Effects of Aerobic Exercise on Uric Acid, Total Antioxidant Activity, Oxidative Stress, and Nitric Oxide in Human Saliva

The aim of this study was to determine the effect of aerobic exercise on uric acid (UA), total antioxidant activity (TAA), lipid hydroperoxides, and nitric oxide (NO) metabolites in human saliva. Twenty-four healthy male and female subjects were studied during a 10,000-m race. Saliva samples were collected 1 h before and immediately after exercise. The NO concentration was determined by the Griess reaction, UA by enzymatic method, TAA by the ABTS method, and lipid hydroperoxide by the ferrous iron/xylenol orange (FOX) method. A repeated measures ANOVA was used to examine the effect of aerobic exercise on salivary UA, TAA, lipid hydroperoxides, and NO metabolites. Aerobic exercise caused an increase in both salivary UA and TAA, and a decrease in salivary lipid hydroperoxide. There was no, however, change in nitrite concentration. These results suggested that aerobic exercise-induced increment in both UA and TAA seems to inhibit lipid hydroperoxide generation, a marker of oxidative stress in human saliva.

Alternative Catalytic Anions Differentially Modulate Human α-Amylase Activity and Specificity

A mechanistic study of the essential allosteric activation of human pancreatic α-amylase by chloride ion has been conducted by exploring a wide range of anion substitutions through kinetic and structural experiments. Surprisingly, kinetic studies indicate that the majority of these alternative anions can induce some level of enzymatic activity despite very different atomic geometries, sizes, and polyatomic natures. These data and subsequent structural studies attest to the remarkable plasticity of the chloride binding site, even though earlier structural studies of wild-type human pancreatic α-amylase suggested this site would likely be restricted to chloride binding. Notably, no apparent relationship is observed between anion binding affinity and relative activity, emphasizing the complexity of the relationship between chloride binding parameters and the activation mechanism that facilitates catalysis. Of the anions studied, particularly intriguing in terms of observed trends in substrate kinetics and their novel atomic compositions were the nitrite, nitrate, and azide anions, the latter of which was found to enhance the relative activity of human pancreatic α-amylase by nearly 5-fold. Structural studies have provided considerable insight into the nature of the interactions formed in the chloride binding site by the nitrite and nitrate anions. To probe the role such interactions play in allosteric activation, further structural analyses were conducted in the presence of acarbose, which served as a sensitive reporter molecule of the catalytic ability of these modified enzymes to carry out its expected rearrangement by human pancreatic α-amylase. These studies show that the largest anion of this group, nitrate, can comfortably fit in the chloride binding pocket, making all the necessary hydrogen bonds. Further, this anion has nearly the same ability to activate human pancreatic α-amylase and leads to the production of the same acarbose product. In contrast, while nitrite considerably boosts the relative activity of human pancreatic α-amylase, its presence leads to changes in the electrostatic environment and active site conformations that substantially modify catalytic parameters and produce a novel acarbose rearrangement product. In particular, nitrite-substituted humnan pancreatic α-amylase demonstrates the unique ability to cleave acarbose into its acarviosine and maltose parts and carry out a previously unseen product elongation. In a completely unexpected turn of events, structural studies show that in azide-bound human pancreatic α-amylase, the normally resident chloride ion is retained in its binding site and an azide anion is found bound in an embedded side pocket in the substrate binding cleft. These results clearly indicate that azide enzymatic activation occurs via a mechanism distinct from that of the nitrite and nitrate anions.

Salivary -amylase: A measure associated with satiety and subsequent food intake in humans

Food intake regulation in humans involves various central and peripheral mechanisms. In this study salivary amylase was examined for functioning as a measure of satiety and food intake. In a 1.25-h session, 32 fasted subjects were given a preload of starch-based custard (849 kJ) followed by ad libitum intake of this custard. Before and after preload intake and after ad libitum consumption, both satiety ratings and -amylase were analysed. Perceived satiety and amylase were increased after preload and ad libitum consumption. Across subjects, the individual amount of ad libitum intake was negatively correlated to -amylase levels before this intake, whereas it was positively associated with -amylase activity after ad libitum consumption. In conclusion, salivary amylase systematically increases upon food consumption and satiation, and serves therefore as a potential measure of satiety and subsequent food intake.


ARTICLE

Formation of an adduct by clenbuterol, a β-adrenoceptor agonist drug, and serum albumin in human saliva at the acidic pH of the stomach

Clenbuterol (CLB) is an antiasthmatic drug used also illegally as a lean muscle mass enhancer in both humans and animals. CLB and amine-related drugs in general are nitrosatable, thus raising concerns regarding possible genotoxic/carcinogenic activity. Oral administration of CLB raises the issue of its possible transformation by salivary nitrite at the acidic pH of gastric juice. In acidic human saliva CLB was rapidly transformed to the CLB arenediazonium ion. This suggests a reaction of CLB with salivary nitrite, as confirmed in aerobic HNO2 solution by a drastic decrease in nitric oxide, nitrite, and nitrate. In human saliva, both glutathione and ascorbic acid were able to inhibit CLB arenediazonium formation and to react with preformed CLB arenediazonium. The effect of ascorbic acid is particularly pertinent because this vitamin is actively concentrated within the gastric juice. EPR spin trapping experiments showed that preformed CLB arenediazonium ion was reduced to the aryl radical by ascorbic acid, glutathione, and serum albumin, the major protein of saliva. As demonstrated by anti-CLB antibodies and MS, the CLB–albumin interaction leads to the formation of a covalent drug–protein adduct, with a preference for Tyr-rich regions. This study highlights the possible hazards associated with the use/abuse of this drug.


ARTICLE

Arsenic Speciation Analysis in Human Saliva

Background: Determination of arsenic species in human saliva is potentially useful for biomonitoring of human exposure and studying arsenic metabolism. Arsenic speciation in saliva has not been reported previously.

Methods: We separated arsenic species in saliva using liquid chromatography (LC) and quantified them by inductively coupled plasma mass spectrometry. We further confirmed the identities of arsenic species by LC coupled with electrospray ionization tandem mass spectrometry. These methods were successfully applied to the determination of arsenite (AsIII), arsenate (AsV), and their methylation metabolites, monomethylarsonic acid (MMAV), and dimethylarsinic acid (DMAV), in >300 saliva samples collected from people who were exposed to varying concentrations of arsenic.

Results: The mean (range) concentrations (µg/L) in the saliva samples from 32 volunteers exposed to background levels of arsenic were AsIII 0.3 [not detectable (ND) to 0.7], AsV 0.3 (ND to 0.5), MMAV 0.1 (ND to 0.2), and DMAV 0.7 (ND to 2.6). Samples from 301 people exposed to increased concentrations of arsenic in drinking water showed detectable AsIII in 99%, AsV in 98%, MMAV in 80%, and DMAV in 68% of samples. The mean (range) concentrations of arsenic species in these saliva samples were (in µg/L) AsIII 2.8 (0.1–38), AsV 8.1 (0.3–120), MMAV 0.8 (0.1–6.0), and DMAV 0.4 (0.1–3.9). Saliva arsenic correlated with drinking water arsenic. Odds ratios for skin lesions increased with saliva arsenic concentrations. The association between saliva arsenic concentrations and the prevalence of skin lesions was statistically significant (P <0.001).

Conclusions: Speciation of AsV, AsIII, MMAV, and DMAV in human saliva is a useful method for monitoring arsenic exposure.

Human saliva can detect breast cancer

NEW YORK: Specific protein markers can be identified and quantified in human saliva to provide an early, non-invasive diagnosis of breast cancer, a new study has found.

The study, published in the Journal of Cancer Investigation , describes how the onset of breast cancer produces a change in the normal type and amount of protein in glandular secretions from the salivary glands.

The protein profile in a healthy person is altered by the presence of cancer, it revealed.

The study is being applied to a "lab-on-a-chip" technology platform developed by biochemists at the University of Texas at Austin.

The ultimate goal is to bring this type of diagnostic test, which is capable of detecting the presence of cancer before a tumour forms, into the dental office or other health care facilities, the University said in a statement.

The technology aims to improve the ease and effectiveness with which dental professionals and other health care providers can provide quick, accurate diagnostic information and physician referrals to their patients, it said.

The study was a collaborative effort of Charles Streckfus, professor of diagnostics at the University of Texas Dental Branch at Houston, and William Dubinsky, a biochemist and professor of integrative biology and pharmacology at the University of Texas Medical School at Houston and Lenora Bigler, clinical research professor with the UT Dental Branch.

The research found that saliva holds the codes to many medical secrets.

Influence of Saliva Medium on Freeing Heavy Metal Ion From Fixed Dentures

In dental-prosthetic practice, various kinds of fixed dentures, crowns and bridges, have very often been used in order to replace natural teeth and to respond to all health and esthetic needs. This study investigated the effect of saliva medium on migration of ions of heavy metals from fixed dentures that were fixed with various cements. Also, the influence of saliva medium on natural human teeth was observed. Potentiometric stripping analysis was used in order to determine the content of toxic heavy metals in the examined samples. The study confirmed that synthetic saliva had no significant influence on heavy metal ion migration from the natural teeth, whereas slight migration of some observed toxic heavy metal ions from the fixed dentures was present. This, however, indicates that these contents, although very low, must be taken seriously, because the above mentioned metals have cumulative effect which after some period of time may lead to functional disorders of some organs, and even to some very serious diseases.

Kalicanin B, Ajduković Z.
University of Nis, Faculty of Medicine, Department of Pharmacy, Nis, Serbia.