[show abstract][hide abstract] ABSTRACT: The maximal rate of O₂ consumption (VO₂ max) constitutes one of the oldest fitness indexes established for the measure of cardiorespiratory fitness and aerobic performance. Procedures have been developed in which VO₂ max is estimated from physiological responses during submaximal exercise. Generally, VO₂ max is estimated using the classical renowned Astrand-Ryhming test. In young adults, poor fitness and low aerobic performance are often associated with a sedentary lifestyle, which is a well-described factor for the development of obesity and its related disorders such as cardiovascular diseases and type 2 diabetes. In the Indian Ocean, the inhabitants of La Reunion Island, a French overseas department, exhibit an increasing prevalence of obesity and type 2 diabetes. At the University of La Reunion, a new laboratory course involving students was designed to teach the indirect evaluation of their VO₂ max from the classical Astrand-Ryhming test and using a cycle ergometer as the exercise mode. Inverse and significant correlations were established between the students' fat mass percentages and their VO₂ max and between their waist-to-hip ratio and VO₂ max as well. Results from the international physical activity questionnaire showed that most participants in this laboratory were sedentary students. Therefore, this laboratory makes the students practice and understand the use of a classical test to estimate their VO₂ max. It also alerts them to the correlation between a sedentary lifestyle and higher body fat content. This exercise allowed students to use a scientific method to engage the problem of sedentary lifestyle, which is a real world issue.
[show abstract][hide abstract] ABSTRACT: The pulp extracts of twenty-one varieties of citrus fruits (oranges, satsumah, clementine, mandarins, tangor, bergamot, lemon, tangelos, kumquat, calamondin and pamplemousses), commonly grown in Mauritius, were characterised in terms of their total soluble solids (TSS), titratable acidity (TA), polyphenol composition and vitamin C contents. Total phenolics ranged from 406.3 ± 14 to 1694 ± 19 μg g− 1 fresh weight (FW). Total flavonoids varied between 133 ± 6 and 965 ± 7 μg g− 1 FW and vitamin C contents were from 166 ± 19 μg/mL to 677 ± 22 μg/mL. The pulp of a pamplemousse variety had the highest TSS/TA ratio whereas lemon pulps had lowest TSS/TA ratios. The antioxidant activities of the pulp extracts were assessed and total phenolics correlated strongly with the trolox equivalent antioxidant capacity (TEAC), ferric reducing antioxidant capacity (FRAP) and hypochlorous acid (HOCl) scavenging activity assays. Based on their antioxidant activities, nine citrus fruits namely, one orange, tangor, kumquat, calamondin and pamplemousse variety and two mandarin and tangelo varieties were further characterised for their flavanone, flavonol and flavone levels by HPLC. Hesperidin (6.89 ± 0.06 to 26.98 ± 0.07 mg/g FW) and narirutin (0.27 ± 0.01 and 20.91 ± 0.10 mg/g FW) were present at high concentrations compared to the other flavonoid glycosides in the pulp extracts. Naringin was detected only in pulp extracts of pamplemousses. In the light of the data obtained, citrus fruit pulps represent an important source of phytochemicals with potent antioxidant capacity.
Food Research International. 01/2011; 44(7):2088-2099.
[show abstract][hide abstract] ABSTRACT: The flavedo extracts of twenty-one varieties of citrus fruits (oranges, satsumah, clementine, mandarins, tangor, bergamot, lemon, tangelos, kumquat, calamondin and pamplemousses) grown in Mauritius were examined for their total phenolic, flavonoid and vitamin C contents and antioxidant activities. Total phenolics correlated strongly with the trolox equivalent antioxidant capacity (TEAC), ferric reducing antioxidant capacity (FRAP) and hypochlorous acid (HOCl) scavenging activity assays (r > 0.85). Based on their antioxidant activities in these three assays nine citrus fruits namely, one orange, clementine, tangor and pamplemousse variety, two tangelo varieties and three mandarin varieties, were further characterized for their flavanone, flavonol and flavone levels by HPLC and their antioxidant activities were assessed by the copper-phenanthroline and iron chelation assays. The flavanone, hesperidin, was present at the highest concentrations in all flavedo extracts except for pamplemousses where it was not detected. Contents in hesperidin ranged from 83 ± 0.06 to 234 ± 1.73 mg/g FW. Poncirin, didymin, diosmin, isorhoifolin and narirutin were also present in all extracts whereas naringin was present only in one mandarin variety. The nine flavedo extracts exhibited good DNA protecting ability in the cuphen assay with IC₅₀ values ranging from 6.3 ± 0.46 to 23.0 ± 0.48 mg FW/mL. Essentially the flavedos were able to chelate metal ions however, tangor was most effective with an IC₅₀ value of 9.1 ± 0.08 mg FW/mL. The flavedo extracts of citrus fruits represent a significant source of phenolic antioxidants with potential prophylactic properties for the development of functional foods.
[show abstract][hide abstract] ABSTRACT: Diabetes is a reactive oxygen species (ROS)-mediated pathology, with a worldwide prevalence estimated to double by 2030. A major effort has been launched to find therapeutic means to improve health conditions of diabetic patients. Recent data show that supplemental natural antioxidants represent a potential strategy as adjunct therapy. Despite the major role of adipocytes in the etiology of diabetes, little is known about the effect of natural antioxidants on adipocyte response to oxidative stress. Using a diabetes-like oxidative stress model, the potential protective effect of antioxidative flavedo, albedo, and pulp extracts of (1) tangor Elendale ( Citrus reticulata × Citrus sinensis ) and (2) tangelo Minneola ( C. reticulata × Citrus paradisis ) was investigated on human adipocytes. Besides the retardation of free-radical-induced hemolysis of human erythrocytes, non-cytotoxic concentrations of tangelo and tangor flavedo extracts significantly reduced the levels of protein carbonyls in response to advanced glycation end products (AGEs) generated by albumin glycation in SW872 cells. Flavedo extracts lowered carbonyl accumulation in H(2)O(2)-treated adipocytes, while tangelo and tangor flavedo, albedo, and pulp extracts suppressed ROS production in SW872 cells with or without the addition of H(2)O(2). Our results clearly show that Mauritian Citrus fruit extracts represent an important source of antioxidants, with a novel antioxidative role at the adipose tissue level.
Journal of Agricultural and Food Chemistry 09/2010; · 2.91 Impact Factor
[show abstract][hide abstract] ABSTRACT: Oxidative stress in adipose tissue constitutes a pathological process involved in obesity-linked metabolic disorders. Apolipoprotein E (apoE), which exhibits antioxidant properties in plasma and brain, is highly produced by adipose tissue and adipocytes. In this study, we investigated the role of apoE in the human adipocyte response to oxidative stress. We first demonstrated that apoE secretion by adipocytes was stimulated by oxidative stress. We also observed that apoE overexpression protected adipocytes from hydrogen peroxide-induced damages, by mitigating intracellular oxidation and exerting extracellular antioxidant properties. Our findings clearly show a novel antioxidant role for apoE in adipose tissue.
[show abstract][hide abstract] ABSTRACT: High levels of oxidative stress were reported in obesity-linked type 2 diabetes and were associated with elevated formation of advanced glycation end products (AGEs). Many studies have focused on the effect of antioxidants on vascular and circulating cells such as macrophages. However, despite the major role of adipocytes in the etiology of diabetes, little is known about the effect of natural antioxidants on adipocyte response to oxidative stress. The present study reports the differential protective effects of plant nutrients toward adipose cells subjected to oxidative stress. Caffeic acid, quercetin, L: -ascorbic acid, and alpha-tocopherol were tested on SW872 liposarcoma cells subjected to a free radical generator or to AGEs. Proliferation, viability, free radical formation, and superoxide dismutase expression were assessed in treated cells. Caffeic acid and quercetin appeared as the most potent antioxidant nutrients. Our findings clearly show a novel antioxidant role for caffeic acid and quercetin at the adipose tissue level. These new data confirm the beneficial role of phytotherapy as an interesting alternative mean for the development of novel therapeutical and nutritional strategy to prevent metabolic disorders inherent to obesity-linked diabetes.
Cell Biology and Toxicology 02/2009; 25(6):635-44. · 2.34 Impact Factor
[show abstract][hide abstract] ABSTRACT: Apolipoprotein E (apoE), a key regulator of lipid metabolism, is highly produced by adipose tissue and adipocytes. However, there is little information about its role on adipocyte functions. Because apoE-deficiency in adipocytes was shown to impair adipocyte differentiation, we investigated the consequences of apoE high expression on differentiation and proliferation of a human adipocytic cell line (SW872). SW872 cells were transfected with human apoE to induce a fivefold increase in apoE production and secretion. Adipocyte differentiation and proliferation were assayed by measuring lipid content, adipogenic gene expression, cell number, cell resistance to serum deprivation, and cell division kinetics. Cultured apoE-transfected cells accumulated less triglycerides and less cholesterol than control cells. This decrease in lipid accumulation was associated with a strong downregulation of peroxisome proliferator-activated receptors gamma1 and gamma2 and stearoyl-CoA desaturase 1. The decrease in lipid accumulation was not dependent on the presence of lipids, lipoproteins, or PPAR-gamma agonists in the culture medium, nor was it observed with exogenously added apoE. Moreover, we observed that apoE-transfected cells were more resistant to death induced by serum deprivation, and that these cells underwent more cell divisions than control cells. These results bring new evidence of apoE-involvement in metabolic disorders at the adipocyte level.
Journal of Cellular Biochemistry 02/2009; 106(4):608-17. · 3.06 Impact Factor
[show abstract][hide abstract] ABSTRACT: Free radicals are a normal component of cellular oxygen metabolism in mammals. However, free radical-associated damage is an important factor in many pathological processes. Glycation and oxidative damage cause protein modifications, frequently observed in numerous diseases. Albumin represents a very abundant and important circulating antioxidant. This review brings together recent insights on albumin antioxidant properties. First, it focuses on the different activities of albumin concerning protein antioxidation. In particular, we describe the role of albumin in ligand binding and free radical-trapping activities. In addition, physiological and pathological situations that modify the antioxidant properties of albumin are reported.
[show abstract][hide abstract] ABSTRACT: Diabetes constitutes an increasingly prevalent disease, dramatically associated with an enhanced mortality risk in the developed world. A high prevalence of diabetes has recently been described at Réunion Island, a French department located in the Indian Ocean. At the University of La Réunion, a laboratory course involving students was designed to teach them blood glucose measurements and to examine the influence of food intake on their glycemic response. Using glucose meters, test strips, lancet devices, and sterile lancets, students determined their basal and postprandial glycemia. After plotting the variation over time of their glycemia, students calculated their glycemic response to a meal as the area under the curve. First, students observed that their glycemia had increased rapidly after food intake to values of <1.4 g/l and then decreased to normal values, proving the existence of a physiological regulatory system for glycemia. Using impedance balances, students then determined their body mass index and fat mass percentages. Positive and significant correlations were established between students' fat mass percentages and the glycemic response to the meal. A higher postprandial response was indeed noticed for students having higher fat percentages. Therefore, this laboratory allows students to observe the regulation of glycemia. It also alerts them to the correlation between higher body fat content and a higher glycemic response, which can be related to diabetic disorders. This laboratory constitutes an active illustration of their plenary lesson in endocrinology and particularly for the session dealing with glucose regulation.
[show abstract][hide abstract] ABSTRACT: A positive correlation is well established between obesity and the susceptibility to develop metabolic syndrome, a multifactorial disease dramatically associated with an enhanced mortality risk in the developed world. A high prevalence of obesity has recently been described at La Réunion Island, a French department in the Indian Ocean. Anthropometry is generally considered as the single most easily obtainable, inexpensive, and noninvasive method that reflects body composition. At the University of La Réunion, a laboratory course involving students was designed to teach anthropometric measurements for the determination of body composition. Using skin fold thickness equations, students determined the fat and total muscular masses of their body composition. The influences of sex and their physical activity or inactivity on these different parameters were compared and interpreted at the end of the course. Positive and significant correlations were established between the students' body mass indexes values and their fat mass percentages and between their fat-free and muscular masses as well. A higher fat mass percentage was found in sedentary students compared with more active ones. Therefore, this laboratory makes the students practice and understand the use of classical techniques to evaluate the body composition of a person. It also alerts them to the correlation between a sedentary attitude and higher body fat content. This laboratory course constitutes an active introduction to a following lesson on more recent and actual techniques used to evaluate body composition.