Thiamine deficiency in the critically ill

There have been recent reports of hospitalised patients developing clinical thiamine deficiency, combined with much debate on the optimal supplementation of thiamine for the parenterally fed patient, particularly in the intensive therapy environment. We performed a retrospective study on 158 patients admitted to the Intensive Care Unit who required nutritional support. Patients who survived had significantly higher body thiamine status than those who died (p less than 0.01). There was no difference between serum albumin concentrations of the two groups. Twenty percent of the patients had biochemical evidence of thiamine deficiency and the mortality rate in these patients was 72% as compared with 50% mortality overall. Follow-up results suggest that current levels of thiamine supplementation are insufficient for critically ill intravenously fed patients. We suggest that patients be given a loading dose of 50-250 mg thiamine on admission to the Intensive Care Unit.

B-vitamin status and concentrations of homocysteine in Austrian omnivores, vegetarians and vegans

BACKGROUND

A vegetarian diet is considered to promote health and longevity and reduce the risk of cardiovascular diseases and cancer. However, a vegetarian diet may be deficient in some nutrients. Exclusion of animal products in vegetarian diets may affect the status of certain B-vitamins, and further cause the rise of plasma homocysteine concentration.

OBJECTIVE

The nutritional status of various B-vitamins (B(1), B(2), B(6), B(12), folic acid) and the concentration of homocysteine in blood plasma of omnivores (n = 40), vegetarians (n = 36) and vegans (n = 42) in Austria was evaluated.

METHODS

The evaluation was done using the functional parameters erythrocyte transketolase (ETK), glutathione reductase (EGR) and glutamic oxaloacetic transaminase (EGOT) activation coefficients. Enzyme activity was measured photometrically. The quantity of vitamins B(1), B(2) and B(6) in urine and the concentrations of vitamin B(6) and homocysteine in plasma were determined by HPLC methods with fluorescence detection. Plasma concentration of vitamin B(12) and folic acid were measured with radioimmunoassay.

RESULTS

Most of the subjects showed a satisfying vitamin B(1) status. Vegans presented a significantly lower mean plasma vitamin B(12) concentration than omnivores and vegetarians and deficiency in 2.4% of the volunteers but the highest mean value of plasma folate among the investigated groups. A deficient status of folate was found in 18% of omnivores and in approximately 10% of vegans and vegetarians. The status of riboflavin is considered to be deficient in about 10% of omnivores and vegetarians and in over 30% of vegans. According to the activation coefficient of GOT, approximately one third of all subjects showed vitamin B(6) deficiency. Elevated homocysteine concentration in plasma was observed in 66% of the vegans and about 45-50% of the omnivores and vegetarians. Vegan subjects had significantly higher mean plasma homocysteine levels than omnivores.

CONCLUSION

Thiamin and folate need not be a problem in a well-planned vegan diet. Vitamins B(12) and B(2) may need attention in the strict vegan diet, especially regarding elevated homocysteine levels in plasma. Pyridoxine status appeared to be independent of the diet.

Postpartum thiamine deficiency in a Karen displaced population

BACKGROUND

Before its recognition, infantile beriberi was the leading cause of infant death in camps for displaced persons of the Karen ethnic minority on Thailand's western border.

OBJECTIVE

This study aimed to document thiamine status in the peripartum period to examine the current supplementation program and the correlation between the clinical manifestations of thiamine deficiency and a biochemical measure of thiamine status.

DESIGN

Women were enrolled prospectively at 30 wk of gestation and were followed up weekly until delivery and at 3 mo postpartum. Thiamine supplementation during pregnancy was based on patient symptoms.

RESULTS

At 3 mo postpartum, thiamine deficiency reflected by an erythrocyte transketolase activity (ETKA) > or = 1.20% was found in 57.7% (15/26) of mothers, 26.9% (7/26) of whom had severe deficiency (ETKA > 1.25%). No significant associations between ETKA and putative maternal symptoms or use of thiamine supplements were found.

CONCLUSIONS

Biochemical postpartum thiamine deficiency is still common in Karen refugee women. This situation may be improved by educating lactating women to reduce their consumption of thiaminase-containing foods and by implementing an effective thiamine supplementation program.

Changes of some vitamin levels during and after normal pregnancy

Most vitamin status parameters change significantly during pregnancy. A number of factors have been associated with this hypovitaminaemia of pregnancy. From our data, it was concluded that the initial value of a vitamin status parameter was by far the main determinant of the changes of vitamin levels during pregnancy: the higher the value, the steeper the decrease. Some hormonal variables were associated with these changes as well. This is highly suggestive of a resetting of vitamin homeostasis in blood, with a retention of vitamins in maternal tissues. The postpartum changes of vitamin levels provide insight into the 'net cost' of vitamins during pregnancy. Most serum blood levels of vitamins normalized shortly after delivery. Serum vitamin B6 levels increased slowly with 25% below the acceptable range at 6 months postpartum. However, the GGOT stimulation ratio, indicative for vitamin B6 cellular content, was completely normal at the time. Serum folacin was the only exception, with 45% serum levels in the marginal or deficient range; 20% of this group had deficient or marginal red cell folacin levels as well. This indicates that the 'net cost' of folacin during pregnancy is considerable, and repletion of folacin stores takes more than 6 months.

Clinical relevance of thiamine status amongst hospitalized elderly patients

BACKGROUND

The prevalence and the consequences of thiamine deficiency among elderly patients admitted to acute geriatric wards are not known.

OBJECTIVES

(1) To assess the prevalence of thiamine deficiency in patients admitted to a geriatric ward compared to age-matched ambulatory outpatients; (2) to identify their diseases and problems associated with thiamine deficiency, and (3) to determine the relationship between the thiamine status and the cognitive and functional status of these patients.

MATERIALS AND METHODS

118 aged hospitalized patients (83 +/- 7 years; mean age +/- SD) were prospectively enrolled on admission to the geriatric ward. Their cognitive status was assessed using the Mini-Mental State Examination (MMSE) and their ability to perform their activities of daily living (ADL) using ADL scales. The effect of exogenous thiamine pyrophosphate (TPP) addition on the blood transketolase (TK) activity (TPP TK effect) served to estimate thiamine deficiency. Socioeconomic data, diseases and treatment were identified as potential associated risk factors. This group of hospitalized patients was divided according to their thiamine status to characterize the conditions associated with thiamine deficiency. Thirty-five outpatients without any functional or cognitive impairment served as a control group.

RESULTS

Of 118 inpatients, 46 (39%) presented with a TPP TK effect of >15%, and 6 with values of >22%, indicating moderate and severe thiamine deficiency, respectively. Only 6 of 30 outpatients (20%) exhibited a TPP TK effect of >15% and none of them reached values of >18%. Although it tended to be lower in outpatients, the mean TPP TK effect did not statistically differ from the mean of inpatients. Thiamine-deficient inpatients comprised a larger proportion of institutionalized subjects than nondeficient inpatients (87 versus 47%, p < 0.001). Functional status, cognitive functions and the occurrence of delirium did not differ according to their thiamine status. By contrast, thiamine-deficient inpatients exhibited a higher proportion of Alzheimer's disease, depression, cardiac failure and falls. Furosemide was more frequently taken by thiamine-deficient patients.

CONCLUSIONS

Severe thiamine deficiency remained quite low among the hospitalized elderly. The prevalence of moderate thiamine deficiency approached 40%. Institutionalized subjects were at particular risk of developing thiamine deficiency. Its clinical relevance on functional status and on cognitive function remained not significant. By contrast, a high proportion of falls, Alzheimer's disease, depression, cardiac failure and furosemide use could have been related to thiamine deficiency.

Blood thiamine levels in outpatients with diabetes mellitus

In 46 diabetic outpatients consisting of 20 males and 26 females not given thiamine treatment, the blood thiamine level was 46.9 +/- 28.5 ng/ml (mean +/- SD) and only 23.9% of all cases had a value of more than the normal lower limit (50 ng/ml). Erythrocyte transketolase activity was 443.8 +/- 107.7 micrograms/ml/h and only 20.9% had a value of ore than the normal lower limit (50 micrograms/ml/h), and the erythrocyte TPP effect was 16.6 +/- 13.2%. Moreover, there was a significant positive correlation (r = 0.97) between the blood thiamine level and erythrocyte transketolase activity, and a significant inverse correlation (r = -0.525, r = -0.576) between blood thiamine level and/or erythrocyte transketolase activity and the erythrocyte TPP effect. In 24 diabetic outpatients consisting of 14 males and 10 females given thiamine treatment, the blood thiamine level was 96.5 +/- 44.5 ng/ml/h excluding one case (621.7 ng/ml), and it was higher than the normal lower limit in 83% of all cases. Erythrocyte transketolase activity was 513.9 +/- 133.4 micrograms/ml/h and it was higher than the normal lower limit in 58.3%. Erythrocyte TPP effect was 5.84 +/- 8.39%. There was also a significant positive correlation (r = 0.663) between blood thiamine level and erythrocyte transketolase activity, and a significant inverse correlation (r = 0.0668, r = 0.834) between blood thiamine level and/or erythrocyte transketolase activity and erythrocyte TPP effect. Blood thiamine level and erythrocyte transketolase activity were significantly higher in diabetic outpatients given thiamine treatment than in diabetic outpatients not given thiamine treatment, while the erythrocyte TPP effect was significantly lower in diabetic outpatients given thiamine treatment than in diabetic outpatients not given thiamine treatment. There was no direct relationship between the lowered response of patellar tendon reflex and the biochemical status of thiamine. From the above findings it was concluded that diabetic outpatients tend to have a low blood thiamine level, with low erythrocyte transketolase activity and high erythrocyte TPP effect, and showed marginal thiamine deficiency.

An erythrocyte transketolase isoenzyme pattern associated with the Wernicke-Korsakoff syndrome

Two techniques were used to seek variants of human erythrocyte transketolase and to test for any association of the Wernicke-Korsakoff syndrome, a thiamin-deficiency disease, with a particular variant of this thiamin-dependent enzyme. Apparent Km values for the cofactor thiamin diphosphate were similar for patients and controls. However, isoelectric focussing separated erythrocyte transketolase into different isoenzymes characterized by pI values in the range 6.6-9.2. Six distinct patterns of isoenzymes were found in thirty-six healthy control subjects. The isoenzyme pattern for thirty-nine out of forty-two patients suffering from the Wernicke-Korsakoff syndrome was identical to a pattern found in only eight of thirty-six control subjects, a highly significant association (P less than 0.001). This association suggests that a variant transketolase and thiamin deficiency together contribute to the pathogenesis of the brain damage of the Wernicke-Korsakoff syndrome by some mechanism independent of apparent Km values for thiamin diphosphate.

Comparison of erythrocyte transketolase activity with thiamine and thiamine phosphate ester levels in chronic alcoholic patients

The effect of chronic alcoholism on biochemical evaluation of thiamine status was studied by the concomitant determination of erythrocyte transketolase (ETK) activity, its relative increase by in vitro addition of thiamine diphosphate (TDP effect) and the direct measurement of thiamine and its phosphate esters by high performance liquid chromatography. Thirty-eight percent of alcoholic subjects showed a thiamine deficiency with decreased thiamine diphosphate concentrations compared with healthy subjects (90.8 +/- 25.7 nmol/l vs. 176 +/- 28.0 nmol/l, respectively, mean +/- S.D., P < 0.001). Thiamine diphosphate concentrations were highly correlated with total thiamine concentrations and TDP effect (respectively r = 0.99 and 0.79, n = 85, P < 0.001). No abnormality in thiamine phosphorylation related to chronic alcoholism was noted. Finally, 47% of these deficient alcoholic patients had normal ETK activity. We concluded that, if indirect evaluation of thiamine status is to be chosen, the determination of ETK activity should be associated with TDP effect since the latter has been shown to be highly linked to total thiamine and thiamine diphosphate in erythrocytes. Furthermore, the direct measurement of thiamine and its phosphate esters was a more sensitive and specific index of thiamine nutrition.

Red cell transketolase as an indicator of nutritional deficiency

Twenty patients who had symptoms that were apparently neurotically functional are reported because they proved to have abnormal red cell transketolase activity. Although in many of the cases the etiology appeared to be associated with heavy consumption of "junk" foods, carbonated or sweet beverages, and candy, this was not so in all of them and the etiology in these cases remains obscure. The symptoms in all 20 patients could be correlated with those well documented in early beriberi and all were clinically improved by the administration of thiamin. In only two cases were other vitamins administered. Such improvement was slow and there were no dramatic recoveries. In 10 patients improved transketolase activity was correlated with clinical well-being. The other 10 patients did not keep their return appointments. Telephone contract revealed that they were asymptomatic.

Magnesium deficiency: a possible cause of thiamine refractoriness in Wernicke-Korsakoff encephalopathy

The determination of blood transketolase before and serially after thiamine administration, and the response of clinical symptomatology after thiamine are reported in two normomagnesaemic patients and one hypomagnesaemic patient with acute Wernicke-Korsakoff encephalopathy. The response of the depressed blood transketolase and the clinical symptoms was retarded in the hypomagnesaemic patient. Correction of hypomagnesaemia was accompanied by the recovery of blood transketolase activity and total clearing of the ophthalmoplegia in this patient, suggesting that hypomagnesaemia may be a cause of the occasional thiamine refractoriness of these patients.

The thiamine status of adult humans depends on carbohydrate intake

Thiamine requirements for humans are generally expressed as absolute values per day (mg/d) or in relation to total caloric intake. Limited data are available on the relation between thiamine requirements and the intake of carbohydrates. This study was performed to investigate the influence of stepwise increases of carbohydrate intake on the status of thiamine in healthy volunteers under isocaloric conditions. During an adaptation phase of four days, the carbohydrate intake of twelve healthy volunteers (6 male, 6 female) was 55% of total energy intake. During the subsequent intervention periods, carbohydrate intake was increased to 65% of total energy for four days and to 75% for another four days. Thiamine intake, total energy intake, and physical activity were kept constant throughout the study. HPLC analysis was used to measure thiamine in plasma, urine and feces. Erythrocyte transketolase activity (ETK) was determined enzymatically. During the intervention periods thiamine decreased significantly (p < 0.05) in plasma (from 19.3 +/- 3.3 to 16.4 +/- 4.0 nmol/l) as well as in urine (from 72 +/- 56 to 58 +/- 21 mumol/mol creatinine). ETK and feces content of thiamine remained unchanged. An increase of dietary carbohydrate intake from 55% to 65% and 75%, respectively, of total caloric intake for four days per period at isocaloric conditions causes a decrease of plasma and urine levels of thiamine without affecting enzyme activities.

Nutrition in cryptogenic cirrhosis and chronic aggressive hepatitis

The nutritional status of 80 patients with non-alcoholic chronic liver disease was assessed by determination of various nutritional parameters in body fluids. With the exception of vitamin C there was a higher incidence (40%) of fat soluble vitamin deficiency (vitamins A, E, and carotene) than of the water soluble vitamins. Less than 10% of patients showed evidence of vitamin B12, nicotinic acid, thiamin, or riboflavin deficiency, and 17% had evidence of folic acid deficiency. The presence of deficiency was not related to age of the patient or fat absorption, and an inadequate dietary intake was not a major cause of deficiency. The incidence of nutritional deficiency is less frequent in non-alcoholic as compared with alcoholic liver disease.

Thiamine, riboflavin, and pyridoxine deficiencies in a population of critically ill children

The unexpected autopsy finding of Wernicke encephalopathy in three children who died after prolonged enteral feeding prompted us to examine the incidence of thiamine deficiency in three high-risk pediatric populations. We also measured riboflavin and pyridoxine activity in the same groups. We used activated enzyme assays (erythrocyte transketolase, glutathione reductase, aspartate aminotransferase) to assess tissue stores of the dependent vitamin cofactors (thiamine (vitamin B1), riboflavin (vitamin B2), and pyridoxine (vitamin B6), respectively). Using our own reference ranges based on data from 80 healthy adults and children, we prospectively investigated the B vitamin status of three groups of children: (1) 27 patients who were fed solely by nasogastric tube for more than 6 months, (2) 80 children admitted to a pediatric intensive care unit for more than 2 weeks, and (3) 6 children receiving intensive chemotherapy. The upper limits for stimulated enzyme activity in control subjects were unaffected by age or gender (16% for transketolase, 63% for glutathione reductase, 123% for aspartate aminotransferase). Using these limits, 10 (12.5%) of 80 patients receiving intensive care and 4 of 6 patients receiving chemotherapy were thiamine deficient. Elevated levels returned to normal after thiamine supplementation. No patients were pyridoxine deficient, but 3 (3.8%) of the 80 patients receiving intensive care and 1 of the 6 patients receiving chemotherapy were also riboflavin deficient. We conclude that unrecognized thiamine deficiency is common in our pediatric intensive care and oncology groups. This potentially fatal but treatable disease can occur in malnourished patients of any age and is probably underdiagnosed among chronically ill children. Our findings may be applicable to other high-risk pediatric groups.

Diabetes mellitus, thiamine-dependent megaloblastic anemia, and sensorineural deafness associated with deficient alpha-ketoglutarate dehydrogenase activity

Three brothers with diabetes mellitus, thiamine-responsive megaloblastic anemia, and sensorineural deafness are reported. Two had, in addition, congenital septal defects. The activities of thiamine-dependent enzymes were determined in one patient, revealing low alpha-ketoglutarate dehydrogenase activity, which could have caused a sideroblastic anemia with secondary megaloblastic changes. The anemia was thiamine dependent. The cause of the diabetes mellitus was not known, but it was not type 1.

Thiamin requirement of the adult human

Young adult male subjects maintained on a metabolic ward were fed diets providing controlled intakes of thiamin and either 2800 or 3600 kcal. The higher level of calories was attained by an increased intake of carbohydrates. Constant weights were maintained by the subjects by adjusting daily activity and exercise schedules. Thiamin requirements were evaluated in terms of erythrocyte transketolase activity and urinary excretion of the vitamin. The results of the study revealed that a relationship exists between thiamin requirement and caloric intake and expenditure. Thus, when the calories being utilized were derived primarily from carbohydrate sources, the minimum adult male requirement for thiamin appeared to be 0.30 mg of thiamin per 1000 kcal. Urinary excretion of thiamin and erythrocyte transketolase activity appear to be reasonably reliable reflections of thiamin intakes and thiamin nutritional status. The use of these measurements in nutrition surveys appears justified. The microbiological assay (Lactobacillus viridescens) for measuring thiamin levels in urine samples appears to be a somewhat more sensitive but valid procedure as an alternate for the thiochrome method. Judged from the results of this study, the recommended intake for the adult human of 0.40 mg of thiamin per 1000 kcal by FAO/WHO and the recommended allowance of 0.5 mg per 1000 kcal by the Food and Nutrition Board of the NAS-NRC appear reasonable and amply allow for biological variations and other factors that may influence the requirement for this vitamin.

Altered heavy metals and transketolase found in autistic spectrum disorder

Autism and autism spectrum disorder (ASD) are developmental brain disorders with complex, obscure, and multifactorial etiology. Our recent clinical survey of patient records from ASD children under the age of 6 years and their age-matched controls revealed evidence of abnormal markers of thiol metabolism, as well as a significant alteration in deposition of several heavy metal species, particularly arsenic, mercury, copper, and iron in hair samples between the groups. Altered thiol metabolism from heavy metal toxicity may be responsible for the biochemical alterations in transketolase, and are mechanisms for oxidative stress production, dysautonomia, and abnormal thiamine homeostasis. It is unknown why the particular metals accumulate, but we suspect that children with ASD may have particular trouble excreting thiol-toxic heavy metal species, many of which exist as divalent cations. Accumulation or altered mercury clearance, as well as concomitant oxidative stress, arising from redox-active metal and arsenic toxicity, offers an intriguing component or possible mechanism for oxidative stress-mediated neurodegeneration in ASD patients. Taken together, these factors may be more important to the etiology of this symptomatically diverse disease spectrum and may offer insights into new treatment approaches and avenues of exploration for this devastating and growing disease.

Prevalence of thiamin deficiency in anorexia nervosa

OBJECTIVE

Deficiency of thiamin (vitamin B1) causes a range of neuropsychiatric symptoms that resemble those reported in patients with anorexia nervosa (AN) but the prevalence of thiamin deficiency in AN has not been reliably established. This study was designed to investigate the prevalence of thiamin deficiency in AN.

METHOD

Thirty-seven patients attending a specialist eating disorders unit and meeting all or some of the DSM-IV criteria for AN were compared with 50 blood donor controls. All subjects underwent measurement of erythrocyte transketolase activation following the addition of thiamin pyrophosphate, the standard biochemical test for thiamin deficiency. Deficiency was defined as a result more than 2 SD above the mean of the control population.

RESULTS

Fourteen patients (38%) had results in the deficient range; 7 (19%) met the most stringent published criterion for deficiency. Deficiency was not related to duration of eating restraint, frequency of vomiting, or alcohol consumption.

DISCUSSION

Thiamin deficiency may account for some of the neuropsychiatric symptoms of AN and routine screening or supplementation may be indicated.

The evaluation of erythrocyte thiamin diphosphate as an indicator of thiamin status in man, and its comparison with erythrocyte transketolase activity measurements

HPLC measurement of the major physiological form of thiamin, thiamin diphosphate, in erythrocytes (ETDP) has been assessed as an indicator of thiamin status and compared with erythrocyte transketolase activity (ETKA) before and after activation with exogenous thiamin diphosphate (TDP effect). The comparison was made by following the response of the parameters to incubation of erythrocytes with thiamin and by measurements in alcoholic, elderly and student groups. All parameters were responsive to the thiamin content of their environment, but ETDP was at least as sensitive as TDP effect and more sensitive than ETKA in reflecting thiamin uptake and utilisation by erythrocytes. There was a better correlation between ETDP and ETKA than between ETDP and TDP effect. All the groups showed a significant positive correlation between ETDP and ETKA, but only the elderly and the alcoholic groups showed a significant negative correlation between ETDP and TDP effect. The lack of correlation between ETDP and TDP effect in the student group may be due to the relative imprecision of TDP effect measurements at the lower end of the reference range. ETDP is more stable than ETKA in frozen erythrocytes, is easier to standardise and is not affected by various factors which can influence the enzyme assay. Measurement of ETDP is, therefore, recommended for first line assessment of thiamin status.

Thiamine deficiency and malaria in adults from southeast Asia

BACKGROUND

Thiamine deficiency (beriberi) is common in some parts of southeast Asia. Acute thiamine deficiency can mimic many complications of malaria, such as encephalopathy and lactic acidosis. We examined the incidence of thiamine deficiency in adults admitted to hospital with malaria in Thailand.

METHODS

For this prospective study, we recruited consecutive patients with malaria or other febrile illness who presented to Paholpolpayuhasena Hospital, Kanchanaburi, Thailand, between May and July, 1992. We used the activation coefficient (alpha) for transketolase activity in erythrocytes to measure thiamine deficiency (defined as alpha>1.31) in patients with severe and uncomplicated malaria and in controls (patients' relatives and healthy volunteers). To exclude the possibility of interference in the assays, transketolase activity was also measured in erythrocytes used to culture parasites.

FINDINGS

12 (52%) of 23 patients with severe malaria and ten (19%) of 54 patients with uncomplicated malaria had alpha values above the normal range (p<0.0001 and p=0.0014, respectively, compared with controls), which indicated severe thiamine deficiency. Thiamine deficiency was more severe in patients with cerebral malaria than in those with uncomplicated malaria and the controls (p=0.008).

INTERPRETATION

In adults admitted to hospital in Thailand, thiamine deficiency commonly complicates acute falciparum malaria, particularly in severe infections, and could contribute to dysfunction of the central nervous system.

Thiamine deficiency in hospitalized elderly patients

Necropsy studies suggest that thiamine deficiency is underdiagnosed in life, in part because the classical clinical presentations are uncommon. Anecdotal reports suggest that thiamine deficiency may contribute to the development of delirium, heart failure and peripheral neuropathy in elderly patients, but little systematic research has been reported. We examined thiamine levels in 36 consecutive non-demented, community-dwelling patients admitted to an acute geriatric unit. Marginal thiamine deficiency [thiamine pyrophosphate effect (TPPE) 15-24%] was present in 11 (31%) and definite thiamine deficiency (TPPE > 25%) in 6 (17%) patients. Delirium occurred in 6/19 (32%) patients with normal thiamine status and 13/17 (76%) thiamine-deficient patients (p < 0.025, chi 2 test). One or more other possible causes for delirium were present in all cases. One patient had ocular signs and a dramatic clinical response to vitamin B complex therapy. Absent ankle jerks were noted in 2/19 (10%) patients with normal thiamine status and 7/17 (41%) patients with thiamine deficiency (p = 0.06). There was no difference in anthropometric indices or in the prevalence of other nutrient deficiencies between the two groups. Thiamine deficiency is common in elderly patients admitted to hospital and may contribute to the development of delirium.

Studies of transketolase abnormality in Alzheimer's disease

The partially purified transketolase from each of eight well-nourished patients with Alzheimer's disease contained significantly less heat-stable component with a significantly longer half-life of heat inactivation than that from eight controls. Immunochemical studies utilizing antibodies to the purified human liver transketolase did not distinguish between red blood cell transketolases of patients with Alzheimer's disease and those of controls. However, three brains from patients with Alzheimer's disease that were deficient in transketolase activity lacked a 69-kilodalton form on immunoblots. Subtle structural abnormalities of transketolase appear to occur in a high proportion of patients with Alzheimer's disease.

Studies on the nutrition of marine flatfish. The thiamin requirement of turbot (Scophthalmus maximus)

1. Seven groups of young turbot (Scophthalmus maximus) were given diets containing graded levels of thiamin (0-19--50 mg/kg) for 16 weeks and their growth rate was measured during this period. 2. Good growth was obtained on all these treatments except in the group given the lowest dietary thiamin level (0-19 mg/kg). These fish grew normally until the 12th week but thereafter their weight did not increase. 3. Measurements of erythrocyte transketolase (sedoheptulose-7-phosphate: D-glyceraldehyde-3-phosphate glycolaldehydetransferase; EC 2.2.1.1) activity at the end of the experiment and of percentage stimulation of erythrocyte transketolase by thiamin pyrophosphate indicated that the apoenzyme was saturated with coenzyme at a dietary thiamin level of 2-6 mg/kg, but not at 1-1 mg/kg. 4. An 8th group of turbot given the thiamin antagonist pyrithiamin (40 mg/kg diet) grew normally for 6 weeks. Thereafter mortalities began to occur and all fish died by the 10th week. No clear-cut signs of thiamin deficiency were observed. 5. The dietary thiamin requirement of turbot is much lower than published requirements of freshwater fish other than carp (Cyprinus carpio) and appears to be between 0-6 and 2-6 mg/kg diet.