Plasma Glycine Concentration but Not Whole Body Production Production Rate Is a Marker of Abdominal Obesity in Older Adults Independent of the Presence of a Chronic Disease

Abstract

ObjectivesPreviously, in healthy older adults, the concentration of the plasma amino acid glycine was found to be negatively related to the amount of visceral adipose tissue (VAT). It remains unclear whether this is due to alterations in the whole body glycine production, and independent of the presence of a concomitant chronic disease in older adults (e.g., Chronic Obstructive Pulmonary Disease (COPD)).MethodsIn this study, 88 healthy older adults (40 males/48 females) and 122 older adults with stable moderate to severe COPD (58 males/64 females) were studied. In all subjects, body composition and VAT (by DXA) were assessed, as well as muscle function (respiratory strength by mouth pressure, hand- and leg peak strength and endurance by dynamometers) and Charlson Comorbidity index. We also measured plasma concentration and whole body production (WBP) of glycine using stable isotope techniques and analyzed them by LC-MS/MS. Statistics performed by ANCOVA included age, gender, and body mass index as covariates. Significance was set at p < 0.05 and results were expressed as means [95% CI].ResultsAlthough plasma glycine concentration was comparable between healthy and COPD older adults (p = 0.21), a negatively association was found with VAT area (p < 0.0002; Slope −0.08 [−0.07, −0.10] μM/cm2 VAT) in the total group as well as in the healthy and COPD subgroups. The ROC area was 0.8801 [0.8329, 0.9273] when separating VAT at 800 cm2. WBP of glycine was also not different between healthy older adults and those with COPD but no significant relationship was found with VAT area (p = 0.49). Also no association was found between VAT and any of the other measured parameters.ConclusionsIndependent of the presence of COPD, a lower plasma glycine concentration, but not the whole body glycine production, relates to a higher amount of visceral fat in older adults. We conclude that plasma glycine concentration is a marker of the amount of visceral adipose tissue in older adults independent of the presence of a chronic disease.Funding SourcesNone.