Obesity arises from a combination of genetic, environmental, and behavioral factors. However, the processes that regulate white adipose tissue (WAT) expansion at the level of the adipocyte are not well understood. The Hedgehog (HH) pathway plays a conserved role in adipogenesis, inhibiting fat formation in vivo and in vitro, but it has not been shown that mice with reduced HH pathway activity have enhanced adiposity. We report that mice lacking the HH coreceptor BOC displayed age-related overweight and excess WAT. They also displayed alterations in some metabolic parameters but normal food intake. Furthermore, they had an exacerbated response to a high-fat diet, including enhanced weight gain and adipocyte hypertrophy, livers with greater fat accumulation, and elevated expression of genes related to adipogenesis, lipid metabolism, and adipokine production. Cultured Boc(-/-) mouse embryo fibroblasts showed enhanced adipogenesis relative to Boc(+/+) cells, and they expressed reduced levels of HH pathway target genes. Therefore, a loss-of-function mutation in an HH pathway component is associated with WAT accumulation and overweight in mice. Variant alleles of such HH regulators may contribute to WAT accumulation in human individuals with additional genetic or lifestyle-based predisposition to obesity.
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