Creatine metabolism is an important component of cellular energy homeostasis. Via the creatine kinase circuit, creatine derived from our diet or synthesized endogenously provides spatial and temporal maintenance of intracellular adenosine triphosphate (ATP) production; this is particularly important for cells with high or fluctuating energy demands. The use of this circuit by tissues within the female reproductive system, as well as the placenta and the developing fetus during pregnancy is apparent throughout the literature, with some studies linking perturbations in creatine metabolism to reduced fertility and poor pregnancy outcomes. Maternal dietary creatine supplementation during pregnancy as a safeguard against hypoxia-induced perinatal injury, particularly that of the brain, has also been widely studied in pre-clinical in vitro and small animal models. However, there is still no consensus on whether creatine is essential for successful reproduction. This review consolidates the available literature on creatine metabolism in female reproduction, pregnancy and the early neonatal period. Creatine metabolism is discussed in relation to cellular bioenergetics and de novo synthesis, as well as the potential to use dietary creatine in a reproductive setting. We highlight the apparent knowledge gaps and the research “road forward” to understand, and then utilize, creatine to improve reproductive health and perinatal outcomes.

The maintenance of muscle mass and muscle strength is important for reducing the risk of chronic diseases. The age- related loss of muscle mass and strength is associated with adverse outcomes of physical disability, frailty and death. β-Hydroxy β-Methyl Butyrate (HMB), a metabolite of leucine, has beneficial effects on muscle mass and strength under various catabolic conditions. The objectives of the present study were to determine if age- related differences existed in endogenous plasma HMB levels, and to assess if HMB levels correlated to total appendicular lean mass and forearm grip strength. Anthropometry, dietary and physical activity assessment, and the estimation of fasting plasma HMB concentrations and handgrip strength were performed on the 305 subjects (children, young adults and older adults). Lean mass, which serves as a surrogate for muscle mass was measured using dual energy X-ray absorptiometry (DEXA). Mean plasma HMB concentrations were significantly lower with increasing age groups, with children having highest mean HMB concentration (p<0.01) followed by young adults and older adults. Female subjects (across all ages) had significantly lower plasma HMB concentrations. A significant positive correlation between HMB concentrations and appendicular lean mass normalized for body weight (%), appendicular lean mass (r=0.37; p<0.001) was observed in the young adults and older adults group. Handgrip strength was positively associated with plasma HMB concentrations in young adults (r=0.58; p<0.01) and the older adults group (r=0.28; p<0.01). The findings of the present study suggest that there is an age- related decline in endogenous HMB concentrations in humans and the HMB concentrations were positively correlated with appendicular lean mass and hand grip strength in young adults and older adults group.

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