In contrast to the general view that IR is a pathological process associated with gestational diabetes, a certain degree of IR may represent an important physiological mechanism for blood glucose maintenance during fasting.

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...

We previously demonstrated an increased liver gluconeogenesis (LG) during insulin-induced hypoglycaemia. Thus, an expected effect of sulphonylureas induced hypoglycaemia (SIH) could be the activation of LG. However, sulphonylureas infused directly in to the liver inhibits LG. Considering these opposite effects we investigated herein LG in rats submitted to SIH. For this purpose, 24 h fasted rats that received glibenclamide (10 mg kg(-1) ) were used (SIH group). Control group received oral saline. Glycaemia at 30, 60, 90, 120 and 150 min after oral administration of glibenclamide were evaluated. Since the lowest glycaemia was obtained 120 min after glibenclamide administration, this time was chosen to investigate LG in situ perfused livers. The gluconeogenesis from precursors that enters in this metabolic pathway before the mitochondrial step, i.e. L-alanine (5 mM), L-lactate (2 mM), pyruvate (5 mM) and L-glutamine were decreased (p < 0·05). However, the gluconeogenic activity using glycerol (2 mM), which enters in the gluconeogenesis after the mitochondrial step was maintained. Taken together, the results suggest that the inhibition of LG promoted by SIH overcome the activation of this metabolic pathway promoted by IIH and could be attributed, at least in part, to its effect on mitochondrial function.

The liver glucose production (LGP) levels of 15-h overnight fasted weaned rats submitted to short-term insulin-induced hypoglycemia (ST-IIH) and long-term IIH (LT-IIH) were compared. Experiments to characterize ST-IIH or LT-IIH that followed an intraperitoneal (ip) injection (1.0 U/kg) of regular (ST-IIH) or insulin detemir (LT-IIH) were performed and glycemia were measured 0 (normoglycemic control), 0.5 h (ST-IIH), 4 h and 6 h (LT-IIH) later. The values of glycemia (mg/dl) were 77.8 ±l 7.2 (normoglycemic control), 26.2 ±l 6.1 (ST IIH 0.5 h), 21.2 ±l 7.6 (LT-IIH 4 h) and 35.3 ±l 14.5 (LT-IIH 6.0). The LGP levels were measured in the rats submitted to ST-IIH (0.5 h) and LT-IIH (4 h or 6 h). The rats that received ip saline were used as the normoglycemic control group (COG). The livers from the COG and IIH groups (ST-IIH or LT-IIH) were perfused in situ with infusion of L-alanine (5 mM), L-glutamine (10 mM), glutamine dipeptide (5 mM), L-lactate (2 mM) or glycerol (2 mM). The ST-IIH rats showed a higher LGP level than COG group following the L-glutamine infusion (p < 0.05), but the LGP levels that were measured following the L-lactate, L-alanine, glutamine dipeptide (5 mM), L-lactate (2 mM) or glycerol infusion remained unchanged. Moreover, if the period of IIH was expanded to 4 h following insulin injection, the LGP levels induced by L-alanine, glutamine dipeptide or glycerol infusion also increased (p < 0.05, LT-IIH vs. COG). However, the LGP from the L-lactate infusion remained unchanged until 6 h after insulin injection. In conclusion, these results suggest that the intensification of liver gluconeogenesis during ST-IIH and LT-IIH in weaned rats is not a synchronous "all or nothing" process; instead, this process integrated in a temporal manner and is specific for each gluconeogenic substrate.

Evidence that L-glutamine is better than L-alanine as gluconeogenic substrate in perfused liver of weaned fasted rats submitted to short-term insulin-induced hypoglycaemia Gluconeogenesis in livers from overnight fasted weaned rats submitted to short-term insulin-induced hypoglycaemia (IIH) was investigated.For this purpose, a condition of hyperinsulinemia/hypoglycaemia was obtained with an intraperitoneal (ip) injection of regular insulin (1.0 U kg À1). Control group (COG group) received ip saline. The studies were performed 30 min after insulin (IIH group) or saline (COG group) injection. The livers from IIH and COG rats were perfused with L-alanine (5 mM), L-lactate (2 mM), L-glutamine (10 mM) or glycerol (2 mM). Hepatic glucose, L-lactate and pyruvate production from L-alanine was not affected by IIH. In agreement with this result, the hepatic ability in producing glucose from L-lactate or glycerol remained unchanged (IIH group vs. COG group). However, livers from IIH rats showed higher glucose production from L-glutamine than livers from COG rats and, in the IIH rats, the production of glucose from L-glutamine was higher than that from L-alanine. The higher glucose production in livers from the IIH group, when compared with the COG group was due to its entrance further on gluconeogenic pathway. Taken together, the results suggest that L-glutamine is better than L-alanine, as gluconeogenic substrate in livers of hypoglyceaemic weaned rats.