Assessing the effect of interaction between an FTO variant (rs9939609) and physical activity on obesity in 15,925 Swedish and 2,511 Finnish adults

AIMS/HYPOTHESIS

Recent reports have suggested that genotypes at the FTO locus interact with physical activity to modify levels of obesity-related traits. We tested this hypothesis in two non-diabetic population-based cohorts, the first from southern Sweden and the second from the Botnia region of western Finland.

METHODS

In total 2,511 Finnish and 15,925 Swedish non-diabetic middle-aged adults were genotyped for the FTO rs9939609 variant. Physical activity was assessed by questionnaires and standard clinical procedures were conducted, including measures of height and weight and glucose regulation. Tests of gene x physical activity interaction were performed using linear interaction effects to determine whether the effect of this variant on BMI is modified by physical activity.

RESULTS

The minor A allele at rs9939609 was associated with higher BMI in both cohorts, with the per allele difference in BMI being about 0.13 and 0.43 kg/m(2) in the Swedish and Finnish cohorts, respectively (p < 0.0001). The test of interaction between physical activity and the rs9939609 variant on BMI was not statistically significant after controlling for age and sex in either cohort (Sweden: p = 0.71, Finland: p = 0.18).

CONCLUSIONS/INTERPRETATION

The present report does not support the notion that physical activity modifies the effects of the FTO rs9939609 variant on obesity risk in the non-diabetic Swedish or Finnish adults studied here.

PPARGC1A sequence variation and cardiovascular risk-factor levels: a study of the main genetic effects and gene x environment interactions in children from the European Youth Heart Study

AIMS/HYPOTHESIS

The PPARGC1A gene coactivates multiple nuclear transcription factors involved in cellular energy metabolism and vascular stasis. In the present study, we genotyped 35 tagging polymorphisms to capture all common PPARGC1A nucleotide sequence variations and tested for association with metabolic and cardiovascular traits in 2,101 Danish and Estonian boys and girls from the European Youth Heart Study, a multicentre school-based cross-sectional cohort study.

METHODS

Fasting plasma glucose concentrations, anthropometric variables and blood pressure were measured. Habitual physical activity and aerobic fitness were objectively assessed using uniaxial accelerometry and a maximal aerobic exercise stress test on a bicycle ergometer, respectively.

RESULTS

In adjusted models, nominally significant associations were observed for BMI (rs10018239, p = 0.039), waist circumference (rs7656250, p = 0.012; rs8192678 [Gly482Ser], p = 0.015; rs3755863, p = 0.02; rs10018239, beta = -0.01 cm per minor allele copy, p = 0.043), systolic blood pressure (rs2970869, p = 0.018) and fasting glucose concentrations (rs11724368, p = 0.045). Stronger associations were observed for aerobic fitness (rs7656250, p = 0.005; rs13117172, p = 0.008) and fasting glucose concentrations (rs7657071, p = 0.002). None remained significant after correcting for the number of statistical comparisons. We proceeded by testing for gene x physical activity interactions for the polymorphisms that showed nominal evidence of association in the main effect models. None of these tests was statistically significant.

CONCLUSIONS/INTERPRETATION

Variants at PPARGC1A may influence several metabolic traits in this European paediatric cohort. However, variation at PPARGC1A is unlikely to have a major impact on cardiovascular or metabolic health in these children.

Assessing gene-treatment interactions at the FTO and INSIG2 loci on obesity-related traits in the Diabetes Prevention Program

AIMS/HYPOTHESIS

The single nucleotide polymorphism (SNP) rs9939609 in the fat mass and obesity associated gene (FTO) and the rs7566605 SNP located 10 kb upstream of the insulin-induced gene 2 gene (INSIG2) have been proposed as risk factors for common obesity.

METHODS

We tested for genotype-treatment interactions on changes in obesity-related traits in the Diabetes Prevention Program (DPP). The DPP is a randomised controlled trial of 3,548 high-risk individuals from 27 participating centres throughout the USA who were originally randomised to receive metformin, troglitazone, intensive lifestyle modification or placebo to prevent the development of type 2 diabetes. Measures of adiposity from computed tomography were available in a subsample (n = 908). This report focuses on the baseline and 1 year results.

RESULTS

The minor A allele at FTO rs9939609 was positively associated with baseline BMI (p = 0.003), but not with baseline adiposity or the change at 1 year in any anthropometric trait. For the INSIG2 rs7566605 genotype, the minor C allele was associated with more subcutaneous adiposity (second and third lumbar vertebrae [L2/3]) at baseline (p = 0.04). During follow-up, CC homozygotes lost more weight than G allele carriers (p = 0.009). In an additive model, we observed nominally significant gene-lifestyle interactions on weight change (p = 0.02) and subcutaneous (L2/3 [p = 0.01] and L4/5 [p = 0.03]) and visceral (L2/3 [p = 0.02]) adipose areas. No statistical evidence of association with physical activity energy expenditure or energy intake was observed for either genotype.

CONCLUSIONS/INTERPRETATION

Within the DPP study population, common variants in FTO and INSIG2 are nominally associated with quantitative measures of obesity, directly and possibly by interacting with metformin or lifestyle intervention.

Genomic variants at the PINK1 locus are associated with transcript abundance and plasma nonesterified fatty acid concentrations in European whites

The purpose of this study was to characterize associations between PINK1 genotypes, PINK1 transcript levels, and metabolic phenotypes in healthy adults and those with type 2 diabetes (T2D). We measured PINK1 skeletal muscle transcript levels and 8 independent PINK1 single nucleotide polymorphisms (SNPs) in a cohort of 208 Danish whites and in a cohort of 1701 British whites (SNPs and metabolic phenotypes only). Furthermore, we assessed the effects of PINK1 transcript ablation in primary adipocytes using RNA interference (RNAi). Six PINK1 SNPs were associated with PINK1 transcript levels (P<0.04 to P<0.0001). Obesity modified the association between PINK1 transcript levels and T2D risk (interaction P=0.005); transcript levels were inversely related with T2D in obese (n=105) [odds ratio (OR) per sd increase in expression levels=0.44; 95% confidence interval (CI): 0.23, 0.84; P=0.013] but not in nonobese (n=103) (OR=1.20; 95% CI: 0.82, 1.76; P=0.34) individuals. In the British cohort, several PINK1 SNPs were associated with plasma nonesterified fatty acid concentrations. Nominal genotype associations were also observed for fasting glucose, 2-h glucose, and maximal oxygen consumption, although these were not statistically significant after correcting for multiple testing. In primary adipocytes, Pink1 knockdown affected fatty acid binding protein 4 (Fabp4) expression, indicating that PINK1 may influence substrate metabolism. We demonstrate that PINK1 polymorphisms are associated with PINK1 transcript levels and measures of fatty acid metabolism in a concordant manner, whereas our RNAi data imply that PINK1 may indirectly influence lipid metabolism.

Testing of diabetes-associated WFS1 polymorphisms in the Diabetes Prevention Program

AIMS/HYPOTHESIS

Wolfram syndrome (diabetes insipidus, diabetes mellitus, optic atrophy and deafness) is caused by mutations in the WFS1 gene. Recently, single nucleotide polymorphisms (SNPs) in WFS1 have been reproducibly associated with type 2 diabetes. We therefore examined the effects of these variants on diabetes incidence and response to interventions in the Diabetes Prevention Program (DPP), in which a lifestyle intervention or metformin treatment was compared with placebo.

METHODS

We genotyped the WFS1 SNPs rs10010131, rs752854 and rs734312 (H611R) in 3,548 DPP participants and performed Cox regression analysis using genotype, intervention and their interactions as predictors of diabetes incidence. We also evaluated the effect of these SNPs on insulin resistance and beta cell function at 1 year.

RESULTS

Although none of the three SNPs was associated with diabetes incidence in the overall cohort, white homozygotes for the previously reported protective alleles appeared less likely to develop diabetes in the lifestyle arm. Examination of the publicly available Diabetes Genetics Initiative genome-wide association dataset revealed that rs10012946, which is in strong linkage disequilibrium with the three WFS1 SNPs (r(2)=0.88-1.0), was associated with type 2 diabetes (allelic odds ratio 0.85, 95% CI 0.75-0.97, p=0.026). In the DPP, we noted a trend towards increased insulin secretion in carriers of the protective variants, although for most SNPs this was seen as compensatory for the diminished insulin sensitivity.

CONCLUSIONS/INTERPRETATION

The previously reported protective effect of select WFS1 alleles may be magnified by a lifestyle intervention. These variants appear to confer an improvement in beta cell function.

Replication of the association between variants in WFS1 and risk of type 2 diabetes in European populations

AIMS/HYPOTHESIS

Mutations at the gene encoding wolframin (WFS1) cause Wolfram syndrome, a rare neurological condition. Associations between single nucleotide polymorphisms (SNPs) at WFS1 and type 2 diabetes have recently been reported. Thus, our aim was to replicate those associations in a northern Swedish case-control study of type 2 diabetes. We also performed a meta-analysis of published and previously unpublished data from Sweden, Finland and France, to obtain updated summary effect estimates.

METHODS

Four WFS1 SNPs (rs10010131, rs6446482, rs752854 and rs734312 [H611R]) were genotyped in a type 2 diabetes case-control study (n = 1,296/1,412) of Swedish adults. Logistic regression was used to assess the association between each WFS1 SNP and type 2 diabetes, following adjustment for age, sex and BMI. We then performed a meta-analysis of 11 studies of type 2 diabetes, comprising up to 14,139 patients and 16,109 controls, to obtain a summary effect estimate for the WFS1 variants.

RESULTS

In the northern Swedish study, the minor allele at rs752854 was associated with reduced type 2 diabetes risk [odds ratio (OR) 0.85, 95% CI 0.75-0.96, p=0.010]. Borderline statistical associations were observed for the remaining SNPs. The meta-analysis of the four independent replication studies for SNP rs10010131 and correlated variants showed evidence for statistical association (OR 0.87, 95% CI 0.82-0.93, p=4.5 x 10(-5)). In an updated meta-analysis of all 11 studies, strong evidence of statistical association was also observed (OR 0.89, 95% CI 0.86-0.92; p=4.9 x 10(-11)).

CONCLUSIONS/INTERPRETATION

In this study of WFS1 variants and type 2 diabetes risk, we have replicated the previously reported associations between SNPs at this locus and the risk of type 2 diabetes.

The Pro12Ala variant at the peroxisome proliferator-activated receptor gamma gene and change in obesity-related traits in the Diabetes Prevention Program

AIMS/HYPOTHESIS

Peroxisome proliferator-activated receptor gamma (PPARgamma), encoded by the PPARG gene, regulates insulin sensitivity and adipogenesis, and may bind polyunsaturated fatty acids (PUFA) and thiazolidinediones in a ligand-dependent manner. The PPARG proline for alanine substitution at position 12 (Pro12Ala polymorphism) has been related with obesity directly and via interaction with PUFA.

METHODS

We tested the effect-modifying role of Pro12Ala on the 1 year change in obesity-related traits in a randomised clinical trial of treatment with metformin (n = 989), troglitazone (n = 363) or lifestyle modification (n = 1,004) vs placebo (n = 1,000) for diabetes prevention in high-risk individuals.

RESULTS

At baseline, Ala12 carriers had larger waists (p < 0.001) and, in a subset, more subcutaneous adipose tissue (SAT; lumbar 2/3; p = 0.04) than Pro12 homozygotes. There was a genotype-by-intervention interaction on 1-year weight change (p = 0.01); in the placebo arm, Pro12 homozygotes gained weight and Ala12 carriers lost weight (p = 0.001). In the metformin and lifestyle arms, weight loss occurred across genotypes, but was greatest in Ala12 carriers (p < 0.05). Troglitazone treatment induced weight gain, which tended to be greater in Ala12 carriers (p = 0.08). In the placebo group, SAT (lumbar 2/3, lumbar 4/5) decreased in Ala12 allele carriers, but was unchanged in Pro12 homozygotes (p < or = 0.005). With metformin treatment, SAT decreased independently of genotype. In the lifestyle arm, SAT (lumbar 2/3) reductions occurred across genotypes, but were greater in Ala12 carriers (p = 0.03). A genotype-by-PUFA intake interaction on reduction in visceral fat (lumbar 4/5; p = 0.04) was also observed, which was most evident with metformin treatment (p < 0.001).

CONCLUSIONS/INTERPRETATION

Within the Diabetes Prevention Program, the Ala12 allele influences central obesity, an effect which may differ by treatment group and dietary PUFA intake (ClinicalTrials.gov ID no: NCT00004992).

Physical activity energy expenditure may mediate the relationship between plasma leptin levels and worsening insulin resistance independently of adiposity

Leptin regulates a constellation of neuroendocrine processes that control energy homeostasis. The infusion of leptin in rodents lacking endogenous leptin promotes physical activity energy expenditure (PAEE) and improves insulin signaling, whereas hyperleptinemia is associated with physical inactivity and insulin resistance (IR). We tested whether baseline leptin levels predict changes in PAEE and IR over time, independent of obesity. We also assessed whether the relationship between leptin and change in IR is mediated by PAEE. The population consisted of 288 nondiabetic UK Caucasian adults (mean age: 49.4 yr; SD: 0.7 yr), in whom leptin, insulin, glucose, PAEE (via heart rate monitoring with individual calibration by indirect calorimetry), and anthropometric characteristics had been measured at baseline and 5 yr later. In linear regression models, baseline leptin levels inversely predicted follow-up PAEE ( P = 0.033). On average, individuals with low leptin levels (below sex-specific median) increased their daily activity 35% more during the 5-yr follow-up period than those with above-median leptin levels. Baseline leptin level also predicted worsening IR (fasting, 30-min, and 2-h insulins, and homeostasis model assessment-IR; all P < 0.01). Associations were independent of potential confounders, such as adiposity, age, and sex. Including baseline PAEE as a cofactor in the leptin-insulin models reduced the strength (1–4% reduction) and significance of the associations, suggesting that PAEE mediates the leptin-insulin relationships. Hyperleptinemia predicts a relative decline in PAEE and worsening insulin resistance, possibly via shared molecular pathways.

PPARGC1A coding variation may initiate impaired NEFA clearance during glucose challenge

AIMS/HYPOTHESIS

The peroxisome proliferator-activated receptor gamma coactivator 1-alpha protein, encoded by the PPARGC1A gene, transcriptionally activates a complex pathway of lipid and glucose metabolism and is expressed primarily in tissues of high metabolic activity such as liver, heart and exercising oxidative skeletal muscle fibre. Ppargc1a-null mice develop systemic dyslipidaemia and hepatic steatosis. In humans, NEFAs downregulate PPARGC1A expression in skeletal muscle. Furthermore, a common non-synonymous coding variant at PPARGC1A (Gly482Ser, rs8192678) is associated with decreased PPARGC1A mRNA levels and increased type 2 diabetes risk.

MATERIALS AND METHODS

In a population-based sample of 691 healthy middle-aged Europids we assessed whether Gly482Ser is associated with levels of NEFA when fasting and in response to an oral glucose challenge. We also assessed the potential effect-modifying role of adipose tissue mass on these phenotypes.

RESULTS

After adjustment for age, sex, fat mass and fat-free mass, the Ser482 allele associated with higher NEFA at 30 min and 2 h and with NEFA AUC (all values p<or=0.02). Furthermore, suggestive evidence of interaction between fat mass and Gly482Ser was observed for fasting NEFA (p=0.059). After stratification by level of obesity, genotype associations were observed in the obese for fasting NEFA (p=0.028) and NEFA at 30 min (p=0.013) and 2 h (p=0.002), and with NEFA AUC (p=0.005), but no significant associations were observed in lean individuals (all values p>0.6).

CONCLUSIONS/INTERPRETATION

Our observations indicate that NEFA clearance is blunted following a glucose load in carriers of the PPARCG1A Ser482 allele. This association is augmented by obesity.

Sex-specific effect of the Val1483Ile polymorphism in the fatty acid synthase gene (FAS) on body mass index and lipid profile in Caucasian children

OBJECTIVE

A Val1483Ile polymorphism in the human fatty acid sythase gene (FAS) has recently been shown to be associated with lower percentage of body fat and substrate oxidation rates in Pima Indians, but its role in other populations has not been described. Here, we investigate the effect of this variant on obesity in Caucasian children and adolescents.

SUBJECTS AND METHODS

In total, 738 Caucasian children and adolescents aged 6-17 years of the Leipzig Schoolchildren cohort, which constitutes an unselected representative German population and 205 obese children (body mass index (BMI) 2.71+/-0.04 SDS) were genotyped for genotype-phenotype associations.

RESULTS

The frequency of the Ile-allele was lower in German Caucasians compared with Pima Indians (0.03 compared to 0.10). Using generalized linear regression models, there was no effect of the polymorphism on BMI in the whole normal population. However, we identified a significant interaction effect between sex and genotype (P=0.004). Subsequent sex stratified analyses revealed a lower BMI SDS in boys with Ile/Val genotype compared to Val/Val (-0.36+/-0.29 vs 0.09+/-0.05, P<0.05), while an opposite effect was observed in girls (0.48+/-0.19 vs 0.09+/-0.05, P<0.05). In genotype-phenotype associations in obese children, the polymorphism did not affect parameters of insulin, glucose, or lipid metabolism in the whole population. Again, however, obese boys with Ile/Val genotype had significantly higher high-density lipoprotein (HDL) cholesterol levels (1.46+/-0.07 vs 1.23+/-0.03 mmol/l, P<0.05).

CONCLUSION

In conclusion, our findings suggest a sex-specific protective effect of the Val1483Ile polymorphism in FAS for obesity in Caucasian boys. In addition, the polymorphism may be associated with a beneficial lipid profile in obese boys.

Meta-analysis of the Gly482Ser variant in PPARGC1A in type 2 diabetes and related phenotypes

AIMS/HYPOTHESIS

Peroxisome proliferator-activated receptor-gamma co-activator-1alpha (PPARGC1A) is a transcriptional co-activator with a central role in energy expenditure and glucose metabolism. Several studies have suggested that the common PPARGC1A polymorphism Gly482Ser may be associated with risk of type 2 diabetes, with conflicting results. To clarify the role of Gly482Ser in type 2 diabetes and related human metabolic phenotypes we genotyped this polymorphism in a case-control study and performed a meta-analysis of relevant published data.

MATERIALS AND METHODS

Gly482Ser was genotyped in a type 2 diabetes case-control study (N=1,096) using MassArray technology. A literature search revealed publications that examined Gly482Ser for association with type 2 diabetes and related metabolic phenotypes. Meta-analysis of the current study and relevant published data was undertaken.

RESULTS

In the pooled meta-analysis, including data from this study and seven published reports (3,718 cases, 4,818 controls), there was evidence of between-study heterogeneity (p<0.1). In the fixed-effects meta-analysis, the pooled odds ratio for risk of type 2 diabetes per Ser482 allele was 1.07 (95% CI 1.00-1.15, p=0.044). Elimination of one of the studies from the meta-analysis gave a summary odds ratio of 1.11 (95% CI 1.04-1.20, p=0.004), with no between-study heterogeneity (p=0.475). For quantitative metabolic traits in normoglycaemic subjects, we also found significant between-study heterogeneity. However, no significant association was observed between Gly482Ser and BMI, fasting glucose or fasting insulin.

CONCLUSIONS/INTERPRETATION

This meta-analysis of data from the current and published studies supports a modest role for the Gly482Ser PPARGC1A variant in type 2 diabetes risk.

Genetic variation in UCP2 (uncoupling protein-2) is associated with energy metabolism in Pima Indians

AIMS/HYPOTHESIS

Uncoupling protein-2 (UCP2) is thought to play a role in insulin secretion and the development of obesity. In this study, we investigated the effects of genetic variation in UCP2 on type 2 diabetes and obesity, as well as on metabolic phenotypes related to these diseases, in Pima Indians.

METHODS

The coding and untranslated regions of UCP2, and approximately 1 kb of the 5' upstream region, were sequenced in DNA samples taken from 83 extremely obese Pima Indians who were not first-degree relatives.

RESULTS

Five variants were identified: (1) a -866G/A in the 5' upstream region; (2) a G/A in exon 2; (3) a C/T resulting in an Ala55Val substitution in exon 4; and (4, 5) two insertion/deletions (ins/del; 45-bp and 3-bp) in the 3' untranslated region. Among the 83 subjects whose DNA was sequenced, the -866G/A was in complete genotypic concordance with the Ala55Val and the 3-bp ins/del polymorphism. The G/A polymorphism in exon 2 was extremely rare. To capture the common variation in this gene for association analyses, the -866G/A variant (as a representative of Ala55Val and the 3-bp ins/del polymorphism) and the 45-bp ins/del were also genotyped for 864 full-blooded Pima Indians. Neither of these variants was associated with type 2 diabetes or body mass index. However, in a subgroup of 185 subjects who had undergone detailed metabolic measurements, these variants were associated with 24-h energy expenditure as measured in a human metabolic chamber (p=0.007 for the 45-bp ins/del and p=0.03 for the -866G/A after adjusting for age, sex, family membership, fat-free mass and fat mass).

CONCLUSIONS/INTERPRETATION

Our data indicate that variation in UCP2 may play a role in energy metabolism, but this gene does not contribute significantly to the aetiology of type 2 diabetes and/or obesity in Pima Indians.

Reliability and validity of the combined heart rate and movement sensor Actiheart

Accurate quantification of physical activity energy expenditure is a key part of the effort to understand disorders of energy metabolism. The Actiheart, a combined heart rate (HR) and movement sensor, is designed to assess physical activity in populations.

OBJECTIVE

To examine aspects of Actiheart reliability and validity in mechanical settings and during walking and running.

METHODS

In eight Actiheart units, technical reliability (coefficients of variation, CV) and validity for movement were assessed with sinusoid accelerations (0.1-20 m/s(2)) and for HR by simulated R-wave impulses (25-250 bpm). Agreement between Actiheart and ECG was determined during rest and treadmill locomotion (3.2-12.1 km/h). Walking and running intensity (in J/min/kg) was assessed with indirect calorimetry in 11 men and nine women (26-50 y, 20-29 kg/m(2)) and modelled from movement, HR, and movement + HR by multiple linear regression, adjusting for sex.

RESULTS

Median intrainstrument CV was 0.5 and 0.03% for movement and HR, respectively. Corresponding interinstrument CV values were 5.7 and 0.03% with some evidence of heteroscedasticity for movement. The linear relationship between movement and acceleration was strong (R(2) = 0.99, P < 0.001). Simulated R-waves were detected within 1 bpm from 30 to 250 bpm. The 95% limits of agreement between Actiheart and ECG were -4.2 to 4.3 bpm. Correlations with intensity were generally high (R(2) > 0.84, P < 0.001) but significantly highest when combining HR and movement (SEE < 1 MET).

CONCLUSIONS

The Actiheart is technically reliable and valid. Walking and running intensity may be estimated accurately but further studies are needed to assess validity in other activities and during free-living.

SPONSORSHIP

The study received financial support from the Wellcome Trust and SB was supported by a scholarship from Unilever, UK.

Objectively measured physical activity correlates with indices of insulin resistance in Danish children

OBJECTIVE

To explore the association between measures of insulin resistance with objectively assessed physical activity.

DESIGN

School-based, cross-sectional study.

SUBJECTS

A randomly selected sample of 589 children (310 girls, 279 boys, mean (standard deviations, s.d.) age=9.7 (0.44) y, weight=33.6 (6.4) kg, height=1.39 (0.06) m) from Denmark.

METHODS

Fasting blood samples were analysed for serum insulin and glucose. Physical activity was measured with the uniaxial Computer Science and Applications (CSA) model 7164 accelerometer, worn for at least 3 days (>/=10 h day(-1)). Adiposity was assessed by the sum of four skinfolds. Multiple linear regression were performed to model insulin and glucose from average CSA output, adjusted for age, gender, puberty, ethnicity, birth weight, parental smoking, socioeconomic group, and CSA unit. In addition, we adjusted for skinfold thickness.

RESULTS

Mean fasting serum glucose ranged from 4.1 to 6.5 mmol l(-1) with a mean (s.d.) of 5.1 (0.37) mmol l(-1). Fasting insulin was negatively correlated with CSA output on levels of adjustment. Fasting glucose was not significantly associated with physical activity. However, in girls both indices of insulin resistance were significantly related to activity, whereas in boys none of the associations were significant.

CONCLUSION

Physical activity is inversely associated with fasting insulin in the nondiabetic range of fasting glucose. The relationship was stronger for insulin than for glucose, indicating compensatory action by the beta cells. Our data emphasise the importance of physical activity in children for the maintenance of metabolic control.

Does peroxisome proliferator-activated receptor gamma genotype (Pro12ala) modify the association of physical activity and dietary fat with fasting insulin level?

Peroxisome proliferator-activated receptor gamma (PPARgamma) has a role in controlling adipogenesis and insulin sensitivity. Previous studies have suggested that a common polymorphism (Pro12Ala) in the PPARgamma-2 isoform of this gene may be associated with markers of insulin resistance. We have previously shown that in combination, the relationships with fasting insulin of dietary polyunsaturated to saturated fatty acid ratio (P:S ratio) and physical activity are additive. We have also demonstrated that the association between P:S ratio and fasting insulin level is modified by the Pro12Ala genotype. The purpose of the present study was to investigate whether the Pro12Ala genotype modified the combined relationships of P:S ratio and physical activity level (PAL) on fasting insulin concentration. A population-based cohort of 506 Caucasian men and women aged 31 to 71 years was genotyped for the Pro12Ala polymorphism. P:S ratio was assessed by food-frequency questionnaire (FFQ) and PAL was estimated from 4 days of free-living heart rate monitoring following individual calibration of heart rate against energy expenditure during an exercise stress test. The combined associations of PAL and P:S ratio on fasting insulin level were examined stratified by Pro12Ala genotypes in a dominant model for the Ala allele. Among Pro allele homozygotes, there was no interaction between PAL and P:S ratio on fasting insulin (P =.929). However, in carriers of the Ala allele the association of P:S ratio with fasting insulin was modified by activity level (interaction P = 0.038). In those who were inactive and carried the Ala allele, the age-, sex-, and body mass-adjusted relationship between P:S ratio and log insulin was not significant (beta = -0.03, P =.93). In contrast, in physically active Ala carriers, the association of P:S ratio with log fasting insulin was highly significant (beta = -0.93, P =.004). In conclusion, this study examined the modification by PPARgamma genotype of the association between energy expenditure, P:S ratio, and fasting insulin level, a measure of insulin resistance. These data show that in Pro allele homozygotes the combined associations of P:S ratio and PAL are additive. In contrast, in Ala allele carriers, PAL modifies the association between P:S ratio and fasting insulin level in a multiplicative manner.

Racial/ethnic inequities in continuity and site of care: location, location, location

OBJECTIVE

To examine how continuity of care with the same provider varies by race/ethnicity and by site of care.

DATA SOURCES/STUDY SETTING

Secondary data analyses of the 1996-97 Community Tracking Study household survey, a representative cross-sectional sample of 34,858 U.S. adults (aged 18 to 64 years), were employed.

STUDY DESIGN

Logistic regression analyses were conducted to explore relationships between respondents' race/ethnicity and having a regular site of care, type of site, and continuity with the same provider at this site.

PRINCIPAL FINDINGS

Racial/ethnic minority group members were less likely than whites to identify a regular site of care. Among respondents who identified a regular site, minorities, particularly Spanish-speaking Hispanics, reported less continuity of care with the same provider. However, these disparities in continuity were largely explained by racial/ethnic differences in the types of places where care was obtained. Compared to those who were seen in physicians' offices, continuity with the same provider was much lower among respondents who were seen in hospital out patient departments or health centers or other clinics.

CONCLUSIONS

Racial and ethnic minority group members receive less continuity of care for reasons including lack of a regular site of care and less continuity with the same provider. Greater use of hospital clinics and community health centers by minorities also contributes to this discontinuity.

Effectiveness of telephone reminders in improving rate of appointments kept at an outpatient clinic: a randomized controlled trial

BACKGROUND

Clinic appointments in which patients do not appear (no-show) result in loss of provider time and revenue. Previous studies have shown variable effectiveness in telephone and mailed reminders to patients.

METHODS

We conducted a randomized controlled trial of telephone reminders 1 day before the scheduled appointments in an urban family practice residency clinic. Patients with appointments were randomized to be telephoned 1 day before the scheduled visit; 479 patients were telephoned and 424 patients were not telephoned.

RESULTS

The proportions of patients not showing up for their appointments were 19% in the telephoned and 26% in the not-telephoned groups (P = .0065). Significantly more cancelations were made when telephoning patients before their visit, 17% compared with 9.9%. The opened scheduling slots were used for appointments for other patients. This additional revenue offset the cost of telephone intervention in our cost analysis.

CONCLUSION

Reminding patients by telephone calls 1 day before their appointments yields increased cancelations that can be used to schedule other patients. Telephone reminders provide substantial net revenue, but the results may be population specific.

Improving physicians' HIV risk-assessment skills using announced and unannounced standardized patients

OBJECTIVE

To evaluate feasibility and to validate a rating scale for two educational programs that use standardized patient-instructors (SPIs) in the office setting to improve physicians' HIV risk communication skills.

DESIGN

Pilot randomized trial of announced and unannounced SPIs.

PARTICIPANTS/SETTINGS

Twenty four primary care physicians in the Rochester, NY, area.

MEASUREMENTS

The Rochester HIV Interview Rating Scale (RHIRS), HIV test ordering, physician satisfaction questionnaire.

RESULTS

Physicians found the intervention useful, and predicted a positive effect on their future HIV-related communication. HIV test ordering and RHIRS scores increased similarly in both intervention groups. Announced SPI visits were more convenient and preferred by physicians. Cost for each SPI visit was $75.

CONCLUSIONS

A brief office-based intervention using SPIs was feasible, well-accepted, convenient, and inexpensive. Announced SPIs were preferred to unannounced SPIs. Pilot results suggesting improvement in HIV-related communication should be confirmed in a larger randomized trial.