Diss. (sammanfattning) Stockholm : Karol. inst., 2003. / Härtill 4 uppsatser.

Bone-derived osteocalcin has been suggested to be a metabolic regulator, potentially improving insulin sensitivity. To scrutinize the relation between osteocalcin and peripheral insulin sensitivity, I analyzed changes of serum osteocalcin relative to changes in insulin sensitivity, low-grade inflammation and bone mineral density following lifestyle-induced weight loss in individuals with metabolic syndrome (MetS). 74 nonsmoking men (45–55 yr) with MetS were randomized to a lifestyle-induced weight loss program (supervision via telemonitoring) or to a control group. Before and after the 6 months intervention period clinical and laboratory parameters and serum osteocalcin levels were determined in fasting blood samples. Lifestyle-induced changes of body composition were analyzed by Dual Energy X Ray-Absorptiometry (DXA). 30 participants in the control and 33 participants in the intervention group completed the study and were included in the data analysis. In participants of the intervention group, weight loss resulted in markedly improved insulin sensitivity and amelioration of low-grade inflammation. Increased serum levels of osteocalcin correlated inversely with BMI (r= -0.63; p< 0.001), total fat mass (r= -0.58, p< 0.001), total lean mass (r= -0.45, p< 0.001), C-reactive protein (CRP) (r= -0.37; p< 0.01), insulin (r= -0.4; p< 0.001), leptin (r= -0.53; p< 0.001), triglycerides (r= -0.42; p< 0.001) and alanine aminotransferase (ALAT) (r=-0.52; p< 0.001). Regression analysis revealed that osteocalcin was associated with changes in CRP but not with changes in insulin concentration, adipose tissue mass or bone mineral density. These results illustrate that the weight loss-induced higher serum osteocalcin is primarily associated with reduced inflammation.:List of abbreviations ................................................................................................................................ 4 Short summary ........................................................................................................................................ 5 Graphical abstract ................................................................................................................................... 6 2 Introduction ......................................................................................................................................... 7 2a The metabolic syndrome ............................................................................................................... 8 2b C-reactive protein (CRP) and its role in MetS .............................................................................. 12 2c Bone-derived osteocalcin and inflammation ............................................................................... 14 2d Study design ................................................................................................................................. 17 3 Original peer-reviewed publication: “Osteocalcin Is Independently Associated with C-Reactive Protein during Lifestyle-Induced Weight Loss in Metabolic Syndrome” .............................................. 19 4 Summary ............................................................................................................................................ 32 5 References ......................................................................................................................................... 36 6 Supplementary data ........................................................................................................................... 45 7 Declaration about the independent preparation of the work ........................................................... 48 8 Presentation of own contribution ..................................................................................................... 49 9 Curriculum vitae ................................................................................................................................. 51 10 Publications ...................................................................................................................................... 57 11 Acknowledgments ............................................................................................................................ 58

The normal adult heart prefers fatty acids as an energy substrate. In the case of heart failure, the heart switches its preference from fatty acids to glucose, adopting a pattern similar to fetal metabolism. PGC-1α is heavily involved in the shift towards glucose oxidation. p65, which belongs to the NF-κB transcription factor family is another crucial molecule involved in maintaining cardiac homeostasis. There is a substantial amount of evidence suggesting that PGC-1α and NF-κB directly interact, thereby connecting metabolic and inflammatory processes. Dysregulation of either PGC-1α or NF-κB signalling correlates to many diseases including heart disease. In this study, we provide further evidence that the NF-κB family has the ability to repress PGC-1α. We also show that the PGC-1α promoter contains a p65 binding site through which p65 imparts control on the PGC-1α gene. Metabolic homeostasis and inflammation pathways are closely linked and play crucial roles in heart dysfunction.

Obesity-associated metabolic disorders are amongst the most prevalent causes of death worldwide. Understanding how obesity leads to the development of the Metabolic Syndrome (MetS) and cardiovascular disease (CVD) will enable the development of novel therapies that dissociate obesity from its cardiometabolic complications. Our laboratory views the functional capacity of white adipose tissue (WAT), the organ designed for safe lipid storage, as a key factor in the development of MetS and CVD. At a genetically-defined stage of the aberrant WAT expansion that occurs during obesity, adipocytes undergo a functional failure, resulting in an impaired control of serum free fatty acid (FFA) concentration. In such setting, FFAs and their metabolic derivatives accumulate in other organs, where they cause lipotoxicity, leading to the development of insulin resistance and CVD. We therefore aim to understand the pathophysiological mechanisms that induce adipocyte dysfunction. The past two decades of research have established the immune system as an important regulator of WAT function. The number of adipose tissue macrophages (ATMs), the most abundant immune cell type in WAT, increases during obesity, resulting in WAT inflammation. Multiple genetic and pharmacological intervention studies of murine models of obesity have assigned a causal link between ATM pro-inflammatory activation and WAT dysfunction. However, while the propagation of inflammation in ATMs during obesity has been extensively studied, factors triggering ATM inflammatory activation are less clear. Recently, our lab has observed lipid accumulation in the ATMs isolated from obese mice. Lipid-laden ATMs were pro-inflammatory, leading us to hypothesise that aberrant lipid build-up in macrophages triggers WAT inflammation during obesity. This thesis expands on the initial findings from our lab and describes two novel mechanisms that potentially contribute to lipid-induced inflammatory activation of ATMs. In chapter 3, the role of de novo phosphatidylcholine (PC) synthesis pathway during lipotoxicity in macrophages is addressed. The first part of the chapter demonstrates that lipotoxic environment increased de novo PC synthesis rate in bone marrow-derived macrophages (BMDMs) and ATMs, and that loss of rate-limiting enzyme in de novo PC synthesis pathway, CTP:phosphocholine cytidylyltransferase a (CCTa) diminished saturated FFA-induced inflammation in BMDMs. In the second part, I show that macrophage-specific CCTa deletion did not impact on the development of WAT inflammation or systemic insulin resistance, but had a minor benefitial effect on hepatic gene transcription during obesity. Chapter 4 develops on recent observations of interactions between sympathetic nerves and macrophages in WAT. In the first part of the chapter, I demonstrate that stimulating B2-adrenergic receptor (B2AR), the main receptor for sympathetic neurotransmitter norepinephrine in macrophages, enhanced intracellular triglyceride storage by up-regulating diacylglycerol O-acyltransferase 1 (Dgat1) gene expression in BMDMs. The second part of the chapter shows that macrophage-specific B2AR deletion did not modulate systemic glucose and lipid metabolism during obesity, but mice lacking B2ARs in macrophages demonstrated augmented hepatic glucose production on a chow diet. Furthermore, systemic B2AR blockade or macrophage-specific B2AR deletion in mice did not affect the thermogenic response to cold exposure. Chapter 5 includes the characterisation of B2AR stimulation-induced changes to the global cellular proteome of BMDMs, and a subsequent validation of the role of candidate transcription factors in regulating B2AR agonism-induced gene expression in BMDMs.