Date of Completion

11-19-2014

Embargo Period

11-19-2014

Keywords

sheep, maternal nutrition, muscle, somatotropic axis, transcriptome

Major Advisor

Dr. Kristen Govoni

Associate Advisor

Dr. Steven Zinn

Associate Advisor

Dr. Sarah Reed

Associate Advisor

Dr. Ji-Young Lee

Associate Advisor

Dr. Rachel O'Neill

Field of Study

Animal Science

Degree

Doctor of Philosophy

Open Access

Open Access

Abstract

Poor maternal nutrition can have long lasting detrimental effects on offspring growth and development. Specifically, these offspring will exhibit increased carcass adiposity, reduced muscularity and altered growth rates resulting in animals that are less productive and yield a less desirable product for consumers. However, the mechanisms by which poor maternal nutrition alters offspring growth and development are not well understood. We hypothesized that maternal under- and over-nutrition will alter the expression of key genes and novel pathways involved in the development of muscle and adipose tissue of lambs at two early postnatal time points. To evaluate these hypotheses, pregnant sheep were fed 100 % [control (CON)], 60 % [restricted (RES)] or 140 % [over-fed (OVER)] of National Research Council requirements based on total digestible nutrients. One lamb from each ewe was necropsied either within 24 hour of birth or 3 months of age. RNA was isolated from adipose and muscle tissue respectively and gene expression quantified using real time RT-PCR. Alternately, transcriptome analysis was performed on isolated RNA using the Ion Torrent Proton sequencer and analyzed using the Cufflinks analysis package. Gene expression of insulin-like growth factor (IGF)-I was increased in the quadriceps muscle tissue of RES lambs at 1 day of age. Expression of β-Catenin, a factor involved in WNT signaling, was greater in the quadriceps muscle tissue of RES and OVER at 1 day compared with CON (P = 0.07). At day 1, the semitendinosus muscle tissue of OVER lambs exhibited increased myostatin (MSTN;P = 0.06) and follistatin (FSTN; P = 0.04) gene expression. Expression of factors involved in the somatotropic axis, IGF-I and insulin-like growth factor binding protein (IGFBP)-3, were also altered in the semitendinosus muscle tissue of lambs born to RES and OVER ewes respectively (P ≤ 0.08). No change in the expression of factors involved in adipogenesis were observed at either time point. As determined by RNA-seq analysis performed on semitendinosus muscle tissue collected from lambs at birth, 35 differentially expressed genes were identified using the bovine reference annotation whereas mapping to the ovine reference yielded 10. The identified genes are involved in various processes including the regulation of metabolism, hypertrophy, nutrient uptake, and muscle protein turnover. In summary, poor maternal nutrition can alter muscle development through several potential mechanisms, including the somatotropic axis and wnt signaling. Additionally, these mechanisms affected by maternal nutrition vary between OVER vs CON and RES vs CON born lambs despite similar alterations to muscle phenotype. Future studies are needed to identify additional factors altered by maternal nutrition as well as determine the effects of poor maternal nutrition on epigenetic mechanisms in offspring.

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