Glycemic index, glycemic load and glycemic response: An International Scientific Consensus Summit from the International Carbohydrate Quality Consortium (ICQC).

BACKGROUND AND AIMS: The positive and negative health effects of dietary carbohydrates are of interest to both researchers and consumers. METHODS: International experts on carbohydrate research held a scientific summit in Stresa, Italy, in June 2013 to discuss controversies surrounding the utility of the glycemic index (GI), glycemic load (GL) and glycemic response (GR). RESULTS: The outcome was a scientific consensus statement which recognized the importance of postprandial glycemia in overall health, and the GI as a valid and reproducible method of classifying carbohydrate foods for this purpose. There was consensus that diets low in GI and GL were relevant to the prevention and management of diabetes and coronary heart disease, and probably obesity. Moderate to weak associations were observed for selected cancers. The group affirmed that diets low in GI and GL should always be considered in the context of diets otherwise understood as healthy, complementing additional ways of characterizing carbohydrate foods, such as fiber and whole grain content. Diets of low GI and GL were considered particularly important in individuals with insulin resistance. CONCLUSIONS: Given the high prevalence of diabetes and pre-diabetes worldwide and the consistency of the scientific evidence reviewed, the expert panel confirmed an urgent need to communicate information on GI and GL to the general public and health professionals, through channels such as national dietary guidelines, food composition tables and food labels.

Effect of baking process on postprandial metabolic consequences: randomized trials in normal and type 2 diabetic subjects.

OBJECTIVE: To determine the impact of the form, fibre content, baking and processing on the glycaemic, insulinaemic and lipidaemic responses of different French breads. DESIGN AND SUBJECTS: First study: Nine healthy subjects were randomized to consume in a crossover design one of six kinds of French bread (each containing 50 g available carbohydrate): classic baguette, traditional baguette, loaf of wholemeal bread (WM-B), loaf of bread fermented with yeast or with leaven, a sandwich and a glucose challenge as reference. RESULTS: The glycaemic index (GI) values ranged from 57+/-9% (mean+/-s.e.m.), for the traditional baguette, to 85+/-27% for the WM-B. No significant difference was found among the different tested bread. The insulinaemic index (II), however, of the traditional baguette and of the bread fermented with leaven were lower than the other breads (analysis of variance: P<0.01). Postprandial plasma triglycerides showed similar profiles. The traditional baguette tended to decrease postprandial free fatty acids compared to levels after the classic baguette. RESULTS: The GI of the traditional baguette was lower than that of the classic baguette (n=8, venous blood: 70+/-4 vs 75+/-4, P=0.002; capillary blood: 69+/-5 vs 83+/-6, P=0.028, respectively). CONCLUSIONS: Some varieties of French bread (the TB) have lower II, in healthy subjects, and lower GI, in type 2 diabetic subjects, than that of the other varieties. These results might be due to bread processing difference rather than fibre content. SPONSORSHIPS: Supported by grants from the National French Milling Association.

Glycaemic and insulinaemic responses to a new hydrogenated starch hydrolysate in healthy and type 2 diabetic subjects.

BACKGROUND: Industrialists are searching for a sugar replacement in confectioneries such as hard candies, gum and chocolate. Lycasin HBC is a suitable candidate. Nevertheless, no information on its plasma glucose and insulin responses exists. Therefore, we aimed to evaluate the glycaemic and insulinaemic indices of Lycasin HBC in healthy subjects and in subjects with type 2 diabetes mellitus. METHODS: Six healthy and six type 2 diabetic men participated in the study. Each subject absorbed, after an overnight fast, a challenge of either 50 g of glucose or 50 g of Lycasin HBC using a randomised double-blind crossover design. Blood samples for measuring plasma glucose and insulin concentrations were collected during a 3 hour period. RESULTS: The calculated glycaemic index of Lycasin HBC was 47 +/- 10% in healthy subjects and 25 +/- 6% in patients with type 2 diabetes mellitus. The insulinaemic index of Lycasin HBC was 23 +/- 4% and 39 +/- 14%, respectively. As glucose levels oscillate in a very limited range in normal healthy subjects, the insulinaemic index must be considered here. On the other hand, it is the glycaemic rather than the insulinaemic index that must be assessed in diabetic subjects due to impairment of insulin secretion. CONCLUSIONS: The tested Lycasin HBC showed a low insulinaemic index in healthy subjects (23 +/- 4%) and a low glycaemic index (25 +/- 6%) in type 2 diabetic patients. Thus, it might be considered as an interesting sucrose substitute in confectionery for individuals with or without diabetes.

Health benefits of low glycaemic index foods, such as pulses, in diabetic patients and healthy individuals.

The present paper covers the health benefits of low glycaemic index foods, such as pulses. Nutritional factors potentially play a crucial role in health and disease. A low-fat, high-carbohydrate diet is often recommended as a part of a healthy life-style. Historical works have shown that carbohydrate foods differ in their ability to affect post-ingestive glycaemia. The glycaemic index concept allows a ranking of carbohydrate-rich foods in terms of their blood glucose raising potential. Pulses are foods with very low glycaemic index values. Numerous studies have documented the health benefits that can be obtained by selecting foods of low glycaemic index. These benefits are of crucial importance in the dietary treatment of diabetes mellitus: glycaemic control is improved as well as several metabolic parameters, such as blood lipids. The results of human studies have been confirmed by animal experiments in the field of diabetes. Diets with low glycaemic index value improve the prevention of coronary heart disease in diabetic and healthy subjects. In obese or overweight individuals, low-glycaemic index meals increase satiety and facilitate the control of food intake. Selecting low glycaemic index foods has also demonstrated benefits for healthy persons in terms of post-prandial glucose and lipid metabolism. Several public health organizations have recently integrated consideration of the glycaemic index in their nutritional recommendations for patients with metabolic diseases and for the general population.

Regulation of glucose transport and transporter 4 (GLUT-4) in muscle and adipocytes of sucrose-fed rats: effects of N-3 poly- and monounsaturated fatty acids.

The goal of this study was to compare the short-term effects of dietary n-3 polyunsaturated (fish oil) and monounsaturated (olive oil) fatty acids on glucose transport, plasma glucose and lipid controls in a dietary insulin resistance model using sucrose-fed rats. The underlying cellular and molecular mechanisms were also determined in the muscle and adipose tissue. Male Sprague-Dawley rats (5 weeks old) were randomized for diets containing 57.5 % (w/w) sucrose and 14 % lipids as either fish oil (SF), olive oil (SO) or a mixture of standard oils (SC) for 3 weeks. A fourth control group (C) was fed a diet containing 57.5 % starch and 14 % standard oils. After three weeks on the diet, body weight was comparable in the four groups. The sucrose-fed rats were hyperglycemic and hyperinsulinemic in response to glucose load. The presence of fish oil in the sucrose diet prevented sucrose-induced hyperinsulinemia and hypertriglyceridemia, but had no effect on plasma glucose levels. Insulin-stimulated glucose transport in adipocytes increased after feeding with fish oil (p < 0.005). These modifications were associated with increased Glut-4 protein (p < 0.05) and mRNA levels in adipocytes. In the muscle, no effect was found on Glut-4 protein levels. Olive oil, however, could not bring about any improvement in plasma insulin, plasma lipids or Glut-4 protein levels. We therefore conclude that the presence of fish oil, in contrast to olive oil, prevents insulin resistance and hypertriglyceridemia in rats on a sucrose diet, and restores Glut-4 protein quantity in adipocytes but not in muscle at basal levels. Dietary regulation of Glut-4 proteins appears to be tissue specific and might depend on insulin stimulation and/or duration of dietary interventions.

Chronic consumption of fresh but not heated yogurt improves breath-hydrogen status and short-chain fatty acid profiles: a controlled study in healthy men with or without lactose maldigestion.

BACKGROUND: Ingestion of fermented dairy products induces changes in the equilibrium and metabolism of the intestinal microflora and may thus have beneficial effects on the host. OBJECTIVE: We compared the effects of chronic consumption of yogurt with (fresh) or without (heated) live bacterial cultures (Lactobacillus bulgaricus and Streptococcus thermophilus) on plasma glucose, insulin, triacylglycerols, cholesterol, fatty acids, and short-chain fatty acids. DESIGN: Two groups of 12 healthy men with or without lactose malabsorption were selected with use of a breath-hydrogen test after a 30-g lactose load. Subjects were randomly assigned in a crossover design to 500 g/d of either fresh or heated yogurt for 2 periods of 15 d each, separated by a 15-d washout interval. RESULTS: Chronic consumption of fresh or heated yogurt had no detrimental effects on plasma glucose, insulin, or fatty acid areas under the curve in response to acute ingestion of 500 g yogurt in healthy men with or without lactose malabsorption. There were also no detectable changes in fasting plasma glucose, insulin, fatty acid, triacylglycerol, or cholesterol concentrations. In contrast, plasma butyrate was higher (P: < 0.03) and plasma propionate tended to be higher (P: = 0.059) in subjects without lactose malabsorption after fresh yogurt consumption than after heated yogurt consumption. There were no significant changes in plasma acetate. In subjects with lactose malabsorption, 15 d of fresh yogurt consumption also increased propionate production compared with values at baseline (P: < 0.04). In the same group, the production of breath hydrogen was lower after fresh yogurt consumption than after heated yogurt consumption (P: < 0.01). CONCLUSIONS: In men with lactose malabsorption, chronic consumption of yogurt containing live bacterial cultures ameliorated the malabsorption, as evidenced by lower breath-hydrogen excretion, but increased propionate concentrations. In subjects without lactose malabsorption, such yogurt tended to increase propionate and increased butyrate.

Negative regulation of leptin by chronic high-glycemic index starch diet.

The response of plasma leptin to a high-glycemic index (high-GI) starch diet after a short (3 weeks) and prolonged (12 weeks) period was determined in Sprague-Dawley rats. Age-matched rats were fed an identical isocaloric diet except that the carbohydrates were from either mung bean starch (low-GI) or waxy cornstarch (high-GI). After a single test meal of the high-GI starch diet, postprandial plasma glucose (P < .05) and insulin (P < .01) peaks and plasma glucose (P < .014) and insulin (P < .05) areas were higher versus the low-GI starch diet (n = 8 per group). Other age-matched control rats were fed the same diets for a longer period. After 3 weeks, ob mRNA levels were decreased by 50% (P < .005) in the epididymal adipose tissue of high-GI-fed rats versus low-GI-fed rats, without a significant decrease in plasma leptin. After 12 weeks of the high-GI starch diet, both plasma leptin and ob mRNA were decreased by 34% (P < .005) and 41% (P < .05), respectively, compared with the low-GI diet. Both relative epididymal adipose tissue weight (adjusted per 100 g body weight) and total fat mass, as measured by dual-energy x-ray absorptiometry (DEXA), were unchanged by the high-GI starch diet. Basal nonfasting plasma insulin, glucose, and triglycerides were not altered by the high-GI starch diet, whereas free fatty acids were significantly elevated and associated with a trend (P < .13) for increased plasma free glycerol. Plasma leptin levels were negatively correlated with free fatty acid levels (r = .56, P < .05). Despite low leptin, rats fed on the high-GI diet did not increase their food intake, suggesting increased leptin sensitivity. These findings might precede weight gain and the increase in fat mass. Chronic nutritional factors might alter plasma leptin via several overlapping factors independently of energy intake.

Chronic consumption of short-chain fructooligosaccharides does not affect basal hepatic glucose production or insulin resistance in type 2 diabetics.

Short-chain fructooligosaccharides (FOS) are prebiotics, which escape digestion in the small intestine and are fermented by the colonic microflora into short-chain fatty acids. Recently, we found that the daily consumption of 20 g FOS decreased basal hepatic glucose production in healthy subjects without any effect on insulin-stimulated glucose metabolism. In this study, we evaluated the effects of the chronic ingestion of FOS on plasma lipid and glucose concentrations, hepatic glucose production and insulin resistance in type 2 diabetics. Type 2 diabetic volunteers (n = 10; 6 men, 4 women) received either 20 g/d FOS or sucrose for 4 wk in a double-blind crossover design. FOS did not modify fasting plasma glucose and insulin concentrations or basal hepatic glucose production. The plasma glucose response to a fixed exogenous insulin bolus did not differ at the end of the two periods. Erythrocyte insulin binding also did not differ. Serum triacylglycerol, total and HDL cholesterol, free fatty acid, apolipoproteins A1 and B and lipoprotein (a) concentrations were not modified by the chronic ingestion of FOS. We conclude that 4 wk of 20 g/d of FOS had no effect on glucose and lipid metabolism in type 2 diabetics.

A high glycemic index starch diet affects lipid storage-related enzymes in normal and to a lesser extent in diabetic rats.

The of this study was to evaluate the chronic effects of a high (waxy corn) vs. a low (mung beans) glycemic index starch diet on the lipogenic enzymes, fatty acid synthase (FAS) and lipoprotein lipase (LPL). Normal and diabetic (streptozotocin-injected on d 2 of life) male Sprague-Dawley rats consumed a diet containing 575 g/kg carbohydrates either as waxy cornstarch (WCS) or as mung bean starch (MBS). After 3 wk, neither body weights nor relative epididymal fat pad weights differed. In diabetic rats, the WCS diet induced high basal plasma insulin levels. Plasma triglycerides were not significantly affected by diet in either normal or diabetic rats. Adipose tissue and liver LPL activities were not modified by the type of starch in the diet. In normal rats, FAS activity and gene expression in epididymal adipose tissue but not in liver were greater in rats consuming the WCS diet than in those consuming MBS. To evaluate the implication of insulin in this regulation, two genes regulated by insulin [GLUT4 and phosphoenolpyruvate carboxykinase (PEPCK)] were also studied. The high glycemic index WCS diet compared with the low glycemic index MBS diet resulted in lower hepatic PEPCK mRNA in both normal and diabetic rats. Normal, but not diabetic rats fed WCS had greater GLUT4 gene expression in adipocytes than did those fed MBS. We conclude that the total replacement of 575 g/kg low glycemic index starch by a high glycemic index starch for 3 wk caused the following in normal rats: 1) high FAS activity and mRNA in adipose tissue but not in liver and 2) high GLUT4 gene expression in adipose tissue. In both normal and diabetic rats this same diet resulted in lower hepatic PEPCK mRNA. Therefore, high glycemic index starch diet is implicated in stimulating FAS activity and lipogenesis and might have undesirable long-term metabolic effects.

Plasma lipids and fatty acid synthase activity are regulated by short-chain fructo-oligosaccharides in sucrose-fed insulin-resistant rats.

The aim of this study was to evaluate the chronic effects of a short-chain fructo-oligosaccharide (FOS)-containing diet on plasma lipids and the activity of fatty acid synthase (FAS) in insulin-resistant rats. Normal male Sprague-Dawley rats, 5 wk old, were randomly assigned to two groups and fed either a sucrose-rich diet (S, 575 g sucrose /kg diet and 140 g lipids/kg diet) or a sucrose-rich diet supplemented with 10 g/100 g short-chain fructo-oligosaccharides (S/FOS). A third reference group (R) was fed a standard nonpurified diet (g/kg, 575 g starch, 50 g fat). After 3 wk the sucrose-fed rats (compared with the R group) were characterized by the following: 1) higher insulin responses after a glucose challenge (P < 0.05); 2) heavier liver (P < 0.001) and retroperitoneal adipose tissue (P < 0.01); 3) hypertriglyceridemia (P < 0.0001) and higher plasma free fatty acids (P < 0.0001); and 4) higher fatty acid synthase activity in the liver but a low activity in the adipose tissue (P < 0.001). The addition of FOS to the diet resulted in 11% lower liver weight than in the S group (P < 0.05) and tended to result in lower adipose tissue weight (P < 0.11). Plasma triglycerides and plasma free fatty acids were lower in S/FOS- than in S-fed rats (P < 0.05). Chylomicrons + VLDL, and intermediate density lipoprotein (IDL) concentrations did not differ between groups, nor was plasma cholesterol influenced by diet. Hepatic FAS activity was lower in S/FOS-fed rats than in the S-fed rats (P < 0.05). In adipose tissue, however, this activity tended to be greater in rats fed S/FOS than in rats fed the S diet (P < 0.07). In conclusion, in a rat model of diet-induced (57.5% sucrose and 14% lipids) insulin resistance, the addition of short-chain FOS prevented some lipid disorders, lowered fatty acid synthase activity in the liver and tended to raise this activity in the adipose tissue. Short-chain FOS, in addition to being a nondigestible sweetener with good bulking capacity, might be useful in the treatment of insulin resistance and hyperlipidemia.

Moderate intake of n-3 fatty acids for 2 months has no detrimental effect on glucose metabolism and could ameliorate the lipid profile in type 2 diabetic men. Results of a controlled study.

OBJECTIVE: To evaluate the effect of a moderate dose of fish oil on glycemic control and in vivo insulin action in type 2 diabetic men with elevated plasma triacylglycerols and to determine the effect of the same treatment on gene expression of GLUT4, lipoprotein lipase (LPL), and hormone-sensitive lipase (HSL) in the abdominal adipose tissue. RESEARCH DESIGN AND METHODS: A total of 12 type 2 diabetic men were randomly allocated to 2 months of 6 g daily of either fish oil or sunflower oil, separated by a 2-month washout interval, in a double-blind crossover design. RESULTS: For glucose metabolism, 2 months of fish oil supplementation compared with sunflower oil led to similar fasting plasma insulin, glucose, and HbA1c. Basal hepatic glucose production did not increase after fish oil. There was no difference in insulin suppression of hepatic glucose production nor in insulin stimulation of whole-body glucose disposal measured by the euglycemic-hyperinsulinemic clamp. Fish oil did not ameliorate the low mRNA level of GLUT4 in adipose tissue of these patients. For lipid profile, fish oil lowered plasma triacylglycerol more than sunflower oil (P < 0.05) and tended to increase the amount of mRNA of both LPL and HSL in adipose tissue. CONCLUSIONS: A moderate dose of fish oil did not lead to deleterious effects on glycemic control or whole-body insulin sensitivity in type 2 diabetic men, with preserved triacylglycerol-lowering capacities.

Dietary amylose-amylopectin starch content affects glucose and lipid metabolism in adipocytes of normal and diabetic rats.

The aim of this study was to evaluate the effects of the chronic consumption of two starches, characterized by different glycemic indices and amylose-amylopectin content, on glucose metabolism in rat epididymal adipocytes. The two chosen starches were from mung bean (32% amylose) and cornstarch (0.5% amylose). The alpha-amylase digestibility was higher for the waxy cornstarch than that of the mung bean starch (60 +/- 4 vs. 45 +/- 3%, mean +/- SEM, respectively). The glycemic index of the waxy cornstarch diet (575 g starch /kg diet) was higher than that of the mung bean starch diet (107 +/- 7 vs. 67 +/- 5%, P < 0.01) when measured in vivo in two groups of normal rats (n = 9). In a subsequent study, normal and diabetic (streptozotocin-injected on d 2 of life) male Sprague-Dawley rats (18 per group) consumed a diet containing 575 g starch/kg diet as either waxy cornstarch or mung bean starch. After 3 wk, food intake, epididymal fat pad weights, and plasma glucose, insulin and triglyceride concentrations did not differ between diet groups. Adipocyte diameter was smaller in rats that consumed mung bean starch compared with those that consumed the waxy cornstarch diet (P < 0.01). The mung bean diet increased maximal insulin-stimulated 14C-glucose oxidation (% of basal values, P < 0. 05). In contrast, incorporation of 14C-glucose into total lipids was significantly lower in rats that consumed the mung bean diet (P < 0. 05). We conclude that in both normal and diabetic rats, the chronic replacement of a high glycemic index starch by a low glycemic index one in a mixed diet increases insulin-stimulated glucose oxidation, decreases glucose incorporation into total lipids and decreases epididymal adipocyte diameter. Thus, the type of starch mixed into the diet has important metabolic consequences at the cellular level in both normal and diabetic rats.

Dietary (n-3) polyunsaturated fatty acids improve adipocyte insulin action and glucose metabolism in insulin-resistant rats: relation to membrane fatty acids.

To study the effects of dietary fish oil on insulin-stimulated glucose metabolism in adipocytes of insulin-resistant rats (rats fed 50% sucrose and 30% fat), eighteen 5-wk-old Sprague-Dawley rats were fed, for 6 wk, a diet containing 30% fat as either fish oil (FO) or a mixture of vegetable and animal oils [control oils (CO)]. A third reference group was fed a standard diet (62% corn starch and 13% fat). At the end of the 6-wk period, the two experimental groups had comparable plasma glucose concentrations that were higher than that found in the reference group. FO feeding corrected the hyperinsulinemia of the experimental rats (P < 0.05) to reach values in the reference group. Plasma triacylglycerol (P < 0.01) and cholesterol (P < 0.001) concentrations were also lower in rats fed FO than in those fed CO. The body weights of FO-fed rats were similar to that of CO-fed rats, but epididymal adipose tissue weight was lower (P < 0.01). Adipocytes of FO-fed rats, compared with those of CO-fed rats, had high insulin-stimulated glucose transport (P < 0.05), oxidation (P < 0.001) and incorporation into total lipids (P < 0.05). The incorporation of (n-3) polyunsaturated fatty acids in adipocyte membrane phospholipids was higher in FO-fed rats than in those fed CO (P < 0.0001). Insulin action was positively correlated with the fatty acid unsaturation index in membrane phospholipids. Thus dietary fish oil has beneficial effects on insulinemia, plasma lipids and insulin-stimulated glucose metabolism in insulin-resistant slightly diabetic rats.

Lack of effect of an acute ileal perfusion of short-chain fatty acids on glucose metabolism in healthy men.

Dietary fiber intake is associated with several beneficial effects on carbohydrate metabolism. Some authors have speculated that this improvement may be due to short-chain fatty acids (SCFA) produced by the colonic fermentation of dietary fibers. To test this hypothesis, six healthy men aged 26 +/- 2 (SE) yr with a body mass index of 20.9 +/- 0.7 received on three occasions an 18-h ileal perfusion infused at a flow rate of 3.3 ml/min, containing either 90 mmol/l of SCFA (60% acetate, 25% propionate, and 15% butyrate) (A), SCFA during the first 12 h and then a saline solution (A/S), or a saline solution (S). Basal hepatic glucose production (BHGP), insulin sensitivity (3-step euglycemic-hyperinsulinic clamp), and erythrocyte insulin binding (EIB) were studied 12 h after the beginning of the ileal perfusion. There was no change in BHGP or insulin sensitivity. However, maximal EIB was significantly different: 7.1 +/- 0.1 (A), 6.8 +/- 0.1 (A/S), vs. 6.5 +/- 0.1% (S) (P = 0.03). We conclude that acute administration of SCFA does not significantly alter glucose metabolism in healthy subjects.

Chronic consumption of short-chain fructooligosaccharides by healthy subjects decreased basal hepatic glucose production but had no effect on insulin-stimulated glucose metabolism.

We aimed to study the effects of chronic ingestion of short-chain fructooligosaccharides (FOS), an indigestible carbohydrate, on hepatic glucose production, insulin-mediated glucose metabolism, erythrocyte insulin binding, and blood lipids in healthy subjects. Twelve healthy volunteers received either 20 g FOS/d or sucrose for 4 wk in a double-blind crossover design. FOS did not modify fasting plasma glucose and insulin concentrations. Mean (+/- SEM) basal hepatic glucose production was lower after FOS than after sucrose consumption (2.18 +/- 0.10 compared with 2.32 +/- 0.09 mg.kg-1, min-1, respectively; P < 0.02, paired Student's t test). However, neither insulin suppression of hepatic glucose production nor insulin stimulation of glucose uptake measured by hyperinsulinemic clamp was significantly different between the two dietary periods. Erythrocyte insulin binding was also comparable. Serum triacylglycerols, total and high-density- lipoprotein cholesterol, apolipoproteins A-I and B, and lipoprotein(a) were not modified by FOS. To try to understand why FOS did not increase serum lipids, the in vitro production of short-chain fatty acids from FOS was evaluated by using human fecal inoculum and compared with that from lactulose, which was found to increase serum lipids. FOS produced an acetate-propionate ratio two times lower than that of lactulose. We conclude that 4 wk of 20 g FOS/d decreased basal hepatic glucose production but had no detectable effect on insulin-stimulated glucose metabolism in healthy subjects. The colonic fermentation pattern of undigestible carbohydrates may be relevant to predicting their metabolic effects.

Effects of long-term low-glycaemic index starchy food on plasma glucose and lipid concentrations and adipose tissue cellularity in normal and diabetic rats.

The present study aimed to assess the metabolic consequences of the chronic ingestion of two starches giving different postprandial glycaemic responses in normal and diabetic rats. The two starches chosen were mung-bean (Phaseolus aureus) starch (97% pure starch) and wheat starch presented as ground French toast. First, we studied the characteristics of these two starches. In vitro the alpha-amylase (EC 3.2.1.1) digestibilities of these starches were 40 (SE 3) and 62 (SE 4)% respectively at 30 min, whereas the contents of resistant starch were 77 (SE 4) and 22 (SE 4) g/kg respectively. In vivo the mung-bean starch produced lower postprandial glycaemic responses than the wheat starch (areas under the curve were: 91 (SE 28) and 208 (SE 33) mmol.min/l, P < 0.05) in normal rats (n 8). We then submitted twenty-eight normal and twenty-eight diabetic (neonatal streptozotocin on second day of birth) male Sprague-Dawley rats (6 weeks old) to a diet containing 570 g starch/kg as either mung-bean starch or wheat starch (n 14 rats/group). After 5 weeks on the diets food intakes and body weights were identical in each group. Liver and kidney weights were comparable when expressed as relative weight. The mung-bean-starch diet slightly decreased epididymal fat-pad weight (P < 0.14, ANOVA) and led to a marked decrease in adipocyte volume (P < 0.05). Plasma triacylglycerol and phospholipid concentrations were lower after the mung-bean-starch diet than after the wheat-starch diet in both normal and diabetic rats, whereas free fatty acid concentrations were lower only in normal rats. Similarly, non-fasting plasma glucose concentrations decreased (P < 0.05) in normal rats fed on mung-bean starch but not in diabetic ones (P < 0.14). Insulin levels tended to be lower, but not significantly, after mung-bean-starch feeding than after wheat starch. We conclude that the replacement of 570 g wheat starch/kg diet with mung-bean starch for 5 weeks resulted in (1) lowered non-fasting plasma glucose and free fatty acid levels in normal but not in diabetic rats, (2) a reduction in plasma triacylglycerol concentration and adipocyte volume in both normal and diabetic rats. Thus, the type of starch mixed into the diet may have important metabolic consequences in normal and diabetic rats.

A fructose-rich diet decreases insulin-stimulated glucose incorporation into lipids but not glucose transport in adipocytes of normal and diabetic rats.

To study the cellular mechanisms underlying fructose-induced insulin resistance in rats, the effects of fructose feeding on insulin-stimulated glucose transport, oxidation and incorporation into lipids in epididymal adipocytes were evaluated in 27 normal and 27 noninsulin-dependent diabetic male Sprague-Dawley rats. Diabetes was induced by streptozotocin injection 2 d after birth. At 5 wk of age, both normal and diabetic rats were fed a diet containing 62% carbohydrate as fructose, dextrose or cornstarch. Fructose feeding for 6 wk induced glucose intolerance in normal rats (P < 0.05) and aggravated that of diabetic rats (P < 0.05). Plasma triacylglycerol concentration was higher in fructose-fed than in starch-fed or dextrose-fed rats (P < 0.05). Adipocytes of fructose-fed rats had significantly lower maximum insulin-stimulated glucose incorporation into total lipids than those of rats fed starch, and tended (P = 0.22) to have lower production of CO2 from glucose than adipocytes of the other dietary groups. Glucose transport in adipocytes of dextrose-, starch- and fructose-fed rats did not differ. We conclude that in both normal and diabetic rats, a chronic fructose-rich diet induced hypertriacylglycerolemia, glucose intolerance and insulin resistance of adipocytes.

Effects of chronic dietary fructose with and without copper supplementation on glycaemic control, adiposity, insulin binding to adipocytes and glomerular basement membrane thickness in normal rats.

Sucrose feeding over a long period has been reported to induce glomerular basement membrane (GBM) thickening and insulin resistance in normal rats. These effects are attributed to the fructose moiety of the sucrose molecule, to Cu deprivation or both. Consequently, our aim was to evaluate the long-term effects of fructose feeding with normal or high amounts of Cu on body weight, plasma lipids, blood glucose regulation, GBM thickening and insulin binding to adipocytes. Four groups of eight Sprague-Dawley rats were fed for 10 weeks on a diet containing 570 g carbohydrate/kg supplied either as starch (S), dextrose (D), fructose (F) or fructose-starch (1:1, w/w; FS), and an adequate amount of Cu (12 micrograms Cu/g diet). A fifth group was fed on diet F supplemented with 24 micrograms Cu/g diet (FCu). After 10 weeks the epididymal adipose tissue and kidney weights expressed per 100 g body weight (relative weight) were heaviest in the F and FCu groups (P < 0.0001, ANOVA). The GBM thickness was within the normal range in the five groups but significantly higher in group D (1.95 (SE 0.04) nm and lower in group FS (1.79 (SE 0.02) nm when compared with group S (1.85 (SE 0.03) nm; P < 0.05). Insulin binding to adipocytes (expressed per cell) was lowest in the F and FCu groups, intermediate in groups D and FS and highest in group S (P < 0.05). Fasting plasma insulin level was higher in group F than in the FCu and FS groups (P < 0.05), whereas fasting plasma glucose, total cholesterol and triacylglycerol levels remained within the normal range in all groups. We conclude that in normal rats a 10-week fructose-rich diet with an adequate amount of Cu produced deleterious metabolic effects on adipose tissue, insulin binding to adipocytes, and plasma insulin, but not on GBM thickening even though kidney weight was significantly increased. However, a moderate fructose intake mixed with other sugars did not have adverse effects.