High-resolution optical imaging deep in tissues is challenging because of optical aberrations and scattering of light caused by the complex structure of living matter. Here we present an adaptive ...optics three-photon microscope based on analog lock-in phase detection for focus sensing and shaping (ALPHA-FSS). ALPHA-FSS accurately measures and effectively compensates for both aberrations and scattering induced by specimens and recovers subcellular resolution at depth. A conjugate adaptive optics configuration with remote focusing enables in vivo imaging of fine neuronal structures in the mouse cortex through the intact skull up to a depth of 750 µm below the pia, enabling near-non-invasive high-resolution microscopy in cortex. Functional calcium imaging with high sensitivity and high-precision laser-mediated microsurgery through the intact skull were also demonstrated. Moreover, we achieved in vivo high-resolution imaging of the deep cortex and subcortical hippocampus up to 1.1 mm below the pia within the intact brain.
Alzheimer's disease (AD) is a devastating neurodegenerative disorder with no disease-modifying treatment. AD progression is characterized by cognitive decline, neuroinflammation, and accumulation of ...amyloid-beta (Aβ) and neurofibrillary tangles in the brain, leading to neuronal and glial dysfunctions. Neuropeptides govern diverse pathophysiological processes and represent key players in AD pathogenesis, regulating synaptic plasticity, glial cell functions and amyloid pathology. Activation of the pro-opiomelanocortin (POMC)-derived neuropeptide and its receptor from the melanocortin receptor (MCR) family have previously been shown to rescue the impairment in hippocampus-dependent synaptic plasticity in the APP/PS1 mouse model of AD. However, the functional roles of MCR signaling in AD conditions, particularly in glial functions, are largely unknown. In this study, we investigated the potential benefits of MCR activation in AD. In APP/PS1 transgenic mice, we demonstrate that MCR activation mediated by the central administration of its agonist D-Tyr MTII substantially reduces Aβ accumulation, while alleviating global inflammation and astrocytic activation, particularly in the hippocampus. MCR activation prominently reduces the A1 subtype of reactive astrocytes, which is considered a key source of astrocytic neurotoxicity in AD. Concordantly, MCR activation suppresses microglial activation, while enhancing their association with amyloid plaques. The blunted activation of microglia may contribute to the reduction in the neurotoxic phenotypes of astrocytes. Importantly, transcriptome analysis reveals that MCR activation restores the impaired homeostatic processes and microglial reactivity in the hippocampus in APP/PS1 mice. Collectively, our findings demonstrate the potential of MCR signaling as therapeutic target for AD.
The cocaine- and amphetamine-regulated transcript (CART) has been the subject of significant interest for over a decade. Work to decipher the detailed mechanism of CART function has been hampered by ...the lack of specific pharmacological tools like antagonists and the absence of a specific CART receptor(s). However, extensive research has been devoted to elucidate the role of the CART peptide and it is now evident that CART is a key neurotransmitter and hormone involved in the regulation of diverse biological processes, including food intake, maintenance of body weight, reward and addiction, stress response, psychostimulant effects and endocrine functions (Rogge et al., 2008; Subhedar et al., 2014). In this review, we focus on knowledge gained on CART's role in controlling appetite and energy homeostasis, and also address certain species differences between rodents and humans.
Neuropepetide Y (NPY) is best known for its powerful stimulation of food intake and its effects on reducing energy expenditure. However, the pathways involved and the regulatory mechanisms behind ...this are not well understood. Here we demonstrate that NPY derived from the arcuate nucleus (Arc) is critical for the control of sympathetic outflow and brown adipose tissue (BAT) function. Mechanistically, a key change induced by Arc NPY signaling is a marked Y1 receptor-mediated reduction in tyrosine hydroxylase (TH) expression in the hypothalamic paraventricular nucleus (PVN), which is also associated with a reduction in TH expression in the locus coeruleus (LC) and other regions in the brainstem. Consistent with this, Arc NPY signaling decreased sympathetically innervated BAT thermogenesis, involving the downregulation of uncoupling protein 1 (UCP1) expression in BAT. Taken together, these data reveal a powerful Arc-NPY-regulated neuronal circuit that controls BAT thermogenesis and sympathetic output via TH neurons.
► Arc NPY reduces TH neuron activity in the PVN via direct Y1 receptor signaling ► Arc NPY signaling leads to reduced TH neuron activity in LC and A1/C1 cell groups ► Arc NPY signaling is associated with decreased UCP1 mRNA and thermogenesis in BAT
Nuclear factor E2-related factor 2 (Nrf2) is a cap-n-collar basic leucine zipper (CNC-bZIP) transcription factor that is well established as a master regulator of phase II detoxification and ...antioxidant gene expression and is strongly expressed in tissues involved in xenobiotic metabolism including liver and kidney. Nrf2 is also abundantly expressed in adipose tissue; however, the exact function of Nrf2 in adipocyte biology is unclear. In the current study we show that targeted knock-out of Nrf2 in mice decreases adipose tissue mass, promotes formation of small adipocytes, and protects against weight gain and obesity otherwise induced by a high fat diet. In mouse embryonic fibroblasts, 3T3-L1 cells, and human subcutaneous preadipocytes, selective deficiency of Nrf2 impairs adipocyte differentiation. Deficiency of Nrf2 also leads to decreased expression of peroxisome proliferator-activated receptor γ (PPARγ), CCAAT enhancer-binding protein α (C/EBPα), and their downstream targets during adipocyte differentiation. Conversely, activation of Nrf2 in 3T3-L1 cells by stable knockdown of its negative regulator Keap1 enhances and accelerates hormone-induced adipocyte differentiation. Transfection of Nrf2 stimulates Pparγ promoter activity, and stable knockdown of Keap1 enhances PPARγ expression in 3T3-L1 cells. In addition, chromatin immunoprecipitation studies show that Nrf2 associates with consensus binding sites for Nrf2 in the Pparγ promoter. These findings demonstrate a novel biologic role for Nrf2 beyond its participation in detoxification and antioxidant pathways and place Nrf2 within the limited network of transcription factors that control adipocyte differentiation by regulating expression of PPARγ.
Obesity is caused by an imbalance between food intake and energy expenditure (EE). Here we identify a conserved pathway that links signalling through peripheral Y1 receptors (Y1R) to the control of ...EE. Selective antagonism of peripheral Y1R, via the non-brain penetrable antagonist BIBO3304, leads to a significant reduction in body weight gain due to enhanced EE thereby reducing fat mass. Specifically thermogenesis in brown adipose tissue (BAT) due to elevated UCP1 is enhanced accompanied by extensive browning of white adipose tissue both in mice and humans. Importantly, selective ablation of Y1R from adipocytes protects against diet-induced obesity. Furthermore, peripheral specific Y1R antagonism also improves glucose homeostasis mainly driven by dynamic changes in Akt activity in BAT. Together, these data suggest that selective peripheral only Y1R antagonism via BIBO3304, or a functional analogue, could be developed as a safer and more effective treatment option to mitigate diet-induced obesity.
Insulin secretion is tightly controlled through coordinated actions of a number of systemic and local factors. Peptide YY (PYY) is expressed in α-cells of the islet, but its role in control of islet ...function such as insulin release is not clear. In this study, we generated a transgenic mouse model (Pyytg/+/Rip-Cre) overexpressing the Pyy gene under the control of the rat insulin 2 gene promoter and assessed the impact of islet-released PYY on β-cell function, insulin release, and glucose homeostasis in mice. Our results show that up-regulation of PYY in islet β-cells leads to an increase in serum insulin levels as well as improved glucose tolerance. Interestingly, PYY-overproducing mice show increased lean mass and reduced fat mass with no significant changes in food intake or body weight. Energy expenditure is also increased accompanied by increased respiratory exchange ratio. Mechanistically, the enhanced insulin levels and improved glucose tolerance are primarily due to increased β-cell mass and secretion. This is associated with alterations in the expression of genes important for β-cell proliferation and function as well as the maintenance of the β-cell phenotype. Taken together, these data demonstrate that pancreatic islet-derived PYY plays an important role in controlling glucose homeostasis through the modulation of β-cell mass and function.
The cocaine- and amphetamine-regulated transcript (CART) codes for a pivotal neuropeptide important in the control of appetite and energy homeostasis. However, limited understanding exists for the ...defined effector sites underlying CART function, as discrepant effects of central CART administration have been reported.
By combining Cart-cre knock-in mice with a Cart adeno-associated viral vector designed using the flip-excision switch (AAV-FLEX) technology, specific reintroduction or overexpression of CART selectively in CART neurons in the arcuate nucleus (Arc) and lateral hypothalamic area (LHA), respectively, was achieved. The effects on energy homeostasis control were investigated.
Here we show that CART neuron-specific reintroduction of CART into the Arc and LHA leads to distinct effects on energy homeostasis control. Specifically, CART reintroduction into the Arc of otherwise CART-deficient Cart
mice markedly decreased fat mass and body weight, whereas CART reintroduction into the LHA caused significant fat mass gain and lean mass loss, but overall unaltered body weight. The reduced adiposity in Arc
;Cart
mice was associated with an increase in both energy expenditure and physical activity, along with significantly decreased Npy mRNA levels in the Arc but with no change in food consumption. Distinctively, the elevated fat mass in LHA
;Cart
mice was accompanied by diminished insulin responsiveness and glucose tolerance, greater spontaneous food intake, and reduced energy expenditure, which is consistent with the observed decrease of brown adipose tissue temperature. This is also in line with significantly reduced tyrosine hydroxylase (Th) and notably increased corticotropin-releasing hormone (Crh) mRNA expressions in the paraventricular nucleus (PVN).
Taken together, these results identify catabolic and anabolic effects of CART in the Arc and LHA, respectively, demonstrating for the first time the distinct and region-specific functions of CART in controlling feeding and energy homeostasis.
Cocaine- and amphetamine-regulated transcript (CART) is widely expressed in the hypothalamus and an important regulator of energy homeostasis; however, the specific contributions of different CART ...neuronal populations to this process are not known. Here, we show that depolarization of mouse arcuate nucleus (Arc) CART neurons via DREADD technology decreases energy expenditure and physical activity, while it exerts the opposite effects in CART neurons in the lateral hypothalamus (LHA). Importantly, when stimulating these neuronal populations in the absence of CART, the effects were attenuated. In contrast, while activation of CART neurons in the LHA stimulated feeding in the presence of CART, endogenous CART inhibited food intake in response to Arc CART neuron activation. Taken together, these results demonstrate anorexigenic but anabolic effects of CART upon Arc neuron activation, and orexigenic but catabolic effects upon LHA-neuron activation, highlighting the complex and nuclei-specific functions of CART in controlling feeding and energy homeostasis.
Y-receptors control energy homeostasis, but the role of Npy6 receptors (Npy6r) is largely unknown. Young Npy6r-deficient (Npy6r−/−) mice have reduced body weight, lean mass, and adiposity, while ...older and high-fat-fed Npy6r−/− mice have low lean mass with increased adiposity. Npy6r−/− mice showed reduced hypothalamic growth hormone releasing hormone (Ghrh) expression and serum insulin-like growth factor-1 (IGF-1) levels relative to WT. This is likely due to impaired vasoactive intestinal peptide (VIP) signaling in the suprachiasmatic nucleus (SCN), where we found Npy6r coexpressed in VIP neurons. Peripheral administration of pancreatic polypeptide (PP) increased Fos expression in the SCN, increased energy expenditure, and reduced food intake in WT, but not Npy6r−/−, mice. Moreover, intraperitoneal (i.p.) PP injection increased hypothalamic Ghrh mRNA expression and serum IGF-1 levels in WT, but not Npy6r−/−, mice, an effect blocked by intracerebroventricular (i.c.v.) Vasoactive Intestinal Peptide (VPAC) receptors antagonism. Thus, PP-initiated signaling through Npy6r in VIP neurons regulates the growth hormone axis and body composition.
Display omitted
•Npy6r are coexpressed in VIP neurons in the hypothalamic SCN•Npy6r deficiency leads to late-onset obesity•PP is the major physiological ligand for Npy6r•PP activates Npy6r in VIP neurons to regulate the GH/IGF-1 axis
Yulyaningsih et al. investigate the role of the Npy6 receptor in mice and show that the satiety factor pancreatic polypeptide (PP) is the physiological activator of Npy6r and that PP-initiated signaling through Npy6r in vasoactive intestinal peptide (VIP) neurons regulates the growth hormone axis and energy balance.
PDF
