Herba H outtuyniae Extract Benefits Hyperlipidemic Mice via Activation of the AMPK/PGC-1α/Nrf2 Cascade

Abstract

Hyperlipidemia is associated with metabolic disorders, but the detailed mechanisms and related interventions remain largely unclear. As a functional food in Asian diets, Herba houttuyniae has been reported to have beneficial effects on health. The present research was to investigate the protective effects of Herba houttuyniae aqueous extract (HAE) on hyperlipidemia-induced liver and heart impairments and its potential mechanisms. Male C57BL/6J mice were administered with 200 or 400 mg/kg/day HAE for 9 days, followed by intraperitoneal injection with 0.5 g/kg poloxamer 407 to induce acute hyperlipidemia. HAE treatment significantly attenuated excessive serum lipids and tissue damage markers, prevented hepatic lipid deposition, improved cardiac remodeling, and ameliorated hepatic and cardiac oxidative stress induced by hyperlipidemia. More importantly, NF-E2 related factor (Nrf2)-mediated antioxidant and peroxisome proliferator-activated receptor gamma coactivator-1 alpha (PGC-1α)-mediated mitochondrial biogenesis pathways as well as mitochondrial complex activities were downregulated in the hyperlipidemic mouse livers and hearts, which may be attributable to the loss of adenosine monophosphate (AMP)-activated protein kinase (AMPK) activity: all of these changes were reversed by HAE supplementation. Our findings link the AMPK/PGC-1α/Nrf2 cascade to hyperlipidemia-induced liver and heart impairments and demonstrate the protective effect of HAE as an AMPK activator in the prevention of hyperlipidemia-related diseases.

Keywords: AMP-activated protein kinase; Herba houttuyniae; hyperlipidemia; mitochondrial biogenesis; oxidative stress.

Figure 1

Herba houttuyniae aqueous extract (HAE) attenuated serum hyperlipidemia and ameliorated hepatic lipid metabolic disorders. (A) Serum TG content. (B) Serum TC level. (C) Serum c-LDL level. (D) Serum FFA level. (E) Serum LDH activity. (F) Serum MDA level. (G) Serum ALT activity. (H) H&E staining of liver tissue. (I) Liver TG level. (J) Liver TC level. (K) Liver FAS, ACC1, and CPT1L protein expression (left, western blot image; right, statistical analysis). The values are the means ± S.E.M. (n = 8); * p < 0.05; ** p < 0.01.

Figure 2

HAE improved cardiac remodeling. Con, control; P407, poloxamer 407; P407 + HAE, poloxamer 407 plus HAE at 200 mg/kg/day. (A) Echocardiogram images and quantitative analyses of (B) IVSd, (C) IVSs, (D) LVPWd, (E) LVIDd, (F) LVIDs, (G) LV-Vol-d, and (H) LV-Vol-s. (I) Heart mRNA contents of ANP, BNP, and ACTA1. The values are the means ± S.E.M. (n = 8); * p < 0.05; ** p < 0.01.

Figure 3

HAE activated the AMPK pathway in mice livers and hearts. Con, control; P407, poloxamer 407; P407 + HAE, poloxamer 407 plus HAE at 200 mg/kg/day. Total proteins were prepared from mice livers and hearts, and p-AMPK as well as AMPK protein contents were determined by western blot. (A) Western blot image, (B) the statistical analysis of p-AMPK, and (C) the ratio of p-AMPK/AMPK in mice livers. (D) Western blot image, (E) the statistical analysis of p-AMPK, and (F) the ratio of p-AMPK/AMPK in mice hearts. The values are the means ± S.E.M. (n = 8); * p < 0.05; ** p < 0.01.

Figure 4

HAE ameliorated oxidative stress by upregulating the phase II enzyme pathway in mice livers and hearts. Con, control; P407, poloxamer 407; P407 + HAE, poloxamer 407 plus HAE at 200 mg/kg/day. (A) Liver protein carbonyl content (left, western blot image; right, statistical analysis). (B) Liver SOD, GST, GPX, and γ-GCS activities. (C) The liver GSH/GSSG ratio. (D) Heart protein carbonyl content (left, western blot image; right, statistical analysis). (E) Heart SOD, GST, GPX, and γ-GCS activities. (F) The heart GSH/GSSG ratio. (G) Liver Nrf2, NQO1, HO1, and MnSOD protein expression (left, western blot image; right, statistical analysis). (H) Heart Nrf2, NQO1, HO1, and MnSOD protein expression (left, western blot image; right, statistical analysis). The values are the means ± S.E.M. (n = 8); * p < 0.05; ** p < 0.01.

Figure 5

HAE activated the mitochondrial biogenesis pathway in mice livers and hearts. Con, control; P407, poloxamer 407; P407 + HAE, poloxamer 407 plus HAE at 200 mg/kg/day. (A) Protein levels of liver PGC-1α and mitochondrial complex subunits I–V (left, western blot image; right, statistical analysis). (B) Liver mtDNA copy number. (C) Liver ATP level. (D) Protein levels of heart PGC-1α and mitochondrial complex subunits I–V (left, western blot image; right, statistical analysis). (E) Heart mtDNA copy number. (F) Heart ATP level. The values are the means ± S.E.M. (n = 8); * p < 0.05; ** p < 0.01.

Figure 6

HAE improved mitochondrial complex activity in mice livers and hearts. Con, control; P407, poloxamer 407; P407 + HAE, poloxamer 407 plus HAE at 200 mg/kg/day. (A) Liver mitochondrial complex I–V activity. (B) Heart mitochondrial complex I–V activity. The values are the means ± S.E.M. (n = 8); * p < 0.05; ** p < 0.01.