Application of Raman spectroscopy in type 2 diabetes screening in blood using leucine and isoleucine amino-acids as biomarkers and in comparative anti-diabetic drugs efficacy studies

Abstract

Diabetes is an irreversible condition characterized by elevated blood glucose levels. Currently, there are no predictive biomarkers for this disease and the existing ones such as hemoglobin A1c and fasting blood glucose are used only when diabetes symptoms are noticed. The objective of this work was first to explore the potential of leucine and isoleucine amino acids as diabetes type 2 biomarkers using their Raman spectroscopic signatures. Secondly, we wanted to explore whether Raman spectroscopy can be applied in comparative efficacy studies between commercially available anti-diabetic drug pioglitazone and the locally used anti-diabetic herbal extract Momordica spinosa (Gilg.)Chiov. Sprague Dawley (SD) rat’s blood was used and were pipetted onto Raman substrates prepared from conductive silver paste smeared glass slides. Prominent Raman bands associated with glucose (926, 1302, 1125 cm−1), leucine (1106, 1248, 1302, 1395 cm−1) and isolecucine (1108, 1248, 1437 and 1585 cm−1) were observed. The Raman bands centered at 1125 cm−1, 1395 cm−1 and 1437 cm−1 associated respectively to glucose, leucine and isoleucine were chosen as biomarker Raman peaks for diabetes type 2. These Raman bands displayed decreased intensities in blood from diabetic SD rats administered antidiabetic drugs pioglitazone and herbal extract Momordica spinosa (Gilg.)Chiov. The intensity decrease indicated reduced concentration levels of the respective biomarker molecules: glucose (1125 cm−1), leucine (1395 cm−1) and isoleucine (1437 cm−1) in blood. The results displayed the power and potential of Raman spectroscopy in rapid (10 seconds) diabetes and pre-diabetes screening in blood (human or rat’s) with not only glucose acting as a biomarker but also leucine and isoleucine amino-acids where intensities of respectively assigned bands act as references. It also showed that using Raman spectroscopic signatures of the chosen biomarkers, the method can be an alternative for performing comparative efficacy studies between known and new anti-diabetic drugs. Reports on use of Raman spectroscopy in type 2 diabetes mellitus screening with Raman bands associated with leucine and isoleucine molecules acting as reference is rare in literature. The use of Raman spectroscopy in pre-diabetes screening of blood for changes in levels of leucine and isoleucine amino acids is particularly interesting as once elevated levels are noticed, necessary interventions to prevent diabetes development can be initiated.

Utility of Raman spectroscopy in diabetes detection based on biomarker Raman bands and in antidiabetic efficacy studies of herbal extract Rotheca myricoides Hochst

“…The tentative assignments of the bands are displayed in Table . The PCA results indicated two things, first, that the antidiabetic effects of the herbal extract Rotheca myricoides Hochst were comparable with those of the commercially available drug pioglitazone, and second, it showed that Raman spectroscopy can be utilized in comparative efficacy studies between new antidiabetic drugs the commercially available conventional variants as was also shown in Birech et al…”

“…In this work, we show that Raman spectroscopy can be an alternative technique for performing quick and label‐free detection of diabetes (or prediabetes) in blood with Raman spectral bands associated collectively with valine, leucine, isoleucine, creatine (creatine monohydrate), and sugar (glucose and fructose) as biomarkers. In Birech et al, it was shown that the intensity of Raman bands associated with isoleucine and leucine is different between blood from diabetic, treated, and nondiabetic rats.…”

“…This spectroscopic technique is increasingly generating a lot of interest in diabetes detection with spectral bands associated with some biomolecules acting as biomarkers. Some of the biomolecules that have been demonstrated using Raman spectroscopy to have a great potential in the detection and monitoring of diabetes mellitus type II include blood glucose, haemoglobin, lipids in erythrocyte membranes, and branched chain amino acids . Its use (i.e., Raman spectroscopy) in comparative efficacy studies of antidiabetic medications, both conventional and traditional, has been reported elsewhere …”

“…Here, we report on Raman spectroscopic studies done on blood extracted from diabetic and nondiabetic Sprague Dawley (SD) rats. The blood was pipetted onto a conductive silver paste smeared glass slide and excited using a 785‐nm laser . Induction of diabetic conditions in the rats was achieved through injection of a beta cell (β‐cell) toxin called streptozotocin (STZ) .…”

Application of Raman spectroscopy in comparative study of antiobesity influence of oxytocin and freeze‐dried extracts of Uvariodendron anisatum Verdeck (Annonaceae) in Sprague Dawley rats

“…Raman spectra were measured using confocal Raman system (STR, Seki Technotron Corp) equipped with a 785‐nm laser and a spectrometer (Princeton Instruments). Before every experimental session, the Raman spectrometer was first calibrated using the 520 cm −1 band of a silicon . The experimental parameters for this study were as follows: grating, 600 groves/mm; centre wavelength, 850.97 nm (980 cm −1 ); excitation power at sample position, ~9 mW; spot size at sample position, ~65 μm; exposure time, 10 s; spectral accumulation, 5 s; and ×10 microscope objective (Olympus MPlanFN, 0.3NA).…”