The effects of diet differing in fat, carbohydrate, and fiber on carbohydrate and lipid metabolism in type II diabetes

This study was designed to determine the effects of varying the proportions of carbohydrate, fiber, and fat on metabolic control in Type II diabetes. Ten men, aged 50 to 69 years, with Type II diabetes participated. Four isocaloric diets were consumed for 2 weeks each, with a break of 6 to 14 weeks between diets to ensure no carryover effects. Two of the diets were high in carbohydrate (63% to 65% energy) and low in fat (10% to 12% energy) but differed in their fiber contents (20 vs. 45 gm/day). The other two diets were low in carbohydrate (23% to 27% energy) with either a low or a high fat content (15% vs. 55% energy) and a high or normal protein content (62% vs. 18% energy). The composition of the subjects' usual diets in the week before each of the experimental diets did not vary significantly: carbohydrate 47% to 50% energy, protein 22% to 25% energy, fat 27% to 31% energy, and fiber 24 to 25 gm/day. A 75-gm oral glucose tolerance test and a 12-hour metabolic profile in response to 3 meals typical of the particular diet were conducted before and at the conclusion of each 2-week dietary period. The most significant improvements in metabolic control (as assessed by the effects of the diets on fasting glucose and on lipids, and on the glucose and insulin responses to oral glucose and the mixed meals) were obtained with the high-fiber, high-carbohydrate, low-fat diet and with the low-carbohydrate, high-protein, low-fat diet. Metabolic control was not significantly affected by the low-fiber, high-carbohydrate, low-fat diet, but it deteriorated significantly on the low-carbohydrate, high-fat diet. The results of this study confirmed the importance of high fiber and low fat in improving metabolic control in Type II diabetes. In conclusion, if high-carbohydrate, low-fat diets are to be recommended to patients with diabetes, it is essential that the type of carbohydrate recommended be unrefined and high in fiber.

Determinants of restenosis and lack of effect of dietary supplementation with eicosapentaenoic acid on the incidence of coronary artery restenosis after angioplasty

The effect of an eicosapentaenoic acid-rich encapsulated preparation of fish oil on the incidence of early restenosis after coronary angioplasty was assessed by a randomized double-blind placebo-controlled study. A total of 108 patients received either 10 capsules of fish oil (1.8 g eicosapentaenoic acid, 1.2 g docosahexaenoic acid) or 10 control capsules (50% olive oil, 50% corn oil), commencing the day before angioplasty and continuing for 4 months after angioplasty, in addition to treatment with aspirin and verapamil. In 101 (94%) of the 108 patients, follow-up angiographic or postmortem result was evaluated at a mean (+/- SD) of 100 (+/- 22) days. Angiographic restenosis was observed in 34% of patients (29% of lesions) in the fish oil-treated group and 33% of patients (31% of lesions) in the control group (no significant difference). The overall incidence of angiographic restenosis was significantly higher in patients with 1) recurrent angina pectoris, 2) a positive exercise test at follow-up after angioplasty, 3) residual stenosis greater than 30% immediately after angioplasty, and 4) dilation of the left anterior descending or right coronary artery. Biochemical investigations showed a greater decrease in the serum triglyceride levels in the fish oil-treated group versus the control group (p less than 0.05) but no differences between the two groups in cholesterol levels or platelet counts over the 4 month period. In conclusion, in this study, the administration of fish oil at a dose of 10 capsules/day did not reduce the incidence of early restenosis after coronary angioplasty.

Effects of dietary butter enrichment on the fatty acid distribution of phospholipid fractions isolated from rat platelets and aortae

Rats were maintained for 2 weeks on a low-fat basal diet (5% energy) and a diet from which 50% of the energy was derived from butter. Lipids were extracted from aortae and platelets and the fatty acid profiles of individual phospholipids were examined. Similar responses to dietary butter enrichment occurred in PI, PS, PE and PC fractions from either tissue: 20:4(n - 6) and all other n - 6 series longer-chain polyunsaturated fatty acids except 20:3(n - 6) decreased in percentage; all n - 3 series polyunsaturated fatty acids increased, including 20:5(n - 3) and 22:6(n - 3); n - 9 series polyunsaturated fatty acids, derived from 18:1(n - 9), increased. Despite the considerable redistribution of polyunsaturated fatty acids, the percentages of total polyunsaturated fatty acids in each phospholipid were, in every case, independent of diet. None of the changes were localized in a particular phospholipid fraction. Quantitation of fatty acids using heptadecanoic acid as an internal standard revealed that the concentrations of 20:4(n - 6) in platelet and aortic PE and PC was higher than in PI fractions. Therefore, in terms of substrate amount, it appears that PC and PE as well as PI have the potential to provide endogenous 20:4(n - 6) for oxygenation to the prostanoids thromboxane A2 and prostacyclin I2.

Butter-enriched diets reduce arterial prostacyclin production in rats

Rats were fed diets containing 10%, 30% or 50% energy as fat derived predominantly from butter or lard. The protein content of the diets was maintained at 20%. After three weeks on the diets, the rats were killed and the following parameters measured: prostacyclin production in vitro from abdominal aorta and mesenteric artery; platelet aggregation to ADP and thrombin; fatty acid composition of the phospholipids in plasma, thoracic aorta and liver; smooth muscle reactivity and release of endothelial derived relaxing factor (EDRF) from aortic endothelium stimulated by acetylcholine. There was no significant effect of increasing fat content of the diets (neither lard nor butter) on platelet aggregation. In contrast, prostacyclin production in both the mesenteric artery and the abdominal aorta fell in a concentration-dependent manner in the butter-supplemented rats. However, no effect on prostacyclin production was detected in arteries from the lard-supplemented animals. The effects of the diets on prostacyclin (PGI2) production correlated very well with the changes in plasma, aortic and liver phospholipid arachidonic acid (AA) and eicosapentaenoic acid (EPA) contents. AA decreased in a concentration-dependent manner in the rats fed the butter-enriched diets but did not change in those fed the lard-enriched diets, whereas EPA rose in a concentration-dependent manner in the butter-fed rats and was unchanged in the lard-fed animals. The clear-cut effects of the butter-enriched diets on aortic phospholipid fatty acid composition and aortic PGI2 production were accompanied by a significant reduction in smooth muscle relaxation to EDRF.(ABSTRACT TRUNCATED AT 250 WORDS)

An investigation of nutrition-related risk factors in an isolated Aboriginal community in northern Australia: advantages of a traditionally-orientated life-style

Australian Aborigines develop a high frequency of type-2 diabetes mellitus when they make the transition from a traditional to an urban life-style. Preliminary studies were conducted at an outstation in northeastern Arnhem Land where the Aborigines have been exposed to Western influence for approximately 20 years only and where they continue to follow a life-style that is largely traditional. At the time of the study 31 persons were resident at the outstation, 20 persons were over 15 years of age (adults) and 11 persons were under 15 years of age (children). Eighteen adults and six children were tested. By standard criteria for body mass index these persons were all underweight (less than 20 kg/m2). In spite of this, they displayed no biochemical evidence of malnutrition. Their plasma fatty-acid profiles were consistent with a low dietary fat intake and a high consumption of lean meat. Levels of linoleic acid were much lower and those of arachidonic acid were much higher than are those in persons who consume a Western diet. Fasting glucose and cholesterol concentrations were low relative to those of urbanized Aborigines and white Australians. However, their fasting insulin and triglyceride levels were inappropriately high for their very low body mass index and fasting glucose levels. The mild elevation of triglyceride and fasting insulin levels is consistent with insulin resistance and suggests that these Aborigines (in common with other Aborigines) may become susceptible to obesity and diabetes if they became urbanized further.

Impaired glucose tolerance, hyperinsulinemia, and hypertriglyceridemia in Australian aborigines from the desert

A cross section of adult full-blooded Aborigines from three small isolated communities in the desert region of northwest Australia was surveyed for diabetes, impaired glucose tolerance (IGT), insulin levels, and lipoprotein lipids. Sixty-three men and 86 women from a total adult population of 330 were tested. Of the people tested, 67.6% had normal glucose tolerance, 25% had IGT, and 7.4% had diabetes. Both diabetes and IGT were strongly age related. Fasting insulin levels and insulin responses to oral glucose (elevation above basal) were elevated. Although fasting insulin rose with age, insulin response did not rise after adjustment for body mass index (BMI). Plasma triglyceride levels were high, particularly in men greater than 35 yr old (3.13 +/- 0.32 mM), but cholesterol levels were not elevated. Multiple regression analysis of fasting glucose, 2-h glucose, plasma triglyceride, fasting insulin, and insulin response for the nondiabetic subjects revealed 1) BMI was an independent risk factor for elevated 2-h glucose levels in women but not in men and was strongly related to fasting insulin concentrations in both genders; 2) fasting insulin concentration was an independent risk factor for increases in fasting glucose, insulin response, and triglyceride levels; 3) insulin response was related to the 2-h glucose level; 4) fasting and 2-h glucose levels and fasting insulin and triglyceride concentrations all rose with age in both genders, with the rate of increase generally greater in men. The most striking difference between these desert Aborigines and previously studied coastal Aborigines from the same geographical region was the significantly higher insulin response.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of short-term consumption of a high fat diet on glucose tolerance and insulin sensitivity in the rat

The mechanism by which the consumption of high fat, low carbohydrate diets impair glucose tolerance and decrease insulin sensitivity is poorly understood. In an attempt to clarify this question, intravenous glucose tolerance and insulin action in the liver and skeletal muscle were examined in rats after two weeks feeding of either a high fat (HF: 66% energy as fat) or a low fat (LF: 12% energy as fat) diet. Both diets had a P/S ratio (ratio of polyunsaturated to saturated fat in the diet) of 1.3. The high fat diet resulted in mild impairment of intravenous glucose tolerance. Postprandial glucose levels were elevated in the presence of a sustained insulin response. In vitro insulin-stimulated glucose utilisation was decreased significantly in soleus muscle of HF rats, as indicated by decreased [14C]glucose incorporation into muscle glycogen. In contrast, muscle lipogenesis from glucose was not affected by dietary composition. There was no difference in insulin binding to soleus muscle of HF and LF rats, indicating a dissociation between insulin receptor binding and post-receptor metabolic events. Dietary composition did not influence the incorporation of increasing [14C]glucose loads into muscle glycogen or lipid in vivo. However, the HF diet was associated with reduced incorporation of [14C]glucose into lipids and glycogen in the liver and, to a smaller extent, reduced incorporation into adipose tissue lipids in vivo. These results suggest that the mechanism by which HF diets impaired glucose tolerance was mainly hepatic in origin. Decreased glucose uptake, secondary to reduced glucokinase activity, may result in a reduction in glucose utilisation in the liver.

Plasma glucose and insulin responses to starchy foods in Australian aborigines: a population now at high risk of diabetes

We compared plasma glucose and insulin responses to an Aboriginal bushfood and its western equivalent in healthy Aborigines and Caucasians. Bush potato (Ipomoea costata), an Aboriginal bushfood which is slowly digested in vitro, and potato (Solanum tuberosum), which has a high glycemic index, were studied. The areas under the glucose and insulin curves for Aborigines were 34% and 42% smaller, respectively, after bush potato than after potato (p less than 0.05). In Caucasians only the insulin response to bush potato was lower (by 19%) than that to potato (p less than 0.05). Compared with Caucasians, Aborigines produced 2.5 times greater glucose and insulin responses to potato (p less than 0.025). Their insulin responses to bush potato were also twice as large (p less than 0.05) although glucose responses were not significantly different. These findings add weight to the hypothesis that rapidly digested carbohydrate in western diets may be one of the factors in the lifestyle change which precipitates diabetes in indigenous populations.

Effects on plasma lipids and fatty acid composition of very low fat diets enriched with fish or kangaroo meat

The effects of very low fat diets (less than 7% energy) enriched with different sources of long chain (C20 and C22) polyunsaturated fatty acids (PUFA) on plasma lipid levels and plasma fatty acid composition were studied in 13 healthy volunteers. Three diets provided 500 g/day of tropical Australian fish (rich in arachidonic acid and docosahexaenoic acid), southern Australian fish (rich in docosahexaenoic acid) or kangaroo meat (rich in linoleic and arachidonic acids). The fourth diet was vegetarian, similarly low in fat but containing no 20- and 22-carbon PUFA. Subjects ate their normal or usual diets on weeks 1 and 4 and the very low fat diets in weeks 2 and 3. Weighed food intake records were kept, and weeks 2, 3 and 4 were designed to be isoenergetic with week 1. Plasma cholesterol levels fell significantly on all diets within one week. There were reductions in both low density (LDL) and high density lipoprotein (HDL) cholesterol levels, with effects on HDL cholesterol being more consistent. There were no consistent or significant effects on total triglyceride levels despite the high carbohydrate content of the diets. On all diets the percentage of linoleic acid fell in the plasma phospholipid and cholesteryl ester fractions, while the percentage of palmitic acid in the phospholipids and cholesteryl esters and palmitoleic acid in the cholesteryl ester fraction rose on all diets. The percentage of arachidonic acid rose in the phospholipid and cholesteryl esters on the two diets that were good sources of this fatty acid (tropical fish and kangaroo meat).(ABSTRACT TRUNCATED AT 250 WORDS)

Evaluation of T4 and T3 binding kinetics in the thyroxine binding globulin abnormality of Australian aborigines

Low serum total T4 associated with subnormal concentrations of thyroxine binding globulin (TBG) has been reported in up to 40% of euthyroid Australian aborigines. It has been suggested that these subjects show both diminished concentration of TBG and reduced TBG affinity for T4 (Sarne et al., 1985). We have compared 12 euthyroid aborigines with low T4 (total T4 44 +/- 5 nmol/l) and aborigines with normal T4 (T4 99 +/- 9 nmol/l, n = 12) using measurements of free T4 and T3 by equilibrium dialysis. TBG was measured both by RIA (Henning, Berlin, FRG) and a method dependent on T4 binding (Corning Immophase). Aborigines with low T4 showed lower levels of free T4 (12.6 +/- 0.6 cf. 18.7 +/- 1.0 pM), free T4 index (66 +/- 8 cf. 98 +/- 13), total T3 (1.1 +/- 0.2 cf. 1.6 +/- 0.3 nmol/l), TBG RIA (14.0 +/- 0.6 cf. 25.0 +/- 1.2 ng/l), and TBG Immophase (9.0 +/- 0.5 cf. 22.0 +/- 1.2 mg/l) (P less than 0.01), but free T3 (5.3 +/- 0.4 cf. 4.7 +/- 0.4 pM) and TSH (1.9 +/- 0.2 cf. 1.8 +/- 0.2 mU/l) were not significantly different from the values found in aborigines with normal T4. Scatchard analysis of T4 and T3 binding was performed using serum diluted 1 : 20,000 for T4 and 1 : 500 for T3 (barbitone buffer pH 8.6, 4 degrees C, dextran-coated charcoal separation). In euthyroid low T4 aborigines compared to those with normal T4, both T4 capacity (106 +/- 14 cf. 238 +/- 13 nM, P less than 0.01) and affinity (5.05 X 10(10) cf. 8.47 X 10(10) M-1, P less than 0.05) were significantly reduced. Similarly, both T3 capacity (62 +/- 10 cf. 154 +/- 16 nM, P less than 0.01) and affinity (1.67 X 10(9) cf. 2.28 X 10(9) M-1, P less than 0.02) were reduced. A substantial minority of euthyroid Australian aborigines have a TBG variant characterized by both reduced capacity and affinity of T4 and T3. These findings suggest that TBG may be both qualitatively and quantitatively abnormal in these subjects.

Effect of short-term consumption of a high-fat, low-carbohydrate diet on metabolic control in insulin-deficient diabetic rats

This study examined the effect of changing the proportion of dietary fat on metabolic control in rats rendered mildly diabetic with streptozotocin (STZ). The high-fat (HF) diet contained 66% energy as fat and 12% as carbohydrate while the low-fat (LF) diet contained 12% energy as fat and 66% as carbohydrate. Both diets had a P/S ratio of 1:3. Young male rats weighing 100 g were treated with STZ (60 mg/kg IV) and randomly allocated to either the LF of HF diet. After 2 weeks, the fasting plasma glucose concentrations were significantly higher in the HF-STZ rats than in the LF-STZ rats (13.2 +/- 1.2 mmol/L v 7.1 +/- 0.8 mmol/L, respectively, P less than 0.001). The increase in plasma glucose above the basal level following the intravenous glucose load (0.5 g/kg body wt) was similar in both groups of STZ-treated rats and glucose clearance was similarly impaired. The fall in glucose concentrations in the 30 minutes following the IV insulin (0.5 U Actrapid insulin/kg body wt) was greater in the LF-STZ rats (delta AUC = -1.60 +/- 0.20 mmol/L 0.5h) than in the HF-STZ group (delta AUC = -0.97 +/- 0.20 mmol/L 0.5 h, P less than 0.05) and either of the control groups (delta AUC = -0.94 +/- 0.37, -0.83 +/- 0.09 mmol/L 0.5 h for LF and HF rats, respectively, P less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Animal foods in traditional Australian aboriginal diets: polyunsaturated and low in fat

Australian Aborigines develop high frequencies of diabetes and cardiovascular diseases when they make the transition to an urban lifestyle. The composition of the traditional diet, particularly its lipid components, is a most important aspect of the hunter-gatherer lifestyle that would bear on the risk of these diseases. We have examined the fat content and fatty acid composition of a variety of animal foods eaten traditionally by Aborigines from different regions of Australia. The muscle samples of the wild animals from all over Australia were uniformly low in fat (less than 2.6% wet weight) with a high proportion of polyunsaturated fatty acids (greater than or equal to 20% PUFA). Liver samples had a higher range of fat content (5-10% wet weight) but were also rich in PUFA (33-42%). Depot fat samples varied widely in their PUFA content (5-40%). In terms of their PUFA composition the foods tended to fall into three groups: (i) those rich in both n-3 and n-6 PUFA, which included land-based, coastal and freshwater animals; (ii) those rich in n-3 PUFA, i.e., marine species; (iii) those rich in n-6 PUFA, mainly land-based species. The results of these analyses suggest that even when the traditional Aboriginal diet contained a high proportion of animal foods it would have been low in fat with a high proportion of PUFA and thereby could have protected Aborigines against cardiovascular diseases and related conditions through a combination of factors: low energy density, low saturated fat and relatively high PUFA content.

Commercial canning increases the digestibility of beans in vitro and postprandial metabolic responses to them in vivo

Six weight-stable subjects consumed three test meals containing 50 g carbohydrate in random order after a 12-h fast: D-glucose, canned baked beans, or home-cooked (boiled) baked beans. Postprandial glucose and insulin responses were greatest to glucose, lowest to home-cooked baked beans, and intermediate to canned baked beans. Profiles of glucose and insulin responses to home-cooked beans were flatter and more attenuated than responses to canned beans or glucose, which correlates with the in vitro data showing a six-to-eight times higher rate of starch hydrolysis in canned beans relative to boiled beans. Increases in temperature (pressure) and duration of pressure-cooking resulted in increased starch digestibility, whereas even mildly acidic conditions (pH 5.0) markedly reduced it. None of the processes studied affected the total amount of available carbohydrate.

Glucose tolerance and insulin sensitivity in ponies and Standardbred horses

The existence of an innate insulin insensitivity in ponies was investigated and compared with the situation in larger breeds of horse. Ponies that were fat or had previously suffered laminitis were found to be far more intolerant to oral glucose loading (1 g/kg bodyweight [bwt]) than normal ponies or Standardbreds. These ponies also exhibited a far greater response in plasma insulin levels after glucose loading. Insulin response tests (0.4 iu/kg bwt insulin intravenously) showed only a minimal and very protracted response in both the fat and laminitic groups. The relevance of these findings in regulation of carbohydrate and lipid metabolism, and their role in the pathogenesis of hyperlipaemia, are discussed.

More severe impairment of oral than intravenous glucose tolerance in rats after eating a high fat diet

Glucose and insulin responses to oral and intravenous glucose (1 g/kg body weight) were measured after consumption of a high fat (HF) or low fat (LF) diet for 3 wk in conscious rats with implanted intravenous and intra-arterial catheters. The HF diet resulted in impaired glucose tolerance and insulin resistance after both oral and intravenous glucose; the effect was more pronounced after oral glucose. In an attempt to understand the basis of the impairment of glucose tolerance after consuming the HF diet, the activity of hepatic glucokinase and the rate of intestinal glucose uptake were also measured. The more severe impairment of glucose tolerance by oral rather than intravenous administration was not explained by an increased rate of intestinal glucose uptake. Indeed, there was a small but significant reduction in the rate of jejunal glucose uptake in the HF rats. However, the greatly reduced activity of hepatic glucokinase in the HF rats was consistent with a reduced capacity for hepatic glucose uptake, which may have contributed significantly to the impaired glucose tolerance. The effects of the HF diet on the insulin response to glucose were much more pronounced after oral rather than intravenous glucose administration. This indicated that the HF diet may have stimulated the enteroinsular axis. However, it is also possible that the particularly high circulating insulin levels, resulting from oral glucose in the HF rats, were a direct response to hyperglycemia, secondary to reduced glucose removal.

The effects of low-fat diets rich in arachidonic acid on the composition of plasma fatty acids and bleeding time in Australian aborigines

In the present study we measured the bleeding times in fourteen Aborigines (10 diabetic, 4 non-diabetic) before and after 2 weeks on a diet of tropical seafood (rich in both arachidonic acid and the omega 3 PUFA), followed by 3 weeks on a diet in which kangaroo and freshwater fish (linoleic and arachidonic acid-rich) were the major fat sources. Both diets were very low in fat. Bleeding times increased in all subjects after the 2 weeks of tropical seafood and continued to rise on the mixed diet. The increase over 5 weeks from 4.1 +/- 0.4 to 5.9 +/- 0.4 min was highly significant (p less than 0.01). Due to the extreme isolation of the study location it was only possible to measure the plasma fatty acid composition at the beginning and end of the study. The concentration of arachidonic acid in the plasma lipids doubled whereas that of linoleic acid was almost halved, despite the fact that the diet in the second part of the study contained considerably more linoleic than arachidonic acid. That there appeared to be preferential incorporation of arachidonic acid into the plasma lipids is further supported by the observation that the rise in arachidonic acid in the cholesterol ester and phospholipid fractions was almost exactly counter-balanced by the fall in linoleic acid. In conclusion, the present study demonstrated a rise in bleeding time associated with an increased concentration of arachidonic acid and decreased concentration of linoleic acid in plasma lipids, and suggests that the mechanism by which diet modulates haemostatic function may be more complex than currently assumed.

Factors affecting the rate of hydrolysis of starch in legumes

In an attempt to understand the mechanism for the extremely slow rate of digestion and absorption of carbohydrate from legumes, we have examined a number of factors which could potentially affect the process in vitro. The rate of hydrolysis of legume starch in vitro was not affected by the presence of fat (as either butter or an emulsion). However, it was significantly increased in commercially available canned bean preparations, suggesting that the high temperatures used in the canning process may alter the availability of starch in legumes. In vitro starch hydrolysis rate was also significantly increased by grinding legumes finely prior to cooking. Finally, the slow rate of digestion and absorption of legume carbohydrate does not appear to be due to viscosity since a) increasing the shaking rate of viscous mixture of either red kidney beans or lentils from 0 to 120 oscillations per minute did not affect the hydrolysis rate, and b) a thick viscous mixture of either of these legumes did not retard the diffusion of free glucose from a dialysis sac into the dialysate.

Optimum effectiveness of intestinal alpha-glucosidase inhibitors: importance of uniform distribution through a meal

A major barrier to the widespread clinical use of an alpha-glucosidase inhibitor such as Acarbose, is the unpleasant gastrointestinal symptoms of carbohydrate malabsorption associated with its use. Acarbose is usually administered as a tablet and eaten with the first mouthful of the meal, making its uniform distribution through the meal unlikely. In the present study, Acarbose was crushed to a powder and mixed through a test meal before it was consumed. Six healthy young men consumed test meals containing 75 g carbohydrate either as whole brown rice or as ground brown rice. When Acarbose was uniformly mixed through a ground rice meal prior to digestion it produced dose-dependent reductions in the postprandial glucose, insulin and GIP responses which were evident at doses as low as 12.5 mg. The responses to whole brown rice were intermediate between those to 12.5 and 25 mg Acarbose in ground brown rice. In tablet form Acarbose was only one quarter as effective in flattening the post prandial glucose and insulin responses as it was in powder form. These results highlight the importance of uniform distribution of Acarbose through a carbohydrate meal in order to achieve maximum effectiveness in delaying digestion and absorption and yet not promoting carbohydrate malabsorption.

Blunted norepinephrine responsiveness to changing energy states in obese subjects

We have previously reported in lean subjects a significant relationship between plasma norepinephrine metabolism and energy state. The present study has examined in six obese men the response in plasma norepinephrine flux to ten day periods of overeating (+ 1000 kcal/m2 above isocaloric requirements) or undereating (400 kcal/d). Despite significant gains or losses in body weight, norepinephrine flux, measured during constant infusions of 3H-l-norepinephrine, failed to change significantly. Measurements of glucose utilization during constant infusions of insulin, showed significant changes with changing energy state, falling with overeating and rising with undereating. Insulin sensitivity was not correlated with plasma norepinephrine metabolism.

Marked improvement in carbohydrate and lipid metabolism in diabetic Australian aborigines after temporary reversion to traditional lifestyle

The rationale for the present study was that temporarily reversing the urbanization process in diabetic Aborigines should improve all aspects of their carbohydrate and lipid metabolism that are linked to insulin resistance. Ten full-blood, diabetic Aborigines from the Mowanjum Community (Derby, Western Australia) agreed to be tested before and after living for 7 wk as hunter-gatherers in their traditional country in north-western Australia. They were middle aged (53.9 +/- 1.8 yr) and overweight (81.9 +/- 3.4 kg), and all lost weight steadily over the 7-wk period (average, 8 kg). A detailed analysis of food intake over 2 wk revealed a low-energy intake (1200 kcal/person/day). Despite the high contribution of animal food to the total energy intake (64%), the diet was low in total fat (13%) due to the very low fat content of wild animals. Oral glucose tolerance tests (75 g glucose) were conducted in the urban setting and repeated at the end of 7 wk of traditional lifestyle. The marked improvement in glucose was due to both a fall in fasting glucose (11.6 +/- 1.2 mM before, 6.6 +/- 0.8 mM after) and an improvement in postprandial glucose clearance (incremental area under the glucose curve: 15.0 +/- 1.2 mmol/L/h before, 11.7 +/- 1.2 mmol/L/h after). Fasting plasma insulin concentration fell (23 +/- 2 mU/L before, 12 +/- 1 mU/L after) and the insulin response to glucose improved (incremental area under the insulin curve: 61 +/- 18 mU/L/h before, 104 +/- 21 mU/L/h after). The marked fall in fasting plasma triglycerides (4.0 +/- 0.5 mM before, 1.2 +/- 0.1 mM after) was due largely to the fall in VLDL triglyceride concentration (2.31 +/- 0.31 mM before, 0.20 +/- 0.03 mM after.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of co-ingestion of fat on the metabolic responses to slowly and rapidly absorbed carbohydrates

The present study examined the acute effects of co-ingestion of fat (37.5 g) on the post-prandial metabolic responses to 75 g of carbohydrate which was either slowly absorbed (lentils) or rapidly absorbed (potatoes). Co-ingestion of fat resulted in a significant flattening of the post-prandial glucose curves, the effect being more pronounced for the rapidly absorbed potatoes. This was probably due to delayed gastric emptying. However, the post-prandial insulin responses to either carbohydrate were not significantly reduced by fat, suggesting that the insulin response to a given glucose concentration was potentiated in the presence of fat. The gastric inhibitory polypeptide (GIP) responses to both carbohydrates were greatly increased in the presence of fat. To investigate further the possible roles of GIP in the entero-insular axis, a 5-g bolus of glucose was injected intravenously 1 h after lentils +/- fat. This was sufficient to raise the glucose levels above the threshold reported for GIP to potentiate insulin secretion. However, despite the large differences in circulating GIP levels, the insulin response to glucose was not affected by the presence of fat. These results suggest that (1) the rate of absorption of carbohydrate is a major determinant of post-prandial metabolic responses even in the presence of fat, (2) fat-stimulated GIP secretion does not potentiate glucose-induced insulin secretion, and (3) the potentiation of the insulin response to glucose when carbohydrate is co-ingested with fat is consistent with the well-documented insulin resistance associated with high fat diets.

Elevated levels of arachidonic acid in fish from northern Australian coastal waters

The fatty acid composition of 10 species of fish caught off the northwest coast of Australia (latitude 17 degrees S) was examined. All species contained high levels of omega 6 fatty acids (9.6-23.1% of total fatty acids) with arachidonic acid being the major omega 6 fatty acid (5.9-14.8% of fatty acids). Docosatetraenoic and docosapentaenoic acids of the omega 6 series accounted for 3-8% of the total fatty acids. The ratio of omega 6 to omega 3 fatty acids in these fish varied from 0.38 to 0.93, compared with an average ratio of 0.16 for fish from the northern hemisphere (latitude greater than 30 degrees N). The present data and figures from the literature indicate that the marine food chain in the southern hemisphere contains significant quantities of omega 6 fatty acids.

The rate of starch hydrolysis in vitro does not predict the metabolic responses to legumes in vivo

The aim of this study was to determine whether legumes in a physical form which is rapidly digested in vitro give rise to proportionately greater metabolic responses in vivo than legumes which are slowly digested in vitro. Samples of cooked whole and ground lentils were incubated in vitro with pancreatic amylase for 30 min and the percentage starch hydrolysis determined. Grinding the lentils before cooking resulted in a 5-fold increase in the rate of starch hydrolysis (whole lentils 12.1%, ground lentils 60.9%). For the in vivo studies six healthy, young, lean subjects consumed two test meals containing 50 g starch: whole lentils and lentils that had been ground finely before cooking. Postprandial glucose and insulin responses were measured over 4 h. Peak glucose and insulin responses occurred 60 min postprandially for the whole lentils and 30 min postprandially for ground lentils. Although the increase in plasma glucose after ground lentils (1.6 mM) was significantly higher (p less than 0.025) than that after whole lentils (0.9 mM), there was no difference in the magnitude of the insulin responses. These results indicate that, unlike for cereals, the rate of intestinal starch hydrolysis is not the major factor determining the metabolic responses to legumes. By virtue of their low postprandial glucose and insulin responses, irrespective of their physical form and digestibility, legumes would appear to be ideal for inclusion in the diet of diabetics.

The effect of coingestion of fat on the glucose, insulin, and gastric inhibitory polypeptide responses to carbohydrate and protein

In the present study we examined the effect of coingestion of 50 g fat (butter) on the postprandial glucose, insulin, and gastric inhibitory polypeptide responses to 50 g carbohydrate (potato) or 50 g protein (low fat veal) in eight normal subjects. The coingestion of fat with either carbohydrate or protein resulted in greatly increased gastric inhibitory polypeptide responses, the effect being more pronounced with carbohydrate. The addition of fat to a carbohydrate meal also reduced the postprandial glucose response. This could have been due to several factors including a delayed glucose absorption, secondary to a fat-induced inhibition of gastric emptying. However, despite the lower blood glucose levels in the presence of fat the insulin response was not reduced, suggesting a potentiation of insulin secretion in the presence of fat. Thus, despite the apparent improvement in glucose tolerance when carbohydrate is ingested together with fat, the accompanying potentiation of insulin secretion could form the basis of long-term changes in insulin sensitivity which accompany alterations in dietary fat intake.

Metabolic adaptation to a low carbohydrate-high protein ('traditional') diet in Australian Aborigines

We have investigated plasma glucose and insulin responses to 75 g glucose in 12 young, full-blood Aborigines before and after 2 weeks on a diet derived almost exclusively from seafood. This diet was low in fat, extremely low in carbohydrate and high in protein and was representative of the diet consumed by these people in their traditional lifestyle during those times of the year when very little vegetable food was available. After an initial weight loss which was probably due to glycogen, salt and water losses associated with the dietary change, body weights stabilised by the end of the first week. Total triglyceride concentrations in fasting plasma fell from 1.32 +/- 0.33 before the diet to 0.61 +/- 0.08 mmol/l after it, while total cholesterol, which was low initially, did not fall significantly. There was a small but significant improvement in glucose tolerance and a small reduction in insulin response indicating that the Aborigines had adapted effectively to the very low carbohydrate-high protein diet in the 2 week period. The insulin response to 50 g protein also fell significantly after the seafood diet. The results suggest that glucose tolerance is not determined solely by the carbohydrate content of the diet, but rather by the availability of carbohydrate either directly or indirectly in precursor form as dietary protein.

Increased proportion of arachidonic acid in plasma lipids after 2 weeks on a diet of tropical seafood

Using capillary GLC we analyzed the plasma fatty acids in a group of full-blood Aborigines in north western Australia before and after 2 wk on a diet in which over 90% of the energy was derived from tropical fish and shellfish. The proportion of saturated fatty acids did not change and all monoenoic and omega 6 fatty acids, except arachidonic, fell significantly. The proportions of arachidonic and all omega 3 PUFA rose significantly on the diet. This striking rise in arachidonic was evident in all lipid fractions (phospholipids, cholesterol esters, and triglycerides). Total triglycerides in fasting plasma fell from 1.32 to 0.61 mM after the diet while total cholesterol, which was low initially, did not fall significantly. Analysis of the fatty acids in lipid extracts from the tropical seafood eaten in the study revealed an arachidonic acid content ranging from 4.8 to 14.3% of the total fatty acids. The seafood contained almost no linoleic acid but was, as expected, a rich source of omega 3 fatty acids (13.6 to 31.0% of the total fatty acids). From these data we are able to conclude that seafood from tropical waters, unlike seafood from colder waters, is a natural source of polyunsaturated fatty acids from both the omega 6 and omega 3 series.

Noradrenaline turnover during under- and over-eating in normal weight subjects

Adjustments to sympathetic nervous system activity may regulate constant body weight despite wide variations in energy intake. To test this six normal weight subjects were studied at three different energy intakes (low, weight maintaining and high). Noradrenaline turnover was measured on the tenth day of each diet. Both noradrenaline appearance rate and noradrenaline clearance increased significantly with increasing energy intake and were a more sensitive indices than the plasma noradrenaline concentrations which rose, but not significantly. Fasting triiodothyronine (T3) rose and reverse T3 fell with increasing energy intake, while thyroxine (T4) concentrations did not change. Systolic blood pressure also rose significantly. Underfeeding resulted in reductions in noradrenaline appearance and clearance rates and in the T3 level. These results demonstrate that sympathetic nervous system activity, as determined by noradrenaline turnover in plasma, varies in response to short-term changes in energy intake in normal weight subjects. These changes may partly explain why some individuals maintain body weight constant despite large differences in food intake. The present findings may also be relevant to the variability in susceptibility to become obese.

Effect of physical form of carbohydrate on the postprandial glucose, insulin, and gastric inhibitory polypeptide responses in type 2 diabetes

In the present study we measured the postprandial glucose, insulin, and gastric inhibitory polypeptide responses to 75 g carbohydrate administered either as glucose, unpolished (brown) rice, or ground brown rice to six recently diagnosed type 2 diabetics and six healthy subjects. The diabetic and normal subjects responded in a qualitatively similar manner to the three meals although there were major quantitative differences. Brown rice elicited significantly lower postprandial glucose, insulin, and gastric inhibitory polypeptide responses than either ground brown rice or glucose in both groups. There were no significant differences in the metabolic responses to ground brown rice (complex carbohydrate) and glucose (simple carbohydrate) in either diabetic or normal subjects. These data highlight the role of the physical form of complex carbohydrate in determining metabolic responses to it in both diabetic and normal subjects, and provide a rationale for designing diabetic diets containing complex carbohydrate in a form which is slowly digested and absorbed.

Impact of Westernization on carbohydrate and lipid metabolism in Australian Aborigines

We have investigated plasma glucose and immunoreactive insulin responses to 75-g oral glucose in lean, young, full-blood Aboriginal men from urban and rural communities and made comparisons with age- and weight-matched Caucasoids. Fasting glucose concentrations were lower in the rural Aborigines than in the urban Aborigines or the Caucasoids. Plasma glucose concentrations 2 h postprandially were significantly higher in both Aboriginal groups (urban 6.7 +/- 0.6 mmol/l, rural 6.4 +/- 0.4 mmol/l) than in the Caucasoids (5.0 +/- 0.3 mmol/l). Insulin responses in the two Aboriginal groups were almost identical and 50% higher than in the Caucasoids. We also investigated glucose tolerance and plasma lipids in 67 full-blood Aborigines living in an isolated rural community. Only three people (two men and one woman) had diabetes while a further eight (six men and two women) had impaired glucose tolerance. Fasting plasma cholesterol concentrations did not increase with age and were significantly lower in the rural Aboriginal community than in either the urban Aborigines or the Caucasoids. These results suggest that elevations in fasting cholesterol and glucose concentrations are lifestyle-associated, but that mild impairment of glucose tolerance and high insulin response in the Aborigines may be inherited metabolic characteristics.

Biochemical quantification of sympathetic nervous activity in humans using radiotracer methodology: fallibility of plasma noradrenaline measurements

We have developed radiotracer techniques for studying noradrenaline kinetics, to assess better sympathetic nervous system function in humans. Tritiated l-noradrenaline was infused intravenously (0.35 microCi/m2/min) to plateau plasma concentration. Noradrenaline plasma clearance was calculated from plasma tritiated noradrenaline concentration at steady state, and the rate of spillover of noradrenaline to plasma derived from plasma noradrenaline specific radioactivity. Mean noradrenaline spillover at rest in 34 normal subjects was 0.33 micrograms/m2/min (range 0.17-0.61 micrograms/m2/min). Predictably, noradrenaline spillover was reduced in patients with subnormal sympathetic nervous system activity, 0.16 +/- 0.09 micrograms/m2/min in eight patients with idiopathic peripheral autonomic insufficiency, and 0.11 +/- 0.07 micrograms/m2/min (mean +/- SD) in six patients with essential hypertension treated with clonidine (0.45 mg daily). Noradrenaline line plasma clearance in normal subjects was 1.32 +/- 0.28 L/m2/min. Clearance fell with age, causing the previously described rise in plasma noradrenaline concentration with aging. Unexpected effects of drugs were encountered, for example chronic beta-adrenergic blockade in patients with essential hypertension reduced noradrenaline clearance. Plasma noradrenaline concentration measurements were not in agreement with noradrenaline release rate values, and do not reliably indicate sympathetic nervous system activity, in instances such as these where noradrenaline clearance is abnormal.

Factors affecting the rate of hydrolysis of starch in food

After accurate determination of the content of available carbohydrate in a wide variety of cereals, as in vitro method was used to study factors that influence hydrolysis rates of starch in foods. Fiber, physical form, cooking, and the possible presence of a natural amylase inhibitor were all shown to affect hydrolysis rates of starch. Fiber only exerted an inhibiting effect on the rate of hydrolysis when it formed a physical barrier to limit access of the hydrolytic enzymes to the starch (as in whole brown rice, for example). Particle size played an important role in determining the rate of hydrolysis. Cooking made the starch much more readily available for enzymic hydrolysis presumably by gelatinizing it. Stoneground wholemeal flour was hydrolyzed more slowly than white flour. This is consistent with the presence of a natural amylase inhibitor that has been isolated from wheat germ in the whole grain. Our results suggest that such amylase inhibitor activity is destroyed by passage through the roller mill, since the starch in wheat germ and standard wholemeal flour (i.e., not stoneground but reconstituted after passage through the roller mill) was hydrolyzed at a rate identical to white flour.

Rate of starch hydrolysis in vitro as a predictor of metabolic responses to complex carbohydrate in vivo

This study was designed to determine whether the rate of hydrolysis of different starches by pancreatic amylase in vitro was proportional to the postprandial glucose and insulin response to those starches after oral ingestion. Lean young men consumed four test meals of rice containing 75 g starch: white rice, unpolished (brown) rice, ground white rice, and ground brown rice. Postprandial glucose and insulin responses were measured over 4 h and showed the following pattern: ground white rice congruent to ground brown rice greater than white rice greater than brown rice. The maximum increases in blood glucose after the four meals were brown rice 0.9 mM, white rice 1.5 mM, ground brown rice 3.3 mM, and ground white rice 3.6 mM. Samples of the cooked rices were incubated in vitro with pancreatic amylase for 30 min and the percentage starch hydrolysis determine. The relative rates of starch hydrolysis correlated very closely with the peak glucose responses: brown rice 17.6%, white rice 30.8%, ground brown rice 68.2% and ground white rice 71.8%. These results indicated that the rate of intestinal hydrolysis of starch is an extremely important determinant of the metabolic responses to a particular starch. The rate of starch hydrolysis can be determine simply by an in vitro method and should assist the design of diets for the treatment of diabetes.

Studies on nonoxynol-9. III. Effect on fibroblasts and spermatozoa

Seven nonionic detergents of the Igepal CO series differing in molecular size and including nonoxynol-9 and a representative anionic (SDS) and cationic (Cepacol) detergent were tested as to their relative cytotoxicity. The biologic effects of these detergents on human W1--38 fibroblasts (DNA and glycosaminoglycans synthesis) and on the motility of human spermatozoa were studied. The relative order of cytotoxicities for both fibroblasts and spermatozoa was cationic greater than nonionic greater than anionic. The concentration of nonoxynol-9-inhibiting fibroblast activity was approximately 30 times less than the amount needed to immobilize spermatozoa. It is concluded that CO-630, used as a source of nonoxynol-9, is the most effective polymer to inhibit spermatozoa and also fibroblasts.

The mechanism of adaptive hyperlipogenesis: insulin receptor binding and glucokinase activity in rat liver during fasting and refeeding

In the present study, rats were fasted for 3 days and subsequently refed for 1, 3, or 5 days. Measurements of insulin binding to its receptors on liver plasma membranes were carried out in conjunction with measurements of the activity of an insulin-regulated enzyme from liver cytosol, glucokinase. In response to the 3-day fast (chronic hypoinsulinemia), the insulin receptor number almost tripled, whereas the glucokinase activity was halved. The insulin receptor number slowly fell to control values during the 5 days of refeeding. In contrast, glucokinase activity rose to levels 2.5 times higher than control (5 times higher than the fasting values) after 1 day of refeeding. Altough the activity fell off somewhat during refeeding it was still dobule control values after 5 days refeeding. It was concluded that in the fasted rat there was a dissociation between insulin receptor concentration and the activity of the insulin-regulated enzyme glucokinase. However, the fasting-induced increase in receptor concentration appeared to play a permissive role in the rapid overshoot of glucokinase activity observed in the early stages of refeeding. Such a scheme would explain the metabolic changes occurring in the fasted-refed rat.

The effect of transition from traditional to urban life-style on the insulin secretory response in Australian Aborigines

Recent epidemiologic studies have revealed a high prevalence of maturity-onset diabetes in certain populations that have undergone comparatively rapid urbanization. There is evidence suggesting that Australian Aborigines may respond to urbanization in this way. Thirteen full-blood Aborigines from the Mowanjum Community, Derby, Western Australia, cooperated in the present study. They spent 3 mo living in their traditional hunter-gatherer life-style, after which their insulin response to glucose was measured in a starch tolerance test. The findings were compared in follow-up studies conducted 3 mo after returning to their urban environment. Similar studies were conducted in Caucasians of comparable age and weight. Fasting glucose concentrations were lower in Aborigines than in Caucasians and were unaffected by life-style changes. Although basal insulin levels were similar in the three groups, there were striking intergroup differences in the insulin responses to glucose. The areas under the insulin curves in the first hour after starch ingestion were: urban Aborigines 4478 +/- 465 microU/ml-1/min, traditional Aborigines 2959 +/- 301 microU/ml-1/min, and Caucasians 2097 +/- 224 microU/ml-1/min. This appeared to reflect differences in the early rates of change of glucose concentrations. The data suggest that these Aborigines have an abnormally high insulin response to glucose, which is ameliorated, but not normalized, by reverting to their traditional life-style.

Effects of fasting and refeeding on the in vitro insulin sensitivity of rat aorta

Rat aorta responds to refeeding after a fast in a manner similar to adopose tissue and liver by developing an enhanced capacity for lipogenesis and glycogen synthesis from glucose. The in vitro incorporation of D-U-14C-glucose into aortic triglycerides and glycogen was two- to four-fold higher in rats refed for three to five days after a three day fast than in ad libitum fed controls. Insulin significantly stimulated this incorporation only during refeeding for three days after a three-day fast. The glycogen synthesizing system appeared to be stimulated and to become sensitive to insulin earlier in the refeeding process than did the lipogenic system. The in vitro incorporation of 14C-glucose into aortic phospholipids was less affected by the nutritional state of the animal, and was not stimulated by insulin at any stage of the experiment. Possible mechanisms for the development of insulin supersensitivity and the implications for lipid accumulation in the artery wall are discussed.

Development of insulin sensitivity in rat aorta after chronic propranolol treatment

Spontaneously hypertensive rats and normotensive Kyoto Wistar controls were divided into 3 groups of 10 animals each and treated with phenoxybenzamine (5 mg/kg once daily), propranolol (25 mg/kg twice daily) or saline (once daily). After 5 weeks the in vitro incorporation of D-[U-14C]-glucose into aortic lipids and glycogen was measured in the presence and absence of insulin (1 mU/ml). In both normotensive and hypertensive rats treated with propranolol 14C-incorporation into triglycerides was reduced. Furthermore, insulin significantly stimulated 14C-incorporation into triglycerides, phospholipids and glycogen in propranolol-treated hypertensive rats. This effect was not statistically significant (0.05 less than p less than 0.1) in propranolol-treated normotensives. Phenoxybenzamine treatment did not significantly modify aortic lipogenesis or glycogen synthesis from glucose. Chronic propranolol treatment of spontaneously hypertensive rats resulted in aortic tissue becoming sensitized to insulin. Possible mechanisms and explanations for this are discussed.

Effect of caloric restriction on basal insulin levels and the in vivo lipogenesis and glycogen synthesis from glucose in the Koletsky obese rat

Fasting plasma immunoreactive insulin levels increased with age in hyperinsulinemic Koletsky obese rats, being almost four times as high as in lean siblings at 3 mo (40 +/- 5 muU/ml) and rising steadily to 82 +/- 4 muU/ml at 6 mo (about seven times higher than lean siblings). Restricting the food intake of the obese rats markedly reduced but did not normalize the hyperinsulinemia, which in these rats was accompanied by normal plasma glucose concentrations. The incorporation in vivo of D-U-14C-glucose into tissue lipids and glycogen was measured 1 hr after the intravenous injection of 1 g glucose (containing 100 muDi D-U-14C-glucose) per kg body weight in obese rats eating ad libitum, obese rats after 3 mo on a restricted food intake, and lean siblings. All tissues (heart, diaphragm, skeletal muscle, and adipose tissues and liver) of obese rats exhibited a significantly greater lipogenesis from glucose than those of lean siblings. Dietary restriction of the obese rats reduced the 14C incorporation into lipid to levels not significantly different from lean controls in all tissues except skeletal muscle and liver, where, although greatly reduced, lipogenesis was still significantly higher than in lean rats. Glycogen synthesis tended to be greater in all tissues of obese rats than in lean animals. Dietary restriction of obese rats did not greatly affect glycogen synthesis.

Antinociceptive action and plasma levels of acetylsalicylic acid in the dog

1. The analgesic potency of acetylsalicylic acid (ASA) is four times greater when administered intravenously than when administered orally. 2. The onset of the ASA analgesia after oral administration is significantly slower (30-60 min) than after intravenous (5-15 min) application. However, the duration of ASA-analgesia after oral administration is significantly longer (5 h) than after i.v. (2-4 h) application. 3. The onset and duration of ASA-analgesia in dogs after oral and i.v. administration cannot be correlated with plasma levels of ASA. During the period of analgesia, ASA can be detected only in extremely low concentrations, since it appears to be very rapidly hydrolysed to SA. 4. The development of an accurate and reproducible method for the separate determination of ASA and SA in plasma facilitated the direct correlation of plasma levels of these substances with ASA-induced analgesia.

Studies on the interaction of isoproterenol with plasma membranes isolated from rat myometrium

Catecholamine stimulation of adenyl cyclase in plasma membranes from rat myometrium was typical of beta-adrenoceptor stimulation. Thus, isoproterenol was the most potent followed by epinephrine and norepinephrine; phenylephrine, a pure alpha-agonist, did not activate the enzyme. The catecholamine-induced activation was potently inhibited by propranolol, whereas phenozybenzamine was without effect. The ED50 for 1-isoproterenol activation was 10- minus 7 M. Binding of [3H]-d-isoproterenol to the same preparations bore little resemblance to the pattern of 1-isoproterenol activation of adenyl cyclase. Propranolol, even at high concentrations, was without significant effect. The degree of binding was inversely rflated to the osmolarity suggesting that diffusion may have contributed to the binding. This contention was further supported by the time course of binding which was biphasic- the first component (smaller than 4 min) being less affected by osmolarity than the second (greater than 4 min). The optimum pH for binding was 7.4.