30 research outputs found
Genetic and pharmacologic blockade of central melanocortin signaling attenuates cardiac cachexia in rodent models of heart failure
The central melanocortin system plays a key role in the regulation of food intake and energy homeostasis. We investigated whether genetic or pharmacologic blockade of central melanocortin signaling attenuates cardiac cachexia in mice and rats with heart failure. Permanent ligation of the left coronary artery (myocardial infarction (MI)) or sham operation was performed in wild-type (WT) or melanocortin-4 receptor (MC4R) knockout mice. Eight weeks after surgery, WT-Sham mice had significant increases in lean body mass (LBM; P<0·05) and fat mass (P<0·05), whereas WT-MI did not gain significant amounts of LBM or fat mass. Resting basal metabolic rate (BMR) was significantly lower in WT-Sham mice compared to WT-MI mice (P<0·001). In contrast, both MC4-Sham and MC4-MI mice gained significant amounts of LBM (P<0·05) and fat mass (P<0·05) over the study period. There was no significant difference in the BMR between MC4-Sham and MC4-MI mice. In the second experiment, rats received aortic bands or sham operations, and after recovery received i.c.v. injections of either artificial cerebrospinal fluid (aCSF) or the melanocortin antagonist agouti-related protein (AGRP) for 2 weeks. Banded rats receiving AGRP gained significant amount of LBM (P<0·05) and fat mass (P<0·05) over the treatment period, whereas banded rats receiving aCSF did not gain significant amounts of LBM or fat mass. These results demonstrated that genetic and pharmacologic blockade of melanocortin signaling attenuated the metabolic manifestations of cardiac cachexia in murine and rat models of heart failure
Perineuronal Net Formation and the Critical Period for Neuronal Maturation in the Hypothalamic Arcuate Nucleus
In leptin-deficient ob/ob mice, obesity and diabetes are associated with abnormal development of neurocircuits in the hypothalamic arcuate nucleus (ARC)1, a critical brain area for energy and glucose homoeostasis2,3. Because this developmental defect can be remedied by systemic leptin administration, but only if given before postnatal day 28, a critical period for leptin-dependent development of ARC neurocircuits has been proposed4. In other brain areas, critical-period closure coincides with the appearance of perineuronal nets (PNNs), extracellular matrix specializations that restrict the plasticity of neurons that they enmesh5. Here we report that in humans and rodents, subsets of neurons in the mediobasal aspect of the ARC are enmeshed in PNN-like structures. In mice, these neurons are densely packed into a continuous ring that encircles the junction of the ARC and median eminence, which facilitates exposure of ARC neurons to the circulation. Most of the enmeshed neurons are both γ-aminobutyric acid-ergic and leptin-receptor positive, including a majority of Agouti-related-peptide neurons. Postnatal formation of the PNN-like structures coincides precisely with closure of the critical period for maturation of Agouti-related-peptide neurons and is dependent on input from circulating leptin, because postnatal ob/ob mice have reduced ARC PNN-like material that is restored by leptin administration during the critical period. We conclude that neurons crucial to metabolic homoeostasis are enmeshed in PNN-like structures and organized into a densely packed cluster situated circumferentially at the ARC–median eminence junction, where metabolically relevant humoral signals are sensed
Transcriptomic analysis links diverse hypothalamic cell types to fibroblast growth factor 1-induced sustained diabetes remission
n rodent models of type 2 diabetes (T2D), sustained remission of hyperglycemia can be induced by a single intracerebroventricular (icv) injection of fibroblast growth factor 1 (FGF1), and the mediobasal hypothalamus (MBH) was recently implicated as the brain area responsible for this effect. To better understand the cellular response to FGF1 in the MBH, we sequenced >79,000 single-cell transcriptomes from the hypothalamus of diabetic Lepob/ob mice obtained on Days 1 and 5 after icv injection of either FGF1 or vehicle. A wide range of transcriptional responses to FGF1 was observed across diverse hypothalamic cell types, with glial cell types responding much more robustly than neurons at both time points. Tanycytes and ependymal cells were the most FGF1-responsive cell type at Day 1, but astrocytes and oligodendrocyte lineage cells subsequently became more responsive. Based on histochemical and ultrastructural evidence of enhanced cell-cell interactions between astrocytes and Agrp neurons (key components of the melanocortin system), we performed a series of studies showing that intact melanocortin signaling is required for the sustained antidiabetic action of FGF1. These data collectively suggest that hypothalamic glial cells are leading targets for the effects of FGF1 and that sustained diabetes remission is dependent on intact melanocortin signaling
Cloning and distribution of galanin-like peptide mRNA in the hypothalamus and pituitary of the macaque
Galanin-like peptide (GALP) is a newly discovered hypothalamic
neuropeptide, which is regulated by leptin and implicated in the
regulation of GnRH secretion in the rodent. We searched the human genome
database and determined that the human GALP gene comprises six exons, as
has been shown for human galanin. We used rapid amplification of cDNA ends
to clone a full-length cDNA (802 bp) of the macaque homologue of GALP and
found it to be highly conserved between human and macaque at both the
nucleotide (93%) and peptide (94%) levels. Mature GALP is predicted to be
60 amino acids in the macaque as in other species, and the region of GALP
(9-21) that shows homology to the N-terminal 13 amino acids of galanin is
perfectly conserved. We mapped the distribution of GALP mRNA in the
hypothalamus and pituitary of the macaque by in situ hybridization and
observed that, as in rodent species, the expression of GALP mRNA is
confined to the arcuate nucleus, median eminence, and neurohypophysis.
Using double-label in situ hybridization, we found that nearly all (98%)
GALP mRNA-expressing cells in the arcuate nucleus also express mRNA for
the long form of the leptin receptor. These findings suggest that a
leptin-GALP signaling pathway exists in a primate species
Prolonged Adherence of Human Immunodeficiency Virus-Derived Vector Particles to Hematopoietic Target Cells Leads to Secondary Transduction In Vitro and In Vivo
Human immunodeficiency virus type 1-derived lentivirus vectors bearing the vesicular stomatitis virus G (VSV-G) envelope glycoprotein demonstrate a wide host range and can stably transduce quiescent hematopoietic stem cells. In light of concerns about biosafety and potential germ line transmission, they have been used predominantly for ex vivo strategies, thought to ensure the removal of excess surface-bound particles and prevent in vivo dissemination. Studies presented here instead reveal prolonged particle adherence after ex vivo exposure, despite serial wash procedures, with subsequent transduction of secondary target cells in direct and transwell cocultures. We explored the critical parameters affecting particle retention and transfer and show that attachment to the cell surface selectively protects virus particles from serum complement-mediated inactivation. Moreover, studies with nonmyeloablated murine recipients show that transplantation of vector-exposed, washed hematopoietic cells results in systemic dissemination of functional VSV-G/lentivector particles. We demonstrate genetic marking by inadvertent transfer of vector particles and prolonged expression of transgene product in recipient tissues. Our findings have implications for biosafety, vector design, and cell biology research
Combined micro-osmotic pump infusion and intracerebroventricular injection to study FGF1 signaling pathways in the mouse brain
Galanin-like peptide as a possible link between metabolism and reproduction in the macaque
Galanin-like peptide (GALP) is a hypothalamic neuropeptide that has been
implicated in the control of feeding, metabolism, and reproduction. The
goal of this study was to examine the effects of central infusions of GALP
on GnRH and LH secretion and to identify physiological factors that
influence the expression of GALP mRNA in the brain of a primate species.
Infusions of GALP into the lateral cerebroventricle of the macaque caused
a significant increase in LH secretion, which was blocked by
administration of the GnRH receptor antagonist acyline. However, the
expression of GALP mRNA in the arcuate nucleus, as determined by in situ
hybridization, was not regulated by either estradiol or progesterone.
Compared with feeding ad libitum, fasting for 48 h produced a significant
reduction in the hypothalamic expression of GALP mRNA. GALP neurons were
found to express both neuropeptide Y Y1 receptor and serotonin 2C receptor
by double-label in situ hybridization. Taken together, these results
suggest that GALP neurons play a role of integrating metabolic signals,
which are relayed to circuits controlling GnRH release in the macaque
Galanin-Like Peptide as a Possible Link between Metabolism and Reproduction in the Macaque
High-fat diet feeding disrupts the coupling of thermoregulation to energy homeostasis
Objective: Preserving core body temperature across a wide range of ambient temperatures requires adaptive changes of thermogenesis that must be offset by corresponding changes of energy intake if body fat stores are also to be preserved. Among neurons implicated in the integration of thermoregulation with energy homeostasis are those that express both neuropeptide Y (NPY) and agouti-related protein (AgRP) (referred to herein as AgRP neurons). Specifically, cold-induced activation of AgRP neurons was recently shown to be required for cold exposure to increase food intake in mice. Here, we investigated how consuming a high-fat diet (HFD) impacts various adaptive responses to cold exposure as well as the responsiveness of AgRP neurons to cold. Methods: To test this, we used immunohistochemistry, in vivo fiber photometry and indirect calorimetry for continuous measures of core temperature, energy expenditure, and energy intake in both chow- and HFD-fed mice housed at different ambient temperatures. Results: We show that while both core temperature and the thermogenic response to cold are maintained normally in HFD-fed mice, the increase of energy intake needed to preserve body fat stores is blunted, resulting in weight loss. Using both immunohistochemistry and in vivo fiber photometry, we show that although cold-induced AgRP neuron activation is detected regardless of diet, the number of cold-responsive neurons appears to be blunted in HFD-fed mice. Conclusions: We conclude that HFD-feeding disrupts the integration of systems governing thermoregulation and energy homeostasis that protect body fat mass during cold exposure