Genetic and Environmental Relationships Between Change in Weight and Insulin Resistance: The Healthy Twin Study

Genetic and environmental associations between insulin resistance and weight-related traits and future weight change

OBJECTIVES

The aims of this study were to investigate the association between initial insulin resistance (IR), weight status, and precedent weight change (PWC) and future weight change and the genetic and environmental contributions affecting these relationships in a prospective cohort of Korean twins and their family members.

METHODS

The PWC (weight change from 20 y of age), baseline body mass index (BMI), baseline homeostasis model assessment of IR (HOMA-IR) score, and future weight change (follow-up interval 3.28 ± 1.32 y) of 1565 adults were assessed. The mixed linear model was applied after adjusting for intrafamilial relationship, age, education, health behaviors, chronic diseases, dietary intake, eating restraint, and menopausal status of women at baseline. A bivariate genetic analysis was performed after adjusting for age and sex.

RESULTS

In the model that simultaneously included all predictors and confounding factors, inverse associations were observed between PWC and baseline HOMA-IR score and future weight change in men, and only baseline BMI was inversely associated with future weight change in women. Men and women with BMI ≥25 kg/m², HOMA-IR score ≥2.5, and PWC greater than or the same as the sex-specific median of PWC were more likely to lose weight than those with the combination of the counterparts. Approximately 63.6% of the correlation between the baseline HOMA-IR score and future weight change was attributed to genetic effects, and 68.4% to 91.3% of the correlations between weight-related traits and future weight change were correlated to environmental effects.

CONCLUSION

An inverse association was observed between the initial IR, weight status, and PWC and future weight change, and genetic or environmental factors contributed to these relationships.

Predation risk modulates diet-induced obesity in male C57BL/6 mice

OBJECTIVE

In this study, the behavioral and physiological changes induced by experimentally varying the risk of predation in male mice fed a high-fat diet were examined. In particular, the study aimed to assess whether the risk of being predated modulates the body weight gain, providing an ecological context for the obesity resistance observed in many species of small mammals.

METHODS

Body weight, food intake, physical activity, and core body temperature of 35 male C57BL/6 mice were monitored for 20 days, while feeding a high-fat diet. A third of the animals were exposed to elevated risk of predation through exposure to the sounds of nocturnal predatory birds, and these were compared to animals exposed to a neutral noise or silence.

RESULTS

Male mice exposed to predation risk had significantly lower weight gain than the neutral or silent groups. Reduced food intake and increased physical activity were the main proximal factors explaining this effect. The risk of predation also induced changes in boldness.

CONCLUSIONS

This study provides evidence supporting the role of predation risk on body weight gain of small mammals.