Shuhei Ebara

Maternal vitamin B12 deficiency affects spermatogenesis at the embryonic and immature stages in rats

ABSTRACTu2003 To evaluate the role of cobalamin (Cbl) on spermatogenesis, the effect of dietary vitamin B12 deficiency on early spermatogenesis was histologically investigated in male fetuses and newborns in the first filial generation (F1 males) of rats. There was no difference in the number of gonocytes and supporting cells of Sertoli in the gonad in male fetuses on dayu200316 of gestation and in the testes in F1 males at 0u2003days of age between vitamin B12‐deficient (VB12‐D) and vitamin B12‐supplemented (VB12‐S) groups. However, at 21u2003days of age, a decreased number of spermatogonia and no spermatocytes were observed in the VB12‐D group. Numerous TUNEL positive cells were located among spermatocytes of the spermatogenic epithelium. The ultrastructural features examined using transmission electron microscopy were considered to be indicative of apoptosis. The incidence of seminiferous tubules having apoptotic cells was 51.5% in the VB12‐D group. At 60u2003days of age, aplasia of the spermatids and spermatozoa was detected in the VB12‐D group. In the connective tissue between the seminiferous tubules, many interstitial Leydig cells and blood vessels were observed in the VB12‐D group, as compared with the VB12‐S group. These changes produced by vitamin B12 deficiency can be reversed by providing a VB12‐S diet after weaning at 21u2003days of age. From these findings, such a vitamin B12 deficiency during gestation and lactation could affect the germ cells and especially damage spermatocytes in F1 male rats, which indicates that Cbl may be an essential constituent in the meiosis of spermatogenesis.

Effects of biotin deficiency on embryonic development in mice

OBJECTIVEnThe purpose of this investigation was to determine the effects of biotin deficiency on maternal metabolism and embryonic development in pregnant mouse dams.nnnMETHODSnThe pregnant mice were randomly assigned to one of three dietary groups and given a biotin-deficient diet, biotin-supplemented diet, or biotin-control diet during gestation. On days of gestation (dgs) 0, 4, 8, 12, and 16, organic acids including 3-hydroxyisovaleric acid in urine were discovered by high-performance liquid chromatography, and the biotin level in the serum and urine was determined by a bioassay. On dg 18, fetuses were examined for morphologic development.nnnRESULTSnIn the biotin-deficient group, biotin excretion in urine decreased on dg 4 and was subsequently below the lower limit, whereas the urinary concentration of 3-hydroxyisovaleric acid increased after dg 12. In contrast, the biotin concentration in urine significantly increased on dgs 4, 8 and 12 in the biotin-supplemented group, but decreased on dg 16 in the biotin-supplemented and biotin-control groups. The urinary excretion of pyruvic acid in the biotin-deficient group was significantly higher than that in the biotin-supplemented group throughout the entire gestation. These concentrations in urine significantly increased on dg 16 compared with dg 0. The inhibition of embryonic development and external malformations such as cleft palate (100%), micrognathia (100%), and micromelia (91.4%) were also detected in biotin-deficient fetuses.nnnCONCLUSIONnThese findings indicated that, as the requirement of biotin increases during gestation and/or embryonic development, a large amount of biotin is necessary for maintaining normal reproductive performance during the late stage of gestation.

The Nutritional Role of Folate

Folate functions as a coenzyme to transfer one‐carbon units that are necessary for deoxythymidylate synthesis, purine synthesis, and various methylation reactions. Ingested folate becomes a functional molecule through intestinal absorption, circulation, transport to cells, and various modifications to its structure. Associations between nutritional folate status and chronic diseases such as cardiovascular disease, cancer, and cognitive dysfunction have been reported. It has also been reported that maternal folate nutritional status is related to the risk of neural tube defects (NTDs) in the offspring. It has also been recommended that folate be consumed in the diet to promote the maintenance of good health. To reduce the risk of NTDs, supplementation with folic acid (a synthetic form of folate) during the periconceptional period has also been recommended. This paper describes the basic features and nutritional role of folate.

Vitamin B12 deficiency results in the abnormal regulation of serine dehydratase and tyrosine aminotransferase activities correlated with impairment of the adenylyl cyclase system in rat liver.

The aim of the present study was to elucidate the mechanism of the vitamin B(12) deficiency-induced changes of the serine dehydratase (SDH) and tyrosine aminotransferase (TAT) activities in the rat liver. When rats were maintained on a vitamin B(12)-deficient diet, the activities of these two enzymes in the liver were significantly reduced compared with those in the B12-sufficient control rats (SDH 2.8 (sd 0.56) v. 17.5 (sd 6.22) nmol/mg protein per min (n 5); P < 0.05) (TAT 25.2 (sd 5.22) v. 41.3 (sd 8.11) nmol/mg protein per min (n 5); P < 0.05). In the B(12)-deficient rats, the level of SDH induction in response to the administration of glucagon and dexamethasone was significantly lower than in the B(12)-sufficient controls. Dexamethasone induced a significant increase in TAT activity in the primary culture of the hepatocytes prepared from the deficient rats, as well as in the cells from the control rats. However, a further increase in TAT activity was not observed in the hepatocytes from the deficient rats, in contrast to the cells from the controls, when glucagon was added simultaneously with dexamethasone. The glucagon-stimulated production of cAMP was significantly reduced in the hepatocytes from the deficient rats relative to the cells from the control rats. Furthermore, the glucagon-stimulated adenylyl cyclase activity in the liver was significantly lower in the deficient rats than in the controls. These results suggest that vitamin B(12) deficiency results in decreases in SDH and TAT activities correlated with the impairment of the glucagon signal transduction through the activation of the adenylyl cyclase system in the liver.

Consumption of a low-carbohydrate and high-fat diet (the ketogenic diet) exaggerates biotin deficiency in mice

OBJECTIVEnBiotin is a water-soluble vitamin that acts as a cofactor for several carboxylases. The ketogenic diet, a low-carbohydrate, high-fat diet, is used to treat drug-resistant epilepsy and promote weight loss. In Japan, the infant version of the ketogenic diet is known as the ketone formula. However, as the special infant formulas used in Japan, including the ketone formula, do not contain sufficient amounts of biotin, biotin deficiency can develop in infants who consume the ketone formula. Therefore, the aim of this study was to evaluate the effects of the ketogenic diet on biotin status in mice.nnnMETHODSnMale mice (Nxa0=xa032) were divided into the following groups: control diet group, biotin-deficient (BD) diet group, ketogenic control diet group, and ketogenic biotin-deficient (KBD) diet group. Eight mice were used in each group.nnnRESULTSnAt 9 wk, the typical symptoms of biotin deficiency such as hair loss and dermatitis had only developed in the KBD diet group. The total protein expression level of biotin-dependent carboxylases and the total tissue biotin content were significantly decreased in the KBD and BD diet groups. However, these changes were more severe in the KBD diet group.nnnCONCLUSIONnThese findings demonstrated that the ketogenic diet increases biotin bioavailability and consumption, and hence, promotes energy production by gluconeogenesis and branched-chain amino acid metabolism, which results in exaggerated biotin deficiency in biotin-deficient mice. Therefore, biotin supplementation is important for mice that consume the ketogenic diet. It is suggested that individuals that consume the ketogenic diet have an increased biotin requirement.

Biochemical alterations in the palatal processes in fetuses of biotin-deficient mice.

To clarify the role of biotin in palatal formation, we investigated the effects of biotin deficiency on the development of palatal processes in mouse fetuses at midgestation. We also investigated protein expressions in the palatal processes. Pregnant mice were given either a biotin‐deficient diet or a biotin‐supplemented (control) diet from day 0 of gestation (dg 0). Some dams in the biotin‐deficient group were changed to a biotin‐supplemented diet on dg 12, 13 or 14. On dg 15, the palatal processes were dissected from these fetuses and their peptides were characterized using two‐dimensional electrophoresis and liquid chromatography/tandem mass spectrometry (LC‐MS/MS) system. Regarding Traslers stage for the growth of the palatal processes in mouse fetuses on dg 15, the average stage of palatal development was 5.83u2003±u20030.39 in the biotin‐supplemented group, 5.39u2003±u20030.66 in the dg 13‐supplemented group, and 4.64u2003±u20030.90 in the biotin‐deficient group. The development of the palatal processes significantly increased in relation to the earlier day of biotin supplementation. In a protein analysis of palatal processes by isoelectro focusing (IEF) and sodium dodecyl sulfate‐polyacrylamide gel electrophoresis (SDS‐PAGE), a 19‐kDa spot was confirmed around position at pI 6–7 in the biotin‐supplemented group, but this protein was not present in either the biotin‐deficient group or the dg 13‐supplemented group. From the MS/MS database of peptides, adenosine diphosphate (ADP)‐ribosylation factor 2 (arf2) and α‐crystallin were detected in the mesenchyme of the palatal processes. It is suggested that the expression of these proteins may be downregulated by biotin deficiency, inducing the inhibited development of palatal processes.

Effects of Biotin Deficiency on Biotinylated Proteins and Biotin-Related Genes in the Rat Brain.

Biotin is a water-soluble vitamin that functions as a cofactor for biotin-dependent carboxylases. The biochemical and physiological roles of biotin in brain regions have not yet been investigated sufficiently in vivo. Thus, in order to clarify the function of biotin in the brain, we herein examined biotin contents, biotinylated protein expression (e.g. holocarboxylases), and biotin-related gene expression in the brain of biotin-deficient rats. Three-week-old male Wistar rats were divided into a control group, biotin-deficient group, and pair-fed group. Rats were fed experimental diets from 3 wk old for 8 wk, and the cortex, hippocampus, striatum, hypothalamus, and cerebellum were then collected. In the biotin-deficient group, the maintenance of total biotin and holocarboxylases, increases in the bound form of biotin and biotinidase activity, and the expression of an unknown biotinylated protein were observed in the cortex. In other regions, total and free biotin contents decreased, holocarboxylase expression was maintained, and bound biotin and biotinidase activity remained unchanged. Biotin-related gene (pyruvate carboxylase, sodium-dependent multivitamin transporter, holocarboxylase synthetase, and biotinidase) expression in the cortex and hippocampus also remained unchanged among the dietary groups. These results suggest that biotin may be related to cortex functions by binding protein, and the effects of a biotin deficiency and the importance of biotin differ among the different brain regions.