Targeting adipose tissue via systemic gene therapy

Abstract

Adipose tissue plays 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 CMV 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 9-10 week old ob/ob mice. Phenotypic changes were measured over an eight 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.

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

“…Replacing the CMV promoter with the human adiponectin enhancer/promoter enhances specificity to adipose tissue, whereas transgene expression is not suppressed in liver. Incorporation of the miR-122 target sequence (miR-122T) into the 3′ UTR of the AAV vector can eliminate hepatic transgene expression, but often at the expense of lower transgene expression in adipose tissue 6 . In addition, the dose of 1 × 10 12 vg per mouse used in this study is approximately 100-fold higher than the dose of Rec2 vector direct fat injection 6, 7.…”

“…One study reports that i.v. administration of the AAV8 vector transduces adipose tissues, liver, and other tissues 6 . Replacing the CMV promoter with the human adiponectin enhancer/promoter enhances specificity to adipose tissue, whereas transgene expression is not suppressed in liver.…”

“…Incorporation of the miR-122 target sequence (miR-122T) into the 3′ UTR of the AAV vector can eliminate hepatic transgene expression, but often at the expense of lower transgene expression in adipose tissue 6 . In addition, the dose of 1 × 10 12 vg per mouse used in this study is approximately 100-fold higher than the dose of Rec2 vector direct fat injection 6, 7. In this work, we designed a novel dual-cassette AAV expression plasmid and combined this liver-restricting strategy with the adipo-trophic Rec2 serotype and i.p.…”

“…Modifications of the capsid or expression cassette are employed to improve efficiency of gene delivery and transgene tropism with either local or systematic delivery. For example, selecting more efficient naturally occurring serotypes plus the use of an adipose-tissue-specific promoter or microRNA-targeting sequence enable specific transduction of adipose tissue but require a high dose to achieve therapeutic effects 5, 6. We recently demonstrated that a novel engineered hybrid serotype Rec2 vector leads to high transduction of adipose tissue that is superior to naturally occurring serotypes (AAV1 and AAV8) and other engineered serotypes (Rec1, Rec3, and Rec4) when the vectors are injected directly to the fat pads at a dose 1 to 2 orders lower than those used in previously reported studies 7, 8, 9, 10.…”

Recombinant adeno-associated virus vectors in the treatment of rare diseases

“…Depending on the rare disease, the therapeutic need could be localized or systemic. The ability to generate designer rAAVs that home to specific tissue types has been describe in numerous reviews about gene therapy of the central nervous system (CNS) 47-50 , eye 51, 52 , heart 53, 54 , lungs 55, 56 , ear 57 , liver 58 , bones and joints 59 , muscle 60, 61 , or adipose 62, 63 tissue. Many of the ongoing clinical trials of rAAV are exploring rare diseases that require tissue specific treatment (Table 1).…”