Degree of Agreement Between Infant Serum and Salivary Concentration of Leptin and Adiponectin and Its Association With Infants’ Feeding

Background: Leptin and adiponectin, two adipokines involved in glucose and lipid metabolism, have been linked to regulation of growth in early infancy, energy balance, and metabolic disorders in childhood. The aim of this study was to determine if concentrations of leptin and adiponectin could be measured reliably in infants’ saliva, to evaluate the degree of agreement with infant serum levels, and to explore their association with infant feeding status. Methods: A total of 34 infants were recruited after birth and followed for 20 weeks. After log-transformation of the values, a Bland-Altman graphical approach was used to summarize the direction of the difference between the serum and saliva values. Repeated measures mixed modeling was used to evaluate differences over time in these outcomes by feeding status. Results: Mean concentration of salivary leptin and adiponectin in infants was 3.7 (SD =.8) ng/mL and 2.9 (SD = 0.7) ng/mL, respectively. The degree of agreement between serum and saliva for log-transformed leptin and adiponectin values were relatively robust, albeit with a non-zero bias between the two methods, given that serum values were greater than corresponding saliva values for both adipokines in all infants. Each of the four repeated measures mixed models (one for each adipokine measure) had a significant main effect; however, the interaction between time and feeding status was not significant in any of the models. Conclusion: This study demonstrated that leptin and adiponectin can be measured in infant saliva, but in some cases leptin concentrations may be more difficult to detect.