HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Google Scholar Articles by Chevalier, S. Articles by Morais, J. A. Articles citing this Article PubMed PubMed Citation Articles by Chevalier, S. Articles by Morais, J. A.

Influence of Adiposity in the Blunted Whole-Body Protein Anabolic Response to Insulin With Aging

McGill Nutrition and Food Science Centre, McGill University Health Centre-Royal Victoria Hospital, Montreal, Quebec, Canada.

Address correspondence to José A. Morais, MD, McGill Nutrition and Food Science Centre, MUHC-Royal Victoria Hospital, 687 Pine Ave West, Montreal, Quebec, Canada H3A 1A1. E-mail: jose.morais{at}muhc.mcgill.ca

Background. Although insulin resistance of glucose is often reported with aging, that of protein metabolism is still debated. We tested if the insulin sensitivity of protein metabolism parallels that of glucose and is altered with aging.

Methods. Whole-body ¹³C-leucine and ³H-glucose kinetics were measured in the postabsorptive state and during an hyperinsulinemic, euglycemic, isoaminoacidemic clamp in 12 young men (age: 27 ± 1 years; body mass index [BMI]: 23 ± 1 kg/m²), 11 young women (age: 25 ± 1 years; BMI: 21 ± 1 kg/m²), 9 elderly men (age: 70 ± 1 years; BMI: 26 ± 1 kg/m²), and 10 elderly women (age: 69 ± 2 years; BMI: 23 ± 1 kg/m²).

Results. Postabsorptive leucine flux rates adjusted for fat-free mass (FFM) were not different between elderly and young participants. During the clamp, leucine flux and protein synthesis rates increased less in the elderly participants, and protein breakdown decreased equally. Thus, the net anabolic (protein balance) response to hyperinsulinemia was lower in elderly versus young participants (p =.007) and was highly correlated with the clamp glucose rate of disposal (r = 0.671, p <.001), indicating insulin resistance of protein concurrent with that of glucose. From regression analysis, FFM explained 73% of the variance in the anabolic response. Age explained an additional 3%, but was accounted for by markers of adiposity. FFM and percent body fat collectively explained 79% of the variance.

Conclusion. Both reduction in absolute FFM and increased adiposity, intrinsic to the aging process, are associated with an altered anabolic action of insulin in stimulating protein synthesis. This alteration may contribute to the progressive muscle loss with aging.