Influence of myogenic regulatory factors on muscle mass of obese zucker rats

Abstract

Skeletal muscle mass of the obese zucker rat (OZR) is reduced compared to the lean zucker rat (LZR). Myogenic regulatory factors (MRFs) are DNA-binding proteins, which increase the transcription of muscle specific genes (MyoD and Myogenin), or decrease the transcription of muscle specific genes (Myostatin). The purpose of this study was to determine if lower levels of MRF expression in muscles of the OZR compared to the LZR may contribute to the decrease in skeletal muscle mass in the OZR. The medial gastrocnemius muscles of 7 OZR and 7 LZR (20–22 weeks old) were collected. Total RNA was reversed transcribed and then amplified by PCR. PCR reactions were co-amplified and normalized with 18S. The medial gastrocnemius was 19% smaller in the OZR compared to LZR (33.92 ± 1.81 vs. 42.14 ± 2.33 g/mm tibial length). Myostatin mRNA was unchanged in the OZR compared to LRZ. MyoD mRNA was reduced 25% in the OZR and myogenin mRNA was reduced 15% in the OZR compared to the lean (p < 0.05). The data are consistent with the hypothesis that decreased mRNA of MyoD and myogenin genes in muscles of the OZR may contribute to decreased levels of muscle specific transcription, which results in decreases in muscle mass in the OZR compared to the LZR. Supported by NIH AG021530.