Don Sharkey

Thermal Imaging to Assess Age-Related Changes of Skin Temperature within the Supraclavicular Region Co-Locating with Brown Adipose Tissue in Healthy Children

OBJECTIVE To establish the feasibility of infrared thermal imaging as a reproducible, noninvasive method for assessing changes in skin temperature within the supraclavicular region in vivo. STUDY DESIGN Thermal imaging was used to assess the effect of a standard cool challenge (by placement of the participants feet or hand in water at 20°C) on the temperature of the supraclavicular region in healthy volunteer participants of normal body mass index in 3 age groups, 3-8, 13-18, and 35-58 years of age. RESULTS We demonstrated a highly localized increase in temperature within the supraclavicular region together with a significant age-related decline under both baseline and stimulated conditions. CONCLUSION Thermogenesis within the supraclavicular region can be readily quantified by thermal imaging. This noninvasive imaging technique now has the potential to be used to assess brown adipose tissue function alone, or in combination with other techniques, in order to determine the roles of thermogenesis in energy balance and, therefore, obesity prevention.

Adipose tissue and fetal programming

Adipose tissue function changes with development. In the newborn, brown adipose tissue (BAT) is essential for ensuring effective adaptation to the extrauterine environment, and its growth during gestation is largely dependent on glucose supply from the mother to the fetus. The amount, location and type of adipose tissue deposited can also determine fetal glucose homeostasis. Adipose tissue first appears at around mid-gestation. Total adipose mass then increases through late gestation, when it comprises a mixture of white and brown adipocytes. BAT possesses a unique uncoupling protein, UCP1, which is responsible for the rapid generation of large amounts of heat at birth. Then, during postnatal life some, but not all, depots are replaced by white fat. This process can be utilised to investigate the physiological conversion of brown to white fat, and how it is re-programmed by nutritional changes in pre- and postnatal environments. A reduction in early BAT deposition may perpetuate through the life cycle, thereby suppressing energy expenditure and ultimately promoting obesity. Normal fat development profiles in the offspring are modified by changes in maternal diet at defined stages of pregnancy, ultimately leading to adverse long-term outcomes. For example, excess macrophage accumulation and the onset of insulin resistance occur in an adipose tissue depot-specific manner in offspring born to mothers fed a suboptimal diet from early to mid-gestation. In conclusion, the growth of the different fetal adipose tissue depots varies according to maternal diet and, if challenged in later life, this can contribute to insulin resistance and impaired glucose homeostasis.

Maternal nutrient restriction during pregnancy differentially alters the unfolded protein response in adipose and renal tissue of obese juvenile offspring

Maternal diet during pregnancy can program an offsprings risk of disease in later life. Obesity adversely alters renal and adipose tissue function, resulting in chronic kidney disease and insulin resistance, respectively, the latter associated with dysregulation of the unfolded protein response (UPR). In view of the current obesity epidemic, we explored the combined effects of in utero early‐ to midgestational nutrient restriction and postnatal obesity on the UPR in ovine juvenile offspring. Nutrient restriction was coincident with fetal kidney development but prior to exponential adipose tissue deposition. Nutrient restricted (NR) and normal diet (control) offspring were exposed to an obesogenic environment throughout adolescence, resulting in similar degrees of juvenile obesity. NR offspring showed enhanced adipose tissue dysregulation characterized by activation of the UPR, perturbed insulin signaling, and marked inflammation, as demonstrated by increased abundance of crownlike structures and proinflammatory genes. Conversely, in renal tissue NR offspring had marked attenuation of cellular stress and inflammation evident as reduced activation of the UPR, down‐regulation of proinflammatory genes, and less histological damage. In conclusion, obesity‐related activation of the UPR can be determined by the in utero nutritional environment, demonstrating organ‐specific effects dependent on the developmental phase targeted within the fetus.— Sharkey, D., Gardner, D. S., Fainberg, H. P., Sebert, S., Bos, P., Wilson, V., Bell, R., Symonds, M. E., Budge, H. Maternal nutrient restriction during pregnancy differentially alters the unfolded protein re‐sponse in adipose and renal tissue of obese juvenile offspring. FASEBJ. 23, 1314–1324 (2009)

Marked variation in newborn resuscitation practice: a national survey in the UK.

Background Although international newborn resuscitation guidance has been in force for some time, there are no UK data on current newborn resuscitation practices. Objective Establish delivery room (DR) resuscitation practices in the UK, and identify any differences between neonatal intensive care units (NICU), and other local neonatal services. Methods We conducted a structured two-stage survey of DR management, among UK neonatal units during 2009–2010 (n = 192). Differences between NICU services (tertiary level) and other local neonatal services (non-tertiary) were analysed using Fishers exact and Students t-tests. Results There was an 89% response rate (n = 171). More tertiary NICUs institute DR CPAP than non-tertiary units (43% vs. 16%, P = 0.0001) though there was no significant difference in frequency of elective intubation and surfactant administration for preterm babies. More tertiary units commence DR resuscitation in air (62% vs. 29%, P < 0.0001) and fewer in 100% oxygen (11% vs. 41%, P < 0.0001). Resuscitation of preterm babies in particular, commences with air in 56% of tertiary units. Significantly more tertiary units use DR pulse oximeters (58% vs. 29%, P < 0.01) and titrate oxygen based on saturations. Almost all services use occlusive wrapping to maintain temperature for preterm infants. Conclusions In the UK, there are many areas of good evidence based DR practice. However, there is marked variation in management, including between units of different designation, suggesting a need to review practice to fulfil new resuscitation guidance, which will have training and resource implications.

Adipose Tissue Inflammation: Developmental Ontogeny and Consequences of Gestational Nutrient Restriction in Offspring

Increasing adiposity predisposes to the development of the metabolic syndrome, in part, through adipose tissue dysregulation and inflammation. In addition, offspring nutrient-restricted (NR) in utero can exhibit an increased risk of early-onset insulin resistance and obesity, although the mechanisms remain unclear. We aimed to: 1) define adipose tissue ontogeny of key proinflammatory and endoplasmic reticulum stress gene expression from late fetal to early adult life and 2) examine the impact on these genes in gestational nutrient restriction. Pregnant sheep were fed 100% (control) or 50% (NR) of their nutritional requirements between early to mid (28-80 d, term approximately 147 d) or late (110-147 d) gestation. In control offspring, toll-like receptor 4 (TLR4), and the macrophage marker CD68, peaked at 30 d of life before declining. IL-18 peaked at 6 months of age, whereas the endoplasmic reticulum chaperone glucose-regulated protein 78 peaked at birth and subsequently declined through postnatal life. TLR4 and CD68 positively correlated with relative adipose tissue mass and with each other. Early to midgestational NR offspring had decreased abundance of IL-18 at 6 months of age. In late gestational NR offspring, CD68 was significantly lower at birth, a pattern that reversed in juvenile offspring, coupled with increased TLR4 abundance. In conclusion, the in utero nutritional environment can alter the adipose tissue inflammatory profile in offspring. This may contribute to the increased risk of insulin resistance or obesity, dependent on the timing of nutrient restriction. Establishing the optimal maternal diet during pregnancy could reduce the burden of later adult disease in the offspring.

Session on 'Obesity': adipose tissue development, nutrition in early life and its impact on later obesity.

It is now apparent that one key factor determining the current obesity epidemic within the developed world is the extent to which adipose tissue growth and function can be reset in early life. Adipose tissue can be either brown or white, with brown fat being characterised as possessing a unique uncoupling protein (uncoupling protein 1) that enables the rapid generation of heat by non-shivering thermogenesis. In large mammals this function is recruited at approximately the time of birth, after which brown fat is lost, not normally reappearing again throughout the life cycle. The origin and developmental regulation of brown fat in large mammals is therefore very different from that of small mammals in which brown fat is retained throughout the life cycle and may have the same origin as muscle cells. In contrast, white adipose tissue increases in mass after birth, paralleled by a rise in glucocorticoid action and macrophage accumulation. This process can be reset by changes in the maternal nutritional environment, with the magnitude of response being further determined by the timing at which such a challenge is imposed. Importantly, the long-term response within white adipocytes can occur in the absence of any change in total fat mass. The present review therefore emphasises the need to further understand the developmental regulation of the function of fat through the life cycle in order to optimise appropriate and sustainable intervention strategies necessary not only to prevent obesity in the first place but also to reverse excess fat mass in obese individuals.

The differential effects of the timing of maternal nutrient restriction in the ovine placenta on glucocorticoid sensitivity, uncoupling protein 2, peroxisome proliferator-activated receptor-γ and cell proliferation

Nutrient restriction (NR) during critical windows of pregnancy has differential effects on placento-fetal growth and development. Our study, therefore, investigated developmental and metabolic adaptations within the ovine placenta following NR at different critical windows during the first 110 days of gestation (term=147 days). Thus, the effects of NR on cell proliferation, glucocorticoid sensitivity, IGF1 and 2 receptor, peroxisome proliferator-activated receptor gamma (PPARG), and uncoupling protein (UCP)2 gene expression in the placenta were examined. Singleton bearing sheep (n=4-8 per group) were fed either 100% of their total metabolizable energy requirements throughout the study or 50% of this amount between 0-30, 31-65, 66-110, and 0-110 days gestation. A significant reduction in cell proliferation and increased gene expression for the glucocorticoid and IGF2 receptors, PPARG, and UCP2 were detected in placentae sampled from mothers who were nutrient restricted between days 66 and 110 of gestation, only, relative to controls. This window of gestation coincides with the maximum placental growth and the start of exponential growth of the fetus when there are substantially increased metabolic demands on the placenta compared with earlier in gestation. Consequently, increased glucocorticoid sensitivity and suppressed IGF2 action could contribute to a switch in the placenta from proliferation to differentiation, thereby improving its nutrient transfer capacity. Upregulation of PPARG and UCP2 would promote placental fatty acid metabolism thereby limiting glucose utilization. These compensatory placental responses may serve to maintain fetal growth but could result in adverse adaptations such as the early onset of the metabolic syndrome in later life.

Impact of Early Onset Obesity and Hypertension on the Unfolded Protein Response in Renal Tissues of Juvenile Sheep

Childhood obesity has reached epidemic proportions. Obesity is an independent risk factor for the development of end-stage renal disease. Endoplasmic reticulum stress and subsequent activation of the unfolded protein response (UPR) are implicated in the development of adipose tissue dysregulation and type 2 diabetes mellitus in obesity. The present study explored the impact of adolescent-onset obesity on the UPR after obesity-related hypertension and nephropathy, using an ovine model in which obesity was induced by increased food intake and reduced activity. Obese young adults had a higher mean arterial pressure (lean, 89.6±1.7 mm Hg versus obese, 101±3.0 mm Hg; P<0.01) and greater sensitivity to low physiological doses of angiotensin II. Obesity increased the glomerular area and was associated with activation of the UPR in renal cells with a greater abundance of glucose-regulated protein 78, C/EBP homologous protein, Bax, phosphorylated c-Jun amino-terminal kinase, and activating transcription factor 6 (all P<0.05). In addition, there was a marked upregulation of proinflammatory genes, most notably those involved in macrophage signaling. Reactive oxygen species production and handling were also perturbed in obese adults. Renal endoplasmic reticulum stress was positively correlated with macrophage content (r=0.83; P<0.001), phosphorylated c-Jun amino-terminal kinase (r=0.73; P<0.01), and adiposity (r=0.71; P<0.01). In conclusion, adolescent-onset, obesity-related renal endoplasmic reticulum stress was associated with activation of the UPR, apoptosis, and inflammation, potentially increasing the associated renal damage observed in young adults. The UPR may prove to be a useful therapeutic target for the treatment and prevention of obesity-related nephropathy and associated hypertension, thereby reducing the burden of end-stage renal disease.

Maternal nutrient restriction during early fetal kidney development attenuates the renal innate inflammatory response in obese young adult offspring

Obesity is an independent risk factor for developing chronic kidney disease. Toll-like receptor 4 (TLR4), interleukin (IL)-18, and uncoupling protein 2 (UCP2) are important components of the innate immune system mediating inflammatory renal damage. Early to midgestation maternal nutrient restriction appears to protect the kidney from the deleterious effects of early onset obesity, although the mechanisms remain unclear. We examined the combined effects of gestational maternal nutrient restriction during early fetal kidney development and early onset obesity on the renal innate immune response in offspring. Pregnant sheep were randomly assigned to a normal (control, 100%) or nutrient-restricted (NR, 50%) diet from days 30 to 80 gestation and 100% thereafter. Offspring were killed humanely at 7 days or, following rearing in an obesogenic environment, at 1 yr of age, and renal tissues were collected. IL-18 and TLR4 expression were strongly correlated irrespective of intervention. Seven-day NR offspring had significantly lower relative renal mass and IL-18 mRNA expression. At 1 yr of age, obesity resulted in increased mRNA abundance of TLR4, IL-18, and UCP2, coupled with tubular atrophy and greater immunohistological staining of glomerular IL-6 and medullary tumor necrosis factor (TNF)-alpha. NR obese offspring had a marked reduction of TLR4 abundance and renal IL-6 staining. In conclusion, maternal nutrient restriction during early fetal kidney development attenuates the effects of early onset obesity-related nephropathy, in part, through the downregulation of the innate inflammatory response. A better understanding of maternal nutrition and the in utero nutritional environment may offer therapeutic strategies aimed at reducing the burden of later kidney disease.

Glucocorticoids modulate human brown adipose tissue thermogenesis in vivo

Introduction Brown adipose tissue (BAT) is a thermogenic organ with substantial metabolic capacity and has important roles in the maintenance of body weight and metabolism. Regulation of BAT is primarily mediated through the β-adrenoceptor (β-AR) pathway. The in vivo endocrine regulation of this pathway in humans is unknown. The objective of our study was to assess the in vivo BAT temperature responses to acute glucocorticoid administration. Methods We studied 8 healthy male volunteers, not pre-selected for BAT presence or activity and without prior BAT cold-activation, on two occasions, following an infusion with hydrocortisone (0.2 mg.kg− 1.min− 1 for 14 h) and saline, respectively. Infusions were given in a randomized double-blind order. They underwent assessment of supraclavicular BAT temperature using infrared thermography following a mixed meal, and during β-AR stimulation with isoprenaline (25 ng.kg fat-free mass− 1.min− 1 for 60 min) in the fasting state. Results During hydrocortisone infusion, BAT temperature increased both under fasting basal conditions and during β-AR stimulation. We observed a BAT temperature threshold, which was not exceeded despite maximal β-AR activation. We conclude that BAT thermogenesis is present in humans under near-normal conditions. Glucocorticoids modulate BAT function, representing important physiological endocrine regulation of body temperature at times of acute stress.