Review: Thinking around abdominal obesity and cardiovascular risk

Obesity, particularly intra-abdominal (visceral) obesity, is a leading cause of cardiovascular disease (CVD), insulin resistance, type 2 diabetes, dyslipidaemia, inflammation and thrombosis. A useful indicator for visceral fat is waist circumference, which is associated with all-cause mortality. Pro-inflammatory adipokines play a causal role in the development of pathologies associated with insulin resistance, type 2 diabetes and CVD. In addition to established anti-obesity therapies, namely orlistat and sibutramine, a new type of agent that inhibits the cannabinoid receptor (CB1) is advanced in development to reduce appetite and act predominantly against intra-abdominal adiposity.

Weight loss for individuals with type 2 diabetes following a very-low-calorie diet in a community-based setting with trained facilitators for 12 weeks

WHAT IS ALREADY KNOWN ABOUT THIS SUBJECT

Approximately 80% of people with type 2 diabetes mellitus (T2DM) are overweight or obese. Weight loss produces numerous benefits in T2DM. People with T2DM have difficulty losing and maintaining weight.

WHAT THIS STUDY ADDS

Provision of a very-low-calorie diet (VLCD) with group support and behaviour therapy for patients with T2DM is feasible within a community-based setting with trained facilitators. VLCD approaches for weight management in T2DM can achieve more than 90% of weight loss as compared with obese individuals without T2DM. Identification of the need to investigate the full impact of this approach in patients with T2DM by assessing changes in glycaemia, liver function and medication. Approximately 80% of people with type 2 diabetes mellitus (T2DM) are overweight or obese, and obesity compounds the cardiovascular risk of T2DM. The aim of this retrospective study was twofold: first, to investigate whether a 12-week community-based very-low-calorie diet (VLCD) programme can result in important weight loss; and second, to investigate any potential difference in the weight loss achieved using this community-based approach in individuals with and without T2DM. Three hundred and fifty-five participants with T2DM were matched for age, body mass index (BMI) and gender to participants without T2DM (total cohort comprised 204 males: 506 females (mean ± standard deviation); age (years) 54.0 ± 9.1; BMI (kg m(-2) ) 41.6 ± 8.1; weight (kg) 116.1 ± 25.1). The programme included a daily intake of 550 kcal in addition to group support and behaviour therapy provided by trained facilitators within a community-based setting. After 12 weeks, there was significant weight loss within each group when compared with baseline (T2DM: 115.0 ± 24.4 kg vs. 96.7 ± 21.4 kg, P < 0.0001; non-T2DM: 117.2 ± 25.8 kg vs. 97.3 ± 22.2 kg, P < 0.0001). At 12 weeks, weight change (-18.3 ± 7.3 kg vs. -19.9 ± 7.0 kg, P = 0.012) and BMI change (-6.7 ± 2.9 kg m(-2) vs. -7.1 ± 2.1 kg m(-2) , P = 0.011) were significantly less in the T2DM group when compared with the non-T2DM group. Our results suggest that the use of VLCD approaches for weight management in T2DM can achieve more than 90% of the weight loss seen in obese individuals without T2DM.

Optimizing acceptability and feasibility of an evidence-based behavioral intervention for obese adults with obesity-related co-morbidities or additional risk factors for co-morbidities: an open-pilot intervention study in secondary care

OBJECTIVE

To test and optimize the feasibility and acceptability of a physical activity (PA) and healthy eating behavior change intervention for obese adults with obesity-related co-morbidities or additional risk factors for co-morbidities.

METHODS

Open-pilot intervention study using an uncontrolled pre and post design with ongoing measures on intervention acceptability and feasibility. Participants received 5 weekly nurse-led one-hour long group sessions. Acceptability and feasibility were assessed throughout. PA, dietary behavior and weight were measured before and after the intervention.

RESULTS

Of 74 consenting participants, 61 (82%) received and 47 (64%) completed the intervention. Average ratings of intervention materials and components by participants ranged between 4.1 and 4.9 out of 5. Average facilitator satisfaction rating was 90% (range 75-100%). The intervention delivery was feasible as indicated by ratings and comments from participants and the facilitator. Participants lost -0.86 kg of weight t(45)=3.84, p=0.0001, and increased PA by an additional 1.6 (SD=2.7) sessions/week, t(31)=-3.3, p=0.002. No significant dietary differences emerged.

CONCLUSION

The intervention was acceptable to the facilitator and participants and feasible for delivery. Several intervention aspects were further optimized.

PRACTICE IMPLICATIONS

The current study outlines a PA and dietary behavior change pilot intervention coupled with a systematic and transparent process of intervention optimization.

Effect of weight loss on adipokine levels in obese patients

BACKGROUND

Adipose tissue functions as an endocrine organ by releasing adipokines which have important roles in the regulation of inflammation and insulin sensitivity. Although there is evidence of improvement in circulating levels of adipokines with weight loss, few studies relate such changes to specific diets. We investigated the effects of weight loss achieved by two different diets on circulating adipokine levels in obese individuals.

METHODS

A total of 120 obese patients (body mass index ≥ 35 kg/m(2)) underwent a three-month screening period on a low-fat, reduced-calorie diet. Patients failing to achieve a 5% weight loss using this approach were randomly allocated to either a low carbohydrate/high protein diet (n = 17) or to a commercial very low calorie diet (LighterLife(®), n = 14) for a period of nine months.

RESULTS

At nine months, a significant weight loss was only maintained for Lighter-Life(®) (-32.3 ± 22.7 kg, P < 0.0001) but not on the low carbohydrate/high protein diet. Changes in adiponectin (15.8 ± 17.1 ng/mL versus -0.8 ± 6.2 ng/mL, P = 0.003) and leptin (-17.6 ± 24.3 ng/mL versus -3.0 ± 9.2 ng/mL, P = 0.049) at nine months were significantly greater for LighterLife(®) than for the low carbohydrate/high protein diet, which may reflect greater weight loss and decrease in fat mass. Changes in tumor necrosis factor-alpha, interleukin-6, and plasminogen activator inhibitor type 1 did not differ significantly between the dietary interventions at nine months.

CONCLUSION

A significant weight loss of 23.8% from baseline weight was observed using a very low calorie diet and resulted in significant improvements in circulating levels of leptin, plasminogen activator inhibitor type 1, and adiponectin, which are likely to be due to weight loss and not macronutrient intake.

The molecular contribution of TNF-α in the link between obesity and breast cancer

Obesity is a growing worldwide medical problem, as it pre-disposes the affected hosts to a number of severe diseases, including postmenopausal breast cancer. Obesity development is characterised, amongst others, by aberrant secretion of adipokines. White fat tissue infiltrating macrophages secrete tumour necrosis factor-α (TNF-α) so that its circulating levels correlate positively with body mass index (BMI). In the study presented here, the effect of TNF-α on cell proliferation, cell signalling pathway activation and cell cycle in two breast cancer cell lines and one breast epithelial cell lines was assessed to determine the contribution of TNF-α on breast cancer progression and aetiology, respectively. TNF-α acted differently on all three cell lines. In MDA-MB-231 breast cancer cells, cell proliferation and PI3-kinase activation were not affected, while MAP-kinase activation and cell cycle progression were decreased, with indications of increased apoptosis. This suggests a growth inhibitory function of TNF-α in these cells. In SK-BR-3 breast cancer cells, cell proliferation and cell signalling pathway activation increased, while cell cycle progression decreased, which contradictorily suggests both growth promoting and growth inhibiting properties of TNF-α on these cells. This makes TNF-α an unlikely candidate for a general contribution to the link between obesity and breast cancer progression, however, individual tumours may be responsive to a proliferative signal of TNF-α. In MCF-10A breast epithelial cells, cell proliferation and MAP-kinase activation increased, while cell cycle progression was unaffected. This suggests a strong proliferative response in these cells, suggesting the possibility that TNF-α may contribute to breast cancer aetiology as a novel link between obesity and increased risk of breast cancer development.

Randomized clinical trial of standard dietary treatment versus a low-carbohydrate/high-protein diet or the LighterLife Programme in the management of obesity*

BACKGROUND

With the current obesity epidemic, the search for effective weight loss approaches is required. In the present study, changes in weight, body composition and cardiovascular (CV) risk in response to a low-fat, reduced-energy diet (LFRE), a low-carbohydrate/high-protein diet (LCHP), or a commercially available very low-calorie diet (LighterLife; LL) were assessed.

METHODS

One hundred and twenty obese patients (body mass index ≥35 kg/m² ) underwent a screening period of 3 months on the LFRE. Those who lost >5% of their body weight were maintained on this approach for an additional 3 months, whereas those who lost >10% at this time were maintained for 1 year. Patients failing to achieve these targets were randomly allocated to either the LCHP (n = 38) or LL (n = 34) for a period of 9 months.

RESULTS

Significantly greater weight loss was seen for patients on the LL than the LCHP at 3 (mean (± SD) -11.6 ± 12.9 vs -2.8 ± 4.5 kg, respectively; P < 0.0001) and 9 months (-15.1 ± 21.1 vs -1.9 ± 5.0 kg, respectively; P < 0.0001) after screening. Significantly greater improvement in total cholesterol, low-density lipoprotein-cholesterol, fasting glucose, and diastolic blood pressure was seen at 3 months in patients on the LL compared with the LCHP (P < 0.05). These differences were no longer significant at 9 months, with the exception of fasting glucose. The attrition rate was elevated in the LCHP group, but did not differ significantly from the LL group.

CONCLUSION

Greater weight loss and improved CV risk were achieved with the LL, which mostly reflects the patient support provided for each dietary treatment.

The influence of birth weight and genetic factors on lipid levels: a study in adult twins

Twins can be used to investigate the biological basis for observed associations between birth weight and later disease risk, as they experiencein uterogrowth restriction compared with singletons, which can differ in magnitude within twin pairs despite partial or total genetic identity. In the present study, sixty monozygotic and seventy-one dizygotic same-sex twin pairs aged 19–50 years and eighty-nine singleton controls matched for age, gestational age, sex, maternal age and parity were recruited from an obstetric database. Associations between fasting lipid levels and birth weight were assessed by linear regression with adjustment for possible confounding factors. Twins were significantly lighter at birth but were not significantly different in adult height, weight or lipid levels from the singleton controls. There was a significant inverse association between birth weight and both total and LDL-cholesterol levels among singleton controls (−0·53mmol/l per kg (95% CI −0·97, −0·09),P=0·02 and −0·39mmol/l per kg (95% CI −0·76, −0·02),P=0·04, respectively), but there was no significant association between birth weight and lipid levels in either unpaired or within-pair analysis of twins. The results suggest that thein uterogrowth restriction and early catch-up growth experienced by twins does not increase the risk of an atherogenic lipid profile in adult life.

The effect of birth weight on clottable and intact fibrinogen levels: a twin study

Several studies in singletons have found an association between low birth weight and increased plasma concentrations of clotting factors in adult life. Twins provide an opportunity to assess the possible contribution of genetic factors to this association. Forty-four monozygotic and 60 dizygotic same-sex twin pairs aged 19-50 years and 78 singleton controls matched for age, gestational age, gender, maternal age and parity were recruited from an obstetric database. Associations between both adult clottable fibrinogen (measured by the Clauss method) and intact fibrinogen (measured by the immunoprecipitation test), and birth weight were assessed by linear regression with adjustment for current age, gender, smoking and body mass index. Twins were significantly lighter at birth than singleton controls, but did not differ significantly in adult height, weight or fibrinogen levels from the singleton controls. There was a significant inverse association between birth weight and clottable fibrinogen levels among singleton controls [-0.22 g L(-1) kg(-1) (95% CI: -0.41,-0.03), P = 0.03], but not in unpaired twins. For intact fibrinogen there was no significant association with birth weight in either singleton controls or twins. In the within-pair analysis in twins there was a significant inverse association between differences in birth weight and clottable fibrinogen levels in dizygotic twin pairs [-0.34 g L(-1) kg(-1) (95% CI: -0.65,-0.02), P = 0.04], but not in monozygotic twin pairs [-0.12 g L(-1) kg(-1) (95% CI: -0.53, 0.28), P = 0.54]. These results support the possibility that genetic factors may contribute to the association between low birth weight and clottable fibrinogen levels.

Effects of Se-depletion on glutathione peroxidase and selenoprotein W gene expression in the colon

Selenium (Se)-containing proteins have important roles in protecting cells from oxidative damage. This work investigated the effects of Se-depletion on the expression of the genes encoding selenoproteins in colonic mucosa from rats fed diets of different Se content and in human intestinal Caco-2 cells grown in Se-adequate or Se-depleted culture medium. Se-depletion produced statistically significant (P<0.05) falls in glutathione peroxidase (GPX) 1 mRNA (60-83%) and selenoprotein W mRNA (73%) levels, a small but significant fall in GPX4 mRNA (17-25%) but no significant change in GPX2. The data show that SelW expression in the colon is highly sensitive to Se-depletion.

Size at Birth, Fasting Glucose and Insulin Levels and Insulin Resistance in Adult Twins

Studies in singletons have found an association between birthweight and Type 2 diabetes in adult life. The aim of this study was to investigate whether this association could also be seen in twins. 59 monozygotic (MZ) and 69 dizygotic (DZ) same-sex twin pairs aged 19-50 years and 89 singleton controls matched for age, gestational age, gender, maternal age and parity were recruited from a local obstetric database. Associations between adult glucose, HbA(1)C and insulin levels and insulin resistance and birthweight were assessed by linear regression with adjustment for confounding variables. Twins were significantly lighter at birth than singleton controls, but there were no significant differences in adult weight, glucose, HbA(1)C and insulin levels or insulin resistance between twins and controls. The relationship between birthweight and fasting glucose and insulin levels, and insulin resistance was not significantly different from zero in either twins or controls, but birthweight was significantly negatively associated with HbA(1)C only in controls. There was no evidence of a difference between MZ and DZ twins in unpaired or within-pair analysis. These results provide little evidence that low birthweight in twins increases the risk of impaired glucose-insulin metabolism in young adults or that genetic factors can account for the association observed in singletons.

Randomised trial of the effect of orlistat on body weight and cardiovascular disease risk profile in obese patients: UK Multimorbidity Study

The potential effect of orlistat on cardiovascular co-morbidities may have been previously underestimated. This study assesses the efficacy of orlistat therapy for weight loss and cardiovascular risk factor reduction in obese patients with cardiovascular risk. This was a 54-week, double-blind, randomised, placebo-controlled, parallel group study with 531 patients being randomised. Mean weight loss was significantly greater with orlistat than with placebo (5.8% vs 2.3%; p<0.0001). Orlistat was also associated with significantly greater improvements than placebo in diastolic BP (-5.5 vs -3.1 mmHg; p<0.01), systolic blood pressure (-6.0 vs -2.3 mmHg; p<0.01), oral glucose tolerance test (-0.37 vs +0.09 mmol/l; p<0.05), fasting glucose (-0.19 vs +0.06 mmol/l; p<0.05), total cholesterol (-1.31% vs +3.78%; p<0.0001), LDL-cholesterol (-7.09% vs -0.55%; p<0.0001) and waist circumference (-5.99 vs -2.60 cm; p<0.0001). Orlistat was well tolerated. Orlistat weight loss is associated with improvements in cardiovascular co-morbidities, and hence cardiovascular risk.

Effects of smoking and abstention from smoking on fibrinogen synthesis in humans

Cigarette smoking and hyperfibrinogenaemia are both significant risk factors for the development of cardiovascular disease. Two studies are described here which aimed to establish the metabolic mechanism responsible for the raised plasma fibrinogen concentration observed in smokers. Chronic smokers had a significantly elevated absolute rate of fibrinogen synthesis (ASR) compared with non-smokers (22.7 +/- 1.3 mg/kg per day versus 16.0 +/- 1.3 mg/kg per day; means +/- S.E.M., P < 0.01), with plasma levels of fibrinogen significantly correlated with fibrinogen synthesis (r = 0.65, P = 0.04). Unlike fibrinogen, plasma albumin concentrations were lower in smokers than in non-smokers (45 +/- 0.4 versus 47 +/- 0.7 g/l, P < 0.05), but there was no difference in rates of albumin synthesis between the two groups. Two weeks cessation from smoking by previously chronic smokers was associated with a rapid and marked fall in plasma fibrinogen concentration (from 3.06 +/- 0.11 g/l to 2.49 +/- 0.14 g/l, P < 0.001), and a significant reduction in ASR (a 33% reduction, from 24.1 +/- 1.7 to 16.1 +/- 1.0 mg/kg per day, P < 0.001). These studies suggest a primary role for increased synthesis in producing the hyperfibrinogenaemia associated with smoking. Moreover, abstention from smoking for a period of only 2 weeks induces a significant decrease in the rate of fibrinogen synthesis by the liver, with a concomitant reduction in the plasma fibrinogen concentration.