Hypothalamic neuropeptides play essential roles in regulating energy and body weight balance. Energy imbalance and obesity have been linked to hypothalamic signaling defects in regulating neuropeptide genes; however, it is unknown whether dysregulation of neuropeptide exocytosis could be critically involved. This study discovered that synaptotagmin-4, an atypical modulator of synaptic exocytosis, is expressed most abundantly in oxytocin neurons of the hypothalamus. Synaptotagmin-4 negatively regulates oxytocin exocytosis, and dietary obesity is associated with increased vesicle binding of synaptotagmin-4 and thus enhanced negative regulation of oxytocin release. Overexpressing synaptotagmin-4 in hypothalamic oxytocin neurons and centrally antagonizing oxytocin in mice are similarly obesogenic. Synaptotagmin-4 inhibition prevents against dietary obesity by normalizing oxytocin release and energy balance under chronic nutritional excess. In conclusion, the negative regulation of synaptotagmin-4 on oxytocin release represents a hypothalamic basis of neuropeptide exocytosis in controlling obesity and related diseases.

Autophagy has been recently demonstrated to control cell and tissue homeostasis, including the functions of various metabolic tissues. However, it remains unclear whether autophagy is critical for the central nervous system and particularly the hypothalamus for exerting metabolic regulation. Using autophagy-related protein 7 (Atg7) as an autophagic marker, this work showed that autophagy was highly active in the mediobasal hypothalamus of normal mice. In contrast, chronic development of dietary obesity was associated with autophagic decline in the mediobasal hypothalamus. To investigate the potential role of autophagy in the hypothalamic control of metabolic physiology, a mouse model was developed with autophagic inhibition in the mediobasal hypothalamus using site-specific delivery of lentiviral shRNA against Atg7. This model revealed that hypothalamic inhibition of autophagy increased energy intake and reduced energy expenditure. These metabolic changes were sufficient to increase body weight gain under normal chow feeding and exacerbate the progression of obesity and whole-body insulin resistance under high-fat diet feeding. To explore the underlying mechanism, this study found that defective hypothalamic autophagy led to hypothalamic inflammation, including the activation of proinflammatory IκB kinase β pathway. Using brain-specific IκB kinase β knockout mice, it was found that the effects of defective hypothalamic autophagy in promoting obesity were reversed by IκB kinase β inhibition in the brain. In conclusion, hypothalamic autophagy is crucial for the central control of feeding, energy, and body weight balance. Conversely, decline of hypothalamic autophagy under conditions of chronic caloric excess promotes hypothalamic inflammation and thus impairs hypothalamic control of energy balance, leading to accelerated development of obesity and comorbidities.

An alkyne-azide addition, i.e., click, reaction in conjunction with an electrostatic self-assembly and covalent fixation (ESA-CF) process has been demonstrated to effectively construct a variety of unprecedented multicyclic polymer topologies. A series of single cyclic poly(tetrahydrofuran), poly(THF), precursors having an alkyne group (Ia), an azide group (Ib), two alkyne groups at the opposite positions (Ic), and an alkyne group and an azide group at the opposite positions (Id) have been prepared by the ESA-CF process. Moreover, a bicyclic 8-shaped precursor having two alkyne groups at the opposite positions (Ie) was synthesized. The subsequent click reaction of Ia with linear (IIa) and three-armed star (IIb) telechelic precursors having azide groups has been performed to construct bridged-type two-way (IIIa) and three-way (IIIb) paddle-shaped polymer topologies, respectively. Likewise, spiro-type tandem tricyclic (IVa) and tetracyclic (IVb) topologies resulted from Ib/Ic and Ib/Ie, respectively. Furthermore, three types of multicyclic topologies that are composed of repeating ring (Va), alternating ring/linear (Vb), and alternating ring/star (Vc) units have been synthesized from Id, Ic/IIa, and Ic/IIb, respectively.

Quantum dots (QDs) offer new and versatile ways to harvest light energy. However, there are few examples involving the utilization of QDs in organic synthesis. Visible-light irradiation of CdSe QDs was found to result in virtually quantitative coupling of a variety of thiols to give disulfides and H2 without the need for sacrificial reagents or external oxidants. The addition of small amounts of nickel(II) salts dramatically improved the efficiency and conversion through facilitating the formation of hydrogen atoms, thereby leading to faster regeneration of the ground-state QDs. Mechanistic studies reveal that the coupling reaction occurs on the QD surfaces rather than in solution and offer a blueprint for how these QDs may be used in other photocatalytic applications. Because no sacrificial agent or oxidant is necessary and the catalyst is reusable, this method may be useful for the formation of disulfide bonds in proteins as well as in other systems sensitive to the presence of oxidants.

An external oxidant-free oxidative coupling for aromatic C-H thiolation by visible-light photoredox cobalt-catalysis has been developed. Various substrates could afford benzothiazoles in good to excellent yields, and only H2 is generated as a side product. When catalytic TBAOH was used as the base, not only 2-aryl but also 2-alkylbenzothiazoles could be obtained through this novel dehydrogenative coupling reaction. This method could be scaled up and applied to the synthesis of biologically active molecules bearing benzothiazole structural scaffolds (potent antitumor agents). Furthermore, the unexpected oxidation byproduct amides, which are often generated in oxidative cyclization of thiobenzanilides, can be completely avoided. Mechanistic studies showed that the H2 originates from the substrates. The kinetic studies indicate that the interaction between the cobalt catalyst and proton might be involved in the rate-limiting process.

The carboxylation of sp 3 -hybridized C–H bonds with CO 2 is a challenging transformation. Herein, we report a visible-light-mediated carboxylation of benzylic C–H bonds with CO 2 into 2-arylpropionic acids under metal-free conditions. Photo-oxidized triisopropylsilanethiol was used as the hydrogen atom transfer catalyst to afford a benzylic radical that accepts an electron from the reduced form of 2,3,4,6-tetra(9H-carbazol-9-yl)-5-(1-phenylethyl)benzonitrile generated in situ . The resulting benzylic carbanion reacts with CO 2 to generate the corresponding carboxylic acid after protonation. The reaction proceeded without the addition of any sacrificial electron donor, electron acceptor or stoichiometric additives. Moderate to good yields of the desired products were obtained in a broad substrate scope. Several drugs were successfully synthesized using the novel strategy.

We present a blueprint for aromatic C-H functionalization via a combination of photocatalysis and cobalt catalysis and describe the utility of this strategy for benzene amination and hydroxylation. Without any sacrificial oxidant, we could use the dual catalyst system to produce aniline directly from benzene and ammonia, and phenol from benzene and water, both with evolution of hydrogen gas under unusually mild conditions in excellent yields and selectivities.

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