Ghimire Pranita, Dhamoon Amit S., Doerr Chaddie
SUNY Upstate Medical University
University of Louisville
Ketoacidosis is a metabolic state associated with pathologically high serum and urine concentrations of ketone bodies, namely acetone, acetoacetate, and beta-hydroxybutyrate. During catabolic states, fatty acids are metabolized to ketone bodies, which can be readily utilized for fuel by individual cells in the body. Of the three major ketone bodies, acetoacetic acid is the only true ketoacid chemically, while beta-hydroxybutyric acid is a hydroxy acid, and acetone is a true ketone. Figure 1 shows the schematic of ketogenesis where the fatty acids generated after lipolysis in the adipose tissues enter the hepatocytes via the bloodstream and undergo beta-oxidation to form the various ketone bodies. This biochemical cascade is stimulated by the combination of low insulin levels and high glucagon levels (i.e., a low insulin/glucagon ratio). Low insulin levels, most often secondary to absolute or relative hypoglycemia as with fasting, activate hormone-sensitive lipase, which is responsible for the breakdown of triglycerides to free fatty acid and glycerol. The clinically relevant ketoacidoses to be discussed include diabetic ketoacidosis (DKA), alcoholic ketoacidosis (AKA), and starvation ketoacidosis. DKA is a potentially life-threatening complication of uncontrolled diabetes mellitus if not recognized and treated early. It typically occurs in the setting of hyperglycemia with relative or absolute insulin deficiency. The paucity of insulin causes unopposed lipolysis and oxidation of free fatty acids, resulting in ketone body production and subsequent increased anion gap metabolic acidosis. Alcoholic ketoacidosis occurs in patients with chronic alcohol abuse, liver disease, and acute alcohol ingestion. Starvation ketoacidosis occurs after the body is deprived of glucose as the primary source of energy for a prolonged time, and fatty acids replace glucose as the major metabolic fuel.
酮症酸中毒是一种代谢状态,与血清和尿液中病理性高浓度的酮体有关,即丙酮、乙酰乙酸和β-羟基丁酸。在分解代谢状态下,脂肪酸被代谢为酮体,酮体可被体内各个细胞轻易用作燃料。在三种主要的酮体中,乙酰乙酸是唯一真正的化学意义上的酮酸,而β-羟基丁酸是一种羟酸,丙酮是一种真正的酮。图1展示了酮体生成的示意图,其中脂肪组织中脂肪分解后产生的脂肪酸通过血液进入肝细胞,并进行β氧化以形成各种酮体。这种生化级联反应受到低胰岛素水平和高胰高血糖素水平(即低胰岛素/胰高血糖素比值)的共同刺激。低胰岛素水平,最常见于禁食等导致绝对或相对低血糖的情况,会激活激素敏感性脂肪酶,该酶负责将甘油三酯分解为游离脂肪酸和甘油。本文将讨论的临床相关酮症酸中毒包括糖尿病酮症酸中毒(DKA)、酒精性酮症酸中毒(AKA)和饥饿性酮症酸中毒。如果不早期识别和治疗,DKA是未控制的糖尿病的一种潜在危及生命的并发症。它通常发生在相对或绝对胰岛素缺乏的高血糖背景下。胰岛素缺乏导致游离脂肪酸不受抑制地进行脂肪分解和氧化,从而产生酮体并随后导致阴离子间隙代谢性酸中毒增加。酒精性酮症酸中毒发生在慢性酒精滥用、肝病和急性酒精摄入的患者中。饥饿性酮症酸中毒发生在身体长时间被剥夺葡萄糖作为主要能量来源后,脂肪酸取代葡萄糖成为主要代谢燃料时。