The molecular genetics of rodent single gene obesities

An obesogenic diet impairs uncoupled substrate oxidation and promotes whitening of the brown adipose tissue in rats

Brown adipose tissue (BAT) is rich in mitochondria containing uncoupling protein 1 (UCP1), and dissipates energy through thermogenesis. However, even though BAT mass and its UCP1 content increase in rodents chronically fed a high-fat sucrose-enriched (HFS) diet, marked expansion of adiposity still occurs in these animals, suggesting insufficient BAT-mediated HFS diet-induced thermogenesis. Thus, the objective of this study was to investigate the metabolic and molecular mechanisms that regulate BAT thermogenesis in HFS-induced obesity. To accomplish this, rats were fed either a standard chow or HFS diet for 8 weeks. Subsequently, glucose and fatty acid metabolism and the molecular mechanisms underlying these processes were assessed in freshly isolated primary BAT adipocytes. Despite increasing BAT mass and its UCP1 content, the HFS diet reduced uncoupled glucose and palmitate oxidation in BAT adipocytes. It also markedly diminished tyrosine hydroxylase content and lipolysis in these cells. Conversely, glucose uptake, lactate production, glycerol incorporation into lipids, palmitate incorporation into triacylglycerol (TAG), phosphoenolpyruvate carboxykinase and glycerol kinase levels, and lipoprotein lipase and cluster of differentiation 36 gene expression were increased. In summary, a HFS diet enhanced glyceroneogenesis and shifted BAT metabolism toward TAG synthesis by impairing UCP1-mediated substrate oxidation and by enhancing fatty acid esterification in intact brown adipocytes. These adaptive metabolic responses to chronic HFS feeding attenuated BAT thermogenic capacity and favoured the development of obesity. KEY POINTS: Despite increasing brown adipose tissue (BAT) mass and levels of thermogenic proteins such as peroxisome proliferator-activated receptor γ coactivator 1α, carnitine palmitoyltransferase 1B and uncoupling protein 1 (UCP1), an obesogenic high-fat sucrose-enriched (HFS) diet attenuated uncoupled glucose and fatty acid oxidation in brown adipocytes. Brown adipocytes diverted glycerol and fatty acids toward triacylglycerol (TAG) synthesis by elevating the cellular machinery that promotes fatty acid uptake along with phosphoenolpyruvate carboxykinase and glycerol kinase levels. The HFS diet increased glucose uptake that supported lactate production and provided substrate for glyceroneogenesis and TAG synthesis in brown adipocytes. Impaired UCP-1-mediated thermogenic capacity and enhanced TAG storage in BAT adipocytes were consistent with reduced adipose triglyceride lipase and tyrosine hydroxylase levels in HFS diet-fed animals.

Chronic Elevation of Skeletal Muscle [Ca2+]i Impairs Glucose Uptake. An in Vivo and in Vitro Study

Skeletal muscle is the primary site of insulin-mediated glucose uptake through the body and, therefore, an essential contributor to glucose homeostasis maintenance. We have recently provided evidence that chronic elevated intracellular Ca²⁺ concentration at rest [(Ca²⁺)_i] compromises glucose homeostasis in malignant hyperthermia muscle cells. To further investigate how chronic elevated muscle [Ca²⁺]_i modifies insulin-mediated glucose homeostasis, we measured [Ca²⁺]_i and glucose uptake in vivo and in vitro in intact polarized muscle cells from glucose-intolerant RYR1-p.R163C and db/db mice. Glucose-intolerant RYR1-p.R163C and db/db mice have significantly elevated muscle [Ca²⁺]_i and reduced muscle glucose uptake compared to WT muscle cells. Dantrolene treatment (1.5 mg/kg IP injection for 2 weeks) caused a significant reduction in fasting blood glucose levels and muscle [Ca²⁺]_i and increased muscle glucose uptake compared to untreated RYR1-p.R163C and db/db mice. Furthermore, RYR1-p.R163C and db/db mice had abnormal basal insulin levels and response to glucose-stimulated insulin secretion. In vitro experiments conducted on single muscle fibers, dantrolene improved insulin-mediated glucose uptake in RYR1-p.R163C and db/db muscle fibers without affecting WT muscle fibers. In muscle cells with chronic elevated [Ca²⁺]_i, GLUT4 expression was significantly lower, and the subcellular fraction (plasma membrane/cytoplasmic) was abnormal compared to WT. The results of this study suggest that i) Chronic elevated muscle [Ca²⁺]_i decreases insulin-stimulated glucose uptake and consequently causes hyperglycemia; ii) Reduced muscle [Ca²⁺]_i by dantrolene improves muscle glucose uptake and subsequent hyperglycemia; iii) The mechanism by which chronic high levels of [Ca²⁺]_i interfere with insulin action appears to involve the expression of GLUT4 and its subcellular fractionation.

The importance of estradiol for body weight regulation in women

Obesity in women of reproductive age has a number of adverse metabolic effects, including Type II Diabetes (T2D), dyslipidemia, and cardiovascular disease. It is associated with increased menstrual irregularity, ovulatory dysfunction, development of insulin resistance and infertility. In women, estradiol is not only critical for reproductive function, but they also control food intake and energy expenditure. Food intake is known to change during the menstrual cycle in humans. This change in food intake is largely mediated by estradiol, which acts directly upon anorexigenic and orexigenic neurons, largely in the hypothalamus. Estradiol also acts indirectly with peripheral mediators such as glucagon like peptide-1 (GLP-1). Like estradiol, GLP-1 acts on receptors at the hypothalamus. This review describes the physiological and pathophysiological mechanisms governing the actions of estradiol during the menstrual cycle on food intake and energy expenditure and how estradiol acts with other weight-controlling molecules such as GLP-1. GLP-1 analogs have proven to be effective both to manage obesity and T2D in women. This review also highlights the relationship between steroid hormones and women's mental health. It explains how a decline or imbalance in estradiol levels affects insulin sensitivity in the brain. This can cause cerebral insulin resistance, which contributes to the development of conditions such as Parkinson's or Alzheimer's disease. The proper use of both estradiol and GLP-1 analogs can help to manage obesity and preserve an optimal mental health in women by reducing the mechanisms that trigger neurodegenerative disorders.

Heart failure in diabetes

Heart failure and cardiovascular disorders represent the leading cause of death in diabetic patients. Here we present a systematic review of the main mechanisms underlying the development of diabetic cardiomyopathy. We also provide an excursus on the relative contribution of cardiomyocytes, fibroblasts, endothelial and smooth muscle cells to the pathophysiology of heart failure in diabetes. After having described the preclinical tools currently available to dissect the mechanisms of this complex disease, we conclude with a section on the most recent updates of the literature on clinical management.

Central 5-HTR2C in the Control of Metabolic Homeostasis

The 5-hydroxytryptamine 2C receptor (5-HTR2C) is a class G protein-coupled receptor (GPCR) enriched in the hypothalamus and the brain stem, where it has been shown to regulate energy homeostasis, including feeding and glucose metabolism. Accordingly, 5-HTR2C has been the target of several anti-obesity drugs, though the associated side effects greatly curbed their clinical applications. Dissecting the specific neural circuits of 5-HTR2C-expressing neurons and the detailed molecular pathways of 5-HTR2C signaling in metabolic regulation will help to develop better therapeutic strategies towards metabolic disorders. In this review, we introduced the regulatory role of 5-HTR2C in feeding behavior and glucose metabolism, with particular focus on the molecular pathways, neural network, and its interaction with other metabolic hormones, such as leptin, ghrelin, insulin, and estrogens. Moreover, the latest progress in the clinical research on 5-HTR2C agonists was also discussed.

Adults with pathogenic MC4R mutations have increased final height and thereby increased bone mass

Pathogenic mutations in the melanocortin-4 receptor (MC4R) are associated with obesity, increased linear growth, and higher bone mass in children, and rodent studies have indicated an effect of the MC4R on bone turnover. Furthermore, GLP-1 receptor agonists (GLP-1 RAs) may influence bone metabolism. However, these associations have not been assessed in adults with pathogenic MC4R mutations. Thus, we wished to assess the impact of the MC4R on bone mass and metabolism. Secondly, we wished to investigate the impact of the GLP-1 RA liraglutide on bone mass in adults with pathogenic MC4R mutations. 17 patients with obesity-causing MC4R mutations (BMI: 35.5 ± 7.6) and 35 matched control participants with common obesity (BMI: 34.3 ± 7.1) underwent a DEXA scan for assessment of bone mineral density (BMD), bone mineral apparent density [BMAD = (BMD/√(bone area)], and bone turnover markers (BTMs). Individuals with a BMI above 28 (14 MC4R mutation carriers and 28 matched control participants) underwent 16 weeks treatment with liraglutide 3.0 mg. The MC4R group had higher BMD [mean difference: 0.065 g/m² (- 0.008 to 0.138), p = 0.03], but BMAD and BTMS were not different compared to the control group. In response to liraglutide, BMAD increased in the control group, compared to no change in the MC4R group [mean group difference: 0.0007 (0.0001-0.001), p = 0.04]. In conclusion, BMD is increased in MC4R causal obesity compared to common obesity, but when corrected for body size (BMAD), bone mass was not increased, and no evidence of an influence of the MC4R on bone metabolism in adults was found. Liraglutide treatment did not change bone metabolism in MC4R causal obesity, but increased bone mass as measured by BMAD in common obesity.

Increased arrhythmia susceptibility in type 2 diabetic mice related to dysregulation of ventricular sympathetic innervation

Patients with type 2 diabetes mellitus (T2DM) have a greater risk of developing life-threatening cardiac arrhythmias. Because the underlying mechanisms and potential influence of diabetic autonomic neuropathy are not well understood, we aimed to assess the relevance of a dysregulation in cardiac autonomic tone. Ventricular arrhythmia susceptibility was increased in Langendorff-perfused hearts isolated from mice with T2DM (db/db). Membrane properties and synaptic transmission were similar at cardiac postganglionic parasympathetic neurons from diabetic and control mice; however, a greater asynchronous neurotransmitter release was present at sympathetic postganglionic neurons from the stellate ganglia of db/db mice. Western blot analysis showed a reduction of tyrosine hydroxylase (TH) from the ventricles of db/db mice, which was confirmed with confocal imaging as a heterogeneous loss of TH-immunoreactivity from the left ventricular wall but not the apex. In vivo stimulation of cardiac parasympathetic (vagus) or cardiac sympathetic (stellate ganglion) nerves induced similar changes in heart rate in control and db/db mice, and the kinetics of pacing-induced Ca²⁺ transients (recorded from isolated cardiomyocytes) were similar in control and db/db cells. Antagonism of cardiac muscarinic receptors did not affect the frequency or severity of arrhythmias in db/db mice, but sympathetic blockade with propranolol completely inhibited arrhythmogenicity. Collectively, these findings suggest that the increased ventricular arrhythmia susceptibility of type 2 diabetic mouse hearts is due to dysregulation of the sympathetic ventricular control.NEW & NOTEWORTHY Patients with type 2 diabetes mellitus have greater risk of suffering from sudden cardiac death. We found that the increased ventricular arrhythmia susceptibility in type 2 diabetic mouse hearts is due to cardiac sympathetic dysfunction. Sympathetic dysregulation is indicated by an increased asynchronous release at stellate ganglia, a heterogeneous loss of tyrosine hydroxylase from the ventricular wall but not apex, and inhibition of ventricular arrhythmias in db/db mice after β-sympathetic blockade.

Enhanced Activity by NKCC1 and Slc26a6 Mediates Acidic pH and Cl- Movement after Cardioplegia-Induced Arrest of db/db Diabetic Heart

Diabetic heart dysfunctions during cardiac surgeries have revealed several clinical problems associated with ion imbalance. However, the mechanism of ion imbalance mediated by cardioplegia and a diabetic heart is largely unclear. We hypothesized that ion transporters might be regulated differently in the diabetic heart and that the differentially regulated ion transporters may involve in ion imbalance of the diabetic heart after cardioplegic arrest. In this study, we modified the Langendorff-free cardioplegia method and identified the involved ion transporters after cardioplegia-induced arrest between wild type and db/db heart. Enhanced expression of Na⁺-K⁺-2Cl⁻ cotransporter 1 (NKCC1) was observed in the db/db heart compared to the wild type heart. Enhanced NKCC1 activity was observed in the left ventricle of db/db mice compared to that of wild type after cardioplegia-induced arrest. The expression and activity of Slc26a6, a dominant Cl⁻/HCO₃⁻ exchanger in cardiac tissues, were enhanced in left ventricle strips of db/db mice compared to that of wild type. The Cl⁻ transporting activity in left ventricle strips of db/db mice was dramatically increased as compared to that of wild type. Interestingly, expression of Slc26a6, as well as carbonic anhydrase IV as a supportive enzyme of Slc26a6, was increased in db/db cardiac strips compared to wild type cardiac strips. Thus, the enhanced Cl⁻ transporting activity and expression by NKCC1 and Slc26a6 in db/db cardiac tissues after cardioplegia-induced arrest provide greater insight into enhanced acidosis and Cl⁻ movement-mediated db/db heart dysfunction. Thus, we suggested that enhanced Cl⁻ influx and HCO₃⁻ efflux through NKCC1 and Slc26a6 offer more acidic circumstances in the diabetic heart after cardioplegic arrest. These transporters should be considered as potential therapeutic targets to develop the next generation of cardioplegia solution for protection against ischemia-reperfusion injury in diabetic hearts.

Anti-inflammatory and angiogenic effects of exercise training in cardiac muscle of diabetic mice

Background: Improved glycemic control and cardiovascular function are major benefits of regular exercise training (ET) in type 2 diabetes. Recent work has demonstrated that ET improves cardiac and vascular functions independent of obesity, inflammation, and glucose control in the diabetic db/db mouse. In this study, we determined whether ET can overcome the effects of elevated inflammatory cytokines and hyperglycemia on markers of cardiac angiogenesis and inflammation in the diabetic mouse. Methods: Male diabetic db/db mice were assigned to a sedentary and exercise-trained group. Sedentary lean control littermates were used as controls. ET was performed at moderate intensity on a treadmill 5 days a week for a period of 8 weeks. After ET, blood was collected for assay of glucose, hemoglobin (HB and HB_1AC), C-reactive protein (CRP), and IL-6. Markers of inflammation and insulin resistance (IL-6, IL-1β, and tumor necrosis factor-alpha [TNF-α]) and angiogenesis (endothelial nitric oxide synthase [eNOS], vascular endothelial growth factor-A [VEGF-A], and hypoxia-inducible factor-1α [HIF-1α]) were measured in hearts. Results: Diabetic db/db mice remained obese and hyperglycemic after ET. Percent total HB and HB_1AC were significantly higher in ET db/db mice compared to sedentary db/db mice, indicating further deterioration of glucose control with ET. Plasma levels of CRP and IL-6 were higher in sedentary db/db mice compared to control mice and were unaffected by ET. However, in the presence of hyperglycemia and elevated plasma cytokines, protein expression of eNOS, mRNA expression of VEGF-A, and HIF-1α was increased in db/db hearts after ET. On the other hand, protein expression of TNF-α and mRNA expression IL-6 and IL-1β was significantly decreased by ET in hearts of db/db mice. Conclusion: Our results indicate that ET improves cardiac markers of angiogenesis, insulin resistance, and endothelial dysfunction in the db/db mouse. This was observed independently of obesity, hyperglycemia, and the systemic inflammatory state.

Central regulation of energy metabolism by estrogens

BACKGROUND

Estrogenic actions in the brain prevent obesity. Better understanding of the underlying mechanisms may facilitate development of new obesity therapies.

SCOPE OF REVIEW

This review focuses on the critical brain regions that mediate effects of estrogens on food intake and/or energy expenditure, the molecular signals that are involved, and the functional interactions between brain estrogens and other signals modulating metabolism. Body weight regulation by estrogens in male brains will also be discussed.

MAJOR CONCLUSIONS

17β-estradiol acts in the brain to regulate energy homeostasis in both sexes. It can inhibit feeding and stimulate brown adipose tissue thermogenesis. A better understanding of the central actions of 17β-estradiol on energy balance would provide new insight for the development of therapies against obesity in both sexes.

Astragaloside IV improves lipid metabolism in obese mice by alleviation of leptin resistance and regulation of thermogenic network

Obesity is a worldwide threat to public health in modern society, which may result from leptin resistance and disorder of thermogenesis. The present study investigated whether astragaloside IV (ASI) could prevent obesity in high-fat diet (HFD)-fed and db/db mice. In HFD-fed mice, ASI prevented body weight gain, lowered serum triglyceride and total cholesterol levels, mitigated liver lipid accumulation, reduced fat tissues and decreased the enlargement of adipose cells. In metabolic chambers, ASI lessened appetite of the mice, decreased their respiratory exchange ratio and elevated VCO₂ and VO₂ without altering circadian motor activity. Moreover, ASI modulated thermogenesis associated gene expressions in liver and brawn fat tissues, as well as leptin resistance evidenced by altered expressions of leptin, leptin receptor (ObR) or appetite associated genes. In SH-SY5Y cells, ASI enhanced leptin signaling transduction. However, in db/db mice, ASI did not change body weight gain and appetite associated genes. But it decreased serum triglyceride and total cholesterol levels as well as liver triglyceride. Meanwhile, it significantly modulated gene expressions of PPARα, PGC1-α, UCP2, ACC, SCD1, LPL, AP2, CD36 and SREBP-1c. Collectively, our study suggested that ASI could efficiently improve lipid metabolism in obese mice probably through enhancing leptin sensitivity and modulating thermogenic network.

A novel animal model of impaired glucose tolerance induced by the interaction of vitamin E deficiency and (60)Co radiation

Impaired glucose tolerance (IGT), known as the prediabetes stage, is usually induced by habits of life or environmental factors. Established IGT animal models are mostly conducted with chemical compounds such as streptozocin or genetic modification. However, the occasion of exposure to these factors in daily life is seldom. The objective of this study was to establish a new animal model of IGT induced by VE deficiency in diet and exposure to radiation. SD rats were treated individually or in combination of these two factors. In the combination group, the calculated insulin sensitivity index decreased; then HOMA-β value increased. Oxidative damage and IGT were observed. Insulin secretion level in perfusate from pancreas response to glucose was characterized by a rapid but reduced first phase and an obviously defective second phase upon pancreas perfusion. Histopathological images demonstrated the pathological changes. Western blotting analysis showed that the insulin signaling pathway was downregulated. The interaction of VE deficiency in diet and exposure to radiation could break the equilibrium of oxidation and antioxidation and result in IGT. More importantly, a new IGT model was successfully established which may be conducive to further research into development of drugs against human IGT.

Innate and ozone-induced airway hyperresponsiveness in obese mice: role of TNF-α

Innate airway hyperresponsiveness (AHR) and augmented responses to ozone, an asthma trigger, are characteristics of obese mice. Systemic inflammation, a condition of increased circulating concentrations of inflammatory moieties, occurs in obesity. We hypothesized that TNF-α, via its effects as a master effector of this systemic inflammation, regulates innate AHR and augmented responses to ozone in obese mice. Therefore, we examined pulmonary inflammation and airway responsiveness in unexposed or ozone-exposed (2 ppm for 3 h) lean wild-type and obese Cpe(fat) mice that were TNF-α sufficient or deficient. Cpe(fat) mice lack carboxypeptidase E, which regulates satiety. Compared with wild type, Cpe(fat) mice had elevated serum IL-17A, G-CSF, KC, MCP-1, IL-9, MIG, and leptin, indicating systemic inflammation. Despite reductions in most of these moieties in TNF-α-deficient vs. -sufficient Cpe(fat) mice, we observed no substantial difference in airway responsiveness in these two groups of mice. Ozone-induced increases in bronchoalveolar lavage (BAL) neutrophils and macrophages were lower, but ozone-induced AHR and increases in BAL hyaluronan, osteopontin, IL-13, and protein carbonyls, a marker of oxidative stress, were augmented in TNF-α-deficient vs. -sufficient Cpe(fat) mice. Our data indicate that TNF-α has an important role in promoting the systemic inflammation but not the innate AHR of obesity, suggesting that the systemic inflammation of obesity is not the major driver of this AHR. TNF-α is required for the augmented effects of acute ozone exposure on pulmonary inflammatory cell recruitment in obese mice, whereas TNF-α protects against ozone-induced AHR in obese mice, possibly by suppressing ozone-induced oxidative stress.

Recent advances in the development of farnesoid X receptor agonists

Farnesoid X receptors (FXRs) are nuclear hormone receptors expressed in high amounts in body tissues that participate in bilirubin metabolism including the liver, intestines, and kidneys. Bile acids (BAs) are the natural ligands of the FXRs. FXRs regulate the expression of the gene encoding for cholesterol 7 alpha-hydroxylase, which is the rate-limiting enzyme in BA synthesis. In addition, FXRs play a critical role in carbohydrate and lipid metabolism and regulation of insulin sensitivity. FXRs also modulate live growth and regeneration during liver injury. Preclinical studies have shown that FXR activation protects against cholestasis-induced liver injury. Moreover, FXR activation protects against fatty liver injury in animal models of nonalcoholic fatty liver disease (NAFLD) and nonalcoholic steatohepatitis (NASH), and improved hyperlipidemia, glucose intolerance, and insulin sensitivity. Obeticholic acid (OCA), a 6α-ethyl derivative of the natural human BA chenodeoxycholic acid (CDCA) is the first-in-class selective FXR agonist that is ~100-fold more potent than CDCA. Preliminary human clinical trials have shown that OCA is safe and effective. In a phase II clinical trial, administration of OCA was well-tolerated, increased insulin sensitivity and reduced markers of liver inflammation and fibrosis in patients with type II diabetes mellitus and NAFLD. In two clinical trials of OCA in patients with primary biliary cirrhosis (PBC), a progressive cholestatic liver disease, OCA significantly reduced serum alkaline phosphatase (ALP) levels, an important disease marker that correlates well with clinical outcomes of patients with PBC. Together, these studies suggest that FXR agonists could potentially be used as therapeutic tools in patients suffering from nonalcoholic fatty and cholestatic liver diseases. Larger and Longer-term studies are currently ongoing.

Recent advances in the development of farnesoid X receptor agonists

Farnesoid X receptors (FXRs) are nuclear hormone receptors expressed in high amounts in body tissues that participate in bilirubin metabolism including the liver, intestines, and kidneys. Bile acids (BAs) are the natural ligands of the FXRs. FXRs regulate the expression of the gene encoding for cholesterol 7 alpha-hydroxylase, which is the rate-limiting enzyme in BA synthesis. In addition, FXRs play a critical role in carbohydrate and lipid metabolism and regulation of insulin sensitivity. FXRs also modulate live growth and regeneration during liver injury. Preclinical studies have shown that FXR activation protects against cholestasis-induced liver injury. Moreover, FXR activation protects against fatty liver injury in animal models of nonalcoholic fatty liver disease (NAFLD) and nonalcoholic steatohepatitis (NASH), and improved hyperlipidemia, glucose intolerance, and insulin sensitivity. Obeticholic acid (OCA), a 6α-ethyl derivative of the natural human BA chenodeoxycholic acid (CDCA) is the first-in-class selective FXR agonist that is ~100-fold more potent than CDCA. Preliminary human clinical trials have shown that OCA is safe and effective. In a phase II clinical trial, administration of OCA was well-tolerated, increased insulin sensitivity and reduced markers of liver inflammation and fibrosis in patients with type II diabetes mellitus and NAFLD. In two clinical trials of OCA in patients with primary biliary cirrhosis (PBC), a progressive cholestatic liver disease, OCA significantly reduced serum alkaline phosphatase (ALP) levels, an important disease marker that correlates well with clinical outcomes of patients with PBC. Together, these studies suggest that FXR agonists could potentially be used as therapeutic tools in patients suffering from nonalcoholic fatty and cholestatic liver diseases. Larger and Longer-term studies are currently ongoing.

Obesity and genomics: role of technology in unraveling the complex genetic architecture of obesity

Obesity is a complex and multifactorial disease that occurs as a result of the interaction between "obesogenic" environmental factors and genetic components. Although the genetic component of obesity is clear from the heritability studies, the genetic basis remains largely elusive. Successes have been achieved in identifying the causal genes for monogenic obesity using animal models and linkage studies, but these approaches are not fruitful for polygenic obesity. The developments of genome-wide association approach have brought breakthrough discovery of genetic variants for polygenic obesity where tens of new susceptibility loci were identified. However, the common SNPs only accounted for a proportion of heritability. The arrival of NGS technologies and completion of 1000 Genomes Project have brought other new methods to dissect the genetic architecture of obesity, for example, the use of exome genotyping arrays and deep sequencing of candidate loci identified from GWAS to study rare variants. In this review, we summarize and discuss the developments of these genetic approaches in human obesity.

Differentiation of hypothalamic-like neurons from human pluripotent stem cells

The hypothalamus is the central regulator of systemic energy homeostasis, and its dysfunction can result in extreme body weight alterations. Insights into the complex cellular physiology of this region are critical to the understanding of obesity pathogenesis; however, human hypothalamic cells are largely inaccessible for direct study. Here, we developed a protocol for efficient generation of hypothalamic neurons from human embryonic stem cells (ESCs) and induced pluripotent stem cells (iPSCs) obtained from patients with monogenetic forms of obesity. Combined early activation of sonic hedgehog signaling followed by timed NOTCH inhibition in human ESCs/iPSCs resulted in efficient conversion into hypothalamic NKX2.1+ precursors. Application of a NOTCH inhibitor and brain-derived neurotrophic factor (BDNF) further directed the cells into arcuate nucleus hypothalamic-like neurons that express hypothalamic neuron markers proopiomelanocortin (POMC), neuropeptide Y (NPY), agouti-related peptide (AGRP), somatostatin, and dopamine. These hypothalamic-like neurons accounted for over 90% of differentiated cells and exhibited transcriptional profiles defined by a hypothalamic-specific gene expression signature that lacked pituitary markers. Importantly, these cells displayed hypothalamic neuron characteristics, including production and secretion of neuropeptides and increased p-AKT and p-STAT3 in response to insulin and leptin. Our results suggest that these hypothalamic-like neurons have potential for further investigation of the neurophysiology of body weight regulation and evaluation of therapeutic targets for obesity.

Description of the sphingolipid content and subspecies in the diabetic cornea

PURPOSE

Diabetes mellitus (DM) is characterized by high blood sugar levels over a prolonged period. Long term complications include but not limited heart disease, stroke, kidney failure, and ocular damage. An estimated 382 million people are diagnosed with Type 2 DM accounting for 90% of the cases. Common corneal dysfunctions associated with DM result in impaired vision due to decreased wound healing, corneal edema, and altered epithelial basement membrane. Lipids play a fundamental role in tissue metabolism and disease states. We attempt to determine the role of sphingolipids (SPL) in human Type I and Type II diabetic corneas.

MATERIALS AND METHODS

Cadaver corneas from healthy (non-diabetic/no ocular trauma), Type I (T1DM), and Type II diabetic (T2DM) donors were obtained and processed for lipidomics using LC-MS/MS.

RESULTS

Our data show significant differences in the SPL composition between control, T1DM and T2DM corneas. Both T1DM and T2DM showed a 10-folddownregulation of sphingomyelin(SM), 5-fold up regulation of Ceramides (Cer) and 2-fold upregulation of monohexosylceramides (MHC). Differences were also seen in total amounts of SPL where Cer was increased by approximately 3 fold in both T1DM and T2DM where SM decreased by 50% in both T1DM and T2DM when compared to healthy controls. No differences were seen in MHC amounts.

CONCLUSIONS

Overall, our data indicate major differences in SPL distribution in human diabetic corneas. Information on the sphingolipids role in cornea, corneal cell physiology, and diseases are very limitedwhich highlights the importance of these findings.

Further characterization of diabetes mellitus and body weight loss in males of the congenic mouse strain DDD.Cg-A(y.)

The A^y allele at the agouti locus causes obesity and promotes linear growth in mice. However, body weight gain stops between 16 and 17 weeks after birth, and then, body weight decreases gradually in DDD.Cg-A^y male mice. Body weight loss is a consequence of diabetes mellitus, which is genetically controlled mainly by a quantitative trait locus (QTL) on chromosome 4. This study aimed to further characterize diabetes mellitus and body weight loss in DDD.Cg-A^y males. The number of β-cells was markedly reduced, and plasma insulin levels were very low in the DDD.Cg-A^y males. Using a backcross progeny of DDD × (B6 × DDD.Cg-A^y) F₁-A^y, we identified one significant QTL for plasma insulin levels on distal chromosome 4, which was coincidental with QTL for hyperglycemia and lower body weight. The DDD allele was associated with decreased plasma insulin levels. When the DDD.Cg-A^y males were housed under three different housing conditions [group housing (4 or 5 DDD.Cg-A^y and DDD males), individual housing (single DDD.Cg-A^y male) and single male housing with females (single DDD.Cg-A^y male with DDD.Cg-A^y or DDD females)], diabetes mellitus and body weight loss were most severely expressed in individually housed mice. Thus, the severity of diabetes and body weight loss in the DDD.Cg-A^y males was strongly influenced by the housing conditions. These results demonstrate that both genetic and nongenetic environmental factors are involved in the development of diabetes mellitus and body weight loss in the DDD.Cg-A^y males.

A gain-of-function mutation in adenylate cyclase 3 protects mice from diet-induced obesity

In a screen for genes that affect the metabolic response to high-fat diet (HFD), we selected one line of N-ethyl-N-nitrosourea (ENU)-mutagenized mice, Jll, with dominantly inherited resistance to diet-induced obesity (DIO). Mutant animals had dramatically reduced body weight and fat mass, and low basal insulin and glucose levels relative to unaffected controls. Both white adipose tissue (WAT) and brown adipose tissue (BAT) depots were smaller in mutant animals. Mutant animals fed a HFD gained only slightly more weight than animals fed regular chow, and were protected from hepatic lipid accumulation. The phenotype was genetically linked to a 5.7-Mb interval on chromosome 12, and sequencing of the entire interval identified a single coding mutation, predicted to cause a methionine-to-isoleucine substitution at position 279 of the Adcy3 protein (Adcy3^M279I, henceforth referred to as Adcy3^Jll). The mutant protein is hyperactive, possibly constitutively so, producing elevated levels of cyclic AMP in a cell-based assay. These mice demonstrate that increased Adcy3 activity robustly protect animals from diet-induced metabolic derangements.

Effect of antigen sensitization and challenge on oscillatory mechanics of the lung and pulmonary inflammation in obese carboxypeptidase E-deficient mice

Atopic, obese asthmatics exhibit airway obstruction with variable degrees of eosinophilic airway inflammation. We previously reported that mice obese as a result of a genetic deficiency in either leptin (ob/ob mice) or the long isoform of the leptin receptor (db/db mice) exhibit enhanced airway obstruction in the presence of decreased numbers of bronchoalveolar lavage fluid (BALF) eosinophils compared with lean, wild-type mice following antigen (ovalbumin; OVA) sensitization and challenge. To determine whether the genetic modality of obesity induction influences the development of OVA-induced airway obstruction and OVA-induced pulmonary inflammation, we examined indices of these sequelae in mice obese as a result of a genetic deficiency in carboxypeptidase E, an enzyme that processes prohormones and proneuropeptides involved in satiety and energy expenditure (Cpe(fat) mice). Accordingly, Cpe(fat) and lean, wild-type (C57BL/6) mice were sensitized to OVA and then challenged with either aerosolized PBS or OVA. Compared with genotype-matched, OVA-sensitized and PBS-challenged mice, OVA sensitization and challenge elicited airway obstruction and increased BALF eosinophils, macrophages, neutrophils, IL-4, IL-13, IL-18, and chemerin. However, OVA challenge enhanced airway obstruction and pulmonary inflammation in Cpe(fat) compared with wild-type mice. These results demonstrate that OVA sensitization and challenge enhance airway obstruction in obese mice regardless of the genetic basis of obesity, whereas the degree of OVA-induced pulmonary inflammation is dependent on the genetic modality of obesity induction. These results have important implications for animal models of asthma, as modeling the pulmonary phenotypes for subpopulations of atopic, obese asthmatics critically depends on selecting the appropriate mouse model.

The genetic basis of obesity-associated type 2 diabetes (diabesity) in polygenic mouse models

Obesity-associated diabetes (“diabesity”) in mouse strains is characterized by severe insulin resistance, hyperglycaemia and progressive failure, and loss of beta cells. This condition is observed in inbred obese mouse strains such as the New Zealand Obese (NZO/HlLt and NZO/HlBomDife) or the TALLYHO/JngJ mouse. In lean strains such as C57BLKS/J, BTBR T+tf/J or DBA/2 J carrying diabetes susceptibility genes (“diabetes susceptible” background), it can be induced by introgression of the obesity-causing mutations Lep<ob> (ob) or Lepr<db> (db). Outcross populations of these models have been employed in the genome-wide search for mouse diabetes genes, and have led to positional cloning of the strong candidates Pctp, Tbc1d1, Zfp69, and Ifi202b (NZO-derived obesity) and Sorcs1,Lisch-like, Tomosyn-2, App, Tsc2, and Ube2l6 (obesity caused by the ob or db mutation). Some of these genes have been shown to play a role in the regulation of the human glucose or lipid metabolism. Thus, dissection of the genetic basis of obesity and diabetes in mouse models can identify regulatory mechanisms that are relevant for the human disease.

Reproductive function of the male obese Zucker rats: alteration in sperm production and sperm DNA damage

Obesity has been considered a public health issue in many countries and is of increasing concern for authorities over the past 6 years. The Zucker rat is a good experimental model for obesity and diabetes studies due to its metabolic characteristics that are similar to those developed by humans. A total of 12 obese Zucker rats and their lean littermates were killed in pubertal and young adult phases for assessing organ weights (testis and epididymis), testicular histomorphometric and stereological analyses, daily sperm production, and transit time in the epididymis. Sperm integrity was also investigated in the adult animals using the Comet assay. Alterations in organ weights, seminiferous epithelium architecture, sperm production, and transit time were noticed in the pubertal fatty rats. The volume density of the lymphatic space was decreased in both the ages. Adult animals had a significant increase in the extent of damage found in sperm DNA. Our results show for the first time that leptin receptor deficiency compromises sperm production during puberty and that genetic obese Zucker rats have increased sperm DNA fragmentation.

Expression of gluconeogenic enzymes and 11β-hydroxysteroid dehydrogenase type 1 in liver of diabetic mice after acute exercise

During acute exercise, normoglycemia is maintained by a precise match between hepatic glucose production and its peripheral utilization. This is met by a complex interplay of hepatic responses and glucose uptake by muscle. However, the effect of a single bout of exercise on hepatic gluconeogenesis, corticosterone (CORT) secretion, and glucose homeostasis in the db/db mouse model of type 2 diabetes is poorly understood. Diabetic db/db and lean control littermates were subjected to a 30 minute session of treadmill running and sacrificed either immediately after exercise or 8 hours later. Plasma glucose levels were markedly increased in db/db mice after exercise, whereas no change in glucose was observed in lean mice. Post-exercise measurements revealed that plasma CORT levels were also significantly increased in db/db mice compared to lean mice. Plasma hypothalamic corticotropin releasing hormone and pituitary adrenocorticotropic hormone levels were reciprocally decreased in both db/db and lean mice after exercise, indicating intact feedback mechanisms. Protein expression, determined by Western blot analysis, of the glucocorticoid receptor in liver was significantly increased in db/db mice subjected to prior exercise. In liver of db/db mice, a significant increase in the expression of phosphoenolpyruvate carboxykinase was noted compared to lean mice after exercise. However, no change in the expression of glucose-6-phosphatase (G6Pase) α or β was observed in db/db mice. Expression of 11β-hydroxysteroid dehydrogenase type 1 was increased significantly in db/db mice compared to lean mice after exercise. Our results show differences in plasma glucose and protein expression of gluconeogenic enzymes after acute exercise between lean and diabetic db/db mice. The db/db diabetic mouse is hyperglycemic after acute exercise. This hyperglycemic state may be explained, in part, by enhanced endogenous CORT secretion and regulated hepatic phosphoenolpyruvate carboxykinase and 11β-hydroxysteroid dehydrogenase type 1 protein expression.

Obese locus in WNIN/obese rat maps on chromosome 5 upstream of leptin receptor

WNIN/Obese (WNIN/Ob) rat a new mutant model of metabolic syndrome was identified in 1996 from an inbred Wistar rat strain, WNIN. So far several papers are published on this model highlighting its physical, biochemical and metabolic traits. WNIN/Ob is leptin resistant with unaltered leptin or its receptor coding sequences - the two well-known candidate genes for obesity. Genotyping analysis of F₂ progeny (raised from WNIN/Ob × Fisher - 344) in the present study localized the mutation to a recombinant region of 14.15cM on chromosome 5. This was further corroborated by QTL analysis for body weight, which narrowed this region to 4.43 cM with flanking markers D5Rat256 & D5Wox37. Interval mapping of body weight QTL shows that the LOD score peak maps upstream of leptin receptor and shows an additive effect suggesting this as a novel mutation and signifying the model as a valuable resource for studies on obesity and metabolic syndrome.

New allogeneic hematopoietic stem cell transplantation method: hematopoietic stem cell transplantation plus thymus transplantation for intractable diseases

Although allogeneic hematopoietic stem cell transplantation (allo-HSCT) has become a valuable strategy for some intractable diseases, a number of problems remain to be resolved. We have developed a new HSCT method, HSCT + thymus transplantation (TT) from the same donor, which induces elevated T cell function with mild graft-versus-host disease (GVHD) in comparison to conventional HSCT alone and HSCT + donor lymphocyte infusion (HSCT + DLI). This new method is effective in the treatment of several intractable diseases and conditions, such as autoimmune diseases in aging, advanced malignant tumors, exposure to supralethal irradiation, multiple organ transplantation from different donors, and type 2 diabetes mellitus, for which conventional methods are ineffective. Our findings suggest that allo-HSCT + TT is preferable to conventional allo-HSCT alone or allo-HSCT + DLI. This method may become a valuable next-generation HSCT technique.

Genetic background (DDD/Sgn versus C57BL/6J) strongly influences postnatal growth of male mice carrying the A(y) allele at the agouti locus: identification of quantitative trait loci associated with diabetes and body weight loss

Background

Mice carrying the A^y allele at the agouti locus become obese and are heavier than their non-A^y littermates. However, this does not hold true for the genetic background of the DDD mouse strain. At 22 weeks of age, DDD.Cg-A^y females are heavier than DDD females, whereas DDD.Cg-A^y males are lighter than DDD males. This study aimed to determine the possible cause and identify the genes responsible for the lower body weight of DDD.Cg-A^y males.

Results

Growth curves of DDD.Cg-A^y mice were analyzed and compared with those of B6.Cg-A^y mice from 5 to 25 weeks. In DDD.Cg-A^y males, body weight gain stopped between 16 and 17 weeks and the body weight gradually decreased; thus, the lower body weight was a consequence of body weight loss. Quantitative trait locus (QTL) mapping was performed in backcrossed (BC) males of DDD × (B6 × DDD.Cg-A^y) F₁-A^y mice. For the body weight at 25 weeks, significant QTLs were identified on chromosomes 1 and 4. The DDD allele was associated with a lower body weight at both loci. In particular, the QTL on chromosome 4 interacted with the A^y allele. Furthermore, suggestive QTLs for plasma glucose and high molecular weight adiponectin levels were coincidentally mapped to chromosome 4. The DDD allele was associated with increased glucose and decreased adiponectin levels. When the body weight at 25 weeks and plasma glucose levels were considered as dependent and independent variables, respectively, BC A^y males were classified into two groups according to statistical analysis using the partition method. Mice of one group had significantly higher glucose and lower adiponectin levels than those of the other group and exhibited body weight loss as observed with DDD-A^y males.

Conclusions

The lower body weight of DDD.Cg-A^y male mice was a consequence of body weight loss. Diabetes mellitus has been suggested to be a possible contributory factor causing body weight loss. The QTL on distal chromosome 4 contained the major responsible genes. This QTL interacted with the A^y allele, implying the reason why body weight loss occurs in DDD.Cg-A^y but not in DDD males.

Augmented pulmonary responses to acute ozone exposure in obese mice: roles of TNFR2 and IL-13

BACKGROUND

Acute ozone (O(3)) exposure results in greater inflammation and airway hyperresponsiveness (AHR) in obese versus lean mice.

OBJECTIVES

We examined the hypothesis that these augmented responses to O(3) are the result of greater signaling through tumor necrosis factor receptor 2 (TNFR2) and/or interleukin (IL)-13.

METHODS

We exposed lean wild-type (WT) and TNFR2-deficient (TNFR2(-/-)) mice, and obese Cpe(fat) and TNFR2-deficient Cpe(fat) mice (Cpe(fat)/TNFR2(-/-)), to O(3) (2 ppm for 3 hr) either with or without treatment with anti-IL-13 or left them unexposed.

RESULTS

O(3)-induced increases in baseline pulmonary mechanics, airway responsiveness, and cellular inflammation were greater in Cpe(fat) than in WT mice. In lean mice, TNFR2 deficiency ablated O(3)-induced AHR without affecting pulmonary inflammation; whereas in obese mice, TNFR2 deficiency augmented O(3)-induced AHR but reduced inflammatory cell recruitment. O(3) increased pulmonary expression of IL-13 in Cpe(fat) but not WT mice. Flow cytometry analysis of lung cells indicated greater IL-13-expressing CD(4+) cells in Cpe(fat) versus WT mice after O(3) exposure. In Cpe(fat) mice, anti-IL-13 treatment attenuated O(3)-induced increases in pulmonary mechanics and inflammatory cell recruitment, but did not affect AHR. These effects of anti-IL-13 treatment were not observed in Cpe(fat)/TNFR2(-/-) mice. There was no effect of anti-IL-13 treatment in WT mice.

CONCLUSIONS

Pulmonary responses to O(3) are not just greater, but qualitatively different, in obese versus lean mice. In particular, in obese mice, O(3) induces IL-13 and IL-13 synergizes with TNF via TNFR2 to exacerbate O(3)-induced changes in pulmonary mechanics and inflammatory cell recruitment but not AHR.

Hyperglycemia induced and intrinsic alterations in type 2 diabetes-derived osteoclast function

Periodontal disease-associated alveolar bone loss is a comorbidity of type-2-diabetes, where the roles of osteoclasts are poorly understood.

OBJECTIVE

To evaluate osteoclast differentiation and function in the context of type-2-diabetes.

MATERIALS AND METHODS

Bone marrow-derived osteoclasts from db/db mice, a model of type-2-diabetes, as well as human osteoclasts derived from peripheral blood of individuals with type-2-diabetes were evaluated for differentiation, resorption, and soluble mediator expression.

RESULTS

While db/db mice were hyperglycemic at time of cell harvest, human participants were glycemically controlled. Although db/db cultures resulted in a higher number of larger osteoclasts, individual cell receptor activator of nuclear factor kappaB ligand (RANKL)-mediated bone resorption was similar to that observed in diabetes-free osteoclasts. Osteoclasts derived from individuals with type-2-diabetes differentiated similarly to controls with again no difference in bone resorbing capacity. Murine and human type-2-diabetes cultures both displayed inhibition of lipopolysaccharide (LPS)-induced deactivation and increased pro-osteoclastogenic mediator expression.

CONCLUSIONS

Hyperglycemia plays a role in aberrant osteoclast differentiation leading to an increased capacity for bone resorption. Osteoclasts derived from murine models of and individuals with type-2-diabetes are unable to be inhibited by LPS, again leading to increased capacity for bone resorption. Here, environmental and intrinsic mechanisms associated with the increased alveolar bone loss observed in periodontal patients with type-2-diabetes are described.

QTL mapping of genes controlling plasma insulin and leptin concentrations: metabolic effect of obesity QTLs identified in an F2 intercross between C57BL/6J and DDD.Cg-A(y) inbred mice

DDD.Cg-A(y) female mice developed massive obesity as compared with B6.Cg-A(y) female mice. We previously identified quantitative trait loci (QTLs) for obesity on chromosomes 1, 6, 9 and 17 in F2 female mice, including F2A(y) (F2 mice with the A(y) allele) and F2 non- A(y) mice (F2 mice without the A(y) allele), produced by crossing C57BL/6J and DDD.Cg-A(y) strains. We here addressed the question whether the obesity QTLs share genetic bases with putative QTLs for plasma glucose, insulin and leptin concentrations. We performed QTL analyses for the first principal component (PC1) extracted from these metabolic measurements to identify the genes that contributed to the comprehensive evaluation of metabolic traits. By single QTL scans, we identified two significant QTLs for insulin concentration on chromosomes 6 and 12, three for leptin concentration on chromosomes 1, 6 and 17, and five for PC1 on chromosomes 1, 6, 12 (two loci) and 17. Although insulin and leptin concentrations and PC1 were not normally distributed in combined F2 mice, results of single QTL scans by parametric and non-parametric methods were very similar. Therefore, QTL scan by the parametric method was performed with the agouti locus genotype as a covariate. A significant QTL × covariate interaction was found for PC1 on chromosome 9. All obesity QTLs had significant metabolic effects. Thus, obesity- and diabetes-related traits in DDD.Cg-A(y) mice were largely controlled by QTLs on chromosomes 1, 6, 9, 12 and 17.

Quantitative trait locus mapping of genes that control body length and plasma insulin-like growth factor 1 level in mice

BACKGROUND

The Ay allele at the agouti locus causes obesity and promotes linear growth in mice. The effect of the Ay allele on obesity has been extensively investigated, whereas its effect on body length is only poorly analyzed. To gain insight into the genetic control of body length, quantitative trait locus (QTL) analysis was performed in F2 female mice produced by crossing C57BL/6 J females and DDD.Cg-Ay males. A congenic DDD.Cg-Ay strain was established by introgressing the Ay allele from the B6.Cg-Ay strain by backcrossing for 12 generations. DDD.Cg-Ay females were longer than B6.Cg-Ay females; therefore, QTLs that interact with the Ay allele may be identified for body length. In addition, QTL analysis was also performed for plasma insulin-like growth factor 1 (IGF1) levels because IGF1 is known to play essential roles in growth and development. If QTLs for IGF1 levels coincide with those for body length, we can gain endocrinological insight into the QTLs for body length.

RESULTS

Correlations between body length and IGF1 levels were statistically significant in F2 populations. For body length, two significant QTLs were identified on chromosomes 15 and 17. For IGF1 levels, three significant QTLs were identified on chromosomes 10, 12, and 19. QTLs on chromosomes 12 and 19 appeared to be novel, and the latter interacted with the Ay allele.

CONCLUSION

QTLs for body length and IGF1 levels contained candidate genes that were components of the growth hormone/insulin-like growth factor axis. However, there was no overlap between QTLs for these two traits. Contrary to our expectations, QTLs that interacted with the Ay allele were identified not for body length but for IGF1 levels. Body length and IGF1 levels were, thus, controlled by different sets of genes.

Hypercytolipidemia-induced nuclear lipoapoptosis: cytochemical analysis and integrated review of hypogonadal, diabetes-obesity syndrome-induced female reproductive axis disruption

Expression of the diabetes (db/db) mutation (i.e., leptin receptor defect) in C57BL/KsJ mice results in the functional suppression of the female pituitary-gonadal axis accompanied by premature utero-ovarian lipocytoatrophy. The current studies define the cytostructural, metabolic and endocrine disturbances associated with hypercytolipidemia and coincident nuclear lipoapoptosis following expression of the db/db-mutation. Adult, female C57BL/KsJ control (+/+ and +/? genotypes) and db/db mutant littermates were monitored for systemic alterations in blood glucose, insulin, luteinizing hormone (LH) and 17-B-estradiol (E2) concentrations associated with db/db-enhanced cytolipid depositions and TUNEL-labeled 3'-DNA fragmentation indexed nuclear lipoapoptosis. Obesity, hyperglycemia and hyperinsulinemia, in addition to depressed LH and E2 concentrations, characterized all db/db-mutants relative to control indices. Structural and cytochemical analysis of basophilic gonadotroph cells, ovarian follicular granulosa cells and uterine endometrial epithelial layers indicated that db/db mutants demonstrated prominent hypercytolipidemia relative to control cytoarchitecture profiles. Vasolipidemia and interstitial cytoadiposity were prominent in all db/db tissue compartments. In each affected cell type within the db/db pituitary-reproductive tract axis, hypercytolipidemia was localized with pronounced nuclear lipo-infiltration and 3'-DNA TUNEL-labeled fragmentation. These data indicate that coincident cytostructural, endocrine and metabolic disturbances associated with hypogonadal pituitary-reproductive tract hypercytolipidemia are functional manifestations of the expressed diabetes-obesity syndrome in db/db-mutants. The progressive vaso-, interstitial-, and cyto-lipidemic alterations in cytoarchitecture correlated with the coincident nuclear lipoapoptotic dissolution and pronounced organo-involution, alterations which contributed to the functional disruption of the pituitary-hypogonadal axis in C57BL/KsJ-db/db mice.

Insulin treatment directly restores neutrophil phagocytosis and bactericidal activity in diabetic mice and thereby improves surgical site Staphylococcus aureus infection

Bacterial infections, including surgical site infections (SSI), are a common and serious complication of diabetes. Staphylococcus aureus, which is eliminated mainly by neutrophils, is a major cause of SSI in diabetic patients. However, the precise mechanisms by which diabetes predisposes to staphylococcal infection are not fully elucidated. The effect of insulin on this infection is also not well understood. We therefore investigated the effect of insulin treatment on SSI and neutrophil function in diabetic mice. S. aureus was inoculated into the abdominal muscle in diabetic db/db and high-fat-diet (HFD)-fed mice with or without insulin treatment. Although the diabetic db/db mice developed SSI, insulin treatment ameliorated the infection. db/db mice had neutrophil dysfunction, such as decreased phagocytosis, superoxide production, and killing activity of S. aureus; however, insulin treatment restored these functions. Ex vivo treatment (coincubation) of neutrophils with insulin and euglycemic control by phlorizin suggest that insulin may directly activate neutrophil phagocytic and bactericidal activity independently of its euglycemic effect. However, insulin may indirectly restore superoxide production by neutrophils through its euglycemic effect. HFD-fed mice with mild hyperglycemia also developed more severe SSI by S. aureus than control mice and had impaired neutrophil phagocytic and bactericidal activity, which was improved by insulin treatment. Unlike db/db mice, in HFD mice, superoxide production was increased in neutrophils and subsequently suppressed by insulin treatment. Glycemic control by insulin also normalized the neutrophil superoxide-producing capability in HFD mice. Thus, insulin may restore neutrophil phagocytosis and bactericidal activity, thereby ameliorating SSI.

Role of TNFR1 in the innate airway hyperresponsiveness of obese mice

The purpose of this study was to examine the role of tumor necrosis factor receptor 1 (TNFR1) in the airway hyperresponsiveness characteristic of obese mice. Airway responsiveness to intravenous methacholine was measured using the forced oscillation technique in obese Cpe(fat) mice that were either sufficient or genetically deficient in TNFR1 (Cpe(fat) and Cpe(fat)/TNFR1(-/-) mice) and in lean mice that were either sufficient or genetically deficient in TNFR1 [wild-type (WT) and TNFR1(-/-) mice]. Compared with lean WT mice, Cpe(fat) mice exhibited airway hyperresponsiveness. Airway hyperresponsives was also greater in Cpe(fat)/TNFR1(-/-) than in Cpe(fat) mice. Compared with WT mice, Cpe(fat) mice had increases in bronchoalveolar lavage fluid concentrations of several inflammatory moieties including eotaxin, IL-9, IP-10, KC, MIG, and VEGF. These factors were also significantly elevated in Cpe(fat)/TNFR1(-/-) vs. TNFR1(-/-) mice. Additional moieties including IL-13 were also elevated in Cpe(fat)/TNFR1(-/-) vs. TNFR1(-/-) mice but not in Cpe(fat) vs. WT mice. IL-17A mRNA expression was greater in Cpe(fat)/TNFR1(-/-) vs. Cpe(fat) mice and in TNFR1(-/-) vs. WT mice. Analysis of serum indicated that obesity resulted in systemic as well as pulmonary inflammation, but TNFR1 deficiency had little effect on this systemic inflammation. Our results indicate that TNFR1 is protective against the airway hyperresponsiveness associated with obesity and suggest that effects on pulmonary inflammation may be contributing to this protection.

Obesity and airway responsiveness: role of TNFR2

Obese mice exhibit innate airway hyperresponsiveness (AHR), a feature of asthma. Tumor necrosis factor alpha (TNFα) is implicated in the disease progression and chronic inflammatory status of both obesity and asthma. TNF acts via two TNF receptors, TNFR1 and TNFR2. To examine the role of TNFR2 in the AHR observed in obese mice, we generated obese Cpe(fat) mice that were either sufficient or deficient in TNFR2 (Cpe(fat) and Cpe(fat)/TNFR2(-/-) mice, respectively) and compared them with their lean controls (WT and TNFR2(-/-) mice). Compared to WT mice, Cpe(fat) mice exhibited AHR to aerosolized methacholine (measured using the forced oscillation technique) which was ablated in Cpe(fat)/TNFR2(-/-) mice. Bioplex or ELISA assay indicated significant increases in serum leptin, G-CSF, IL-7, IL-17A, TNFα, and KC in obese versus lean mice, as well as significant obesity-related increases in bronchoalveolar lavage fluid (BALF) G-CSF and IP-10, regardless of TNFR2 status. Importantly, BALF IL-17A was significantly increased over lean controls in Cpe(fat) but not Cpe(fat)/TNFR2(-/-) mice. Functional annotation clustering of significantly affected genes identified from microarray analysis comparing gene expression in lungs of Cpe(fat) and WT mice, identified blood vessel morphogenesis as the gene ontology category most affected by obesity. This category included several genes associated with AHR, including endothelin and trkB. Obesity increased pulmonary mRNA expression of endothelin and trkB in TNFR2 sufficient but not deficient mice. Our results indicate that TNFR2 signaling is required for the innate AHR that develops in obese mice, and suggest that TNFR2 may act by promoting IL-17A, endothelin, and/or trkB expression.

Diabetes in mice with monogenic obesity: the db/db mouse and its use in the study of cardiac consequences

The leptin receptor deficient db/db mouse has served as a rodent model for obesity and type 2 diabetes for more than 40 years. Diabetic features in db/db mice follow an age-dependent progression, with early insulin resistance followed by an insulin secretory defect resulting in profound hyperglycemia. Diabetic db/db mice have been utilized to assess the cardiac consequences of diabetes, specifically evidence for a distinct diabetic cardiomyopathy. The db/db model is characterized by a contractile function deficit in the heart which becomes manifest 8-10 weeks after birth. Metabolic changes include an increased reliance on fatty acids and a decreased reliance on glucose as a fuel source for oxidative metabolism within the heart. As a mouse model for type 2 diabetes, both drug treatment and transgenic manipulation have proven beneficial towards improving metabolism and contractile function. The db/db mouse model has provided a useful resource to understand and treat the type 2 diabetic condition.

Central nervous control of energy and glucose balance: focus on the central melanocortin system

Studies have suggested that manipulations of the central melanocortin circuitry by pharmacological agents produce robust effects on the regulation of body weight and glucose homeostasis. In this review, we discuss recent findings from genetic mouse models that have further established the physiological relevance of this circuitry in the context of glucose and energy balance. In addition, we will discuss distinct neuronal populations that respond to central melanocortins to regulate food intake, energy expenditure, insulin sensitivity, and insulin secretion, respectively. Finally, multiple hormonal and neural cues (e.g., leptin, estrogen, and serotonin) that use the melanocortin systems to regulate energy and glucose homeostasis will be reviewed. These findings suggest that targeting the specific branches of melanocortin circuits may be potential avenues to combat the current obesity and diabetes epidemics.

Role of suppressor of cytokine signaling 3 in lipid metabolism: analysis based on a phage-display human liver cDNA library

Suppressor of cytokine signaling 3 (SOCS3) is a likely mediator of feedback inhibition on the leptin receptor and may cause physiological leptin-resistance, leading to the development of obesity. The aim of this study was to identify potential peptides interacting with purified SOCS3 by using a phage-display human liver cDNA library. We developed a T7 select phage-display system with purified SOCS3 as bait to screen a human liver cDNA library. After 4 rounds of screening and sequencing analysis, we found that phage-presenting peptide RGGVVTSNPLGF show significant binding to SOCS3. The peptide sequence was similar to the sequence of amino acids 644-655 of C-terminal extra-polypeptide of very-long-chain acyl-CoA dehydrogenase (VLCAD), which is 1 of 4 flavoproteins that catalyzing the initial step of the mitochondrial fatty acid β-oxidation, implying a close relationship between SOCS3 and VLCAD. We identified VLCAD as a novel SOCS3 interacting protein both in vitro and vivo, and found that SOCS3 mediates the ubiquitination pathway for proteasomal degradation of VLCAD C-terminal extra-polypeptide via its SOCS-box. Animal experimentation demonstrated that VLCAD is functionally involved in SOCS3 binding and thus, SOCS3 play an important role in the regulation of fatty acid β-oxidation. In conclusion, SOCS3 is an important factor for lipid metabolism and a potential drug-target for treatment of widespread obesity.

Molecular hydrogen improves obesity and diabetes by inducing hepatic FGF21 and stimulating energy metabolism in db/db mice

Recent extensive studies have revealed that molecular hydrogen (H(2)) has great potential for improving oxidative stress-related diseases by inhaling H(2) gas, injecting saline with dissolved H(2), or drinking water with dissolved H(2) (H(2)-water); however, little is known about the dynamic movement of H(2) in a body. First, we show that hepatic glycogen accumulates H(2) after oral administration of H(2)-water, explaining why consumption of even a small amount of H(2) over a short span time efficiently improves various disease models. This finding was supported by an in vitro experiment in which glycogen solution maintained H(2). Next, we examined the benefit of ad libitum drinking H(2)-water to type 2 diabetes using db/db obesity model mice lacking the functional leptin receptor. Drinking H(2)-water reduced hepatic oxidative stress, and significantly alleviated fatty liver in db/db mice as well as high fat-diet-induced fatty liver in wild-type mice. Long-term drinking H(2)-water significantly controlled fat and body weights, despite no increase in consumption of diet and water. Moreover, drinking H(2)-water decreased levels of plasma glucose, insulin, and triglyceride, the effect of which on hyperglycemia was similar to diet restriction. To examine how drinking H(2)-water improves obesity and metabolic parameters at the molecular level, we examined gene-expression profiles, and found enhanced expression of a hepatic hormone, fibroblast growth factor 21 (FGF21), which functions to enhance fatty acid and glucose expenditure. Indeed, H(2) stimulated energy metabolism as measured by oxygen consumption. The present results suggest the potential benefit of H(2) in improving obesity, diabetes, and metabolic syndrome.

Leptin promotes fibroproliferative acute respiratory distress syndrome by inhibiting peroxisome proliferator-activated receptor-γ

RATIONALE

Diabetic patients have a lower incidence of acute respiratory distress syndrome (ARDS), and those who develop ARDS are less likely to die. The mechanisms that underlie this protection are unknown.

OBJECTIVES

To determine whether leptin resistance, a feature of diabetes, prevents fibroproliferation after lung injury.

METHODS

We examined lung injury and fibroproliferation after the intratracheal instillation of bleomycin in wild-type and leptin-resistant (db/db) diabetic mice. We examined the effect of leptin on transforming growth factor (TGF)-β(1)-mediated transcription in primary normal human lung fibroblasts. Bronchoalveolar lavage fluid (BAL) samples from patients with ARDS and ventilated control subjects were obtained for measurement of leptin and active TGF-β(1) levels.

MEASUREMENTS AND MAIN RESULTS

Diabetic mice (db/db) were resistant to lung fibrosis. The db/db mice had higher levels of peroxisome proliferator-activated receptor-γ (PPARγ), an inhibitor of the transcriptional response to TGF-β(1), a cytokine critical in the pathogenesis of fibroproliferative ARDS. In normal human lung fibroblasts, leptin augmented the transcription of profibrotic genes in response to TGF-β(1) through a mechanism that required PPARγ. In patients with ARDS, BAL leptin levels were elevated and correlated with TGF-β(1) levels. Overall, there was no significant relationship between BAL leptin levels and clinical outcomes; however, in nonobese patients, higher BAL leptin levels were associated with fewer intensive care unit- and ventilator-free days and higher mortality.

CONCLUSIONS

Leptin signaling is required for bleomycin-induced lung fibrosis. Leptin augments TGF-β(1) signaling in lung fibroblasts by inhibiting PPARγ. These findings provide a mechanism for the observed protection against ARDS observed in diabetic patients.

New aspects of melanocortin signaling: a role for PRCP in α-MSH degradation

The role of the central melanocortin system in the regulation of energy metabolism has received much attention during the past decade since gene mutations of key components in melanocortin signaling cause monogenic forms of obesity in animals and humans. In the arcuate nucleus of the hypothalamus the prohormone proopiomelanocortin (POMC) is posttranslationally cleaved to produce α-melanocyte stimulating hormone (α-MSH), a peptide with anorexigenic effects upon activation of the melanocortin receptors (MCRs). α-MSH undergoes extensive post-translational processing and its in vivo activity is short lived due to rapid degradation. The enzymatic process that controls α-MSH inactivation is incompletely understood. Recent evidence suggests that prolyl carboxypeptidase (PRCP) is an enzyme responsible for α-MSH degradation. As for many key melanocortin peptides, gene mutation of PRCP causes a change in the metabolic phenotype of rodents. This review summarizes the current knowledge on the melanocortin system with particular focus on PRCP, a newly discovered component of the melanocortin system.

The genetic basis of obesity and type 2 diabetes: lessons from the new zealand obese mouse, a polygenic model of the metabolic syndrome

The New Zealand obese (NZO) mouse is a polygenic model of severe obesity and type 2 diabetes-like hyperglycaemia. Outcross experiments with lean strains have led to the identification of numerous susceptibility loci (quantitative trait loci (QTL)) for adiposity and/or hyperglycaemia. Several major QTL were successfully introgressed into lean strains, and two responsible genes, the RabGAP Tbc1d1 and the transcription factor Zfp69, were so far identified by a conventional strategy of positional cloning. Tbc1d1 controls substrate utilization in muscle; SJL mice carry a loss-of-function variant that shifts substrate oxidation from glucose to fat and suppresses adiposity as well as development of diabetes. The zinc finger domain transcription factor Zfp69 appears to regulate triglyceride storage in adipose tissue. Its normal allele Zfp69 causes a redistribution of triglycerides from gonadal stores to liver, and consequently enhances diabetes when introgressed from SJL into NZO, whereas the loss-of-function variant present in NZO and C57BL/6J reduces the prevalence of diabetes. Data from human patients suggest that the orthologs of both genes may play a role in the pathogenesis of the human metabolic syndrome. In addition to Tbc1d1 and Zfp69, variants of Lepr, Pctp, Abcg1, and Nmur2 located in other QTL were identified as potential candidates by sequencing and functional studies. These results indicate that dissection of the genetic basis of obesity and diabetes in mouse models can identify novel regulatory mechanisms that are relevant for the human disease.

Identification of 9-cis-retinoic acid as a pancreas-specific autacoid that attenuates glucose-stimulated insulin secretion

The all-trans-retinoic acid (atRA) isomer, 9-cis-retinoic acid (9cRA), activates retinoic acid receptors (RARs) and retinoid X receptors (RXRs) in vitro. RARs control multiple genes, whereas RXRs serve as partners for RARs and other nuclear receptors that regulate metabolism. Physiological function has not been determined for 9cRA, because it has not been detected in serum or multiple tissues with analytically validated assays. Here, we identify 9cRA in mouse pancreas by liquid chromatography/tandem mass spectrometry (LC/MS/MS), and show that 9cRA decreases with feeding and after glucose dosing and varies inversely with serum insulin. 9cRA reduces glucose-stimulated insulin secretion (GSIS) in mouse islets and in the rat β-cell line 832/13 within 15 min by reducing glucose transporter type 2 (Glut2) and glucokinase (GK) activities. 9cRA also reduces Pdx-1 and HNF4α mRNA expression, ∼8- and 80-fold, respectively: defects in Pdx-1 or HNF4α cause maturity onset diabetes of the young (MODY4 and 1, respectively), as does a defective GK gene (MODY2). Pancreas β-cells generate 9cRA, and mouse models of reduced β-cell number, heterozygous Akita mice, and streptozotocin-treated mice have reduced 9cRA. 9cRA is abnormally high in glucose-intolerant mice, which have β-cell hypertropy, including mice with diet-induced obesity (DIO) and ob/ob and db/db mice. These data establish 9cRA as a pancreas-specific autacoid with multiple mechanisms of action and provide unique insight into GSIS.