Proceedings of The Physiological Society
University of Oxford (2011) Proc Physiol Soc 23, C52
Clock gene expression in offspring skeletal muscles in a mouse model of developmental origins of the metabolic syndrome
N. R. Patel1, K. D. Bruce1, M. A. Hanson1, C. D. Byrne1, F. R. Cagampang1
1. Institute of Developmental Sciences, Academic Unit of Human Development and Health, Faculty of Medicine, Southampton General Hospital (MP 887), SO16 6YD, University of Southampton, Southampton, United Kingdom.
The metabolic syndrome represents a cluster of cardio-metabolic risk factors (1,2). It is suggested that this syndrome in adulthood has its origins in early development, where maternal obesity during pregnancy can confer increased susceptibility in the adult offspring (3,4). Most physiological processes follow a period of around 24h (termed 'circadian'), and are regulated by endogenous timing system involving a set of 'clock' genes. Disrupting the circadian clock system leads to dysfunction of metabolic processes and the development of the metabolic syndrome (5). However, it is unknown whether high fat (HF) nutrition during early and late development can affect the clock system in the adult skeletal muscles. Therefore, we examined day-night expression of clock and clock-controlled genes in this key metabolic tissue. Female C57/BL6J mice were fed either a HF (45% kcal fat) or control chow (C, 21% kcal fat) diet prior to and during pregnancy and lactation. Weaned offspring were fed the HF or C diet, generating the dam-offspring dietary groups: C/C, C/HF, HF/C, HF/HF. Skeletal muscle tissue from 15-week old male offspring were taken 8h into the light and dark periods of a 12h light-12h dark lighting schedule (n=5-6 per time point per treatment group), and gene transcript levels for the clock genes, BMAL1, CLOCK and PER2, and clock-controlled genes, Rev-Erbβ, IRS1 and SIRT1, were determined using quantitative real-time PCR. BMAL1 expression was between 2.5 to 6.5 fold higher (p<0.05, t-test analysis) at night in the C/HF, HF/HF and C/C groups, respectively. This pattern was lost in HF/C offspring. CLOCK expression was 1.6 fold higher (p<0.05) at night in HF/HF, but this pattern was lost in the other offspring groups. In contrast, PER2 was 2.6 to 2.4 fold lower (p<0.05) at night in C/C and HF/HF, respectively, but this pattern was lost in C/HF and HF/C. Rev-Erbβ was 2.1 fold and 1.8 fold lower (p<0.05) at night in C/C and HF/HF, respectively, but again no day-night changes were observed in C/HF and HF/C. ANOVA followed by post-hoc analysis showed that overall expression of BMAL1 was higher (p<0.05) in HF/HF vs. C/C, while PER2 was lower (p<0.05) in C/HF and HF/C vs. C/C. SIRT1 was lower (p<0.05) in C/HF, HF/C and HF/HF vs. C/C. IRS1 was higher (p<0.05) in HF/HF vs. C/C. Overall expression of CLOCK was similar in all treatment groups. The results suggest that maternal dietary fat intake alters day-night expression patterns of most of the clock and clock-controlled genes in offspring skeletal muscles, whilst extended HF exposure to adulthood alters overall expression level of most of these genes. Such changes could alter downstream metabolic processes, increasing susceptibility to the metabolic syndrome in adulthood.
Where applicable, experiments conform with Society ethical requirements