Influence of Ultraviolet Radiation on the Association between 25-Hydroxy Vitamin D Levels and Cardiovascular Risk Factors in Obesity.

OBJECTIVE: To establish if the correction with estimates of ultraviolet (UV) exposure influences the association between 25-OH-vitamin D (25OHD) levels and metabolic variables. STUDY DESIGN: A cross-sectional study was performed in 575 obese children and adolescents (>6 years of age) in a tertiary referral center. Cardiovascular risk factors were measured. The estimate of UV exposure was evaluated by 3 methods: (1) season; (2) mean of UV radiation (UVR); and (3) mean of UV index (UVI). UVR and UVI were considered at 1 (UVR 1 month prior to testing [UVR1], UVI 1 month prior to testing [UVI1]) or 3 (UVR 3 months prior to testing [UVR3], UVI 3 months prior to testing [UVI3]) months prior to testing. All analyses were corrected for confounders (sex, age, puberty, body mass index, waist circumference, the inclusion and exclusion of estimates of UV exposure). RESULTS: The 25OHD levels were associated with seasons, UVR1, UVR3, UVI1, and UVI3, and best associations with UVR3 and UVI3. In all models, total cholesterol, low-density lipoprotein cholesterol and triglycerides were negatively associated with 25OHD levels. The strength of the association increased with no correction, correction for seasons, UVR, and UVI. UVR3 and UVI3 performed better than UVR1 and UVI3. CONCLUSIONS: Higher lipid concentrations were associated with low 25OHD levels in obese children and adolescents with the power of the association dependent on the estimates of UVR. As the mean values 3 months prior to testing for both UVR and UVI determined the best associations, the interval of the steady state time of 25OHD levels could be preferentially used in the metabolic studies. Controlling for an estimate of UVR is important to decrease the heterogeneity of studies.

Obesity and infection: two sides of one coin.

The prevalence of obesity has exponentially risen worldwide. The etiology of obesity is multifactorial, and genetic inheritance and behavioral/environmental causes are considered the main etiological factors. Moreover, evidence that specific infections might promote the development of obesity has steadily accumulated. Only a few works investigate the impact of obesity on the immune response to infections and the risk of infections in the obese population. The aim of this paper was to review the available data regarding the various aspects of the association between obesity and infections and to highlight the possibility that infectious agents may have an etiological role in obesity, an idea known as "infectobesity". Several microbes have been considered as possible promoter of obesity, but most of the data concern adenovirus-36 that exerts an adipogenic action mainly via a direct effect on adipose tissue leading to weight gain, at least in animal models.Obesity affects the immune response leading to an increased susceptibility to infections. Obese adults and children show an increased incidence of both nosocomial and community-acquired infections. Furthermore, obesity may alter the pharmacokinetics of antimicrobial drugs and impact on vaccine response. However, the various aspects of the association of obesity infections remain poorly studied, and a call to research is necessary to better investigate the problem.In conclusion, obesity impacts millions globally, and greater understanding of its etiology and its effects on immunity, infections, and prevention and management strategies is a key public health concern.