You Jin Lee; Yang Yoon Kyoung; You Jin Kim; Oran Kwon

doi:10.4163/jnh.2015.48.1.1

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Lee, Kyoung, Kim, and Kwon: Effects of an aqueous extract of purple sweet potato on nonalcoholic fatty liver in high fat/cholesterol-fed mice∗

Research Article

Progress in Medical Physics 2015;48(1):1-8.

Published online: 19 January 2015

DOI: https://doi.org/10.4163/jnh.2015.48.1.1

Effects of an aqueous extract of purple sweet potato on nonalcoholic fatty liver in high fat/cholesterol-fed mice^∗

You Jin Lee¹, Yang Yoon Kyoung², You Jin Kim¹, Oran Kwon^1,^†

¹Department of Nutritional Science and Food Management, Ewha Womans University, Seoul 120-750, Korea

²Department of Nutritional Science and Food Management, Soongeui Women's College, Seoul 100-751, Korea

^†To whom correspondence should be addressed. tel: +82-2-3277-6860, e-mail: orank@ewha.ac.kr

^∗ This study was performed with the support of the Food Functionality Evaluation Program funded by the Ministry of Agriculture, Food and Rural Affairs through Korea Food Research Institute and "Cooperative Research Program for Agriculture Science & Technology Development (Project title: Research on New Functional Food Materials with Domestic Agricultural Products, Project No. PJ00845002)" Rural Development Administration, Republic of Korea.

Received 12 November 2014 Revised 14 December 2014 Accepted 28 January 2015

This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/3.0/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Purpose:

Anthocyanins from purple sweet potato (PSP) have been investigated in vitro and in animals and found to have a protective effect against oxidative hepatic damage. In this study, we investigated that aqueous extract of PSP can ameliorate the dysfunction of lipid metabolism in mice fed a high fat/cholesterol diet.

Methods:

Forty C57BL/6J mice were randomly divided into 5 groups (n = 8) and fed one of the following diets for 8 weeks; normal fat (NF) diet; high fat/ cholesterol (HFC) diet; HFC with 1.25% PSP (HFPL) diet; HFC with 2.5% PSP (HFPM) diet; HFC with 5% PSP (HFPH) diet.

Results:

Nonalcoholic fatty liver was manifested in the HFC group by showing increased levels in plasma alanine aminotransferase (ALT) activity, total cholesterol (TC) and low density lipoprotein cholesterol (LDL-C), increased level of TC and presence of many large lipid droplets in the liver, and increased fat cell size in the HFC group compared with the NF group. However, administration of HFC induced a significant decrease in food intake, resulting in decrease in fat mass. Coadministration of PSP did not lead to reversal of body weight changes, ALT activity, and lipid levels in plasma and the liver, but suppressed excess enlargement of the fat cell size through increasing carnitine palmitoyltransferase-1 (CPT-1) gene expression in the liver. Accordingly, the number of fat droplets in the liver was reduced in PSP administered groups.

Conclusion:

Taken together, these results suggest that PSP may have a protective effect on the dysfunction of lipid metabolism. Conduct of further studies on the coordinated regulation of PSP for lipid metabolic homeostasis at the liver-adipose tissue axis is needed.

Keywords: purple sweet potato, aqueous extract, high fat/cholesterol diet, nonalcoholic fatty liver

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Fig. 1.

Effects of purple sweet potato extract on food intake and body weight in high fat/cholesterol diet-fed C57BL/6 mice: (A) food intake, (B) energy intake, (C) total body weight gain and (D) body weight changes by week. NF, normal fat control; HFC, high fat control; HFPL, HFC + PSP 1.25%; HFPM; HFC + PSP 2.5%; HFPH, HFC + PSP 5%. Values are expressed as Mean ± SE (n = 8 for each group). Means with different letters on the bar are significantly different from each other at p < 0.05 by Duncan's multiple range test.

Fig. 2.

Effects of purple sweet potato extract on liver enzymes in plasma and liver histology in high fat/cholesterol-fed C57BL/6 mice: (A) AST, (B) ALT and (C) liver histology. NF, normal fat control; HFC, high fat control; HFPL, HFC + PSP 1.25%; HFPM; HFC + PSP 2.5%; HFPH, HFC + PSP 5%. Values are expressed as Mean ± SE (n = 8 for each group). Means with different letters on the bar are significantly different from each other at p < 0.05 by Duncan's multiple range test. Histology bar represents 50 μm.

Fig. 3.

Effects of purple sweet potato extract on plasma lipid levels in high fat/cholesterol-fed C57BL/6 mice: (A) TG, (B) TC, and (C) LDL-C. NF, normal fat control; HFC, high fat control; HFPL, HFC + PSP 1.25%; HFPM; HFC + PSP 2.5%; HFPH, HFC + PSP 5%. Values are expressed as Mean ± SE (n = 8 for each group). Means with different letters on the bar are significantly different from each other at p < 0.05 by Duncan's multiple range test.

Fig. 4.

Effects of purple sweet potato extract on lipid and mRNA levels in the liver of high fat/cholesterol-fed C57BL/6 mice: (A) TC, (B) TG, and (C) mRNA levels. NF, normal fat control; HFC, high fat control; HFPL, HFC + PSP 1.25%; HFPM; HFC + PSP 2.5%; HFPH, HFC + PSP 5%; SREBP-1c, sterol regulatory element-binding protein-1c; FAS, fatty acid synthase; CPT-1, carnitine palmitoyltransferase-1. Values are expressed as Mean ± SE (n = 8 for each group). Means with different letters on the bar are significantly different from each other at p < 0.05 by Duncan's multiple range test.

Fig. 5.

Effects of purple sweet potato extract on fat mass and epididymal fat tissue histology in high fat/cholesterol-fed mice: (A) adipose tissue weight and (B) adipose tissue histology. NF, normal fat control; HFC, high fat control; HFPL, HFC + PSP 1.25%; HFPM; HFC + PSP 2.5%; HFPH, HFC + PSP 5%. Values are expressed as Mean ± SE (n = 8 for each group). Means with different letters on the bar are significantly different from each other at p < 0.05 by Duncan's multiple range test. Histology bar represents 50 μm.

Table 1.

Composition of experimental diets¹⁾(Unit: g/kg diet)

Ingredients	Group NF	High-fat/cholesterol diet
Ingredients	Group NF	HFC	HFPL	HFPM	HFPH
Cornstarch	150	150	150	150	150
Sucrose	500	337	324.5	312	287
Casein	200	200	200	200	200
Corn oil	50	30	30	30	30
Lard	0	170	170	170	170
Cholesterol	0	10	10	10	10
Sodium cholate	0	3	3	3	3
Cellulose	50	50	50	50	50
Mineral mix#200000²⁾	35	35	35	35	35
Vitamin mix#300050³⁾	10	10	10	10	10
DL-Methionine	3	3	3	3	3
Choline Bitrate	2	2	2	2	2
Purple sweet potato	0	0	12.5	25	50
Total	1,000	1,000	1,000	1,000	1,000
Total calorie (kcal)	3,920	4,708	4,708	4,708	4,708
Carbohydrates (% as k	kcal) 67.5	42	42	42	42
Protein (% as kcal)	20.8	17	17	17	17
Lipid (% as kcal)	11.7	41	41	41	41

¹⁾ NF, normal fat control (AIN 73A diet); HFC, high fat control; HFPL, HFC + PSP 1.25%; HFPM, HFC + PSP 2.5%; HFPH, HFC + PSP 5% 2) Mineral mixture (g/kg mix): CaHPO₄ 500; NaCl 74; K₂H₆O₇H₂O 220; K₂SO₄ 52; MgO 24; MnCO₃ 3.50; Fe(C₆H₅O₇)·6H₂O₆; ZnCO₃ 1.6; CuCO₃ 0.3; KIO₃ 0.01; Na₂SeO₃·5H₂O 0.01; CrK(SO₄)₂ 0.55; sucrose, finely powdered 118 3) Vitamin mixture (g/kg mix): thi-amin·HCl 0.6; riboflavin 0.6; pyridoxin·HCl 0.7; niacin 3.0; calcium pantothenate 1.6; folic acid 0.2; biotin 0.02; vitamin B12 (0.1%) 1.0; vitamin A palmitate (500,000 IU/g) 0.8; vitamin D3 (400,000 IU/g)0.25; vitamin E acetate (500 IU/g) 10.0; menadione sodium bisulfate 0.08; sucrose finely powdered 981.15

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