Dietary FA Research Articles

Impact of dietary FA and energy restriction on plasma leptin and ob gene expression in mice.

The aim of the present study was to elucidate whether the qualitative composition of dietary fat influences plasma leptin and adipose tissue ob gene expression differentially. Two high-fat diets and a diet rich in carbohydrate were each administered both ad libitum and with a 25% energy restriction. The high-fat diets contained 58 energy percent as either monounsaturated FA (MUFA) or saturated FA (SAFA), whereas the carbohydrate-rich diet (CH) contained 7 energy percent as fat. We aimed at obtaining the same final weight for the animals in the ad libitum group as in the energy-restricted groups. This goal was reached at the same time (days 22-24) for all groups except for the ad libitum animals fed on saturated fat (day 36). The plasma leptin concentrations on ad libitum CH and MUFA diets did not differ significantly (24.3 +/- 2.1 and 34.7 +/- 6.7 ng/mL, respectively) whereas the saturated fat diet caused a lower concentration (13.9 +/- 1.9 ng/mL; P < 0.05). Interestingly, no differences in plasma leptin levels between groups were seen in the energy-restricted groups (mean 8.0 +/- 1.0 ng/mL). The type of diet did not alter the ob gene expression in intraabdominal white adipose tissue; however, a lower expression level was found in the energy-restricted groups. The percentage of body fat in the three ad libitum fed groups did not differ (23 +/- 1%). Thus, short-term administration of a diet rich in SAFA suppresses circulating leptin levels without altering the adipose tissue ob gene expression. This indicates that saturated fat may alter protein handling by adipose tissue or the whole body clearance of leptin.

Natural abundance stable carbon isotope evidence for the routing and de novo synthesis of bone FA and cholesterol.

This research reported in this paper investigated the relationship between diet and bone FA and cholesterol in rats raised on a variety of isotopically controlled diets comprising 20% C3 or C4 protein (casein) and C3 and/or C4 nonprotein or energy (sucrose, starch, and oil) macronutrients. Compound-specific stable carbon isotope analysis (delta13C) was performed on the FA (16:0, 18:0, 18:1, and 18:2) and cholesterol isolated from the diet (n = 4) and bone (n = 8) of these animals. The dietary signals reflected by the bone lipids were investigated using linear regression analysis. delta13C values of bone cholesterol and stearic (18:0) acid were shown to reflect whole-diet delta13C values, whereas the delta13C values of bone palmitic (16:0), oleic (18:1), and linoleic (18:2) acids reflected dietary FA delta13C values. Dietary signal differences are a result of the balance between direct incorporation (or routing) and de novo synthesis of each of these bone lipids. Estimates of the degree of routing of these bone lipids gleaned from correlations between delta13C(dlipid-wdiet) (= delta13C(diet lipid) - delta13C(whole diet)) spacings and delta13C(blipid-wdiet) (= delta13C(bone lipid) - delta13C(whole diet)) fractionations demonstrated that the extent of routing, where 18:2 > 16:0 > 18:1 > 18:0 > cholesterol, reflected the relative abundances of these lipids in the diet. These findings provide the basis for more accurate insights into diet when the delta13C analysis of bone fatty FA or cholesterol is employed.

Antihypertensive effects of a dietary unsaturated FA mixture in spontaneously hypertensive rats.

The aim of the present study was to investigate whether a mixture of dietary n-6 and n-3 PUFA could lower blood pressure in spontaneously hypertensive rats (SHR) of different ages. In addition, we studied how such a treatment could normalize the FA composition of plasma TAG and cholesterol esters (CE), and of red blood cell (RBC) total lipids. SHR (ages 4, 19, and 50 wk) were fed a normal diet (control groups) or a semisynthetic diet containing a mixture of gamma-linolenic acid (GLA), EPA, and DHA (experimental groups). Systolic blood pressure was measured at regular intervals. After 11 wk of consuming this diet, plasma TAG and CE were separated by TLC and analyzed for their FA composition. Total FA composition of RBC was also determined. The degree to which blood pressure was elevated was reduced in SHR after 11 wk of diet. The largest decrease was obtained with the oldest animals. In RBC, EPA and DHA contents increased. In plasma TAG and CE, EPA, DHA, and GLA increased whereas arachidonic acid decreased. The n-6 and n-3 unsaturated FA mix slowed the development of hypertension in young SHR and decreased blood pressure in adult and aged SHR. In addition, the present treatment altered the n-3 and n-6 PUFA content of SHR lipids to that seen in normotensive rats.

DIETARY FATTY ACID (FA) EFFECTS UPON GROUP B STREPTOCOCCAL (GBS) INFECTION.† 1893

Dietary FA effects upon the immune response may be mediated in part by effects upon proinflammatory cytokines and eicosanoids. The impact of maternal diet FA composition upon mortality from GAS infection was studied in neonatal rat pups. Methods: Timed pregnant dams were fed, beginning on day 2 of gest. and throughout lactation, either chow (control) or a purified diet whose fat source (22% of cals) was either corn oil (high n6) or menhaden fish oil (high n3). On day 3 of life, pups were culled to 10 pups per dam and were randomly cross-fostered among dams fed the same diets to minimize litter effects. Milk was removed from culled pup stomachs for FA analysis. Exp 1: On day 7 of life, pups were injected i.p. with 0.1 ml of a suspension of GAS Type I as follows: one litter per diet with 106.5 organisms, and one litter per diet with 107.5 organisms. Data from both doses were combined for statistical analyses. Exp 2: On day 7 of life, pups (n=1 litter per diet group) were injected with 107 GAS organisms and sacrificed 48 hours later. Blood was collected for GAS culture and analysis of serum TNFα levels; spleen weights were determined. Results: FA composition of milk reflected maternal diet (Table). Exp 1: 100% of pups in the chow and corn oil groups died within 96 hours, while 33% survived in the fish oil group (p=0.002 fisher's exact (permutation) test). Exp 2: Spleen weights (as% body weight) were significantly higher in the fish vs corn and chow groups. Preliminary cytokine data suggest lower serum levels of TNFα and a trend towards fewer positive blood culture in pups of the fish group. Conclusion: The FA composition pre- and/or postnatal diet may affect immune response to bacterial sepsis. Funded in part by Ross Laboratories.

P.29 Mucosal n3/n6 fatty acid (FA) status in the colorectal adenoma-carcinoma sequence

Background/Aim: Studies on rat models have shown that dietary n3 FA inhibit colon carcinogenesis as compared to n6 FA. Although there are some data in human colon cancer, no study has focused on mucosal n3/n6 FA status in the adenoma-carcinoma sequence. Methods: FAfrom C16:0 to C24:0 were measured by GLC in endoscopic biopsy specimens from human colon cancer (n = 15; 8 Dukes'B, 7 Dukes'C-D), sporadic adenoma of size >1 cm (n = 21; 15 benign, 6 with in situ carcinoma), and associated normal mucosa in all cases. 8 ageand sex-matched patients with normal colon formed the control group. FA in plasma phospholipids, and nutritional/vitamin status were also assessed. Results: There were no differences in nutritional/vitamin status, plasma IFA pattern, and FA levels in normal mucosa between adenoma and control groups. However, there were marked changes in mucosal FA of adenomas as compared with paired normal mucosa: