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

Wilsey, Jared; Zolotukhin, Sergei; Prima, Victor; Shek, Eugene W.; Matheny, Michael; Scarpace, Philip J.

doi:10.1038/sj.gt.3301835

Cited by 20 publications

(18 citation statements)

References 34 publications

(43 reference statements)

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“…Animals that had their leptin transgene continuously activated for 2 months tended to have reduced hypothalamic leptin receptor expression relative to rats receiving control vector. Furthermore, when the transgene expression was silenced for 1 month, leptin receptor expression increased significantly [22].…”

Section: Discussionmentioning

confidence: 99%

“…In our earlier study, we employed a form of rAAV-leptin containing a tetracycline-responsive promoter. This system allows us to regulate leptin transgene expression via doxycycline in the drinking water [22]. Animals that had their leptin transgene continuously activated for 2 months tended to have reduced hypothalamic leptin receptor expression relative to rats receiving control vector.…”

Section: Discussionmentioning

confidence: 99%

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Leptin resistance exacerbates diet-induced obesity and is associated with diminished maximal leptin signalling capacity in rats

et al. 2005

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Aims/hypothesis: Leptin resistance is generally considered a consequence of obesity. We postulated that leptin resistance is associated with diminished hypothalamic leptin signalling capacity and that leptin resistance is causal to obesity. We assessed maximal leptin-mediated binding of the transcription factor signal transducer and activator of transcription 3 (STAT3), and the response to high-fat feeding in lean leptin-resistant rats. Materials and methods: Recombinant adeno-associated virus encoding rat leptin cDNA (rAAV-leptin) or control vector were administered by intracerebroventricular injection to lean F344×BN rats for up to 150 days, and food consumption, body weight, serum leptin and glucose tolerance were measured. Leptin-mediated hypothalamic transcription factor binding was assessed at day 150 following an intracerebroventricular injection of 2 μg leptin. Rats pretreated with either control or rAAV-leptin vector for 94 days were given a high-fat diet, and energy intake, body weight gain and adiposity were examined. Results: The rAAV-leptin-treated rats initially responded to leptin gene delivery then became leptin-resistant. They displayed persistent submaximal hypothalamic leptin signalling and enhanced insulin sensitivity, yet maximal hypothalamic signalling capacity was decreased by more than 50%. On a high-fat diet, the leptinresistant rats consumed more energy, gained more weight and accumulated greater visceral fat mass than controls. Conclusions/interpretation: The maximal hypothalamic leptin signalling capacity was diminished in leptin-resistant rats receiving central rAAV-leptin gene therapy. Moreover, this leptin-invoked leptin resistance perturbs the regulation of energy homeostasis in response to high fat exposure, producing augmented energy consumption. This, coupled with potential hypersensitivity to insulin, creates a milieu favouring fat deposition. Our data suggest that leptin resistance is both a consequence and cause of obesity.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Leptin resistance exacerbates diet-induced obesity and is associated with diminished maximal leptin signalling capacity in rats

et al. 2005

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“…This model of central leptin resistance shares many common characteristics with the leptin resistance induced by diet-induced obesity. Moreover, most of the consequences of diet-induced obesity on central leptin resistance can be mimicked by elevation of central leptin, suggesting that the central component of leptin resistance may be mainly due to elevated leptin secondary to obesity (Scarpace et al, 2002b(Scarpace et al, , 2005Wilsey et al, 2002). Therefore, mechanistic studies with our overexpression model should aid in understanding the central leptin resistance associated with diet-induced obesity.…”

Section: Discussionmentioning

confidence: 99%

Leptin Antagonist Reveals an Uncoupling between Leptin Receptor Signal Transducer and Activator of Transcription 3 Signaling and Metabolic Responses with Central Leptin Resistance

Scarpace¹,

Matheny²,

Zhang³

et al. 2006

J Pharmacol Exp Ther

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Leptin-resistant rats have reduced leptin receptors and signaling and are refractory to exogenous leptin. However, it is unclear how leptin-mediated hypothalamic signal transducer and activator of transcription 3 (STAT3) signaling relates to the loss of physiological responsiveness. We hypothesized that if leptin resistance is associated with leptin receptors that are no longer functionally coupled to leptin responses, then a leptin antagonist should be less effective in leptin-resistant compared with leptin-responsive rats. Hypothalamic leptin resistance was induced in lean rats with a recombinant adeno-associated viral (rAAV) vector encoding leptin by intracerebroventricular injection. Following development of leptin resistance, at day 153, these rats and control rats were infused centrally either with vehicle or a rat leptin antagonist for 14 days. Food intake, body weight, adiposity, and uncoupling protein 1 expression increased with antagonist infusion in controls but elevated only marginally in leptin-resistant rats. Basal hypothalamic STAT3 signaling remained unchanged with antagonist infusion in control rats despite the pronounced orexigenic response in these animals. STAT3 phosphorylation in rats pretreated with rAAVleptin to induce leptin resistance was elevated 2-fold. Paradoxically, in these leptin-resistant rats, the antagonist fully reversed the 2-fold elevated phosphorylated STAT3, but it evoked minimal physiological responses. These data reveal an uncoupling between leptin receptor activation and metabolic responses with central leptin resistance.Peripherally produced leptin acts within the central nervous system to regulate energy homeostasis by curtailing food consumption and boosting energy expenditure (Elmquist et al., 1998;Friedman and Halaas, 1998). These central effects of leptin are often diminished or fully lost in humans and animals with genetic, diet-induced, or adultonset obesity (Caro et al., 1996;Considine et al., 1996;Halaas et al., 1997;Scarpace et al., 2000), a phenomenon identified as leptin resistance. Despite intensive investigation, the nature of leptin resistance remains elusive. Central leptin resistance is characterized by reduced leptin receptors and diminished leptin signaling through both the STAT3 phosphorylation and PI3 kinase pathways (Scarpace et al., 2001;Sahu and Metlakunta, 2005). Stimulation of the central melanocortin system downstream of the leptin receptor with ␣-melanocyte-stimulating hormone agonists circumvents leptin resistance associated with diet-induced obesity (Hansen et al., 2001), adult-onset obesity (Zhang et al., 2004), or chronic exposure to high levels of leptin . These data suggest that leptin resistance lies primarily within the first-order, leptin-receptor-containing neurons, and they argue that leptin resistance is a result of diminished leptin receptor activity.However, the reductions in leptin receptors and hypothalamic STAT3 signaling apparently do not match either the magnitude or temporal loss of physiological leptin responses. ...

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“…The physiological responses to this TET-Ob gene therapy system, as well as details about its production and delivery, have been previously described in detail (Wilsey et al 2002). All rats received doxycycline hydrochloride (Sigma, St Louis, MO, USA) (400 µg/ml) in their drinking water for 34 days, activating the leptin transgene.…”

Section: Experimental Design 3: Effect Of Central Leptin Overexpressimentioning

confidence: 99%

Caloric restriction reverses the deficits in leptin receptor protein and leptin signaling capacity associated with diet-induced obesity: role of leptin in the regulation of hypothalamic long-form leptin receptor expression

Wilsey

Scarpace

2004

Journal of Endocrinology

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The objectives of this study were to determine if reduced long-form leptin receptor (ObRb) expression in dietinduced obese (DIO) animals is associated with deficits in maximal leptin signaling and, secondly, to establish the effects of short-term caloric restriction (CR) on ObRb expression and function. Groups of DIO and life-long chow-fed (CHOW) F344 BN male rats, aged 6 months, were given an i.c.v. injection containing 2 µg leptin or artificial cerebrospinal fluid (ACSF) vehicle. Leptin induced a .6-fold increase in STAT3 phosphorylation in CHOW rats, but less than 2-fold increase in DIO. Reduced maximal leptin-stimulated STAT3 phosphorylation in DIO rats was coupled with a decline in both ObRb expression and protein. At this point, subgroups of DIO and CHOW animals underwent CR for 30 days and were then tested for acute leptin responsiveness. CR resulted in a 45 and 85% increase respectively in leptinstimulated STAT3 phosphorylation in CHOW and DIO animals. Similarly, CR increased ObRb expression and protein in both CHOW and DIO animals. To explore the role of leptin in regulating ObRb expression, we reversibly overexpressed leptin in the hypothalamus and found that ObRb mRNA inversely follows central leptin expression. By enhancing both ObRb expression and signaling capacity, CR may enhance leptin responsiveness in leptinresistant DIO animals.

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

Cited by 20 publications

References 34 publications

Leptin resistance exacerbates diet-induced obesity and is associated with diminished maximal leptin signalling capacity in rats

Leptin resistance exacerbates diet-induced obesity and is associated with diminished maximal leptin signalling capacity in rats

Leptin Antagonist Reveals an Uncoupling between Leptin Receptor Signal Transducer and Activator of Transcription 3 Signaling and Metabolic Responses with Central Leptin Resistance

Caloric restriction reverses the deficits in leptin receptor protein and leptin signaling capacity associated with diet-induced obesity: role of leptin in the regulation of hypothalamic long-form leptin receptor expression

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