Long-term correction of obesity and diabetes in genetically obese mice by a single intramuscular injection of recombinant adeno-associated virus encoding mouse leptin

TW68, cryptochromes stabilizer, regulates fasting blood glucose levels in diabetic ob/ob and high fat-diet-induced obese mice

Cryptochromes (CRYs), transcriptional repressors of the circadian clock in mammals, inhibit cAMP production when glucagon activates G-protein coupled receptors. Therefore, molecules that modulate CRYs have the potential to regulate gluconeogenesis. In this study, we discovered a new molecule called TW68 that interacts with the primary pockets of mammalian CRY1/2, leading to reduced ubiquitination levels and increased stability. In cell-based circadian rhythm assays using U2OS Bmal1-dLuc cells, TW68 extended the period length of the circadian rhythm. Additionally, TW68 decreased the transcriptional levels of two genes, Phosphoenolpyruvate carboxykinase 1 (PCK1) and Glucose-6-phosphatase (G6PC), which play crucial roles in glucose biosynthesis during glucagon-induced gluconeogenesis in HepG2 cells. Oral administration of TW68 in mice showed good tolerance, a good pharmacokinetic profile, and remarkable bioavailability. Finally, when administered to fasting diabetic animals from ob/ob and HFD-fed obese mice, TW68 reduced blood glucose levels by enhancing CRY stabilization and subsequently decreasing the transcriptional levels of Pck1 and G6pc. These findings collectively demonstrate the antidiabetic efficacy of TW68 in vivo, suggesting its therapeutic potential for controlling fasting glucose levels in the treatment of type 2 diabetes mellitus.

Inhaled drug delivery for the targeted treatment of asthma

Asthma is a chronic lung disease affecting millions worldwide. While classically acknowledged to result from allergen-driven type 2 inflammatory responses leading to IgE and cytokine production and the influx of immune cells such as mast cells and eosinophils, the wide range in asthmatic pathobiological subtypes lead to highly variable responses to anti-inflammatory therapies. Thus, there is a need to develop patient-specific therapies capable of addressing the full spectrum of asthmatic lung disease. Moreover, delivery of targeted treatments for asthma directly to the lung may help to maximize therapeutic benefit, but challenges remain in design of effective formulations for the inhaled route. In this review, we discuss the current understanding of asthmatic disease progression as well as genetic and epigenetic disease modifiers associated with asthma severity and exacerbation of disease. We also overview the limitations of clinically available treatments for asthma and discuss pre-clinical models of asthma used to evaluate new therapies. Based on the shortcomings of existing treatments, we highlight recent advances and new approaches to treat asthma via inhalation for monoclonal antibody delivery, mucolytic therapy to target airway mucus hypersecretion and gene therapies to address underlying drivers of disease. Finally, we conclude with discussion on the prospects for an inhaled vaccine to prevent asthma.

Astragalus mongholicus powder, a traditional Chinese medicine formula ameliorate type 2 diabetes by regulating adipoinsular axis in diabetic mice

The global morbidity of obesity and type 2 diabetes mellitus (T2DM) has dramatically increased. Insulin resistance is the most important pathogenesis and therapeutic target of T2DM. The traditional Chinese medicine formula Astragalus mongholicus powder (APF), consists of Astragalus mongholicus Bunge [Fabaceae], Pueraria montana (Lour.) Merr. [Fabaceae], and Morus alba L. [Moraceae] has a long history to be used to treat diabetes in ancient China. This work aims to investigate the effects of APF on diabetic mice and its underlying mechanism. Diabetic mice were induced by High-fat-diet (HFD) and streptozotocin (STZ). The body weight of mice and their plasma levels of glucose, insulin, leptin and lipids were examined. Reverse transcription-polymerase chain reaction, histology, and Western blot analysis were performed to validate the effects of APF on diabetic mice and investigate the underlying mechanism. APF reduced hyperglycemia, hyperinsulinemia, and hyerleptinemia and attenuate the progression of obesity and non-alcoholic fatty liver disease (NAFLD). However, these effects disappeared in leptin deficient ob/ob diabetic mice and STZ-induced insulin deficient type 1 diabetic mice. Destruction of either these hormones would abolish the therapeutic effects of APF. In addition, APF inhibited the protein expression of PTP1B suppressing insulin–leptin sensitivity, the gluconeogenic gene PEPCK, and the adipogenic gene FAS. Therefore, insulin–leptin sensitivity was normalized, and the gluconeogenic and adipogenic genes were suppressed. In conclusion, APF attenuated obesity, NAFLD, and T2DM by regulating the balance of adipoinsular axis in STZ + HFD induced T2DM mice.

Secretion of functional α1-antitrypsin is cell type dependent: Implications for intramuscular delivery for gene therapy

Heterologous expression of proteins is used widely for the biosynthesis of biologics, many of which are secreted from cells. In addition, gene therapy and messenger RNA (mRNA) vaccines frequently direct the expression of secretory proteins to nonnative host cells. Consequently, it is crucial to understand the maturation and trafficking of proteins in a range of host cells including muscle cells, a popular therapeutic target due to the ease of accessibility by intramuscular injection. Here, we analyzed the production efficiency for α1-antitrypsin (AAT) in Chinese hamster ovary cells, commonly used for biotherapeutic production, and myoblasts (embryonic progenitor cells of muscle cells) and compared it to the production in the major natural cells, liver hepatocytes. AAT is a target protein for gene therapy to address pathologies associated with insufficiencies in native AAT activity or production. AAT secretion and maturation were most efficient in hepatocytes. Myoblasts were the poorest of the cell types tested; however, secretion of active AAT was significantly augmented in myoblasts by treatment with the proteostasis regulator suberoylanilide hydroxamic acid, a histone deacetylase inhibitor. These findings were extended and validated in myotubes (mature muscle cells) where AAT was transduced using an adeno-associated viral capsid transduction method used in gene therapy clinical trials. Overall, our study sheds light on a possible mechanism to enhance the efficacy of gene therapy approaches for AAT and, moreover, may have implications for the production of proteins from mRNA vaccines, which rely on the expression of viral glycoproteins in nonnative host cells upon intramuscular injection.

Evaluation of the Central Effects of Systemic Lentiviral-Mediated Leptin Delivery in Streptozotocin-Induced Diabetic Rats

Type 1 diabetes (T1D) is characterized by hyperphagia, hyperglycemia and activation of the hypothalamic-pituitary-adrenal (HPA) axis. We have reported previously that daily leptin injections help to alleviate these symptoms. Therefore, we hypothesized that leptin gene therapy could help to normalize the neuroendocrine dysfunction seen in T1D. Adult male Sprague Dawley rats were injected i.v. with a lentiviral vector containing the leptin gene or green fluorescent protein. Ten days later, they were injected with the vehicle or streptozotocin (STZ). HPA function was assessed by measuring norepinephrine (NE) levels in the paraventricular nucleus (PVN) and serum corticosterone (CS). Treatment with the leptin lentiviral vector (Lepvv) increased leptin and insulin levels in non-diabetic rats, but not in diabetic animals. There was a significant reduction in blood glucose levels in diabetic rats due to Lepvv treatment. Both NE levels in the PVN and serum CS were reduced in diabetic rats treated with Lepvv. Results from this study provide evidence that leptin gene therapy in STZ-induced diabetic rats was able to partially normalize some of the neuroendocrine abnormalities, but studies with higher doses of the Lepvv are needed to develop this into a viable option for treating T1D.

Genetics and the Elite Athlete: Our Understanding in 2020

Modern competitive sport has evolved so much that athletes would go to great extremes to develop themselves into champions; medicine has also evolved to the point that many genetic elements have been identified to be associated with specific athletic traits, and genetic alterations are also possible. The current review examines the published literature and looks at three important factors: genetic polymorphism influencing sporting ability, gene doping and genetic tendency to injury. The ACTN3 gene has an influence on type II muscle fibres, with the R allele being advantageous to power sports like sprinting and the XX genotype being associated with lower muscle strength and sprinting ability. The ACE gene polymorphisms are associated with cardio-respiratory efficiency and could influence endurance athletes. Many other genes are being looked at, with specific focus on those that are potentially related to enhancement of athletic ability. Recognition of these specific gene polymorphisms brings into play the concept of genetic engineering in athletes, which constitutes gene doping and is outlawed. This has the potential to develop into the next big threat in elite sports; gene doping could have dangerous and even fatal outcomes, as the knowledge of gene therapy is still in its infancy. Genetic predisposition to injury is also being identified; recent publications have increased the awareness of gene polymorphisms predisposing to injuries of ligaments and tendons due to influence on collagen structure and extracellular matrix. Ongoing work is looking at identifying the same genes from different races and different sexes to see if there are quantitative racial or sexual differences. All of the above have led to serious ethical concerns; in the twenty-first century some sports associations and some countries are looking at genetic testing for their players. Unfortunately, the science is still developing, and the experience of its application is limited worldwide. Nevertheless, this field has caught the imagination of both the public and the sportsperson, and hence the concerned doctors should be aware of the potential problems and current issues involved in understanding genetic traits and polymorphisms, genetic testing and genetic engineering.

Mouse Embryonic Fibroblasts Protect ob/ob Mice From Obesity and Metabolic Complications

The global obesity epidemic is fueling alarming rates of diabetes, associated with increased risk of cardiovascular disease and cancer. Leptin is a hormone secreted by adipose tissue that is a key regulator of body weight (BW) and energy expenditure. Leptin-deficient humans and mice are obese, diabetic, and infertile and have hepatic steatosis. Although leptin replacement therapy can alleviate the pathologies seen in leptin-deficient patients and mouse models, treatment is costly and requires daily injections. Because adipocytes are the source of leptin secretion, we investigated whether mouse embryonic fibroblasts (MEFs), capable of forming adipocytes, could be injected into ob/ob mice and prevent the metabolic phenotype seen in these leptin-deficient mice. We performed a single subcutaneous injection of MEFs into leptin-deficient ob/ob mice. The MEF injection formed a single fat pad that is histologically similar to white adipose tissue. The ob/ob mice receiving MEFs (obRs) had significantly lower BW compared with nontreated ob/ob mice, primarily because of decreased adipose tissue mass. Additionally, obR mice had significantly less liver steatosis and greater glucose tolerance and insulin sensitivity. obR mice also manifested lower food intake and greater energy expenditure than ob/ob mice, providing a mechanism underlying their metabolic improvement. Furthermore, obRs have sustained metabolic protection and restoration of fertility. Collectively, our studies show the importance of functional adipocytes in preventing metabolic abnormalities seen in leptin deficiency and point to the possibility of cell-based therapies for the treatment of leptin-deficient states.

Antibody gene transfer with adeno-associated viral vectors as a method for HIV prevention

Broadly neutralizing antibodies (bNAbs) against human immunodeficiency virus (HIV) show great promise in HIV prevention as they are capable of potently neutralizing a considerable breadth of genetically diverse strains. Passive transfer of monoclonal bNAb proteins can confer protection in animal models of HIV infection at modest concentrations, inspiring efforts to develop an HIV vaccine capable of eliciting bNAb responses. However, these antibodies demonstrate high degrees of somatic mutation and other unique characteristics that may hinder the ability of conventional approaches to consistently and effectively produce bNAb analogs. As an alternative strategy, we and others have proposed vector-mediated gene transfer to generate long-term, systemic production of bNAbs in the absence of immunization. Herein, we review the use of adeno-associated virus (AAV) vectors for delivery of HIV bNAbs and antibody-like proteins and summarize both the advantages and disadvantages of this strategy as a method for HIV prevention.

Targeting Visceral Fat by Intraperitoneal Delivery of Novel AAV Serotype Vector Restricting Off-Target Transduction in Liver

It is challenging to genetically manipulate fat in adults. We demonstrate that intraperitoneal (i.p.) injection of an engineered adeno-associated virus (AAV) serotype Rec2 leads to high transduction of multiple visceral fat depots at a dose of 1 to 2 orders lower than commonly used doses for systemic gene delivery. To target adipose tissue, we develop a single AAV vector harboring two expression cassettes: one using the CBA promoter to drive transgene expression and one using the liver-specific albumin promoter to drive a microRNA-targeting WPRE sequence that only exists in this AAV vector. This dual-cassette vector achieves highly selective transduction of visceral fat while severely restricting off-target transduction of liver. As proof of efficacy, i.p. administration of an adipose-targeting Rec2 vector harboring the leptin gene corrects leptin deficiency, obesity, and metabolic syndromes of ob/ob mice. This study provides a powerful tool to genetically manipulate fat for basic research and gene therapies of genetic and acquired diseases.

Delivery of Adeno-Associated Virus Gene Therapy by Intravascular Limb Infusion Methods

Recombinant adeno-associated virus (rAAV) can be delivered to the skeletal muscle of the limb (pelvic or thoracic) by means of regional intravascular delivery. This review summarizes the evolution of this technique to deliver rAAV either via the arterial blood supply or via the peripheral venous circulation. The focus of this review is on applications in large animal models, including preclinical studies. Based on this overview of past research, we aim to inform the design of preclinical and clinical studies.

The herbal composition GGEx18 from Laminaria japonica, Rheum palmatum, and Ephedra sinica inhibits visceral obesity and insulin resistance by upregulating visceral adipose genes involved in fatty acid oxidation

CONTEXT

The herbal composition Gyeongshingangjeehwan 18 (GGEx18) extracted from Rheum palmatum L. (Polygonaceae), Laminaria japonica Aresch (Laminariaceae), and Ephedra sinica Stapf (Ephedraceae) is traditionally used as an anti-obesity drug by local clinics in Korea.

OBJECTIVE

This study investigates the effects of GGEx18 on visceral obesity and insulin resistance and determines the molecular mechanisms involved in this process.

MATERIALS AND METHODS

After C57BL/6J mice were fed a high-fat diet supplemented with GGEx18 (125, 250, and 500 mg/kg) for 8 weeks and 3T3-L1 adipocytes were treated with GGEx18 (0.1, 1, and 10 μg/ml); variables and determinants of visceral obesity and insulin resistance were measured using in vivo and in vitro approaches.

RESULTS

Administration of GGEx18 to obese mice decreased visceral adipose tissue weight with an ED50 value of 232 mg/kg. 3T3-L1 adipocytes treated with GGEx18 showed a reduction in lipid accumulation with an ED50 value of 0.7 µg/ml. GGEx18 significantly increased the expression of fatty acid oxidation genes, including adiponectin, AMPKs, PPARα and its target enzymes, and CPT-1, in both mesenteric adipose tissues and 3T3-L1 cells. However, GGEx18 treatment decreased the mRNA levels of adipocyte marker genes such as PPARγ, aP2, TNFα, and leptin. GGEx18 normalized hyperglycemia and hyperinsulinemia in obese mice. Blood glucose levels of GGEx18-treated mice were significantly reduced during oral glucose tolerance tests compared with obese controls.

DISCUSSION AND CONCLUSION

These results suggest that GGEx18 may treat visceral obesity and visceral obesity-related insulin resistance by upregulating the visceral adipose expression of fatty acid oxidative genes.

Targeting adipose tissue via systemic gene therapy

Adipose tissue has a critical role in energy and metabolic homeostasis, but it is challenging to adapt techniques to modulate adipose function in vivo. Here we develop an in vivo, systemic method of gene transfer specifically targeting adipose tissue using adeno-associated virus (AAV) vectors. We constructed AAV vectors containing cytomegalovirus promoter-regulated reporter genes, intravenously injected adult mice with vectors using multiple AAV serotypes, and determined that AAV2/8 best targeted adipose tissue. Altering vectors to contain adiponectin promoter/enhancer elements and liver-specific microRNA-122 target sites restricted reporter gene expression to adipose tissue. As proof of efficacy, the leptin gene was incorporated into the adipose-targeted expression vector, package into AAV2/8 and administered intravenously to 9- to 10-week-old ob/ob mice. Phenotypic changes were measured over an 8-week period. Leptin mRNA and protein were expressed in adipose and leptin protein was secreted into plasma. Mice responded with reversal of weight gain, decreased hyperinsulinemia and improved glucose tolerance. AAV2/8-mediated systemic delivery of an adipose-targeted expression vector can replace a gene lacking in adipose tissue and correct a mouse model of human disease, demonstrating experimental application and therapeutic potential in disorders of adipose.

A long journey to effective obesity treatments: is there light at the end of the tunnel?

As the obesity epidemic continues, more Americans are getting fatter, having more weight-related problems such as cardiovascular disease, and are experiencing new metabolic dysfunctions. For over 50 years, the adipose tissue (AT), commonly referred to as fat, has been of interest to academic and clinical scientists, public health officials and individuals interested in body composition and image including much of the average public, athletes, parents, etc. On one hand, efforts to alter body shape, weight and body fat percentage still include bizarre and scientifically unfounded methods. On the other hand, significant new scientific strides have been made in understanding the growth, function and regulation of anatomical and systemic AT. Markers of transition/conversion of precursor cells that mature to form lipid assimilating adipocytes have been identified. Molecular 'master' regulators such as peroxisome proliferator-activated receptor gamma and CCAAT-enhancer-binding proteins were uncovered and regulatory mechanisms behind variables of adiposity defined and refined. Interventions including pharmaceutical compounds, surgical, psychosocial interventions have also been tested. Has all of the preceding research helped alleviate the adverse physiologies of overweight and/or obese people? Does research to date point to new modalities that should be the focus of efforts to rid the world of obesity-related problems in the 21st century? This review provides a general overview of scientific efforts to date and a provocative view of the future for adiposity.

Leptin's regulation of obesity-induced cardiac extracellular matrix remodeling

Obesity-induced remodeling of cardiac extracellular matrix (ECM) leads to myocardial fibrosis and ultimately diastolic dysfunction. Leptin, an adipocyte hormone, is emerging as a novel mechanistic link between obesity and heart diseases. Despite the known essential role of leptin in hepatic and renal fibrosis, the in vivo effects of leptin on cardiac ECM remodeling remain unclear. Our objective was to define the role of leptin as a key mediator of pro-fibrogenic responses in the heart. In vitro administration of leptin to primary cardiofibroblasts resulted in significant stimulation of pro-collagen Iα ( 1 ) and a decrease in pro-matrix metalloproteinase (MMP)-8, -9 and -13 gene expressions at 24 h. To study the in vivo pro-fibrotic effect, leptin was administrated to C57BL/6 and leptin-deficient ob/ob mice for 8 weeks. With exogenous leptin ob/ob mice displayed passive diastolic filling dysfunction, coincided with significant increase in myocardial collagen compared with ob/ob controls. We also observed a marked stimulation of pro-collagen IIIα ( 1 ) and suppression of pro-MMP-8, TIMP-1 and -3 gene expressions in leptin-treated ob/ob mice. Our findings suggest pro-fibrotic effects of leptin in the heart, primarily through the predominance of collagen synthesis over degradation.

Leptin gene therapy in the fight against diabetes

IMPORTANCE OF THE FIELD

The incidence of diabetes is increasing worldwide, yet current treatments are not always effective for all patient or disease types.

AREAS COVERED IN THIS REVIEW

Here, we summarize the biologic and clinical roles of leptin in diabetes, and discuss candidate viral vectors that may be employed in the clinical use of central leptin gene therapy for diabetes.

WHAT THE READER WILL GAIN

We discuss how studies on leptin, a regulator of the insulin-glucose axis, have significantly advanced our understanding of the roles of energy homeostasis and insulin resistance in the pathogeneses of metabolic syndrome and diabetes. Recent studies have demonstrated the long-term therapeutic effects of central leptin gene therapy in obesity and diabetes via decreased insulin resistance and increased glucose metabolism. Many of these studies have employed viral vectors, which afford high in vivo gene transduction efficiencies compared with non-viral vectors.

TAKE HOME MESSAGE

Adeno-associated viral vectors are particularly well suited for central leptin gene therapy owing to their low toxicity and ability to drive transgene expression for extended periods.

Pivotal role of leptin-hypothalamus signaling in the etiology of diabetes uncovered by gene therapy: a new therapeutic intervention?

The incidence of diabetes mellitus has soared to epidemic proportion worldwide. The debilitating chronic hyperglycemia is caused by either lack of insulin as in diabetes type 1 or its ineffectiveness as in diabetes type 2. Frequent replacement of insulin with or without insulin analogs for optimum glycemic control are the conventional cumbersome therapies. Recent application of leptin gene transfer technology has uncovered the participation of adipocytes-derived leptin-dependent hypothalamic neural signaling in glucose homeostasis and demonstrated that a breakdown in this communication due to leptin insufficiency in the hypothalamus underlies the etiology of chronic hyperglycemia. Reinstatement of central leptin sufficiency by hyperleptinemia produced either by intravenous leptin infusion or a single systemic injection of recombinant adenovirus vector encoding leptin gene suppressed hyperglycemia and evoked euglycemia only transiently in rodent models of diabetes type 1. In contrast, stable restoration of leptin sufficiency, solely in the hypothalamus, with biologically active leptin transduced by an intracerebroventicular injection of recombinant adeno-associated virus vector encoding leptin gene (rAAV-lep) abolished hyperglycemia and imposed euglycemia through the extended duration of experiment by stimulating glucose disposal in the periphery in models of diabetes type 1. Further, similar hypothalamic leptin transgene expression abrogated chronic hyperglycemia and hyperinsulinemia, the predisposing risk factors of the age and environmentally acquired diabetes type 2, and instituted euglycemia by independently activating relays that stimulate glucose metabolism and repress hyperinsulinemia and improve insulin sensitivity in the periphery. Consequently, this durable antidiabetic efficacy of one time rAAV-lep neurotherapy offers a potential novel substitute for insulin therapy following preclinical trials in subhuman primates and humans.

The Korean traditional medicine gyeongshingangjeehwan inhibits adipocyte hypertrophy and visceral adipose tissue accumulation by activating PPARalpha actions in rat white adipose tissues

AIM OF THE STUDY

Gyeongshingangjeehwan (GGEx), which is a polyherbal drug composed of four medicinal plants, has traditionally been used as anti-obesity drug in Korean local clinics. Thus, we investigated the effects of GGEx on visceral adiposity and examined whether adipose peroxisome proliferator-activated receptor alpha (PPARalpha) activation is involved in this process.

MATERIALS AND METHODS

After Obese Otsuka Long-Evans Tokushima Fatty (OLETF) rats and differentiated 3T3-L1 adipocytes were treated with GGEx, we studied the effects of GGEx on not only visceral white adipose tissue (WAT) mass and adipocyte size, but also the expression of adipocyte marker and PPARalpha target genes.

RESULTS

Administration of GGEx to obese rats for 8 weeks decreased visceral WAT weight by 30% and the size of adipocytes in mesenteric WAT by 31% without weight changes of other organs. Concomitantly, GGEx increased mRNA levels of PPARalpha target genes responsible for fatty acid beta-oxidation in mesenteric WAT whereas decreased mRNA expression of adipocyte markers, such as PPARgamma, aP2 and leptin. Serological studies demonstrated that plasma levels of free fatty acids and triglycerides as well as insulin and glucose were decreased following GGEx treatment. Consistent with the in vivo data, GGEx increased PPARalpha reporter gene activity and induced the mRNA expression of PPARalpha target genes involved in mitochondrial fatty acid beta-oxidation in 3T3-L1 cells. GGEx also inhibited triglyceride accumulation in these cells.

CONCLUSION

These results suggest that GGEx promotes the reductions in visceral fat mass and adipocyte size in obese animals, and that this event may be mediated by adipose PPARalpha activation.

Central leptin gene therapy ameliorates diabetes type 1 and 2 through two independent hypothalamic relays; a benefit beyond weight and appetite regulation

Although its role in energy homeostasis is firmly established, the evidence accumulated over a decade linking the adipocyte leptin-hypothalamus axis in the pathogenesis of diabetes mellitus has received little attention in the contemporary thinking. In this context various lines of evidence are collated here to show that (1) under the direction of leptin two independent relays emanating from the hypothalamus restrain insulin secretion from the pancreas and mobilize peripheral organs--liver, skeletal muscle and brown adipose tissue--to upregulate glucose disposal, and (2), leptin insufficiency in the hypothalamus produced by either leptinopenia or restriction of leptin transport across the blood brain barrier due to hyperleptinemia of obesity and aging, initiate antecedent pathophysiological sequalae of diabetes type 1 and 2. Further, we document here the efficacy of leptin replenishment in vivo, especially by supplying it to the hypothalamus with the aid of gene therapy, in preventing the antecedent pathophysiological sequalae--hyperinsulinemia, insulin resistance and hyperglycemia--in various animal models and clinical paradigms of diabetes type 1 and 2 with or without attendant obesity. Overall, the new insights on the long-lasting antidiabetic potential of two independent hypothalamic relays engendered by central leptin gene therapy and the preclinical safety indicators in rodents warrant further validation in subhuman primates and humans.

Fenofibrate inhibits adipocyte hypertrophy and insulin resistance by activating adipose PPARalpha in high fat diet-induced obese mice

Peroxisome proliferator-activated receptor alpha (PPARalpha) activation in rodents is thought to improve insulin sensitivity by decreasing ectopic lipids in non-adipose tissues. Fenofibrate, a lipid-modifying agent that acts as a PPARalpha agonist, may prevent adipocyte hypertrophy and insulin resistance by increasing intracellular lipolysis from adipose tissue. Consistent with this hypothesis, fenofibrate decreased visceral fat mass and adipocyte size in high fat diet-fed obese mice, and concomitantly increased the expression of PPARalpha target genes involved in fatty acid beta-oxidation in both epididymal adipose tissue and differentiated 3T3-L1 adipocytes. However, mRNA levels of adipose marker genes, such as leptin and TNFalpha, were decreased in epididymal adipose tissue by fenofibrate treatment. Fenofibrate not only reduced circulating levels of free fatty acids and triglycerides, but also normalized hyperinsulinemia and hyperglycemia in obese mice. Blood glucose levels of fenofibrate-treated mice were significantly reduced during intraperitoneal glucose tolerance test compared with obese controls. These results suggest that fenofibrate-induced fatty acid beta-oxidation in visceral adipose tissue may be one of the major factors leading to decreased adipocyte size and improved insulin sensitivity.

Central leptin gene therapy, a substitute for insulin therapy to ameliorate hyperglycemia and hyperphagia, and promote survival in insulin-deficient diabetic mice

Long-term benefits of central leptin gene therapy in insulin-deficient diabetes are not known despite its therapeutic effects in obesity animal models such as ob/ob and diet-induced obese mice. Adult male mice were injected intraperitoneally with streptozotocin (STZ, 200mg/kg) to induce insulitis. A week later, only diabetic STZ-pretreated mice (blood glucose >350 mg/dl) received intracerebroventricularly (icv) an injection of recombinant adeno-associated virus vector (rAAV) encoding either green fluorescent protein (control), or leptin gene (rAAV-lep). Body weight (BW), food intake, blood glucose, insulin and survival rate responses were monitored post-icv injection at regular intervals for 52 weeks. The STZ pre-injected diabetic mice remained hyperphagic, gradually lost BW and died by week 6 after receiving control vector. In marked contrast, injection of rAAV-lep to raise hypothalamic leptin levels, rescued the STZ-pretreated mice from early mortality, gradually curbed hyperphagia to normalize intake by week 20, and maintained BW at significantly lower than the control range. Blood glucose levels in these mice started to recede dramatically by week 2-3 to normalize by week 8, and euglycemia was sustained during the remaining course of the experiment. rAAV-lep injected mice did not exhibit any discernible untoward gross behavioral changes and diabetic complications and showed a partial return of pancreatic beta-cell function. These results show for the first time that one time central leptin gene therapy is effective and durable in reinstating euglycemia and energy homeostasis for extended periods in the absence of insulin.

The role of the adeno-associated virus capsid in gene transfer

Adeno-associated virus (AAV) is one of the most promising viral gene transfer vectors that has been shown to effect long-term gene expression and disease correction with low toxicity in animal models, and is well tolerated in human clinical trials. The surface of the AAV capsid is an essential component that is involved in cell binding, internalization, and trafficking within the targeted cell. Prior to developing a gene therapy strategy that utilizes AAV, the serotype should be carefully considered since each capsid exhibits a unique tissue tropism and transduction efficiency. Several approaches have been undertaken in an effort to target AAV vectors to specific cell types, including utilizing natural serotypes that target a desired cellular receptor, producing pseudotyped vectors, and engineering chimeric and mosaic AAV capsids. These capsid modifications are being incorporated into vector production and purification methods that provide for the ability to scale-up the manufacturing process to support human clinical trials. Protocols for small-scale and large-scale production of AAV, as well as assays to characterize the final vector product, are presented here. The structures of AAV2, AAV4, and AAV5 have been solved by X-ray crystallography or cryo-electron microscopy (cryo-EM), and provide a basis for rational vector design in developing customized capsids for specific targeting of AAV vectors. The capsid of AAV has been shown to be remarkably stable, which is a desirable characteristic for a gene therapy vector; however, recently it has been shown that the AAV serotypes exhibit differential susceptibility to proteases. The capsid fragmentation pattern when exposed to various proteases, as well as the susceptibility of the serotypes to a series of proteases, provides a unique fingerprint for each serotype that can be used for capsid identity validation. In addition to serotype identification, protease susceptibility can also be utilized to study dynamic structural changes that must occur for the AAV capsid to perform its various functions during the virus life cycle. The use of proteases for structural studies in solution complements the crystal structural studies of the virus. A generic protocol based on proteolysis for AAV serotype identification is provided here.

Central leptin insufficiency syndrome: an interactive etiology for obesity, metabolic and neural diseases and for designing new therapeutic interventions

This review critically reappraises recent scientific evidence concerning central leptin insufficiency versus leptin resistance formulations to explain metabolic and neural disorders resulting from subnormal or defective leptin signaling in various sites in the brain. Research at various fronts to unravel the complexities of the neurobiology of leptin is surveyed to provide a comprehensive account of the neural and metabolic effects of environmentally imposed fluctuations in leptin availability at brain sites and the outcome of newer technology to restore leptin signaling in a site-specific manner. The cumulative new knowledge favors a unified central leptin insufficiency syndrome over the, in vogue, central resistance hypothesis to explain the global adverse impact of deficient leptin signaling in the brain. Furthermore, the leptin insufficiency syndrome delineates a novel role of leptin in the hypothalamus in restraining rhythmic pancreatic insulin secretion while concomitantly enhancing glucose metabolism and non-shivering thermogenic energy expenditure, sequelae that would otherwise promote fat accrual to store excess energy resulting from consumption of energy-enriched diets. A concerted effort should now focus on development of newer technologies for delivery of leptin or leptin mimetics to specifically target neural pathways for remediation of diverse ailments encompassing the central leptin insufficiency syndrome.

Terapia gênica, doping genético e esporte: fundamentação e implicações para o futuro

A busca pelo desempenho ótimo tem sido uma constante no esporte de alto rendimento. Para tanto, muitos atletas acabam utilizando drogas e métodos ilícitos, os quais podem ter importantes efeitos adversos. A terapia gênica é uma modalidade terapêutica bastante recente na medicina, cujos resultados têm, até o momento, indicado sua eficácia no tratamento de diversas doenças graves. O princípio da terapia gênica consiste na transferência vetorial de materiais genéticos para células-alvo, com o objetivo de suprir os produtos de um gene estruturalmente anormal no genoma do paciente. Recentemente, o potencial para uso indevido da terapia gênica entre atletas tem despertado a atenção de cientistas e de órgãos reguladores de esporte. A transferência de genes que poderiam melhorar o desempenho esportivo por atletas saudáveis, método proibido em 2003, foi denominado de doping genético. Os genes candidatos mais importantes para doping genético são os que codificam para GH, IGF-1, bloqueadores da miostatina, VEGF, endorfinas e encefalinas, eritropoetina, leptina e PPAR-delta. Uma vez inserido no genoma do atleta, o gene se expressaria gerando um produto endógeno capaz de melhorar o desempenho atlético. Assim, os métodos atuais de detecção de doping não são sensíveis a esse tipo de manipulação, o que poderia estimular seu uso indevido entre atletas. Além disso, a terapia gênica ainda apresenta problemas conhecidos de aplicação, como resposta inflamatória e falta de controle da ativação do gene. Em pessoas saudáveis, é provável que tais problemas sejam ainda mais importantes, já que haveria excesso do produto do gene transferido. Há também outros riscos ainda não conhecidos, específicos para cada tipo de gene. Em vista disso, debates sobre o doping genético devem ser iniciados no meio acadêmico e esportivo, para que sejam estudadas medidas de prevenção, controle e detecção do doping genético, evitando assim futuros problemas de uso indevido dessa promissora modalidade terapêutica.

Chalcone based aryloxypropanolamines as potential antihyperglycemic agents

A series of chalcone based aryloxypropanolamines were synthesized and evaluated for their antihyperglycemic activity in SLM and STZ rat models. Most of the compounds exhibited moderate to good activity ranging from 6.5% to 31.1% in SLM and 8.3% to 22.6% in STZ models, respectively. The most potent compound 5 g exhibited glucose lowering of 26.7% in SLM and 22.6% in STZ models. A definite structure-activity relationship was observed while varying the nature as well as the position of the amine in ring B.

Effect of genetic variation in the leptin gene promoter and the leptin receptor gene on obesity risk in a population-based case-control study in Spain

There are no good genetic markers for incorporating the study of genetic susceptibility to obesity in epidemiological studies. In animal models, the leptin (LEP) and the leptin receptor (LEPR) genes have been shown to be very important in obesity because leptin functions as a negative feedback signal in regulating body-weight through reducing food intake and stimulating energy expenditure. In humans, several polymorphisms in these genes have been described. However, their association with obesity is still very controversial because there are no good case-control studies designed to specifically test this association. Our objective has been to conduct a population-based case-control study to estimate the risk of obesity arising from the -2548G > A and Q223R polymorphisms in the LEP and LEPR genes, respectively. 303 obese cases (101 men and 202 women) and 606 controls (202 men and 404 women) were selected from a Spanish Mediterranean population. Genetic, clinical and life-style characteristics were analyzed. No association was found between the -2548G > A polymorphism and obesity. However, the Q223R variant was significantly associated with obesity in a recessive model, the RR genotype being more prevalent in controls than in obese subjects. The inverse association between the Q223R polymorphism and obesity (OR = 0.62; 95% CI: 0.39-0.99) remained significant even after additional adjustment for education, tobacco smoking, alcohol, physical activity, origin of the obese patient, and the -2548G > A polymorphism in the LEP gene (OR = 0.54; 95% CI: 0.32-0.89). In conclusion, the -2548G > A polymorphism is not a relevant obesity marker in this Mediterranean population, although Q223R does seen to be so.

Treatment of human disease by adeno-associated viral gene transfer

During the past decade, in vivo administration of viral gene transfer vectors for treatment of numerous human diseases has been brought from bench to bedside in the form of clinical trials, mostly aimed at establishing the safety of the protocol. In preclinical studies in animal models of human disease, adeno-associated viral (AAV) vectors have emerged as a favored gene transfer system for this approach. These vectors are derived from a replication-deficient, non-pathogenic parvovirus with a single-stranded DNA genome. Efficient gene transfer to numerous target cells and tissues has been described. AAV is particularly efficient in transduction of non-dividing cells, and the vector genome persists predominantly in episomal forms. Substantial correction, and in some instances complete cure, of genetic disease has been obtained in animal models of hemophilia, lysosomal storage disorders, retinal diseases, disorders of the central nervous system, and other diseases. Therapeutic expression often lasted for months to years. Treatments of genetic disorders, cancer, and other acquired diseases are summarized in this review. Vector development, results in animals, early clinical experience, as well as potential hurdles and challenges are discussed.

Gene therapy for obesity

A sedentary life-style and an environment of caloric abundance have contributed to the recent rise in the incidence of obesity. Treating such a complex disease requires an understanding of its underlying molecular mechanisms that has only recently become possible with the sequencing of the human genome and the mapping of hundreds of genes associated with increased risk of obesity. With few safe and efficacious weight-maintenance drugs available on the market, gene therapy offers an alternative long-term treatment modality. Still in its infancy, gene therapy for obesity is poised for significant progress, due in large part to a wide variety of available gene targets and the development of novel systems to control gene expression. Coincidently, novel vectors are being developed based on adeno-associated virus providing efficient and sustained expression of a transgene in metabolically important tissues. These advances are driving the development of gene therapy as a viable therapeutic option in treating obesity and its associated disorders.

Role of islet amyloid in type 2 diabetes mellitus

Diabetes mellitus is one of the most common metabolic diseases worldwide and its prevalence is rapidly increasing. Due to its chronic nature (diabetes mellitus can be treated but as yet not cured) and its serious complications, it is one of the most expensive diseases with regard to total health care costs per patient. The elevated blood glucose levels in diabetes mellitus are caused by a defect in production and/or secretion of the polypeptide hormone insulin, which normally promotes glucose-uptake in cells. Insulin is produced by the pancreatic 'beta-cells' in the 'islets of Langerhans', which lie distributed within the exocrine pancreatic tissue. In type 2 diabetes mellitus, the initial defect in the pathogenesis of the disease in most of the patients is believed to be 'insulin resistance'. Hyperglycemia (clinically overt diabetes mellitus) will not develop as long as the body is able to produce enough insulin to compensate for the reduced insulin action. When this compensation fails ('beta-cell failure') blood glucose levels will become too high. In this review, we discuss one of the mechanisms that have been implicated in the development of beta-cell failure, i.e. amyloid formation in the pancreatic islets. This islet amyloid is a characteristic histopathological feature of type 2 diabetes mellitus and both in vitro and in vivo studies have revealed that its formation causes death of islet beta-cells. Being a common pathogenic factor in an otherwise heterogeneous disease, islet amyloidosis is an attractive novel target for therapeutic intervention in type 2 diabetes mellitus.

AAV-mediated leptin receptor installation improves energy balance and the reproductive status of obese female Koletsky rats

Leptin is a hormone secreted primarily by white adipocytes that regulates energy homeostasis and reproduction via CNS receptors. Koletsky (f/f) rats with a leptin receptor (OB-Rb) gene mutation are obese, diabetic and infertile. We employed recombinant adeno-associated viral (rAAV) vectors to transfer the human OB-Rb gene into the brains of female Koletsky rats to identify sites of leptin action in the brain. rAAV-OB-Rb was microinjected into the medial preoptic area (MPOA), the paraventricular nucleus (PVN), the ventromedial hypothalamus, the arcuate nucleus (ARC), or the dorsal vagal complex in the brainstem. Food intake and body weight were monitored bi-weekly for 55 days. Vaginal cytology was examined daily to assess estrous cyclicity. After sacrifice, uncoupling protein-1 (UCP-1) mRNA in brown adipose tissue and serum concentrations of leptin, insulin, glucose, estradiol and progesterone were measured. Expression of OB-Rb was documented by RT-PCR and site specificity of microinjection was verified by immunohistochemical detection of green fluorescent protein following a control microinjection of rAAV-GFP. OB-Rb installation in the ARC reduced food intake, however, energy expenditure, assessed by UCP-1 mRNA expression, was increased by OB-Rb installation in all sites except the PVN. When injected into the MPOA and ARC, rAAV-OB-Rb stimulated the reproductive axis as evidenced by normalization of estrous cycle length and increased luteinizing hormone releasing hormone concentrations in the hypothalamus. These studies show that long-term installation of a functional leptin receptor in the CNS is achievable using rAAV vectors and further show that leptin acts on specific sites in the brain to produce differential effects on food intake, energy expenditure and reproduction.

Gene-transfer technology: a preventive neurotherapy to curb obesity, ameliorate metabolic syndrome and extend life expectancy

Leptin insufficiency at crucial target sites in the hypothalamic circuitries that integrate energy intake and expenditure underlies abnormal rates of fat accumulation. The payload of this "fat burden" is metabolic syndrome, a cluster of life-threatening metabolic afflictions, and a shorter lifespan. Currently available therapies employed to combat obesity have disadvantages such as poor compliance for lifestyle modification or transient effectiveness and undesirable side-effects of pharmacological interventions. Recent studies suggest that neurotherapy comprising a single central administration of recombinant adeno-associated virus vector encoding the leptin gene severely depletes fat and ameliorates the major symptoms of metabolic syndrome for extended periods in rodents. These persistent benefits avert the deleterious impact of the "fat burden" and extend life expectancy. Thus, the novel approach of central gene-transfer technology has distinct advantages over current therapies and has the potential to correct or slow the progression of inherited or acquired hypothalamic diseases.

Dose-related steady states of fat loss in long-term leptin-treated ob/ob mice: leptin resistance or desensitization versus counterregulatory signaling

We tried to unravel why leptin's fat store depleting action levels off in the course of long-term applications. Supplying leptin by minipump infusion for 2 months to ob/ob mice at rates between 115 pmol day(-1) and 460 pmol day(-1) resulted in stable plasma leptin levels between 0.2 ng ml(-1) and 8 ng ml(-1). Initial treatment effects were leptin dose-dependent reductions in food intake and body mass, especially in fat content, followed by re-increases of food intake to levels only 4-18% below pre-treatment levels. Decreased body mass subsequently stabilized dose-dependently with body fat contents between 4% and 33% showing that total fat depletion was not a precondition for the progressive reduction of leptin-induced anorexia. Oxygen consumption measurements excluded contributions of enhanced energy dissipation to fat depletion. Plasma insulin concentrations declined from excessively high pre-treatment levels to steady, leptin dose-dependent levels within the normal range. Temporary anorexia in response to repeated additional 1-day leptin injections (100 pmol g(-1) day(-1)) remained unchanged throughout long-term leptin infusion. Among various alternatives considered to explain the adipostatic equilibrium attained at new, dose-dependent levels under long-term leptin treatment, interaction between the leptin signal and at least one counteracting signal increasing with fat depletion is proposed as the most plausible working hypothesis.

Contemporary approaches into obesity: drugs and genes

Obesity is a global epidemic effecting the health and life style of millions of people in both developed and developing countries. In this article, current medical treatments, recent scientific progresses toward understanding obesity, and future potentials in biotechnology applications in pharmaceutical research are reviewed in detail.

Gene doping in sports

Gene or cell doping is defined by the World Anti-Doping Agency (WADA) as "the non-therapeutic use of genes, genetic elements and/or cells that have the capacity to enhance athletic performance". New research in genetics and genomics will be used not only to diagnose and treat disease, but also to attempt to enhance human performance. In recent years, gene therapy has shown progress and positive results that have highlighted the potential misuse of this technology and the debate of 'gene doping'. Gene therapies developed for the treatment of diseases such as anaemia (the gene for erythropoietin), muscular dystrophy (the gene for insulin-like growth factor-1) and peripheral vascular diseases (the gene for vascular endothelial growth factor) are potential doping methods. With progress in gene technology, many other genes with this potential will be discovered. For this reason, it is important to develop timely legal regulations and to research the field of gene doping in order to develop methods of detection. To protect the health of athletes and to ensure equal competitive conditions, the International Olympic Committee, WADA and International Sports Federations have accepted performance-enhancing substances and methods as being doping, and have forbidden them. Nevertheless, the desire to win causes athletes to misuse these drugs and methods. This paper reviews the current status of gene doping and candidate performance enhancement genes, and also the use of gene therapy in sports medicine and ethics of genetic enhancement.

Soluble Interleukin-13Rα2 Decoy Receptor Inhibits Hodgkin’s Lymphoma Growth in Vitro and in Vivo

Recent studies have demonstrated that the malignant Reed-Sternberg cells of Hodgkin's lymphoma (HL) secrete and are responsive to interleukin (IL)-13. We hypothesized that overexpression of a soluble IL-13 decoy receptor (sIL-13Ralpha2) via adenoviral-mediated gene transfer would inhibit IL-13-induced Reed-Sternberg cell proliferation. Western blot and ELISA analysis verified expression of sIL-13Ralpha2 in cell lysates and supernatants of AdsIL-13Ralpha2-transduced COS-7 cells. Treatment of two IL-13-responsive HL-derived cell lines, HDLM-2 and L-1236, with AdsIL-13Ralpha2-conditioned medium, resulted in the inhibition of cell proliferation, and down-regulated the phosphorylation of signal transducer and activator of transcription 6 (STAT6), an important mediator of IL-13 signaling. i.v. delivery of AdsIL-13Ralpha2 in NOD/SCID mice with s.c. implanted HDLM-2 cells delayed tumor onset and growth while enhancing survival compared with control mice. Intratumoral administration of AdsIL-13Ralpha2 led to the regression or stabilization of established tumors and was associated with diminished STAT6 phosphorylation. Our data demonstrate that AdsIL-13Ralpha2 can suppress HL growth in vitro and in vivo.

Tetracycline-regulated secretion of human insulin in transfected primary myoblasts

A mechanism for safely regulating transgene expression will be necessary for gene therapy approaches to endocrine disorders. In this study, a two-plasmid tetracycline-inducible system was used to regulate expression of human proinsulin (hppI1) and a mutated proinsulin construct (hppI4, allowing cleavage by furin) in primary rat soleus myoblasts. In hppI1 and hppI4 transient transfections, the presence of 0.01 and 0.1 microg/ml tetracycline for 48 h inhibited pro/insulin secretion to 19-27% and 7-12%, respectively, compared to tetracycline untreated myoblasts. Following a 48 h tetracycline incubation (1.0 microg/ml), pro/insulin secretion in hppI1 and hppI4 transfected myoblasts was reduced to <4% of that in cells incubated without tetracycline. Pro/insulin secretion equivalent to that of untreated cells was restored following tetracycline withdrawal and incubation for a further 72 h. Conversion of proinsulin to insulin in transfected myoblasts was <1% for hppI1 and >45% for hppI4. In conclusion, regulated insulin secretion has been achieved in a dose-dependent and reversible manner in primary myoblasts.

Gene and cell therapies for diabetes mellitus: strategies and clinical potential

The last 5 years have witnessed an explosion in the use of genes and cells as biomedicines. While primarily aimed at cancer, gene engineering and cell therapy strategies have additionally been used for Mendelian, neurodegenerative and metabolic disorders. The main focus of gene and cell therapy strategies in metabolism has been diabetes mellitus. This disease is a disorder of glucose homeostasis, either due to the immune-mediated eradication of pancreatic beta cells in the islets of Langerhans (type 1 diabetes) or resulting from insulin resistance and obesity syndromes where the insulin-producing capability of the beta cell is ultimately exhausted in the face of insensitivity to the effects of insulin in the peripheral glucose-utilising tissues (type 2 diabetes). A significant number of animal studies have demonstrated the potential in restoring normoglycaemia by islet transplantation in the context of immunoregulation achieved by gene transfer of immunoregulatory genes to allo- and xenogeneic islets ex vivo. Additionally, gene and cell therapy has also been used to induce tolerance to auto- and alloantigens and to generate the tolerant state in autoimmune rodent animal models of type 1 diabetes or rodent recipients of allogeneic/xenogeneic islet transplants. The achievements of gene and cell therapy in type 2 diabetes are less evident, but seminal studies promise that this modality can be relevant to treat and perhaps prevent the underlying causes of the disease. Here we present an overview of the current status of gene and cell therapy for type 1 and 2 diabetes and we propose potential therapeutic options that could be clinically useful. For type 1 diabetes, transplantation of islets engineered to evade or suppress the recipient immune response is the most readily-available technology today. A number of gene delivery vectors encoding proteins that impair a variety of immune cells have already been examined and proven versatile. More challenging but, nonetheless, just over the horizon are attempts to promote tolerance to islet allografts. Type 2 diabetes will likely require a better understanding of the processes that determine insulin sensitivity in the periphery. Targeting tissues such as muscle and fat with vectors encoding genes whose products promote insulin sensitivity and glucose uptake is an approach that does not carry with it the side-effects often associated with pharmacologic agents currently in use. In the end, progress in vector design, elucidation of antigen-specific immunity and insulin sensitivity will provide the framework for gene drug use in the treatment of type 1 and type 2 diabetes.

Treatment of experimental asthma by long-term gene therapy directed against IL-4 and IL-13

The clinical manifestations of allergic asthma are believed to result from a dysregulated, T helper 2 lymphocyte (Th2)-biased response to antigen. Although asthma symptoms can be controlled acutely, there is a need for a therapy that will address the underlying immune dysfunction and provide continuous control of chronic airway inflammation. The Th2-type cytokines, IL-13 and IL-4, have been demonstrated to play a crucial role in asthma pathogenesis and their selective neutralization results in the alleviation of asthmatic symptoms in mouse models. The activity of both of these cytokines can be inhibited by a mutant IL-4 protein, IL-4 receptor antagonist (IL-4RA), and thus, continual IL-4RA therapy might be beneficial in treatment of chronic asthma. To explore the potential utility of long-term gene therapy for the treatment of asthma we used a recombinant adeno-associated virus (AAV) vector to deliver and provide sustained expression of IL-4RA in vivo. We show that AAV-mediated delivery of IL-4RA to the airways of mice reduces airway hyperresponsiveness (AHR) and airway eosinophilia triggered by either IL-13 or IL-4. Furthermore, AAV-delivered IL-4RA, expressed either systemically or in the airways of mice following allergen sensitization, significantly inhibited development of airway eosinophilia and mucus production and reduced the levels of asthma-associated Th2 cytokines and AHR in the experimental mouse model of allergic asthma. Thus, gene therapy can be a potential therapeutic option to treat and control chronic airway inflammation and asthmatic symptoms.

Gene therapy delivery of endostatin enhances the treatment efficacy of radiation

BACKGROUND AND PURPOSE

To evaluate whether sustained expression of mouse endostatin by adeno-associated virus (AAV)-mediated gene transfer can enhance the treatment efficacy of ionizing radiation.

MATERIALS AND METHODS

Mouse endostatin was cloned into recombinant AAV (rAAV) under the control of CMV beta-actin promoter. Recombinant mouse endostatin expressed via AAV gene transfer was tested for biological activity in endothelial cells. The impact of elevated serum levels of endostatin on tumor-induced angiogenesis was evaluated using an in vivo angiogenesis assay. The anti-tumor efficacy of combining rAAV-mediated endostatin delivery with radiation was evaluated in a human colorectal tumor model (HT29).

RESULTS

Recombinant mouse endostatin expressed through an AAV vector (rAAV-mEndo) inhibited endothelial cell proliferation (by 40-45%) and migration (by 22-33%). Intramuscular injection of rAAV-mEndo (1x10(9) i.u.) led to a sustained serum endostatin level of approximately 500 ng/ml. Compared to control animals this endostatin level was sufficient to inhibit tumor cell-induced vessel formation (37 vs. 28.5, P<0.05) and delay the growth of HT29 xenografts (time from 200 to 1,000 mm(3), 21 vs. 34.5 days, P<0.05). When combined with ionizing radiation, elevated serum endostatin levels significantly enhanced the time for tumors to grow from 200 to 1,000 mm(3) (radiation, 34 days; endostatin plus radiation, 50 days, P<0.05).

CONCLUSION

The delivery of endostatin via rAAV vectors may provide an effective means of enhancing the anti-tumor efficacy of radiation therapy.

Intramuscular administration of recombinant adeno-associated virus 2 alpha-1 antitrypsin (rAAV-SERPINA1) vectors in a nonhuman primate model: safety and immunologic aspects

We performed a series of studies in baboons to evaluate the safety of intramuscular administration of rAAV vector expressing the alpha-1 antitrypsin (AAT) gene (SERPINA1) in a nonhuman primate model. Initial experiments performed with an rAAV vector expressing the human SERPINA1 gene (at doses of up to 5 x 10(12) vector genomes/kg) resulted in the generation of anti-human AAT antibodies, which correlated with a loss of detectable transgene expression. Subsequent studies made use of the baboon SERPINA1 gene tagged with a short (10-amino-acid) c-myc tag. When animals were sacrificed, 4 months after vector injection, transduced myofibers showed efficient transgene expression without detectable humoral immune responses. Mild inflammation was observed in and near the sites of injection in some vector- and saline-injected animals, but serum creatine kinase (CK) values were normal in nearly every case. Real-time PCR was also performed 4 months after injection on gonadal tissue to evaluate the risk of germline transmission. No vector sequences were detected in the gonadal tissues from these animals. These studies indicate that the risks of immune reaction and germline transmission after intramuscular injection of rAAV-SERPINA1 in nonhuman primates are relatively low within the range of vector doses studied.

Generation of neutralizing activity against human immunodeficiency virus type 1 in serum by antibody gene transfer

Although several human immunodeficiency virus (HIV) vaccine approaches have elicited meaningful antigen-specific T-cell responses in animal models, no single vaccine candidate has engendered antibodies that broadly neutralize primary isolates of HIV type 1 (HIV-1). Thus, there remains a significant gap in the design of HIV vaccines. To address this issue, we exploited the existence of rare human monoclonal antibodies that have been isolated from HIV-infected individuals. Such antibodies neutralize a wide array of HIV-1 field isolates and have been shown to be effective in vivo. However, practical considerations preclude the use of antibody preparations as a prophylactic passive immunization strategy in large populations. Our concept calls for an antibody gene of choice to be transferred to muscle where the antibody molecule is synthesized and distributed to the circulatory system. In these experiments, we used a recombinant adeno-associated virus (rAAV) vector to deliver the gene for the human antibody IgG1b12 to mouse muscle. Significant levels of HIV-neutralizing activity were found in the sera of mice for over 6 months after a single intramuscular administration of the rAAV vector. This approach allows for predetermination of antibody affinity and specificity prior to "immunization" and avoids the need for an active humoral immune response against the HIV envelope protein.

Long-term suppression of weight gain, adiposity, and serum insulin by central leptin gene therapy in prepubertal rats: effects on serum ghrelin and appetite-regulating genes

Intracerebroventricular administration of recombinant adeno-associated virus (rAAV) encoding the rat leptin gene (rAAV-lep) to 24-d-old female and male rats suppressed postpubertal weight gain for extended periods by decreasing food consumption and adiposity, as reflected by lowered serum leptin, insulin, and FFA. Serum ghrelin levels were increased in young but not older rats. Central rAAV-lep therapy also increased energy expenditure through nonshivering thermogenesis in younger rats as shown by expression of uncoupling protein mRNA in brown adipose tissue. The sustained decrease in appetite seemingly resulted from attenuation of appetite-stimulating neuropeptide Y and enhancement of appetite-inhibiting melanocortin signalings in the hypothalamus. Neither the onset of pubertal sexual maturation nor reproductive cyclicity in adult female rats was affected by the sustained reduction in energy consumption and weight gain. These findings demonstrate that central leptin gene therapy in prepubertal rats is a novel therapy to control postpubertal weight gain, adiposity, and hyperinsulinemia for extended periods.

Adeno-associated virus-mediated gene transfer of endostatin inhibits angiogenesis and tumor growth in vivo

A variety of approaches has demonstrated that interfering with tumor-induced angiogenesis may be an effective strategy in cancer therapy. However, it is likely that to be most effective such strategies will require extended suppression of the angiogenic process. Gene therapy offers a possible approach to achieve sustained release of a therapeutically potent transferred gene product. In the present study the angiogenesis inhibitor endostatin was expressed through a recombinant adeno-associated viral (rAAV) vector and shown to be biologically active in vitro and in vivo. Intramuscular injection of rAAV-HuEndo (1 x 10(9) i.u.) led to a sustained serum endostatin level of approximately 35-40 ng/mL. This endostatin level was sufficient to inhibit tumor cell-induced angiogenesis and to suppress both the initiation and subsequent growth of a human colorectal cancer model.

Central leptin gene delivery evokes persistent leptin signal transduction in young and aged-obese rats but physiological responses become attenuated over time in aged-obese rats

The purpose of this study was to determine if long-term leptin treatment desensitizes leptin signal transduction and the subsequent downstream anorexic and thermogenic responses in normal and leptin-resistant age-related obese rats. To this end, we administered, i.c.v., recombinant adeno-associated virus encoding rat leptin cDNA (rAAV-leptin) or control virus into young and aged-obese rats and after 9 or 46 days, examined food intake, oxygen consumption, body weight, serum leptin, STAT3 phosphorylation, hypothalamic NPY and POMC mRNAs, and UCP1 expression and protein level in brown adipose tissue (BAT). In young rats, rAAV-leptin depleted body fat and both anorexic and thermogenic mechanisms contributed to this effect. Moreover, leptin signal transduction was not desensitized, and there were persistent physiological responses. Similarly, in the aged-obese rats, there was unabated leptin signal transduction, however, both the anorexic and thermogenic responses completely attenuated sometime after day 9. This attenuation, downstream of the leptin receptor, may be contributing to the leptin-resistance and age-related weight gain in these aged-obese rats. Finally, in young rats, although the initial responses to rAAV-leptin were dominated by anorexic responses, by 46 days, the predominant response was thermogenic rather than anorexic, suggesting that energy expenditure may be an important component of long-term weight maintenance.

Transcriptional profiling reveals global defects in energy metabolism, lipoprotein, and bile acid synthesis and transport with reversal by leptin treatment in ob/ob mouse liver

Leptin, a hormone secreted by adipose tissue, has been shown to have a major influence on hepatic lipid and lipoprotein metabolism. To characterize changes in lipid and lipoprotein gene expression in mouse liver, suppression subtractive hybridization and cDNA microarray analysis were used to identify mRNAs differentially expressed after leptin treatment of ob/ob mice. Ob/ob mice showed a profound decrease in mRNAs encoding genes controlling bile acid synthesis and transport as well as a variety of apolipoprotein genes and hepatic lipase with reversal upon leptin administration, suggesting that leptin coordinately regulates high density lipoprotein and bile salt metabolism. Leptin administration also resulted in decreased expression of genes involved in fatty acid and cholesterol synthesis, glycolysis, gluconeogenesis, and urea synthesis, and increased expression of genes mediating fatty acid oxidation, ATP synthesis, and oxidant defenses. The changes in mRNA expression are consistent with a switch in energy metabolism from glucose utilization and fatty acid synthesis to fatty acid oxidation and increased respiration. The latter changes may produce oxidant stress, explaining the unexpected finding that leptin induces a battery of genes involved in antioxidant defenses. Expression cluster analysis revealed responses of several sets of genes that were kinetically linked. Thus, the mRNA levels of genes involved in fatty acid and cholesterol synthesis are rapidly (<1 h) repressed by leptin administration, in association with an acute decrease in plasma insulin levels and decreased sterol regulator element-binding protein-1 expression. In contrast, genes participating in fatty acid oxidation and ketogenesis were induced more slowly (24 h), following an increase in expression of their common regulatory factor, peroxisome proliferator-activated receptor alpha. However, the regulation of genes involved in high density lipoprotein and bile salt metabolism shows complex kinetics and is likely to be mediated by novel transcription factors.

Protection from experimental endotoxemia by a recombinant adeno-associated virus encoding interleukin 10

BACKGROUND

Interleukin 10 (IL-10) is a homodimeric cytokine that shows considerable clinical promise. Adeno-associated virus (AAV) vectors appear increasingly useful for in vivo gene-transfer applications.

METHODS

A recombinant AAV type 2 vector encoding human IL-10 (rAAVhIL10) was constructed by using an adenoviral-free, three-plasmid co-transfection. Cytokine production was measured by using an enzyme-linked immunosorbent assay. Endotoxic shock was induced by lipopolysaccharide (LPS) injection.

RESULTS

As media from rAAVhIL10-infected COS cells caused a dose-dependent blockade of IL-12 secretion from spleen cells of IL-10 knockout (KO) mice challenged with Brucella abortus, it was clear that vector-derived hIL-10 was biologically active in vitro. Intravenous or intramuscular administration of relatively modest levels of rAAVhIL10 (10(10) genomes) to IL-10 KO mice resulted in hIL-10 secretion into the bloodstream, which, at 8 weeks, gave median serum levels of 0.9 and 0.45 pg/ml, respectively. Acute endotoxic shock led to a 33% mortality rate, and severe morbidity, in control IL-10 KO mice, whereas no mortality and little morbidity were seen in IL-10 KO mice given rAAVhIL10 7 weeks earlier.

CONCLUSIONS

The findings demonstrate that a modest dose of rAAVhIL10 administered in vivo provides long-term protection against LPS-induced endotoxic shock in a murine model. Thus, this vector may be useful for clinical applications requiring sustained IL-10 expression, for example in the treatment of several autoimmune diseases.

Dose-dependent effects of central leptin gene therapy on genes that regulate body weight and appetite in the hypothalamus

We have examined the dose-dependent effects and central action of intraventricular administration of a recombinant adeno-associated virus encoding rat leptin (rAAV-leptin) in suppressing body weight (BW) gain in adult female rats. A low dose of rAAV-leptin (5x10(10) particles) suppressed weight gain (15%) without changing daily food intake (FI), but a twofold higher dose decreased BW by 30% along with a reduction in daily FI. Reduced BW was due to a loss in body adiposity because serum leptin was reduced. Serum insulin levels were decreased (96%) by only the high dose along with a slight reduction in glucose. Uncoupling protein-1 (UCP-1) mRNA expression in brown adipose tissue (BAT), reflecting energy expenditure through thermogenesis, was upregulated to the same magnitude by the two rAAV-leptin doses. We analyzed by in situ hybridization the expression in the hypothalamus of genes encoding the appetite-regulating neuropeptides. Only the high dose decreased expression of neuropeptide Y (NPY), the orexigenic peptide, and increased proopiomelanocortin (POMC), precursor of the an orexigenic peptide, alpha-MSH. Our studies show for the first time that increased availability of leptin within the hypothalamus through central leptin gene therapy dose-dependently decreases weight gain, adiposity, and serum insulin by increasing energy expenditure and decreasing FI. The decrease in FI occurs only when NPY is reduced and alpha-MSH is increased in the hypothalamus by the high dose of rAAV-leptin. Delivery of the leptin gene centrally through rAAV vectors is a viable therapeutic modality for long-term control of weight and metabolic hormones.