True Niacin Deficiency in Quinolinic Acid Phosphoribosyltransferase (QPRT) Knockout Mice.

Pyridine nucleotide coenzymes (PNCs) are involved in over 500 enzyme reactions. PNCs are biosynthesized from the amino acid L-tryptophan (L-Trp), as well as the vitamin niacin. Hence, "true" niacin-deficient animals cannot be "created" using nutritional techniques. We wanted to establish a truly niacin-deficient model animal using a protocol that did not involve manipulating dietary L-Trp. We generated mice that are missing the quinolinic acid phosphoribosyltransferase (QPRT) gene. QPRT activity was not detected in qprt(-/-)mice. The qprt(+/+), qprt(+/-) or qprt(-/-) mice (8 wk old) were fed a complete diet containing 30 mg nicotinic acid (NiA) and 2.3 g L-Trp/kg diet or an NiA-free diet containing 2.3 g L-Trp/kg diet for 23 d. When qprt(-/-)mice were fed a complete diet, food intake and body weight gain did not differ from those of the qprt(+/+) and the qprt(+/-) mice. On the other hand, in the qprt(-/-) mice fed the NiA-free diet, food intake and body weight were reduced to 60% (p<0.01) and 70% (p<0.05) of the corresponding values for the qprt(-/-) mice fed the complete diet at day 23, respectively. The nutritional levels of niacin such as blood and liver NAD concentrations were also lower in the qprt(-/-) mice than in the qprt(+/+) and the qprt(+/-) mice. Urinary excretion of quinolinic acid was greater in the qprt(-/-) mice than in the qprt(+/+) and the qprt(+/-) mice (p<0.01). These data suggest that we generated truly niacin-deficient mice.

Effect of vitamin B6 deficiency on S-adenosylhomocysteine hydrolase activity as a target point for methionine metabolic regulation.

The objective of this study was to clarify the relationship between the accumulation of S-adenosylhomocysteine (SAH) and the change in the SAH hydrolase activity in vitamin B6 (B6). Male Wistar rats were fed a control diet (control and pair-fed groups) or B6-free diet (B6-deficient group) for 5 wk. Although the SAH-synthetic activity of SAH hydrolase significantly increased in the B6-deficient group, SAH-hydrolytic activity of SAH hydrolase showed no significant difference in the liver among the three groups. On the other hand, SAH hydrolase mRNA in the liver did not show any significant change. Thus, the accumulation of SAH would be due to the increased SAH-synthetic activity of SAH hydrolase. The disturbed methionine metabolism by B6-deficiency, such as a significant increase of plasma homocysteine, might induce the activation of SAH hydrolase in the direction of SAH synthesis.

Poly(ADP-ribose) polymerase activity and DNA strand breaks are affected in tissues of niacin-deficient rats.

The niacin cofactor, NAD, is the substrate for poly(ADP-ribose) polymerase, an enzyme associated with DNA repair. We investigated, therefore, whether hepatic poly(ADP-ribose) polymerase activity was altered and DNA strand breaks in lymphocytes and liver were greater in niacin-deficient rats. A niacin deficiency was established in weanling rats with diets containing 1.5 mg/kg of niacin. Based on lower growth rates and NAD concentrations in blood, liver and skeletal muscle, this diet maintained rats in a deficient state for 1 mo, and, when the dietary niacin was reduced to 0.5 mg/kg, rats remained deficient for an additional month. The hepatic poly(ADP-ribose) polymerase activity was decreased in one experiment when mean hepatic NAD concentrations were 0.60 and 0.51 mumol/g at d 34 and d 60, respectively, compared with 0.77 and 0.80 mumol/g in pair-fed controls. Enzyme activity, however, was greater than in controls when hepatic NAD concentrations were < 0.30 mumol/g. Strand breaks in DNA did not accumulate except after tissues were exposed to hypoxanthine-xanthine oxidase, a free radical-generating system. Exposure to this system caused more DNA strand breaks in lymphocytes and hepatic nuclei from niacin-deficient rats compared with the same tissues from controls. The results suggest that, in rats, although hepatic poly(ADP-ribose) polymerase activity can be elevated, a severe niacin deficiency may increase the susceptibility of DNA to oxidative damage, likely due to a lower availability of NAD.

Vitamin B-6 nutriture and plasma diamine oxidase activity in pregnant Hispanic teenagers.

Vitamin B-6 status was assessed by measuring erythrocyte glutamic-pyruvic transaminase (EGPT) indices in 122 pregnant Hispanic teenagers. Seventeen percent were vitamin B-6 deficient (EGPT indices greater than 1.25) at the initial interview (first or second trimester). A daily supplement of 5 mg vitamin B-6, beginning at initial interview, did not reduce prevalence of vitamin B-6 deficiency at final interview (third trimester). No association was found between EGPT indices greater than 1.25 and the outcome of pregnancy. The activity of diamine oxidase (DAO), a vitamin B-6-dependent enzyme produced by the placental decidua, was measured in maternal plasma. At initial and final interviews, plasma-DAO activity was increased by in vitro addition of pyridoxal-5'-phosphate. The activity in early pregnancy was positively associated with dietary vitamin B-6 intake and was lower in teenagers with EGPT indices greater than 1.25 at the final interview. Findings suggest that plasma-DAO activity is influenced by vitamin B-6 status.

Vitamin B 1, B 2 and B 6 deficiency in neurological disorders.

The activities of the red blood cell enzymes transketolase, glutathione reductase, and glutamic oxaloacetate transaminase were measured with and without in vitro addition of their respective coenzyme components thiamine, riboflavin, and pyridoxine in a group of patients with neurological disorders which may have been caused by malnutrition, intestinal malabsorption, hepatic failure or neoplasms arising outside the nervous system. The incidence of thiamine deficiency was 31%, of riboflavin deficiency 22% and of pyridoxine deficiency 6%. Alcoholics in particular suffered from deficiencies of vitamin B 1, and B 2. There was a correlation of vitamin B 1 and B 2 deficiency and signs of a cerebellar and/or brainstem lesion. The most frequent symptoms in this connection were gait disturbances and oculomotor signs like spontaneous and gaze nystagmus, disturbed eye tracking, diminished optokinetic nystagmus, decreased ability to suppress vestibular nystagmus by fixation. These signs hardly ever occurred in alcoholic patients who showed no deficiency of vitamin B 1, B 2 or B 6. Whenever they do appear, a vitamin B supplementation has to be performed in order to prevent the manifestation of Wernicke's encephalopathy, cerebral or cerebellar atrophy. Alcoholics showed the same incidence of polyneuropathy, whether they suffered from a deficiency of B vitamins or not. Deficiencies of vitamin B 1, B 2 or B 6 were also found in patients with intestinal malabsorption and polyneuropathy, diabetic polyneuropathy, optic atrophy, myelopathy and cerebellar ataxia of unknown etiology, neurological manifestations of neoplasms arising outside the nervous system, B 12 myeloencephalopathy and Thévenard's syndrome.

Apoenzyme activities of erythrocyte transketolase, glutathione reductase, and glutamic-pyruvic transaminase during pregnancy.

The erythrocyte apoenzyme activities of transketolase, glutathione reductase, and glutamic-pyruvic transaminase were determined in 236 pregnant women during the first or second trimester and again during the third trimester. There were no differences in erythrocyte glutathione reductase and erythrocyte glutamic-pyruvic transaminase activities during these two periods. In contrast, erythrocyte transketolase decreased significantly in the third trimester. No statistically significant correlations were found between levels of activity for the various enzymes and dietary intakes of protein, vitamins or calories. The percent of subjects with low erythrocyte transketolase activity (a value one standard deviation or more below the mean initial value) increased significantly during the third trimester. The percent of subjects with low erythrocyte glutamic-pyruvic transaminase activity was significantly reduced during the third trimester although the mean apoenzyme level did not change. Vitamin deficiencies as measured by enzyme stimulation tests tended to occur less frequently among subjects with low enzyme activities but in no instance was there a statistically significant difference. Hence, no association could be found between apoenzyme activity and the incidence of vitamin deficiencies.

The B-vitamin group and the activity of hepatic microsomal mixed-function oxidases of the growing Wistar rat.

1. Male Wistar rats were given isoenergetic, semi-synthetic diets deficient in thiamin, riboflavin, pyridoxine or all the B-vitamins. 2. In rats given these deficient diets the 'sleeping time' induced with pentobarbital (PB) and the 'paralysis time' with zoxazolamine (Zz) were prolonged. 3. The tolerance effect against both drugs was nearly independent of the levels of B-vitamins in the diets. 4. In preparations from vitamin-B deficient animals the activities of the following hepatic microsomal enzymes were reduced: the aliphatic hydroxylase of PB, the aromatic hydroxylases of aniline (EC 1.14.14.1) and of Zz, the N-demethylase of aminopyrine, the UDP glucuronyltransferase (EC 2.4.1.17) of p-nitrophenol. The reactions most influenced were those of 'type-1' substrates, particularly those involving the hydroxylases. 5. The effects observed were caused mainly by deficiency of riboflavin and to a lesser extent of thiamin or pyridoxine.

Influence of norethindrone on drug-metabolizing enzymes of female rat liver in various B-vitamin deficiency states.

Ingestion of high levels of thiamin significantly decreased the activity of cytochrome P-450, NADPH cytochrome c reductase, and the metabolism of aniline and ethylmorphine. Apparent VmaxS for ethylmorphine N-demethylase and aniline hydroxylase were decreased by high levels of riboflavin even though NADPH cytochrome c reductase was elevated. High levels of dietary pyridoxine significantly decreased only the Vmax for aniline hydroxylase. Generally, norethindrone produces either no change or slight depression of cytochrome P-450 regardless or diet, whereas the administration of norethindrone produced no change or an increase in activity of c reductase and ethylmorphine N-demethylase. Norethindrone induces aniline hydroxylase in animals fed all diets except those deficient in thiamin and riboflavin. The activities of the four parameters of the drug metabolizing system measured in these studies as well as the effects of norethindrone are clearly affected by the dietary status of the animal.

PIP: Sprague-Dawley rats were fed a synthetic diet deficient in or containing thiamin (20 mcg/gm food), riboflavin (50 mcg/gm), or pyridoxine (50 mcg/gm) while receiving either norethindrone (1.0 or 10.0 mg/rat/day) or methocel solution to determine the influence of this oral contraceptive on drug-metabolizing enzymes of female rat liver. Ingestion of high levels of thiamin significantly decreased the activity of cytochrome P-450, NADPH cytochrome c reductase, and the metabolism of aniline and ethylmorphine. Diets containing riboflavin significantly depressed V max for aniline hydroxylation and ethylmorphine demethylation while NADPH cytochrome c reductase was elevated. V max for aniline hydroxylase was the only drug-metabolizing enzyme which was affected by high levels of dietary pyridoxine. Norethindrone slightly depressed or left unaffected the activity of cytochrome P-450 regardless of diet. Norethindrone increased activity of c reductase and ethylmorphine N-demethylase or left it unchanged. Norethindrone induces aniline hydroxylase in all diets except those deficient in thiamin and riboflavin. The effects of norethindrone on the kinetics of aniline metabolism were unexplained by substrate enzyme-binding kinetics. However, it is apparent that dietary status affects the parameters studied and the effects of norethindrone.

The vitamin B1, B2 and B6 status of school children in two resettlement areas in Northeast Thailand.

The vitamin B1, B2 and B6 status of school children were studied in the Khon Kaen resettlement and irrigation area and in the Lam-takong settlement in northease Thailand using the in vitro tests based on the erythrocyte transketolase, glutathione reductase and glutamate-oxaloacetate transaminase activities. Healthy school children from the Khon Kaen University School were selected as a reference group. The results demonstrate that the vitamin B1 status in the resettlement area is sufficient, but about 20% to 35% of all the children show evidence of vitamin B2 and B6 deficiencies. It is noticed that besides a high prevalence of parasitic infections and poor hygienic conditions the protein and vitamin intake is low and improvement of the situation is necessary.

Interactions between malnutrition and primaquine studied on Wistar rats. II. Complex vitamin B deficiency and thiamine deficiency.

The action of primaquine was investigated on male Wistar rats depleted on the vitamin B complex (approximately 50% of their requirement for optimal growth), on thiamine (approximately 50% of their requirement for optimal growth), and pair-fed control animals. There was only a marginal increase in adverse primaquine reactions in the malnourished, especially in the thiamine deficient rats.

Vitamin B-1, B-2 and B-6 deficiencies in geriatric patients, measured by coenzyme stimulation of enzyme activities.

The vitamin B-1, B-2 and B-6 nutritional status of 153 geriatric patients was determined by measurement of the activities of transketolase (TK), glutathione reductase (GR) and glutamic-oxaloacetic transaminase (GOT) from hemolyzed erythrocytes before and after in vitro stimulation with their respective coenzymes. The change in enzyme activity after incubation of the hemolysate with the coenzyme was used to determine the activation coefficient, which was taken as an index for the vitamin B-1, B-2 and B-6 nutritional status. Determination of the normal values in 54 healthy blood donors showed that activation coefficients of TK greater than 1.27 indicated a biochemical vitamin B-1 deficiency. Activation coefficients of GR greater than 1.29 and GOT greater than 1.86 indicated, respectively, deficiencies of vitamins B-2 and B-6. On the basis of these findings 22.9% of the geriatric patients appeared to suffer from vitamin B-1 deficiency, 11.7% from vitamin B-2 deficiency and 19.0% from vitamin B-6 deficiency. Of the total number of patients, 44% showed a deficiency of one or more of these three vitamins. Oral administration of vitamin B-1 (20 mg/day), vitamin B-2 (10 mg/day) and vitamin B-6 (20 mg/day) for twelve days normalized nearly all activation coefficients. Determination of enzyme activities without coenzyme stimulation revealed significantly lower values in the deficient patients as compared with the blood donors. However, the distribution of activities for both groups overlapped to a great extent. Oral administration of vitamins raised the enzyme activities to normal values.