Date of Award

1-2009

Degree Name

MS in Agriculture - Food Science and Nutrition

Department

Food Science and Nutrition

Advisor

Scott Reaves

Abstract

Loss of muscle due to aging is often associated with significant detrimental effects. Therefore, it is crucial to understand signaling molecules that may trigger the muscle loss or prevent the process. The transcription factor, Nuclear Factor Kappa-B (NF-κB), is associated with both catabolic and anabolic pathways of muscle metabolism and may be involved in age-related muscle loss. Leucine is an essential amino acid that is required for both protein synthesis and intracellular signaling pathways that regulate protein synthesis and degradation. The current study examined muscle NF-kB levels in male Sprague-Dawley rats, aged 6 (adult) and 21 months (old) fed a diet containing suboptimal leucine levels for 10-17 days. We found that old rats consumed less grams of food per body weight (BW) each day than adult rats (1.45% g diet/g BW vs. 2.4% g diet/g BW). Weight loss during the study was not significantly different between age groups. However the average mass of gastrocnemius and soleus muscles (g muscle/g BW) was significantly lower in old rats. Reduction in gastrocnemius (g muscle/g BW*10²) was associated with 1.8 fold higher muscle cell NF-κB in old vs. adult rats (p = 0.0443). There was also a higher level of ubiquitinated proteins in old gastrocnemius muscle cells relative to the adult gastrocnemius, however differences did not reach statistical significance. For tibialis anterior muscle, the average mass (g muscle/g BW*10²), NF-κB levels and ubiquitinated proteins were not significantly different between adult and old rats. Our findings suggest that aging affects muscle loss and NF-kB in a tissue-specific manner in rats fed a diet with suboptimal leucine levels.

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