Increased fasting triglyceride levels are associated with hepatic insulin resistance in Caucasian but not African-American adolescents

Total bilirubin and bilirubin-to-triglycerides ratio predict changes in glycated hemoglobin in healthy children

Objective

Bilirubin and triglycerides can regulate insulin secretion and glucose uptake. The aim of our study is to analyze associations between total bilirubin (TB) and the bilirubin-to-triglycerides ratio (BTR) with metabolic markers in healthy prepubertal children.

Methods

Subjects were 246 healthy children (mean age 8), of whom 142 (58%) were reevaluated 4 years later (mean age 12). The subjects were stratified according to age into three groups (<7.8 years; 7.8-9.6 years; and >9.6 years; n=82 each) at baseline and into two groups (<12.9 years and ≥12.9 years; n=71 each) at follow-up. Anthropometrics and laboratory parameters [TB and its fractions (direct and indirect bilirubin), triglycerides, HDL-cholesterol, glucose, insulin, HOMA-IR, HOMA-B and glycated hemoglobin (HbA1c)] were assessed at both baseline and follow-up.

Results

TB and BTR showed independent and negative association with baseline and follow-up HbA1c. These associations were stronger for BTR and in the highest age group. No independent associations were observed with HOMA-IR or HOMA-B.

Conclusion

TB and BTR are independently associated with HbA1c and predict its changes over time in healthy children. Our results indicate that TB and BTR may be useful parameters in studies of glucose tolerance in healthy children.

Oral glucose tolerance response curve predicts disposition index but not other cardiometabolic risk factors in healthy adolescents

OBJECTIVES

In obese adults the shape of the glucose response curve during an oral glucose tolerance test (OGTT) predicts future type 2 diabetes. Patients with an incessant increase or monophasic curves have increased risk compared to those with biphasic curves. Since type 2 diabetes is associated with increased cardiometabolic risk, we studied whether differences in OGTT response curve are associated with differences in cardiometabolic risk factors in healthy adolescents across a wide body mass index (BMI) range.

METHODS

Sixty-nine (33F/36M), white adolescents (age: 15.2 ± 1.7 years; BMI: 21.5 ± 4.7 kg/m²; mean ± SD) were studied. Risk factors measured included percent body fat, blood pressure, lipids, augmentation index, reactive hyperemia, endothelin 1, plasminogen activator 1, inflammatory markers (interleukin 6, c-reactive protein), insulin secretion, insulin sensitivity (Matusda index), and disposition index (DI).

RESULTS

Thirty-two subjects had biphasic responses; 35 subjects had monophasic responses and two females had incessant increases. Sex did not affect the frequency of responses. Glucose area under the curve during OGTT was greater in those with a mono vs. biphasic curves (p=0.01). Disposition index was markedly lower in subjects with a monophasic curve than in those with a biphasic curve (3.6 [2.3-5.0] vs. 5.8 [3.8-7.6], median [25th, 75th%] p=0.003). Triglyceride to high-density lipoprotein cholesterol (HDL) ratio was higher in subjects with a monophasic curve (p=0.046).

CONCLUSIONS

The decreased disposition index indicates that in healthy adolescents a monophasic response to OGTT is due to decreased insulin secretion relative to the degree of insulin resistance present. This was not associated with differences in most other cardiometabolic risk markers.

TRIAL REGISTRATION

Clinical Trials.gov, NCT02821104.

Obesity preventive function of novel edible mushroom, Basidiomycetes-X (Echigoshirayukidake): Manipulations of insulin resistance and lipid metabolism

Echigoshirayukidake is an edible mushroom found in Uonuma, Japan in 1994. It was assigned to a new species of Basidiomycetes (BDM-X) but is uniquely defect of forming bashidium. The high antioxidant activity and β-glucan content of BDM-X suggest possible functions preventing type 2 diabetes. In the present study, anti-obesity and insulin resistance preventive functions of BDM-X were examined using genetically defined obese model rat, OLETF (Otsuka Long Evans Tokushima Fatty) by feeding regular diet with and without supplementation of 5% dried BDM-X powder (BDMP) for 15 weeks. BDMP supplementation to the diet significantly (p < 0.01) suppressed the body weight gain and also visceral fat accumulation during the feeding period compared to control diet. Simultaneously, the insulin resistance and the plasma levels of adiponectin and triglycerides were significantly (p = 0.003) ameliorated in the BDMP supplemented diet group. A statistical multivariate analysis showed the weight of three types of adipose tissue (epididymal, retroperirenal, and mesenteric fat) positively correlated with HOMA-IR (Homeostasis Model Assessment of Insulin Resistance), and negatively correlated with plasma adiponectin. These results indicate BDM-X is a new resource applicable to the functional foods or the complementary biomedicines to prevent metabolic syndromes leading to type 2 diabetes.

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A new mushroom, Echigoshirayukidake (BDM-X), ameliorates postprandial sugar and insulin spike enhancing insulin sensitivity.

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BDM-X prevented body weight gain, hyperlipidemia, NEFA, and visceral fat deposition.

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HOMA-IR was improved by BDM-X.

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Anti-metabolic syndrome effect of BDM-X could be related to increase of adiponectin level.

Ethnic distinctions in the pathophysiology of type 2 diabetes: a focus on black African-Caribbean populations

Type 2 diabetes (T2D) is a global public health priority, particularly for populations of black African-Caribbean ethnicity, who suffer disproportionately high rates of the disease. While the mechanisms underlying the development of T2D are well documented, there is growing evidence describing distinctions among black African-Caribbean populations. In the present paper, we review the evidence describing the impact of black African-Caribbean ethnicity on T2D pathophysiology. Ethnic differences were first recognised through evidence that metabolic syndrome diagnostic criteria fail to detect T2D risk in black populations due to less central obesity and dyslipidaemia. Subsequently more detailed investigations have recognised other mechanistic differences, particularly lower visceral and hepatic fat accumulation and a distinctly hyperinsulinaemic response to glucose stimulation. While epidemiological studies have reported exaggerated insulin resistance in black populations, more detailed and direct measures of insulin sensitivity have provided evidence that insulin sensitivity is not markedly different to other ethnic groups and does not explain the hyperinsulinaemia that is exhibited. These findings lead us to hypothesise that ectopic fat does not play a pivotal role in driving insulin resistance in black populations. Furthermore, we hypothesise that hyperinsulinaemia is driven by lower rates of hepatic insulin clearance rather than heightened insulin resistance and is a primary defect rather than occurring in compensation for insulin resistance. These hypotheses are being investigated in our ongoing South London Diabetes and Ethnicity Phenotyping study, which will enable a more detailed understanding of ethnic distinctions in the pathophysiology of T2D between men of black African and white European ethnicity.

Black African men with early type 2 diabetes have similar muscle, liver and adipose tissue insulin sensitivity to white European men despite lower visceral fat

AIMS/HYPOTHESIS

Type 2 diabetes is more prevalent in black African than white European populations although, paradoxically, black African individuals present with lower levels of visceral fat, which has a known association with insulin resistance. Insulin resistance occurs at a tissue-specific level; however, no study has simultaneously compared whole body, skeletal muscle, hepatic and adipose tissue insulin sensitivity between black and white men. We hypothesised that, in those with early type 2 diabetes, black (West) African men (BAM) have greater hepatic and adipose tissue insulin sensitivity, compared with white European men (WEM), because of their reduced visceral fat.

METHODS

Eighteen BAM and 15 WEM with type 2 diabetes underwent a two-stage hyperinsulinaemic-euglycaemic clamp with stable glucose and glycerol isotope tracers to assess tissue-specific insulin sensitivity and a magnetic resonance imaging scan to assess body composition.

RESULTS

We found no ethnic differences in whole body, skeletal muscle, hepatic or adipose tissue insulin sensitivity between BAM and WEM. This finding occurred in the presence of lower visceral fat in BAM (3.72 vs 5.68 kg [mean difference -1.96, 95% CI -3.30, 0.62]; p = 0.01). There was an association between skeletal muscle and adipose tissue insulin sensitivity in WEM that was not present in BAM (r = 0.78, p < 0.01 vs r = 0.25 p = 0.37).

CONCLUSIONS/INTERPRETATION

Our data suggest that in type 2 diabetes there are no ethnic differences in whole body, skeletal muscle, hepatic and adipose tissue insulin sensitivity between black and white men, despite differences in visceral adipose tissue, and that impaired lipolysis may not be contributing to skeletal muscle insulin resistance in men of black African ethnicity.

Prevalence and Associated Factors of Insulin Resistance in Adults from Maracaibo City, Venezuela

Background and Aim. Insulin resistance (IR) is a prominent pathophysiologic component in a myriad of metabolic disorders, including obesity, prediabetes, and type 2 diabetes mellitus, which are common in our locality. The objective of this study was to determine the prevalence of IR and factors associated with this condition in an adult population from Maracaibo city, Venezuela. Methodology. A cross-sectional, descriptive study with multistaged randomized sampling was carried out in 2026 adults. IR was defined as HOMA2-IR ≥ 2. A multiple logistic regression model was constructed in order to evaluate factors associated with IR. Results. The prevalence of IR was 46.5% (n = 943), with 46.7% (n = 450) in the general population, 46.4% (n = 493) in females, and 47.90% (n = 970) in males (p = 0.895). IR prevalence tended to increase with age and was significantly greater in subjects aged ≥30 years (χ (2) = 16.726; p = 2.33 × 10(-4)). Employment, alcohol consumption, obesity, high triacylglycerides, low HDL-C, and dysglycemia were associated with greater odds of IR, whereas a high level of physical activity appeared to be weak protective factor against IR. Conclusions. The prevalence of IR is elevated in our locality. The main determinants of this condition appear to be the presence of obesity, high triacylglycerides, low HDL-C, dysglycemia, and alcohol intake.

Increased Pre- and Post-Meal Free Fatty Acid Levels in Black, Obese Adolescents

BACKGROUND

Black adolescents are at increased risk of cardiometabolic disease but have lower fasting triglyceride, which is usually associated with decreased risk. No one has studied racial differences in triglycerides or free fatty acids (FFAs) after a high-fat meal.

METHODS

Oral glucose tolerance testing was used to assess insulin secretion, sensitivity, and disposition index (DI). Endothelial function, triglycerides, FFA, c-reactive protein, interleukin 6 (IL6), and adiponectin were measured both pre- and 3 hr postprandially (McDonald's Big Breakfast(®) and 12 ounce Sprite(®)) in obese adolescents (10-13 years, 9 black and 7 white). Endothelial function was assessed using reactive hyperemic changes in forearm vascular resistance (FVR).

RESULTS

Oral glucose tolerance test (OGTT) showed no difference in insulin sensitivity, but blacks tended to have (P = 0.08) higher insulin secretion and had increased DI (P = 0.003). After a high-fat meal, triglycerides increased in both groups (P < 0.001), tended to be lower in blacks compared with whites preprandially (64 ± 33 mg/dL vs 110 ± 80, P = 0.064), and was lower postprandially (112 ± 63 vs 188 ± 112, P = 0.039). Pre- and postprandial FFA (Black: 0.58 ± 0.15 and 0.39 ± 0.18 vs. white: 0.44 ± 0.14 and 0.26 ± 0.06, P = 0.020) and adiponectin (P = 0.002) were increased in blacks. FFA decreased in both groups postprandially (P = 0.002). IL6 increased after the meal (P = 0.022). Endothelial function decreased postprandially (P < 0.02), but this was due to a decrease in preocclusion FVR.

CONCLUSIONS

These results indicate that differences in fat metabolism are present in both black and white obese adolescents. How these differences explain higher rates of cardiometabolic disease in blacks is unclear.

Surrogate measures of insulin sensitivity when compared to euglycemic hyperinsulinemic clamp studies in Asian Indian men without diabetes

AIM

Fasting surrogate measures of insulin sensitivity are increasingly used in research and clinical practice. To assess the reliability of these measures, we aimed to evaluate multiple fasting surrogate measures simultaneously in non-diabetic subjects in comparison with the euglycemic hyperinsulinemic clamp study.

METHODS

Sixteen normoglycemic male South Indian subjects were studied. After an overnight fast, blood samples were collected for glucose, insulin and lipid profile measurements, and stepped euglycemic hyperinsulinemic clamp studies were performed on all subjects. Steady state glucose infusion rates (M value) during low and high insulin phases of the clamp were calculated. Correlation of M value with surrogate markers of insulin sensitivity was performed. Predictive accuracy of surrogate indices was measured in terms of Root Mean Squared Error (RMSE) and leave-one-out cross-validation-type RMSE of prediction using a calibration model.

RESULTS

M values showed a strong and significant correlation (p<0.01) with the following surrogate markers: Fasting insulin (r=-0.714), Fasting glucose to insulin ratio (FGIR, r=0.747) and Raynaud index (r=0.714). FGIR had a significantly lower RMSE when compared with HOMA-IR and QUICKI.

CONCLUSIONS

Among the surrogate measures, FGIR had the strongest correlation with M values. FGIR was also the most accurate surrogate measure, as assessed by the calibration model.

Combined dyslipidemia in childhood

Combined dyslipidemia (CD) is now the predominant dyslipidemic pattern in childhood, characterized by moderate-to-severe elevation in triglycerides and non-high-density lipoprotein cholesterol (non-HDL-C), minimal elevation in low-density lipoprotein cholesterol (LDL-C), and reduced HDL-C. Nuclear magnetic resonance spectroscopy shows that the CD pattern is represented at the lipid subpopulation level as an increase in small, dense LDL and in overall LDL particle number plus a reduction in total HDL-C and large HDL particles, a highly atherogenic pattern. In youth, CD occurs almost exclusively with obesity and is highly prevalent, seen in more than 40% of obese adolescents. CD in childhood predicts pathologic evidence of atherosclerosis and vascular dysfunction in adolescence and young adulthood, and early clinical cardiovascular events in adult life. There is a tight connection between CD, visceral adiposity, insulin resistance, nonalcoholic fatty liver disease, and the metabolic syndrome, suggesting an integrated pathophysiological response to excessive weight gain. Weight loss, changes in dietary composition, and increases in physical activity have all been shown to improve CD significantly in children and adolescents in short-term studies. Most importantly, even small amounts of weight loss are associated with significant decreases in triglyceride levels and increases in HDL-C levels with improvement in lipid subpopulations. Diet change focused on limitation of simple carbohydrate intake with specific elimination of all sugar-sweetened beverages is very effective. Evidence-based recommendations for initiating diet and activity change are provided. Rarely, drug therapy is needed, and the evidence for drug treatment of CD in childhood is reviewed.

Racial Disparities in the Pathogenesis of Type 2 Diabetes and its Subtypes in the African Diaspora: A New Paradigm

The global epidemic of diabetes has extended to the developing countries including Sub-Sahara Africa. In this context, blacks with type 2 diabetes in the African Diaspora continue to manifest 1.5-2 times higher prevalent rates than in their white counterparts. Previous studies have demonstrated that blacks with and without type 2 diabetes have alterations in hepatic and peripheral insulin sensitivity, beta-cell function, and hepatic insulin clearance as well as hepatic glucose dysregulation when compared to whites. In addition, non-diabetic blacks in the African Diaspora manifest multiple metabolic mediators that predict type 2 diabetes and its subtypes. These pathogenic modifiers include differences in subclinical inflammation, oxidative stress burden, and adipocytokines in blacks in the African Diaspora prior to clinical diagnosis. Consequently, blacks in the African Diaspora manifest subtypes of type 2 diabetes, including ketosis-prone diabetes and J type diabetes. Given the diversity of type 2 diabetes in blacks in the African Diaspora, we hypothesize that blacks manifest multiple early pathogenic defects prior to the diagnosis of type 2 diabetes and its subtypes. These metabolic alterations have strong genetic component, which appears to play pivotal and primary role in the pathogenesis of type 2 diabetes and its subtypes in blacks in the African Diaspora. However, environmental factors must also be considered as major contributors to the higher prevalence of type 2 diabetes and its subtypes in blacks in the African Diaspora. These multiple alterations should be targets for early prevention of type 2 diabetes in blacks in the African Diaspora.

Relationship between elevated triglyceride levels with the increase of HOMA-IR and HOMA-β in healthy children and adolescents with normal weight

To test the hypothesis that mildly elevated triglyceride levels are associated with the increase of homeostasis model assessment of insulin resistance (HOMA-IR) and β-cell function (HOMA-β) indices in healthy children and adolescents with normal weight, we conducted a cross-sectional population study. Based on fasting triglyceride levels, participants were allocated into groups with and without triglyceride levels ≥1.2 mmol/L. Normal weight was defined by body mass index between the 15th and 85th percentiles, for age and gender. Insulin resistance and insulin secretion were estimated using HOMA-IR and HOMA-β indices. A total of 1660 children and adolescents were enrolled, of them 327 (19.7%) with mildly elevated triglycerides. The multivariate linear regression analysis showed that mildly elevated triglyceride levels in children were associated with HOMA-IR (β = 0.214, p < 0.001), HOMA-β (β = 0.139, p = 0.001), systolic (β = 0.094, p = 0.01), and diastolic blood pressure (β = 0.102, p = 0.007), whereas in adolescents, HOMA-IR (β = 0.267, p < 0.001) and HOMA-β (β = 0.154, p < 0.001), but not systolic (β = 0.029, p = 0.38) and diastolic blood pressure (β = 0.015, p = 0.642), showed association with mildly elevated triglycerides.

CONCLUSION

Mildly elevated triglyceride levels are associated with increased HOMA-IR and HOMA-β indices in healthy children and adolescents with normal weight.

The association between the triglyceride to high-density lipoprotein cholesterol ratio with insulin resistance (HOMA-IR) in the general Korean population: based on the National Health and Nutrition Examination Survey in 2007-2009

AIMS

This study explores the association between the ratio of triglyceride (TG) and high-density lipoprotein cholesterol (HDL-C) and insulin resistance according to waist circumference in the general Korean population.

METHODS

7623 participants were selected from the Korean National Health and Nutrition Examination Survey (KNHANES) conducted during 2007-2009 and included in this cross-sectional study. Insulin resistance was defined as the values equal to or greater than the 75th percentile of the homeostasis model assessment of insulin resistance (HOMA-IR).

RESULTS

Positive correlation was found between the ratio of TG and HDL-C and other variables such as waist circumference, total cholesterol, and HOMA-IR for both men and women. The odds ratios (ORs) (95% confidence interval) for insulin resistance for the highest quartile of TG/HDL-C were 2.48 in men and 3.05 in women. The significant relationship between the TG/HDL-C ratio and insulin resistance was not only maintained across all quartiles of waist circumference but also seemed to be enhanced in the higher quartiles of waist circumference.

CONCLUSION

In the general Korean population, there seems to be a linear association between TG/HDL-C ratio and insulin resistance, regardless of degrees of waist circumference.

The triglyceride-to-HDL cholesterol ratio: association with insulin resistance in obese youths of different ethnic backgrounds

OBJECTIVE

We evaluated whether the triglyceride-to-HDL cholesterol (TG/HDL-C) ratio is associated with insulin resistance (IR) in a large multiethnic cohort of obese youths.

RESEARCH DESIGN AND METHODS

Obese youths (1,452) had an oral glucose tolerance test and a fasting lipid profile. Insulin sensitivity was estimated using the whole body insulin sensitivity index (WBISI) and homeostasis model assessment (HOMA)-IR and evaluated, in a subgroup of 146 obese youths, by the hyperinsulinemic-euglycemic clamp. The cohort was divided by ethnicity (612 whites, 357 Hispanics, and 483 African Americans) and then stratified into ethnicity-specific tertiles of TG/HDL-C ratio. Differences across tertiles were evaluated, and the association between the TG/HDL-C ratio and insulin sensitivity (WBISI) was defined by a multiple stepwise linear regression analysis. The area under the receiver operating characteristic (ROC) curve (AUC) was determined to calculate the TG/HDL-C ratio cutoff to identify insulin-resistant subjects by ethnicity.

RESULTS

In each ethnic group and across rising tertiles of TG/HDL-C ratio, insulin sensitivity (WBISI) progressively decreased, whereas 2-h glucose and the AUC-glucose progressively increased. The cutoff for TG/HDL-C ratio was 2.27, and the odds of presenting with IR, in youths with TG/HDL-C ratio higher than the cutoff, was 6.023 (95% CI 2.798-12.964; P < 0.001) in white girls and boys, whereas for both Hispanics and African Americans the AUC-ROCs were not significant, thus not allowing the calculation of an optimal cutoff TG/HDL-C value.

CONCLUSIONS

The TG/HDL-C ratio is associated with IR mainly in white obese boys and girls and thus may be used with other risk factors to identify subjects at increased risk of IR-driven morbidity.

Relationships between lipid profiles and metabolic syndrome, insulin resistance and serum high molecular adiponectin in Japanese community-dwelling adults

Background

There are few studies to demonstrate the associations between newly addressed lipid profiles and metabolic syndrome (MetS)-associated variables.

Methods

Study participants without medications for hypertension, diabetes, or dyslipidemia {614 men aged 58 ± 14 (mean ± standard deviation; range, 20-89) years and 779 women aged 60 ± 12 (range, 21-88) years} were randomly recruited from a single community at the time of their annual health examination. The association between lipid profiles (total cholesterol (T-C), triglycerides (TG), low-density lipoprotein cholesterol (LDL-C), high-density lipoprotein cholesterol (HDL-C), non-HDL-C, T-C/HDL-C, TG/HDL-C, LDL-C/HDL-C ratio and MetS, Insulin resistance by homeostasis model assessment of insulin resistance (HOMA-IR), and serum HMW adiponectin were analyzed.

Results

In multiple linear regression analysis, TG/HDL-C and T-C/HDL-C ratios as well as TG showed significantly strong associations with all three MetS-associated variables in both men and women. In men, the ROC curve analyses showed that the best marker for these variables was TG/HDL-C ratio, with the AUC for presence of MetS (AUC, 0.82; 95% CI, 0.77-0.87), HOMA-IR (AUC, 0.75; 95% CI, 0.70-0.80), and serum HMW adiponectin (AUC, 0.67; 95% CI, 0.63-0.71), respectively. The T-C/HDL-C ratio, TG, HDL-C, LDL-C/HDL-C ratio, and non-HDL-C also discriminated these markers; however all their AUC estimates were lower than TG/HDL-C ratio. These results were similar in women.

Conclusion

In Japanese community-dwelling adults, lipid ratios of TG/HDL-C, T-C/HDL-C, LDL-C/HDL-C as well as TG and HDL-C were consistently associated with MetS, insulin resistance and serum HMW adiponectin. Lipid ratios may be used as reliable markers.

Growth curves for cardio-metabolic risk factors in children and adolescents

OBJECTIVE

This study developed percentile curves for anthropometric (waist circumference) and cardiovascular (lipid profile) risk factors for US children and adolescents.

STUDY DESIGN

A representative sample of US children and adolescents from the National Health and Nutrition Examination Survey from 1988 to 1994 (NHANES III) and the current national series (NHANES 1999-2006) were combined. Percentile curves were constructed, nationally weighted, and smoothed using the Lambda, Mu, and Sigma method. The percentile curves included age- and sex-specific percentile values that correspond with and transition into the adult abnormal cut-off values for each of these anthropometric and cardiovascular components. To increase the sample size, a second series of percentile curves was also created from the combination of the 2 NHANES databases, along with cross-sectional data from the Bogalusa Heart Study, the Muscatine Study, the Fels Longitudinal Study and the Princeton Lipid Research Clinics Study.

RESULTS

These analyses resulted in a series of growth curves for waist circumference, total cholesterol, LDL cholesterol, triglycerides, and HDL cholesterol from a combination of pediatric data sets. The cut-off for abnormal waist circumference in adult males (102 cm) was equivalent to the 94(th) percentile line in 18-year-olds, and the cut-off in adult females (88 cm) was equivalent to the 84(th) percentile line in 18-year-olds. Triglycerides were found to have a bimodal pattern among females, with an initial peak at age 11 and a second at age 20; the curve for males increased steadily with age. The HDL curve for females was relatively flat, but the male curve declined starting at age 9 years. Similar curves for total and LDL cholesterol were constructed for both males and females. When data from the additional child studies were added to the national data, there was little difference in their patterns or rates of change from year to year.

CONCLUSIONS

These curves represent waist and lipid percentiles for US children and adolescents, with identification of values that transition to adult abnormalities. They could be used conditionally for both epidemiological and possibly clinical applications, although they need to be validated against longitudinal data.

Indices of insulin action calculated from fasting glucose and insulin reflect hepatic, not peripheral, insulin sensitivity in African-American and Caucasian adolescents

Insulin stimulates muscle glucose uptake and inhibits hepatic glucose production. Measures of insulin sensitivity or insulin resistance must take both of these actions into account. Homeostatic model assessment of insulin resistance (HOMA(IR)) and quantitative insulin sensitivity check index (QUICKI) are two simple measures of insulin resistance and insulin sensitivity that are derived from fasting glucose and insulin levels as such it is likely that they reflect primary hepatic insulin action and not muscular effects. To prove this hypothesis, the relationships of HOMA(IR) and QUICKI to peripheral insulin sensitivity (S(I)(*)) and hepatic insulin resistance (HIR) were assessed in 34 adolescents (age 13.5 +/- 2.9 yr, body mass index 23.0 +/- 5.7, mean +/- SD; 16 Caucasian and 14 African-American). S(I)(*) and HIR were determined using the stable-labeled, frequently sampled intravenous glucose tolerance test (250 mg total glucose/kg, 13% [6,6]-D(2)-glucose). The former was calculated using the one-compartment minimal model and stable glucose concentration (S(I)(*)), and the latter was determined over the last hour of the study by multiplying hepatic glucose production (Steele's equation) by mean plasma insulin concentration. As expected, HOMA(IR) and QUICKI were significantly related to HIR (log HOMA(IR) and log HIR, r = 0.73, p < 0.001; QUICKI and log HIR, r = -0.69, p < 0.001) but not S(I)(*). When both S(I)(*) and HIR were included in the equations, only the relationships to log HIR were significant (log HOMA(IR), p < 0.001; QUICKI, p < 0.001). The relationships were similar in African-American and Caucasian subjects. These results demonstrate that in adolescents, HOMA(IR) and QUICKI assess hepatic but not peripheral insulin action.

Ethnicity and nonalcoholic fatty liver disease in an obesity clinic: the impact of triglycerides

Nonalcoholic fatty liver disease (NAFLD) is a growing problem that is associated with the metabolic syndrome. The goal of the present study was to evaluate for ethnic differences in NAFLD and clinical correlates of NAFLD. The study population consisted of 567 patients seen at an urban obesity clinic. Elevated aminotransferase levels were used as a surrogate marker for NAFLD. The prevalence of elevated aminotransferases was highest in Hispanics (39%), followed by Caucasians (28%), and African Americans (12%). In univariate analysis, elevated aminotransferase levels were associated with ethnicity (Hispanic > African American, P < 0.001, and Caucasian > African American P = 0.030), hypertriglyceridemia (P < 0.001), and male gender (P < 0.001). The pattern of results was confirmed in multivariate analysis, except that the differences between Caucasians and African Americans was no longer significant. In conclusion, in an obesity clinic population, elevated aminotransferase levels and hypertriglyceridemia were most common in Hispanics and least common in African Americans.

Does the association of the triglyceride to high-density lipoprotein cholesterol ratio with fasting serum insulin differ by race/ethnicity?

Background

The triglyceride to high-density lipoprotein cholesterol (TG/HDL-C) ratio has been reported to be as closely correlated with insulin resistance as is the fasting serum insulin concentration (FSI), and therefore it is seen as a clinically useful way to identify the concomitant presence of insulin resistance and dyslipidemia. However, conflicting findings exist for the association of the TG/HDL-C ratio with FSI by race/ethnicity.

Methods

The associations of FSI concentration, serum triglyceride concentrations, and HDL-C were analyzed using log-binomial regression analyses and receiver operating characteristic (ROC) curve analysis among nondiabetic adults (n = 2652, aged ≥ 20 years, 51.2% men) in the United States.

Results

After adjustment for potential confounding effects, the prevalence ratio of hyperinsulinemia was 2.16 (95% confidence interval [CI], 1.74 to 2.08) when using a single cutoff point of 3.5, and 2.23 (95% CI, 1.83 to 2.72) when using race/ethnicity-specific cutoff points of 3.0 for non-Hispanic whites and Mexican Americans and 2.0 for non-Hispanic blacks for the TG/HDL-C ratio. The area under the ROC curve of the TG/HDL-C ratio for predicting hyperinsulinemia was 0.77 (95% CI, 0.74 to 0.79), 0.75 (95% CI, 0.69 to 0.77), and 0.74 (95% CI, 0.69 to 0.76) for non-Hispanic whites, non-Hispanic blacks, and Mexican Americans, respectively.

Conclusion

There was a significant association between the TG/HDL-C ratio and FSI among three major racial/ethnic groups in the United States. Our results add further support to the notion that the TG/HDL-C ratio may be a clinically simple and useful indicator for hyperinsulinemia among nondiabetic adults regardless of race/ethnicity.