Pagano C, Granzotto M, Giaccari A, Fabris R, Serra R, Lombardi A M, Federspil G, Vettor R
Endocrine-Metabolic Laboratory, University of Padua, Italy.
Am J Physiol. 1997 Dec;273(6):R2072-9. doi: 10.1152/ajpregu.1997.273.6.R2072.
Both hyperglycemia and hyperinsulinemia stimulate whole body and muscle glucose disposal. To define the impact of increased lactate concentration (4-5 mM) on muscle glucose disposal during hyperglycemia, we studied anesthetized normal rats infused with either sodium lactate or sodium bicarbonate as control. Animals were studied under hyperglycemic clamp (13 mM) using [3-3H]glucose (study 1) and 2-deoxy-[1-3H]glucose (study 2) to assess glucose rate of disappearance (Rd), glycolytic flux (GF), glycogen synthesis, and glucose utilization index by different tissues. Moreover, in study 3, the effect of lactate on the pattern of plasma insulin response to hyperglycemia was evaluated. In study 1, lactate infusion resulted in an increased Rd (38.7 +/- 1.7 vs. 32.3 +/- 1.3 mg.min-1.kg-1; P < 0.01), which was explained by an enhanced rate of glycogen synthesis (23.0 +/- 1.7 vs. 14.7 +/- 1.2 mg.min-1.kg-1; P < 0.001), whereas GF was unchanged. In study 2, lactate-infused animals showed an increased 2-deoxy-glucose disposal and a stimulated glycogen synthase activity as well as an increased glycogen accumulation at the end of the study in several skeletal muscles. In study 3, lactate did not induce any change in either early or late insulin response to hyperglycemia. In conclusion, our results show that muscle glycogen deposition may be enhanced by elevated lactate levels under hyperglycemic conditions and support a role for lactate in the regulation of glucose homeostasis.
高血糖和高胰岛素血症均会刺激全身及肌肉对葡萄糖的摄取。为明确高血糖期间乳酸浓度升高（4 - 5 mM）对肌肉葡萄糖摄取的影响，我们以输注乳酸钠或碳酸氢钠作为对照，对麻醉状态下的正常大鼠进行了研究。使用[3 - 3H]葡萄糖（研究1）和2 - 脱氧 - [1 - 3H]葡萄糖（研究2）在高血糖钳夹（13 mM）条件下对动物进行研究，以评估不同组织的葡萄糖消失率（Rd）、糖酵解通量（GF）、糖原合成及葡萄糖利用指数。此外，在研究3中，评估了乳酸对高血糖时血浆胰岛素反应模式的影响。在研究1中，输注乳酸导致Rd增加（38.7 ± 1.7 vs. 32.3 ± 1.3 mg·min⁻¹·kg⁻¹；P < 0.01），这是由糖原合成速率加快所致（23.0 ± 1.7 vs. 14.7 ± 1.2 mg·min⁻¹·kg⁻¹；P < 0.001），而GF未改变。在研究2中，输注乳酸的动物在研究结束时，多个骨骼肌的2 - 脱氧葡萄糖摄取增加，糖原合酶活性增强，糖原积累增多。在研究3中，乳酸对高血糖的早期或晚期胰岛素反应均未产生任何影响。总之，我们的结果表明，在高血糖条件下，升高的乳酸水平可能会增强肌肉糖原沉积，并支持乳酸在葡萄糖稳态调节中的作用。
