Quantitative measurement of induced skin reddening using optical reflection spectroscopy--methodology and clinical application]

Optical reflection spectroscopy is a simple and quick method for the quantification of colour intensity, and is thus suitable for the determination of changes in skin reddening (erythema) due to local vasodilatation. To quantify the time course of this erythema, the oxyhaemoglobin absorption double peak with maxima at 542 and 577 nm is an appropriate parameter. A compact handheld optical spectrometer makes the technique applicable to clinical use, an example being the niacin patch test described herein. This noninvasive test provides information about the cell membrane metabolism via the skin flush induced by niacin (vitamin B3) and mediated by prostaglandin. The aim of this study was to adapt optical reflection spectroscopy to the requirements of the clinical niacin patch test. To that end, we investigated 60 healthy volunteers. Analysis of the spectroscopic data with regard to physiological covariables of niacin sensitivity revealed faster and more intense erythema in females--a gender effect that to our knowledge has not previously been reported. In the light of these results, the findings of other researchers based on semi-quantitative test methods should be reassessed, with consideration given to the gender effect.     

Hepatic pyridine nucleotides content in rat--a better indicator for determining available niacin values of food.

After 10 days depletion period with niacin free diet, weanling rats were repleted with either reference diets containing niacin at four levels (2, 4, 8 and 12 mg/kg diet) or test diets containing test material at two levels as source of niacin. Gains in body weight and hepatic pyridine nucleotides content increased with increase in niacin intake. The correlation coefficient for hepatic pyridine nucleotides content and niacin intake was 0.98, whereas for weight gain and niacin intake was 0.89. Dried skim milk and pearl millet were taken as test materials. Dried skim milk with most of its niacin in free form showed 98% niacin equivalent to be bioavailable whereas in pearl millet niacin was in bound form and bioavailability equivalent was only 48 per cent.     

Hydrogen cyanide and cyanogen chloride formation by the myeloperoxidase-H2O2-Cl- system.

The chlorination of glycine by the myeloperoxidase-H2O2-Cl- system at acidic pH values yielded N-monochloroglycine and a mixture of HCN and ClCN. HCN was formed as a product of N-dichloroglycine decomposition and cyanogen chloride formation resulted from simultaneous chlorination of HCN by N-chloroglycine or directly by the myeloperoxidase-H2O2-Cl- system. HCN was readily chlorinated by the myeloperoxidase-H2O2Cl- system yielding cyanogen chloride. This dissociation constants of the myeloperoxidase-CN- complex were estimated as 2.5.10(-6)--1.15.10(-5) M within the pH range of 6.2 to 3.4, respectively. Chloride competed with cyanide for binding at the active site of myeloperoxidase. The lower the pH the more pronounced was the competitive effect of chloride. This accounted for chlorination by myeloperoxidase in the presence of CN-.     

Test–retest stability of the oral niacin test and electrodermal activity in patients with schizophrenia

In schizophrenia, well-replicated findings support an attenuated niacin skin-flush response. We have previously reported a delayed skin-flush after niacin ingestion and also an association between niacin non-responding and electrodermal non-responding in schizophrenia. The stability of the niacin and electrodermal tests was now studied in a test–retest design. An additional aim was to assess the association previously found.Twenty-three patients with schizophrenia underwent two sessions 3 months apart during which an oral niacin test was conducted and electrodermal activity was measured. Despite similar values for niacin outcome variables at the group level, there was high intraindividual variation. Test–retest stability for the oral niacin test was thus low, although a trend toward correlation for the dichotomous response criterion was found. Most electrodermal measures correlated between baseline and retest. A significant association between the tests was again found; niacin non-responding implied electrodermal non-responding, providing further support for a common underlying aberration in schizophrenia.     

Niacin skin-flush response and electrodermal activity in patients with schizophrenia and healthy controls

Patients with schizophrenia have in different studies shown reduced niacin sensitivity and lower electrodermal activity (EDA) after auditory stimulation. Peripheral mediation of prostaglandins may have a physiological role in both responses. This motivates study of both niacin response and electrodermal responding in the same patients with schizophrenia. Thirty patients with schizophrenia and 17 controls were investigated with EDA and thereafter given 200mg niacin orally with continuous assessment of skin temperature. The patients showed a delayed temperature increase after niacin ingestion (P=0.002) and a higher frequency of electrodermal non-responding (P<0.05). Response/non-response for niacin correlated with EDA response/non-response in the patient group (P=0.009). The niacin test revealed a slower vasodilation reaction in the patients. The association between response patterns for the niacin test and EDA suggests that a common aberration in skin physiology may be of importance for both reactions in schizophrenia.     

The topical niacin sensitivity test: an inter- and intra-rater reliability study in healthy controls

Topical application of nicotinic acid results in erythema, and in some cases oedema of the skin, supporting a strong relationship between niacin sensitivity and prostaglandin D2. The aim of this study was to examine the inter-rater and intra-rater reliability of a 12-min niacin sensitivity test in healthy adults. Three raters assessed the skin reaction of 12 volunteers, over 3-min intervals across four niacin concentrations (0.1, 0.01, 0.001, and 0.0001), and over six sessions. Inter-rater reliability estimates ranged from 0.85 to 0.97 for the total niacin sensitivity score. Similar inter-rater reliability estimates were found for niacin sensitivity ratings by concentration and time. Intra-rater reliability estimates ranged from 0.63 to 0.93 for the total niacin sensitivity score. These data indicate that the 12-min topical niacin sensitivity test has excellent reliability.     

Effect of Amino Acid Supplementation to a Rice Diet on Niacin Requirement of Rats

The effect of amino acid supplementation to a rice diet on the niacin requirement of rats was studied in relation to the phenomenon of niacin or tryptophan deficiency caused by the addition of threonine or gelatin to a low casein diet. Supplementation of a mixture of all limiting amino acids other than tryptophan to a 90% rice diet stimulated the growth of rats only temporarily without additional supplementation of niacin. However, the supplementation of the same mixture of limiting amino acids to a diet containing an amino acid mixture simulating rice protein, clearly decreased the growth of rats after a temporary increase. The growth was then remarkably improved by the further addition of niacin or niacin plus tryptophan. This result supports the hypothesis that the addition of all limiting amino acids other than tryptophan, increases the use of tryptophan for protein synthesis and may lead to niacin deficiency.     

The influence of bond chemistry on immobilized enzyme systems for ex vivo use

The ideal derivatized support for the clinical use of an immobilized enzyme system should irreversibly bind active enzyme. We have investigated the behavior of heparinase and bilirubin oxidase immobilized via cyanogen bromide, tresyl chloride, epoxide, or carbodiimidazole activated natural and synthetic matrices. The protein bound to each activated support was 90% for cyanogen bromide (CNBr) activated agarose, 50-80% for tresyl chloride activated agarose, and 50% for oxirane activated acrylic (Eupergit C). The activity retention of immobilized heparinase was greatest (50%) with CNBr activated agarose while for the immobilization of bilirubin oxidase, the activity retention was greatest (25-30%) with tresyl chloride activated agarose and oxirane activated acrylic.The stability of the different covalent bonds was studied in vitro with radioiodinated enzymes. The leaching profiles showed the same trends for each support and chemistry. A plateau in portein leaching was reached after a few hours of incubatttion and the transient leaching period was well represented byu a logarithimic function of time. The amount of enzyme released from the least stable support (CNBr activated agarose) in 24 h was injected intravenously in New Zealand white rabbits. Using an indirect enzyme-linked immunnosorbant assay (ELISA), no immune responce was detected. The transient leaching profile was shortenend by washingthe enzyme-support conjugate with 1M hydroxylamine, pH8.5 intermolecular cross-linking with glutaraldehyde also improves the enzyme-support stability. Tresyl chloride and oxirane activated supports produce bonds with improved stability without adversely affecting enzymatic activity.     

Effects of fatty liver induced by niacin-free diet with orotic acid on the metabolism of tryptophan to niacin in rats

The effects of dietary orotic acid on the metabolism of tryptophan to niacin in weaning rats was investigated. The rats were fed with a niacin-free, 20% casein diet containing 0% (control diet) or 1% orotic acid diet (test diet) for 29 d. Retardation of growth, development of fatty liver, and enlargement of liver were observed in the test group in comparison with the control group. The concentrations of NAD and NADP in liver significantly decreased, while these in blood did not decrease compared to the control group. The formation of the upper metabolites of tryptophan to niacin such as anthranilic acid, kynurenic acid, and 3-hydroxyanthranilic acid were not affected, but the quinolinic acid and beyond, such as nicotinamide, N1-methylnicotinamide, N1-methyl-2-pyridone-5-carboxamide, and N1-methyl-4-pyridone-3-carboxamide, were significantly reduced by the administration of orotic acid. Therefore, the conversion ratio of tryptophan to niacin significantly decreased in the test group in comparison with the control group.     

Growth-promoting activity of pyrazinoic acid,a putative active compound of antituberculosis drug pyrazinamide,in niacin-deficient rats through the inhibition of ACMSD activity

We have recently reported that the antituberculosis drug, pyrazinamide (PZA), caused a significant increase in the conversion ratio of tryptophan to niacin in rats. In the present work, we investigated whether or not pyrazinoic acid (POA), a putative metabolite of PZA, increased the conversion ratio of tryptophan to niacin. Weaning rats were fed with a niacin-free and tryptophan-limited diet (negative control diet), or with the negative control diet supplemented with 0.003% nicotinic acid (positive control diet) or 1% POA (test diet) for 27 days. The growth rate was almost same between the groups fed on the positive control diet and the test diet. Dietary POA significantly increased the conversion ratio of tryptophan to niacin. Although POA did not directly inhibit the activity of alpha-amino-beta-carboxymuconate-epsilon-semialdehyde decarboxylase (ACMSD), the rate-limiting enzyme in the tryptophan-niacin pathway, liver ACMSD activity was only not detected in the test diet group. These results suggest that a derivative of POA metabolized by rats inhibited the ACMSD activity.     

Niacin in cardiovascular prevention: mechanisms, efficacy, and safety

PURPOSE OF REVIEW: This review describes niacin's mechanism of action, efficacy in cardiovascular prevention, and safety. RECENT FINDINGS: A G-protein-coupled receptor [GPR109A/HM74A, mouse PUMA-G (protein upregulated in macrophages by interferon-gamma)] was found to mediate the antilipolytic effect of niacin via inhibition of adenylyl cyclase in adipocytes. The same receptor in skin Langerhans cells mediates the common flushing side effect. The endogenous ligand for the receptor may be beta-hydroxybutyrate. Among nine controlled clinical trials using niacin, mostly combined with other drugs, statistically significant positive impact on clinical or anatomic cardiovascular end-points was found in seven, which represents a remarkably consistent record of benefit. Although niacin induces insulin resistance, deterioration of glycemic control in diabetes is usually minor, and there is no evidence of increased incidence of new onset diabetes. Hepatic toxicity is common with higher doses of sustained-release niacin but rare with immediate-release and extended-release niacin at doses up to 2000 mg/day. Extended-release and immediate-release niacin do not substantially potentiate myopathic effects when given in combination with statins. SUMMARY: Recently developed understanding of the mechanisms, efficacy, and safety of niacin, along with progress in reducing the chief side effect of flushing, should enhance the use of this valuable agent for cardiovascular prevention.     

Anisakiasis: preparation of a stable antigen for indirect fluorescent antibody test

By coupling Anisakis larval hemoglobin with cyanogen bromide-activated Sepharose, a stable and sensitive antigen for the indirect fluorescent antibody test for anisakiasis was prepared. Using this antigen, cross-reaction with other helminth infections was minimized and the test was greatly simplified.Furthermore, the results obtained indicate that this technique may be useful not only in the sero-diagnosis of anisakiasis but may also be applicable to the diagnosis of other helminthic diseases.     

Thematic Review Series: New Lipid and Lipoprotein Targets for the Treatment of Cardiometabolic Diseases: Niacin,an old drug with a new twist

Niacin (nicotinic acid) has been used for decades as a lipid-lowering drug. The clinical use of niacin to treat dyslipidemic conditions is limited by its side effects. Niacin, along with fibrates, are the only approved drugs which elevate high density lipoprotein cholesterol (HDLc) along with its effects on low density lipoprotein cholesterol (LDLc) and triglycerides. Whether niacin has a beneficial role in lowering cardiovascular risk on the background of well-controlled LDLc has not been established. In fact, it remains unclear whether niacin, either in the setting of well-controlled LDLc or in combination with other lipid-lowering agents, confers any therapeutic benefit and if so, by which mechanism. The results of recent trials reject the hypothesis that simply raising HDLc is cardioprotective. However, in the case of the clinical trials, structural limitations of trial design complicate their interpretation. This is also true of the most recent Heart Protection Study 2-Treatment of HDLc to Reduce the Incidence of Vascular Events (HPS2-THRIVE) trial in which niacin is combined with an antagonist of the D prostanoid (DP) receptor. Human genetic studies have also questioned the relationship between cardiovascular benefit and HDLc. It remains to be determined whether niacin may have clinical utility in particular subgroups, such as statin intolerant patients with hypercholesterolemia or those who cannot achieve a sufficient reduction in LDLc. It also is unclear whether a potentially beneficial effect of niacin is confounded by DP antagonism in HPS2-THRIVE.     

Niacin assay by monitoring changes in electrical conductance caused by microbial growth

A computerized Malthus 128 H Growth Analyser was used to determine the changes in conductance produced by growth of a niacin-dependent strain of Lactobacillus plantarum ATCC 8014 in different concentrations of niacin in the growth medium. Changes in conductance varied linearly with the niacin concentration in the range 5-50 ng/ml. The time required to complete a test is inversely related to the inoculum size, and results can be obtained after 6 h.     

Niacin assay by monitoring changes in electrical conductance caused by microbial growth

A computerized Malthus 128 H Growth Analyser was used to determine the changes in conductance produced by growth of a niacin-dependent strain of Lacto-bacillus plantarum ATCC 8014 in different concentrations of niacin in the growth medium. Changes in conductance varied linearly with the niacin concentration in the range 5–50 ng/ml. The time required to complete a test is inversely related to the inoculum size, and results can be obtained after 6 h.     

The structure of bovine rhodopsin

We have isolated 16 peptides from a cyanogen bromide digest of rhodopsin. These cyanogen bromide peptides account for the complete composition of the protein. Methionine-containing peptides from other chemical and enzymatic digests of rhodopsin have allowed us to place the cyanogen bromide peptides in order, yielding the sequence of the protein. We have completed the sequence of most of the cyanogen bromide peptides. This information, in conjunction with that from other laboratories, forms the basis for our prediction of the secondary structure of the protein and how it may be arranged in the disk membrane.     

Influence of adenine-induced renal failure on tryptophan-niacin metabolism in rats.

To discover the role of the kidney in tryptophan degradation, especially tryptophan to niacin, rat kidneys were injured by feeding a diet containing a large amount of adenine. The kidney contains very high activity of aminocarboxymuconate-semialdehyde decarboxylase (ACMSD), which leads tryptophan into the glutaric acid pathway and then the TCA cycle, but not to the niacin pathway. On the other hand, kidneys contain significant activity of quinolinate phosphoribosyltransferase (QPRT), which leads tryptophan into the niacin pathway. The ACMSD activity in kidneys were significantly lower in the adenine group than in the control group, while the QPRT activity was almost the same, however, the formations of niacin and its compounds such as N1-methylnicotinamide and its pyridones did not increase, and therefore, the conversion ratio of tryptophan to niacin was lower in the adenine group than in the control group. The contents of NAD and NADP in liver, kidney, and blood were also lower in the adenine group. The decreased levels of niacin and the related compounds were consistent with the changes in the enzyme activities involved in the tryptophan-niacin metabolism in liver. It was concluded from these results that the conversion of tryptophan to niacin is due to only the liver enzymes and that the role of the kidney would be extremely low.     

Relationship between the niacin skin flush response and essential fatty acids in schizophrenia

The skin flush response to niacin is selectively mediated by the release of vasodilatory prostaglandins from the skin. The normal skin flush response to niacin is attenuated in many individuals with schizophrenia (SCZ). This finding suggests abnormal prostaglandin signaling in SCZ. Since prostaglandins are derived from arachidonic acid (AA), the finding of an abnormal skin flush response is consistent with biochemical data suggesting relative depletion of AA, and other essential fatty acids (EFAs), in a substantial portion of people with SCZ. This paper will describe the mechanism of the skin flush response to niacin, and will review evidence that the response to niacin is abnormal in SCZ, that this abnormality is not related to psychotropic medications, and that it may be a marker of the EFA deficiency which has been documented to be present in many patients with SCZ.