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Biomedical subjects

Peter M Clifton

Publications and source records attributed to Peter M Clifton.

30 records · Page 2Linked to original sources
PubMed2004

Trans fatty acids in adipose tissue and the food supply are associated with myocardial infarction.

Metabolic studies have clearly shown that trans fatty acids (TFAs) elevate LDL and lower HDL cholesterol. Epidemiologic studies showed a relation between TFA intake and the risk of myocardial infarction (MI), but studies examining adipose tissue TFAs have not uniformly confirmed this. We performed a case control study examining both adipose tissue levels and dietary intake of TFAs and first MI. Between 1995 and 1997, 209 cases of first MI completed a 300-item FFQ and 79 had an adipose tissue biopsy; 179 matched controls completed the FFQ and 167 had a biopsy. During the course of the study (mid-1996), TFAs were eliminated from margarines sold in Australia. Cases biopsied before mid-1996 had greater levels of trans 18:1(n-9) (32% P < 0.03) and trans 18:1(n-11) (23%, P < 0.001) than controls biopsied before mid-1996. After June 1996, there were no differences between cases and controls in any of the adipose tissue TFAs measured. Logistic regression showed that trans 18:1(n-11) (P = 0.03) was an independent predictor of a first MI. Cases consumed 0.5 g/d (P = 0.002) more TFAs than controls. Subjects in the highest quintile of TFA intake had an OR for first MI of 2.1 (95% CI, 1.1-4.3), which was not independent of saturated fat intake. Apparent TFA intake from margarine was related to adipose tissue 18:1t[(n-9) and (n-10)] in 1995 (r = 0.66, 0.66, respectively). We conclude that TFAs in adipose tissue are associated with an increased risk of coronary artery disease and rapidly disappear from adipose tissue when not included in margarines.

Adipose Tissue↗
PubMed2004

Very low-fat (12%) and high monounsaturated fat (35%) diets do not differentially affect abdominal fat loss in overweight, nondiabetic women.

Studies in women with type 2 diabetes demonstrated adverse effects on body fat distribution of a low-fat diet relative to a high monounsaturated fat diet. We performed a randomized 12-wk parallel design study of two 6000-kJ diets: 35% energy from fat (high monounsaturated fat diet, HIMO), or 12% energy from fat (very low-fat diet, VLF) to determine whether this also occurred in nondiabetic women. Body fat distribution, fasting plasma glucose, blood pressure, and fasting serum lipids were measured at wk 0 and 12 in 62 women (BMI > 27 kg/m(2)). Weight loss (9.5 +/- 2.4 vs. 9.4 +/- 3.4 kg, VLF vs. HIMO) and total fat loss (6.1 +/- 2.4 vs. 6.3 +/- 2.7 kg, VLF vs. HIMO) did not differ in the groups. There was a diet x menopausal status interaction in lean mass changes (P = 0.005) such that in premenopausal women, HIMO produced a lower loss of lean mass than the low-fat diet (0.4 +/- 2.3 vs. 2.9 +/- 2.7 kg, P = 0.006) with the opposite but nonsignificant effect seen in postmenopausal women. There was a greater decrease in total plasma cholesterol in women who consumed VLF compared with those who consumed HIMO (0.82 +/- 0.0.51 vs. 0.50 +/- 0.48 mmol/L, P < 0.001 for time, P < 0.05 for diet effect). This was also true for the change in HDL cholesterol (0.18 +/- 0.23 vs. 0.04 +/- 0.19 mmol/L, VLF and HIMO, respectively, P < 0.001 for time, P < 0.05 for diet effect). The LDL/HDL ratio was reduced in both groups with no effect of diet (0.16 +/- 0.51 vs. 0.16 +/- 0.45, VLF and HIMO, respectively, P < 0.05). In conclusion, weight, total fat mass, and regional fat mass loss did not differ in the 2 groups of women but there was an apparent preservation of lean mass in premenopausal women consuming HIMO.

Blood Glucose↗
PubMed2004

Meal replacements are as effective as structured weight-loss diets for treating obesity in adults with features of metabolic syndrome.

Meal replacements are widely used as a weight-loss strategy; however, their effectiveness outside controlled clinical trial environments is unknown. We compared meal replacements with a structured weight-reduction diet in overweight/obese Australians with raised triglycerides. In a randomized parallel design, 2 groups [meal replacement (MR) and control (C)] of 66 matched subjects underwent a 6000 kJ intervention for 3 mo (stage 1) and a further 3 mo (stage 2). The groups were provided oral and written information. The C group was supplied with shopping vouchers and followed a low fat/energy diet. The MR group was supplied with Slim-Fast trade mark products for 2 meals (1800 kJ) and consumed a low-fat evening meal. Clients were weighed every 2 wk and received structured supervision without professional dietary input, with compliance assessed by 3-d weighed food records. Blood biomarkers were used to assess fruit/vegetable intake and a questionnaire was used to assess attitudes to treatment. Fifty-five subjects completed stage 1 (withdrawals: 7 in the MR group, 4 in the C group) and 42 subjects completed stage 2. Weight loss was 6.0 +/- 4.2 kg (6.3%) for the MR group and 6.6 +/- 3.4 kg (6.9%) for the C group at 3 mo, and 9.0 +/- 6.9 kg (9.4%) for the MR group and 9.2 +/- 5.1 kg (9.3%) for the C group at 6 mo (different over time within but not between treatments). Serum folate and plasma beta-carotene were higher in the MR group. Plasma homocysteine fell in both groups (P < 0.005). Dietary fiber intake was higher in the C group (P < 0.02) and calcium was higher in the MR group (P < 0.001). We concluded meal replacement is equally effective for losing weight compared with conventional but structured weight-loss diets. Dietary compliance and convenience were viewed more favorably by participants who consumed meal replacements than by those in a conventional weight-loss program.

Adult↗
PubMed2004

A longitudinal study of bone-related biochemical changes at the menopause.

OBJECTIVE: To evaluate the effects of the menopause on bone-related biochemical variables in a longitudinal study. DESIGN: Recruitment by advertisement of premenopausal women over the age of 44 for measurement of selected variables and collection of blood and urine samples for deep freezing, followed by annual check of menopausal status and repeat collection of blood and urine samples for deep freezing after the menopausal transition. PATIENTS: A total of 104 women with confirmed premenopausal status and on no treatment likely to affect calcium or bone metabolism were admitted to the study over a period of 2 years. After 8 years, 43 of the volunteers had passed through the menopause and the study was closed. MEASUREMENTS: Radiocalcium absorption was measured at the first attendance and again after the menopausal transition. Calcium and other relevant variables were measured consecutively on paired thawed-out samples of blood and urine. RESULTS: The data were complete in 34 subjects. In these women, there were highly significant correlations between the first and second measurements of most variables - serum calcium and fractions, radiocalcium absorption, vitamin D metabolites, PTH and others - indicating significant 'tracking' of these variables across the menopause. Within that framework there were significant rises in serum total and calculated ionized calcium (both P < 0.001) without change in mean serum parathyroid hormone (PTH). Radiocalcium absorption fell (P < 0.001) without change in serum 1,25D. There was a rise in fasting urinary calcium (P < 0.001) which could not be explained by the rise in filtered load and therefore represented a fall in TmCa (P < 0.001). There were significant rises in urinary bone resorption markers, pyridinoline and deoxypyridinoline (P < 0.001). CONCLUSIONS: We conclude that the menopausal rise in calculated serum ionized calcium without fall in PTH, indicates a change in PTH set-point, and that the falls in gastrointestinal absorption and renal tubular reabsorption of calcium reflect the loss of an oestrogen action at these two sites. Although these changes are sufficient to explain the rise in calcium requirement at the menopause, the association of high bone resorption with normal serum PTH suggests also an increased sensitivity of bone to the action of parathyroid hormone. There is significant 'tracking' of many variables across the menopause despite very significant changes in their absolute values.

Adult↗
PubMed2004

Effect of Grape Seed Extract and Quercetin on Cardiovascular and Endothelial Parameters in High-Risk Subjects.

Grape seed extract (GSE) has in vitro antioxidant activity but whether or not it works in vivo is not clear. In a fully randomised, crossover trial with 4-week treatment periods on 36 men and women with above-average vascular risk, we aimed to demonstrate that 2 g/day of GSE (1 g of polyphenols) alone, or with 1 g/day of added quercetin in yoghurt, favourably alters vascular function, endothelial function, and degree of oxidative damage in comparison to a control yoghurt. GSE alone improved flow-mediated dilatation determined ultrasonically by an absolute $1.1$ % compared with control. There was no effect of the combination of GSE with quercetin. No other blood or urine measure was altered. Thus sufficient polyphenols from GSE appear to be absorbed to influence endothelial nitric oxide production, and GSE has the potential to favourably influence vascular function.

Journal Article↗
PubMed2003

Diet and C-reactive protein.

C-reactive protein (CRP) is an independent predictor of cardiovascular events in healthy individuals and those with pre-existing disease. It also probably contributes to the disease process. CRP levels are higher in obese subjects and this link is almost certainly because of increased insulin resistance. Interventions that alter insulin resistance, such as weight loss, exercise, and conjugated linoleic acid, also alter CRP. Glycemic load is associated with CRP, but there have been no interventions with altered macronutrient composition. In the context of weight loss, macronutrient composition is probably not important. Alcohol lowers CRP, but the mechanism is unknown. The interaction between gender and obesity needs further work, but it appears that obesity has a greater effect on CRP levels in women.

Alcohol Drinking↗
PubMed2003

-308 Nco I polymorphism of tumour necrosis factor alpha in overweight Caucasians.

We investigated whether a polymorphism in the promoter region of the TNFalpha gene (-308 A/G) is associated with reduced weight loss in obese Australian subjects on an energy restricted diet. 189 healthy subjects and 91 subjects with type II diabetes were genotyped for the -308 Nco I polymorphism using PCR-RFLP techniques. A subset of these subjects (211 females and 45 males), were placed on a 30% energy restricted diet (6200 kJ) for 12 weeks. Subjects were assessed every 2 weeks and changes in body weight, waist circumference and BMI were used as determinants of weight loss. Fasting plasma was analysed for glucose, insulin, lipids and free fatty acids. 64% of subjects were GG homozygotes, 31% were AG heterozygotes and 5% were AA homozygotes. There was no significant difference between the allele frequency in healthy subjects (0.21) and type 2 diabetic patients (0.24). The presence of the -308 A/G polymorphism did not significantly influence initial BMI, the amount of weight lost (GG, 8.1+/-0.65 kg, AG, 6.9+/-0.77 kg, AA, 7.6+/-0.12 kg), waist circumference or any metabolic variable. The AA variant at position -308 in the promoter region of the TNFalpha gene does not influence the amount of weight lost in overweight and obese men and women on a 30% energy restricted diet.

Australia↗
PubMed2003

Effect of a high-protein, energy-restricted diet on body composition, glycemic control, and lipid concentrations in overweight and obese hyperinsulinemic men and women.

BACKGROUND: It is not clear whether varying the protein-to-carbohydrate ratio of weight-loss diets benefits body composition or metabolism. OBJECTIVE: The objective was to compare the effects of 2 weight-loss diets differing in protein-to-carbohydrate ratio on body composition, glucose and lipid metabolism, and markers of bone turnover. DESIGN: A parallel design included either a high-protein diet of meat, poultry, and dairy foods (HP diet: 27% of energy as protein, 44% as carbohydrate, and 29% as fat) or a standard-protein diet low in those foods (SP diet: 16% of energy as protein, 57% as carbohydrate, and 27% as fat) during 12 wk of energy restriction (6-6.3 MJ/d) and 4 wk of energy balance ( approximately 8.2 MJ/d). Fifty-seven overweight volunteers with fasting insulin concentrations > 12 mU/L completed the study. RESULTS: Weight loss (7.9 +/- 0.5 kg) and total fat loss (6.9 +/- 0.4 kg) did not differ between diet groups. In women, total lean mass was significantly (P = 0.02) better preserved with the HP diet (-0.1 +/- 0.3 kg) than with the SP diet (-1.5 +/- 0.3 kg). Those fed the HP diet had significantly (P < 0.03) less glycemic response at weeks 0 and 16 than did those fed the SP diet. After weight loss, the glycemic response decreased significantly (P < 0.05) more in the HP diet group. The reduction in serum triacylglycerol concentrations was significantly (P < 0.05) greater in the HP diet group (23%) than in the SP diet group (10%). Markers of bone turnover, calcium excretion, and systolic blood pressure were unchanged. CONCLUSION: Replacing carbohydrate with protein from meat, poultry, and dairy foods has beneficial metabolic effects and no adverse effects on markers of bone turnover or calcium excretion.

Blood Glucose↗
PubMed2002

Effect of maternal feed restriction during pregnancy on glucose tolerance in the adult guinea pig.

Maternal nutrient restriction and impaired fetal growth are associated with postnatal insulin resistance, hyperinsulinemia, and glucose intolerance in humans but not consistently in other species, such as the rat or sheep. We therefore determined the effect of mild (85% ad libitum intake/kg body wt) or moderate (70% ad libitum intake/kg body wt) maternal feed restriction throughout pregnancy on glucose and insulin responses to an intravenous glucose tolerance test (IVGTT) in the young adult guinea pig. Maternal feed restriction reduced birth weight (mild and moderate: both P < 0.02) in male offspring. Moderate restriction increased plasma glucose area under the curve (P < 0.04) and decreased the glucose tolerance index (K(G)) (P < 0.02) during the IVGTT in male offspring compared with those of mildly restricted but not of ad libitum-fed mothers. Moderate restriction increased fasting plasma insulin (P < 0.04, adjusted for litter size) and the insulin response to IVGTT (P < 0.001), and both moderate and mild restriction increased the insulin-to-glucose ratio during the IVGTT (P < 0.003 and P < 0.02) in male offspring. When offspring were classed into tertiles according to birth weight, glucose tolerance was not altered, but fasting insulin concentrations were increased in low compared with medium birth weight males (P < 0.03). The insulin-to-glucose ratio throughout the IVGTT was increased in low compared with medium (P < 0.01) or high (P < 0.05) birth weight males. Thus maternal feed restriction in the guinea pig restricts fetal growth and causes hyperinsulinemia in young adult male offspring, suggestive of insulin resistance. These findings suggest that mild to moderate prenatal perturbation programs postnatal glucose homeostasis adversely in the guinea pig, as in the human.

Aging↗
PubMed2002

The effect of high- and low-glycemic index energy restricted diets on plasma lipid and glucose profiles in type 2 diabetic subjects with varying glycemic control.

OBJECTIVE: To determine whether glycemic index (GI) differentially affects improved glucose and lipid profiles observed during weight loss in overweight subjects previously diagnosed with type 2 diabetes with variable glucose tolerance. METHODS: Twenty-three female and twenty-two male overweight subjects participated in 12 weeks of energy restriction (average BMI 33.2 kg/m2, age 56.7 years, glycated hemoglobin (GHb) 6.7%). After a four-week run-in on a high saturated fat (SFA) diet (1540 kcal/day, 17% SFA), the free-living subjects were randomly assigned to either a high- (75 GI units) or low- (43 GI units) GI diet (1440 kcal/day, 60% carbohydrate, 5% SFA) for eight weeks. Weight, serum lipids, plasma glucose and glycated hemoglobin were measured every four weeks. An oral glucose tolerance test (OGTT) was also performed at baseline, weeks 4 and 12. From the baseline OGTT results subjects were divided into three groups of low, median and high glucose tolerance. RESULTS: At baseline, BMI, age and glycated hemoglobin concentrations were not different between subjects allocated to the high- or low-GI diets. After four weeks, weight loss was 3.6+/-0.3 kg. Fasting glucose (-5.6%), glycated hemoglobin (-2.8%), area under the glucose curve (-13.0%) and triglyceride (-13.8%) concentrations were reduced (p < 0.02). Between weeks 4 and 12 reductions were observed in weight (-4.9%), fasting glucose (-4.6%), area under glucose curve (-10.1%), glycated hemoglobin (-7.2%), triglyceride (-7.5%) and LDL-C (-13.2%) concentrations. Weight loss was not different between low and high-GI diets. However, glycated hemoglobin was reduced twofold more in subjects consuming a low-GI diet as compared to subjects consuming a high-GI diet, but this was not statistically significant. LDL concentrations were also reduced more in subjects with low glucose tolerance on the low-GI diet (p = 0.02). CONCLUSION: Weight loss produces substantial improvements in glycemic control and lipoprotein metabolism. Lowering the glycemic index of high carbohydrate, low fat diets increases the fall in LDL cholesterol in subjects with type 2 diabetes with low glucose tolerance, but has little effect on glycemic control.

Blood Glucose↗
PubMed2002

Effect of maternal feed restriction on blood pressure in the adult guinea pig.

Small size at birth has been associated with increased blood pressure in adult men and women. In rats, isocaloric protein restriction reduces fetal growth and increases systolic blood pressure in adult offspring. Balanced maternal undernutrition in the rat also increases adult blood pressure, but not consistently. The aim of this study was to determine the effect of moderate balanced maternal undernutrition (85% of ad libitum intake from 4 weeks before, and throughout pregnancy) on blood pressure of adult offspring in the guinea pig, a species that is relatively mature at birth. Blood pressure was measured in chronically catheterised offspring of ad libitum fed or feed-restricted mothers, at 3 months of age (young adult). Maternal feed restriction reduced birth weight (-17%) and increased systolic blood pressure (+9%, P < 0.03) in young adult male offspring. In offspring of ad libitum fed and feed-restricted mothers, combined data showed that systolic blood pressure and mean arterial pressure correlated negatively with head width at birth (P = 0.02 and P = 0.04, respectively, n = 28). Systolic blood pressure also correlated negatively with birth weight and the ratio birth weight/birth length, but only in offspring of ad libitum fed mothers (P = 0.04 and P = 0.03, respectively, n = 22). The effect of maternal feed restriction on systolic blood pressure in male offspring was not significant when adjusted for these measures of size at birth. Thus, moderate balanced undernutrition in the guinea pig increases systolic blood pressure in young adult male offspring; however, these effects may be mediated, at least in part, through effects on fetal growth.

Aging↗