Reduced sensory and motor nerve conduction velocities in moderate drinkers

Association between neuropathy and B-vitamins: A systematic review and meta-analysis

BACKGROUND

Peripheral neuropathy (PN) is common in patients with diseases that are in turn associated with deficiency of the B-vitamins, and vitamin treatment has shown mixed results.

METHODS

This systematic review and meta-analysis studied the association between PN/pain and B-vitamin biomarkers and investigated whether vitamin treatment can ameliorate the symptoms. PubMed and Web of Science were searched according to the study protocol.

RESULTS

A total of 46 observational and seven interventional studies were identified and included in the data synthesis. The presence of PN was associated with lowered B12 levels (pooled estimate [95% CIs] = 1.51 [1.23-1.84], n = 34, Cochran Q Test I²  = 43.3%, p = 0.003) and elevated methylmalonic acid (2.53 [1.39-4.60], n = 9, I²  = 63.8%, p = 0.005) and homocysteine (3.48 [2.01-6.04], n = 15, I²  = 70.6%, p < 0.001). B12 treatment (vs. the comparators) showed a non-significant association with symptom improvement (1.36 (0.66-2.79), n = 4, I²  = 28.9%). Treatment with B1 was associated with a significant improvement in symptoms (5.34 [1.87-15.19], n = 3, I²  = 64.6%, p = 0.059). Analysis of seven trials combined showed a non-significant higher odds ratio for improvement under treatment with the B-vitamins (2.58 [0.98-6.79], I²  = 80.0%, p < 0.001).

CONCLUSIONS

PN is associated with lowered plasma vitamin B12 and elevated methylmalonic acid and homocysteine. Overall, interventional studies have suggested that B-vitamins could improve symptoms of PN. Available trials have limitations and generally did not investigate vitamin status prior to treatment. Well-designed studies, especially in non-diabetes PN, are needed. This meta-analysis is registered at PROSPERO (ID: CRD42020144917).

Central Nervous System Correlates of "Objective" Neuropathy in Alcohol Use Disorder

BACKGROUND

Among the neurological consequences of alcoholism is peripheral neuropathy. Relative to human immunodeficiency virus (HIV) or diabetes-related neuropathies, neuropathy associated with alcohol use disorders (AUD) is understudied. In both the diabetes and HIV literature, emerging evidence supports a central nervous system (CNS) component to peripheral neuropathy.

METHODS

In seeking a central substrate for AUD-related neuropathy, the current study was conducted in 154 individuals with AUD (43 women, age 21 to 74 years) and 99 healthy controls (41 women, age 21 to 77 years) and explored subjective symptoms (self-report) and objective signs (perception of vibration, deep tendon ankle reflex, position sense, 2-point discrimination) of neuropathy separately. In addition to regional brain volumes, risk factors for AUD-related neuropathy, including age, sex, total lifetime ethanol consumed, nutritional indices (i.e., thiamine, folate), and measures of liver integrity (i.e., γ-glutamyltransferase), were evaluated.

RESULTS

The AUD group described more subjective symptoms of neuropathy and was more frequently impaired on bilateral perception of vibration. From 5 correlates, the number of AUD-related seizures was most significantly associated with subjective symptoms of neuropathy. There were 15 correlates of impaired perception of vibration among the AUD participants: Of these, age and volume of frontal precentral cortex were the most robust predictors.

CONCLUSIONS

This study supports CNS involvement in objective signs of neuropathy in AUD.

Reliability of superficial peroneal, sural, and medial plantar nerve conduction studies: analysis of statistical methods

The reliability of medial plantar, sural, and superficial peroneal nerve conduction studies (NCS) has not been widely studied. These nerves are usually involved in distal sensory neuropathies and their serial study is relevant in the clinical setting.

PURPOSE

To determine the inter- and intrarater reliability of superficial peroneal, sural, and medial plantar NCS in healthy participants.

METHODS

Two raters performed the bilateral NCS twice in 20 healthy participants (23.5 +/- 3.5 years). Reliability was analyzed by the Bland-Altman method and intraclass correlation coefficient (ICC). Variability was established by the coefficient of variation.

RESULTS

The Bland-Altman method showed a good level of intra- and interrater agreement for all nerves. The amplitude (rater 1) and latency of the medial plantar nerve and the amplitude of the sural nerve (rater 2) had an intrarater ICC of >or=0.75. Interrater analysis showed concordance levels between moderate and very low. The highest coefficients of variations were found for amplitude and the lowest for nerve conduction velocity.

CONCLUSIONS

Although the Bland-Altman method confirmed a good intra- and interrater reliability of the studied nerves, ICC analyses showed mixed results. These statistical approaches are complementary, and each one has advantages and disadvantages that must be considered in their application and interpretation.

Pyrithiamine as a substrate for thiamine pyrophosphokinase

Thiamine pyrophosphokinase transfers a pyrophosphate group from a nucleoside triphosphate, such as ATP, to the hydroxyl group of thiamine to produce thiamine pyrophosphate. Deficiencies in thiamine can result in the development of the neurological disorder Wernicke-Korsakoff Syndrome as well as the potentially fatal cardiovascular disease wet beriberi. Pyrithiamine is an inhibitor of thiamine metabolism that induces neurological symptoms similar to that of Wernicke-Korsakoff Syndrome in animals. However, the mechanism by which pyrithiamine interferes with cellular thiamine phosphoester homeostasis is not entirely clear. We used kinetic assays coupled with mass spectrometry of the reaction products and x-ray crystallography of an equilibrium reaction mixture of thiamine pyrophosphokinase, pyrithiamine, and Mg2+/ATP to elucidate the mechanism by which pyrithiamine inhibits the enzymatic production of thiamine pyrophosphate. Three lines of evidence support the ability of thiamine pyrophosphokinase to form pyrithiamine pyrophosphate. First, a coupled enzyme assay clearly demonstrated the ability of thiamine pyrophosphokinase to produce AMP when pyrithiamine was used as substrate. Second, an analysis of the reaction mixture by mass spectrometry directly identified pyrithiamine pyrophosphate in the reaction mixture. Last, the structure of thiamine pyrophosphokinase crystallized from an equilibrium substrate/product mixture shows clear electron density for pyrithiamine pyrophosphate bound in the enzyme active site. This structure also provides the first clear picture of the binding pocket for the nucleoside triphosphate and permits the first detailed understanding of the catalytic requirements for catalysis in this enzyme.