Comparative effects on blood lipids and faecal steroids of five legume species incorporated into a semi-purified, hypercholesterolaemic rat diet.

The cholesterolaemic effects in rats of a diet (VS) containing Bambara groundnuts (Vigna subterranea), a popular legume eaten in Nigeria, were compared with diets PV, PS, LC and PL, containing baked beans (Phaseolus vulgaris), marrowfat peas (Pisum sativum), lentils (Lens culinaris Medik.) and butter beans (Phaseolus lunatus) respectively. Sixty Sprague-Dawley rats were fed on hypercholesterolaemic semi-purified diets supplemented with 10 g cholesterol and 5 g cholic acid/kg and formulated to provide 40% of energy from fat, as in a typical Western-type human diet. Legumes were substituted for 330 g/kg of the semi-purified diet on a dry-matter basis, which was modified to maintain the same contribution of energy sources as the control diet C3. Another ten rats were fed on control diet C2, which was similar to diet C3 but with no added cholesterol. The rats were fed for 8 weeks and plasma cholesterol levels were measured at weeks 4 and 8. The diets incorporating the five different legume species produced very different cholesterolaemic effects. Diets PV and PL were more potent at lowering raised plasma cholesterol levels than diets PS and LC. Inclusion of the Bambara groundnut into the semi-purified diet resulted in an exaggeration of hypercholesterolaemia. Differences in cholesterol-lowering capacity of the various legume diets in this experiment could not be related to concentrations of faecal bile acids or neutral sterols. However, there was evidence that the inclusion of legumes in the diets reduced the faecal excretion of secondary bile acids.

Comparative effects of four legume species on plasma lipids and faecal steroid excretion in hypercholesterolaemic pigs.

The effect of four species of legume seeds on plasma cholesterol levels and faecal steroid excretion was studied in pigs. Thirty-six growing boars were randomly allocated in groups of six to six diets which they ate continuously for 42 d. The diets fed were: 1, a semi-purified (SP; control group 1) diet; 2, SP + 10 g cholesterol/kg (control group 2); 3, 4, 5, 6, SP + cooked legumes (70:30, w/w; respectively baked beans (Phaseolus vulgaris), peas (Pisum sativum), lentils (Lens culinaris Medik.), butter beans (Phaseolus lunatus)) + 10 g cholesterol/kg. Fasting blood samples were taken on days 0, 14, 28, and 42 for the determination of total plasma cholesterol, high-density-lipoprotein (HDL)-cholesterol and triacylglycerols. Between days 7 and 11 and days 28 and 32 complete 5 d faecal collections were made for the measurement of neutral, acidic and conjugated steroids. After 42 d total cholesterol and HDL-cholesterol levels were raised significantly in all groups, but to different extents. In comparison with control group 2, diet-induced hypercholesterolaemia was significantly inhibited in the groups consuming baked beans, peas and butter beans, although HDL-cholesterol levels were maintained. Faecal steroid excretion by the legume groups was not significantly different from that of control group 2. The results suggest that the mechanism for the hypocholesterolaemic effect does not involve increased hepatic bile acid synthesis and thereby increased cholesterol clearance via the intestinal route.

Measurement of transit time of digesta through sections of gastrointestinal tract of pigs fed with diets containing various sources of dietary fibre (non-starch polysaccharides).

The effects of various sources of dietary fibre (defined as non-starch polysaccharides (NSP] on the transit time (TT) of digesta through sections of digestive tract were measured in pigs of 30-85 kg. The pigs were fitted with simple cannulas in the terminal ileum, caecum and mid-colon. Diets in experiments 1-3 were based on barley, wheat, soya bean meal and fish meal with NSP added in the form of wood cellulose (experiment 1), guar gum (experiment 2), wheat bran, pectin (experiment 3). Lactulose was also included in experiment 3 because of its NSP-like effects. Diets in experiments 4 and 5 were based on starch and casein and contained Phaseoluos vulgaris or Pisum sativum (experiment 4) and sugar beet pulp or wheat bran (experiment 5). Transit time (TT) was measured using 103Ruthenium phenanthroline to label solids and 51Chromium complexed to EDTA for liquids. Samples were taken every 3 h after marker administration for 51 h from all cannulas and the faecal output was collected every 3 h. The values obtained were very variable. The range of TT (h) defined as first arrival of markers and peak marker level was 3-12.2 and 3-12.2 to the ileum, 3-22.3 and 4.5-22.3 to the caecum, 4.5-50.3 and 16.5-48.8 to the colon and 24- less than 51 and 30- less than 51 to the rectum respectively.

Subcutaneous implantation of a ferrocene-mediated glucose sensor in pigs.

Miniature, amperometric glucose sensors were constructed using entrapped 1,1'-dimethylferrocene to mediate electron transfer between immobilised glucose oxidase and a carbon base electrode. Electrodes were calibrated in buffered glucose solutions and then implanted in the subcutaneous tissue of anaesthetised, non-diabetic pigs. Subcutaneous tissue glucose concentrations, as measured by the sensor, were about 20% of blood glucose values, measured by a conventional glucose oxidase assay. After an intravenous 0.07 mol bolus glucose injection, electrode responses increased with almost no time lag, but the subsequent rates of rise and fall of electrode-measured tissue glucose concentrations were slower than that of the blood values. After an intravenous 0.2 U/Kg bolus short-acting insulin injection the electrode response was also rapid, but decreased at a slower rate than the blood glucose concentrations. We conclude that this is a feasible technology for future development as an implantable glucose sensor for use in diabetic man.

The effect of guar gum and level and source of dietary fat on glucose tolerance in growing pigs.

Six growing pigs (30-75 kg) were fed on semi-purified diets containing either 30 g maize oil/kg diet (LFM), 30 g soya-bean oil-tallow mixture (1:1, w/w)/kg diet (LFST) or 160 g soya-bean oil-tallow mixture (1:1, w/w)/kg diet (HFST) without and with the addition of guar gum (40 g/kg diet). Plasma glucose and insulin concentrations following twice daily feeding at 09.00 and 21.00 h were measured, during 24 h periods, in blood sampled from a permanent indwelling vena cava catheter. The source and level of dietary fat had no significant effect on pre-prandial plasma glucose or insulin concentrations except for insulin with diet LFST in the morning (P less than 0.05). Addition of guar gum to the diets had no significant effect on pre-prandial plasma glucose and insulin levels. The peak post-prandial plasma glucose and insulin levels were not significantly affected by dietary fat. The addition of guar gum, however, significantly reduced (P less than 0.05) the peak post-prandial plasma glucose concentration with diets LFM and LFST and also the peak plasma insulin concentration for all diets except for diet HFST in the morning. The time taken to reach the peak post-prandial plasma glucose and insulin concentrations was not significantly affected by dietary fat but it was increased by the addition of guar gum, although the differences were not always significant.

The influence of diet on the exocrine pancreatic secretion of growing pigs.

1. Pancreatic juice was collected from six pigs of 48 kg initial weight fitted with a collection catheter in the pancreatic duct and a return catheter in the duodenum. 2. Measurements of flow and composition of the juice were made during 24 h periods after adaptation to isonitrogenous diets based on barley, wheatings and fish meal (diet BWF) or starch, sucrose, casein, maize oil and cellulose (diet SSC), given in a change-over design. Measurements were also made during the periods of adaptation to a change from one diet to the other. 3. Mean flow-rates for pigs adapted to diets showed a highly significant four-fold difference between diets; values were 4962 ml/d for diet BWF and 1273 ml/d for diet SSC. The hourly volumes of juice were very variable and showed no clear response to feeding and no consistent diurnal pattern for either diet. 4. There were no significant differences between diets in the specific activities of the proteases. Average values were (units/mg protein) trypsin (EC 3.4.21.4) 29.6, chymotrypsin (EC 3.4.21.1) 7.7, carboxypeptidase A diet BWF than with diet SSC. The specific activities and total outputs of alpha-amylase (EC 3.2.1.1) and lipase (EC 3.1.1.3) were significantly higher for diet BWF than for diet SSC; specific activities for the two diets respectively were: (units/mg protein) alpha-amylase 95-6 and 42.3, lipase 59.0 and 14.5. 5. The higher daily volume of juice with diet BWF was associated with significantly (but only slightly) higher levels of both sodium and potassium, compared with diet SSC. 6. The results are discussed in relation to previous studies on digestion at this Institute, in which pigs with intestinal cannulas were given the same diets.

Studies on digestion and absorption in the intestines of growing pigs. 8. Measurements of the flow of total lipid, acid-detergent fibre and volatile fatty acids.

1. Seventeen pigs fitted with single re-entrant cannulas in either the duodenum (posterior to the point of entry of the bile and pancreatic ducts), the mid-jejunum, or the terminal ileum, and a further twenty-four non-cannulated pigs were used. 2. Three diets were used: these contained barley, fine wheat offal, white fish meal, minerals and vitamins (diet BWF); starch, sucrose, maize oil, cellulose, minerals, vitamins and either groundnut meal (diet SSG) or casein (diet SSC). 3. The quantities of total lipid (TL), acid-detergent fibre (ADF) and volatile fatty acids (VFA) passing through the re-entrant cannulas and excreted in the faeces in 24 h were measured. These were used to determine the net absorption (or synthesis or secretion) in the different regions of the intestine. 4. There was substantial secretion of TL into the proximal small intestine and major absorption from the distal portion for all three diets. In the large intestine there was little or no further net absorption for diets SSG and SSC, but significant synthesis or secretion for diet BWF. 5. Fibre digestion occurred in both the small and large intestines and the apparent absorption of ADF in the different regions studied was influenced by diet. 6. There were detectable amounts of VFA at all sites but only at the ileum and in the faeces could they be accurately measured. Diet did not affect the molar proportions of acetate, propionate and butyrate in ileal digesta, but did have an effect on these VFA in the faeces.

Studies on digestion and absorption in the intestines of growing pigs. 7. Measurements of the flow of total carbohydrate, total reducing substances and glucose.

1. Seventeen pigs were fitted with single re-entrant cannulas in either the duodenum (posterior to the entry of the bile and pancreatic ducts), the mid-jejunum, or the terminal ileum. A further twenty-four pigs were used in a conventional digestibility trial. 2. Three diets were used: these contained barley, fine wheat offal, white fish meal, minerals and vitamins (diet BWF) ; starch, sucrose, maize oil, cellulose, minerals, vitamins and either groundnut meal (diet SSG) or casein (diet SSC). 3. The quantities of total carbohydrate (TC), total reducing substances (TRS) and glucose (G) passing through the re-entrant cannulas and excreted in the faeces in 24 h were measured. These were used to determine the net absorption of the carbohydrate fractions in the different regions of the intestine. 4. The small intestine was the principal site of absorption of TC, TRS and G, but there were differences between the diets in the quantities of each of these carbohydrate fractions that were absorbed in the different regions of the small intestine studied. 5. The quantities of TRS and G in solution were very low for all diets at all sites, indicating that the rate of absorption of the products of hydrolysis kept pace with their rate of formation.

Studies on digestion and absorption in the intestines of growing pigs. 2. Measurements of the flow of dry matter, ash and water.

1. Digesta were collected from twenty-three pigs, initially of 30 kg live weight, and fitted with single Ash re-entrant cannulas in either the duodenum, jejunum or ileum. A further twenty-four pigs were used in a conventional digestibility trial. 2. The diets contained: barley, fine wheat offal, white fish meal, minerals and vitamins (diet BWF); starch, sucrose, maize oil, cellulose, minerals, vitamins and either groundnut (diet SSG) or casein (diet SSC). 3. The flow-rates of dry matter (DM), ash and water were measured hourly in the duodenum and jejunum, and every 6 h in the ileum during 24 h collection periods. Faeces were collected during 5 d periods. 4. Marked increases in the flow rates of each of the digesta components after feeding each diet were observed in the duodenum and jejunum, but not in the ileum. The total flow in 24 h periods was much lower in the ileum than at the other sites. 5. Values for the ratio, DM output: intake for DM outputs from the duodenal, jejunal or ileal cannulas, and in faeces, in 24 h periods were respectively 0.94, 0.81, 0.28 and 0.22 for diet BWF; 0.96, 0.76, 0.20 and 0.15 for diet SSG; 0.96, 0.73, 0.08 and 0.04 for diet SSC. The corresponding values for ash were: 1.47, 1.65, 0.74 and 0.53 for diet BWF; 1.28, 1.34, 0.59 and 0.51 for diet SSG; 1.63, 1.35, 0.50 and 0.26 for diet SSC. The corresponding values for water were: 3.49, 3.41, 0.88 and 0.18 for diet BWF, 2.75, 2.80, 0.80 and 0.08 for diet SSG and 2.61, 1.87, 0.23 and 0.01 for diet SSC.