Leptin attenuates cerebral ischemic injury in rats by modulating the mitochondrial electron transport chain via the mitochondrial STAT3 pathway

[Exogenous leptin improves cerebral ischemia-reperfusion-induced glutamate excitotoxic injury in mice by up-regulating GLT-1 and GLAST expression in astrocytes]

OBJECTIVE

To investigate the protective effect of exogenous leptin against focal cerebral ischemia-reperfusion (I/R) injury in mice and explore the underlying mechanism.

METHODS

A total of 100 C57BL/6 mice were randomly divided into 5 groups, including a sham-operated group, cerebral I/R model group, and 3 leptin treatment groups with intraperitoneal injections of 0.5, 1.0 or 2.0 leptin immediately after occlusion of the internal carotid artery. At 24 h after reperfusion, neurological function scores of the mice were assessed, and TTC staining was used to determine the area of cerebral infarction. The pathological changes in the cortical brain tissue of the mice were observed using HE staining, and degenerative damage of the cortical neurons were assessed with Fluoro-Jade C staining. The expression of glial fibrillary acidic protein in cortical brain tissues was detected using immunohistochemistry and Western blotting. In another 45 C57BL/6 mice with sham operation, I/R modeling, or leptin (1 mg/kg) treatment, glutamic acid in the cortical brain tissue was detected using glutamate assay, and cortical glutamate-aspartate transporter (GLAST) and glutamate transporter-1 (GLT-1) protein expressions were detected using immunohistochemistry.

RESULTS

Compared with the I/R model mice, the leptin-treated mice had significantly lower neurological deficit scores, smaller cerebral infarct area, milder pathologies in the cortical brain tissue, and lessened cortical neuronal damage with normal morphology and less excessive proliferation of the astrocytes. Leptin treatment significantly up-regulated the expressions of GLT-1 and GLAST and lowered the content of glutamic acid in the brain tissue of the I/R mice.

CONCLUSION

Exogenous leptin has obvious neuroprotective effect against cerebral I/R injury in mice, mediated probably by controlling excessive astrocyte proliferation and up-regulating cortical GLT-1 and GLAST expressions to reduce glutamate-mediated excitotoxic injury of the astrocytes.

Oxidative stress: A common pathological state in a high-risk population for osteoporosis

Osteoporosis is becoming a major concern in the field of public health. The process of bone loss is insidious and does not directly induce obvious symptoms. Complications indicate an irreversible decrease in bone mass. The high-risk populations of osteoporosis, including postmenopausal women, elderly men, diabetic patients and obese individuals need regular bone mineral density testing and appropriate preventive treatment. However, the primary changes in these populations are different, increasing the difficulty of effective treatment of osteoporosis. Determining the core pathogenesis of osteoporosis helps improve the efficiency and efficacy of treatment among these populations. Oxidative stress is a common pathological state secondary to estrogen deficiency, aging, hyperglycemia and hyperlipemia. In this review, we divided oxidative stress into the direct effect of reactive oxygen species (ROS) and the reduction of antioxidant enzyme activity to discuss their roles in the development of osteoporosis. ROS initiated mitochondrial apoptotic signaling and suppressed osteogenic marker expression to weaken osteogenesis. MAPK and NF-κB signaling pathways mediated the positive effect of ROS on osteoclast differentiation. Antioxidant enzymes not only eliminate the negative effects of ROS, but also directly participate in the regulation of bone metabolism. Additionally, we also described the roles of proinflammatory factors and HIF-1α under the pathophysiological changes of inflammation and hypoxia, which provided a supplement of oxidative stress-induced osteoporosis. In conclusion, our review showed that oxidative stress was a common pathological state in a high-risk population for osteoporosis. Targeted oxidative stress treatment would greatly optimize the therapeutic schedule of various osteoporosis treatments.

Elevated serum levels of bone morphogenetic protein-9 are associated with better outcome in AQP4-IgG seropositive NMOSD

Lymphatic drainage in the central nervous system is regulated by meningeal lymphatic vasculature, and recurrent neuroinflammation alters lymphatic vessel remodeling. Patients with aquaporin-4 antibody-positive neuromyelitis optica spectrum disorder (AQP4 + NMOSD) were reported to demonstrate worse outcomes compared with patients with anti-myelin oligodendrocyte glycoprotein-associated disorders (MOGAD). This study aimed to investigate the serum cytokines relevant to vascular remodeling after attacks and their prognostic role in patients with AQP4 + NMOSD. This study measured the serum levels of 12 cytokines relevant to vascular remodeling, including bone morphogenetic protein-9 (BMP-9) and leptin, in 20 patients with AQP4 + NMOSD and 17 healthy controls (HCs). Disease controls included 18 patients with MOGAD. Serum and cerebrospinal fluid interleukin-6 levels were also measured. Clinical severity was evaluated with Kurtzke's Expanded Disability Status Scale (EDSS). Compared with HCs, patients with AQP4 + NMOSD showed higher BMP-9 (median; 127 vs. 80.7 pg/mL; P = 0.0499) and leptin levels (median; 16,081 vs. 6770 pg/mL; P = 0.0224), but not those with MOGAD. Better improvement in EDSS at 6 months was associated with baseline BMP-9 levels in patients with AQP4 + NMOSD (Spearman's rho =  - 0.47; P = 0.037). Serum BMP-9 is upregulated at relapse and may contribute to vascular remodeling in AQP4 + NMOSD. Serum BMP-9 levels could predict clinical recovery 6 months after the attack.

Neuroprotective effect of meglumine cyclic adenylate against ischemia/reperfusion injury via STAT3-Ser727 phosphorylation

OBJECTIVES

Ischemia/reperfusion can induce neuronal apoptosis in the brain and lead to function deficits. The activation of cyclic adenosine monophosphate (cAMP)-dependent protein kinase (PKA) is neuroprotective against transient cerebral ischemia. The neuroprotective mechanisms of PKA mainly involve the regulation of gene transcription via the PKA/CREB pathway. The present study aims to investigate the neuroprotective effect of meglumine cyclic adenylate, an activator of PKA, under a rat model of global cerebral ischemia/reperfusion and to reveal the underlying mechanism involving signal transducer and activator of transcription 3 (STAT3)-Ser727 phosphorylation and mitochondrion modulation.

MATERIALS AND METHODS

Male Sprague-Dawley rats were subjected to 15 min global cerebral ischemia, and meglumine cyclic adenylate was treated through tail intravenous injection 30 min before ischemia. Cresyl violet staining was used to evaluate neuron injury at 5 d of reperfusion. Western blotting was used to detect p-Ser⁷²⁷-STAT3, total STAT3, cytochrome c (Cyt c) and active caspase-3 in the tissues of hippocampal CA1 region at 6 h of reperfusion. STAT3-S727A was overexpressed in HT22 cells to reveal the significance of STAT3-Ser727 phosphorylation in the neuroprotective effect of meglumine cyclic adenylate.

RESULTS

Pretreatment with meglumine cyclic adenylate not only significantly ameliorated neuron loss in CA1 region after global cerebral ischemia but also enhanced STAT3-Ser727 phosphorylation, increased mitochondrial STAT3, and decreased cytosolic Cyt c and active caspase-3. Overexpression of STAT3-S727A in HT22 cells eliminated meglumine cyclic adenylate-induced increase of p-Ser⁷²⁷-STAT3, mitochondrial STAT3, cytosolic Cyt c and active caspase-3.

CONCLUSION

Meglumine cyclic adenylate protects neurons against ischemia/reperfusion injury via promoting p-Ser⁷²⁷-STAT3-associated mitochondrion modulation and inhibiting apoptosis pathway.

Leptin alleviates endoplasmic reticulum stress induced by cerebral ischemia/reperfusion injury via the PI3K/Akt signaling pathway

BACKGROUND

Cerebral ischemic/reperfusion injury (CIRI) is a key factor for the prognosis of ischemic stroke (IS), the leading disease in terms of global disability and fatality rates. Recent studies have shown that endoplasmic reticulum stress (ERS) may be a target against CIRI and that leptin, a peptide hormone, has neuroprotective activity to mitigate CIRI.

METHODS

An in vitro CIRI model was induced in primary cortical neurons by oxygen-glucose deprivation and reoxygenation (OGD/R) after pretreatment with LY294002 (10 µmol/L) and/or leptin (0.4 mg/L), and cell viability, neuronal morphology and endoplasmic reticulum (ER) dysfunction were evaluated. An in vivo CIRI model was established in rats by middle cerebral artery occlusion and reperfusion (MCAO/R) after the injection of LY294002 (10 μmol/L) and/or leptin (1 mg/kg), and neurological function, infarct volume, cerebral pathological changes, the expression of ERS-related proteins and cell apoptosis were examined.

RESULTS

In vitro, leptin treatment improved the cell survival rate, ameliorated neuronal pathological morphology and alleviated OGD/R-induced ERS. In vivo, administration of leptin significantly reduced the infarct volume, neurological deficit scores and neuronal apoptosis as well as pathological alterations. In addition, leptin suppressed MCAO/R-induced ERS and may decrease apoptosis by inhibiting ERS-related death and caspase 3 activation. It also regulated expression of the antiapoptotic protein Bcl-2 and the proapoptotic protein Bax in the cortex. Furthermore, the inhibitory effect of leptin on ERS was significantly decreased by the effective phosphatidylinositol 3-kinase (PI3K) inhibitor LY294002.

CONCLUSIONS

These results confirm that ERS plays an important role in CIRI and that leptin can inhibit the activation of ERS through the PI3K/Akt pathway, thereby alleviating CIRI. These findings provide novel therapeutic targets for IS.

Effect of leptin on the growth and expression of STAT3 in yak mammary epithelial cells

Background and Aim: Leptin (LEP) is an autocrine and paracrine factor produced by the fat pad and acinar epithelial cells of the breast. This study aimed to investigate the effects of LEP on yak mammary epithelial cells (YMECs) and the expression of STAT3. In addition, we evaluated the possible effects of prolactin (PRL) on the function of LEP. Materials and Methods: The YMECs were treated with 0, 50, 100, 200, 400, and 800 ng/mL LEP for 48 h in the absence of PRL and the presence of 500 ng/mL PRL. The growth activity of YMECs was measured using the cell counting kit-8 assay. The changes in the lactation signaling pathway-related factor STAT3 were detected at the mRNA, protein, and protein phosphorylation levels using the reverse transcriptase-quantitative polymerase chain reaction and Western blotting. To explore whether LEP affects the activation of STAT3 through JAK2/JAK3 in YMECs, the JAK2/3 signaling pathway inhibitor AG490 was used at a fixed concentration of LEP. Results: Each concentration of LEP significantly promoted the expression of STAT3 mRNA (p < 0.05) in YMECs in the presence of PRL. In the absence of PRL, all concentrations of LEP were found to inhibit the expression of the STAT3 protein (p < 0.05). The expression of the STAT3 protein in YMECs was found to first increase followed by a decrease with an increase in the concentration of LEP. In addition, the phosphorylation level of STAT3 increased in all groups, except the 100 ng/mL concentration group. The STAT3 phosphorylation trend and protein expression were different, such that the level of protein phosphorylation was higher than that of the STAT3 protein (p < 0.05). The addition of AG490 reduced the expression of the STAT3 mRNA, STAT3 protein, and STAT3 phosphorylation in the LEP and LEP + PRL groups. Conclusion: Altogether, the results indicated that different concentrations of LEP exerted varying effects on the growth of YMECs and the expression of STAT3, and the activity of STAT3 was primarily activated by JAK2. The addition of LEP can effectively inhibit the downregulation of the JAK2/STAT3 signal pathway by AG490, mitigate its inhibitory effect on the proliferation of YMECs, and reduce apoptosis. We believe that these findings will provide a theoretical and experimental basis for future research in this field.

Gallbladder Cancer Cell-Derived Exosome-Mediated Transfer of Leptin Promotes Cell Invasion and Migration by Modulating STAT3-Mediated M2 Macrophage Polarization

Tumor-associated macrophage (TAM) is a major component of tumor microenvironment (TME) and plays critical role in the progression of cancer metastasis. However, TAM-mediated regulation in gallbladder cancer (GBC) has not been fully characterized. Here, we found that exosomes derived from GBC cell polarized macrophage to M2 phenotype, which then facilitated the invasion and migration of GBC cells. We discovered that leptin was enriched in GBC cell-derived exosomes. Exosomal leptin levels promoted invasion and migration of GBC-SD cells. The inhibition of leptin not only attenuated M2 macrophage of polarization but also inhibited the invasive and migratory ability of GBC cell. In addition, GBC-SD cell-derived exosomal leptin induced M2 polarization of macrophage via activation of STAT3 signal pathway. Taken together, our results suggested that GBC cells secrete exosome-enclosed leptin facilitated cell invasion and migration via polarizing TAM.

Leptin Gene Protects Against Cold Stress in Antarctic Toothfish

Leptin is a cytokine-like peptide, predominantly biosynthesized in adipose tissue, which plays an important role in regulating food intake, energy balance and reproduction in mammals. However, how it may have been modified to enable life in the chronic cold is unclear. Here, we identified a leptin-a gene (lepa) in the cold-adapted and neutrally buoyant Antarctic toothfish Dissostichus mawsoni that encodes a polypeptide carrying four α-helices and two cysteine residues forming in-chain disulfide bonds, structures shared by most vertebrate leptins. Quantitative RT-PCR confirmed that mRNA levels of the leptin-a gene of D. mawsoni (DM-lepa) were highest in muscle, followed by kidney and liver; detection levels were low in the gill, brain, intestine, and ovary tissues. Compared with leptin-a genes of fishes living in warmer waters, DM-lepa underwent rapid evolution and was subjected to positive selection. Over-expression of DM-lepa in the zebrafish cell line ZFL resulted in signal accumulation in the cytoplasm and significantly increased cell proliferation both at the normal culture temperature and under cold treatment. DM-lepa over-expression also reduced apoptosis under low-temperature stress and activated the STAT3 signaling pathway, in turn upregulating the anti-apoptotic proteins bcl2l1, bcl2a, myca and mdm2 while downregulating the pro-apoptotic baxa, p53 and caspase-3. These results demonstrate that DM-lepa, through STAT3 signaling, plays a protective role in cold stress by preventing apoptotic damage. Our study reveals a new role of lepa in polar fish.

Leptin attenuates hypoxia-induced apoptosis in human periodontal ligament cells via the reactive oxygen species-hypoxia-inducible factor-1α pathway

NEW FINDINGS

What is the central question of this study? Does leptin have an effect on hypoxia-induced apoptosis in human periodontal ligament cells (hPDLCs), and what is the potential underlying mechanism? What is the main finding and its importance? Hypoxia induces cell apoptosis and leptin expression in hPDLCs through the induction of hypoxia-inducible factor-1α and accumulation of reactive oxygen species (ROS). Leptin shows feedback inhibition on hypoxia-induced ROS-mediated apoptosis in hPDLCs, suggesting a new application of leptin for hypoxic damage in periodontal diseases.

ABSTRACT

Hypoxia-induced apoptosis of human periodontal ligament cells (hPDLCs) is an important contributor to the progression of various periodontal diseases. Although leptin has been shown to protect connective tissue cells against hypoxia-induced injury, whether it might do so by attenuating hypoxia-induced apoptosis in hPDLCs remains unclear. Here, using CoCl₂ treatment, we simulated hypoxic conditions in hPDLCs and explored whether apoptosis and reactive oxygen species (ROS) levels were related to hypoxia. After small interfering RNA (siRNA) inhibition of leptin and hypoxia-inducible factor-1α (HIF-1α), the levels of apoptosis, ROS and leptin expression were measured. We showed that in CoCl₂ -treated hPDLCs, significantly higher cell apoptosis rates and ROS accumulation were observed. Cobalt chloride also increased leptin and HIF-1α expression in hPDLCs. Further investigation of the pathway demonstrated that inhibition of ROS attenuated hypoxia-induced cell apoptosis and leptin expression, whereas siRNA inhibition of leptin aggravated hypoxia-induced cell apoptosis and ROS accumulation. Hypoxia induces cell apoptosis and leptin expression in hPDLCs through the induction of ROS and HIF-1α pathways, and leptin shows feedback inhibition on ROS-mediated apoptosis in hPDLCs. These findings suggest a new application of leptin for hypoxic damage in periodontal diseases.

Perinatal hypoxic-ischemic damage: review of the current treatment possibilities

Neonatal hypoxic-ischemic encephalopathy is a disorder with heterogeneous manifestation due to asphyxia during perinatal period. It affects approximately 3-12 children per 1000 live births and cause death of 1 million neonates worldwide per year. Besides, motor disabilities, seizures, impaired muscle tone and epilepsy are few of the consequences of hypoxic-ischemic encephalopathy. Despite an extensive research effort regarding various treatment strategies, therapeutic hypothermia with intensive care unit supportive treatment remains the only approved method for neonates who have suffered from moderate to severe hypoxic-ischemic encephalopathy. However, these protocols are only partially effective given that many infants still suffer from severe brain damage. Thus, further research to systematically test promising neuroprotective treatments in combination with hypothermia is essential. In this review, we discussed the pathophysiology of hypoxic-ischemic encephalopathy and delved into different promising treatment modalities, such as melatonin and erythropoietin. However, preclinical studies and clinical trials are still needed to further elucidate the mechanisms of action of these modalities.

Chronic exposure to methylmercury enhances the anorexigenic effects of leptin in C57BL/6J male mice

Several studies have demonstrated that heavy metals disrupt energy homeostasis. Leptin inhibits food intake and decreases body weight through activation of its receptor in the hypothalamus. The impact of heavy metals on leptin signaling in the hypothalamus is unclear. Here, we show that the environmental pollutant, methylmercury (MeHg), favors an anorexigenic profile in wild-type males. C57BL/6J mice were exposed to MeHg via drinking water (5 ppm) up to 30 days. Our data shows that MeHg exposure was associated with changes in leptin induced activation of Janus kinase 2 (JAK2)/signal transducer and activator of transcription 3 (STAT3) signaling pathway in the hypothalamus. In males, the activation of JAK2/STAT3 signaling pathway was sustained by an increase in SOCS3 protein levels. In females, MeHg-activated STAT3 was inhibited by a concomitant increase in PTP1B. Taken together, our data suggest that MeHg enhanced leptin effects in males, favoring an anorexigenic profile in males, which notably, have been shown to be more sensitive to the neurological effects of this organometal than females. A better understanding of MeHg-induced molecular mechanism alterations in the hypothalamus advances the understanding of its neurotoxicity and provides molecular sites for novel therapies.

Folic Acid Deficiency Enhances the Tyr705 and Ser727 Phosphorylation of Mitochondrial STAT3 in In Vivo and In Vitro Models of Ischemic Stroke

Ischemic stroke remains one of the most common causes of death and disability worldwide. The stroke patients with an inadequate intake of folic acid tend to have increased brain injury and poorer prognosis. However, the precise mechanisms underlying the harmful effects of folic acid deficiency (FD) in ischemic stroke is still elusive. Here, we aimed to test the hypothesis that mitochondrial localized STAT3 (mitoSTAT3) expression may be involved in the process of neuronal damage induced by FD in in vivo and in vitro models of ischemic stroke. Our results exhibited that FD increased infarct size and aggravated the damage of mitochondrial ultrastructure in ischemic brains. Meanwhile, FD upregulated the phosphorylation levels of mitoSTAT3 at Tyr705 (Y705) and Ser727 (S727) sites in the rat middle cerebral artery occlusion/reperfusion (MCAO/R) model and oxygen-glucose deprivation followed by reperfusion (OGD/R) N2a cells. Furthermore, the inhibition of JAK2 by AG490 led to a significant decrease in FD-induced phosphorylation of Y705, while S727 phosphorylation was unaffected. Conversely, U0126 and LY294002, which respectively inhibited phosphorylation of ERK1/2 and Akt, partially prevented S727 phosphorylation, but had limited effects on the level of pY705, suggesting that phosphorylation of Y705 and S727 is regulated via independent mechanisms in FD-treated brains.

Leptin protects brain from ischemia/reperfusion-induced infarction by stabilizing the blood-brain barrier to block brain infiltration by the blood-borne neutrophils

The cellular and molecular mechanisms underlying leptin-mediated brain protection against cerebral ischemia were investigated at the blood-brain barrier (BBB) and neutrophil level. Through the ischemia/reperfusion (I/R) animal model, we found that leptin expression level was significantly decreased in ischemic hemisphere. Brain injection with leptin (15 μg/kg, intracisternally) could block the I/R-increased BBB permeability, activation of matrix metallopeptidase 9 (MMP-9) and brain infiltration of blood-borne neutrophils to reduce the infarct volume of ischemic brain. The brain expression level of tight junction protein ZO-1 as well as number and motility of neutrophils in blood was all increased by the same injection, indicating BBB stability (rather than reduction in neutrophils) played a major role in the leptin-inhibited brain infiltration of neutrophils. Leptin-mediated protection of BBB was further confirmed in vitro, through a BBB cellular model under the in vitro ischemic condition (G/R: glucose-oxygen-serum deprivation followed by GOS restoration). The results showed that leptin again could block the G/R-increased neutrophil adherence to EC layer as well as BBB permeability, likely by stimulating the endothelial expression of ZO-1 and VE-Cadherin. The study has demonstrated that leptin could protect ischemic brain via multiple ways (other than neuronal protection), by inhibiting the BBB permeability, brain infiltration of the blood-borne neutrophils and neutrophil adherence to vascular ECs. The role of leptin in vascular biology of stroke could further support its therapeutic potential in other neurodegenerative diseases, associated with BBB disorder.

Sirt1-ROS-TRAF6 Signaling-Induced Pyroptosis Contributes to Early Injury in Ischemic Mice

Stroke is an acute cerebro-vascular disease with high incidence and poor prognosis, most commonly ischemic in nature. In recent years, increasing attention has been paid to inflammatory reactions as symptoms of a stroke. However, the role of inflammation in stroke and its underlying mechanisms require exploration. In this study, we evaluated the inflammatory reactions induced by acute ischemia and found that pyroptosis occurred after acute ischemia both in vivo and in vitro, as determined by interleukin-1β, apoptosis-associated speck-like protein, and caspase-1. The early inflammation resulted in irreversible ischemic injury, indicating that it deserves thorough investigation. Meanwhile, acute ischemia decreased the Sirtuin 1 (Sirt1) protein levels, and increased the TRAF6 (TNF receptor associated factor 6) protein and reactive oxygen species (ROS) levels. In further exploration, both Sirt1 suppression and TRAF6 activation were found to contribute to this pyroptosis. Reduced Sirt1 levels were responsible for the production of ROS and increased TRAF6 protein levels after ischemic exposure. Moreover, N-acetyl-L-cysteine, an ROS scavenger, suppressed the TRAF6 accumulation induced by oxygen-glucose deprivation via suppression of ROS bursts. These phenomena indicate that Sirt1 is upstream of ROS, and ROS bursts result in increased TRAF6 levels. Further, the activation of Sirt1 during the period of ischemia reduced ischemia-induced injury after 72 h of reperfusion in mice with middle cerebral artery occlusion. In sum, these results indicate that pyroptosis-dependent machinery contributes to the neural injury during acute ischemia via the Sirt1-ROS-TRAF6 signaling pathway. We propose that inflammatory reactions occur soon after oxidative stress and are detrimental to neuronal survival; this provides a promising therapeutic target against ischemic injuries such as a stroke.

Intermittent fasting, adipokines, insulin sensitivity, and hypothalamic neuropeptides in a dietary overload with high-fat or high-fructose diet in mice

The intermittent fasting (IF) might have benefits on metabolism and food intake. Twelve-week old C57BL/6 J mice were fed a control diet (C, 10% kcal fat), a high-fat diet (HF, 50% kcal fat) or a high-fructose diet (HFru, 50% kcal fructose) for 8 weeks, then half of the animals in each group underwent IF (24 h fed, 24 h fasting) for an additional 4 weeks. Although food intake on the fed day remained the same for all groups, all fasting groups showed a reduction in body mass compared to their counterparts. IF reduced total cholesterol, triacylglycerol, fasting glucose, fasting insulin resistance index, and plasma leptin, but increased plasma adiponectin. IF reduced Leptin gene expression in the HF-IF group, but increased proinflammatory markers in the hypothalamus, also in the C-IF group. Both groups HFru-IF and C-IF, showed alterations in the leptin signaling pathway (Leptin, OBRb, and SOCS3), mainly in the HFru-IF group, suggesting leptin resistance. NPY and POMC neuropeptides labeled the neurons of the hypothalamus by immunofluorescence, corroborating qualitatively other quantitative findings of the study. In conclusion, current results are convincing in demonstrating the IF effect on central regulation of food intake control, as shown by NPY and POMC neuropeptide expressions, resulting in a lower weight gain. Besides, IF improves glycemia, lipid metabolism, and consequently insulin and leptin resistance. However, there is increased expression of inflammatory markers in mouse hypothalamus challenged by the HF and HFru diets, which in the long term may induce adverse effects.

Diffusion Kurtosis Imaging of Leptin Intervention in Early Hypoxic-Ischemic Brain Edema

The role of leptin in neuroprotection has recently been recognized. However, there are few reports on the use of imaging methods to dynamically evaluate the neuroprotection role of leptin. Diffusion kurtosis imaging (DKI), which is a method used to measure non-Gaussian water diffusion, can reflect the real water diffusion in brain tissues. In this study, a newborn piglet model was used to dynamically evaluate the leptin intervention in early hypoxic-ischemic brain edema via DKI. Thirty-two Yorkshire newborn piglets were divided into three groups: the hypoxic-ischemic encephalopathy (HIE) group, the leptin group, and the control group. DKI scanning was performed at time points of 3, 6, 9, 12, 16, and 24 h after hypoxic-ischemic exposure. After scanning, arterial blood was extracted from all piglets to measure NSE and S100β levels. Then, the brain was completely extracted for pathological examination. In the lesion areas, the MK, Ka, and Kr values in the leptin group were significantly lower than those in the HIE group, the MD, Da, and Dr values showed an opposite trend. The lesion areas in the leptin group were smaller than those of in the HIE group. In addition, the pathological results showed that less cell and organelle injury occurred in the leptin group. Our findings indicate that leptin can effectively reduce hypoxic-ischemic brain edema, and DKI can be more sensitive than conventional diffusivity metrics for visualizing the microstructural changes of HIE. This provides a new clue for the treatment and evaluation of HIE.

Neuroendocrine drivers of risk and resilience: The influence of metabolism & mitochondria

The manifestation of risk versus resilience has been considered from varying perspectives including genetics, epigenetics, early life experiences, and type and intensity of the challenge with which the organism is faced. Although all of these factors are central to determining risk and resilience, the current review focuses on what may be a final common pathway: metabolism. When an organism is faced with a perturbation to the environment, whether internal or external, appropriate energy allocation is essential to resolving the divergence from equilibrium. This review examines the potential role of metabolism in the manifestation of stress-induced neural compromise. In addition, this review details the current state of knowledge on neuroendocrine factors which are poised to set the tone of the metabolic response to a systemic challenge. The goal is to provide an essential framework for understanding stress in a metabolic context and appreciation for key neuroendocrine signals.

Leptin attenuates cerebral ischemic injury in rats by modulating the mitochondrial electron transport chain via the mitochondrial STAT3 pathway

BACKGROUND

According to recent studies, leptin may exert a neuroprotective function by affecting the phosphorylation of signal transducer and activator of transcription 3 (STAT3). During stress, STAT3 regulates mitochondrial oxidative stress and reduces apoptosis.

OBJECTIVE

In the present study, we hypothesized that leptin increases STAT3 phosphorylation in the mitochondria and protects against mitochondrial oxidative stress in rats subjected to permanent middle cerebral artery occlusion (MCAO).

RESULTS

Leptin reduced reactive oxygen species (ROS) production, and we confirmed that the mechanism underlying this change involved the enzymatic activities of mitochondrial respiratory chain complexes I and II. In addition, leptin increased the level of STAT3 Ser727 phosphorylation in the mitochondria.

CONCLUSIONS

Based on these results, leptin may regulate mitochondrial respiratory chain enzymatic activities via mitochondria-targeted STAT3 to reduce ROS production and protect brain tissues from mitochondrial oxidative stress during cerebral ischemia.