Vitamin E: action, metabolism and perspectives

Natural vitamin E includes four tocopherols and four tocotrienols. RRR-alpha-tocopherol is the most abundant form in nature and has the highest biological activity. Although vitamin E is the main lipid-soluble antioxidant in the body, not all its properties can be assigned to this action. As antioxidant, vitamin E acts in cell membranes where prevents the propagation of free radical reactions, although it has been also shown to have pro-oxidant activity. Non-radical oxidation products are formed by the reaction between alpha-tocopheryl radical and other free radicals, which are conjugated to glucuronic acid and excreted through the bile or urine. Vitamin E is transported in plasma lipoproteins. After its intestinal absorption vitamin E is packaged into chylomicrons, which along the lymphatic pathway are secreted into the systemic circulation. By the action of lipoprotein lipase (LPL), part of the tocopherols transported in chylomicrons are taken up by extrahepatic tissues, and the remnant chylomicrons transport the remaining tocopherols to the liver. Here, by the action of the "alpha-tocopherol transfer protein", a major proportion of alpha-tocopherol is incorporated into nascent very low density lipoproteins (VLDL), whereas the excess of alpha-tocopherol plus the other forms of vitamin E are excreted in bile. Once secreted into the circulation, VLDL are converted into IDL and LDL by the action of LPL, and the excess of surface components, including alpha-tocopherol, are transferred to HDL. Besides the LPL action, the delivery of alpha-tocopherol to tissues takes place by the uptake of lipoproteins by different tissues throughout their corresponding receptors. Although we have already a substantial information on the action, effects and metabolism of vitamin E, there are still several questions open. The most intriguing is its interaction with other antioxidants that may explain how foods containing small amounts of vitamin E provide greater benefits than larger doses of vitamin E alone.

Vitamin E: action, metabolism and perspectives

Natural vitamin E includes four tocopherols and four tocotrienols. RRR-alpha-tocopherol is the most abundant form in nature and has the highest biological activity. Although vitamin E is the main lipid-soluble antioxidant in the body, not all its properties can be assigned to this action. As antioxidant, vitamin E acts in cell membranes where prevents the propagation of free radical reactions, although it has been also shown to have pro-oxidant activity. Non-radical oxidation products are formed by the reaction between alpha-tocopheryl radical and other free radicals, which are conjugated to glucuronic acid and excreted through the bile or urine. Vitamin E is transported in plasma lipoproteins. After its intestinal absorption vitamin E is packaged into chylomicrons, which along the lymphatic pathway are secreted into the systemic circulation. By the action of lipoprotein lipase (LPL), part of the tocopherols transported in chylomicrons are taken up by extrahepatic tissues, and the remnant chylomicrons transport the remaining tocopherols to the liver. Here, by the action of the "alpha-tocopherol transfer protein", a major proportion of alpha-tocopherol is incorporated into nascent very low density lipoproteins (VLDL), whereas the excess of alpha-tocopherol plus the other forms of vitamin E are excreted in bile. Once secreted into the circulation, VLDL are converted into IDL and LDL by the action of LPL, and the excess of surface components, including alpha-tocopherol, are transferred to HDL. Besides the LPL action, the delivery of alpha-tocopherol to tissues takes place by the uptake of lipoproteins by different tissues throughout their corresponding receptors. Although we have already a substantial information on the action, effects and metabolism of vitamin E, there are still several questions open. The most intriguing is its interaction with other antioxidants that may explain how foods containing small amounts of vitamin E provide greater benefits than larger doses of vitamin E alone.

Oxidative damage in pregnant diabetic rats and their embryos

Free radical mechanisms may be involved in the teratogenesis of diabetes. The contribution of oxidative stress in diabetic complications was investigated from the standpoint of oxidative damage to DNA, lipids, and proteins in the livers and embryos of pregnant diabetic rats. Diabetes was induced prior to pregnancy by the administration of streptozotocin (45 mg/kg). Two groups of diabetic rats were studied, one without any supplementation (D) and another treated during pregnancy with vitamin E (150 mg/d by gavage) (D + E). A control group was also included (C). The percentage of malformations in D rats were 44%, higher than the values observed in C (7%) and D + E (12%) animals. D Group rats showed a higher concentration of thiobarbituric acid reactive substances in the mother's liver, however, treatment with vitamin E decreased this by 58%. The levels of protein carbonyls in the liver of C, D, and D + E groups were similar. The "total levels" of the DNA adducts measured, both in liver and embryos C groups were similar to the D groups. Treatment of D groups with vitamin E reduced the levels by 17% in the liver and by 25% in the embryos. In terms of the "total levels" of DNA adducts, the embryos in diabetic pregnancy appear to be under less oxidative stress when compared with the livers of their mothers. Graziewicz et al. (Free Radical Biology & Medicine, 28:75-83, 1999) suggested "that Fapyadenine is a toxic lesion that moderately arrests DNA synthesis depending on the neighboring nucleotide sequence and interactions with the active site of DNA polymerase." Thus the increased levels of Fapyadenine in the diabetic livers and embryos may similarly arrest DNA polymerase, and in the case of this occurring in the embryos, contribute to the congenital malformations. It is now critical to probe the molecular mechanisms of the oxidative stress-associated development of diabetic congenital malformations.

Maternal hypertriglyceridemia during late pregnancy does not affect the increase in circulating triglycerides caused by the long-term consumption of a sucrose-rich diet by rats

Feeding a sucrose-rich diet (SRD) during pregnancy enhances maternal hypertriglyceridemia. The goal of this study was to investigate whether this effect is modified when pregnancy is initiated in rats at different times during feeding of a SRD (63 g sucrose/100 g). One group of rats was fed the SRD; another group received the same diet except that the sucrose was replaced by an equal amount of cornstarch. At different times during the feeding of the diets, i.e., 5, 45 or 90 d, half of the rats were mated; after serial tail blood collections, rats were studied at d 20 of pregnancy. Virgin rats fed the same diets were always studied in parallel. Plasma triglycerides increased progressively in virgin rats fed the SRD from d 1 to 35, declined thereafter up to d 50, increased again to attain the highest level at d 65-70, partially declined at d 100 and increased again at d 110. During late pregnancy, rats fed the control diet (CD) always had greater plasma triglyceride concentrations than virgin rats, whereas triglyceride levels did not differ between pregnant and virgin rats fed the SRD. These intergroup differences were similar to those seen for plasma VLDL-triglycerides. The liver triglyceride concentration in virgin rats fed the SRD was always significantly higher than that of rats fed the CD, whereas it did not differ in pregnant rats fed the SRD for either 25 or 65 d from those fed the CD. However, in those fed the SRD for 110 d, values were higher than in either pregnant or virgin rats fed the CD. We propose that the known capability of the liver to enhance triglyceride secretion during pregnancy protects dams from developing a fatty liver when fed a SRD for short periods of time, although not for long-term treatments.

Low arachidonic acid rather than alpha-tocopherol is responsible for the delayed postnatal development in offspring of rats fed fish oil instead of olive oil during pregnancy and lactation

This study was designed to compare in rats the effects of dietary fish oil and olive oil during pregnancy and lactation on offspring development, fatty acid profile and vitamin E concentration. From d 0 of pregnancy, female Sprague-Dawley rats were divided into two groups that were fed purified diets that differed only in their nonvitamin lipid components. One diet contained 10 g fish oil/100 g diet (FOD), whereas the other contained 10 g olive oil/100 g diet (OOD). At d 20 of gestation, maternal adipose tissue fatty acid profile did not differ between rats fed the two diets, whereas both maternal and fetal plasma and liver arachidonic acid (AA) contents were proportionally lower and eicosapentaenoic (EPA) and docosahexaenoic (DHA) acid contents were higher in the FOD group than in the OOD group. alpha-Tocopherol concentration was lower in maternal and fetal plasma, liver and brain in the FOD group than in the OOD group. The postnatal increase in body weight and length was less and body and psychomotor maturation indices were delayed in pups from FOD-fed dams compared with those from OOD-fed dams. This difference was maintained when pups were cross-fostered at birth, with the delay in postnatal development present in the pups suckling dams fed FOD during lactation. At age 21 d, pups suckling dams fed FOD had lower AA and higher EPA and DHA concentrations in brain phospholipids. Although alpha-tocopherol in plasma and liver was lower in pups suckling dams fed FOD rather than OOD, brain alpha-tocopherol concentrations did not differ. Milk yield and milk alpha-tocopherol and AA concentrations were lower and EPA and DHA were higher in the milk of dams fed FOD compared with those fed OOD. Postnatal development indices and the proportion of plasma, liver and brain AA concentrations, although not plasma, liver and brain alpha-tocopherol concentrations, recovered to the values found in dams fed OOD when the FOD was supplemented with gamma-linolenic acid. However, postnatal development indices were not recovered when the FOD was supplemented with sufficient exogenous vitamin E to increase plasma and liver alpha-tocopherol concentrations above those in dams fed OOD. Thus, although feeding FOD during pregnancy and lactation decreases both alpha-tocopherol and AA concentrations, the latter deficiency rather than the former seems to be responsible for delayed postnatal development of rat pups.

Plasma leptin levels in rat mother and offspring during pregnancy and lactation

The profiles of plasma leptin levels in pregnant and lactating rats and their offspring were determined. The plasma leptin levels increased on days 12 and 20 of gestation and declined on day 21 of gestation, remaining at this level during lactation. These changes were similar for lumbar adipose tissue weight, and a significant correlation was found when both variables were plotted with individual values. During the last 2 days of intrauterine life, the plasma leptin levels in the fetuses were in the same range as in their mothers, declining from day 20 to day 21. On the 1st day of life, the leptin levels increased to decline in suckling newborns after 4 days, remaining stable until day 20 of life. The enhancement in maternal white adipose tissue mass that takes place during pregnancy and its decline around parturition and lactation are proposed to contribute actively to the changes in the plasma leptin profile detected at these stages. Besides the contribution of placental leptin for the fetus and milk leptin for the suckling newborn, it is proposed that brown adipose tissue, which is the first form of adipose tissue that appears during development in the rat, is responsible for most of the changes in plasma leptin levels seen around birth, whereas its later decline could be mediated by the hormonal changes occurring after birth.

Nitric oxide inhibits isoproterenol-stimulated adipocyte lipolysis through oxidative inactivation of the beta-agonist

Nitric oxide has been implicated in the inhibition of catecholamine-stimulated lipolysis in adipose tissue by as yet unknown mechanisms. In the present study, it is shown that the nitric oxide donor, 2,2-diethyl-1-nitroso-oxyhydrazine, antagonized isoproterenol (isoprenaline)-induced lipolysis in rat adipocytes, freshly isolated from white adipose tissue, by decreasing the potency of the beta-agonist without affecting its efficacy. These data suggest that nitric oxide did not act downstream of the beta-adrenoceptor but reduced the effective concentration of isoproterenol. In support of the latter hypothesis, we found that pre-treatment of isoproterenol with nitric oxide abolished the lipolytic activity of the catecholamine. Spectroscopic data and HPLC analysis confirmed that the nitric oxide-mediated inactivation of isoproterenol was in fact because of the modification of the catecholamine through a sequence of oxidation reactions, which apparently involved the generation of an aminochrome. Similarly, aminochrome was found to be the primary product of isoproterenol oxidation by 3-morpholinosydnonimine and peroxynitrite. Finally, it was shown that nitric oxide released from cytokine-stimulated adipocytes attenuated the lipolytic effect of isoproterenol by inactivating the catecholamine. In contrast with very recent findings, which suggest that nitric oxide impairs the beta-adrenergic action of isoproterenol through intracellular mechanisms and not through a chemical reaction between NO and the catecholamine, we showed that nitric oxide was able to attenuate the pharmacological activity of isoproterenol in vitro as well as in a nitric oxide-generating cellular system through oxidation of the beta-agonist. These findings should be taken into account in both the design and interpretation of studies used to investigate the role of nitric oxide as a modulator of isoproterenol-stimulated signal transduction pathways.

Angiosarcoma arising on rhinophyma

We report an 82-year-old man who presented with a tumor which had developed over the previous year on the right nasal ala of a rhinophyma. Histopathological, immunohistochemical, and electron microscopic study confirmed the diagnosis of angiosarcoma on the head and neck. He was treated with radiotherapy of the tumor and cervical adenopathy, which developed later. The possible etiological and pathogenetic role of lymphedema due to inflammatory flares of rosacea on the nose is discussed, together with the histological and immunohistochemical data leading to the diagnosis of this tumor.

Changes in dietary fatty acids modify the decreased lipolytic beta3-adrenergic response to hyperinsulinemia in adipocytes from pregnant and nonpregnant rats

The effect of dietary olive oil and fish oil on the lipolytic dose-response of the beta3-adrenergic agonists, epinephrine, isoproterenol, BRL-37344, and CGP-12177, in adipocytes was studied in pregnant and virgin rats either untreated or under hyperinsulinemic-euglycemic conditions. Rats were fed a semisynthetic diet containing 5% of either olive oil or fish oil and studied at day 20 of treatment and/or gestation. Plasma glucose was lower and plasma insulin, triglycerides, and free fatty acids (FFAs) were higher in pregnant versus virgin rats, and the insulin sensitivity index was lower in the former. Lumbar adipose tissue phospholipid fatty acids showed a significantly higher monounsaturated fatty acid and a lower (n - 3) fatty acid content in rats fed the olive oil diet versus the fish oil diet. The lipolytic dose-response curve of either adrenergic agent was always lower in adipocytes from untreated pregnant rats versus virgin rats, and whereas the hyperinsulinemic-euglycemic clamp decreased these responses in adipocytes from virgin rats fed the olive oil diet only, adipocytes from pregnant rats always showed a decreased dose-response lipolytic curve. Thus, the lipolytic responsiveness of beta3-adrenoceptor (beta3-AR) agonists by adipocytes is impaired in cells from rats made hyperinsulinemic chronically by pregnancy or acutely by the hyperinsulinemic-euglycemic clamp, but such response to the acute condition disappears when the adipocyte phospholipid composition is modified by changes in dietary fatty acids.

Energy metabolism and its linkage to intracellular Ca2+ and pH regulation in rat spermatogenic cells

Energy metabolism and intracellular adenine nucleotides of meiotic and postmeiotic spermatogenic cells are highly dependent on external substrates for oxidative phosphorylation and glycolysis. Using fluorescent probes to measure the changes in cytosolic [Ca2+] ([Ca2+]i) and pH (pHi), we were able to demonstrate that changes in energy metabolism of meiotic and postmeiotic spermatogenic cells were rapidly translated into changes of pHi and [Ca2+]i in the absence or presence of external Ca2+. Under these conditions, mitochondria were gaining cytosolic calcium in these cells. Our results indicate that Ca2+ mobilised by changes in metabolic energy pathways originated in thapsigargin-sensitive intracellular Ca2+ stores. Changes in intracellular adenine nucleotides, measured by HPLC, and a likely colocalization of ATP-producing and ATP-consuming processes in the cells seemed to provide the linkage between metabolic fluxes and the changes in pHi and [Ca2+]i in pachytene spermatocytes and round spermatids. Glucose metabolism produced an increase of [Ca2+]i in round spermatids but not in pachytene spermatocytes, and a decrease in pHi in both cell types. Hence, glucose emerges as a molecule that can differentially modulate [Ca2+]i and pHi in pachytene spermatocytes and round spermatids in rats.

Peroxisome proliferator-activated receptor-alpha expression in rat liver during postnatal development

The expression of the peroxisome proliferator-activated receptor-alpha (PPARalpha) as well as of some related genes was studied in rat liver at different stages of development (from 19-day-old fetuses to 1 month-old rats). The level of PPARalpha mRNA appeared higher in neonates than in fetuses or 1 month-old rats. Whereas the pattern for phosphoenolpyruvate carboxykinase (PEPCK) mRNA level was similar to that of PPARalpha, the mRNA level of both acyl-CoA oxidase (ACO) and apolipoprotein CIII (apo CIII) showed diverse profiles. Western blotting analysis also revealed an increased level of PPARalpha protein in liver of suckling rats. Similarities of mRNA PEPCK and PPARalpha expression indicate a common control mechanism, where both nutritional and hormonal factors may be involved.

Cutaneous cryptococcosis in two patients with acquired immunodeficiency syndrome

We present 2 cases of systemic cryptococcosis with cutaneous involvement in patients with acquired immunodeficiency syndrome (AIDS). Both patients were male, intravenous drug abusers, 31 and 35 years old, with severe immunodepression and a CD4+ lymphocyte count of 10/ml and 1/ml, respectively. They both had papular lesions reminiscent of molluscum contagiosum and in one patient with concomitant systemic leishmaniasis, there were spores of Cryptococcus neoformans coexisting with the leishmanias in the cutaneous lesions, constituting the first reported case of this particular association. Both patients responded well to amphotericin B followed by fluconazole.

Lipid metabolism in the fetus and the newborn

During late gestation, although maternal adipose tissue lipolytic activity becomes enhanced, lipolytic products cross the placenta with difficulty. Under fasting conditions, free fatty acids (FFA) are used for ketogenesis by the mother, and ketone bodies are used as fuels and lipogenic substrates by the fetus. Maternal glycerol is preferentially used for glucose synthesis, saving other gluconeogenic substrates, like amino acids, for fetal growth. Placental transfer of triglycerides is null, but essential fatty acids derived from maternal diet, which are transported as triglycerides in lipoproteins, become available to the fetus owing to the presence of both lipoprotein receptors and lipase activities in the placenta. Diabetes in pregnancy promotes lipid transfer to the fetus by increasing the maternal-fetal gradient, which may contribute to an increase in body fat mass in newborns of diabetic women. Deposition of fat stores in the fetus is very low in the rat but high in humans, where body fat accretion occurs essentially during the last trimester of intra-uterine life. This is sustained by the intense placental transfer of glucose and by its use as a lipogenic substrate, as well as by the placental transfer of fatty acids and to their low oxidation activity. During the perinatal period an active ketonemia develops, which is maintained in the suckling newborn by several factors: (i) the high-fat and low-carbohydrate content in milk, (ii) the enhanced lipolytic activity occurring during the first few hours of life, and (iii) both the uptake of circulating triglycerides by the liver due to the induction of lipoprotein lipase (LPL) activity in this organ, and the presence of ketogenic activity in the intestinal mucose. Changes in LPL activity, lipogenesis and lipolysis contribute to the sequential steps of adipocyte hyperplasia and hypertrophia occurring during the extra-uterine white adipose tissue development in rat, and this may be used as a model to extrapolate the intra-uterine adipose tissue development in other species, including humans.

Metabolic adaptations in pregnancy and their implications for the availability of substrates to the fetus

During the first two-thirds of gestation, the mother is in an anabolic condition, increasing her fat depots thanks to both hyperphagia and enhanced lipogenesis. During the last third of gestation, the mother switches to a catabolic condition. Glucose is the most abundant nutrient crossing the placenta, which causes maternal hypoglycemia despite an increase in the gluconeogenetic activity. Adipose tissue lipolytic activity becomes enhanced, increasing plasma levels of FFA and glycerol that reach the liver; consequently there is an enhanced production of triglycerides that return to the circulation in the form of very low density lipoproteins (VLDL). Glycerol is also used as a preferential gluconeogenetic substrate, saving other more essential substrates, like amino acids, for the fetus. Under fasting conditions, fatty acids are converted into ketone bodies throughout the beta-oxidation pathway, and these compounds easily cross the placental barrier and are metabolized by the fetus. An enhanced liver production of VLDL-triglycerides together with a decrease in adipose tissue lipoprotein lipase (LPL) and an increase in plasma activity of cholesterol ester transfer protein causes both an intense increment in these lipoproteins and a proportional enrichment of triglycerides in both low and high density lipoproteins. Maternal triglycerides do not cross the placenta, but the presence of LPL and other lipases allows their hydrolysis, releasing fatty acids to the fetus. Under fasting conditions, the maternal liver uses circulating triglycerides as ketogenic substrates. Around parturition there is an induction of LPL activity in the mammary glands, driving circulating triglycerides to this organ for milk synthesis, allowing essential fatty acids derived from the mother's diet to become available to the suckling newborn.

Impaired germinal center reaction in mice with short telomeres

Reduction of germinal center reactivity is a landmark of immunosenescence and contributes to immunological dysfunction in the elderly. Germinal centers (GC) are characterized by extensive clonal expansion and selection of B lymphocytes to generate the pool of memory B cells. Telomere maintenance by telomerase has been proposed to allow the extensive proliferation undergone by B lymphocytes in the GC during the immune response. We show here that late generation mTR(-/-) mice, which lack the mouse telomerase RNA (mTR) and have short telomeres, present a dramatic reduction in GC number following antigen immunization. Upon immunization with an antigen, wild-type splenocyte telomeres are elongated and this is accompanied by a high expression of the telomerase catalytic subunit in the spleen GC. In contrast, telomerase-deficient mTR(-/-) splenocytes show telomere shortening after immunization, presumably due to cell proliferation in the absence of telomerase. All together, these results demonstrate the importance of telomere maintenance for antibody-mediated immune responses and support the notion that telomere elongation detected in wild-type spleens following immunization is mediated by telomerase.

Squamous cell carcinoma secondary to recessive dystrophic epidermolysis bullosa: report of eight tumours in four patients

BACKGROUND

The development of squamous cell carcinomas is the main cause of death of patients with Dystrophic epidermolysis bullosa. We think it is of interest to know their clinical characteristics and the treatment difficulties they cause.

METHODS

We followed the clinical evolutions and carried out histopathological studies of eight primary cutaneous squamous cell carcinomas on three males and one female with recessive dystrophic epidermolysis bullosa. Patient ages ranged from 16 to 34 years (mean 27).

RESULTS

Two patients had two tumours and one three, all were in characteristically scarred skin; four on upper limbs; four on lower. Maximum tumour dimensions ranged from 2 to 28 cm (mean 13), and represented 6 or more months of evolution. In three cases the affected limb must be amputated. Five tumours were well differentiated, three were moderately differentiated.

CONCLUSIONS

The patients consulted too late and their large lesions needed aggressive treatment. Appropriate information and regular examination of patients with RDEB helps early diagnosis of tumours and may avoid disabling operations.

Apolipoprotein E polymorphism in men and women from a Spanish population: allele frequencies and influence on plasma lipids and apolipoproteins

The apolipoprotein (apo) E phenotype and its influence on plasma lipid and apolipoprotein levels were determined in men and women from a working population of Madrid, Spain. The relative frequencies of alleles epsilon(2), epsilon(3) and epsilon(4) for the study population (n=614) were 0.080, 0.842 and 0.078, respectively. In men, apo E polymorphism was associated with variations in plasma triglyceride and very low-density lipoprotein (VLDL) lipid levels. It was associated with the proportion of apo C-II in VLDL, and explained 5.5% of the variability in the latter parameter. In women apo E polymorphism was associated with the concentrations of plasma cholesterol and low-density lipoprotein (LDL) and high-density lipoprotein (HDL) related variables. The allelic effects were examined taking allele epsilon(3) homozygosity as reference. In men, allele epsilon(2) significantly increased VLDL triglyceride and VLDL cholesterol concentrations, and this was accompanied by an increase of the apo C-II content in these particles. Allele epsilon(4) did not show any significant influence on men's lipoproteins. In women, allele epsilon(2) lowered LDL cholesterol and apo B levels, while allele epsilon(4) increased LDL cholesterol and decreased the concentrations of HDL cholesterol, HDL phospholipid and apo A-I. These effects were essentially maintained after excluding postmenopausal women and oral contraceptive users from the analysis.

IN CONCLUSION

(1) the population of Madrid, similar to other Mediterranean populations, exhibits an underexpression of apo E4 compared to the average prevalence in Caucasians, (2) gender interacts with the effects of apo E polymorphism: in women, it influenced LDL and HDL levels, whereas in men it preferentially affected VLDL, and (3) allele epsilon(2) decreased LDL levels in women, while it increased both VLDL lipid levels and apo C-II content in men, but, in contrast to allele epsilon(4), it did not show an impact on HDL in either sex.

Alpha-tocopherol concentration in fetal and maternal tissues of pregnant rats supplemented with alpha-tocopherol

We wanted to determine whether alpha-tocopherol supplementation to pregnant rats could increase the concentration of alpha-tocopherol in maternal and fetal plasma and tissues. Pregnant rats were treated with alpha-tocopherol on days 18 and 19 gestation and studied at day 20. A control group was studied in parallel. Treatment of pregnant rats with alpha-tocopherol increased its concentration in maternal and fetal plasma, in all maternal plasma lipoprotein fractions, in maternal and fetal liver and in the placenta. The fetal and maternal concentration of alpha-tocopherol were positively correlated.

Disease states associated with telomerase deficiency appear earlier in mice with short telomeres

Mice deficient for the mouse telomerase RNA (mTR-/-) and lacking telomerase activity can only be bred for approximately six generations due to decreased male and female fertility and to an increased embryonic lethality associated with a neural tube closure defect. Although late generation mTR-/- mice show defects in the hematopoietic system, they are viable to adulthood, only showing a decrease in viability in old age. To assess the contribution of genetic background to the effect of telomerase deficiency on viability, we generated mTR-/- mutants on a C57BL6 background, which showed shorter telomeres than the original mixed genetic background C57BL6/129Sv. Interestingly, these mice could be bred for only four generations and the survival of late generation mTR-/- mice decreased dramatically with age as compared with their wild-type counterparts. Fifty percent of the generation 4 mice die at only 5 months of age. This decreased viability with age in the late generation mice is coincident with telomere shortening, sterility, splenic atrophy, reduced proliferative capacity of B and T cells, abnormal hematology and atrophy of the small intestine. These results indicate that telomere shortening in mTR-/- mice leads to progressive loss of organismal viability.

Treadmill training enhances glucose tolerance more in pregnant than in virgin rats

To determine whether aerobic training throughout gestation modifies glucose tolerance, female Wistar rats were mated or kept nonpregnant and run or not on a 10 degrees slope treadmill for 5 days/week at 20 m/min, starting with a 20-min run, and with a progressive daily increase of 5 min, reaching a 75-min run on the 20th day of protocol or gestation. The exercise protocol did not modify food intake, maternal and fetal weights, litter size or blood lactic acid levels. The rise in blood glucose after an oral glucose load (2 g/kg body weight) did not differ between trained and untrained nonpregnant rats but was lower in trained than in untrained pregnant rats. In the untrained rats the rise in plasma insulin levels after the glucose load was much greater in pregnant than in nonpregnant rats; in trained rats this difference between groups was attenuated by the greater effect of exercise decreasing the plasma insulin response to the glucose load in pregnant than in nonpregnant rats. Thus, an aerobic exercise protocol that does not modify the outcome of pregnancy does significantly reduce the altered oral glucose tolerance in pregnant rats and only has a minor effect in nonpregnant rats.

Ethanol intake during lactation impairs milk production in rats and affects growth and metabolism of suckling pups

From parturition, lactating Wistar rats were given 20% alcohol in drinking water and fed a solid diet ad lib (group AL). Pair-fed (PF) and control (C) rats were fed solid diet and given water ad lib (C). All animals were sacrificed on the 12th day of lactation. Ethanol treatment decreased food intake and milk production in lactating rats to a greater level than in PF rats, and a greater reduction in body weight of the AL pups was noted. Brain weight, protein concentration, and DNA content were also lower in pups of AL dams than of PF dams, whereas liver glycogen concentration was higher in the former. Pups from AL dams had higher circulating levels of beta-OH-butyrate, triglyceride, and free fatty acids than those from either C or PF dams. Plasma glucose concentration was lower in both PF and AL than in C pups, whereas the AL group had lower plasma protein concentration than any of the other groups. We conclude that maternal alcohol intake during lactation greatly impairs milk production, and although the known increase of lipid content in milk in rats studied under similar conditions allows an enhanced lipidic components in the pups, this adaptation does not allow normal growth and brain development.

[Effect of variation of the dietary fat content in rats during gestation on the fatty acid profile in maternal and fetal plasma]

With the aim of knowing how changes in the fatty acid composition of the diet affect the fatty acid profile in the plasma during gestation, and the repercussions on the fetuses, in the present study we have administered semi-synthetic diets containing palm oil, olive oil, sunflower seed oil, or fish oils as the sole non-vitamin fat component to pregnant rats. The animals were studied on day 20 of the gestation and after being fed the corresponding diet. As was expected, in the palm oil diet the most abundant fatty acids were saturated, in the olive oil diet is was oleic acid, in the sunflower seed and fish oil diets while the linoleic acid was considerably higher in the sunflower seed oil diet is was linoleic acid, and the fish oil diet it was the only one to show appreciable amounts of eicosepentaenoic and docosehexacnoic acids. In turn, none of the diets contained arachidonic acid. In the plasma of the mothers the proportion of saturated fatty acids was similar in all the groups, the oleic acid was higher in the palm and olive oil diets than in the sunflower seed oil diet. In turn, although a certain proportion of arachidonic acid was found in all the groups, its proportion was lowest in the group of rats with the fish oil diet and these same fish oil rats showed a higher proportion of eicosepentaenoic and docosehexaenoic acids than the other groups did. The profile of the saturated and monounsaturated fatty acids in the plasma of the fetuses differed from that of the mothers, and the changes in the rest of the fatty acids studied were similar to those of the mother with there being a linear and significant correlation of the polyunsaturated acids values between the maternal and the fetal plasma. The fetuses of rats fed with the first dietshowed and intense deficiency of arachidonic acid, and this could have negative consequences for the post-natal development.

Determination of alpha-tocopherol and alpha-tocopherol acetate in diets of experimental animals. Study of stability in the diets

A simple method is described which permits, avoiding saponification, alpha-tocopherol and alpha-tocopheryl acetate measurement in semi-synthetic diets for experimental animals by HPLC, with both UV and fluorescence detection. Phenyldodecane was chosen as internal standard with remarkable performances, and EDTA and BHT were added to prevent oxidation in aqueous and non-aqueous phases respectively. The mobile phase was methanol-water (94:6 v/v) at a flow-rate of 2 ml/min. Samples were homogenized and extracted twice with n-hexane by probe sonication. Extracts were evaporated to dryness and redissolved with chloroform-methanol (1:1, v/v). Validation parameters were studied between 25 ng and 6 micrograms for alpha-tocopherol and between 3 and 24.2 micrograms for alpha-tocopheryl acetate, which corresponds to the range of values in the existing diets. Results had correlation coefficients > 0.99; recoveries > 85%; R.S.D. < 6%, so the method is adequate to control vitamin E intake in animals as well as vitamin E stability in food during storage.

Telomere shortening in mTR-/- embryos is associated with failure to close the neural tube

Mice genetically deficient for the telomerase RNA (mTR) can be propagated for only a limited number of generations. In particular, mTR-/- mice of a mixed C57BL6/129Sv genetic background are infertile at the sixth generation and show serious hematopoietic defects. Here, we show that a percentage of mTR-/- embryos do not develop normally and fail to close the neural tube, preferentially at the forebrain and midbrain. The penetrance of this defect increases with the generation number, with 30% of the mTR-/- embryos from the fifth generation showing the phenotype. Moreover, mTR-/- kindreds in a pure C57BL6 background are only viable up to the fourth generation and also show defects in the closing of the neural tube. Cells derived from mTR-/- embryos that fail to close the neural tube have significantly shorter telomeres and decreased viability than their mTR-/- littermates with a closed neural tube, suggesting that the neural tube defect is a consequence of the loss of telomere function. The fact that the main defect detected in mTR-/- embryos is in the closing of the neural tube, suggests that this developmental process is among the most sensitive to telomere loss and chromosomal instability.