Leptin gene therapy and daily protein administration: a comparative study in the ob/ob mouse

Abstract

We have compared the efficacy of daily injection of recomgiven as mean ± standard error of the mean.) Importantly, binant leptin protein (rh-leptin) with adenovirus-mediated rh-leptin and ex vivo-expressed Ad-leptin were equivalently delivery of the murine or human leptin gene (Ad-leptin) for active in a functional cell-based assay. The primary differtreatment of obesity in the obese (ob/ob) mouse model. ence in the two therapeutic approaches is the continuous We demonstrate an improved correction profile for obesity chronic secretion of leptin mediated by gene delivery, verand associated surrogate markers using the adenovirus sus the intermittent bolus delivery and rapid clearance of delivery method. Rate of weight loss and percentage satthe daily injection of rh-leptin protein. Thus, in vivo findings iety were significantly greater in the mice treated with Adsuggest that leptin effects are better achieved at lower leptin. These findings were associated with lower peak steady-state levels, a pharmacological feature attained serum leptin levels with Ad-leptin (22.9 ± 2.6 ng/ml for the here by gene therapy. These findings may have implihuman gene, and 48.9 ± 11.5 ng/ml for the murine gene) cations for the potential use of leptin in the treatment of compared to rh-leptin (385.2 ± 36.0 ng/ml). (Values are obesity.

An adenoviral vector deleted for all viral coding sequences results in enhanced safety and extended expression of a leptin transgene

“…Construction of Ad-leptin and Ad-␤-galalactosidase (␤-gal) recombinant vectors has been described (30). The expression cassettes contain the human cytomegalovirus (HCMV) promoter (Invitrogen), the transgene, and the bovine growth hormone poly(A) sequence.…”

“…For Northern blot analysis, total RNA was extracted (Trizol, GIBCO) from livers of Ad-leptin-treated and HD-leptin-treated mice at 1-, 2-, 4-, and 8-week intervals, and untreated mice. Leptin RNA message was detected by Northern blot analysis (35) using leptin cDNA as a probe that recognizes a single Ϸ500 bp band (30). A probe for ␤-actin was used as the internal control (Ϸ1 kb) (Biochain, San Leandro, CA).…”

“…Daily delivery of recombinant leptin protein was shown to induce weight reduction, suppress appetite, and decrease blood insulin and glucose levels in ob͞ob (leptindeficient) mice (27)(28)(29). It has been shown that delivery of the leptin cDNA by first-generation Ad vectors (Ad-leptin) may substitute for daily recombinant leptin protein treatment, although the effects were transient in both lean and ob͞ob treated mice (7,30). In the present study, we delivered the leptin cDNA using the HD virus (HD-leptin), testing the hypothesis that elimination of the viral protein coding sequences would diminish the vector's cellular immunogenicity and toxicity, and hence support its longevity in vivo.…”

Methodological approaches to assess body-weight regulation and aetiology of obesity

“…Furthermore, treatment of these animals with a recombinant adenovirus expressing the mouse leptin cDNA (AdRSV-leptin) resulted in a rapid reduction in food consumption and drastic weight loss, which led to a complete, although transient, correction of obesity and diabetes as serum leptin levels decreased after 2-3 weeks (Muzzin et al 1996). Comparing the efficacy of daily injection of recombinant leptin protein with adenovirusmediated delivery of leptin for obesity treatment, Morsy et al (1998b) found that there is a continuous chronic secretion of leptin mediated by gene delivery v. the intermittent bolus delivery and rapid clearance of the daily leptin protein injection. Furthermore, in vivo studies suggest that leptin effects are better achieved at the lower steady-state levels achieved by gene therapy.…”

Hypothalamic delivery of doxycycline-inducible leptin gene allows for reversible transgene expression and physiological responses

“…1 Leptin gene delivery is substantially more effective in correcting genetic obesity than daily leptin infusion, despite higher peak serum leptin levels with the latter. 2 Peripheral administration of virally encoded leptin requires that the leptin crosses the blood-brain barrier (BBB) to reach its primary hypothalamic targets, but this transport system is saturated at serum leptin levels seen in obese animals. 3 Since several obese, leptin-resistant models respond better to central versus peripheral administration of recombinant leptin, [4][5][6] it has been reasoned that central delivery of the leptin gene would be superior to peripheral delivery.…”