Racial/ethnic differences in hepatic steatosis in a population-based cohort of post-menopausal women: the Michigan Study of Women's Health Across the Nation

Prevalence and Characteristics of Metabolic Dysfunction-Associated Fatty Liver Disease among an Iranian Adult Population with Ethnic and Genetic Diversity: Results of the PolyIran-Liver Study

Background

Metabolic dysfunction-associated fatty liver disease (MAFLD) is a rising global public health concern. It has been demonstrated that its prevalence and characteristics vary by region and racial/ethnicity. We aimed to investigate the prevalence of MAFLD and its characteristics among Turkmen and non-Turkmen ethnic groups in a multiethnic population region of Iran.

Methods

In this cross-sectional study, we analyzed baseline data for 1614 participants, aged above 50 years, from the PolyIran-Liver trial who were randomly selected from Gonabad city and determined the prevalence of MAFLD and its demographic and metabolic disorders for both the Turkmen and non-Turkmen ethnic groups. Multivariate binary logistic regressions were applied to identify MAFLD-associated factors for men and women separately for the Turkmen and non-Turkmen populations.

Results

The mean (SD) age of the participants was 59.1(6.7) years. Of the participants, 51.5% (n=831) were men, and 52.9% (n=854) were Turkmen. The prevalence of MAFLD among the overall study population was 39.8% (n=614). It was more common among women (45.8% vs. 34.1% in men, P<0.001), non-Turkmens (43.9% vs. 36.1% in Turkmens, P<0.001), and at age 50-64 (41.5% vs.36.1% in age≥65 P=0.004). The fully adjusted multivariate analysis in sex strata exhibited an independent negative association between Turkmen ethnicity only among men but not among women. The increased waist circumference (WC) was the most common metabolic disorder, observed in more than 95.5% of patients with MAFLD (P<0.001). Multivariate analysis in sex/ethnic strata with adjustment for potential confounders revealed an independent association of MAFLD with increased WC, insulin resistance, impaired fasting glucose/diabetes type 2, and high alanine aminotransferase (ALT) among women in both ethnic groups while with elevated triglyceride (TG) only among Turkmen and high body mass index (BMI) only among non-Turkmen women. Increased WC had the strongest independent association with MAFLD among women and the highest odds ratio (OR) with MAFLD in Turkmen women (OR: 6.10; 95% CI 1.56-23.86 vs. 4.80 in non-Turkmen women). Among men, MAFLD was independently associated with insulin resistance, high BMI, and high ALT in both ethnic groups and elevated TG only in non-Turkmen men (all P<0.001). Insulin resistance had the strongest independent OR with MAFLD among men with similar size in both ethnic groups (4.68 [95% CI 2.56-8.55]) in non-Turkmen men and 4.37 (95% CI 2.27-8.42 in Turkmen men).

Conclusion

This study revealed the high prevalence of MAFLD with a sex and ethnic disparity in the middle-aged population of Gonabad city. Further research is needed to understand the factors contributing to the higher prevalence of MAFLD in this region, particularly in women. Furthermore, considering the diverse ethnic population of Iran, it is suggested that future investigations on the sex and ethnic aspects of MAFLD in the Iranian population be conducted to provide targeted prevention strategies better suited for the Iranian population.

Metabolic Risk Profiles for Hepatic Steatosis Differ by Race/Ethnicity: An Elastography-Based Study of US Adults

BACKGROUND AND AIMS

Most population-based studies of risk profiles for liver steatosis have relied upon serum markers (e.g., ALT or FIB-4) or ultrasound steatosis index to define cases. We sought to examine racial/ethnic differences in metabolic risk factors associated with liver steatosis and fibrosis at the population level using elastography-based measures.

METHODS

In total, 4509 adults completed vibration-controlled transient elastography (VCTE) with controlled attenuated parameter (CAP) examinations in the 2017-2018 National Health and Nutrition Examinations Survey. Race/ethnicity was self-identified; metabolic parameters included waist circumference, obesity, diabetes, hypertension, and hyperlipidemia. Primary outcome was steatosis defined by CAP score ≥ 280 decibels per meter and secondary outcome significant fibrosis by VCTE median stiffness ≥ 8 kilopascals. Race-specific logistic regression models were performed to assess the relationship between metabolic parameters and hepatic steatosis and fibrosis.

RESULTS

Prevalence of elastography-based hepatic steatosis was > 30% for all race/ethnicities. Steatosis was associated with increasing waist circumference for all race/ethnicities (OR ranging 1.7-2.3, p < 0.01). Steatosis was associated with diabetes for Whites (OR 2.4, 95% CI 1.2-4.7), Asians (OR 3.0, 1.4-6.3), and Hispanics (OR 2.2, 1.3-3.6), but not Blacks (OR 1.3, 0.8-2.2); hypertension for Whites (OR 1.7, 1.3-4.7) and Asians (OR 2.1, 1.1-3.8); and hyperlipidemia for Blacks only (OR 2.2, 1.3-3.7). Of metabolic risk factors, higher odds of fibrosis were demonstrated with higher waist circumference per 10 cm increase (OR 2.1, 1.8-2.4) and diabetes (OR 2.5, 1.6-3.7), but the effect of diabetes was present in all racial/ethnic groups except Blacks (p-interaction < 0.05).

CONCLUSION

Blacks have a distinct metabolic phenotype for steatosis, while Asians, Whites, and Hispanics are more similar. Racial/ethnic differences in risk profiles are important to consider in prevention, screening strategies, and interventions for fatty liver disease.

The Association Between Metabolic Syndrome and Non-Alcoholic Fatty Liver Disease Diagnosis Varies by Race

Objectives: This study investigated how the association between metabolic syndrome (MetS) and nonalcoholic fatty liver disease (NAFLD) diagnosis varies between non-Hispanic African American and white patients. Methods: A retrospective cohort study was performed using electronic medical records from an integrated health care system (2010-2018). Adults with records for all MetS measurements (body mass index, lipids, blood pressure, and blood glucose) in 2011, who did not have a NAFLD diagnosis before their last MetS measurement, were included. Results: The study cohort consisted of 139,336 patients (age 56.1 ± 15.2 years, 57.9% female, 79.4% non-Hispanic white). The rate of NAFLD diagnosis was higher in MetS patients compared with non-MetS patients [adjusted hazards ratio (AHR) = 1.99, 95% CI = 1.91-2.09] with a significant interaction by race (AHR = 2.05, 95% CI = 1.95-2.15 in non-Hispanic whites vs. AHR = 1.76, 95% CI = 1.58-1.96 non-Hispanic African Americans, P = 0.017). Secondary analyses revealed that the relative NAFLD diagnosis rate was higher in non-Hispanic whites with MetS compared with non-Hispanic African Americans with MetS among females and patients 18-39 years of age and 40-59 years, but not among males and those ≥60 years of age. Conclusions: Non-Hispanic white patients with MetS, particularly females and those <60 years of age, may be at increased risk of NAFLD compared with non-Hispanic African American MetS patients and may benefit from extra attention regarding NAFLD screening.

Changes in kidney function during the menopausal transition: the Study of Women's Health Across the Nation (SWAN) - Michigan site

OBJECTIVE

The aim of the study was to examine changes in kidney function during the menopausal transition (MT) and associations with levels of sex hormones (follicle stimulating hormone [FSH], sex hormone binding globulin [SHBG], estradiol, and testosterone).

METHODS

We used data from the Michigan site of Study of the Women's Health Across the Nation, a longitudinal study of the MT. For this analysis, we included women who had at least one creatinine measure before the final menstrual period (FMP) and at least one creatinine measure after the FMP (n = 101 women with 440 observations). To determine whether the declines in estimated glomerular filtration rate (eGFR) remained constant during the MT, we used local weighted regression curves to fit eGFR estimates. We examined the association between sex hormones and eGFR with longitudinal mixed models adjusting for baseline age, day of menstrual cycle, and time from FMP.

RESULTS

At baseline, women had a mean age of 45.4 ± 2.5 years; 54% were African-American and 46% were white. Although eGFR declined significantly over time, declines were linear, consistent with declines in eGFR due to age alone rather than the MT. Total testosterone, estradiol, ratio of testosterone:estradiol, and free androgen index were not significantly associated with eGFR, whereas lower FSH (-0.039, 95% confidence interval [CI] -0.067 to -0.012) and higher SHBG (0.050, 95% CI 0.004-0.096) were associated with higher eGFR.

CONCLUSIONS

Kidney function declines during the MT. Although associated with levels of FSH and SHBG, the rate of decline in eGFR is consistent with what would be expected of age alone.

Decreased Mitochondrial Dynamics Is Associated with Insulin Resistance, Metabolic Rate, and Fitness in African Americans

CONTEXT

African American women (AAW) have a higher incidence of insulin resistance and are at a greater risk for the development of obesity and type 2 diabetes than Caucasian women (CW). Although several factors have been proposed to mediate these racial disparities, the mechanisms remain poorly defined. We previously demonstrated that sedentary lean AAW have lower peripheral insulin sensitivity, reduced maximal aerobic fitness (VO2max), and lower resting metabolic rate (RMR) than CW. We have also demonstrated that skeletal muscle mitochondrial respiration is lower in AAW and appears to play a role in these racial differences.

OBJECTIVE

The goal of this study was to assess mitochondrial pathways and dynamics to examine the potential mechanisms of lower insulin sensitivity, RMR, VO2max, and mitochondrial capacity in AAW.

DESIGN

To achieve this goal, we assessed several mitochondrial pathways in skeletal muscle using gene array technology and semiquantitative protein analysis.

RESULTS

We report alterations in mitochondrial pathways associated with inner membrane small molecule transport genes, fusion-fission, and autophagy in lean AAW. These differences were associated with lower insulin sensitivity, RMR, and VO2max.

CONCLUSIONS

Together these data suggest that the metabolic racial disparity of insulin resistance, RMR, VO2max, and mitochondrial capacity may be mediated by perturbations in mitochondrial pathways associated with membrane transport, fission-fusion, and autophagy. The mechanisms contributing to these differences remain unknown.

A Systematic Review of Beta Cell Function in Adults of Black African Ethnicity

BACKGROUND

Understanding ethnic differences in beta cell function has important implications for preventative and therapeutic strategies in populations at high risk of type 2 diabetes (T2D). The existing literature, largely drawn from work in children and adolescents, suggests that beta cell function in black African (BA) populations is upregulated when compared to white Europeans (WE).

METHODS

A systematic literature search was undertaken in June 2018 to identify comparative studies of beta cell function between adults (>age 18 years) of indigenous/diasporic BA and WE ethnicity. All categories of glucose tolerance and all methodologies of assessing beta cell function in vivo were included.

RESULTS

41 studies were identified for inclusion into a qualitative synthesis. The majority were studies in African American populations (n = 30) with normal glucose tolerance (NGT)/nondiabetes (n = 25), using intravenous glucose stimulation techniques (n = 27). There were fewer studies in populations defined as only impaired fasting glucose/impaired glucose tolerance (IFG/IGT) (n = 3) or only T2D (n = 3). Although BA broadly exhibited greater peripheral insulin responses than WE, the relatively small number of studies which measured C-peptide to differentiate between beta cell insulin secretion and hepatic insulin extraction (n = 14) had highly variable findings. In exclusively IGT or T2D cohorts, beta cell insulin secretion was found to be lower in BA compared to WE.

CONCLUSIONS

There is inconsistent evidence for upregulated beta cell function in BA adults, and they may in fact exhibit greater deficits in insulin secretory function as glucose intolerance develops.

Racial and Ethnic Disparities in Nonalcoholic Fatty Liver Disease Prevalence, Severity, and Outcomes in the United States: A Systematic Review and Meta-analysis

BACKGROUND & AIMS

Nonalcoholic fatty liver disease (NAFLD) is the most common chronic liver disease in the United States, affecting 75-100 million Americans. However, the disease burden may not be equally distributed among races or ethnicities. We conducted a systematic review and meta-analysis to characterize racial and ethnic disparities in NAFLD prevalence, severity, and prognosis.

METHODS

We searched MEDLINE, EMBASE, and Cochrane databases through August 2016 for studies that reported NAFLD prevalence in population-based or high-risk cohorts, NAFLD severity including presence of nonalcoholic steatohepatitis (NASH) and significant fibrosis, and NAFLD prognosis including development of cirrhosis complications and mortality. Pooled relative risks, according to race and ethnicity, were calculated for each outcome using the DerSimonian and Laird method for a random-effects model.

RESULTS

We identified 34 studies comprising 368,569 unique patients that characterized disparities in NAFLD prevalence, severity, or prognosis. NAFLD prevalence was highest in Hispanics, intermediate in Whites, and lowest in Blacks, although differences between groups were smaller in high-risk cohorts (range 47.6%-55.5%) than population-based cohorts (range, 13.0%-22.9%). Among patients with NAFLD, risk of NASH was higher in Hispanics (relative risk, 1.09; 95% CI, 0.98-1.21) and lower in Blacks (relative risk, 0.72; 95% CI, 0.60-0.87) than Whites. However, the proportion of patients with significant fibrosis did not significantly differ among racial or ethnic groups. Data were limited and discordant on racial or ethnic disparities in outcomes of patients with NAFLD.

CONCLUSIONS

In a systematic review and meta-analysis, we found significant racial and ethnic disparities in NAFLD prevalence and severity in the United States, with the highest burden in Hispanics and lowest burden in Blacks. However, data are discordant on racial or ethnic differences in outcomes of patients with NAFLD.

Alternative indices of glucose homeostasis as biochemical diagnostic tests for abnormal glucose tolerance in an African setting

AIMS

Accurate diabetes diagnosis is important in Africa, where rates are increasing, and the disease largely undiagnosed. The cumbersome oral glucose tolerance test (OGTT) remains the reference standard, while alternative diagnostic methods are not yet established in Africans. We assessed the ability of fasting plasma glucose (FPG), HbA1c and fructosamine, to diagnose OGTT-based abnormal glucose tolerance in mixed-ancestry South Africans.

METHODS

Mixed-ancestry adults, residing in Cape Town were examined between February and November 2015. OGTT values were used to classify glucose tolerance status as: screen-detected diabetes, prediabetes, dysglycaemia (combination of diabetes and prediabetes) and normal glucose tolerance.

RESULTS

Of the 793 participants included, 65 (8.2%) had screen-detected diabetes, 157 (19.8%) prediabetes and 571 (72.0%) normal glucose tolerance. Correlations of FPG and 2-h glucose with HbA1c (r=0.51 and 0.52) were higher than those with fructosamine (0.34 and 0.30), both p<0.0001. The highest c-statistic for the prediction of abnormal glucose tolerance was recorded with 2-h glucose [c-statistic=0.997 (screen-detected diabetes), 0.979 (prediabetes) and 0.984 (dysglycaemia)] and the lowest with fructosamine (0.865, 0.596 and 0.677). At recommended or data-specific optimal cut-offs, no combination of FPG, HbA1c and fructosamine did better than 2-h glucose, while FPG was better than HbA1c and fructosamine on a range of performance measures.

CONCLUSIONS

Abnormal glucose tolerance in this population is overwhelmingly expressed through 2-h glucose's abnormalities; and no combination of FPG, HbA1c and fructosamine was effective at accurately discriminating OGTT-defined abnormal glucose tolerance. Tested non-glucose based strategies are unreliable alternatives to OGTT for dysglycaemia diagnosis in this population.

Endogenous sex steroid hormones and glucose in a South-Asian population without diabetes: the Metabolic Syndrome and Atherosclerosis in South-Asians Living in America pilot study

AIMS

To examine the associations between endogenous sex steroid hormones (oestradiol, testosterone and sex hormone-binding globulin) with diabetes risk in a South-Asian population living in the USA.

METHODS

We used data from the Metabolic Syndrome and Atherosclerosis in South-Asians Living in America pilot study. The analytical sample included 60 women and 45 men of Asian Indian origin living in the San Francisco Bay Area, who were free from diabetes and cardiovascular disease and did not use exogenous sex steroids. Sex steroid hormone levels were assessed by validated conventional radioimmunoassays, and visceral and hepatic adiposity were assessed by computed tomography. We used multivariable regression to examine the association between endogenous sex steroid hormone levels (log-transformed) and fasting glucose and 2-h glucose levels in a series of sex-stratified models adjusted for age, waist circumference, visceral and hepatic adiposity, and insulin resistance.

RESULTS

In age-adjusted models, lower levels of sex hormone-binding globulin (β = -0.18, 95% CI -0.30, -0.06) and higher levels of free testosterone (β = 0.14, 95% CI 0.02, 0.26) were associated with elevated fasting glucose levels in South-Asian women, whereas lower levels of sex hormone-binding globulin (β = -0.14, 95% CI -0.26, -0.02) and lower levels of total testosterone (β = -0.12, 95% CI -0.24, 0.00) were associated with elevated fasting glucose levels in South-Asian men. Adjustment for waist circumference, visceral adiposity and insulin resistance attenuated most of these associations, while adjustment for hepatic adiposity strengthened some of the observed associations. Similar results were found for 2-h glucose levels.

CONCLUSIONS

Results were consistent with previous research, which suggests that endogenous sex steroid hormones are a risk factor for diabetes across multiple race/ethnic groups. Additional studies are needed to determine whether visceral fat is a mediator or confounder of associations between sex steroid hormone and glucose levels.

Central obesity and nonalcoholic fatty liver disease risk after adjusting for body mass index

AIM: To investigate whether central obesity is associated with nonalcoholic fatty liver disease (NAFLD) formation after adjusting for general obesity.

METHODS: The online databases PubMed, EMBASE, and ISI Web of Science were searched for studies estimating the influence of central obesity on NAFLD occurrence published through April 2014. Studies that did not adjust for body mass index (BMI) were excluded. In addition, the independent effect of BMI was also assessed with the included studies. The pooled effect sizes and 95% confidence intervals (CIs) were calculated using random- or fixed-effects models based on the degree of heterogeneity. Furthermore, subgroup analyses, meta-regression, sensitivity analyses, and publication bias were performed.

RESULTS: Twenty eligible studies were identified. The summary odds ratio (OR) values per-unit increase in waist circumference (WC) and BMI for NAFLD formation were 1.07 (95%CI: 1.03-1.10, I² = 73.9%, n = 11 studies) and 1.25 (95%CI: 1.13-1.38, I² = 88.7%, n = 11 studies), respectively. When the indices were expressed as binary variables (with the non-obesity group as reference), the pooled OR in WC, waist-to-hip ratio, and BMI were 2.34 (95%CI: 1.83-3.00, I² = 41.8%, n = 7 studies), 4.06 (95%CI: 1.53-10.79, I² = 65.7%, n = 3 studies), and 2.85 (95%CI: 1.60-5.08, I² = 57.8%, n = 5 studies), respectively. Using the same studies as the latter (n = 5), pooled OR in WC was 3.14 (95%CI: 2.07-4.77), which is greater than that in BMI.

CONCLUSION: Central obesity may pose a greater threat to national health than general obesity, although both are independently associated with increased risk of NAFLD.

Reproductive history and chronic hepatic steatosis in the Michigan Study of Women's Health Across the Nation

BACKGROUND

Reproductive history, particularly maternal age at most recent birth, may reflect lower risk for chronic disease and mortality due to socioeconomic factors, lifestyle behaviors, or genetics. Reproductive history has not been examined with respect to hepatic steatosis, the most common liver disease in the United States. Our objective was to examine the association between reproductive history and hepatic steatosis.

METHODS

We examined the association between reproductive history characteristics--specifically age at most recent birth--and the odds of moderate to severe hepatic steatosis using a population-based retrospective cohort study of women who underwent hepatic ultrasound at the Michigan site of the Study of Women's Health Across the Nation (n=331).

RESULTS

Women who gave birth at ≥ 35 years of age comprised 19% of the study population and were similar to other women regarding sociodemographic history and health behaviors. In multivariable analyses adjusting for age, race/ethnicity, chronic disease, and medications associated with hepatic steatosis, age at birth ≥ 35 years was associated with significantly decreased odds of hepatic steatosis (adjusted odds ratio [OR] 0.41, 95% confidence interval [CI] 0.20-0.87), which was attenuated after adjustment for waist circumference (OR 0.51, 95% CI 0.24-1.10). Other reproductive factors including gravidity, parity, miscarriages and abortions, recall of gestational weight gain, breastfeeding, age at first birth, and age at final menstrual period were not associated with hepatic steatosis.

CONCLUSIONS

Women who were older at their most recent birth had a reduced odds of hepatic steatosis, possibly associated with their lower waist circumference.