Gene R. Herzberg

The Influence of Dietary Fatty Acid Composition on Lipogenesis

The steps involved in the conversion of nonlipid precursors into lipid are illustrated in Fig. 1 a. These steps may be conveniently divided into four parts: 1. Generation of cytoplasmic acetyl-CoA. 2. Conversion of acetyl-CoA to fatty acyl-CoA, predominantly palmitoylCoA. 3. Incorporation of fatty acyl-CoA into triglyceride. 4. Generation of NADPH for fatty acid synthesis by fatty acid synthetase. Lipid synthesis and its regulation have been the subject of a number of recent reviews (Geelen et al.,1980; Freedland and Szepesi, 1971; Numa, 1974; Numa and Yamashita, 1974; Romsos and Leveille, 1974; Volpe and Vagelos, 1976). Readers who desire a more detailed treatment than presented below are advised to consult one or more of these reviews.

Visual acuity development and fatty acid composition of erythrocytes in full-term infants fed breast milk, commercial formula, or evaporated milk

&NA; The effects of feeding breast milk (BM), commercial formula (F), or evaporated cow milk (EM) formula on visual acuity and erythrocyte phosphatidylethanolamine fatty acid levels were examined in full‐term infants. Visual acuity was assessed at 3, 6 (BM, F, EM), and 18 (BM, EM) months, and erythrocyte phosphatidylethanolamine levels were determined at birth, 3, and 6 months of age. Visual acuity was significantly higher in the BM‐fed than in the EM‐fed group at 3 months and at 6 months, with intermediate but not significantly different values in the F‐fed group at both ages. Docosahexaenoic acid levels were significantly higher in the BM‐fed than in the F‐fed or EM‐fed group at 3 and 6 months of age and were lowest in the F‐fed group; this might be related to high levels of linoleic acid in F. F‐fed and EM‐fed infants had lower arachidonic acid levels than did BM‐fed infants at 3 months but not at 6 months.

Regulation of hepatic lipogenesis by dietary maize oil or tripalmitin in the meal-fed mouse

1. The effect of varying dietary levels of maize oil and tripalmitin (0--250 g fat/kg) on hepatic lipogenesis and the levels of hepatic fatty acid synthetase (FAS), glucose-6-phosphate dehydrogenase (EC 1.1.1.49; G6PD), malic enzyme (EC 1.1.1.38, 1.1.1.39, 1.1.1.40; ME) and glucokinase (EC 2.7.1.2; GK) was examined in meal-fed mice. 2. Meal-fed mice compared to mice fed ad lib. show enhanced hepatic lipogenesis as demonstrated by an increased rate of in vivo fatty acid synthesis and increased levels of FAS, ME and G6PD. The level of GK in meal-fed mice was unchanged by meal feeding. 3. Maize oil more effectively reduced in vivo hepatic lipogenesis than tripalmitin in meal-fed mice. 4. Maize oil more effectively reduced the hepatic levels of FAS, G6PD, ME and GK than tripalmitin in meal-fed mice. 5. The increased inhibition by maize oil observed at all levels of fat in the diet investigated and has been shown not to be due to decreased carbohydrate intake nor to differences between the absorption of maize oil and tripalmitin.

Triacylglycerol composition of adipose tissue, muscle and liver of rats fed diets containing fish oil or corn oil

Abstract The effect of dietary fish oil and corn oil on the fatty acid composiion of triacylglycerol in adipose tissue, muscle and liver was studied for a period of seven weeks in young, growing rats. In all tissus, three fatty acids, palmitic (16:0), oleic (18:1, n-9) and linoleic (18:2, n-6) accounted for approximately 85% of the fatty acids in corn oil-fed and 65% in fish oil-fed rats. Eicosapentaenoic acid (20:5, n-3, EPA) and docosahexaenoic acid (22:6, n-3, DHA) were very low or undetectable in animals consuming corn oil. In rats consuming fish oil, these fatty acids each accounted for approximately 4% of the fatty acids present. However, in liver these two fatty acids accounted for about 25% of the triacylglycerol fatty acids by week two which declined to about 11% by week seven. Interestingly, in all tissues, EPA was underrepresented relative to DHA compared with their content in the diet. This suggests that there is either selective utilization of EPA or selective retention of DHA. The results confirm the effect of diet fatty acid composition on triacylglycerol composition and show clearly that long chain n-3 fatty acids are efficiently stored in triacylglycerol deposits of tissues.

The role of dietary protein in hepatic lipogenesis in the young rat.

1. The effect of varying dietary levels of casein (40-140 g/kg) on hepatic lipogenesis and the levels of hepatic fatty acid synthetase (FAS), glucose-6-phosphate dehydrogenase (EC 1.1.1.49; G6PD), malic enzyme (EC 1.1.1.40; ME), citrate cleavage enzyme (EC 4.1.3.8; CCE), acetyl CoA carboxylase (EC 6.4.1.2; AcCx), glucokinase (EC 2.7.1.2; GK), and pyruvate dehydrogenase (PDH) was examined in young, growing rats. 2. The activities of AcCx, FAS, G6PD and in vivo fatty acid synthesis were generally found to increase with increased dietary protein. 3. The levels of GK and PDH were not related to dietary protein. 4. ME decreased with increasing dietary protein. 5. The results demonstrate a dissociation between hepatic fatty acid synthesis and ME and suggest that when rats consume low-protein diets the NADPH needed for fatty acid synthesis is generated primarily by ME but that as the level of dietary protein is increased the contribution of ME is reduced while that of the phosphogluconate pathway becomes more important.

Thiamine, Riboflavin, Folate, and Vitamin B12 Status of Low Birth Weight Infants Receiving Parenteral and Enteral Nutrition

Thirty infants were randomly assigned to receive either 3 mL of MVI-Pediatric supplement (PAR3 group, parenterally fed) or 2 mL (PAR2 group, parenterally fed). For the first week, 100% received total parenteral nutrition (TPN), 50% by the second, and less than 33% by the third. Eighteen control infants received enteral feeds of infant formula. Baseline (before TPN) and subsequent weekly blood samples, dietary data, and 24-hour urine collections were obtained. The adequacies of thiamine and riboflavin were assessed by the thiamine pyrophosphate effect and erythrocyte glutathione reductase activity, respectively. Urinary thiamine and riboflavin levels were measured by fluorometry. Plasma folate, red blood cell folate, urinary folate, and plasma vitamin B12 concentrations were determined by radioassay. No differences between groups were observed in thiamine pyrophosphate effect, erythrocyte glutathione reductase activity, urinary B1 or B2, or red blood cell folate levels at any time. Plasma folate differed (p less than .05) among the PAR3 group (24 +/- 7 ng/mL), and both the PAR2 (13 +/- 5 ng/mL) and enterally fed (ENT) groups (16 +/- 3 ng/mL) before the initiation of feeds, at week 1 (PAR3 = 32 +/- 15 ng/mL; PAR2 = 18 +/- 4 ng/mL; ENT = 19 +/- 9, ng/mL) and between the PAR3 (30 +/- 16 ng/mL) and PAR2 (16 +/- 4 ng/mL) infants at week 2. Plasma vitamin B12 levels differed among the ENT groups (551 +/- 287 pg/mL) and both the parenteral groups (PAR2 = 841 +/- 405 pg/mL; PAR3 = 924 +/- 424 pg/mL) at week 1 and between the ENT (530 +/- 238 pg/mL) and PAR3 (999 +/- 425 pg/mL) groups at week 2.(ABSTRACT TRUNCATED AT 250 WORDS)

Role for fatty acid binding protein in the regulation of hepatic lipogenesis by dietary linoleic acid

Abstract The effect of added dietary ethyl palmitate or ethyl linoleate on hepatic lipogenic enzymes and the amount of hepatic fatty acid binding protein was examined in meal-fed rats. Dietary linoleate reduced the activities of fatty acid synthetase, glucose-6-phosphate dehydrogenase, NADP-malic enzyme, ATP-citrate lyase, and the amount of fatty acid binding protein compared to rats fed a fat-free or palmitate supplemented diet. The possible role of fatty acid biding protein in the regulation of lipogenesis by dietary fat is discussed.

Eicosapentaenoic acid is oxidized more rapidly than docosahexaenoic acid by muscle and liver

Abstract Fatty acid oxidation was studied in soleus muscle homogenates and hepatocytes from rats. Eicosapentaenoic acid (20:5, n-3) was oxidized faster than docosahexaenoic acid (22:6, n-3) by muscle homogenates and isolated hepatocytes. Ketogenesis was greater from eicosapentaenoic acid in isolated hepatocytes. These observations may explain the previously reported under-representation of eicosapentaenoic acid relative to docosahexaenoic acid in triacylglycerol stores of fish oil-fed rats.

Fasting-induced, selective loss of fatty acids from muscle triacylglycerols

We studied the loss of fatty acids from soleus muscle triacylglycerol (TAG) in rats fasted for 48 hours. During the 48 h fast the TAG content of the muscle decreased from 2.432 ± 0.632 mg to 1.376 ± 0.354 mg (X ± s.d, n=8.) although the muscle weight was unchanged (0.255 ± 0.016 vs. 0.273 ± 0.032 g). Fatty acid mobilization was calculated as the percentage of the mass of a given fatty acid lost during the fast. The average mobilization for all fatty acids was 43.2%. The mobilization of individual fatty acids, varied from 30% for 20:1, the least mobilized fatty acid to 78.5% for EPA (20:5 n3) the most mobilized fatty acid. The polyunsaturated fatty acids were mobilized to a significantly greater extent than the monounsaturated and saturated fatty acids. This resulted in an enrichment in monounsaturated and saturated fatty acids in the muscle TAGs following the fast.

Effects of dietary fish oil and corn oil on bile flow and composition in rats

Abstract A study was undertaken to compare the effects of n-3 and n-6 fatty acids on bile flow and bile composition in rats. Male Sprague-Dawley rats were fed diets containing either 10% corn oil or 8% fish oil (MaxEPA) and 2% corn oil for a period of 2 weeks. At the end of the feeding period, rats were fitted with exteriorized cannulas in the duodenum and bile duct. While a glucose-saline solution was infused through the duodenal cannula at 3.0 mL/h, bile was collected hourly for 6 hours. Bile secretion was found to be greater in the fish oil fed rats than the corn oil fed animals. As a function of bile flow per hour, the bile acid, cholesterol and phospholipid output appeared to be greater in the group receiving fish oil. However, when concentration was determined, the effect of diet disappeared. Diet had an effect on the fatty acid composition of bile phospholipids. Rats fed fish oil had significantly more eicosapentaenoic and docosahexaenoic acids in the bile phospholipids than those fed corn oil while those fed corn oil had higher levels of arachidonic acid.