Abstract
Dysregulated skeletal muscle metabolism (DSMM) is associated with increased inter- and intramuscular fat deposition in low birth weight (L) individuals. The mechanisms behind DSMM in L individuals are not completely understood but decreased muscle mass and shifts in lipid and carbohydrate utilisation may contribute. Previously, we observed lower fat oxidation in a porcine model of low birth weight. To elucidate the biological activities underpinning this difference microfluidic arrays were used to assess mRNA associated with lipid metabolism in longissimus dorsi (LD) and semitendinosus (ST) skeletal muscle samples from thirty-six female L and normal birth weight (N) pigs. Plasma samples were collected from a sub-population to measure metabolite concentrations. Following overnight fasting, skeletal muscle and plasma samples were collected and the association with birth weight, diet and age was assessed. Reduced dietary fat was associated with decreased LD intermuscular fat deposition and beta-oxidation associated mRNA, in both birth weight groups. Lipid uptake and intramuscular fat deposition associated mRNA was reduced in only L pigs. Abundance of ST mRNA associated with lipolysis, lipid synthesis and transport increased in both birth weight groups. Lipid uptake associated mRNA reduced in only L pigs. These changes were associated with decreased plasma L glucose and N triacylglycerol. Post-dietary fat reduction, LD mRNA associated with lipid synthesis and inter- and intramuscular fat deposition increased in L, whilst beta-oxidation associated mRNA remains elevated for longer in N. In the ST, mRNA associated with lipolysis and intramuscular fat deposition increased in both birth weight groups, however this increase was more significant in L pigs and associated with reduced beta-oxidation. Analysis of muscle lipid metabolism associated mRNA revealed that profile shifts are a consequence of birth weight. Whilst, many of the adaptions to diet and age appear to be similar in birth weight groups, the magnitude of response and individual changes underpin the previously observed lower fat oxidation in L pigs.
Highlights
Skeletal muscle is the primary metabolic organ for the disposal of lipids and energy dissipation, where it plays a central role in regulating whole body energy homeostasis [1]
The regulation of lipid metabolism is a complex process that exists in a cycle of uptake, storage, release and energy generation [1]
In order to evaluate the potential effects of birth weight, diet and the post-diet change adaptation had on the metabolic status of L and N pigs, TAG, cholesterol, non-esterified fatty acid (NEFA), glucose and urea were measured
Summary
Skeletal muscle is the primary metabolic organ for the disposal of lipids (and carbohydrates) and energy dissipation, where it plays a central role in regulating whole body energy homeostasis [1]. The regulation of lipid metabolism is a complex process that exists in a cycle of uptake, storage (lipid synthesis: when exogenous energy supply is in excess), release (lipolysis: when exogenous energy supply is not sufficient) and energy generation (beta-oxidation: when there is a demand for ATP) [1]. Dysregulation of these processes has been linked to the development of metabolic disorders such as obesity and type 2 diabetes, which have chronic negative impacts on an individual’s health and development [2]. As fibre number and / or size changes, due to birth weight [10], breed [11] so does the ability of skeletal muscle to metabolise fats (and carbohydrates)
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