Leptin Receptor Mutation Research Articles

Generation of LEPR Knockout Rabbits with CRISPR/CAS9 System.

The LEPR gene encodes a leptin hormone receptor, and its mutations are associated with morbid obesity, dysregulation of lipid metabolism, and fertility defects in humans. Spontaneous Lepr mutations have been described in rodents, and Lepr knockout animals have been generated, in particular, using the CRISPR/Cas9 system. Lipid metabolism in rodents significantly differs from that in humans or rabbits, and rabbits are therefore considered as the most relevant model of morbid obesity and lipid metabolism dysregulation in humans. LEPR knockout rabbits have not been reported so far. In this work a LEPR knockout rabbit was generated by introducing a deletion of the region around LEPR exon 10 using the CRISPR/Cas9 system. The body weight of the knockout rabbit was significantly higher than the average body weight of the wild type rabbits. CRISPR/Cas9-mediated generation of LEPR knockout rabbits will allow the development of a model of morbid obesity and endocrine defects due to leptin receptor mutations in humans.

Anti-hyperglycemic effects of Cissus quadrangularis extract via regulation of gluconeogenesis in type 2 diabetic db/db mice.

Introduction: Cissus quadrangularis is a vining plant widely used as a traditional herbal remedy for various ailments. In this study, the therapeutic effects of C. quadrangularis extract (CQR-300) on type 2 diabetes mellitus (T2DM) were investigated in a leptin receptor-mutated db/db mouse model. Methods: CQR-300 was orally administered to db/db mice (n = 6/group) at different doses (50, 100, and 200mg/kg) for 8weeks. Blood glucose levels and oral glucose tolerance were assessed using the AccuCheck glucometer. Enzyme-linked immunosorbent assay was performed to evaluate insulin and hemoglobin A1c (HbA1c) levels in the blood of db/db mice. Liver and pancreatic tissues from db/db mice were examined by hematoxylin and eosin (H&E) and immunohistochemical staining. The protein levels of gluconeogenesis-, lipogenesis-, and oxidative stress-related factors were evaluated using western blotting. Results and discussion: CQR-300 treatment effectively reduced body weight, blood glucose, and insulin levels. HbA1c levels were increased by leptin receptor mutation. Additionally, in the oral glucose tolerance tests, the CQR-300 treated group had a faster blood glucose recovery rate than the db/db group. H&E and Oil red-O staining of the liver showed decreased lipid accumulation in the CQR-300 treated group than the db/db group. Western blot analysis confirmed that CQR-300 effectively inhibited gluconeogenesis, lipogenesis, and oxidative stress-related factors. Our findings suggest that CQR-300 has the potential to be used as a T2DM supplement.

#1870 Uninephrectomized diabetic rats delay onset of hyperglycemia via down-regulation of SGLT2 mRNA

Abstract Background and Aims The kidney is essential for glucose metabolism. Reabsorption of almost all the glucose filtered by the glomerulus is performed by the sodium-glucose cotransporters (the SGLTs) in the proximal tubules, with SGLT2 responsible for about 90%. In addition, the kidney, along with the liver, plays an important role in gluconeogenesis, especially in the long fasting state. SGLT2 inhibitors originally developed for the treatment of type 2 diabetes mellitus (DM) are clinically very effective drugs halting chronic kidney disease progression. The underlying mechanisms are, however, not fully understood. Furthermore, SGLT2 expression in diabetic patients has been reported to increase and decrease but remains unclear. Therefore, this study aimed to evaluate how uninephrectomy (UNx) and SGLT2 inhibitor treatment affects the dynamics of blood glucose and SGLTs in SDT fatty rats with obese type 2 DM (leptin receptor mutation), which is hyperglycemic from an early stage. Method 24 male SDT fatty rats were divided into four groups: sham + placebo group (n=6); sham + dapagliflozin (dapa, 1.5 mg/kg/day) group (n=6); UNx + placebo group (n=6); UNx + dapa group (n=6). UNx or sham operations were undergone at week 6. Measurements included body weight, food intake, water consumption, urine output, blood pressure, serum creatinine, and blood glucose in the experiment. At week 12, the rats were sacrificed, and the kidneys were sampled to measure SGLT1 and SGLT2 mRNA in the renal cortex by real-time PCR quantification. Results Blood glucose levels continued to rise from week 7 in the sham + placebo group, but the rate of increase was still slower in the UNx + placebo group, and the increase in blood glucose levels was mostly suppressed with dapa administration (Fig. 1). Only the Sham + placebo group showed increased urinary volume and weight loss after week 10 due to hyperglycemia. There were no significant differences in serum creatinine or blood pressure during the study. Real-time PCR results showed that SGLT2 mRNA in the renal cortex was significantly decreased by 26% in the UNx group (P=0.0386), but SGLT1 mRNA was not significantly different. Conclusion Uninephrectomized diabetic rats delayed onset of hyperglycemia and reduced SGLT2 mRNA; SGLT2 inhibitor treatment further delayed the onset of hyperglycemia but did not alter SGLT2 mRNA expression. In animal models of diabetes, renal glucose reabsorption appeared to be a major contributor to the development of hyperglycemia.

Kidney disease associated with pre-pubertal obesity initiates pathological alterations in the brain of Dahl salt-sensitive rats

Childhood/pre-pubertal obesity (PPO) is implicated in the development of chronic kidney disease (CKD), and there is evidence that PPO also increases the risk of developing Alzheimer disease (AD) later in life. In the current study, we aim to investigate the correlation between CKD and the development of AD-like pathology in a rat model of CKD associated with PPO. We hypothesize that systemic inflammation due to PPO exacerbates CKD and induces AD-like pathology in the brain at older age. In our preliminary studies, we utilized the Dahl salt sensitive leptin receptor mutant rat (SSLepRmutant), which is a novel model of PPO. 6-week-old Dahl salt-sensitive (SS) (control, n=3) and SSLepRmutant rats (n=5) were monitored for proteinuria every 3 weeks, for a 12-week period. Throughout the study, we observed significantly elevated proteinuria in SSLepRmutant rats (Week-6: 337±81 mg/day, Week-9: 371±147 mg/day, Week-18: 1920±318 mg/day) compared to SS rats (Week-6: 25±7 mg/day, Week-9: 35±39 mg/day, Week-18: 35±33 mg/day). At 18-week, creatinine levels were significantly higher in SSLepRmutant rats (1.5±0.5 mg/dL) versus SS rats (0.4±0.03 mg/dL) indicating CKD. Additionally, we found significant elevation of triglycerides in SSLepRmutant rats (5134±1211 mg/dL) compared to SS rats (79±21 mg/dL). To investigate the brain pathology, we performed immunochemical analysis (dot-blot assay) using A11 antibody to determine the levels of Amyloid-beta oligomers (Aβo). Our results show that there was tendency for Aβo levels to be increased in the brains from obese SSLepRmutant rats compared to SS. Finally, we tested the permeability of the blood-brain barrier to Evans blue dye and observed that the brain of SSLepRmutant rats was more permeable to the dye compared to SS rats as early as 8 weeks of age. Overall, these results indicate that PPO obesity not only increases the susceptibility to develop CKD but also causes Alzheimer-like pathology during the prepubescent stage. NIDDK (DK109133) and AG (AG057842) awarded to Jan M. Williams. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Time restricted feeding improves insulin resistance and reduces progressive proteinuria in young obese Dahl salt-sensitive rats prior to puberty

Prepubertal obesity (PPO) is now associated with early signs of renal disease. An improper eating behavior is one of the leading causes of PPO. Time restricted feeding (TRF) has been shown to be beneficial in obese patients without reducing body weight. However, the effects of TRF on renal injury during PPO have not been investigated. Therefore, the current study examined whether TRF reduces renal injury in obese Dahl salt-sensitive leptin receptor mutant (SSLepRmutant) rats before puberty. Four-week-old SS and SSLepRmutant rats were given either ad libitum access to food for 24 hrs (control) or 8 hrs during their active phase (TRF) for 4 weeks. Body weight and food intake were significantly higher in SSLepRmutant rats versus SS rats throughout the study, and TRF did not have an impact on both parameters. Fasting blood glucose levels were similar in all groups (≤120 mg/dL). Fasting plasma insulin levels were significantly higher in SSLepRmutant rats vs SS rats (5±1 vs. 1.0±0.1 ng/mL; p<0.05), and TRF reduced fasting plasma insulin by 70% in SSLepRmutant rats. Moreover, TRF markedly improved insulin resistance in SSLepRmutant rats. At the end of the study, we did not observe any differences in MAP (via carotid catheter) among the groups. Proteinuria was significantly higher in SSLepRmutant vs SS rats (361±32 vs. 17±4 mg/day; p<0.05), and TRF only reduced proteinuria in SSLepRmutant rats (144±19 mg/day; p<0.05). We observed a significant increase in GFR (via creatinine clearance) in SSLepRmutant rats compared to SS rats (0.71±0.08 vs. 0.39±0.07 mL/min/gkwt; p<0.05), and TRF normalized GFR in SSLepRmutant rats (0.37±0.07 mL/min/gkwt; p<0.05). Glomerular injury and renal fibrosis were markedly elevated in SSLepRmutant vs SS rats, and TRF improved these histological changes. Overall, these data suggest that TRF prevents the early progression of proteinuria by possibly reducing the insulin resistant effects on GFR during PPO. NIDDK (DK109133) and AG (AG057842). This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Leptin Receptor Deficiency Impairs Lymph Node Development and Adaptive Immune Response.

Activation and clonal expansion of the Ag-specific adaptive immune response in the draining lymph node is essential to clearing influenza A virus infections. Activation sufficient for virus clearance is dependent on the lymph node's architectural organization that is maintained by stromal cells, chiefly fibroblastic reticular cells. During an analysis of influenza A virus clearance in leptin receptor knockout (DB/DB) mice, we observed that the DB/DB mice have markedly reduced numbers of lymph node fibroblastic reticular cells at the steady state. The reduction in lymph node fibroblastic reticular cells resulted in abnormal lymph node organization and diminished numbers of adaptive immune cells in the lymph nodes under homeostatic conditions. As a consequence, the DB/DB mice were impaired in their ability to generate an effective influenza-specific adaptive immune response, which prevented virus clearance. Using leptin receptor mutant mice with point mutations at distinct signaling sites in the leptin receptor, we were able to link the leptin receptor's signaling domain tyrosine 985, which does not contribute to obesity, to lymph node fibroblastic reticular cell development and function. These results demonstrate a novel role for leptin receptor signaling in regulating lymph node development in a manner that is crucial to the generation of Ag-specific adaptive immune responses.

Unbiased gene expression analysis of the delayed fracture healing observed in Zucker diabetic fatty rats.

Impaired fracture repair in patients with type 2 diabetes mellitus (T2DM) is not fully understood. In this study, we aimed to characterize the local changes in gene expression (GE) associated with diabetic fracture. We used an unbiased approach to compare GE in the fracture callus of Zucker diabetic fatty (ZDF) rats relative to wild-type (WT) littermates at three weeks following femoral osteotomy. Zucker rats, WT and homozygous for leptin receptor mutation (ZDF), were fed a moderately high-fat diet to induce T2DM only in the ZDF animals. At ten weeks of age, open femoral fractures were simulated using a unilateral osteotomy stabilized with an external fixator. At three weeks post-surgery, the fractured femur from each animal was retrieved for analysis. Callus formation and the extent of healing were assessed by radiograph and histology. Bone tissue was processed for total RNA extraction and messenger RNA (mRNA) sequencing (mRNA-Seq). Radiographs and histology demonstrated impaired fracture healing in ZDF rats with incomplete bony bridge formation and an influx of intramedullary inflammatory tissue. In comparison, near-complete bridging between cortices was observed in Sham WT animals. Of 13,160 genes, mRNA-Seq analysis identified 13 that were differentially expressed in ZDF rat callus, using a false discovery rate (FDR) threshold of 10%. Seven genes were upregulated with high confidence (FDR = 0.05) in ZDF fracture callus, most with known roles in inflammation. These findings suggest that elevated or prolonged inflammation contributes to delayed fracture healing in T2DM. The identified genes may be used as biomarkers to monitor and treat delayed fracture healing in diabetic patients.

Congenital leptin receptor deficiency: A novel leptin receptor gene mutation in an Indian family producing severe early-onset monogenic obesity

Congenital leptin receptor (LEPR) deficiency is a rare autosomal recessive condition producing early-onset severe monogenic obesity with around 90 cases reported worldwide to date. It is associated with early-onset obesity, hyperphagia, and various hormone deficiencies. We describe siblings born to consanguineous parents with progressive early-onset obesity associated with hyperphagia. Genetic analysis revealed a novel homozygous mutation in LEPR (c.1752G>A) gene on chromosome 1p31. Both parents were heterozygous carriers for the same mutation. This is only the second reported case from India where siblings have been affected with LEPR gene mutation. This will provide further insight into the physiologic role of leptin and its receptor LEPR in monogenic obesity.

Detecting fa leptin receptor mutation in Zucker rats with tetra-primer amplification-refractory mutation system (ARMS)-PCR

Due to the genetic mutation (fa) in the gene encoding for leptin receptor, homozygous Zucker rats (fa−/−) develop excessive adiposity and become an experimental animal model in obesity and metabolic-related diseases research. Based on tetra-primer amplification refractory mutation system-polymerase chain reaction (ARMS-PCR), we developed a method to quickly genotype Zucker rats with a mutated fa allele from their wildtype littermates. The three genotypes are clearly discriminated on 2.0% agarose gel. Our method can be used as a reliable tool to set up and maintain the breeding colony in animal facilities as well as assign animals to control and treatment groups based on their genotypes for animal studies.

The tyrosine kinase inhibitor Dasatinib reduces cardiac steatosis and fibrosis in obese, type 2 diabetic mice

BackgroundCardiac steatosis is an early yet overlooked feature of diabetic cardiomyopathy. There is no available therapy to treat this condition. Tyrosine kinase inhibitors (TKIs) are used as first or second-line therapy in different types of cancer. In cancer patients with diabetes mellitus, TKIs reportedly improved glycemic control, allowing insulin discontinuation. They also reduced liver steatosis in a murine model of non-alcoholic fatty liver disease. The present study aimed to determine the therapeutic effect of the second-generation TKI Dasatinib on lipid accumulation and cardiac function in obese, type 2 diabetic mice. We also assessed if the drug impacts extra-cardiac fat tissue depots.MethodsTwo studies on 21-week-old male obese leptin receptor mutant BKS.Cg-+Leprdb/+Leprdb/OlaHsd (db/db) mice compared the effect of Dasatinib (5 mg/kg) and vehicle (10% DMSO + 90% PEG-300) given via gavage once every three days for a week or once every week for four weeks. Functional and volumetric indices were studied using echocardiography. Post-mortem analyses included the assessment of fat deposits and fibrosis using histology, and senescence using immunohistochemistry and flow cytometry. The anti-adipogenic action of Dasatinib was investigated on human bone marrow (BM)-derived mesenchymal stem cells (MSCs). Unpaired parametric or non-parametric tests were used to compare two and multiple groups as appropriate.ResultsDasatinib reduced steatosis and fibrosis in the heart of diabetic mice. The drug also reduced BM adiposity but did not affect other fat depots. These structural changes were associated with improved diastolic indexes, specifically the E/A ratio and non-flow time. Moreover, Dasatinib-treated mice had lower levels of p16 in the heart compared with vehicle-treated controls, suggesting an inhibitory impact of the drug on the senescence signalling pathway. In vitro, Dasatinib inhibited human BM-MSC viability and adipogenesis commitment.ConclusionsOur findings suggest that Dasatinib opposes heart and BM adiposity and cardiac fibrosis. In the heart, this was associated with favourable functional consequences, namely improvement in an index of diastolic function. Repurposing TKI for cardiac benefit could address the unmet need of diabetic cardiac steatosis.

Metformin reduces insulin resistance and attenuates progressive renal injury in prepubertal obese Dahl salt-sensitive rats.

Prepubertal obesity is currently an epidemic and is considered as a major risk factor for renal injury. Previous studies have demonstrated that insulin resistance contributes to renal injury in obesity, independent of diabetes. However, studies examining the relationship between insulin resistance and renal injury in obese children are lacking. Recently, we reported that progressive renal injury in Dahl salt-sensitive (SS) leptin receptor mutant (SSLepRmutant) rats was associated with insulin resistance before puberty. Therefore, the aim of the present study was to examine whether decreasing insulin resistance with metformin will reduce renal injury in SSLepRmutant rats. Four-wk-old SS and SSLepRmutant rats were separated into the following two groups: 1) vehicle and 2) metformin (300 mg/kg/day) via chow diet for 4 wk. Chronic administration of metformin markedly reduced insulin resistance and dyslipidemia in SSLepRmutant rats. We did not detect any differences in mean arterial pressure between vehicle and metformin-treated SS and SSLepRmutant rats. Proteinuria was significantly greater in SSLepRmutant rats versus SS rats throughout the study, and metformin administration significantly reduced proteinuria in SSLepRmutant rats. At the end of the protocol, metformin prevented the renal hyperfiltration observed in SSLepRmutant rats versus SS rats. Glomerular and tubular injury and renal inflammation and fibrosis were significantly higher in vehicle-treated SSLepRmutant rats versus SS rats, and metformin reduced these parameters in SSLepRmutant rats. These data suggest that reducing insulin resistance with metformin prevents renal hyperfiltration and progressive renal injury in SSLepRmutant rats before puberty and may be therapeutically useful in managing renal injury during prepubertal obesity.NEW & NOTEWORTHY Childhood/prepubertal obesity is a public health concern that is associated with early signs of proteinuria. Insulin resistance has been described in obese children. However, studies investigating the role of insulin resistance during childhood obesity-associated renal injury are limited. This study provides evidence of an early relationship between insulin resistance and renal injury in a rat model of prepubertal obesity. These data also suggest that reducing insulin resistance with metformin may be renoprotective in obese children.

1678-P: B6-Alms1-del Mice, a Metabolic Syndrome Animal Model, Shows Semaglutide Benefits on Obesity, Hyperglycemia, and NAFL

Metabolic syndrome is a cluster of conditions that occur together, increasing the risk of heart disease, stroke and type 2 diabetes. These conditions include obesity, hyperglycemia, hypertension, hyperlipidemia. Leptin and leptin receptor mutant mice, ob/ob and db/db, are two classic metabolic syndrome animal model. However, the transient hyperglycemia of ob/ob and severe hyperglycemia induced premature death of db/db limit the application of these two models. To fill the gap, GemPharmatech developed a metabolic disorder model based on the mutation of Alms1 gene in mice (B6-Alms1-del mice). B6-Alms1-del mice gradually developed obesity from 8 weeks old with chow diet, accompanied by hyperglycemia, glucose and insulin intolerance, dyslipidemia and impaired liver function. Moreover, B6-Alms1-del mice developed severe non alcoholic fatty liver spontaneously as early as 21 weeks old and no premature death was observed around 5~8 months of ages. As B6-Alms1-del mice copied major features of metabolic syndrome, we further tested whether B6-Alms1-del mice could response to the positive drug semaglutide, an agonist of GLP-1R. 16 weeks old B6-Alms1-del mice were treated with vehicle and semaglutide for 5 weeks, respectively. Our results indicate that semaglutide lead to benefit on metabolic syndrome, including body weight control, improvement in hyperglycemia, hyperlipidemia, liver injury and hepatic steatosis. In conclusion, we have established a metabolic syndrome animal model that develop clinically relevant metabolic phenotypes and overcome the limitation of ob/ob and db/db. Furthermore, B6-Alms1-del mice responds to the approval anti-obesity drug semaglutide, which provide a useful model to assess the efficacy of novel metabolic syndrome therapies. Disclosure Z.Chen: None. M.Gao: None. X.Zhao: None. Z.Li: None. J.Zhao: None. C.Ju: None. X.Gao: None.

Transcriptional regulation of adipogenin expression in liver steatosis by hepatic peroxisome proliferator-activated receptor gamma.

The nuclear receptors peroxisome proliferator-activated receptor gamma (PPARγ) and adipogenin (ADIG) play vital roles in lipid metabolism. However, the interaction between PPARγ and ADIG during liver steatosis remains unclear. In this study, we aimed to investigate the role of PPARγ in the transcriptional regulation of hepatic ADIG expression. Adig was found to be highly expressed in various fatty liver mouse models. Although hepatic Adig was expressed at high levels in the fatty liver of type 2 diabetic ob/ob mice and was upregulated by PPARγ agonist treatment, it was expressed at significantly low levels in liver-specific Pparg-knockout mice. Moreover, hepatic Adig expression was observed in other mouse models of liver steatosis, such as the leptin receptor mutant db/db and alcohol-fed mice. Adig was also highly expressed in the white and brown adipose tissues, skeletal muscles, and heart of ob/ob mice. Reporter and electromobility shift assays showed that PPARγ positively regulates Adig transcriptional activity by directly binding to a functional PPARγ-responsive element in the promoter region. Our results indicate that Adig is a novel target gene of hepatic PPARγ in liver steatosis.

Chronic treatment with IL-25 increases renal M2 macrophages and reduces renal injury in obese Dahl salt-sensitive rats during the prepubescent stage.

Recently, we have reported that the early progression of proteinuria in the obese Dahl salt-sensitive (SS) leptin receptor mutant (SSLepRmutant) strain was associated with increased renal macrophage infiltration before puberty. Macrophages can be divided into two distinct phenotypes: M1 (proinflammatory) and M2 (anti-inflammatory). Moreover, previous studies have demonstrated that interleukin (IL)-25 converts resting macrophages and M1 into M2. Therefore, the present study examined whether treatment with IL-25 would reduce the early progression of renal injury in SSLepRmutant rats by increasing renal M2. We also investigated the impact of IL-25 on M2 subtypes: M2a (wound healing/anti-inflammatory), M2b (immune mediated/proinflammatory), M2c (regulatory/anti-inflammatory), and M2d (tumor associated/proangiogenic). Four-wk-old SS and SSLepRmutant rats were treated with either control (IgG) or IL-25 (1 µg/day ip every other day) for 4 wk. The kidneys from SSLepRmutant rats displayed progressive proteinuria and renal histopathology versus SS rats. IL-25 treatment had no effect on these parameters in SS rats. However, in the SSLepRmutant strain, proteinuria was markedly reduced after IL-25 treatment. Chronic treatment with IL-25 significantly decreased glomerular and tubular injury and renal fibrosis in the SSLepRmutant strain. Although the administration of IL-25 did not change total renal macrophage infiltration in both SS and SSLepRmutant rats, IL-25 increased M2a by >50% and reduced M1 by 60% in the kidneys of SSLepRmutant rats. Overall, these data indicate that IL-25 reduces the early progression of renal injury in SSLepRmutant rats by inducing M2a and suppressing M1 and suggest that IL-25 may be a therapeutic target for renal disease associated with obesity. NEW & NOTEWORTHY For the past few decades, immune cells and inflammatory cytokines have been demonstrated to play an important role in the development of renal disease. The present study provides strong evidence that interleukin-25 slows the early progression of renal injury in obese Dahl salt-sensitive rats before puberty by increasing systemic anti-inflammatory cytokines and renal M2a macrophages.

Neutralizing MIP3α Reduces Renal Immune Cell Infiltration and Progressive Renal Injury in Young Obese Dahl Salt-Sensitive Rats.

Recently, we reported that the early progression of renal injury in obese Dahl salt-sensitive leptin receptor mutant (SSLepRmutant) rats was associated with increased macrophage inflammatory protein 3-α (MIP3α) expression prior to puberty. Therefore, this study tested the hypothesis that MIP3α plays a role in recruiting immune cells, thereby triggering renal inflammation and early progressive renal injury in SSLepRmutant rats prior to puberty. Four-week-old Dahl salt-sensitive (SS) and SSLepRmutant rats either served as control (IgG; intraperitoneal, every other day) or received MIP3α-neutralizing antibody (MNA; 100 µg/kg) for 4 weeks. MNA reduced circulating and renal MIP3α levels and proinflammatory immune cells by 50%. Although MNA treatment did not affect blood glucose and plasma cholesterol levels, MNA markedly decreased insulin resistance and triglyceride levels in SSLepRmutant rats. We observed no differences in mean arterial pressure (MAP) between SS and SSLepRmutant rats, and MNA had no effect on MAP in either strain. Proteinuria was significantly increased in SSLepRmutant rats versus SS rats over the course of the study. Treatment with MNA markedly decreased proteinuria in SSLepRmutant rats while not affecting SS rats. Also, MNA decreased glomerular and tubular injury and renal fibrosis in SSLepRmutant rats while not affecting SS rats. Overall, these data indicate that MIP3α plays an important role in renal inflammation during the early progression of renal injury in obese SSLepRmutant rats prior to puberty. These data also suggest that MIP3α may be a novel therapeutic target to inhibit insulin resistance and prevent progressive proteinuria in obese children. SIGNIFICANCE STATEMENT: Childhood obesity is increasing at an alarming rate and is now being associated with renal disease. Although most studies have focused on the mechanisms of renal injury associated with adult obesity, few studies have examined the mechanisms of renal injury involved during childhood obesity. In the current study, we observed that the progression of renal injury in obese Dahl salt-sensitive leptin receptor mutant rats was associated with an increase in MIP3α, a chemokine, before puberty, and inhibition of MIP3α markedly reduced renal injury.

Interplay between obesity and aging on myocardial geometry and function: Role of leptin-STAT3-stress signaling

BackgroundUncorrected obesity facilitates premature aging and cardiovascular anomalies. This study examined the interaction between obesity and aging on cardiac remodeling and contractile function. Methods: Cardiac echocardiographic geometry, function, morphology, intracellular Ca2+ handling, oxidative stress (DHE fluorescence), STAT3 and stress signaling were evaluated in young (3-mo) and old (12- and 18-mo) lean and leptin deficient ob/ob obese mice. Cardiomyocytes from young and old lean and ob/ob mice were treated with leptin (1 nM) for 4 h in vitro prior to assessment of mechanical and biochemical properties. High fat diet (45% calorie from fat) and the leptin receptor mutant db/db obese mice at young and old age were evaluated for comparison. Results: Our results displayed reduced survival in ob/ob mice. Obesity but less likely older age dampened echocardiographic, geometric, cardiomyocyte function and intracellular Ca2+ properties, elevated O2− and p47phox NADPH oxidase levels with a more pronounced geometric change at older age. Immunoblot analysis revealed elevated p47phox NADPH oxidase and dampened phosphorylation of STAT3, with a more pronounced response in old ob/ob mice, the effects were restored by leptin. Obesity and aging inhibited phosphorylation of Akt, eNOS, AMPK, and p38 while promoting phosphorylation of JNK and IκB. Leptin reconciled cardiomyocyte dysfunction, O2− yield, p47phox upregulation, STAT3 dephosphorylation and stress signaling in ob/ob mice although its action on stress signaling cascades were lost at old age. High fat diet-induced and db/db obesity displayed aging-associated cardiomyocyte anomalies reminiscent of ob/ob model albeit lost leptin response. ConclusionsOur data suggest disparate age-associated obesity response in cardiac remodeling and contractile dysfunction due to phosphorylation of Akt, eNOS and stress signaling-related oxidative stress.

A promising rat model of heart failure with preserved ejection fraction associated to multiple comorbidities

Abstract Background and aims Heart failure with preserved ejection fraction (HFpEF) is a complex clinical phenotype often associated to the presence of multiple non-cardiac interrelated comorbidities including diabetes, obesity, hypertension. A major challenge in the development of new therapies for HFpEF is the lack of animal models that truly recapitulate the complexities of the disease. One promising candidate is the Lund MetS rat, a congenic BBDR.cg-lepr.cp model generated by introgression of the Koletsky leptin receptor mutation into the BioBreeding Diabetes Resistant (BBDR) rat. Methods 14-week-old Lund MetS obese T2D rats were exposed to salt enriched diet (0.8% NaCl in diet) for 6 weeks. Age-matched lean rats (ctrl) were fed a normal chow diet. Cardiovascular phenotyping was assessed by echocardiography and blood pressure measurement. Vascular function of isolated thoracic aortas, as well as kidney and cardiac parameters were also evaluated at the end of the 6-week diet period. Results After 6-week enriched salt diet period, mean arterial pressure increased from 120mmHg to 160mmHg (vs 100mmHg in chow-fed lean rat). The hypertensive state also led to renal hypertrophy with up to a 2-fold higher kidney weights. Echocardiography showed a preserved systolic function with quite similar ejection fraction and fractional shortening in Lund MetS and lean rats. In contrast, high salt-fed Lund MetS rats developed cardiac hypertrophy confirmed by a large increase in heart, left ventricle, and left atria weights as compared to lean rats. Diastolic dysfunction was also highlighted with inverted E/A and E'/A' ratios along with a prolongation of the isovolumic relaxation time (IVRT). This was accompanied by an increase in circulating levels of soluble ST2 and NT- proBNP. Finally, aortic rings assays showed that both endothelium dependent and independent vasodilating properties were impaired in the high salt-fed Lund MetS rats. Conclusions The present data demonstrate that the Lund MetS rat fed a high salt diet developed a marked hypertension, pathological cardiac remodeling and diastolic dysfunction without modification of ejection fraction, along with obesity and type 2 diabetes. Thus, this could be a relevant model to bring forward effective new treatments for HFpEF patients. Funding Acknowledgement Type of funding sources: None.

Impact of metabolic substrate modification on myocardial efficiency in a rat model of obesity and diabetes

Abstract Background Congenic leptin receptor deficient rat generated by introgression of the Koletsky leptin receptor mutation into BioBreeding Diabetes Resistant rat (BBDR.lepr−/−) is a novel animal model combining obesity, systemic insulin resistance and diabetes. Systemic insulin resistance is associated with reduced myocardial glucose utilization, but its effect on myocardial external efficiency, i.e. the ability of the myocardium to convert energy into external stroke work, remains uncertain. Purpose To characterize cardiac energy metabolism and function in BBDR.lepr−/− rats and to study the effect of dipeptidyl peptidase 4 (DPP-4) inhibitor linagliptin in this model. Methods Cardiac phenotype was evaluated in six-month-old male BBDR.lepr−/− rats (n=11) and age-matched male non-diabetic lean control littermates (BBDR.lepr+/− or BBDR.lepr+/+ rats, n=14). Of these, 7 BBDR.lepr−/− rats and 6 controls underwent cardiac ultrasound, 2-deoxy-2-[18F]fluoro-D-glucose ([18F]FDG) positron emission tomography/computed tomography (PET/CT), and [11C]acetate PET in order to evaluate cardiac structure and function as well as glucose and oxidative metabolism. In the remaining rats, fatty acid metabolism was evaluated by [18F]fluorothia-6-heptadecanoic acid ([18F]FTHA) PET/CT. In the linagliptin intervention study, 25 BBDR.lepr−/− male rats were randomly divided into control group (n=11) that received regular chow diet and linagliptin group (n=14) that received linagliptin (10mg/kg/d) mixed in the chow diet for three months. After the intervention, the rats underwent cardiac ultrasound, [18F]FDG PET/CT, and [11C]acetate PET. Results Compared with controls, BBDR.lepr−/− rats showed increased left ventricle (LV) mass (∼40%, p>0.001) and higher systolic blood pressure (∼10%, p=0.02). However, fractional shortening and cardiac output were similar in both groups. Myocardial fractional uptake rate of glucose measured with [18F]FDG PET was significantly reduced (∼86%, p=0.004) (Fig. 1A, E), whereas myocardial fatty acid uptake measured by [18F]FTHA PET was not significantly increased (free fatty acid (FFA) corrected standardized uptake value (SUV) ∼21%, p=0.54) (Fig. 1B) in BBDR.lepr−/− compared to controls. Myocardial oxygen consumption assessed by [11C]acetate PET was similar in both groups (Fig. 1C, E), but LV work per gram of myocardium was reduced (∼28%, p=0.001) resulting in reduced myocardial external efficiency (∼21%, p=0.03) (Fig. 1D) in BBDR.lepr−/− compared to controls. Treatment with linagliptin significantly enhanced myocardial fractional uptake rate of glucose (∼166%, p=0.006) (Fig. 2A, C), but had no effect on efficiency of cardiac work (Fig. 2B). Conclusions Obese and diabetic BBDR.lepr−/− rats demonstrate LV hypertrophy and markedly reduced myocardial glucose utilization associated with impaired myocardial external efficiency despite normal LV systolic function. Enhancement of myocardial glucose uptake by linagliptin did not improve efficiency of cardiac work. Funding Acknowledgement Type of funding sources: Public grant(s) – EU funding. Main funding source(s): IMI-SUMMIT

Early onset obesity due to a mutation in the human leptin receptor gene.

SummaryLeptin is secreted by adipocytes in response to fat storage and binds to its receptor (LEPR), which is ubiquitously expressed throughout the body. Leptin regulates energy expenditure and is anorexigenic. In this study, we describe the clinical and hormonal findings of three siblings with a personal history of rapid weight gain during the first months of life. They had delayed puberty, high levels of FSH (15.6 ± 3.7 mUI/mL; reference: 1.5–12.4) and LH (12.3 ± 2.2 mUI/mL; reference: 1.7–8.6), normal oestradiol and total testosterone and successful fertility. None of the patients had dyslipidemia, diabetes or thyroid disease. Next-generation sequencing identified a pathogenic homozygous variant c.2357T>C, p.(Leu786Pro) in LEPR. Their parents and children were heterozygous for this mutation. We compared clinical and biochemical findings of homozygous carriers with first-degree heterozygous family members and ten randomly selected patients with adult-onset morbid obesity. Homozygous carriers of the mutation had significantly higher BMI (32.2 ± 1.7 kg/m2 vs 44.5 ± 7.1 kg/m2, P = 0.023) and increased serum levels of leptin (26.3 ± 9.3 ng/mL vs 80 ± 36.4 ng/mL, P = 0.028) than their heterozygous relatives. Compared with the ten patients with adult-onset morbid obesity, serum levels of leptin were not significantly higher in homozygous carriers (53.8 ± 24.1 ng/mL vs 80 ± 36.4 ng/mL, P = 0.149), and thus serum levels of leptin were not a useful discriminative marker of LEPR mutations. We described a rare three-generation family with monogenic obesity due to a mutation in LEPR. Patients with early onset obesity should be considered for genetic screening, as the identification of mutations may allow personalized treatment options (e.g. MC4R-agonists) and targeted successful weight loss.Learning pointsThe early diagnosis of monogenic forms of obesity can be of great interest since new treatments for these conditions are becoming available.Since BMI and leptin levels in patients with leptin receptor mutations are not significantly different from those found in randomly selected morbid obese patients, a careful medical history is mandatory to suspect this condition.Loss of leptin receptor function has been associated with infertility. However, our patients were able to conceive, emphasizing the need for genetic counselling in affected patients with this condition.

MO615: The Lund Mets Rat, An Obese Type 2 Diabetic Preclinical Model, Develops Non-Alcoholic Steatohepatitis, Diabetic Nephropathy and Heart Failure with Preserved Ejection Fraction Under High Fat/Cholesterol/Fructose Diet

Abstract BACKGROUND AND AIMS Beyond the glucose control, anti-diabetic drugs need to demonstrate benefits on metabolic comorbidities. An animal model that recapitulates obesity and type 2 diabetes (T2D) comorbidities [i.e. non-alcoholic steato-hepatitis (NASH), nephropathy and heart failure with preserved ejection fraction (HFpEF)] is still needed for preclinical drug development. To overcome this limitation, we evaluated the effects of a high fat/cholesterol/fructose (HFCF) diet in the Lund MetS rat, a congenic BBDR.cg-lepr.cp model generated by introgression of the Koletsky leptin receptor mutation into the BioBreeding Diabetes Resistant (BBDR) rat. METHOD 17-week-old, male, lean control (ctrl) or Lund MetS obese T2D rats were fed a control chow (CC) diet or a HFCF diet, respectively for 8 weeks. Blood biochemistry was measured at 0, 4 and 8 weeks of diet. Kidney, heart and liver parameters were assessed at the end of the 8-week diet period. RESULTS Compared with ctrl, Lund MetS rats were obese (56% higher body weight) and diabetic with significantly higher %HbA1c (up to + 3%) and blood glucose levels (up to 3-fold higher) during the 8-week HFCF diet period. Significantly higher plasma insulin (up to 11-fold), total cholesterol (up to 5-fold), triglycerides (up to 8-fold), transaminases (up to 10-fold higher) levels were also observed in Lund MetS rats, as compared with ctrl. Hepatic total cholesterol, triglycerides and fatty acids levels were significantly higher in Lund Mets rats (14-, 7.3- and 6.7-fold higher as compared to ctrl, respectively). Liver histopathological scoring confirmed a NASH phenotype in Lund MetS rats fed the HFCF diet with strong liver steatosis, hepatic inflammation and portal to bridging fibrosis. Kidney function was substantially altered with a 60% decline in glomerular filtration rate and a 16-fold increase in urine albumin-to-creatinine ratio (both P < 0.0001 versus ctrl). Finally, echocardiography indicated diastolic dysfunction with significantly reduced E/A and greater E/e’ ratios, along with a preserved ejection fraction in Lund MetS rats, as compared with lean ctrl. CONCLUSION The present data demonstrate that the Lund MetS rat fed an HFCF diet that recapitulates the major metabolic comorbidities of obesity/T2D and may be a useful model for preclinical drug development.