Fasting salivary glucose levels is not a better measure for identifying diabetes mellitus than serum or capillary blood glucose levels: comparison in a Ghanaian population

Exploring Saliva as a Sample for Non-Invasive Glycemic Monitoring in Diabetes: A Scoping Review

Background/Objectives: Diabetes mellitus is characterized by a dysregulated glucose metabolism, necessitating frequent and often invasive monitoring techniques for its effective management. Saliva, a non-invasive and readily accessible biofluid, has been proposed as a potential alternative for glycemic monitoring due to its biochemical correlation with blood glucose levels. This scoping review aims to evaluate the evidence regarding the use of salivary glucose as a biomarker to track glycemic changes in diabetic populations. Methods: This study adhered to the Joanna Briggs Institute guidelines and the PRISMA Extension for Scoping Reviews. A literature search was performed across the PubMed, Scopus, and Web of Science databases, supplemented by manual searches. Results: A total of fifty-seven studies were included, representing populations affected by type 1 diabetes (T1D), type 2 diabetes (T2D), and gestational diabetes (GD). The findings indicated consistent positive correlations between the salivary and blood glucose levels in most studies, although there were significant variations in the sensitivity, specificity, and methodological approaches. Salivary glucose showed promise as a complementary biomarker for glycemic monitoring, particularly due to its non-invasive nature. Conclusions: Challenges such as variability in salivary composition, the absence of standardized collection protocols, and the limited availability of portable devices were noted. This review highlights the potential of saliva as an adjunct sample for diabetes management while stressing the need for further research to bridge existing gaps.

Efficacy of nonsurgical periodontal therapy affecting salivary biomarkers in non-diabetic and type 2 diabetic periodontitis patients. An observational study

Objectives

To assess the effects of non-surgical periodontal therapy on salivary biomarkers in non-diabetic and type 2 diabetic periodontitis patients and to investigate if saliva may be used to monitor glucose levels in type 2 diabetes.

Material and methods

250 participants with chronic generalized periodontitis aged 35-70 years were divided into two groups: test group with type 2 diabetes (125 subjects with 64 males & 61 females) and control group with non-diabetic (125 subjects with 83 males & 42 females). Participants received non-surgical periodontal treatment. Pre-NSPT and 6-week post-NSPT saliva glucose, amylase, total protein, and C-reactive protein (CRP) levels were measured. Intergroup correlations were assessed using Karl Pearson's correlation coefficient and paired t-test.

Results

Non-surgical periodontal therapy significantly decreased CRP (p < 0.05) in diabetics and non-diabetics. CRP mean values changes from baseline 1.79 to post op 1.5 and baseline 1.5 to post-op 1.24 in males and females of test group, respectively. In control group males and females, mean values change from baseline 1.48 to post-op 1.42 and 1.499 to 1.40. Other parameters Glucose, amylase & total protein showed improvement in the level, but statistically non-significant (p > 0.05). Salivary glucose levels corresponded favorably with HbA1C levels.

Conclusion

In individuals with type 2 diabetes and non-diabetic generalized chronic periodontitis, non-surgical periodontal therapy may play a role in lowering the level of significant salivary biomarkers. Saliva can be utilized as a non-invasive approach for monitoring glucose levels in people with type 2 diabetes and chronic periodontitis.

Salivary Biomarkers Associated with Psychological Alterations in Patients with Diabetes: A Systematic Review

The care of individuals with diabetes needs a holistic perspective, taking into account both the physical disease and the mental health problems that may be associated. Different studies show a higher prevalence of depression or anxiety issues in diabetes patients than in the general population, which is why diabetes can be considered one of the chronic diseases in which psychological care is crucial to maintain quality of life. The objective of this review is to examine the published articles that relate the bidirectional associations between objective and subjective measures of anxiety, depressive symptomatology, stress, sleep quality, and salivary biomarkers in patients with diabetes. For this, a search was carried out in the electronic databases PubMed, Cochrane, and SCOPUS using the keywords "diabetes", "saliva", "sleep", "anxiety", "depression", and "stress" for works published up until May 2022 and limited to the English and Spanish languages. The sample comprised 14 articles, 5 of which analysed the associations between depressive symptomatology and salivary biomarkers in people with diabetes. Among the salivary biomarkers most frequently used to evaluate psychological alterations in persons with diabetes are cortisol and melatonin. Thus, significant changes in the levels of these biomarkers were observed in most studies. Four out of five studies reported a statistically significant relationship between increased salivary cortisol in the evening/midnight or the cortisol awakening response and depressive symptoms. In contrast, lower cortisol levels upon waking in the morning were observed when there was no depression or anxiety. Regarding the association between salivary cortisol values and sleep quality in patients with diabetes, lower morning cortisol values related to prolonged nighttime sleep were common in the analysed studies. Low melatonin concentrations showed a negative correlation with sleep quality. As it is an easy-to-apply and non-invasive method, the measurement of salivary biomarkers can be very useful for predicting psychological alterations in patients with diabetes. Further scientific studies are required to determine the sensitivity of these biological substances acting as biomarkers for detecting sleep disorders and psychological alterations.

Correlations of Salivary and Blood Glucose Levels among Six Saliva Collection Methods

Background: Saliva has been studied as a better indicator of disorders and diseases than blood. Specifically, the salivary glucose level is considered to be an indicator of diabetes mellitus (DM). However, saliva collection methods can affect the salivary glucose level, thereby affecting the correlation between salivary glucose and blood glucose. Therefore, this study aims to identify an ideal saliva collection method and to use this method to determine the population and individual correlations between salivary glucose and blood glucose levels in DM patients and healthy controls. Finally, an analysis of the stability of the individual correlations is conducted. Methods: This study included 40 age-matched DM patients and 40 healthy controls. In the fasting state, saliva was collected using six saliva collection methods, venous blood was collected simultaneously from each study participant, and both samples were analyzed at the same time using glucose oxidase peroxidase. A total of 20 DM patients and 20 healthy controls were arbitrarily selected from the above participants for one week of daily testing. The correlations between salivary glucose and blood glucose before and after breakfast were analyzed. Finally, 10 DM patients and 10 healthy controls were arbitrarily selected for one month of daily testing to analyze the stability of individual correlations. Results: Salivary glucose levels were higher in DM patients than healthy controls for the six saliva collection methods. Compared with unstimulated saliva, stimulated saliva had decreased glucose level and increased salivary flow. In addition, unstimulated parotid salivary glucose was most correlated with blood glucose level (R² = 0.9153), and the ROC curve area was 0.9316, which could accurately distinguish DM patients. Finally, it was found that the correlations between salivary glucose and blood glucose in different DM patients were quite different. The average correlation before breakfast was 0.83, and the average correlation after breakfast was 0.77. The coefficient of variation of the correlation coefficient before breakfast within 1 month was less than 5%. Conclusion: Unstimulated parotid salivary glucose level is the highest and is most correlated with blood glucose level, which can be accurately used to distinguish DM patients. Meanwhile, the correlation between salivary glucose and blood glucose was found to be relatively high and stable before breakfast. In general, the unstimulated parotid salivary glucose before breakfast presents an ideal saliva collecting method with which to replace blood-glucose use to detect DM, which provides a reference for the prediction of DM.

Exhaled Breath Analysis for Diabetes Diagnosis and Monitoring: Relevance, Challenges and Possibilities

With the global population prevalence of diabetes surpassing 463 million cases in 2019 and diabetes leading to millions of deaths each year, there is a critical need for feasible, rapid, and non-invasive methodologies for continuous blood glucose monitoring in contrast to the current procedures that are either invasive, complicated, or expensive. Breath analysis is a viable methodology for non-invasive diabetes management owing to its potential for multiple disease diagnoses, the nominal requirement of sample processing, and immense sample accessibility; however, the development of functional commercial sensors is challenging due to the low concentration of volatile organic compounds (VOCs) present in exhaled breath and the confounding factors influencing the exhaled breath profile. Given the complexity of the topic and the skyrocketing spread of diabetes, a multifarious review of exhaled breath analysis for diabetes monitoring is essential to track the technological progress in the field and comprehend the obstacles in developing a breath analysis-based diabetes management system. In this review, we consolidate the relevance of exhaled breath analysis through a critical assessment of current technologies and recent advancements in sensing methods to address the shortcomings associated with blood glucose monitoring. We provide a detailed assessment of the intricacies involved in the development of non-invasive diabetes monitoring devices. In addition, we spotlight the need to consider breath biomarker clusters as opposed to standalone biomarkers for the clinical applicability of exhaled breath monitoring. We present potential VOC clusters suitable for diabetes management and highlight the recent buildout of breath sensing methodologies, focusing on novel sensing materials and transduction mechanisms. Finally, we portray a multifaceted comparison of exhaled breath analysis for diabetes monitoring and highlight remaining challenges on the path to realizing breath analysis as a non-invasive healthcare approach.

Salivary Redox Biomarkers in Insulin Resistance: Preclinical Studies in an Animal Model

Insulin resistance (IR) is a condition of impaired tissue response to insulin. Although there are many methods to diagnose IR, new biomarkers are still being sought for early and noninvasive diagnosis of the disease. Of particular interest in laboratory diagnostics is saliva collected in a stress-free, noninvasive, and straightforward manner. The purpose of the study was to evaluate the diagnostic utility of salivary redox biomarkers in preclinical studies in an animal model. The study was conducted on 20 male Wistar rats divided into two equal groups: a standard diet and a high-fat diet (HFD). In all rats fed the HFD, IR was confirmed by an elevated homeostasis model assessment (HOMA-IR) index. We have shown that IR is responsible for the depletion of the enzymatic (↓superoxide dismutase) and nonenzymatic (↓ascorbic acid, ↓reduced glutathione (GSH)) antioxidant barrier at both the central (serum/plasma) and salivary gland (saliva) levels. In IR rats, we also demonstrated significantly higher concentrations of protein/lipid oxidation (↑protein carbonyls, ↑4-hydroxynoneal (4-HNE)), glycation (↑advanced glycation end products), and nitration (↑3-nitrotyrosine) products in both saliva and blood plasma. Salivary nonenzymatic antioxidants and oxidative stress products generally correlate with their blood levels, while GSH and 4-HNE have the highest correlation coefficient. Salivary GSH and 4-HNE correlate with body weight and BMI and indices of carbohydrate metabolism (glucose, insulin, HOMA-IR) and proinflammatory adipokines (leptin, resistin, TNF-α). These biomarkers differentiate IR from healthy controls with very high sensitivity (100%) and specificity (100%). The high diagnostic utility of salivary GSH and 4-HNE is also confirmed by multivariate regression analysis. Summarizing, saliva can be used to assess the systemic antioxidant status and the intensity of systemic oxidative stress. Salivary GSH and 4-HNE may be potential biomarkers of IR progression. There is a need for human clinical trials to evaluate the diagnostic utility of salivary redox biomarkers in IR conditions.

Changes in Salivary Amylase and Glucose in Diabetes: A Scoping Review

BACKGROUND AND OBJECTIVE

Diabetes mellitus (DM) is a common long-term disease which can be related with salivary amylase levels. DM has recently been associated with salivary amylase diagnostics that could further impair diagnoses in the diabetic population, as well as being an interesting alternative to traditional methods of determine glucose levels. The main advantage of this method is related to the fact that it is a fast diagnostic method. The DM population experiences changes to their metabolism which affects their salivary parameters, making this an alternative procedure for diagnosis and follow-up of the illness due to the non-invasive nature of salivary analyzes. The objective of this review is to summarize the evidence regarding the changes in salivary amylase and glucose levels, and their relationship with blood markers of glycemic control used in clinical settings such as blood glucose and glycated hemoglobin. The differences in salivary amylase levels depending on the method of saliva collection under fasting or non-fasting conditions. The changes in salivary amylase depends on the type of diabetes, the type of insulin treatment or the quality of glycemic control.

CONCLUSIONS

Salivary amylase concentration is increased in diabetic patients in most of the studies and salivary glucose concentration in all studies in both fasting and non-fasting (post-prandial) conditions. Salivary amylase and glucose concentration represent potential non-invasive biomarkers to evaluate glycemic control and clinical management of diabetic patients, although it is necessary to evaluate the influence of potential modulating factors such as age, duration diseases, sex and the effects of pharmacological treatments in these outcomes which remained to be elucidated.

Salivary Fructosamine as a Noninvasive Glycemic Biomarker: A Systematic Review

BACKGROUND

Standard diagnostic and monitoring methods for glycemic status involve invasive sample collection through venous puncture or fingerstick. Recent attention has been focused on exploring noninvasive methods through oral biofluids. Specifically, serum fructosamine has been established as a short-term (2- to 3-wk) marker of disease status in patients with diabetes. Fructosamine measured through noninvasive means such as saliva has shown promise, but its clinical applicability is unknown.

OBJECTIVE

Evaluate the available evidence on using salivary fructosamine as a reliable noninvasive marker to screen and diagnose patients with diabetes mellitus in the clinical setting. A comparative analysis of the correlative accuracy of salivary fructosamine measurements with established blood glycemic biomarkers such as serum fructosamine, blood glucose, and HbA1c will be conducted.

METHODS

Six electronic databases (PubMed, PubMed Central, MEDLINE, EMBASE, Scopus, Cochrane Library) were searched for original research papers (clinical and animal studies) that were relevant to the objective of this systematic review. The search was initiated on May 28, 2020. The systematic review was conducted in accordance with Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. Bias risk assessment, overall quality, and level of evidence were based on the Oxford Centre for Evidence-Based Medicine, Appraisal Tool for Cross-Sectional Studies, and Collaborative Approach to Meta-Analysis and Review of Animal Data from Experimental Studies tool. Heterogeneity was assessed using the National Institutes of Health quality assessment tool for cross-sectional studies.

RESULTS

A total of 174 records were identified. Full-text articles screened for eligibility (n = 21) identified only 6 original research articles relevant to the research question and were thus included in the systematic review. The types of studies identified were cross-sectional and in vivo studies. Three studies (3/6) showed positive correlation of salivary fructosamine with blood glucose levels, while 1 study (1/6) demonstrated a positive correlation with glycated hemoglobin (HbA1c). Limitations related to sample size and selection were identified along with a fair level of interstudy heterogeneity.

CONCLUSION

Based on the evidence evaluated, the utility of salivary fructosamine as a noninvasive marker to screen and diagnose patients with diabetes is doubtful. The overall level of evidence was low (IIIB) and the risk of bias was determined to be high.

KNOWLEDGE TRANSFER STATEMENT

Further evidence in the form of large-scale well-controlled studies is needed prior to recommending salivary fructosamine as a noninvasive diagnostic tool for glycemic status in patients with diabetes mellitus.

Determination of soluble CD44 in serum by using a label-free aptamer based electrochemical impedance biosensor

CD44 is a promising biomarker in the diagnosis and prognosis of malignancies. The serum CD44 level is closely related to disease progression and metastasis of malignancies. It is of great clinical significance for the detection of serum soluble CD44. In this study, a facile, label-free aptamer based electrochemical impedance sensor for serum CD44 has been proposed. The aptamer showing high affinity to CD44 was immobilized on the gold electrodes through Au-S interaction. The interaction between target CD44 and the immobilized aptamer will cause a complex structure change of the aptamer, which makes the diffusion of [Fe(CN)₆]^3-/4- toward the electrode surface easy, thus resulting in the decrease of the impedance of the system. The decreased degree of the impedance had a good linear relationship with the logarithm of the CD44 concentration in the range of 0.1-1000 ng mL^-1 with a detection limit of 0.087 ng mL^-1 (S/N = 3). The developed biosensor has been applied to detect CD44 in serum samples with satisfactory results.