Effects of Dried Onion Powder and Quercetin on Obesity-Associated Hepatic Menifestation and Retinopathy

Abstract

Onion (Allium cepa L.), rich in flavonoids (particularly quercetin), reportedly has anti-obesity properties, but the underlying mechanisms and associated health issues remain unclear. In this study, we compared the effects of dried onion powder (DO) with that of quercetin on high-fat diet (HFD)-induced obesity, nonalcoholic fatty liver disease, and retinal neovascularization. Briefly, rats (n = 9–10 per group) were divided into control, HFD alone (43% fat), HFD + DO (1% DO), HFD + 5DO (5% DO, w/w), and HFD + quercetin (180 mg/kg). After 12 weeks, body fat, markers of metabolism, fatty liver, steatohepatitis, and retinopathy were analyzed. The results revealed that DO and 5DO dose-dependently suppressed body weight, visceral and subcutaneous fat accumulation, and epididymal adipocyte in HFD-fed rats. DO also decreased HFD-induced ALT, AST, free fatty acid, glucose, proinflammatory cytokines, and oxidative stress. DO and 5DO groups had lower triglycerides, total cholesterol, proinflammatory cytokine levels, and ACC-α (a fatty acid synthesis–associated enzyme) expression but higher hepatic antioxidant enzyme activities and fecal lipids. 5DO exhibited better or similar efficacy to quercetin. Both 5DO and quercetin increased fecal levels of acetic acid and butyric acid similarly. They also reduced lipid peroxidation of the eye, retinal adiposity, and neovascularization. However, quercetin resulted in a more apparent decrease in regulation of the Raf/MAPK pathway than DO in eye specimens. Conclusively, DO suppresses visceral, subcutaneous, and liver fat accumulation better than quercetin likely due to higher fecal fat excretion and lower oxidative stress, proinflammatory cytokine levels, and ACC-α expression. Quercetin regulating signal pathways is better than DO at reducing retinal adiposity and neovascularization.

Antioxidant, anti-inflammatory and anti-obesity effects of onion and its by-products in high-fat fed rodents: a systematic review

“…In this review, 22% of the selected articles showed an improvement in the lipid profile, especially in LDL levels, of animals supplemented with onion oil compared to the group that was submitted only to a high-fat diet, confirming the protective effect of onion (Yang et al, 2018). Also, studies have demonstrated improvements in all lipid profiles, with a decreased serum determination of total cholesterol and TG, and an increase in HDL-C, confirming that animals benefited from the powder, tea, oil or extracts of onion concentrated of protocatechuic acid (Benítez et al, 2012;Matsunaga et al, 2014;Emamat et al, 2018;Yang et al, 2018;Grzelak-Błaszczyk et al, 2020;Yu et al, 2021;Chang et al, 2022;Momoh et al,2022).…”

“…The main benefits of onion and its by-products, found in this review, lipid profile and cardiovascular risk with decreased total cholesterol, low-density lipoprotein cholesterol (LDL-C), triglycerides (TG), atherosclerosis index and aorta elastic modulus, and increased high-density lipoprotein cholesterol (HDL-C) (Hamauzu et al, 2011;Benítez et al, 2012;Matsunaga et al, 2014;Emamat et al, 2018;Yang et al, 2018;Grzelak-Błaszczyk et al, 2020;Yu et al, 2021;Momoh et al, 2022;Chang et al, 2022).…”

“…Increased LPS levels in the liver inhibit the fasting-induced adipose factor (Fiaf) that regulates lipoprotein lipase, whose function is to store fat in organs such as the liver and adipose tissue (Poggi et al, 2007;Aguirre and Venema, 2015;Larsen et al, 2019). Studies using powder, oil or extracts of onion concentrated with quercetin monoglycosides showed an improvement in the activity scores of NAFLD, improving the degree of steatosis, decreasing hepatic ALT and AST enzymes and lobular and portal inflammation (Emamat et al, 2016(Emamat et al, , 2018Yang et al, 2018;Grzelak-Błaszczyk et al, 2018;Yu et al, 2021;Chang et al, 2022;Momoh et al,2022).…”

“…Decreased or non-altered mesenteric, epididymal, perirenal, retroperitoneal, inguinal, and weight gain adiposity were also observed (Lee et al, 2012;Benítez et al, 2012;Kim et al, 2012;Moon et al, 2013;Matsunaga et al, 2014;Henagan et al, 2015;Emamat et al, 2016Emamat et al, , 2018Lee et al, 2017;Forney et al, 2018;Yang et al, 2018;Grzelak-Błaszczyk et al, 2018;Yu et al, 2021;Chang et al, 2022).…”

“…Liver abnormalities were also attenuated, with decreases observed in liver enzymes alanine aminotransferase (ALT) and aspartate aminotransferase (AST), the degree of steatosis and lobular and portal inflammation (Emamat et al, 2016(Emamat et al, , 2018Yang et al, 2018;Grzelak-Błaszczyk et al, 2018;Momoh et al, 2022;Chang et al, 2022).…”