Cinnamon plays a key role in the anti-obesity action of Hachimijiogan by ameliorating leptin resistance in the hypothalamus.

OBJECTIVES

Hachimijiogan (MIX8), a traditional herbal formulation comprising eight crude drugs, is used clinically to alleviate symptoms associated with cold conditions. Although anti-obesity effects have been suggested, the bioactive constituents and underlying mechanisms remain poorly understood. Thus, we aimed to identify the key bioactive components responsible for the anti-obesity effects of MIX8 and elucidate the underlying mechanisms.

METHODS

Modified MIX8 formulations lacking processed aconite root (PAR) (MIX7) or PAR and cinnamon (MIX6) were administered to diet-induced obese C57BL/6J mice. Body weight, fat mass, insulin sensitivity, hepatic lipid accumulation, and circulating leptin levels were evaluated. To assess the underlying mechanisms, a leptin challenge test was conducted following cinnamon extract administration.

KEY FINDINGS: MIX7 suppressed weight gain, adipocyte hypertrophy, systemic insulin resistance, hepatic steatosis, and hyperleptinemia. MIX6 failed to suppress weight gain, implicating cinnamon as having anti-obesity activity. Cinnamon extract enhanced the acute anorexigenic response to leptin and restored hypothalamic leptin signalling, indicating the reversal of central leptin resistance.

CONCLUSIONS

Cinnamon is an essential component of MIX8 that mediates its anti-obesity effects by restoring central leptin sensitivity. The present study provides mechanistic insights into the pharmacological basis of MIX8, supporting the preventive potential of cinnamon in managing diet-induced obesity.