Integrated Autofluorescence Characterization of a Modified-Diet Liver Model with Accumulation of Lipids and Oxidative Stress

Abstract

Oxidative stress in fatty livers is mainly generated by impaired mitochondrial β-oxidation, inducing tissue damages and disease progression. Under suitable excitation, light liver endogenous fluorophores can give rise to autofluorescence (AF) emission, the properties of which depend on the organ morphofunctional state. In this work, we characterized the AF properties of a rat liver model of lipid accumulation and oxidative stress, induced by a 1–9-week hypercaloric methionine-choline deficient (MCD) diet administration. The AF analysis (excitation at 366 nm) was performed in vivo, via fiber optic probe, or ex vivo. The contribution of endogenous fluorophores involved in redox reactions and in tissue organization was estimated through spectral curve fitting analysis, and AF results were validated by means of different histochemical and biochemical assays (lipids, collagen, vitamin A, ROS, peroxidised proteins, and lipid peroxidation -TBARS-, GSH, and ATP). In comparison with the control, AF spectra changes found already at 1 week of MCD diet reflect alterations both in tissue composition and organization (proteins, lipopigments, and vitamin A) and in oxidoreductive pathway engagement (NAD(P)H, flavins), with a subsequent attempt to recover redox homeostasis. These data confirm the AF analysis potential to provide a comprehensive diagnostic information on negative effects of oxidative metabolism alteration.

Fatty liver oxidative events monitored by autofluorescence optical diagnosis: Comparison between subnormothermic machine perfusion and conventional cold storage preservation

“…Methionine/choline‐deficient diet in rat livers was already shown to affect mitochondrial functionality, affecting the tissue redox state and inducing progressive changes in tissue AF properties, including an increase in the AF emission of lipofuscin‐like lipopigment, resulting from the accumulation of oxidized products. Interestingly, at early diet times, AF data revealed an energy metabolism engagement still able to counteract the MCD adverse effects, consistent with initial adaptive and protective liver responses to homeostasis alterations . Hence, in this work, the MCD diet was given to rats for 12 days to obtain livers still maintaining a metabolic balance in the presence of lipid accumulation and oxidative stress, to investigate their AF responses to different preservation conditions and causes of external stimuli consisting in temperature and oxygenation changes.…”

Autofluorescence‐based optical biopsy: An effective diagnostic tool in hepatology

“…The development of light‐based procedures for the in situ, in vivo, real‐time monitoring of organ energy state and response to ischaemia/reoxygenation have relied on hepatocyte mitochondria, hepatocytes, liver tissue or whole liver organs from animal models. NAD(P)H and flavins have been confirmed as AF biomarkers of organ functionality, suitable for application during surgery or transplantation . Notably, both AF‐based spectroscopy and imaging have allowed real‐time, in situ monitoring of transient events (Figure ), otherwise undetectable or requiring the collection of sequential samples from far more numerous organs to perform ex vivo biochemical and histological analyses.…”

“…Notably, both AF‐based spectroscopy and imaging have allowed real‐time, in situ monitoring of transient events (Figure ), otherwise undetectable or requiring the collection of sequential samples from far more numerous organs to perform ex vivo biochemical and histological analyses. Additionally, cell energy metabolism and redox balance could be upset during specimen collection, at least as an immediate consequence of the oxygen supply interruption . Besides limiting the number of experimental animals, AF analysis thus helps to avoid alteration of analysis results.…”

“…The possibility of simultaneously detecting different EFs ensures that AF optical biopsy can provide a comprehensive picture of liver state and functionality . However, the procedure requires direct contact via optical fibres in order to probe the liver or to collect liver tissue or bile specimens.…”

“…59 The possibility of simultaneously detecting different EFs ensures that AF optical biopsy can provide a comprehensive picture of liver state and functionality. 59,76,92,93,132 However, the procedure requires direct contact via optical fibres in order to probe the liver or to collect liver tissue or bile specimens. The consequent invasiveness can be acceptable during surgery or transplantation, but hinders routine follow-up of liver disorder, because of drawbacks which are comparable to those affecting conventional liver biopsy.…”