Catecholamines are crucial signaling molecules that initiate thermogenesis in adipocytes through beta-adrenergic receptors (ADRBs). Adipocyte catecholamine resistance is a common feature of pediatric obesity, often impeding weight loss and the maintenance of a healthy body fat percentage. Our aim was to identify possible mechanisms that may be responsible for the development of catecholamine resistance in adipocytes. We demonstrate that Lim homeobox 8 (LHX8), a transcription factor previously known for its role in gametogenesis, is essential for catecholamine-induced thermogenesis in human adipocytes. LHX8 is expressed in developing human adipocytes throughout intrauterine and perinatal life, as well as in adulthood, and its expression levels positively correlate with the expression of key thermogenesis genes. Pediatric obesity diminished adipocyte expression of LHX8. Functionally, ADRB stimulation failed to induce thermogenesis in both mouse and human adipocytes when LHX8 was absent. Conversely, LHX8 overexpression enhanced thermogenesis in murine adipocytes. Mechanistically, LHX8 stimulated adipocyte interleukin-33 (IL-33) synthesis in response to ADRB activation, which subsequently increased thermogenic gene expression in both human and mouse adipocytes. In conclusion, adipocyte LHX8 is indispensable for catecholamine-responsive thermogenesis and represents a promising novel therapeutic target to overcome catecholamine resistance and promote effective weight management.

The 3xTg-AD mouse model is widely used to study the pathomechanisms of Alzheimer's disease (AD) and to test potential therapies. During food-motivated cognitive tasks, however, increased food-directed behavior was observed in these animals, raising the possibility that metabolic factors may influence task performance. This prompted us to investigate the metabolic background of AD, with a focus on the hypothalamic-pituitary-thyroid (HPT) axis. Testing of food-motivated behavior (single pellet reaching, radial arm maze, staircase, and operant conditioning tests) started at 6 months of age in male mice and confirmed increased motivation for food in 3xTg-AD animals. The molecular background was examined at 8 months of age. Separate cohorts of 4- and 8-month-old male mice underwent metabolic measurements. Transgenic mice showed increased food and water intake, reduced fat mass, elevated lean mass, and a stable respiratory exchange ratio (RER), in contrast to the age-related decline in RER observed in controls. Free T4 levels were higher in 3xTg-AD than control animals, and molecular profiling revealed elevated thyrotropin-releasing hormone (TRH) and thyroid hormone-activating deiodinases DIO1 and DIO2 mRNA, alongside reduced expression of the thyroid hormone receptor beta 2 (THRB2) in the paraventricular nucleus (PVN) and pituitary. Expression levels of key appetite-regulating neuropeptides, including pro-opiomelanocortin (POMC), neuropeptide Y (NPY), cocaine- and amphetamine-regulated transcript (CART), and agouti-related peptide (AgRP) were significantly lower in 3xTg-AD mice. These findings indicate early alterations in energy homeostasis and HPT axis-related signaling in 3xTg-AD mice that may be associated with increased food-seeking behavior. Our data provide evidence for metabolic and neuroendocrine changes that accompany the behavioral phenotype of this model.