Novel Relationship Between Plasmalogen Lipid Signatures and Carnosine in Humans.

INTRODUCTION: Carnosine is a naturally occurring dipeptide abundant in the skeletal and cardiac muscle and brain, which has been shown to improve glucose metabolism and cardiovascular risk. This study showed that carnosine supplementation had positive changes on plasma lipidome. Here, this study aimed to establish the relationship of muscle carnosine and serum carnosinase-1 with cardiometabolic risk factors and the lipidome. METHODS AND RESULTS: This study profiles >450 lipid species in 65 overweight/obese nondiabetic individuals. Intensive metabolic testing is conducted using direct gold-standard measures of adiposity, insulin sensitivity and secretion, as well as measurement of serum inflammatory cytokines and adipokines. Muscle carnosine is negatively associated with 2-h glucose concentrations, whereas serum carnosinase-1 levels are negatively associated with insulin sensitivity and positively with IL-18. O-PLS and machine learning analyses reveal a strong association of muscle carnosine with ether lipids, particularly arachidonic acid-containing plasmalogens. Carnosinase-1 levels are positively associated with total phosphatidylethanolamines, but negatively with lysoalkylphosphatidylcholines, trihexosylceramides, and gangliosides. In particular, alkylphosphatidylethanolamine species containing arachidonic acid are positively associated with carnosinase-1. CONCLUSION: These associations reinforce the role of muscle carnosine and serum carnosinase-1 in the interplay among low-grade chronic inflammation, glucose homeostasis, and insulin sensitivity.

The Effects of Hyperbaric Oxygen Treatment on Total Antioxidant Capacity and Prolidase Activity after Bile Duct Ligation in Rats.

BACKGROUND: Hyperbaric oxygen (HBO) therapy may improve cholestasis, increase hepatic regeneration, and decrease oxidative stress in liver. In this study, we aimed to investigate the effects of HBO therapy on hepatic oxidative stress parameters, such as total thiol groups (T-SH), protein carbonyl (PCO), and total antioxidant capacity (TAC) as well as the predictive value of the noninvasive biochemical marker, sialic acid (SA), and prolidase activity in bile duct ligation (BDL)-induced oxidative damage and fibrosis in rats. METHODS: We divided 32 adult male Sprague Dawley rats into four groups: sham, sham + HBO, BDL, and BDL + HBO; each group contained eight animals. We placed the sham + HBO and BDL + HBO groups in an experimental hyperbaric chamber, in which we administered pure oxygen at 2.5 atmospheres for 90 min on 14 consecutive days. RESULTS: The application of BDL significantly increased PCO levels and prolidase activity, and decreased T-SH and TAC levels. HBO significantly decreased PCO levels and prolidase activity and increased T-SH and TAC levels in the liver tissues. There was no significant difference in sialic acid levels between any groups. CONCLUSIONS: These results indicate that HBO therapy has hepatoprotective effects on BDL-induced injury by decreasing PCO and prolidase activity and increasing antioxidant activities. We therefore suggest that HBO therapy may be useful after BDL-induced injury.

Protective effects of ginseng extracts and common anti-aggregant drugs on ischaemia-reperfusion injury.

OBJECTIVE: Ginseng is a traditional herbal medicinal product widely used for various types of diseases because of its cellular protective effects. Possible protective effects of ginseng were investigated in blood, cardiac and renal tissue samples and compared with common anti-aggregant agents in an animal ischaemia-reperfusion (I/R) model. METHODS: Twenty rats were equally divided into four different groups as follows: control group (I/R-induced group without drug use), group I (acetylsalicylic acid-administered group), group II (clopidogrel bisulfate-administered group), group III (ginsenoside Rb1-administered group). For the groups assigned to a medication, peripheral I/R was induced by clamping the femoral artery one week after initiation of the specified medication. After reperfusion was initiated, cardiac and renal tissues and blood samples were obtained from each rat with subsequent analysis of nitrogen oxide (NOx), malondialdehyde (MDA), paraoxonase 1 (PON1) and prolidase. RESULTS: NOx levels were similar in each group. Significant decrements were observed in serum PON1 levels in each group when compared with the control (p < 0.05). Serum MDA levels were significantly lower in groups II and III (p < 0.05). Ameliorated renal prolidase levels were detected in study groups (p < 0.05) and recovered cardiac prolidase levels were obtained in groups II and III (p < 0.05). CONCLUSION: These findings indicate that ginseng extracts may have a potential beneficial effect in I/R injury. However, more comprehensive studies are required to clarify the hypothetical cardiac, renal and systemic protective effects in reperfusion-induced oxidative damage.

Does low serum carnosinase activity favor high-intensity exercise capacity?

Given the ergogenic properties of ß-alanyl-L-histidine (carnosine) in skeletal muscle, it can be hypothesized that elevated levels of circulating carnosine could equally be advantageous for high-intensity exercises. Serum carnosinase (CN1), the enzyme hydrolyzing the dipeptide, is highly active in the human circulation. Consequently, dietary intake of carnosine usually results in rapid degradation upon absorption, yet this is less pronounced in subjects with low CN1 activity. Therefore, acute carnosine supplementation before high-intensity exercise could be ergogenic in these subjects. In a cross-sectional study, we determined plasma CN1 activity and content in 235 subjects, including 154 untrained controls and 45 explosive and 36 middle- to long-distance elite athletes. In a subsequent double-blind, placebo-controlled, crossover study, 12 men performed a cycling capacity test at 110% maximal power output (CCT 110%) following acute carnosine (20 mg/kg body wt) or placebo supplementation. Blood samples were collected to measure CN1 content, carnosine, and acid-base balance. Both male and female explosive athletes had significantly lower CN1 activity (14% and 21% lower, respectively) and content (30% and 33% lower, respectively) than controls. Acute carnosine supplementation resulted only in three subjects in carnosinemia. The CCT 110% performance was not improved after carnosine supplementation, even when accounting for low/high CN1 content. No differences were found in acid-base balance, except for elevated resting bicarbonate following carnosine supplementation and in low CN1 subjects. In conclusion, explosive athletes have lower serum CN1 activity and content compared with untrained controls, possibly resulting from genetic selection. Acute carnosine supplementation does not improve high-intensity performance.

Vascular origin of vildagliptin-induced skin effects in Cynomolgus monkeys: pathomechanistic role of peripheral sympathetic system and neuropeptide Y.

The purpose of this article is to characterize skin lesions in cynomolgus monkeys following vildagliptin (dipeptidyl peptidase-4 inhibitor) treatment. Oral vildagliptin administration caused dose-dependent and reversible blister formation, peeling and flaking skin, erosions, ulcerations, scabs, and sores involving the extremities at ≥5 mg/kg/day and necrosis of the tail and the pinnae at ≥80 mg/kg/day after 3 weeks of treatment. At the affected sites, the media and the endothelium of dermal arterioles showed hypertrophy/hyperplasia. Skin lesion formation was prevented by elevating ambient temperature. Vildagliptin treatment also produced an increase in blood pressure and heart rate likely via increased sympathetic tone. Following treatment with vildagliptin at 80 mg/kg/day, the recovery time after lowering the temperature in the feet of monkeys and inducing cold stress was prolonged. Ex vivo investigations showed that small digital arteries from skin biopsies of vildagliptin-treated monkeys exhibited an increase in neuropeptide Y-induced vasoconstriction. This finding correlated with a specific increase in NPY and in NPY1 receptors observed in the skin of vildagliptin-treated monkeys. Present data provide evidence that skin effects in monkeys are of vascular origin and that the effects on the NPY system in combination with increased peripheral sympathetic tone play an important pathomechanistic role in the pathogenesis of cutaneous toxicity.

Low plasma carnosinase activity promotes carnosinemia after carnosine ingestion in humans.

A polymorphism in the carnosine dipeptidase-1 gene (CNDP1), resulting in decreased plasma carnosinase activity, is associated with a reduced risk for diabetic nephropathy. Because carnosine, a natural scavenger/suppressor of ROS, advanced glycation end products, and reactive aldehydes, is readily degraded in blood by the highly active carnosinase enzyme, it has been postulated that low serum carnosinase activity might be advantageous to reduce diabetic complications. The aim of this study was to examine whether low carnosinase activity promotes circulating carnosine levels after carnosine supplementation in humans. Blood and urine were sampled in 25 healthy subjects after acute supplementation with 60 mg/kg body wt carnosine. Precooled EDTA-containing tubes were used for blood withdrawal, and plasma samples were immediately deproteinized and analyzed for carnosine and ß-alanine by HPLC. CNDP1 genotype, baseline plasma carnosinase activity, and protein content were assessed. Upon carnosine ingestion, 8 of the 25 subjects (responders) displayed a measurable increase in plasma carnosine up to 1 h after supplementation. Subjects with no measurable increment in plasma carnosine (nonresponders) had ∼2-fold higher plasma carnosinase protein content and ∼1.5-fold higher activity compared with responders. Urinary carnosine recovery was 2.6-fold higher in responders versus nonresponders and was negatively dependent on both the activity and protein content of the plasma carnosinase enzyme. In conclusion, low plasma carnosinase activity promotes the presence of circulating carnosine upon an oral challenge. These data may further clarify the link among CNDP1 genotype, carnosinase, and diabetic nephropathy.

Vegetarianism, female gender and increasing age, but not CNDP1 genotype, are associated with reduced muscle carnosine levels in humans.

Carnosine is found in high concentrations in skeletal muscles, where it is involved in several physiological functions. The muscle carnosine content measured within a population can vary by a factor 4. The aim of this study was to further characterize suggested determinants of the muscle carnosine content (diet, gender and age) and to identify new determinants (plasma carnosinase activity and testosterone). We investigated a group of 149 healthy subjects, which consisted of 94 men (12 vegetarians) and 55 women. Muscle carnosine was quantified in M. soleus, gastrocnemius and tibialis anterior using magnetic resonance proton spectroscopy and blood samples were collected to determine CNDP1 genotype, plasma carnosinase activity and testosterone concentrations. Compared to women, men have 36, 28 and 82% higher carnosine concentrations in M. soleus, gastrocnemius and tibialis anterior muscle, respectively, whereas circulating testosterone concentrations were unrelated to muscle carnosine levels in healthy men. The carnosine content of the M. soleus is negatively related to the subjects' age. Vegetarians have a lower carnosine content of 26% in gastrocnemius compared to omnivores. In contrast, there is no difference in muscle carnosine content between omnivores with a high or low ingestion of ß-alanine. Muscle carnosine levels are not related to the polymorphism of the CNDP1 gene or to the enzymatic activity of the plasma carnosinase. In conclusion, neither CNDP1 genotype nor the normal variation in circulating testosterone levels affects the muscular carnosine content, whereas vegetarianism, female gender and increasing age are the factors associated with reduced muscle carnosine stores.

Serum prolidase activity in postmenopausal osteoporosis.

AIM: Prolidase is a specific imidodipeptidase involved in collagen degradation. The increase in the enzyme activity is believed to be correlated with increased intensity of collagen degradation and may be a useful tool in diagnosis and/or monitoring osteoporosis. The study aimed to evaluate serum prolidase activity in postmenopausal osteoporosis and its relation with several metabolic bone markers. METHODS: Sixty-one postmenopausal women with menopause times = or >1 year without any hormone replacement treatment were recruited in this study. Bone mineral density (BMD) was obtained from antero-posterior spine L2-L4 and femoral neck scanning with dual energy X-ray absorptiometry (DXA). Thirty-one subjects with T scores lower than -2.5 were accepted as osteoporotic and control group consisted of 30 subjects. Urinary deoxypyridinoline (Dpd), calcium, creatinine, serum total calcium, phosphorus (Pi), alkaline phosphatase, parathyroid hormone levels and prolidase activity were analysed with colorimetric or immunochemical RESULTS: Serum prolidase activity was neither significantly different in osteoporosis nor correlate with other bone turnover markers. Urinary Dpd/creatinine and serum Pi levels of postmenopausal osteoporotic group were significantly higher than in the control group. CONCLUSION: Serum prolidase activity does not correlate with BMD in postmenopausal osteoporosis with menopause time over 1 year. However, its role during premenopausal accelerated decrease in BMD is not established yet.

Biochemical properties of new synthetic carnosine analogues containing the residue of 2,3-diaminopropionic acid: the effect of N-acetylation.

Three novel carnosine analogues 7-9 containing the residue of L(+)2,3-diaminopropionic acid with different degree of N-acetylation instead of beta-alanine have been synthesized and characterized. Comparative analysis of hydrolysis by carnosinase revealed that the mono- and bis-acetylated compounds 8 and 9 are resistant to enzymatic hydrolysis and act as competitive inhibitors of this enzyme. The hydroxyl radical scavenging potential of the three analogues was evaluated by their ability to inhibit iron/H(2)O(2)-induced degradation of deoxyribose. The second-order rate constants of the reaction of compounds 7-9 with hydroxyl radical were almost identical to that of carnosine. These compounds were also found to act as protective agents against peroxynitrite-dependent damage as assessed by their ability to prevent nitration of free tyrosine induced by this species.

Effect of an acute dose of ethanol on lipid peroxidation in rats: action of vitamin E.

Free radical generation is an important step in the pathogenesis of ethanol-associated liver injury. Administration of ethanol induces an increase in lipid peroxidation both by enhancing the production of oxygen reactive species and by decreasing the levels of endogenous antioxidants. This work focuses on the generation of free radicals provoked by an acute ethanol dose in rats, and the role of different dietary levels of vitamin E. The objective of this investigation was to study the effect of three different dietary levels of vitamin E (deficient, control and supplemented with 20 times higher levels) on plasma and liver lipid peroxidation (assayed by TBARS), vitamin E in plasma and liver, and hepatic glutathione concentration, in rats receiving the different diets. The animals were submitted to an acute dose of ethanol (5 g/kg body weight) administered by gavage at the end of an experimental 4 week period and were sacrificed at 0, 2, 4, 8 and 24 h after ethanol administration. Dietary vitamin E caused a dose-dependent increase in liver and plasma concentration of the vitamin, but ethanol administration decreased hepatic vitamin E in all groups. TBARS concentrations were higher in liver of rats that received the deficient diet, independent of ethanol, however, liver TBARS concentrations were low in control and supplemented groups, but increased with ethanol ingestion. Glutathione levels were lowered by ethanol administration in all groups, in different times, but recovered to this original level in 24 h time. In conclusion, vitamin E deficiency alone induces liver lipid peroxidation in rats, acute administration of ethanol affect vitamin E and GSH level and maintenance of adequate or higher vitamin E levels acts as a protective factor against free radical generation.

A biochemical study on combined treatment of experimental silicosis with tetradrine-PVNO and tetradrine-QOHP in rats.

A better understanding is needed to explain the mechanism of therapeutic effect of combined use of tetradrine-PVNO and tetradrine-QOHP which play very important roles in treatment of silicosis. Blood prolidase (PLD), monamine oxidase (MAO) and plasminogen (PLG) in silicotic rats after treatment with tetradrine-PVNO or tetradrine-QOHP were measured. The values obtained were compared with the untreated silicotic rats. It was found that the silicotic rats that received tetradrine-PVNO showed significant increase in PLD and decrease in PLG, but no significant change in MAO. The PLD in plasma of silicotic rats that received tetradrine-QOHP were elevated significantly, but PLG and MAO did not change appreciably. These findings suggest that the combined use of tetradrine-PVNO and tetradrine-QOHP can accelerate the degradation of collagen in silicotic rats.