Serum sialic acid, hs-CRP and oxidative stress parameters in obese children

Acrylamide reduces plasma antioxidant vitamin levels in rats due to increased oxidative damage

ABSTRACT Objective Acrylamide is a potentially neurotoxic and carcinogenic chemical and naturally creates during the heating process of carbohydrate-rich foods, such as potato chips and breakfast cereals. Acrylamide might be ingested by people via consuming food that contains it. Therefore, we investigated the effect of acrylamidegiven orally to male and female rats on plasma retinoic acid and α-tocopherol and serum sialic acid and malondialdehyde levels. Method A total of 50 Wistar rats were used (25 female and 25 male, three-four weeks old). The rats of each sex were given 2 and 5mg/kg/day acrylamide via drinking water for 90 days. At the end of the treatment, the animals were euthanized by cervical dislocation. Blood specimens were collected through cardiac puncture, and serum and plasma samples were analysed using the high-performance liquid chromatography technique with a Ultraviolet detector. Results The analysis of the plasma and serum samples revealed that serum sialic acid and malondialdehyde levels in both sexes given 5mg/kg/day acrylamide were significantly increased, and the serum sialic acid levels were higher in female rats given 2mg/kg/day acrylamide. The plasma retinoic acid and α-tocopherol levels significantly decreased in both sexes given only the highest dose. Conclusion The results show that acrylamide causes an increase in oxidative stress and leads to a decrease in the levels of retinoic acid and α-tocopherol which play a role in the defense mechanism against this stress.

Evaluation of Mn-superoxide dismutase and catalase gene expression in childhood obesity: its association with insulin resistance

Background Obesity is associated with oxidative stress. Superoxide dismutase (SOD) is the first line of defense against reactive oxygen species (ROS), eliminating the strong superoxide radical and producing H2O2, which can then be degraded by catalase (CAT). The main objective of this study was to evaluate the gene expression antioxidant enzymes (Mn-SOD and CAT) in peripheral blood mononuclear cells (PBMCs) of obese and normal-weight children, and its association with anthropometric and biochemical parameters. Methods Thirty obese and 30 control subjects between the ages of 8 and 16 years were enrolled in this study. Serum insulin levels were measured using enzyme-linked immunosorbent assay (ELISA), and insulin resistance was calculated using the homeostasis model assessment of insulin resistance (HOMA-IR). Biochemical parameters were also measured. PBMCs of the subjects were separated and Mn-SOD and CAT gene expression was measured using real-time polymerase chain reaction (PCR). Results Mn-SOD and CAT gene expression was significantly lower in the obese group compared with the control group (p<0.01). Also, a positive correlation was observed between the gene expression of Mn-SOD and CAT and body mass index (BMI), fasting blood sugar, insulin resistance, low density lipoprotein-cholesterol (LDL-C) cholesterol, triglycerides (TG) and systolic blood pressure (SBP). Conclusions Induction of antioxidants, especially Mn-SOD and CAT, can lead to reduction of oxidative stress and prevent the complications of obesity in children.

Assessment of total sialic acid levels in patients with hyperemesis gravidarum: a preliminary study

To determine the levels of serum total sialic acid (TSA) in patients with hyperemesis gravidarum (HG) and their gestational age-matched controls. Thirty pregnant women with HG, and 30 healthy pregnant women at up to 14 weeks of gestation were enrolled in this preliminary study. Total sialic acid levels in maternal serum were measured using the quantitative sandwich ELISA method. We observed statistically significant difference in TSA levels between HG and the control groups (p = .003). The identification of the role of SA in the prediction, diagnosis and follow-up of HG warrants more comprehensive studies in the future. Impact Statement What is already known on this subject? The derivatives of neuraminic acid are collectively referred to as sialic acid (SA). Changes in SA levels are known to trigger various conditions and disorders, including inflammatory, cardiovascular, neurological and endocrine diseases. Although a sensitive test capable of identifying hyperemesis gravidarum (HG) would be useful for diagnosis purposes, such a test is currently not available. Studies focussing on identifying new potential indicators and biomarkers for HG - as well as identifying their relevance in establishing diagnosis and assessing disease severity - would not only assist in elucidating the underlying causes of this condition but would also contribute to the development of new diagnostic tests for HG. What the results of this study add? Total sialic acid levels are significantly higher in sera of the patients with HG. The present study is the first in the literature to assess total sialic acid levels in patients with HG and healthy pregnant women before 14 weeks of gestation. What the implications are of these findings for clinical practice and/or further research? Total sialic acid levels could give an idea to clinicians in the etiopathogenesis of HG. The identification of the role of sialic acid in the prediction, diagnosis and follow-up of HG warrants more comprehensive studies in the future.

Diminished complement-activating capacity through the classical pathway in sera from type 2 diabetes mellitus

Complement-activating capacity through the classical pathway in type 2 diabetes mellitus (T2DM) was examined in the context of free sialic acid as a potential modulator of complement activation. Complement-activating capacity was investigated in an incubation study of heat-aggregated IgG (HAG) and sera from 42 T2DM patients. The study demonstrated diminished in-vitro complement-activating capacity through the classical pathway in T2DM. Various doses of N-acetyl neuraminic acid (NANA) were incubated with normal serum and HAG. Complement activation product levels decreased in a NANA dose-dependent manner. Isoelectrofocusing analysis in a mixture of NANA and purified C3 indicated that C3 changed pI dose-dependently, resulting in the downregulation of complement activation. The serum levels of free sialic acid were determined by fluorometric assay in the 42 T2DM sera samples, and were significantly increased in patients with diminished complement activation. These data indicate that increased serum sialic acid may become a candidate for decreasing complement-activating capacity in T2DM.

Childhood obesity and the metabolic syndrome in developing countries

Rapidly changing dietary practices accompanied by an increasingly sedentary lifestyle predispose to nutrition-related non-communicable diseases, including childhood obesity. Over the last 5 y, reports from several developing countries indicate prevalence rates of obesity (inclusive of overweight) >15 % in children and adolescents aged 5-19 y; Mexico 41.8 %, Brazil 22.1 %, India 22.0 % and Argentina 19.3 %. Moreover, secular trends also indicate an alarming increase in obesity in developing countries; in Brazil from 4.1 % to 13.9 % between 1974 and 1997; in China from 6.4 % to 7.7 % between 1991 and 1997; and in India from 4.9 % to 6.6 % between 2003-04 to 2005-06. Other contributory factors to childhood obesity include: high socio-economic status, residence in metropolitan cities and female gender. Childhood obesity tracks into adulthood, thus increasing the risk for conditions like the metabolic syndrome, type 2 diabetes mellitus (T2DM), polycystic ovarian syndrome, hypertension, dyslipidemia and coronary artery disease later in life. Interestingly, prevalence of the metabolic syndrome was 35.2 % among overweight Chinese adolescents. Presence of central obesity (high waist-to-hip circumference ratio) along with hypertriglyceridemia and family history of T2DM increase the odds of T2DM by 112.1 in young Asian Indians (< 40 y). Therapeutic lifestyle changes and maintenance of regular physical activity are most important strategies for preventing childhood obesity. Effective health awareness educational programs for children should be immediately initiated in developing countries, following the successful model program in India (project 'MARG').

Childhood obesity in developing countries: epidemiology, determinants, and prevention

Rapidly changing dietary practices and a sedentary lifestyle have led to increasing prevalence of childhood obesity (5-19 yr) in developing countries recently: 41.8% in Mexico, 22.1% in Brazil, 22.0% in India, and 19.3% in Argentina. Moreover, secular trends indicate increasing prevalence rates in these countries: 4.1 to 13.9% in Brazil during 1974-1997, 12.2 to 15.6% in Thailand during 1991-1993, and 9.8 to 11.7% in India during 2006-2009. Important determinants of childhood obesity include high socioeconomic status, residence in metropolitan cities, female gender, unawareness and false beliefs about nutrition, marketing by transnational food companies, increasing academic stress, and poor facilities for physical activity. Childhood obesity has been associated with type 2 diabetes mellitus, the early-onset metabolic syndrome, subclinical inflammation, dyslipidemia, coronary artery diseases, and adulthood obesity. Therapeutic lifestyle changes and maintenance of regular physical activity through parental initiative and social support interventions are the most important strategies in managing childhood obesity. Also, high-risk screening and effective health educational programs are urgently needed in developing countries.

Oxidant mechanisms in childhood obesity: the link between inflammation and oxidative stress

Evidence of obesity-induced oxidative stress in adults has emerged in the past several years, and similar evidence has been demonstrated in children more recently. The reactive species of oxygen or nitrogen can chemically alter all major classes of biomolecules by modifying their structure and function. Organisms have developed mechanisms to protect biomolecules from the deleterious effects of free radicals. These include the enzymes superoxide dismutase, catalase, and glutathione peroxidase, as well as water and lipid-soluble antioxidants, such as glutathione, ascorbate (vitamin C), α-tocopherol (vitamin E), and β-carotene. Obesity creates oxidant conditions that favor the development of comorbid diseases. Energy imbalances lead to the storage of excess energy in adipocytes, resulting in both hypertrophy and hyperplasia. These processes are associated with abnormalities of adipocyte function, particularly mitochondrial stress and disrupted endoplasmic reticulum function. In this sense, oxidative stress can also be induced by adipocyte associated inflammatory macrophages. There is a close link among obesity, a state of chronic low-level inflammation, and oxidative stress. In addition, the dysregulation of adipocytokines, which are secreted by adipose tissue and promoted by oxidative stress, act synergistically in obesity-related metabolic abnormalities. Adipocytokines link the local and systemic inflammation responses in the context of obesity. It is thought that the evaluation of oxidative status may allow for the identification of patients at an increased risk of complications. Decreasing the levels of chronic inflammation and oxidative stress in childhood may decrease cardiovascular morbidity and mortality in adulthood.

Sialic acid modification of adiponectin is not required for multimerization or secretion but determines half-life in circulation

Adiponectin is an adipocyte-secreted, insulin-sensitizing hormone the circulating levels of which are reduced in conditions of insulin resistance and diabetes. Previous work has demonstrated the importance of posttranslational modifications, such as proline hydroxylation and lysine hydroxylation/glycosylation, in adiponectin oligomerization, secretion, and function. Here we describe the first functional characterization of adiponectin sialylation. Using a variety of biochemical approaches we demonstrated that sialylation occurs on previously unidentified O-linked glycans on Thr residues of the variable domain in human adiponectin. Enzymatic removal of sialic acid or its underlying O-linked sugars did not affect adiponectin multimer composition. Expression of mutant forms of adiponectin (lacking the modified Thr residues) or of wild-type adiponectin in cells defective in sialylation did not compromise multimer formation or secretion, arguing against a structural role for this modification. Activity of desialylated adiponectin was comparable to control adiponectin in L6 myotubes and acute assays in adiponectin(-/-) mice. In contrast, plasma clearance of desialylated adiponectin was accelerated compared with that of control adiponectin, implicating a role for this modification in determining the half-life of circulating adiponectin. Uptake of desialylated adiponectin by isolated primary rat hepatocytes was also accelerated, suggesting a role for the hepatic asialoglycoprotein receptor. Finally, after chronic administration in adiponectin(-/-) mice steady-state levels of desialylated adiponectin were lower than control adiponectin and failed to recapitulate the improvements in glucose and insulin tolerance tests observed with control adiponectin. These data suggest an important role for sialic acid content in the regulation of circulating adiponectin levels and highlight the importance of understanding mechanisms regulating adiponectin sialylation/desialylation.