1. Investigación

To study the effect of prolonged diabetes on protein synthesis and on the activities of initiation factors elF-2 and elF-2B in the liver, female rats were treated with streptozotocin. Some animals were mated and studied on day 20 of pregnancy, whereas others were kept virgin and studied in parallel. The protein synthesis rate was measured with an 'in vitro' cellfree system, and was lower in diabetic pregnant and virgin animals than in pregnant and virgin controls (30-60%). The fetuses of diabetic rats had a lower protein synthesis rate than those from controls, although they always showed a higher protein synthesis rate than their mothers or virgin rats. Protein synthesis rate, RNA concentration, and initiation factor 2 activity were higher in pregnant than in virgin rats. Both activity and level of elF-2 factor changed in parallel to the protein synthesis rate, although no differences could be detected between control and diabetic animals. The eIF-2B activity in tissue extracts from diabetic virgin rats and fetuses was lower than in extracts from their controls, whereas no differences could be detected between pregnant and virgin control rats nor between pregnant control and pregnant diabetic animals. The percentage of the phosphorylated form of eIF-2 factor, eIF-2(uP), was slightly lower in virgin than in pregnant rats but was unaffected by the diabetic condition, while in diabetic fetuses this parameter was lower than in their corresponding controls. The cyclic adenosine monophosphate dependent protein kinase level was lower in diabetic rats than in controls, whereas no changes in the activity of casein kinase II were found. The isoelectric forms of the 13 subunit of eIF-2 factor, eIF-213, were different in the diabetic and the control animals, indicating that insulin deficiency modifies the phosphorylation of specific substrates. Since no differences were detected in RNA or eIF-2 content between control and diabetic rats, translation may, at least partly, be inhibited in the liver by an impairment of peptide chain initiation caused by the decreased eIF-2B activity which nevertheless is independent of eIF2u phosphorylation.

Para estudiar el efecto de la gestación y la diabetes sobre la actividad y la expresión (ARNm) de la lipoproteína lipasa (LPL) y de la lipasa sensible a las hormonas (HSL) en tejidos, las ratas recibieron 40 mg de estreptozotocina/kg y se sacrificaron al día 20 de gestación. En el tejido adiposo blanco {T AB), la actividad y el ARNm de la LPL eran más bajos en las ratas preñadas controles (PC) que en las vírgenes controles (VC), siendo también inferior la actividad en las diabéticas (D) que en las controles(C), tanto vírgenes (V) como preñadas (P). En la glándula mamaria (GM), la actividad y el ARNm de la LPL estaban más altos en las PC que en las VC, y disminuyeron en las PD y VD respecto de las C. En el T AB, la actividad HSL estaba más alta en las P que en las V y era similar en las PC y PD, sin cambios en los niveles de ARNm. En la GM, la actividad y el ARNm de la HSL estaban más bajos en las P que en las V y eran menores en las D que en las C. Estos resultados permiten concluir que los mecanismos de regulación de la actividad y de la expresión molecular (ARNm) de la LPL y de la HSL durante la gestación y la diabetes son específicos de cada tejido. El paralelismo en los cambios de la actividad y el nivel de ARNm de la LPL en el T AB y GM, así como entre la actividad y el ARNm de la HSL en la GM, indican que la regulación a nivel transcripcional de la expresión de estos genes es un mecanismo importante para la captación y movilización de los TO en estos tejidos.

Nuestros resultados permiten sugerir que la administración de antioxidantes capaces de reducir la producción de radicales libres, podrían desempeñar un importante papel en la prevención de los efectos teratogénicos asociados a la diabetes. Tal vez lo más relevante es que los antioxidantes actuarían independientemente del grado de control metabólico alcanzado, por lo que sus efectos podrían añadirse a los conseguidos al obtener un mejor control metabólico.

The aim of the present study was to determine in the BALB/c mice, a model of development of atherosclerosis when both hyperglycemia and hypercholesterolemia are present, whether the atherogenic effects of these parameters could be decreased with the administration of Vitamin E. BALB/c mice were made diabetic and divided in three groups: one fed the standard rodent chow diet (D); the other two fed an atherogenic diet (D + A); one of them supplemented with Vitamin E (D +A+ E). Two groups of non diabetic animals were also performed, one fed the standard diet (C) and the other the atherogenic diet (C + A). After 16 weeks of treatment all the control animals survived, in contrast, a mortality rate of 12, 70 and 37% was observed, respectively, in the D, D + A and D +A+ E groups. Neither fatty deposits nor macrophages were observed in the arterial wall of the animals fed the standard diet (D and C animals). In contrast, this finding was observed in 25% of the C + A, 71% of the D + A and 33% of the D +A+ E. In conclusion, diabetic mice fed an atherogenic diet showed in the aorta a higher number of fatty deposits and macrophages than the control animals. These effects were partially reversed with the administration of Vitamin E, supporting in this model the role of oxidative stress in the development of atherosclerosis.

Diabetes during pregnancy results in congenital malformations and long-term postnatal diseases. Experimental models are still needed to investigate the mechanism responsible for these alterations. Thus, by the administration of different doses of streptozotocin (STZ) (0, 25, 30, or 35 mg/kg body weight, intravenous) at the onset of pregnancy in rats, the present study sought an appropriate animal model for this pathology. At day 6 of pregnancy, plasma glucose was progressively higher with an increasing STZ dose, and in rats receiving the 35-mg dose, 2 subgroups were detected: some animals had plasma glucose levels above controls but below 200 mg/dL (mildly diabetic, MD), whereas others had levels above 400 mg/dL (severely diabetic, SD). At day 20 of pregnancy, the MD rats had normal glycemia, but after an oral glucose load (2 g/kg body weight), plasma glucose increased more and insulin increased less than in controls. The SD rats maintained their hyperglycemia and had a greatly impaired oral glucose tolerance. At day 20, fetuses of SD dams were fewer, weighed less, and had enhanced plasma glucose and triglycerides and decreased insulin, whereas those from MD dams did not differ from controls. At birth, newborns from MD dams had higher body weight, plasma insulin, and liver triglycerides as well as total body lipid concentrations than controls, and on day 21, remained macrosomic and showed higher plasma glucose and liver triglyceride concentrations. At 70 days of age, offspring of MD dams had impaired oral glucose tolerance but normal plasma insulin change in the case of females, whereas plasma insulin increased less in males. These alterations were manifest more in those offspring from dams that had >50% macrosomic newborns than in those from dams that had <50% macrosomic newborns. In conclusion, whereas our MD rats mimic the changes taking place in gestational diabetic women and show the long-term risk of macrosomia, the SD rats are more similar to uncontrolled diabetics. Thus these two rat models, obtained with moderate amounts of STZ, could be used to study the pathophysiological consequences of these different diabetic conditions.

Three days after a single injection of streptozotocin rats showed hyperglycemia, hyperketonemia and hypoinsulinemia. Body and liver weights were reduced and the concentration of DNA-P, phospholipid-P, proteins and acetyl-CoA in the liver was augmented, while the concentration of glycogen and citric acid in these animals compared with the controls which did not receive the drug was decreased. After 48 h starvation, blood glucose remained higher in the streptozotocin-treated animals, while circulating ketones and insulin were not different from those in the controls. With the exception of body and liver weights, which were lower, and of liver DNA-P, which was higher than when fed, neither of the other parameters studied in the s:reptozotocin treated animals changed with fasting, while the response in the c0ntrols was normal; The incapacity of increasing the postprandial insulin secretion in these animals may contribute to the metabolic alterations found in the fed state.

To determine whether changes in uterine blood flow affect placental glucose transfer in the diabetic pregnant rat, on the 7th day of gestation rats were intravenously treated with either streptozotocin (45 mg/kg) (diabetics) or buffer (controls). On the 20th day of gestation, fetal body weight and uterine blood flow appeared reduced whereas fetal/maternal plasma glucose was enhanced and lactate ratios were unchanged in diabetics versus controls. After 20 min of (U- 14C)-D-glucose infusion through the maternal left uterine artery, plasma values of fetuses from left and right uterine horns were higher for 14C-glucose and lower for 14C-lactate in diabetics versus controls, and placental glucose transfer was greatly augmented in diabetics whether or not uterine blood flow was included in its calculation. Whereas a linear correlation existed between placental glucose transfer and maternal plasma glucose concentration, transferred glucose conversion into lactate remained stable even when the maternal glucose level was high. It was concluded that enhanced placental glucose transfer in the pregnant diabetic rat is not modified by reduced uterine blood flow. The limited capacity of the fetus to handle the great incoming flux of glucose through the placenta of a severely diabetic mother produces permanent hyperglycemia which may impair fetal growth.

Background/Aims: Previously we have shown that administration of 150 mg of vitamin E (·-tocopherol) per day to rats having diabetes decreases the rate of embryo malformations and increases their maturation and size. The present study was addressed to determine the effects of different doses of vitamin E upon these parameters. Methods: Female rats were made diabetic (D) with streptozotocin, and from day 0 of gestation they were treated daily with 25 (D+25), 50 (D+50), 100 (D+100), 150 (D+150), and 500 (D+500) mg of vitamin E administered orally and were compared with control (C) animals. Results: On day 11.5 of gestation, crown-rump length, somite number, and protein and DNA levels were lower in D than in C embryos. Crown-rump length and somite number increased with 100 mg or higher doses of vitamin E, although the values observed in C embryos were not reached. The proportions of reabsorption and malformations were 24.7 and 50%, respectively, in D rats, and in the rats supplemented with vitamin E they decreased to 22.7 and 19% in D+25, 16.4 and 21.3% in D+50, 16.2 and 12% in D+100, 12.9 and 13.9% in D+150, and to 43.9 and 10.8% in D+500 rats, whereas the values were 6.8 and 4.9% in C animals. Conclusions: Administration of vitamin E to D rats decreases the rate of embryo malformations, dependent on the dose administered. However, high doses have a negative effect in the conceptus, as shown by the increased rate of reabsorptions in the D+500 group.