Conjugated linoleic acid (CLA), a family of fatty acids found in beef, dairy foods, and dietary supplements, reduces adiposity in several animal models of obesity and in some humans. However, the isomer-specific antiobesity mechanisms of action of CLA are unclear, and its use in humans is controversial. This review will summarize in vivo and in vitro findings from the literature regarding potential mechanisms by which CLA reduces adiposity including its impact on 1) energy metabolism, 2) adipogenesis, 3) inflammation, 4) lipid metabolism, and 5) apoptosis.

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Long-term exposure to peroxisome proliferator-activated receptor g (PPARg) agonists such as rosiglitazone induces browning of rodent and human adipocytes; however, the transcriptional mechanisms governing this phenotypic switch in adipocytes are largely unknown. Here we show that rosiglitazone-induced browning of human adipocytes activates a comprehensive gene program that leads to increased mitochondrial oxidative capacity. Once induced, this gene program and oxidative capacity are maintained independently of rosiglitazone, suggesting that additional browning factors are activated. Browning triggers reprogramming of PPARg binding, leading to the formation of PPARg ''superenhancers'' that are selective for brown-in-white (brite) adipocytes. These are highly associated with key brite-selective genes. Based on such an association, we identified an evolutionarily conserved metabolic regulator, Kruppel-like factor 11 (KLF11), as a novel browning transcription factor in human adipocytes that is required for rosiglitazone-induced browning, including the increase in mitochondrial oxidative capacity. KLF11 is directly induced by PPARg and appears to cooperate with PPARg in a feed-forward manner to activate and maintain the brite-selective gene program.