QUALITATIVE ANALYSIS OF LIPOPROTEINS AND STUDY OF THE METABOLIC PROFILE IN DIFFERENT CLINICAL SETTINGS BY RAMAN SPECTROSCOPY

Raman spectroscopy (RS) is a promising optical technique, able to offer a rapid specific overview of the biochemical composition of the analyzed sample without any preparation or labeling. This non-invasive technique is based on the radiation/matter interaction where a sample is illuminated by a laser which interacts with the vibrational motions of the molecules, leading to the emission of light at wavelengths different from the incident one. This property is used to obtain a spectrum characterized by peaks referable to the biochemical composition of the sample analyzed. This approach has been integrated with conventional biochemical assay to study metabolic disorders such as: obesity (Ob) and type 2 diabetes mellitus (T2DM). RS was used to study the metabolic/biochemical profile of obese diabetic patients undergoing bariatric surgery (BS), to evaluate the impact of the surgery on body composition and systemic metabolism. The results obtained showed that, despite the improvement of the clinical parameters and levels of adipokines, ghrelin and FGF-19 dosed, Raman data identified a persistent alteration of the patients’ biochemical profile in the post-operative follow-up period (6-12 months), underlining the need for more extended longitudinal studies to assess the powerful of RS to monitor the progression of the disease. This method has also been used to study the quality of lipoproteins (LPs), multimolecular complexes responsible for the transport of lipids in the body. Currently, the amount of cholesterol carried by LPs is one of the main parameters used in clinical practice to assess the risk of cardiovascular events. In particular, the level of circulating low-density lipoprotein cholesterol (LDL-C) is considered one of the main risk factors for cardiovascular disease (CVD). It can deposit on the wall of the arteries, causing the formation and progression of atherosclerotic plaques. Conversely, elevated levels of circulating high-density lipoprotein (HDL-C) cholesterol have long been associated with decreased risk of CVD, given their ability to remove cholesterol deposited on arterial walls. However, recent clinical studies have challenged the concept that high HDL-C levels would automatically translate into clinical benefits. In this regard, the research is focusing on the study of the composition and function of the LPs which are altered in different pathological contexts. However, the study of the quality of LPs lacks a universally accepted gold standard. The development of new methods capable of providing indications on the biochemical profile of the LPs, in a rapid and simple way, is therefore of great interest. In this context, LPs extracted from a cohort of obese patients and a control group of healthy subjects were analyzed by RS. The results obtained demonstrated the suitability of RS to obtain an immediate measure of the LPs quality, defined by their biochemical composition and oxidative state. Overall, this thesis work reveals the potential efficacy of the RS in clinical studies and opens the way to a better understanding of metabolic disorders, for an improved definition of CVD risk.