Leptin, an adipocyte-derived peptide hormone, has been shown to facilitate breathing. However, the central sites and circuit mechanisms underlying the respiratory effects of leptin remain incompletely understood. The present study aimed to address whether neurons expressing leptin receptor b (LepRb) in the nucleus tractus solitarii (NTS) contribute to respiratory control. Both chemogenetic and optogenetic stimulation of LepRb-expressing NTS (NTS^LepRb) neurons notably activated breathing. Moreover, stimulation of NTS^LepRb neurons projecting to the lateral parabrachial nucleus (LPBN) not only remarkably increased basal ventilation to a level similar to that of the stimulation of all NTS^LepRb neurons, but also activated LPBN neurons projecting to the preBötzinger complex (preBötC). By contrast, ablation of NTS^LepRb neurons projecting to the LPBN notably eliminated the enhanced respiratory effect induced by NTS^LepRb neuron stimulation. In brainstem slices, bath application of leptin rapidly depolarized the membrane potential, increased the spontaneous firing rate, and accelerated the Ca²⁺ transients in most NTS^LepRb neurons. Therefore, leptin potentiates breathing in the NTS most likely via an NTS-LPBN-preBötC circuit.
Leptin/pharmacology* ; Membrane Potentials ; Neurons/metabolism* ; Solitary Nucleus/metabolism*

OBJECTIVE: To investigate the the effects of leptin on the proliferation, differentiation and PTEN expression of rat retinal progenitor cells (RPCs) cultured under hypoxic condition. METHODS: SD rat RPCs were cultured in normoxic conditions or exposed to hypoxia in the presence of 0, 0.3, 1.0, 3.0, 10, and 30 nmol/L leptin for 12, 48 and 72 h, and the cell viability was assessed using cell counting kit 8 (CCK 8) assay. The RPCs in primary culture were divided into control group, hypoxia group, and hypoxia+leptin group, and after 48 h of culture, the cell medium was replaced with differentiation medium and the cells were further cultured for 6 days. Immunofluorescence staining was employed to detect the cells positive for β-tubulin III and GFAP, and Western blotting was used to examine the expression of PTEN at 48 h of cell culture. RESULTS: The first generation of RPCs showed suspended growth in the medium with abundant and bright cellular plasma and formed mulberry like cell spheres after 2 days of culture. Treatment with low-dose leptin (below 3.0 nmol/L) for 48 h obviously improved the viability of RPCs cultured in hypoxia, while at high concentrations (above 10 nmol/L), leptin significantly suppressed the cell viability (P < 0.05). The cells treated with 3.0 nmol/L leptin for 48 h showed the highest viability (P < 0.05). After treatment with 3.0 nmol/L leptin for 48 h, the cells with hypoxic exposure showed similar GFAP and β-tubulin Ⅲ positivity with the control cells (P>0.05), but exhibited an obvious down-regulation of PTEN protein expression compared with the control cells (P < 0.05). CONCLUSION In rat RPCs with hypoxic exposure, treatment with low dose leptin can promote the cell proliferation and suppress cellular PTEN protein expression without causing significant effects on cell differentiation.
Animals ; Cell Differentiation/drug effects* ; Cell Hypoxia/drug effects* ; Cell Proliferation/drug effects* ; Cells, Cultured ; Leptin/pharmacology* ; PTEN Phosphohydrolase/metabolism* ; Rats ; Rats, Sprague-Dawley ; Retina/metabolism* ; Stem Cells/metabolism* ; Tubulin

OBJECTIVES: Acute kidney injury (AKI) can be caused by ischemia/reperfusion (I/R), nephrotoxin, and sepsis, with poor prognosis and high mortality. Leptin is a protein molecule that regulates the body's energy metabolism and reproductive activities via binding to its specific receptor. Leptin can inhibit cardiomyocyte apoptosis caused by I/R, but its effect on I/R kidney injury and the underlying mechanisms are still unclear. This study aims to investigate the effect and mechanisms of leptin on renal function, renal histopathology, apoptosis, and autophagy during acute I/R kidney injury. METHODS: Healthy adult male mice were randomly divided into 4 groups: a sham+wild-type mice (ob/+) group, a sham+leptin gene-deficient mice (ob/ob) group, an I/R+ob/+ group, and an I/R+ob/ob group (n=8 per group). For sham operation, a longitudinal incision was made on the back of the mice to expose and separate the bilateral kidneys and renal arteries, and no subsequent treatment was performed. I/R treatment was ischemia for 30 min and reperfusion for 48 h. The levels of BUN and SCr were detected to evaluate renal function; HE staining was used to observe the pathological changes of renal tissue; TUNEL staining was used to observe cell apoptosis, and apoptosis-positive cells were counted; Western blotting was used to detect levels of apoptosis-related proteins (caspase 3, caspase 9), autophagy-related proteins [mammalian target of rapamycin (mTOR), phosphorylated mTOR (p-mTOR), LC3 I, LC3 II], mTOR-dependent signaling pathway proteins [phosphate and tension homology (PTEN), adenosine monophosphate-activated protein kinase (AMPK), protein kinase B (AKT), extracellular regulated protein kinase (ERK), phosphorylated PTEN (p-PTEN), phosphorylated AMPK (p-AMPK), phosphorylated AKT (p-AKT), phosphorylated ERK (p-ERK)]. RESULTS: There was no significant difference in the levels of BUN and SCr between the sham+ob/+ group and the sham+ob/ob group (both P>0.05). The levels of BUN and SCr in the I/R+ob/+ group were significantly higher than those in the sham+ob/+ group (both P<0.05). Compared with the mice in the sham+ob/ob group or the I/R+ob/+ group, the levels of BUN and SCr in the I/R+ob/ob group were significantly increased (all P<0.05). There was no obvious damage to the renal tubules in the sham+ob/+ group and the sham+ob/ob group. Compared with sham+ob/+ group and sham+ob/ob group, both the I/R+ob/+ group and the I/R+ob/ob group had cell damage such as brush border shedding, vacuolar degeneration, and cast formation. Compared with the I/R+ob/+ group, the renal tubules of the mice in the I/R+ob/ob group were more severely damaged. The pathological score of renal tubular injury showed that the renal tubular injury was the most serious in the I/R+ob/ob group (P<0.05). Compared with the sham+ob/+ group, the protein levels of caspase 3, caspase 9, PTEN, and LC3 II were significantly up-regulated, the ratio of LC3 II to LC3 I was significantly increased, and the protein levels of p-mTOR, p-PTEN, p-AMPK, p-AKT, and p-ERK were significantly down-regulated in the I/R+ob/+ group (all P<0.05). Compared with the sham+ob/ob group, the protein levels of caspase 3, caspase 9, PTEN, and LC3 II were significantly up-regulated, and the ratio of LC3 II to LC3 I was significantly increased, while the protein levels of p-mTOR, p-PTEN, p-AMPK, p-AKT, and p-ERK were significantly down-regulated in the I/R+ob/ob group (all P<0.05). Compared with the I/R+ob/+ group, the levels of p-mTOR, p-PTEN, p-AMPK, p-AKT were more significantly down-regulated, while the levels of caspase 3, caspase 9, PTEN, and LC3 II were more significantly up-regulated, and the ratio of LC3 II to LC3 I was more significantly increase in the I/R+ob/ob group (all P<0.05). CONCLUSIONS Renal function and tubular damage, and elevated levels of apoptosis and autophagy are observed in mice kidneys after acute I/R. Leptin might relieve I/R induced AKI by inhibiting apoptosis and autophagy that through a complex network of interactions between mTOR-dependent signaling pathways.
AMP-Activated Protein Kinases/metabolism* ; Acute Kidney Injury/pathology* ; Animals ; Apoptosis ; Apoptosis Regulatory Proteins/pharmacology* ; Autophagy ; Caspase 3/metabolism* ; Caspase 9/metabolism* ; Female ; Humans ; Ischemia ; Kidney/pathology* ; Leptin/pharmacology* ; Male ; Mammals/metabolism* ; Mice ; Proto-Oncogene Proteins c-akt/metabolism* ; Reperfusion/adverse effects* ; Reperfusion Injury/metabolism* ; TOR Serine-Threonine Kinases/metabolism*

Combined radiation-wound injury (CRWI) is characterized by blood vessel damage and pro-inflammatory cytokine deficiency. Studies have identified that the direct application of leptin plays a significant role in angiogenesis and inflammation. We established a sustained and stable leptin expression system to study the mechanism. A lentivirus method was employed to explore the angiogenic potential and peripheral inflammation of irradiated human umbilical vein endothelial cells (HUVECs). Leptin was transfected into human placenta-derived mesenchymal stem cells (HPMSCs) with lentiviral vectors. HUVECs were irradiated by X-ray at a single dose of 20 Gy. Transwell migration assay was performed to assess the migration of irradiated HUVECs. Based on the Transwell systems, co-culture systems of HPMSCs and irradiated HUVECs were established. Cell proliferation was measured by cell counting kit-8 (CCK-8) assay. The secretion of pro-inflammatory cytokines (human granulocyte macrophage-colony stimulating factor (GM-CSF), interleukin (IL)-1α, IL-6, and IL-8) was detected by enzyme-linked immunosorbent assay (ELISA). The expression of pro-angiogenic factors (vascular endothelial growth factor (VEGF) and basic fibroblast growth factor (bFGF)) mRNA was detected by real-time quantitative polymerase chain reaction (RT-qPCR) assay. Relevant molecules of the nuclear factor-κB (NF-κB) and Janus kinase (JAK)/signal transducer and activator of transcription (STAT) signaling pathways were detected by western blot assay. Results showed that leptin-modified HPMSCs (HPMSCs/ leptin) exhibited better cell proliferation, migration, and angiogenic potential (expressed more VEGF and bFGF). In both the single HPMSCs/leptin and the co-culture systems of HPMSCs/leptin and irradiated HUVECs, the increased secretion of pro-inflammatory cytokines (human GM-CSF, IL-1α, and IL-6) was associated with the interaction of the NF-κB and JAK/STAT signaling pathways. We conclude that HPMSCs/leptin could promote angiogenic potential and peripheral inflammation of HUVECs after X-ray radiation.
Cell Proliferation ; Cells, Cultured ; Cytokines/biosynthesis* ; Female ; Human Umbilical Vein Endothelial Cells/radiation effects* ; Humans ; Inflammation/etiology* ; Leptin/pharmacology* ; Mesenchymal Stem Cells/physiology* ; Neovascularization, Physiologic/physiology* ; Placenta/cytology* ; Pregnancy ; STAT3 Transcription Factor/genetics* ; Transcription Factor RelA/genetics* ; X-Rays

OBJECTIVE: To investigate the effects of aerobic exercise and glutamine (Gln) on anti-oxidative stress and inflammatory factors in type 2 diabetes mellitus (T2MD) rats. METHODS: Diabetic rat model was induced by streptozotocin (STZ). Fifty 6-week old male SD rats were randomly divided into 5 groups (n=10), including quiet control group (N), diabetes control group (D), diabetic aerobic exercise group (DE), diabetic glutamine group (DG) and diabetic aerobic exercise glutamine group (DEG). After 6 weeks, the related indicators of glucose and lipid metabolism, anti-oxidative stress and inflammatory factors in diabetic rats were detected, and the possible mechanism affecting inflammatory response were explored. RESULTS: Compared with group N, the levels of serum malondialdehyde(MDA), blood glucose, total cholesterol(TC), triglyceride(TG), insulin, leptin and tumor necrosis factor-α(TNF-α) in group D were increased significantly (P＜0.01). Compared with group D, serum levels of MDA, blood glucose, TC, TG, insulin, leptin and TNF-α in three intervention groups were decreased significantly, while the levels of SOD, GSH-Px and adiponectin were increased, and the combined effect was more obvious (P＜0.01). CONCLUSION Both aerobic exercise and Gln can relieve the glucose and lipid metabolism and disturbance, oxidative stress injury and inflammation in diabetic rats.
Animals ; Blood Glucose ; analysis ; Diabetes Mellitus, Experimental ; Diabetes Mellitus, Type 2 ; therapy ; Glutamine ; pharmacology ; Leptin ; blood ; Lipid Metabolism ; Lipids ; blood ; Male ; Malondialdehyde ; blood ; Oxidative Stress ; Physical Conditioning, Animal ; Random Allocation ; Rats ; Rats, Sprague-Dawley

Accumulating evidence suggests that obesity is associated with chronic pain. However, whether obesity is associated with acute inflammatory pain is unknown. Using a well-established obese mouse model induced by a high-fat diet, we found that: (1) the acute thermal pain sensory threshold did not change in obese mice; (2) the model obese mice had fewer nociceptive responses in formalin-induced inflammatory pain tests; restoring the obese mice to a chow diet for three weeks partly recovered their pain sensation; (3) leptin injection induced significant phosphorylation of STAT3 in control mice but not in obese mice, indicating the dysmodulation of topical leptin-leptin receptor signaling in these mice; and (4) leptin-leptin receptor signaling-deficient mice (ob/ob and db/db) or leptin-leptin receptor pathway blockade with a leptin receptor antagonist and the JAK2 inhibitor AG 490 in wild-type mice reduced their nociceptive responses in formalin tests. These results indicate that leptin plays a role in nociception induced by acute inflammation and that interference in the leptin-leptin receptor pathway could be a peripheral target against acute inflammatory pain.
Animals ; Diet, High-Fat ; adverse effects ; Inflammation ; chemically induced ; metabolism ; Leptin ; metabolism ; pharmacology ; Male ; Mice ; Mice, Inbred C57BL ; Nociception ; drug effects ; physiology ; Nociceptive Pain ; etiology ; metabolism ; Obesity ; complications ; metabolism ; Pain Measurement ; Pain Threshold ; drug effects ; physiology ; Receptors, Leptin ; metabolism ; Signal Transduction ; drug effects ; physiology

OBJECTIVETo investigate the neuroprotective effect of leptin by observing its effect on spatial memory of rats with white matter damage in developing brain.

METHODSA total of 80 neonatal rats were randomly divided into 3 groups: sham-operation (n=27), model (n=27) and leptin intervention (n=27). The rats in the model and leptin intervention groups were used to prepare a model of white matter damage in developing brain, and the rats in the leptin intervention group were given leptin (100 μg/kg) diluted with normal saline immediately after modelling for 4 consecutive days. The survival rate of the rats was observed and the change in body weight was monitored. When the rats reached the age of 21 days, the Morris water maze test was used to evaluate spatial memory.

RESULTSThere was no significant difference in the survival rate of rats between the three groups (P>0.05). Within 10 days after birth, the leptin intervention group had similar body weight as the sham-operation group and significantly lower body weight than the model group (P<0.05); more than 10 days after birth, the leptin intervention group had rapid growth with higher body weight than the model and sham-operation groups (P>0.05). The results of place navigation showed that from the second day of experiment, there was a significant difference in the latency period between the three groups (P<0.05); from the fourth day of experiment, the leptin intervention group had a similar latency period as the sham-operation and a significantly shorter latency period than the model group (P<0.05). The results of space search experiment showed that compared with the sham-operation group, the model group had a significant reduction in the number of platform crossings and a significantly longer latency period (P<0.05); compared with the model group, the leptin intervention group had a significantly increased number of platform crossings and a significantly shortened latency period (P<0.05), while there was no significant difference between the leptin intervention and sham-operation groups.

CONCLUSIONSLeptin can alleviate spatial memory impairment of rats with white matter damage in developing brain. It thus exerts a neuroprotective effect, and is worthy of further research.

Animals ; Female ; Leptin ; pharmacology ; Maze Learning ; drug effects ; Neuroprotective Agents ; pharmacology ; Pregnancy ; Rats ; Rats, Sprague-Dawley ; Reaction Time ; Spatial Memory ; drug effects ; White Matter ; pathology

OBJECTIVETo investigate whether exogenous hydrogen sulfide (H2S) inhibits the high-glucose (HG)-induced injury by modulating leptin/leptin receptor (LEPR) signal pathway in human umbilical vein endothelial cells (HUVECs).

METHODSHUVECs were treated with 40 mmol/L glucose for 3-24 h, and the cell viability was examined by CCK-8 assay. The changes of cell morphology and the number of apoptotic cells were assessed by Hoechst 33258 nuclear staining followed by photofluorography. The intracellular levels of reactive oxygen species (ROS) was detected by DCFH-DA staining followed by photofluorography. Mitochondrial membrane potential (MMP) was determined by Rhodamine 123 (Rh123) staining and photofluorography. The expression levels of leptin and LEPR protein were measured by Western blotting.

RESULTSs The expression of leptin and LERP in HUVECs began to significantly increase at 3 h after HG exposure and reached the peak levels at 9 h (P<0.01). Pretreatment of HUVECs with 400 µmol/L sodium hydrosulfide (H2S donor) for 30 min inhibited HG-induced increase in leptin and leptin receptor expressions in HUVECs (P<0.01). Pretreatment of HUVECs with 400 µmol/L NaHS for 30 min or 50 ng/mL leptin antagonists (LA) for 1 h obviously alleviated HG-induced injury by increasing cell viability, decreasing cell apoptosis and lowering accumulation of intracellular ROS and MMP loss (P<0.01).

CONCLUSIONExogenous H2S protects against HG-induced injury by inhibiting leptin/LEPR pathway in HUVECs.

Apoptosis ; Cell Survival ; Cells, Cultured ; Glucose ; adverse effects ; Human Umbilical Vein Endothelial Cells ; drug effects ; metabolism ; Humans ; Hydrogen Sulfide ; pharmacology ; Leptin ; metabolism ; Membrane Potential, Mitochondrial ; Reactive Oxygen Species ; metabolism ; Receptors, Leptin ; metabolism ; Signal Transduction

OBJECTIVETo study the effect of leptin on the expression of calcium-activated neutral protease 1 (calpain-1) and B cell lymphoma-2 (Bcl-2) and apoptosis in the myocardial tissue of neonatal rats after asphyxia.

METHODSA total of 48 neonatal rats were randomly and equally divided into normal control group, asphyxia group, leptin treatment groups, and calpain-1 inhibitor (CAI-1) group. The neonatal rat model of asphyxia under normal atmospheric condition was established in all groups except the control group. For the leptin treatment groups, rats received 20, 80, and 160 μg/kg leptin by intraperitoneal injection immediately after model establishment, respectively. For the CAI-1 group, rats received 10 mg/kg CAI-1 by intraperitoneal injection immediately after model establishment. For all the groups, the myocardial tissue was collected at 2 hours after model establishment. Immunohistochemistry was used to measure the expression of calpain-1 and Bcl-2. The TUNEL method was used to evaluate apoptosis of myocardial cells.

RESULTSThe expression of calpain-1 and Bcl-2 and apoptosis index (AI) were significantly higher in the asphyxia group than in the normal control group (P˂0.05). The leptin treatment groups and the CAI-1 group had significantly lower expression of calpain-1, significantly lower AI, and significantly higher expression of Bcl-2 than the asphyxia group (P˂0.05). The CAI-1 group had the largest changes in all the indices compared with the asphyxia group. However, there were no significant differences in all indices between the 160 μg/kg leptin treatment group and the CAI-1 group. After asphyxia, the expression of calpain-1 was positively correlated with AI, while the expression of Bcl-2 was negatively correlated with AI and the expression of calpain-1 (P˂0.05).

CONCLUSIONSLeptin reduces apoptosis of myocardial cells in asphyxiated neonatal rats by the inhibition of calpain-1 activation and upregulation of Bcl-2 expression.

Animals ; Animals, Newborn ; Apoptosis ; drug effects ; Asphyxia Neonatorum ; metabolism ; pathology ; Calpain ; analysis ; antagonists & inhibitors ; Leptin ; pharmacology ; Myocardium ; metabolism ; pathology ; Proto-Oncogene Proteins c-bcl-2 ; analysis ; Rats ; Rats, Sprague-Dawley

OBJECTIVETo determine the changes in the expression of leptin and its receptor in the lungs of mice with varying degrees of asthma before and after budesonide treatment.

METHODSForty Balb/c mice were randomly assigned into 4 groups with 10 animals in each. One group received no treatment (control group) and the other groups were challenged with either nebulized ovalbumin (OVA) for three days (3-day group) or seven days (7-day group), or with nebulized ovalbumin followed by budesonide administration (treatment group). Changes in airway inflammation were observed using hematoxylin-eosin staining. The protein and mRNA levels of leptin and its receptor in lung tissues were determined using immunohistochemistry/Western blot and real-time PCR, respectively.

RESULTSThe two asthmatic groups showed more significant pathological changes in the airway than the control and the treatment groups. Mice that were challenged by OVA for seven days showed more marked pathological changes in the airway compared with mice challenged by OVA for three days. The protein and mRNA levels of leptin in the lung tissues of the 3-day group were significantly higher than those of the control group (P<0.01), but significantly lower than those of the 7-day group (P<0.01). The protein levels of leptin receptor in the lung tissues of the 3-day group were significantly lower than those of the control group (P<0.01). The treatment group showed increased protein levels of leptin receptor compared with the 7-day group (P<0.01). No significant difference was noted between the four groups with respect to the mRNA levels of leptin receptor in the lung tissues.

CONCLUSIONSLeptin is highly expressed whereas its receptor is lowly expressed in the lung tissues of asthmatic mice. Budesonide can increase the expression of leptin receptor, but has no significant impact on the expression of leptin.

Animals ; Asthma ; drug therapy ; metabolism ; pathology ; Blotting, Western ; Budesonide ; pharmacology ; Immunohistochemistry ; Leptin ; analysis ; genetics ; Lung ; chemistry ; pathology ; Male ; Mice ; Mice, Inbred BALB C ; RNA, Messenger ; analysis ; Receptors, Leptin ; analysis ; genetics