Comparison of regional fat measurements by dual-energy X-ray absorptiometry and conventional anthropometry and their association with markers of diabetes and cardiovascular disease risk.

BACKGROUND/OBJECTIVES: Fat distribution is a strong and independent predictor of type 2 diabetes (T2D) and cardiovascular disease (CVD) and is usually determined using conventional anthropometry in epidemiological studies. Dual-energy X-ray absorptiometry (DXA) can measure total and regional adiposity more accurately. Nonetheless, whether DXA provides more precise estimates of cardiovascular risk in relation to total and regional adiposity is not known. We determined the strength of the associations between DXA- and conventional anthropometry determined fat distribution and T2D and CVD risk markers. SUBJECTS/METHODS: Waist (WC) and hip circumference (HC) and DXA was used to measure total and regional adiposity in 4950 (2119 men) participants aged 29-55 years from the Oxford Biobank without pre-existing T2D or CVD. Cross-sectional associations were compared between WC and HC vs. DXA-determined regional adiposity (all z-score normalised) with impaired fasting glucose, hypertriglyceridemia, hypertension and insulin resistance (IR). RESULTS: Following adjustment for total adiposity, upper body adiposity measurements showed consistently increased risk of T2D and CVD risk markers except for abdominal subcutaneous fat in both sexes, and arm fat in men, which showed protective associations. Among upper adiposity depots, visceral fat mass showed stronger odds ratios (OR) ranging from 1.69 to 3.64 compared with WC 1.07-1.83. Among lower adiposity depots, HC showed modest protection for IR in both sexes (men: OR 0.80 (95% confidence interval 0.67, 0.96); women: 0.69 (0.56, 0.86)), whereas gynoid fat and in particular leg fat showed consistent and strong protective effects for all outcomes in both men and women. The differential effect of body fat distribution on CVD and T2D were more pronounced at higher levels of total adiposity. CONCLUSIONS: Compared with DXA, conventional anthropometry underestimates the associations of regional adiposity with T2D and CVD risk markers. After correcting for overall adiposity, greater subcutaneous fat mass in particular in the lower body is protective relative to greater android or visceral adipose tissue mass.

MicroRNAs in adipose tissue: their role in adipogenesis and obesity.

MicroRNAs (miRNAs) are endogenous small RNAs that posttranscriptionally regulate gene expression and that have been shown to have important roles in numerous disease processes. There is growing evidence for an important role of miRNAs in regulating the pathways in adipose tissue that control a range of processes including adipogenesis, insulin resistance and inflammation. Several high-throughput studies have identified differentially expressed miRNAs in adipose tissue pathology and during adipogenesis and a number of these have now been characterised functionally in terms of their actions and targets. This review will summarise the current literature on miRNAs in adipose tissue, as well as discussing the methodologies used in this area of research and the potential application of miRNAs as biomarkers and as therapeutic targets.

Markers of de novo lipogenesis in adipose tissue: associations with small adipocytes and insulin sensitivity in humans.

AIMS/HYPOTHESIS: Previous studies have shown relationships between fatty acid ratios in adipose tissue triacylglycerol (TG), adipocyte size and measures of insulin sensitivity. We hypothesised that variations in adipose tissue de novo lipogenesis (DNL) in relation to adiposity might explain some of these observations. METHODS: In a cross-sectional study, subcutaneous abdominal adipose tissue biopsies from 59 people were examined in relation to fasting and post-glucose insulin sensitivity. Adipocyte size, TG fatty acid composition and mRNA expression of lipogenic genes were determined. RESULTS: We found strong positive relationships between adipose tissue TG content of the fatty acids myristic acid (14:0) and stearic acid (18:0) with insulin sensitivity (HOMA model) (p < 0.01 for each), and inverse relationships with adipocyte size (p < 0.01, p < 0.05, respectively). Variation in 18:0 content was the determinant of the adipose tissue TG 18:1 n-9/18:0 ratio, which correlated negatively with insulin sensitivity (p < 0.01), as observed previously. Adipose tissue 18:0 content correlated positively with the mRNA expression of lipogenic genes (e.g. FASN, p < 0.01). Lipogenic gene expression (a composite measure derived from principal components analysis) was inversely correlated with adipocyte cell size (p < 0.001). There was no relationship between dietary saturated fatty acid intake and adipose tissue 18:0 content. CONCLUSIONS/INTERPRETATION: Our data suggest a physiological mechanism whereby DNL is downregulated as adipocytes expand. Taken together with other data, they also suggest that hepatic and adipose tissue DNL are not regulated in parallel. We also confirm a strong relationship between small adipocytes and insulin sensitivity, which is independent of BMI.

Aprotinin, blood loss, and renal dysfunction in deep hypothermic circulatory arrest.

BACKGROUND: The technique of deep hypothermic circulatory arrest (DHCA) for cardiothoracic surgery is associated with increased risk for perioperative blood loss and renal dysfunction. Although aprotinin, a serine protease inhibitor, reduces blood loss in patients undergoing cardiopulmonary bypass, its use has been limited in the setting of DHCA because of concerns regarding aprotinin-induced renal dysfunction. Therefore, we assessed the affect of aprotinin on both blood transfusion requirements and renal function in patients undergoing cardiovascular surgery and DHCA. METHODS AND RESULTS: We reviewed the records of 853 patients who underwent aortic or thoracoabdominal surgery at Stanford University Medical Center between January 1992 and March 2000. Two hundred three of these patients were treated with DHCA, and 90% (183) survived for more than 24 hours. Preoperative patient characteristics and intraoperative and postoperative clinical and surgical variables were recorded, and creatinine clearance (CRCl) was calculated for the preoperative and postoperative periods; renal dysfunction was prospectively defined as a 25% reduction in CRCl. The association between perioperative variables, including aprotinin use, and renal dysfunction was assessed by ANOVA techniques. Total urine output was 1294+/-1024 mL and 3492+/-1613 mL during and after surgery, respectively. CRCl decreased significantly after DHCA from 86+/-8 mL/min (before surgery) to 67+/-4 mL/min (in the intensive care unit) (P<0.01). Thirty-eight percent of patients (70 of 183) had postoperative renal dysfunction. Multivariate regression analyses identified 5 factors independently associated with a >25% reduction in CRCl: requirement for >/=5 U of packed red blood cells(P=0.0002; OR=2.1),

Similar neurobehavioral outcome after valve or coronary artery operations despite differing carotid embolic counts.

OBJECTIVES: The interrelationships among coronary and valvular operations, microemboli, and neurobehavioral outcome are unclear. We hypothesized that adult patients undergoing cardiac valve operations would have more total emboli delivered to the brain than patients undergoing coronary artery bypass grafting and that this would associate with worse neurobehavioral outcomes. METHODS: One hundred ninety-three patients undergoing coronary artery bypass grafting and 73 patients undergoing cardiac valve operations were compared. Patients received neurologic, neuro-ophthalmologic, and 11 standardized neurobehavioral tests preoperatively and 5 to 7 days, 1 month, and 6 months postoperatively. Left common carotid Doppler ultrasonographic embolus detection was performed intraoperatively. Repeated measures and logistic regression analyses of outcome were performed. RESULTS: Patients undergoing either coronary or valve operations were well matched by age (61 +/- 10 and 59 +/- 12 years, respectively), but a significantly greater fraction of patients undergoing valve operations were female, diabetic, or had undergone previous cardiac operations. Neurobehavioral scores of patients undergoing either coronary artery bypass grafting or cardiac valve operations did not differ significantly at any time. Total embolus counts differed significantly: the median was 105 during coronary artery bypass grafting and 479 during cardiac valve operations (geometric means of 104 and 412, respectively; P =.0001). Significantly more emboli were detected in the patients undergoing cardiac valve operations after removal of the left ventricular vent and after separation from cardiopulmonary bypass, but comparable numbers of emboli were seen in the 2 groups before cardiopulmonary bypass. In both groups decreased neurobehavioral performance was apparent at 5 to 7 days, with improvement at 1 and 6 months. Increasing numbers of carotid emboli significantly associated with worse performance on the letter cancellation test. There were no significant differences between patients undergoing valve and coronary operations in neurobehavioral outcomes, strokes, transient ischemic attacks, or deaths. CONCLUSIONS: The significantly greater number of emboli in the group of patients undergoing cardiac valve operations is likely the result of the entrainment of intracardiac air. The greater numbers of emboli during cardiac valve operations do not appear associated with a commensurately greater risk of adverse neurologic or neurobehavioral outcome.

The in vivo effects of the Pro12Ala PPARgamma2 polymorphism on adipose tissue NEFA metabolism: the first use of the Oxford Biobank.

AIMS/HYPOTHESIS: To investigate the phenotypic effects of common polymorphisms on adipose tissue metabolism and cardiovascular risk factors, we set out to establish a biobank with the unique feature of allowing a prospective recruit-by-genotype approach. The first use of this biobank investigates the effects of the peroxisome proliferator-activated receptor (PPAR) Pro12Ala polymorphism on integrative tissue-specific physiology. We hypothesised that Ala12 allele carriers demonstrate greater adipose tissue metabolic flexibility and insulin sensitivity. MATERIALS AND METHODS: From a comprehensive population register, subjects were recruited into a biobank, which was genotyped for the Pro12Ala polymorphism. Twelve healthy male Ala12 carriers and 12 matched Pro12 homozygotes underwent detailed physiological phenotyping using stable isotope techniques, and measurements of blood flow and arteriovenous differences in adipose tissue and muscle in response to a mixed meal containing [1,1,1-(13)C]tripalmitin. RESULTS: Of 6,148 invited subjects, 1,072 were suitable for inclusion in the biobank. Among Pro12 homozygotes, insulin sensitivity correlated with HDL-cholesterol concentrations, and inversely correlated with blood pressure, apolipoprotein B, triglyceride and total cholesterol concentrations. Ala12 carriers showed no such correlations. In the meal study, Ala12 carriers had lower plasma NEFA concentrations, higher adipose tissue and muscle blood flow, and greater insulin-mediated postprandial hormone-sensitive lipase suppression along with greater insulin sensitivity than Pro12 homozygotes. CONCLUSIONS/INTERPRETATION: This study shows that a recruit-by-genotype approach is feasible and describes the biobank's first application, providing tissue-specific physiological findings consistent with the epidemiological observation that the PPAR Ala12 allele protects against the development of type 2 diabetes.

A new member of the Ig superfamily and a V-ATPase G subunit are among the predicted products of novel genes close to the TNF locus in the human MHC.

It is becoming increasingly apparent that many of the genes in the class III region of the human MHC encode proteins involved in the immune and inflammatory responses. Furthermore, genetic studies have indicated that genes within the class III region, particularly the telomeric segment containing the TNF gene, could contribute to susceptibility to diseases of immune-related etiology. We have sequenced an 82-kb segment of DNA around the TNF gene to identify candidate disease susceptibility genes in this region. The 10 known genes in this region have been precisely positioned with the order allograft inflammatory factor 1, G1, 1C7, leukocyte-specific transcript 1 (B144), lymphotoxin B, TNF, lymphotoxin A, NB6, IKBL, BAT1 (centromere to telomere), and their genomic structures have been defined. Comparison of the G1 genomic region with previously described cDNA and genomic sequences, together with the results of reverse transcriptase-PCR, indicates that three alternative transcripts, G1, allograft inflammatory factor 1, and IFN-gamma-responsive transcript, are all derived from this gene. The completion of the sequence of 1C7 (D6S2570) has revealed that this gene encodes a putative novel member of the Ig superfamily. A number of alternatively spliced transcripts of 1C7 were identified by reverse transcriptase-PCR, all of which are expressed in immune-related cell lines. Alternative splicing within the Ig domain-encoding region was seen to result in possible set switching between an IgV domain and an IgC2 domain. Lastly, a previously unidentified gene, homologous to a number of V-ATPase G subunits, has been located 1 kb telomeric of IKBL.

Single-nucleotide polymorphism detection by denaturing high-performance liquid chromatography and direct sequencing in genes in the MHC class III region encoding novel cell surface molecules.

The class III region of the human major histocompatibility complex (MHC) contains approximately 59 genes, many of which encode polypeptides with a variety of different functions. Eight of these genes are of particular interest because they encode novel surface molecules that could be involved in immune and/or inflammatory responses and are excellent candidates as disease susceptibility loci. These molecules are members of two different superfamilies, the immunoglobulin superfamily (1C7, G6B, and G6F genes) and the leucocyte antigen-6 superfamily (G6C, G6D, G6E, G5C, and G5B genes). Some level of variation was found when overlapping genomic DNAs from different haplotypes were compared. The present work describes a systematic search for single-nucleotide polymorphisms (SNPs) in these genes using direct sequencing and denaturing high-performance liquid chromatography (DHPLC) in 24 unrelated healthy individuals. We validated the DHPLC methodology by first studying the 1C7 gene. This gene was directly sequenced in all 24 samples, and DHPLC was found to resolve all the polymorphic sites present in the heterozygote samples tested. We screened the rest of the genes by DHPLC only, and only those chromatograms that revealed a polymorphic profile were sequenced. We detected one SNP every 489 bp in the 18 kb of DNA studied, corresponding to theta = 4.61x10-4. The diversity in noncoding regions is 1 SNP/560 bp, but a higher frequency was detected in coding regions with 1 SNP/423 bp corresponding to theta =5.33x10-4. Of the coding SNPs, 63.6% caused amino acid substitutions. The power of this study is emphasized by the fact that of the 37 SNPs/indels detected, only 6 can be found in the SNP database at the NCBI.

Direct effects of propofol on myocardial and vascular tissue from mature and immature rats.

OBJECTIVE: To determine the effect of age on the direct myocardial and vascular effects of propofol in rats. DESIGN: Randomized, prospective with repeated measures. SETTING: University research laboratory. PARTICIPANTS: Myocardial and aortic tissue from 12 immature (4-week-old) and 12 mature (16-week-old) male Sprague-Dawley rats. INTERVENTIONS: Change in force of contraction was measured in isolated myocardial strips or in isolated descending thoracic aorta rings during exposure to propofol or intralipid. MEASUREMENTS AND MAIN RESULTS: Propofol produced a dose-dependent decrease in vascular tone (p < 0.05). This effect was similar for intralipid. Propofol was more potent in the younger animals (EC(50), 5.3 microg/mL [confidence interval, 2.5 to 11.1] for 4-week-old and 26.6 microg/mL [confidence interval, 6.8 to 103.7] for 16-week-old rats; p < 0.05). In contrast, propofol produced a dose-dependent decrease in contractility (p = 0.001), whereas intralipid produced no decrease in contractility. CONCLUSIONS: Although propofol does produce a dose-dependent decrease in contractility, this effect is similar at different ages. Propofol produces more direct vascular relaxation in the immature tissue. Propofol's direct cardiovascular effect and its indirect cardiovascular effects should be considered in the young and old, especially when cardiovascular reserve is limited.