Noninvasive monitoring of glucose levels: is exhaled breath the answer?

Recent Advancement in Biofluid-Based Glucose Sensors Using Invasive, Minimally Invasive, and Non-Invasive Technologies: A Review

Biosensors have potentially revolutionized the biomedical field. Their portability, cost-effectiveness, and ease of operation have made the market for these biosensors to grow rapidly. Diabetes mellitus is the condition of having high glucose content in the body, and it has become one of the very common conditions that is leading to deaths worldwide. Although it still has no cure or prevention, if monitored and treated with appropriate medication, the complications can be hindered and mitigated. Glucose content in the body can be detected using various biological fluids, namely blood, sweat, urine, interstitial fluids, tears, breath, and saliva. In the past decade, there has been an influx of potential biosensor technologies for continuous glucose level estimation. This literature review provides a comprehensive update on the recent advances in the field of biofluid-based sensors for glucose level detection in terms of methods, methodology and materials used.

What can we learn from β-cell failure biomarker application in diabetes in childhood? A systematic review

BACKGROUND

The prevalence of diabetes as a catastrophic disease in childhood is growing in the world. The search for novel biomarkers of β-cell failure has been an elusive task because it requires several clinical and biochemical measurements in order to integrate the risk of metabolic syndrome.

AIM

To determine which biomarkers are currently used to identify β-cell failure among children and adolescents with high risk factors for diabetes mellitus.

METHODS

This systematic review was carried out using a modified version of the PICO protocol (Participants/Intervention/Comparison/Outcome). Once our research question was established, terms were individually researched on three different databases (PubMed, BIREME and Web of Science). The total articles obtained underwent a selection process from which the 78 most relevant articles were retrieved to undergo further analysis. They were assessed individually according to quality criteria.

RESULTS

First, we made the classification of the β-cell-failure biomarkers by the target tissue and the evolution of the disease, separating the biomarkers in relation to the types of diabetes. Second, we demonstrated that most biomarkers currently used as early signs of β-cell failure are those that concern local or systemic inflammation processes and oxidative stress as well as those related to endothelial dysfunction processes. Third, we explored the novelties of diabetes as a protein conformational disease and the novel biomarker called real human islet amyloid polypeptide amyloid oligomers. Finally, we ended with a discussion about the best practice of validation and individual control of using different types of biomarkers in type 1 and type 2 diabetes in order to assess the role they play in the progress of diabetes in childhood.

CONCLUSION

This review makes widely evident that most biomarkers currently used as early signs of β-cell failure are those that concern local or systemic inflammation processes and oxidative stress as well as those related to endothelial dysfunction processes. Landing in the clinical practice we propose that real human islet amyloid polypeptide amyloid oligomers is good for identifying patients with β-cell damage and potentially could substitute many biomarkers.

Investigating the relationship between particulate matter and inflammatory biomarkers of exhaled breath condensate and blood in healthy young adults

Inflammatory biomarkers in exhaled breath condensate (EBC) are measured to estimate the effects of air pollution on humans. The present study was conducted to investigate the relationship between particulate matter and inflammatory biomarkers in blood plasma and exhaled air in young adults. The obtained results were compared in two periods; i.e., winter and summer. GRIMM Dust Monitors were used to measure PM₁₀, PM_2.5, and PM₁ in indoor and outdoor air. A total of 40 healthy young adults exhaling air condensate were collected. Then, biomarkers of interleukin-6 (IL-6), Nitrosothiols (RS-NOs), and Tumor necrosis factor-soluble receptor-II (sTNFRII) were measured by 96 wells method ELISA and commercial kits (HS600B R&D Kit and ALX-850–037-KI01) in EBC while interleukin-6 (IL-6), sTNFRII and White Blood Cell (WBC) were measured in blood plasma in two periods of February 2013 (winter) and May 2013 (summer). Significant association was found between particulate matter and the white blood cell count (p < 0.001), as well as plasma sTNFRII levels (p-value = 0.001). No significant relationship was found between particulate matter with RS-NOs (p = 0.128), EBC RSNOs (p-value = 0.128), and plasma IL-6 (p-value = 0.167). In addition, there was no significant relationship between interleukin-6 of exhaled air with interleukin-6 of plasma (p-value < 0.792 in the first period and < 0.890 in the second period). sTNFRII was not detected in EBC. Considering the direct effect between increasing some biomarkers in blood and EBC and particulate matter, it is concluded that air pollution causes this increasing.

Noninvasive glucose detection in exhaled breath condensate

Two-thirds of patients with diabetes avoid regularly monitoring their blood glucose levels because of the painful and invasive nature of current blood glucose detection. As an alternative to blood sample collection, exhaled breath condensate (EBC) has emerged as a promising noninvasive sample from which to monitor glucose levels. However, this dilute sample matrix requires sensors capable of detecting glucose with high resolution at nanomolar and micromolar concentrations. Recent developments in EBC collection methods and highly sensitive glucose biosensors provide a path toward enabling robust and sensitive glucose detection in EBC. This review addresses current and emerging EBC collection and glucose sensing modalities capable of quantifying glucose in EBC samples. We highlight the opportunities and challenges for development and integration of EBC glucose detection systems that will enable clinically robust and accurate EBC glucose measurements for improved glycemic control.

Insulin signaling via the PI3-kinase/Akt pathway regulates airway glucose uptake and barrier function in a CFTR-dependent manner

Cystic fibrosis-related diabetes is the most common comorbidity associated with cystic fibrosis (CF) and correlates with increased rates of lung function decline. Because glucose is a nutrient present in the airways of patients with bacterial airway infections and because insulin controls glucose metabolism, the effect of insulin on CF airway epithelia was investigated to determine the role of insulin receptors and glucose transport in regulating glucose availability in the airway. The response to insulin by human airway epithelial cells was characterized by quantitative PCR, immunoblot, immunofluorescence, and glucose uptake assays. Phosphatidylinositol 3-kinase/protein kinase B (Akt) signaling and cystic fibrosis transmembrane conductance regulator (CFTR) activity were analyzed by pharmacological and immunoblot assays. We found that normal human primary airway epithelial cells expressed glucose transporter 4 and that application of insulin stimulated cytochalasin B-inhibitable glucose uptake, consistent with a requirement for glucose transporter translocation. Application of insulin to normal primary human airway epithelial cells promoted airway barrier function as demonstrated by increased transepithelial electrical resistance and decreased paracellular flux of small molecules. This provides the first demonstration that airway cells express insulin-regulated glucose transporters that act in concert with tight junctions to form an airway glucose barrier. However, insulin failed to increase glucose uptake or decrease paracellular flux of small molecules in human airway epithelia expressing F508del-CFTR. Insulin stimulation of Akt1 and Akt2 signaling in CF airway cells was diminished compared with that observed in airway cells expressing wild-type CFTR. These results indicate that the airway glucose barrier is regulated by insulin and is dysfunctional in CF.

Monitoring glycemia in diabetes

Monitoring of glycemic control is a key component of the diabetes treatment plan. Patients who are not meeting targets often require more intensive monitoring, ranging from frequent self-monitored glucose to continuous glucose monitoring in order to facilitate medication and lifestyle changes. However, more intensive monitoring demands more training and a structured plan for interpretation and use of the data. Better patient and provider tools to support decision-making and progress toward an artificial pancreas may help to alleviate this burden.

Glucose prediction by analysis of exhaled metabolites - a systematic review

Background

In critically ill patients, glucose control with insulin mandates time– and blood–consuming glucose monitoring. Blood glucose level fluctuations are accompanied by metabolomic changes that alter the composition of volatile organic compounds (VOC), which are detectable in exhaled breath. This review systematically summarizes the available data on the ability of changes in VOC composition to predict blood glucose levels and changes in blood glucose levels.

Methods

A systematic search was performed in PubMed. Studies were included when an association between blood glucose levels and VOCs in exhaled air was investigated, using a technique that allows for separation, quantification and identification of individual VOCs. Only studies on humans were included.

Results

Nine studies were included out of 1041 identified in the search. Authors of seven studies observed a significant correlation between blood glucose levels and selected VOCs in exhaled air. Authors of two studies did not observe a strong correlation. Blood glucose levels were associated with the following VOCs: ketone bodies (e.g., acetone), VOCs produced by gut flora (e.g., ethanol, methanol, and propane), exogenous compounds (e.g., ethyl benzene, o–xylene, and m/p–xylene) and markers of oxidative stress (e.g., methyl nitrate, 2–pentyl nitrate, and CO).

Conclusion

There is a relation between blood glucose levels and VOC composition in exhaled air. These results warrant clinical validation of exhaled breath analysis to monitor blood glucose levels.