Severence M. MacLaughlin

The early origins of later obesity: pathways and mechanisms.

Excess bodyweight is the sixth most important risk factor contributing to the overall burden of disease worldwide. In excess of a billion adults and 10% of all children are now classified as overweight or obese. The main adverse consequences of obesity are the metabolic syndrome, cardiovascular disease and type 2 diabetes and a diminished average life expectancy. It has been argued that the complex pathological processes underlying obesity reflect environmental and genetic interactions, and individuals from disadvantaged communities seem to have greater risks than more affluent individuals partly because of fetal and postnatal programming interactions. Abundant evidence indicates that the obesity epidemic reflects progressive secular and age-related decreases in physical activity, together with passive over-consumption of energy dense foods despite neurobiological processes designed to regulate energy balance. The difficulty in treating obesity, however, highlights the deficits in our current understanding of the pathophysiology which underlies the initiation and chronic nature of this disorder. Large population based studies in Europe and North America in healthy women and in women with gestational diabetes have demonstrated that there are clear relationships between maternal and fetal nutrient supply, fetal growth patterns and the subsequent risk of obesity and glucose intolerance in childhood and adult life. In this review we discuss the impact of fetal nutrition on the biology of the developing adipocyte and brain and the growing evidence base supporting an intergenerational cycle of obesity.

Periconceptional undernutrition in normal and overweight ewes leads to increased adrenal growth and epigenetic changes in adrenal IGF2/H19 gene in offspring

Adverse conditions in early life result in increased activation of the hypothalamo‐pituitary‐adrenal axis and in stress responsiveness in offspring. We have developed a model in which “donor” ewes are either normally nourished or overnourished prior to a period of dietary restriction, before transfer of the embryo at 6–7 d after conception to a ewe of normal weight and nutritional history. A moderate restriction of energy intake during the periconceptional period in both normal weight and overweight ewes resulted in increased adrenal mass in male and female lambs and an increased cortisol response to stress in female lambs. The increase in adrenal weight in lambs exposed to periconceptional under‐nutrition was associated with a decrease in the adrenal mRNA expression of IGF2 and decreased methylation in the proximal CTCF‐binding site in the differentially methylated region of the IGF2/H19 gene. Thus, weight loss in both normal and overweight mothers during the periconceptional period results in epigenetic modification of IGF2 in the adrenal gland, adrenal overgrowth, and increased vulnerability to stress in offspring. Determining the appropriate approach to weight loss in the periconceptional period may therefore be important in overweight or obese women seeking to become pregnant.—Zhang, S., Rattanatray, L., MacLaughlin, S. M., Cropley, J. E., Suter, C. M., Molloy, L., Kleemann, D., Walker, S. K., Muhlhausler, B. S., Morrison, J. L., and McMillen, I. C. Periconceptional undernutrition in normal and overweight ewes leads to increased adrenal growth and epigenetic changes in adrenal IGF2/H19 gene in offspring. FASEB J. 24, 2772–2782 (2010). www.fasebj.org

Differential effects of maternal obesity and weight loss in the periconceptional period on the epigenetic regulation of hepatic insulin-signaling pathways in the offspring

Our aim was to determine the effect of exposure to maternal obesity or to maternal weight loss around conception on the programming of hepatic insulin signaling in the offspring. We used an embryo transfer model in sheep to investigate the effects of exposure to either maternal obesity or to weight loss in normal and obese mothers preceding and for 1 wk after conception on the expression of hepatic insulin‐signaling and gluconeogenic factors and key miRNAs involved in insulin signaling in the offspring. We found that exposure to maternal obesity resulted in increased hepatic miR‐29b (P<0.05), miR‐103 (P<0.01), and miR‐107 (P<0.05) expression, a decrease in IR (P<0.05), phopsho‐Akt (P<0.01), and phospho‐FoxO1 (P<0.01) abundance, and a paradoxical decrease in 11βHSD1 (P<0.05), PEPCK‐C (P<0.01), and PEPCK‐M (P<0.05) expression in lambs. These changes were ablated by a period of moderate dietary restriction imposed during the periconceptional period. Maternal dietary restriction alone also resulted in decreased abundance of a separate subset of hepatic insulin‐signaling molecules, namely, IRS1 (P<0.05), PDK1 (P<0.01), phospho‐PDK1 (P<0.05), and aPKCξ (P<0.05) and in decreased PEPCK‐C (P<0.01) and G6Pase (P<0.01) expression in the lamb. Our findings highlight the sensitivity of the epigenome to maternal nutrition around conception and the need for dietary interventions that maximize metabolic benefits and minimize metabolic costs for the next generation.—Nicholas, L. M., Rattanatray, L., MacLaughlin, S. M., Ozanne, S. E., Kleemann, D. O., Walker, S. K., Morrison, J. L., Zhang, S., Muhlhausler, B. S., Martin‐Gronert, M. S., McMillen, I. C., Differential effects of maternal obesity and weight loss in the periconceptional period on the epigenetic regulation of hepatic insulin‐signaling pathways in the offspring. FASEB J. 27, 3786–3796 (2013). www.fasebj.org

Impact of Maternal Periconceptional Overnutrition on Fat Mass and Expression of Adipogenic and Lipogenic Genes in Visceral and Subcutaneous Fat Depots in the Postnatal Lamb

Women entering pregnancy with a high body weight and fat mass have babies who are at increased risk of becoming overweight or obese in later life. We investigated whether maternal overnutrition in the periconceptional period results in an increased fat mass and expression of adipogenic and lipogenic genes in offspring and whether dietary restriction can reverse these changes. Nonpregnant donor ewes (n = 23) were assigned to one of four groups: control-control fed at 100% maintenance energy requirements (MER) for at least 5 months, control-restricted fed 100% MER for 4 months and 70% MER for 1 month, high-high (HH) fed ad libitum (170-190% MER) for 5 months, or high-restricted (HR) fed ad libitum for 4 months and 70% MER for 1 month. Single embryos were transferred to nonobese recipient ewes, and lamb fat depots were weighed at 4 months. Peroxisome proliferator-activated receptor-γ, glyceraldehyde-3-phosphate dehydrogenase, lipoprotein lipase, leptin, and adiponectin mRNA expression was measured in the lamb fat depots. Total fat mass was higher in female lambs in the HH but not HR group than controls. There was a relationship between donor ewe weight and total fat mass and G3PDH mRNA expression in perirenal fat in female lambs. There was no effect of periconceptional nutritional treatment on peroxisome proliferator-activated receptor-γ, glyceraldehyde-3-phosphate dehydrogenase, lipoprotein lipase, leptin, and adiponectin mRNA expression in any fat depot. Thus, exposure to maternal overnutrition in the periconceptional period alone results in an increased body fat mass in the offspring and that a short period of dietary restriction can reverse this effect.

Periconceptional Undernutrition Programs Changes in Insulin Signaling Molecules and MicroRNAs in Skeletal Muscle in Singleton and Twin Fetal Sheep

ABSTRACT Maternal undernutrition around the time of conception is associated with an increased risk of insulin resistance in adulthood. We determined the effect of maternal undernutrition in the periconceptional period (PCUN, i.e., 60 days prior to 6 days after conception) and the preimplantation period (PIUN, i.e., 0–6 days after conception) on mRNA expression and protein abundance of key insulin-signaling molecules as well as the global microRNA expression in quadriceps muscle of singleton and twin fetal sheep in late gestation. In singleton fetuses, exposure to PCUN resulted in lower protein abundance of PIK3CB (P < 0.01), PRKCZ (P < 0.05), and pPRKCZ (Thr410) (P < 0.05) in skeletal muscle compared to controls. In PIUN singletons, there was a higher protein abundance of IRS1 (P < 0.05), PDPK1 (P < 0.05), and SLC2A4 (P < 0.05) compared to controls. In twins, PCUN resulted in higher protein abundance of IRS1 (P < 0.05), AKT2 (P < 0.05), PDPK1 (P < 0.05), and PRKCZ (P < 0.001), while PIUN also resulted in higher protein abundance of IRS1 (P < 0.05), PRKCZ (P < 0.001), and SLC2A4 (P < 0.05) in fetal muscle compared to controls. There were specific patterns of the types and direction of changes in the expression of 22 microRNAs in skeletal muscle after exposure to PCUN or PIUN and clear differences in these patterns between singleton and twin pregnancies. These findings provide evidence that maternal undernutrition around the time of conception induces changes in the expression of microRNAs, which may play a role in altering the abundance of the key insulin-signaling molecules in skeletal muscle and in the association between PCUN undernutrition and insulin resistance in adult life.

Maternal obesity or weight loss around conception impacts hepatic fatty acid metabolism in the offspring

To determine the impact of maternal obesity or weight loss during the periconceptional period on programming of lipid metabolism in the liver of the offspring.

Impact of embryo number and maternal undernutrition around the time of conception on insulin signaling and gluconeogenic factors and microRNAs in the liver of fetal sheep

This study aimed to determine whether exposure of the oocyte and/or embryo to maternal undernutrition results in the later programming of insulin action in the liver and factors regulating gluconeogenesis. To do this, we collect livers from singleton and twin fetal sheep that were exposed to periconceptional (PCUN; -60 to 7 days) or preimplantation (PIUN; 0-7 days) undernutrition at 136-138 days of gestation (term = 150 days). The mRNA and protein abundance of insulin signaling and gluconeogenic factors were then quantified using qRT-PCR and Western blotting, respectively, and global microRNA expression was quantified using deep sequencing methodology. We found that hepatic PEPCK-C mRNA (P < 0.01) and protein abundance and the protein abundance of IRS-1 (P < 0.01), p110β (P < 0.05), PTEN (P < 0.05), CREB (P < 0.01), and pCREB (Ser(133); P < 0.05) were decreased in the PCUN and PIUN singletons. In contrast, hepatic protein abundance of IRS-1 (P < 0.01), p85 (P < 0.01), p110β (P < 0.001), PTEN (P < 0.01), Akt2 (P < 0.01), p-Akt (Ser(473); P < 0.01), and p-FOXO-1 (Thr24) (P < 0.01) was increased in twins. There was a decrease in PEPCK-C mRNA (P < 0.01) but, paradoxically, an increase in PEPCK-C protein (P < 0.001) in twins. Both PCUN and PIUN altered the hepatic expression of 23 specific microRNAs. We propose that the differential impact of maternal undernutrition in the presence of one or two embryos on mRNAs and proteins involved in the insulin signaling and gluconeogenesis is explained by changes in the expression of a suite of specific candidate microRNAs.

Embryo number and periconceptional undernutrition in the sheep have differential effects on adrenal epigenotype, growth, and development

Exposure to poor maternal nutrition around the time of conception results in an early prepartum activation of the fetal pituitary-adrenal axis and in increased adrenal growth and stress response after birth associated with epigenetic changes in a differentially methylated region (DMR) of adrenal IGF2/H19. We have determined the effects of maternal undernutrition during the periconceptional period (PCUN: 70% of control intake from 60 days before until 6 days after conception) and early preimplantation period (PIUN: 70% of control intake for 6 days after conception) on fetal plasma ACTH and cortisol concentrations and fetal adrenal ACTHR, StAR, 3βHSD, CYP11B, CYP17, TGFβ1, IGF1, IGF1R, IGF2, and IGF2R mRNA expression and the methylation level of sites within the DMRs of IGF2/H19 and IGF2R in the adrenal of twin and singleton fetuses at 136-138 days gestation. Being a twin resulted in a delayed prepartum increase in fetal ACTH and in a lower cortisol response to CRH in the control but not PCUN and PIUN groups. PCUN, but not PIUN, resulted in an increase in adrenal weight and CYP17 expression in singletons, a decrease in adrenal IGF2 expression in singletons, and an increase in adrenal IGF2R expression in both twins and singletons. IGF2/H19 and IGF2R DMR methylation levels and ACTHR expression were lower in the twin adrenal. Thus, exposure of the oocyte and embryo to maternal undernutrition or to the environment of a twin pregnancy have differential effects on epigenetic and other factors that regulate fetal adrenal growth and IGF2 and IGF2R expression.

The periconceptional environment and cardiovascular disease: does in vitro embryo culture and transfer influence cardiovascular development and health?

Assisted Reproductive Technologies (ARTs) have revolutionised reproductive medicine; however, reports assessing the effects of ARTs have raised concerns about the immediate and long-term health outcomes of the children conceived through ARTs. ARTs include manipulations during the periconceptional period, which coincides with an environmentally sensitive period of gamete/embryo development and as such may alter cardiovascular development and health of the offspring in postnatal life. In order to identify the association between ARTs and cardiovascular health outcomes, it is important to understand the events that occur during the periconceptional period and how they are affected by procedures involved in ARTs. This review will highlight the emerging evidence implicating adverse cardiovascular outcomes before and after birth in offspring conceived through ARTs in both human and animal studies. In addition, it will identify the potential underlying causes and molecular mechanisms responsible for the congenital and adult cardiovascular dysfunctions in offspring whom were conceived through ARTs.

Differential Effects of Exposure to Maternal Obesity or Maternal Weight Loss during the Periconceptional Period in the Sheep on Insulin Signalling Molecules in Skeletal Muscle of the Offspring at 4 Months of Age

Exposure to maternal obesity before and/or throughout pregnancy may increase the risk of obesity and insulin resistance in the offspring in childhood and adult life, therefore, resulting in its transmission into subsequent generations. We have previously shown that exposure to maternal obesity around the time of conception alone resulted in increased adiposity in female lambs. Changes in the abundance of insulin signalling molecules in skeletal muscle and adipose tissue precede the development of insulin resistance and type 2 diabetes. It is not clear, however, whether exposure to maternal obesity results in insulin resistance in her offspring as a consequence of the impact of increased adiposity on skeletal muscle or as a consequence of the programming of specific changes in the abundance of insulin signalling molecules in this tissue. We have used an embryo transfer model in the sheep to investigate the effects of exposure to either maternal obesity or to weight loss in normal and obese mothers preceding and for one week after conception on the expression and abundance of insulin signalling molecules in muscle in the offspring. We found that exposure to maternal obesity resulted in lower muscle GLUT-4 and Ser 9 phospho-GSK3α and higher muscle GSK3α abundance in lambs when compared to lambs conceived in normally nourished ewes. Exposure to maternal weight loss in normal or obese mothers, however, resulted in lower muscle IRS1, PI3K, p110β, aPKCζ, Thr 642 phospho-AS160 and GLUT-4 abundance in the offspring. In conclusion, maternal obesity or weight loss around conception have each programmed specific changes on subsets of molecules in the insulin signalling, glucose transport and glycogen synthesis pathways in offspring. There is a need for a stronger evidence base to ensure that weight loss regimes in obese women seeking to become pregnant minimize the metabolic costs for the next generation.