Exercise effects on perivascular adipose tissue: endocrine and paracrine determinants of vascular function.

Obesity is a global epidemic, accompanied by increased risk of type 2 diabetes and cardiovascular disease. Adipose tissue hypertrophy is associated with adipose tissue inflammation, which alters the secretion of adipose tissue-derived bioactive products, known as adipokines. Adipokines determine vessel wall properties such as smooth muscle tone and vessel wall inflammation. Exercise is a mainstay of prevention of chronic, non-communicable diseases, type 2 diabetes and cardiovascular disease in particular. Aside from reducing adipose tissue mass, exercise has been shown to reduce inflammatory activity in this tissue. Mechanistically, contracting muscles release bioactive molecules known as myokines, which alter the metabolic phenotype of adipose tissue. In adipose tissue, myokines induce browning, enhance fatty acid oxidation and improve insulin sensitivity. In the past years, the perivascular adipose tissue (PVAT) which surrounds the vasculature, has been shown to control vascular tone and inflammation through local release of adipokines. In obesity, an increase in mass and inflammation of PVAT culminate in dysregulation of adipokine secretion, which contributes to vascular dysfunction. This review describes our current understanding of the mechanisms by which active muscles interact with adipose tissue and improve vascular function. Aside from the exercise-dependent regulation of canonical adipose tissue function, we will focus on the interactions between skeletal muscle and PVAT and the role of novel myokines, such as IL-15, FGF21 and irisin, in these interactions. LINKED ARTICLES: This article is part of a themed section on Molecular Mechanisms Regulating Perivascular Adipose Tissue - Potential Pharmacological Targets? To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v174.20/issuetoc.

Associations of birth weight, linear growth and relative weight gain throughout life with abdominal fat depots in adulthood: the 1982 Pelotas (Brazil) birth cohort study.

BACKGROUND: Several studies have reported on associations of size at birth and early growth with general and central obesity; however, few have examined the potential effects of birth weight and postnatal growth on separate abdominal fat compartments. We investigated the effects of size at birth, linear growth and relative weight gain from birth to adulthood on visceral (VFT) and subcutaneous abdominal (SAFT) fat thicknesses at age 30 years. METHODS: A total of 2663 participants from the 1982 Pelotas (Brazil) birth cohort study had complete information on ultrasound measures of abdominal fat at age 30 years, and anthropometric measurements for at least five visits (0/2/4/23/30 years). We estimated weight and height Z-score changes, conditional relative weight gain and conditional height at several ages. RESULTS: In both men and women, VFT and SAFT showed positive associations with conditional relative weight gain during all age periods beyond 2 years and birth, respectively (all P⩽0.01). Women born with intrauterine growth restriction (IUGR) had greater VFT than other women (difference=0.15 s.d., 95% CI: 0.01-0.29), and they showed a stronger positive influence of infant weight gain 0-2 years on VFT (IUGR: ß=0.17 s.d., 95% CI: 0.05-0.29; non-IUGR: ß=0.01 s.d., 95% CI: -0.04 to 0.06; Pinteraction=0.02). Stunting at 2 years was associated with lower SAFT but not VFT, and it modified the influence of weight gain 2-4 years on SAFT in both sexes (both Pinteraction<0.05). CONCLUSIONS: Our findings reinforce the advantages of being born with an appropriate birth weight, and the hazards of rapid postnatal gains in weight relative to linear growth, particularly after the critical window of the first 1000 days.

Cardiovascular and all-cause mortality in relation to various anthropometric measures of obesity in Europeans.

BACKGROUND AND AIMS: Cardiovascular and all-cause mortality in relation to various anthropometric measures of obesity is still controversial. METHODS AND RESULTS: Body mass index (BMI), waist circumference (WC), waist-to-height ratio (WHtR), waist-to-hip ratio (WHR), A Body Shape Index (ABSI) and waist-to-hip-to-height ratio (WHHR) were measured at baseline in a cohort of 46,651 European men and women aged 24-99 years. The relationship between anthropometric measures of obesity and mortality was evaluated by the Cox proportional hazards model with age as a time-scale and with threshold detected by a piecewise regression model. Over a median follow-up of 7.9 years, 2381 men and 1055 women died, 1071 men (45.0%) and 339 women (32.1%) from cardiovascular disease (CVD). BMI had a J-shaped relationship with CVD mortality, whereas anthropometric measures of abdominal obesity had positive linear relationships. BMI, WC and WHtR showed J-shaped associations with all-cause mortality, whereas WHR, ABSI and WHHR demonstrated positive linear relationships. Accordingly, a threshold value was detected at 29.29 and 30.98 kg/m(2) for BMI, 96.4 and 93.3 cm for WC, 0.57 and 0.60 for WHtR, 0.0848 and 0.0813 m(11/6) kg(-2/3) for ABSI with CVD mortality in men and women, respectively; 29.88 and 29.50 kg/m(2) for BMI, 104.3 and 105.6 for WC, 0.61 and 0.67 for WHtR, 0.95 and 0.86 for WHR, 0.0807 and 0.0765 for ABSI in men and women, respectively, and 0.52 for WHHR in women with all-cause mortality. CONCLUSION: All anthropometric measures of abdominal obesity had positive linear associations with CVD mortality, whereas some showed linear and the others J-shaped relationships with all-cause mortality. BMI had a J-shaped relationship with either CVD or all-cause mortality. Thresholds detected based on mortality may help with clinical definition of obesity in relation to mortality.

Comparison of various surrogate obesity indicators as predictors of cardiovascular mortality in four European populations.

BACKGROUND/OBJECTIVES: Body mass index (BMI) is the most commonly used surrogate marker for evaluating the risk of cardiovascular disease (CVD) mortality in relation to general obesity, while abdominal obesity indicators have been proposed to be more informative in risk prediction. SUBJECT/METHODS: A prospective cohort study consisting of 46 651 Europeans aged 24-99 years was conducted to investigate the relationship between CVD mortality and different obesity indicators including BMI, waist circumference (WC), waist-to-hip ratio (WHR), waist-to-stature ratio (WSR), A Body Shape Index (ABSI) and waist-to-hip-to-height ratio (WHHR). Hazard ratio (HR) was estimated by the Cox proportional hazards model using age as timescale, and compared using paired homogeneity test. RESULTS: During a median follow-up of 7.9 years, 3435 participants died, 1409 from CVD. All obesity indicators were positively associated with increased risk of CVD mortality, with HRs (95% confidence intervals) per standard deviation increase of 1.19 (1.12-1.27) for BMI, 1.29 (1.21-1.37) for WC, 1.28 (1.20-1.36) for WHR, 1.35 (1.27-1.44) for WSR, 1.34 (1.26-1.44) for ABSI and 1.34 (1.25-1.42) for WHHR in men and 1.37 (1.24-1.51), 1.49 (1.34-1.65), 1.45 (1.31-1.60), 1.52 (1.37-1.69), 1.32 (1.18-1.48) and 1.45 (1.31-1.61) in women, respectively. The prediction was stronger with abdominal obesity indicators than with BMI or ABSI (P<0.05 for all paired homogeneity tests). WSR appeared to be the strongest predictor among all the indicators, with a linear relationship with CVD mortality in both men and women. CONCLUSIONS: Abdominal obesity indicators such as WC, WHR, WSR and WHHR, are stronger predictors for CVD mortality than general obesity indicator of BMI.

Insulin's microvascular vasodilatory effects are inversely related to peripheral vascular resistance in overweight, but insulin-sensitive subjects.

OBJECTIVE: The mechanisms underlying obesity-related hypertension are incompletely understood. Microvascular dysfunction might play a role by increasing peripheral vascular resistance (PVR). Metabolic and microvascular effects of insulin are impaired in obesity, but how these impairments contribute to disturbed blood pressure homeostasis is unclear. Specifically, it is unknown whether local microvascular vasoactive effects of insulin play a role in determining systemic vascular resistance. The aim of this study was to investigate the association between PVR and local microvascular effects of insulin. DESIGN AND METHODS: Thirty-seven healthy, overweight subjects (age 25-55 years, BMI 25-30 kg/m(2) ) were cross-sectionally studied. Local insulin-mediated vasodilation was measured using skin laser Doppler fluxmetry combined with transcutaneous iontophoresis of insulin. For comparison, local vasodilatory effects of acetylcholine and sodium nitroprusside were measured. PVR was calculated from mean arterial pressure and cardiac output, assessed by pulse-dye densitometry. RESULTS: PVR was inversely correlated with insulin-mediated vasodilation (r = -0.50; P < 0.01). This finding was maintained after adjustment for age, sex, blood pressure, and smoking. PVR was not associated with local microvascular effects of acetylcholine. CONCLUSIONS: Our study in overweight subjects suggests that insulin's role in the microvasculature may contribute to blood pressure control.

The insulin dilemma in resource-limited countries. A way forward?

The International Insulin Foundation (IIF) has developed and validated a needs-assessment instrument called the Rapid Assessment Protocol for Insulin Access (RAPIA) which has been used in seven countries in four continents to analyse the constraints to delivering effective continuing care for people with diabetes. One major contributor to the difficulties in availability of insulin is a failure to use the least costly sources and types of insulin and other effective drugs for diabetes. The purchase of insulins can consume as much as 10% of government expenditure on drugs, this being highly sensitive to the selection of newer analogue insulins as first-choice options, which cost between three and 13 times more than biosynthetic human insulin. Insulin cartridges for use with injection pens further add to costs. Similar considerations apply to most of the newer treatments for people with type 2 diabetes, which may cost up to 40 times more than metformin and sulfonylureas, still considered first-line drugs by European and US guidelines. Both biosynthetic human insulin and the first-line oral hypoglycaemic drugs are available from generic manufacturers. With the present price differentials, there is thus a growing need for countries involved in tendering for sourcing insulin to be provided with the guarantees of Good Manufacturing Practice, quality and bioequivalence, which would come from a WHO Pre-Qualification Scheme as currently exists for a variety of drugs for chronic diseases, both communicable and non-communicable. The IIF has developed a position statement on the provision and choice of diabetes treatments in resource-limited settings which should be applicable wherever consideration of resources is a component of therapeutic decision making.

The Diabetes UK Mozambique Twinning Programme. Results of improvements in diabetes care in Mozambique: a reassessment 6 years later using the Rapid Assessment Protocol for Insulin Access.

OBJECTIVE: To assess improvements in diabetes care in Mozambique between 2003 and 2009 following the implementation of the Diabetes UK Twinning Programme. METHODS: As in 2003, a Rapid Assessment Protocol was implemented from August to September 2009 in order to assess the improvements in diabetes care and impact of the Diabetes UK Twinning Programme. One hundred and eighty-four interviews were carried out at different levels of the health system in different areas of Mozambique. RESULTS: The Diabetes UK Twinning Programme in Mozambique allowed the development of the first comprehensive non-communicable disease plan in sub-Saharan Africa. The other main improvements include a strengthening of the diabetes association with an 8-fold increase in membership, 265 health workers trained in diabetes care in all provinces, the development of patient education materials inspired by some Diabetes UK tools and the expansion of public awareness, particularly from events associated with World Diabetes Day. CONCLUSIONS: Much progress has been made in Mozambique with regard to diabetes and non-communicable diseases. Besides the direct impact of specific activities supported by Diabetes UK, this project allowed for 'collateral' benefits in the overall provision of diabetes care. As diabetes and non-communicable diseases have a low profile on the global health agenda, twinning partnerships based on rigorous needs assessment have the capacity to make significant improvements in diabetes care at a relatively low level of investment. Moreover, this study suggests that the tool used might be of value in assessing progress in health system strengthening as well as in conducting the initial needs assessment.

Adiposity, inflammation and hyperglycaemia in rural and urban Indian men: Coronary Risk of Insulin Sensitivity in Indian Subjects (CRISIS) Study.

AIMS/HYPOTHESIS: The aim of this study was to investigate whether the higher prevalence of insulin resistance and glucose intolerance in urban compared with rural Indian men is related to their higher adiposity (percentage body fat) and the associated inflammatory state. METHODS: We studied 149 rural, 142 urban slum and 150 urban middle-class male residents (age 30-50 years), who were selected by stratified random sampling. We measured body fat (bioimpedance), waist circumference, glucose tolerance (75 g OGTT), insulin resistance [homeostasis model assessment (HOMA-IR)], beta cell function (insulinogenic index) and inflammatory markers (total leucocyte count, IL-6, TNF-alpha and C-reactive protein). RESULTS: Adiposity, waist circumference, HOMA-IR, insulinogenic index and both fasting and 120 min plasma glucose concentrations increased progressively from rural through to urban slum and urban middle-class men. Inflammatory markers were higher in urban than in rural men. Adiposity was strongly related to HOMA-IR (r = 0.57, p < 0.001) and to insulinogenic index and glycaemic parameters (r = 0.25, p < 0.001 for both). Adiposity explained approximately two thirds of the difference in HOMA-IR between the urban middle-class men and the rural and slum residents, but its contribution to the difference in insulinogenic index and 120 min plasma glucose concentration was not significant. Inclusion of C-reactive protein, IL-6 and total leucocyte count in the models did not further explain these results, nor did the inclusion of waist circumference. There was a significant residual difference after these adjustments. CONCLUSIONS/INTERPRETATION: Adiposity is a major contributor to the difference in insulin resistance between rural and urban Indian men; there was no additional contribution from inflammation or central obesity. Other unmeasured factors also seem to contribute to the metabolic differences between rural and urban men.

Inflammation, obesity, and the metabolic syndrome.

Adipose tissue expresses cytokines which inhibit insulin signalling pathways. Obesity also results in impairment of endothelium-dependent vasodilatation to insulin. We have previously suggested that adipocytokines might contribute to the coexistence of insulin resistance and endothelial dysfunction. However, the adipocytokine best characterised as causing insulin resistance is tumour necrosis factor-alpha (TNF-alpha), a molecule which under normal circumstances circulates in low concentrations. We propose a vasoregulatory role for local deposits of fat around blood vessels, which may contribute both to insulin action and to vascular endothelial dysfunction. In particular, we propose that the localised fat depot around the origin of skeletal muscle arterioles may play a physiological role in blood flow distribution. Isolated rat arterioles are under dual regulation by insulin, which activates both endothelin-1 mediated vasoconstriction and nitric oxide mediated vasodilatation. In obese rat arterioles, insulin-stimulated nitric oxide synthesis is impaired, resulting in unopposed vasoconstriction. We propose this to be the consequence of production of TNF-alpha from the fat surrounding the vessel origin - a depot to which we ascribe a specialist vasoregulatory role. We suggest that this cytokine accesses the nutritive vascular tree to inhibit insulin-mediated capillary recruitment - a mechanism we term 'vasocrine' signalling. We also suggest a homology between periarteriolar fat and both periarterial and visceral fat, which may, through outside-to-inside signalling, play a direct role in producing the inflammatory changes found in atherosclerotic plaques, so explaining relationships between visceral fat, insulin resistance, and vascular disease.

Association of plasminogen activator inhibitor (PAI)-1 (SERPINE1) SNPs with myocardial infarction, plasma PAI-1, and metabolic parameters: the HIFMECH study.

OBJECTIVE: The purpose of this study was to investigate the effects of plasminogen activator inhibitor-1 (PAI-1) gene (SERPINE1) single nucleotide polymorphisms (SNPs) on the risk of myocardial infarction (MI), on PAI-1 levels, and factors related to the metabolic syndrome. METHODS AND RESULTS: Eleven SNPs capturing the common genetic variation of the SERPINE1 gene were genotyped in the HIFMECH study. In the 510 male cases and their 543 age-matched controls, a significant gene-smoking interaction was observed. In nonsmokers, the rs7242-G allele was more frequent in cases than in controls (0.486 versus 0.382, P=0.013) whereas the haplotype derived from the rs2227631 (-844A>G)-G and rs2227683-A alleles was approximately 3-fold lower in cases than in controls (0.042 versus 0.115, P=0.006). SERPINE1 haplotypes explained 3.5% (P=0.007) of the variability of PAI-1 levels, which was attributable to the combined effects of 3 SNPs, -844A>G, rs2227666, and rs2227694. The rs6092 (Ala15Thr) and rs7242 SNPs acted additively to explain 4.4% of the variability of plasma insulin levels and 1.6% of the variability of BMI (P<10(-3) and P=0.023, respectively). CONCLUSIONS: SERPINE1 haplotypes are mildly associated with plasma levels of PAI-1 and with the risk of MI in nonsmokers. They are also associated with insulin levels and BMI.

Insulin resistance and the metabolic syndrome--or the pitfalls of epidemiology.

The clustering of dyslipidaemia, hypertension and glucose intolerance, predominantly in overweight individuals, has been ascribed many names, including syndrome X and the metabolic syndrome. In Reaven's original description of syndrome X, a central aetiological role was attributed to insulin resistance, and this assumption has remained as the dominant paradigm for the metabolic syndrome. There are a number of conceptual problems in such a model, particularly those arising from observations that several novel markers, including measures of endothelial dysfunction and of low-grade inflammation, are as closely related to insulin resistance as are the classic components of the syndrome. Because it is difficult to envisage how these traits might develop as a consequence of insulin resistance, such observations indicate the need for a new paradigm to explain the mechanisms of association better. It has been proposed that a state of low-grade inflammation, consequent upon the production of adipocytokines, particularly from truncal fat, explains the observed relationships between insulin resistance and endothelial dysfunction better than does a model revolving around insulin resistance. Furthermore, the inflammatory cytokines generated from adipose tissue may influence vessel endothelial function without elevations in circulating concentrations. This review alludes to several problems inherent in the epidemiological method in understanding disease mechanisms. These include crude biological measures, the use of venous systemic fasting samples, imprecision of assays, naive physiological models, simplistic statistical approaches and, without clinical trials, an inability to test causation. Integrated systems biology needs more complex approaches to investigate disease mechanisms, involving cell, organ, whole organism and population studies.

Vitamin B12 deficiency and hyperhomocysteinemia in rural and urban Indians.

BACKGROUND: Low vitamin B12 concentration in South Asian Indians is common, but the exact prevalence is not known. AIM: To investigate prevalence and associations of low vitamin B12 concentration and hyperhomocysteinemia in rural and urban Indian men living in and around Pune, Maharashtra. METHOD: We studied 441 middle-aged men (149 rural, 142 slum and 150 urban middle-class residents, mean age 39 y). Data on lifestyle, socio-economic status, nutrition and medical history were obtained. Circulating concentrations of vitamin B12, folate, ferritin, total homocysteine (tHcy), and haematological indices, and cardiovascular risk variables were measured. RESULTS: Median plasma B12 concentration was low (110 pmol/L): Overall, 67% of men had low vitamin B12 concentration (<150 pmol/L) and 58% had hyperhomocysteinemia (>15 micromol/L). Of the urban middle class, 81% had low vitamin B12 concentration and 79% had hyperhomocysteinemia. Low vitamin B12 concentration contributed 28% to the risk of hyperhomocysteinemia (population attributable risk) while low red cell folate contributed 2%. Vegetarians had 4.4 times (95% CI 2.1, 9.4) higher risk of low vitamin B12 concentrations and 3.0 times (95% CI 1.4, 6.5) higher risk of hyperhomocysteinemia compared to those who ate non-vegetarian foods frequently. Urban middle-class residence was an additional independent risk factor of hyperhomocysteinemia (odds ratio 7.6 (95% CI 2.5, 22.6), compared to rural men). Low vitamin B12 concentration was related to lower blood haemoglobin concentration and higher mean corpuscular volume, but macrocytic anemia was rare. CONCLUSION: Low vitamin B12 concentration and hyperhomocysteinemia are common in Indian men, particularly in vegetarians and urban middle class residents. Further studies are needed to confirm these findings in other parts of India.

EPCR Ser219Gly: elevated sEPCR, prothrombin F1+2, risk for coronary heart disease, and increased sEPCR shedding in vitro.

We have progressively analysed three studies of coronary heart disease (CHD) for a variant in EPCR (Ser219Gly). Initially, in a prospective study, NPHSII, while no overall CHD-risk was identified in heterozygotes, homozygotes for 219Gly exhibited a three-fold elevated risk (HR 3.3, CI 1.22-8.96). In diabetics within NPHSII, there was a suggestion that 219Gly+ was associated with elevated CHD-risk (HR 1.89, CI 0.39-9.06) although numbers were small. To further assess the effect of the variant in diabetes, a case-control study of MI, HIFMECH, was used, in which previous analysis had defined a group with metabolic syndrome, by factor analysis. A significant CHD-risk interaction was identified between genotype and the 'metabolic syndrome' factor (interaction p=0.009). To further assess CHD-risk for this variant in type-2 diabetes and to assess the effect of the variant upon thrombin generation and plasma levels of soluble EPCR, a cross-sectional study of type-2 diabetes was used. A significant CHD-risk was identified for European Whites (OR 2.84, CI 1.38-5.85) and Indian Asians in this study (OR 1.6, CI 1.00-2.57) and the frequency of 219Gly was two-fold higher in Indian Asians. Soluble EPCR levels were strongly associated with genotype, with homozygotes for 219Gly having four-fold higher levels (p<0.0001). In vitro studies of EPCR-transfected cells suggested increased basal release of sEPCR from cells expressing the 219Gly EPCR phenotype. Furthermore, in base-line samples from NPHSII and in the diabetic study, a significant increase in prothrombin F1+2 level was observed for 219Gly. The increased CHD-risk and thrombin generation appears to be acting through increased shedding of the Gly allele from the cell surface.

Body fat measurement in Indian men: comparison of three methods based on a two-compartment model.

UNLABELLED: Obesity is a major risk factor for diabetes and related disorders. The current classification of obesity is based on body mass index (BMI, kg/m(2)), which is a surrogate for the total body fat. Since the relationship between BMI and body fat varies in different populations, an independent validation of the BMI-body fat relationship in the population of interest is desirable. OBJECTIVES: (1) To study the validity of field methods of measuring body fat (multiple skinfolds and bioimpedance) against a criterion method (deuterium dilution) and (2) To compare the prevalence of obesity (WHO 2000 criteria for BMI) with adiposity (body fat >25%) in middle-aged Indian men in rural and urban Pune. DESIGN: Community-based multistage stratified random sampling of middle-aged men from rural and urban Pune for study of body composition and cardiovascular risk. A third of these men, selected to represent wide BMI distribution, were studied for body fat measurements by specific methods. SUBJECTS: A total of 141 healthy men, approximately similar number from rural, urban slums and middle class from Pune. They were 39.3 (+/-6.2) y old and had a BMI of 21.9 (+/-3.7) kg/m(2). MEASUREMENTS: Anthropometry (height, weight and multiple skinfold thicknesses) by trained observers using standardised technique to calculate body fat by Durnin and Womersley's equation. Total body water and body fat by bioelectrical impedance analysis (BIA) and deuterium oxide dilution (D(2)O). RESULTS: Mean total body fat was 14.3 kg (23.0%) by anthropometry, 16.5 kg (26.0%) by BIA and 15.3 kg (24.6%) by D(2)O method. Although there was a good correlation between fat estimation by three methods (r= approximately 0.9, P<0.001 all), compared to D(2)O method anthropometry underestimated body fat by 1.0 kg and BIA overestimated fat by 1.2 kg (P<0.001 both). Using the standard cut-point of 25% body fat for 'adiposity' 29.5% rural, 46.0% slum and 75.0% middle class men were adipose. These proportions were considerably higher than the number of men who were 'preobese' (BMI> or =25-29.9 kg/m(2), 9.0% rural, 22.0% urban slums and 27.0% urban middle class) and 'obese' (BMI >30 kg/m(2), 4.0% urban slums, none in rural and urban middle class). CONCLUSION: We recommend that future studies assessing risk for chronic diseases in Indians should measure adiposity by anthropometry (multiple skinfolds) or BIA (calibrated for Indians) rather than relying only on BMI cut-points.