Metabolome analysis reveals that cyclic adenosine diphosphate ribose contributes to the regulation of differentiation in mice adipocyte.

Adipocytes play a key role in energy storage and homeostasis. Although the role of transcription factors in adipocyte differentiation is known, the effect of endogenous metabolites of low molecular weight remains unclear. Here, we analyzed time-dependent changes in the levels of these metabolites throughout adipocyte differentiation, using metabolome analysis, and demonstrated that there is a positive correlation between cyclic adenosine diphosphate ribose (cADPR) and Pparγ mRNA expression used as a marker of differentiation. We also found that the treatment of C3H10T1/2 adipocytes with cADPR increased the mRNA expression of those marker genes and the accumulation of triglycerides. Furthermore, inhibition of ryanodine receptors (RyR), which are activated by cADPR, caused a significant reduction in mRNA expression levels of the marker genes and triglyceride accumulation in adipocytes. Our findings show that cADPR accelerates adipocytic differentiation via RyR pathway.

Inflammation-induced nitric oxide suppresses PPARα expression and function via downregulation of Sp1 transcriptional activity in adipocytes.

The activation of peroxisome proliferator-activated receptor alpha (PPARα), a ligand-dependent transcription factor that regulates lipid oxidation-related genes, has been employed to treat hyperlipidemia. Emerging evidence indicates that Ppara gene expression decreases in adipose tissue under obese conditions; however, the underlying molecular mechanisms remain elusive. Here, we demonstrate that nitric oxide (NO) suppresses Ppara expression by regulating its promoter activity via suppression of specificity protein 1 (Sp1) transcriptional activity in adipocytes. NO derived from lipopolysaccharide (LPS) -activated macrophages or a NO donor (NOR5) treatment, suppressed Ppara mRNA expression in 10T1/2 adipocytes. In addition, Ppara transcript levels were reduced in the white adipose tissue (WAT) in both acute and chronic inflammation mouse models; however, such suppressive effects were attenuated via a nitric oxide synthase 2 (NOS2) inhibitor. Endoplasmic reticulum (ER) stress inhibitors attenuated the NO-induced repressive effects on Ppara gene expression in 10T1/2 adipocytes. Promoter mutagenesis and chromatin immunoprecipitation assays revealed that NO decreased the Sp1 occupancy in the proximal promoter regions of the Ppara gene, which might partially result from the reduced Sp1 expression levels by NO. This study delineated the molecular mechanism that modulates Ppara gene transcription upon NO stimulation in white adipocytes, suggesting a possible mechanism for the transcriptional downregulation of Ppara in WAT under obese conditions.

8-Prenyl daidzein and 8-prenyl genistein from germinated soybean modulate inflammatory response in activated macrophages.

Soy isoflavones have been shown to have anti-inflammatory properties; however, the anti-inflammatory effects of isoflavone metabolites produced during soybean germination remain unclear. We found that the daidzein and genistein derivatives, 8-prenyl daidzein (8-PD) and 8-prenyl genistein (8-PG), demonstrated a more potent effect than daidzein and genistein on repressing inflammatory responses in macrophages. Although IkB protein levels were unaltered, 8-PD and 8-PG repressed nuclear factor kappa B (NF-κB) activation, which was associated with reduced ERK1/2, JNK, and p38 MAPK activation and suppressed mitogen- and stress-activated kinase 1 phosphorylation. Inflammatory responses induced by the medium containing hypertrophic adipocyte secretions were successfully suppressed by 8-PD and 8-PG treatment. In the ex vivo study, 8-PD and 8-PG significantly inhibited proinflammatory C-C motif chemokine ligand 2 (CCL2) secretion from the adipose tissues of mice fed a long-term high-fat diet. The data suggest that 8-PD and 8-PG could regulate macrophage activation under obesity conditions.

Subcutaneous Transplantation of White Adipose Tissue.

In the research setting, white adipose tissue (WAT) transplantation, also known as fat transplantation, is often used to understand the physiological function of adipocytes or associated stromal vascular cells such as macrophages in the context of local and systemic metabolism. The mouse is the most common animal model used where WAT from a donor is transferred either to a subcutaneous site of the same organism or to a subcutaneous region of a recipient. Here, we describe in detail the procedure for heterologous fat transplantation, and, given the need for survival surgery, peri- and postoperative care and subsequent histological confirmation of fat grafts will also be discussed.

Mevalonate biosynthesis pathway regulates the development and survival of brown adipocytes.

The high thermogenic activity of brown adipose tissue (BAT) has received considerable attention. Here, we demonstrated the role of the mevalonate (MVA) biosynthesis pathway in the regulation of brown adipocyte development and survival. The inhibition of 3-hydroxy-3-methylglutaryl-CoA reductase (HMGCR), the rate-limiting enzyme in the MVA pathway and the molecular target of statins, suppressed brown adipocyte differentiation by suppressing protein geranylgeranylation-mediated mitotic clonal expansion. The development of BAT in neonatal mice exposed to statins during the fetal period was severely impaired. Moreover, statin-induced geranylgeranyl pyrophosphate (GGPP) deficiency led to the apoptosis of mature brown adipocytes. Brown adipocyte-specific Hmgcr knockout induced BAT atrophy and disrupted thermogenesis. Importantly, both genetic and pharmacological inhibition of HMGCR in adult mice induced morphological changes in BAT accompanied by an increase in apoptosis, and statin-treated diabetic mice showed worsened hyperglycemia. These findings revealed that MVA pathway-generated GGPP is indispensable for BAT development and survival.

Combined treatment with teneligliptin and canagliflozin additively suppresses high-fat diet-induced body weight gain in mice with modulation of lipid metabolism-related gene expression.

In the treatment of type 2 diabetes mellitus (T2DM), comprehensive management of multiple risk factors, such as blood glucose, body weight, and lipids, is important to prevent disease progression. Although the combination of dipeptidyl peptidase-4 (DPP-4) inhibitor and sodium-glucose co-transporter 2 (SGLT2) inhibitor is often used clinically, the effects of this combination, other than glucose metabolism, have yet to be thoroughly investigated. In this study, we evaluated the effects of combined treatment with a DPP-4 inhibitor, teneligliptin, and an SGLT2 inhibitor, canagliflozin, on the body weight and lipid metabolism in high-fat diet (HFD)-induced obese mice. We found that monotherapy with teneligliptin or canagliflozin showed suppressive effects on high-fat diet-induced body weight gain and reduced inguinal white adipose tissue (iWAT) mass, and combined treatment additively reduced body weight gain and iWAT mass. Teneligliptin significantly increased oxygen consumption during the light phase, and this effect was preserved in the combined treatment. The combined treatment did not alter the mRNA expression levels of thermogenesis-related genes in adipose tissue but showed the tendency to additively induce mRNA of fatty acid oxidation-related genes in brown adipose tissue and tended to additively decrease mRNA of fatty acid synthesis-related genes in iWAT and liver tissues. These results suggest that combined treatment with teneligliptin and canagliflozin additively suppresses HFD-induced body weight gain with increasing oxygen consumption and modulating the expression of lipid metabolism-related genes. This combination therapy may provide effective body weight management for patients with T2DM and obesity.

Metabolomics reveals inosine 5'-monophosphate is increased during mice adipocyte browning.

Adipocyte browning is one of the potential strategies for the prevention of obesity-related metabolic syndromes, but it is a complex process. Although previous studies make it increasingly clear that several transcription factors and enzymes are essential to induce browning, it is unclear what dynamic and metabolic changes occur in induction of browning. Here, we analyzed the effect of a beta-adrenergic receptor agonist (CL316243, accelerator of browning) on metabolic change in mice adipose tissue and plasma using metabolome analysis and speculated that browning is regulated partly by inosine 5'-monophosphate (IMP) metabolism. To test this hypothesis, we investigated whether Ucp-1, a functional marker of browning, mRNA expression is influenced by IMP metabolism using immortalized adipocytes. Our study showed that mycophenolic acid, an IMP dehydrogenase inhibitor, increases the mRNA expression of Ucp-1 in immortalized adipocytes. Furthermore, we performed a single administration of mycophenolate mofetil, a prodrug of mycophenolic acid, to mice and demonstrated that mycophenolate mofetil induces adipocyte browning and miniaturization of adipocyte size, leading to adipose tissue weight loss. These findings showed that IMP metabolism has a significant effect on adipocyte browning, suggesting that the regulator of IMP metabolism has the potential to prevent obesity.

Involvement of mechano-sensitive Piezo1 channel in the differentiation of brown adipocytes.

Brown adipocytes expend energy via heat production and are a potential target for the prevention of obesity and related metabolic disorders. Piezo1 is a Ca2+-permeable non-selective cation channel activated by mechanical stimuli. Piezo1 is reported to be involved in mechano-sensation in non-sensory tissues. However, the expression and roles of Piezo1 in brown adipocytes have not been well clarified. Here, we generated a brown adipocyte line derived from UCP1-mRFP1 transgenic mice and showed that Piezo1 is expressed in pre-adipocytes. Application of Yoda-1, a Piezo1 agonist, suppressed brown adipocyte differentiation, and this suppression was significantly attenuated by treatment with a Piezo1 antagonist and by Piezo1 knockdown. Furthermore, the suppression of brown adipocyte differentiation by Yoda-1 was abolished by co-treatment with a calcineurin inhibitor. Thus, these results suggest that activation of Piezo1 suppresses brown adipocyte differentiation via the calcineurin pathway.

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

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.

Comparative Analysis of the Preventive Effects of Canagliflozin, a Sodium-Glucose Co-Transporter-2 Inhibitor, on Body Weight Gain Between Oral Gavage and Dietary Administration by Focusing on Fatty Acid Metabolism.

PURPOSE: Sodium-glucose co-transporter-2 (SGLT2) inhibitors have various pleiotropic effects, including body weight reduction, and therefore have the potential to be used in various applications. However, such effects have not been fully investigated; thus, non-clinical studies using animal models are needed. In animal experiments, SGLT2 inhibitors are usually administered by oral or dietary methods. However, the detailed characteristics of these dosing methods, especially to induce their pleiotropic effects, have not been reported. Therefore, we compared the preventive effects of canagliflozin, an SGLT2 inhibitor, on body weight gain following oral gavage and dietary administration methods in a mouse model of diet-induced obesity. METHODS: Canagliflozin was dosed by oral gavage or dietary administration for 9 weeks to 6-week-old C57BL/6N mice fed a high-fat diet, and parameters related to obesity were evaluated. RESULTS: The suppression of body weight gain, fat mass, and hepatic lipid content was observed following both dosing methods, whereas the effect on body weight tended to be stronger in the dietary administration group. In adipose tissue, fatty acid synthase expression was significantly decreased in the dietary administration group, and its expression was significantly correlated with fat mass. However, the expression of genes related to fatty acid oxidation was unchanged, indicating that the preventive effect on body weight gain was mediated mainly through the suppression of lipid synthesis rather than the promotion of lipid oxidation. CONCLUSION: Canagliflozin prevented body weight gain through the suppression of lipid synthesis via both dosing methods, although there were some differences in the efficacy. The findings of our study can help to identify new mechanisms of action of SGLT2 inhibitors and potential applications.

ß-Cryptoxanthin Induces UCP-1 Expression via a RAR Pathway in Adipose Tissue.

While ß-cryptoxanthin is hypothesized to have a preventive effect on lifestyle-related diseases, its underlying mechanisms are unknown. We investigated the effect of ß-cryptoxanthin on energy metabolism in adipose tissues and its underlying mechanism. C57BL/6J mice were fed a high-fat diet (60% kcal fat) containing 0 or 0.05% ß-cryptoxanthin for 12 weeks. ß-cryptoxanthin treatment was found to reduce body fat gain and plasma glucose level, while increasing energy expenditure. The expression of uncoupling protein (UCP) 1 was elevated in adipose tissues in the treatment group. Furthermore, the in vivo assays showed that the Ucp1 mRNA expression was higher in the ß-cryptoxanthin treatment group, an effect that disappeared upon cotreatment with a retinoic acid receptor (RAR) antagonist. In conclusion, we report that ß-cryptoxanthin reduces body fat and body weight gain and that ß-cryptoxanthin increases the expression of UCP1 via the RAR pathway.

A new mouse model for noninvasive fluorescence-based monitoring of mitochondrial UCP1 expression.

Mitochondrial uncoupling protein 1 (UCP1) is well known for its thermogenic function in brown adipose tissue (BAT). Since UCP1 expends energy on thermogenesis, UCP1 activation has been considered an approach to ameliorate obesity. As a tool for uncovering yet unknown mechanisms of UCP1 activation, we generated a transgenic mouse model in which UCP1 expression levels are reflected in fluorescence derived from monomeric red fluorescent protein 1 (mRFP1). In these UCP1-mRFP1 BAC transgenic mice, fluorescence intensity mimics the change in UCP1 expression levels evoked through physiological or pharmacological stimulation. This transgenic mouse model will be useful in the search for bioactive compounds with the ability to induce UCP1 and for revealing undiscovered mechanisms of BAT activation.

The Mevalonate Pathway Is Indispensable for Adipocyte Survival.

The mevalonate pathway is essential for the synthesis of isoprenoids and cholesterol. Adipose tissue is known as a major site for cholesterol storage; however, the role of the local mevalonate pathway and its synthesized isoprenoids remains unclear. In this study, adipose-specific mevalonate pathway-disrupted (aKO) mice were generated through knockout of 3-hydroxy-3-methylglutaryl-CoA (HMG-CoA) reductase (HMGCR). aKO mice showed serious lipodystrophy accompanied with glucose and lipid metabolic disorders and hepatomegaly. These metabolic variations in aKO mice were dramatically reversed after fat transplantation. In addition, HMGCR-disrupted adipocytes exhibited loss of lipid accumulation and an increase of cell death, which were ameliorated by the supplementation of mevalonate and geranylgeranyl pyrophosphate but not farnesyl pyrophosphate and squalene. Finally, we found that apoptosis may be involved in adipocyte death induced by HMGCR down-regulation. Our findings indicate that the mevalonate pathway is essential for adipocytes and further suggest that this pathway is an important regulator of adipocyte turnover.

ß-adrenergic Receptor Stimulation Revealed a Novel Regulatory Pathway via Suppressing Histone Deacetylase 3 to Induce Uncoupling Protein 1 Expression in Mice Beige Adipocyte.

Browning of adipose tissue has been prescribed as a potential way to treat obesity, marked by the upregulation of uncoupling protein 1 (Ucp1). Several reports have suggested that histone deacetylase (HDAC) might regulate Ucp1 by remodelling chromatin structure, although the mechanism remains unclear. Herein, we investigate the effect of ß-adrenergic receptor (ß-AR) activation on the chromatin state of beige adipocyte. ß-AR-stimulated Ucp1 expression via cold (in vivo) and isoproterenol (in vitro) resulted in acetylation of histone activation mark H3K27. H3K27 acetylation was also seen within Ucp1 promoter upon isoproterenol addition, favouring open chromatin for Ucp1 transcriptional activation. This result was found to be associated with the downregulation of class I HDAC mRNA, particularly Hdac3 and Hdac8. Further investigation showed that although HDAC8 activity decreased, Ucp1 expression was not altered when HDAC8 was activated or inhibited. In contrast, HDAC3 mRNA and protein levels were simultaneously downregulated upon isoproterenol addition, resulting in reduced recruitment of HDAC3 to the Ucp1 enhancer region, causing an increased H3K27 acetylation for Ucp1 upregulation. The importance of HDAC3 inhibition was confirmed through the enhanced Ucp1 expression when the cells were treated with HDAC3 inhibitor. This study highlights the novel mechanism of HDAC3-regulated Ucp1 expression during ß-AR stimulation.

Responses of gas-exchange rates and water relations to annual fluctuations of weather in three species of urban street trees.

The frequency of extreme weather has been rising in recent years. A 3-year study of street trees was undertaken in Tokyo to determine whether: (i) street trees suffer from severe water stress in unusually hot summer; (ii) species respond differently to such climatic fluctuations; and (iii) street trees are also affected by nitrogen (N) deficiency, photoinhibition and aerosol pollution. During the study period (2010-12), midsummers of 2010 and 2012 were unusually hot (2.4-2.8 °C higher maximum temperature than the long-term mean) and dry (6-56% precipitation of the mean). In all species, street trees exhibited substantially decreased photosynthetic rate in the extremely hot summer in 2012 compared with the average summer in 2011. However, because of a more conservative stomatal regulation (stomatal closure at higher leaf water potential) in the hot summer, apparent symptoms of hydraulic failure were not observed in street trees even in 2012. Compared with Prunus × yedoensis and Zelkova serrata, Ginkgo biloba, a gymnosperm, was high in stomatal conductance and midday leaf water potential even under street conditions in the unusually hot summer, suggesting that the species had higher drought resistance than the other species and was less susceptible to urban street conditions. This lower susceptibility might be ascribed to the combination of higher soil-to-leaf hydraulic conductance and more conservative water use. Aside from meteorological conditions, N deficiency affected street trees significantly, whereas photoinhibition and aerosol pollution had little effect. The internal CO2 and δ(13)C suggested that both water and N limited the net photosynthetic rate of street trees simultaneously, but water was more limiting. From these results, we concluded that the potential risk of hydraulic failure caused by climatic extremes could be low in urban street trees in temperate regions. However, the size of the safety margin might be different between species.