Developmental programming of the cell stress response and metabolic inflammation in liver and adipose tissue in an ovine model

A state of chronic metabolic inflammation and activation of the cell stress response in organs such as liver and adipose tissue are important pathogenic adaptations with the onset of obesity and the metabolic syndrome. The extent to which these processes are modulated by the early life nutritional experience is not well established, especially in large animal models. The overall aim of this thesis was to identify whether nutritional programming during prenatal and postnatal development enhances metabolic inflammation and cell stress response of obesity. A nutritional model of fetal growth restriction achieved by maternal nutrient restriction (NR) to 60% of requirements during late gestation (110 days to term at 147 days) in twin bearing sheep was used. Combination of prenatal and postnatal nutritional interventions were studied with the following three study protocols: 1. Offspring of twin bearing sheep born to mothers nutrient restricted or fed to appetite were separated after weaning at 3 months of age and then exposed to either restricted physical activity leading to obesity or to unrestricted activity and remained lean. 2. Following maternal NR, both twins or only one twin were reared on their mother’s milk during suckling period in order to achieve a relatively faster growth rate in the latter. 3. Twin offspring of sheep randomised to NR or feeding to requirement during late gestation were separated after birth and randomised to either formula feeding or being fed by the mother until weaning followed by obesogenic rearing. Total body weight of sheep in the obese group was raised by ~30% and was unaffected by any intervention. Obesity led to an increased insulin response to the glucose tolerance test, together with hepatic triglyceride deposition, and adipocyte hypertrophy with macrophage infiltration in omental adipose tissue. NR exacerbated obesity associated hepatic triglyceride deposition and upregulated gene expression of hepatic autophagy and omental unfolded protein response. Formula feeding of sheep offspring following NR was associated with slower weight gain and decreased gene expression for MTOR. Sheep offspring fed by mother as singleton gained weight at faster rate during suckling period as compared to offspring fed by their mothers as twins. Neither postnatal interventions exacerbated the state of obesity associated metabolic inflammation and cell stress response. It is possible that the increased hepatic autophagic gene expression is a reflection of defective autophagy and future work should include study of markers of autophagic function. Possible mechanisms of upregulated omental adipose UPR in offspring of sheep undergoing NR could include a programmed decrease in adipocyte number or selective survival of preadipocytes with effective ER stress response. Such adaptations followed by obesity would predispose the adipocytes to initiate inflammation and cell death pathways

Developmental programming of the cell stress response and metabolic inflammation in liver and adipose tissue in an ovine model

A state of chronic metabolic inflammation and activation of the cell stress response in organs such as liver and adipose tissue are important pathogenic adaptations with the onset of obesity and the metabolic syndrome. The extent to which these processes are modulated by the early life nutritional experience is not well established, especially in large animal models. The overall aim of this thesis was to identify whether nutritional programming during prenatal and postnatal development enhances metabolic inflammation and cell stress response of obesity. A nutritional model of fetal growth restriction achieved by maternal nutrient restriction (NR) to 60% of requirements during late gestation (110 days to term at 147 days) in twin bearing sheep was used. Combination of prenatal and postnatal nutritional interventions were studied with the following three study protocols: 1. Offspring of twin bearing sheep born to mothers nutrient restricted or fed to appetite were separated after weaning at 3 months of age and then exposed to either restricted physical activity leading to obesity or to unrestricted activity and remained lean. 2. Following maternal NR, both twins or only one twin were reared on their mother’s milk during suckling period in order to achieve a relatively faster growth rate in the latter. 3. Twin offspring of sheep randomised to NR or feeding to requirement during late gestation were separated after birth and randomised to either formula feeding or being fed by the mother until weaning followed by obesogenic rearing. Total body weight of sheep in the obese group was raised by ~30% and was unaffected by any intervention. Obesity led to an increased insulin response to the glucose tolerance test, together with hepatic triglyceride deposition, and adipocyte hypertrophy with macrophage infiltration in omental adipose tissue. NR exacerbated obesity associated hepatic triglyceride deposition and upregulated gene expression of hepatic autophagy and omental unfolded protein response. Formula feeding of sheep offspring following NR was associated with slower weight gain and decreased gene expression for MTOR. Sheep offspring fed by mother as singleton gained weight at faster rate during suckling period as compared to offspring fed by their mothers as twins. Neither postnatal interventions exacerbated the state of obesity associated metabolic inflammation and cell stress response. It is possible that the increased hepatic autophagic gene expression is a reflection of defective autophagy and future work should include study of markers of autophagic function. Possible mechanisms of upregulated omental adipose UPR in offspring of sheep undergoing NR could include a programmed decrease in adipocyte number or selective survival of preadipocytes with effective ER stress response. Such adaptations followed by obesity would predispose the adipocytes to initiate inflammation and cell death pathways

Sex differences in metabolic and adipose tissue responses to juvenile-onset obesity in sheep

Sex is a major factor determining adipose tissue distribution and the subsequent adverse effects of obesity-related disease including type 2 diabetes. The role of gender on juvenile obesity and the accompanying metabolic and inflammatory responses is not well established. Using an ovine model of juvenile onset obesity induced by reduced physical activity, we examined the effect of gender on metabolic, circulatory, and related inflammatory and energy-sensing profiles of the major adipose tissue depots. Despite a similar increase in fat mass with obesity between genders, males demonstrated a higher storage capacity of lipids within perirenal-abdominal adipocytes and exhibited raised insulin. In contrast, obese females became hypercortisolemic, a response that was positively correlated with central fat mass. Analysis of gene expression in perirenal-abdominal adipose tissue demonstrated the stimulation of inflammatory markers in males, but not females, with obesity. Obese females displayed increased expression of genes involved in the glucocorticoid axis and energy sensing in perirenal-abdominal, but not omental, adipose tissue, indicating a depot-specific mechanism that may be protective from the adverse effects of metabolic dysfunction and inflammation. In conclusion, young males are at a greater risk than females to the onset of comorbidities associated with juvenile-onset obesity. These sex-specific differences in cortisol and adipose tissue could explain the earlier onset of the metabolic-related diseases in males compared with females after obesity

What is the easier and more reliable dose calculation for iv Phenytoin in children at risk of developing convulsive status epilepticus, 18 mg/kg or 20 mg/kg?

Background: With the Convulsive Status Guidelines due for renewal, we wondered if a phenytoin dose of ‘20 mg/kg’ would be easier to calculate correctly and therefore safer than the current ‘18 mg/kg’. An educational exercise in dose calculation was therefore undertaken to assess ease of calculation. Method: A standard question paper was prepared, comprising five clinical scenarios with children of varying ages and estimated body weights. Medical students, trainee doctors at registrar and senior house officer level, and consultant paediatricians were asked to complete the exercise, in private, by one of two medical students (SD, PS). Calculations were done with and without a calculator, for 18 mg/kg and for 20 mg/kg in randomised order. Speed and errors (greater than 10%) were determined. The data analysis was performed using SPSS version 18. Results: All answered all 20 scenarios, giving a total of 300 answers per doctor/student group, and 300 answers per type of calculation. When comparing the 2 doses, the numbers of errors more than 10% were significantly less in 20 mg/kg dose (0.33%) as compared to the 18 mg/kg dose (9.3%) (p<0.0001). Speed off calculation was significantly decreased in 20 mg/kg dose when compared with 18 mg/kg dose, with (p<0.001) or without (p<0.0001) the calculator. Speed was more than halved and errors were much less frequent by using a calculator, for the 18 mg/kg dose but no difference with or without the calculator for 20 mg/kg dose. Conclusion: We recommend that the future guidelines should suggest iv Phenytoin at 20 mg/kg rather than 18 mg/kg. This will make the calculation easier and reduce the risk of significant errors

Tissue cell stress response to obesity and its interaction with late gestational diet

Intra-uterine growth restriction in late pregnancy can contribute to adverse long term metabolic health in the offspring. We utilised an animal (sheep) model of maternal dietary manipulation in late pregnancy, combined with exposure of the offspring to a low activity, obesogenic environment after weaning, to characterise the effects on glucose homeostasis. Dizygotic twin-pregnant sheep were either fed to 60% of requirements (nutrient restriction (R)) or fed ad libitum (~ 140% of requirements (A)) from 110 days gestation until term (~147d). After weaning (~3 months of age), their offspring were kept in either a standard (in order to remain lean) or low activity, obesogenic environment. R mothers gained less weight and produced smaller offspring. As adults, obese offspring were heavier and fatter with reduced glucose tolerance, irrespective of maternal diet. Molecular markers of stress and autophagy in liver and adipose tissue were increased with obesity, with gene expression of hepatic Grp78 and of omental Atf6, Grp78 and Edem1 only being increased in R offspring. In conclusion, the adverse effect of juvenile onset obesity on insulin responsive tissues can be amplified by previous exposure to a suboptimal nutritional environment in utero, thereby contributing to earlier onset of insulin resistance

Tissue cell stress response to obesity and its interaction with late gestation diet

Abstract Intrauterine growth restriction in late pregnancy can contribute to adverse long-term metabolic health in the offspring. In the present study we used an animal (sheep) model of maternal dietary manipulation in late pregnancy, combined with exposure of the offspring to a low-activity, obesogenic environment after weaning, to characterise the effects on glucose homeostasis. Dizygotic twin-pregnant sheep were either fed to 60% of requirements (nutrient restriction (R)) or fed ad libitum (~140% of requirements (A)) from 110 days gestation until term (~147 days). After weaning (~3 months of age), the offspring were kept in either a standard (in order to remain lean) or low-activity, obesogenic environment. R mothers gained less weight and produced smaller offspring. As adults, obese offspring were heavier and fatter with reduced glucose tolerance, regardless of maternal diet. Molecular markers of stress and autophagy in liver and adipose tissue were increased with obesity, with gene expression of hepatic glucose-related protein 78 (Grp78) and omental activation transcription factor 6 (Atf6), Grp78 and ER stress degradation enhancer molecule 1 (Edem1) only being increased in R offspring. In conclusion, the adverse effect of juvenile-onset obesity on insulin-responsive tissues can be amplified by previous exposure to a suboptimal nutritional environment in utero, thereby contributing to earlier onset of insulin resistance