Biomedical subjects

A B Awad

Publications and source records attributed to A B Awad.

At least 19 recordsLinked to original sources

PubMed1997

Type of dietary fiber, not fat, alters phospholipase D and ornithine decarboxylase activities in the rat large intestine.

We investigated the effect of dietary fatty acid composition (n-6 vs. n-3) and fiber (highly fermentable vs. less fermentable) on the activities of phospholipase D (PLD) and ornithine decarboxylase (ODC) in the rat large intestine (cecum and proximal and distal colon). Twenty-four Sprague-Dawley rats (215-270 g) ate synthetic diets with 2% safflower oil plus 21.5% safflower or fish oil and 10% cellulose or guar gum for four weeks. Cecal bile acids and free fatty acids were higher in rats fed guar gum than in rats fed cellulose. Rats fed fish oil had more proximal colonic mucosal and cecal bile acids than those fed safflower oil. PLD activity was 23% lower in the proximal colon of rats fed guar gum than in those fed cellulose, but the mucosal weight was not different. ODC activity was lower but cecal mucosal wet weight was higher in the cecum of the rats fed guar gum than in the cecum of the rats fed cellulose. The activities of PLD and ODC are affected by dietary fiber and may not be accurate markers for tissue growth in the colonic mucosa.

Animals↗

PubMed1997

Effect of dietary phytosterols on cell proliferation and protein kinase C activity in rat colonic mucosa.

The present study investigated the role of phytosterols in colonic cell proliferation and examined the possible role of protein kinase C (PKC) in this process. A total of 18 male Sprague-Dawley rats weighing 240-270 g were fed, for a period of 22 days, one of three experimental diets: a control diet, a diet supplemented with 0.2% cholic acid, or a diet supplemented with 0.2% cholic acid + 2% dietary phytosterols. Two hours before decapitation, animals were injected with 5'-bromo-2'-deoxyuridine (BrdU, 50 mg/kg body wt ip). Cell proliferation in the proximal colon was measured using a monoclonal antibody to BrdU. PKC activity in the proximal colonic mucosa was assayed using a myelin basic protein as a substrate. Cell proliferation was significantly increased by 276% with 0.2% cholic acid feeding compared with controls. The presence of 2% phytosterols in the diet abolished the cholic acid-induced hyperplasia. Cholic acid induced a 31% expansion of the proliferative zone. Only the cytosolic PKC was significantly lower in the phytosterol-fed group. Neither the total PKC nor the particulate PKC demonstrated an effect of phytosterols on enzyme activity. In conclusion, we found that dietary supplementation with 2% phytosterol has a significant protective effect on enhanced cell proliferation and that this effect is not mediated through the PKC system.

Animals↗

PubMed1996

The effect of unsaturated fatty acids on membrane composition and signal transduction in HT-29 human colon cancer cells.

The objective of the present study was to investigate the effect of membrane fatty acid (FA) composition on the activity of phospholipase C (PLC) in HT-29 human colon cancer cells. The membrane FA composition was altered by supplementing cultured cells with FAs of different composition. The FAs were stearic acid (18:0; SA), gamma linolenic acid (18:3 omega 6; gamma LnA); alpha linolenic acid (18:3 omega 3; alpha LnA;); eicosapentaenoic acid (20:5 omega 3; EPA) and docosahexaenoic acid (22:6 omega 3; DHA). The fatty acids were supplemented as a FA/BSA complex. Cells supplemented with SA served as the control. Tumor growth was followed by counting the number of cells in culture. The results indicate that polyunsaturated fatty acid (PUFA) supplementation had no consistent effect on tumor growth from 1 day to another throughout the 15 days of growth. The fatty acid composition of membranes indicates that cells incorporated and modified the supplemented fatty acids by desaturation, elongation and retroconversion. The unsaturation index (UI) of membranes of cells supplemented with EPA and DHA was higher than other groups. PLC activity; measured in the absence of GTP gamma(S) in the assay mixture; was not influenced by membrane FA modification. However, in the presence of GTP gamma(S) PLC of cells supplemented with 18:3(omega 6) was the lowest among the groups. It has been shown that 18:3(omega 6) accumulated the most in the phosphatidylethanolamine (PE) fraction. There was a negative correlation between the activity of PLC in the presence of G protein activation and PE 18:3 (omega 6) content without affecting UI. It was concluded that G protein may be sensitive to the level of 18:3(omega 6) content and not to the general fluidity of the membranes.

Animals↗

PubMed1996

Effect of membrane lipid alteration on the growth, phospholipase C activity and G protein of HT-29 tumor cells.

The objective of the present study was to examine the effect of modifying the fatty acid composition of membranes on cell growth and phosphoinositide specific phospholipase C (PLC) activity in HT-29 colon cancer cells. Cells were seeded at a density of 12 x 10(3) cells/cm2 and supplemented with 30 microM of either 18:0, 18:2 (n6) or 18:3 (n3) complexed to bovine serum albumin (BSA) in DMEM medium. Cell growth was followed for 12 days. The 18:0 supplemented cells (control) reached maximum growth at day nine which was greater than either 18:2 (n6) or 18:3 (n3) supplemented cells. There was no difference between the latter two groups in their growth. To investigate the fatty acid incorporation of the supplemented fatty acid and how they may influence composition in the cell membrane, we examined the fatty acid composition of each phospholipid (PL) species. Both phosphatidylcholine (PC) and phosphatidylethanolamine (PE) were significantly influenced by the type of fatty acid supplemented. Supplementation with 18:0 resulted in HT-29 cell membranes having more monounsaturated fatty acids than the cells grown in the other fatty acids. Polyunsaturated fatty acid (PUFA) supplementation (both 18:2 and 18:3) resulted in the enrichment of PUFA in the PL fractions. Cells supplemented with 18:3 (n3) had the highest unsaturation index in membrane PE as compared to the other phospholipid species. PLC activity of the membranes was measured using PIP2 as a substrate in the presence of 15 micrograms alamethicin and 42 microM free calcium. The contribution of G protein to the activity of the enzyme was assessed using GTP gamma(S). PLC activity of HT-29 cells was 16% higher in the presence of GTP gamma(S) response. GTP gamma(S)-activated PLC activity of 18:3 (n3) supplemented cells was 81% of those supplemented with either 18:0 or 18:2 (n6) cells. It is concluded that the decrease in cell proliferation with supplementation with 18:3 (n3) may be mediated through its inhibitory effect on PLC, which provides the second messengers for protein kinase C (PKC) activation. PLC may be influenced by an increased unsaturation index of the PE fraction of the HT-29 tumor cell membranes.

Alamethicin↗

PubMed1995

18:1 n7 fatty acids inhibit growth and decrease inositol phosphate release in HT-29 cells compared to n9 fatty acids.

Studies have shown that trans fatty acids may play a role in the development of chronic diseases such as heart disease and cancer. The objective of the present project was to examine the effect of supplementation with 18:1 isomers, both positional and geometrical, as compared to 18:0 on the growth, membrane fatty acid composition and the phosphoinositide cycle of HT-29 human colon cancer cells. Cells were supplemented with 30 microM stearic acid (18:0), elaidic acid (18:1, n9, trans), oleic acid (18:1, n9, cis), vaccenic acid (18:1, n7, cis) or trans-vaccenic acid (18:1, n7, trans) as sodium salts complexed to fatty acid-free bovine serum. Cells were grown in these media for 9 days. Cell growth was examined by counting the number of cells and expressed as percentage of control (18:0 supplemented cells). The phosphoinositide (PI) cycle was examined by measuring the inositol phosphate (IP) released from phosphoinositides in the absence (basal) or presence of stimuli (0.1 mM carbachol, 0.1 mM A23187 or 20 mM NaF). The results obtained indicated that cis and trans n7 fatty acids inhibited the growth of HT-29 cells by 11% and 23%, respectively, as compared to 18:0 supplementation. 18:1, n9 had no effect on tumor growth. Supplementation with all forms of 18:1 resulted in an increase in IP and IP2 production as compared to 18:0 supplemented cells without influencing IP3. The presence of the double bond at the 9 position in the supplemented fatty acid increases total IP production by 59% and in the cis form by 37% above the control. The breakdown of phosphoinositides in the absence and presence of several stimuli supports the observed finding on IP. Trans fatty acid supplementation resulted in lower hydrolysis of PI as compared to cis fatty acids. It is concluded that the observed inhibition of tumor growth by the vaccenic acids may be mediated by their effect(s) on the PI cycle which may be associated with their incorporation into membrane lipids.

Cell Division↗

PubMed1995

Prostaglandin synthesis in human cancer cells: influence of fatty acids and butyrate.

Previous research has suggested that prostaglandins (PGs) may play a role in the development of colon cancer since tumor cells produce more PGs than normal cells. However, the exact mechanism by which PGs play a role in the development of cancer is not known. In addition, factors that influence PG synthesis are not known since they are complicated by the presence of homeostatic mechanisms. To avoid the homeostatic mechanisms, the present research was designed to examine factors that may influence PG synthesis in an in vitro system, i.e., a tissue culture. We have chosen two human colon cancer cell lines that differ in their ability to metabolize long-chain fatty acids (LCFAs), LS174T cells and HT-29 cells. We examined the effect of LCFAs on their membrane fatty acid composition, growth, and ability to release the main PGs (PGE2 and PGI). The LCFAs used were those most common in the colonic lumen [18:0, 18:2 (n-6), and 18:3 (n-3)]. In addition, we examined the effect of butyrate on the above mentioned parameters. Butyrate is produced in the colon through fermentation of dietary fibers. The data obtained suggest that although both of these tumor cell lines are of human colonic origin, they differ in their response to LCFAs and butyrate in some of the characteristics studied, such as growth, composition of membranes, and the relationship between membrane FA composition and PG synthesis. Polyunsaturated fatty acid supplementation stimulated the growth of HT-29 cells but not of LS174T cells when compared with growth in media supplemented with 18:0.(ABSTRACT TRUNCATED AT 250 WORDS)

Butyrates↗

PubMed1995

In vitro [U-14C]glucose utilization by tissues of weanling rats with lateral hypothalamic area lesions one month after lesion production.

The role of the lateral hypothalamic area (LHA) in intermediary metabolism was investigated by quantitation of [U-14C]glucose oxidation to 14CO2 and 14C incorporation into the glycogen and lipid fraction of the liver, epididymal fat pad, and diaphragm. Weanling male Sprague-Dawley rats received bilateral electrolytic lesions in the LHA (LHAL rats). Sham operated rats were either fed ad libitum (CON-ADLIB) or pair-gained to the LHAL rats (CON-PG). The experiment was terminated 1 month after lesion production. LHAL rats were significantly (SIG) lighter and shorter and ate less than CON-ADLIB; LHAL rats were also SIG shorter than CON-PG, pointing to a food intake-independent lesion effect. Both LHAL and CON-PG rats had SIG less percent carcass fat than CON-ADLIB, but there was no SIG difference between LHAL and CON-PG rats. Also, LHAL rats had a SIG higher percentage of carcass protein than both CON-ADLIB and CON-PG. Furthermore, LHAL rats incorporated SIG less glucose into liver glycogen than CON-ADLIB but SIG more into CON-PG, whereas CON-PG rats incorporated SIG less into liver glycogen than CON-ADLIB, again suggesting a food intake-independent effect. There was no difference among the groups in glucose oxidation and incorporation into lipids and glycogen in both diaphragm and epididymal fat pads and liver total lipid. However, livers of CON-PG metabolized SIG more [U-14C]glucose to CO2 than did livers of CON-ADLIB, suggesting a food intake-dependent effect. There was no difference between LHAL and CON-PG rats in this parameter.(ABSTRACT TRUNCATED AT 250 WORDS)

Adipose Tissue↗

PubMed1994

In vitro activation and inhibition of rat colonic phospholipase D by fatty acids.

The present study was designed to examine the effect of long-chain fatty acids on phospholipase D (PLD) of the proximal colon mucosa of the rat. These fatty acids are present in the colon, in close contact with the membranes which contain the enzyme. The results indicate that unsaturated fatty acids activate the enzyme. At 4 mM, trienes are more potent activators as compared to 18:2 and 18:1. The number of double bonds and the configuration around the double bond were found to be important factors in activation of the enzyme. The metabolism of polyunsaturated fatty acids may be involved in the activation since the presence of antioxidants and cyclooxygenase inhibitors were found to influence the activation of PLD by polyunsaturated fatty acids.

Animals↗

PubMed1994

Influence of dietary fat and feeding period on phosphoinositide metabolism in rat colonocytes.

The objective of the present study was to examine the effect of dietary fat content on phosphoinositide (PI) metabolism, fatty acid composition in colonocytes, and colonic luminal content of bile acids (BA) and free fatty acids (FFA) in rats. Male Sprague-Dawley rats weighing approximately 166 g were fed to semipurified diet containing 3% or 21.5% beef fat and 2% corn oil. The nonfat ingredients were adjusted to correct for differences in food consumption of these diets. Animals were fed these diets ad libitum for one or four weeks. The isolated colonocytes had a viability of 88.9% in all groups. PI metabolism was examined in the absence (basal) or presence of agonists, 2 mM deoxycholic acid or 10 microM A23187. Dietary fat concentration had no effect on PI metabolism, but the length of feeding had a significant effect on basal and stimulated PI metabolism. Colonocytes of animals fed the diets for four weeks were less sensitive to stimulation of PI cycle by agonists than those of animals fed for one week. Colonocyte fatty acid composition was influenced by dietary fat and feeding period. Only the relative percentage of 20:3(n-6) was significantly lower in rats fed the high-fat diet for one week; 18:0 was lower and 18:3(n-6) was higher in colonocytes of animals fed the diets for one week than in those fed for four weeks. Several colonic fatty acids, namely, 16:0, 20:3(n-6), and 22:5(n-6), also exhibited diet-by-feeding period interaction. Intracolonic luminal contents from rats fed the high-fat diet contained elevated concentrations of BA and FFA (44% and 62%, respectively). It was concluded that despite the effects of dietary fat concentration on increased colonic BA and FFA and on altered membrane fatty acid composition, dietary fat had no effect on PI metabolism in colonocytes under the conditions in the present experiment. A difference in components between the purified diet and the commercial rat chow and/or an aging effect of the rats may alter the PI cycle of colonocytes.

Animals↗

PubMed1994

Differential response of glucose utilization by three rat muscle tissues to dietary fatty acid composition.

Rats were fed a semisynthetic diet containing 14% of either beef fat, safflower oil, or menhaden oil plus 2% corn oil for 7 weeks, and three tissues, diaphragm, heart, and skeletal muscle, were examined for fatty acid composition in their phospholipids and triglycerides. In addition, the lipid concentrations in these tissues were examined. The in vitro oxidation and incorporation of glucose into lipids of these tissues were also examined. Skeletal muscle showed the greatest change in phospholipid composition with diet. All tissues were responsive to changes in diet in regards to the triglyceride fraction. Dietary alteration of tissue phospholipid composition did not alter lipid concentration in these tissues. However, in diaphragm tissue, rats fed the beef fat diet had lower phospholipid and higher triglyceride synthesis compared with those fed either menhaden oil or safflower oil. In addition, triglyceride synthesis was higher in the diaphragm of animals fed the menhaden oil diet as compared with the safflower oil diet. Therefore, dietary fatty acid composition may play a role in the triglyceride and phospholipid metabolism of rat diaphragm.

Animals↗

PubMed1994

Effect of dietary fat on metabolic adjustments to maximal VO2 and endurance in runners.

The present study examined the effects of dietary manipulations on six trained runners. The percent energy contributions from carbohydrate, fat, and protein were 61/24/14, 50/38/12, and 73/15/12 for the normal (N), fat (F), and carbohydrate (C) diets, respectively. Expiratory gases and blood responses to a maximum (VO2max) and a prolonged treadmill run were determined following 7 d on each diet. Free fatty acids (FFA), triglycerides, glycerol, glucose, and lactate were measured. Dietary assessment of subjects' N diet indicated that they were consuming approximately 700 kcal.d-1 less than estimated daily expenditures. Running time to exhaustion was greatest after the F diet (91.2 +/- 9.5 min, P < 0.05) as compared with the C (75.8 +/- 7.6 min, P < 0.05) and N (69.3 +/- 7.2 min, P < 0.05) diets. VO2max was also higher on the F diet (66.4 +/- 2.7 ml.kg-1 x min-1, P < 0.05) as compared with the C (59.6 +/- 2.8 ml.kg-1 x min-1, P < 0.05) and N (63.7 +/- 2.6 ml.kg-1 x min-1, P < 0.05) diets. Plasma FFA levels were higher (P < 0.05) and glycerol levels were lower (P < 0.05) during the F diet than during the C and N diets. Other biochemical measures did not differ significantly among diets. These data suggest that increased availability of FFA, consequent to the F diet, may provide for enhanced oxidative potential as evidenced by an increase in VO2max and running time. This implies that restriction of dietary fat may be detrimental to endurance performance.

Analysis of Variance↗

PubMed1993

Alteration of membrane fatty acid composition and inositol phosphate metabolism in HT-29 human colon cancer cells.

The present study was designed to investigate the role of membrane fatty acid (FA) composition on inositol phosphate (InsP) release by a human colon tumor cell line. Cells were supplemented for five days in culture with 0, 10, 30, or 100 microM sodium stearate (18:0), linoleate [18:2(omega-6)], or linolineate [18:3(omega-3)]. These FAs were supplied as a complex with FA-free bovine serum albumin. InsP release was examined in these cells with or without stimulation with deoxycholic acid (DCA) after they were labeled with [3H]myoinositol. FA enrichment was found to influence inositol incorporation into membrane lipids. Although 18:0 had no effect, 18:2(omega-6) decreased the incorporation. On the other hand, 18:3(omega-3) increased the incorporation of inositol compared with the cells supplemented with the other FAs, but they were not different from control. Basal release of total InsP was elevated only with supplementation of 10 and 30 microM 18:3(omega-3). FA supplementation with 18:0 at 30 microM and 18:2 at 30 and 100 microM resulted in downregulation of bsal release of InsP. Enrichment of HT-29 cell membranes with polyunsaturated FAs resulted in a significant increase in stimulated release of InsP, but this was not seen with saturated FA supplementation. At 10 microM supplementation, 18:2 had the greatest effect on stimulated InsP release. This effect of 18:2 disappeared at 30 microM. However, the increase in the stimulated InsP release caused by 18:3 occurred at 10 and 30 microM. DCA-stimulated release of InsP was not downregulated by any FA supplementation. This study showed that enrichment of the membranes with polyunsaturated FAs increases the response of the phosphatidylinositol cycle to DCA stimulation. In addition, enrichment with 18:3(omega-3) increases the basal turnover of InsP. It is concluded that alteration of membrane FAs has a profound effect on the phosphatidylinositol cycle.

Colonic Neoplasms↗

PubMed1993

Differential effect of butyrate on lipids of human colon cancer cells.

Recently, we demonstrated that treatment of LS174T cells with 2 mM butyrate for one day had a significant effect on the composition of cellular fatty acids. In an attempt to further explore this phenomenon, we investigated the effect of long-term butyrate treatment in the presence of different fatty acids in the medium on cellular phospholipids (PLs) and triacylglycerol (TG). Cells were supplemented with 100 microM sodium salts of 18:2 (n-6), 20:4 (n-6), 20:5 (n-3), or 22:6 (n-3) as a fatty acid-free-albumin complex. The molar ratio of the albumin and these long-chain fatty acids (LCFAs) was 3:1. One-half of these cultures were supplied with 2 mM butyrate, and the pH was adjusted to 7.4. The supplementation of the LCFAs and butyrate was maintained for eight days. The present study indicates that butyrate had a differential effect on the fatty acid composition of PLs and TG of LS174T cells. This includes an increase in monounsaturates and elongation of the supplemented LCFA, and this effect was more pronounced on TG than PL fatty acids. Butyrate resulted in a significant reduction in polyunsaturated fatty acid concentration only in PLs. In general, butyrate decreased the unsaturation index (UI) of the PLs but increased that of TG. The present study also confirmed our previous observation regarding the effect of LCFAs on cellular lipids. PL and TG fatty acid chain lengths reflect those of supplemented fatty acids. The UI of these two lipid fractions increased more with supplementation of n-3 than n-6 fatty acids.(ABSTRACT TRUNCATED AT 250 WORDS)

Butyrates↗

PubMed1993

Effect of dietary fat on glomerular lipid composition and angiotensin II receptors.

Nutritional factors are major etiologic determinants which may affect the incidence or severity of hypertension. Since angiotensin II (Ang II) has a role in some forms of hypertension, the influence of dietary lipid composition on glomerular lipid content and on Ang II receptor parameters was determined. Three groups of rats were fed diets containing 14% by weight of 1) beef fat (saturated fatty acid rich), 2) safflower oil (n-6 fatty acid rich), or 3) fish oil (n-3 fatty acid rich), each supplemented with 2% corn oil. A fourth group of rats was fed rat chow which contained 6.5% fat. At the end of 7 weeks, the rats were sacrificed, the kidneys removed, and renal glomeruli isolated using a sieving technique. Feeding diets which varied in the quantity and composition of fatty acids altered glomerular fatty acid composition of n-6 and n-3 fatty acids and the unsaturation indices of glomeruli. The cholesterol content, but not the phospholipid content, was decreased in glomeruli of animals fed the high fat diets. This resulted in a lower cholesterol/phospholipid ratio, indicative of an increase in membrane fluidity. Glomerular binding was determined using 125I-Ang II in a radioreceptor assay. Binding was proportional to glomerular protein and was time dependent. Receptor affinity (Ka) and number were determined by Scatchard analysis of binding inhibition data. Glomerular Ka was significantly lower for animals fed the rat chow as compared to the semisynthetic diets. There was no significant difference in the concentration of Ang II receptors in glomeruli of animals fed the different diets. The data indicate that the induced alteration in glomerular lipid composition is associated with alteration in the binding affinity of glomerular Ang II receptors.

Animals↗

PubMed1991

Influence of butyrate on lipid metabolism, survival, and differentiation of colon cancer cells.

The present work was designed to study the differentiating effect of butyrate on LS174T cells after modification of their lipids with long-chain fatty acid (LCFA) supplementation. The LCFAs 18:1(n-9), 18:2(n-6), 20:4(n-6), 20:5(n-3), and 22:6(n-3) bound to added to the media of confluent cells for eight days. The fatty acid-to-albumin ratio was 3:1. The concentration of fatty acids in the media was 100 microM. On the last day, half of the flasks were treated with 2 mM butyrate. The data indicate that supplementation with polyunsaturated LCFAs having 20-22 carbon atoms resulted in a significant reduction in cell density and viability, whereas all LCFA supplementation reduced differentiation as measured by alkaline phosphatase activity. Butyrate treatment increased the density, viability, and differentiation of the tumor cells. The effect of butyrate on differentiation was mainly with cells supplemented with 18:1, 20:5, and 22:6. In the absence of LCFA supplementation, butyrate reduced the concentration of 22:5(n-6) in the cellular lipids. Also, butyrate modified the LCFAs incorporated in cells supplemented with 18:2 and 20:5, with changes occurring in 20:5(n-3), 22:5(n-3), and 22:5(n-6). Thus the present study suggests an interaction between butyrate and LCFA on differentiation and LCFA metabolism of human colon cancer cells.

Adenocarcinoma↗

PubMed1991

Dietary fat and phospholipase A2 activity of Sprague-Dawley rat large intestine.

The present studies were conducted to examine the effect of dietary lipid content and composition [(n-6) vs. (n-3) fatty acids] on the activity of mucosal phospholipase (PL)A2 of the large intestinal tract of rats. Three segments of the large intestinal tract were examined: cecum, proximal colon and distal colon. Weanling male Sprague-Dawley rats were fed diets containing either 5% (LS) or 16% safflower (HS) or 14% menhaden oil plus 2% safflower oil (HM) for 3 wk with the oil replacing starch in the HS and HM diets on a weight basis. The lipid extracts of microsomal fractions from mucosal scrapings were examined for phospholipid and cholesterol content and fatty acid composition. Phospholipase A2 was assayed using a fluorescent substrate. Rats fed the high fat diets had lower PLA2 specific activities. The (n-3) or (n-6) fatty acid enrichment of the membranes had no effect of the activity of the enzyme. The activity of the enzyme decreased aborally from the cecum to the distal colon; the proximal colon had an intermediate specific activity.

Animal Nutritional Physiological Phenomena↗

PubMed1990

Effect of excess dietary calcium on colon mucosal membranes and fecal lipids.

The objective of the present studies was to examine the biochemical alterations in colon apical membranes upon feeding excess calcium to animals on a saturated fatty acid-rich diet. It has been suggested recently that excess dietary calcium may offer a protection to colon membranes as judged by histologic examination. Sprague-Dawley weanling male rats were fed a semisynthetic diet containing 14% beef fat plus 2% corn oil and either the calcium requirement or excess calcium in the form of calcium carbonate. Animals were fed the diets for 4 weeks. Feces were collected in the last 3 days. The results indicate that excess dietary calcium resulted in alteration in the density of 4 protein bands of colon apical membranes upon examination on SDS-gel electrophoresis. These bands contain 20% of membrane proteins. The diet had no effect on either the lipid content or fatty acid composition of the membranes. Excess dietary calcium resulted in a 54% reduction in fecal water bile acids and a 44% reduction in fecal water free fatty acids. The reduction in fecal water lipids was due to alterations in the solubility of these lipids. This was not mediated through alterations in the pH of fecal water. The observed alterations in protein patterns of these membranes may be due to either the reduction of fecal water bile acids and free fatty acids or may be a direct effect of dietary calcium on membrane proteins.

Animals↗

PubMed1990

Effect of dietary fat on the lipid composition and utilization of short-chain fatty acids by rat colonocytes.

The objective of the present studies was to examine the effect of dietary fat on the lipid composition of rat colonocytes and their utilization of short-chain fatty acids (SCFA). Rats were fed 14% beef fat, fish oil or safflower oil plus 2% corn oil in a semi-synthetic base diet for 4 wk. Colonocytes were isolated and their lipid composition was examined. Feeding beef fat and fish oil resulted in an increase in monounsaturated fatty acids and a reduction in omega-6 fatty acids. Feeding fish oil resulted in an enrichment with omega-3 fatty acids. There was no dietary influence on the amount of either cholesterol or phospholipids of colonocytes. Fish oil feeding resulted in significant increase in colonocyte free fatty acids (FFA) as compared to other diets. Dietary fat was found to have no effect on SCFA utilization by colonocytes. Colonocytes were found to utilize SCFA in the order of butyrate greater than or equal to acetate greater than or equal to propionate. The presence of acetate and propionate in the medium had no effect on the rate of butyrate utilization.

Animals↗