Screening of flavor compounds using Ucp1-luciferase reporter beige adipocytes identified 5-methylquinoxaline as a novel UCP1-inducing compoundsss

Uncoupling protein 1 (UCP1) in brown or beige adipocytes is a mitochondrial protein that is expected to enhance whole-body energy expenditure. For the high-throughput screening of UCP1 transcriptional activity regulator, we established a murine inguinal white adipose tissue-derived Ucp1-luciferase reporter preadipocyte line. Using this reporter preadipocyte line, 654 flavor compounds were screened, and a novel Ucp1 expression-inducing compound, 5-methylquinoxaline, was identified. Adipocytes treated with 5-methylquinoxaline showed increased Ucp1 mRNA expression levels and enhanced oxygen consumption. 5-methylquinoxaline induced Ucp1 expression through peroxisome proliferator-activated receptor γ coactivator 1α (PGC1α), and 5-methylquinoxaline-induced PGC1α activation seemed to be partially regulated by its phosphorylation or deacetylation. Thus, our Ucp1-luciferase reporter preadipocyte line is a useful tool for screening of Ucp1 inductive compounds.

Naked mole-rat brown fat thermogenesis is diminished during hypoxia through a rapid decrease in UCP1

Naked mole-rats are among the most hypoxia-tolerant mammals. During hypoxia, their body temperature (Tb) decreases via unknown mechanisms to conserve energy. In small mammals, non-shivering thermogenesis in brown adipose tissue (BAT) is critical to Tb regulation; therefore, we hypothesize that hypoxia decreases naked mole-rat BAT thermogenesis. To test this, we measure changes in Tb during normoxia and hypoxia (7% O2; 1–3 h). We report that interscapular thermogenesis is high in normoxia but ceases during hypoxia, and Tb decreases. Furthermore, in BAT from animals treated in hypoxia, UCP1 and mitochondrial complexes I-V protein expression rapidly decrease, while mitochondria undergo fission, and apoptosis and mitophagy are inhibited. Finally, UCP1 expression decreases in hypoxia in three other social African mole-rat species, but not a solitary species. These findings suggest that the ability to rapidly down-regulate thermogenesis to conserve oxygen in hypoxia may have evolved preferentially in social species.

Increased Energy Expenditure and Protection from Diet-Induced Obesity in Mice Lacking the cGMP-Specific Phosphodiesterase PDE9

Cyclic nucleotides, cAMP and cGMP, are important second messengers for the regulation of adaptive thermogenesis. Their levels are controlled not only by their synthesis but also their degradation. Since pharmacological inhibitors of cGMP-specific phosphodiesterase 9 (PDE9) can increase PKG signaling and UCP1 expression in adipocytes, we sought to elucidate the role of PDE9 on energy balance and glucose homeostasis <i>in vivo</i>. Mice with targeted disruption of the PDE9 gene, <i>Pde9a</i>, were fed nutrient matched high-fat (HFD) or low-fat diets (LFD). <i>Pde9a</i>^‑/‑ mice were resistant to HFD induced obesity, exhibiting a global increase in energy expenditure, while brown adipose tissue (AT) had increased respiratory capacity and elevated expression of <i>Ucp1 </i>and other thermogenic genes. Reduced adiposity of HFD-fed <i>Pde9a</i>^‑/‑ mice was associated with improvements in glucose handling and hepatic steatosis. Cold exposure or treatment with β-adrenergic receptor agonists markedly decreased <i>Pde9a</i> expression in brown AT and cultured brown adipocytes, while <i>Pde9a^‑/‑</i> mice exhibited a greater increase in AT browning; together suggesting that the PDE9-cGMP pathway augments classical cold-induced β-adrenergic/cAMP AT browning and energy expenditure. These findings suggest PDE9 is a previously unrecognized regulator of energy metabolism and that its inhibition may be a valuable avenue to explore for combating metabolic disease.

Increased Energy Expenditure and Protection from Diet-Induced Obesity in Mice Lacking the cGMP-Specific Phosphodiesterase PDE9

Cyclic nucleotides, cAMP and cGMP, are important second messengers for the regulation of adaptive thermogenesis. Their levels are controlled not only by their synthesis but also their degradation. Since pharmacological inhibitors of cGMP-specific phosphodiesterase 9 (PDE9) can increase PKG signaling and UCP1 expression in adipocytes, we sought to elucidate the role of PDE9 on energy balance and glucose homeostasis <i>in vivo</i>. Mice with targeted disruption of the PDE9 gene, <i>Pde9a</i>, were fed nutrient matched high-fat (HFD) or low-fat diets (LFD). <i>Pde9a</i>^‑/‑ mice were resistant to HFD induced obesity, exhibiting a global increase in energy expenditure, while brown adipose tissue (AT) had increased respiratory capacity and elevated expression of <i>Ucp1 </i>and other thermogenic genes. Reduced adiposity of HFD-fed <i>Pde9a</i>^‑/‑ mice was associated with improvements in glucose handling and hepatic steatosis. Cold exposure or treatment with β-adrenergic receptor agonists markedly decreased <i>Pde9a</i> expression in brown AT and cultured brown adipocytes, while <i>Pde9a^‑/‑</i> mice exhibited a greater increase in AT browning; together suggesting that the PDE9-cGMP pathway augments classical cold-induced β-adrenergic/cAMP AT browning and energy expenditure. These findings suggest PDE9 is a previously unrecognized regulator of energy metabolism and that its inhibition may be a valuable avenue to explore for combating metabolic disease.

Globin Digest Improves Visceral Adiposity Through UCP1 Upregulation in Diet-Induced Obese Zebrafish and Mice

Globin digest (GD), a bioactive oligopeptide derived from porcine hemoglobin proteins, has been demonstrated to have beneficial effects on improving postprandial hyperlipidemia, hyperglycemia, and liver injury. We previously reported the lipid-lowering effects of GD using a zebrafish obesogenic test. Here, we sought to evaluate the effect of GD on visceral adiposity and the underlying molecular mechanisms using zebrafish and mouse obesity models. GD ameliorated dyslipidemia and suppressed the accumulation of visceral adipose tissue (VAT) in adult obese zebrafish. Transcriptomic analysis by RNA sequencing of GD-treated adult zebrafish revealed that GD upregulated UCP1-related pathways. Further, we performed mouse experiments and found that GD intake (2 mg/g body weight/day) was associated with lowered plasma triglyceride and total cholesterol levels, decreased VAT accumulation, and improved adipocyte hypertrophy with the upregulation of Ucp1 expression in white adipose tissue at both the mRNA and protein levels. Taken together, these results indicate that GD improves visceral adiposity by upregulating UCP1 expression, providing a novel perspective on combating obesity.

UCP1 modulates Immune Infiltration Level and Survival Outcome in Ovarian Cancer Patients

BackgroundThe uncoupling proteins (UCPs) are critical genes associated with tumorigenesis and chemoresistance. However, little is known about the molecular mechanism of the UCPs in ovarian cancer (OV). Material and methodsUCPs expression analysis was conducted using Gene Expression Profiling Interactive Analysis (GEPIA), and its potential in clinical prognosis was analyzed using Kaplan- Meier analyses. The influence of UCPs on immune infiltration was analyzed by TIMER. In addition, the correlation between UCPs expression and molecular mechanisms was investigated by TIMER and Cancer Single-cell State Atlas (CancerSEA). ResultsUCP1, UCP2, UCP3 and UCP5 expression levels correlated with a favorable prognosis and tumor progression. Moreover, UCP1 expression correlated to several immune cell markers and regulated tumorigenesis, such as tumor invasion, EMT, metastasis and DNA repair. In addition, UCP1 potentially involved in genes expression of SNAI2, MMP2, BRCA1 and PARP1. ConclusionsThese results implied a critical role of UCP1 in the prognosis and immune infiltration of ovarian cancer. In addition, UCP1 expression participated in regulating multiple oncogenes and tumorigenesis.

Treatment with atrial natriuretic peptide induces adipose tissue browning and exerts thermogenic actions in vivo

Increasing evidence suggests natriuretic peptides (NPs) coordinate inter-organ metabolic crosstalk with adipose tissues and play a critical role in energy metabolism. We recently reported A-type NP (ANP) raises intracellular temperature in cultured adipocytes in a low-temperature-sensitive manner. We herein investigated whether exogenous ANP-treatment exerts a significant impact on adipose tissues in vivo. Mice fed a high-fat-diet (HFD) or normal-fat-diet (NFD) for 13 weeks were treated with or without ANP infusion subcutaneously for another 3 weeks. ANP-treatment significantly ameliorated HFD-induced insulin resistance. HFD increased brown adipose tissue (BAT) cell size with the accumulation of lipid droplets (whitening), which was suppressed by ANP-treatment (re-browning). Furthermore, HFD induced enlarged lipid droplets in inguinal white adipose tissue (iWAT), crown-like structures in epididymal WAT, and hepatic steatosis, all of which were substantially attenuated by ANP-treatment. Likewise, ANP-treatment markedly increased UCP1 expression, a specific marker of BAT, in iWAT (browning). ANP also further increased UCP1 expression in BAT with NFD. Accordingly, cold tolerance test demonstrated ANP-treated mice were tolerant to cold exposure. In summary, exogenous ANP administration ameliorates HFD-induced insulin resistance by attenuating hepatic steatosis and by inducing adipose tissue browning (activation of the adipose tissue thermogenic program), leading to in vivo thermogenesis during cold exposure.

The Effect of Hyperbaric Therapy on Brown Adipose Tissue in Rats

Brown adipose tissue (BAT) plays an important role in thermogenic regulation, which contributes to alleviating diet-induced obesity through uncoupling protein 1 (UCP1) expression. While cold exposure and physical exercise are known to increase BAT development and UCP1 expression, the contribution of hyperbaric oxygen (HBO) therapy to BAT maturation remains largely unknown. Here, we show that HBO treatment sufficiently increases BAT volumes and thermogenic protein levels in Sprague-Dawley rats. Through 18F-FDG PET/CT analysis, we found that exposure to high-pressure oxygen (1.5–2.5 ATA) for 7 consecutive days increased radiolabeled glucose uptake and BAT development to an extent comparable to cold exposure. Consistent with BAT maturation, thermogenic protein levels, such as those of UCP1 and peroxisome proliferator-activated receptor γ coactivator 1α (PGC−1α), were largely increased by HBO treatment. Taken together, we suggest HBO therapy as a novel method of inducing BAT development, considering its therapeutic potential for the treatment of metabolic disorders.