Lipid-Derived Modifications of Plasma Proteins in Experimental and Human Diabetes

Changes in urine headspace composition as an effect of strenuous walking

The present investigation uses proton transfer reaction mass spectrometry (PTR-MS) combined with multivariate and univariate statistical analyses to study potential biomarkers for altered metabolism in urine due to strenuous walking. Urine samples, in concurrence with breath and blood samples, were taken from 51 participants (23 controls, 11 type-1 diabetes, 17 type-2 diabetes) during the Dutch endurance walking event, the International Four Days Marches. Multivariate analysis allowed for discrimination of before and after exercise for all three groups (control, type-1 and type-2 diabetes) and on three out of 4 days. The analysis highlighted 12 molecular ions contributing to this discrimination. Of these, acetic acid in urine is identified as a significant marker for exercise effects induced by walking; an increase is observed as an effect of walking. Analysis of acetone concentration with univariate tools resulted in different information when compared to breath as a function of exercise, revealing an interesting effect of time over the 4 days. In breath, acetone provides an immediate snapshot of metabolism, whereas urinary acetone will result from longer term diffusion processes, providing a time averaged view of metabolism. The potential to use PTR-MS measurements of urine to monitor exercise effects is exhibited, and may be utilized to monitor subjects in mass participation exercise events.

Advanced glycation endproducts and its receptor for advanced glycation endproducts in obesity

PURPOSE OF REVIEW

To highlight the potential importance of advanced glycation endproducts (AGEs) and advanced-lipoxidation endproducts (ALEs) in obesity and obesity-related complications, and the contribution of the receptor for advanced glycation endproducts (RAGE) and the glyoxylase defense system therein.

RECENT FINDINGS

Formation of AGEs/ALEs and its precursors, including methylglyoxal (MGO), are increased in conditions characterized by hyperglycemia, hyperlipidemia and enhanced oxidative stress. This metabolic profile is generally considered typical for obesity. Increased plasma and/or tissue levels of MGO and of specific AGEs/ALEs, such as N(ε)-(carboxymethyl)lysine (CML), in obesity have recently been described. In addition to increased formation, the suppressed defense system in obesity against AGEs/ALEs formation, that is, the glyoxylase system, will further contribute to AGEs/ALEs formation in obesity. AGEs/ALEs are not inert. In-vitro studies showed that AGEs induced the production of inflammatory mediators in adipocytes and macrophages via RAGE activation, which may subsequently contribute to the development of obesity-related complications.

SUMMARY

The recognition of an enhanced AGEs/ALEs formation in adipose tissue and the biological consequences thereof may lead to a further understanding of underlying mechanisms in dysregulated production of adipokines in obesity.

Metabolomics reveals reduction of metabolic oxidation in women with polycystic ovary syndrome after pioglitazone-flutamide-metformin polytherapy

Polycystic ovary syndrome (PCOS) is a variable disorder characterized by a broad spectrum of anomalies, including hyperandrogenemia, insulin resistance, dyslipidemia, body adiposity, low-grade inflammation and increased cardiovascular disease risks. Recently, a new polytherapy consisting of low-dose flutamide, metformin and pioglitazone in combination with an estro-progestagen resulted in the regulation of endocrine clinical markers in young and non-obese PCOS women. However, the metabolic processes involved in this phenotypic amelioration remain unidentified. In this work, we used NMR and MS-based untargeted metabolomics to study serum samples of young non-obese PCOS women prior to and at the end of a 30 months polytherapy receiving low-dose flutamide, metformin and pioglitazone in combination with an estro-progestagen. Our results reveal that the treatment decreased the levels of oxidized LDL particles in serum, as well as downstream metabolic oxidation products of LDL particles such as 9- and 13-HODE, azelaic acid and glutaric acid. In contrast, the radiuses of small dense LDL and large HDL particles were substantially increased after the treatment. Clinical and endocrine-metabolic markers were also monitored, showing that the level of HDL cholesterol was increased after the treatment, whereas the level of androgens and the carotid intima-media thickness were reduced. Significantly, the abundance of azelaic acid and the carotid intima-media thickness resulted in a high degree of correlation. Altogether, our results reveal that this new polytherapy markedly reverts the oxidant status of untreated PCOS women, and potentially improves the pro-atherosclerosis condition in these patients.

The Nε-(carboxymethyl)lysine-RAGE axis: putative implications for the pathogenesis of obesity-related complications

Obesity is an important contributor to the burden of insulin resistance, Type 2 diabetes and cardiovascular disease. An important mechanism by which excess adiposity causes obesity-associated complications is the dysregulated production and secretion of biologically active molecules derived from adipocytes. These adipokines affect the vascular wall and contribute to the development of insulin resistance and Type 2 diabetes. However, factors that cause an increased production of pro-inflammatory adipokines, while decreasing anti-inflammatory adipokines, have not been fully clarified. Owing to local conditions in adipose tissue, that is, increased fatty acids, hypoxia and oxidative stress, we speculate that an increased formation of the major advanced lipoxidation end product, N^ε-(carboxymethyl)lysine (CML), may play a role. CML-adducts in proteins are major ligands for the receptor for advanced glycation end products (RAGE). The consequence of RAGE activation by CML is the activation of important signaling inflammatory pathways. The putative role of CML-modified proteins in obesity is addressed in this article. The identification of this pathway may provide an important strategy for novel therapeutic approaches against obesity-associated complications.