Total body potassium differs by sex and race across the adult age span

Association of calf circumference with osteoporosis and hip fracture in middle-aged and older adults: a secondary analysis

BACKGROUND

Osteosarcopenia is a geriatric syndrome associated with an increased risk of frailty, falls, fractures, disability, and death. Calf circumference (CC) has been used as a simple and practical skeletal muscle marker to diagnose sarcopenia. This study aimed to explore the relationship of calf circumference and osteoporosis (OP) and hip fractures (HF) in middle-aged and older adults. This is important for screening OP and HF in the community and improving the quality of life of older adults.

METHODS

This study was based on the National Health and Nutrition Examination Survey (NHANES) 1999-2006. Logistic regression analysis and restricted cubic spline were used to investigate the correlation of CC with OP and HF. The receiver operating characteristic (ROC) curve was utilized to determine the optimal cut-off value for CC. Finally, logistic regression model analysis was applied to test the predictive efficacy of CC.

RESULTS

Among 4575 individuals with a mean age of 63.0 ± 11.5 years, the OP group had higher proportions of females (P < 0.001) and non-Hispanic whites (P < 0.001). Logistic regression and RCS demonstrated that lower CC was associated with a greater risk of OP and HF in the female group (P < 0.001). ROC curves showed that CC of 33.65 cm and 33.85 cm were the best cut-off values for predicting OP and HF in middle-aged and older females. Logistic regression analyses found good predictive efficacy for cut-off values of CC in females.

CONCLUSION

In middle-aged and older women, low CC is associated with a higher risk of OP and HF. These findings have important implications for managing osteosarcopenia and associated fractures in older adults.

CLINICAL TRIAL NUMBER

Not applicable.

Overview of research progress on the association of dietary potassium intake with serum potassium and survival in hemodialysis patients, does dietary potassium restriction really benefit hemodialysis patients?

For the general population, increasing potassium intake can reduce the incidence of cardiovascular and cerebrovascular diseases. However, since hyperkalemia is a common and life-threatening complication in maintenance hemodialysis patients, which can increase the risk of malignant arrhythmia and sudden death, the current mainstream of management for hemodialysis patients is dietary potassium restriction in order to prevent hyperkalemia. Hemodialysis patients are usually advised to reduce dietary potassium intake and limit potassium-rich fruits and vegetables, but there is limited evidence to support this approach can reduce mortality and improve quality of life. There is still no consistent conclusion on the association between dietary potassium intake and serum potassium and survival in hemodialysis patients. According to the current small observational studies, there was little or even no association between dietary potassium intake and serum potassium in hemodialysis patients when assurance of adequate dialysis and specific dietary patterns (such as the plant-based diet mentioned in the article) are being followed, and excessive dietary potassium restriction may not benefit the survival of hemodialysis patients. Additionally, when assessing the effect of diet on serum potassium, researchers should not only focus on the potassium content of foods, but also consider the type of food and the content of other nutrients. However, more large-scale, multi-center clinical trials are required to provide high-quality evidence support. Besides, further research is also needed to determine the optimal daily potassium intake and beneficial dietary patterns for hemodialysis patients.

An Intervention of 12 Weeks of Nordic Walking and Recreational Walking to Improve Cardiorespiratory Capacity and Fitness in Older Adult Women

(1) Background: The main aim of this study was to examine the effect of an intervention of 12 weeks in three groups on anthropometric measurement and heart rate (HR) variables, fitness index, and maximal oxygen consumption (VO2max) in older women. (2) Methods: In total, 166 Serbian adult women, aged 50 to 69 years old, participated in this study, comprising a control group (60 participants, μage = 57.8 + 6.6), Nordic-walking (NW) group (53 participants, μage = 57.5 + 6.8), and recreational-walking (RW) group (53 participants, μage = 57.8 + 6.6) in a physical fitness programme for 12 weeks. (3) Results: Anthropometric measurement variables were measured using a stadiometer and an electronic scale. The data showed differences in walking heart rate (bt/min) (p < 0.001; η2 = 0.088) between control, NW, and RW groups in the pretest analysis. Moreover, there were significant differences in walking heart rate (bt/min) (η2 = 0.155), heart rate at the end of the test (bt/min) (η2 = 0.093), total time of fitness index test (min) (η2 = 0.097), fitness index (η2 = 0.130), and VO2max (η2 = 0.111) (all, p < 0.001) between control, NW, and RW groups in the posttest analysis. (4) Conclusions: NW group training resulted in slightly greater benefits than RW group training. The present study demonstrated that both groups could act as modalities to improve the functionality and quality of life of people during the ageing process, reflected mainly in HR variables; UKK test measurements, and VO2max. It also contributes to the extant research on older women during exercise and opens interesting avenues for future research.

Calf circumference: cutoff values from the NHANES 1999-2006

BACKGROUND

Calf circumference (CC) is used in geriatric studies as a simple and practical skeletal muscle (SM) marker for diagnosing low SM and sarcopenia. Currently applied CC cutoff points were developed in samples including older participants; values representative of the full adult lifespan are lacking.

OBJECTIVES

We aimed to develop CC cutoff points and to identify relevant confounding factors from the large and diverse NHANES 1999-2006 population sample.

METHODS

Demographic, anthropometric, and imaging data (DXA, appendicular lean mass) from the adult (age ≥18 y) NHANES sample were partitioned into subgroups according to sex, age, ethnicity, and race. Adults aged 18-39 y and BMI (in kg/m2) 18.5-24.9 were set as a reference population; CC cutoff points were derived at 1 and 2 SDs below the mean.

RESULTS

The sample included 17,789 participants, 51.3% males and 48.7% females, with respective ages (mean ± SD) of 43.3 ± 16.1 y and 45.5 ± 16.9 y. CC was strongly correlated with appendicular lean mass, r = 0.84 and 0.86 for males and females (both P < 0.001), respectively. Significant differences in mean CC were present across sex, ethnic, self-reported race, and BMI groups. Adjusting CC for adiposity using BMI revealed a decrease in CC beginning after the second decade in males and third decade in females. Rounded CC cutoff values for moderately and severely low CC were 34 cm and 32 cm (males), and 33 cm and 31 cm (females), respectively. Our findings support the use of BMI-adjusted CC values for participants outside the normal-weight BMI range (18-24.9).

CONCLUSIONS

This study defined CC values in a diverse population sample along with a BMI-adjustment approach that helps to remove the confounding effects of adiposity and thereby improves CC as a useful clinical estimate of SM mass.

Coronavirus Disease 19 from the Perspective of Ageing with Focus on Nutritional Status and Nutrition Management-A Narrative Review

The novel severe acute respiratory syndrome coronavirus (COVID-19) has hit older adults harder due to a combination of age-related immunological and metabolic alterations. The aim of this review was to analyze the COVID-19 literature with respect to nutritional status and nutrition management in older adults. No studies only on people aged 65+ years were found, and documentation on those 80+ was rare. Age was found to be strongly associated with worse outcomes, and with poor nutritional status. Prevalence of malnutrition was high among severely and critically ill patients. The studies found a need for nutrition screening and management, and for nutrition support as part of follow-up after a hospital stay. Most tested screening tools showed high sensitivity in identifying nutritional risk, but none were recognized as best for screening older adults with COVID-19. For diagnosing malnutrition, the Global Leadership Initiative on Malnutrition (GLIM) criteria are recommended but were not used in the studies found. Documentation of olfactory and gustatory dysfunction in relation to nutritional status is missing in older adults. Other COVID-19-associated factors with a possible impact on nutritional status are poor appetite and gastrointestinal symptoms. Vitamin D is the nutrient that has attracted the most interest. However, evidence for supplementation of COVID-19 patients is still limited and inconclusive.

Association between the transtubular potassium gradient and progression of chronic kidney disease: results from KNOW-CKD

BACKGROUND

The transtubular potassium gradient which reflects potassium secretion by the kidney through the cortical collecting duct, has not yet been tested as a surrogate marker of kidney function decline. Here, we investigate the relationship between the transtubular potassium gradient and chronic kidney disease (CKD) progression.

METHODS

We studied 1672 patients from the KoreaN Cohort Study for Outcome in Patients With Chronic Kidney Disease (KNOW-CKD) cohort. The transtubular potassium gradient was calculated using a standard equation. The study endpoint was CKD progression, defined as a composite of a ≥ 50% decrease in estimated glomerular filtration rate (eGFR) from baseline values or end-stage kidney disease.

RESULTS

During a median follow-up of 4.1 years (7149 person-years), 441 participants reached the endpoint. In cause-specific competing risk analysis, the highest tertile was associated with a significantly lower risk of an adverse kidney outcome compared with the lowest tertile [hazard ratio (HR), 0.73; 95% confidence interval (CI), 0.55-0.97]. When the transtubular potassium gradient was treated as a continuous variable, an increase of 1 in the transtubular potassium gradient was associated with a 6% lower risk of CKD progression (95% CI, 0.90-0.99). This association was particularly evident in patients with an eGFR ≥ 45 mL/min/1.73 m². A time-updated transtubular potassium gradient model showed similar results. The predictive performance of the transtubular potassium gradient was significantly less than that of the eGFR, but similar to that of proteinuria, serum bicarbonate, and urine osmolality.

CONCLUSIONS

A higher transtubular potassium gradient is associated with a significantly lower risk of CKD progression, suggesting that it may offer insights into the prognosis of CKD.

Associations of changes in fat free mass with risk for type 2 diabetes: Hispanic Community Health Study/Study of Latinos

AIMS

To determine whether loss of muscle mass (approximated using fat free mass [FFM]) is associated with risk for type 2 diabetes mellitus (T2DM) in Hispanic/Latino adults in the United States.

METHODS

Participants were Hispanic/Latino adults (18-74-year-olds) who completed Visit 2 of the Hispanic Community Health Study/Study of Latinos (HCHS/SOL; multi-site, prospective cohort study; 6.1-year follow-up) and did not have T2DM at baseline (n = 6264). At baseline and Visit 2, FFM was measured using bioelectrical impedance analysis and fasting glucose, HbA1c, and fasting insulin were measured by examiners. Diabetes was defined according to American Diabetes Association criteria. Survey-weighted Poisson regression models examined the association of percent change in relative FFM (%ΔFFM) with incident prediabetes and T2DM. Survey-weighted multivariable regression models examined associations of %ΔFFM with changes in glucose and insulin measures.

RESULTS

Relative FFM declined by 2.1% between visits. %ΔFFM was inversely associated with incident prediabetes (p-for-trend = 0.001) and with changes in glucose and insulin measures (p-for-trend <0.0001). Findings were null, except for HOMA-IR, after adjustment for changes in adiposity measures. Associations were generally stronger for individuals with baseline overweight/obesity.

CONCLUSIONS

Reducing loss of FFM during adulthood may reduce prediabetes risk (primarily insulin resistance), particularly among individuals with overweight/obesity.

Urinary Potassium Excretion and Progression of CKD

BACKGROUND AND OBJECTIVES

Data on whether low or high urinary potassium excretion is associated with poor kidney outcome have been conflicting. The aim of this study was to clarify the association between urinary potassium excretion and CKD progression.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

We investigated the relationship between lower urinary potassium excretion and CKD progression and compared three urinary potassium indices among 1821 patients from the Korean Cohort Study for Outcome in Patients with CKD. Urinary potassium excretion was determined using spot urinary potassium-to-creatinine ratio, spot urinary potassium concentration, and 24-hour urinary potassium excretion. Patients were categorized into four groups according to quartiles of each urinary potassium excretion metric. The study end point was a composite of a ≥50% decrease in eGFR from baseline values and ESKD.

RESULTS

During 5326 person-years of follow-up, the primary outcome occurred in 392 (22%) patients. In a multivariable cause-specific hazard model, lower urinary potassium-to-creatinine ratio was associated with higher risk of CKD progression (adjusted hazard ratio, 1.47; 95% confidence interval, 1.01 to 2.12) comparing the lowest quartile with the highest quartile. Sensitivity analyses with other potassium metrics also showed consistent results in 855 patients who completed 24-hour urinary collections: adjusted hazard ratios comparing the lowest quartile with the highest quartile were 3.05 (95% confidence interval, 1.54 to 6.04) for 24-hour urinary potassium excretion, 1.95 (95% confidence interval, 1.05 to 3.62) for spot urinary potassium-to-creatinine ratio, and 3.79 (95% confidence interval, 1.51 to 9.51) for spot urinary potassium concentration.

CONCLUSIONS

Low urinary potassium excretion is associated with progression of CKD.

Age- and gender-dependent associations of blood pressure and serum sodium and potassium-renal and extrarenal regulations

Association analyses between blood pressure (BP) and serum sodium and potassium for 14,657 men and 16,977 women between ages 12 and 85 years show that responses of BP to serum sodium and potassium are age and gender dependent. The data were from the National Health and Nutrition Examination Survey between 2003 and 2014. Associations between serum sodium and BP are positive only for advanced age groups and for serum sodium level greater than 139-140 mmol/L in less advanced groups. These positive associations can be explained by traditional renal-centered mechanism. Inverse associations between systolic BP and serum sodium exist when sodium is less than ∼140 mmol/L in less advanced age groups (<60 for men and <70 for women). These inverse associations can partially be explained by the extrarenal regulatory mechanism in which sodium storage in negatively charged glycosaminoglycans in the interstitium may be involved. Associations of high serum potassium and low BP are consistent and exist in most age groups. Effect of potassium on systolic BP and diastolic BP are more prominent in less advanced age groups. Age-dependent associations between sodium and BP support the theory that sodium homeostasis in the body may not be regulated by renal-centered responses alone. There might be regulation of an extrarenal system in which sodium attraction by negatively charged glycosaminoglycans plays a role.

ASSESSMENT OF BODY POTASSIUM LEVEL BY GENDER AND AGE IN KOREAN ADULT GROUP

Most internal radiation dose resulting from natural radionuclides is due to radon and radioactive potassium. Total body potassium (TBK) in human body may vary by ethnic group, gender and age. The objective of this study was to measure TBK and body potassium concentration in Korean subjects. Body potassium concentrations of the subjects were measured with a whole-body counter for 283 adult males and 181 adult females. Average TBK value and body potassium level were 111.2 g and 1.5 g kg-1 for males, while for females they were 71.7 g and 1.4 g kg-1. TBK increased with increasing body weight. Body potassium level per body weight was inversely proportional to age in both genders. The annual effective doses due to 40K in the human body of Korean population were calculated to be 0.15 and 0.13 mSv for males and females, respectively.

Factors Affecting Sarcopenia in Korean Adults by Age Groups

Objectives

This study aimed to investigate factors affecting sarcopenia in different age groups among Korean adults aged 20 years or older.

Methods

In this secondary analysis, data were collected from records for 17,968, participants who participated in the Korea National Health and Nutrition Examination Survey during 2008–2011. Data were analyzed using multiple logistic regression to determine the associated factors of sarcopenia by age groups.

Results

The prevalence of sarcopenia increased significantly with age. Physical activity, blood pressure, waist circumference, triglycerides, vitamin D level were found to be factors significantly associated with sarcopenia in all age groups. Total energy intake was found to be a factor that is significantly associated with sarcopenia among the adults aged 20–39 years. Fasting glucose, suicidal ideation, perceived health status, mobility problem, pain/discomfort, total energy intake were found to be factors associated with sarcopenia in the adults aged 40–64 years. Sex, residential area, smoking, drinking, fasting glucose, osteoarthritis, fall experience, usual activity problem, protein intake were factors associated with sarcopenia in the adults over 65 years of age.

Conclusion

The findings show that sarcopenia in adults and the associated factors were different by age groups. Thus, these factors should be considered in the development of intervention programs for the care and prevention of sarcopenia, and such programs should be modified according to different age groups.

Body Potassium Content and Radiation Dose from 40K for the Urals Population (Russia)

Long-term whole-body monitoring of radionuclides in residents of the Urals Region has been performed at the Urals Research Center for Radiation Medicine (URCRM, Chelyabinsk). Quantification of ⁴⁰K was achieved by measuring the ⁴⁰K photopeak with four phoswich detectors in whole body counter SICH-9.1M. The current study presents the results of ⁴⁰K measurements in 3,651 women and 1,961 t-test; U-test men aged 11–90; measurements were performed in 2006–2014. The residents belonged to two ethnic groups, Turkic (Tatar, Bashkir) and Slavs (mainly Russian). The levels of ⁴⁰K-body contents depend upon gender, age, and body mass. Significant ethnic-differences were not found in ⁴⁰K-body contents and ⁴⁰K concentrations in terms of Bq per kg of body weight (in groups homogenous by age and gender). Both ⁴⁰K-body contents and concentrations were significantly higher in men than in women in all age-groups; the difference was about 25%. The measured ⁴⁰K-body content in men of 20–50 years was about 4200 Bq (134 g of K) and about 3000 Bq (95 g of K) in women. By the age of 80 these values decreased to 3200 Bq (102 g of K) in men and 2500 Bq (80 g of K) in women. Annual dose rates were maximal in the age group of 20–30 years– 0.16 mGy/y for men and 0.13 mGy/y for women. Further, the dose-rates decreased with age and in the groups of 60–80 years were 0.13 mGy/y for men and 0.10 mGy/y for women. Within groups homogeneous by age and gender, individual dose rates are described by a normal statistical distribution. The coefficient of variation ranges from 9 to 14%, and on the average is 12.5%. Doses from naturally occurring ⁴⁰K accumulated over 70 years were found to be 9.9 mGy for men and 8.3 mGy for women; over 90 years - 12.5 and 10.4 mGy.

Sex and race/ethnic disparities in the cross-sectional association between depressive symptoms and muscle mass: the Multi-ethnic Study of Atherosclerosis

BACKGROUND

The cross-sectional area of total muscle mass has been reported to decrease by about 40% for those 20-60 years of age. Depressive symptoms may discourage motivation to engage in physical activity such as strength training shown to negate muscle loss. Inflammation related to depressive symptoms may also contribute to muscle atrophy. Physiological differences by sex and race/ethnicity may also modify the association between depression and muscle mass. Evidence on the relationship between depression (or depressive symptoms) and adiposity has been mounting; however, little is known about the depressive symptoms-muscle mass association. We sought to determine the association between elevated depressive symptoms (EDS) and lean muscle mass and whether this varies by sex and race/ethnicity.

METHODS

Evaluating 1605 adults (45-84 years of age) from the Multi-ethnic Study of Atherosclerosis Abdominal Body Composition, Inflammation and Cardiovascular Disease Study, we examined the cross-sectional association between EDS (Center for Epidemiologic Studies for Depression Scale score≥16 and/or antidepressant use) and computed tomography-measured abdominal lean muscle mass using linear regression. Muscles were evaluated as a whole and by functionality (locomotion vs. stabilization/posture). Covariates included height, body mass index, sociodemographics, comorbidities, inflammatory markers and health behaviors (pack-years of smoking, alcohol locomotion compared to men, total intentional exercise, daily caloric intake). Sex and race/ethnicity were assessed as potential modifiers. Statistical significance was at a p<0.05 for main effects and <0.20 for interaction.

RESULTS

Men with elevated depressive symptoms had 5.9 cm2 lower lean muscle mass for locomotion compared to men without EDS, fully-adjusted (CI=-10.5, -1.4, p=0.011). This was statistically significantly different from the null finding among women (interaction p=0.05). Chinese participants with EDS had 10.2 cm2 lower abdominal lean muscle mass for locomotion compared to those without EDS (fully-adjusted, CI=-18.3, -2.1, p=0.014), which was significantly different from the null relationship among White participants (interaction p=0.04). No association was observed between elevated depressive symptoms and muscle for stabilization/posture evaluating the whole population or stratified by sex or race/ethnicity.

CONCLUSIONS

In the presence of elevated depressive symptoms, men and Chinese participants may have lower muscle mass, particularly for locomotion.

Effects of HIV Infection on Body Composition Changes Among Men of Different Racial/Ethnic Origins

PURPOSE

To compare racial/ethnic differences and effects of HIV on body composition among antiretroviral (ART)-naïve HIV seropositive (HIV+) men to a representative sample of HIV seronegative (HIV-) men. We hypothesized that the effect of HIV infection will be uniform across all racial/ethnic groups.

METHOD

A cross-sectional analysis was performed comparing HIV- (NHANES 1999-2002) and ART-naïve HIV+ men (CPCRA 061). Regional subcutaneous fat area was estimated by skinfold caliper. Total body fat (TBF), fat-free mass (FFM), and body fat index (BFI) were derived by Durnin-Womersley formula (TBF-DW, FFM-DW, BFI [TBF-DW/height(2)]). Bioelectric impedance analyses (BIA) was used to assess TBF-BIA, FFM-BIA, and body cell mass (BCM). Multivariate regression modeling adjusted for age, smoking, and hepatitis C for each measurement was performed.

RESULTS

HIV+ men (n = 321) were older and more likely to be smokers than HIV- men (n = 1,996). The HIV- men were heavier in weight (+17.8 kg, p < .001) and had higher BMI (+4.3 kg/m(2), p < .001), BCM (+2.4 kg, p = .02), FFM (+5.9 kg, p < .001), TBF-DW (+5.95 kg, p < .001), BFI (+1.6 kg/m(2), p < .001), and regional fat mass than the HIV+ men. In the multivariate model, there were significant percentage differences between HIV- and HIV+ African American men for all body composition measurements (weight +15.3%; BMI +14.5%; BCM +5.2%; TBF-DW +15%; BFI 13.9%; FFM-DW 7.9%) and all circumference and skinfold measurements; all ps < .05. For Caucasian men, the following differences were significant between HIV- and HIV+: weight +14.4%; BMI +14.0%; BCM +6.0%; TBF-DW +17.7%; BFI 17.1%; FFM-DW 8.7%; and all circumference and skinfold measurements. Similarly, among Latino men the following differences were significant: weight +10.1%; BMI +12.3%; FFM-DW +7.7%; and arm, waist, and thigh circumferences and mid-arm skinfold fat area. The interaction terms for race/ethnicity were not significant across the three racial groups for weight, BMI, BCM, TBF-BIA, and BFI.

CONCLUSION

Compared to HIV uninfected men, among HIV-infected ART-naïve men there was a significant effect of HIV infection itself on body composition among all racial/ethnic groups.

Guidelines for the treatment of hypothyroidism: prepared by the american thyroid association task force on thyroid hormone replacement

BACKGROUND

A number of recent advances in our understanding of thyroid physiology may shed light on why some patients feel unwell while taking levothyroxine monotherapy. The purpose of this task force was to review the goals of levothyroxine therapy, the optimal prescription of conventional levothyroxine therapy, the sources of dissatisfaction with levothyroxine therapy, the evidence on treatment alternatives, and the relevant knowledge gaps. We wished to determine whether there are sufficient new data generated by well-designed studies to provide reason to pursue such therapies and change the current standard of care. This document is intended to inform clinical decision-making on thyroid hormone replacement therapy; it is not a replacement for individualized clinical judgment.

METHODS

Task force members identified 24 questions relevant to the treatment of hypothyroidism. The clinical literature relating to each question was then reviewed. Clinical reviews were supplemented, when relevant, with related mechanistic and bench research literature reviews, performed by our team of translational scientists. Ethics reviews were provided, when relevant, by a bioethicist. The responses to questions were formatted, when possible, in the form of a formal clinical recommendation statement. When responses were not suitable for a formal clinical recommendation, a summary response statement without a formal clinical recommendation was developed. For clinical recommendations, the supporting evidence was appraised, and the strength of each clinical recommendation was assessed, using the American College of Physicians system. The final document was organized so that each topic is introduced with a question, followed by a formal clinical recommendation. Stakeholder input was received at a national meeting, with some subsequent refinement of the clinical questions addressed in the document. Consensus was achieved for all recommendations by the task force.

RESULTS

We reviewed the following therapeutic categories: (i) levothyroxine therapy, (ii) non-levothyroxine-based thyroid hormone therapies, and (iii) use of thyroid hormone analogs. The second category included thyroid extracts, synthetic combination therapy, triiodothyronine therapy, and compounded thyroid hormones.

CONCLUSIONS

We concluded that levothyroxine should remain the standard of care for treating hypothyroidism. We found no consistently strong evidence for the superiority of alternative preparations (e.g., levothyroxine-liothyronine combination therapy, or thyroid extract therapy, or others) over monotherapy with levothyroxine, in improving health outcomes. Some examples of future research needs include the development of superior biomarkers of euthyroidism to supplement thyrotropin measurements, mechanistic research on serum triiodothyronine levels (including effects of age and disease status, relationship with tissue concentrations, as well as potential therapeutic targeting), and long-term outcome clinical trials testing combination therapy or thyroid extracts (including subgroup effects). Additional research is also needed to develop thyroid hormone analogs with a favorable benefit to risk profile.

Non-traditional risk factors are important contributors to the racial disparity in diabetes risk: the atherosclerosis risk in communities study

BACKGROUND

Traditional risk factors, particularly obesity, do not completely explain the excess risk of diabetes among African Americans compared to whites.

OBJECTIVE

We sought to quantify the impact of recently identified, non-traditional risk factors on the racial disparity in diabetes risk.

DESIGN

Prospective cohort study.

PARTICIPANTS

We analyzed data from 2,322 African-American and 8,840 white participants without diabetes at baseline from the Atherosclerosis Risk in Communities (ARIC) Study.

MAIN MEASURES

We used Cox regression to quantify the association of incident diabetes by race over 9 years of in-person and 17 years of telephone follow-up, adjusting for traditional and non-traditional risk factors based on literature search. We calculated the mediation effect of a covariate as the percent change in the coefficient of race in multivariate models without and with the covariate of interest; 95 % confidence intervals (95 % CI) were calculated using boot-strapping.

KEY RESULTS

African American race was independently associated with incident diabetes. Body mass index (BMI), forced vital capacity (FVC), systolic blood pressure, and serum potassium had the greatest explanatory effects for the difference in diabetes risk between races, with mediation effects (95 % CI) of 22.0 % (11.7 %, 42.2 %), 21.7 %(9.5 %, 43.1 %), 17.9 % (10.2 %, 37.4 %) and 17.7 % (8.2 %, 39.4 %), respectively, during 9 years of in-person follow-up, with continued effect over 17 years of telephone follow-up.

CONCLUSIONS

Non-traditional risk factors, particularly FVC and serum potassium, are potential mediators of the association between race and diabetes risk. They should be studied further to verify their importance and to determine if they mark causal relationships that can be addressed to reduce the racial disparity in diabetes risk.

24-weeks Pilates-aerobic and educative training to improve body fat mass in elderly Serbian women

Background

The purpose of this study was to examine the differences in anthropometric measurements using an aerobic and Pilates exercise program which lasted 24 weeks.

Method

This was a clinical intervention study of 303 women over the age of 60 living in Novi Sad, Serbia. Changes in body mass index and skinfold thickness were estimated through height, weight, and anthropometric measurements. The program comprised Pilates exercises for upper- and lower-body strength, agility, and aerobic capacity.

Results

Fat mass (FM) improved significantly (pre-test, 32.89%, 8.65; post-test, 28.25%, 6.58; P<0.01). Bone diameters and muscle perimeters showed no significant changes pre- and post-test (P>0.05), but there was a higher correlation between FM (%) and waist–hip ratio (rho, 0.80; P<0.01).

Conclusion

A mixed program of aerobics and Pilates, controls and improves baseline muscle mass and decreases FM values, without causing deterioration during practice and follow-up exercises.

Gastrointestinal and renal excretion of potassium in African-Americans and White Americans

OBJECTIVE

Several studies have confirmed the remarkable observation that cumulative urinary potassium (K(+)) excretion is less in African-Americans than White Americans even when identical amounts of potassium are provided in the diet. This study was designed to examine whether this decrease in urinary potassium could be compensatory to an increase in gastrointestinal excretion of potassium in African-Americans.

METHODS

Twenty-three young, healthy, normotensive participants of both sexes and races were placed on a fixed diet of 100 mEq per day of K(+) and 180 mEq per day of sodium (Na(+)) for 9 days. All urine and stool were collected daily and analyzed for electrolytes. Blood was obtained for determination of electrolytes, blood urea nitrogen (BUN), creatinine, glucose, insulin, renin, and aldosterone at the beginning and at the end of the study period.

RESULTS

Cumulative urinary excretion of K(+) was significantly less in African-Americans (609 ± 31 mEq) compared with White Americans (713 ± 22 mEq, P = 0.015). There was no significant racial difference, however, in the cumulative gastrointestinal excretion of K (105 ± 11 versus 95 ± 9 mEq, P = 0.28) in African-Americans versus White Americans, respectively.

CONCLUSION

The racial difference in urinary K(+) handling manifested by decreased excretion of K(+) in African-Americans cannot be attributed to an increase in net gastrointestinal excretion of this cation.

Serum potassium is associated with prediabetes and newly diagnosed diabetes in hypertensive adults from the general population: the KORA F4-study

AIMS/HYPOTHESIS

Evidence suggests that low serum potassium concentrations or hypokalaemia induced by the intake of diuretics are associated with incident diabetes and increased risk for diabetes in persons with hypertension. We examined a possible association between serum potassium and prediabetes (defined as isolated impaired fasting glucose [i-IFG], isolated impaired glucose tolerance [i-IGT] or combined IFG/IGT), as well as known and newly diagnosed diabetes (NDD), in 32- to 81-year-old men and women with and without hypertension.

METHODS

This cross-sectional analysis was based on 2,948 participants in the Cooperative Health Research in the Region of Augsburg (KORA) F4 study conducted in 2006-2008 in southern Germany. Serum concentrations of potassium were measured by indirect potentiometry.

RESULTS

In the total sample there was no association between serum potassium concentrations and prediabetes. In hypertensive persons however serum potassium levels in the first and second quartile compared with the highest quartile were independently significantly associated with prediabetes after multivariable adjustment (OR for prediabetes, 2.02 [95% CI 1.27, 3.21] for quartile 2 and 2.00 [95% CI 1.27, 3.15] for quartile 1), while in persons without hypertension no association was found. In multinomial logistic regression analysis these findings could be confirmed. In hypertensive participants after multivariable adjustment the associations were statistically significant for i-IGT and NDD (i-IGT OR 1.23; NDD OR 1.41). However, in non-hypertensive persons, all associations between serum potassium levels and each of the categories of impaired glucose regulation were non-significant.

CONCLUSIONS/INTERPRETATION

Serum potassium levels were independently associated with prediabetes and NDD in hypertensive adults from the general population.

Hypokalaemia and Renal Tubular Acidosis due to Abuse of Nurofen Plus

Nurofen Plus is a common analgesic containing ibuprofen and codeine. We present a case of a 38-year-old lady who developed renal tubular acidosis with severe hypokalaemia, after chronic abuse of Nurofen Plus tablets. She presented with confusion and profound biochemical abnormalities requiring critical care admission for electrolyte replacement. Ibuprofen causes renal tubular acidosis due to its effects on carbonic anhydrase activity.

Area under the curve as a tool to measure kinetics of tumor growth in experimental animals

Measurement of tumor diameters or tumor volumes has been traditionally used to quantitate and compare tumor growth curves in mice and rats. Here, we describe the use of area under the curve (AUC) as an alternative method to do the same. This single numerical value (a) is easy to obtain for individual curves, (b) reflects the entire tumor growth curve through a single number, (c) can be easily modified to obtain data for defined sections of the growth curve (for example, to determine stable disease), and (d) allows easier comparisons between groups. Using tumor growth data from a large number of mice challenged with live tumor cells, we demonstrate the utility of this tool over the conventional methods for these purposes.

Influence of urine creatinine on the relationship between the albumin-to-creatinine ratio and cardiovascular events

BACKGROUND AND OBJECTIVES

In the albumin-to-creatinine ratio (spot-ACR), urine creatinine corrects for tonicity but also reflects muscle mass. Low muscle mass is associated with cardiovascular disease (CVD). We hypothesized that the spot-ACR would be higher in women, lower-weight persons, and older individuals, independent of timed urine albumin excretion (24hr-UAE), and accordingly, that spot-ACR would be more strongly associated with CVD events than 24hr-UAE in these subgroups.

DESIGN, SETTING, PARTICIPANTS, & METHODS

2627 PREVEND (Prevention of Renal and Vascular End-stage Disease) participants with 24hr-UAE <30 mg/d were followed for CVD events for 11 years. Cox regression evaluated associations of spot-ACR and 24hr-UAE with CVD events by sex, weight, and age.

RESULTS

Female sex (26%), lower weight (2% per 5 kg), and older age (4% per 5 years) were associated with higher spot-ACR independent of 24hr-UAE (P<0.001). Spot urine albumin concentration (hazard ratio [HR], 1.26 per ln-SD higher) and 1/spot urine creatinine concentration (HR, 1.16 per ln-SD higher) were associated with CVD events. Spot-ACR was more strongly associated with CVD events than either component of the ratio (HR, 1.41 per ln-SD higher). Associations of spot-ACR ≥10 mg/g versus less (HR, 2.33) and 24hr-UAE ≥10 mg/d versus less (HR, 2.09) with CVD events were similar, and there were no significant differences across subgroups (P for interactions >0.06).

CONCLUSIONS

In community-living individuals with 24hr-UAE <30 mg/d, spot-ACR is higher in women, older persons, and lower-weight persons, independent of 24hr-UAE. Low spot urine creatinine is associated with CVD risk, but high urine albumin is a stronger determinant of the association of spot-ACR with CVD than is low urine creatinine.

Percentage of body fat cutoffs by sex, age, and race-ethnicity in the US adult population from NHANES 1999-2004

BACKGROUND

To date, there is no consensus regarding adult cutoffs of percentage of body fat or estimated cutoffs on the basis of nationally representative samples with rigorous body-composition measurements.

OBJECTIVE

We developed cutoffs of percentage of body fat on the basis of the relation between dual-energy x-ray absorptiometry-measured fat mass and BMI (in kg/m(2)) stratified by sex, age, and race-ethnicity by using 1999-2004 NHANES data.

DESIGN

A simple regression (percentage of body fat = β(0) + β(1) × 1 ÷ BMI) was fit for each combination of sex (men and women), 3 age groups (18-29, 30-49, and 50-84 y of age), and 3 race-ethnicity groups (non-Hispanic whites, non-Hispanic blacks, and Mexican Americans). Model fitting included a consideration of complex survey design and multiple imputations. Cutoffs of percentage of body fat were computed that corresponded to BMI cutoffs of 18.5, 25, 30, 35, and 40 on the basis of estimated prediction equations.

RESULTS

R(2) ranged from 0.54 to 0.72 for men (n = 6544) and 0.58 to 0.79 for women (n = 6362). In men, the percentage of body fat that corresponded to a BMI of 18.5, 25, 30, 35, and 40 across age and racial-ethnic groups ranged from 12.2% to 19.0%, 22.6% to 28.0%, 27.5% to 32.3%, 31.0% to 35.3%, and 33.6% to 37.6%, respectively; the corresponding ranges in women were from 24.6% to 32.3%, 35.0% to 40.2%, 39.9% to 44.1%, 43.4% to 47.1%, and 46.1% to 49.4%, respectively. The oldest age group had the highest cutoffs of percentage of body fat. Non-Hispanic blacks had the lowest cutoffs of percentage of body fat. Cutoffs of percentage of body fat were higher in women than in men.

CONCLUSIONS

Cutoffs of percentage of body fat that correspond to the current US BMI cutoffs are a function of sex, age, and race-ethnicity. These factors should be taken into account when considering the appropriateness of levels of percentage of body fat.

Association of hypo- and hyperkalemia with disease progression and mortality in males with chronic kidney disease: the role of race

BACKGROUND/AIMS

Abnormal serum potassium is associated with higher mortality in dialysis patients, but its impact on outcomes in predialysis chronic kidney disease (CKD) is less clear. Furthermore, blacks with normal kidney function have lower urinary potassium excretion, but it is unclear if such differences have a bearing on race-associated outcomes in CKD.

METHODS

We studied predialysis mortality and slopes of estimated glomerular filtration rate, eGFR) associated with serum potassium in 1,227 males with CKD. Mortality was examined in time-dependent Cox models, and slopes of eGFR in linear mixed effects models with adjustments for case mix and laboratory values.

RESULTS

Both hypo- and hyperkalemia were associated with mortality overall and in 933 white patients, but in 294 blacks hypokalemia was a stronger death predictor. Hypokalemia was associated with loss of kidney function independent of race: a 1 mEq/l lower potassium was associated with an adjusted difference in slopes of eGFR of -0.13 ml/min/1.73 m(2)/year (95% CI: -0.20 to -0.07), p < 0.001.

CONCLUSION

Hypo- and hyperkalemia are associated with higher mortality in CKD patients. Blacks appear to better tolerate higher potassium than whites. Hypokalemia is associated with faster CKD progression independent of race. Hyperkalemia management may warrant race-specific consideration, and hypokalemia correction may slow CKD progression.

The differences of sarcopenia-related phenotypes: effects of gender and population

Sarcopenia is a serious condition especially in the elderly population mainly characterized by the loss of skeletal muscle mass and strength with aging. Extremity skeletal muscle mass index (EMMI) (sum of skeletal muscle mass in arms and legs/height2) is gaining popularity in sarcopenia definition (less than two standard deviations below the mean of a young adult reference group), but little is known about the gender- and population-specific differences of EMMI. This study aimed at investigating the differences of EMMI, arm muscle mass index (AMMI), and leg muscle mass index (LMMI) between gender groups and populations (Chinese vs. Caucasians). The participants included 1,809 Chinese and 362 Caucasians with normal weight aged from 19 to 45 years old. Extremity muscle mass, arm muscle mass, and leg muscle mass were measured by using dual energy x-ray absorptiometry. Independent sample t tests were used to analyze the differences in muscle mass indexes between the studied groups. All the study parameters including EMMIs, AMMIs, and LMMIs were significantly higher (P ≤ 0.0003) in the Caucasian group than in the Chinese group and also higher in the male group than in the female group, and these significant differences (P ≤ 0.0005) remained after adjusting for age by simple regressions. The detected differences of muscle mass indexes between different gender and ethnic groups may provide important implications in their different risk of future sarcopenia.

Serum potassium and the racial disparity in diabetes risk: the Atherosclerosis Risk in Communities (ARIC) Study

BACKGROUND

Low serum potassium appears to be independently associated with incident type 2 diabetes, and low dietary potassium is more common in African Americans than in whites.

OBJECTIVE

We hypothesized that low serum potassium contributes to the excess risk of diabetes in African Americans.

DESIGN

We analyzed data collected from 1987 to 1996 from the Atherosclerosis Risk in Communities (ARIC) Study. At baseline, we identified 2716 African American and 9493 white participants without diabetes. We used multivariate Cox models to estimate the relative hazards (RHs) of incident diabetes related to baseline serum potassium during 9 y of follow-up.

RESULTS

Mean serum potassium concentrations were lower in African Americans than in whites at baseline (4.2 compared with 4.5 mEq/L; P < 0.01), and African Americans had a greater incidence of diabetes than did whites (26 compared with 13 cases/1000 person-years). The adjusted RHs (95% CI) of incident diabetes for those with serum potassium concentrations of <4.0, 4.0-4.4, and 4.5-4.9 mEq/L, compared with those with serum potassium concentrations of 5.0-5.5 mEq/L (referent), were 2.28 (1.21, 4.28), 1.97 (1.06, 3.65), and 1.85 (0.99, 3.47) for African Americans and 1.53 (1.14, 2.05), 1.49 (1.19, 1.87), and 1.27 (1.02, 1.58) for whites, respectively. Racial differences in serum potassium appeared to explain 18% of the excess risk of diabetes in African Americans, which is comparable with the percentage of risk explained by racial differences in body mass index (22%).

CONCLUSIONS

Low serum potassium concentrations in African Americans may contribute to their excess risk of type 2 diabetes relative to whites. Whether interventions to increase serum potassium concentrations in African Americans might reduce their excess risk deserves further study. The ARIC Study is registered at clinicaltrials.gov as NCT00005131.

Body composition phenotypes in pathways to obesity and the metabolic syndrome

Dynamic changes in body weight have long been recognized as important indicators of risk for debilitating diseases. While weight loss or impaired growth can lead to muscle wastage, as well as to susceptibility to infections and organ dysfunctions, the development of excess fat predisposes to type 2 diabetes and cardiovascular diseases, with insulin resistance as a central feature of the disease entities of the metabolic syndrome. Although widely used as the phenotypic expression of adiposity in population and gene-search studies, body mass index (BMI), that is, weight/height(2) (H(2)), which was developed as an operational definition for classifying both obesity and malnutrition, has considerable limitations in delineating fat mass (FM) from fat-free mass (FFM), in particular at the individual level. After an examination of these limitations within the constraints of the BMI-FM% relationship, this paper reviews recent advances in concepts about health risks related to body composition phenotypes, which center upon (i) the partitioning of BMI into an FM index (FM/H(2)) and an FFM index (FFM/H(2)), (ii) the partitioning of FFM into organ mass and skeletal muscle mass, (iii) the anatomical partitioning of FM into hazardous fat and protective fat and (iv) the interplay between adipose tissue expandability and ectopic fat deposition within or around organs/tissues that constitute the lean body mass. These concepts about body composition phenotypes and health risks are reviewed in the light of race/ethnic variability in metabolic susceptibility to obesity and the metabolic syndrome.

Evaluation of the Chronic Kidney Disease Epidemiology Collaboration equation for estimating the glomerular filtration rate in multiple ethnicities

An equation from the Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) provides more accurate estimates of the glomerular filtration rate (eGFR) than that from the modification of diet in renal disease (MDRD) Study, although both include a two-level variable for race (Black and White and other). Since creatinine generation differs among ethnic groups, it is possible that a multilevel ethnic variable would allow more accurate estimates across all groups. To evaluate this, we developed an equation to calculate eGFR that includes a four-level race variable (Black, Asian, Native American and Hispanic, and White and other) using a database of 8254 patients pooled from 10 studies. This equation was then validated in 4014 patients using 17 additional studies from the United States and Europe (validation database), and in 1022 patients from China (675), Japan (248), and South Africa (99). Coefficients for the Black, Asian, and Native American and Hispanic groups resulted in 15, 5, and 1% higher levels of eGFR, respectively, compared with the White and other group. In the validation database, the two-level race equation had minimal bias in Black, Native American and Hispanic, and White and other cohorts. The four-level ethnicity equation significantly improved bias in Asians of the validation data set and in Chinese. Both equations had a large bias in Japanese and South African patients. Thus, heterogeneity in performance among the ethnic and geographic groups precludes use of the four-level race equation. The CKD-EPI two-level race equation can be used in the United States and Europe across a wide range of ethnicity.

Fat-free mass index: changes and race/ethnic differences in adulthood

OBJECTIVE

Nutritional status is assessed by measuring BMI or percent body fat (%fat). BMI can misclassify persons who carry more weight as fat-free mass and %fat can be misleading in cases of malnutrition or in disease states characterized by wasting of lean tissue. The fat-free mass index (FFMI) is proposed to assess body composition in individuals who have a similar body composition but differ in height allowing identification of those suffering from malnutrition, wasting or those that possess a relatively high muscle mass. The purpose was to determine whether the FFMI differs in a group of racially/ethnically diverse adults.

DESIGN

Cross-sectional.

SUBJECTS

Subjects were a multi-ethnic sample (Caucasian, CA; African American, AA; Hispanic, HIS and Asian, AS) of 1339 healthy males (n = 480) and females (n = 859) ranging in age from 18-110 years. Total body fat, total fat-free mass and bone mineral density were estimated using dual energy X-ray absorptiometry.

RESULTS

FFMI differed among the four ethnic groups (P ≤ 0.05) for both genders. A curvilinear relationship was found between age and FFMI for both genders although the coefficients in the quadratic model differed between genders (P ≤ 0.001) indicating the rate of change in FFMI differed between genders. The estimated turning point where FFMI started to decline was in the mid 20s for male and mid 40s for female participants. An age × gender interaction was found such that the rate of decline was greater in male than female participants (P ≤ 0.001). For both genders, FFMI was greatest in AA and the least in AS (P ≤ 0.001). There was no significant interaction between race and age or age(2) (P = 0.06). However, male participants consistently had a greater FFMI than female participants (P ≤ 0.001).

CONCLUSIONS

These findings have clinical implications for identifying individuals who may not be recognized as being malnourished based on their BMI or %fat but whose fat-free mass corrected for height is relatively low.

Ethnicity-related skeletal muscle differences across the lifespan

Despite research and clinical significance, limited information is available on the relations between skeletal muscle (SM) and age in adults, specifically among Hispanics, African Americans (AA), and Asians. The aim was to investigate possible sex and ethnic SM differences in adults over an age range of 60 years. Subjects were 468 male and 1280 female adults (> or =18 years). SM was estimated based on DXA-measured appendicular lean-soft tissue using a previously reported prediction equation. Locally weighted regression smoothing lines were fit to examine SM trends and to localize age cutoffs; piecewise multiple linear regression models were then applied, controlling for weight and height, to identify age cutoffs for sex-specific changes in SM among the ethnic groups. The age of 27 years was identified for women and men as the cut-off after which SM starts to show a negative association with age. Both sexes had a similar ethnic pattern for expected mean SM at the age cutoff, with AA presenting the highest SM values, followed by Whites, Hispanics, and Asians. After the age cutoffs, the lowering of SM differed by ethnicity and sex: AA women showed the greatest SM lowering whereas Hispanic women had the least. Hispanic men tended to show a higher negative association of SM with age followed by AA and Whites. To conclude, significant sex and ethnic differences exist in the magnitude of negative associations of SM with age >27 years. Further studies using a longitudinal design are needed to explore the associations of ethnicity-related decline of SM with health risks.

Elderly Mexicans have less muscle and greater total and truncal fat compared to African-Americans and Caucasians with the same BMI

BACKGROUND

How body composition, specifically skeletal muscle mass, compares in Mexican elderly to other ethnic groups has not previously been reported. We tested the hypothesis that older adults from Northwest Mexico (Mex) would have similar total appendicular skeletal muscle (TASM) compared with New York dwelling Caucasians (Cauc) and African-Americans (AA).

METHODS

Two hundred and eighty nine Mex (135 males and 154 females), 166 AA (36 males and 130 females) and 229 Cauc (64 males and 165 females), aged 60-98 years were assessed. Total and regional fat and lean tissues were measured by whole-body dual energy X-ray absorptiometry where TASM is the sum of arm and leg bone-free and fat-free lean tissue. Differences in TASM were tested by ANCOVA, with age, height, and body mass index (BMI) as covariates.

RESULTS

TASM adjusted for ethnicity, age, height and BMI, were 22.6 +/- 0.2 kg and 17.8 +/- 0.1 kg for males and females, respectively (p < 0.001). Among males with similar age, height, and BMI, Mex had less TASM compared with AA and Cauc (p < 0.001). Total body fat and truncal fat were higher (p < 0.001) and FFM lower (p < 0.001) in Mex compared to both AA and Cauc males after adjusting for age and BMI. Among females, Mex had higher total and truncal fat (p < 0.001) after adjusting for age and BMI, and significantly lower TASM (p < 0.001) after adjusting for age, height, and BMI compared to AA and Cauc females.

CONCLUSIONS

Elderly Mex have a different body composition compared with AA and Cauc of a similar BMI and age. Mex have significantly less TASM with greater total and truncal fat. In the long-term, Mex elderly may be at greater risk for sarcopenic obesity compared to other ethnic groups.

Sodium, blood pressure, and ethnicity: what have we learned?

An enormous amount of research has yielded significant knowledge about ethnic differences in sodium homeostasis and blood pressure regulation. Consistent findings such as greater sodium-sensitivity, lower potassium excretion and high higher serum sodium levels in African Americans need further exploration to define more precise physiological mechanisms. The genetic alleles associated with sodium homeostasis in relation to blood pressure have accounted for only a small proportion of the variance in blood pressure. Several allelic variants differ in frequency among ethnic groups and heat-adapted genetic variants have a high prevalence in low latitudes and hot, wet climates which lends support to the "sodium retention" hypothesis. The blood pressure disparities between African Americans and whites may, in part, be due to different allelic frequencies of genes associated with sodium homeostasis. However, with advances in genomics, environmental factors tend to be neglected in research. Better measures of environmental stress have recently been developed by anthropologists and should be included in research designs by investigators in other disciplines. Public health efforts should encourage food producers to reduce sodium content of its products, and physicians should encourage patients to reduce consumption of high sodium packaged and fast foods.

Smaller organ mass with greater age, except for heart

Autopsy/cadaver data indicate that many organs and tissues are smaller in the elderly compared with young adults; however, in vivo data are lacking. The aim of this study was to determine whether the mass of specific high-metabolic-rate organs is different with increasing age, using MRI. Seventy-five healthy women (41 African-Americans and 34 Caucasians, age range 19-88 yr) and 36 men (8 African-Americans and 28 Caucasians, age range 19-84 yr) were studied. MRI-derived in vivo measures of brain, heart, kidneys, liver, and spleen were acquired. Left ventricular mass (LVM) was measured by either echocardiography or cardiac gated MRI. Total body fat mass and fat-free mass (FFM) were measured with a whole body dual-energy X-ray absorptiometry (DXA) scanner. Multiple regression analysis was used to investigate the association between the organ mass and age after adjustment for weight and height (or DXA measures of FFM), race, sex, and interactions among these variable. No statistically significant interaction was found among age, sex, and race in any regression model. Significant negative relationships between organ mass and age were found for brain (P < 0.0001), kidneys (P = 0.01), liver (P = 0.001), and spleen (P < 0.0001). A positive relationship between LVM and age was found after adjustment for FFM (P = 0.037). These findings demonstrate that age has a significant effect on brain, kidneys, liver, spleen, and heart mass. The age effect was independent of race and sex.

Adipose tissue distribution is different in type 2 diabetes

BACKGROUND

The extent to which adipose tissue (AT) distribution is different between persons with type 2 diabetes (T2DM) and nondiabetic control subjects remains unclear.

OBJECTIVE

The aim of this study was to establish whether total body adiposity and its distribution, quantified by using state-of-the-art whole-body magnetic resonance imaging, differs between these 2 groups.

DESIGN

This cross-sectional evaluation included 93 participants (n = 56 women and 37 men) in the Look AHEAD (Action for HEAlth in Diabetes) Trial with T2DM who had a mean (+/-SD) age of 58.3 +/- 6.6 y and body mass index (in kg/m(2)) of 31.6 +/- 3.1 and 93 healthy non-T2DM control subjects (n = 64 women and 29 men) who had a mean (+/-SD) age of 60.6 +/- 17.1 y and body mass index of 29.6 +/- 3.0. All participants self-reported being of African American or white ancestry. Magnetic resonance imaging-derived in vivo measures of total-body AT (TAT) and its distribution, subcutaneous AT (SAT), visceral AT (VAT), and intermuscular AT (IMAT) were acquired. Linear regression models were developed for each AT compartment to adjust for important covariates of race, sex, age, height, and weight and to examine potential interactions of covariates.

RESULTS

These models showed significantly less SAT (African American: -1.2 kg; white: -2.4 kg; both P = 0.001), including less femoral-gluteal SAT, more VAT (African American: 0.7 kg, P < 0.001; white: 1.8 kg, P = 0.007), and more IMAT (0.5 kg, P = 0.001) in the T2DM group.

CONCLUSION

We concluded that AT distribution is significantly altered in T2DM, ie, more VAT and IMAT--2 depots known to exacerbate insulin resistance--and less SAT in persons with T2DM than in healthy control subjects, a novel finding that we posit may compound the risk of insulin resistance.

The relationship between skinfold thickness and body mass index in North European Caucasian and East Asian women with anorexia nervosa: implications for diagnosis and management

OBJECTIVE

To investigate the relationship between skinfold thickness and body mass index (BMI) in North European Caucasian and East Asian young women with and without anorexia nervosa (AN) in two countries.

METHOD

Height, weight and skinfold thicknesses were assessed in 137 young women with and without AN, in Australia and Singapore. The relationship between BMI and the sum of triceps, biceps, subscapular and iliac crest skinfolds was analysed with clinical status, ethnicity, age and country of residence as covariates.

RESULTS

For the same BMI, women with AN had significantly smaller sums of skinfolds than women without AN. East Asian women both with and without AN had significantly greater skinfold sums than their North European Caucasian counterparts after adjusting for BMI.

CONCLUSION

Lower BMI goals may be appropriate when managing AN patients of East Asian ancestry and the weight for height diagnostic criterion should be reconsidered for this group.

Evaluation of between-methods agreement of extracellular water measurements in adults and children

BACKGROUND

Extracellular water (ECW), a relevant molecular level component for clinical assessment, is commonly obtained by 2 methods that rely on assumptions that may not be possible to test at the time the measurements are made.

OBJECTIVE

The aim of the current study was to evaluate the degree of agreement between ECW assessment by the sodium bromide dilution (ECW(NaBr)) and total body potassium (TBK; whole-body (40)K counting) to total body water (TBW; isotope dilution) methods (ECW(TBK-TBW)) in an ethnically mixed group of children and adults.

DESIGN

ECW was measured with the ECW(NaBr) and ECW(TBK-TBW) methods in 526 white and African American males and females (86 nonobese children, 193 nonobese adults, and 247 obese adults). Fat mass was assessed with dual-energy X-ray absorptiometry. Multiple regression analysis was used to examine the variables related to between-ECW method differences.

RESULTS

Significant but generally small group mean (+/-SD) differences in ECW were found in the obese adults (1.28 +/- 2.54 kg) and children (-0.71 +/- 1.78 kg). The magnitude of the differences was related to mean ECW in obese adults, children, and nonobese adults, and the relations between these variables were modified by sex for nonobese adults. ECW differences were also dependent on age, weight, sex, and race or on interactions between these variables.

CONCLUSIONS

Overall, although good between-method agreement was found across the 3 groups, the degree of agreement varied according to subject characteristics, particularly at the extremes of ECW and body weight. We advance a possible mechanism that may link subject characteristics with the degree of agreement between ECW measurement methods and their underlying assumptions.

Racial differences in urinary potassium excretion

Racial differences in potassium (K) intake and urinary K excretion may contribute to the higher BP observed in black compared with white individuals. Although black individuals typically consume less dietary K than white individuals, the lower urinary K excretion observed in black individuals may reflect more than differences in intake. In this study, data from the Dietary Approaches to Stop Hypertension (DASH) trial (413 white and black participants) were used to evaluate urinary K excretion in black and white individuals with similar K intake. At screening, mean urinary K excretion was higher in white than black individuals (mean Delta = 645 mg/d for white minus black individuals, adjusted for age, gender, and weight; P < 0.001). After a 3-wk run-in period during which all participants received a low-K control diet, a significant racial difference remained (mean Delta = 201 mg/d, adjusted for age, gender, and caloric intake; P < 0.001). Participants were then randomly assigned to continue the control diet or switch to a high-K diet (either a high fruit/vegetable diet or the DASH diet) for 8 wk. At the end of intervention, the mean difference in urinary K in white compared with black individuals after adjustment for age, gender, and caloric intake was -6 mg/d (P = 0.95) in the control group, 163 mg/d in the fruits/vegetables group (P = 0.39), and 903 mg/d in the DASH group (P < 0.001). Racial differences in urinary K excretion seem to reflect more than intake differences; further studies are needed to understand their potential impact on clinical outcomes.

Renal and gastrointestinal potassium excretion in humans: new insight based on new data and review and analysis of published studies

OBJECTIVES

Little is known about the relationship between the renal and gastrointestinal excretion of potassium in humans. This information is important in light of strong associations of potassium intake with hypertension and occlusive stroke.

METHODS

We determined the relationship between fecal and urinary excretion of potassium under both fixed and variable potassium intakes using our unpublished archival data and published data of others. Twenty-five subjects were evaluated.

RESULTS

On a fixed, low oral potassium intake (61.2 +/- 4.7 mmol/day; mean +/- SD), there was an inverse relationship between fecal and urinary potassium excretion (r = -0.66, p = 0.040). In studies in which potassium intake varied between 61-135 mmol/day, fecal and urinary potassium excretions were positively correlated (r = 0.58, p = 0.024). Considerable within-and-between-subject variation was observed in the relationship between fecal and urinary potassium excretion.

CONCLUSIONS

Inter-individual variation in fecal potassium excretion may arise from both variation in dietary potassium intake and intrinsic individual differences in the renal versus gastrointestinal handling of potassium.

Use of height3:waist circumference3 as an index for metabolic risk assessment?

Current anthropometric indices for health risk assessment are indirect measures of total or visceral body fat mass that do not consider the inverse relationship of lean body mass to metabolic risk as well as the non-linear relationship between central obesity and insulin resistance.We examined a new anthropometric index that reflects the relationship of waist circumference (WC) as a risk factor to fat-free mass (FFM) as a protective parameter of body composition. In apopulation of 335 adults (191 females and 144 males; mean age 53 (sd 13·9) years) with ahigh prevalence of obesity (27%) and metabolic syndrome (30%) we derived FFM:WC3 from the best fit of the relationship with metabolic risk factors (plasma triacylglycerol levels and insulin resistance by homeostasis model assessment index). Because FFM is known to be proportional to the cube of height, FFM was subsequently replaced by height3 yielding height3:WC3 as an easily applicable anthropometric index. Significant inverse relationships of height3:WC3 to metabolic risk factorswere observed for both sexes. They slightly exceeded those of conventional anthropometric indicessuch as BMI, WC or WC:hip ratio in women but not in men. The exponential character of the denominator WC3 implies that at a given FFM with gradually increasing WC the increasein metabolic risk is lower than proportional. Further studies are needed to evaluate height3:WC3 as an anthropometric index for health risk assessment.