Central resistance to the actions of insulin and leptin is strongly associated with obesity and type 2 diabetes mellitus (T2DM). These anorexigenic hormones modulate one another’s actions at the neuronal level. To investigate the cellular events underlying the effect of insulin resistance on leptin modulation of hypothalamic neurons, a neuronal cell model was established. The rHypoE-19 cell line expresses the insulin and leptin receptors alongside a complement of signaling molecules rendering it an appropriate model to study the molecular events underlying leptin and insulin crosstalk. Hyperinsulinemia was used to induce insulin resistance and leptin regulation of the rHypoE-19 neurons was analyzed prior to and following the induction of insulin resistance. It was found that the attenuation of insulin signal transduction affects leptin signaling and transcriptional modulation of the rHypoE-19 neurons. These studies will ultimately lend itself to an improved understanding of the complex cellular events that accompany neuronal hormone resistance.

Being able to effectively match energy intake to energy expenditure (EE) is an important aspect in preventing weight re-gain in the post-obese. Although it is generally agreed upon that resting EE decreases concomitantly with weight loss, there is no set standard comparing the deviations with differing weight loss protocols and additionally, controversy remains as to whether this decrease is greater than can predicted. In order to address these issues 2977 subjects were analyzed using a systematic review and the differences of both the protocol and length of various interventions in addition to sex were compared. Next, data was selected from this systematic review and 815 subjects were analyzed for weight loss-induced changes in resting EE, FM and FFM. Another subgroup of studies (n = 1450) was analyzed and compared against the Harris-Benedict prediction equation to determine whether the changes in resting EE were greater than what was expected. Finally, in order to determine which factors may be involved in regulating changes in resting EE during weight loss, a secondary analysis was performed on 28 post-menopausal women (age= 50.4 ± 2.0 yrs; BMI= 32.4 ± 5.2 kg/m²) who were submitted to a 6-month caloric restriction. Body composition (DXA), resting EE (indirect calorimetry), physical activity EE (PAEE) and total EE (TEE) (doubly-labelled water) were measured before and after the 6 month weight loss. Blood samples were collected before and after to measure leptin and peptide YY. The results indicate that there was indeed a depression in resting EE during weight loss regardless of the type of intervention utilized. Furthermore, these findings suggest that the changes could not fully be explained by changes of FM and FFM alone and that leptin may be an important contributor to the changes of resting EE during weight loss.

Objective The prevalence of obesity and related diseases such as type 2 diabetes mellitus (T2DM) is increasing worldwide, and the Asian Indian population seems to be particularly susceptible to developing T2DM, even at a low body mass index (BMI). In Sweden, the age-adjusted prevalence of diabetes has not increased despite increasing self-reported obesity. However, modern data on the prevalence of obesity and T2DM in Scandinavia are absent.The biochemical links between obesity and subsequent T2DM are unknown, but the adipocyte-derived hormones leptin and adiponectin (adipokines) have been suggested as potential links because they both are related to insulin and glucose physiology. Some studies have found leptin to be an independent predictor of T2DM in men but not in women, although these results are inconsistent. In contrast, adiponectin has more consistently been linked to development of T2DM in both men and women. Furthermore, the leptin–adiponectin ratio may predict incident T2DM better than either of the two hormones separately.The aims of this thesis were to describe time trends in obesity and T2DM in northern Sweden, to evaluate leptin and adiponectin as predictors of deterioration in glucose metabolism including T2DM, and to evaluate leptin as a risk marker regarding ethnic differences, circ-annual variation, and intra-individual stability. Materials and methods Three large population surveys were used, the Northern Sweden MONICA (MONitoring of Trends and Determinants in CArdiovascular Disease) study, the Västerbotten Intervention Programme (VIP), and the Mauritius Non-Communicable Disease Study. Within the MONICA study, six cross-sectional surveys were performed in Sweden’s two northernmost counties, Norrbotten and Västerbotten, between 1986 and 2009. A total of 1000 men and 1000 women ages 25–64 years, also including from 1994 250 men and 250 women ages 65–74 years, were independently chosen for each survey. The overall participation rate was 75%. In 1999, a reinvestigation was performed in 74% of all participants from the three first surveys. Data from the MONICA surveys were used in papers I and IV and data from the reinvestigation survey in paper II. VIP is an ongoing population intervention program that started in the mid-eighties targeting cardiovascular risk factors and has covered the whole county of Västerbotten since 1991. Inhabitants are invited the years they turn 40, 50, and 60 years old, and the annual participation rate has varied between 48% and 67%. A subset (n=1780) from VIP was used in paper II for the circ-annual leptin analysis, and VIP data linked to the diabetes register in Västerbotten (DiabNorr) were used in a case referent study (640 patients with T2DM) in paper III. The Mauritius Non-Communicable Disease Study was performed in 1987 in 10 randomly selected (with probability proportional to size) population clusters. All eligible adults ages 25–74 years were invited, and the participation rate was 86% (n=5083). In 1992, a follow-up survey was performed in 49% of the initial participants. The Mauritius survey data were used in paper II. Results I. BMI increased in men ages 25–74 years and in women ages 25–44 years in northern Sweden between 1986 and 2004. The prevalence of obesity (BMI 30) increased in men ages 25–44 and 55–74 years and in women ages 25–44 years. The prevalence of obesity increased from 10.4% to 19.1% in men and from 12.9% to 17.9% in women ages 25–64 years. Waist circumference (WC) decreased in women of all ages and in men ages 55–64 years between 1986 and 1990. After 1990, WC increased again, and the prevalence of abdominal obesity rose markedly in women ages 25–64 years. II. Differences in circulating levels of leptin, leptin per BMI unit (leptin/BMI), and leptin per cm in WC (leptin/waist) were tested in men and women of Asian Indian, Creole (African), and Caucasian ethnicity. Asian Indian men and women had the highest leptin concentrations and Caucasian men and women the lowest while Creole men and women had intermediate values for leptin, leptin/BMI, and leptin/waist. No circ-annual variation in leptin concentrations was seen in Caucasians. The intra-individual test– retest stability for leptin was equal in men and women of different ethnicities, over 5–13 years, with an intra-class correlation of 0.65–0.82. III. High adiponectin concentrations predicted decreased risk of T2DM in both insulin-sensitive and insulin-resistant men and women, whereas high leptin levels predicted increased risk for T2DM only in insulinsensitive men. A high leptin–adiponectin ratio predicted T2DM in both men and women, and men with a high ratio had a shorter time to diagnosis than those with a low ratio. IV. In northern Sweden, fasting and post-load glucose increased in women ages 24–65 years with 0.2 mmol/l and 0.7 mmol/l, respectively, between 1990 and 2009. Consequently, the prevalence of impaired fasting glucose and impaired glucose tolerance (IGT) rose from 4.5% to 7.7%, and from 7.8% to 14.5%, respectively. In men, post-load glucose increased at 0.5 mmol/l, and the prevalence of IGT rose from 3.5% to 10.1%. The prevalence of diabetes did not increase. An independent relationship between leptin and changes in fasting and post-load glucose was seen in men but not in women. Conclusion An increasing obesity and concomitant deterioration in glucose metabolism was seen in northern Sweden in the period studied. High adiponectin concentrations predicted a decreased risk of T2DM in both men and women, whereas high leptin concentrations predicted an increase in fasting and post-load glucose as well as an increased risk of T2DM in men but not in women. Individual insulin resistance status modified the association between leptin and T2DM, and the leptin–adiponectin ratio may add further predictive information beyond the measures of the separate hormones. In relation to traditional anthropometric measures of obesity, Asian Indian men and women had the highest and Caucasians the lowest concentrations of leptin while Creole (African) men and women had intermediate levels. As a risk marker, leptin has a high intra-individual stability, equal in men and women and among different ethnicities over 5–13 years with no circ-annual variation.

Abstract Nutritional status affects every aspect of a child?s health. Thorough nutritional assessment is hampered by the lack of a single comprehensive tool, which can cover all aspects of nutritional assessment. In three distinct studies, this thesis investigated the nutritional status of hospitalised children, children with coeliac disease and children with inflammatory bowel disease. Study 1 The objectives of this study were to assess prevalence of malnutrition and nutritional risk, and define demographic and anthropometric factors associated with nutritional risk among hospitalized children. In this cross sectional study, 157 hospitalised children were assessed for nutritional status using nutritional risk score (NRS) and anthropometric measurements. We found that 4.5%, 8.9%, 15.1% and 10.4% children were wasted, stunted, overweight and obese respectively. However, with the NRS, 47.8% of the children were at high nutritional risk. These children at high risk had lower weight for age (p=0.02), lower BMI percentiles for age (p=0.001) and longer hospitalization (p=0.001) than children at no risk. Study 2 The objectives of this study were to determine nutritional parameters in children with coeliac disease. Twenty-five children with coeliac disease and an equal number of age and gender matched controls were enrolled and anthropometric measurements, BIA and leptin levels were analysed in all. No significant differences were found between the children with coeliac disease and controls in these parameters. BMI percentile correlated with leptin levels in children with coeliac disease. Study 3 The objectives of this study were to determine anthropometric parameters and leptin levels in children with IBD and ascertain if BMI correlates with leptin levels in these children. Thirty children with IBD and 60 age and gender matched controls were enrolled. Anthropometric measurements and leptin levels were analysed and compared with controls. IBD children had significantly low weight for age (p=0.002), BMI percentiles (p=0.001) and leptin levels (p=0.009) compared to controls. There was a correlation between BMI and leptin levels in IBD children. In conclusion, this thesis has shown that one quarter of hospitalized children were overweight or obese, and further, that half of the hospitalised children were at high risk of nutritional deterioration and these children had longer hospital stay than children at no risk. Children with coeliac disease had similar anthropometric measurements, body compartments and leptin levels to controls. However, children with IBD had lower anthropometric measurements and leptin levels, indicating under-nutrition. Nutritional assessment should be a mandatory part of clinical management with nutritional status assessed by various tools including NRS, anthropometry, BIA and leptin levels.

Abstract Nutritional status affects every aspect of a child?s health. Thorough nutritional assessment is hampered by the lack of a single comprehensive tool, which can cover all aspects of nutritional assessment. In three distinct studies, this thesis investigated the nutritional status of hospitalised children, children with coeliac disease and children with inflammatory bowel disease. Study 1 The objectives of this study were to assess prevalence of malnutrition and nutritional risk, and define demographic and anthropometric factors associated with nutritional risk among hospitalized children. In this cross sectional study, 157 hospitalised children were assessed for nutritional status using nutritional risk score (NRS) and anthropometric measurements. We found that 4.5%, 8.9%, 15.1% and 10.4% children were wasted, stunted, overweight and obese respectively. However, with the NRS, 47.8% of the children were at high nutritional risk. These children at high risk had lower weight for age (p=0.02), lower BMI percentiles for age (p=0.001) and longer hospitalization (p=0.001) than children at no risk. Study 2 The objectives of this study were to determine nutritional parameters in children with coeliac disease. Twenty-five children with coeliac disease and an equal number of age and gender matched controls were enrolled and anthropometric measurements, BIA and leptin levels were analysed in all. No significant differences were found between the children with coeliac disease and controls in these parameters. BMI percentile correlated with leptin levels in children with coeliac disease. Study 3 The objectives of this study were to determine anthropometric parameters and leptin levels in children with IBD and ascertain if BMI correlates with leptin levels in these children. Thirty children with IBD and 60 age and gender matched controls were enrolled. Anthropometric measurements and leptin levels were analysed and compared with controls. IBD children had significantly low weight for age (p=0.002), BMI percentiles (p=0.001) and leptin levels (p=0.009) compared to controls. There was a correlation between BMI and leptin levels in IBD children. In conclusion, this thesis has shown that one quarter of hospitalized children were overweight or obese, and further, that half of the hospitalised children were at high risk of nutritional deterioration and these children had longer hospital stay than children at no risk. Children with coeliac disease had similar anthropometric measurements, body compartments and leptin levels to controls. However, children with IBD had lower anthropometric measurements and leptin levels, indicating under-nutrition. Nutritional assessment should be a mandatory part of clinical management with nutritional status assessed by various tools including NRS, anthropometry, BIA and leptin levels.

Abstract Nutritional status affects every aspect of a child?s health. Thorough nutritional assessment is hampered by the lack of a single comprehensive tool, which can cover all aspects of nutritional assessment. In three distinct studies, this thesis investigated the nutritional status of hospitalised children, children with coeliac disease and children with inflammatory bowel disease. Study 1 The objectives of this study were to assess prevalence of malnutrition and nutritional risk, and define demographic and anthropometric factors associated with nutritional risk among hospitalized children. In this cross sectional study, 157 hospitalised children were assessed for nutritional status using nutritional risk score (NRS) and anthropometric measurements. We found that 4.5%, 8.9%, 15.1% and 10.4% children were wasted, stunted, overweight and obese respectively. However, with the NRS, 47.8% of the children were at high nutritional risk. These children at high risk had lower weight for age (p=0.02), lower BMI percentiles for age (p=0.001) and longer hospitalization (p=0.001) than children at no risk. Study 2 The objectives of this study were to determine nutritional parameters in children with coeliac disease. Twenty-five children with coeliac disease and an equal number of age and gender matched controls were enrolled and anthropometric measurements, BIA and leptin levels were analysed in all. No significant differences were found between the children with coeliac disease and controls in these parameters. BMI percentile correlated with leptin levels in children with coeliac disease. Study 3 The objectives of this study were to determine anthropometric parameters and leptin levels in children with IBD and ascertain if BMI correlates with leptin levels in these children. Thirty children with IBD and 60 age and gender matched controls were enrolled. Anthropometric measurements and leptin levels were analysed and compared with controls. IBD children had significantly low weight for age (p=0.002), BMI percentiles (p=0.001) and leptin levels (p=0.009) compared to controls. There was a correlation between BMI and leptin levels in IBD children. In conclusion, this thesis has shown that one quarter of hospitalized children were overweight or obese, and further, that half of the hospitalised children were at high risk of nutritional deterioration and these children had longer hospital stay than children at no risk. Children with coeliac disease had similar anthropometric measurements, body compartments and leptin levels to controls. However, children with IBD had lower anthropometric measurements and leptin levels, indicating under-nutrition. Nutritional assessment should be a mandatory part of clinical management with nutritional status assessed by various tools including NRS, anthropometry, BIA and leptin levels.

The developmental origins of health and disease hypothesis suggests that exposure to adverse prenatal environmental influences can determine an individual’s susceptibility to obesity in adult life. However, the specific causal mechanisms which underlie this hypothesis have yet to be identified. Focusing on the potential mechanistic role of the leptin endocrine axis, the main objective of this thesis was to investigate the long term effects of prenatal undernutrition and different levels of postnatal nutrition on leptin sensitivity and the development of diet-induced obesity (DIO) in the Wistar rat. A well established animal model of maternal undernutrition during pregnancy was used to induce prenatal undernutrition in experimental offspring. To investigate the interaction between prenatal nutrition and postnatal diet, and its effects on obesity development, female offspring were placed on three different diets: standard chow, a high fat diet or a calorie restricted diet. The effects of prenatal undernutrition and postnatal diet on leptin sensitivity were investigated, in adult offspring, by measuring the response to 14 days of peripheral leptin treatment. Changes in gene expression in the liver, retroperitoneal adipose tissue and soleus muscle were then characterised by custom microarray and quantitative real-time RT-PCR (QPCR) analysis. Adult female offspring exposed to prenatal undernutrition (UN offspring) were found to exhibit leptin resistance in adulthood, independent of postnatal DIO. This result demonstrates for the first time that exposure to prenatal undernutrition has a long term effect on adult leptin sensitivity. In UN offspring fed on a high-fat diet, leptin resistance significantly accelerated the development of DIO while in contrast, offspring maintained on calorie restriction remained lean. These findings suggest that prenatal nutrition can shape future susceptibility to DIO by altering postnatal leptin sensitivity. An analysis of gene expression suggests that prenatal undernutrition causes the development of peripheral tissue-specific leptin resistance, and may also further enhance an offspring’s susceptibility to DIO by altering the regulation of peripheral tissue lipogenesis, mitochondrial function, glucocorticoid metabolism and insulin sensitivity. In conclusion, these studies identify peripheral leptin resistance as a key mechanism that can influence postnatal susceptibility to DIO in female offspring exposed to prenatal undernutrition. Furthermore, the identification of specific changes in peripheral gene expression highlights four additional metabolic mechanisms which may also facilitate the development of DIO in leptin resistant UN offspring.

The developmental origins of health and disease hypothesis suggests that exposure to adverse prenatal environmental influences can determine an individual’s susceptibility to obesity in adult life. However, the specific causal mechanisms which underlie this hypothesis have yet to be identified. Focusing on the potential mechanistic role of the leptin endocrine axis, the main objective of this thesis was to investigate the long term effects of prenatal undernutrition and different levels of postnatal nutrition on leptin sensitivity and the development of diet-induced obesity (DIO) in the Wistar rat. A well established animal model of maternal undernutrition during pregnancy was used to induce prenatal undernutrition in experimental offspring. To investigate the interaction between prenatal nutrition and postnatal diet, and its effects on obesity development, female offspring were placed on three different diets: standard chow, a high fat diet or a calorie restricted diet. The effects of prenatal undernutrition and postnatal diet on leptin sensitivity were investigated, in adult offspring, by measuring the response to 14 days of peripheral leptin treatment. Changes in gene expression in the liver, retroperitoneal adipose tissue and soleus muscle were then characterised by custom microarray and quantitative real-time RT-PCR (QPCR) analysis. Adult female offspring exposed to prenatal undernutrition (UN offspring) were found to exhibit leptin resistance in adulthood, independent of postnatal DIO. This result demonstrates for the first time that exposure to prenatal undernutrition has a long term effect on adult leptin sensitivity. In UN offspring fed on a high-fat diet, leptin resistance significantly accelerated the development of DIO while in contrast, offspring maintained on calorie restriction remained lean. These findings suggest that prenatal nutrition can shape future susceptibility to DIO by altering postnatal leptin sensitivity. An analysis of gene expression suggests that prenatal undernutrition causes the development of peripheral tissue-specific leptin resistance, and may also further enhance an offspring’s susceptibility to DIO by altering the regulation of peripheral tissue lipogenesis, mitochondrial function, glucocorticoid metabolism and insulin sensitivity. In conclusion, these studies identify peripheral leptin resistance as a key mechanism that can influence postnatal susceptibility to DIO in female offspring exposed to prenatal undernutrition. Furthermore, the identification of specific changes in peripheral gene expression highlights four additional metabolic mechanisms which may also facilitate the development of DIO in leptin resistant UN offspring.

The developmental origins of health and disease hypothesis suggests that exposure to adverse prenatal environmental influences can determine an individual’s susceptibility to obesity in adult life. However, the specific causal mechanisms which underlie this hypothesis have yet to be identified. Focusing on the potential mechanistic role of the leptin endocrine axis, the main objective of this thesis was to investigate the long term effects of prenatal undernutrition and different levels of postnatal nutrition on leptin sensitivity and the development of diet-induced obesity (DIO) in the Wistar rat. A well established animal model of maternal undernutrition during pregnancy was used to induce prenatal undernutrition in experimental offspring. To investigate the interaction between prenatal nutrition and postnatal diet, and its effects on obesity development, female offspring were placed on three different diets: standard chow, a high fat diet or a calorie restricted diet. The effects of prenatal undernutrition and postnatal diet on leptin sensitivity were investigated, in adult offspring, by measuring the response to 14 days of peripheral leptin treatment. Changes in gene expression in the liver, retroperitoneal adipose tissue and soleus muscle were then characterised by custom microarray and quantitative real-time RT-PCR (QPCR) analysis. Adult female offspring exposed to prenatal undernutrition (UN offspring) were found to exhibit leptin resistance in adulthood, independent of postnatal DIO. This result demonstrates for the first time that exposure to prenatal undernutrition has a long term effect on adult leptin sensitivity. In UN offspring fed on a high-fat diet, leptin resistance significantly accelerated the development of DIO while in contrast, offspring maintained on calorie restriction remained lean. These findings suggest that prenatal nutrition can shape future susceptibility to DIO by altering postnatal leptin sensitivity. An analysis of gene expression suggests that prenatal undernutrition causes the development of peripheral tissue-specific leptin resistance, and may also further enhance an offspring’s susceptibility to DIO by altering the regulation of peripheral tissue lipogenesis, mitochondrial function, glucocorticoid metabolism and insulin sensitivity. In conclusion, these studies identify peripheral leptin resistance as a key mechanism that can influence postnatal susceptibility to DIO in female offspring exposed to prenatal undernutrition. Furthermore, the identification of specific changes in peripheral gene expression highlights four additional metabolic mechanisms which may also facilitate the development of DIO in leptin resistant UN offspring.

The developmental origins of health and disease hypothesis suggests that exposure to adverse prenatal environmental influences can determine an individual’s susceptibility to obesity in adult life. However, the specific causal mechanisms which underlie this hypothesis have yet to be identified. Focusing on the potential mechanistic role of the leptin endocrine axis, the main objective of this thesis was to investigate the long term effects of prenatal undernutrition and different levels of postnatal nutrition on leptin sensitivity and the development of diet-induced obesity (DIO) in the Wistar rat. A well established animal model of maternal undernutrition during pregnancy was used to induce prenatal undernutrition in experimental offspring. To investigate the interaction between prenatal nutrition and postnatal diet, and its effects on obesity development, female offspring were placed on three different diets: standard chow, a high fat diet or a calorie restricted diet. The effects of prenatal undernutrition and postnatal diet on leptin sensitivity were investigated, in adult offspring, by measuring the response to 14 days of peripheral leptin treatment. Changes in gene expression in the liver, retroperitoneal adipose tissue and soleus muscle were then characterised by custom microarray and quantitative real-time RT-PCR (QPCR) analysis. Adult female offspring exposed to prenatal undernutrition (UN offspring) were found to exhibit leptin resistance in adulthood, independent of postnatal DIO. This result demonstrates for the first time that exposure to prenatal undernutrition has a long term effect on adult leptin sensitivity. In UN offspring fed on a high-fat diet, leptin resistance significantly accelerated the development of DIO while in contrast, offspring maintained on calorie restriction remained lean. These findings suggest that prenatal nutrition can shape future susceptibility to DIO by altering postnatal leptin sensitivity. An analysis of gene expression suggests that prenatal undernutrition causes the development of peripheral tissue-specific leptin resistance, and may also further enhance an offspring’s susceptibility to DIO by altering the regulation of peripheral tissue lipogenesis, mitochondrial function, glucocorticoid metabolism and insulin sensitivity. In conclusion, these studies identify peripheral leptin resistance as a key mechanism that can influence postnatal susceptibility to DIO in female offspring exposed to prenatal undernutrition. Furthermore, the identification of specific changes in peripheral gene expression highlights four additional metabolic mechanisms which may also facilitate the development of DIO in leptin resistant UN offspring.