Reduction in hyperglycemia by mild food restriction in streptozotocin induced diabetic rats improves insulin sensitivity

Hyperglycemia has been shown to contribute to the development and maintenance of insulin resistance in diabetic subjects and animal models of diabetes. Normalisation of circulating glucose levels is effective in restoring insulin action. The aim of the current study was to investigate the effects of mild food restriction on hyperglycemia in streptozotocin (STZ) treated (50 mg/kg) diabetic rats and to determine if the reductions in glycemia following food restriction were sufficient to alter insulin sensitivity. Food restriction was achieved in STZ diabetic and normal rats by limiting food access to two one-hourly meals daily and further in normal rats by restricting the feeding period to a single two-hour meal daily. Food intake was lowered by 39.7% (p < 0.01) in the food restricted STZ rats, without significant alteration in weight gain over 4 weeks. Similarly, in the normal rats once and twice daily meals lowered food intake by 37.6% and 21.6% when compared to the ad-libitum fed group, respectively. After 3 weeks food restriction in the STZ diabetic rats mean plasma glucose levels over a 12 hour period were reduced by 13.9%, glucose levels after a 6 hr fast were reduced by 33% (p < 0.05). Plasma insulin levels remained unaltered by food restriction. After 4 weeks food restriction in STZ diabetic rats basal glucose turnover was reduced (p < 0.05) and the metabolic clearance rate of glucose (MCR) increased (p < 0.05). During the hyperinsulinemic clamp hepatic glucose output (HGO) was suppressed and MCR elevated more effectively in the food restricted STZ than the ad-libitum STZ rats.(ABSTRACT TRUNCATED AT 250 WORDS)

A cross-sectional and short-term longitudinal characterisation of NIDDM in Psammomys obesus

The present study was undertaken to examine the cross-sectional and short-term longitudinal changes in glucose and insulin concentrations as well as measure the enzymatic activity of PEPCK and glycogen synthase in our Psammomys obesus colony. In the cross-sectional study, blood samples were taken from one group of animals at 19 weeks of age (n = 37) in the fed state and following a 4-h fast. In a separate group of 19-week-old animals (n = 69), samples were taken 1 h following an OGTT (1 g/kg body weight) in Psammomys subjected to a 16-h fast. In the longitudinal study, blood samples were taken from one group of animals in the fed state at 7, 11, 15 and 19 weeks of age. All of the cross-sectional data have described the classic inverted U-shaped curve (Starling's curve of the pancreas) in the relationship between glucose and insulin levels. This trend was also reflected by Psammomys subjected to the OGTT; a mild impairment in glucose tolerance was associated with an increase in the insulin response and a further impairment in glucose tolerance was associated with a reduction in the insulin response. Similar results were obtained following a 4-h fast. The short-term longitudinal glucose and insulin data revealed that of the 37 animals examined over the 12-week period, 16 progressed along the inverted U-shaped curve described by the cross-sectional data. Of the other animals, 8 remained unchanged, 7 were unclassifiable and 6 hyperglycaemic Psammomys developed normoglycaemia at the expense of elevated insulin levels.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of propionate on in vivo carbohydrate metabolism in streptozocin-induced diabetic rats

Undigested carbohydrates and some dietary fibers are fermented in the large intestine to form short-chain fatty acids (SCFA), including acetate, propionate, and butyrate. It has been suggested that some of the beneficial effects of high-carbohydrate, high-fiber diets on carbohydrate and lipid metabolism are mediated by the metabolism of SCFA in the liver. Propionate has been shown in vitro to decrease glucose production in rat hepatocytes. The aim of the present study was to investigate the effects of propionate on carbohydrate metabolism in normal and streptozocin (STZ)-induced diabetic male Sprague-Dawley rats. Rats were fed a high-fat diet with or without sodium propionate supplementation (either 0.5% or 5% wt/wt) for 4 weeks. At the completion of the feeding period, body weight and liver glycogen concentrations were significantly decreased in STZ-diabetic rats and were unaffected by propionate supplementation. Although STZ-diabetic animals had elevated fasting plasma glucose, cholesterol, and triglyceride levels relative to nondiabetic rats, propionate supplementation had no significant effect on these parameters in either group. Basal and insulin-stimulated carbohydrate metabolism were assessed using the euglycemic clamp technique in overnight-fasted animals with 3(H)-6-glucose infusion. As expected, basal hepatic glucose production (HGP) was higher and the metabolic clearance rate of glucose (MCR) was lower in STZ-diabetic rats. High-dose insulin infusion (3 mU.kg-1.min-1) suppressed HGP in nondiabetic and diabetic animals and increased the MCR in nondiabetic animals. However, propionate supplementation did not alter basal or insulin-stimulated HGP or the MCR in either nondiabetic or diabetic animals.(ABSTRACT TRUNCATED AT 250 WORDS)

Apparent dietary intake in remote aboriginal communities

Apparent per capita food and nutrient intake in six remote Australian Aboriginal communities using the 'store-turnover' method is described. The method is based on the analysis of community-store food invoices. The face validity of the method supports the notion that, under the unique circumstances of remote Aboriginal communities, the turnover of foodstuffs from the community store is a useful measure of apparent dietary intake for the community as a whole. In all Aboriginal communities studied, the apparent intake of energy, sugars and fat was excessive, while the apparent intake of dietary fibre and several nutrients, including folic acid, was low. White sugar, flour, bread and meat provided in excess of 50 per cent of the apparent total energy intake. Of the apparent high fat intake, fatty meats contributed nearly 40 per cent in northern coastal communities and over 60 per cent in central desert communities. Sixty per cent of the apparent high intake of sugars was derived from sugar per se in both regions. Compared with national Australian apparent consumption data, intakes of sugar, white flour and sweetened carbonated beverages were much higher in Aboriginal communities, and intakes of wholemeal bread, fruit and vegetables were much lower. Results of the store-turnover method have important implications for community-based nutrition intervention programs.

Letters

THE IMPORTANCE OF PRESSURE RELIEF PATIENT CONFIDENTIALITY RELIABLE PRESSURE DAMAGE DATA.

Diets rich in lean beef increase arachidonic acid and long-chain omega 3 polyunsaturated fatty acid levels in plasma phospholipids

Diets rich in meat are claimed to contribute to the high tissue arachidonic acid (20:4 omega 6) content in people in Westernized societies, but there are very few direct data to substantiate this assertion. Because meat contains a variety of long-chain polyunsaturated fatty acids (PUFA) that are susceptible to oxidation, we initially examined the effect of cooking on the long-chain PUFA content of beef, and then determined the effect of ingestion of lean beef on the concentration of long-chain PUFA in plasma phospholipids (PL). First, we examined the effect of grilling (5-15 min) and frying (10 min) different cuts of fat-trimmed lean beef on the long-chain PUFA content. Second, we investigated the effect of including 500 g lean beef daily (raw weight) for 4 wk on the fatty acid content and composition of plasma PL in 33 healthy volunteers. This study was part of a larger trial investigating the effect of lean beef on plasma cholesterol levels. In the first two weeks, the subjects ate a very low-fat diet (10% energy) followed by an increase in the dietary fat by 10% each week for the next 2 wk. The added fat consisted of beef fat, or olive oil (as the oil or a margarine) or safflower oil (as the oil or a margarine). This quantity of beef provided 60, 230, 125, 140 and 20 mg/d, respectively, of eicosatrienoic acid (20:3 omega 6), 20:4 omega 6, eicosapentaenoic acid (20:5 omega 3), docosapentaenoic acid (22:5 omega 3) and docosahexaenoic acid (22:6 omega 3).(ABSTRACT TRUNCATED AT 250 WORDS)

n-3 fatty acids reduce in vitro thromboxane production while having little effect on in vitro prostacyclin production in the rat

Male Sprague-Dawley rats were fed diets with 50% of the energy from fat over a 20-day period. The fats used were hydrogenated beef-fat (HBF), or HBF supplemented with ethyl arachidonate A, safflower oil (SO), or a mixture of SO and linseed oil (LO). For comparative purposes, another group of animals was fed a diet providing 50% of the energy as butter-fat. In vitro aortic prostacyclin (PGI2) and serum thromboxane (TXA2) levels (from clotting blood) were determined by radioimmunoassay of 6-keto PGF1 alpha and TXB2, respectively. The HBF diet had similar AA levels relative to the butter-fed rats but significantly reduced tissue levels of eicosapentaenoic acid (EPA) and this was associated with an increased production of serum TXB2. Supplementing the HBF diet with AA increased tissue levels of AA while maintaining low levels of n-3 fatty acids. These changes were accompanied by significant increases of both TXB2 and 6-keto-PGF1 alpha. LO supplementation to the HBF diet (with constant SO) led to elevated levels of EPA and relatively constant AA levels and this was associated with reduced production of TXB2. These results highlight the responsiveness of TXA2 to n-3 fatty acids in contrast to PGI2 which was more influenced by the level of AA in the tissue phospholipids in the rat.

Energy intake, anthropometry and blood pressure of expeditioners in the Antarctic

The energy intakes, anthropometry and blood pressure of 62 expeditioners at one Australian sub-Antarctic (Macquarie Island) and two Antarctic stations (Davis and Casey) were examined over a 12 month period. High mean energy intakes were found at all stations (approximately 16,000 kJ/subject/day). Mean subject body weight tended to rise during the winter months (midway during the study) and fall during the spring, although there were no significant changes (p < 0.05) seen at any of the stations over the year. Subjects were generally leaner at the end of 12 months as evidenced by significant falls (p < 0.01) in mean sum of skinfold thickness at two stations over the year. At all stations, blood pressure trended downwards during the year, with significant rises (p < 0.01) seen at one station during the spring. Two 12-week dietary intervention periods were introduced during the year at one of the Antarctic stations to investigate the effects of low-cholesterol (< 300 mg/day), low-fat (< 30% of energy) and high-fibre (> 30 g/day) diets. The average energy intake/day during these two periods (14,973 kJ and 14,515 kJ) was slightly less than during the baseline diet (average of 16,228 kJ). This was reflected in the anthropometric measurements with the mean body weight, sum of skinfold thickness and waist/hip ratios trending down during the diet periods. The study confirms earlier reports of high mean energy intake in Antarctica and suggests that the techniques of measuring intake may have been more accurate than those used in large population studies where intake may have been under-estimated. The results indicate seasonal fluctuations in blood pressure and anthropometric parameters and demonstrate that these anthropometric parameters were affected by the balance of energy intake and activity.

Effect of soluble dietary fibre on the viscosity of gastrointestinal contents and the acute glycaemic response in the rat

The postprandial glycaemic response following a meal is reduced with the addition of soluble dietary fibre. The reductions in the glycaemia are thought to be due largely to increased viscosity of the gastrointestinal (GI) contents retarding digestion and absorption. The aims of the present study were to determine the effect that the GI tract has on the viscosity of meals containing different soluble fibres and to determine whether the glycaemic response of a meal (containing the soluble fibre) was predicted by the viscosity of the digesta in the small intestine. High carbohydrate diets containing 70 g soluble fibre guar gum, xanthan gum or methylcellulose)/kg or 70 g insoluble fibre (wheat bran)/kg were diluted in water to a final fibre concentration of 18 g/kg. Following dilution the wheat bran diet had no measurable viscosity, while the viscosities of the soluble fibre diets were elevated. When the diets were fed to male Sprague-Dawley rats for 2 weeks the viscosities of the stomach and small intestinal digesta were not predicted by the viscosity of the diets measured before ingestion. The action of the GI tract on the viscosity of the soluble fibres was investigated in vitro by dilution of the diets with acidic and neutralizing solutions, mimicking gastric and duodenal secretions. Dilution of diets with either acidic and neutralizing solutions or saline control significantly lowered the viscosity of all diets, while alterations in the pH of the diets had little impact on the resultant viscosity.(ABSTRACT TRUNCATED AT 250 WORDS)

Development of the Melbourne FFQ: a food frequency questionnaire for use in an Australian prospective study involving an ethnically diverse cohort

Objective. To develop an optically scannable food frequency questionnaire (FFQ), 'The Melbourne FFQ', suitable for classifying Australian-, Greek- and Italian-born individuals into quantiles of intake for a range of foods and nutrients. The FFQ would provide the primary measure of dietary exposure in a prospective cohort study. Design. The FFQ was modelled on that used for the (US) Nurses' Health Study. Food items were chosen on the basis of their relative contribution to the intake of a range of nutrients computed from weighed food records. Setting. Metropolitan Melbourne, Australia, a city of 3 million people, of whom 75.5% were born in Australia, 2.7% were born in Italy and 1.7% were born in Greece. Participants. Weighed Food Survey (1987-1989): A volunteer sample of 810 healthy middle-aged (40-69 years) men and women of whom 35% were born in Greece, 33% were born in Italy, and 32% were born in Australia. Melbourne Collaborative Cohort Study (1990-1993): A volunteer sample of 17 949 healthy men and women aged between 40 and 69 years of whom 61% were born in Australia, 21% were born in Italy and 17% were born in Greece. Results. A 121 item FFQ was developed, together with a customized nutrient database. The optical scanning format was generally well received with the majority of subjects requiring no assistance. The FFQ appeared to overestimate the consumption of fruit and vegetables. Conclusions. The Melbourne FFQ provides a convenient method of measuring habitual dietary intake in a large population setting. A separate study is required to assess how well the instrument characterizes diet at the level of the individual.

Blood pressure, lipids and other risk factors for cardiovascular disease in Aborigines and persons of European descent of southeastern Australia

Based on a survey in two country towns of southeastern Australia, cardiovascular risk-factor prevalence data from Aborigines and persons of European descent are presented. The mean diastolic blood pressure in 123 Aboriginal males was 83.2 mmHg, compared with 79.2 mmHg in 272 European males (P = 0.005). In 178 Aboriginal females, mean diastolic pressure was 79.2 mmHg, compared with 76.3 mmHg in 281 European females (P = 0.006). Mean plasma total cholesterol was higher in Europeans (both males and females: 5.7 mmol/L) than in Aborigines (in males 5.2 and females 5.0 mmol/L) (male comparison, P = 0.02, female comparison, P < 0.001). The prevalence in participants aged 25 to 64 years of at least one major risk factor (diastolic blood pressure 95 mmHg or higher, plasma cholesterol 6.5 mmol/L or higher, or smoking more than one cigarette daily) was higher in both these samples of Aborigines (94 per cent in males, 89 per cent in females) and Europeans (70 per cent in males, 59 per cent in females) than in the 1989 urban sample of the National Heart Foundation (47 per cent in males, 36 per cent in females). Multivariate analyses showed statistically significant independent contributions of body mass index and the variable 'ethnicity' (unidentified genetic and environmental differences between the groups) to blood pressure and other risk factors. The higher cardiovascular mortality of Aborigines may be explained partly by the higher prevalence of risk factors in this group compared with other Australians. Further, the risk-factor profile may be worse among rural compared with urban Europeans.

The effect of linoleic, arachidonic and eicosapentaenoic acid supplementation on prostacyclin production in rats

We examined the effect of dietary supplementation of linoleic acid (LA), arachidonic acid (AA) or eicosapentaenoic acid (EPA) to rats fed a diet low in linoleic acid on in vitro and in vivo production of prostacyclin. Male Sprague Dawley rats were fed a high-fat diet (50% energy as fat, 1.5% linoleic acid) for two weeks. Three of the groups were then supplemented orally with either 90 mg/d of LA, AA or EPA, all as the ethyl esters, for a further two weeks while remaining on the high-fat diet. Forty-eight hour urine samples were collected at the end of the second and fourth weeks. In vivo prostacyclin production was determined by a stable isotope dilution, gas chromatography/mass spectrometry assay for the major urinary metabolite of prostacyclins (2,3-dinor-6-keto-PGF1 alpha or PGI2-M and delta 17-2,3-dinor-6-keto-PGF1 alpha or PGI3-M). In vitro prostacyclin production was determined by radioimmunoassay of the stable metabolite (6-keto-PGF 1 alpha) following incubation of arterial tissue. Oral supplementation with AA resulted in a rise in plasma and aorta 20:4n-6, and increased in vitro prostacyclin and urinary PGI2-M production. EPA supplementation resulted in a rise in plasma and aorta 20:5n-3 and 22:5n-3, and a decline in plasma 20:4n-6, but not in the aorta. In the EPA-supplemented group, the in vitro prostacyclin and the urinary PGI3-M increased, but urinary PGI2-M decreased. The increase in in vitro prostacyclin production in the EPA-supplemented rats was unexpected and without obvious explanation.(ABSTRACT TRUNCATED AT 250 WORDS)

The effect of dietary fat level and quality on plasma lipoprotein lipids and plasma fatty acids in normocholesterolemic subjects

This study examined the effect on the plasma lipids and plasma phospholipid and cholesteryl ester fatty acids of changing froma typical western diet to a very low fat (VLF) vegetarian diet containing one egg/day. The effect of the addition of saturated, monounsaturated or polyunsaturated fat (PUFA) to the VLF diet was also examined. Three groups of 10 subjects (6 women, 4 men) were fed the VLF diet (10% energy as fat) for two weeks, and then in the next two weeks the dietary fat in each group was increased by 10% energy/week using butter, olive oil or safflower oil. The fat replaced dietary carbohydrate. The VLF diet reduced both the low density lipoprotein (LDL)- and high density lipoprotein (HDL)-cholesterol levels; addition of the monounsaturated fats and PUFA increased the HDL-cholesterol levels, whereas butter increased the cholesterol levels in both the LDL- and HDL-fractions. The VLF diet led to significant reductions in the proportion of linoleic acid (18:2 omega 6) and eicosapentaenoic acid (20:5 omega 3) and to increases in palmitoleic (16:1), eicosatrienoic (20:3 omega 6) and arachidonic acids (20:4 omega 6) in both phospholipids and cholesteryl esters. Addition of butter reversed the changes seen on the VLF diet, with the exception of 16:1, which remained elevated. Addition of olive oil resulted in a significant rise in the proportion of 18:1 and significant decreases in all omega 3 PUFA except 22:6 compared with the usual diet. The addition of safflower oil resulted in significant increases in 18:2 and 20:4 omega 6 and significant decreases in 18:1, 20:5 omega 3 and 22:5 omega 3. These results indicate that the reduction of saturated fat content of the diet (< 6% dietary energy), either by reducing the total fat content of the diet or by exchanging saturated fat with unsaturated fat, reduced the total plasma cholesterol levels by approximately 12% in normocholesterolemic subjects. Although the VLF vegetarian diet reduced both LDL- and HDL-cholesterol levels, the long-term effects of VLF diets are unlikely to be deleterious since populations which habitually consume these diets have low rates of coronary heart disease. The addition of safflower oil or olive oil to a VLF diet produced favorable changes in the lipoprotein lipid profile compared with the addition of butter. The VLF diets and diets rich in butter, olive oil or safflower oil had different effects on the 20 carbon eicosanoid precursor fatty acids in the plasma.(ABSTRACT TRUNCATED AT 400 WORDS)

Food habits in Aborigines and persons of European descent of southeastern Australia

As part of a study of risk factors for glucose intolerance and heart disease in Australian Aborigines and persons of European descent, we elicited the prevalence of food habits that may be associated with high fat and high salt intakes. Interview data were gathered from population-based samples in country towns and visitors to an Aboriginal health service in a state capital city, all in southeastern Australia. Among persons aged 13 years and over, the frequency of eating takeaway food as a meal was categorised as monthly or less, weekly, more than once per week, and daily or more often. The prevalence of eating such meals was higher among city Aborigines than those living in the country town; the prevalence was lowest among the country-town Europeans (chi 2 = 184, 6 df, P < 0.001). The prevalence of adding salt during cooking and food consumption was higher among Aborigines compared with Europeans. Among country-town Aboriginal males aged 35 or under, 25 of 40 (63 per cent) added salt to cooked food 'most of the time', compared with 66 of 185 (36 per cent) Europeans (chi 2 = 9.8, P = 0.002). Among Aboriginal females, 47 of 64 (64 per cent) were in the highest category of salt use, compared with 35 of 190 (18 per cent) of Europeans (chi 2 = 66.3, P < 0.001). About one-third of country-town Aboriginal males used dripping to fry food, but in the other ethnicity, gender and location groups, vegetable oil was the most frequent choice. The main differences in food habits were associated with ethnicity, rather than location.(ABSTRACT TRUNCATED AT 250 WORDS)

Nucleotide sequence analysis and epitope mapping of the merozoite surface protein 1 from Plasmodium chabaudi chabaudi AS

The complete nucleotide sequence of the gene encoding the merozoite surface protein 1 (MSP-1) from the rodent malaria parasite Plasmodium chabaudi chabaudi AS has been determined by direct sequencing of overlapping PCR derived fragments. Comparison of the P. c. chabaudi AS nucleotide sequence with the previously published P. c. chabaudi IP-PC1 sequence indicates that although the MSP-1 gene of these two P. c. chabaudi strains is highly conserved, with sequence identity often approaching 100%, interspersed throughout the molecule are 5 regions of divergence. This is at variance with published data which suggested that the P. c. chabaudi AS and P. c. chabaudi IP-PC1 MSP-1 sequences are largely identical. Epitope mapping studies with a panel of anti-P. c. chabaudi AS MSP-1 monoclonal antibodies demonstrate that whilst most of these mAbs recognise epitopes at the N-terminus of the MSP-1 molecule, two mAbs, including one capable of inhibiting challenge infections in mice in an in vivo passive transfer assay, recognise epitopes which map to the C-terminus.

A single amino acid determines the specificity of a monoclonal antibody which inhibits Plasmodium chabaudi AS in vivo

The in vivo inhibitory action of NIMP23, a monoclonal antibody raised against the rodent parasite Plasmodium chabaudi chabaudi AS, has previously been shown to be strain-specific, capable of delaying significantly the onset of P. c. chabaudi AS but not a P. c. chabaudi CB challenge parasitaemia. The epitope to which this mAb binds has been mapped to the second of two epidermal growth factor-like domains located at the C-terminus of the merozoite surface protein 1 (MSP-1) of P. c. chabaudi AS. The C-terminus region of the MSP-1 of P. c. chabaudi is a region of heterogeneity with AS and CB strain parasites showing only 78% identity at the amino acid level. The critical amino acid substitution which accounts for the strain specificity of the NIMP23 monoclonal antibody has now been identified. Polymerase chain reaction directed mutagenesis experiments demonstrate that a single proline to asparagine substitution at position 1722 in the primary amino acid sequence is sufficient to convert NIMP23-negative P. c. chabaudi CB expression constructs into NIMP23-positive clones whilst the converse substitution of an asparagine for a proline residue converts P. c. chabaudi AS expression constructs into NIMP23-negative clones.

Forearm arterial vascular responsiveness in insulin-dependent diabetic subjects

The vascular reactivity of forearm arterioles was measured in 16 control subjects (C) and 30 insulin-dependent diabetic (IDDM) subjects, 16 of whom were shown to have microvascular and/or neuropathic complications (DC) including 8 with autonomic neuropathy (DCa) and 14 were shown to be free of complications (DNC). Forearm blood flow was measured by strain gauge plethysmography basally, following a cold pressor stress and following a period of arterial occlusion (reactive hyperaemia). The tests were repeated 24 h later following aspirin treatment. Both C and DNC showed a significant reduction in blood flow in the cold pressor test (C 0.64 +/- 0.12, DNC 0.89 +/- 0.22 ml/100 ml forearm tissue/min reduction in flow P < 0.005), while DC showed no significant response. Reactive hyperaemia was significantly greater in C than in DNC or DC (8.37 +/- 1.14, 5.51 +/- 1.27 and 4.95 +/- 0.75 ml/100 ml tissue/min, respectively, P < 0.02). In the DC group, DCa had significantly less response than those without autonomic neuropathy. Aspirin treatment restored the response of DNC but not DC to normal, suggesting that the abnormality in the former group may have been due to overproduction of a vasoconstrictive cyclooxygenase product (such as thromboxane A2). It is concluded that the abnormalities of vasomotor responses in diabetic subjects are complex and are apparently dependent on autonomic neuropathy, humoral and perhaps structural changes.

Prevalence of pressure damage in hospital patients in the UK

This paper describes a method of determining the prevalence of pressure damage in hospital patients and gives some preliminary results. The same method and data collection systems were applied to seven different hospitals in the UK, and involved over 3 000 patients. The approach allows comparisons between hospitals and permits some interpretation of the national data. The methodology can be shown to be valid, reliable and reproducable, enabling it to be used to measure the effectiveness of policies and protocols. The cost of treating full-thickness pressure sores, and the resulting increase in patient length of stay has made it vital for hospitals to develop effective strategies both for prevention and treatment. Such a survey is an excellent tool for identifying opportunities to improve both these strategies. Such a survey is, ideally, part of a 'total quality outcome management' approach to the issue of pressure damage.

Obesity, diabetes, and hyperlipidemia in a central Australian aboriginal community with a long history of acculturation

OBJECTIVE

To determine the age- and sex-specific prevalence of diabetes and to examine associations between related anthropometric and metabolic abnormalities in an Aboriginal community in central Australia with a long history of acculturation.

RESEARCH DESIGN AND METHODS

We used a cross-sectional survey of 353 adults > 15 yr of age (87% response rate) and measured the following parameters: weight, height, circumferences of waist and hips; glucose, insulin, cholesterol, triglyceride, and high-density lipoprotein cholesterol in fasting plasma; and plasma glucose and insulin 2 h after 75 g oral glucose.

RESULTS

The prevalence of diabetes was 29.6% in survey participants > 35 yr of age and 5.3% in those < 35 yr of age. Impaired glucose tolerance also occurred with higher frequency in those > 35 yr of age (14.8 vs. 4.7%). Of those > 35 yr of age, 75% of the women and 51% of the men were overweight or obese, with a body mass index > or = 25 kg/m2. A large insulin response to oral glucose was evident, with the upper tertile of the 2-h insulin response six times higher than the lower tertile (113 +/- 43 vs. 19 +/- 8 mU/L). Hyperinsulinemia showed a strong, positive association with impaired glucose tolerance, body mass index, waist-to-hip ratio, cholesterol, and triglyceride levels and a negative association with high-density lipoprotein cholesterol levels. Cholesterol levels were on average 0.5 mM higher in men than in women. Deteriorations in carbohydrate and lipid metabolism occurred before 40 yr of age: diabetes, body mass index, waist-to-hip ratio, and fasting triglycerides and cholesterol concentrations peaked and high-density lipoprotein cholesterol concentrations reached their nadir at the end of the fourth decade.

CONCLUSIONS

These data suggest that any intervention programs developed to prevent or reduce diabetes prevalence in this population should be targeted at adolescents and young adults.

Effect on serum lipids of addition of safflower oil or olive oil to very-low-fat diets rich in lean beef

The cholesterol-lowering effect of very-low-fat diets rich in lean beef has previously been shown to be reversed with the addition of beef fat. The aim of this study was to determine the effect on serum lipid levels of the addition of safflower oil or olive oil to a very-low-fat diet rich in lean beef. Subjects were assigned to either the safflower oil or the olive oil group. In the first week the subjects ate their usual diet; in the second and third weeks all subjects ate a very-low-fat (9% of energy) diet rich in lean beef. In the fourth and fifth weeks the fat content of the diet was increased in a stepwise fashion to 20% and 30% of energy, respectively, by substituting safflower oil or olive oil for carbohydrate. Low-density lipoprotein cholesterol (LDL-C) concentrations decreased by 13% to 14%, and high-density lipoprotein cholesterol (HDL-C) concentrations decreased by 20% to 25% in subjects after 2 weeks of the very-low-fat, lean-beef diet. The LDL-C concentrations remained low after the addition of safflower oil or olive oil to the very-low-fat diet. These results indicate that a reduction in saturated fat, not total fat, is required to reduce serum total cholesterol and LDL-C levels. Provided that the total diet is low in saturated fat, these serum lipid responses can be achieved even when the diet is rich in fat-trimmed lean beef.

Hyperinsulinaemia and obesity in aborigines of south-eastern Australia, with comparisons from rural and urban Europid populations

Diabetes is more common in Aborigines than in other Australian populations, even in groups that have lived in contact with Europids for 150 years. Prevalence data on hyperinsulinaemia and obesity from urbanized south eastern Australian Aborigines are presented with Europid comparisons. Aborigines had higher mean insulin levels than Europids. In females, mean fasting insulin was 15.5 mU/l in Aborigines, compared with 9.5 mU/l in Europids (P < 0.001). The means for males were 15.1 mU/l (Aborigines) and 8.3 (Europids) (P < 0.005). Obesity was more prevalent in Aborigines. In Aboriginal females aged 25-64 years, 41/108 (38%) had BMI > 30.0, compared with 37/208 (18%) Europids (P < 0.001). In males, the difference in the prevalence of obesity in Aborigines (17/69, 25%) and Europids (34/195, 17%) was not statistically significant. Waist-hip ratio was significantly greater among Aboriginal females (mean 0.87 in persons aged 25-64 years) than among Europids (mean 0.81, P < 0.001). In males, the mean ratio in Aborigines and Europids was the same (0.94). Abdominal obesity was most prevalent among Aboriginal females. For females aged 20-49 years, 83/110 (75%) Aborigines had a waist-hip ratio > 0.80, compared with 71/165 (43%) Europids (P < 0.001). Being overweight or obese is perceived with least accuracy by Aboriginal males of the four ethnicity/gender groups. Comparisons with national data suggest a gradient in the prevalence of obesity, lowest in urban groups, more in the country, and higher still among Aborigines, which is in reciprocal order to socio-economic status. In multivariate analyses, the association of BMI with insulin was highly significant. Hyperinsulinaemia in an Aboriginal group after many years of contact with Europids may result from environmental as well as genetic influences. Relative hyperinsulinaemia is not found among those Aborigines who have developed glucose intolerance, which could be explained by earlier pancreatic exhaustion in this group.

Validation of an in vitro assay for predicting the amount of starch that escapes digestion in the small intestine of humans

The aim of the present study was to validate an in vitro assay for quantifying resistant starch (RS) in foods against an in vivo model. The amount of starch escaping digestion in the small intestine of ileostomates was compared with that observed by using the in vitro assay. Subjects with ileostomies were fed five foods containing different types and amounts of RS (baked beans, pearl barley, cornflakes, and whole and ground rice). The total amount of starch escaping digestion and recovered in the effluent (ranging from 5.7% in baked beans to 0.7% in ground rice) was compared with results obtained by using the in vitro assay with an incubation time of 6 h. The assay was found to be a good qualitative predictor (r = 0.90, P < 0.05), but a poor quantitative predictor of RS amounts. Increasing the duration of incubation with alpha-amylase and amyloglucosidase to 15 h resulted in a very close agreement between results from the in vitro technique and the in vivo model. These data indicate that for a variety of foods the in vitro assay produced an excellent estimate of starch escaping digestion in the small intestine of humans.

Arachidonic acid supplementation dose-dependently reverses the effects of a butter-enriched diet in rats

Male Sprague Dawley rats were fed a butter-enriched diet (50% fat) for 2 weeks which was supplemented orally with 9, 18, 36, or 72 mg/day of ethyl arachidonate for a further 2 weeks. The control group of animals were fed a 5% fat diet for 4 weeks. Aortic prostacyclin (PGI2) production, platelet aggregation and thromboxane A2 (TXA2) production and plasma and aortic phospholipid (PL) fatty acids were measured. 50% butter-feeding resulted in a significant reduction in aortic PGI2 production and collagen-induced platelet aggregation and TXA2 production. These changes were accompanied by a reduction in plasma and aortic PL arachidonic acid levels and an increase in eicosapentaenoic acid (EPA), docosahexaenoic acid (DHA), 5,8,11-eicosatrienoic acid (ETA) and dihomo-gamma-linolenic acid (DGLA). These changes in prostanoid production, platelet aggregation and PL fatty acid composition were dose-dependently reversed by the daily oral administration of ethyl arachidonate (9, 18, 36, or 72 mg). The threshold dose being as little as 9 mg of ethyl arachidonate/rat/day for reversal of PL fatty acid composition, collagen-induced platelet aggregation and TXA2 production, and 18 mg of ethyl arachidonate/rat/day for reversal of aortic PGI2 production. Full reversal was seen generally with 36 or 72 mg of ethyl arachidonate/rat/day. The data highlight the responsiveness of tissue eicosanoid production to small quantities (ppm) of dietary eicosanoid precursors.

Low-dose acarbose improves glycemic control in NIDDM patients without changes in insulin sensitivity

OBJECTIVE

To examine the impact on metabolic control in NIDDM patients of the alpha-glucosidase inhibitor, acarbose, when administered at a low dose in powdered form.

RESEARCH DESIGN AND METHODS

Six subjects were recruited for a double-blind cross-over trial using 25 mg powdered acarbose and a placebo 3 times a day with meals for 3 mo. In addition to parameters of diabetes control and body weight, glucose turnover and insulin sensitivity were measured with the hyperinsulinemic/euglycemic clamp technique combined with tracer kinetics.

RESULTS

None of the subjects showed significant changes in FPG levels or body weight either on the 3-mo course of acarbose or placebo. HbA1c fell significantly from 10.6 +/- 1.0 to 9.4 +/- 1.3% (P = 0.05) during treatment with acarbose but failed to change on placebo (10.1 +/- 1.0 to 11.1 +/- 2.0%; P = 0.36). Basal HGP and glucose utilization were unchanged during either of the treatment periods, and hyperinsulinemia produced a similar degree of suppression of HGP before and after each treatment. At a physiological concentration, insulin failed to stimulate glucose clearance in these diabetic patients, and no improvement was seen with acarbose treatment. No changes in plasma lipids or lipoprotein profiles were demonstrated after 3 mo on acarbose. In acute studies, it was shown that administration of acarbose at a dose of 25 mg powder per meal significantly decreased the postprandial glycemic excursion.

CONCLUSIONS

When administered in the powdered form at the low dose of 25 mg 3 times/day with meals over 3 mo, acarbose was well tolerated by the NIDDM patients and was without side effects. It improved glycemic control by reducing postprandial hyperglycemia, but had no effect on glucose turnover, insulin sensitivity, or lipid profile.

Effect of fatty acid oxidation inhibition on glucose metabolism in diabetic rats

Inhibition of fatty acid (FA) oxidation has been shown previously to lower blood glucose levels acutely in diabetic rats. However, the longer term effects of FA oxidation inhibition have not been determined. This study examines the effect of inhibition of (FA) oxidation for 3 weeks on carbohydrate metabolism in rats rendered diabetic with streptozotocin (STZ). STZ treated rats (50 mg/kg) were randomized into 3 groups: a non-treated diabetic group and 2 groups treated with either 12.5 or 25 mg/kg/day Etomoxir (a specific carnitine palmitoyl transferase inhibitor) for 3 weeks. The 3 groups of rats had ad libitum access to a high fat diet (50% energy fat, 30% carbohydrate and 20% protein) throughout the study. After 3 weeks hepatic glucose production (HGP) was estimated using a constant infusion of (3H)-6-glucose in-vivo after an overnight fast. Inhibition of FA oxidation in diabetic rats resulted in a significant reduction in fasting glucose levels and hepatic glucose production. In addition, experiments with adipocytes isolated from diabetic rats treated with etomoxir demonstrated an increase in sensitivity and responsiveness to insulin of glucose utilization and pyruvate dehydrogenase (PDH) activity. It is important to note that these improvements in carbohydrate metabolism were not accompanied by increases in circulating FFA or triglyceride levels which were unchanged or lower after inhibition of FA oxidation.

Smoking in aborigines and persons of European descent in southeastern Australia: prevalence and associations with food habits, body fat distribution and other cardiovascular risk factors

As part of a population-base study of risk factors for heart disease, we aimed to establish the prevalence of smoking and to identify associations between smoking and other risk factors in Australian Aborigines (n = 306) and persons of European descent (n = 553) in two country towns. Smoking prevalence was first analysed as a dichotomy (current smokers compared with nonsmokers), and according to three levels of exposure (< 10, 10-20 and > 20 cigarettes per day), and two levels of nonexposure (never and former smoker). Other behavioural, biochemical and physical variables were included in multivariable analyses. Of the Aborigines, 64.4 per cent (95 per cent confidence interval (CI) 59.0 per cent to 69.8 per cent) were current cigarette smokers, compared with 22.8 per cent of non-Aborigines (CI 19.3 per cent to 26.3 per cent). For persons aged 13 to 54 years, using the five categories of exposure, smoking in Aborigines again far exceeded that in non-Aborigines in all age groups (for males chi 2 = 72.8, for females chi 2 = 94.6, 4 df, P = < 0.0001 for both sexes). In non-Aboriginal females, the highest prevalence was in the youngest group (56 per cent of those aged 13 to 17 years). Food habit was associated with smoking. Subjects who ate meat without trimming the fat were more likely to smoke. In Australian country towns, Aborigines and all young women need smoking cessation programs. The nutritional status of smokers requires further study.

Diabetes in aborigines and other Australian populations

The aetiology of diabetes mellitus is reviewed in the light of Australian epidemiological studies. The prevalence of diabetes has been studied in a wide variety of Australian settings. Comparisons of prevalences in Aborigines and other populations suggest that occurrence of this disease has both genetic and environmental determinants. Diet and obesity are associated with diabetes, but to increase physical exercise may be the most feasible intervention. Public health approaches are discussed.

Short-term effects of alterations in dietary fat on metabolic control in IDDM

OBJECTIVE

Two experimental diets were evaluated to investigate the hypothesis that dietary fat has an independent influence on metabolic control in IDDM.

RESEARCH DESIGN AND METHODS

The diets had similar CHO contents (26 and 22% of energy intake) but differed markedly in fat (53 vs. 16% energy) and protein (20 vs. 62% energy). We had 10 subjects follow the low-CHO, high-fat diet, and 8 subjects follow the low-CHO, low-fat, high-protein diet. In each case, markers of glycemic and lipid control obtained after adherence to the experimental diet for 2 wk were compared with corresponding data from a preceding control period during which subjects had followed their usual diet (protein 18-19%, CHO 41-46%, fat 33-37%).

RESULTS

Despite the low CHO content of the high-fat diet, insulin requirements were unchanged relative to the control diet. Moreover, the glycemic response to a standard breakfast was elevated significantly (P < 0.001), suggesting that insulin resistance had either been induced or exacerbated. The small rise in total cholesterol concentration in response to the high-fat diet was accounted for by a rise in HDL cholesterol. Glycemic control and lipid metabolism were unchanged after the low-CHO, low-fat diet, although insulin requirements fell by an average of 6 U/day (P < 0.05) relative to those recorded during the 2-wk control period.

CONCLUSIONS

Diets high in fat are deleterious to glycemic control in IDDM, but general applicability is limited by the small sample size and short duration of this study.

Identification of early metabolic defects in diabetes-prone Australian aborigines

The aim of the present study was to identify in young, diabetes-prone subjects the early abnormalities which may predispose to the development of type 2 diabetes. We studied 10 full-blood Australian Aborigines all of whom had a family history of diabetes and who were from an urbanised community with a high prevalence of this disorder. They were compared to 10 age- and body-mass-index-matched Caucasian controls with no family history of diabetes. Glucose kinetics were measured basally and following an oral glucose load. Fasting plasma glucose was equal in the two groups, but 2 h following the 75 g glucose load, the Aboriginal subjects had higher glycaemia than the controls (P less than 0.01). Insulinaemia was higher in the Aborigines both basally and following the glucose drink (P less than 0.05). Despite the hyperinsulinaemia, hepatic glucose production was higher in the Aboriginal subjects (P less than 0.01), while metabolic clearance rate was lower. It is concluded that in young Australian Aborigines with a strong family history of type 2 diabetes, both hepatic and peripheral insulin resistance are early abnormalities.

The longitudinal effect of inhibiting fatty acid oxidation in diabetic rats fed a high fat diet

This study was designed to examine the time-course of response to inhibition of fatty acid (FA) oxidation in rats rendered mildly diabetic with streptozotocin and fed a high fat diet (50% of energy derived from fat). Etomoxir, a specific carnitine palmitoyltransferase (CPT-1) inhibitor, was administered subcutaneously (12.5 mg/kg) to inhibit long chain fatty acid oxidation. Diabetic and non-diabetic control rats were maintained on the high fat diet. Following an overnight fast, glucose, free fatty acid (FFA) and triglyceride (TG) concentrations were determined after three days, one week and four weeks of treatment. The effect of Etomoxir treatment in reducing fasting glucose concentrations was not evident until after one week, while fasting FFA and TG concentrations were already reduced after three days treatment. All of these changes were maintained over the four week period (P less than 0.001), resulting in reduced levels of fasting plasma glucose (17.6 +/- 2.4 vs 22.3 +/- 1.9 mmol/l), fasting plasma TG (0.32 +/- 0.07 vs 0.98 +/- 0.14 mmol/l) and fasting serum FFA (1.52 +/- 0.26 vs 3.51 +/- 0.69 mEq/l). In addition, the improvements in glucose and lipid levels were accompanied by restored rates of growth towards that of non-diabetic control rats. These results suggest that the short term inhibition of FA oxidation improves fasting glucose, FFA and TG concentrations in diabetic rats fed a high fat diet.

A high-fat diet worsens metabolic control in streptozotocin-treated rats by increasing hepatic glucose production

The aim of this study was to determine the mechanism by which a high-fat diet exacerbates the diabetes produced by a low dose of streptozotocin (STZ). The glucose clamp technique was used to determine hepatic glucose production (HGP) and the disappearance rate (Rd) of glucose, basally and during insulin infusions of 1.0 and 3.0 mU/kg/min in control of STZ-treated rats fed either a low-fat or high-fat diet. Fasting plasma glucose in the high fat-STZ (HFS) group was significantly higher than in any of the other groups: low fat-STZ (LFS), high-fat controls (HFC), or low-fat controls (LFC) (18.1 +/- 1.6 v 8.1 +/- 0.8 mmol/L, P less than .001; 6.0 +/- 0.2 mmol/L, P less than .001; 5.4 +/- 0.1 mmol/L, P less than .001, respectively). Basal HGP was markedly higher in the HFS group compared with each of the other three groups (98.8 +/- 5.9 v 61.4 +/- 3.7, P less than .001; 42.9 +/- 1.6, P less than .001; 39.6 +/- 1.3 mumol/kg/min, P less than .001; HFS v LFS, HFC, and LFC, respectively). Following insulin infusion, no differences were observed in HGP between the LFC and LFS groups at either insulin dose. However, HGP was not suppressed to control levels in either of the high-fat diet groups, and this defect was more marked in the HFS group. It is concluded that a high-fat diet exacerbates mild STZ diabetes primarily by increasing HGP.

Measurement of resistant starch: factors affecting the amount of starch escaping digestion in vitro

We developed an in vitro assay system that mimics the physiological conditions for starch digestion. In this system all undigested starch was termed resistant starch (RS). The richest sources of RS were firm bananas and roasted chickpeas. Different food-processing techniques produced different amounts of RS. RS in uncooked oats (0.161 g/g dry wt) and firm bananas (0.247 g/g dry wt) was reduced by cooking to 0.028 and 0.032 g/g dry wt, respectively. Cooling boiled potato overnight at 4 degrees C produced a 2.8-fold increase in the amounts of RS. Whole rice contained more RS than did ground rice whereas grinding did not affect amounts of RS in roasted chickpeas. Amounts of RS in food decreased with increased chewing, indicating that chewing can also affect the amount of starch escaping digestion. This assay may be useful in predicting which foods and processing techniques result in high amounts of starch escaping digestion in the small intestine.

A comparison of the effects of beef, chicken and fish protein on satiety and amino acid profiles in lean male subjects

We compared postprandial satiety and plasma amino acid, insulin, and glucose concentrations in six lean male subjects after the ingestion of three types of protein (beef, chicken and fish). Satiety was greater after the fish meal (P less than 0.01). The observed difference in satiety could be correlated with two of the putative satiety signals measured in this study: 1) serotoninergic activity, due to differences observed in the postprandial tryptophan to large neutral amino acid ratio; and 2) digestibility, reflected in the significantly (P less than 0.05) longer time it took for the plasma amino acid concentrations to peak after the fish meal. Correlations between dietary and plasma amino acid concentrations were determined and good correlations (r = 0.90) were observed for essential amino acids other than lysine and tryptophan. There were no differences in insulin or glucose concentrations in subjects after consuming each of the three meals. Whether other differences that we observed, such as increased concentrations of taurine and methionine following the fish meal, had any effect on satiety or were of biological significance is not known.

The prevalence of glucose intolerance in aborigines and Europids of south-eastern Australia

Based on oral glucose tolerance testing, the prevalence of diabetes in Australian adults has ranged from 2.3% in Europids in 1966 to 20% in small surveys of Aborigines. We have surveyed Aborigines and Europids simultaneously for further comparison of diabetes prevalence between these population groups. The samples were drawn from two adjacent country towns in south-eastern Australia, where Aborigines and Europids have been in contact for 150 years. By the 2-h (post-75 g oral glucose load) criterion (venous plasma glucose greater than or equal to 11.1 mmol/l), the crude prevalence of diabetes among 306 Aborigines was 7.8%, significantly higher than the 3.4% among 553 Europids (P less than 0.01). The prevalence of impaired glucose tolerance was similar in both groups (6.9% in Aborigines, 6.0% in Europids, no significant difference). Adjustment for the marked differences in age distribution between Aborigines and Europids by direct standardization to the 1980 world population increased the apparent differences, with the finding of a four-fold greater prevalence among Aborigines (8.1% compared with 1.9%). The greater frequency of glucose intolerance among Aborigines appears to persist despite the higher proportion of Europid genetic mix with these urbanized south-eastern groups than with Aborigines from remote settings.

Protein-bound cobalamin absorption declines in the elderly

A modified protein-bound cobalamin absorption test was used to study dietary cobalamin absorption in healthy adults of different age groups and patients with isolated low serum concentrations of cobalamin. Dietary cobalamin absorption was significantly reduced in healthy adults aged 55-75 years compared with young adults, with a further reduction in those older than 75 years. No difference was detected between dietary cobalamin absorption in patients with isolated low serum cobalamin and controls of a similar age group. Cobalamin malabsorption was associated with elevated serum gastrin. The diagnostic value of this protein-bound cobalamin absorption test in the elderly was limited by the frequent finding of reduced absorption in healthy elderly people with normal serum cobalamin concentrations. The performance of such tests should be evaluated in different age groups before application in diagnosis.

Potential regulators of feeding behavior in anorexia nervosa

We recruited 10 patients with anorexia nervosa and 6 age- and height-matched control subjects. Basal and postprandial concentrations of glucose, insulin, cholesterol, amino acids, gastrin, and pancreatic polypeptide (PP) were measured in response to a standard mixed meal. The only satiety signal that was significantly different between the anorectic group and the control group was PP (P less than 0.001). Tryptophan-LNAA and tyrosine-LNAA ratios were not significantly different in the two groups; however, there was a trend toward a lower tryptophan-LNAA ratio in the anorectic group. Gastrin concentrations were significantly decreased in the anorectic group (P less than 0.001) as were basal insulin concentrations (P less than 0.05). Decreased gastrin concentrations may play a role in the gastric symptoms associated with anorexia nervosa. Previous findings that PP release is diminished in obesity, together with the present findings of PP increase in anorexia nervosa, suggest that this peptide may play a role in appetite control mechanisms.

Traditional diet and food preferences of Australian aboriginal hunter-gatherers

Until European settlement of Australia 200 years ago, Aborigines lived as nomadic hunter-gatherers all over the continent under widely varying geographic and climatic conditions. Successful survival depended on a comprehensive knowledge of the flora and fauna of their territory. Available data suggest that they were physically fit and lean, and consumed a varied diet in which animal foods were a major component. Despite this, the diet was not high in fat, as wild animal carcasses have very low fat contents through most of the year, and the meat is extremely lean. Everything on an animal carcass was eaten, including the small fat depots and organ meats (which were highly prized), bone marrow, some stomach contents, peritoneal fluid and blood. A wide variety of uncultivated plant foods was eaten in the traditional diet: roots, starchy tubers, seeds, fruits and nuts. The plant foods were generally high in fibre and contained carbohydrates, which was slowly digested and absorbed. Traditional methods of food preparation (usually baked whole or eaten raw) ensured maximum retention of nutrients. In general, traditional foods had a low energy density but high density of some nutrients. The low energy density of the diet and the labour intensity of food procurement provided a natural constraint on energy intake.(ABSTRACT TRUNCATED AT 250 WORDS)

Westernisation, insulin resistance and diabetes in Australian aborigines

OBJECTIVE

To examine the published data on the impact of westernisation on obesity, non-insulin dependent diabetes mellitus (NIDDM), and coronary heart disease (CHD) in Australian Aborigines.

DATA SOURCES

Fifty-five articles from Australian and international sources (primarily peer-reviewed journals) are cited.

STUDY SELECTION

Twenty-eight reports providing data on the diet, lifestyle, health and "lifestyle diseases" of Australian Aborigines before and after westernisation are included in this review. A further 27 articles on obesity, NIDDM, CHD, insulin resistance, and the impact of diet and exercise were used to help interpret the Aboriginal data.

DATA EXTRACTION

Information on dietary composition, anthropometry, disease and risk factor prevalence, and relevant biochemical measurements were used for comparative and interpretive purposes.

DATA SYNTHESIS

The traditional hunter-gatherer lifestyle of Australian Aborigines, characterised by high physical activity and a diet of low energy density (low fat, high fibre), promoted the maintenance of a very lean body weight and minimised insulin resistance. In contrast, for most Aborigines a Western lifestyle is characterised by reduced physical activity and an energy-dense diet (high in refined carbohydrate and fat) which promotes obesity and maximises insulin resistance. When they make the transition from their traditional hunter-gatherer lifestyle to a westernised lifestyle, Aborigines develop high prevalence rates for obesity (with an android pattern of fat distribution), non-insulin dependent diabetes, impaired glucose tolerance, hypertriglyceridaemia, hypertension and hyperinsulinaemia. The striking improvements in carbohydrate and lipid metabolism in diabetic and non-diabetic Aborigines after a temporary reversion to a traditional hunter-gatherer lifestyle highlight the potentially reversible nature of the detrimental effects of lifestyle change, particularly in young people who have not yet developed diabetes.

CONCLUSION

It is suggested that insulin resistance was important to the survival of Aborigines as hunter-gatherers, but is also the underlying metabolic characteristic predisposing them to obesity, NIDDM and CHD after westernisation. Intervention strategies to prevent chronic diseases related to insulin resistance should be directed at lifestyle modification. To be effective such programmes will have to be developed and implemented at the community level.

Quantitation of tryptophan and other plasma amino acids by automated pre-column o-phthaldialdehyde derivatization high-performance liquid chromatography: improved sample preparation

Pre-column derivatization with o-phthaldialdehyde is a rapid and sensitive method for the quantitation of amino acids in biological fluids. This method uses acetonitrile as a deproteinizing reagent which gives improved recovery of tryptophan compared with 5-sulfosalicylic acid and permits the measurement of aspartic acid which coelutes with 5-sulfosalicylic acid. The method is automated to increase reproducibility and convenience. Mean coefficients of variation for peak areas relative to internal standard were 3.2 and 5.2% for amino acid standards and plasma samples, respectively. The presence of nitrilotriacetic acid stabilized the o-phthaldialdehyde reagent which is important in an automated system. The method is suitable for the analysis of large numbers of plasma samples where total tryptophan and aspartic acid are of interest.

Cardiovascular disease risk factors in Australian aborigines

1. Aborigines from all over Australia develop unusually high prevalence rates for obesity, non-insulin dependent diabetes mellitus (NIDDM) and cardiovascular disease when they make the transition from their traditional hunter-gatherer lifestyle to a Westernized lifestyle. 2. There is no evidence that they experienced these diseases as hunter-gatherers. Data from the few extant traditionally orientated groups in very remote areas of northern Australia indicate that they were very lean (BMI less than 20 kg/m2), with low blood pressure, and that neither blood pressure nor BMI rose with age. 3. In addition, fasting glucose and cholesterol levels were low (usually below 4 mmol/L). However, in view of their extreme leanness and regular physical activity, fasting insulin and triglyceride levels were inappropriately elevated, suggestive of insulin resistance. 4. When Westernized diabetic Aborigines reverted temporarily to a traditional hunter-gatherer diet and lifestyle, all of the metabolic abnormalities of diabetes were greatly ameliorated (fasting glucose and triglyceride levels fell markedly and glucose tolerance and insulin secretion improved). In addition, they lost weight and there was a reduction in the major risk factors for cardiovascular disease (reduction in hypertriglyceridaemia and blood pressure, increase in bleeding time). 5. The hunter-gatherer lifestyle was associated with increased physical activity and a low-fat, high-fibre diet of low-energy density and high-nutrient density derived from very lean wild meat, and uncultivated vegetable foods. It has important therapeutic implications for the treatment and prevention of many of the chronic degenerative diseases of affluent Western societies.

Effects of dietary fats on prostanoid production and aortic and plasma fatty acid composition in rats

Male Sprague-Dawley rats were fed diets with 10%, 30%, or 50% of energy derived from fat for two weeks. The fats used were beef tallow, olive oil, peanut oil and butter. Aortic prostacyclin (PGI2) production, platelet aggregation and thromboxane A2 (TXA2) production and plasma and aortic phospholipid (PL) content were measured. Butter- and beef tallow-feeding reduced aortic PGI2 production and collagen-induced TXA2 production in a dose-dependent manner as the level of fat in the diet increased. Neither olive oil nor peanut oil had any effect on aortic PGI2 production or collagen-induced TXA2 production. Butter-feeding also resulted in a decrease in collagen-induced platelet aggregation; however, none of the other fats had any effect on collagen-induced platelet aggregation. The observed decreases in aortic PGI2 and collagen-induced TXA2 production were paralleled by similar decreases in aortic and plasma PL arachidonic acid content and an increase in eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). Only the most saturated fats, butter and beef tallow, had significant inhibitory effects on prostanoid production and platelet aggregation.

Cholesterol-lowering effect of a low-fat diet containing lean beef is reversed by the addition of beef fat

The aim of this study was to differentiate between lean beef and beef fat as risk factors for elevated plasma cholesterol concentrations. Ten healthy weight-stable subjects (five men, five women) participated. Energy intake was kept constant over the 5-wk study. Total cholesterol concentrations fell significantly within 1 wk of commencing the very-low fat (9%) energy from fat) lean-beef (500 g/d) diet (5.91 +/- 0.47 to 4.72 +/- 0.42 mmol/L, p less than 0.001) and rose as beef drippings were added in a stepwise manner in weeks 4 and 5 (5.45 +/- 0.56 mmol/L in week 5). The changes in total cholesterol concentrations were due almost entirely to changes in the concentration of low-density lipoprotein cholesterol levels. These results indicate that it is the beef fat, not lean beef itself, that is associated with elevations in cholesterol concentrations and that lean beef can be included in cholesterol-lowering diets provided it is free of all visible fat and the saturated fatty acid content of the diet is low.

Ingestion of different types of fat in the evening meal does not affect metabolic responses to a standard breakfast

High-fat diets produce insulin resistance, but it is not known how quickly changes become evident or whether different types of fat produce different responses. The aim of this study was to determine whether a high-fat evening meal affected glucose response to a standard breakfast 12 h later. On six occasions eight weight-stable subjects consumed a standard evening meal (109 g carbohydrate, 27 g protein, 6 g fat, and 10.6 g fiber) that was either unsupplemented or supplemented with 41 g fat (safflower oil, olive oil, butter, or medium-chain triglyceride) or 75 g carbohydrate followed by a standard breakfast. Glucose, insulin, and free fatty acid responses were measured over 3 h. There were no differences in metabolic responses to the standard breakfast after the different evening meals, indicating that a single high-fat meal has no deleterious effects on carbohydrate metabolism 12 h later, regardless of the type of fat ingested.

Arachidonic acid and linoleic acid supplementation increase prostanoid production in rats fed a butter-enriched diet

Male Sprague Dawley rats were fed a butter-enriched diet (50% fat) for 2 weeks and then supplemented orally with either 90 mg of ethyl arachidonate or ethyl linoleate daily for 2 weeks. For comparative reasons, one group of animals was fed standard laboratory rat chow for 4 weeks. Aortic prostacyclin (PGI2) production, platelet aggregation and thromboxane A2 (TXA2) production and plasma and aortic phospholipid (PL) fatty acids were measured. When compared to butter-fed rats, aortic PGI2 production, collagen-induced platelet aggregation and TXA2 production were significantly increased in rats supplemented with ethyl arachidonate to levels similar to those seen in chow-fed rats. Ethyl linoleate supplementation also tended to increase aortic PGI2 production, collagen-induced platelet aggregation and TXA2, but not to the same extent. These changes were accompanied by increases in the level of arachidonic acid and linoleic acid in aortic and plasma PL and a decrease in the level of eicosapentaenoic acid (EPA) and docsahexaenoic acid (DHA). These data indicate that supplementation with small doses of preformed arachidonic acid was more effective than supplementation with its precursor, linoleic acid, in reversing the effects on prostanoid production and phospholipid fatty acid composition in rats fed diets enriched with butter.

Diabetes, hyperinsulinemia, and hyperlipidemia in small aboriginal community in northern Australia

A small rural Aboriginal community in northern Australia was surveyed for diabetes, impaired glucose tolerance (IGT), hyperinsulinemia, and lipid levels. Of the 122 adults greater than 17 yr of age who participated (95% response rate), 11.5% had diabetes, 7.4% had IGT, and the remaining 81.1% had normal glucose tolerance. Both diabetes and IGT were strongly age related. This high frequency of diabetes occurred, despite the population being relatively lean. Although the body mass index (BMI) increased with age in both men and women, only 25% of the population overall had BMI greater than 25 kg/m2. There were wide ranges of insulin responses to glucose, with the upper tertile of 2-h insulin levels being more than seven times higher than the lower tertile (144 +/- 13 vs. 19 +/- 1 mU/L). Hyperinsulinemia was associated with IGT, elevated triglycerides, and lower high-density lipoprotein cholesterol levels. Lipid abnormalities were much more frequent among men than women. Cholesterol levels were an average of 0.55 mM higher and triglycerides an average of 1.05 mM higher in men than in women, and both increased with age. In conclusion, this small isolated Aboriginal population from northern Australia had an unexpectedly high frequency of diabetes (in view of their relative leanness) in association with a high frequency of metabolic abnormalities indicative of insulin resistance (hyperinsulinemia, IGT, hypertriglyceridemia).

The effects of very low fat diets enriched with fish or kangaroo meat on cold-induced vasoconstriction and platelet function

Eighteen healthy volunteers consumed very low fat diets (less than 7% of daily energy) enriched with different sources of long chain (C20 and C22) polyunsaturated fatty acids (PUFA). Three diets provided 500 g/day of fish caught in the tropical waters of Australia (rich in arachidonic acid and docosahexaenoic acid), fish caught in the southern waters of Australia (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. An increase in the percentage of a particular C20 or C22 PUFA in the plasma phospholipid fraction in subjects consuming these low fat diets corresponded to the dietary PUFA composition. This study examined the effect of dietary modification of the level of arachidonic acid in plasma phospholipids on both traditional measures of platelet function and on cold-induced vasoconstriction. The cold pressor response, measured by venous occlusion plethysmography, was depressed in diets which elevated the levels of arachidonic acid in plasma lipids (kangaroo and tropical fish), enhanced after subjects consumed a diet which increased the levels of docosahexaenoic acid and eicosapentaenoic acid (southern fish diet), and was unchanged by the low fat vegetarian diet. There was no effect on bleeding time or platelet responsiveness.