Comparisons of insulin related parameters in commercial-type chicks: Evidence for insulin resistance in broiler chicks |
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Authors: | Shiraishi Jun-Ichi Yanagita Kouichi Fukumori Rika Sugino Toshihisa Fujita Masanori Kawakami Shin-Ichi McMurtry John P Bungo Takashi |
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Institution: | a Laboratory of Animal Behavior and Physiology, Graduate School of Biosphere Science, Hiroshima University, Higashi-Hiroshima 739-8528, Japanb Laboratory of Animal Nutrition and Feeding, Graduate School of Biosphere Science, Hiroshima University, Higashi-Hiroshima 739-8528, Japanc United States Department of Agriculture, Agricultural Research Service, Animal and Natural Resources Institute, Animal Biosciences and Biotechnology Laboratory, Beltsville, MD 20705-2350, USA |
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Abstract: | The aim of this study is to elucidate whether insulin acts differentially within the central nervous system (CNS) of two types of commercial chicks to control ingestive behavior. Male layer and broiler chicks (4-day-old) were intracerebroventricularly (ICV) injected with saline or insulin under satiated and starved conditions. Feed intake was measured at 30, 60 and 120 min after treatment. Secondly, blood and hypothalamus were collected from both chick types under ad libitum feeding and fasting for 24 h. Plasma insulin concentration was measured by time-resolved fluoro-immunoassay. Hypothalamic insulin receptor mRNA expression levels were measured by quantitative RT-PCR. The ICV injection of insulin significantly inhibited feed consumption in layer chicks when compared with saline (P < 0.05), but not broiler chicks (P > 0.1). Plasma insulin concentration of both chick types significantly decreased following 24 h of fasting, while insulin concentrations in the broiler chicks were significantly higher compared to the layers fed under ad libitum conditions. Hypothalamic insulin receptor mRNA expression levels were significantly lower (P < 0.05) in broiler chicks than in layer ones under ad libitum feeding. Feed deprivation significantly decreased insulin receptor mRNA levels in layer chicks (P < 0.01), but not in broiler chicks (P > 0.1). Moreover, plasma insulin concentrations correlated negatively with hypothalamic insulin receptor protein expression in the two types of chicks fed ad libitum (P < 0.05). These results suggest that insulin resistance exists in the CNS of broiler chicks, possibly due to persistent hyperinsulinemia, which results in a down-regulation of CNS insulin receptor expression compared to that in layer chicks. |
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Keywords: | Central nervous system Insulin Layer Broiler Feed intake |
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