In This Issue

Visceral fat induces T-cell-mediated lymph node apoptosis in mice

Obesity is known to impair the immune system. Obese patients are more susceptible to cancer and infectious disease. Because high-fat intake promotes obesity and contributes to its pathology, Kim et al. sought to assess the impact of a high-fat diet on lymph nodes in adipose tissue. The authors found that the mesenteric lymph nodes of mice fed a high-fat diet were significantly smaller than those from control animals. Greater T-cell activation and apoptosis were also observed in the mesenteric lymph nodes of the fat-fed mice. These findings suggest that visceral fat contributes to mesenteric lymph node atrophy, which could account for the immunity impairment caused by obesity. See page 1261

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Postpartum depression doubles weight-retention risk

Herring and colleagues have found that postpartum depression more than doubles the likelihood of retaining at least 5 kg of the weight gained during pregnancy 1 year after childbirth. Adjustments for mediators such as physical inactivity, lack of sleep, and poor diet only moderately reduced this risk. The authors speculate that the decline in serotonin that accompanies postnatal decreases in estrogen and progesterone may cause sufferers to consume more carbohydrate-rich foods to regulate serotonin and alleviate depression. The higher cortisol levels in postpartum depression may also increase appetite and visceral fat accumulation in these women. Because weight retained postpartum tends to be deposited centrally and is therefore more physiologically harmful, future work examining the impact of depression management on weight loss is needed. See page 1296

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Staying the course: adolescent weight-control program attrition and response trends

The prevalence of obesity has increased dramatically in children and adolescents over the past few decades, but the efficacy of weight-control programs developed for adolescents varies greatly. For this age group in particular, factors that affect attrition rates and program response need further study. Looking for such predictors in an adolescent weight-control program, Jelalian et al. found that parental BMI had a significant impact on participant retention. Adolescents whose parents had an elevated BMI were nearly five times more likely to drop out of the 16-week program. Ethnic minority participants were less likely to lose 5% or more of their body weight, and a univariate analysis indicated a higher rate of attrition in this group. This study highlights the importance of developing adolescent-oriented intervention programs that consider the potential impact of ethnicity and parental BMI in enrollment and response. See page 1318

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β2 protein variant in Japanese Americans suggests role of obesity

Mice with defects in the integrin αMβ2 are predisposed to obesity when fed a Western diet rich in fat. Studies in humans, however, have previously shown no association between variations in the β2 gene ITGB2 and obesity. A study by Awaya et al. evaluating the incidence of an ITGB2 polymorphism and obesity in native Japanese and Japanese American populations suggests a link. Japanese Americans who were homozygous for the rs235326 polymorphism showed a threefold greater susceptibility for obesity compared with C carriers, a trend not observed in native Japanese. Because Japanese Americans tend to adopt a high-fat Westernized diet, both genetics and environment may determine the impact of β2 defects in humans. See page 1463

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