Postprandial Increment Research Articles

Effects of Acarbose on Serum Lipoproteins in Healthy Individuals during Prolonged Administration of a Fiber-Free Formula Diet

The effects of the disaccharidase inhibitor acarbose on serum lipoprotein lipid concentrations were investigated in healthy subjects during prolonged feeding of a fiber-free formula diet. Acarbose was shown to decrease cholesterol and fasting triglyceride concentrations, whereas the postprandial increment of triglycerides was not diminished. The response of fasting triglycerides to acarbose treatment appeared to be related to dietary fat intake, but not to the drug-induced reduction of postprandial glucose and insulin concentrations. Both the triglyceride and the cholesterol lowering efficacy were less pronounced with a higher amount of saturated fat than with a lower intake of fat mainly composed of polyunsaturated fatty acids. The decrease in total cholesterol was shown to be a consequence of a significant reduction in low density lipoprotein (LDL) cholesterol. Since high density lipoprotein (HDL) cholesterol concentrations remained unaltered, the ratio of HDL/LDL cholesterol changed in a beneficial way.

Improved carbohydrate tolerance and stimulation of carbohydrate oxidation and lipogenesis during short-term carbohydrate overfeeding

The carbohydrate intake of seven healthy men was increased from 220–265 g/d to 620–770 g/d for 17 days, while protein and fat intake remained constant. Carbohydrate loading did not affect the preprandial plasma glucose levels after an overnight fast, but reduced the postprandial increment in plasma glucose levels after 5, 11, and 17 days of overfeeding. Preprandial plasma insulin levels were slightly increased during carbohydrate overfeeding, but no increase in the postprandial rise in insulin levels was found until 11 days after the start of carbohydrate loading. Whole-body rates of carbohydrate oxidation and of glucose conversion to fat were estimated by indirect calorimetry. Basal carbohydrate oxidation rate was increased by 95% at the end of 17 days of overfeeding, but there was no potentiation in the stimulation of the carbohydrate oxidation rate induced by a meal. There was no net fat synthesis from glucose before carbohydrate loading; carbohydrate overfeeding produced nonprotein respiratory exchange ratios greater than 1.00, suggesting net fat synthesis from glucose. Meals did not stimulate net lipogenesis from glucose, either before or after overfeeding. These results indicate that the improvement in carbohydrate tolerance associated with short-term carbohydrate loading does not appear to depend on elevated insulin levels. Increased carbohydrate oxidation and lipogenesis elevated carbohydrate disposal is more than necessary to account for the improvement in carbohydrate tolerance.

Influence de la cinétique d'évacuation gastrique de l'aliment sur l'insulinémie chez le veau préruminant

The aim of this work was to clarify the possible role of blood metabolites (glucose, aminoacids, triglycerides) in the regulation of postprandial blood insulin in the preruminant calf. The animals used were 6 male Friesian bull calves with an average weight of 80 kg. They were divided into groups I and II. During the first experimental period (A), group I received a control diet that contained skim-milk powder as the only protein source, whereas group II received an experimental diet containing fish protein concentrate as the main protein source. During the second experimental period (B), the diets were switched. It was previously shown that the rate of fat and amino acid absorption increased when milk proteins in such milk substitutes were replaced by hydrolyzed fish proteins (Guilloteau et al., 1975). The results showed that during any experimental period in the control group, there was a decrease in the postprandial blood free amino nitrogen. Blood triglycerides exhibited a small increase at 0.5 h after the meal but a large decrease at 1-4.5 h. The meal also resulted in a very large increase in blood glucose with maximal values occurring at 1-4.5 h. Blood insulin showed a large increment at 0.5 h then increased slowly, peaking at 2-3 h. The postprandial increase in blood insulin was less during the first experimental period than during the second one. In calves fed the fish diet, blood free amino nitrogen and blood triglycerides showed a large postprandial increase. Blood glucose exhibited a smaller postprandial increment than in the controls and began to decrease at half an hour. In contrast, the trend of changes in blood insulin was the same as in the controls (i.e. a maximum at 3 h occurring after a large increase at 0.5 h). There were no significant differences in blood insulin between the two experimental periods. It was lower in the calves fed the fish diet than in the controls during the first experimental period; during the second period, it was similar in both groups. From these observations, it may be inferred that, as compared to the control diet, the fish diet resulted in a decrease in glucose stimulation of postprandial insulin secretion; in contrast, the effect of aminoacids and lipids may be increased.

Serum gastrin in patients with chronic renal failure.

The realisation that circulating gastrin is heterogeneous necessitates a reappraisal of gastrin's role in the increased incidence of duodenal ulcer disease that occurs in chronic renal failure. Radioimmunoassays employing region-specific antisera have been used to examine renal and extrarenal factors controlling serum gastrin concentration in patients with chronic renal failure. The present study has shown that basal serum gastrin concentrations measured with a carboxyl-terminal specific antibody were significantly higher in eight patients with chronic renal failure treated by dietary restriction (388+/-196 pM) than in 14 patients with chronic renal failure treated by haemodialysis (28.7+/-4.6 pM). However, basal gastrin concentrations in both groups of patients were significantly higher than in 25 normal subjects (12.3+/-1.8 pM) and showed significant negative correlations with maximal gastric acid secretion (p < 0.01). Markedly raised basal gastrin concentrations were observed only in chronic renal failure patients who were also achlorhydric. Although the peak postprandial increment in big gastrin concentration in 11 chronic renal failure patients (34.0+/-7.5 pM) was significantly greater (p < 0.05) than in 25 normal subjects (19.5+/-4.6 pM), the little gastrin responses were not significantly different. In addition, clearance of exogenous little gastrin was similar in four chronic failure patients (clearance half time: 8.1+/-0.7 min) and four normal subjects (clearance half time: 6.5+/-1.2 min). These studies suggest that the human kidney is unimportant in the metabolism of little gastrin. As circulating little gastrin is six times more potent than big gastrin in stimulating acid secretion, these studies suggest that the raised gastrin concentrations observed in patients with chronic renal failure have little significance in terms of their increased incidence of duodenal ulcer disease.

Comparisons of chromium status in diabetic and normal men

Diabetes mellitus has been shown to develop as a consequence of chromium (Cr) deficiency in experimental animals and humans sustained by prolonged total parenteral nutrition. However, a relative lack in body Cr stores has not been demonstrated in the adult American diabetic population. In the present study, we measured fasting and postprandial total Cr in plasma, RBC and urine, and total Cr in hair, as well as volatile and ultrafilterable Cr in plasma and urine from 46 adult male diabetics and from 20 age-matched nondiabetic subjects. Diabetics were in the following categories: 21 ketosis-prone, 7 non-ketosis-prone and nonobese, and 18 non-ketosis-prone and obese. In addition, plasma lipids, glucose, and glucose tolerance were measured in all populations. A wide individual variation in Cr levels, amounting in some instances to an order of magnitude, was seen in the various samples from both diabetics and normals. Ketosis-prone, insulin-requiring diabetics had significantly higher plasma Cr than either of the other diabetic subgroups or the normals. The non-ketosis-prone, nonobese diabetics had elevated urinary Cr output as contrasted to the other groups. Although the mean values for hair and RBC Cr did not differ significantly among the groups, analysis of distribution indicated that the lowest values were found in the diabetics. No correlations were found among the hair, RBC, plasma, or urine, suggesting that these samples may reflect different Cr body stores. Cr levels were generally unrelated to obesity, use of alcohol and tobacco, modality of diabetes therapy (i.e., diet, oral hypoglycemic agents, or insulin), age, race, cholesterol or triglyceride levels. However, a significant inverse correlation was seen between RBC Cr and fasting plasma glucose in the diabetic population. There was a similarly significant inverse correlation between the postprandial increment in plasma Cr and fasting plasma glucose. Although these observations do not confirm the presence of Cr deficiency in the male diabetic population, there is suggestive evidence for a relationship between certain body pools of Cr and carbohydrate metabolism in diabetes.

Effect of atropine and vagotomy on pancreatic polypeptide response to a meal in dogs.

In four conscious dogs the pancreatic polypeptide (PP) response to a standard beef-liver meal was measured by specific radioimmunoassay and compared with the response seen after the intravenous injection of 25 or 100 microgram/kg atropine. All three tests were performed twice in each animal and then repeated after truncal vagotomy. The mean prevagotomy postprandial PP increment was 85 +/- 16 pmol/liter in the first 2-h period and 54.5 +/- 13 pmol/liter in the second. After the injection of 25 microgram/kg atropine there was significant reduction in the early response (mean delta PP = 39 +/- 17 pmol/liter, P less than 0.05), but not the late (mean delta PP = 62 +/- 18 pmol/liter). After 100 microgram/kg atropine sulfate, the response was significantly reduced during both periods (mean delta PP = 5.5 +/- 5.2 and 20 +/- 8.8 pmol/liter, respectively, P less than 0.01). Truncal vagotomy significantly (P less than 0.01) reduced the PP response over both time periods (mean delta PP = 6.4 +/- 2.2 and 5.8 +/- 3.8 pmol/liter), and the small residual response was completely abolished by atropine. In five additional dogs an infusion of bethanechol (100 microgram . kg-1.h-1) caused a significant increase (P less than 0.05) in the plasma concentration (mean delta PP = 40.9 +/- 11.8 pmol/liter), which was abolished by pretreatment with atropine (mean delta PP = -2.9 +/- 2.1 pmol/liter). These studies suggest that PP release in response to a meal in the dog is largely under vagal-cholinergic control.

Effects of Glipizide and Food Intake on the Blood Levels of Glucose and Insulin in Diabetic Patients

ABSTRACT. The blood levels of glucose and insulin were monitored in 15 patients with non‐ketotic maturity‐onset diabetes mellitus given a single 5 mg oral dose of a novel sulfonylurea drug, glipizide, together with, and 30 min prior to, a standardized breakfast meal. In addition, the effect of the meal only was examined. The mean preprandial levels of blood glucose and plasma insulin on the three occasions were similar. Following glipizide administration, the early postprandial increment of blood glucose was reduced, and there was a subsequent decrease to values below the preprandial level. Both the decrease and the reduction of the early increase were significantly more marked when the drug was given 30 min prior to than together with the meal. Apparently, this did not result from a stronger effect of the drug on insulin release when given before than together with the meal, as the plasma insulin levels and the corresponding concentration curve areas did not differ. Rather, the difference was due to a more optimal timing between insulin release and the blood glucose increment evoked by the meal. In addition, there seemed to be only a minor interindividual variation in the bioavailability of the drug, as its effect on insulin levels varied rather little. Hence, 5 mg of glipizide three times daily 30 min before meals can be recommended as a standard regimen.

Calorigenic response in obese and nonobese women

The calorigenic response to a high protein test meal was studied in women with a history of childhood onset obesity. Obese and nonobese individuals were fasted overnight and basal oxygen consumptions determined the following morning. A semisynthetic 823 kcal high protein test meal was ingested within a 1-hr period followed by hourly determinations of oxygen consumption and plasma levels of insulin, free fatty acids, triglycerides, glucose, amino acids, and urea nitrogen. Amino acid levels increased faster and to a higher plateau in the nonobese group, while insulin levels increased and eventually decreased in a similar fashion in both groups. No differences in basal metabolic rate were detected. The postprandial increment in oxygen consumption was significantly less among the obese subjects. Diminished calorigenesis after each meal would result in accumulation of extra calories provided that caloric consumption is not appropriately decreased. These data suggest that a physiological aberration of energy metabolism may contribute to the development of childhood onset obesity.