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Agouti-Related Peptide

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Andrew S. I. Loudon – One of the best experts on this subject based on the ideXlab platform.

  • photoperiodic regulation of leptin resistance in the seasonally breeding siberian hamster phodopus sungorus
    Endocrinology, 2002
    Co-Authors: Karine Rousseau, Zeenat Atcha, Felino R Cagampang, Philippe Le Rouzic, Anne J Stirland, Tina R Ivanov, Francis J P Ebling, Martin Klingenspor, Andrew S. I. Loudon

    Abstract:

    Seasonal Siberian hamsters lose fat reserves, decrease body weight and leptin concentrations, and suppress reproduction on short-day photoperiod (SD). Chronic leptin infusion at physiological doses caused body weight and fat loss in SD animals but was ineffective in long-day (LD) hamsters. Using ovariectomized estrogen-treated females, we tested the hypothesis that responsiveness to leptin is regulated by photoperiod. On SD, hypothalamic neuroPeptide Y, Agouti-Related Peptide, and cocaine- and amphetamine-regulated transcript gene expression in the arcuate nucleus did not exhibit significant changes, and despite SD-induced fat loss, the catabolic Peptide proopiomelanocortin was down-regulated. Food restriction of LD-housed animals caused significant reduction of fat reserves and serum leptin concentrations to SD levels, suppressed serum gonadotropins, and induced increased anabolic (neuroPeptide Y, Agouti-Related Peptide) and decreased catabolic (proopiomelanocortin, cocaine- and amphetamineregulated transcript) gene expression in the arcuate nucleus. Leptin infusion in food-restricted animals had no effect on fat reserves or gonadotropins and did not modulate neuroPeptide gene expression. Also, leptin treatment did not blunt the refeeding responses or weight and fat gain in LD-housed foodrestricted animals. In conclusion, our results strongly suggest that hypothalamic responses to leptin are regulated primarily by photoperiod, rather than seasonal changes in fat reserves, sex steroids, or leptin concentrations. (Endocrinology 143: 3083–3095, 2002)

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  • Photoperiodic regulation of leptin resistance in the seasonally breeding Siberian hamster (Phodopus sungorus)
    Endocrinology, 2002
    Co-Authors: Karine Rousseau, Zeenat Atcha, Felino R Cagampang, Philippe Le Rouzic, Tina R Ivanov, Francis J P Ebling, Martin Klingenspor, J. Anne Stirland, Andrew S. I. Loudon

    Abstract:

    Seasonal Siberian hamsters lose fat reserves, decrease body weight and leptin concentrations, and suppress reproduction on short-day photoperiod (SD). Chronic leptin infusion at physiological doses caused body weight and fat loss in SD animals but was ineffective in long-day (LD) hamsters. Using ovariectomized estrogen-treated females, we tested the hypothesis that responsiveness to leptin is regulated by photoperiod. On SD, hypothalamic neuroPeptide Y, Agouti-Related Peptide, and cocaine- and amphetamine-regulated transcript gene expression in the arcuate nucleus did not exhibit significant changes, and despite SD-induced fat loss, the catabolic Peptide proopiomelanocortin was down-regulated. Food restriction of LD-housed animals caused significant reduction of fat reserves and serum leptin concentrations to SD levels, suppressed serum gonadotropins, and induced increased anabolic (neuroPeptide Y, Agouti-Related Peptide) and decreased catabolic (proopiomelanocortin, cocaine- and amphetamine-regulated transcript) gene expression in the arcuate nucleus. Leptin infusion in food-restricted animals had no effect on fat reserves or gonadotropins and did not modulate neuroPeptide gene expression. Also, leptin treatment did not blunt the refeeding responses or weight and fat gain in LD-housed food-restricted animals. In conclusion, our results strongly suggest that hypothalamic responses to leptin are regulated primarily by photoperiod, rather than seasonal changes in fat reserves, sex steroids, or leptin concentrations.

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Francis J P Ebling – One of the best experts on this subject based on the ideXlab platform.

  • Short-days induce weight loss in Siberian hamsters despite overexpression of the Agouti-Related Peptide gene.
    Journal of Neuroendocrinology, 2010
    Co-Authors: Preeti H. Jethwa, Roger A.h. Adan, Amy Warner, Maxine J Fowler, Michelle Murphy, M.w.a. De Backer, Perry Barrett, John M. Brameld, Francis J P Ebling

    Abstract:

    Many vertebrates express profound annual cycles of body fattening, although it is not clear whether these represent differential activity of the central pathways known to mediate homeostatic control of food intake and energy expenditure, or whether the recent discovery of a major role for pars tuberalis-ependymal signalling points towards novel mechanisms. We examined this in the Siberian hamster (Phodopus sungorus) by using gene transfection to up-regulate a major orexigenic Peptide, Agouti-Related Peptide (AgRP), and then determined whether this increased anabolic drive could prevent the short-day induced winter catabolic state. Infusions of a recombinant adeno-associated virus encoding an AgRP construct into the hypothalamus of hamsters in the long-day obese phase of their seasonal cycle produced a 20% gain in body weight over 6 weeks compared to hamsters receiving a control reporter construct, reflecting a significant increase in food intake and a significant decrease in energy expenditure. However, all hamsters showed a significant, prolonged decrease in body weight when exposed to short photoperiods, despite the hamsters expressing the AgRP construct maintaining a higher food intake and lower energy expenditure relative to the control hamsters. Visualisation of the green fluorescent protein reporter and analysis of AgRP-immunoreactivity confirmed widespread expression of the construct in the hypothalamus, which was maintained for the 21-week duration of the study. In conclusion, the over-expression of AgRP in the hypothalamus produced a profoundly obese state but did not block the seasonal catabolic response, suggesting a separation of rheostatic mechanisms in seasonality from those maintaining homeostasis of energy metabolism.

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  • photoperiodic regulation of leptin resistance in the seasonally breeding siberian hamster phodopus sungorus
    Endocrinology, 2002
    Co-Authors: Karine Rousseau, Zeenat Atcha, Felino R Cagampang, Philippe Le Rouzic, Anne J Stirland, Tina R Ivanov, Francis J P Ebling, Martin Klingenspor, Andrew S. I. Loudon

    Abstract:

    Seasonal Siberian hamsters lose fat reserves, decrease body weight and leptin concentrations, and suppress reproduction on short-day photoperiod (SD). Chronic leptin infusion at physiological doses caused body weight and fat loss in SD animals but was ineffective in long-day (LD) hamsters. Using ovariectomized estrogen-treated females, we tested the hypothesis that responsiveness to leptin is regulated by photoperiod. On SD, hypothalamic neuroPeptide Y, Agouti-Related Peptide, and cocaine- and amphetamine-regulated transcript gene expression in the arcuate nucleus did not exhibit significant changes, and despite SD-induced fat loss, the catabolic Peptide proopiomelanocortin was down-regulated. Food restriction of LD-housed animals caused significant reduction of fat reserves and serum leptin concentrations to SD levels, suppressed serum gonadotropins, and induced increased anabolic (neuroPeptide Y, Agouti-Related Peptide) and decreased catabolic (proopiomelanocortin, cocaine- and amphetamineregulated transcript) gene expression in the arcuate nucleus. Leptin infusion in food-restricted animals had no effect on fat reserves or gonadotropins and did not modulate neuroPeptide gene expression. Also, leptin treatment did not blunt the refeeding responses or weight and fat gain in LD-housed foodrestricted animals. In conclusion, our results strongly suggest that hypothalamic responses to leptin are regulated primarily by photoperiod, rather than seasonal changes in fat reserves, sex steroids, or leptin concentrations. (Endocrinology 143: 3083–3095, 2002)

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  • Photoperiodic regulation of leptin resistance in the seasonally breeding Siberian hamster (Phodopus sungorus)
    Endocrinology, 2002
    Co-Authors: Karine Rousseau, Zeenat Atcha, Felino R Cagampang, Philippe Le Rouzic, Tina R Ivanov, Francis J P Ebling, Martin Klingenspor, J. Anne Stirland, Andrew S. I. Loudon

    Abstract:

    Seasonal Siberian hamsters lose fat reserves, decrease body weight and leptin concentrations, and suppress reproduction on short-day photoperiod (SD). Chronic leptin infusion at physiological doses caused body weight and fat loss in SD animals but was ineffective in long-day (LD) hamsters. Using ovariectomized estrogen-treated females, we tested the hypothesis that responsiveness to leptin is regulated by photoperiod. On SD, hypothalamic neuroPeptide Y, Agouti-Related Peptide, and cocaine- and amphetamine-regulated transcript gene expression in the arcuate nucleus did not exhibit significant changes, and despite SD-induced fat loss, the catabolic Peptide proopiomelanocortin was down-regulated. Food restriction of LD-housed animals caused significant reduction of fat reserves and serum leptin concentrations to SD levels, suppressed serum gonadotropins, and induced increased anabolic (neuroPeptide Y, Agouti-Related Peptide) and decreased catabolic (proopiomelanocortin, cocaine- and amphetamine-regulated transcript) gene expression in the arcuate nucleus. Leptin infusion in food-restricted animals had no effect on fat reserves or gonadotropins and did not modulate neuroPeptide gene expression. Also, leptin treatment did not blunt the refeeding responses or weight and fat gain in LD-housed food-restricted animals. In conclusion, our results strongly suggest that hypothalamic responses to leptin are regulated primarily by photoperiod, rather than seasonal changes in fat reserves, sex steroids, or leptin concentrations.

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Karine Rousseau – One of the best experts on this subject based on the ideXlab platform.

  • photoperiodic regulation of leptin resistance in the seasonally breeding siberian hamster phodopus sungorus
    Endocrinology, 2002
    Co-Authors: Karine Rousseau, Zeenat Atcha, Felino R Cagampang, Philippe Le Rouzic, Anne J Stirland, Tina R Ivanov, Francis J P Ebling, Martin Klingenspor, Andrew S. I. Loudon

    Abstract:

    Seasonal Siberian hamsters lose fat reserves, decrease body weight and leptin concentrations, and suppress reproduction on short-day photoperiod (SD). Chronic leptin infusion at physiological doses caused body weight and fat loss in SD animals but was ineffective in long-day (LD) hamsters. Using ovariectomized estrogen-treated females, we tested the hypothesis that responsiveness to leptin is regulated by photoperiod. On SD, hypothalamic neuroPeptide Y, Agouti-Related Peptide, and cocaine- and amphetamine-regulated transcript gene expression in the arcuate nucleus did not exhibit significant changes, and despite SD-induced fat loss, the catabolic Peptide proopiomelanocortin was down-regulated. Food restriction of LD-housed animals caused significant reduction of fat reserves and serum leptin concentrations to SD levels, suppressed serum gonadotropins, and induced increased anabolic (neuroPeptide Y, Agouti-Related Peptide) and decreased catabolic (proopiomelanocortin, cocaine- and amphetamineregulated transcript) gene expression in the arcuate nucleus. Leptin infusion in food-restricted animals had no effect on fat reserves or gonadotropins and did not modulate neuroPeptide gene expression. Also, leptin treatment did not blunt the refeeding responses or weight and fat gain in LD-housed foodrestricted animals. In conclusion, our results strongly suggest that hypothalamic responses to leptin are regulated primarily by photoperiod, rather than seasonal changes in fat reserves, sex steroids, or leptin concentrations. (Endocrinology 143: 3083–3095, 2002)

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  • Photoperiodic regulation of leptin resistance in the seasonally breeding Siberian hamster (Phodopus sungorus)
    Endocrinology, 2002
    Co-Authors: Karine Rousseau, Zeenat Atcha, Felino R Cagampang, Philippe Le Rouzic, Tina R Ivanov, Francis J P Ebling, Martin Klingenspor, J. Anne Stirland, Andrew S. I. Loudon

    Abstract:

    Seasonal Siberian hamsters lose fat reserves, decrease body weight and leptin concentrations, and suppress reproduction on short-day photoperiod (SD). Chronic leptin infusion at physiological doses caused body weight and fat loss in SD animals but was ineffective in long-day (LD) hamsters. Using ovariectomized estrogen-treated females, we tested the hypothesis that responsiveness to leptin is regulated by photoperiod. On SD, hypothalamic neuroPeptide Y, Agouti-Related Peptide, and cocaine- and amphetamine-regulated transcript gene expression in the arcuate nucleus did not exhibit significant changes, and despite SD-induced fat loss, the catabolic Peptide proopiomelanocortin was down-regulated. Food restriction of LD-housed animals caused significant reduction of fat reserves and serum leptin concentrations to SD levels, suppressed serum gonadotropins, and induced increased anabolic (neuroPeptide Y, Agouti-Related Peptide) and decreased catabolic (proopiomelanocortin, cocaine- and amphetamine-regulated transcript) gene expression in the arcuate nucleus. Leptin infusion in food-restricted animals had no effect on fat reserves or gonadotropins and did not modulate neuroPeptide gene expression. Also, leptin treatment did not blunt the refeeding responses or weight and fat gain in LD-housed food-restricted animals. In conclusion, our results strongly suggest that hypothalamic responses to leptin are regulated primarily by photoperiod, rather than seasonal changes in fat reserves, sex steroids, or leptin concentrations.

    Free Register to Access Article