Microemulsion-based drug delivery system identifies pepper alkaloids as anti-obesity compounds.

Obesity is a significant contributor to various metabolic diseases such as heart disease and diabetes. Due to the adverse effects of synthetic anti-obesity drugs, natural products from functional food plants, which mimic the effects of synthetic chemicals, present promising alternatives. However, many natural plant-derived compounds are poorly soluble in water, resulting in low bioavailability within the gastrointestinal tract, a key limitation for the effectiveness of many hydrophobic substances. In this study we developed a microemulsion-based drug delivery system in Drosophila, which effectively enhanced the solubility of hydrophobic compounds without noticeable effects on food intake or survival in fruit flies. This system consisted of cremophor EL, ethanol and ethyl oleate (7:6:1), which enabled the establishment of an emulsion-based liquid high-fat diet (LHFD) model, followed by a pilot screening of 161 standard substances from traditional Chinese medicine. We found that piperine (PIP), an alkaloid derived from black pepper, significantly decreased triacylglycerol (TAG) levels in both the intestine and in whole flies. We demonstrated that piperine (1 mg/ml) significantly elevated cytosolic Ca(2+) levels in enterocytes by activating Transient receptor potential (TRP) channels. TRPV1 agonists such as capsaicin and evodiamine (another alkaloid identified during the screening) also exhibited anti-obesity effects. Increased Ca(2+) levels resulted in the suppression of dietary lipase Magro expression through the activation of the transcription factor cAMP response element binding protein (CREB). Furthermore, hydrophobic compounds in the microemulsion were successfully delivered to distal tissues including liver and brain blood vessels in mice, and PIP in the microemulsion was sufficient to reduce body weight in mice. In conclusion, we have developed a microemulsion-based U-GLAD platform for drug delivery, and piperine is identified as a weight-controlling compound, providing a novel approach to the treatment of obesity and its associated symptoms.