Higher levels of abdominal body fat are associated with an increase in pro-inflammatory immunoglobulin G N-glycans: Results from the Busselton Healthy Ageing Study
School of Medical and Health Sciences
It has been postulated that the N-glycan moieties of immunoglobulin G represent intermediate phenotypes of subclinical and chronic disease. By definition this would mean they are a link between the genetic makeup of our cells and the cellular environment, which is largely under the influence of our habits and daily routines. Increased body fat may be associated with an increased risk of developing an underlying pro-inflammatory state, thus leading to a greater risk of developing certain chronic diseases. Immunoglobulin G, an immune glycoprotein, has the ability to exert both anti-inflammatory and pro-inflammatory effects, and the N-glycosylation of the fragment crystallisable portion of immunoglobulin G is involved in this process. Previous research demonstrated that body mass index, a rudimentary yet gold standard indication for body fat used in many types of public health research, is weakly associated with immunoglobulin G N-glycans, particularly a reduction in galactosylation. The current study aimed to determine the association between increased levels of body fat and immunoglobulin G N-glycans, comparing a number of different available methods. Six hundred and thirty-seven community-based “Baby Boomers” residing in Busselton, Western Australia, were investigated. As well as calculating body mass index and the waist-to-hip and waist-to-height ratios using anthropometry, dual-energy x-ray absorptiometry was performed to gain an accurate measure of total and area specific body fat. Serum immunoglobulin G N-glycans were analysed by ultra-performance liquid chromatography. Linear regression models, controlling for age and gender, were used for all data analyses. In total, seventeen glycan peaks were found to be associated with the fat measures, with the android-to-gynoid ratio, measured using dual-energy X-ray absorptiometry, as well as the waist-to-height ratio explaining the most variation in the glycan peaks. Overall, there was a decreased abundance of glycans containing galactose as levels of body fat, and particularly abdominal fat, increased. This study suggested that abdominal fat is associated with an increase in pro-inflammatory immunoglobulin G N-glycans. Thus, accurate measures of body fat should be considered in future N-glycan biomarkers studies.