PhD, The University of Sydney
Obesity is well-known as a global health concern. Obesity before and during pregnancy can significantly affect both the mothers and their babies' health. Particularly, maternal obesity can lead to fetal overgrowth, primarily contributing to the development of obesity and associated diseases such as diabetes, liver and kidney diseases later in life. Unfortunately, the mechanisms underlying such transmissible effects are still unclear. On the other hand, lifestyle intervention trials to manage gestational weight gain through diets, physical activities and behavioural modification techniques have achieved modest success in improving the babies' health outcomes. As such, investigation of alternative approaches to mitigate the effects of maternal obesity across generations has become imperative. Sirtuin (SIRT)1 is a potent regulator of cell growth, metabolism and stress responses, and one of the most appealing targets for aging and weight gain related disorders. In obesity, SIRT1 activity is significantly suppressed in multiple organs such as liver and fat tissues. Increasing the expression and/or reactivation of SIRT1 has been shown to be of particularly beneficial against obesity-associated comorbidities. The effects of such therapeutic approaches on the offspring of obese mothers, which were largely unknown, has been the focus of my research. To investigate the topic, we made female mice become obese by feeding them a high-fat diet before and during pregnancy and used genetically modified mice with increased levels of SIRT1. We looked at various tissues from brain to fat tissue and liver to understand the systemic reactions of the body. We also compared the effects when the intervention was on the offspring themselves or their mothers or fathers. The results not only suggest SIRT1 can indeed be used as a target for managing the effects of maternal obesity on the offspring but also specify newborns as the superior subject compared to mothers and fathers for the intervention.
Abstract: Obesity is a complex metabolic disease, attributed to diverse and interactive genetic and environmental factors. The associated health consequences of obesity are pleiotropic, with individuals being more susceptible to chronic diseases such as type 2 diabetes mellitus, hypertension, and lipotoxicity-related chronic diseases. The contribution of maternal obesity to the offspring's predisposition to both obesity and its complications is increasingly recognized. Understanding the mechanisms underlying these "transmissible" effects is critical to develop therapeutic interventions to reduce the risk for "programmed" obesity. Sirtuins (SIRTs), particularly SIRT1 and SIRT3, are NAD(+)-dependent deacetylases that regulate metabolic balance and stress responses in both central and peripheral tissues, of which dysregulation is a well-established mediator for the development and effects of obesity. Nevertheless, their implication in the transmissible effects of maternal obesity across generations remains largely elusive. In this review, we examine multiple pathways and systems that are likely to mediate such effects, with particular emphasis on the role of SIRTs.-Nguyen, L. T., Chen, H., Pollock, C. A., Saad, S. Sirtuins-mediators of maternal obesity-induced complications in offspring?
Pub.: 17 Dec '15, Pinned: 30 Aug '17
Abstract: Maternal obesity has been shown to increase the risk of obesity and related disorders in the offspring, which has been partially attributed to changes of appetite regulators in the offspring hypothalamus. On the other hand, endoplasmic reticulum (ER) stress and autophagy have been implicated in hypothalamic neuropeptide dysregulation, thus may also play important roles in such transgenerational effect. In this study, we show that offspring born to HFD-fed dams showed significantly increased body weight and glucose intolerance, adiposity and plasma triglyceride level at weaning. Hypothalamic mRNA level of the orexigenic neuropeptide Y (NPY) was increased while the levels of the anorexigenic pro-opiomelanocortin (POMC), NPY1 receptor (NPY1R) and melanocortin-4 receptor (MC4R) were significantly downregulated. In association, the expression of Unfolded protein response (UPR) markers including Glucose-regulated protein (GRP)94 and Endoplasmic reticulum DNA J domain-containing protein (Erdj)4 were reduced. By contrast, protein levels of autophagy-related genes Atg5 and Atg7, as well as mitophagy marker Parkin, were slightly increased. The administration of 4-phenyl butyrate (PBA), a chemical chaperone of protein folding and UPR activator, in the offspring from postnatal day 4 significantly reduced their body weight, fat deposition, which were in association with increased Activating transcription factor (ATF)4, immunoglobin-binding protein (BiP) and Erdj4 mRNA as well as reduced Parkin, PTEN-induced putative kinase (PINK)1 and Dynamin-related protein (Drp)1 protein expression levels. These results suggest that hypothalamic ER stress and mitophagy are among the regulatory factors of offspring metabolic changes due to maternal obesity.
Pub.: 14 May '17, Pinned: 30 Aug '17
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