Race affects the association of obesity measures with insulin sensitivity

Genetic Risk Phenotypes for Type 2 Diabetes Differ with Ancestry in US Adults with Diabetes and Overweight/Obesity

BACKGROUND

Type 2 diabetes (T2D) risk is higher among non-Hispanic black (NHB) and Hispanic individuals, for reasons that are unclear.

AIMS

With this cross-sectional study, we tested the hypothesis that racial disparities in T2D prevalence can be partially traced to heterogeneity in etiology, as indicated by genetic subtypes that reflect distinct T2D phenotypes.

METHODS

Using a diverse sample of 361 US adults with T2D (69.5% women; 34.1% NHB; 13.9% Hispanic), we derived genetic risk scores (GRS) representing five distinct T2D pathophysiological pathways from 94 loci: β-cell, proinsulin, obesity, lipodystrophy, and liver/lipid. Genetic predisposition for insulin resistance (IR) was also assessed using a 52-SNP IR risk score.

RESULTS

The β-cell and proinsulin scores (as median [IQR]) were higher among NHB participants relative to NHW and Hispanics (β-cell GRS [NHB, 0.842(0.784-0.887) vs. NHW, 0.762(0.702-0.835) and Hispanic, 0.772(0.717-0.848)]); proinsulin GRS (NHB, 1.006[0.973-1.070] vs. NHW, 0.969[0.853-1.044] and Hispanic, 0.976[0.901-1.048]), whereas the liver/lipid and 52-SNP IR scores were higher in both NHB and Hispanic participants versus NHW (liver/lipid GRS [NHB, 1.09(0.78-1.18) and Hispanic, 0.895(0.736-1.227) vs. NHW, 0.794(0.666-1.157)]); 52-SNP IR GRS (NHB, 0.0095[0.009-0.010] and Hispanic, 0.0096 [0.0092-0.0101] vs. NHW, 0.0090[0.0084-0.0095]).

CONCLUSIONS

Impaired β-cell function may underlie T2D etiology more profoundly in NHB, whereas hepatic dysfunction, lipid metabolism abnormalities, and genetic IR contribute to T2D etiology to a greater degree in both NHB and Hispanics. Further validation of these findings may form the basis for a personalized medicine approach to prevention and treatment of T2D.

Predictability of genetic risk score for insulin resistance is influenced by both BMI and race

OBJECTIVE

The study objective was to determine whether associations between a genetic risk score (GRS) for insulin resistance (IR) and measures of insulin sensitivity differ by race and/or BMI status in African American (AA) and European American (EA) adults without diabetes.

METHODS

Fifty-three AA and 54 EA participants were classified into "high" or "low" BMI groups using the sample median (25.9 kg/m2) as the cut point. The GRS was derived from 52 previously identified genetic variants. Skeletal muscle insulin sensitivity was measured with the hyperinsulinemic-euglycemic clamp. The homeostasis model assessment of insulin resistance (HOMA-IR) and the Matsuda index of insulin sensitivity were calculated from oral glucose tolerance test values to determine hepatic and whole-body insulin sensitivity, respectively. Linear regression models, stratified by race, assessed interactions between BMI status and GRS on measures of insulin sensitivity.

RESULTS

In EA participants, associations of GRS with HOMA-IR and the Matsuda index differed by BMI status, where the GRS was associated with IR in the high-BMI group only. In AA participants, associations from the clamp differed by BMI status, but an association was observed only in the low-BMI group.

CONCLUSIONS

These results highlight the heterogeneity of IR and support the hypothesis that the relationship between genetic predisposition for IR and obesity is race- and tissue-specific.

Pathophysiological hallmarks in type 2 diabetes heterogeneity (review)

The mechanistic complexity in type 2 diabetes (T2DM) is primarily responsible for the degrees of heterogeneity and development of complications. A complex mode of interactions between different pathophysiological events and diabetogenic environmental factors support for the genesis of diabetes heterogeneity both in phenotypic and clinical contexts. The currently used diabetes classification strategies suffer from several inconsistencies that cannot fully capture the inherent heterogeneity among the diabetes patients. To effectively address this pathobiological and heterogeneity-related issue in diabetes research, the current review proposes nine pathophysiological hallmarks of T2DM that aims to mechanistically explain complexities of diabetes associated pathophysiological events and their underlying features. These pathophysiological hallmarks are pancreatic beta cell dysfunction, insulin sensitivity, insulin resistance, obesity, aging, subclinical inflammation, metabolic dysregulation, prothrombotic state induction and hypertension. Detail knowledge of these pathophysiological hallmarks with their key molecular mediators, influencing factors, clinical biomarkers and clinical assessment methodologies will greatly support precision medicine approaches in diabetes including patient stratification, subtype diagnosis and treatment.

Supplementary Information

The online version contains supplementary material available at 10.1007/s13340-024-00783-w.

Trends and Racial/Ethnic Differences in Age at Diagnosis of Adult-Onset Type 1 and Type 2 Diabetes in the United States, 2016-2022

INTRODUCTION

Age at diagnosis of diabetes is important for informing public health planning and treatment strategies. This study aimed to estimate trends and racial/ethnic differences in age at diagnosis of adult-onset diabetes by type in the U.S.

METHODS

This serial nationwide cross-sectional study used data from the National Health Interview Survey in 2016-2022. Adults aged ≥18 years with self-reported age at diagnosis of adult-onset type 1 diabetes or type 2 diabetes were included. Trends in mean age at diagnosis of type 1 diabetes and type 2 diabetes and in proportions of people with type 1 diabetes or type 2 diabetes diagnosed at different ages were assessed by linear and logistic regressions. Racial/ethnic differences in mean age at diagnosis of type 1 diabetes and type 2 diabetes were determined.

RESULTS

Included were 1,224 type 1 diabetes cases and 14,221 type 2 diabetes cases. From 2016 to 2022, the mean age at diagnosis of type 2 diabetes increased by 0.18 years annually (95% CI=0.05, 0.30 years, p=0.005), but no significant trend was observed for type 1 diabetes. The proportion of type 2 diabetes cases with diagnosis age ≥60 years increased by 3.17% and with diagnosis age in 18-29 years decreased by 5.62% annually (p≤0.01). On average, Hispanic individuals had type 1 diabetes diagnosed 3.2 years older and minority groups had type 2 diabetes diagnosed 2.0-6.1 years younger than non-Hispanic White individuals (p≤0.02).

CONCLUSIONS

Among U.S. adults, the mean age at diagnosis of adult-onset type 1 diabetes remained stable, and of adult-onset type 2 diabetes increased significantly from 2016 to 2022. Substantial and opposite differences in mean diagnosis age of type 1 diabetes and type 2 diabetes by race/ethnicity were identified.

Ethnic differences in the relationship between ectopic fat deposition and insulin sensitivity in Black African and White European men across a spectrum of glucose tolerance

AIM

To examine the hypothesis that there would be ethnic differences in the relationship between ectopic fat and tissue-specific insulin resistance (IR) across a spectrum of glucose tolerance in Black African (BA) and White European (WE) men.

MATERIALS AND METHODS

Fifty-three WE men (23/10/20 normal glucose tolerance [NGT]/impaired glucose tolerance [IGT]/type 2 diabetes [T2D]) and 48 BA men (20/10/18, respectively) underwent a two-step hyperinsulinaemic-euglycaemic clamp with infusion of D-[6,6-2H2]-glucose and [2H5]-glycerol to assess hepatic, peripheral and adipose tissue IR. Magnetic resonance imaging was used to measure subcutaneous adipose tissue, visceral adipose tissue (VAT) and intrahepatic lipid (IHL). Associations between ectopic fat and IR were assessed using linear regression models.

RESULTS

There were no differences in tissue-specific IR between ethnic groups at any stage of glucose tolerance. VAT level was consistently lower in the BA population; NGT (p = 0.013), IGT (p = 0.006) and T2D (p = 0.015). IHL was also lower in the BA compared with the WE men (p = 0.013). VAT and IHL levels were significantly associated with hepatic IR in the BA population (p = 0.001) and with peripheral IR in the WE population (p = 0.027).

CONCLUSIONS

The present study suggests that BA and WE men exhibit the same degree of IR across a glucose tolerance continuum, but with lower VAT and IHL levels in the BA population, suggesting that IR may be driven by a mechanism other than increased ectopic fat accumulation in BA men.

Diet and Survival in Black Women With Epithelial Ovarian Cancer

Importance

Ovarian cancer survival among Black women is the lowest across all racial and ethnic groups. Poor dietary quality also disproportionately affects Black populations, but its association with ovarian cancer survival in this population remains largely unknown.

Objective

To examine associations between dietary patterns and survival among Black women diagnosed with epithelial ovarian cancer (EOC).

Design, Setting, and Participants

This prospective cohort study was conducted among self-identified Black women aged 20 to 79 years newly diagnosed with histologically confirmed EOC in the African American Cancer Epidemiology Study (AACES) between December 2010 and December 2015, with follow-up until October 2022. AACES is a population-based study of ovarian cancer risk and survival among Black women in 11 US regions. Data were analyzed from March 2023 to June 2024.

Exposures

Dietary patterns were assessed by the Healthy Eating Index-2020 (HEI-2020) and Alternative Healthy Eating Index-2010 (AHEI-2010), with scores calculated based on dietary intake in the year prior to diagnosis and collected via the validated Block 2005 Food Frequency Questionnaire. Higher scores indicate better dietary quality.

Main outcomes and measures

Hazard ratios (HRs) and 95% CIs were estimated from multivariable Cox models for the association between adherence to dietary recommendations and overall mortality among all participants and those with high-grade serous ovarian cancer (HGSOC).

Results

Among 483 Black women with EOC (mean [SD] age, 58.1 [10.5] years), 310 deaths were recorded during a median (IQR) follow-up of 4.3 (2.0-8.2) years. No association of dietary patterns with mortality was found among women with EOC overall. However, among 325 women with HGSOC, better adherence to HEI-2020 was associated with decreased mortality in later quartiles compared with the first quartile (HR, 0.63; 95% CI, 0.44-0.92 for quartile 2; HR, 0.67; 95% CI, 0.46-0.97 for quartile 3; HR, 0.63; 95% CI, 0.44-0.91 for quartile 4 ). Similar results were observed with AHEI-2010 among women with HGSOC for the second (HR, 0.62; 95% CI, 0.43-0.89) and fourth (HR, 0.67; 95% CI, 0.45-0.98) quartiles compared with quartile 1.

Conclusions and relevance

In this study, women with moderate and high prediagnosis dietary quality had significantly lower mortality rates from HGSOC compared with women with the lowest prediagnosis dietary quality. These findings suggest that even moderate adherence to dietary guidelines prior to diagnosis may be associated with improved survival among Black women with HGSOC, the most lethal form of ovarian cancer.

Insulin sensitivity and skeletal muscle mitochondrial respiration in Black and White women with obesity

OBJECTIVES

Non-Hispanic black women (BW) have a greater risk of type 2 diabetes (T2D) and insulin resistance (IR) compared to non-Hispanic white women (WW). The mechanisms leading to these differences are not understood, and it is unclear whether synergistic effects of race and obesity impact disease risk. To understand the interaction of race and weight, hepatic and peripheral IR were compared in WW and BW with and without obesity.

METHODS

Hepatic and peripheral IR was measured by a labeled, hyperinsulinemic-euglycemic clamp in BW (n=32) and WW (n=32) with and without obesity. Measurements of body composition, cardiorespiratory fitness, and skeletal muscle (SM) respiration were completed. Data were analyzed by mixed model ANOVA.

RESULTS

Subjects with obesity had greater hepatic and peripheral IR and lower SM respiration (P<0.001). Despite 14% greater insulin (P=0.066), BW tended to have lower peripheral glucose disposal (Rd; P=0.062), which was driven by women without obesity (P=0.002). BW had significantly lower glucose production (P=0.005), hepatic IR (P=0.024), and maximal coupled and uncoupled respiration (P<0.001) than WW. Maximal coupled and uncoupled SM mitochondrial respiration was strongly correlated with peripheral and hepatic IR (P<0.01).

CONCLUSION

While BW without obesity had lower Rd than WW, race and obesity did not synergistically impact peripheral IR. Paradoxically, WW with obesity had greater hepatic IR compared to BW. Relationships between SM respiration and IR persisted across a range of body weight. These data provide support for therapies in BW, like exercise, that improve SM mitochondrial respiration to reduce IR and T2D risk.

Myofiber-specific lipidomics unveil differential contributions to insulin sensitivity in individuals of African and European ancestry

Aims

Individuals of African ancestry (AA) present with lower insulin sensitivity compared to their European counterparts (EA). Studies show ethnic differences in skeletal muscle fiber type (lower type I fibers in AA), muscle fat oxidation capacity (lower in AA), whilst no differences in total skeletal muscle lipids. However, skeletal muscle lipid subtypes have not been examined in this context. We hypothesize that lower insulin sensitivity in AA is due to a greater proportion of type II (non-oxidative) muscle fibers, and that this would result in an ancestry-specific association between muscle lipid subtypes and peripheral insulin sensitivity. To test this hypothesis, we examined the association between insulin sensitivity and muscle lipids in AA and EA adults, and in an animal model of insulin resistance with muscle-specific fiber types.

Methods

In this cross-sectional study, muscle biopsies were obtained from individuals with a BMI ranging from normal to overweight with AA (N = 24) and EA (N = 19). Ancestry was assigned via genetic admixture analysis; peripheral insulin sensitivity via hyperinsulinaemic-euglycemic clamp; and myofiber content via myosin heavy chain immunohistochemistry. Further, muscle types with high (soleus) and low (vastus lateralis) type I fiber content were obtained from high-fat diet-induced insulin resistant F1 mice and littermate controls. Insulin sensitivity in mice was assessed via intraperitoneal glucose tolerance test. Mass spectrometry (MS)-based lipidomics was used to measure skeletal muscle lipid.

Results

Compared to EA, AA had lower peripheral insulin sensitivity and lower oxidative type 1 myofiber content, with no differences in total skeletal muscle lipid content. Muscles with lower type I fiber content (AA and vastus from mice) showed lower levels of lipids associated with fat oxidation capacity, i.e., cardiolipins, triacylglycerols with low saturation degree and phospholipids, compared to muscles with a higher type 1 fiber content (EA and soleus from mice). Further, we found that muscle diacylglycerol content was inversely associated with insulin sensitivity in EA, who have more type I fiber, whereas no association was found in AA. Similarly, we found that insulin sensitivity in mice was associated with diacylglycerol content in the soleus (high in type I fiber), not in vastus (low in type I fiber).Conclusions; Our data suggest that the lipid contribution to altered insulin sensitivity differs by ethnicity due to myofiber composition, and that this needs to be considered to increase our understanding of underlying mechanisms of altered insulin sensitivity in different ethnic populations.

Proinsulin-to-C-Peptide Ratio as a Marker of β-Cell Function in African American and European American Adults

OBJECTIVE

The primary purpose of the current study was to test the hypothesis that the proinsulin-to-C-peptide (PI-to-CP) ratio, as an index of proinsulin secretion, would be higher and associated with indices of β-cell function in African American adults relative to European American adults without type 2 diabetes.

RESEARCH DESIGN AND METHODS

Participants were 114 African American and European American adult men and women. A 2-h oral glucose tolerance test was conducted to measure glucose, insulin, C-peptide, and proinsulin and derive indices of β-cell response to glucose. The Matsuda index was calculated as a measure of insulin sensitivity. The disposition index (DI), the product of insulin sensitivity and β-cell response, was calculated for each phase of β-cell responsivity. Pearson correlations were used to investigate the relationship of the PI-to-CP ratio with each phase of β-cell response (basal, Φb; dynamic, Φd; static, Φs; total, Φtot), disposition indices (DId, DIs, DItot), and insulin sensitivity. Multiple linear regression analysis was used to evaluate independent contributions of race, BMI, and glucose tolerance status on PI-to-CP levels before and after adjustment for insulin sensitivity.

RESULTS

African American participants had higher fasting and 2-h PI-to-CP ratios. The fasting PI-to-CP ratio was positively associated with Φb, and the fasting PI-to-CP ratio and 2-h PI-to-CP ratio were inversely associated with DId and insulin sensitivity only in African American participants.

CONCLUSIONS

The PI-to-CP ratio could be useful in identifying African American individuals at highest risk for β-cell dysfunction and ultimately type 2 diabetes.

Metabolic Syndrome and Its Association with Nonalcoholic Steatohepatitis

The relationship between insulin resistance, metabolic syndrome (MetS), and nonalcoholic fatty liver disease (NAFLD) is complicated. Although insulin resistance is almost universal in people with NAFLD and MetS, NAFLD may be present without features of MetS and vice versa. While NAFLD has a strong correlation with cardiometabolic risk factors, these are not intrinsic components of this condition. Taken together, our knowledge gaps call for caution regarding the common assertion that NAFLD is the hepatic manifestation of the MetS, and for defining NAFLD in broad terms as a "metabolic dysfunction" based on a diverse and poorly understood constellation of cardiometabolic features.

Associations of atrial natriuretic peptide with measures of insulin and adipose depots

Low concentrations of natriuretic peptides (NPs) have been associated with greater risk for Type 2 diabetes (T2D). African American individuals (AA) have lower NP levels and are disproportionately burdened by T2D. The purpose of this study was to test the hypothesis that higher post-challenge insulin in AA adults is associated with lower plasma N-terminal pro-atrial natriuretic peptide (NT-proANP). A secondary purpose was to explore associations between NT-proANP and adipose depots. Participants were 112 AA and European American (EA) adult men and women. Measures of insulin were obtained from an oral glucose tolerance test and hyperinsulinemic-euglycemic glucose clamp. Total and regional adipose depots were measured from DXA and MRI. Multiple linear regression analysis was used to assess associations of NT-proANP with measures of insulin and adipose depots. Lower NT-proANP concentrations in AA participants was not independent of 30-min insulin area under the curve (AUC). NT-proANP was inversely associated with 30-min insulin AUC in AA participants, and with fasting insulin and HOMA-IR in EA participants. Thigh subcutaneous adipose tissue and perimuscular adipose tissue were positively associated with NT-proANP in EA participants. Higher post-challenge insulin may contribute to lower ANP concentrations in AA adults.

Associations of renal sinus fat with blood pressure and ectopic fat in a diverse cohort of adults

Background

Renal sinus fat (RSF) is an ectopic fat depot shown to be associated with visceral adiposity and hypertension in predominantly white populations. The purpose of this analysis is to investigate RSF and associations between RSF and blood pressure in a cohort of African American (AA) and European American (EA) adults. A secondary purpose was to explore risk factors associated with RSF.

Methods

Participants were 116 A A and EA adult men and women. Ectopic fat depots were assessed with MRI: RSF, intraabdominal adipose tissue (IAAT), intermuscular adipose tissue (IMAT), perimuscular adipose tissue (PMAT), and liver fat. Cardiovascular measures included diastolic blood pressure (DBP), systolic blood pressure (SBP), pulse pressure, mean arterial pressure, and flow mediated dilation. Matsuda index was calculated for insulin sensitivity. Pearson correlations were used to investigate associations of RSF with cardiovascular measures. Multiple linear regression was used to evaluate contributions of RSF on SBP and DBP and to explore factors associated with RSF.

Results

No difference was observed in RSF between AA and EA participants. RSF was positively associated with DBP in AA participants, but this was not independent of age and sex. Age, male sex, and total body fat were positively associated with RSF in AA participants. Insulin sensitivity was inversely and IAAT and PMAT were positively associated with RSF in EA participants.

Conclusions

Differential associations of RSF with age, insulin sensitivity, and adipose depots among AA and EA adults suggest unique pathophysiological mechanisms influence RSF deposition, which may contribute to chronic disease etiology and progression.

Obesity Pillars Roundtable: Body mass index and body composition in Black and Female individuals. Race-relevant or racist? Sex-relevant or sexist?

Background

Body mass index (BMI or weight in kilograms/height in meters2) is the most common metric to diagnose overweight and obesity. However, a body composition analysis more thoroughly assesses adiposity, percent body fat, lean body mass (i.e., including skeletal muscle), and sometimes bone mineral density. BMI is not an accurate assessment of body fat in individuals with increased or decreased muscle mass; the diagnostic utility of BMI in individuals is also influenced by race and sex.

Methods

Previous Obesity Pillars Roundtables addressed the diagnostic limitations of BMI, the importance of android and visceral fat (especially among those with South and East Asian ancestry), and considerations of obesity among individuals who identify as Hispanic, diverse in sexual-orientation, Black, Native American, and having ancestry from the Mediterranean and Middle East regions. This roundtable examines considerations of BMI in Black and female individuals.

Results

The panelists agreed that body composition assessment was a more accurate measure of adiposity and muscle mass than BMI. When it came to matters of race and sex, one panelist felt: "race is a social construct and not a defining biology." Another felt that: "BMI should be a screening tool to prompt further evaluation of adiposity that utilizes better diagnostic tools for body composition." Regarding bias and misperceptions of resistance training in female individuals, another panelist stated: "I have spent my entire medical career taking care of women and have never seen a woman unintentionally gain 'too much' muscle mass and bulk up from moderate strength training."

Conclusions

Conveying the importance of race and sex regarding body composition has proven challenging, with the discussion sometimes devolving into misunderstandings or misinformation that may be perceived as racist or sexist. Body composition analysis is the ultimate diagnostic equalizer in addressing the inaccuracies and biases inherent in the exclusive use of BMI.

Association between long-term air pollution exposure and insulin resistance independent of abdominal adiposity in Korean adults

Significant associations between air pollution (AP) and insulin resistance (IR) have been reported in limited populations or certain patient groups, but few studies have addressed this association in the general population, especially in Asians. Although abdominal fat is a major contributor to IR, previous studies have not fully controlled for its effect in the association between AP and IR. We investigated the association between exposure to AP and IR in Korean adults in the general population and whether this association is maintained even after controlling for the effects of abdominal fat, particularly visceral fat. This was a cross-sectional study. Data were obtained for Korean adults who participated in screening health checkups at Seoul National University Health Examination Center from 2006 to 2014. A total of 4251 men and women aged 22-84 years were included. IR was represented by the homeostasis model assessment of insulin resistance (HOMA-IR). Adiposity traits such as visceral adipose tissue (VAT) and subcutaneous adipose tissue areas were measured by computed tomography. We assessed the annual mean concentrations of air pollutants, including particulate matter with an aerodynamic diameter of 10 µm or less (PM₁₀), nitrogen dioxide, sulfur dioxide, and carbon monoxide. HOMA-IR was significantly associated with increased annual mean exposure to PM₁₀ in both men (β = 0.15; 95% CI 0.09, 0.22) and women (β = 0.16; 95% CI 0.09, 0.23), and these associations were maintained even after controlling for VAT area (both p < 0.05). The adjusted mean HOMA-IR increased gradually with the level of long-term PM₁₀ exposure (low, intermediate, and high exposure) (all p for trend < 0.001) in the subgroup analysis. After adjusting for possible confounding factors, including VAT area, the annual mean exposure to PM₁₀ was significantly associated with the presence of IR in both men (OR 1.18; 95% CI 1.03, 1.35) and women (OR 1.44; 95% CI 1.18, 1.76). Other air pollutants, such as NO₂, SO₂ and CO, did not show any significant associations with HOMA-IR or the presence of IR. Persistent exposure to PM₁₀ is the main independent risk factor for IR and exhibits a dose-dependent association regardless of visceral fatness in both men and women.

Insulin Resistance and Cardiometabolic Risk Profile Among Nondiabetic American Young Adults: Insights From NHANES

BACKGROUND

The burden of insulin resistance (IR) among young American adults has not been previously assessed. We evaluated (1) the prevalence and trends of IR and cardiometabolic risk factors and (2) the association between measures of adiposity and IR among adults 18 to 44 years of age without diabetes and preexisting cardiovascular disease.

METHODS

Cross-sectional survey data from six consecutive National Health and Nutrition Examination Survey (2007-2008 to 2017-2018) cycles were analyzed. IR was defined by the homeostatic model assessment for IR (HOMA-IR) of ≥2.5. The temporal trends of IR, cardiometabolic risk factors, and the relationship between IR and measures of adiposity were assessed using multivariable-adjusted regression models.

RESULTS

Among 6247 young adults 18 to 44 years of age, the prevalence of IR was 44.8% (95% CI: 42.0%-47.6%) in 2007-2010 and 40.3% (95% CI: 36.4%-44.2%) in 2015-2018 (P for trend = 0.07). There was a modest association of HOMA-IR with higher body mass index (BMI), waist circumference, total lean fat mass, and total and localized fat mass (all Ps < 0.001). Participants with IR had a higher prevalence of hypertension [31.3% (95% CI: 29.2%-33.5%) vs 14.7% (95% CI: 13.2%-16.2%)], hypercholesterolemia [16.0% (95% CI: 12.4%-19.5%) vs 7.0% (95% CI: 5.8%-8.5%)], obesity [56.6% (95% CI: 53.9%-59.3%) vs 14.7% (95% CI: 13.0%-16.5%)], and poor physical activity levels [18.3% (95% CI: 16.4%-20.2%) vs 11.7% (95%CI: 10.3-13.1%)] compared to participants without IR (all Ps < 0.05).

CONCLUSIONS

Four-in-10 young American adults have IR, which occurs in a cluster with cardiometabolic risk factors. Nearly half of young adults with IR are nonobese. Screening efforts for IR irrespective of BMI may be required.

Obesity and cancer death in white and black adults: A prospective cohort study

OBJECTIVE

This study aimed to determine whether race modifies the association between obesity and cancer death.

METHODS

The Pennington Center Longitudinal Study included 18,296 adults; 35.0% were male and 34.3% were Black. The primary end point was death from cancer.

RESULTS

During a follow-up of 14.3 years, 346 cancer deaths occurred. Among men, race modified the association of BMI and cancer death (p_interaction = 0.045); compared with a BMI of 22 kg/m² , a BMI of 35 in White men was associated with a hazard ratio of 1.74 (95% CI: 1.38-2.21), and in Black men, the hazard ratio was 0.64 (95% CI: 0.45-0.90). Among women, race did not modify the association of BMI and cancer death (p_interaction =0.43); however, compared with a BMI of 22, a BMI of 35 in White women was associated with a hazard ratio of 1.42 (95% CI: 1.18-1.70) and in Black women, the hazard ratio was 0.99 (95% CI: 0.82-1.20).

CONCLUSIONS

In this diverse cohort of adults, having obesity was associated with an increased risk of cancer death in White men and women. In contrast, having obesity was associated with a reduced risk of cancer death in Black men and did not influence risk in Black women.

Genetic risk score prediction of leg fat and insulin sensitivity differs by race/ethnicity in early pubertal children

BACKGROUND

In the United States, the underlying reasons for racial/ethnic disparities in type 2 diabetes risk remain unclear. However, differences in genetic risk for insulin resistance and peripheral adipose tissue distribution may be contributing factors.

OBJECTIVE

To investigate racial/ethnic differences in associations of genetic risk for insulin resistance with leg fat and insulin sensitivity in a cohort of American children.

METHODS

Participants were healthy European-American (n = 83), African-American (n = 79) and Hispanic-American (n = 74) children aged 7-12 years. Genetic risk scores were derived from published variants associated with insulin resistance phenotypes in European adults. Body composition was assessed using dual-energy X-ray absorptiometry. Insulin sensitivity was determined from the frequently sampled intravenous glucose tolerance test and minimal modelling. Statistical models were adjusted for age, sex, pubertal stage and body composition.

RESULTS

In the combined cohort, risk score was inversely associated with insulin sensitivity (p = 0.033) but not leg fat (p = 0.170). Within Hispanic Americans, risk score was inversely associated with insulin sensitivity (p = 0.027) and leg fat (p = 0.005), while associations were non-significant in European and African Americans (p > 0.200).

CONCLUSIONS

The higher type 2 diabetes risk observed among Hispanic Americans may have a genetic basis related to an inability to store lipid in peripheral adipose tissue.

Relative associations of abdominal and thigh compositions with cardiometabolic diseases in African Caribbean men

BACKGROUND

Regional body compositions are differentially associated with cardiometabolic risk factors. Simultaneous inclusion of both upper and lower body composition predictors in models is not often done, and studies which do include both measures (1) tend to exclude some tissue(s) of potential metabolic relevance, and (2) have used study populations with underrepresentation of individuals with African ancestries. Further, most body composition analyses do not employ compositional data analytic approaches, which may result in spurious associations.

OBJECTIVE

The objective of this analysis was to assess associations of abdominal and thigh adipose (AT) and muscle tissues with hypertension and type 2 diabetes using compositional data analytic methods.

RESEARCH DESIGN AND METHODS

This cross-sectional analysis included 610 African Caribbean men (median age: 62 years; mean BMI: 27.8 kg/m2). Abdominal (three components: subcutaneous [ASAT] and visceral [VAT] AT, 'other' abdominal tissue) and mid-thigh (four components: subcutaneous and intermuscular AT, muscle, bone) compositions were measured by computed tomography; additive log ratio transformations were applied to each composition. Regression models were used to simultaneously assess associations of abdominal and thigh component ratios with continuous risk factors (blood pressures, fasting glucose and insulin, HOMA-IR) and disease categories.

RESULTS

A two-fold increase in ASAT:'Other' ratio was associated with higher continuous risk factors and with odds of being in a higher hypertension (OR: 1.77, 95%CI: 1.10-2.84) or diabetes (OR: 1.81, 95%CI: 1.06-3.10) category. A two-fold increased VAT ratio was only associated with higher log-insulin and log-HOMA-IR (β = 0.10, p < 0.05 for both), while a two-fold increased thigh muscle:bone ratio was associated with a lower diabetes category (OR: 0.37, 95%CI: 0.14-1.01).

CONCLUSIONS

These findings support ASAT as a significant driver of cardiometabolic disease in African Ancestry populations, independent of other abdominal and thigh tissues.

Associations between obesity indices and both type 2 diabetes and impaired fasting glucose among West African adults: Results from WHO STEPS surveys

BACKGROUND AND AIM

Various obesity indices such as BMI, waist circumference (WC), waist-hip ratio, (WHR) and waist-to-height ratio (WHtR) are associated with the risk of type 2 Diabetes Mellitus (T2DM). Given few studies examining the strength of the association in this population, we aimed to identify which obesity indices are most strongly associated with T2DM and impaired fasting glucose (IFG) among adults from five West African countries.

METHODS AND RESULTS

Data from 15,520 participants from the World Health Organisation (WHO) STEPs surveys in Burkina Faso, Benin, Mali, Liberia, and Ghana were included in analyses. Multinomial logistic regression was used to calculate the relative risk (RR) per standard deviation (SD) of each anthropometric measure, modelled as both continuous variables and as categorical variables based on established cut-points. In the analyses with continuous variables, the unadjusted RRs for T2DM per SD were 1.30 (1.23, 1.37) for body mass index (BMI); 1.56 (1.46, 1.67) for WC; 2.57 (2.15, 3.09) for WHtR and 1.16 (1.03, 1.31) for WHR. WHtR showed the strongest association with T2DM in all adjusted analyses. For models using categorical variables based on established cut-points, obesity defined using waist circumference (OB-WC) and OB-BMI showed the strongest associations with T2DM, and OB-WHR, the weakest association in all adjusted analyses.

CONCLUSION

WHtR and WC appear to be the indices most strongly associated with T2DM and IFG respectively. Given its simplicity, WC may be the metric that most usefully conveys risk for T2DM in West African adults.

The Triple Health Threat of Diabetes, Obesity, and Cancer-Epidemiology, Disparities, Mechanisms, and Interventions

Obesity and type 2 diabetes are both chronic, relapsing, progressive diseases that are recognized as risk factors for the development of multiple types of cancer. In a recent symposium titled "Hitting A Triple-Diabetes, Obesity, and the Emerging Links to Cancer Risk," convened by The Obesity Society during ObesityWeek 2019, experts in the field presented the current science and highlighted existing research gaps. Topics included (1) the epidemiology of obesity and diabetes and their links to cancer risk; (2) racial and ethnic differences in obesity, diabetes, and cancer risk; (3) biological mechanisms common to obesity and diabetes that may increase cancer risk; and (4) innovative interventions that can be used to prevent the development of cancers related to obesity and diabetes. This report provides an overview of the symposium and describes key research gaps and pressing questions in need of answers to advance the field. The collective burden of obesity, diabetes, and cancer represents one of the largest public health challenges of the century. Although the symposium was titled "hitting a triple," it was recognized that being able to disrupt the linkages among obesity, diabetes, and cancer would be a "grand slam" for public health and medicine.

Obesity and Cancer Risk in White and Black Adults: A Prospective Cohort Study

OBJECTIVE

Anthropometric measures of obesity, including BMI and waist circumference (WC), do not quantify excess adiposity and metabolic abnormalities consistently across racial populations. This study tested the hypothesis that participant race modifies the association of anthropometric measures of obesity and cancer risk.

METHODS

This prospective cohort (The Pennington Center Longitudinal Study) included 18,296 adults, 6,405 (35.0%) male sex and 6,273 (34.3%) Black race. The primary exposures were BMI (weight in kilograms/height in meters squared) and WC (centimeters). The primary end point was the time from study enrollment to diagnosis of histologically confirmed invasive cancer.

RESULTS

During a median follow-up of 14.0 years (interquartile range: 9.8-19.0 years), invasive cancer occurred in 1,350 participants. Among men, race modified the association of BMI (P_interaction = 0.02) and WC (P_interaction = 0.01) with cancer incidence; compared with a BMI of 22 kg/m² , a BMI of 35 kg/m² in White men was associated with a hazard ratio of 1.83 (95% CI: 1.58-2.12), whereas in Black men, the hazard ratio was 0.89 (95% CI: 0.72-1.11). Among women, race did not modify the association of BMI (P_interaction = 0.41) or WC (P_interaction = 0.36) with cancer incidence.

CONCLUSIONS

In this diverse cohort of adults, participant race and sex modified the prognostic associations of anthropometric measures of obesity and cancer risk.

Race, ethnicity, and racism in the nutrition literature: an update for 2020

Social disparities in the US and elsewhere have been terribly highlighted by the current COVID-19 pandemic but also an outbreak of state-sponsored violence. The field of nutrition, like other areas of science, has commonly used 'race' to describe research participants and populations, without the recognition that race is a social, not a biologic, construct. We review the limitations of classifying participants by race, and recommend a series of steps for authors, researchers and policymakers to consider when producing and reading the nutrition literature. We recommend that biomedical researchers, especially those in the field of nutrition, abandon the use of racial categories to explain biologic phenomena but instead rely on a more comprehensive framework of ethnicity; that authors consider not just race and ethnicity but many social determinants of health, including experienced racism; that race and ethnicity not be conflated; that dietary pattern descriptions inform ethnicity descriptions; and that depersonalizating language be avoided.

The Relationship Between Corneal Nerve Density and Hemoglobin A1c in Patients With Prediabetes and Type 2 Diabetes

Purpose

Decreased corneal nerve fiber density and higher corneal epithelial dendritic cells have been reported in established patients with type 2 diabetes; however, alterations in the subbasal nerve plexus in prediabetes with healthy subjects or subjects with diabetes is limited. The study aimed to determine corneal nerve fiber density and morphology and dendritic cell density between healthy subjects and those with prediabetes or type 2 diabetes.

Methods

Fifty-two subjects (aged 30-70 years) were recruited. Blood samples and body metrics were taken. Subjects were grouped as: healthy controls (hemoglobin A1c [HbA1c] < 5.7%), prediabetes (5.7-6.4%), and type 2 diabetes (> 6.4% or physician diagnosis). Central corneal subbasal nerve plexus was imaged using in vivo confocal microscopy. Corneal nerve fiber density and morphology, including interconnections and tortuosity, and dendritic cell density were assessed. Kruskal-Wallis tests were carried out to compare differences in the examined variables between groups. Spearman correlations were carried out to examine the associations between body metrics with HbA1c and corneal findings.

Results

Seventeen healthy controls, 20 subjects with prediabetes, and 15 subjects with type 2 diabetes completed this study. Central corneal nerve fiber density was significantly lower in type 2 diabetes compared to prediabetes (P = 0.045) and healthy controls (P = 0.001). No differences were found in central corneal nerve fiber interconnections, tortuosity, or dendritic cell density between groups. There was a significant association between HbA1c and corneal nerve fiber density (rho = -0.45, P = 0.001) and body mass index (BMI; rho = -0.30, P = 0.04).

Conclusions

Increased HbA1c values are associated with decreased corneal nerve fiber density across the spectrum of type 2 diabetes.

Obesity in African-Americans: The role of physiology

The disproportionate obesity in African American (AA) women has a physiologic basis and can be explained by the interactive effects of insulin secretion, insulin clearance, insulin sensitivity and the glycaemic load of the diet. This review will present data supporting a physiologic basis for obesity propensity in obesity-prone AA women that resides in their unique metabolic/endocrine phenotype: high beta-cell responsiveness, low hepatic insulin extraction and relatively high insulin sensitivity, which together result in a high exposure of tissues and organs to insulin. When combined with a high-glycaemic (HG) diet (that stimulates insulin secretion), this underlying propensity to obesity becomes manifest, as ingested calories are diverted from energy production to storage. Our data indicate that both weight loss and weight loss maintenance are optimized with low-glycaemic (LG) vs HG diet in AA. Whether greater obesity in AA is mechanistically related to their greater prevalence of type 2 diabetes is debatable. This review provides data indicating that obesity is not strongly related to insulin resistance in AA. Rather, insulin resistance in AA is associated with relatively low adipose tissue in the leg, consistent with a genetic predisposition to impaired lipid storage. Greater bioenergetic efficiency has been reported in AA and, via resultant oxidative damage, could plausibly contribute to insulin resistance. In summary, it is proposed here that a subset of AA women are predisposed to obesity due to a specific metabolic/endocrine phenotype. However, greater diabetes risk in AA has an independent aetiology based on impaired lipid storage and mitochondrial efficiency/oxidative stress.

Validity assessment of the single-point insulin sensitivity estimator (spise) for diagnosis of cardiometabolic risk in post-pubertal hispanic adolescents

Insulin measurements are not advised for cardiometabolic risk screening in large groups. Here we assessed the accuracy of the single-point insulin sensitivity estimator (SPISE) to diagnose cardiometabolic risk in Chilean adolescents. In 678 post-pubertal adolescents (52% males, M(SD) age = 16.8 (0.2) years), height, weight, waist circumference, blood lipids, glucose, insulin, and blood pressure were measured. BMI, HOMA-IR, and SPISE were estimated; HOMA-IR values ≥ 2.6 were considered insulin resistance (IR). Metabolic syndrome (MetS) was defined with the joint IDF/AHA/NHBLI standard. Using receiver operating characteristic curves, we obtained optimal SPISE cutpoints for IR and MetS diagnosis. The prevalence of MetS and IR was 8.2% and 17.1%, respectively. In males, the optimal cutoff for MetS diagnosis was 5.0 (sensitivity: 97%; specificity: 82%), and the optimal cutoff for IR diagnosis was 5.9 (sensitivity: 71%; specificity: 83%). In females, a SPISE of 6.0 had the highest sensitivity (90%) and specificity (74%) for MetS diagnosis. A SPISE of 6.4 was the optimal cutoff for IR diagnosis; however, sensitivity and specificity were 61% and 75%. In males and female post-pubertal adolescents, SPISE had a very good and good diagnostic performance, respectively, in predicting MetS. It was an accurate diagnostic tool for IR prediction in males, but not necessarily in females.