Vitamin B6 repletion in cirrhosis with oral pyridoxine: failure to improve amino acid metabolism

The Role of Vitamin Deficiency in Liver Disease: To Supplement or Not Supplement?

Over the past few years, growing interest has been shown for the impact of dietary requirements and nutritional factors on chronic diseases. As a result, nutritional programs have been reinforced by public health policies. The precise role of micronutrients in chronic liver disease is currently receiving particular attention since abnormalities in vitamin levels are often detected. At present, treatment programs are focused on correcting vitamin deficiencies, which are frequently correlated to higher rates of comorbidities with poor outcomes. The literature reviewed here indicates that liver diseases are often related to vitamin disorders, due to both liver impairment and abnormal intake. More specific knowledge about the role of vitamins in liver disease is currently emerging from various results and recent evidence. The most significant benefits in this area may be observed when improved vitamin intake is combined with a pharmacological treatment that may also affect the progression of the liver disease, especially in the case of liver tumors. However, further studies are needed.

Impact of Glutathione and Vitamin B-6 in Cirrhosis Patients: A Randomized Controlled Trial and Follow-Up Study

Vitamin B-6 and glutathione (GSH) are antioxidant nutrients, and inadequate vitamin B-6 may indirectly limit glutathione synthesis and further affect the antioxidant capacities. Since liver cirrhosis is often associated with increased oxidative stress and decreased antioxidant capacities, we conducted a double-blind randomized controlled trial to assess the antioxidative effect of vitamin B-6, GSH, or vitamin B-6/GSH combined supplementation in cirrhotic patients. We followed patients after the end of supplementation to evaluate the association of vitamin B-6 and GSH with disease severity. In total, 61 liver cirrhosis patients were randomly assigned to placebo, vitamin B-6 (50 mg pyridoxine/d), GSH (500 mg/d), or B-6 + GSH groups for 12 weeks. After the end of supplementation, the condition of patient’s disease severity was followed until the end of the study. Neither vitamin B-6 nor GSH supplementation had significant effects on indicators of oxidative stress and antioxidant capacities. The median follow-up time was 984 d, and 21 patients were lost to follow-up. High levels of GSH, a high GSH/oxidized GSH ratio, and high GSH-St activity at baseline (Week 0) had a significant effect on low Child–Turcotte–Pugh scores at Week 0, the end of supplementation (Week 12), and the end of follow-up in all patients after adjusting for potential confounders. Although the decreased GSH and its related enzyme activity were associated with the severity of liver cirrhosis, vitamin B-6 and GSH supplementation had no significant effect on reducing oxidative stress and increasing antioxidant capacities.

Seizures caused by pyridoxine (vitamin B6) deficiency in adults: A case report and literature review

Pyridoxine (vitamin B6) deficiency is a recognised cause of intractable seizures in neonates. However, pyridoxine deficiency related seizures in adults were rarely reported. This article reports a case of a 79 year old lady who suffered from new-onset seizures and was successfully treated with vitamin B6. The patient had chronic renal disease and weight loss due to anepithymia following a pelvic fracture. This article also reviews literatures of seizures caused by pyridoxine deficiency in adults. Seizures caused by vitamin B6 deficiency in adults may result from dietary deficiency, liver disease, pregnancy and certain medications and can be easily treated by vitamin B6 with excellent outcome. Clinicians should consider vitamin B6 deficiency as a potential aetiology of seizures, even in patients who suffer from other underlying diseases which can cause seizures.

Activity of glycogen synthase and glycogen phosphorylase in normal and cirrhotic rat liver during glycogen synthesis from glucose or fructose

Cirrhotic patients often demonstrate glucose intolerance, one of the possible causes being a decreased glycogen-synthesizing capacity of the liver. At the same time, information about the rates of glycogen synthesis in the cirrhotic liver is scanty and contradictory. We studied the dynamics of glycogen accumulation and the activity of glycogen synthase (GS) and glycogen phosphorylase (GP) in the course of 120min after per os administration of glucose or fructose to fasted rats with CCl4-cirrhosis or fasted normal rats. Blood serum and liver pieces were sampled for examinations. In the normal rat liver administration of glucose/fructose initiated a fast accumulation of glycogen, while in the cirrhotic liver glycogen was accumulated with a 20min delay and at a lower rate. In the normal liver GS activity rose sharply and GPa activity dropped in the beginning of glycogen synthesis, but 60min later a high synthesis rate was sustained at the background of a high GS and GPa activity. Contrariwise, in the cirrhotic liver glycogen was accumulated at the background of a decreased GS activity and a low GPa activity. Refeeding with fructose resulted in a faster increase in the GS activity in both the normal and the cirrhotic liver than refeeding with glucose. To conclude, the rate of glycogen synthesis in the cirrhotic liver is lower than in the normal one, the difference being probably associated with a low GS activity.

Refractory epileptic seizures due to vitamin B6 deficiency in a patient with Parkinson's disease under duodopa® therapy

Levodopa/carbidopa intestinal gel (LCIG) infusion for the treatment of advanced Parkinson's disease (PD) has been suspected to provoke polyneuropathy in conjunction with vitamin B6, B12 and folate deficiency and elevated homocysteine levels. We describe a PD patient under LCIG therapy developing refractory epileptic seizures obviously promoted by vitamin B6 deficiency.

Effect of vitamin B-6 supplementation on fuels, catecholamines, and amino acids during exercise in men

PURPOSE

In two separate but identical studies, the effect of vitamin B-6 supplementation was examined on plasma energy substrates, catecholamines, and 13 amino acid concentrations during exercise.

METHODS

Eleven trained men performed two separate exhaustive exercise tests at 71.0+/-4.6% VO2max during two separate 9-d controlled diet periods. Exercise test 1 (T1C) occurred following a control diet, and test 2 (T2B6) occurred following a vitamin B-6 supplemented diet (20 mg PN.d(-1)). Blood was drawn pre, during (60 min), post, and post-60 min of exercise, and plasma was analyzed for glucose, lactate, glycerol, free fatty acids (FFA), catecholamines (N = 5), and amino acids (N = 5).

RESULTS

Mean FFA concentrations changed over time in both tests (P < 0.001) and were lower in T2B6 compared to T1C at pre (P = 0.03), during (P = 0.05), and post-60 min (P = 0.04) of exercise. Mean lactate, glycerol, and catecholamine concentrations only changed over time (P < 0.0001). The only significant changes in amino acid concentrations were for lower tyrosine (P = 0.007) and methionine (P = 0.03) concentrations in T2B6 relative to TIC at post-60 min of exercise and postexercise, respectively. No differences were observed in exercise times to exhaustion between TIC (108+32.6 min) and T2B6 (109+51.2 min).

CONCLUSIONS

These results indicate that vitamin B-6 supplementation can alter plasma FFA and amino acid concentrations during exhaustive endurance exercise without affecting endurance.

Vitamin B6 metabolism by human liver

The B6 vitamers (pyridoxine, pyridoxamine, and pyridoxal) are primarily metabolized in liver to pyridoxal 5'-phosphate (PLP) and the deadend catabolite 4-pyridoxic acid. We have built on the elegant early work of Snell and others to describe the activities of the human liver enzymes responsible for vitamin B6 metabolism and to develop a model of the relative rates of these interconversions in vivo. This model is consistent with changes in plasma B6 after a load, the clearance of different vitamers (e.g., pyridoxine versus pyridoxal), and with the low plasma PLP in patients with cirrhosis. Because cirrhotics were found to be capable of PLP synthesis, we have used oral supplementation with pyridoxine to restore plasma PLP to the normal range, and have evaluated the effects of this intervention on amino acid metabolism. No significant differences were observed in plasma or urinary clearance of methionine (or cystathionine) after an oral load, nor in amino acid clearance from circulation after a protein load for cirrhotic patients before and after restoration of normal plasma PLP. Hence, the abnormal metabolism of vitamin B6 does not appear to be an important factor in the deranged amino acid metabolism in this disease. Nonetheless, this approach may be generally useful in assessing the importance of PLP in other abnormalities.