Adiponectin and leptin in African Americans

Alterations in metabolic status of healthy individuals with and without obesity during transition from adolescence to young adulthood

Aim: Extensive research is carried out throughout the world in healthy persons with obesity phenotype in concern with prevalence, metabolic profiling, etc. To the best of the authors’ knowledge, not many studies have investigated the status of adiponectin, specific inflammatory changes, oxidative damage in healthy adolescents and young adults with obesity. Present study was undertaken in adolescents and young adults of urban population in a district of North Karnataka, India, in a view to understand relationship between hormone adiponectin, oxidative stress markers like C3, C4, high sensitivity C-reactive protein (hs-CRP) in non-hypertensive, non-diabetic, euthyroid individuals with and without obesity. Methods: Participant selection was done using cluster sampling technique. Participating adolescents and young adults, each with and without obesity were included in the study. Screening of participants for diabetes, hypertension, and thyroid disorders was done, their serum level of adiponectin, hs-CRP, C3, C4, ceruloplasmin (Cp), thiobarbituric acid reactive substances (TBARS), and total antioxidant capacity (TAC) were estimated using standardized methods in National Accreditation Board for Testing and Calibration Laboratories (NABL) laboratory. Results: Adiponectin (young adults lower than adolescents, P = 0.01) levels were low, while hs-CRP and Cp (young adults higher than adolescents, P = 0.01) levels were high with increasing age in non-obese. While in persons having obesity, aging adiponectin levels were low while hs-CRP, C3, Cp levels were high significantly. Females without obesity had significantly higher values of C3 than males. Adiponectin showed higher levels in females than males, however, statistical significance could not be achieved (P = 0.308). While females with obesity, exhibited statistically lower levels of adiponectin, and higher levels of C3 and C4. Conclusions: Being non-diabetic and non-hypertensive yet obese, tagged by one time of assay, does not suffice to be categorized as healthy. Healthy young adults with obesity are exhibiting lower levels of adiponectin and higher levels of inflammatory and oxidative stress markers compared to adolescents with obesity. This implies, the so categorized “healthy obese” participants are in a phase of transition towards an unhealthy state.

Lower Life Satisfaction and Inflammation in African American Adults: Body Adiposity Mediation and Sex Moderation

Both lower life satisfaction (LLS) and chronic inflammation are underlying conditions for numerous diseases. We investigated their associations in African American adults, within the context of three hypotheses: (a) perceived LLS will be positively associated with inflammation measured by serum C-reactive protein (CRP); (b) this association will be mediated by body adiposity; and (c) these associations will be moderated by sex. Participants (n = 83; >45 years; 59% women) were a subsample of a larger church-based intervention to reduce cardiovascular risks and were assessed at baseline and after 6 months. Body adiposity (BMI/hip/waist circumferences) was measured by standardized methods and CRP with ELISA. LLS was self-reported. The analyses were conducted in the structural equation modeling (SEM) framework. The direct relationship between LLS and CRP was significant for all participants but was mediated by BMI/hip/waist circumferences. Multi-group SEM analysis provided evidence for sex moderation by showing that the mediating pathway from LLS to CRP through BMI, and to a lesser extent through hip/waist circumferences, was significant only in women. In conclusion, perceived LLS was positively associated with the level of inflammation mediated by BMI/hip/waist circumference, with the association between LLS and CRP being stronger in women. These findings contribute to the current literature untangling mediation/moderation processes in which perceived LLS may contribute to adiposity-related inflammation. They also add to precision medicine development, suggesting that stress and inflammation-reducing interventions should focus on African Americans, particularly women.

Sex and Body Circumferences Associated with Serum Leptin in African American Adults

Objective: Cardiovascular disease (CVD) continues to be a leading cause of death for U.S. adults, especially African Americans (AA). Yet, few studies have examined a comprehensive set of metabolic health and health behavior factors related to CVD risk in this population. This study investigated the relationship between serum leptin and anthropometries (body mass index [BMI], circumferences [waist-WC, hip-HC, and waist/hip ratio W/H]), metabolic health (systolic and diastolic blood pressure [BP], serum lipids, glucose, and C-reactive protein [CRP]), and health behaviors (hours of sleep, physical activity) in midlife and older AAs. Materials and Methods: Participants (n = 89, ≥45 years of age) were AAs in six churches in North Florida enrolled in a broader church-based longitudinal study. Anthropometric measurements, serum analyses, and self-reported items. Results: Serum leptin was positively correlated with gender (being female) (r = 0.623, p < 0.001), BMI log transformed (r = 0.469, p < 0.001), WC (r = 0.440, p < 0.001), HC (r = 0.658, p < 0.001), use of BP medication (r = 0.216, p < 0.05), and serum CRP (r = 0.277, p < 0.01). Correlations by sex showed significant relationships for both men and women between leptin and BMI log transformed, WC, and HC. The final multiple regression model [R² = 0.758, F(4, 66) = 55.871, p < 0.001] showed that 75.8% of the variance in leptin was explained by being female (β = 0.65, p < 0.001), WC (β = 0.26, p < 0.02), and HC (β = 0.28, p < 0.01). Conclusions: Findings more specifically delineate the variables associated with serum leptin in AAs, particularly WC and HC, and suggest greater attention to possible risk for leptin resistance in AA females. Clinical Trial Registration: This study is registered at www.clinicaltrials.gov NCT03339050.

Leptin Concentrations in Non-Obese and Obese Non-Diabetes Nigerian-Africans

BACKGROUND

Controversial findings exist on the role of leptin in obesity and its correlation with metabolic variables, with few data emanating from Nigerian-Africans. Plasma leptin was therefore determined in obese and non-obese. Its relationship with obesity indices and metabolic variables were further envisaged.

MATERIALS AND METHODS

A cross-sectional comparative study on 87 randomly-selected non-diabetes Nigerians distributed into 3 groups (24 normal, 23 pre-obese and 40 obese). Obesity indices, fasting Insulin (FI) and homeostasis model assessment-insulin resistance (HOMA-IR) were determined. Plasma leptin was determined by sandwich enzyme-linked immunosorbent assay. Mann-Whitney U-test, Independent Kruskal-Wallis test, Spearman correlation and Step-wise Multivariate Logistic Regression analysis determined outcomes.

RESULTS

Median+IQR leptin concentrations were higher in obese {61.8(40.8, 91.4) ng/mL, p<0.001} than pre-obese {42.7(28.0, 51.7) ng/mL, p=0.003} and normal {28.6(20.7, 39.8) ng/mL, p=0.03} BMI categories. Leptin was higher (p<0.001) in females than males {Median+IQR, 52.0 (35.0, 80.0) ng/mL versus 34.0(24, 65.0 ng/mL)}. Leptin was positively correlated with body fat percentage (BFP), r=0.57; waist circumference (WC), r=0.46 and body mass index (BMI), r=0.50, p<0.001, respectively in all subjects, with higher correlation coefficient in males than females. Leptin showed sex-specific correlations to age, FI and HOMA-IR. In the unadjusted models, central obesity/generalized obesity, WC, BMI, BFP, combined pre-obesity/obesity, younger age and female sex were significantly (p<0.001) associated with log-transformed leptin. WC (OR: 1.2, 95% CI, 1.05-1.38, p=0.009), BFP (OR: 1.41, 95% CI, 1.07-1.84, p=0.013) and BMI (OR: 1.6, 95% CI, 1.13-2.31, p=0.008) in men and all subjects, were independently associated with hyperleptinaemia following adjustments.

CONCLUSION

Plasma leptin concentrations, fasting insulin and insulin resistance are higher in obese and pre-obese than normal controls, with females showing higher leptin concentrations than males. Leptin is independently related to BMI, BFP, WC, female sex and generalized/central obesity in Nigerian-Africans especially males. It showed sex-specific relations to age, fasting insulin and HOMA-IR.

The biology of human overfeeding: A systematic review

This systematic review has examined more than 300 original papers dealing with the biology of overfeeding. Studies have varied from 1 day to 6 months. Overfeeding produced weight gain in adolescents, adult men and women and in older men. In longer term studies, there was a clear and highly significant relationship between energy ingested and weight gain and fat storage with limited individual differences. There is some evidence for a contribution of a genetic component to this response variability. The response to overfeeding was affected by the baseline state of the groups being compared: those with insulin resistance versus insulin sensitivity; those prone to obesity versus those resistant to obesity; and those with metabolically abnormal obesity versus those with metabolically normal obesity. Dietary components, such as total fat, polyunsaturated fat and carbohydrate influenced the patterns of adipose tissue distribution as did the history of low or normal birth weight. Overfeeding affected the endocrine system with increased circulating concentrations of insulin and triiodothyronine frequently present. Growth hormone, in contrast, was rapidly suppressed. Changes in plasma lipids were influenced by diet, exercise and the magnitude of weight gain. Adipose tissue and skeletal muscle morphology and metabolism are substantially altered by chronic overfeeding.

Association of Leptin: Adiponectin ratio and metabolic risk markers in postmenopausal women

Leptin and adiponectin play an important role in the regulation of body weight and energy homeostasis. The purpose of the present study was to ascertain the relationship between leptin to adiponectin ratio (L:A) and metabolic risk factors in postmenopausal women.This is a cross sectional case-control study. A total of 523 postmenopausal women were recruited for the study 270 postmenopausal women with metabolic syndrome and 253 apparently healthy control postmenopausal women without metabolic syndrome. Biochemical and Anthropometrical parameters were measured. Leptin and adiponectin levels were determined by sandwich enzyme-linked immunosorbent assay, insulin resistance was determined by homeostasis model assessment for insulin resistance (HOMA-IR). Results of this study indicate that leptin (15.92 ± 10.50 vs.9.43 ± 4.39 pg/ml, p < 0.001), L:A ratio (1.08 ± 1.06 vs.0.42 ± 0.38 pg/ml, p < 0.001), HOMA-IR, the lipid profile, and other metabolic risk factors (waist circumference (WC), waist-to-hip ratio(WHR), body mass index((BMI)), fasting plasma glucose (FPG) level and fasting plasma insulin(FPI)) were significantly higher but HDL, HDL/LDL and adiponectin level (20.55 ± 10.76 vs.30.08 ± 13.08 pg/ml, p < 0.001)were significantly lower in postmenopausal women with metabolic syndrome than in women without the syndrome (p < 0.001). Further, in postmenopausal women with metabolic syndrome, L: A ratio was significantly positive (p < 0.05 or p < 0.001) correlated with WC, BMI, WHR, TG, FPG, TC/HDL, LDL/HDL, FPI and HOMA-IR (p < 0.01), and negatively correlated with HDL and HDL/LDL (p < 0.001). Conclusively L: A ratio was found to be significantly associated with central obesity and other metabolic risk factors so that high L:A ratio may act as a diagnostic marker for metabolic syndrome in postmenopausal women.

Tumor expression of adiponectin receptor 2 and lethal prostate cancer

To investigate the role of adiponectin receptor 2 (AdipoR2) in aggressive prostate cancer we used immunohistochemistry to characterize AdipoR2 protein expression in tumor tissue for 866 men with prostate cancer from the Physicians' Health Study and the Health Professionals Follow-up Study. AdipoR2 tumor expression was not associated with measures of obesity, pathological tumor stage or prostate-specific antigen (PSA) at diagnosis. However, AdipoR2 expression was positively associated with proliferation as measured by Ki-67 expression quartiles (P-trend < 0.0001), with expression of fatty acid synthase (P-trend = 0.001), and with two measures of angiogenesis (P-trend < 0.1). An inverse association was observed with apoptosis as assessed by the TUNEL assay (P-trend = 0.006). Using Cox proportional hazards regression and controlling for age at diagnosis, Gleason score, year of diagnosis category, cohort and baseline BMI, we identified a statistically significant trend for the association between quartile of AdipoR2 expression and lethal prostate cancer (P-trend = 0.02). The hazard ratio for lethal prostate cancer for the two highest quartiles, as compared to the two lowest quartiles, of AdipoR2 expression was 1.9 (95% confidence interval [CI]: 1.2-3.0). Results were similar when additionally controlling for categories of PSA at diagnosis and Ki-67 expression quartiles. These results strengthen the evidence for the role of AdipoR2 in prostate cancer progression.

Cancer risks among patients with type 2 diabetes: a 10-year follow-up study of a nationwide population-based cohort in Taiwan

BACKGROUND

This study aims to determine cancer risks among patients with type 2 diabetes through a follow-up study on a nationwide population-based cohort that included Taiwanese diabetic patients and general population in Taiwan as well as to estimate the population attributable fraction (PAF) of site-specific cancer risks that can be attributed to type 2 diabetes in Taiwanese population by using standardized incidence ratios (SIRs, 95% CI).

METHODS

Subjects with type 2 diabetes consisted of 472,979 patients aged ≥ 20 years, whereas general population consisted of 9,411,249 individuals of the same age limit but are not diabetic. Subjects were identified from 1997 to 1998 and followed up until December 31, 2007 or until the first manifestation of any cancer.

RESULTS

Cancer sites with increased risks in men, which were consistent with the main and sensitivity analyses, included pancreas (SIR=1.62; 95% CI=1.53 to 1.72), liver (1.61; 1.57 to 1.64), kidney (1.32; 1.25 to 1.40), oral (1.16, 1.12 to 1.21), and colorectal (1.19, 1.15 to 1.22). Cancer sites with increased risks in women included liver (1.55; 1.51 to 1.60), pancreas (1.44; 1.34 to 1.55), kidney (1.38; 1.30 to 1.46), endometrium (1.36; 1.26 to 1.47), bladder (1.19; 1.11 to 1.27), colorectal (1.16; 1.13 to 1.20), and breast (1.14; 1.09 to 1.18). Overall, PAFs were highest for liver cancer in men (4.0%) and women (3.7%), followed by pancreas (3.4%) and kidney (1.6%) cancers in men, and then for endometrium (1.8%) and kidney (1.8%) cancers in women.

CONCLUSION

Our data suggested that increased cancer risks are associated with type 2 diabetes.

Weight Loss Programs May Have Beneficial or Adverse Effects on Fat Mass and Insulin Sensitivity in Overweight and Obese Black Women

Objective

Weight loss interventions have produced little change in insulin sensitivity in black women, but mean data may obscure metabolic benefit to some and adverse effects for others. Accordingly, we analyzed insulin sensitivity relative to fat mass change following a weight loss program.

Design and Methods

Fifty-four black women (BMI range 25.9 to 54.7 kg/m²) completed the 6-month program that included nutrition information and worksite exercise facilities. Fat mass was measured by dual-energy X-ray absorptiometry, and insulin sensitivity index (S_I) was calculated from an insulin-modified intravenous glucose tolerance test using the minimal model.

Results

Baseline S_I (range 0.74 to 7.58 l/mU⁻¹•min⁻¹) was inversely associated with fat mass (r = −0.516, p < 0.001), independent of age. On average, subjects lost fat mass (baseline 40.8 ± 12.4 to 39.4 ± 12.6 kg [mean ± SD], P < 0.01), but 17 women (32 %) actually gained fat mass. S_I for the group was unchanged (baseline 3.3 ± 1.7 to 3.2 ± 1.6, P = 0.67). However, the tertile with greatest fat mass loss (−3.6 kg, range −10.7 to −1.7 kg) improved insulin sensitivity (S_I +0.3 ± 1.2), whereas the tertile with net fat mass gain (+0.9 kg, range −0.1 to +3.8 kg) had reduced insulin sensitivity (S_I −0.7 ± 1.3) from baseline values (P < 0.05 by ANOVA).

Conclusions

Black women in a weight loss program who lose fat mass may have improved insulin sensitivity, but fat mass gain with diminished sensitivity is common. Additional support for participants who fail to achieve fat mass loss early in an intervention may be required for success.

Different associations of subscapular and triceps skinfold thicknesses with pathogen load: an ecogeographical analysis

OBJECTIVES

The dominant evolutionary perspective on adipose tissue has considered it a relatively inert energy store. However, variability in adipose tissue distribution has recently been associated with age, parity, thermal environment and immune function. Genes regulating the innate immune system are more strongly expressed in deep-lying than peripheral adipose tissue. We hypothesized that central adiposity would correlate more strongly than peripheral adiposity with pathogen load across populations.

METHODS

Primary outcomes were subscapular and triceps skinfolds from 133 male and 106 female populations. National values for disability-adjusted life years lost, attributable to infectious diseases, were used to index pathogen load. Linear mixed-effects models were fitted, including a random effect term by country to investigate the association of each skinfold with pathogen load, adjusting for the other skinfold, mean annual temperature and clustering of the populations across countries.

RESULTS

Adjusting for subscapular skinfold, triceps skinfold was not associated with pathogen load in either sex. Adjusting for triceps skinfold, subscapular skinfold was negatively associated with pathogen load in both sexes (P < 0.02). These associations were independent of variability in annual temperature. Adjusting for pathogen load and temperature, Oceanic populations had a different fat distribution compared to other populations.

CONCLUSIONS

Across populations, higher pathogen load was associated with reduced central but not peripheral skinfolds, supporting the hypothesis that central adiposity is more closely associated with immune function. This scenario might explain why some populations increase disproportionately in central adiposity when the environment shifts from low-energy high-pathogen status to high-energy low-pathogen status.

Gender differences in the association of visceral and subcutaneous adiposity with adiponectin in African Americans: the Jackson Heart Study

BACKGROUND

Adiponectin, paradoxically reduced in obesity and with lower levels in African Americans (AA), modulates several cardiometabolic risk factors. Because abdominal visceral adipose tissue (VAT), known to be reduced in AA, and subcutaneous adipose tissue (SAT) compartments may confer differential metabolic risk profiles, we investigated the associations of VAT and SAT with serum adiponectin, separately by gender, with the hypothesis that VAT is more strongly inversely associated with adiponectin than SAT.

METHODS

Participants from the Jackson Heart Study, an ongoing cohort of AA (n = 2,799; 64% women; mean age, 55 ± 11 years) underwent computer tomography assessment of SAT and VAT volumes, and had stored serum specimens analyzed for adiponectin levels. These levels were examined by gender in relation to increments of VAT and SAT.

RESULTS

Compared to women, men had significantly lower mean levels of adiponectin (3.9 ± 3.0 μg/mL vs. 6.0 ± 4.4 μg/mL; p < 0.01) and mean volume of SAT (1,721 ± 803 cm(3) vs. 2,668 ± 968 cm(3); p < 0.01) but significantly higher mean volume of VAT (884 ± 416 cm(3) vs. 801 ± 363 cm(3); p < 0.01). Among women, a one standard deviation increment in VAT was inversely associated with adiponectin (β = - 0.13; p < 0.0001) after controlling for age, systolic blood pressure, fasting plasma glucose, high-density lipoprotein cholesterol, triglycerides, education, pack-years of smoking and daily intake of alcohol. The statistically significant inverse association of VAT and adiponectin persisted after additionally adjusting for SAT, body mass index (BMI) and waist circumference (WC), suggesting that VAT provides significant information above and beyond BMI and WC. Among men, after the same multivariable adjustment, there was a direct association of SAT and adiponectin (β = 0.18; p = 0.002) that persisted when controlling for BMI and WC, supporting a beneficial effect of SAT. Insulin resistance mediated the association of SAT with adiponectin in women.

CONCLUSION

In African Americans, abdominal visceral adipose tissue had an inverse association with serum adiponectin concentrations only among women. Abdominal subcutaneous adipose tissue appeared as a protective fat depot in men.

Paradoxical Hyperadiponectinemia is Associated With the Metabolically Healthy Obese (MHO) Phenotype in African Americans

BACKGROUND: It has been suggested that adiponectin may offer protection against the adverse health effects of obesity. In this study, we determined the prevalence of paradoxically high adiponectin or paradoxical hyperadiponectinemia (PHA) among obese African Americans and investigated its relationship with the metabolically healthy obese (MHO) phenotype. METHODS: Total adiponectin and metabolic markers including fasting glucose, insulin, serum lipids and obesity measures were determined in 822 unrelated participants from the Howard University Family Study (HUFS). Logistic regression models were used to evaluate the association between MHO phenotype and PHA while adjusting for relevant covariates. RESULTS: Overall, men had significantly lower adiponectin levels than women. However, adiponectin level was associated with obesity measures, glucose, insulin and insulin resistance index in both men and women. Equal proportion of the obese male and female subjects (19.2%; 66/343) had PHA; these obese individuals with PHA had a healthier metabolic profile including higher HDL-cholesterol, lower insulin levels and smaller waist circumference and insulin levels compared to those without PHA. Also, 28% (96/343) of the study participants met the criteria of MHO phenotype. Interestingly, 42% (28/66) of the obese individuals with PHA also had the MHO phenotype. Finally, the MHO phenotype was associated with PHA in both men and women. CONCLUSIONS: These findings confirm the presence of MHO in African Americans and demonstrate the association of PHA with the MHO phenotype. In all, our findings along with other published results provide evidence for a more systematic investigation of the mechanisms underlying the protective function of adiponectin and its potential therapeutic applications in human metabolic disorders.

Central obesity, leptin and cognitive decline: the Sacramento Area Latino Study on Aging

BACKGROUND/AIMS

Central obesity is a risk factor for cognitive decline. Leptin is secreted by adipose tissue and has been associated with better cognitive function. Aging Mexican Americans have higher levels of obesity than non-Hispanic Whites, but no investigations examined the relationship between leptin and cognitive decline among them or the role of central obesity in this association.

METHODS

We analyzed 1,480 dementia-free older Mexican Americans who were followed over 10 years. Cognitive function was assessed every 12-15 months with the Modified Mini Mental State Exam (3MSE) and the Spanish and English Verbal Learning Test (SEVLT).

RESULTS

For females with a small waist circumference (≤35 inches), an interquartile range difference in leptin was associated with 35% less 3MSE errors and 22% less decline in the SEVLT score over 10 years. For males with a small waist circumference (≤40 inches), an interquartile range difference in leptin was associated with 44% less 3MSE errors and 30% less decline in the SEVLT score over 10 years. There was no association between leptin and cognitive decline among females or males with a large waist circumference.

CONCLUSION

Leptin interacts with central obesity in shaping cognitive decline. Our findings provide valuable information about the effects of metabolic risk factors on cognitive function.

Relationship of adipokines with insulin sensitivity in African Americans

INTRODUCTION

Cytokines produced by adipose tissue, including adiponectin, have been associated with metabolic abnormalities. The purpose of this study was to examine the relationship of insulin sensitivity measured by euglycemic hyperinsulinemic insulin clamp with plasma adiponectin and other adipokines in young adult African Americans.

METHODS

Participants were healthy African Americans. Anthropometric measures, blood pressure, an oral glucose tolerance test and an euglycemic hyperinsulinemic insulin clamp were performed. Insulin sensitivity measurements were adjusted for percentage of fat mass. Plasma concentrations of adiponectin, plasminogen activator inhibitor-1 (PAI-1) and interleukin-6 (IL-6) were assayed on plasma from fasting blood samples. Pearson correlation coefficients and multiple regression models were fitted to assess the association between glucose sensitivity and cytokines.

RESULTS

In univariate analysis, there were statistically significant correlations of plasma adiponectin level (r = 0.19, P = 0.004), PAI-1 (r = -0.19, P = 0.020) and IL-6 (r = -0.24, P < 0.001) with measures of insulin sensitivity after adjustment for both fat mass and insulin clamp concentration. In multivariate analysis, adiponectin [geometric mean ratios (GMR) 1.15, P = 0.007], PAI-1 (GMR 0.998, P = 0.021) and body mass index (GMR 0.95, P < 0.001) were each independently associated with insulin sensitivity. For IL-6, there was no significant association with insulin sensitivity independent of obesity.

CONCLUSION

These data show a significant and independent positive correlation of adiponectin with insulin sensitivity. The relationship of IL-6 with insulin sensitivity seems to be dependent on adiposity.

Glucose intolerance in the West African Diaspora: a skeletal muscle fibre type distribution hypothesis

In the United States, Black Americans are largely descendants of West African slaves; they have a higher relative proportion of obesity and experience a higher prevalence of diabetes than White Americans. However, obesity rates alone cannot explain the higher prevalence of type 2 diabetes. Type 2 diabetes is characterized by insulin resistance and beta-cell dysfunction. We hypothesize that the higher prevalence of type 2 diabetes in African Americans (as compared to White Americans) is facilitated by an inherited higher percentage of skeletal muscle fibre type II and a lower percentage of skeletal muscle fibre type I. Skeletal muscle fibre type II is less oxidative and more glycolytic than skeletal muscle fibre type I. Lower oxidative capacity is associated with lower fat oxidation and a higher disposal of lipids, which are stored as muscular adipose tissue in higher amounts in Black compared to White Americans. In physically active individuals, the influence of muscle fibre composition will not be as detrimental as in physically inactive individuals. This discrepancy is caused by the plasticity in the skeletal muscle fibre characteristics towards a higher activity of oxidative enzymes as a consequence of physical activity. We suggest that a higher percentage of skeletal muscle fibre type II combined with physical inactivity has an impact on insulin sensitivity and high prevalence of type 2 diabetes in Blacks of West African ancestry.

Weight regain after a diet-induced loss is predicted by higher baseline leptin and lower ghrelin plasma levels

CONTEXT

Appetite-related hormones may play an important role in weight regain after obesity therapy.

OBJECTIVE

Our objective was to investigate the potential involvement of ghrelin, leptin, and insulin plasma levels in weight regain after a therapeutic hypocaloric diet.

DESIGN

A group of obese/overweight volunteers (49 women and 55 men; 35 ± 7 yr; 30.7 ± 2.4 kg/m(2)) followed an 8-wk hypocaloric diet (-30% energy expenditure) and were evaluated again 32 wk after treatment. Body weight as well as plasma fasting ghrelin, leptin, and insulin concentrations were measured at three points (wk 0, 8, and 32).

RESULTS

After the 8-wk hypocaloric diet, the average weight loss was -5.0 ± 2.2% (P < 0.001). Plasma leptin and insulin concentrations decreased significantly, whereas ghrelin levels did not markedly change. In the group regaining more than 10% of the weight loss, leptin levels were higher (P < 0.01), whereas ghrelin levels were lower (P < 0.05). No differences were observed in insulin levels. Weight regain at wk 32 was negatively correlated with ghrelin and positively associated with leptin levels at baseline (wk 0) and endpoint (wk 8). These outcomes showed a gender-specific influence, being statistically significant among men for ghrelin and between women for leptin. Moreover, a decrease in ghrelin after an 8-wk hypocaloric diet was related to an increased risk for weight regain (odds ratio = 3.109; P = 0.008) whereas a greater reduction in leptin (odds ratio = 0.141; P = 0.001) was related to weight-loss maintenance.

CONCLUSIONS

Subjects with higher plasma leptin and lower ghrelin levels at baseline could be more prone to regain lost weight, and hormones levels could be proposed as biomarkers for predicting obesity-treatment outcomes.

Insulin resistance in African-American and Caucasian women: differences in lipotoxicity, adipokines, and gene expression in adipose tissue and muscle

OBJECTIVES

We tested whether African-American (AA) women are different from Caucasian women in regard to lipotoxicity, adipokines, and gene expression in adipose tissue and muscle.

DESIGN

Insulin sensitivity (S(I)), plasma adipocytokine levels, intramyocellular lipid (IMCL), and the expression of candidate genes in adipose tissue and muscle were measured in AA and Caucasian women.

SETTING

This study was performed in an ambulatory general clinical research center.

SUBJECTS

Subjects were healthy, nondiabetic AA and Caucasian women.

INTERVENTIONS

There were no interventions.

MAIN OUTCOME MEASURES

Comparison of S(I), IMCL, plasma adiponectin, and the expression of candidate genes regulating adipogenesis, lipogenesis, and inflammation in adipose tissue and muscle.

RESULTS

AA had lower plasma adiponectin and IMCL when compared with Caucasian women with similar S(I). In sc adipose tissue (SAT), the expression of genes involved in adipogenesis including peroxisomal proliferator-activated receptor-gamma (PPARgamma) and lipin-1beta were also reduced in SAT of AA subjects (19%, P = 0.06, and 25%, P = 0.05, respectively). Similarly, 1-acylglycerol-3-phosphate acyltransferase 2 (AGPAT 2), stearoyl-coenzyme A desaturase-1 (SCD1), and CD36 mRNA expression was significantly reduced in SAT by 19, 54, and 28% respectively (P < 0.01 for all) in AA compared with Caucasian women. Yet the expression of CD68 in SAT was similar in both ethnic groups. Gene expression studies in muscle revealed a 31% reduction in expression of AGPAT 2 and a 72% reduction in SCD1 genes in AA.

CONCLUSION

AA women demonstrated lower expression of several PPARgamma-responsive genes in adipose tissue, lower plasma adiponectin, and decreased IMCL levels as compared with Caucasians, which suggests that African-Americans may be protected from lipotoxicity. Together these data suggest significant ethnic differences in the pathophysiology of insulin resistance.

Genetic variation in adiponectin (ADIPOQ) and the type 1 receptor (ADIPOR1), obesity and prostate cancer in African Americans

Background

Adiponectin is a protein derived from adipose tissue suspected to play an important role in prostate carcinogenesis. Variants in the adiponectin gene (ADIPOQ) and its type I receptor (ADIPOR1) have been recently linked to risk of both breast and colorectal cancer. Therefore, we set out to examine the relationship between polymorphisms in these genes, obesity and prostate cancer in study of African American men.

Methods

Ten single nucleotide polymorphisms (SNPs) in ADIPOQ and ADIPOR1 were genotyped in DNA samples from 131 African American prostate cancer cases and 344 controls participating in the Flint Men's Health Study. Logistic regression was then used to estimate their association with prostate cancer and obesity.

Results

While no significant associations were detected between any of the tested SNPs and prostate cancer, the rs1501299 SNP in ADIPOQ was significantly associated with body mass (p=0.03).

Conclusions

Genetic variation in ADIPOQ and ADIPOR1 did not predict risk of prostate cancer in this study of African American men. However, the rs1501299 SNP in ADIPOQ was associated with obesity. Further investigation is warranted to determine if racial differences exist in the influence of the adiponectin pathway on prostate cancer risk.

Sex and ethnic differences in 47 candidate proteomic markers of cardiovascular disease: the Mayo Clinic proteomic markers of arteriosclerosis study

BACKGROUND

Cardiovascular disease (CVD) susceptibility differs between men and women and varies with ethnicity. This variability is not entirely explained by conventional CVD risk factors. We examined differences in circulating levels of 47 novel protein markers of CVD in 2561 men and women of African-American (AA) and non-Hispanic White (NHW) ethnicity, enrolled at geographically distinct sites.

METHODOLOGY/PRINCIPAL FINDINGS

Participants (1,324 AAs, mean age 63.5 y, 71% women; 1,237 NHWs, mean age 58.9 y, 57% women) belonged to sibships ascertained on the basis of hypertension. Solid-phase immunoassays and immunoturbidometric, clot-based, chromogenic, and electrophoretic assays were used to measure the 47 protein markers in plasma or serum. Marker levels were log transformed and outliers were adjusted to within 4 SD. To identify markers independently associated with sex or ethnicity, we employed multivariable regression analyses that adjusted for conventional risk factors, prior history of CVD, medication use and lifestyle factors (physical activity, alcohol consumption and education). Generalized estimating equations were used to correct for intrafamilial correlations. After adjustment for the above covariates, female sex was associated with higher levels of 29 markers and lower levels of 6 markers. Female sex was independently associated with higher levels of several inflammatory markers as well as lipoproteins, adipokines, natriuretic peptides, vasoconstrictor peptides and markers of calcification and thrombosis. AA ethnicity was associated with higher levels of 19 markers and lower levels of 6 markers, including higher levels of several inflammatory makers, higher leptin and lower adiponectin levels, lower levels of vasodilator-natriuretic peptides, higher levels of vasoconstrictor-antidiuretic peptides and markers of calcification and thrombosis.

CONCLUSIONS/SIGNIFICANCE

Plasma levels of several novel protein markers of CVD differ significantly in the context of sex and ethnicity. These results have implications for individualized CVD risk assessment.

Correlation of the leptin:adiponectin ratio with measures of insulin resistance in non-diabetic individuals

AIMS/HYPOTHESIS

Obesity is the dominant cause of insulin resistance. In adult humans it is characterised by a combination of adipocyte hypertrophy and, to a lesser extent, adipocyte hyperplasia. As hypertrophic adipocytes secrete more leptin and less adiponectin, the plasma leptin:adiponectin ratio (LAR) has been proposed as a potentially useful measure of insulin resistance and vascular risk. We sought to assess the usefulness of the LAR as a measure of insulin resistance in non-diabetic white adults.

METHODS

Leptin and adiponectin levels were measured in 2,097 non-diabetic individuals from the Ely and European Group for the Study of Insulin Resistance (EGIR) Relationship between Insulin Sensitivity and Cardiovascular Risk (RISC) study cohorts. LAR was compared with fasting insulin and HOMA-derived insulin sensitivity (HOMA-S) in all individuals and with the insulin sensitivity index (M/I) from hyperinsulinaemic-euglycaemic clamp studies in 1,226 EGIR RISC participants.

RESULTS

The LAR was highly correlated with HOMA-S in men (r = -0.58, p = 4.5 x 10(-33) and r = -0.65, p = 1.1 x 10(-66) within the Ely and EGIR RISC study cohorts, respectively) and in women (r = -0.51, p = 2.8 x 10(-36) and r = -0.61, p = 2.5 x 10(-73)). The LAR was also strongly correlated with the clamp M/I value (r = -0.52, p = 4.5 x 10(-38) and r = -0.47, p = 6.6 x 10(-40) in men and women, respectively), similar to correlations between HOMA-S and the M/I value.

CONCLUSIONS/INTERPRETATION

The leptin:adiponectin ratio is a useful measure of insulin resistance in non-diabetic white adults. These data highlight the central role of adipocyte dysfunction in the pathogenesis of insulin resistance. Given that variations between fasting and postprandial leptin and adiponectin levels tend to be small, the leptin to adiponectin ratio might also have potential value in assessing insulin sensitivity in the non-fasted state.

The metabolic syndrome, insulin resistance, and its surrogates in African and white subjects with type 2 diabetes in South Africa

BACKGROUND

Coronary heart disease (CHD) is rare in diabetic Africans in South Africa, unlike diabetic African-Americans, despite moderate levels of conventional risk factors, with absence of the usual male predominance. Because the metabolic syndrome and insulin resistance (IR) are associated with CHD, we have analyzed the prevalence and severity of the metabolic syndrome, and IR, in African and white subjects with type 2 diabetes.

METHODS

A total of 500 African and 254 white diabetic patients were evaluated for features of the metabolic syndrome (International Diabetes Federation [IDF] definition); insulin resistance (homeostasis model assessment-insulin resistance [HOMA-IR]) was calculated in subgroups.

RESULTS

In men, Africans had a lower body mass index (BMI) and smaller waists than white subjects (p < 0.0001); the metabolic syndrome was present in 46.5% and 74.1% of African and white patients respectively (p < 0.0001). In women, frequencies of the metabolic syndrome were similar, but severe metabolic syndrome (4 or 5 criteria) was more frequent in the white group (73.1%) than in the Africans (52.9%) (p = 0.0003). The prevalence of hypertriglyceridemia was lower in African men and women (p < 0.0001) and contributed to their lower prevalence of the metabolic syndrome/severe metabolic syndrome. Compared with the white patients, in African subjects HOMA-IR was 40% lower (p < 0.0001), and correlated with the triglyceride:high-density lipoprotein cholesterol ratio (TG:HDL-C) (r = 0.409, p < 0.0001).

CONCLUSIONS

In diabetic Africans, in comparison with white patients, the lower prevalence of the metabolic syndrome in men and severe metabolic syndrome in women, and lesser insulin resistance, might contribute to their lower risk of CHD; the higher prevalence in women might contribute to the reversal of the male:female ratio. The TG:HDL-C ratio appears to be a valid estimate of insulin resistance in diabetic Africans.