Kinetics of Human Homocysteine Metabolism

描述（由申请人提供）：本提案的目标是解决血糖控制不良的II型糖尿病（DM2）患者由于Hcy代谢受损而具有较高水平的基础同型半胱氨酸（Hcy）的假设。血浆中测量的Hcy水平是通过转甲基化（TM）从蛋氨酸产生的速率与通过再甲基化（RM）返回蛋氨酸或转硫化（TS）到半胱硫氨酸的处理速率之间的平衡。先前的研究支持这样一种观点，即Hcy升高是心血管疾病（CVD）的一个强大的独立危险因素，特别是在DM2中。因此，研究DM2中Hcy水平升高的原因对这一人群的心血管疾病风险管理具有重要意义。我将在普通临床研究中心（GCRC）使用同位素标记的蛋氨酸和亮氨酸量化患者和对照组的Hcy代谢动力学，并使用气相色谱/质谱（GC/MS）进行分析。患者和对照组将在年龄和性别上匹配，所有受试者的血浆叶酸和维生素B水平都将正常，这是通过直接测量确定的。我还将讨论通过胰岛素治疗改善血糖控制的假设，通过改变最初血糖控制较差的DM2患者的Hcy产生和/或处置率来降低基础Hcy水平。稳定同位素动力学和GC/MS分析也将用于解决这一假设。血糖控制水平将通过直接测量糖化血红蛋白（HbA,c）来评估。职业发展规划包括：1)监督培训，学习使用同位素标记底物评估1-碳代谢；2)监督在佛罗里达大学尚兹医疗广场糖尿病中心的临床培训，对DM2患者的诊断和管理，最终申请成为一名注册糖尿病教育者；3)正式的教学课程（K30奖学金）；4)继续专业教育（即美国糖尿病协会研究生课程）。在GCRC、内分泌与代谢学部、食品科学与人类营养学部的指导和支持下，这段时间的监督研究和临床培训对于增强我对疾病和健康状态下人体代谢调节的理解至关重要。在这个申请中提出的具体研究将使我获得关于DM2中Hcy代谢动力学的新数据，这将在这个K01奖的第二年演变成正式的R01申请，以促进我过渡到一个独立的，联邦资助的研究者。这与我的长期目标直接相关，我的目标是将实验室技术应用于基于gcrc的、以机制为导向的代谢扰动（如运动训练和药物治疗）对糖尿病预防和治疗的影响的研究。

DESCRIPTION (provided by applicant):The goal of this proposal is to address the hypothesis that type II diabetes (DM2) patients with poor glycemic control have higher levels of basal homocysteine (Hcy) due to impaired Hcy metabolism. The level of Hcy measured in plasma is the balance between its rate of production from methionine, via transmethylation (TM), and disposal, through remethylation (RM) back to methionine or transulfuration (TS) to cystathionine. Previous research supports the notion that elevated Hcy is a strong, independent risk factor for cardiovascular disease (CVD), particularly in DM2. Thus, studies addressing the cause(s) of the elevated Hcy levels in DM2 have important implications for CVD risk management in this population. I will quantify the kinetics of Hcy metabolism in patients and controls on the General Clinical Research Center (GCRC) using isotopically labeled methionine and leucine, and analysis using gas chromatography/mass spectrometry (GC/MS). Patients and controls will be matched for age and sex, and all subjects will have normal plasma folate and B vitamin levels, as established by direct measurement. I will also address the hypothesis that improved glycemic control, achieved through insulin therapy, decreases basal Hcy levels by altering the rate of Hcy production and/or disposal in DM2 patients who initially have poor glycemic control. Stable isotope kinetics and GC/MS analysis will also be used to address this hypothesis. Level of glycemic control will be assessed by direct measurement of glycated hemoglobin (HbA,c). The career development plan includes: 1) supervised training to learn the assessment of 1-carbon metabolism using isotopically labeled substrates, 2) supervised clinical training in the Diabetes Center, Shands Medical Plaza at the University of Florida, in the diagnosis and management of DM2 patients, to culminate with my application to become a Certified Diabetes Educator, 3) formal didactic coursework (K30 Fellowship), and 4) continuing professional education (i.e., American Diabetes Association Postgraduate Course). This period of supervised research and clinical training, with guidance and support from the GCRC, the Division of Endocrinology and Metabolism, and the Department of Food Science and Human Nutrition, is vital to enhance my understanding of human metabolic regulation in both diseased and healthy states. The specific research proposed in this application will allow me to obtain novel data on the kinetics of Hcy metabolism in DM2 that will evolve into a formal R01 application during year 02 of this K01 award, to facilitate my transition to an independent, federally funded investigator. This is directly related to my long-term goal of applying laboratory techniques to GCRC-based, mechanistically oriented studies of the effects of metabolic perturbations (e.g., exercise training and pharmacotherapy) on diabetes prevention and therapy.