Hepatic lipase deficiency. Clinical, biochemical, and molecular genetic characteristics

Hepatic lipase (HL) is an important enzyme in the metabolism of triglyceride-rich lipoproteins and high density lipoproteins. The clinical syndrome of HL deficiency is rare and difficult to identify. We studied carriers of mutant HL to ascertain whether there are distinctive clinical and/or biochemical characteristics of the heterozygous state. In an Ontario kindred, compound heterozygosity for two HL mutations, S267F and T383M, underlies the clinical syndrome of complete HL deficiency. We report that simple heterozygotes for either HL mutant do not have a discrete lipoprotein abnormality, except for relative triglyceride enrichment of lipoprotein fractions with d > 1.006 g/mL. Postheparin HL activity is depressed to a greater degree in carriers of S267F compared with carriers of T383M. Retinyl palmitate loading studies in a compound heterozygote revealed impaired clearance of chylomicron remnants. The dyslipoproteinemia in a compound heterozygote was ameliorated by lovastatin. There was no difference in the quantity and distribution of HL mRNA in the liver of a compound heterozygote when compared with that of a normal subject. Thus, HL deficiency associated with structural variation of the HL gene is characterized by premature atherosclerosis, triglyceride enrichment of lipoprotein fractions with d > 1.006 g/mL, the presence of circulating beta-very low density lipoproteins, and abnormal catabolism of postprandial triglyceride-rich lipoproteins.

Plasma acetate levels in a group of obese diabetic, obese normoglycemic, and control subjects and their relationships with other blood parameters

Acetate is a short-chain fatty acid derived from colonic fermentation of carbohydrate and dietary fiber, and from endogenous glucose and fatty acid metabolism in the liver. An impaired acetate metabolism has been reported in diabetic subjects. The aim of the study was to evaluate plasma acetate levels in a group of obese diabetic subjects, compared with obese normoglycemic subjects and normal control subjects. Eleven noninsulin-dependent diabetic patients taking oral antidiabetic drugs, eight obese normoglycemic subjects, and seven control subjects were studied. Liver, kidney, and gut functions were normal in all subjects. Blood acetate, glucose, insulin, and C-peptide were evaluated in all subjects. Acetate levels were significantly higher in the diabetic subjects than in obese normoglycemic and normal subjects. Significant correlations between HbA1c, glucose, and acetate levels, but not between acetate and C-peptide or insulin, were also observed.

The apolipoprotein E gene and the serum low-density lipoprotein cholesterol response to dietary fiber

Our goal was to determine whether differences in apolipoprotein E (apo E) influenced the response to dietary changes aimed at reducing serum cholesterol levels, especially increases in fiber. Apo E phenotype and genotype were determined in 43 men and 24 women who had previously taken part in parallel 2-week metabolic dietary studies involving either wheat bran or oat bran supplementation at a level of 6.8 g fiber/1,000 kcal. Fasting blood lipid measurements had been made at the beginning and end of the 2-week metabolic period. Reductions in low-density lipoprotein (LDL) cholesterol levels across both oat and wheat bran diets were significantly different depending on the E allele (P = .048). The LDL cholesterol level reduction for E2 carriers (0.60 +/- 0.14 mmol/L, n = 13) was greater than that for E3 homozygotes (0.21 +/- 0.07 mmol/L, n = 38; P = .014) and E4 carriers (0.28 +/- 0.12 mmol/L, n = 16; P = .09). Only the change in dietary fiber on the oat bran diet was related significantly to the decrease in LDL cholesterol levels (r = -.47, P = .007; n = 32). No such relationship was seen on the wheat bran diet (r = -.010, P = .59; n = 33). Carriers of the E2 allele appear to be more responsive than noncarriers to a dietary change involving increased fiber intake. The data also support a lipid-lowering advantage of oat bran over wheat bran. Current dietary recommendations to reduce serum lipid levels may vary in effectiveness depending on distribution of apo E alleles in the different populations studied.

High alpha-linolenic acid flaxseed (Linum usitatissimum): some nutritional properties in humans

Although high alpha-linolenic acid flaxseed (Linum usitatissimum) is one of the richest dietary sources of alpha-linolenic acid and is also a good source of soluble fibre mucilage, it is relatively unstudied in human nutrition. Healthy female volunteers consumed 50 g ground, raw flaxseed/d for 4 weeks which provided 12-13% of energy intake (24-25 g/100 g total fat). Flaxseed raised alpha-linolenic acid and long-chain n-3 fatty acids in both plasma and erythrocyte lipids, as well as raising urinary thiocyanate excretion 2.2-fold. Flaxseed also lowered serum total cholesterol by 9% and low-density-lipoprotein-cholesterol by 18%. Changes in plasma alpha-linolenic acid were equivalent when 12 g alpha-linolenic acid/d was provided as raw flaxseed flour (50 g/d) or flaxseed oil (20 g/d) suggesting high bioavailability of alpha-linolenic acid from ground flaxseed. Test meals containing 50 g carbohydrate from flaxseed or 25 g flaxseed mucilage each significantly decreased postprandial blood glucose responses by 27%. Malondialdehyde levels in muffins containing 15 g flaxseed oil or flour/kg were similar to those in wheat-flour muffins. Cyanogenic glycosides (linamarin, linustatin, neolinustatin) were highest in extracted flaxseed mucilage but were not detected in baked muffins containing 150 g flaxseed/kg. We conclude that up to 50 g high-alpha-linolenic acid flaxseed/d is palatable, safe and may be nutritionally beneficial in humans by raising n-3 fatty acids in plasma and erythrocytes and by decreasing postprandial glucose responses.

Morphological characterization of adult Echinococcus granulosus as a means of determining transmission patterns

Host induced changes in morphological characters of the rostellar hooks of Echinococcus granulosus were used to determine the origin of infection in definitive hosts in rural areas of southeastern Australia where wild and domestic cycles of transmission may interact. The morphological characters studied vary depending on the species of intermediate host (macropod marsupials, sheep) in which protoscoleces develop, and these characters are retained in adult worms. It was therefore possible to determine whether definitive hosts (dingoes and foxes) acquired infection by consuming protoscoleces of E. granulosus from macropods or from sheep. The results correlated well with the known distribution of intermediate hosts and illustrate the practical value of such morphological markers in epidemiological studies.

The role of foxes Vulpes vulpes in the epidemiology of Echinococcus granulosus in urban environments

OBJECTIVE

To survey the prevalence of intestinal worms, particularly Echinococcus granulosus, in foxes in Canberra.

DESIGN

The locations of foxes seen in Canberra during this study were recorded. Foxes and macropod marsupials killed on the roads of Canberra were collected and examined for the presence of intestinal helminths and hydatid cysts respectively.

METHOD

The intestinal contents of the foxes were washed through a fine sieve and examined microscopically. All helminths recovered were collected and identified. All the internal organs of the macropods were examined for any cystic lesions.

RESULTS

Forty-five foxes and 44 macropods were examined. Echinococcus granulosus was found in three of the foxes (7%). Hydatid cysts were not found in the internal organs of any of the macropods examined.

CONCLUSIONS

Echinococcus granulosus is present in the urban fox population of Canberra. This hitherto unreported aspect of the epidemiology of E. granulosus in Australia could be a potential public health risk to urban populations.

Use of Echinococcus granulosus worm antigens for immunodiagnosis of E. granulosus infection in dogs

Echinococcus granulosus worm excretory/secretory antigens (WES) were used in ELISA for diagnosis of E. granulosus infection in dogs and compared with protoscolex somatic antigens (PSM). Sera from 224 dogs were tested. There was no correlation between ELISA absorbance values and E. granulosus worm burdens using either antigen. There was a significant linear relationship between absorbance values of sera tested in the ELISA using WES (W-ELISA) and the ELISA using PSM (P-ELISA). However, there was a small but significant difference between the absorbance values of the sera tested against the two antigens. Western blot analysis of WES using sera from E. granulosus-infected and uninfected dogs revealed antigenic components of relative molecular mass (Mr) larger than 94,000, Mr 94,000-68,000 and Mr 43,000-39,000 in worms, and these were specific for E. granulosus and not identified in PSM; these antigenic differences may be responsible for differences in reactivity in ELISA. The sensitivities of W-ELISA and P-ELISA were 80.8% and 75.6%, respectively. The specificities of W-ELISA and P-ELISA were 93.7% and 97.9%, respectively. The reduced specificity in W-ELISA was mainly attributable to increased background reactivity of sera from Taenia hydatigena-infected dogs. Despite the reduction in specificity, both ELISAs are valuable epidemiological tools to determine the prevalence of antibody to E. granulosus in dog populations and to monitor the success of hydatid control campaigns.

Beneficial effect of a low glycaemic index diet in type 2 diabetes

Low glycaemic index foods produce low blood glucose and insulin responses in normal subjects, and improve blood glucose control in Type 1 and well-controlled Type 2 diabetic patients. We studied the effects of a low glycaemic index diet in 15 Type 2 diabetic patients with a mean fasting blood glucose of 9.5 mmol l-1 using a randomized, crossover design. Patients were given pre-weighed diets (59% energy as carbohydrate, 21% fat, and 24 g 1000-kcal-1 dietary fibre) for two 2-week periods, with a diet glycaemic index of 60 during one period and 87 during the other. On the low glycaemic index diet, the blood glucose response after a representative breakfast was 29% less than on the high glycaemic index diet (874 +/- 108 (+/- SE) vs 204 +/- 112 mmol min l-1; p less than 0.001), the percentage reduction being almost identical to the 28% difference predicted from the meal glycaemic index values. After the 2-week low glycaemic index diet, fasting serum fructosamine and cholesterol levels were significantly less than after the high glycaemic index diet (3.17 +/- 0.12 vs 3.28 +/- 0.16 mmol l-1, p less than 0.05, and 5.5 +/- 0.4 vs 5.9 +/- 0.5 mmol l-1, p less than 0.02, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Wheat-bran and oat-bran supplements' effects on blood lipids and lipoproteins

To compare the effects of oat-bran fiber on blood lipids, we studied 84 healthy middle-aged men and women who were placed on metabolic diets, for 2 wk, that were supplemented with either wheat bran (n = 42) or oat bran (n = 42). Fiber supplementation was 1.6 micrograms dietary fiber/J (6.8 g dietary fiber/1000 kcal) to a maximum of 16.4 g fiber/d. Significantly greater decrease with oat than with wheat were seen in total cholesterol (0.56 +/- 0.08 mmol/L and 0.29 +/- 0.08 mmol/L, P = 0.022) and low-density-lipoprotein cholesterol (0.39 +/- 0.07 mmol/L and 0.15 +/- 0.07 mmol/L, P = 0.024). No significant differences were seen in high-density lipoprotein, apolipoproteins A-1 and B, or triglyceride. We conclude that oat bran has an advantage over wheat bran in lowering serum lipids when tested in metabolic diets on large numbers of individuals with an initial mean serum cholesterol concentration above the desirable range, at 5.61 +/- 0.16 mmol/L.

Effect of a diet high in monounsaturated fat from almonds on plasma cholesterol and lipoproteins

The effect of almonds as part of a low saturated fat, low cholesterol, high-fiber diet was studied in 26 adults (13 men, 13 women). The baseline diet was modified in a similar way for all subjects by limiting meat, fatty fish, high-fat milk products, eggs, and saturated fat. Grains, beans, vegetables, fruit, and low-fat milk products were the foundation of the diet. During the almond diet period, raw almonds (100 mg/day) supplied 34 g/day of monounsaturated fatty acid (MUFA), 12 g/day of polyunsaturated fatty acid, and 6 g/day of saturated fatty acid. Almond oil was the only oil allowed for food preparation. There was a rapid and sustained reduction in low-density lipoprotein cholesterol without changes in high-density lipoprotein cholesterol. This was reflected in a total plasma cholesterol decrease from (means +/- SEM) 235 +/- 5.0 at baseline to 215 +/- 5.0 at 3 weeks, and to 214 +/- 5.0 mg/dl at 9 weeks (p less than 0.001). When the consumption of nuts high in MUFA increases the fat content of the diet, reduction rather than elevation of plasma cholesterol has to be expected, possibly due to the MUFA content of these nuts.

Beneficial effect of low-glycemic index diet in overweight NIDDM subjects

OBJECTIVE

To determine whether low-glycemic index (GI) diets have clinical utility in overweight patients with non-insulin-dependent diabetes mellitus (NIDDM).

RESEARCH DESIGN AND METHODS

Six patients with NIDDM were studied on both high- and low-GI diets of 6-wk duration with metabolic diets with a randomized crossover design. Both diets were of similar composition (57% carbohydrate, 23% fat, and 34 g/day dietary fiber), but the low-GI diet had a GI of 58 compared with 86 for the high-GI diet.

RESULTS

Small and similar amounts of weight were lost on both diets: 2.5 kg on high-GI diet and 1.8 kg on low-GI diet. On the low-GI diet, the mean level of serum fructosamine, as an index of overall blood glucose control, was lower than on the high-GI diet by 8% (P less than 0.05), and total serum cholesterol was lower by 7% (P less than 0.01).

CONCLUSIONS

In overweight patients with NIDDM, reducing diet GI improves overall blood glucose and lipid control.

Colonic fermentation and markers of colorectal-cancer risk

The aim of this study was to determine the effect of soluble fiber on indexes of colon-cancer risk in postpolypectomy and nonpolyp patients. Forty-five postpolypectomy and 49 nonpolyp volunteers completed 2-wk metabolic studies where half of the group received oat-bran supplements and the other half took wheat-brain supplements. Colonic biopsies taken before and after the intervention showed no difference in the index of thymidine colonic-crypt-cell labeling, thymidine-labeling pattern, or nuclear aberrations. Nevertheless, fecal pH was significantly reduced by 0.23 +/- 0.07 pH units (P less than 0.002) as an index of increased colonic fermentation on oat bran. This was not associated with increased basal breath hydrogen concentrations; fecal butyrate concentrations were higher on wheat bran. We conclude that soluble fiber as oat brain appears to have no advantage over wheat bran in modifying putative risk factors for colonic cancer.

Metabolic advantages of spreading the nutrient load: effects of increased meal frequency in non-insulin-dependent diabetes

The acute effect of increasing meal frequency as a model of slow absorption was studied for 1 d in 11 patients with non-insulin-dependent diabetes. On 1 d they took 13 snacks (the nibbling diet) and on another day the same diet was taken as three meals and one snack (the three-meal diet). The nibbling diet reduced mean blood glucose, serum insulin, and C peptide concentrations over the 9.5 h of observation and 24-h urinary C peptide output by 12.7 +/- 3.7% (mean +/- SE) (P = 0.0062), 20.1 +/- 5.8% (P = 0.0108), 9.2 +/- 2.6% (P = 0.0073), and 20.37 +/- 8.12% (P = 0.039), respectively, compared with the three-meal diet. Serum triglyceride concentrations were lower by 8.5 +/- 3.2% (P = 0.037). Despite lower insulin concentrations on the nibbling diet, the concentrations of free fatty acids, 3-hydroxybutyrate, and the insulin-sensitive branched-chain amino acids responded similarly on both treatments. Metabolic benefits seen with increased meal frequency may explain the success of similar agents that prolong absorption, including fiber and enzyme inhibitors.

Effect of dietary fiber on total carbohydrate losses in ileostomy effluent

Studies were performed in three ileostomate subjects to determine the effect of intake of various carbohydrate-containing foods on the ileostomy losses of macronutrients. The percent recovery of available carbohydrate in ileostomy effluent varied between 1.09% and 22.63% for the various foods. Available carbohydrate recovery (%) was positively correlated with fiber (r = 0.91) and protein (r = 0.46) intake, but negatively with available carbohydrate intake (r = -0.66). Stepwise regression indicated that dietary fiber intake was the principal factor determining the amount of available carbohydrate in ileostomy effluent. Fiber intake was negatively correlated with water concentration of the effluent (r = -0.61). This study demonstrates that although fiber has been considered the chief substrate available for colonic fermentation, as the fiber intake increases, so the total fermentable load entering the colon is likely to increase due to losses of available carbohydrates in addition to fiber. Simple assessment of dietary fiber is likely to grossly underestimate the fermentable load on high-fiber, high-carbohydrate diets.

Detection of Echinococcus coproantigens by enzyme-linked immunosorbent assay in dogs, dingoes and foxes

An enzyme-linked immunosorbent assay (ELISA) was developed for the detection of Echinococcus coproantigens in fecal samples from dogs, dingoes or foxes infected with either E. granulosus or E. multilocularis. The ELISA was based on protein-A-purified polyclonal antibodies [anti-E. granulosus excretory/secretory (E/S) antigens]. The specificity of the assay as determined in 155 samples derived from carnivores that were free of helminth infection (n = 37) or infected with non-Echinococcus cestodes (n = 76) or with various nematodes (n = 42) was found to be 98% overall. The diagnostic sensitivity was strongly dependent on the homologous worm burden. All 13 samples from foxes harboring greater than 1,000 E. multilocularis worms and 13 of 15 (87%) samples from dogs or dingoes containing greater than 200 E. granulosus worms were ELISA-positive, whereas 34 of 46 samples from foxes harboring less than 1,000 E. multilocularis and 9 of 10 samples from dogs or dingoes bearing less than 200 E. granulosus tested negative. Experimental prepatent infections of dogs with E. granulosus revealed positive ELISA reactions within the prepatent period (10-20 days post-infection) for six animals bearing greater than 1,000 E. granulosus each; a low worm burden (less than 1,000 tapeworms/animal) resulted in ELISA positivity in only 2 of 3 animals at 30 days post-infection at the earliest. All five dogs that had been experimentally infected with E. multilocularis tested positive in the coproantigen ELISA as early as on day 5 post-infection.

The glycemic index: methodology and clinical implications

There is controversy regarding the clinical utility of classifying foods according to their glycemic responses by using the glycemic index (GI). Part of the controversy is due to methodologic variables that can markedly affect the interpretation of glycemic responses and the GI values obtained. Recent studies support the clinical utility of the GI. Within limits determined by the expected GI difference and by the day-to-day variation of glycemic responses, the GI predicts the ranking of the glycemic potential of different meals in individual subjects. In long-term trials, low-GI diets result in modest improvements in overall blood glucose control in patients with insulin-dependent and non-insulin-dependent diabetes. Of perhaps greater therapeutic importance is the ability of low-GI diets to reduce insulin secretion and lower blood lipid concentrations in patients with hypertriglyceridemia.

Propionate lowers blood glucose and alters lipid metabolism in healthy subjects

Incorporation of 3.3 g sodium propionate per 50 g available carbohydrate portion of bread reduced acutely the blood glucose response area in six healthy volunteers by 47.6 +/- 12.1% Similarly, in vitro digestibility was reduced by 47.4 +/- 1.1% (P less than 0.01). One week of dietary supplementation with 9.9 g sodium propionate in bread/d reduced the blood glucose area in comparison with standard propionate-free bread by 38.0 +/- 8.7% (P less than 0.05), but increased fecal bulk by 28.3 +/- 8.7% (P less than 0.05) and anaerobic microflora by 0.564 +/- 0.165 X 10(6)/g feces (P less than 0.05), specifically as bifidobacteria. Day-long breath hydrogen concentrations did not increase after 1 wk on propionate bread but methane production increased in the three methane producers. Although lipid changes were not significant, five subjects showed reduced high-density-lipoprotein and increased triglyceride concentrations, both of which correlated with increased fecal weight (P less than 0.05). Because propionate reduces the rate of starch digestion, studies using oral propionate must take into account its action as an enzyme inhibitor.

Effect of method of administration of psyllium on glycemic response and carbohydrate digestibility

To determine whether there was any advantage to taking a soluble fiber supplement separate from food, as opposed to incorporated into a food, we used psyllium as a model, either taken in water just before a flaked bran cereal test meal, sprinkled on top of the cereal, or actually incorporated into the flake. In normal subjects, psyllium reduced the glycemic response when sprinkled onto or incorporated into the cereal, but not when taken before the cereal. Varying the amount of psyllium incorporated into the cereal from 0 to 20% resulted in a linear dose-dependent reduction of the glycemic index (GI) (GI = 101 -2.2 x % psyllium; r = 0.950; p less than 0.002). In subjects with diabetes, the blood-glucose-lowering effect of the psyllium flake cereal was similar to that in normal subjects. Mixing psyllium with the cereal or incorporating it into the cereal reduced the rate of digestion of bran flakes in vitro but was not associated with increased breath hydrogen levels in vivo as an index of rapid colonic fermentation. The bran flakes with psyllium incorporated was rated as no less palatable than the bran flakes cereal alone, and significantly more palatable (p less than 0.05) than taking psyllium in water before the cereal or sprinkling psyllium onto the cereal. These studies confirm earlier reports that viscous fibers must be intimately mixed with the food to have the effect of reducing blood glucose responses, and that the mechanism of action relates to a reduced rate of digestion rather than carbohydrate malabsorption.(ABSTRACT TRUNCATED AT 250 WORDS)

Specific types of colonic fermentation may raise low-density-lipoprotein-cholesterol concentrations

To assess the effects of increased colonic fermentation on serum lipids, eight healthy volunteers were placed on two identical 2-wk metabolic diets, one of which was supplemented with lactulose (18-25 g/d). Lactulose raised day-long concentrations of breath hydrogen and serum glutamine as indicators of increased colonic fermentation by 78 +/- 13% (P less than 0.001) and 24.7 +/- 9.5% (P less than 0.05), respectively). Unexpectedly, however, fasting serum total and low-density-lipoprotein cholesterol and apolipoprotein B concentrations were higher at 2 wk by 8.9 +/- 1.5% (P less than 0.001), 10.9 +/- 2.2% (P less than 0.005), and 18.9 +/- 5.9% (P less than 0.02), respectively, compared with the control diet. With lactulose, mean free fatty acid concentrations were reduced over the day by 19.5 +/- 5.9% (P less than 0.02), with no change in mean day-long blood glucose, serum insulin, or C-peptide concentrations. We conclude that certain rapidly fermented substrates may raise rather than lower serum lipids, possibly through increasing the amount of acetate absorbed from the colon.

Is colonic fermentation minimized by increasing meal frequency?

It has been suggested that, although increasing meal frequency has metabolic advantages in terms of carbohydrate and lipid metabolism, the efficiency of small intestinal absorption may be enhanced, thus reducing the extent of colonic fermentation. Since this may be undesirable, we have tested whether increasing meal frequency reduces the amount of carbohydrate fermented into the colon. Accordingly, seven healthy male volunteers took, in random order, two identical 2-week metabolic diets divided into either seventeen or three meals daily. On day 13 of each period measurements were made throughout the day of breath H2 and serum acetate, as markers of colonic fermentation. Mean levels of both breath H2 and acetate were similar on both diets, being lower on nibbling by 3.2 +/- 0.8 ppm and 25 +/- 9 mumols/l respectively (not significant). This study failed to demonstrate an effect of more efficient carbohydrate absorption with increased meal frequency.

Antibody responses against natural Taenia hydatigena infection in dogs in Kenya

Antibody responses (IgG) against Taenia hydatigena infection in dogs in Kenya were analysed in ELISA using excretory/secretory products of T. hydatigena scoleces derived from goat cysticercus cysts. Helminth infections of individual dogs were confirmed at autopsy. T. hydatigena worms were found in 89.5% of 143 dogs, and positive anti-T. hydatigena antibody levels were detected in 58.7% of infected dogs. Positive antiscolex antibody levels were detected in 40.0% of Turkana dogs uninfected with T. hydatigena, suggesting previous infection. Antibody was not detected in 34.4% of infected dogs. There was no relationship between individual T. hydatigena worm burdens and absorbance values for sera in ELISA. It was not possible to distinguish between sera from T. hydatigena-infected and uninfected dogs.

Manipulation of fecal pH by dietary means

Epidemiological and animal studies suggest that colonic fermentation and fecal pH may be risk factors for colorectal cancer. To modify these factors, we sought to develop a simple instrument for use in intervention studies. Three 14-day studies with 32, 40, and 30 healthy volunteers maintained on their regular diet were carried out to evaluate the effect of various food supplements on fecal pH. The interventions tested included supplementary lactulose, Metamucil, oat bran, wheat bran, or no supplement. The results showed that it is possible to provide a simple intervention to reduce fecal pH by 0.4 unit with oat bran administered at 75-100 g/day over a 14-day period, using a wheat combination, equivalent in macronutrients and fiber, as a control.

Metabolic effects of reducing rate of glucose ingestion by single bolus versus continuous sipping

Modifying the rate of absorption has been proposed as a therapeutic principle of specific relevance to diabetes. To demonstrate clearly the metabolic benefits that might result from reducing the rate of nutrient delivery, nine healthy volunteers took 50 g glucose in 700 ml water on two occasions: over 5-10 min (bolus) and at a constant rate over 3.5 h (sipping). Despite similar 4-h blood glucose areas, large reductions were seen in serum insulin (54 +/- 10%, P less than 0.001) and C-peptide (47 +/- 12%, P less than 0.01) areas after sipping, together with lower gastric inhibitory polypeptide and enteroglucagon levels and urinary catecholamine output. There was also prolonged suppression of plasma glucagon, growth hormone, and free-fatty acid (FFA) levels after sipping, whereas these levels rose 3-4 h after the glucose bolus. An intravenous glucose tolerance test at 4 h demonstrated a 48 +/- 10% (P less than 0.01) more rapid decline in blood glucose (Kg) after sipping than after the bolus. Furthermore, FFA and total branched-chain amino acid levels as additional markers of insulin action were lower over this period despite similar absolute levels of insulin and C-peptide. These findings indicate that prolonging the rate of glucose absorption enhances insulin economy and glucose disposal.

Glycemic index of foods in individual subjects

We studied 12 subjects with diabetes to determine how well the glycemic index (GI) predicted the ranking of glycemic responses of different foods in individuals. All subjects ate three mixed meals (bread, rice, or spaghetti with GIs of 100, 79, and 61, respectively) four times in a randomized complete block design. The mean glycemic response areas of the different meals ranked according to the predicted GI in every individual. The observed mean +/- SD GI values of the meals were significantly different from each other (bread 100 +/- 7, rice 75 +/- 9, spaghetti 54 +/- 9), with no significant difference in response between subjects. It is concluded that individuals share common mean GI values for different foods. Within confidence limits determined by the variability of glycemic responses, the number of repeated tests conducted, and the expected GI difference, the GI can be used to predict the ranking of the mean glycemic responses of mixed meals taken by individuals.

[Comparative effects of couscous and pasta on glycemia in normal subjects and type I diabetics]

8 healthy subjects have eaten in the morning, after an overnight fast, in two separated occasions and in a randomised order 50 gr of CHO as pasta or couscous. Blood glucose after pasta ingestion was lower at 30 mn (p less than 0.05) at 45 mn (p less than 0.01) and at 60 mn (p less than 0.05). Area under the curve after pasta was significantly reduced (p less than 0.01). In a second time 6 IDDM patients have eaten in a randomised order a meal made of pasta with tomato sauce (P = 11%, F = 30%, G = 59%) or couscous with vegetables and sauce (P = 10%, F = 37%, G = 53%). Blood glucose after the pasta was lower than couscous at 90 mn (p less than 0.05) the area under the curve after the pasta ingestion was reduced of 38% but did'nt reach significance. In conclusion couscous has a higher glycemic effect than pasta although it has a similar composition. This phenomenon is still observed when the cereal products are mixed with other foods and ingested by IDDM patients.

Nibbling versus gorging: metabolic advantages of increased meal frequency

We studied the effect of increasing the frequency of meals on serum lipid concentrations and carbohydrate tolerance in normal subjects. Seven men were assigned in random order to two metabolically identical diets. One diet consisted of 17 snacks per day (the nibbling diet), and the other of three meals per day (the three-meal diet); each diet was followed for two weeks. As compared with the three-meal diet, the nibbling diet reduced fasting serum concentrations of total cholesterol, low-density lipoprotein cholesterol, and apolipoprotein B by a mean (+/- SE) of 8.5 +/- 2.5 percent (P less than 0.02), 13.5 +/- 3.4 percent (P less than 0.01), and 15.1 +/- 5.7 percent (P less than 0.05), respectively. Although the mean blood glucose level and serum concentrations of free fatty acids, 3-hydroxybutyrate, and triglyceride were similar during both diets, during the nibbling diet the mean serum insulin level decreased by 27.9 +/- 6.3 percent (P less than 0.01) and the mean 24-hour urinary C-peptide output decreased by 20.2 +/- 5.6 percent (P less than 0.02). In addition, the mean 24-hour urinary cortisol excretion was lower by 17.3 +/- 5.9 percent (P less than 0.05) at the end of the nibbling diet than at the end of the three-meal diet. The blood glucose, serum insulin, and C-peptide responses to a standardized breakfast and the results of an intravenous glucose-tolerance test conducted at the end of each diet were similar. We conclude that in addition to the amount and type of food eaten, the frequency of meals may be an important determinant of fasting serum lipid levels, possibly in relation to changes in insulin secretion.

Effect of rectal infusion of short chain fatty acids in human subjects

Solutions containing 90 mmol sodium acetate plus 30 mmol sodium propionate (90 mM; isotonic), 180 mmol acetate plus 60 mmol propionate (180 mM; hypertonic) or an equivalent volume of isotonic saline were given over a 30-min period in random order by rectal infusion to six healthy subjects. Peripheral venous blood samples were obtained at 30-min intervals over the next 2 h. After the 90 mM infusion, the serum acetate response reached a peak at 60 min and had fallen to baseline by 120 min. The incremental area under the serum acetate response curve after 180 mM was twice that after 90 mM. Propionate was undetectable in serum at any time. Blood glucose fell after all of the infusions, but there was no significant difference between the saline- and short chain fatty acid (SCFA)-containing infusions. SCFA had no significant effect on serum insulin or c-peptide concentrations. However, compared with the saline control, the 180 mM solution resulted in a significant fall in serum free-fatty acids (FFA) and a significant rise in serum total cholesterol and triglyceride, with no change in beta-hydroxybutyrate levels. The data provide strong evidence that colonic SCFA are absorbed and metabolized in the human subject. The fall in FFA suggests that colonic SCFA have an effect on carbohydrate metabolism. In addition, the data provide indirect evidence for utilization of SCFA for lipid synthesis.

Hypocholesterolemic effect of vegetable protein in a hypocaloric diet

Eleven obese volunteers took part in a 12-week study during 8 weeks of which 2 meals of their control 1000 kcal diets were replaced by a soya based liquid formula (1 month) or a milk based liquid formula (1 month). The mean weight loss per month was 2.5 kg (P less than 0.05). On the soya formula total and LDL cholesterol levels were reduced significantly over the month by 10.0 +/- 2.7% (P less than 0.01) and 17.5 +/- 5.6% (P less than 0.02), respectively. Neither the milk based formula or the control low calorie diet lowered serum cholesterol significantly over the diet period. No change was seen in serum triglycerides on any of the 3 diets. No difference was seen between treatments in 24-h urinary C-peptide excretion. The results indicated that use of a vegetable protein supplement in a weight loss program which induced moderate weight loss was associated with a reduction in blood lipids, whereas moderate weight loss on a control low calorie diet or milk based formula was not.

Low glycemic index foods and reduced glucose, amino acid, and endocrine responses in cirrhosis

Carbohydrate intolerance is common in patients with cirrhosis. The aim of the present study was to determine whether the beneficial metabolic effects of low glycemic index diets observed in noncirrhotic diabetics also occurred in patients with cirrhosis. Therefore, for one day, five patients with cirrhosis were fed diets in which low glycemic index foods were substituted, replacing those which produced higher blood glucose rises. Reduction in the estimated glycemic impact of the diet by approximately 30% reduced the mean incremental blood glucose level over the day by 40 +/- 5% (p less than 0.001). Measurement at breakfast of amino acid, insulin, and gastric inhibitory polypeptide profiles confirmed a reduction of similar magnitude. No change was seen in pancreatic glucagon, whereas enteroglucagon levels tended to be higher. In view of these findings and the possible long-term benefits of chronic reduction of hyperinsulinism and alteration in amino acid metabolism, this approach to dietary management of cirrhosis warrants further consideration.

The glycemic index: variation between subjects and predictive difference

It is not known whether the variability of the glycemic index (GI) in different subjects is due to within- or between-individual variation. In addition, it is not known how large a difference in GI between different meals is clinically important for individuals with diabetes. Therefore, insulin-dependent (IDDM) and non-insulin-dependent (NIDDM) diabetic subjects tested four foods, with each food taken by each subject on two separate occasions. For each food, most of the variation of absolute glycemic responses was due to differences between the subjects. However, when the results were expressed as the GI, there were no significant differences between the subjects, and most of the variation was due to within-individual variation. Using the within-individual variance, we estimated the so-called "predictive difference" of GI values. Its reliability was assessed by consideration of published data from eight studies where different mixed meals were taken by the same group of subjects. There were 37 cases where the difference between the GI of any two meals was greater than the predictive difference. Of these 37 pairs of meals, the GI correctly ranked the glycemic responses in 36 (97%). We conclude that GI values for the same food do not vary significantly between different individuals. For a subject with NIDDM a difference in GI of 34 will predict the ranking of glycemic responses of two meals with 95% probability. The corresponding value for a subject with IDDM is 50.

Evaluation of a serological test system for the diagnosis of natural Echinococcus granulosus infection in dogs using E. granulosus protoscolex and oncosphere antigens

Serum antibody responses in feral or domesticated dogs naturally infected with Echinococcus granulosus or/and other common helminths were examined in an enzyme-linked immunosorbent assay (ELISA) using antigens prepared from E. granulosus protoscoleces or oncospheres. The ELISA using the protoscolex antigen was optimised with serums from experimental dogs monospecifically infected with E. granulosus or other helminth parasites, and helminth-free dogs. Anti-protoscolex antibody was detected in 16 of 22 (72.7%) serums from feral dogs with E. granulosus burdens ranging from 300 to 302,600 worms per dog. Seven serums from feral dogs which did not harbour E. granulosus at autopsy but which originated from an endemic hydatid region were tested using protoscolex antigen, and 1 serum gave a positive reaction. One hundred and two serums from dogs known never to have been infected with E. granulosus all gave negative reactions to protoscolex antigen. The sensitivity of the ELISA test proved to be superior to that which has been achieved by arecoline purging as a method of diagnosis for E. granulosus infection in dogs. For use of the assay in hydatid control or eradication campaigns, its sensitivity can be increased by choosing a lower absorbance discrimination value above which serums are regarded as having positive reactions. However, this does introduce positive reactions of some serums from dogs infected with helminths other than E. granulosus. In further development of the assay, use of defined recombinant antigens may improve both sensitivity and specificity.(ABSTRACT TRUNCATED AT 250 WORDS)

Relationship between fasting serum tryptophan/large neutral amino acid ratio and reported hunger in subjects with diabetes

Food intake regulation is influenced by serum amino acid (AA) ratios. The objectives of this study were to determine whether non-obese subjects with diabetes have normal serum AA ratios, and to see if AA ratios relate to perceived hunger. We therefore measured fasting serum AA in nine normal subjects on two occasions and 19 patients with diabetes on four occasions over a two month period. At the time of the blood samples, the subjects with diabetes were asked to rate how hungry they felt on a scale of -3 (very hungry) to +3 (very full). There were no significant differences between the mean AA ratios of normal and diabetic subjects. There was a positive correlation between reported hunger score and the ratio of serum tryptophan (TRP) to the sum of the concentrations of the other large neutral AA (LNAA) (r = 0.286, n = 78, p less than 0.05). The relationships between hunger and other AA ratios were not significant. Variations of the TRP/LNAA ratio within each subject did not relate to differences in hunger from day-to-day. However, there was a positive correlation between the mean TRP/LNAA ratio and mean hunger score of the different subjects (r = 0.495, n = 19, p less than 0.05). The relationships between TRP/LNAA ratio and body weight or hunger score were not significant. It is concluded that the serum AA ratios are normal in patients with diabetes. The data is consistent with the hypothesis that a low serum TRP/LNAA ratio causes increased feelings of hunger in different individuals.

Wholemeal versus wholegrain breads: proportion of whole or cracked grain and the glycaemic response

STUDY OBJECTIVE

To determine the effect on the glycaemic response to bread of the ratio of whole cereal grains to milled flour.

DESIGN

Randomised assignment of groups of diabetic volunteers to test and control meals, taken after an overnight fast. Test foods were also analysed for in vitro digestion with human saliva.

SETTING

Tertiary care centre.

PATIENTS

Groups of six drawn from pool of 16 volunteers with diabetes mellitus (11 men, five women; mean age 64 (SE 3); 10 taking insulin, five taking oral agents, one controlled by diet; other characteristics comparable).

INTERVENTIONS

All patients took standard white bread control meals on three occasions spanning the study and on different mornings took test meals containing varying ratios of whole cereal grains (barley or cracked wheat) to milled flour (75:25, 50:50, 0:100). All meals contained 50 g available carbohydrate and were eaten in 15 minutes. Capillary blood samples were taken for determination of glucose concentrations every 30 minutes for three hours.

END POINT

Glycaemic index of foods (= increase in area under blood glucose concentration curve for test food divided by increase in area under curve for white bread control X 100).

MEASUREMENTS AND MAIN RESULTS

Significant trend to lower glycaemic index with increasing proportion of whole cereal grains in test bread (p less than 0.05) and lower in vitro digestibility (p less than 0.001). Breads containing up to 75% whole grain were considered palatable.

CONCLUSIONS

Breads containing a high proportion of whole cereal grains may be useful in reducing the postprandial blood glucose profile in diabetics because they are more slowly digested. These breads should be called "wholegrain" in distinction to "wholemeal" breads made from milled flour.

Second-meal effect: low-glycemic-index foods eaten at dinner improve subsequent breakfast glycemic response

The effects of the glycemic index (GI) of carbohydrate eaten the previous night on the glycemic response to a standard test meal eaten subsequently in the morning (breakfast) was studied. On separate evenings normal subjects ate low- or high-GI test meals of the same nutrient composition. The dinners consisted of single foods in two experiments and mixed meals containing several foods in the third. The differences between the observed glycemic responses to low- and high-GI dinners were predicted by their GIs. The glycemic responses to breakfast were significantly lower on mornings after low-GI dinners than after high-GI dinners. Eating, at dinner, foods with different fiber contents but the same GI had no effect on postbreakfast glycemia. We conclude that the GI predicts the difference between glycemic responses of mixed dinner meals; breakfast carbohydrate tolerance is improved when low-GI foods are eaten the previous evening.

Low-glycemic-index starchy foods in the diabetic diet

Eight patients with noninsulin-dependent diabetes underwent two 2-wk study periods in random order during which they were provided with carbohydrate foods with either a high or low glycemic index (GI). Over both high-GI and low-GI periods there were significant reductions in body weight, serum fructosamine, and cholesterol. Reductions in fasting blood glucose, HbA1c, and urinary c-peptide-to-creatinine ratio were significant only over the low-GI period despite a smaller mean weight loss. Reductions in triglyceride were significant only over the high-GI diet. Inclusion of low-GI foods into diets of patients with diabetes may be an additional measure that favorably influences carbohydrate metabolism without increasing insulin demand.

Comparison of ileal effluents, dietary fibers, and whole foods in predicting the physiological importance of colonic fermentation

An in vitro fermentation system that simulates the human colon was used in conjunction with the human ileostomy model to determine whether whole foods or dietary fiber isolates from the same foods could be used in lieu of ileal effluent to estimate the daily colonic production of short chain fatty acids (SCFA). A basal diet and a test food were fed for 3 days to a healthy ileostomate, and the ileal effluent was collected. Dietary fiber intake significantly increased ileal dry matter, ash, protein, and available carbohydrate (total carbohydrate minus dietary fiber) (p less than 0.05). Basal diet, test foods, ileal effluents, and dietary fiber isolates then were fermented in vitro with mixed human fecal microflora for 24 h, and SCFA production (mmol SCFA/g organic matter) was measured. SCFA production from ileal effluent significantly correlated with that from dietary fiber isolates (r = 0.86, p less than 0.05), but not with that from whole foods. Therefore, dietary fiber isolates, rather than whole foods, can provide the closest estimates of colonic SCFA production when ileostomates are not available. Test foods significantly changed molar ratios of individual SCFA within the ileal effluent and dietary fiber isolate groupings (p less than 0.05). In view of the different ileal loads arriving in the colon, we conclude that large differences in SCFA production probably depend on the food consumed.

Manipulation of gut hormone response to food by soluble fiber and alpha-glucosidase inhibition

Preliminary data indicated that viscous fiber (guar) and alpha-glycosidase inhibition (acarbose) used in combination to slow carbohydrate absorption have an apparently additive effect in reducing the postprandial glycemic response. The full endocrine data reported here also demonstrate that reductions in insulin and gastric inhibitory polypeptide are most significant when guar and acarbose are used in combination. The results are divergent for enteroglucagon when guar and acarbose were given singly. Raised enterglucagon levels seen after acarbose are in keeping with inhibition of proximal absorption resulting in more distal absorption of carbohydrate. However, with viscous fiber, the enteroglucagon response was reduced, and this reduction was maintained even after addition of acarbose. The results demonstrate that the gut endocrine response can be manipulated by pharmacological interventions which alter the pattern of carbohydrate absorption.

Starchy foods and glycemic index

Different starchy foods produce different glycemic responses when fed individually, and there is some evidence that this also applies in the context of the mixed meal. A major reason appears to relate to the rate at which the foods are digested and the factors influencing this. A similar ranking in terms of glycemic response to specific foods is seen independent of the carbohydrate tolerance status of the groups tested. Potentially clinically useful starchy foods producing relatively flat glycemic responses have been identified. Many of these are considered ethnic or traditional and include legumes; pasta; grains such as barley, parboiled rice, and bulgur (cracked wheat); and whole-grain breads such as pumpernickel. Specific incorporation of these foods into diets has been associated with reductions in low-density lipoprotein cholesterol and triglyceride levels in hyperlipidemia and with improved blood glucose control in insulin-dependent diabetic patients. To facilitate identification of such foods, it has been suggested that the glycemic response should be indexed to a standard (e.g., white bread) to allow comparisons to be made between the glycemic index of foods tested in different groups of subjects. The scope of application of this principle is subject to further investigation. It may be used to expand the range of possibly useful starchy foods for trial in the diets of diabetic patients.

The acute effect of fat on insulin secretion

Previous studies suggest that the rate of rise of the plasma glucose-dependent insulinotropic peptide (GIP) concentration, rather than the steady state level achieved, may be the stimulus of the increased insulin secretion that occurs when fat is ingested with carbohydrate. To test this hypothesis six normal men were given a 5-g iv bolus dose of glucose 15 min after a carbohydrate meal with or without fat. At the time of the iv glucose injection after the fat-containing meal, the rate of rise of plasma GIP was maximum, but the level was only 40% of the achieved by 30 min. Plasma GIP did not change after the meal without fat. After the fat meal, peak insulin and C-peptide levels in response to iv glucose were 60% greater than those after carbohydrate alone despite similar peak blood glucose levels. The calculated insulin clearance was not altered by the fat meal. We conclude that glucose-stimulated insulin secretion is increased early after fat ingestion, possibly due to a rise in GIP or other incretins.

Dietary fiber in management of diabetes

Current evidence suggests that high-fiber diets, especially of the soluble variety, and soluble fiber supplements may offer some improvement in carbohydrate metabolism, lower total cholesterol and low-density lipoprotein (LDL) cholesterol, and have other beneficial effects in patients with non-insulin-dependent diabetes mellitus (NIDDM). Diets enriched with wheat bran and guar gum induce 10-20% reductions in serum cholesterol and LDL in both normo- and hypercholesterolemic subjects and have the ability to blunt the hypertriglyceridemic effects of diets high in carbohydrate and low in fiber. In insulin-dependent diabetes mellitus (IDDM) the situation is less clear, but a decrement of the circadian glucose profile has been shown. Americans, in general, consume too little fiber. With the need to restrict fat and reduce protein, an increase in carbohydrates is mandatory. A practical goal would be to establish the present level of fiber intake (15-30 g/day) and to gradually increase it. An intake of up to 40 g of fiber per day or 25 g/1000 kcal of food intake appears beneficial; in many individuals on weight-reducing diets higher levels may be unacceptable because of gastrointestinal side effects. The level of maximum benefit has not been determined. Fiber supplementation appears beneficial only if given with a diet comprising approximately half of the calories as carbohydrate. Foods should be selected with moderate to high amounts of dietary fiber from a wide variety of choices to include both soluble and insoluble types of fiber. Insufficient data are available on the long-term safety of high-fiber supplements. People at risk for deficiencies, such as postmenopausal women, the elderly, or growing children, may require supplements of calcium and trace minerals. People with upper gastrointestinal dysfunction are at risk of bezoar formation and cautioned against a diet high in fiber of the leafy vegetable type. Careful attention must be paid to insulin dose because hypoglycemia can result if there is a radical change in fiber intake and insulin dose is not reduced appropriately. Care must be exercised in the use of "novel" fibers, including the wood celluloses, because little is known of their safety and efficacy.

Metabolic effects of a low-glycemic-index diet

Six healthy male volunteers underwent 2-wk metabolically controlled high-glycemic-index (GI) and low-GI diets in random order. Over the low-GI diet significant reductions were seen in serum fructosamine (7.0 +/- 1.0%, p less than 0.01), 12-h blood glucose profile (37 +/- 7%, p less than 0.01), and total serum cholesterol (15 +/- 3%, p less than 0.01). As a measure of insulin secretion, 24-h urinary C-peptide levels were 32 +/- 10% lower (p less than 0.05) after the low-GI than after the high-GI diet. Lower C-peptide levels were maintained after a standard carbohydrate challenge after the low-GI diet despite higher blood glucose levels. Differences in blood glucose were not seen after a 5-g intravenous glucose challenge. These results are of interest with respect to the effect that prolonged postprandial reductions in nutrient fluxes and insulin secretion may have on carbohydrate and lipid metabolism and renal function.

Wheat fiber and laxation: dose response and equilibration time

We studied the dose response to soft white winter wheat fiber on fecal output in a group of healthy volunteers whose breakfasts consisted of wheat fiber cereals in amounts that provided 0.3 g, 5.6 g, 9.5 g, 11.2 g, 19.0 g, and 28.4 g dietary fiber per day for 14 days; no other aspects of their diet were altered. A linear dose response was observed between the six levels of fiber intake (r = 0.983, p less than 0.01) with a 1-g increase in wheat fiber, producing a mean 2.7-g increase in fecal weight. This increase was independent of the initial daily fecal weight of the volunteer (mean 117 +/- 64 g/day, range 5-297 g/day, n = 73). The maximum increase in fecal output due to cereal fiber was reached after the first week on the supplement. These data support the use of graded amounts of cereal fiber in the management of constipation.