Effects of a High Fructose Diet on Lipogenic Enzyme Activities in Some Organs of Rats Fed ad libitum1
ABSTRACT The effect of a high fructose diet on lipogenesis was studied in rats. Male and female rats were divided into three groups and were fed a high carbohydrate diet ad libitum for 4 days: group 1 was fed a high cornstarch diet, group 2 was fed a high fructose diet without starvation, and group 3 was fed a high fructose diet after 2 days of starvation. The activities of lipogenic enzymes, i.e., glucose-6-phosphate dehydrogenase and malic enzyme were assayed in liver, adipose tissue, and small intestine. The lipid content of liver was also determined. On day 4, the lipid content of group 1 was about 45 mg, that of group 2 was about 70 mg, and that of group 3 was about 115 nig (female) and 145 mg (male) per gram of wet weight. Groups 2 and 3 showed significantly higher activity of hepatic malic enzyme than group 1. The activity of intestinal malic enzyme was highest in group 1 and not significantly different between groups 2 and 3. The malic enzyme activity in adipose tissue of females of group 3 was higher than that in either sex of the other groups. J. Nutr. 105: 1377-1383, 1975. INDEXING KEY WORDS high fructose diet adipose tissue •small intestine
Many investigations have suggested that an excess intake of fructose causes meta bolic disorders (1-7)." An increase in the lipid content of blood or liver and en hanced activities of lipogenic enzymes in the liver have been reported in fructosefed rats. Sugawa-Katayama et al. (8) in vestigated the change with time of glucose-6-phosphate dehydrogenase activity in the liver of rats refed a high fructose diet. Fructose showed a greater effect on the induction of hepatic glucose-6-phosphate dehydrogenase than did glucose. The enzyme activity became maximum be tween 3 to 7 days after the refeeding with either a high fructose or a high glucose diet. After 14 days, the enzyme activity returned to the control level in the liver of glucose-refed rats, but the activity was higher in the fructose-refed rats than in the control rats. Johnson and Sassoon (9), Szepesi and Michaelis (10), and Michaelis and Szepesi ( 11 ) also reported an increase in glucose-6-phosphate dehydrogenase ac tivity in male rats refed fructose for 2 or 4 days. On the other hand, fructose refeed ing had different effects on lipogenic en
•lipogenic enzymes
•liver
•
zymes in adipose tissue than on those in liver (12). Recently a lower activity of lipoprotein lipase in adipose tissue was observed by Cryer et al. (13) in male rats given fructose by stomach tube, and there was a correlation between lipoprotein lipase and serum insulin level (13). The research reported here was de signed to determine whether or not female rats, fed ad libitum, respond to a high fructose diet similarly to male rats. The effects of a high fructose diet on food in take, hepatic lipid and protein contents, and lipogenic enzyme activity in small in testine, liver, and adipose tissue were studied. MATERIALS
AND METHODS
Animals and feeding conditions. Male and female Sprague-Dawley rats,3 four Received (or publication January 27, 1975. 1Effect of high fructose diet, part 1. 2Aoyama, Y., Izumichi, T., Sakakibara, H., Toshida, A. & Asida, K. (1973) Accumulation of hepatic lipids by fructose feeding. Presented at the Annual Meeting of the Agricultural Chemical Society of Japan. Shôwa48, 265. (Abstr.) 3Purchased from CLEA, Japan, Inc., TakatsukI Breeding Laboratory, 4-234 Otsuka-cho, Takatsuki City, Osaka 5(>9, Japan.
1377
Downloaded from https://academic.oup.com/jn/article-abstract/105/11/1377/4768644 by East Carolina University user on 13 January 2019
YOHKO SUGAWA-KATAYAMA AND NOBUKO MORITA Department of Food and Nutrition, Faculty of the Science of Living, Osaka City University, Sugimotocho, Sumiyoshi-ku, Osaka 558, Japan
137S
YOHKO SUGAWA-KATAYAMA
0.1 M Tris-HCl buffer (pH 8.0). The supernatant obtained by centrifugation at 105,000 X g for 60 minutes was used for assay of malic enzyme. In a preliminary experiment,9 it was found that in the upper portion of the small intestine, malic en zyme showed the highest activity, but none was detected in the lower portion. The ratio of the enzyme activity at the upper, intermediate, and lower portions was 3:1:0. In this experiment, the upper portion (30 cm in length) was examined. Determination of lipid content. Liver was homogenized in a CHCl:t-methanol (2:1, v/v) mixture. Lipid extraction was completed by stirring at room temperature for 2 hours with a CHCl:,-methanol (2:1, v/v ) mixture of 20 times the tissue volume. After filtering the residues, the filtrate was washed with a 0.73% NaCl solution of 0.2 times the filtrate volume ( 16). The extracts were washed twice with 0.73% NaCl solu tion, which had been previously equili brated with a CHCl:,-methanol (2:1, v/v) mixture. After the extracts were evaporated to dryness under N2 in vacuo, the weight of the lipids was determined. Statistical analysis. The data given in the tables and figures are the averages of the values ±SEMfrom four rats. Statistical significance was calculated using Student's i test. RESULTS
AND DISCUSSION
Food intake and body weight gain. Each male rat ate approximately 21 g of the laboratory diet daily ( mean ±SEM, 20.7 ±0.5 g), while each female rat ate 4 Purchased from Tanabe Amino Acid Research Foundation, 3-33 Hirano-cho, Higaslii-ku, Osaka 541, Japan.
ABSTRACT The effect of a high fructose diet on lipogenesis was studied in rats. Male and female rats were divided into three groups and were fed a high carbohydrate diet ad libitum for 4 days: group 1 was fed a high cornstarch diet, group 2 was fed a high fructose diet without starvation, and group 3 was fed a high fructose diet after 2 days of starvation. The activities of lipogenic enzymes, i.e., glucose-6-phosphate dehydrogenase and malic enzyme were assayed in liver, adipose tissue, and small intestine. The lipid content of liver was also determined. On day 4, the lipid content of group 1 was about 45 mg, that of group 2 was about 70 mg, and that of group 3 was about 115 nig (female) and 145 mg (male) per gram of wet weight. Groups 2 and 3 showed significantly higher activity of hepatic malic enzyme than group 1. The activity of intestinal malic enzyme was highest in group 1 and not significantly different between groups 2 and 3. The malic enzyme activity in adipose tissue of females of group 3 was higher than that in either sex of the other groups. J. Nutr. 105: 1377-1383, 1975. INDEXING KEY WORDS high fructose diet adipose tissue •small intestine
Many investigations have suggested that an excess intake of fructose causes meta bolic disorders (1-7)." An increase in the lipid content of blood or liver and en hanced activities of lipogenic enzymes in the liver have been reported in fructosefed rats. Sugawa-Katayama et al. (8) in vestigated the change with time of glucose-6-phosphate dehydrogenase activity in the liver of rats refed a high fructose diet. Fructose showed a greater effect on the induction of hepatic glucose-6-phosphate dehydrogenase than did glucose. The enzyme activity became maximum be tween 3 to 7 days after the refeeding with either a high fructose or a high glucose diet. After 14 days, the enzyme activity returned to the control level in the liver of glucose-refed rats, but the activity was higher in the fructose-refed rats than in the control rats. Johnson and Sassoon (9), Szepesi and Michaelis (10), and Michaelis and Szepesi ( 11 ) also reported an increase in glucose-6-phosphate dehydrogenase ac tivity in male rats refed fructose for 2 or 4 days. On the other hand, fructose refeed ing had different effects on lipogenic en
•lipogenic enzymes
•liver
•
zymes in adipose tissue than on those in liver (12). Recently a lower activity of lipoprotein lipase in adipose tissue was observed by Cryer et al. (13) in male rats given fructose by stomach tube, and there was a correlation between lipoprotein lipase and serum insulin level (13). The research reported here was de signed to determine whether or not female rats, fed ad libitum, respond to a high fructose diet similarly to male rats. The effects of a high fructose diet on food in take, hepatic lipid and protein contents, and lipogenic enzyme activity in small in testine, liver, and adipose tissue were studied. MATERIALS
AND METHODS
Animals and feeding conditions. Male and female Sprague-Dawley rats,3 four Received (or publication January 27, 1975. 1Effect of high fructose diet, part 1. 2Aoyama, Y., Izumichi, T., Sakakibara, H., Toshida, A. & Asida, K. (1973) Accumulation of hepatic lipids by fructose feeding. Presented at the Annual Meeting of the Agricultural Chemical Society of Japan. Shôwa48, 265. (Abstr.) 3Purchased from CLEA, Japan, Inc., TakatsukI Breeding Laboratory, 4-234 Otsuka-cho, Takatsuki City, Osaka 5(>9, Japan.
1377
Downloaded from https://academic.oup.com/jn/article-abstract/105/11/1377/4768644 by East Carolina University user on 13 January 2019
YOHKO SUGAWA-KATAYAMA AND NOBUKO MORITA Department of Food and Nutrition, Faculty of the Science of Living, Osaka City University, Sugimotocho, Sumiyoshi-ku, Osaka 558, Japan
137S
YOHKO SUGAWA-KATAYAMA
0.1 M Tris-HCl buffer (pH 8.0). The supernatant obtained by centrifugation at 105,000 X g for 60 minutes was used for assay of malic enzyme. In a preliminary experiment,9 it was found that in the upper portion of the small intestine, malic en zyme showed the highest activity, but none was detected in the lower portion. The ratio of the enzyme activity at the upper, intermediate, and lower portions was 3:1:0. In this experiment, the upper portion (30 cm in length) was examined. Determination of lipid content. Liver was homogenized in a CHCl:t-methanol (2:1, v/v) mixture. Lipid extraction was completed by stirring at room temperature for 2 hours with a CHCl:,-methanol (2:1, v/v ) mixture of 20 times the tissue volume. After filtering the residues, the filtrate was washed with a 0.73% NaCl solution of 0.2 times the filtrate volume ( 16). The extracts were washed twice with 0.73% NaCl solu tion, which had been previously equili brated with a CHCl:,-methanol (2:1, v/v) mixture. After the extracts were evaporated to dryness under N2 in vacuo, the weight of the lipids was determined. Statistical analysis. The data given in the tables and figures are the averages of the values ±SEMfrom four rats. Statistical significance was calculated using Student's i test. RESULTS
AND DISCUSSION
Food intake and body weight gain. Each male rat ate approximately 21 g of the laboratory diet daily ( mean ±SEM, 20.7 ±0.5 g), while each female rat ate 4 Purchased from Tanabe Amino Acid Research Foundation, 3-33 Hirano-cho, Higaslii-ku, Osaka 541, Japan.
