Proceedings of The Physiological Society
University of Oxford (2011) Proc Physiol Soc 23, PC258
Impact of in-utero and postnatal exposure to a high fat nutritional environment on clock and clock-controlled genes in murine hearts.
A. J. Stokes1, 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, University of Southampton, Southampton General Hospital (MP 887), Southampton, United Kingdom.
The prevalence of the metabolic syndrome, which represents a cluster of cardio-metabolic risk factors, is increasing at an alarming rate. It has previously been shown that suboptimal in-utero and postnatal nutritional environments can increase the offspring’s susceptibility to the metabolic syndrome in adulthood (1-3). Emerging evidence demonstrates the role of the circadian clock system in the pathogenesis of the metabolic syndrome (3). In this study, we examined whether in-utero and postnatal exposure to high fat nutritional environment can alter the expression pattern of clock and clock-controlled genes in the adult offspring heart. Female C57/BL6J mice were fed either a high fat (HF, 45% kcal fat) or control chow (C, 21% kcal fat) diet pre-conception and throughout 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. Whole hearts were taken from 15-week old male offspring killed at 6 time points over a 24h light-dark period (n=5-6 per time point per treatment group). Initially, we examined the effect of our experimental treatments on the stability in expression of housekeeping genes (HKGs) in the offspring heart, to determine those suitable for use as reference when analysing genes of interest. We then determined gene transcript levels for the clock genes, CLOCK and PER2, and clock-controlled genes, PAI-1 and SIRT1, using quantitative real-time PCR. The stability in expression of the HKGs (analysed using the geNorm qBasePLUS software) in the adult offspring heart was affected by pre- and post-natal exposure to HF, as well as the time of sampling over the 24h period. We found that the most stable HKG were β-actin and YWHAZ. Expression levels for CLOCK was found to be 1.5 (p<0.001) and 1.4 fold higher in HF/C and HF/HF groups, respectively, vs. C/C (analysed by ANOVA). PAI-1 levels were 2.3 fold higher (p<0.001) in HF/HF vs. C/C, and for PER2 this was 1.6 fold higher (p<0.05) in HF/C vs. C/C. No differences in expression levels were observed for SIRT1 between treatment groups. Cosinor analysis showed that pre- and post-natal exposure to HF diet resulted in phase shifting in peak expression of CLOCK, PER2 and PAI-1 genes. SIRT1 also showed a phase shift in peak expression but only in the C/HF group, suggesting that prenatal HF exposure may prevent the phase shift brought about by post-weaning HF feeding. The results suggest that rhythmic expression of clock and clock-controlled genes can be disrupted following early life exposure to maternal HF nutrition, and could be further modified by post-natal HF feeding. These changes may have deleterious effects on cardiovascular function, increasing cardiovascular risk associated with the metabolic syndrome in adulthood.
Where applicable, experiments conform with Society ethical requirements