GlycA, a biomarker of low-grade inflammation, is increased in male night shift workers

Sustained night shift work is associated with various adverse health risks, including an increased risk of cardiovascular disease, type II diabetes and susceptibility to infectious respiratory diseases. The extent of these adverse health effects, however, seems to greatly vary between night shift workers, yet the underlying reasons and mechanisms underlying these interindividual differences remain poorly understood. Metabolomics assays in blood have recently gained a lot of attention as a minimally invasive biomarker platform capturing information predictive of metabolic and cardiovascular diseases. In this cross-sectional study, we explore and compare the metabolic profiles of 1,010 night shift workers and 1,010 age- and sex-matched dayworkers (non-shift workers) from the Lifelines Cohort Study. The metabolic profiles were determined using the 1H-NMR Nightingale platform for quantification of 250 parameters of metabolism, including routine lipids, extensive lipoprotein subclasses, fatty acid composition, and various low‐molecular metabolites, including amino acids, ketone bodies, and gluconeogenesis-related metabolites. 
Night shift workers had an increased BMI (26.6 vs. 25.9 kg/m2) compared to dayworkers (non-shift workers), were slightly more often ever smokers (only in males) (54% vs. 46%), worked on average 5.9 ±3.7 night shifts per month and had been working in night shifts for 18.3 ±10.5 years on average. We observed changes in several metabolic markers in male night shift workers compared to non-shift workers, but not in women. In men, we observed an increase in levels of glycoprotein acetyls (GlycA), triglycerides and fatty acids compared to non-shift workers. The changes were seen in the ratio of triglycerides and cholesterol(esters) to total lipids in different sizes of VLDL particles. Glycoprotein acetyls (GlycA), are of particular interest as a marker, since it is known as a biomarker for low-grade chronic inflammation. When the analyses were adjusted for BMI no significant associations were observed. Further studies are needed to better understand the relationship between night shift work and metabolic profiles, in particular with respect to the role of sex and BMI in this relationship.