LDB1 Regulates Energy Homeostasis During Diet-Induced Obesity.

The broadly expressed transcriptional coregulator LDB1 is essential for beta-cell development and glucose homeostasis. However, it is unclear whether LDB1 has metabolic roles beyond the beta-cell, especially under metabolic stress. Global Ldb1 deletion results in early embryonic lethality; thus, we used global heterozygous Ldb1(+/-) and inducible beta-cell-specific Ldb1-deficient (Ldb1(Delta beta-cell)) mice. We assessed glucose and insulin tolerance, body composition, feeding, and energy expenditure during high-fat diet exposure. Brown adipose tissue (BAT) biology was evaluated by thermogenic gene expression and LDB1 chromatin immunoprecipitation analysis. We found that partial loss of Ldb1 does not impair the maintenance of glucose homeostasis; rather, we observed improved insulin sensitivity in these mice. Partial loss of Ldb1 also uncovered defects in energy expenditure in lean and diet-induced obese (DIO) mice. This decreased energy expenditure during DIO was associated with significantly altered BAT gene expression, specifically Cidea, Elovl3, Cox7a1, and Dio2. Remarkably, the observed changes in energy balance during DIO were absent in Ldb1(Delta beta-cell) mice, despite a similar reduction in plasma insulin, suggesting a role for LDB1 in BAT. Indeed, LDB1 is expressed in brown adipocytes and occupies a regulatory domain of Elovl3, a gene crucial to normal BAT function. We conclude that LDB1 regulates energy homeostasis, in part through transcriptional modulation of critical regulators in BAT function.