Impact of housing temperature on adipose tissue HDAC9 expression and adipogenic differentiation in high fat-fed mice.

OBJECTIVE: Impaired adipogenic differentiation exacerbates metabolic disease in obesity. This study reported that high-fat diet (HFD)-fed mice housed at thermoneutrality exhibited impaired adipogenic differentiation, attributed to increased expression of histone deacetylase 9 (HDAC9). However, the impact of HFD on adipogenic differentiation is reportedly variable, possibly reflecting divergent environmental conditions such as housing temperature. METHODS: C57BL/6J (wild-type [WT]) mice were housed at either thermoneutral (28-30°C) or ambient (20-22°C) temperature and fed HFD or chow diet (CD) for 12 weeks. For acute exposure experiments, WT or transient receptor potential cation channel subfamily M member 8 (TRPM8) knockout mice housed under thermoneutrality were acutely exposed to ambient temperature for 6 to 24 h. RESULTS: WT mice fed HFD and housed at thermoneutrality, compared with ambient temperature, gained more weight despite reduced food intake. They likewise exhibited increased inguinal adipose tissue HDAC9 expression and reduced adipogenic differentiation in vitro and in vivo compared with CD-fed mice. Conversely, HFD-fed mice housed at ambient temperature exhibited minimal change in adipose HDAC9 expression or adipogenic differentiation. Acute exposure of WT mice to ambient temperature reduced adipose HDAC9 expression independent of sympathetic ß-adrenergic signaling via a TRPM8-dependent mechanism. CONCLUSIONS: Adipose HDAC9 expression is temperature sensitive, regulating adipogenic differentiation in HFD-fed mice housed under thermoneutrality.

Successful Catheter Ablation of Two Macro-reentrant Atrial Tachycardias in a Patient with Congenitally Corrected Transposition of the Great Arteries: A Case Report.

Adults with congenital heart disease represent a complex and growing patient population. By virtue of their variant anatomy and the complex surgical repair often required in infancy, these patients are at risk of developing unique atrial and ventricular arrhythmias throughout their lifetimes. Electrophysiologists involved in the care of these patients should have a detailed understanding of their underlying anatomy and any prior surgical procedures to guide procedural planning and should have knowledge of the range of possible arrhythmia mechanisms that may differ from patients without structural heart disease. Despite this complexity, standard mapping techniques and electrophysiologic maneuvers may still be used to elucidate arrhythmia mechanisms, map tachycardia circuits, and guide catheter ablation. We report a case of two different macroreentrant right atrial tachycardias that were successfully ablated in a patient with congenitally-corrected transposition of the great arteries.

Beetle, Dendroides canadensis, antifreeze proteins increased high temperature survivorship in transgenic fruit flies, Drosophila melanogaster.

Paradoxically, some insects have an increased capacity to survive higher temperatures in winter than summer. Possible contributors to this increased heat tolerance in winter could be their sub-zero adaptations (high polyol concentrations, antifreeze proteins, antifreeze glycolipids, etc.). To investigate if a sub-zero adaptation can increase organismal high temperature survivorship, we tested transgenic fruit flies, Drosophila melanogaster, with antifreeze proteins from the fire-colored beetle, Dendroides canadensis (DAFPs). Transgenic Drosophila melanogaster with individual DAFPs-1 and -4 had increased survivorship compared to control flies after 24 h when placed at 35-36.5 °C. The 24 h ULT50 (Upper Lethal Temperature at which 50% mortality occurred) was calculated to be 36.3 °C for DAFP-1 flies, 36.2 °C for DAFP-4 flies, 35.4 °C for wild-type controls, and 34.9 °C for GAL4 controls. The results indicate that DAFPs may have an alternative function in insects and be a contributor in the unexpected phenomenon of increased higher temperature survivorship in winter.