High-protein diets in hyperlipidemia: effect of wheat gluten on serum lipids, uric acid, and renal function

BACKGROUND

The metabolic effects of diets high in vegetable protein have not been assessed despite much recent interest in the effect of soy proteins in reducing serum cholesterol.

OBJECTIVE

We assessed the metabolic effects of diets high in vegetable protein (specifically, wheat gluten) on serum lipids, uric acid concentrations, and renal function.

DESIGN

Twenty hyperlipidemic men and women consumed isoenergetic test (high-protein) and control metabolic diets for 1 mo in a randomized crossover design. In the high-protein diet, 11% of the total dietary energy from starch in the control bread was replaced by vegetable protein (wheat gluten), resulting in 27% of total energy from protein compared with 16% in the control diet. In other respects, the 2 diets were identical.

RESULTS

Compared with the control, the high-protein diet resulted in lower serum concentrations of triacylglycerol (by 19.2 +/- 5.6%; P = 0.003), uric acid (by 12.7 +/- 2.0%; P < 0.001), and creatinine (by 2.5 +/- 1.1%; P = 0.035) and higher serum concentrations of urea (by 42.2 +/- 5.8%; P < 0.001) and a higher 24-h urinary urea output (by 99.2 +/- 17.2%; P < 0.001). No significant differences were detected in total or HDL cholesterol or in the renal clearance of creatinine. LDL oxidation, assessed as the ratio of conjugated dienes to LDL cholesterol in the LDL fraction, was lower with the high-protein diet (by 10.6 +/- 3.6%; P = 0.009).

CONCLUSIONS

High intakes of vegetable protein from gluten may have beneficial effects on cardiovascular disease risk by reducing oxidized LDL, serum triacylglycerol, and uric acid. Further studies are required to assess the longer-term effects on renal function.

Diabetes Screening in Canada (DIASCAN) Study: prevalence of undiagnosed diabetes and glucose intolerance in family physician offices

OBJECTIVE

To assess the prevalence of undiagnosed diabetes and glucose intolerance in individuals > or =40 years of age who contacted their family physician for routine care.

RESEARCH DESIGN AND METHODS

The study used a stratified randomized selection of family physicians across Canada that was proportional to provincial and urban/rural populations based on Statistics Canada Census data (1996). Consecutive patients > or =40 years of age were screened for diabetes. If a casual fingerprick blood glucose was >5.5 mmol/l, the patient returned for a fasting venous blood glucose test. If the fasting blood glucose was 6.1-6.9 mmol/l, a 2-h 75-g post-glucose load venous blood glucose was obtained. Results of these tests were used to classify patients in diagnostic categories.

RESULTS

Data were available for 9,042 patients. Previously undiagnosed diabetes was discovered in 2.2% of the patients, and new glucose intolerance was found in an additional 3.5% of patients. Overall, 16.4% of patients had previously known diabetes. The decrease in fasting plasma glucose criterion from 7.8 to 7.0 mmol/l resulted in a 2.2% versus a 1.6% prevalence of new diabetes. Several risk factors were reported in a significantly greater proportion of patients with new glucose intolerance and either new and known diabetes compared with the normal glucose tolerance group of patients.

CONCLUSIONS

Routine screening for diabetes by family physicians is justified in patients > or =40 years of age, given the finding of previously undiagnosed diabetes in 2.2% of these patients and newly diagnosed glucose intolerance in an additional 3.5% of these patients. Another 16.4% of primary care patients > or =40 years of age have known diabetes. This has important implications regarding health resources and physician education.

American ginseng (Panax quinquefolius L.) attenuates postprandial glycemia in a time-dependent but not dose-dependent manner in healthy individuals

BACKGROUND

We previously showed that 3 g American ginseng administered 40 min before an oral glucose challenge significantly reduces postprandial glycemia in subjects without diabetes. Whether this effect can be replicated with doses <3 g and administration times closer to the oral glucose challenge is unclear.

OBJECTIVE

Our objective was to study the dosing and timing effects of American ginseng on postprandial glycemia.

DESIGN

In a random crossover design, 12 healthy individuals [X +/- SEM age: 42 +/- 7 y; body mass index (BMI; in kg/m2): 24.1 +/- 1.1] received 16 treatments: 0 (placebo), 1, 2, or 3 g American ginseng at 40, 20, 10, or 0 min before a 25-g oral glucose challenge. Capillary blood was collected before administration and at 0, 15, 30, 45, 60, and 90 min after the start of the glucose challenge.

RESULTS

Two-way analysis of variance showed that the main effects of treatment and administration time were significant (P < 0.05). Glycemia was lower over the last 45 min of the test after doses of 1, 2, or 3 g ginseng than after placebo (P < 0.05); there were no significant differences between doses. The reductions in the areas under the curve for these 3 doses were 14.4 +/- 6.5%, 10.6 +/- 4.0%, and 9.1 +/- 6%, respectively. Glycemia in the last hour of the test and area under the curve were significantly lower when ginseng was administered 40 min before the challenge than when it was administered 20, 10, or 0 min before the challenge (P < 0.05).

CONCLUSIONS

American ginseng reduced postprandial glycemia in subjects without diabetes. These reductions were time dependent but not dose dependent: an effect was seen only when the ginseng was administered 40 min before the challenge. Doses within the range of 1-3 g were equally effective.

Simple skinfold-thickness measurements complement conventional anthropometric assessments in predicting glucose tolerance

BACKGROUND

Skinfold-thickness measurements are considered to have limited clinical utility.

OBJECTIVE

To assess whether skinfold-thickness measurements may be a useful adjunct to conventional anthropometric assessments in predicting glucose and insulin regulation, we studied responses to replicate 75-g oral-glucose-tolerance tests (OGTTs) and performed simple anthropometry in a cross section of subjects.

DESIGN

Thirty-five subjects completed the study: 11 lean [mean (+/-SEM) age: 33 +/- 3.2 y; body mass index (BMI; in kg/m(2)): 24.1 +/- 0.8; and percentage body fat (%BF): 11.5 +/- 1.5%], 12 normal-weight (age: 33 +/- 2.9 y; BMI: 23.9 +/- 0.7; and %BF: 24.3.5 +/- 1.3%), and 12 obese (age: 41 +/- 4.5 y; BMI: 34.5 +/- 1.7; and %BF: 34.2 +/- 1.5%) individuals. The lean and normal-weight groups were selected to have similar BMIs but different %BFs. We measured the participants' heights, weights, %BFs, waist circumferences, hip circumferences, and truncal and peripheral skinfold thicknesses. Subjects received nine 75-g OGTTs and blood samples were collected at 0, 15, 30, 45, 60, 90, and 120 min. Mean plasma glucose and insulin values were used to calculate the insulin sensitivity index.

RESULTS

The obese group had higher plasma glucose concentrations and areas under the curve (AUCs) than did the normal-weight or lean group and higher plasma insulin concentrations and AUCs than did the lean group (P < 0.05). Stepwise multiple regression, with adjustment for demographic and anthropometric measurements, identified the following predictors: waist circumference, peripheral skinfold thickness, and BMI for fasting plasma glucose (partial R(2) = 0.20, 0.13, and 0.13, P < 0.05); waist circumference and truncal skinfold thickness for plasma glucose AUC (partial R(2) = 0.20 and 0.13, P < 0.05); age, waist-to-hip ratio, and peripheral skinfold thickness for fasting plasma insulin (partial R(2) = 0.26, 0.22, and 0.15, P < 0.05); truncal skinfold thickness for plasma insulin AUC (partial R(2) = 0.41, P < 0.001); and peripheral skinfold thickness for both 2-h plasma glucose (partial R(2) = 0.59, P < 0.001) and the insulin sensitivity index (partial R(2) = 0.49, P < 0.001).

CONCLUSION

Skinfold-thickness measurements may complement other established measurements for predicting abnormal glucose and insulin regulation.

American ginseng improves glycemia in individuals with normal glucose tolerance: effect of dose and time escalation

OBJECTIVE

We studied the effect of escalating the dose and administration time of American ginseng (AG, Panax quinquefolius L.) in nondiabetic individuals to achieve further improvements in glucose tolerance seen previously when 3 g of AG was taken 40 minutes before a 25 g glucose challenge.

METHODS

Ten nondiabetic individuals (6M:4F; mean +/- STD: age = 41 +/- 13 years, BMI = 24.8 +/- 3.5 kg/m2, FBG = 4.5 +/- 0.1 mmol L(-1)) on 12 separate occasions, randomly received 0 (placebo), 3, 6 or 9 g of ground AG root at 40, 80, or 120 minutes before a 25 g oral glucose challenge. Capillary blood glucose was measured prior to ingestion of AG or placebo capsules and at 0, 15, 30, 45, 60 and 90 minutes from start of challenge.

RESULTS

Compared with the placebo, 3, 6 and 9 g of AG reduced (p<0.05) postprandial incremental glucose at 30, 45 and 60 minutes; also, 3 and 9 g of AG did so at 90 minutes. At 60 minutes, 9 g of AG reduced incremental postprandial glucose relative to 3 g of AG (p<0.05). All AG doses reduced (p<0.05) area under the incremental glucose curve (3 g, 26.6%; 6 g, 29.3%; 9 g, 38.5%). AG taken at different times did not have an additional influence on postprandial glycemia.

CONCLUSIONS

In nondiabetic individuals, 3, 6 or 9 g of AG taken 40, 80 or 120 minutes before a glucose challenge similarly improved glucose tolerance.

Similar postprandial glycemic reductions with escalation of dose and administration time of American ginseng in type 2 diabetes

OBJECTIVE

We previously demonstrated that 3 g American ginseng (AG) reduced postprandial glycemia (PPG) in type 2 diabetic individuals. We investigated whether further reductions can be achieved with escalation of dose and time of AG administration.

RESEARCH DESIGN AND METHODS

Ten type 2 diabetic patients (6 men, 4 women; age 63+/-2 years; BMI 27.7+/-1.5 kg/m2; HbA1c 7.3+/-0.3%) were randomly administered 0 g (placebo) or 3, 6, or 9 g ground AG root in capsules at 120, 80, 40, or 0 min before a 25-g oral glucose challenge. Capillary blood glucose was measured before ingestion of AG or placebo and at 0, 15, 30, 45, 60, 90, and 120 min from the start of the glucose challenge.

RESULTS

Two-way analysis of variance (ANOVA) demonstrated that treatment (0, 3, 6, and 9 g AG) but not time of administration (120, 80, 40, or 0 min before the challenge) significantly affected PPG (P<0.05), with significant (P = 0.037) interaction for area under the curve (AUC). Pairwise comparisons showed that compared with 0 g (placebo), 3, 6, or 9 g significantly (P<0.05) reduced AUC (19.7, 15.3, and 15.9%, respectively) and incremental glycemia at 30 min (16.3, 18.4, and 18.4%, respectively), 45 min (12.5, 14.3, and 14.3%, respectively), and 120 min (59.1, 40.9, and 45.5%, respectively). However, pairwise comparisons showed no differences between the 3-, 6-, or 9-g doses and any of the times of administration.

CONCLUSIONS

AG reduced PPG irrespective of dose and time of administration. No more than 3 g AG was required at any time in relation to the challenge to achieve reductions. Because these reductions included glycemia at the 2-h diagnostic end point, there may be implications for diabetes diagnosis and treatment.

Case 1. Cardiovascular dysfunction syndrome

A 56-year-old woman is referred with angina. A number of sequential management strategies have been attempted with varying results. Upon examination of her case, it is clear that she has cardiovascular dysmetabolic syndrome and is thus at high risk for adverse cardiovascular events. Two opinions for further management are presented.

Estrogens are indicated for the prevention of coronary artery disease: a debate for estrogen

For the vast majority of women, the overall potential benefits associated with hormone replacement therapy (HRT) outweigh any harm. There is a large body of epidemiological evidence demonstrating an association between postmenopausal use of HRT and a decreased risk for cardiovascular disease. There are multiple mechanisms by which this cardiovascular benefit may occur. The only study to suggest that estrogen does not play a cardioprotective role was conducted on women with known coronary artery disease, ie, secondary prevention. The results of this study may be specific to the population and the regimen studied; in any case, several confounding factors limit the interpretation of the data. If these factors are adequately addressed in future trials, it is probable that the cardiovascular benefits of HRT will be clinically evident.

1999 Canadian recommendations for the management of hypertension. Task Force for the Development of the 1999 Canadian Recommendations for the Management of Hypertension

OBJECTIVE

To provide updated, evidence-based recommendations for health care professionals on the management of hypertension in adults.

OPTIONS

For patients with hypertension, there are both lifestyle options and pharmacological therapy options that may control blood pressure. For those patients who are using pharmacological therapy, a range of antihypertensive drugs is available. The choice of a specific antihypertensive drug is dependent upon the severity of the hypertension and the presence of other cardiovascular risk factors and concurrent diseases.

OUTCOMES

The health outcomes considered were changes in blood pressure and in morbidity and mortality rates. Because of insufficient evidence, no economic outcomes were considered.

EVIDENCE

MEDLINE searches were conducted from the period of the last revision of the Canadian Recommendations for the Management of Hypertension (January 1993 to May 1998). Reference lists were scanned, experts were polled and the personal files of the authors were used to identify other studies. All relevant articles were reviewed, classified according to study design and graded according to levels of evidence.

VALUES

A high value was placed on the avoidance of cardiovascular morbidity and premature death caused by untreated hypertension.

BENEFITS

Harms and costs: The diagnosis and treatment of hypertension with pharmacological therapy will reduce the blood pressure of patients with sustained hypertension. In certain settings, and for specific drugs, blood pressure lowering has been associated with reduced cardiovascular morbidity and mortality.

RECOMMENDATIONS

This document contains detailed recommendations pertaining to all aspects of the diagnosis and pharmacological therapy of hypertensive patients. With respect to diagnosis, the recommendations endorse the greater use of non-office-based measures of blood pressure control (i.e., using home blood pressure and automatic ambulatory blood pressure monitoring equipment) and greater emphasis on the identification of other cardiovascular risk factors, both in the assessment of prognosis in hypertension and in the choice of therapy. On the treatment side, lower targets for blood pressure control are advocated for some subgroups of hypertensive patients, in particular, those with diabetes and renal disease. Implicit in the recommendations for therapy is the principle that for the vast majority of hypertensive patients treated pharmacologically, practitioners should not follow a stepped-care approach. Instead, therapy should be individualized, based on consideration of concurrent diseases, both cardiovascular and noncardiovascular.

VALIDATION

All recommendations were graded according to the strength of the evidence and the consensus of all relevant stakeholders.

SPONSORS

The Canadian Hypertension Society and the Canadian Coalition for High Blood Pressure Prevention and Control.

Low density lipoprotein cholesterol: is lower better?

Low density lipoprotein cholesterol (LDL-C) reduction leads to significant decreases in coronary events, as well as in most large trials performed recently, cardiovascular and total mortality. The lowest risk of coronary events occurs among people with the lowest LDL-C levels. Achieving a target LDL-C level less than 2.5 mM in individuals at high risk of a coronary event often necessitates the use of lipid-lowering drugs, primarily statins. Review of the major clinical trials involving statins reveals that LDL-C reduction is associated with a significant reduction in coronary events in men and women, older individuals, those with various other risk factors and those with either coronary artery disease or a high risk of developing it. The greatest clinical benefits have been associated with the greatest LDL-C reductions, although the incremental benefit is less at lower levels. Ongoing studies will help determine optimal new treatment targets for LDL-C.

The effect on serum lipids and oxidized low-density lipoprotein of supplementing self-selected low-fat diets with soluble-fiber, soy, and vegetable protein foods

An increased intake of soluble fiber and soy protein may improve the blood lipid profile. To assess any additional benefit on serum lipids of providing soy protein and soluble-fiber foods to hyperlipidemic subjects already consuming low-fat, low-cholesterol therapeutic diets, 20 hyperlipidemic men and postmenopausal women completed 8-week test and control dietary treatments in a randomized crossover design as part of an ad libitum National Cholesterol Education Program (NCEP) step 2 therapeutic diet (<7% saturated fat and <200 mg/d cholesterol). During the test phase, foods high in soy, other vegetable proteins, and soluble fiber were provided. During the control phase, low-fat dairy and low-soluble-fiber foods were provided. Fasting blood lipid and apolipoprotein levels were measured at 4 and 8 weeks of each phase. On the test diet, 12 +/- 2 g/d soy protein was selected from the foods chosen. Direct comparison of test and control treatments indicated an elevated high-density lipoprotein (HDL) cholesterol concentration on the test diet (6.4% +/- 2.4%, P = .013) and a significantly reduced total to HDL cholesterol ratio (-5.9% +/- 2.3%, P = .020). The proportion of conjugated dienes in the low-density lipoprotein (LDL) cholesterol fraction was significantly reduced (8.5% +/- 3.3%, P = .020) as a marker of oxidized LDL. A combination of acceptable amounts of soy, vegetable protein, and soluble-fiber foods as part of a conventional low-fat, low-cholesterol therapeutic diet is effective in further reducing serum lipid risk factors for cardiovascular disease.

Beneficial effects of viscous dietary fiber from Konjac-mannan in subjects with the insulin resistance syndrome: results of a controlled metabolic trial

OBJECTIVE

Dietary fiber has recently received recognition for reducing the risk of developing diabetes and heart disease. The implication is that it may have therapeutic benefit in prediabetic metabolic conditions. To test this hypothesis, we investigated the effect of supplementing a high-carbohydrate diet with fiber from Konjac-mannan (KJM) on metabolic control in subjects with the insulin resistance syndrome.

RESEARCH DESIGN AND METHODS

We screened 278 free-living subjects between the ages of 45 and 65 years from the Canadian-Maltese Diabetes Study. A total of 11 (age 55+/-4 years, BMI 28+/-1.5 kg/m2) were recruited who satisfied the inclusion criteria: impaired glucose tolerance, reduced HDL cholesterol, elevated serum triglycerides, and moderate hypertension. After an 8-week baseline, they were randomly assigned to take either KJM fiber-enriched test biscuits (0.5 g of glucomannan per 100 kcal of dietary intake or 8-13 g/day) or wheat bran fiber (WB) control biscuits for two 3-week treatment periods separated by a 2-week washout. The diets were isoenergetic, metabolically controlled, and conformed to National Cholesterol Education Program Step 2 guidelines. Serum lipids, glycemic control, and blood pressure were the outcome measures.

RESULTS

Decreases in serum cholesterol (total, 12.4+/-3.1%, P<0.004; LDL, 22+/-3.9%, P<0.002; total/HDL ratio, 15.2+/-3.4%, P<0.003; and LDL/HDL ratio, 22.2+/-4.1%, P< 0.002), apolipoprotein (apo) B (15.1+/-4.3%, P<0.0004), apo B/A-1 ratio (13.1+/-3.4%, P< 0.0003), and serum fructosamine (5.2+/-1.4%, P<0.002) were observed during KJM treatment compared with WB-control. Fasting blood glucose, insulin, triglycerides, HDL cholesterol, and body weight remained unchanged.

CONCLUSIONS

A diet rich in high-viscosity KJM improves glycemic control and lipid profile, suggesting a therapeutic potential in the treatment of the insulin resistance syndrome.

Day-to-day consistency in amount and source of carbohydrate intake associated with improved blood glucose control in type 1 diabetes

OBJECTIVE

To determine if a relationship exists between blood glucose control and variability in nutrient intake from day-to-day in subjects with type 1 diabetes.

METHODS

Two three-day diet records and one measurement of glycated hemoglobin (HbA1c) were obtained from 272 subjects with type 1 diabetes treated with a mixture of regular and NPH insulins before breakfast and supper and using a standardized algorithm to adjust insulin dose according to the results of self-monitoring of blood glucose two to four times daily. Day-to-day variation in nutrient intake was expressed as the coefficient of variation (CV = SDx100/mean).

RESULTS

Nutrient intakes in the study population (mean +/- SD) were energy 8.35+/-2.43 MJ, fat 81+/-30 g, protein 94+/-28 g, carbohydrate 227+/-68 g, starch 126+/-38 g and dietary fiber 20+/-6 g with diet glycemic index being 84.2+/-7.4. Neither energy, nutrient intakes nor insulin dose was significantly related to HbA1c. Day-to-day variation of carbohydrate (p = 0.0097) and starch (p = 0.0016) intakes and diet glycemic index (p = 0.033) was positively related to HbA1c, and the associations remained significant when adjusted for age, sex, duration of diabetes and BMI. Day-to-day variation in energy, protein or fat intakes was not related to HbA1c.

CONCLUSIONS

Consistency in the amount and source of carbohydrate intake from day-to-day is associated with improved blood glucose control in people with type 1 diabetes, a result which supports continued educational efforts to achieve adherence to a diabetes diet plan. This conclusion may not apply to people on intensified insulin therapy who adjust their insulin dose based on their actual carbohydrate intake at each meal.

Konjac-mannan (glucomannan) improves glycemia and other associated risk factors for coronary heart disease in type 2 diabetes. A randomized controlled metabolic trial

OBJECTIVE

To examine whether Konjac-mannan (KJM) fiber improves metabolic control as measured by glycemia, lipidemia, and blood pressure in high-risk type 2 diabetic patients.

RESEARCH DESIGN AND METHODS

A total of 11 hyperlipidemic and hypertensive type 2 diabetic patients treated conventionally by a low-fat diet and drug therapy participated. After an 8-week baseline, all were randomly assigned to take either KJM fiber-enriched test biscuits (0.7 g/412 kJ [100 kcal] of glucomannan) or matched placebo wheat bran fiber biscuits during two 3-week treatment phases separated by a 2-week washout period. The diet in either case was metabolically controlled and conformed to National Cholesterol Education Program Step 2 guidelines, while medications were maintained constant. Efficacy measures included serum fructosamine, lipid profiles, apolipoproteins, blood pressure, body weight, and nutritional analysis.

RESULTS

Compared with placebo, KJM significantly reduced the metabolic control primary end points: serum fructosamine (5.7%, P = 0.007, adjusted alpha = 0.0167), total:HDL cholesterol ratio (10%, P = 0.03, adjusted alpha = 0.05), and systolic blood pressure (sBP) (6.9%, P = 0.02, adjusted alpha = 0.025). Secondary end points, including body weight, total, LDL, and HDL cholesterol, triglycerides, apolipoproteins A-1, B, and their ratio, glucose, insulin, and diastolic blood pressure, were not significant after adjustment by the Bonferroni-Hochberg procedure.

CONCLUSIONS

KJM fiber added to conventional treatment may ameliorate glycemic control, blood lipid profile, and sBP in high-risk diabetic individuals, possibly improving the effectiveness of conventional treatment in type 2 diabetes.

Lifestyle modifications to prevent and control hypertension. 2. Recommendations on obesity and weight loss. Canadian Hypertension Society, Canadian Coalition for High Blood Pressure Prevention and Control, Laboratory Centre for Disease Control at Health Canada, Heart and Stroke Foundation of Canada

OBJECTIVE

To provide updated, evidence-based recommendations concerning the effects of weight loss and maintenance of healthy weight on the prevention and control of hypertension in otherwise healthy adults (except pregnant women).

OPTIONS

The main options are to attain and maintain a healthy body weight (body mass index [BMI] 20-25 kg/m2) or not to do so. For those at risk for hypertension, weight loss and maintenance of healthy weight may prevent the condition. For those who have hypertension, weight loss and maintenance of healthy weight may reduce or obviate the need for antihypertensive medications.

OUTCOMES

The health outcome considered was change in blood pressure. Because of insufficient evidence, no economic outcomes were considered.

EVIDENCE

A MEDLINE search was conducted for the years 1992-1996 with the terms hypertension and obesity in combination and antihypertensive therapy and obesity in combination. Other relevant evidence was obtained from the reference lists of the articles identified, from the personal files of the authors and through contacts with experts. The articles were reviewed, classified according to study design and graded according to level of evidence.

VALUES

A high value was placed on the avoidance of cardiovascular morbidity and premature death caused by untreated hypertension.

BENEFITS, HARMS AND COSTS

Weight loss and the maintenance of healthy body weight reduces the blood pressure of both hypertensive and normotensive people. The indirect benefits of a health body weight are well known. The negative effects of weight loss are primarily the frustrations associated with attaining and maintaining a healthy weight. The costs associated with weight loss programs were not measured in the studies reviewed.

RECOMMENDATIONS

(1) It is recommended that health care professionals determine weight (in kilograms), height (in metres) and BMI for all adults. (2) To reduce blood pressure in the population at large, it is recommended that Canadians attain and maintain a healthy BMI (20-25). (3) All overweight hypertensive patients (BMI greater than 25) should be advised to reduce their weight.

VALIDATION

These recommendations are similar to those of the World Hypertension League, the National High Blood Pressure Education Program Working Group on Primary Prevention of Hypertension, the Canadian Hypertension Society and the Canadian Coalition for High Blood Pressure Prevention and Control. They have not been clinically tested.

SPONSORS

The Canadian Hypertension Society, the Canadian Coalition for High Blood Pressure Prevention and Control, the Laboratory Centre for Disease Control at Health Canada, and the Heart and Stroke Foundation of Canada.

Lifestyle modifications to prevent and control hypertension. 1. Methods and an overview of the Canadian recommendations. Canadian Hypertension Society, Canadian Coalition for High Blood Pressure Prevention and Control, Laboratory Centre for Disease Control at Health Canada, Heart and Stroke Foundation of Canada

OBJECTIVE

To provide updated, evidence-based recommendations for health care professionals on lifestyle changes to prevent and control hypertension in otherwise healthy adults (except pregnant women).

OPTIONS

For people at risk for hypertension, there are a number of lifestyle options that may avert the condition--maintaining a healthy body weight, moderating consumption of alcohol, exercising, reducing sodium intake, altering intake of calcium, magnesium and potassium, and reducing stress. Following these options will maintain or reduce the risk of hypertension. For people who already have hypertension, the options for controlling the condition are lifestyle modification, antihypertensive medications or a combination of these options; with no treatment, these people remain at risk for the complications of hypertension.

OUTCOMES

The health outcomes considered were changes in blood pressure and in morbidity and mortality rates. Because of insufficient evidence, no economic outcomes were considered.

EVIDENCE

A MEDLINE search was conducted for the period January 1996 to September 1996 for each of the interventions studied. Reference lists were scanned, experts were polled, and the personal files of the authors were used to identify other studies. All relevant articles were reviewed, classified according to study design and graded according to level of evidence.

VALUES

A high value was placed on the avoidance of cardiovascular morbidity and premature death caused by untreated hypertension.

BENEFITS, HARMS AND COSTS

Lifestyle modification by means of weight loss (or maintenance of healthy body weight), regular exercise and low alcohol consumption will reduce the blood pressure of appropriately selected normotensive and hypertensive people. Sodium restriction and stress management will reduce the blood pressure of appropriately selected hypertensive patients. The side effects of these therapies are few, and the indirect benefits are well known. There are certainly costs associated with lifestyle modification, but they were not measured in the studies reviewed. Supplementing the diet with potassium, calcium and magnesium has not been associated with a clinically important reduction in blood pressure in people consuming a healthy diet.

RECOMMENDATIONS

(1) It is recommended that health care professionals determine the body mass index (weight in kilograms/[height in metres]2) and alcohol consumption of all adult patients and assess sodium consumption and stress levels in all hypertensive patients. (2) To reduce blood pressure in the population at large, it is recommended that Canadians attain and maintain a healthy body mass index. For those who choose to drink alcohol intake should be limited to 2 or fewer standard drinks per day (maximum of 14/week for men and 9/week for women). Adults should exercise regularly. (3) To reduce blood pressure in hypertensive patients, individualized therapy is recommended. This therapy should emphasize weight loss for overweight patients, abstinence from or moderation in alcohol intake, regular exercise, restriction of sodium intake and, in appropriate circumstances, individualized cognitive behaviour modification to reduce the negative effects of stress.

VALIDATION

The recommendations were reviewed by all of the sponsoring organizations and by participants in a satellite symposium of the fourth international Conference on Preventive Cardiology. They are similar to those of the World Hypertension League and the Joint National committee, with the exception of the recommendations on stress management, which are based on new information. They have not been clinically tested.

SPONSORS

The Canadian Hypertension Society, the Canadian Coalition for High Blood Pressure Prevention and Control, the Laboratory Centre for Disease Control at health Canada, and the Heart and Stroke Foundation of Canada.

Efficacy and safety of cerivastatin in primary hypercholesterolemia: a long term comparative titration study with simvastatin

OBJECTIVE

To compare cerivastatin with simvastatin in their long term safety and efficacy in reducing low density lipoprotein cholesterol (LDL-C).

DESIGN

Multicentre, randomized, double-blind, parallel group study.

SETTING

Thirteen Canadian centres.

PATIENTS AND METHODS

A total of 387 patients with primary hypercholesterolemia received treatment with either cerivastatin (0. 05 to 0.3 mg/day) or simvastatin (5 to 40 mg/day) to achieve plasma LDL-C levels below 3.36 mmol/L (130 mg/dL) for an initial 32-week dose-titration phase and a subsequent 72-week extension phase.

MAIN RESULTS

Cerivastatin and simvastatin produced clinically significant reductions in LDL-C of 28.4% and 35.4%, respectively, at the end point for the 32-week study, and reductions of 32.8% and 35. 0%, respectively, at the end of the extension phase of the study. Response rates (a greater than 15% drop in LDL-C) were comparable for the two treatments (88.9% cerivastatin versus 93.2% simvastatin) at the 32-week end point. Response rates were 100% for both treatments at the end of the 72-week extension phase. Both treatments also reduced total cholesterol, apolipoprotein B and very low density lipoprotein cholesterol levels. Cerivastatin and simvastatin increased HDL-C levels significantly by 8.8% and 11.0%, respectively, at the end point for the 32-week study, and by 8.6% and 12.1%, respectively, at the end of the extension phase of the study. Treatments were well tolerated, and the incidence of adverse effects was similar in both groups.

CONCLUSIONS

This forced titration study demonstrates that cerivastatin, given once daily at doses up to 0.3 mg/day, is effective and well tolerated. The results of this study support further investigation of higher doses of cerivastatin given the excellent safety profile at doses up to 0.3 mg.

Effect of wheat bran on serum lipids: influence of particle size and wheat protein

OBJECTIVE

Wheat fiber appears to protect from cardiovascular disease despite its lack of consistent effect on serum lipids. We therefore wished to determine whether reported inconsistencies in the effect of wheat bran resulted from differences in particle size or its high gluten content.

METHODS

Two studies were conducted. In one-month metabolic diets, 24 hyperlipidemic subjects consumed breads providing an additional 19 g/d dietary fiber as medium or ultra-fine wheat bran and extra protein (10% of energy as wheat gluten). In two-week ad libitum diets, 24 predominantly normolipidemic subjects consumed breakfast cereals providing an additional 19 g/d of dietary fiber as coarse or a mixture of ultra-fine and coarse wheat bran with no change in gluten intake. Both studies followed a randomized crossover design with control periods when subjects ate low-fiber breads and cereals respectively with no added gluten. Fasting blood lipids were measured on day zero and at the end of each phase.

RESULTS

Wheat bran had no effect on total, LDL or HDL cholesterol irrespective of particle size or level of gluten in the diet. However, consumption of increased gluten in the metabolic study was associated with a 13+/-4% reduction in serum triglycerides (p = 0.005) which was not seen in the normal-gluten ad libitum study.

CONCLUSIONS

The protective effect of wheat fiber in cardiovascular disease cannot be explained by an effect of wheat bran in reducing serum cholesterol although in hyperlipidemic subjects displacement of carbohydrate by gluten on the high-fiber phases was associated with lower serum triglycerides.

Time of day and glucose tolerance status affect serum short-chain fatty acid concentrations in humans

Short-chain fatty acids (SCFA) are derived from endogenous (metabolism of fat, carbohydrate, and amino acids) and exogenous (colonic fermentation) sources. To see how time of day and glucose tolerance status influenced serum SCFA concentrations, we determined serum SCFA throughout the day in 22 subjects with impaired glucose tolerance (IGT) and 10 young and eight middle-aged normal controls. On 1 day, insulin sensitivity was assessed as the steady-state plasma glucose (SSPG) level achieved during intravenous infusion of glucose insulin, and somatostatin. On another day, plasma glucose and insulin and serum SCFA levels were measured 12 times over 12 hours with subjects eating a standard diet. SSPG in young controls (5.5 +/- 1.1 mmol/L) was less than in middle-aged controls (9.3 +/- 1.6 mmol/L), which in turn was less than in IGT subjects (13.7 +/- 0.6 mmol/L; P < .01). Mean plasma glucose in IGT subjects was greater than in normal controls, and mean plasma insulin in IGT subjects was higher than in young controls but similar to the levels in middle-aged controls. Mean 12-hour serum acetate in young controls (143 +/- 13 mumol/L) was greater than in middle-aged controls (104 +/- 11 mumol/L) and IGT subjects (113 +/- 5 mumol/L; P < .05). Mean 12-hour serum propionate in young controls (3.8 +/- 0.5 mumol/L) was less than in IGT subjects (5.4 +/- 0.3 mumol/L; P < .01), with middle-aged controls being intermediate (4.6 +/- 0.3 mumol/L). Both young (1.6 +/- 0.3 mumol/L) and middle-aged (1.0 +/- 0.2) controls had lower mean butyrate than IGT subjects (3.1 +/- 0.4 mumol/L; P < .05). Levels of all three SCFA varied significantly during the day, tending to decrease after breakfast and increase transiently after lunch and dinner. It is concluded that both time of day and glucose tolerance status affect serum SCFA levels in nondiabetic humans. The results suggest that serum acetate is derived primarily from colonic fermentation, serum butyrate primarily from endogenous fatty acid metabolism, and serum propionate from both exogenous and endogenous sources.

The effect of acarbose on insulin sensitivity in subjects with impaired glucose tolerance

OBJECTIVE

To study the effect of acarbose, an alpha-glucosidase inhibitor, on postprandial plasma glucose and insulin and insulin sensitivity in subjects with impaired glucose tolerance (IGT).

RESEARCH DESIGN AND METHODS

Subjects with IGT were randomly treated in a double-blind fashion with placebo (n = 10) or acarbose (n = 8) at 100 mg t.i.d. for 4 months. All subjects were submitted before randomization and at the end of the study to a standardized breakfast and a 12-h daytime plasma glucose and plasma insulin profile, and insulin sensitivity was measured as steady-state plasma glucose (SSPG) using the insulin suppression test.

RESULTS

While placebo had no effect on postprandial plasma glucose and plasma insulin incremental area under the curve (AUC) (3.03 +/- 0.5 vs. 3.76 +/- 0.6 mmol.h-1.l-1, P = NS; 1,488 +/- 229 vs. 1,609 +/- 253 pmol.h-1.l-1, P = NS), acarbose resulted in a significant reduction for both glucose (1.44 +/- 0.3 vs. 4.45 +/- 0.9 mmol.h-1.l-1, P = 0.002) and insulin (626.7 +/- 104.3 vs. 1,338.3 +/- 220.5 pmol.h-1.l-1, P = 0.003). The reduction in 12-h plasma glucose and insulin AUC on acarbose (11.2 +/- 2.1 mmol.h-1.l-1 and 7.5 +/- 0.7 nmol.h-1.l-1) was significantly greater than that on placebo (4.0 +/- 1.6 mmol.h-1.l-1 and 0.8 +/- 0.4 nmol.h-1.l-1) (P = 0.014 and 0.041). While SSPG was not affected by placebo (13.9 +/- 0.4 vs. 13.8 +/- 0.3 mmol/l; P = NS), it was significantly improved by acarbose (10.9 +/- 1.4 vs. 13.1 +/- 1.5 mmol/l, P < 0.004) and was also significantly different from placebo at 4 months (P < 0.02).

CONCLUSIONS

It is concluded that in subjects with IGT, acarbose treatment decreases postprandial plasma glucose and insulin and improves insulin sensitivity. Acarbose may therefore be potentially useful to prevent the progression of IGT to NIDDM.

Use of bioelectrical impedance analysis measurements in patients with diabetes. The Diabetes Control and Complications Trial Research Group

Weight gain is an important consequence of the intensive treatment of insulin-dependent diabetes mellitus (IDDM). Despite this, body composition in this disorder has not been well studied. Bioelectrical impedance analysis (BIA) has been shown to be a reliable, noninvasive method of assessing body composition but little is known about its use in IDDM. Therefore, a regression model estimating fat-free volume mass from bioelectrical impedance measurements obtained with proximal electrode placements was developed in 46 adults with IDDM through use of dual-energy X-ray absorptiometry (DXA) for reference values of fat-free mass. No effect of blood glucose concentration or prandial state on the impedance characteristics was observed. A regression model was developed incorporating the ratio of height squared to the minimum resistance of four limb-lead combinations (H2/R), total body weight, and a weight-sex interaction. With this model, BIA correlated closely with DXA (R2 = 0.982, residual SD = 1.3 kg). The applicability of these equations to non-insulin-dependent diabetes mellitus is unknown.

Combination therapy with oral antihyperglycemic agents in the treatment of non-insulin-dependent diabetes mellitus

Combination therapy, using drugs from different classes of oral hypoglycemic agents, offers several advantages in the treatment of non-insulin-dependent diabetes mellitus (NIDDM). Appropriate combinations can significantly improve glycemia and often obviate insulin treatment. In general, no increased toxicity or significant interactions are observed.

Case report: retinopathy and neuropathy associated with complete apolipoprotein A-I deficiency

Genetic deficiencies of plasma high-density lipoprotein cholesterol are associated variably with diseases of the eyes and nervous system. We ascertained a proband with undetectable plasma HDL-cholesterol due to homozygosity for a DNA mutation, APOA1 Q[-2]X, which encodes premature termination of translation of apolipoprotein in HDL. This person had a unique retinopathy, ataxia, and electrophysiologic abnormalities suggesting multifocal central nervous system deficits. Other gene carriers in this family had similar neurologic features, but only the proband had the retinopathy. The presence of retinopathy and neuropathy in affected family members was highly variable. This heterogeneity might results from time-dependent interactions with other genetic or environmental factors.

Positive methane-producing status associated with increased serum cholesterol in subjects with impaired glucose tolerance

OBJECTIVE

To determine if those who produce methane (i.e., have presence of methane in breath) have higher serum cholesterol than those who do not produce methane in subjects with impaired glucose tolerance (IGT).

RESEARCH DESIGN AND METHODS

We measured breath gases and fasting serum total and high-density lipoprotein (HDL) cholesterol and triglyceride (TG) levels in 21 subjects with IGT.

RESULTS

The 11 methane-producers were well matched to the 10 non-methane-producers for age, sex, and body mass index. Methane-producers had higher fasting serum total (6.5 +/- 0.3 vs. 5.5 +/- 0.2 mmol/l; P < 0.02) and low-density lipoprotein (4.3 +/- 0.3 vs. 3.4 +/- 0.2 mmol/l; P < 0.05) cholesterol concentrations with no difference in TG or HDL levels.

CONCLUSIONS

The results suggest that in subjects with IGT, positive methane-producing status may be associated with increased serum cholesterol levels.

Stimulation of glucose uptake and increased plasma membrane content of glucose transporters in L6 skeletal muscle cells by the sulfonylureas gliclazide and glyburide

Many studies suggest that sulfonylureas (SUs) have direct extrapancreatic actions. The action of gliclazide, a new SU, was examined and compared to that of glyburide in L6 myotubes, a model of skeletal muscle. Gliclazide and glyburide increased 2-deoxy-D-glucose (2DG) uptake in a time- and dose-dependent fashion after 24 h to a maximum of 179% and 202% of the basal value, respectively (P < 0.001). Acute (30-min) insulin (10(-7) M) stimulated 2DG uptake to similar levels (203% of basal), but this effect was absent after maximum stimulation by SU. SU action did not require insulin and was not blocked by the protein synthesis inhibitor cycloheximide. To investigate the mechanism of stimulation of 2DG uptake, cells were fractionated, and total plasma membrane and internal membrane levels of glucose transporter (GLUT) isoforms were determined by immunoblotting. Both drugs significantly increased the total content (1.7-fold) and plasma membrane level (1.8-fold) of GLUT1, with no change in internal membrane. Total content and plasma membrane levels of GLUT4 and GLUT3 did not change or showed a small decrease. We conclude that the stimulation of glucose uptake in L6 cells by gliclazide and glyburide is associated not with a redistribution but, rather, with an increase in the total membrane content and plasma membrane level of GLUT1, which is independent of protein synthesis. These data suggest a novel action of SU to stabilize GLUT1 protein at the plasma membrane.

The use of bioelectrical impedance analysis (BIA) to estimate body composition in the Diabetes Control and Complications Trial (DCCT)

Although weight gain often accompanies intensive treatment regimens designed to achieve near-normal glycemia in insulin-dependent diabetes mellitus (IDDM), body composition (BC) has not been well studied. Bioelectrical impedance analysis (BIA) is a safe, rapid, and non-invasive method of assessing BC but has not been utilized widely in IDDM. Data from 46 adults with IDDM were used to develop a regression model estimating fat-free body mass (FFM) from bioimpedance measurements obtained using a proximal electrode placement. Reference values of FFM were determined by dual x-ray absorptiometry (DXA). A model using the ratio of height squared to the minimum resistance of 4 limb-lead combinations (H2/R), total body weight, and a weight-gender interaction achieved a high level of accuracy (R2 = 0.982, residual standard deviation = 1.43 kg), while studies of 10 subjects before and after a light meal found no short-term effect of glycemia on measured BIA variables. BIA will therefore be used in combination with waist-to-hip ratios to study the composition and distribution of the increased weight associated with intensive therapy in the DCCT.

Detection of a new apolipoprotein-E mutation in type III hyperlipidemia using deoxyribonucleic acid restriction isotyping

While determining the apolipoprotein-E (apo-E) genotype of 22 patients with type III hyperlipidemia (HLP III) by restriction isotyping, we identified a new mutant form of apo-E by its unusual DNA restriction fragment length polymorphism pattern. DNA sequence analysis of a polymerase chain reaction-amplified portion of the proband's apo-E gene revealed the substitution of cysteine (TGC) for arginine (CGC) at position 136 in the mutant allele (designated R136C). Lipoproteins containing this mutant protein bound defectively to macrophages in vitro, confirming the contribution of R136C to the expression of HLP III in the proband. The proband's two siblings carried the mutant allele and were also heterozygous for E2. Each also had dysbetalipoproteinemia (indicated by the presence of beta-very low density lipoprotein), but neither was hyperlipidemic, attesting to the importance of other factors for the full expression of HLP III. The mutant allele appears to contribute to the inheritance of HLP III in a recessive fashion. Restriction isotyping facilitates the diagnosis of subjects with HLP III, aids in the identification of affected individuals through family screening, and can contribute to the discovery of new mutations that help explain the pathogenesis of HLP III.

Apolipoprotein A-I Q[-2]X causing isolated apolipoprotein A-I deficiency in a family with analphalipoproteinemia

We report a Canadian kindred with a novel mutation in the apolipoprotein (apo) A-I gene causing analphalipoproteinemia. The 34-yr-old proband, product of a consanguineous marriage, had bilateral retinopathy, bilateral cataracts, spinocerebellar ataxia, and tendon xanthomata. High density lipoprotein cholesterol (HDL-C) was < 0.1 mM and apoA-I was undetectable. Genomic DNA sequencing of the proband's apoA-I gene identified a nonsense mutation at codon [-2], which we designate as Q[-2]X. This mutation causes a loss of endonuclease digestion sites for both BbvI and Fnu4HI. Genotyping identified four additional homozygotes, four heterozygotes, and two unaffected subjects among the first-degree relatives. Q[-2]X homozygosity causes a selective failure to produce any portion of mature apoA-I, resulting in very low plasma level of HDL. Heterozygosity results in approximately half-normal apoA-I and HDL. Gradient gel electrophoresis and differential electroimmunodiffusion assay revealed that the HDL particles of the homozygotes had peak Stokes diameter of 7.9 nm and contained apoA-II without apoA-I (Lp-AII). Heterozygotes had an additional fraction of HDL3-like particles. Two of the proband's affected sisters had documented premature coronary heart disease. This kindred, the third reported apoA-I gene mutation causing isolated complete apoA-I deficiency, appears to be at significantly increased risk for atherosclerosis.

Consuming aspartame with and without taste: differential effects on appetite and food intake of young adult males

Despite some reports that aspartame (APM)-sweetened beverages may increase subjective appetite, previously we demonstrated that drinking 280 ml of an APM-sweetened soft drink (170 mg APM) had no effect on appetite, and 560 ml of the same soft drink (340 mg APM) reduced appetite. The present study examined this appetite reduction to determine its cause. Eighteen normal weight young adult males received five treatments (beverage preloads) at 1100 h in a randomized order, one per week: 280 ml of carbonated mineral water (CMW) (control), 560 ml of CMW, 280 ml of CMW with 340 mg of encapsulated APM, 280 ml of CMW sweetened with 340 mg APM, 560 ml of an APM-sweetened soft drink (340 mg APM). Subjective hunger and food appeal were measured from 0930 a.m. to 1230 h, and food intake from a buffet lunch offered at 1205 h was measured. Treatment had no effect on food intake or macronutrient selection. Both 560 ml of CMW or soft drink suppressed appetite, although 280 ml of APM-sweetened mineral water significantly increased subjective appetite relative to the control. Encapsulated APM had no effect on appetite. Therefore, appetite reduction following consumption of an APM-sweetened drink is likely due to drink volume and not the APM content. In addition, consuming APM-sweetened CMW produces a short-term increase in subjective appetite.

Glucose transport in human skeletal muscle cells in culture. Stimulation by insulin and metformin

Primary human muscle cell cultures were established and the regulation of glucose transport was investigated. Primary cultures were allowed to proceed to the stage of myotubes through fusion of myoblasts or were used for clonal selection based on fusion potential. In clonally selected cultures, hexose (2-deoxy-glucose) uptake into myotubes was linear within the time of study and inhibitable by cytochalasin B (IC50 = 400 nM). Cytochalasin B photolabeled a protein(s) of 45,000-50,000 D in a D-glucose-protectable manner, suggesting identity with the glucose transporters. In the myotube stage, the cells expressed both the GLUT1 and GLUT4 glucose transporter protein isoforms at an average molar ratio of 7:1. Preincubation in media of increasing glucose concentrations (range 5-25 mM) progressively decreased the rate of 2-deoxyglucose uptake. Insulin elevated 2-deoxyglucose uptake in a dose-dependent manner, with half maximal stimulation achieved at 3.5 nM. Insulin also stimulated the transport of the nonmetabolizable hexose 3-O-methylglucose, as well as the activity of glycogen synthase, responsible for nonoxidative glucose metabolism. The oral antihyperglycemic drug metformin stimulated the cytochalasin B-sensitive component of both 2-deoxyglucose and 3-O-methylglucose uptake. Maximal stimulation was observed at 8 h of exposure to 50 microM metformin, and this effect was not prevented by incubation with the protein-synthesis inhibitor cycloheximide. The relative effect of metformin was higher in cells incubated in 25 mM glucose than in 5 mM glucose, consistent with its selective action in hyperglycemic conditions in vivo. Metformin (50 microM for 24 h) was more effective than insulin (1 microM for 1 h) in stimulating hexose uptake and the hormone was effective on top of the stimulation caused by the biguanide, suggesting independent mechanisms of action.

Cellular mechanism of metformin action involves glucose transporter translocation from an intracellular pool to the plasma membrane in L6 muscle cells

The effects of the oral hypoglycemic drug metformin on glucose and amino acid transporter activity and subcellular localization of GLUT1 and GLUT4 glucose transporters were tested in cultured L6 myotubes. In muscle cells preexposed to maximal doses of metformin (2 mM, for 16 h), 2-deoxyglucose uptake was stimulated by over 2-fold from 5.9 +/- 0.3 to 13.3 +/- 0.5 pmol/min.mg protein. Uptake of the nonmetabolizable amino acid analog methylaminoisobutyrate was unaffected by treatment with the drug under identical conditions. Extracellular calcium was required to preserve the full response to the biguanide. Exposure of muscle cells to insulin in the presence of metformin resulted in further activation of 2-deoxyglucose transport. The latter effect was additive to the maximum effect of metformin, suggesting that the biguanide stimulates hexose uptake into muscle cells by an insulin-independent mechanism. Glucose transporter number quantified by performing studies of D-glucose-protectable binding of cytochalasin-B in plasma membranes (PM) and internal membranes (IM) prepared from L6 myotubes revealed that a 16-h treatment with 800 microM metformin significantly elevated glucose transporter number in the PM (by 47%), with an equivalent decrement in glucose transporter number (47%) in the IM. Western blot analysis using antisera reactive with the GLUT1 and GLUT4 isoforms of glucose transporters showed that metformin caused a reduction in GLUT1 content in the IM fraction and a concomitant increase in the PM. Unlike insulin, metformin treatment had no effect on the subcellular distribution of GLUT4. We propose that the molecular basis of metformin action in skeletal muscle involves the subcellular redistribution of GLUT1 proteins from an intracellular compartment to the plasma membrane. Such a recruitment process may form an integral part of the mechanism by which the drug stimulates glucose uptake (and utilization) in skeletal muscle and facilitates lowering of blood glucose in the management of type II diabetes.

Stimulation of hexose transport by metformin in L6 muscle cells in culture

L6 muscle cells grown in culture to the stage of fused myotubes were incubated with the oral hypoglycemic drug metformin to test the effects of this drug on glucose transport. Metformin increased the initial rate of uptake of 2-deoxyglucose and 3-O-methylglucose. The effect was time dependent, with half-maximal stimulation at 5-6 h and maximal stimulation by about 16 h. The stimulation of hexose uptake was not prevented by cycloheximide. In 15 mM glucose medium, the basal rate of transport was lower than in 5 mM glucose medium. The stimulation of hexose uptake by metformin was comparable in absolute units in both media; hence, relative to basal uptake, stimulation was greater in the high glucose medium than in the low glucose medium. In 5 mM glucose medium, half-maximal stimulation was obtained with 800 microM metformin when tested for 24 h. The stimulation of hexose transport by metformin was only detectable in fused myotubes and not in perfusion myoblasts. No significant changes were observed in glucose transporter levels in total cell membranes from L6 myotubes (measured as D-glucose-protectable binding sites for cytochalasin-B) or in the total levels of the immunoreactive glucose transporter isoforms GLUT4 or GLUT1. It is concluded that metformin stimulates hexose transport into differentiated muscle cells by acting at a posttranslational level. We speculate that this might also constitute the basis for the ability of the drug to lower glycemia in diabetic individuals.

Soft drinks with aspartame: effect on subjective hunger, food selection, and food intake of young adult males

Ingestion of aspartame-sweetened beverages has been reported to increase subjective measures of appetite. This study examined the effects of familiar carbonated soft drinks sweetened with aspartame on subjective hunger, energy intake and macronutrient selection at a lunch-time meal. Subjects were 20 normal weight young adult males, classified as either restrained or nonrestrained eaters. Four treatments of carbonated beverages included 280 ml of mineral water, one can of a soft drink (280 ml) consumed in either 2 or 10 minutes, or two cans of a soft drink (560 ml) consumed in 10 minutes, administered at 11:00 a.m. Subjective hunger and food appeal were measured from 9:30 a.m. to 12:30 p.m., and food intake data were obtained from a buffet lunch given at 12:00 noon. There were no treatment effects on energy intake, macronutrient selection or food choice at the lunch-time meal, or food appeal, though restrained eaters consumed more than nonrestrained eaters in all four treatment conditions. Consumption of two soft drinks (560 ml, 320 mg aspartame) significantly reduced subjective hunger from 11:05 a.m. to 11:30 a.m. compared to one soft drink (280 ml, 160 mg aspartame) or 280 ml of mineral water. Thus ingestion of soft drinks containing aspartame did not increase short-term subjective hunger or food intake.

Aspartame: effects on learning, behavior, and mood

The effect of aspartame on the learning, behavior, and mood of children was evaluated in two experiments. After an overnight fast and a standard breakfast, 20 healthy 9- to 10-year-old children were given the treatments in a double-blind crossover design at 10:30 AM. Lunch was served at 12:00 noon. In experiment 1, the treatment consisted of an ice slurry of strawberry Kool-Aid containing 1.75 g/kg of carbohydrate (polycose) plus either aspartame (34 mg/kg) or the equivalent sweetness as sodium cyclamate and amino acids as alanine. In experiment 2, the treatment consisted of a drink of cold unsweetened strawberry Kool-Aid, containing either 1.75 g/kg of sucrose or 9.7 mg/kg of aspartame. Measures of associative learning, arithmetic calculation, activity level, social interaction, and mood were unaffected by treatment in experiment 1. In experiment 2, the only significant treatment effect was that on the frequency of minor and gross motor behaviors, which were less frequent after the consumption of sucrose than after aspartame. Thus, the effect of aspartame on the short-term behavior of healthy 9- to 10-year-old children appears to be related to its absence of metabolic consequences rather than to its amino acid composition and putative neurochemical impact.

Cellular mechanism of action of metformin

Metformin is a hypoglycemic drug effective in the treatment of non-insulin-dependent diabetes mellitus and increasingly used in Canada and Europe. Effects on intestinal glucose absorption, insulin secretion, and hepatic glucose production are insufficient to explain its hypoglycemic action, with most evidence suggesting that the major effect of the drug is on glucose utilization. In vivo and in vitro studies have demonstrated that metformin stimulates the insulin-induced component of glucose uptake into skeletal muscle and adipocytes in both diabetic individuals and animal models. This increase is more significant in diabetic than in nondiabetic animals, suggesting an enhanced action of the drug in the hyperglycemic state. The increase in glucose uptake is also reflected in an increase in the insulin-dependent portion of glucose oxidation. Potential sites of action of metformin are the insulin receptor and the glucose transporters. Although metformin increases insulin binding in various cell types, this effect is not universal and does not correlate with stimulation of glucose utilization. In contrast, direct effects of the drug on the glucose-transport system have been demonstrated. Metformin elevates the uptake of nonmetabolizable analogues of glucose in both nondiabetic rat adipocytes and diabetic mouse muscle. In the latter, the stimulatory effect of the drug is additive to that of insulin. In human and rat muscle cells in culture, metformin increases glucose-analogue transport independently of and additive to insulin, suggesting an insulin-dependent action. Most of these results suggest that the basis for the hypoglycemic effect of this biguanide is probably at the level of skeletal muscle by increasing glucose transport across the cell membrane.

Aspartame: effect on lunch-time food intake, appetite and hedonic response in children

Two experiments were conducted, each with 20 healthy 9-10-year-old children. After an overnight fast, subjects were given a standardized breakfast at 0830 hrs, the treatments at 1030 hrs, and a lunch containing an excess of foods at 1200 hrs. Visual analog scales of hunger, fullness, and desire to eat were administered 5 min before and 20 and 85 min after treatment. Lunch-time food intake was measured. In experiment 1, either aspartame (34 mg/kg), or the equivalent sweetness of sodium cyclamate, was given in an ice slurry (300 ml) of unsweetened strawberry Kool-Aid with carbohydrate (1.75 g/kg polycose). In experiment 2, drinks (300 ml) contained either sucrose (1.75 g/kg) or aspartame (9.7 mg/kg). In both experiments, significant meal- and time-dependent effects were observed for subjective feelings of hunger, fullness and desire to eat. Treatments, however, did not affect either subjective feelings of appetite or lunch-time food intake. Thus, aspartame consumed without or with carbohydrate, did not affect either hunger or food intake of children when compared with the sweeteners sodium cyclamate and sucrose, respectively.

Comparison of daily diets containing 400 kcal (1.67 MJ) of either protein or glucose, and their effects on the response to subsequent total fasting in obese subjects

Eleven obese subjects (body mass index, 41.3 kg/m2) were examined to determine their metabolic and acid-base responses during two hypoenergetic diets, and the diets' influence on subsequent responses to prolonged total fasting. Subjects were first treated for 2 wk with 400-kcal/d (1.67-MJ/d) diets of either protein (13.2 g nitrogen, 23 mmol potassium) or glucose with 16 mmol potassium chloride and a multivitamin supplement. Mild acidosis developed during the protein diet as well as greater excretions of urinary ammonium and urea N, a greater degree of ketosis, and significantly better N balance (-42.7 vs -80.4 g, p less than 0.05) than during the glucose diet. The subsequent fast was associated with greater negative N balance after protein (-129 vs 83 g), mainly as urea N, but despite similar ketosis there was a greater acidosis after glucose and greater ammonium N excretion and cumulative K losses. These data support the concept of a labile N pool, depleted during a glucose diet and resulting in a decreased loss with the subsequent fast. We suggest a role for K depletion in augmenting fasting ammonium excretion.

Menstrual cycle effects on the metabolism of tryptophan loads

The metabolism of tryptophan (Trp) was examined during the follicular and luteal phases of the human menstrual cycle. Eight healthy women were administered capsulated Trp (3 g) or placebo (3 g lactose) during two follicular and two luteal phases of their menstrual cycles. Trp loading resulted in increased plasma concentrations of Trp and kynurenine, in an increase in the ratio of Trp to neutral amino acids in plasma, and in an increase in urinary excretion of Trp and kynurenine at both phases of the menstrual cycle. However at 3 h after Trp ingestion, plasma kynurenine levels in the luteal phase (23.6 +/- 3.1 mumol/L) were 40% higher than in the follicular phase (16.7 +/- 1.1 mumol/L) (p less than 0.05). Urinary kynurenine excretion in the luteal phase (81.6 +/- 14.4 mumol/24 h) was 28% greater than in the follicular phase (63.9 +/- 13.0 mumol/24 h) (p less than 0.05). The results indicate that the catabolism of Trp via the kynurenine pathway is affected by the phase of the human menstrual cycle.

Metabolic responses to intense exercise in lean and obese subjects

Sustained elevations of plasma glucose and insulin concentrations follow intense (80% maximum oxygen uptake) exercise performed in the postabsorptive state. To provide insights into possible mechanisms and influence of obesity, 8 lean and 12 obese subjects [106 +/- 11% (SD) and 193 +/- 31% of reference table weight, respectively] eating previously isocaloric diets were exercised to exhaustion (7 +/- 3 min) on a cycle ergometer, then followed for 60 min of recovery. The obese subjects at rest had slightly increased plasma glucose and insulin and elevated blood glycerol concentrations. Both lean and obese subjects had little or no changes in plasma glucose or insulin during exercise, but the increases during the recovery period were greater and/or sustained longer in the obese. Such results raise the possibility of transient hepatic insulin resistance after exercise and are possibly relevant to restoration of depleted muscle glycogen. Both groups had a marked fall in plasma FFA during exercise; the reduction was sustained in the lean but not in the obese subjects. Blood glycerol increased during the recovery period to higher values in the obese than in the lean subjects. Plasma norepinephrine increased about 4-fold in both groups, returning promptly to preexercise values. In contrast, the exercise-induced increment in plasma epinephrine [values at exhaustion, 933 +/- 548 vs. 1970 +/- 787 pmol/L; P less than 0.005] was markedly attenuated in the obese subjects. Thus, the obese subjects had exercise-induced changes in glucose and inulin metabolism consistent with greater postexercise insulin resistance, despite an impaired plasma epinephrine response to intense exercise.

Severe metabolic acidosis induced in a patient during fasting by KCl administration

The purpose of this study was to determine the cause of an acute metabolic acidosis of the normal anion gap type which developed during a 3 day period when 64 mmol of KCl was administered daily to an obese but otherwise healthy subject fasted for 2 weeks (called the index case). She had typical ketoacidosis of fasting for the first 13 days of fasting; since the plasma [K] was 3.6 mmol/l, she was given 64 mmol of KCl daily for 3 days. On day 3 of KCl treatment, the plasma [HCO3] was 13 mmol/l with no change in the plasma anion gap or 3-hydroxybutyrate concentration; the plasma [K] had risen to 4.3 mmol/l. The cause of the acidosis was a reduction of urine ammonium excretion by 42 mmol/day without a parallel fall in the rate of 3-hydroxybutyrate excretion. Since renal ammonium production can be inhibited by K administration, 5 other obese subjects were studied in a similar fashion to gain insight into the problem. They had a similar reduction in the daily rate of ammonium excretion (41 mmol) after KCl; however, their daily 3-hydroxybutyrate excretions declined by a similar amount (47 mmol) and thus metabolic acidosis did not develop.

Hyperglycemia after intense exercise in IDDM subjects during continuous subcutaneous insulin infusion

Exercise is conventionally considered a modality for improvement of glycemia in diabetes. We have found that a short period of intense exercise (80% VO2max) in normal lean subjects produces sustained postexercise hyperglycemia 20% above basal with a corresponding 100% increase in plasma insulin. In people with insulin-dependent diabetes mellitus (IDDM) incapable of this insulin response, it was predicted that postexercise hyperglycemia would be of greater magnitude and/or duration. To investigate this possibility, the effects of the same intense exercise (80% VO2max) were studied in 8 IDDM subjects (2 on 2 occasions) in the postabsorptive state with continuous subcutaneous (abdominal) insulin infusion (CSII). When the preexercise plasma glucose was normal (n = 6, 86 +/- 4 mg/dl), there ensued a postexercise hyperglycemia to 127 +/- 7 mg/dl (P less than .001) sustained for 2 h postexhaustion. Plasma free immunoreactive insulin (IRI) was 1.43 +/- 0.12 ng/ml before exercise and did not change postexercise. When mean preexercise plasma glucose was 149 +/- 9 mg/dl (n = 4), it rose progressively throughout the 2 h of recovery to 229 +/- 28 mg/dl (P less than .025). A small but statistically significant decrease in free IRI occurred during the last 80 min of recovery. Hyperglycemia in the diabetic subjects was not explained by abnormal or differing responses of glucagon or catecholamines. Thus, with intense exercise, diabetic control deteriorates rather than improves. Therefore, different therapeutic strategies may be required for intense compared with moderate exercise in IDDM patients.

Whole-body protein turnover in adult hemodialysis patients as measured by 13C-leucine

Muscle wasting may occur in patients with chronic renal failure (CRF). To determine whether this is due to a decrease in the synthesis or an increase in the breakdown of muscle protein, we evaluated postabsorptive whole-body protein breakdown, oxidation, and synthesis rates at steady state during a primed, continuous infusion of 13C-leucine. This was done in seven subjects on chronic maintenance hemodialysis (MHD) and in seven normal control subjects. The protein breakdown rate in MHD was not different from that in controls (103 +/- 19 and 106 +/- 19 mumol leucine.kg-1.h-1, respectively). In MHD, however, the protein oxidation rate was 43% greater than that in controls (20 +/- 6 and 14 +/- 4 mumol leucine.kg-1.h-1, p less than 0.05), whereas net protein synthesis was less (p less than 0.05). Reduced net synthesis and increased oxidation rates of protein in the postabsorptive state may therefore contribute to the muscle-wasting syndrome in patients with CRF.

Urine C-peptide as index of integrated insulin secretion in hypocaloric states in obese human subjects

To determine the effects of different hypocaloric diets on insulin secretion, 24-h urine C-peptide was measured in 11 obese subjects on a weight-maintaining baseline diet, and the results were compared with values obtained during 14-day periods of diets containing 400 kcal/day of only protein (n = 6) or glucose (n = 5), followed by 14 days of fasting and 14 days of refeeding on 800-1000 kcal/day. A significant positive correlation between total caloric intake and urine C-peptide excretion was found once the C-peptide excretion reached steady state after several days on each diet. Multiple regression analysis showed no contribution of body weight to urine C-peptide during the different diets. In contrast, a significant correlation was found between body weight and urine C-peptide in the fasting state. A marked and identical decrease of approximately 75% in urine C-peptide occurred over the first 5-7 days of the two 400-kcal diets, followed by a further decrease during fasting to 5% of baseline values. Refeeding was associated with a progressive increase. Plasma insulin and C-peptide followed the same trends as found for urine C-peptide, although the magnitude of change was much smaller. C-peptide clearance was not assessed because of the variation in plasma levels on eating meals. However, the same responses were found when C-peptide excretion was factored for creatinine excretion. Thus, the major determinant of urine C-peptide excretion appears to be food intake, and adaptations take 5-7 days to reach steady state.(ABSTRACT TRUNCATED AT 250 WORDS)

Phenylalanine and aspartame fail to alter feeding behavior, mood and arousal in men

Two experiments were designed to investigate the neurobehavioral effects of phenylalanine (PHE; 0.84, 2.52, 5.04, and 10.08 g) and aspartame (APM; 5.04 and 10.08 g) on energy and macronutrient selection and on subjective feelings of hunger, mood and arousal in normal weight adult males. Neither phenylalanine nor aspartame altered mean energy intakes or macronutrient selection at a lunch begun 60 to 105 min after the amino acids were consumed. During this time, increased (p less than 0.05) visual analog scale (VAS) scores for emptiness, rumbling, weakness, degree of hunger and urge to eat were found in both experiments, but no treatment effects or interactions were seen for any variable in either experiment. Plasma PHE levels and ratios to other large neutral amino acids (NAA) rose significantly (p less than 0.05) after all treatments except 0.84 g PHE; plasma tyrosine (TYR) levels increased (p less than 0.05) only when greater than or equal to 2.52 g PHE was given. TYR/NAA ratios were higher (p less than 0.05) after 2.52 and 5.04 g PHE, and 10.08 g APM. No relationships were found between food intake and plasma amino acid levels. We conclude that, in normal weight men, PHE and APM, in doses up to 10 g, do not affect short-term energy and macronutrient intakes, or subjective feelings of hunger, mood and arousal.

Obesity: overview of pathogenesis and treatment

This paper presents an overview of selected current concepts of the pathogenesis and treatment of obesity. It has been estimated using the 1981 Canada Fitness Survey data that 14.1% of Canadian adult men and 20.6% of women are greater than 20% above reference table weight. Recent advances in adipocyte metabolism and control have shown that hyperplastic obesity can occur at any age and that there are differences in the replicative rate of adipocyte precursor cells from the massively obese. Furthermore, a number of the complications of obesity, including hypertension, have been related to regional body fat distribution, independent of total body fat. It is suggested that some of the controversy on the relationship between body weight/weight loss and hypertension may be due to failure to account for this. There is now suggestive evidence that abnormalities in diet-induced thermogenesis and (or) brown adipose tissue may result in human obesity. The roles of the major treatment modalities (diet, behaviour therapy, and exercise) are reviewed as are the potential hazards of the weight loss process.

Skeletal muscle function in chronic renal failure: an index of nutritional status

To determine whether skeletal muscle function testing (SMF) provides an index of nutritional status in patients with chronic renal failure (CRF), two groups with comparable CRF were studied. In 48 well-nourished (WN) and 17 malnourished (MN) patients with stable CRF, and in 33 WN nonazotemic controls, adductor pollicis function was assessed. The force at 10 Hz was expressed as a % of force at 100 Hz (F10/F100), and maximal relaxation rate (MRR) as % force loss/10 ms. Standard nutritional assessment was also performed. The WN group was not significantly different from controls for either F10/F100 or MRR. The F10/F100 of the MN group was significantly greater than either the WN group or controls (p less than 0.001), while MRR was less (p less than 0.001). Significant malnutrition by conventional parameters was shown in patients with abnormal F10/F100, and also in patients with abnormal MRR. Hence, SMF as described is unaffected by azotemia, and provides a functional measure of nutritional status in CRF.

Excretion of urinary catecholamine metabolites in anorexia nervosa: effect of body composition and energy intake

Metabolites of norepinephrine and dopamine were measured in urine from 12 women of normal body weight and from six women undergoing treatment for anorexia nervosa. The women with anorexia nervosa had 48% less body fat (14 +/- 1 versus 27 +/- 1%, p less than 0.001), 9% less fat-free mass (36 +/- 1 versus 40 +/- 1 kg, p = 0.05), and 26% higher energy intake (2217 +/- 147 versus 1750 +/- 43 kcal, p less than 0.01) on collection days compared to the normal weight women. Twenty-four-hour excretions of norepinephrine metabolites, 3-methoxy-4-hydroxyphenylethylglycol, 3,4-dihydroxyphenylethylglycol, and vanilmandelic acid were reduced (p less than 0.01) in anorexia nervosa by 44, 48, and 39%, respectively. Excretion of homovanillic acid, the dopamine metabolite, was the same for both groups. Urinary 3-methoxy-4-hydroxyphenylethylglycol content was best predicted by percentage body fat in the normals (r = 0.63, p less than 0.05) and for both groups combined (r = 0.79, p less than 0.001). Urinary vanilmandelic acid showed a strong relationship with fat-free mass in the normal group (r = 0.84, p less than 0.001) and for both groups combined (r = 0.79, p less than 0.001). In contrast, urinary 3-methoxy-4-hydroxyphenylethylglycol and vanilmandelic acid and energy intakes were only weekly associated in the normals, but unrelated in the anorexics, or when the data from both groups were combined.(ABSTRACT TRUNCATED AT 250 WORDS)