Adipose tissue, the skeleton and cardiovascular disease

Sammanfattning: Cardiovascular disease (CVD) is the leading cause of death in the Western World, although the incidence of myocardial infarction (MI) has declined over the last decades. However, obesity, which is one of the most important risk factors for CVD, is increasingly common. Osteoporosis is also on the rise because of an aging population. Based on considerable overlap in the prevalence of CVD and osteoporosis, a shared etiology has been proposed. Furthermore, the possibility of interplay between the skeleton and adipose tissue has received increasing attention the last few years with the discovery that leptin can influence bone metabolism and that osteocalcin can influence adipose tissue.A main aim of this thesis was to investigate the effects of fat mass distribution and bone mineral density on the risk of MI. Using dual-energy x-ray absorptiometry (DEXA) we measured 592 men and women for regional fat mass in study I. In study II this was expanded to include 3258 men and women. In study III 6872 men and women had their bone mineral density measured in the total hip and femoral neck using DEXA. We found that a fat mass distribution with a higher proportion of abdominal fat mass was associated with both an adverse risk factor profile and an increased risk of MI. In contrast, a higher gynoid fat mass distribution was associated with a more favorable risk factor profile and a decreased risk of MI, highlighting the different properties of abdominal and gynoid fat depots (study I-II). In study III, we investigated the association of bone mineral density and risk factors shared between CVD and osteoporosis, and risk of MI. We found that lower bone mineral density was associated with hypertension, and also tended to be associated to other CVD risk factors. Low bone mineral density was associated with an increased risk of MI in both men and women, apparently independently of the risk factors studied (study III).In study IV, we investigated 50 healthy, young men to determine if a high-impact loading intervention in the form of a series of jumps would lead to changes in glucose and lipid metabolism. We found that the intervention group had significantly lowered serum glucose levels compared to the control group. Changes in all metabolic parameters favored the intervention group with an increase in lipolysis from baseline and a decrease in cholesterol.In summary, the proportion of abdominal and gynoid fat mass displayed contrasting associations to both CVD risk factors and MI risk. Abdominal fat mass was associated with a higher risk while a high proportion of gynoid fat mass was associated with a lower risk. Bone mineral density displayed an inverse association with MI risk, seemingly independently of CVD risk factors, suggesting other explanations to a shared pathogenesis. Finally, high impact loading on the skeleton in young, healthy men decreased serum glucose levels and tended to improve other metabolic parameters, suggesting that the skeleton can affect energy metabolism.