Posterior Cervical Brown Fat and CXCL14 Levels in the First Year of Life: Sex Differences and Association With Adiposity

Abstract

Context Brown adipose tissue (BAT) is particularly abundant in neonates but its association with measures of adiposity and metabolic health in early infancy is poorly delineated. Besides sustaining non-shivering thermogenesis, BAT secretes brown adipokines that act on systemic metabolism. The chemokine CXCL14 has been identified as a brown adipokine in experimental studies. Objective To determine the relationships among BAT activity, adiposity and circulating CXCL14 levels in the first year of life in girls and boys. Design, setting and participants Indices of fat accretion, circulating endocrine-metabolic parameters and serum CXCL14 levels were assessed longitudinally in a cohort of infants at birth and at 4 and 12 months. BAT activity was estimated using infrared thermography only at age 12 months. Main outcome measures Weight and length Z-scores, total and abdominal fat content (by DXA), BAT activity at the posterior-cervical and supraclavicular regions, serum levels of glucose, insulin, insulin-like growth factor-I, high-molecular-weight adiponectin and CXCL14; CXCL14 transcript levels in neonatal BAT and liver. Results Posterior-cervical BAT was more active in girls than in boys (P=0.02). BAT activity was negatively associated with adiposity parameters only in girls. CXCL14 levels were higher in girls than in boys at age 12 months and correlated positively with the area of active posterior-cervical BAT in girls. Neonatal BAT showed high CXCL14 gene expression levels. Conclusions BAT activity and the levels of CXCL14 -a potential surrogate of BAT activity, are sex-specific in the first year of life. Posterior-cervical BAT activity associates negatively with indices of adiposity only in girls.

Bone Morphogenetic Protein-8B Levels at Birth and in the First Year of Life: Relation to Metabolic-Endocrine Variables and Brown Adipose Tissue Activity

“…The study cohort consisted of 50 infants (27 girls and 23 boys) who were enrolled prenatally during the customary third trimester visit among those Caucasian pregnant mothers (age, 34.0 ± 0.7 years) consecutively seen in the outpatient clinic of Hospital Sant Joan de Déu and Hospital de Sant Boi – Parc Sanitari Sant Joan de Déu (Barcelona, Spain) ( Supplementary Figure 1 ). Forty-three out of those 50 infants (23 girls and 20 boys) had previously participated in a longitudinal study assessing BAT activity and the circulating levels of CXCL14 in the first year of life ( 3 ).…”

“…Specific inclusion and exclusion criteria have been previously described in detail ( 3 ). Briefly, the inclusion criteria were: singleton uncomplicated pregnancies at term (37–42 weeks), exclusive breastfeeding or formula-feeding in the first 4 months, postnatal follow-up completed (at 15 days, 4 and 12 months) and written informed consent.…”

“…Serum glucose, insulin, insulin-like growth factor (IGF)-I, high-molecular-weight (HMW) adiponectin and CXCL14 were assessed as reported ( 3 ). Serum BMP8B levels were determined with a specific human enzyme-linked immunosorbent assay kit (MBS944757, MyBioSource, San Diego, CA, United States; sensitivity: 2.34 pg/ml; intra-assay coefficient of variation (CV): <8%; inter-assay CV: <10%).…”

“…As previously detailed ( 3 ), BAT activity at age 12 months was estimated through the infrared thermography-based measurement of the skin temperature overlying BAT depots. The parameters assessed included the maximal temperature at the posterior cervical (T PCR ) and supraclavicular (T SCR ) regions, and the extent of active BAT in these regions (Area PCR and Area SCR ).…”

“…The identification of batokines that could serve as circulating biomarkers of BAT activity could be useful in clinical practice. In this regard, we recently showed that BAT activity and the levels of the batokine C-X-C motif chemokine ligand 14 (CXCL14) -a purported surrogate of BAT activity- are sex-specific in the first year of life ( 3 ).…”