynamics. 3. Identify the effect of exogenous DAG and sphingolipids on mitochondrial function in vitro, before and after insulin sensitizing lifestyle interventions. The working hypothesis is that DAG and sphingolipids will reduce mitochondrial respiration and increase ROS and acyl-carnitine content, but will be attenuated after endurance exercise training. The proposed research is innovative because it represents a substantive departure from the status quo by addressing cellular compartmentalization of bioactive lipids. The investigators contribution will be significant by identifying key species and locations of DAG and sphingolipids promoting insulin resistance, as well as mechanisms explaining accumulation that could be modified by insulin sensitizing therapeutic interventions.

• Study Type: Interventional
• Enrollment (Actual): 62
• Phase: Not Applicable

Contacts and Locations

Study Locations

• United States
  • Colorado
    • Aurora, Colorado, United States, 80045
      • University of Colorado

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: 30 years to 50 years (Adult)
• Accepts Healthy Volunteers: No
• Genders Eligible for Study: All

Description

Inclusion Criteria:

• BMI: 30-40 kg/m2
• Planned physical activity: <2 hrs/week

• Glucose tolerance:

  1. Normal glucose tolerance (NGT) defined as:

     1. HbA1c of <5.7%,
     2. pre-diabetes as HbA1c of 5.7-6.4%, and
     3. type 2 diabetes as HbA1c of ≥6.5%
  2. pre-diabetes, and
  3. Type 2 diabetes
• Oral contraceptive use: Yes or No as long as there is no change during the study
• Thyroid status: TSH between 0.5-5.0 mU/L

Exclusion Criteria:

• Currently taking

  1. Thiazolidinediones
  2. Insulin
• Pregnant
• Smoker (tobacco and any form of marijuana use)
• Fasting triglycerides >400mg/dl

Study Plan

How is the study designed?

Design Details

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

Number of Arms

3

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Experimental: Weight loss only	Behavioral: Lifestyle; Lifestyle changes to lose weight or become more fit
Experimental: Exercise Only	Behavioral: Lifestyle; Lifestyle changes to lose weight or become more fit
No Intervention: Delayed Intervention Control

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Percent Change in Insulin Sensitivity Compared to Baseline Measurement.	Hyperinsulinemic/euglycemic clamp measured as glucose infusion rate in mg/kg/min.	Baseline and 12 weeks
Percent Change in Localized Muscle Lipids Compared to Baseline	We measured changes in sarcolemmal, mitochondrial, nuclear and cytosolic lipids measured in pmol/ug protein after compared to before the interventions	Baseline and 12 weeks
Percent Change in Body Weight Compared to Baseline Measurement	This is the percent change in body weight for each group after the 12 week intervention.	Baseline, 3 Months

Collaborators and Investigators

• Sponsor: University of Colorado, Denver
• Collaborators: National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)
• Investigators: Principal Investigator: Bryan Bergman, University of Colorado, Denver

Study record dates

Study Major Dates

• Study Start (Actual): February 1, 2017
• Primary Completion (Actual): November 19, 2020
• Study Completion (Actual): November 19, 2020

Study Registration Dates

• First Submitted: March 1, 2017
• First Submitted That Met QC Criteria: March 6, 2017
• First Posted (Actual): March 10, 2017

Study Record Updates

• Last Update Posted (Actual): June 21, 2022
• Last Update Submitted That Met QC Criteria: May 24, 2022
• Last Verified: May 1, 2022

More Information

Terms related to this study

• Additional Relevant MeSH Terms: Glucose Metabolism Disorders; Metabolic Diseases; Endocrine System Diseases; Hyperinsulinism; Diabetes Mellitus; Diabetes Mellitus, Type 2; Prediabetic State; Insulin Resistance
• Other Study ID Numbers: 16-1404; 5R01DK111559 (U.S. NIH Grant/Contract)

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: No

Drug and device information, study documents

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