Association of serum concentrations of retinol and carotenoids with overweight in children and adolescents

Lipid metabolism in mammalian tissues and its control by retinoic acid

Evidence has accumulated that specific retinoids impact on developmental and biochemical processes influencing mammalian adiposity including adipogenesis, lipogenesis, adaptive thermogenesis, lipolysis and fatty acid oxidation in tissues. Treatment with retinoic acid, in particular, has been shown to reduce body fat and improve insulin sensitivity in lean and obese rodents by enhancing fat mobilization and energy utilization systemically, in tissues including brown and white adipose tissues, skeletal muscle and the liver. Nevertheless, controversial data have been reported, particularly regarding retinoids' effects on hepatic lipid and lipoprotein metabolism and blood lipid profile. Moreover, the molecular mechanisms underlying retinoid effects on lipid metabolism are complex and remain incompletely understood. Here, we present a brief overview of mammalian lipid metabolism and its control, introduce mechanisms through which retinoids can impact on lipid metabolism, and review reported activities of retinoids on different aspects of lipid metabolism in key tissues, focusing on retinoic acid. Possible implications of this knowledge in the context of the management of obesity and the metabolic syndrome are also addressed. This article is part of a Special Issue entitled Retinoid and Lipid Metabolism.

Antioxidant intake among Brazilian adults--the Brazilian Osteoporosis Study (BRAZOS): a cross-sectional study

BACKGROUND

Antioxidant nutrient intake and the lesser formation of free radicals seem to contribute to chronic diseases. The aim of the present study was to evaluate the intake profile of the main dietary antioxidants in a representative sample of the adult Brazilian population and discuss the main consequences of a low intake of these micronutrients on overall health.

METHODS

The sample comprised 2344 individuals aged 40 years or older from 150 cities and was based on a probabilistic sample from official data. The research was conducted through in-home interviews administered by a team trained for this purpose. Dietary intake information was obtained through 24-h recall. The Nutrition Data System for Research software program was used to analyze data on the intake of vitamins A, C and E, selenium and zinc, which was compared to Dietary Reference Intakes (DRIs). Differences in intake according to sex, anthropometrics, socioeconomic status and region were also evaluated. The SPSS statistical package (version 13) was used for the statistical analysis. P-values < 0.05 were considered significant.

RESULTS

Higher proportions of low intake in relation to recommended values were found for vitamin E (99.7%), vitamin A (92.4%) and vitamin C (85.1%) in both genders. Intake variations were found between different regions, which may reflect cultural habits.

CONCLUSION

These results should lead to the development of public health policies that encourage educational strategies for improving the intake of micronutrients, which are essential to overall health and prevention of non-communicable diseases.

Antioxidant nutrient intakes and corresponding biomarkers associated with the risk of atopic dermatitis in young children

BACKGROUND/OBJECTIVES

To investigate the association of antioxidant nutritional status with the risk of atopic dermatitis (AD) in young children in a case-control, population-based study.

SUBJECTS/METHODS

Identified from preschools by using the Korean version of the International Study of Asthma and Allergies in Childhood (ISAAC). Final analysis included 180 AD (mean age 5.3+/-0.9 years) and 242 non-AD (mean age 5.2+/-1.0 years) children. Diet was assessed using a validated semi-quantitative food frequency questionnaire. Fasting blood samples were used for analyses of fat-soluble vitamins (retinol, alpha-tocopherol, and beta-carotene) and vitamin C.

RESULTS

AD was associated negatively with intakes of antioxidant-related nutrients. The adjusted odds ratio (OR) and 95% confidence interval (95% CI) were 0.44 (0.22-0.88) for the highest (vs lowest) quintile of beta-carotene. A similar association was observed for dietary vitamin E (OR=0.33, 95% CI=0.16-0.67), folic acid (OR=0.37, 95% CI=0.18-0.73), and iron (OR=0.39, 95% CI=0.19-0.79). Reduced AD risk was found with 1 s.d. increase of serum alpha-tocopherol [OR=0.64, 95% CI=0.41-0.98) and retinol (OR=0.74, 95% CI=0.58-0.96) concentrations, and marginally with that of serum beta-carotene levels (P=0.0749 for trend). There was no relationship of AD risk with dietary and plasma vitamin C as well as nutrient supplement intake regardless of nutrient type. AD was predicted better by the intake measure than the corresponding blood biomarker regarding vitamin E and beta-carotene.

CONCLUSIONS

These findings suggest that higher antioxidant nutritional status reduces the risk of AD and that such risk-reduction effects depend on nutrient type.

Impact of micronutrient deficiencies on obesity

Micronutrient deficiencies have been found in obese individuals across age groups worldwide. While the effects of micronutrient deficiencies on human functions have been studied widely in different populations, there is limited information on how these micronutrient deficiencies affect obese populations. An examination of the available literature suggests associations exist between micronutrient deficiencies and obesity in different populations. These associations and possible mechanisms of the deficiencies' metabolic effects, such as their influence on leptin and insulin metabolism, are discussed here. Further studies are needed to clarify the roles of the different micronutrient deficiencies with respect to obesity and its comorbid conditions.

Nutritional deficiencies in obesity and after bariatric surgery

The presence of nutritional deficiencies in overweight and obesity may seem paradoxical in light of excess caloric intake, but several micronutrient deficiencies appear to be higher in prevalence in overweight and obese adults and children. Causes are multifactorial and include decreased consumption of fruits and vegetables, increased intake of high-calorie, but nutritionally poor-quality foods, and increased adiposity, which may influence the storage and availability of some nutrients. As the obesity epidemic continues unabated and the popularity of bariatric surgery rises for severely obese adults and adolescents, medical practitioners must be aware of pre-existing nutritional deficiencies in overweight and obese patients and appropriately recognize and treat common and rare nutritional deficiencies that may arise or worsen following bariatric surgery. This article reviews current knowledge of nutritional deficits in obese and overweight individuals and those that commonly present after bariatric surgery and summarizes current recommendations for screening and supplementation.

Class III obesity and its relationship with the nutritional status of vitamin A in pre- and postoperative gastric bypass

BACKGROUND

Epidemiological findings have shown the rise of the prevalence of obesity in several segments of the world population, and more recent evidences point to a possible association with vitamin A deficiency (VAD). The aim of this study was to investigate vitamin A nutritional status in individuals with class III obesity in the preoperative period and 30 and 180 days after Roux-en-Y gastric bypass, correlating these findings with lipid profile and body mass index (BMI).

METHODS

The sample was composed of class III obese individuals, males and females, in the preoperative period (T1) and 30 (T2) and 180 days (T3) after bariatric surgery with 5,000 IU of supplementation of retinol acetate. Vitamin A nutritional status was assessed through biochemical indicators (retinol and beta-carotene serum levels), which were quantified by high-performance liquid chromatography with an inadequacy cutoff of <1.05 micromol/L and >or=40 microg/dL, respectively.

RESULTS

Out of the 114 assessed patients, the mean age was 36.9+/-11.6 years and BMI was >or=40 kg/m2. The prevalence of VAD was 14%, being 37.5% in T1, 50.8% and 67.8% in T2, and 52.9% and 67% in T3, according to retinol and serum beta-carotene, respectively. A decrease of retinol and beta-carotene serum levels was observed with BMI increase in T1. An increase of very-low-density lipoprotein cholesterol (VLDLc) and triglycerides was verified with the increase of retinol, being VLDLc in T3 and triglycerides in T1 and T2. In T1, high-dense lipoprotein cholesterol presented a positive and significant correlation with beta-carotene and a negative and significant correlation in T3.

CONCLUSION

High prevalence of VAD in the preoperative period and in 30 and 180 postoperative days, even during supplementation, with higher inadequacy of beta-carotene in all the three studied time periods, probably occurred because of its bioconversion to retinol due to the increased demand to which those individuals were exposed. It is suggested that the oral intake supplementation does not present the expected impact, and the need of assessing the nutritional status of vitamin A in the pre- and postoperative Roux-en-Y gastric bypass is emphasized. High prevalence of VAD in T1, with severity in T2 and T3, corroborates the utilization of the cutoff of <1.05 micromol/L as a VAD marker in the studied segment and reinforces its utilization as a tool in clinical practice to identify VAD in morbid obese patients who underwent bariatric surgery.

Análise crítica de estudos brasileiros sobre deficiência de vitamina A no grupo materno-infantil

OBJETIVO: Apresentar uma análise crítica de estudos da literatura sobre a deficiência de vitamina A (DVA) no Brasil, segundo o indicador bioquímico retinol sérico, considerando-se o impacto negativo da DVA na saúde reprodutiva e no desenvolvimento infantil. FONTES DE DADOS: os bancos de dados Medline e BVS, no período de 1994 a 2007, foram rastreados com a combinação de descritores: "vitamin A deficiency", "Brazil", "pregnant", "children" e "retinol serum level". A inclusão dos artigos foi realizada com base em critérios de elegibilidade referentes à população, desenho do estudo e idioma, enfatizando-se estudos com gestantes, puérperas, nutrizes, lactentes e pré-escolares que não apresentassem doenças crônicas não-transmissíveis ou infecciosas. SÍNTESE DOS DADOS: dos 27 artigos selecionados, 25 eram estudos transversais, um era caso-controle e um estudo longitudinal. Identificou-se que 71% e 25% dos trabalhos com gestantes e crianças, respectivamente, adotaram valores de retinol sérico <1,05µmol/L como ponto de corte. Todos os estudos apontaram a DVA como um problema de proporção preocupante. Reconhece-se a emergente inserção dos adolescentes no grupo de risco potencial para DVA e da antropometria como variável independente para tal deficiência nutricional. CONCLUSÕES: Aponta-se uma necessidade de incluir estratégias de intervenção adicionais à suplementação, reavaliar pontos de corte na interpretação do diagnóstico da DVA e refletir sobre a pertinência da inclusão de novas áreas e grupos com risco potencial para DVA em programas de intervenção.

Penalised regression splines: theory and application to medical research

Generalised additive models (GAMs) allow for flexible functional dependence of a response variable on covariates. The aim of this article is to provide an accessible overview of GAMs based on the penalised likelihood approach with regression splines. In contrast to the classical backfitting, the penalised likelihood framework taken here provides researchers with an efficient computational method for automatic multiple smoothing parameter selection, which can determine the functional form of any relationship from the data. We illustrate through an example how the use of this methodology can help to gain insights into medical research.