Identification of New Potent Human Uncoupling Protein 1 (UCP1) Agonists Using Virtual Screening and in vitro Approaches.

Recent studies suggested that activation of Uncoupling Protein 1 (UCP1) has become an appealing therapeutic strategy against obesity and diabetes. In our research, the 3D structure of UCP1 was constructed through homology modelling, refined through molecular dynamics simulation, and evaluated by Ramachandran plot, the molecular docking of UCP1 activators brought about the proposal of an interaction mode inside the UCP1 active site. Remarkably, Reside Lys126 formed hydrogen bond; residues Pro121, Val125, Tyr146, Tyr149 and Arg150 formed hydrophobic interaction, which are key amino acids within UCP1 site. Then a pharmacophore model was generated consisting of three hydrophobic groups, a negative center and an additional hydrophobic group. Pharmacophore-based virutal screening of Specs database yield 5 hits. In vitro assay indicated ZINC 04660290 significantly increased the protein expression of UCP1 and decreased the fat droplet in a dose-dependent manner. Besides, pharmacokinetic properties were predicted for those five compounds through ADME/T prediction. All of these will guide us to design new UCP1 activators for the treatment of obesity and diabetes.

A pivotal role of AMPK signaling in medicarpin-mediated formation of brown and beige.

Obesity poses a substantial threat of a worldwide epidemic and requires better understanding of adipose-tissue biology as well as necessitates research into the etiology and therapeutic interventions. In this study, Medicarpin (Med), a natural pterocarpan, was selected (by screening) as a small-molecule inducer of adipocyte differentiation among 854 candidates by using C3H10T1/2 mesenchymal stem cell; a cellular model of adipogenesis. Med induced the expression of brown-adipocyte commitment marker Bmp7 as well as the early regulators of brown fat fate Pparγ, Prdm16, and Pgc-1α during differentiation of C3H10T1/2 mesenchymal stem cells. Med also induced the expression of a key thermogenic marker-uncoupling protein 1 (UCP1)-along with expression of other brown-fat-specific markers and beige-fat-specific markers. Of note, Med significantly reduced the expression of white fat markers too. Furthermore, Med treatment promoted formation of multilocular lipid droplets (LDs), expression of mitochondrial-biogenesis-related genes, and increased oxygen consumption. Gene silencing study revealed that Med promotes the development of brown- and beige-adipocyte characteristics in C3H10T1/2 mesenchymal stem cells through activation of the AMPK pathway, and our data allow us to propose Med as a candidate for therapeutics against obesity or related metabolic disorders. © 2017 BioFactors, 44(2):168-179, 2018.

T3 and Glucose Coordinately Stimulate ChREBP-Mediated Ucp1 Expression in Brown Adipocytes From Male Mice.

Increasing brown adipose tissue (BAT) activity is regarded as a potential treatment of obese, hyperglycemic patients with metabolic syndrome. Triiodothyronine (T3) is known to stimulate BAT activity by increasing mitochondrial uncoupling protein 1 (Ucp1) gene transcription, leading to increased thermogenesis and decreased body weight. Here we report our studies on the effects of T3 and glucose in two mouse models and in mouse immortalized brown preadipocytes in culture. We identified carbohydrate response element binding protein (ChREBP) as a T3 target gene in BAT by RNA sequencing and studied its effects in brown adipocytes. We found that ChREBP was upregulated by T3 in BAT in both hyperglycemic mouse models. In brown preadipocytes, T3 and glucose synergistically and dose dependently upregulated Ucp1 messenger RNA 1000-fold compared with low glucose concentrations. Additionally, we observed increased ChREBP and Ucp1 protein 11.7- and 19.9-fold, respectively, along with concomitant induction of a hypermetabolic state. Moreover, downregulation of ChREBP inhibited T3 and glucose upregulation of Ucp1 100-fold, whereas overexpression of ChREBP upregulated Ucp1 5.2-fold. We conclude that T3 and glucose signaling pathways coordinately regulate the metabolic state of BAT and suggest that ChREBP is a target for therapeutic regulation of BAT activity.

Chronic high-sucrose diet increases fibroblast growth factor 21 production and energy expenditure in mice.

Excess carbohydrate intake causes obesity in humans. On the other hand, acute administration of fructose, glucose or sucrose in experimental animals has been shown to increase the plasma concentration of anti-obesity hormones such as glucagon-like peptide 1 (GLP-1) and Fibroblast growth factor 21 (FGF21), which contribute to reducing body weight. However, the secretion and action of GLP-1 and FGF21 in mice chronically fed a high-sucrose diet has not been investigated. To address the role of anti-obesity hormones in response to increased sucrose intake, we analyzed mice fed a high-sucrose diet, a high-starch diet or a normal diet for 15 weeks. Mice fed a high-sucrose diet showed resistance to body weight gain, in comparison with mice fed a high-starch diet or control diet, due to increased energy expenditure. Plasma FGF21 levels were highest among the three groups in mice fed a high-sucrose diet, whereas no significant difference in GLP-1 levels was observed. Expression levels of uncoupling protein 1 (UCP-1), FGF receptor 1c (FGFR1c) and ß-klotho (KLB) mRNA in brown adipose tissue were significantly increased in high sucrose-fed mice, suggesting increases in FGF21 sensitivity and energy expenditure. Expression of carbohydrate responsive element binding protein (ChREBP) mRNA in liver and brown adipose tissue was also increased in high sucrose-fed mice. These results indicate that FGF21 production in liver and brown adipose tissue is increased in high-sucrose diet and participates in resistance to weight gain.

UCP1 in adipose tissues: two steps to full browning.

The possibility that brown adipose tissue thermogenesis can be recruited in order to combat the development of obesity has led to a high interest in the identification of "browning agents", i.e. agents that increase the amount and activity of UCP1 in brown and brite/beige adipose tissues. However, functional analysis of the browning process yields confusingly different results when the analysis is performed in one of two alternative steps. Thus, in one of the steps, using cold acclimation as a potent model browning agent, we find that if the browning process is followed in mice initially housed at 21 °C (the most common procedure), there is only weak molecular evidence for increases in UCP1 gene expression or UCP1 protein abundance in classical brown adipose tissue; however, in brite/beige adipose depots, there are large increases, apparently associating functional browning with events only in the brite/beige tissues. Contrastingly, in another step, if the process is followed starting with mice initially housed at 30 °C (thermoneutrality for mice, thus similar to normal human conditions), large increases in UCP1 gene expression and UCP1 protein abundance are observed in the classical brown adipose tissue depots; there is then practically no observable UCP1 gene expression in brite/beige tissues. This apparent conundrum can be resolved when it is realized that the classical brown adipose tissue at 21 °C is already essentially fully differentiated and thus expands extensively through proliferation upon further browning induction, rather than by further enhancing cellular differentiation. When the limiting factor for thermogenesis, i.e. the total amount of UCP1 protein per depot, is analyzed, classical brown adipose tissue is by far the predominant site for the browning process, irrespective of which of the two steps is analyzed. There are to date no published data demonstrating that alternative browning agents would selectively promote brite/beige tissues versus classical brown tissue to a higher degree than does cold acclimation. Thus, to restrict investigations to examine adipose tissue depots where only a limited part of the adaptation process occurs (i.e. the brite/beige tissues) and to use initial conditions different from the thermoneutrality normally experienced by adult humans may seriously hamper the identification of therapeutically valid browning agents. The data presented here have therefore important implications for the analysis of the potential of browning agents and the nature of human brown adipose tissue.

A nutritional perspective on UCP1-dependent thermogenesis.

Uncoupling protein 1 (UCP1) is the hallmark protein responsible for cold- and diet-induced thermogenesis in brown adipose tissue (BAT). UCP1 activity is protective against body fat accumulation. UCP1 has re-gained researchers' attention in the context of obesity following the realization that BAT is present and can be activated in adult humans and of inducible UCP1-expressing cells in white fat depots. UCP1-mediated thermogenesis is activated by specific food compounds, which function by stimulating sympathetic nervous system activity to adipose tissues and/or by acting on the adipose cells directly or indirectly, through humoral factors released upon their intake. The impact, functional consequences and potential mechanism of action of macronutrients, micronutrients and bioactive compounds impinging on UCP1 expression/activity is discussed, as well as emerging links between human genetic variation and differential responses to potential thermogenic food ingredients. Advances in this field can help dietary recommendations and strategies for long-term weight loss/maintenance and improved metabolic health.

Artepillin C, a Typical Brazilian Propolis-Derived Component, Induces Brown-Like Adipocyte Formation in C3H10T1/2 Cells, Primary Inguinal White Adipose Tissue-Derived Adipocytes, and Mice.

Induction of brown-like adipocytes (beige/brite cells) in white adipose tissue (WAT) suggests a new approach for preventing and treating obesity via induction of thermogenesis associated with uncoupling protein 1 (UCP1). However, whether diet-derived factors can directly induce browning of white adipocytes has not been well established. In addition, the underlying mechanism of induction of brown-like adipocytes by diet-derived factors has been unclear. Here, we demonstrate that artepillin C (ArtC), which is a typical Brazilian propolis-derived component, significantly induces brown-like adipocytes in murine C3H10T1/2 cells and primary inguinal WAT (iWAT)-derived adipocytes. This significant induction is due to activation of peroxisome proliferator-activated receptor γ and stabilization of PRD1-BF-1-RIZ1 homologous domain-containing protein-16 (PRDM16). Furthermore, the oral administration of ArtC (10 mg/kg) for 4 weeks significantly induced brown-like adipocytes accompanied by significant expression of UCP1 and PRDM16 proteins in iWAT of mice, and was independent of the ß3-adrenergic signaling pathway via the sympathetic nervous system. These findings may provide insight into browning of white adipocytes including the molecular mechanism mediated by dietary factors and demonstrate that ArtC has a novel biological function with regard to increasing energy expenditure by browning of white adipocytes.

mTORC1 Is a Major Regulatory Node in the FGF21 Signaling Network in Adipocytes.

FGF21 improves the metabolic profile of obese animals through its actions on adipocytes. To elucidate the signaling network responsible for mediating these effects, we quantified dynamic changes in the adipocyte phosphoproteome following acute exposure to FGF21. FGF21 regulated a network of 821 phosphosites on 542 proteins. A major FGF21-regulated signaling node was mTORC1/S6K. In contrast to insulin, FGF21 activated mTORC1 via MAPK rather than through the canonical PI3K/AKT pathway. Activation of mTORC1/S6K by FGF21 was surprising because this is thought to contribute to deleterious metabolic effects such as obesity and insulin resistance. Rather, mTORC1 mediated many of the beneficial actions of FGF21 in vitro, including UCP1 and FGF21 induction, increased adiponectin secretion, and enhanced glucose uptake without any adverse effects on insulin action. This study provides a global view of FGF21 signaling and suggests that mTORC1 may act to facilitate FGF21-mediated health benefits in vivo.