Optimized mixture of hops rho iso-alpha acids-rich extract and acacia proanthocyanidins-rich extract reduces insulin resistance in 3T3-L1 adipocytes and improves glucose and insulin control in db/db mice

Rho iso-alpha acids-rich extract (RIAA) from Humulus lupulus (hops) and proanthocyanidins-rich extracts (PAC) from Acacia nilotica exert anti-inflammatory and anti-diabetic activity in vitro and in vivo. We hypothesized that a combination of these two extracts would exert enhanced effects in vitro on inflammatory markers and insulin signaling, and on nonfasting glucose and insulin in db/db mice. Over 49 tested combinations, RIAA:PAC at 5:1(6.25 ㎍/mL) exhibited the greatest reductions in TNFα-stimulated lipolysis and IL-6 release in 3T3-L1 adipocytes, comparable to 5 ㎍/mL troglitazone. Pretreatment of 3T3-L1 adipocytes with this combination (5 ㎍/mL) also led to a 3-fold increase in insulin-stimulated glucose uptake that was comparable to 5 ㎍/mL pioglitazone or 901 mu g/mL aspirin. Finally, db/db mice fed with RIAA:PAC at 5:1(100 mg/kg) for 7 days resulted in 22% decrease in nonfasting glucose and 19% decrease in insulin that was comparable to 0.5 mg/kg rosiglitazone and better than 100 mg/kg metformin. RIAA:PAC mixture may have the potential to be an alternative when conventional therapy is undesirable or ineffective, and future research exploring its long-term clinical application is warranted.