Physiological effects of resistant starches on fecal bulk, short chain fatty acids, blood lipids and glycemic index

OBJECTIVE

To assess the effects on fecal bulking, fecal short chain fatty acid (SCFA) production, blood lipids and glycemic indices of two different forms of resistant starch (RS2 and RS3) from a high-amylose cornstarch.

METHODS

Twenty-four healthy subjects (12 men; 12 women) consumed four supplements taken for 2 weeks in random order separated by 2-week washout periods. The supplements were a low-fiber (control) and supplements providing an additional 30 g dietary fiber as wheat bran (high-fiber control) or the equivalent amount of resistant starch analyzed gravimetrically as dietary fiber from RS2 or RS3. Four-day fecal collections and 12-hour breath gas collections were obtained at the end of each period. Fasting blood was taken at the beginning and end of each period. Glycemic indices of supplements were also assessed.

RESULTS

The wheat bran supplement increased fecal bulk 96+/-14 g/day compared with the low-fiber control (p<0.001) with the mean for both resistant starches also being greater (22+/-8 g/day) than the low-fiber control (p=0.013). On the resistant starch phases, the mean fecal butyrate:SCFA ratio, which has been suggested to have positive implications for colonic health, was significantly above the low-fiber control by 31+/-14% (p=0.035). Resistant starches did not alter serum lipids, urea or breath H2 or CH4. No significant differences in glycemic index were seen between the RS and control supplements.

CONCLUSION

The potential physiological benefits of the resistant starches studied appear to relate to colonic health in terms of effects on fecal bulk and SCFA metabolism.

Factors influencing the development and carbohydrate metabolism of Echinococcus granulosus in dogs

Echinococcus granulosus adult worms, 35 days postinfection, were measured for dispersion in the intestines of 10 dogs, a range of morphological characters, and the excreted end products of carbohydrate catabolism following 4 hr incubation in vitro. Most worms were found in the proximal sections of the small intestine, but the pattern of dispersion differed between dogs. Worm development varied both between dogs and between different regions of the small intestine of individual dogs. Overall there was a high level of variability with no simple patterns. Worm metabolism was related to worm development and, also independently, to local population density within the intestine. Larger, more mature worms produced less lactate and, at higher densities, worms tended to produce more acetate and succinate (pathways with a higher energy yield than lactate) and less ethanol. Thus, both more developed worms and high population density are associated with a shift from cytosolic to mitochondrial metabolism. The variation between worm populations along the small intestine along with the observed variation between worm populations from sibling dogs infected with genetically identical parasites suggests that the local host environment has a significant effect on parasite development.

New 11 beta-aryl-substituted steroids exhibit both progestational and antiprogestational activity

The syntheses of three 11 beta-aryl-19-norpregna-4,9-dien-3-one derivatives with 17-spirolactone and 17 beta-hydroxy-17 alpha-cyanoethyl substitutions are described. The progesterone agonist/antagonist activities of the new compounds are investigated using a recently developed tissue culture system that relies on the progesterone agonist up-regulation of the prostate-specific antigen (PSA) gene in female breast tumor cell lines. Two of the newly synthesized compounds exhibit mixed agonistic/antagonistic progestational activity.

Modulation of androgen and progesterone receptors by phytochemicals in breast cancer cell lines

We have used a tissue culture system based on breast carcinoma cell lines to investigate a large number of naturally occurring compounds and beverages for steroid hormone agonist and antagonist activity. The cell lines used, T-47D and BT-474, produce prostate specific antigen (PSA) upon stimulation with androgens, progestins, glucocorticoids and mineralocorticoids. This biomarker is secreted and can be measured in the tissue culture supernatant with very high sensitivity by an immunofluorometric procedure. Steroid hormone antagonist activity can be assessed with the same system by adding the candidate antagonist first and then stimulating the cells with a known agonist. By using this system we have identified three natural compounds, apigenin, naringenin and syringic acid which exhibited weak progestational activity and eleven other compounds which exhibited weak antiandrogenic/antiprogestational activity. Our study indicates that a significant number of natural compounds have the ability to bind to steroid hormone receptors and act as weak blockers. A fewer number of compounds not only bind to the receptors but they also mediate transcriptional activity, acting as agonists. The agonists and antagonists were active at levels around 10(-5) M, in accordance with previous reports for other phytochemicals. In comparison to synthetic and natural steroid hormones, the biological activity of these compounds is weaker by a factor of approximately 10(4)-fold.

What is a high fiber diet?

There is no recognized definition of what constitutes a high fiber diet. Intakes of dietary fiber in different populations internationally vary widely from less than 20 g to more than 80 g per day. The types of foods contributing fiber also vary; in some countries cereals contribute the most fiber, in others leafy or root vegetables predominate. Vegetables have the highest fiber content per Kcal, and in most populations with fiber intakes over 50 g, vegetables contribute over 50% of total fiber intake. In rural Uganda, where the fiber hypothesis was first developed by Burkitt and Trowell, vegetables contribute over 90% of fiber intake. An experimental diet, the "Simian" diet, has been developed to mimic as closely as possible using human foods, the diet consumed by our simian ancestors the great apes. It is also similar to the Ugandan diet in containing large amounts of vegetables and 50 g fiber/1000 Kcal. Though nutritionally adequate, this diet is very bulky and not a suitable model for general recommendations. Dietary guidelines are that fat intake should be < 30% of energy, with a fiber intake of 20-35 g/d. These recommendations are inconsistent with a high fiber diet because, for people consuming more than about 2400 Kcal, low fiber choices for fruits and grains must be selected to keep dietary fiber intake within the range of 20-35 g. In a 30% fat, 1800 Kcal omnivorous diet, selection of wholemeal bread and whole fruit, results in a fiber intake over 35 g/d, and for and 1800 Kcal vegetarian diet, with substitution of modest amounts of peanut butter and beans for meats, dietary fiber intake goes up to 45 g/d. Thus, if it is desirable to promote the use of unrefined foods, the recommended dietary fiber intake should be a minimum of 15-20 g/1000 Kcal.

Disaccharide polyphosphates based upon adenophostin A activate hepatic D-myo-inositol 1,4,5-trisphosphate receptors

The glyconucleotides adenophostin A and B are the most potent known agonists at type 1 inositol trisphosphate [Ins(1,4,5)P3] receptors, although their stuctures differ markedly from that of Ins(1,4,5)P3. Equilibrium competition binding with [3H]Ins(1,4,5)P3 and unidirectional 45Ca2+ flux measurements were used to examine the effects of adenophostin A in hepatocytes, which express predominantly type 2 Ins(1,4,5)P3 receptors. Both Ins(1,4,5)P3 (Kd = 8.65 +/- 0.98 nM) and adenophostin A (Kd = 0.87 +/- 0.20 nM) bound to a single class of [3H]Ins(1,4,5)P3-binding site and each fully mobilized the same intracellular Ca2+ pool; although, adenophostin A (EC50 = 10.9 +/- 0.7 nM) was more potent than Ins(1,4,5)P3 (EC50 = 153 +/- 11 nM). Working on the assumption that it is the phosphorylated glucose component of the adenophostins that mimics the critical features of Ins(1,4,5)P3, we synthesized various phosphorylated disaccharide analogs containing this structure. The novel disaccharide-based analogs, sucrose 3,4,3'-trisphosphate [Sucr(3,4,3')P3], alpha,alpha'-trehalose 3,4,3',4'-tetrakisphosphate [Trehal(3,4,3',4')P4], alpha,alpha'-trehalose 2,4,3', 4'-tetrakisphosphate [Trehal(2,4,3',4')P4], and methyl 3-O-(alpha-d-glucopyranosyl)-beta-d-ribofuranoside 2,3', 4'-trisphosphate [Rib(2,3',4')P3], were all able to mobilize the same intracellular Ca2+ pool as Ins(1,4,5)P3 and adenophostin A; although, none was as potent as adenophostin A. The rank order of potency of the analogs, adenophostin A > Ins(1,4,5)P3 approximately Rib(2,3',4')P3 > Trehal(2,4,3',4')P4 > Glc(2',3,4)P3 approximately Trehal(3,4,3',4')P4 > Sucr(3,4,3')P3, was the same in radioligand binding and functional assays of hepatic Ins(1,4,5)P3 receptors. Both Rib(2,3',4')P3, which was as potent as Ins(1,4,5)P3, and Trehal(2,4,3',4')P4 bound with significantly higher affinity ( approximately 27 and approximately 3-fold, respectively) than the only active carbohydrate agonist of Ins(1,4,5)P3 receptors previously examined [Glc(2',3,4)P3]. We conclude that phosphorylated disaccharides provide novel means of developing high-affinity ligands of Ins(1,4,5)P3 receptors.

Structural analogues of D-myo-inositol-1,4,5-trisphosphate and adenophostin A: recognition by cerebellar and platelet inositol-1,4,5-trisphosphate receptors

Adenophostins A and B, which are metabolic products of the fungus Penicillium brevicompactum, are potent agonists at the D-myo-inositol-1,4,5-trisphosphate [Ins(1,4,5)P3] receptor. In the current study, adenophostin A was approximately 50-fold more potent than Ins(1,4,5)P3 at both releasing Ca2+ from the intracellular stores of permeabilized platelets and displacing [3H]Ins(1,4,5)P3 from its receptor on rat cerebellar membranes. Various analogues bearing structural features found in the adenophostins and/or Ins(1, 4,5)P3 were examined to elucidate the molecular basis for the observed enhanced potency. 2-AMP did not induce Ca2+ release from permeabilized platelets or have any effect on Ins(1,4,5)P3-induced Ca2+ release. Two carbohydrate-based analogues, (2-hydroxyethyl)-alpha-D-glucopyranoside-2',3,4-trisphosphate and alpha,alpha'-trehalose-3,4,3',4'-tetrakisphosphate, could induce release of Ca2+ and displace [3H]Ins(1,4,5)P3 from its binding site on rat cerebellar membranes, although both were less potent than Ins(1,4,5)P3. In common with adenophostin A, release of Ca2+ from the intracellular stores could be inhibited by heparin, and both analogues were metabolically resistant. This study is the first to demonstrate the activity of a synthetic disaccharide at the Ins(1,4, 5)P3 receptor and that the Ins(1,4,5)P3 receptor is capable of accommodating an increased steric bulk. The minimal importance of the 2-hydroxyl group of Ins(1,4,5)P3 (occupied by the pyranoside oxygen in adenophostin) was confirmed by comparing the activity of DL-scyllo-Ins(1,2,4)P3 [which differs from Ins(1,4,5)P3 solely by the orientation of this hydroxyl group] with that of Ins(1,4,5)P3. An analogue of this compound, namely, DL-6-CH2OH-scyllo-Ins(1,2,4)P3, which possesses an equatorial hydroxymethyl group analogous to the 5'-hydroxymethyl group of adenophostin, was found to be equipotent to Ins(1,4,5)P3, demonstrating the tolerance of the Ins(1,4,5)P3 receptor to additional steric bulk at this position.

The western lowland gorilla diet has implications for the health of humans and other hominoids

We studied the western lowland gorilla diet as a possible model for human nutrient requirements with implications for colonic function. Gorillas in the Central African Republic were identified as consuming over 200 species and varieties of plants and 100 species and varieties of fruit. Thirty-one of the most commonly consumed foods were collected and dried locally before shipping for macronutrient and fiber analysis. The mean macronutrient concentrations were (mean +/- SD, g/100 g dry basis) fat 0.5 +/- 0.4, protein 11.8 +/- 8.2, available carbohydrate 7.7 +/- 6.3 and dietary fiber 74.0 +/- 12.9. Assuming that the macronutrient profile of these foods was reflective of the whole gorilla diet and that dietary fiber contributed 6.28 kJ/g (1.5 kcal/g), then the gorilla diet would provide 810 kJ (194 kcal) metabolizable energy per 100 g dry weight. The macronutrient profile of this diet would be as follows: 2.5% energy as fat, 24.3% protein, 15.8% available carbohydrate, with potentially 57.3% of metabolizable energy from short-chain fatty acids (SCFA) derived from colonic fermentation of fiber. Gorillas would therefore obtain considerable energy through fiber fermentation. We suggest that humans also evolved consuming similar high foliage, high fiber diets, which were low in fat and dietary cholesterol. The macronutrient and fiber profile of the gorilla diet is one in which the colon is likely to play a major role in overall nutrition. Both the nutrient and fiber components of such a diet and the functional capacity of the hominoid colon may have important dietary implications for contemporary human health.

Psyllium-enriched cereals lower blood total cholesterol and LDL cholesterol, but not HDL cholesterol, in hypercholesterolemic adults: results of a meta-analysis

We conducted a meta-analysis to determine the effect of consumption of psyllium-enriched cereal products on blood total cholesterol (TC), LDL cholesterol (LDL-C) and HDL cholesterol (HDL-C) levels and to estimate the magnitude of the effect among 404 adults with mild to moderate hypercholesterolemia (TC of 5.17-7.8 mmol/L) who consumed a low fat diet. Studies of psyllium cereals were identified by a computerized search of MEDLINE and Current Contents and by contacting United States-based food companies involved in psyllium research. Published and unpublished studies were reviewed by one author and considered eligible for inclusion in the meta-analysis if they were conducted in humans, were randomized, controlled experiments, and included a control group that ate cereal providing </=3 g soluble fiber/d. Eight published and four unpublished studies, conducted in four countries, met the criteria. Analysis of a linear model was performed, controlling for sex and age. Female subjects were divided into two groups to provide a rough estimate of the effect of menopausal status (premenopausal = <50 y, postmenopausal = >/=50 y) on blood lipids. The meta-analysis showed that subjects who consumed a psyllium cereal had lower TC and LDL-C concentrations [differences of 0.31 mmol/L (5%) and 0.35 mmol/L (9%), respectively] than subjects who ate a control cereal; HDL-C concentrations were unaffected in subjects eating psyllium cereal. There was no effect of sex, age or menopausal status on blood lipids. Results indicate that consuming a psyllium-enriched cereal as part of a low fat diet improves the blood lipid profile of hypercholesterolemic adults over that which can be achieved with a low fat diet alone.

Intestinal fatty acid-binding protein variation associated with variation in the response of plasma lipoproteins to dietary fibre

Increased dietary fibre intake is a component of prudent dietary advice, although the mechanism of its beneficial effect is unclear. Furthermore, plasma lipoprotein response to dietary fibre seems to vary both between individuals and according to the type of fibre consumed. Two common genetic variants, A54 and T54, of the intestinal fatty acid-binding protein gene (FABP2) have different in vitro binding affinities for long-chain fatty acids. We have hypothesized that variation in FABP2 would be associated with interindividual variation in the response of plasma lipoproteins to either dietary soluble or insoluble fibre. We studied 43 subjects who participated in a year-long cross-over study of the effect of insoluble and soluble fibre on plasma lipoproteins. We tested for associations between FABP2 genotypes and the response of plasma lipoproteins to dietary fibre. When compared with subjects homozygous for FABP2 A54, we found that subjects with FABP2 T54 had significantly greater decreases in plasma total and low-density lipoprotein (LDL)-cholesterol and apoB during the period when the diet was high in soluble fibre than during the period when the diet was high in insoluble fibre. Furthermore, compared with subjects with the FABP2 A54 allele, subjects with the FABP2 T54 allele had significantly lower secretion of total fecal bile acids, but this did not increase with dietary soluble fibre. Genetic variation in FABP2 may thus contribute to interindividual variation in the response of plasma lipoproteins to different dietary fibres, but the mechanism does not appear to be related to increases in fecal bile acid secretion.

Apolipoprotein E R112; R251G: a carboxy-terminal variant found in patients with hyperlipidemia and coronary heart disease

A 49 year-old hypercholesterolemic male with marked electrocardiographic ST segment depression on exercise testing was found to have an apo E E3/3 phenotype by isoelectric focusing, but an APOE E4/3 genotype using HhaI restriction isotyping. DNA sequence analysis of the proband's APOE gene found a G-->C point mutation at codon 251. This predicted a change in the amino acid encoded by codon 251, from arginine to glycine. The mutation occurred on an allele that encoded arginine at position 112 and this variant was named APOE R112; R251G. The R251G change altered a recognition site for the endonuclease StuI and was the basis for a restriction isotyping method to rapidly screen for this mutation. In relatives of the proband, APOE R112; R251G was consistently found in subjects with both hyperlipidemia and atherosclerosis. Apo E R112; R251G-containing very low density lipoproteins bound normally to macrophages in vitro. However, the proband had an abnormal post-prandial lipoprotein response to a dietary fat challenge. The association of APOE R112; R251G with abnormal phenotypes suggests that the amino acid change in the carboxy-terminal, perhaps in combination with the common amino acid polymorphism at codon 112, has a functional impact upon lipoprotein metabolism in members of this family.

Long-term effect of soluble-fiber foods on postprandial fat metabolism in dyslipidemic subjects with apo E3 and apo E4 genotypes

To determine the long-term effect of soluble fiber on postprandial fat metabolism, we studied 33 dyslipidemic subjects, 16 with apolipoprotein (apo) E3/3 (E3) and 17 with E3/4 or E4/4 (E4) genotypes. They ate preweighed low-fat (20% of energy), high-fiber (> 5.7 g/MJ) diets for two 4-mo periods separated by a 2-mo washout period according to a randomized, crossover design. One diet contained foods rich in insoluble fiber and the other foods rich in soluble fiber. On 1 d during the last 2 wk of each diet, subjects ingested a standard, fiber-free, fatty liquid meal containing retinyl palmitate as a marker of intestinally derived lipoproteins. Plasma samples were obtained at hourly intervals for 10 h. Compared with the insoluble-fiber diet, soluble fiber reduced fasting plasma total cholesterol in both E3 (6.6 +/- 2.1%, P = 0.007)and E4 subjects (5.6 +/- 2.1%, P = 0.017). Soluble fiber increased fecal total bile acid output in both E3 (76 +/- 18%, P < 0.001) and E4 subjects (85 +/- 19%, P < 0.001). The incremental area under the chylomicron triacylglycerol response curve was significantly greater after soluble fiber than after insoluble fiber in E3 (3.56 +/- 0.56 compared with 2.87 +/- 0.38 mmol x h/L, respectively, P = 0.046) but not in E4 subjects (5.19 +/- 0.78 compared with 4.92 +/- 0.81 mmol x h/L). Kinetic analysis suggested an increase in retinyl palmitate absorption in E3 subjects after soluble fiber, but no difference in E4 subjects. These results suggest that a long-term increase in dietary soluble fiber has no effect on postprandial fat metabolism in subjects with an apo E3/4 or E4/4 genotype. However, soluble fiber enhances apparent fat absorption in E3 subjects, which could be due to an increased bile acid pool and increased micelle formation.

Effect of a diet high in vegetables, fruit, and nuts on serum lipids

We assessed the effect of a diet high in leafy and green vegetables, fruit, and nuts on serum lipid risk factors for cardiovascular disease. Ten healthy volunteers (seven men and three women aged 33 +/- 4 years [mean +/- SEM]; body mass index, 23 +/- 1 kg/m2) consumed their habitual diet (control diet, 29% +/- 2% fat calories) and a diet consisting largely of leafy and other low-calorie vegetables, fruit, and nuts (vegetable diet, 25% +/- 3% fat calories) for two 2-week periods in a randomized crossover design. After 2 weeks on the vegetable diet, lipid risk factors for cardiovascular disease were significantly reduced by comparison with the control diet (low-density lipoprotein [LDL] cholesterol, 33% +/- 4%, P < .001; ratio of total to high-density lipoprotein [HDL] cholesterol, 21% +/- 4%, P < .001; apolipoprotein [apo] B:A-I, 23% +/- 2%, P < .001; and lipoprotein (a) [Lp(a)], 24% +/- 9%, P = .031). The reduction in apo B was related to increased intakes of soluble fiber (r = .84, P = .003) and vegetable protein (r = -.65, P = .041). On the vegetable compared with the control diet, the reduction in total serum cholesterol was 34% to 49% greater than would be predicted by differences in dietary fat and cholesterol. A diet consisting largely of low-calorie vegetables and fruit and nuts markedly reduced lipid risk factors for cardiovascular disease. Several aspects of such diets, which may have been consumed early in human evolution, have implications for cardiovascular disease prevention.

Effect of psyllium in hypercholesterolemia at two monounsaturated fatty acid intakes

We performed two studies to determine whether the lipid-lowering effect of viscous soluble fiber was modified by monounsaturated fatty acid (MUFA). First, psyllium (1.4 g/MJ) was compared with wheat bran (control) in 1-mo metabolic diets by using a randomized crossover design (n = 32 hyperlipidemic subjects). The background diet contained approximately 6% of energy as MUFA (20% of total fat). The second study (n = 27 hyperlipidemic subjects) was similar to the first but the background diet contained approximately 12% MUFA (29% of total fat) because of the addition of canola oil. At both fat intakes, psyllium resulted in significant reductions in total, low-density-lipoprotein (LDL), and high-density-lipoprotein (HDL) cholesterol compared with the wheat bran control. For the psyllium diet at 6% compared with 12% MUFA, the decreases in LDL cholesterol were 12.3 +/- 1.5% (P < 0.001) and 15.3 +/- 2.4% (P < 0.001), respectively. With the higher-MUFA diet triacylglycerol fell significantly over the control phase (16.6 +/- 5.5%, P = 0.006) and the ratio of LDL to HDL cholesterol fell significantly over the psyllium phase (7.3 +/- 2.8%, P = 0.015). Psyllium and MUFA intakes were negatively related to the percentage change in the ratio of LDL to HDL cholesterol (r = -0.34, P = 0.019 and r = -0.44, P = 0.002, respectively). Chenodeoxycholate synthesis rate increased (30 +/- 13%, P = 0.038) with the psyllium diet in the 12 subjects in whom this was assessed. We conclude that psyllium lowered LDL- and HDL-cholesterol concentrations similarly at both MUFA intakes. However, there may be some advantage in combining soluble fiber and MUFA to reduce the ratio of LDL to HDL cholesterol.

Adenophostin A can stimulate Ca2+ influx without depleting the inositol 1,4,5-trisphosphate-sensitive Ca2+ stores in the Xenopus oocyte

Adenophostin A possesses the highest known affinity for the inositol 1,4,5-trisphosphate (Ins(1,4,5)P3) receptor (InsP3R). The compound shares with Ins(1,4,5)P3 those structural elements essential for binding to the InsP3R. However, its adenosine 2'-phosphate moiety has no counterpart in the Ins(1,4,5)P3 molecule. To determine whether its unique structure conferred a distinctive biological activity, we characterized the adenophostin-induced Ca2+ signal in Xenopus oocytes using the Ca2+-gated Cl- current assay. In high concentrations, adenophostin A released Ca2+ from Ins(1,4, 5)P3-sensitive stores and stimulated a Cl- current that depended upon the presence of extracellular Ca2+. We used this Cl- current as a marker of Ca2+ influx. In low concentrations, however, adenophostin A stimulated Ca2+ influx exclusively. In contrast, Ins(1,4,5)P3 and (2-hydroxyethyl)-alpha-D-glucopyranoside 2',3, 4-trisphosphate, an adenophostin A mimic lacking most of the adenosine moiety, always released intracellular Ca2+ before causing Ca2+ influx. Ins(1,4,5)P3 could still release Ca2+ during adenophostin A-induced Ca2+ influx, confirming that the Ins(1,4, 5)P3-sensitive intracellular Ca2+ stores had not been emptied. Adenophostin- and Ins(1,4,5)P3-induced Ca2+ influx were not additive, suggesting that both agonists stimulated a common Ca2+ entry pathway. Heparin, which blocks binding to the InsP3R, prevented adenophostin-induced Ca2+ influx. These data indicate that adenophostin A can stimulate the influx of Ca2+ across the plasma membrane without inevitably emptying the Ins(1,4,5)P3-sensitive intracellular Ca2+ stores.

Carbohydrate tolerance and food frequency

Dietary and pharmacological approaches to slowing the rate of glucose absorption and blunting the insulin response show promise in the treatment of diabetes and hyperlipidaemia. These approaches include dietary fibre, low-glycaemic-index foods and gastrointestinal digestive enzyme inhibitors. One common feature is that they spread the nutrient load over time. A potentially simpler approach is to take more frequent smaller meals over a longer period of the day. Early studies suggested that frequent glucose and insulin administration to diabetic patients improved diabetes control. More recent acute studies of one test meal or 1 d blood metabolite profiles have identified a significant economy in insulin secretion when glucose is sipped or when meal frequency is increased in both diabetic or non-diabetic subjects. In diabetic subjects improvement in mean blood glucose levels has also been reported. However, despite the demonstration of an alteration in response over time in glucose tolerance in healthy volunteers, no longer-term improvement in glycaemic control was reported in the only study in diabetes to examine a change from three to nine meals daily over a 1-month period. The disparity between longer-term and acute studies requires further investigation. At present, although this nutritional approach holds considerable theoretical promise, specific advice is premature.

Dietary fiber, glycemic load, and risk of NIDDM in men

OBJECTIVE

Intake of carbohydrates that provide a large glycemic response has been hypothesized to increase the risk of NIDDM, whereas dietary fiber is suspected to reduce incidence. These hypotheses have not been evaluated prospectively.

RESEARCH DESIGN AND METHODS

We examined the relationship between diet and risk of NIDDM in a cohort of 42,759 men without NIDDM or cardiovascular disease, who were 40-75 years of age in 1986. Diet was assessed at baseline by a validated semiquantitative food frequency questionnaire. During 6-years of follow-up, 523 incident cases of NIDDM were documented.

RESULTS

The dietary glycemic index (an indicator of carbohydrate's ability to raise blood glucose levels) was positively associated with risk of NIDDM after adjustment for age, BMI, smoking, physical activity, family history of diabetes, alcohol consumption, cereal fiber, and total energy intake. Comparing the highest and lowest quintiles, the relative risk (RR) of NIDDM was 1.37 (95% CI, 1.02-1.83, P trend = 0.03). Cereal fiber was inversely associated with risk of NIDDM (RR = 0.70; 95% CI, 0.51-0.96, P trend = 0.007; for > 8.1 g/day vs. < 3.2 g/day). The combination of a high glycemic load and a low cereal fiber intake further increased the risk of NIDDM (RR = 2.17, 95% CI, 1.04-4.54) when compared with a low glycemic load and high cereal fiber intake.

CONCLUSIONS

These findings support the hypothesis that diets with a high glycemic load and a low cereal fiber content increase risk of NIDDM in men. Further, they suggest that grains should be consumed in a minimally refined form to reduce the incidence of NIDDM.

Metabolic effects of non-absorbable carbohydrates

Food components which are incompletely absorbed in the small intestine or not absorbed at all but are delivered to the colon have been part of the diet throughout the course of human evolution. Our great ape cousins may derive 30% or more of their dietary calories from colonic uptake of short-chain fatty acids (SCFAs) generated in the colon. The metabolic effects of dietary carbohydrate entering the colon are many and include laxation, the growth of the fecal biomass, nitrogen entrapment and SCFA generation. These SCFAs in turn may nourish mucosal cells, spare glutamine utilization, enhance hepatic gluconeogenesis and lipogenesis and possibly influence renal handling of uric acid. The health implications are significant in terms of modifying risk factors for disease and disease prevention and justify interest in the metabolic effects of non-absorbable sugars such as lactulose.

Chiral Cyclopentane-Based Mimics of D-myo-Inositol 1,4,5-Trisphosphate from D-Glucose

Two routes from D-glucose to chiral, ring-contracted analogs of the second messenger D-myo-inositol 1,4,5-trisphosphate are described. Methyl alpha-D-glucopyranoside was converted by an improved procedure into methyl 4,6-O-(p-methoxybenzylidene)-alpha-D-glucopyranoside (6) and thence into methyl 2-O-benzyl-3,4-bis-O-(p-methoxybenzyl)-alpha-D-gluco-hexodialdopyranoside (1,5) (14) in four steps. In the first ring-contraction method 14 was converted into methyl 2-O-benzyl-6,7-dideoxy-3,4-bis-O-(p-methoxybenzyl)-alpha-D-gluco-hept-6-enopyranoside (1,5) (15), which on sequential treatment with Cp(2)Zr(n-Bu)(2) followed by BF(3).Et(2)O afforded a mixture of (1R,2S,3S,4R,5S)-3-(benzyloxy)-4-hydroxy-1,2-bis[(p-methoxybenzyl)oxy]-5-vinylcyclopentane (16) and its 4S,5R diastereoisomer 17. Removal of the p-methoxybenzyl groups of 16 and subsequent phosphorylation and deprotection afforded the first target compound, (1R,2R,3S,4R,5S)-3-hydroxy-1,2,4-tris(phosphonooxy)-5-vinylcyclopentane (3). In the second route, intermediate 14 was subjected to SmI(2)-mediated ring contraction to give (1R,2S,3S,4R,5S)-3-(benzyloxy)-4-hydroxy-5-(hydroxymethyl)-1,2-bis[(p-methoxybenzyl)oxy]cyclopentane (20). Benzylation of 20 provided (1R,2S,3S,4R,5S)-3-(benzyloxy)-6-[(benzyloxy)methyl]-4-hydroxy-1,2-bis[(p-methoxybenzyl)oxy]cyclopentane (22) and (1R,2S,3S,4R,5S)-3,4-bis(benzyloxy)-5-(hydroxymethyl)-1,2-bis[(p-methoxybenzyl)oxy]cyclopentane (21), which were elaborated to the target trisphosphates (1R,2R,3S,4R,5S)-3-hydroxy-5-(hydroxymethyl)-1,2,4-tris(phosphonooxy)cyclopentane (4) and (1R,2S,3R,4R,5S)-1,2-dihydroxy-3,4-bis(phosphonooxy)-5-[(phosphonooxy)methyl]cyclopentane (5), respectively. Both 3 and 4 mobilized intracellular Ca(2+), but 4 was only a few fold less potent than D-myo-inositol 1,4,5-trisphosphate, demonstrating that effective mimics can be designed that do not bear a six-membered ring.

Transmission of hydatid disease to sheep from wild dogs in Victoria, Australia

Adult tapeworms and metacestodes of Echinococcus granulosus were found commonly in wildlife on Crown Land (Alpine National Park or State Forest) in the area around Mansfield, Victoria. A total of 756 sheep from 32 farms in the areas were examined at slaughter. Seventeen of the farms (Group A) adjoined Crown Land and wild dogs commonly entered these farms and killed sheep. A high prevalence of hydatid infection was found in sheep from 15 of these farms. Serology and arecoline purging failed to identify infection with E. granulosus in any domestic dogs on these farms, despite some farmers sometimes feeding their dogs with offal of sheep and/or kangaroos. The remaining 15 farms (Group B) were in an area where wild dogs did not occur. Sheep infected with hydatid cysts were present on 2 farms in Group B, but E. granulosus infection was not evident in wildlife species examined from this area. The only sheepdog to have detectable serum antibodies against E. granulosus was a dog from a farm separating the 2 Group B farms where infected sheep were found. Echinococcus granulosus were not found when this dog was purged. The implications of the results of this study are discussed in terms of transmission and control.