Relative Contribution of Intramyocellular Lipid to Whole-Body Fat Oxidation Is Reduced With Age but Subsarcolemmal Lipid Accumulation and Insulin Resistance Are Only Associated With Overweight Individuals

Chee, Carolyn; Shannon, Chris E.; Burns, Aisling; Selby, Anna L.; Wilkinson, Daniel; Smith, Kenneth; Greenhaff, Paul L.; Stephens, Francis B.

Abstract

© 2016 by the American Diabetes Association. Insulin resistance is closely related to intramyocellular lipid (IMCL) accumulation, and both are associated with increasing age. It remains to be determined to what extent perturbations in IMCL metabolism are related to the aging process per se. On two separate occasions, whole-body and muscle insulin sensitivity (euglycemic-hyperinsulinemic clamp with 2-deoxyglucose) and fat utilization during 1 h of exercise at 50% VO2max ([U-13C]palmitate infusion combined with electron microscopy of IMCL) were determined in young lean (YL), old lean (OL), and old overweight (OO) males. OL displayed IMCL content and insulin sensitivity comparable with those in YL, whereas OO were markedly insulin resistant and had more than twofold greater IMCL in the subsarcolemmal (SSL) region. Indeed, whereas the plasma free fatty acid Ra and Rd were twice those of YL in both OL and OO, SSL area only increased during exercise in OO. Thus, skeletal muscle insulin resistance and lipid accumulation often observed in older individuals are likely due to lifestyle factors rather than inherent aging of skeletal muscle as usually reported. However, age per se appears to cause exacerbated adipose tissue lipolysis, suggesting that strategies to reduce muscle lipid delivery and improve adipose tissue function may be warranted in older overweight individuals.

Citation

Chee, C., Shannon, C. E., Burns, A., Selby, A. L., Wilkinson, D., Smith, K., Greenhaff, P. L., & Stephens, F. B. (2016). Relative Contribution of Intramyocellular Lipid to Whole-Body Fat Oxidation Is Reduced With Age but Subsarcolemmal Lipid Accumulation and Insulin Resistance Are Only Associated With Overweight Individuals. Diabetes, 65(4), 840-850. https://doi.org/10.2337/db15-1383

• Journal Article Type: Article
• Acceptance Date: Dec 28, 2015
• Online Publication Date: Jan 6, 2016
• Publication Date: Apr 1, 2016
• Deposit Date: Jul 18, 2016
• Publicly Available Date: Jul 18, 2016
• Journal: Diabetes
• Print ISSN: 0012-1797
• Electronic ISSN: 1939-327X
• Publisher: American Diabetes Association
• Peer Reviewed: Peer Reviewed
• Volume: 65
• Issue: 4
• Pages: 840-850
• DOI: https://doi.org/10.2337/db15-1383
• Public URL: https://nottingham-repository.worktribe.com/output/977268
• Publisher URL: https://diabetes.diabetesjournals.org/content/65/4/840
• Additional Information: This is an author-created, uncopyedited electronic version of an article accepted for publication in Diabetes. The American Diabetes Association (ADA), publisher of Diabetes, is not responsible for any errors or omissions in this version of the manuscript or any version derived from it by third parties. The definitive publisher-authenticated version will be available in a future issue of Diabetes in print and online at http://diabetes.diabetesjournals.org.
• Contract Date: Jul 18, 2016