Ghrelin's role in glucose homestasis during aging

描述（由申请人提供）：葡萄糖耐受不良和肥胖相关的2型糖尿病的发病率随年龄增加而增加。与年龄相关的葡萄糖耐受不良的机制尚不清楚，但似乎与B细胞功能受损和胰岛素敏感性降低有关。对肥胖和糖尿病相关基因的鉴定和表征将为我们对糖尿病机制的理解增加必要的知识，并导致可以改善老年人生活质量的干预措施。Ghrelin是已知的唯一刺激食欲的循环肽，从而促进肥胖。我们产生并表征了生长素释放肽缺失小鼠;出乎意料的是，成年生长素释放肽-/-小鼠不受饮食诱导的肥胖的保护。令人惊讶地发现，饥饿素失活增加了响应于葡萄糖激发的胰岛素分泌，并增加了外周胰岛素敏感性。Ghrelin和Leptin是能量平衡中的相互拮抗剂。瘦素缺陷小鼠（ob/ob）是贪食、肥胖和高血糖的。为了研究生长素释放肽和瘦素之间的相互作用，我们还产生了生长素释放肽缺陷的ob/ob小鼠。生长素释放肽在ob/ob小鼠中的失活未能挽救肥胖的超噬表型，这表明ob/ob表型不是生长素释放肽不受瘦素对抗的结果;然而，尽管它们的体重相似，但生长素释放肽-/-.ob/ob小鼠的血糖显著降低。我们的数据表明，低ghrelin水平可能对糖尿病患者有有益的影响。我们的初步研究表明，小鼠的ghrelin水平可能会随着年龄的增长而增加，因此我们假设ghrelin水平越高，衰老期间糖尿病的发病率越高。因此，Ghrelin拮抗剂可以预防和/或降低衰老期间2型糖尿病的发病率。该提议的具体目的是1）使用我们独特的小鼠模型来鉴定介导生长素释放肽对衰老小鼠中恶化的葡萄糖耐受不良的作用的调节剂，以及2）随后确定它们的表达是否由生长素释放肽调节并且与年龄相关。这些研究将进一步阐明衰老过程中糖尿病和葡萄糖稳态的分子机制，并可能导致发现预防和/或治疗衰老相关糖尿病的新方法。

DESCRIPTION (provided by applicant): The incidence of glucose intolerance and obesity-related Type 2 diabetes increases with age. The mechanisms of age-related glucose intolerance are not clear, but it appears to be related to both impaired b- cell function and decreased insulin sensitivity. Identification and characterization of the genes involved in obesity and diabetes will add essential knowledge to our understanding of the mechanisms of diabetes and lead to interventions that can improve the quality of life in the elderly. Ghrelin is the only circulating peptide known to stimulate appetite and; thereby, promote obesity. We generated and characterized ghrelin-null mice; unexpectedly adult ghrelin-/- mice are not protected against diet-induced obesity. It was surprising to find that ghrelin inactivation augments insulin secretion in response to glucose challenge and increases peripheral insulin sensitivity. Ghrelin and leptin are mutual antagonists in energy homeostasis. Leptin-deficient mice (ob/ob) are hyperphagic, obese and hyperglycemic. To investigate the interplay between ghrelin and leptin, we also generated ghrelin-deficient ob/ob mice. The inactivation of ghrelin in ob/ob mice fails to rescue the obese hyperphagic phenotype, which indicates that the ob/ob phenotype is not a consequence of ghrelin unopposed by leptin; however, despite their similar body weights, blood glucose is markedly reduced in ghrelin-/-.ob/ob mice. Our data suggest that low ghrelin levels may have a beneficial effect for diabetes patients. Our preliminary studies show that ghrelin levels may increase with age in mice, so we hypothesize that higher ghrelin levels contribute to a higher incidence of diabetes during aging. Ghrelin antagonists may; therefore, prevent and/or reduce the Incidence of Type 2 diabetes during aging. The specific aims of this proposal are 1) to use our unique mouse models to identify the regulators which mediate ghrelin's effect on the worsened glucose intolerance in aging mice and 2) to subsequently determine if their expression is regulated by ghrelin and correlated with age. These studies will shed more light on the molecular mechanisms of diabetes and glucose homeostasis during aging, and may potentially lead to the discovery of new means for the prevention and/or treatment of aging-related diabetes.