[Daily changes in the carbon isotope composition of CO2 in expired air of persons with various metabolic disorders].

Daily variations of the aspiration CO2 carbon isotope content (CIC) were studied at three metabolic states: norm, insulin-dependent diabetes (IDD), and obesity. The groups of subjects were studied in a clinic during 24 hours. Analysis of the delta 13C daily curves of the exhaled air CO2 allowed us to find the link between variations of CIC with daily rhythms in the organism and with metabolic shifts at IDD and obesity. At metabolic norm it is possible two phases on the daily curve, corresponding to daytime and nighttime metabolism types with hormonally regulated transition between them. The daytime phase of the curve consists of altering maxima and minima, linked to periodicity in feeding and movement activity. The nighttime phase is characterized by continuous enrichment of CO2 by 12C. At IDD in insulin therapy conditions the most prominent difference from norm and obesity is the stable CIC at nighttime. At daytime during weakening of the exogenous insulin action there appear horizontal regions on the delta 13C CO2 curves, similar to the nighttime behaviour. At obesity the daily curves are close to the normal ones, but they are more smooth and impoverished in 13C. No clear transition between the daytime and nighttime metabolism types can be observed. At obesity and IDD the character of the daily curves can be observed.