Irradiation of carotid baroreceptor with low-intensity pulsed ultrasound exerts different metabolic protection in perirenal, epididymal white adipose tissue and interscapular brown adipose tissue of obese rats.

This study was designed to clarify whether the irradiation of carotid baroreceptor (CB) with low-intensity pulsed ultrasound (LIPUS) protects against obesity by rebalancing the autonomic nervous system (ANS). Obesity was induced using a high-fat diet (HFD) for 8 weeks in Sprague-Dawley rats. Irradiation with LIPUS was daily (20 minutes a day) applied to the right CB. In our study, LIPUS significantly ameliorated metabolic disorders in obese rats. LIPUS partly restored norepinephrine (NE) and acetylcholine (ACH) levels in the perirenal white adipose tissue (PWAT), epididymal white adipose tissue (EWAT), interscapular brown adipose tissue (IBAT), and plasma of obese rats. LIPUS partially rectified the dysregulated AMP-activated protein kinase (AMPK)/peroxisome proliferator-activated receptor (PPAR) α/É£ pathway in the PWAT, EWAT, and IBAT of obese rats. PPARγ and PPARγ target genes respond more sensitively to HFD and LIPUS in PWAT and EWAT than in IBAT. NE, ACH, uncoupling protein-1, phosphorylated AMPK, PPARα, and PPARα target genes respond more sensitively to HFD and LIPUS in IBAT than in PWAT and EWAT. Conclusion: LIPUS irradiation of CB exerts different metabolic protection in PWAT, EWAT, and IBAT by rebalancing the ANS and rectifying the AMPK/PPARα/É£ pathway in obese rats.

Ionising radiation triggers fat accumulation in white adipose tissue.

PURPOSE: To investigate changes in gonadal white adipose tissue and lipogenesis-related gene expression induced by radiation exposure. MATERIALS AND METHODS: Groups of two-month-old C57BL/6 mice were exposed whole-body to ¹³7Cs γ-rays at a single dose (5 gray [Gy]) or fractionated doses (1 Gy x 5 times, 0.5 Gy x 10 times, or 0.2 Gy x 25 times). Six months after irradiation, gonadal white adipose tissue was isolated from mice. Two and 25-month-old mice were used as young and old study references. Real-time reverse transcriptase-polymerase chain reaction (RT-PCR) was used to measure messenger RNA (mRNA) expression of genes related to: (i) Primary lipid metabolism (ATP-citrate lyase [ACL], malic enzyme1 [ME1] and glucose-6-phosphate dehydrogenase 2 [G6PD2]), (ii) glucose uptake (glucose transporter 4 [GLUT4]), (iii) fatty acid synthesis (sterol regulatory element binding transcription factor 1 [SREBP-1c], fatty acid synthetase [FAS] and acetyl-coenzyme A carboxylase beta [ACC]), (iv) triglyceride synthesis (diacylglycerol O-acyltransferase 1 [DGAT1] and diacylglycerol O-acyltransferase 2 [DGAT2]), and (v) adipose-derived hormones (leptin [LEP]). RESULTS: The weight of gonadal white adipose tissue in the irradiated groups tended to increase compared to the non-irradiated group though the radiation-induced increase in white adipose tissue was only significant for the 5 x 1 Gy group. The mRNA levels of SREBP-1c, ACC, FAS, ACL, GLUT4, ME1 and G6PD2 were relatively lower in γ-irradiated groups than in non-irradiated groups. The mRNA levels of leptin and DGAT were relatively higher than non-irradiated groups. The changes in expression of these lipogenesis-related genes caused by γ-irradiation showed a very similar pattern to changes caused by ageing. CONCLUSIONS: A physical agent such as γ-rays can trigger biological responses resulting in fat accumulation of gonadal white adipose tissue in mice.

Short photoperiod-induced decrease of histamine H3 receptors facilitates activation of hypothalamic neurons in the Siberian hamster.

Nonhibernating seasonal mammals have adapted to temporal changes in food availability through behavioral and physiological mechanisms to store food and energy during times of predictable plenty and conserve energy during predicted shortage. Little is known, however, of the hypothalamic neuronal events that lead to a change in behavior or physiology. Here we show for the first time that a shift from long summer-like to short winter-like photoperiod, which induces physiological adaptation to winter in the Siberian hamster, including a body weight decrease of up to 30%, increases neuronal activity in the dorsomedial region of the arcuate nucleus (dmpARC) assessed by electrophysiological patch-clamping recording. Increased neuronal activity in short days is dependent on a photoperiod-driven down-regulation of H3 receptor expression and can be mimicked in long-day dmpARC neurons by the application of the H3 receptor antagonist, clobenproprit. Short-day activation of dmpARC neurons results in increased c-Fos expression. Tract tracing with the trans-synaptic retrograde tracer, pseudorabies virus, delivered into adipose tissue reveals a multisynaptic neuronal sympathetic outflow from dmpARC to white adipose tissue. These data strongly suggest that increased activity of dmpARC neurons, as a consequence of down-regulation of the histamine H3 receptor, contributes to the physiological adaptation of body weight regulation in seasonal photoperiod.