Metabolism of panthethine in the rat

Safety Assessment of Panthenol, Pantothenic Acid, and Derivatives as Used in Cosmetics

The Expert Panel for Cosmetic Ingredient Safety (Panel) assessed the safety of Panthenol, Pantothenic Acid, and 5 derivatives as used in cosmetics. These ingredients named in this report are reported to function in cosmetics as hair conditioning agents, and Panthenol also is reported to function as a skin-conditioning agent-humectant and a solvent. The Panel reviewed relevant data for these ingredients, and concluded that these 7 ingredients are safe in cosmetics in the present practices of use concentration described in this safety assessment.

Biological Properties of Vitamins of the B-Complex, Part 1: Vitamins B1, B2, B3, and B5

This review summarizes the current knowledge on essential vitamins B₁, B₂, B₃, and B₅. These B-complex vitamins must be taken from diet, with the exception of vitamin B₃, that can also be synthetized from amino acid tryptophan. All of these vitamins are water soluble, which determines their main properties, namely: they are partly lost when food is washed or boiled since they migrate to the water; the requirement of membrane transporters for their permeation into the cells; and their safety since any excess is rapidly eliminated via the kidney. The therapeutic use of B-complex vitamins is mostly limited to hypovitaminoses or similar conditions, but, as they are generally very safe, they have also been examined in other pathological conditions. Nicotinic acid, a form of vitamin B₃, is the only exception because it is a known hypolipidemic agent in gram doses. The article also sums up: (i) the current methods for detection of the vitamins of the B-complex in biological fluids; (ii) the food and other sources of these vitamins including the effect of common processing and storage methods on their content; and (iii) their physiological function.

Natural Molecules and Neuroprotection: Kynurenic Acid, Pantethine and α-Lipoic Acid

The incidence of neurodegenerative diseases has increased greatly worldwide due to the rise in life expectancy. In spite of notable development in the understanding of these disorders, there has been limited success in the development of neuroprotective agents that can slow the progression of the disease and prevent neuronal death. Some natural products and molecules are very promising neuroprotective agents because of their structural diversity and wide variety of biological activities. In addition to their neuroprotective effect, they are known for their antioxidant, anti-inflammatory and antiapoptotic effects and often serve as a starting point for drug discovery. In this review, the following natural molecules are discussed: firstly, kynurenic acid, the main neuroprotective agent formed via the kynurenine pathway of tryptophan metabolism, as it is known mainly for its role in glutamate excitotoxicity, secondly, the dietary supplement pantethine, that is many sided, well tolerated and safe, and the third molecule, α-lipoic acid is a universal antioxidant. As a conclusion, because of their beneficial properties, these molecules are potential candidates for neuroprotective therapies suitable in managing neurodegenerative diseases.

Regulation of coenzyme A levels by degradation: the 'Ins and Outs'

Coenzyme A (CoA) is the predominant acyl carrier in mammalian cells and a cofactor that plays a key role in energy and lipid metabolism. CoA and its thioesters (acyl-CoAs) regulate a multitude of metabolic processes at different levels: as substrates, allosteric modulators, and via post-translational modification of histones and other non-histone proteins. Evidence is emerging that synthesis and degradation of CoA are regulated in a manner that enables metabolic flexibility in different subcellular compartments. Degradation of CoA occurs through distinct intra- and extracellular pathways that rely on the activity of specific hydrolases. The pantetheinase enzymes specifically hydrolyze pantetheine to cysteamine and pantothenate, the last step in the extracellular degradation pathway for CoA. This reaction releases pantothenate in the bloodstream, making this CoA precursor available for cellular uptake and de novo CoA synthesis. Intracellular degradation of CoA depends on specific mitochondrial and peroxisomal Nudix hydrolases. These enzymes are also active against a subset of acyl-CoAs and play a key role in the regulation of subcellular (acyl-)CoA pools and CoA-dependent metabolic reactions. The evidence currently available indicates that the extracellular and intracellular (acyl-)CoA degradation pathways are regulated in a coordinated and opposite manner by the nutritional state and maximize the changes in the total intracellular CoA levels that support the metabolic switch between fed and fasted states in organs like the liver. The objective of this review is to update the contribution of these pathways to the regulation of metabolism, physiology and pathology and to highlight the many questions that remain open.

D-pantethine has vitamin activity equivalent to d-pantothenic acids for recovering from a deficiency of D-pantothenic acid in rats

D-Pantethine is a compound in which two molecules of D-pantetheine bind through an S-S linkage. D-Pantethine is available from commercial sources as well as from D-pantothenic acid. We investigated if D-pantethine has the same vitamin activity as D-pantothenic acid by comparing the recovery from a deficiency of D-pantothenic acid in rats. D-Pantothenic acid-deficient rats were developed by weaning rats on a diet lacking D-pantothenic acid for 47 d. At that time, the urinary excretion of D-pantothenic acid was almost zero, and the body weight extremely low, compared with the control (p<0.05); the contents of free D-pantothenic acid were also significantly reduced in comparison with those of controls (p<0.05). D-Pantothenic acid-deficient rats were administered a diet containing D-pantothenic acid or D-pantethine for 7 d. D-Pantethine and D-pantothenic acid contents of the diets were equimolar in forms of D-pantothenic acid. We compared various parameters concerning nutritional status between rats fed D-pantothenic acid- and D-pantethine-containing diets. The recoveries of body weight, tissue weights, and tissue concentrations of free D-pantothenic acid, dephospho-CoA, CoA, and acetyl-CoA were identical between rats fed diets containing D-pantothenic acid and D-pantethine. Thus, the biological efficiency for recovering from a deficiency of D-pantothenic acid in rats was equivalent between D-pantothenic acid and D-pantethine.

Treatment With Pantethine

The current increase in cardiovascular and cerebrovascular morbidity is a growing burden for society. Consideration must therefore be given to compounds capable of slowing down these pathological processes without significant adverse effects. The natural vitamins pantetheine/pantothenic acid are major precursors of coenzyme A and acyl carrier protein, which are essential for fatty acid oxidation and participate in the metabolism of cholesterol and carbohydrates and in at least 70 other enzymatic processes. Following a number of theoretical considerations and clinical observations, various clinical studies have revealed that they possess significant beneficial effects. In particular, they demonstrate useful moderating effects on vascular pathological processes, lowering lipid levels, and inhibiting platelet functions and lipid peroxidation. Although they are natural, well-tolerated therapeutic agents, few controlled clinical trials have been conducted. The available data suggest the need for larger clinical trials and possible use of pantetheine/pantothenic acid as adjuvant therapy.

Pantothenic acid in health and disease

In summary, the vitamin pantothenic acid is an integral part of the acylation carriers, CoA and acyl carrier protein (ACP). The vitamin is readily available from diverse dietary sources, a fact which is underscored by the difficulty encountered in attempting to induce pantothenate deficiency. Although pantothenic acid deficiency has not been linked with any particular disease, deficiency of the vitamin results in generalized malaise clinically. In view of the fact that pantothenate is required for the synthesis of CoA, it is surprising that tissue CoA levels are not altered in pantothenate deficiency. This suggests that the cell is equipped to conserve its pantothenate content, possibly by a recycling mechanism for utilizing pantothenate obtained from degradation of pantothenate-containing molecules. Although the steps involved in the conversion of pantothenate to CoA have been characterized, much remains to be done to understand the regulation of CoA synthesis. In particular, in view of what is known about the in vitro regulation of pantothenate kinase, it is surprising that the enzyme is active in vivo, since factors that are known to inhibit the enzyme are present in excess of the concentrations known to inhibit the enzyme. Thus, other physiological regulatory factors (which are largely unknown) must counteract the effects of these inhibitors, since the pantothenate-to-CoA conversion is operative in vivo. Another step in the biosynthetic pathway that may be rate limiting is the conversion of 4'-phosphopantetheine (4'-PP) to dephospho-CoA, a step catalyzed by 4'-phosphopantetheine adenylyl-transferase. In mammalian systems, this step may occur in the mitochondria or in the cytosol. The teleological significance of these two pathways remains to be established, particularly since mitochondria are capable of transporting CoA from the cytosol. Altered homeostasis of CoA has been observed in diverse disease states including starvation, diabetes, alcoholism, Reye syndrome (RS), medium-chain acyl CoA dehydrogenase deficiency, vitamin B12 deficiency, and certain tumors. Hormones, such as glucocorticoids, insulin, and glucagon, as well as drugs, such as clofibrate, also affect tissue CoA levels. It is not known whether the abnormal metabolism observed in these conditions is the result of altered CoA metabolism or whether CoA levels change in response to hormonal or nonhormonal perturbations brought about in these conditions. In other words, a cause-effect relation remains to be elucidated. It is also not known whether the altered CoA metabolism (be it cause or result of abnormal metabolism) can be implicated in the manifestations of a disease. Besides CoA, pantothenic acid is also an integral part of the ACP molecule.(ABSTRACT TRUNCATED AT 400 WORDS)

Dose- and time-response effects of pantethine on open-field behavior, and on central neurotransmission in rats

In this study the dose- and time-related effects of pantethine on open-field behavior and central neurotransmissions were investigated in rats. Pantethine administered in low doses (0.48-0.96 mM/kg SC) only marginally influenced the activity of the animals, but induced a significant decrease of hypothalamic noradrenaline level without influencing the concentrations of dopamine and DOPAC. Injected in higher doses (1.95-3.90 mM/kg SC), the compound produced a marked depression of both open-field activity and noradrenaline levels, but increased the concentrations of dopamine and DOPAC in the hypothalamus. Twelve hr after the administration of the substance, its effect was attenuated, and 24 hr after the treatment neither the behavioral nor the monoamine parameters differed significantly from the control values. Concerning the somatostatin, pantethine administered in high doses (1.95-3.90 mM/kg SC) decreased the striatal concentration of somatostatin 4 hr after the injection, and this effect was attenuated 24 hr after the treatment. These data suggest that the pantethine-induced behavioral changes are correlated with its effect on central catecholaminergic and somatostatinergic transmission.

Pantethine lipomodulation: evidence for cysteamine mediation in vitro and in vivo

Recent human studies suggest rapid in vivo hydrolysis of the lipid-lowering drug, pantethine, to the vitamin pantothenic acid and the small aminothiol compound, cysteamine. To test whether the active agent is a hydrolysis product, we repeated three experimental models of pantethine's effect with pantothenate and cysteamine. In vitro experiments with human fetal fibroblasts showed equivalent modulation of cholesterol and methyl sterol synthesis by pantethine, cysteamine, or cystamine (the disulfide of cysteamine), but pantothenate had no effect. Similarly, in vivo experiments with 0.5% cholesterol-fed rabbits showed oral pantethine or equimolar cystamine significantly lowered plasma cholesterol, while pantothenate, cystine, and 2-hydroxyethyl disulfide did not. Lastly, diabetic male rats (40 mg/kg streptozotocin) fed 0.1% pantethine and lower plasma free fatty acids after 2 weeks than controls, an effect not seen with pantothenate and largely duplicated by cystamine. The efficacy of pantethine has previously been attributed to altered vitamin metabolism and increased coenzyme A concentration. Pantethine did increase CoA levels 45% in rat liver homogenates while equivalent amounts of cystamine or pantothenate did not. However, a causal relationship between CoA levels and pantethine's action as a hypolipemic agent has never been shown. At least in 3 independent experimental models, the lipomodulating effect of pantethine appears instead to be mediated by the hydrolysis product cysteamine.

Metabolism of pantethine in cystinosis

D-Pantethine is a conjugate of the vitamin pantothenic acid and the low-molecular-weight aminothiol cysteamine. Pantethine is an experimental hypolipemic agent and has been suggested as a source of cysteamine in the treatment of nephropathic cystinosis. We treated four cystinotic children with 70-1,000 mg/kg per d oral D-pantethine and studied its metabolism. Pantethine was rapidly hydrolyzed to pantothenic acid and cysteamine; we could not detect pantethine in plasma after oral administration. The responsible enzyme, "pantetheinase," was highly active in homogenates of small intestinal mucosa and plasma. The Michaelis constant of the rat intestinal enzyme was 4.6 microM and its pH profile showed a broad plateau between 4 and 9. Pantothenate pharmacokinetics after orally administered pantethine followed an open two-compartment model with slow vitamin elimination (t1/2 = 28 h). Peak plasma pantothenate occurred at 2.5 h and levels over 250 microM were seen at 300 times normal. Apparent total body storage of pantothenate was significant (25 mg/kg), and plasma levels were elevated threefold for months after pantethine therapy. Plasma cysteamine concentrations after pantethine were similar to those reported after equivalent doses of cysteamine. However, at best only 80% white blood cell cystine depletion occurred. We conclude that pantethine is probably less effective than cysteamine in the treatment of nephropathic cystinosis and should only be considered in cases of cysteamine intolerance. Serum cholesterol was decreased an average of 14%, which supports the potential clinical significance of pantethine as a hypolipemic agent. Rapid in vivo hydrolysis of pantethine suggests that pantothenate or cysteamine may be the effectors of its hypolipemic action.

Pantethine and cystamine deplete cystine from cystinotic fibroblasts via efflux of cysteamine-cysteine mixed disulfide

Children suffering from cystinosis, a genetic disease characterized by high levels of lysosomal cystine, are currently being treated with cysteamine to lower the cystine levels in their cells. In fibroblasts from these patients, cysteamine and its disulfide, cystamine, are equally effective in lowering cystine levels. We recently reported that pantethine, a dietary precursor of coenzyme A, depletes cystine from cultured, cystinotic fibroblasts as effectively as cystamine. To determine the mechanism of action of pantethine, and of cystamine, we have compared the fate of [35S]cystine-derived metabolites in the presence and absence of these agents. The results indicate that the ability of pantethine to deplete cystine resides in its being a metabolic precursor of cysteamine. Furthermore, both pantethine and cystamine act by generating the mixed disulfide of cysteamine and cysteine in the lysosomes, which is then rapidly excreted from the cells. The fall in intracellular [35S]cystine caused by these agents was not accompanied by a comparable increase in any intracellular metabolite; rather, it could be accounted for by the appearance of mixed disulfide in the medium. There was no accumulation of mixed disulfide in the cells. Radioactivity in cytoplasmic glutathione was, however, increased by cystamine or pantethine. Thus, cysteamine (formed intracellularly in these experiments) undergoes thiol-disulfide exchange with cystine in the lysosomes, producing cysteamine-cysteine mixed disulfide and free cysteine, which enter the cytoplasm. The free cysteine is available to several pathways, including oxidation to the disulfide or the mixed disulfide, and synthesis of glutathione. The mixed disulfide is excreted from the cell, which ultimately depletes the cell of its excess cystine.

Transport and metabolism of pantothenic acid by rat kidney

Transport of [14C]pantothenic acid was studied using brush-border membrane vesicles prepared from rat kidney. In the presence of a Na+ gradient an accumulation of pantothenic acid 3-fold above equilibrium was observed. The Km and Vmax found were 7.30 microM and 23.8 pmol/mg protein per min, respectively. Isolated perfused rat kidneys were employed to study excretion of pantothenic acid at various concentrations in the perfusate. At physiological plasma concentrations, the filtered pantothenic acid was largely reabsorbed by the active process observed in the vesicles. At higher concentrations, pantothenic acid was found to undergo tubular secretion. Penicillin inhibited this secretory process indicating that both compounds share a secretory mechanism. Live animal studies indicated that the only compound excreted after injection of [14C]pantothenic acid was free pantothenic acid. After 1 week only 38% of the administered dose was excreted in the urine, indicating that effective conservation was taking place in the whole animal.