Oral Glutamine Dipeptide Prevents against Prolonged Hypoglycemia Induced by Detemir Insulin in Rats

Abstract

Most episodes of short-term symptomatic hypoglycemia are effectively treated by the ingestion of carbohydrates 1) or glucagon injection.2) However, in spite the fact that glucose and glucagon are very effective to treat short term insulin-induced hypoglycemia (IIH), both antidotes show transitory effect 1,2) and for this reason they are not effective to prevent prolonged IIH. Moreover, patients who receive insulin therapy frequently experience prolonged IIH, particularly nocturnal hypoglycemia that represents 55-75% of severe episodes of IIH. 3)Therefore, for episodes of prolonged IIH during sleep, when the subject is unable to self-treat, new strategies to prevent IIH are necessary. 4) However, there are few studies in the prevention of nocturnal hypoglycemia. 5,6) Because rats show a suitable experimental model to study hypoglycemia [7][8][9][10] and considering the night habits of these animals, nocturnal IIH can be simulated with a diurnal pharmacological dose of Detemir insulin. Moreover, in spite the fact that glutamine dipeptide has been shown effective to promote acute glycemia recovery during long term IIH, 11) its rule to prevent prolonged hypoglycemia was not investigated. Thus, by using this rat model [7][8][9][10][11] we investigated if L-alanyl-L-glutamine peptide (glutamine dipeptide) could help against prolonged IIH. The choice of glutamine dipeptide was based in the following facts: 1) glutamine dipeptide results of the combination of the most abundant blood amino acid, i.e., L-glutamine 12) and the most important liver glucose precursor, i.e., L-alanine, 13) 2) very high doses of oral glutamine dipeptide did not show acute or subchronic toxicity, 14) 3) glutamine dipeptide overcomes the intestinal catabolism of Lglutamine, 15) 4) L-alanine from glutamine dipeptide catabolism stimulates the release of glucagon. 16,17) In addition the contribution of the liver gluconeogenesis from glutamine dipeptide and their metabolites L-alanine and L-glutamine to prevent prolonged hypoglycemia were investigated. Animals Adult male Wistar rats (180-220 g) were maintained on food and water ad libitum before the initiation of experimental procedures. The manipulation of the animals was approved by the ethical committee of the State University of Maringá, PR, Brazil (approval number 042/2006). On the day before the experiment the animals were food deprived from 5:00 p.m. All experiments were performed with overnight fasted rats (5:00 p.m.-9:00 a.m.). MATERIALS AND METHODS MaterialsExperimental Prolonged IIH A preliminary experiment to characterize the prolonged IIH after an intraperitoneal (i.p.) injection of Detemir insulin (1.0 U/kg) was done. Detemir insulin was not diluted but intraperitoneally injected (9:00 a.m.) with help of an infusion pump (Insight The role of glutamine dipeptide (GDP) to prevent against prolonged insulin induced hypoglycemia (IIH) in overnight fasted rats was investigated. The glycemia was measured 0, 2, 4, 8, and 10 h after an intraperitoneal (i.p.) injection (1 U/kg) of Detemir in...

Paradoxical increase in liver ketogenesis during long-term insulin-induced hypoglycemia in diabetic rats

“…Long-term IIH can be achieved with the administration of a pharmacological dose of Detemir insulin. 20 Therefore, as we expected, hypoglycemia with at least six hours of duration was obtained (Table 2). Additionally, considering that IIH was well established two hours after insulin injection, this time was used to evaluate not only the liver ketogenesis but also the liver production of glucose (from glycogenolysis and gluconeogenesis), l -lactate (from glycolysis), urea (from catabolism of amino acids) and its correlation with blood levels of KB, glucose, l -lactate, ammonia and urea.…”

A Comparison of the Effects of Oral Glutamine Dipeptide, Glutamine, and Alanine on Blood Amino Acid Availability in Rats Submitted to Insulin-Induced Hypoglycemia

“…We produced IIH in the rats by the intraperitoneal (ip) injection of insulin detemir (1 U/kg). We chose the dose of insulin on the basis of a previous study [ 18 ]. The insulin was not diluted, and it was injected with an infusion pump.…”

“…Blood was collected 15 min ( Table 1 ), 30 min ( Table 2 ), and 120 min ( Table 3 ) after oral administration to measure glucose and amino acid levels. The dose of GDP was based on a previous study [ 18 ], and the doses of ALA and GLN reflected their proportions in the GDP molecule. An additional control group received ip saline + oral vehicle.…”

“…The concentrations of ALA (5 mM), GLN (5 mM), or GDP (5 mM) to be dissolved in the perfusion fluid were chosen on the basis of a previous study [ 18 ]. As shown in Figure 1 and Figure 2 , after a pre-infusion period (10 min), ALA, GLN, or GDP was dissolved in KHB and infused over 60 min.…”

“…A proper evaluation of the efficacy of GDP compared to GLN requires controlled conditions [ 16 ]. Fasted rats submitted to insulin-induced hypoglycemia (IIH) represent a suitable experimental model to evaluate changes in blood levels of amino acids [ 17 , 18 ]. Therefore, we compared the effects of oral GDP, GLN plus ALA, GLN, or ALA on the blood availability of amino acids in hypoglycemic rats.…”