Leptin Receptors Are Not Required for Roux-en-Y Gastric Bypass Surgery to Normalize Energy and Glucose Homeostasis in Rats.

Sensitization to the adipokine leptin is a promising therapeutic strategy against obesity and its comorbidities and has been proposed to contribute to the lasting metabolic benefits of Roux-en-Y gastric bypass (RYGB) surgery. We formally tested this idea using Zucker fatty fa/fa rats as an established genetic model of obesity, glucose intolerance, and fatty liver due to leptin receptor deficiency. We show that the changes in body weight in these rats following RYGB largely overlaps with that of diet-induced obese Wistar rats with intact leptin receptors. Further, food intake and oral glucose tolerance were normalized in RYGB-treated Zucker fatty fa/fa rats to the levels of lean Zucker fatty fa/+ controls, in association with increased glucagon-like peptide 1 (GLP-1) and insulin release. In contrast, while fatty liver was also normalized in RYGB-treated Zucker fatty fa/fa rats, their circulating levels of the liver enzyme alanine aminotransferase (ALT) remained elevated at the level of obese Zucker fatty fa/fa controls. These findings suggest that the leptin system is not required for the normalization of energy and glucose homeostasis associated with RYGB, but that its potential contribution to the improvements in liver health postoperatively merits further investigation.

Leptin-resistant Zucker rats with trinitrobenzene sulfonic acid colitis present a reduced inflammatory response but enhanced epithelial damage.

The role of leptin in the development of intestinal inflammation remains controversial, since proinflammatory and anti-inflammatory effects have been described. This study describes the effect of the absence of leptin signaling in intestinal inflammation. Experimental colitis was induced by intrarectal administration of trinitrobenzene sulfonic acid (TNBS) to lean and obese Zucker rats (n = 10). Effects on inflammation and mucosal barrier were studied. Bacterial translocation and LPS concentration were evaluated together with colonic permeability to 4-kDa FITC-dextran. Obese Zucker rats showed a lower intestinal myeloperoxidase and alkaline phosphatase activity, reduced alkaline phosphatase sensitivity to levamisole, and diminished colonic expression of Nos2, Tnf, and Il6, indicating attenuated intestinal inflammation, associated with attenuated STAT3, AKT, and ERK signaling in the colonic tissue. S100a8 and Cxcl1 mRNA levels were maintained, suggesting that in the absence of leptin signaling neutrophil activation rather than infiltration is hampered. Despite the lower inflammatory response, leptin resistance enhanced intestinal permeability, reflecting an increased epithelial damage. This was shown by augmented LPS presence in the portal vein of colitic obese Zucker rats, associated with induction of tissue nonspecific alkaline phosphatase, LPS-binding protein, and CD14 hepatic expression (involved in LPS handling). This was linked to decreased ZO-1 immunoreactivity in tight junctions and lower occludin expression. Our results indicate that obese Zucker rats present an attenuated inflammatory response to TNBS, but increased intestinal epithelial damage allowing the passage of bacterial antigens.NEW & NOTEWORTHY Obese Zucker rats, which are resistant to leptin, exhibit a diminished inflammatory response in the trinitrobenzenesulfonic acid (TNBS) model of colitis, suggesting leptin role is proinflammatory. At the same time, obese Zucker rats present a debilitated intestinal barrier function, with increased translocation of LPS. Zucker rats present a dual response in the TNBS model of rat colitis.

New Insight Into Metformin-Induced Cholesterol-Lowering Effect Crosstalk Between Glucose and Cholesterol Homeostasis via ChREBP (Carbohydrate-Responsive Element-Binding Protein)-Mediated PCSK9 (Proprotein Convertase Subtilisin/Kexin Type 9) Regulation.

[Figure: see text].

Biochemical and Behavioral Consequences of Ethanol Intake in a Mouse Model of Metabolic Syndrome.

Ethanol abuse is a common issue in individuals with sedentary lifestyles, unbalanced diets, and metabolic syndrome. Both ethanol abuse and metabolic syndrome have negative impacts on the central nervous system, with effects including cognitive impairment and brain oxidative status deterioration. The combined effects of ethanol abuse and metabolic syndrome at a central level have not yet been elucidated in detail. Thus, this work aims to determine the effects of ethanol intake on a mouse model of metabolic syndrome at the behavioral and biochemical levels. Seven-week-old male control (B6.V-Lep ob/+JRj) and leptin-deficient (metabolic syndrome) (B6.V-Lep ob/obJRj) mice were used in the study. Animals were divided into four groups: control, ethanol, obese, and obese-ethanol. Ethanol consumption was monitored for 6 weeks. Basal glycemia, insulin, and glucose overload tests were performed. To assess short- and long-term memory, an object recognition test was used. In order to assess oxidative status in mouse brain samples, antioxidant enzyme activity was analyzed with regard to glutathione peroxidase, glutathione reductase, glutathione, glutathione disulfide, lipid peroxidation products, and malondialdehyde. Ethanol intake modulated the insulin response and impaired the oxidative status in the ob mouse brain.

Leptin signaling and the intervertebral disc: Sex dependent effects of leptin receptor deficiency and Western diet on the spine in a type 2 diabetes mouse model.

Type 2 diabetes and obesity are associated with back pain in juveniles and adults and are implicated in intervertebral disc (IVD) degeneration. Hypercaloric Western diets are associated with both obesity and type 2 diabetes. The objective of this study was to determine if obesity and type 2 diabetes result in spinal pathology in a sex-specific manner using in vivo diabetic and dietary mouse models. Leptin is an appetite-regulating hormone, and its deficiency leads to polyphagia, resulting in obesity and diabetes. Leptin is also associated with IVD degeneration, and increased expression of its receptor was identified in degenerated IVDs. We used young, leptin receptor deficient (Db/Db) mice to mimic the effect of diet and diabetes on adolescents. Db/Db and Control mice were fed either Western or Control diets, and were sacrificed at 3 months of age. Db/Db mice were obese, while only female mice developed diabetes. Female Db/Db mice displayed altered IVD morphology, with increased intradiscal notochordal band area, suggesting delayed IVD cell proliferation and differentiation, rather than IVD degeneration. Motion segments from Db/Db mice exhibited increased failure risk with decreased torsional failure strength. Db/Db mice also had inferior bone quality, which was most prominent in females. We conclude that obesity and diabetes due to impaired leptin signaling contribute to pathological changes in vertebrae, as well as an immature IVD phenotype, particularly of females, suggesting a sex-dependent role of leptin in the spine.

Inhibition of myeloperoxidase increases revascularization and improves blood flow in a diabetic mouse model of hindlimb ischaemia.

OBJECTIVE: Diabetes mellitus is a significant risk factor for peripheral artery disease. Diabetes mellitus induces chronic states of oxidative stress and vascular inflammation that increase neutrophil activation and release of myeloperoxidase. The goal of this study is to determine whether inhibiting myeloperoxidase reduces oxidative stress and neutrophil infiltration, increases vascularization, and improves blood flow in a diabetic murine model of hindlimb ischaemia. METHODS: Leptin receptor-deficient (db/db) mice were subjected to hindlimb ischaemia. Ischaemic mice were treated with N-acetyl-lysyltyrosylcysteine-amide (KYC) to inhibit myeloperoxidase. After ligating the femoral artery, effects of treatments were determined with respect to hindlimb blood flow, neutrophil infiltration, oxidative damage, and the capability of hindlimb extracellular matrix to support human endothelial cell proliferation and migration. RESULTS: KYC treatment improved hindlimb blood flow at 7 and 14 days in db/db mice; decreased the formation of advanced glycation end products, 4-hydroxynonenal, and 3-chlorotyrosine; reduced neutrophil infiltration into the hindlimbs; and improved the ability of hindlimb extracellular matrix from db/db mice to support endothelial cell proliferation and migration. CONCLUSION: These results demonstrate that inhibiting myeloperoxidase reduces oxidative stress in ischaemic hindlimbs of db/db mice, which improves blood flow and reduces neutrophil infiltration such that hindlimb extracellular matrix from db/db mice supports endothelial cell proliferation and migration.

Updates on Monogenic Obesity in a Multifactorial Disease.

Obesity is a worldwide epidemic with rates nearly doubling over the last 30 years. Despite increasing prevalence, the multifactorial pathogenesis of obesity continues to be widely misunderstood. Investigating genetic drivers in the development of obesity is an important area of focus, as genetics move to the forefront of medicine and personalized treatment evolves. Thus, this narrative review focused on four genes which have genome-wide association study-documented links to obesity and obesity syndromes. We explored their involvement in the predisposition, progression, and prognosis of obesity. Leptin, leptin receptor, pro-opiomelanocortin, and melanocortin 4 receptor are our four genes of interest, and herein we elaborated on the current literature, pathogenesis, and available treatments for patients with these specific genetic mutations.

High-fat-diet-induced modulations of leptin signaling and gastric microbiota drive precancerous lesions in the stomach.

OBJECTIVES: Obesity is a risk factor for malignancy in various tissues, and has been associated with gut microbiota alterations. However, the link between obesity-associated microbiota and gastric pathogenesis has not been clarified. We demonstrated that high-fat-diet (HFD) feeding causes intestinal metaplasia, which are precancerous lesions of the stomach, with augmented gastric leptin signaling. The aim of this study was to investigate the precise role of leptin signaling in the altered microbiota composition and pathogenesis in the stomach during diet-induced obesity. METHODS: Male C57 BL/6 J, leptin receptor (Lepr)-mutated db/db, and gastrointestinal epithelium-specific Lepr conditional knockout (T3 b-Lepr cKO) mice were fed a HFD or control diet. Gastrointestinal microbiota was analyzed by 16 S rRNA gene sequences and quantitative polymerase chain reaction. Transplantation of gastric microbiota of HFD-fed mice was performed to evaluate metaplasia onset in recipient mice. RESULTS: One week of HFD caused severe microbial dysbiosis in the stomach. The microbiota changes were accompanied by increased gastric leptin, leading to the consequent development of intestinal metaplasia. Transplantation of gastric microbiota from HFD-fed mice induced intestinal metaplasia in recipient mice; however, only a limited effect on pathogenesis was noted. HFD-fed db/db mice did not show a decrease in microbial abundance. Moreover, T3 b-Lepr cKO mice failed spontaneous obesity, and suppressed decreased abundance of gastric microbiota and occurrence of intestinal metaplasia during HFD feeding similar to db/db mice. CONCLUSIONS: Gastric leptin signaling modulates the gastric microbiota community and regulates the pathogenesis in the gastric mucosa.

Cx3CR1 Expression Identifies Distinct Macrophage Populations That Contribute Differentially to Inflammation and Repair.

Bone marrow (BM)-derived classical monocytes are critical to wound repair, where they differentiate into macrophages and purge foreign materials and dead cells while also laying the framework for tissue repair and regeneration. A subset of this recruited population persists in the wound and acquires alternative activation states to promote cell proliferation and matrix remodeling. In diabetes, this phenotypic switch is impaired and inflammation persists in an elevated state, contributing to delayed wound healing. Long-term tissue-resident macrophages can also play a key role in the resolution of inflammation to varying degrees across different organs. In this study, we investigated different macrophage subpopulations in nondiabetic and diabetic wounds over time using Cx3CR1eGFP transgenic mice and BM transplants. We show Cx3CR1eGFP-hi macrophages in skin wounds are derived from long-term tissue-resident macrophages and predominantly exhibit an alternative activation state, whereas cells expressing low-intermediate Cx3CR1eGFP are derived from the BM, contribute to both early and later stages of wound healing, and show both classical and alternative activation states. Diabetic mice showed significant differences in the dynamics of these subpopulations, which likely contribute to elevated and persisting inflammatory states over time. In particular, failure of Cx3CR1int macrophages to mature into Cx3CR1hi links maturation to resolution of inflammation. Thus strategies to promote macrophage maturation may be effective therapeutic tools in chronic inflammatory environments.

Proinsulin misfolding is an early event in the progression to type 2 diabetes.

Biosynthesis of insulin - critical to metabolic homeostasis - begins with folding of the proinsulin precursor, including formation of three evolutionarily conserved intramolecular disulfide bonds. Remarkably, normal pancreatic islets contain a subset of proinsulin molecules bearing at least one free cysteine thiol. In human (or rodent) islets with a perturbed endoplasmic reticulum folding environment, non-native proinsulin enters intermolecular disulfide-linked complexes. In genetically obese mice with otherwise wild-type islets, disulfide-linked complexes of proinsulin are more abundant, and leptin receptor-deficient mice, the further increase of such complexes tracks with the onset of islet insulin deficiency and diabetes. Proinsulin-Cys(B19) and Cys(A20) are necessary and sufficient for the formation of proinsulin disulfide-linked complexes; indeed, proinsulin Cys(B19)-Cys(B19) covalent homodimers resist reductive dissociation, highlighting a structural basis for aberrant proinsulin complex formation. We conclude that increased proinsulin misfolding via disulfide-linked complexes is an early event associated with prediabetes that worsens with ß-cell dysfunction in type two diabetes.

Role of bone morphogenetic protein-9 in the regulation of glucose and lipid metabolism.

Bone morphogenetic protein (BMP)-9 has been reported to regulate energy balance in vivo. However, the mechanisms underlying BMP9-mediated regulation of energy balance remain incompletely understood. Here, we investigated the role of BMP9 in energy metabolism. In the current study, we found that hepatic BMP9 expression was down-regulated in insulin resistance (IR) mice and in patients who are diabetic. In mice fed a high-fat diet (HFD), the overexpression of hepatic BMP9 improved glucose tolerance and IR. The expression of gluconeogenic genes was down-regulated, whereas the level of insulin signaling molecule phosphorylation was increased in the livers of Adenovirus-BMP9-treated mice and glucosamine-treated hepatocytes. Furthermore, BMP9 overexpression ameliorated triglyceride accumulation and inhibited the expression of lipogenic genes in both human hepatocellular carcinoma HepG2 cells treated with a fatty acid mixture as well as the livers of HFD-fed mice. In hepatocytes isolated from sterol regulatory element-binding protein (SREBP)-1c knockout mice, the effects of BMP9 were ablated. Mechanistically, BMP9 inhibited SREBP-1c expression through the inhibition of liver X receptor response element 1 activity in the SREBP-1c promoter. Taken together, our results show that BMP9 is an important regulator of hepatic glucose and lipid metabolism.-Yang, M., Liang, Z., Yang, M., Jia, Y., Yang, G., He, Y., Li, X., Gu, H. F., Zheng, H., Zhu, Z., Li, L. Role of bone morphogenetic protein-9 in the regulation of glucose and lipid metabolism.

Angiotensin II-mediated MYH9 downregulation causes structural and functional podocyte injury in diabetic kidney disease.

MYH9, a widely expressed gene encoding nonmuscle myosin heavy chain, is also expressed in podocytes and is associated with glomerular pathophysiology. However, the mechanisms underlying MYH9-related glomerular diseases associated with proteinuria are poorly understood. Therefore, we investigated the role and mechanism of MYH9 in diabetic kidney injury. MYH9 expression was decreased in glomeruli from diabetic patients and animals and in podocytes treated with Ang II in vitro. Ang II treatment and siRNA-mediated MYH9 knockdown in podocytes resulted in actin cytoskeleton reorganization, reduced cell adhesion, actin-associated protein downregulation, and increased albumin permeability. Ang II treatment increased NOX4 expression and ROS generation. The Ang II receptor blocker losartan and the ROS scavenger NAC restored MYH9 expression in Ang II-treated podocytes, attenuated disrupted actin cytoskeleton and decreased albumin permeability. Furthermore, MYH9 overexpression in podocytes restored the effects of Ang II on the actin cytoskeleton and actin-associated proteins. Ang II-mediated TRPC6 activation reduced MYH9 expression. These results suggest that Ang II-mediated MYH9 depletion in diabetic nephropathy may increase filtration barrier permeability by inducing structural and functional podocyte injury through TRPC6-mediated Ca2+ influx by NOX4-mediated ROS generation. These findings reveal a novel MYH9 function in maintaining urinary filtration barrier integrity. MYH9 may be a potential target for treating diabetic nephropathy.

Endothelial TFEB (Transcription Factor EB) Restrains IKK (IκB Kinase)-p65 Pathway to Attenuate Vascular Inflammation in Diabetic db/db Mice.

Objective- TFEB (transcription factor EB) was recently reported to be induced by atheroprotective laminar flow and play an anti-atherosclerotic role by inhibiting inflammation in endothelial cells (ECs). This study aims to investigate whether TFEB regulates endothelial inflammation in diabetic db/db mice and the molecular mechanisms involved. Approach and Results- Endothelial denudation shows that TFEB is mainly expressed in ECs in mouse aortas. Western blotting shows TFEB total protein level decreases whereas the p-TFEB S142 (phosphorylated form of TFEB) increases in db/db mouse aortas, suggesting a decreased TFEB activity. Adenoviral TFEB overexpression reduces endothelial inflammation as evidenced by decreased expression of vascular inflammatory markers in db/db mouse aortas, and reduced expression of a wide range of adhesion molecules and chemokines in human umbilical vein ECs. Monocyte attachment assay shows TFEB suppresses monocyte adhesion to human umbilical vein ECs. RNA sequencing of TFEB-overexpressed human umbilical vein ECs suggested TFEB inhibits NF-κB (nuclear factor-kappa B) signaling. Indeed, luciferase assay shows TFEB suppresses NF-κB transcriptional activity. Mechanistically, TFEB suppresses IKK (IκB kinase) activity to protect IκB-α from degradation, leading to reduced p65 nuclear translocation. Inhibition of IKK by PS-1145 abolished TFEB silencing-induced inflammation in human umbilical vein ECs. Lastly, we identified KLF2 (Krüppel-like factor 2) upregulates TFEB expression and promoter activity. Laminar flow experiment showed that KLF2 is required for TFEB induction by laminar flow and TFEB is an anti-inflammatory effector downstream of laminar flow-KLF2 signaling in ECs. Conclusions- These findings suggest that TFEB exerts anti-inflammatory effects in diabetic mice and such function in ECs is achieved by inhibiting IKK activity and increasing IκBα level to suppress NF-κB activity. KLF2 mediates TFEB upregulation in response to laminar flow.

Endothelial Leptin Receptor Deletion Promotes Cardiac Autophagy and Angiogenesis Following Pressure Overload by Suppressing Akt/mTOR Signaling.

BACKGROUND: Cardiac remodeling is modulated by overnutrition or starvation. The adipokine leptin mediates energy balance between adipose tissue and brain. Leptin and its receptors are expressed in the heart. METHODS AND RESULTS: To examine the importance of endothelial leptin signaling in cardiac hypertrophy, transverse aortic constriction was used in mice with inducible endothelium-specific deletion of leptin receptors (End.LepR-KO) or littermate controls (End.LepR-WT). End.LepR-KO was associated with improved left ventricular function (fractional shortening, 28.4% versus 18.8%; P=0.0114), reduced left ventricular dilation (end-systolic inner left ventricular diameter, 3.59 versus 4.08 mm; P=0.0188) and lower heart weight (133 versus 173 mg; P<0.0001) 20 weeks after transverse aortic constriction. Histology and quantitative polymerase chain reaction analysis confirmed reduced cardiomyocyte hypertrophy. STAT3 (signal transducer and activator of transcription) activation was reduced, and Akt (protein kinase B) and mTOR (mammalian target of rapamycin) phosphorylation after transverse aortic constriction were blunted in End.LepR-KO hearts. Elevated LC3 (microtubule associated protein 1 light chain 3)-I/-II conversion ( P=0.0041) and increased (LC3II-positive) endothelial cells ( P=0.0042) in banded hearts of End.LepR-KO mice suggested improved cardiac angiogenesis because of activated autophagy. Microscopy confirmed autophagosome accumulation after genetic or small interfering RNA-mediated LepR downregulation. Enhanced sprouting angiogenesis was observed in endothelial cells ( P<0.0001) and aortic rings ( P=0.0060) from End.LepR-KO mice, and murine and human endothelial sprouting angiogenesis was reduced after mTOR inhibition using rapamycin or autophagy inhibition using 3-methyladenine. Banded End.LepR-KO mouse hearts exhibited less apoptosis ( P=0.0218), inflammation ( P=0.0251), and fibrosis ( P=0.0256). Reduced endothelial autophagy was also observed in myocardial biopsies of heart failure patients with cardiac fibrosis. CONCLUSIONS: Our findings suggest that endothelial leptin signaling contributes to cardiac fibrosis and functional deterioration by suppressing endothelial autophagy and promoting endothelial dysfunction in a chronic pressure overload model.

Adiponectin homolog novel osmotin protects obesity/diabetes-induced NAFLD by upregulating AdipoRs/PPARα signaling in ob/ob and db/db transgenic mouse models.

BACKGROUND: In metabolic disorders, adiponectin and adiponectin receptors (AdipoR1/R2) signaling has a key role in improving nonalcoholic fatty liver disease (NAFLD) in obesity-associated diabetes. OBJECTIVE: To the best of our knowledge, here, we reported for the first time the underlying mechanistic therapeutic efficacy of the novel osmotin, a homolog of mammalian adiponectin, against NAFLD in leptin-deficient ob/ob and db/db mice. METHODS: The ob/ob and db/db mice were treated with osmotin at a dose of 5 µg/g three times a week for two weeks. To co-relate the in vivo results we used the human liver carcinoma HepG2 cells, subjected to knockdown with small siRNAs of AdipoR1/R2 and PPARα genes and treated with osmotin and palmitic acid (P.A.). MTT assay, Western blotting, immunohistofluorescence assays, and plasma biochemical analyses were applied. RESULTS: Osmotin stimulated AdipoR1/R2 and its downstream APPL1/PPAR-α/AMPK/SIRT1 pathways in ob/ob and db/db mice, and HepG2 cells exposed to P.A. Mechanistically, we confirmed that knockdown of AdipoR1/R2 and PPARα by their respective siRNAs abolished the osmotin activity in HepG2 cells exposed to P.A. Overall, the in vivo and in vitro results suggested that osmotin protected against NAFLD through activation of AdipoR1/R2 and its downstream APPL1/PPAR-α/AMPK/SIRT1 pathways as shown by the reduced body weight, blood glucose level and glycated hemoglobin, improved glucose tolerance, attenuated insulin resistance and hepatic glucogenesis, regulated serum lipid parameters, and increased fatty acid oxidation and mitochondrial functions. CONCLUSION: Our findings strongly suggest that novel osmotin might be a potential novel therapeutic tool against obesity/diabetes-induced NAFLD and other metabolic disorders.

Rodent models of leptin receptor deficiency are less sensitive to amylin.

The pancreatic hormone amylin is released from beta cells following nutrient ingestion and contributes to the control of body weight and glucose homeostasis. Amylin reduces food intake by activating neurons in the area postrema (AP). Amylin was also shown to synergize with the adipokine leptin, with combination therapy producing greater weight loss and food intake reduction than either hormone alone. Although amylin and leptin were initially thought to interact downstream of the AP in the hypothalamus, recent findings show that the two hormones can act on the same AP neurons, suggesting a more direct relationship. The objective of this study was to determine whether amylin action depends on functional leptin signaling. We tested the ability of amylin to induce satiation and to activate its primary target neurons in the AP in two rodent models of LepR deficiency, the db/db mouse and the Zucker diabetic fatty (ZDF) rat. When compared with wild-type (WT) mice, db/db mice exhibited reduced amylin-induced satiation, reduced amylin-induced Fos in the AP, and a lower expression of calcitonin receptor (CTR) protein, the core component of all amylin receptors. ZDF rats also showed no reduction in food intake following amylin treatment; however, unlike the db/db mice, levels of amylin-induced Fos and CTR in the AP were no different than WT rats. Our results suggest that LepR expression is required for the full anorexic effect of amylin; however, the neuronal activation in the AP seems to depend on the type of LepR mutation.

Therapeutic Effects of Adipose Stem Cells from Diabetic Mice for the Treatment of Type 2 Diabetes.

To assess the potential therapeutic effects of adipose tissue-derived mesenchymal stem cells (ASCs) for the treatment of type 2 diabetes (T2D), we compared the phenotype and functionality of ASCs isolated from high-fat diet and streptozotocin (STZ)-induced T2D and the leptin receptor-deficient (db/db) mice with cells from healthy C57BL/6 mice. ASCs from T2D or db/db mice showed similar expression patterns of cellular markers and abilities to differentiate into adipocytes, osteoblasts, and chondrocytes. However, the rate of proliferation was reduced. ASCs from db/db mice secreted less hepatocyte growth factor (HGF). T2D mice receiving a single intravenous injection of T2D or db/db ASCs showed increased insulin sensitivity, reduced inflammation and fat content in adipose tissue and the liver and increased pancreatic ß cell mass through 5 weeks post-infusion. Our data show that, although ASCs from T2D or db/db mice had inferior proliferative capacity compared to cells from healthy controls, improved insulin sensitivity and less ß cell death was seen in T2D mice receiving mesenchymal stem cell (MSC) therapy. This study offers evidence that ASCs from diabetic donors have the potential to be used for cell therapy in the treatment of insulin resistance and T2D.

MC4R agonism promotes durable weight loss in patients with leptin receptor deficiency.

Genetic defects underlying the melanocortin-4 receptor (MC4R) signaling pathway lead to severe obesity. Three severely obese LEPR-deficient individuals were administered the MC4R agonist setmelanotide, resulting in substantial and durable reductions in hyperphagia and body weight over an observation period of 45-61 weeks. Compared to formerly developed and tested MC4R agonists, setmelanotide has the unique capability of activating nuclear factor of activated T cell (NFAT) signaling and restoring function of this signaling pathway for selected MC4R variants. Our data demonstrate the potency of setmelanotide in treatment of individuals with diverse MC4R-related pathway deficiencies.

Genetic identification of leptin neural circuits in energy and glucose homeostases.

Leptin, a hormone produced in white adipose tissue, acts in the brain to communicate fuel status, suppress appetite following a meal, promote energy expenditure and maintain blood glucose stability1,2. Dysregulation of leptin or its receptors (LEPR) results in severe obesity and diabetes3-5. Although intensive studies on leptin have transformed obesity and diabetes research2,6, clinical applications of the molecule are still limited 7 , at least in part owing to the complexity and our incomplete understanding of the underlying neural circuits. The hypothalamic neurons that express agouti-related peptide (AGRP) and pro-opiomelanocortin (POMC) have been hypothesized to be the main first-order, leptin-responsive neurons. Selective deletion of LEPR in these neurons with the Cre-loxP system, however, has previously failed to recapitulate, or only marginally recapitulated, the obesity and diabetes that are seen in LEPR-deficient Lepr db/db mice, suggesting that AGRP or POMC neurons are not directly required for the effects of leptin in vivo8-10. The primary neural targets of leptin are therefore still unclear. Here we conduct a systematic, unbiased survey of leptin-responsive neurons in streptozotocin-induced diabetic mice and exploit CRISPR-Cas9-mediated genetic ablation of LEPR in vivo. Unexpectedly, we find that AGRP neurons but not POMC neurons are required for the primary action of leptin to regulate both energy balance and glucose homeostasis. Leptin deficiency disinhibits AGRP neurons, and chemogenetic inhibition of these neurons reverses both diabetic hyperphagia and hyperglycaemia. In sharp contrast to previous studies, we show that CRISPR-mediated deletion of LEPR in AGRP neurons causes severe obesity and diabetes, faithfully replicating the phenotype of Lepr db/db mice. We also uncover divergent mechanisms of acute and chronic inhibition of AGRP neurons by leptin (presynaptic potentiation of GABA (γ-aminobutyric acid) neurotransmission and postsynaptic activation of ATP-sensitive potassium channels, respectively). Our findings identify the underlying basis of the neurobiological effects of leptin and associated metabolic disorders.

Targeted inhibition of RAGE reduces amyloid-ß influx across the blood-brain barrier and improves cognitive deficits in db/db mice.

AIMS: To investigate restorative effects of the receptor for advanced glycation end products (RAGE)-specific inhibitor FPS-ZM1 on abnormal amyloid ß (Aß) influx across the blood brain-barrier (BBB) and cognitive deficits in db/db mice. METHODS: Aß influx across the BBB was determined by intra-arterial infusion of 125I-Aß1-40. Receptor for advanced glycation end products (RAGE), Aß, NF-κB p65, caspase-3, Bax, Bcl-2, PSD-95 and synaptophysin were assayed by Western blot, immunohistochemistry or RT-PCR. Apoptosis was quantified by TUNEL assay. In vivo hippocampal long term potentiation (LTP) recording, Golgi Staining, Morris water maze (MWM) task and Y-maze test were performed. RESULTS: FPS-ZM1 (1.0 mg/kg i.p.) inhibited Aß influx across the BBB and expression of RAGE participating in Aß influx, consequently decreased hippocampal Aß1-40 and Aß1-42 in db/db mice. After FPS-ZM1 treatment, NF-κB signaling was inhibited, and neuronal apoptosis was reduced, which revealed by less TUNEL + cells, reduced caspase-3 activity and higher ratio of Bcl-2/Bax. In addition, FPS-ZM1 improved hippocampal plasticity evidenced by enhanced in vivo LTP and the restoration of spine deficit and increased PSD-95 expression in hippocampal neuron. Further studies found that FPS-ZM1 treatment alleviated cognitive deficits shown by better performance in behavioral tests, without significant metabolic effects on blood glucose, insulin and cerebral AGEs. CONCLUSION: Downregulation of abnormal Aß influx across the BBB by FPS-ZM1 at higher dosage contributes to reduced neuronal apoptosis, improved hippocampal plasticity and cognitive impairment in db/db mice.