Responses of gut microbiota and glucose and lipid metabolism to prebiotics in genetic obese and diet-induced leptin-resistant mice

OBJECTIVE

To investigate deep and comprehensive analysis of gut microbial communities and biological parameters after prebiotic administration in obese and diabetic mice.

RESEARCH DESIGN AND METHODS

Genetic (ob/ob) or diet-induced obese and diabetic mice were chronically fed with prebiotic-enriched diet or with a control diet. Extensive gut microbiota analyses, including quantitative PCR, pyrosequencing of the 16S rRNA, and phylogenetic microarrays, were performed in ob/ob mice. The impact of gut microbiota modulation on leptin sensitivity was investigated in diet-induced leptin-resistant mice. Metabolic parameters, gene expression, glucose homeostasis, and enteroendocrine-related L-cell function were documented in both models.

RESULTS

In ob/ob mice, prebiotic feeding decreased Firmicutes and increased Bacteroidetes phyla, but also changed 102 distinct taxa, 16 of which displayed a >10-fold change in abundance. In addition, prebiotics improved glucose tolerance, increased L-cell number and associated parameters (intestinal proglucagon mRNA expression and plasma glucagon-like peptide-1 levels), and reduced fat-mass development, oxidative stress, and low-grade inflammation. In high fat-fed mice, prebiotic treatment improved leptin sensitivity as well as metabolic parameters.

CONCLUSIONS

We conclude that specific gut microbiota modulation improves glucose homeostasis, leptin sensitivity, and target enteroendocrine cell activity in obese and diabetic mice. By profiling the gut microbiota, we identified a catalog of putative bacterial targets that may affect host metabolism in obesity and diabetes.

The association between symptomatic, severe hypoglycaemia and mortality in type 2 diabetes: retrospective epidemiological analysis of the ACCORD study

OBJECTIVE

To determine whether there is a link between hypoglycaemia and mortality among participants in the Action to Control Cardiovascular Risk in Diabetes (ACCORD) trial.

DESIGN

Retrospective epidemiological analysis of data from the ACCORD trial. Setting Diabetes clinics, research clinics, and primary care clinics.

PARTICIPANTS

Patients were eligible for the ACCORD study if they had type 2 diabetes, a glycated haemoglobin (haemoglobin A(1C)) concentration of 7.5% or more during screening, and were aged 40-79 years with established cardiovascular disease or 55-79 years with evidence of subclinical disease or two additional cardiovascular risk factors. Intervention Intensive (haemoglobin A(1C) <6.0%) or standard (haemoglobin A(1C) 7.0-7.9%) glucose control.

OUTCOME MEASURES

Symptomatic, severe hypoglycaemia, manifest as either blood glucose concentration of less than 2.8 mmol/l (<50 mg/dl) or symptoms that resolved with treatment and that required either the assistance of another person or medical assistance, and all cause and cause specific mortality, including a specific assessment for involvement of hypoglycaemia.

RESULTS

10 194 of the 10 251 participants enrolled in the ACCORD study who had at least one assessment for hypoglycaemia during regular follow-up for vital status were included in this analysis. Unadjusted annual mortality among patients in the intensive glucose control arm was 2.8% in those who had one or more episodes of hypoglycaemia requiring any assistance compared with 1.2% for those with no episodes (53 deaths per 1924 person years and 201 deaths per 16 315 person years, respectively; adjusted hazard ratio (HR) 1.41, 95% CI 1.03 to 1.93). A similar pattern was seen among participants in the standard glucose control arm (3.7% (21 deaths per 564 person years) v 1.0% (176 deaths per 17 297 person years); adjusted HR 2.30, 95% CI 1.46 to 3.65). On the other hand, among participants with at least one hypoglycaemic episode requiring any assistance, a non-significantly lower risk of death was seen in those in the intensive arm compared with those in the standard arm (adjusted HR 0.74, 95% 0.46 to 1.23). A significantly lower risk was observed in the intensive arm compared with the standard arm in participants who had experienced at least one hypoglycaemic episode requiring medical assistance (adjusted HR 0.55, 95% CI 0.31 to 0.99). Of the 451 deaths that occurred in ACCORD up to the time when the intensive treatment arm was closed, one death was adjudicated as definitely related to hypoglycaemia.

CONCLUSION

Symptomatic, severe hypoglycaemia was associated with an increased risk of death within each study arm. However, among participants who experienced at least one episode of hypoglycaemia, the risk of death was lower in such participants in the intensive arm than in the standard arm. Symptomatic, severe hypoglycaemia does not appear to account for the difference in mortality between the two study arms up to the time when the ACCORD intensive glycaemia arm was discontinued.

TRIAL REGISTRATION

NCT00000620.

Lipid lowering and plaque regression. New insights into prevention of plaque disruption and clinical events in coronary disease

The consensus of evidence from angiographic trials demonstrates both coronary artery and clinical benefits from lowering of lipids by a variety of regimens. The findings of reduced arterial disease progression and increased regression have been convincing but, at best, modest in their magnitude. For example, among those treated intensively in FATS, the mean improvement in proximal stenosis severity per patient was < 1% stenosis, and only 12% of all lesions showed convincing regression. In view of these modest arterial benefits, the associated reductions in cardiovascular events have been surprisingly great. For example, coronary events were reduced 75% in FATS; this was entirely a result of a 93% reduction in the likelihood that a mildly or moderately diseased arterial segment would experience substantial progression to a severe lesion at the time of a clinical event. We believe that the magnitude of the clinical benefit is best explained in terms of this observation, according to the following lines of reasoning. Clinical events most commonly spring from lesions that are initially of mild or moderate severity and then abruptly undergo a disruptive transformation to a severe culprit lesion. The process of plaque fissuring, leading to plaque disruption and thrombosis, triggers most clinical coronary events. Fissuring is predicted by a large accumulation of core lipid in the plaque and by a high density of lipid-laden macrophages in its thinned fibrous cap. Lesions with these characteristics constitute only 10-20% of the overall lesion population but account for 80-90% of the acute clinical events. In the experimental setting, normalization of an atherogenic lipid profile substantially decreases the number of lipid-laden intimal macrophages (foam cells) and depletes cholesterol from the core lipid pool. In the clinical setting, intensive lipid lowering virtually halts the progression of mild and moderate lesions to clinical events. Thus, the reduction in clinical events observed in these trials appears to be best explained by the relation of the lipid and foam cell content of the plaque to its likelihood of fissuring and by the effects of lipid-lowering therapy on these "high-risk" features of plaque morphology. The composite of data presented here supports the hypothesis that lipid-lowering therapy selectively depletes (regresses) that relatively small but dangerous subgroup of fatty lesions containing a large lipid core and dense clusters of intimal macrophages. By doing so, these lesions are effectively stabilized and clinical event rate is accordingly decreased.

Interaction of cardiovascular risk factors with myocardial ischemia/reperfusion injury, preconditioning, and postconditioning

Therapeutic strategies to protect the ischemic myocardium have been studied extensively. Reperfusion is the definitive treatment for acute coronary syndromes, especially acute myocardial infarction; however, reperfusion has the potential to exacerbate lethal tissue injury, a process termed "reperfusion injury." Ischemia/reperfusion injury may lead to myocardial infarction, cardiac arrhythmias, and contractile dysfunction. Ischemic preconditioning of myocardium is a well described adaptive response in which brief exposure to ischemia/reperfusion before sustained ischemia markedly enhances the ability of the heart to withstand a subsequent ischemic insult. Additionally, the application of brief repetitive episodes of ischemia/reperfusion at the immediate onset of reperfusion, which has been termed "postconditioning," reduces the extent of reperfusion injury. Ischemic pre- and postconditioning share some but not all parts of the proposed signal transduction cascade, including the activation of survival protein kinase pathways. Most experimental studies on cardioprotection have been undertaken in animal models, in which ischemia/reperfusion is imposed in the absence of other disease processes. However, ischemic heart disease in humans is a complex disorder caused by or associated with known cardiovascular risk factors including hypertension, hyperlipidemia, diabetes, insulin resistance, atherosclerosis, and heart failure; additionally, aging is an important modifying condition. In these diseases and aging, the pathological processes are associated with fundamental molecular alterations that can potentially affect the development of ischemia/reperfusion injury per se and responses to cardioprotective interventions. Among many other possible mechanisms, for example, in hyperlipidemia and diabetes, the pathological increase in reactive oxygen and nitrogen species and the use of the ATP-sensitive potassium channel inhibitor insulin secretagogue antidiabetic drugs and, in aging, the reduced expression of connexin-43 and signal transducer and activator of transcription 3 may disrupt major cytoprotective signaling pathways thereby significantly interfering with the cardioprotective effect of pre- and postconditioning. The aim of this review is to show the potential for developing cardioprotective drugs on the basis of endogenous cardioprotection by pre- and postconditioning (i.e., drug applied as trigger or to activate signaling pathways associated with endogenous cardioprotection) and to review the evidence that comorbidities and aging accompanying coronary disease modify responses to ischemia/reperfusion and the cardioprotection conferred by preconditioning and postconditioning. We emphasize the critical need for more detailed and mechanistic preclinical studies that examine car-dioprotection specifically in relation to complicating disease states. These are now essential to maximize the likelihood of successful development of rational approaches to therapeutic protection for the majority of patients with ischemic heart disease who are aged and/or have modifying comorbid conditions.

Health Benefits of the Mediterranean Diet: Metabolic and Molecular Mechanisms

Consuming a Mediterranean diet rich in minimally processed plant foods has been associated with a reduced risk of developing multiple chronic diseases and increased life expectancy. Data from several randomized clinic trials have demonstrated a beneficial effect in the primary and secondary prevention of cardiovascular disease, type 2 diabetes, atrial fibrillation, and breast cancer. The exact mechanism by which an increased adherence to the traditional Mediterranean diet exerts its favorable effects is not known. However, accumulating evidence indicates that the five most important adaptations induced by the Mediterranean dietary pattern are: (a) lipid-lowering effect, (b) protection against oxidative stress, inflammation and platelet aggregation, (c) modification of hormones and growth factors involved in the pathogenesis of cancer, (d) inhibition of nutrient sensing pathways by specific amino acid restriction, and (e) gut microbiota-mediated production of metabolites influencing metabolic health. More studies are needed to understand how single modifications of nutrients typical of the Mediterranean diet interact with energy intake, energy expenditure, and the microbiome in modulating the key mechanisms that promote cellular, tissue, and organ health during aging.

Inflammatory bio-markers and cardiovascular risk prediction

Inflammatory processes are now recognized to play a central role in the pathogenesis of atherosclerosis and its complications. Plasma levels of several markers of inflammation have been found to be associated with future cardiovascular risk in a variety of clinical settings. These markers include cell adhesion molecules, cytokines, pro-atherogenic enzymes and C-reactive protein (CRP). Initially thought of as an inactive downstream marker of the inflammatory cascade, emerging evidence suggests that CRP may be directly involved in atherogenesis, and that arterial plaque can produce CRP, independent of traditional hepatic pathways. In addition to being a strong predictor of future cardiovascular risk amongst patients presenting with acute coronary syndromes, numerous studies have found that baseline levels of CRP are associated with risk of future myocardial infarction, stroke, peripheral vascular disease and cardiovascular death amongst apparently healthy populations. The combination of measurement of a marker of inflammation with lipid testing may improve upon risk stratification based on lipid testing alone, and intensification of programmes for exercise, weight loss, and smoking cessation is recommended for those with elevated CRP levels. Further trials are needed to confirm the potential benefits of statins amongst individuals with elevated CRP levels.

Reduction in incidence of diabetes, hypertension and lipid disturbances after intentional weight loss induced by bariatric surgery: the SOS Intervention Study

OBJECTIVE

To examine the effect of a large, long standing and intentional weight reduction on the incidence of diabetes, hypertension and lipid disturbances in severely obese individuals as compared to weight-stable obese controls.

RESEARCH METHODS AND PROCEDURES

The ongoing prospective SOS (Swedish Obese Subjects) intervention consists of a surgically treated group and a matched control group obtaining conventional obesity treatment. This report is based on 845 surgically treated patients and 845 controls (BMI 41.0+/-4.6 kg/m2 (mean+/-standard deviation [S])) followed for 2 years.

RESULTS

Surgically treated patients lost 28+/-15 kg and controls 0.5+/-8.9 kg (p<0.0001). Two-year incidence of hypertension, diabetes, hyperinsulinemia, and lipid disturbances was compared in the two treatment groups. Adjusted odds ratios (95% CI) for the surgically treated group versus controls were 0.38 (0.22, 0.65) for hypertension, 0.02 (0.00, 0.16) for diabetes, 0.10 (0.03, 0.28) for hyperinsulinemia, 0. 10 (0.04, 0.25) for hypertriglyceridemia, 0.28 (0.16, 0.49) for low HDL-cholesterol and 1.24 (0.84, 1.8) for hypercholesterolemia. Compared to controls, the 2-year recovery rates from hypertension, diabetes, hypo-HDL, and hypertriglyceridemia were significantly higher in the surgically treated group.

DISCUSSION

Intentional weight loss in the obese causes a marked reduction in the 2-year incidence of hypertension, diabetes and some lipid disturbances. The results suggest that severe obesity can and should be treated.

Dietary strategies for improving post-prandial glucose, lipids, inflammation, and cardiovascular health

The highly processed, calorie-dense, nutrient-depleted diet favored in the current American culture frequently leads to exaggerated supraphysiological post-prandial spikes in blood glucose and lipids. This state, called post-prandial dysmetabolism, induces immediate oxidant stress, which increases in direct proportion to the increases in glucose and triglycerides after a meal. The transient increase in free radicals acutely triggers atherogenic changes including inflammation, endothelial dysfunction, hypercoagulability, and sympathetic hyperactivity. Post-prandial dysmetabolism is an independent predictor of future cardiovascular events even in nondiabetic individuals. Improvements in diet exert profound and immediate favorable changes in the post-prandial dysmetabolism. Specifically, a diet high in minimally processed, high-fiber, plant-based foods such as vegetables and fruits, whole grains, legumes, and nuts will markedly blunt the post-meal increase in glucose, triglycerides, and inflammation. Additionally, lean protein, vinegar, fish oil, tea, cinnamon, calorie restriction, weight loss, exercise, and low-dose to moderate-dose alcohol each positively impact post-prandial dysmetabolism. Experimental and epidemiological studies indicate that eating patterns, such as the traditional Mediterranean or Okinawan diets, that incorporate these types of foods and beverages reduce inflammation and cardiovascular risk. This anti-inflammatory diet should be considered for the primary and secondary prevention of coronary artery disease and diabetes.

The acute versus the chronic response to exercise

PURPOSE

There is strong and consistent evidence that a single exercise session can acutely reduce triglycerides and increase high-density lipoprotein (HDL) cholesterol (HDL-C), reduce blood pressure, and improve insulin sensitivity and glucose homeostasis. Such observations suggest that at least some of the effects on atherosclerotic cardiovascular disease (ASCVD) risk factors attributed to exercise training may be the result of recent exercise.

RESULTS

These acute and chronic exercise effects cannot be considered in isolation. Exercise training increases the capacity for exercise, thereby permitting more vigorous and/or more prolonged individual exercise sessions and a more significant acute effect. The intensity, duration, and energy expenditure required to produce these acute exercise effects are not clearly defined. The acute effect of exercise on triglycerides and HDL-C appears to increase with overall energy expenditure possibly because the effect maybe mediated by reductions in intramuscular triglycerides. Prolonged exercise appears necessary for an acute effect of exercise on low-density lipoprotein (LDL) cholesterol (LDL-C) levels. The acute effect of exercise on blood pressure is a low threshold phenomenon and has been observed after energy expenditures requiring only 40% maximal capacity. The acute effect of exercise on glucose metabolism appears to require exercise near 70% maximal, but this issue has not been carefully examined.

CONCLUSIONS

Exercise has definite acute effects on blood lipids, blood pressure, and glucose homeostasis. Exercise also has acute effects on other factors related to atherosclerosis such as immunological function, vascular reactivity, and hemostasis. Considerable additional research is required to define the threshold of exercise required to produce these putatively beneficial effects.

Pyridoxamine inhibits early renal disease and dyslipidemia in the streptozotocin-diabetic rat

BACKGROUND

Nonenzymatic reactions between sugars or lipids and protein and formation of advanced glycation and lipoxidation end products (AGE/ALEs) contribute to the chemical modification and cross-linking of tissue proteins with age. Accelerated formation of AGE/ALEs during hyperglycemia is implicated in the development of diabetic complications. In this study, we examined the effect of the AGE/ALE inhibitor pyridoxamine on chemical modification and cross-linking of collagen and development of renal disease in the streptozotocin-diabetic rat.

METHODS

Diabetic rats were treated with pyridoxamine; parallel experiments were conducted with aminoguanidine, the prototype AGE inhibitor. Progression of renal disease was evaluated by measurements of albuminuria and plasma creatinine concentration. Plasma triglycerides, cholesterol, lactate and pyruvate were measured by enzymatic assays, and AGE/ALEs in skin collagen by HPLC and GC-MS assays.

RESULTS

Pyridoxamine significantly inhibited the increase in albuminuria, plasma creatinine, hyperlipidemia and plasma lactate/pyruvate ratio in diabetic rats, without an effect on blood glucose or glycated hemoglobin. AGE/ALEs, fluorescence and cross-linking of skin collagen increased approximately twofold in diabetic versus control rats after seven months of diabetes. Pyridoxamine caused a significant (25 to 50%) decrease the AGE/ALEs, carboxymethyllysine and carboxyethyllysine, cross-linking and fluorescence in skin collagen of diabetic rats, but did not affect pentosidine.

CONCLUSIONS

Pyridoxamine inhibits the progression of renal disease, and decreases hyperlipidemia and apparent redox imbalances in diabetic rats. Pyridoxamine and aminoguanidine had similar effects on parameters measured, supporting a mechanism of action involving AGE/ALE inhibition.

Nut consumption and blood lipid levels: a pooled analysis of 25 intervention trials

BACKGROUND

Epidemiological studies have consistently associated nut consumption with reduced risk for coronary heart disease. Subsequently, many dietary intervention trials investigated the effects of nut consumption on blood lipid levels. The objectives of this study were to estimate the effects of nut consumption on blood lipid levels and to examine whether different factors modify the effects.

METHODS

We pooled individual primary data from 25 nut consumption trials conducted in 7 countries among 583 men and women with normolipidemia and hypercholesterolemia who were not taking lipid-lowering medications. In a pooled analysis, we used mixed linear models to assess the effects of nut consumption and the potential interactions.

RESULTS

With a mean daily consumption of 67 g of nuts, the following estimated mean reductions were achieved: total cholesterol concentration (10.9 mg/dL [5.1% change]), low-density lipoprotein cholesterol concentration (LDL-C) (10.2 mg/dL [7.4% change]), ratio of LDL-C to high-density lipoprotein cholesterol concentration (HDL-C) (0.22 [8.3% change]), and ratio of total cholesterol concentration to HDL-C (0.24 [5.6% change]) (P < .001 for all) (to convert all cholesterol concentrations to millimoles per liter, multiply by 0.0259). Triglyceride levels were reduced by 20.6 mg/dL (10.2%) in subjects with blood triglyceride levels of at least 150 mg/dL (P < .05) but not in those with lower levels (to convert triglyceride level to millimoles per liter, multiply by 0.0113). The effects of nut consumption were dose related, and different types of nuts had similar effects on blood lipid levels. The effects of nut consumption were significantly modified by LDL-C, body mass index, and diet type: the lipid-lowering effects of nut consumption were greatest among subjects with high baseline LDL-C and with low body mass index and among those consuming Western diets.

CONCLUSION

Nut consumption improves blood lipid levels in a dose-related manner, particularly among subjects with higher LDL-C or with lower BMI.

Effects of pioglitazone on adipose tissue remodeling within the setting of obesity and insulin resistance

Obesity and dysfunctional energy partitioning can lead to the development of insulin resistance and type 2 diabetes. The antidiabetic thiazolidinediones shift the energy balance toward storage, leading to an increase in whole-body adiposity. These studies examine the effects of pioglitazone (Pio) on adipose tissue physiology, accumulation, and distribution in female Zucker (fa/fa) rats. Pio treatment (up to 28 days) decreased the insulin-resistant and hyperlipidemic states and increased food consumption and whole-body adiposity. Magnetic resonance imaging (MRI) analysis and weights of fat pads demonstrated that the increase in adiposity was not only limited to the major fat depots but also to fat deposition throughout the body. Adipocyte sizing profiles, fat pad histology, and DNA content show that Pio treatment increased the number of small adipocytes because of both the appearance of new adipocytes and the shrinkage and/or disappearance of existing mature adipocytes. The remodeling was time dependent, with new small adipocytes appearing in clusters throughout the fat pad, and accompanied by a three- to fourfold increase in citrate synthase and fatty acid synthase activity. The appearance of new fat cells and the increase in fat mass were depot specific, with a rank order of responsiveness of ovarian > retroperitoneal > subcutaneous. This differential depot effect resulted in a redistribution of the fat mass in the abdominal region such that there was an increase in the visceral:subcutaneous ratio, as confirmed by MRI analysis. Although the increased adiposity is paradoxical to an improvement in insulin sensitivity, the quantitative increase of adipose mass should be viewed in context of the qualitative changes in adipose tissue, including the remodeling of adipocytes to a smaller size with higher lipid storage potential. This shift in energy balance is likely to result in lower circulating free fatty acid levels, ultimately improving insulin sensitivity and the metabolic state.

Comparison of the instructional efficacy of Internet-based CME with live interactive CME workshops: a randomized controlled trial

CONTEXT

Despite evidence that a variety of continuing medical education (CME) techniques can foster physician behavioral change, there have been no randomized trials comparing performance outcomes for physicians participating in Internet-based CME with physicians participating in a live CME intervention using approaches documented to be effective.

OBJECTIVE

To determine if Internet-based CME can produce changes comparable to those produced via live, small-group, interactive CME with respect to physician knowledge and behaviors that have an impact on patient care.

DESIGN, SETTING, AND PARTICIPANTS

Randomized controlled trial conducted from August 2001 to July 2002. Participants were 97 primary care physicians drawn from 21 practice sites in Houston, Tex, including 7 community health centers and 14 private group practices. A control group of 18 physicians from these same sites received no intervention.

INTERVENTIONS

Physicians were randomly assigned to an Internet-based CME intervention that could be completed in multiple sessions over 2 weeks, or to a single live, small-group, interactive CME workshop. Both incorporated similar multifaceted instructional approaches demonstrated to be effective in live settings. Content was based on the National Institutes of Health National Cholesterol Education Program--Adult Treatment Panel III guidelines.

MAIN OUTCOME MEASURES

Knowledge was assessed immediately before the intervention, immediately after the intervention, and 12 weeks later. The percentage of high-risk patients who had appropriate lipid panel screening and pharmacotherapeutic treatment according to guidelines was documented with chart audits conducted over a 5-month period before intervention and a 5-month period after intervention.

RESULTS

Both interventions produced similar and significant immediate and 12-week knowledge gains, representing large increases in percentage of items correct (pretest to posttest: 31.0% [95% confidence interval {CI}, 27.0%-35.0%]; pretest to 12 weeks: 36.4% [95% CI, 32.2%-40.6%]; P<.001 for all comparisons). Chart audits revealed high baseline screening rates in all study groups (> or =93%) with no significant postintervention change. However, the Internet-based intervention was associated with a significant increase in the percentage of high-risk patients treated with pharmacotherapeutics according to guidelines (preintervention, 85.3%; postintervention, 90.3%; P = .04).

CONCLUSIONS

Appropriately designed, evidence-based online CME can produce objectively measured changes in behavior as well as sustained gains in knowledge that are comparable or superior to those realized from effective live activities.

Effects of tree nuts on blood lipids, apolipoproteins, and blood pressure: systematic review, meta-analysis, and dose-response of 61 controlled intervention trials

BACKGROUND

The effects of nuts on major cardiovascular disease (CVD) risk factors, including dose-responses and potential heterogeneity by nut type or phytosterol content, are not well established.

OBJECTIVES

We examined the effects of tree nuts (walnuts, pistachios, macadamia nuts, pecans, cashews, almonds, hazelnuts, and Brazil nuts) on blood lipids [total cholesterol, low-density lipoprotein (LDL) cholesterol, high-density lipoprotein, and triglycerides], lipoproteins [apolipoprotein A1, apolipoprotein B (ApoB), and apolipoprotein B100], blood pressure, and inflammation (C-reactive protein) in adults aged ≥18 y without prevalent CVD.

DESIGN

We conducted a systematic review and meta-analysis following Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. Two investigators screened 1301 potentially eligible PubMed articles in duplicate. We calculated mean differences between nut intervention and control arms, dose-standardized to one 1-oz (28.4 g) serving/d, by using inverse-variance fixed-effects meta-analysis. Dose-response for nut intake was examined by using linear regression and fractional polynomial modeling. Heterogeneity by age, sex, background diet, baseline risk factors, nut type, disease condition, duration, and quality score was assessed with meta-regression. Publication bias was evaluated by using funnel plots and Egger's and Begg's tests.

RESULTS

Sixty-one trials met eligibility criteria (n = 2582). Interventions ranged from 3 to 26 wk. Nut intake (per serving/d) lowered total cholesterol (-4.7 mg/dL; 95% CI: -5.3, -4.0 mg/dL), LDL cholesterol (-4.8 mg/dL; 95% CI: -5.5, -4.2 mg/dL), ApoB (-3.7 mg/dL; 95% CI: -5.2, -2.3 mg/dL), and triglycerides (-2.2 mg/dL; 95% CI: -3.8, -0.5 mg/dL) with no statistically significant effects on other outcomes. The dose-response between nut intake and total cholesterol and LDL cholesterol was nonlinear (P-nonlinearity < 0.001 each); stronger effects were observed for ≥60 g nuts/d. Significant heterogeneity was not observed by nut type or other factors. For ApoB, stronger effects were observed in populations with type 2 diabetes (-11.5 mg/dL; 95% CI: -16.2, -6.8 mg/dL) than in healthy populations (-2.5 mg/dL; 95% CI: -4.7, -0.3 mg/dL) (P-heterogeneity = 0.015). Little evidence of publication bias was found.

CONCLUSIONS

Tree nut intake lowers total cholesterol, LDL cholesterol, ApoB, and triglycerides. The major determinant of cholesterol lowering appears to be nut dose rather than nut type. Our findings also highlight the need for investigation of possible stronger effects at high nut doses and among diabetic populations.

A mechanism by which high-density lipoproteins may slow the atherogenic process

There is a well-documented negative correlation between plasma concentrations of high-density lipoproteins (H.D.L.) and risk of clinically evident atherosclerosis. This may relate to the postulated role of H.D.L. in the transport of cholesterol out of cells. Studies of the metabolism of lipoproteins by arterial smooth-muscle cells suggest that a second mechanism also operates, H.D.L. binds to the surface of porcine arterial smooth-muscle cells as effectively as low-density lipoprotein (L.D.L.) but is internalised and degraded much more slowly. When incubated with L.D.L. these cells show a net increment in cholesterol content. However, cells incubated with equal or higher concentration of H.D.L. under comparable conditions show no cholesterol accumulation. The presence of H.D.L. in the medium partially inhibits uptake and degradation of L.D.L. and, most important, also partially suppresses the net increment in cell sterol content induced by L.D.L. The demonstrated interaction of H.D.L. and L.D.L. could be a second mechanism contributing to the apparent protective effect of high plasma-H.D.L. concentrations in relation to atherogenesis.

Apolipoprotein B: a clinically important apolipoprotein which assembles atherogenic lipoproteins and promotes the development of atherosclerosis

Apolipoprotein (apo) B exists in two forms apoB100 and apoB48. ApoB100 is present on very low-density lipoproteins (VLDL), intermediate density lipoproteins (IDL) and LDL. ApoB100 assembles VLDL particles in the liver. This process starts by the formation of a pre-VLDL, which is retained in the cell unless converted to the triglyceride-poor VLDL2. VLDL2 is secreted or converted to VLDL1 by a bulk lipidation in the Golgi apparatus. ApoB100 has a central role in the development of atherosclerosis. Two proteoglycan-binding sequences in apoB100 have been identified, which are important for retaining the lipoprotein in the intima of the artery. Retention is essential for the development of the atherosclerotic lesion.

Clinical guideline, part 2. Screening for thyroid disease: an update. American College of Physicians

PURPOSE

To review information on the benefits of screening with a sensitive thyroid-stimulating hormone (TSH) test for thyroid dysfunction in asymptomatic patients seeking primary care for other reasons. This paper focuses on whether screening should be aimed at detection of subclinical thyroid dysfunction and whether persons with mildly abnormal TSH levels can benefit.

DATA SOURCES

A MEDLINE search for studies of screening for thyroid dysfunction and of treatment for complications of subclinical thyroid dysfunction.

STUDY SELECTION

Studies of screening with thyroid function tests in the general adult population or in patients seen in the general office setting were selected (n=33). All controlled studies of treatment in patients with subclinical hypothyroidism or subclinical hyperthyroidism were also included (n=23).

DATA EXTRACTION

The prevalence of overt and subclinical thyroid dysfunction, the evidence for the efficacy of treatment, and the incidence of complications in defined age and sex groups were extracted from each study.

DATA SYNTHESIS

Screening can detect symptomatic but unsuspected overt thyroid dysfunction. The yield is highest for women older than 50 years of age: In this group, 1 in 71 women screened could benefit from relief of symptoms. Evidence of the efficacy of treatment for subclinical thyroid dysfunction is inconclusive.

CONCLUSIONS

Even though treatment for subclinical thyroid dysfunction is controversial, office-based screening to detect overt thyroid dysfunction may be indicated in women older than 50 years of age. Large randomized trials are needed to determine the likelihood that treatment will improve quality of life in otherwise healthy patients who have mildly elevated TSH levels.

A randomized, multicenter comparison of tacrolimus and cyclosporine immunosuppressive regimens in cardiac transplantation: decreased hyperlipidemia and hypertension with tacrolimus

BACKGROUND

Tacrolimus-based immunosuppression seems safe and effective in liver and kidney transplantation. To assess the safety and efficacy of tacrolimus (TAC)-based immunosuppression after cardiac transplantation as well as the relative impact of tacrolimus on immunosuppression-related side effects such as hypertension and hyperlipidemia, we conducted a prospective, randomized, open-label, multicenter study of otherwise identical tacrolimus- and cyclosporine-based immunosuppressive regimens in adult patients undergoing cardiac transplantation.

METHODS

Eighty-five adult patients (pts) at six United States cardiac transplant centers, undergoing their first cardiac transplant procedure, were prospectively randomized to receive either TAC-based (n = 39) or cyclosporine (CYA)-based (n = 46) immunosuppression. All pts received a triple-drug protocol with 15 pts (18%) receiving peri-operative OKT3 to delay TAC/CYA due to pre-transplant renal dysfunction. Endomyocardial biopsies were performed at Weeks 1, 2, 3, 4, 6, 8, 10, 12, 24, and 52. The study duration was 12 months.

RESULTS

Patients were mostly male (87%) Caucasian (90%) with a mean age of 54 years and primary diagnoses of coronary artery disease (55%) and idiopathic dilated cardiomyopathy (41%). There were no significant demographic differences between groups. Patient and allograft survival were not different in the two groups. The probability and overall incidence of each grade of rejection, whether treated or not, and the types of treatment required did not differ between the groups. At baseline and through 12 months of follow-up, chemistry and hematology values were similar between the groups except serum cholesterol was higher in the CYA group at 3, 6, and 12 months (239 vs 205 mg/dL, 246 vs 191 mg/dL, 212 vs 186 mg/dL, respectively, p < 0.001). Likewise, LDL-cholesterol, HDL-cholesterol and triglycerides were significantly higher in the CYA group. More CYA patients received therapy for hypercholesterolemia (71% vs 41% at 12 months, p = 0.01). There were no significant differences in renal function, hyperglycemia, hypomagnesemia, or hyperkalemia during the first 12 months. More CYA patients developed new-onset hypertension requiring pharmacologic treatment (71% vs 48%, p = 0.05). The incidence of infection was the same for the two groups (2.6 episodes/pt/12 month follow-up).

CONCLUSION

Tacrolimus-based immunosuppression seems effective for rejection prophylaxis during the first year after cardiac transplantation and is associated with less hypertension and hyperlipidemia and no difference in renal function, hyperglycemia or infection incidence when compared to cyclosporine-based immunosuppression.

Effect of fenofibrate on amputation events in people with type 2 diabetes mellitus (FIELD study): a prespecified analysis of a randomised controlled trial

BACKGROUND

Amputations in people with type 2 diabetes mellitus substantially impair their quality of life and impose high costs on health-care systems. Our aim was to assess the effect of fenofibrate on amputation events in a large cohort of patients with type 2 diabetes.

METHODS

In the Fenofibrate Intervention and Event Lowering in Diabetes (FIELD) study, 9795 patients aged 50-75 years with type 2 diabetes were randomly assigned by computer-generated randomisation sequence to receive fenofibrate 200 mg per day (n=4895) or matching placebo (n=4900) for 5 years' duration. Information about non-traumatic amputation-a prespecified tertiary endpoint of the study-was routinely gathered. Clinicians who were masked to treatment allocation adjudicated amputations as minor or major (below or above the ankle, respectively). Amputations were also classified on the basis of whether or not large-vessel disease was present in the limb, to distinguish those related to large-artery atherosclerosis from those predominantly related to microvascular disease. Analysis was by intention to treat (ITT). The FIELD study is registered as an International Standard Randomised Controlled Trial, number ISRCTN64783481.

FINDINGS

All 9795 patients were included in the ITT population. 115 patients had one or more non-traumatic lower-limb amputations due to diabetes. Previous cardiovascular disease, microvascular disease, previous non-traumatic amputation or skin ulcer, smoking, and longer duration of diabetes were more frequent in patients who had amputations during the trial than in those who had other cardiovascular events or in those who had neither event (all p<0.001 for three-way comparison). Mean lipid concentrations differed between patients who had on-study amputations and those who had other cardiovascular events or neither event, but by no more than 0.2 mmol/L. The risks of first amputation (45 vs 70 events; hazard ratio [HR] 0.64, 95% CI 0.44-0.94; p=0.02) and minor amputation events without known large-vessel disease (18 vs 34 events; 0.53, 0.30-0.94; p=0.027) were lower for patients assigned to fenofibrate than for patients assigned to placebo, with no difference between groups in risk of major amputations (24 vs 26 events; 0.93, 0.53-1.62; p=0.79).

INTERPRETATION

Classic markers of macrovascular and microvascular risk were associated with lower extremity amputations in patients with type 2 diabetes. Treatment with fenofibrate was associated with a lower risk of amputations, particularly minor amputations without known large-vessel disease, probably through non-lipid mechanisms. These findings could lead to a change in standard treatment for the prevention of diabetes-related lower-limb amputations.

FUNDING

Laboratoires Fournier SA (now part of Solvay Pharmaceuticals) and National Health and Medical Research Council of Australia.