Intramyocellular Lipid Droplet Size Rather Than Total Lipid Content is Related to Insulin Sensitivity After 8 Weeks of Overfeeding.
Study Goal
The researchers aimed to examine the effects of overfeeding a high-fat diet on intramyocellular lipid (IMCL) accumulation and its relationship with insulin sensitivity.
Results Summary
Overfeeding for 8 weeks did not increase overall IMCL but altered lipid droplet size and location, with larger droplets correlating inversely with glucose disposal rate. Smaller, peripherally located lipid droplets were associated with better lipid oxidation and resistance to weight gain.
Population
29 males
Effective Dosage
140% caloric intake (44% from fat)
Duration
8 weeks
Interactions
None mentioned
| Intervention | Direction | Endpoint | Population | Dosage | Impact | Claim # |
|---|---|---|---|---|---|---|
overfeeding a high-fat diet (140% caloric intake, 44% from fat) for 8 weeks | no change | overall intramyocellular lipid (IMCL) | twenty-nine males | - | did not increase | #1 |
overfeeding a high-fat diet (140% caloric intake, 44% from fat) for 8 weeks | decrease | content of smaller lipid droplets peripherally located in the myofiber | twenty-nine males | - | decreased | #2 |
overfeeding a high-fat diet (140% caloric intake, 44% from fat) for 8 weeks | decrease | glucose disposal rate | twenty-nine males | - | increases in larger droplets correlated inversely with | #3 |
overfeeding a high-fat diet (140% caloric intake, 44% from fat) for 8 weeks | decrease | Akt activity | twenty-nine males | - | resulted in inhibition of | #4 |
overfeeding a high-fat diet (140% caloric intake, 44% from fat) for 8 weeks | increase | ceramide content | twenty-nine males | - | drastic increases in | #5 |
- | increase | more efficient lipid oxidation | - | - | were associated with | #6 |
overfeeding a high-fat diet (140% caloric intake, 44% from fat) for 8 weeks | decrease | weight gain | participants who maintained a greater number of smaller, peripherally located lipid droplets | - | displayed a better resistance to | #7 |
OBJECTIVE: Intramyocellular lipid (IMCL) is inversely related to insulin sensitivity in sedentary populations, yet no prospective studies in humans have examined IMCL accumulation with overfeeding. METHODS: Twenty-nine males were overfed a high-fat diet (140% caloric intake, 44% from fat) for 8 weeks. Measures of IMCL, whole-body fat oxidation from a 24-hour metabolic chamber, muscle protein extracts, and muscle ceramide measures were obtained before and after the intervention. RESULTS: Eight weeks of overfeeding did not increase overall IMCL. The content of smaller lipid droplets peripherally located in the myofiber decreased, while increases in larger droplets correlated inversely with glucose disposal rate. Overfeeding resulted in inhibition of Akt activity, which correlated with the reductions in smaller, peripherally located lipid droplets and drastic increases in ceramide content. Additionally, peripherally located lipid droplets were associated with more efficient lipid oxidation. Finally, participants who maintained a greater number of smaller, peripherally located lipid droplets displayed a better resistance to weight gain with overfeeding. CONCLUSIONS: These results show that lipid droplet size and location rather than mere IMCL content are important to understanding insulin sensitivity.