Joshua Silva

Dihydromyricetin is a natural bioactive flavonoid with unique GABA_A receptor activity with a putative mechanism of action to reduce the intoxication effects of ethanol. Although dihydromyricetin’s poor oral bioavailability limits clinical utility, the promise of this mechanism for the treatment of alcohol use disorder warrants further investigation into its specificity and druggable potential. These experiments investigated the bioavailability of dihydromyricetin in the brain and serum associated with acute anti-intoxicating effects in C57BL/6J mice. Dihydromyricetin (50 mg/kg IP) administered 0 or 15-min prior to ethanol (PO 5 g/kg) significantly reduced ethanol-induced loss of righting reflex. Total serum exposures (AUC0_→24) of dihydromyricetin (PO 50 mg/kg) via oral (PO) administration were determined to be 2.5 µM × h (male) and 0.7 µM × h (female), while intraperitoneal (IP) administration led to 23.8-fold and 7.2- increases in AUC0_→24 in male and female mice, respectively. Electrophysiology studies in α5β3γ2 GABA_A receptors expressed in Xenopus oocytes suggest dihydromyricetin (10 µM) potentiates GABAergic activity (+43.2%), and the metabolite 4-O-methyl-dihydromyricetin (10 µM) negatively modulates GABAergic activity (−12.6%). Our results indicate that administration route and sex significantly impact DHM bioavailability in mice, which is limited by poor absorption and rapid clearance. This correlates with the observed short duration of DHM’s anti-intoxicating properties and highlights the need for further investigation into mechanism of DHM’s potential anti-intoxicating properties.

Alcohol use disorder (AUD) affects over 18 million people in the US. Unfortunately, pharmacotherapies available for AUD have limited clinical success and are under prescribed. Previously, we established that avermectin compounds (ivermectin [IVM] and moxidectin) reduce alcohol (ethanol/EtOH) consumption in mice, but these effects are limited by P-glycoprotein (Pgp/ABCB1) efflux. The current study tested the hypothesis that dihydromyricetin (DHM), a natural product suggested to inhibit Pgp, will enhance IVM potency as measured by changes in EtOH consumption. Using a within-subjects study design and two-bottle choice study, we tested the combination of DHM (10 mg/kg; i.p.) and IVM (0.5–2.5 mg/kg; i.p.) on EtOH intake and preference in male and female C57BL/6J mice. We also conducted molecular modeling studies of DHM with the nucleotide-binding domain of human Pgp that identified key binding residues associated with Pgp inhibition. We found that DHM increased the potency of IVM in reducing EtOH consumption, resulting in significant effects at the 1.0 mg/kg dose. This combination supports our hypothesis that inhibiting Pgp improves the potency of IVM in reducing EtOH consumption. Collectively, we demonstrate the feasibility of this novel combinatorial approach in reducing EtOH consumption and illustrate the utility of DHM in a novel combinatorial approach.

Herbal remedies are consumed by approximately 50% of the population in the United States for health and wellness, including products promoted for liver health and alcohol (ethanol [EtOH]). Previously, we have shown that dihydromyricetin (DHM), a bioflavonoid, can counteract EtOH intoxication and withdrawal via GABA_A receptor (GABA_AR) activity. Through evaluation of GABA_AR potentiation using DHM, resveratrol, genistein, daidzein, and turmeric, we found that the activity of DHM is unique. Furthermore, using the loss of right reflex induced by EtOH in rats, we discovered that DHM was superior in reducing EtOH intoxication and EtOH actions on GABA_ARs. However, the combination of DHM with turmeric, daidzein, or resveratrol diminished the DHM effects. Here, we report that combinations of DHM should be evaluated, as we have found that combining DHM with other flavonoids diminished efficacy. Collectively, these data support the utility of DHM as a unique antialcohol intoxication therapy.

High circulating lipids occurring in obese individuals and insulin resistant patients are considered a contributing factor to Type 2 Diabetes (T2D). Exposure to high lipids initially causes the beta-cells to expand in population. Long-term exposure to high lipids however is associated with failure of beta-cells and the development of T2D. To prevent the failure of beta-cells and development of Type 2 Diabetes, this study focuses on understanding the molecular mechanisms that underlie this biphasic response of beta-cells to lipid exposure. Using palmitic acid (PA) in cultured beta-cells and islets, we demonstrated that chronic exposure to lipids leads to reduced viability and inhibition of cell cycle progression concurrent with downregulation of a pro-growth/survival kinase AKT, independent of glucose. This AKT downregulation by PA treatment is correlated with a consistent induction of mTOR/S6K activity concurrent with AKT downregulation. Inhibiting mTOR activity restores AKT activity and allows beta-cells to gain proliferation capacity that are lost after high fat diet exposure. In summary, we elucidated a novel mechanism for which lipid exposure may cause the dipole effects on beta-cell growth, where mTOR acts as a lipid sensor. These mechanisms can be novel targets for future therapeutic developments.

Background: Excess alcohol (ethanol, EtOH) consumption is a significant cause of chronic liver disease, accounting for nearly half of the cirrhosis‐associated deaths in the United States. EtOH‐induced liver toxicity is linked to EtOH metabolism and its associated increase in proinflammatory cytokines, oxidative stress, and the subsequent activation of Kupffer cells. Dihydromyricetin (DHM), a bioflavonoid isolated from Hovenia dulcis, can reduce EtOH intoxication and potentially protect against chemical‐induced liver injuries. But there remains a paucity of information regarding the effects of DHM on EtOH metabolism and liver protection. As such, the current study tests the hypothesis that DHM supplementation enhances EtOH metabolism and reduces EtOH‐mediated lipid dysregulation, thus promoting hepatocellular health.Methods: The hepatoprotective effect of DHM (5 and 10 mg/kg; intraperitoneal injection) was evaluated using male C57BL/6J mice and a forced drinking ad libitum EtOH feeding model and HepG2/VL‐17A hepatoblastoma cell models. EtOH‐mediated lipid accumulation and DHM effects against lipid deposits were determined via H&E stains, triglyceride measurements, and intracellular lipid dyes. Protein expression of phosphorylated/total proteins and serum and hepatic cytokines was determined via Western blot and protein array. Total NAD⁺/NADH Assay of liver homogenates was used to detect NAD + levels.Results: DHM reduced liver steatosis, liver triglycerides, and liver injury markers in mice chronically fed EtOH. DHM treatment resulted in increased activation of AMPK and downstream targets, carnitine palmitoyltransferase (CPT)‐1a, and acetyl CoA carboxylase (ACC)‐1. DHM induced expression of EtOH‐metabolizing enzymes and reduced EtOH and acetaldehyde concentrations, effects that may be partly explained by changes in NAD⁺. Furthermore, DHM reduced the expression of proinflammatory cytokines and chemokines in sera and cell models.Conclusion: In total, these findings support the utility of DHM as a dietary supplement to reduce EtOH‐induced liver injury via changes in lipid metabolism, enhancement of EtOH metabolism, and suppressing inflammation responses to promote liver health.