PATHOGENESIS OF KETOSIS-PRONE DIABETES

这个子项目是许多利用资源的研究子项目之一 由NIH/NCRR资助的中心拨款提供。子项目的主要支持 而子项目的主要调查员可能是由其他来源提供的， 包括其它NIH来源。 列出的子项目总成本可能 代表子项目使用的中心基础设施的估计数量， 而不是由NCRR赠款提供给子项目或子项目工作人员的直接资金。 摘要 酮症倾向性糖尿病（KPD）是一种新出现的、广泛分布的糖尿病，其特征在于表现为糖尿病酮症酸中毒（DKA）。 KPD最常见的形式是称为A-b+ KPD的亚组。 除了在最初表现时易发生酮症和非免疫介导的严重β细胞功能障碍外，A-b+ KPD患者的临床特征与典型的2型糖尿病患者非常相似，他们是中年人，超重或肥胖，具有高频率的代谢综合征，并具有残余的β细胞功能储备。 这种新型综合征的病理生理学尚不清楚。 在仔细分型的患者中使用代谢组学方法，与瘦和肥胖的非糖尿病对照相比，我们发现临床稳定的新发A-b+ KPD患者具有较低的总脂肪酸和酰基肉毒碱浓度，较高浓度的β-羟基丁酸酯的酰基肉毒碱标记物，以及显著较高浓度的谷氨酰胺/谷氨酸盐，以及较高的鸟氨酸，较低的瓜氨酸和精氨酸，并降低通过回补作用进入TCA循环的氨基酸水平。 我们假设A-b+ KPD患者具有较高的脂肪酸处置率，其特征为与通过TCA循环的氧化通量受损相关的向生酮的分流增加，以及将氮从谷氨酰胺/谷氨酸盐转移到尿素循环和将碳从谷氨酰胺/谷氨酸盐转移到TCA循环的缺陷。 总的来说，这些缺陷可能导致TCA循环受损和线粒体中ATP生成减少，导致酮生成增加（肝脏中）和胰岛素分泌受损（β细胞中）。 我们建议使用稳定同位素/质谱方案对这些假设进行检验，在DKA定义发作后8周接受稳定胰岛素治疗的10名新发A-b+ KPD成人中，10名年龄、BMI、性别和血糖匹配的最近诊断为2型糖尿病的接受稳定胰岛素治疗的患者，以及10名年龄、BMI和性别匹配的非糖尿病对照者中，具体目标如下：1。 测量全身总的和净的脂肪分解和脂肪氧化; 2.通过测量乙酰辅酶A的内源性通量（使用Ra乙酸盐作为替代物）、β-羟基丁酸盐的内源性通量、乙酰辅酶A转化为β-羟基丁酸盐的速率以及在TCA循环中经历完全氧化的乙酰辅酶A通量的分数来确定乙酰辅酶A的产生、氧化及其用于生酮的利用; 3. 通过测量整个谷氨酰胺分子的总通量，确定全身谷氨酰胺的产生速率、脱酰胺转化为谷氨酸的速率、酰胺氮转化为瓜氨酸的速率，以及谷氨酸碳进入和退出TCA循环的速率（碳部分），谷氨酰胺的酰胺基团的通量，酰胺氮从谷氨酰胺转移到瓜氨酸的速率，瓜氨酸通量，谷氨酸碳通量（作为[13 C]的替代品？酮戊二酸富集）和从谷氨酸产生13 CO2的速率。 这些研究的结果可以详细说明一种独特形式的糖尿病的病理生理学，也揭示了常见形式的2型糖尿病中β细胞衰竭的可能机制。

This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. Primary support for the subproject and the subproject's principal investigator may have been provided by other sources, including other NIH sources. The Total Cost listed for the subproject likely represents the estimated amount of Center infrastructure utilized by the subproject, not direct funding provided by the NCRR grant to the subproject or subproject staff. ABSTRACT Ketosis-prone Diabetes (KPD) is an emerging, widespread form of diabetes characterized by presentation with diabetic ketoacidosis (DKA). The most common form of KPD is a subgroup termed A-b+ KPD. Apart from their proneness to ketosis and non-immune mediated, severe beta cell dysfunction at the time of initial presentation, the clinical features of A-b+ KPD patients are very similar to those of typical patients with type 2 diabetes they are middle-aged, overweight or obese, have a high frequency of metabolic syndrome, and have residual beta cell functional reserve. The pathophysiology of this novel syndrome is unknown. Using a metabolomic approach in carefully phenotyped patients compared to lean and obese non-diabetic controls, we have found that clinically stable, new onset A-b+ KPD patients have lower concentrations of total fatty acids and acyl carnitines, higher concentrations of an acyl carnitine marker of beta-hydroxybutyrate, and markedly higher concentrations of glutamine / glutamate, together with higher ornithine, lower citrulline and arginine, and depressed levels of amino acids that enter the TCA cycle via anaplerosis. We hypothesize that A-b+ KPD patients have a high rate of disposal of fatty acids, marked by an increased shunt towards ketogenesis associated with impaired oxidative flux through the TCA cycle, and defects in transfering nitrogen from glutamine / glutamate to the urea cycle and carbon from glutamine / glutamate to the TCA cycle. Collectively, these defects could result in impaired TCA cycling and decreased ATP generation in mitochondria, leading to increased ketogenesis (in the liver) and impaired insulin secretion (in beta cells). We propose to test these hypotheses using stable isotope / mass spectrometric protocols by carrying out, in 10 adults with new onset A-b+ KPD on stable insulin therapy 8 weeks after the defining episode of DKA, 10 age-, BMI-, gender- and glycemia-matched, recently diagnosed type 2 diabetic patients on stable insulin therapy, and 10 age-, BMI- and gender-matched non-diabetic controls, the following Specific Aims: 1. Measure whole body total and net lipolysis and fat oxidation; 2. Determine acetyl CoA production, oxidation and its utilization for ketogenesis by measuring the endogenous flux of acetyl CoA (using Ra acetate as a surrogate), endogenous flux of beta-hydroxybutyrate, the rate of conversion of acetyl CoA to beta-hydroxybutyrate, and the fraction of acetyl CoA flux that undergoes complete oxidation in the TCA cycle; 3. Determine whole body rate of production of glutamine, its deamidation to glutamate and rate of transfer of its amide nitrogen to citrulline, as well as the rate of glutamate carbon entry into and exit out of the TCA cycle, by measuring total flux of the whole glutamine molecule (carbon moiety), flux of the amide group of glutamine, rate of transfer of the amide nitrogen from glutamine into citrulline, citrulline flux, flux of glutamate carbon (as a surrogate for [13C]?-ketoglutarate enrichment) and rate of production of 13CO2 from glutamate. The results of these investigations could specify the pathophysiology of a unique form of diabetes, and also shed light on possible mechanisms of beta cell failure in common forms of type 2 diabetes.