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Expression of beta 1- and beta 2-receptor genes and correlation to lipolysis in human adipose tissue during childhood
Insights
Infants show higher beta-2 adrenoceptor (bar2) mRNA and increased bar2-induced lipolysis compared to adults. Beta-1 adrenoceptor (bar1) mRNA levels remain constant across age groups.
Area of Science:
- Adipose tissue biology
- Adrenergic receptor signaling
- Pediatric endocrinology
Background:
- Adrenergic receptors (bar1 and bar2) play a crucial role in regulating lipolysis in adipose tissue.
- Developmental changes in adrenergic receptor expression and function are not fully understood.
Purpose of the Study:
- To investigate age-related differences in beta-1 and beta-2 adrenoceptor mRNA expression in human adipose tissue.
- To examine the functional consequences of these developmental changes on lipolytic sensitivity.
Main Methods:
- Measurement of bar1 and bar2 mRNA levels in adipose tissue from infants, children, and adults.
- Assessment of lipolytic sensitivity to various adrenergic agonists (noradrenaline, adrenaline, isoprenaline, dobutamine, terbutaline) in different age groups.
Main Results:
- Bar1 mRNA levels were constant across all age groups.
- Bar2 mRNA levels were significantly higher in infants and young children (<7 years) compared to adults.
- Infants exhibited significantly higher bar2-induced lipolysis and a different maximal lipolytic response profile compared to adults.
Conclusions:
- Significant subtype-specific developmental changes in bar expression occur during human infancy.
- Higher bar2 mRNA levels in infants are associated with increased bar2-mediated lipolytic capacity.
Abstract:
beta 1- and beta 2-adrenoceptor (bar1 and bar2) mRNA levels were measured in adipose tissue obtained from children (between 1 month and 10 yr of age) and adults during inguinal hernia operations. Bar1 mRNA levels were constant in all age groups studied. In infants and children less than 7 yr old, bar2 levels were twice as high (P < 0.01) as those in adults, and in infants 1-4 months old, bar2 mRNA levels were higher than bar1 levels (P < 0.01). The bar2/bar1 ratio gradually decreased, and in adults, there was 2.3-fold higher bar1 mRNA expression (P < 0.01). In infants 1-5 months old, the lipolytic sensitivity to noradrenaline was 5 times lower (P < 0.05) than that in adults, whereas the sensitivity to adrenaline and isoprenaline was unchanged. The maximal lipolytic response to adrenaline was higher than that to noradrenaline in infants (P < 0.01), whereas the opposite was found in adults (P < 0.01). The lipolytic sensitivity to the bar1-selective agonist dobutamine was not influenced by age, whereas the sensitivity to the bar2-selective agonist terbutaline was 10,000 times higher in infants than in adults. In conclusion, these data indicate subtype-specific developmental changes in bar expression, with higher bar2 mRNA levels accompanied by increased bar2-induced lipolysis during infancy.