Two-Year Treatment With Metformin During Puberty Does Not Preserve β-Cell Function in Youth With Obesity

CONTEXT

Youth-onset type 2 diabetes is a disease of pubertal onset, associated with additional burden of pubertal insulin resistance on the β-cell.

OBJECTIVE

Evaluate the impact of metformin treatment during puberty, a critical window of cardiometabolic change, on insulin sensitivity (Si) and compensatory β-cell response in youth with obesity.

SETTING

Pediatric academic hospital clinical translational research center.

PARTICIPANTS

Healthy youth in early puberty [Tanner stage (T) 2-3] with normoglycemia and obesity (n = 44).

INTERVENTION

Double-blinded placebo-control trial of metformin during puberty (until T5).

MAIN OUTCOME MEASURES

Insulin sensitivity (Si), insulin response [acute insulin response to glucose (AIRg)], and disposition index (DI), estimated from frequently sampled intravenous glucose tolerance testing; body fat (dual X-ray absorptiometry); and other laboratory parameters, collected at baseline, T4, and T5. Placebo-subtracted treatment effect was calculated using linear mixed models.

RESULTS

At T5, metformin treatment, adjusting for sex, race, and baseline value, was associated with improved BMI z-score (-0.44 ± 0.16, P = 0.02), percentage body fat (%body fat; -3.4 ± 1.2%, P = 0.06), and waist circumference (-11.3 ± 3.2cm, P = 0.003). There were no significant treatment effects at T5 on Si or secretion: Si (0.85 ± 0.87 × 10-4/min-1/μIU/mL, P = 0.34), AIRg (-259 ± 386 μIU/mL, P = 0.51), or DI (508 ± 802 × 10-4/min-1, P = 0.53). High baseline DI predicted longitudinal decline in DI.

CONCLUSIONS

Two years of metformin treatment in obese youth during puberty improved BMI and body fat, but not Si or β-cell function. Of note, high DI in early puberty may be predictive of later decline in DI. Further studies are needed to develop strategies for preservation of β-cell function in youth at risk for type 2 diabetes.

The Impact of Obesity On Insulin Sensitivity and Secretion During Pubertal Progression: A Longitudinal Study

CONTEXT

Physiologic changes in glucose metabolism are well-described to occur during puberty. However, there are important gaps in understanding the interaction between obesity and the normal physiologic changes during puberty, as well as how these changes could contribute to the increased risk of comorbidities, such as type 2 diabetes and dyslipidemia, in youth with obesity.

OBJECTIVE

The objective of this study was to compare longitudinal changes in insulin sensitivity (Si) and secretion during pubertal progression in youth with obesity versus those with normal weight.

DESIGN

Longitudinal observational study evaluating youth from early puberty (Tanner [T]2-T3) until puberty completion (T5).

SETTING

Pediatric academic hospital Clinical Translational Research Center.

PARTICIPANTS

Pubertal youth with normal weight (n = 47; 22 female, 25 male) and obesity (n = 37; 23 female, 14 male).

MAIN OUTCOME MEASURES

Si, insulin response (acute insulin response to glucose, AIRg) and disposition index (DI) by intravenous glucose tolerance test at baseline (T2-T3), T4, and T5.

RESULTS

Youth with obesity had significantly lower Si and higher AIRg at each time point (P < 0.001), but DI was similar between the groups. There were no group differences in trajectory of Si, AIRg or DI over time. Leptin, insulin-like growth factor-1, and obesity were most strongly associated with Si and AIRg at all time points.

CONCLUSIONS

Obesity significantly impacts Si during puberty, even at the earliest stages. However, in general, obese youth have adequate β-cell compensation for the significantly reduced Si of puberty. Future studies are needed to better predict the subset of youth who fail to maintain β-cell compensation during puberty.

Acute estradiol treatment reduces skeletal muscle protein breakdown markers in early- but not late-postmenopausal women

OBJECTIVES

Menopause and decline in estradiol (E₂) may contribute to sarcopenia (i.e., age-related decline in muscle mass and strength) in women. E₂ may directly impact skeletal muscle protein breakdown via estrogen receptor (ER) signaling, primarily ERα. It is not yet known whether: 1) E₂ regulates pathways of skeletal muscle protein breakdown; 2) E₂-mediated changes in protein breakdown markers are associated with ERα activation and insulin sensitivity; and 3) the effects of E₂ on protein breakdown markers differ by increasing time since menopause.

STUDY DESIGN

We studied 27 women who were ≤6 years past menopause (early postmenopausal, EPM; n = 13) or ≥10 years past menopause (late postmenopausal, LPM; n = 14). Fasted skeletal muscle samples were collected following 1 week of transdermal E₂ or placebo treatment in a randomized cross-over design.

MAIN OUTCOME MEASURES

We analyzed for cytosolic protein content of the: 1) structural proteins myosin heavy chain (MHC) and tropomyosin; and 2) protein regulatory markers: protein kinase B (Akt), muscle-specific ring finger protein1 (MuRF1), atrogin1, and forkhead box O3 (FOXO3) using Western blot.

RESULTS

In response to acute E₂, FOXO3 activation (dephosphorylation) and MuRF1 protein expression decreased in EPM but increased in LPM women (p < 0.05). ERα activation was not associated with these protein breakdown markers, but FOXO3 activation tended to be inversely correlated (r = -0.318, p = 0.065) to insulin sensitivity.

CONCLUSIONS

These preliminary studies suggest the effects of E₂ on skeletal muscle protein breakdown markers were dependent on time since menopause, which is consistent with our previous study on insulin sensitivity.

Postprandial Triglycerides Predict Newborn Fat More Strongly than Glucose in Women with Obesity in Early Pregnancy

OBJECTIVE

Maternal obesity (OB) accounts for the majority of large-for-gestational-age infants, and newborn percent fat (NB%fat) correlates strongest with childhood OB. In addition to maternal glucose, fasting triglycerides (TGs) may contribute, but postprandial triglycerides (PPTGs) are unstudied. It was hypothesized that fasting TGs and PPTGs are higher in women with OB compared with women with normal weight (NW) throughout pregnancy, correlate more strongly with NB%fat than glucose, and may relate to dietary chylomicron TGs.

METHODS

Fasting TGs and PPTGs, free fatty acids, glucose, and insulin were prospectively measured 10 times over 4 hours after a controlled liquid breakfast early (14-16 weeks) and later (26-28 weeks) in pregnancy in 27 mothers with NW and 27 with OB. NB%fat was measured by dual x-ray absorptometry.

RESULTS

Fasting TGs and PPTGs were already ≥ 30% higher in mothers with OB at 14 to 16 weeks (P < 0.001) versus mothers with NW. In mothers with OB, a simple 1-hour (r = 0.71; P < 0.01) or 2-hour (r = 0.69; P < 0.01) PPTG at 14 to 16 weeks correlated strongest with NB%fat. In mothers with NW, the increase in TGs from early to later pregnancy correlated strongest with NB%fat (r = 0.57; P < 0.01). Maternal glucose did not statistically add to prediction models.

CONCLUSIONS

These novel data suggest that 1- or 2-hour PPTGs might be a new target for early intervention in pregnancies with OB to prevent excess newborn adiposity and attenuate child OB risk.

Time since menopause and skeletal muscle estrogen receptors, PGC-1α, and AMPK

Objective:

Short-term administration of estradiol (E₂) improves insulin-stimulated glucose disposal rate in early postmenopausal (EPM) women compared with a reduction in late postmenopausal (LPM) women. The underlying mechanisms by which E₂ action on glucose disposal rate reversed from beneficial early to harmful late in menopause is unknown, but might include adverse changes in estrogen receptors (ERs) or other biomarkers of cellular energy metabolism with age or duration of estrogen deficiency.

Methods:

We retrospectively analyzed skeletal muscle samples from 27 postmenopausal women who were 6 years or less past menopause (EPM; n = 13) or at least 10 years past menopause (LPM; n = 14). Fasted skeletal muscle (vastus lateralis) samples were collected after 1 week administration of transdermal E₂ or placebo, in random cross-over design.

Results:

Compared with EPM, LPM had reduced skeletal muscle ERα and ERβ nuclear protein. Short-term E₂ treatment did not change nuclear ERα or ERβ, but decreased cytosolic ERα, so the proportion of ERα in the nucleus compared with the cytosol tended to increase. There was a group-by-treatment interaction (P < 0.05) for nuclear proliferator-activated receptor γ co-activator 1-α and phosphorylated adenosine monophosphate-activated protein kinase, such that E₂ increased these proteins in EPM, but decreased these proteins in LPM.

Conclusions:

These preliminary studies of skeletal muscle from early and late postmenopausal women treated with E₂ suggest there may be declines in skeletal muscle ER and changes in the E₂-mediated regulation of cellular energy homeostasis with increasing time since menopause.

Placental lipoprotein lipase activity is positively associated with newborn adiposity

INTRODUCTION

Recent data suggest that in addition to glucose, fetal growth is related to maternal triglycerides (TG). To reach the fetus, TG must be hydrolyzed to free fatty acids (FFA) and transported across the placenta, but regulation is uncertain. Placental lipoprotein lipase (pLPL) hydrolyzes TG, both dietary chylomicron TG (CM-TG) and very-low density lipoprotein TG (VLDL-TG), to FFA. This may promote fetal fat accretion by increasing the available FFA pool for placental uptake. We tested the novel hypothesis that pLPL activity, but not maternal adipose tissue LPL activity, is associated with newborn adiposity and higher maternal TG.

METHODS

Twenty mothers (n = 13 normal-weight; n = 7 obese) were prospectively recruited. Maternal glucose, insulin, TG (total, CM-TG, VLDL-TG), and FFA were measured at 14-16, 26-28, and 36-37 weeks, and adipose tissue LPL was measured at 26-28 weeks. At term delivery, placental villous biopsies were immediately analyzed for pLPL enzymatic activity. Newborn percent body fat (newborn %fat) was assessed by skinfolds.

RESULTS

Placental LPL activity was positively correlated with birthweight (r = 0.48;P = 0.03) and newborn %fat (r = 0.59;P = 0.006), further strengthened by correcting for gestational age at delivery (r = 0.75;P = 0.0001), but adipose tissue LPL was not. Maternal TG and BMI were not correlated with pLPL activity. Additionally, pLPL gene expression, while modestly correlated with enzymatic activity (r = 0.53;P < 0.05), was not correlated with newborn adiposity.

DISCUSSION

This is the first study to show a positive correlation between pLPL activity and newborn %fat. Placental lipase regulation and the role of pLPL in pregnancies characterized by nutrient excess and fetal overgrowth warrant further investigation.

Factors Associated with Achievement of Clinically Significant Weight Loss by Women in a National Nonprofit Weight Loss Program

BACKGROUND

Clinically significant weight loss (CSWL) is ≥5% of initial weight. The purpose of the study is to determine factors associated with women achieving CSWL in Take Off Pounds Sensibly (TOPS), a national, nonprofit weight loss program.

METHODS

This is a retrospective analysis of 48,674 females who joined TOPS from 2005 to 2011 and had a birth date in the database. Predictors of CSWL were evaluated using log-binomial regression and adjusted relative risks [99% CI] for participant age, initial weight, number of members per chapter, and chapter age.

RESULTS

Older women were more likely to achieve CSWL, with women ≥70 years 1.23 (1.18, 1.28) times more likely to achieve CSWL compared to women 18 to <45 years. Women who weighed 113 to <136 kg and ≥136 kg were 1.06 (1.02, 1.10) and 1.07 (1.02, 1.14) times more likely to achieve CSWL compared to women <80 kg, respectively. Women in chapters with 25 to <35 members and ≥35 members more were 1.09 (1.05, 1.13) and 1.14 (1.10, 1.18) times more likely to achieve CSWL than those in chapters with less than 15 members. Women in older chapters were less likely to achieve CSWL, with women in chapters 10 to 20 years old 0.95 (0.92, 0.99) times as likely to lose weight as those in chapters less than 10 years old.

CONCLUSIONS

Women in TOPS were more likely to achieve CSWL if older, ≥113 kg, and in larger, newer chapters. Future studies should address ways to modify the program to improve achievement of CSWL.

Estradiol-mediated improvements in adipose tissue insulin sensitivity are related to the balance of adipose tissue estrogen receptor α and β in postmenopausal women

We recently demonstrated that short-term estradiol (E₂) treatment improved insulin-mediated suppression of lipolysis in postmenopausal women, but to a greater extent in those who were late compared to early postmenopausal. In this follow-up study we tested whether subcutaneous adipose tissue (SAT) expression of estrogen receptors (ER) α and β differs between early and late postmenopausal women. We further tested whether the balance of ERα to ERβ in SAT determined the effect of E₂ on SAT insulin sensitivity. The present study included 35 women who were ≤6 years past menopause (EPM; n = 16) or ≥10 years past menopause (LPM; n = 19). Fasted SAT samples were taken following 1-week transdermal E₂ treatment or placebo (PL) in a random cross-over design. Samples were analyzed for nuclear/cytosolic protein content and mRNA expression using Western blot and qPCR, respectively. While ESR1 increased slightly (~1.4-fold) following E₂ treatment in both groups, ERα and ERβ protein expression did not differ between groups at baseline or in response to E₂. However, the balance of ERα/ERβ protein in the SAT nuclear fraction increased 10% in EPM compared to a 25% decrease in LPM women (group x treatment interaction, p<0.05). A greater proportion of ERα/ERβ protein in the nuclear fraction of SAT at baseline (placebo day) was associated with greater reduction in SAT insulin resistance (i.e., better suppression of lipolysis, EC₅₀) in response to E₂ (r = -0.431, p<0.05). In conclusion, there do not appear to be differences in the proportion of adipose tissue ERα/ERβ protein in late, compared to early, postmenopausal women. However, the balance of ERα/ERβ may be important for E₂-mediated improvement in adipose tissue insulin sensitivity.

Trial Registration: Clinical Trials#:NCT01605071

Age- and menopause-related differences in subcutaneous adipose tissue estrogen receptor mRNA expression

OBJECTIVES

Changes in estrogen receptor (ER) expression likely underlie differential metabolic effects of estrogen in pre- and postmenopausal women. The aim of the current study was to determine whether ER gene expression in abdominal and femoral subcutaneous adipose tissue (SAT) was associated with age, menopause, or regional adiposity.

METHODS

We studied pre- and post-menopausal (n=23 and 22, respectively; age 35-65y) normal weight (mean±SD; BMI 23.7±2.5kg/m²) women with similar total fat mass. Abdominal and femoral SAT ERα (ESR1) and ERβ (ESR2) mRNA expression was determined by qPCR.

RESULTS

Total fat mass did not differ between pre- and postmenopausal women (22.7±5.3vs. 21.7±5.3kg). Compared to premenopausal women, ESR1 and the ratio of ESR1 to ESR2 were lower (p≤0.05) in postmenopausal abdominal and femoral SAT. ESR1 and ESR1:ESR2 were inversely associated with age in abdominal SAT (r=-0.380 and r=-0.463, respectively; p<0.05) and femoral SAT (r=-0.353 and r=-0.472, respectively; p<0.05). ESR2 was not related to age or menopause. The inverse association between ESR1 and age persisted after adjusting for trunk fat mass, estradiol, or leptin.

CONCLUSION

Among healthy pre- and postmenopausal women, increased age was associated with a decreased balance of ERα to ERβ in abdominal and femoral subcutaneous adipose tissue.

Sex Hormones and Cardiometabolic Health: Role of Estrogen and Estrogen Receptors

With increased life expectancy, women will spend over three decades of life postmenopause. The menopausal transition increases susceptibility to metabolic diseases such as obesity, diabetes, cardiovascular disease, and cancer. Thus, it is more important than ever to develop effective hormonal treatment strategies to protect aging women. Understanding the role of estrogens, and their biological actions mediated by estrogen receptors (ERs), in the regulation of cardiometabolic health is of paramount importance to discover novel targeted therapeutics. In this brief review, we provide a detailed overview of the literature, from basic science findings to human clinical trial evidence, supporting a protective role of estrogens and their receptors, specifically ERα, in maintenance of cardiometabolic health. In so doing, we provide a concise mechanistic discussion of some of the major tissue-specific roles of estrogens signaling through ERα. Taken together, evidence suggests that targeted, perhaps receptor-specific, hormonal therapies can and should be used to optimize the health of women as they transition through menopause, while reducing the undesired complications that have limited the efficacy and use of traditional hormone replacement interventions.

Region-specific effects of oestradiol on adipose-derived stem cell differentiation in post-menopausal women

The goal of this study was to determine the effect of acute transdermal 17β‐oestradiol (E₂) on the adipogenic potential of subcutaneous adipose‐derived stem cells (ASC) in post‐menopausal women. Post‐menopausal women (n = 11; mean age 57 ± 4.5 years) were treated for 2 weeks, in a randomized, cross‐over design, with transdermal E₂ (0.15 mg) or placebo patches. Biopsies of abdominal (AB) and femoral (FEM) subcutaneous adipose tissue (SAT) were obtained after each treatment and mature adipocytes were analysed for cell size and ASC for their capacity for proliferation (growth rate), differentiation (triglyceride accumulation) and susceptibility to tumour necrosis factor alpha‐induced apoptosis. Gene expression of oestrogen receptors α and β (ESR1 and ESR2), perilipin 1 and hormone‐sensitive lipase (HSL), was also assessed. In FEM SAT, but not AB SAT, 2 weeks of E₂ significantly (P = 0.03) increased ASC differentiation and whole SAT HSL mRNA expression (P = 0.03) compared to placebo. These changes were not associated with mRNA expression of oestrogen receptors α and β, but HSL expression was significantly increased in FEM SAT with transdermal E₂ treatment. Adipose‐derived stem cells proliferation and apoptosis did not change in either SAT depot after E₂ compared with placebo. Short‐term E₂ appeared to increase the adipogenic potential of FEM, but not AB, SAT in post‐menopausal women with possible implications for metabolic disease. Future studies are needed to determine longer term impact of E₂ on regional SAT accumulation in the context of positive energy imbalance.

Striking differences in estimates of infant adiposity by new and old DXA software, PEAPOD and skin-folds at 2 weeks and 1 year of life

BACKGROUND

Infant adiposity better predicts childhood obesity/metabolic risk than weight, but technical challenges fuel controversy over the accuracy of adiposity estimates.

OBJECTIVE

We prospectively measured adiposity (%fat) in term newborns (NB) at 2 weeks (n = 41) and 1 year (n = 30).

METHODS

%fat was measured by dual X-ray absorptiometry (DXA), PEAPOD and skin-folds (SF). DXAs were analyzed using Hologic Apex software 3.2(DXAv1) and a new version 5.5.2(DXAv2).

RESULTS

NB %fat by DXAv2 was 55% higher than DXAv1 (14.2% vs. 9.1%), 45% higher than SF (9.8%), and 36% higher than PEAPOD (10.4%). Among NB, Pearson correlations were 0.73-0.89, but agreement (intra-class correlations) poor between DXAv2 and DXAv1 (0.527), SF (0.354) and PEAPOD (0.618). At 1 year, %fat by DXAv2 was 51% higher than DXAv1 (33.6% vs. 22.4%), and twice as high compared with SF (14.6%). Agreement was poor between DXAv2 and DXAv1 (0.204), and SF (0.038). The absolute increase in %fat from 2 weeks to 1 year was 19.7% (DXAv2), 13.6% (DXAv1) and only 4.8% by SF.

CONCLUSION

Analysis of the same DXA scans using new software yielded considerably higher adiposity estimates at birth and 1 year compared with the previous version. Using different modalities to assess body composition longitudinally is problematic. Standardization is gravely needed to determine how early life exposures affect childhood obesity/metabolic risk.

Women With Gestational Diabetes Mellitus Randomized to a Higher-Complex Carbohydrate/Low-Fat Diet Manifest Lower Adipose Tissue Insulin Resistance, Inflammation, Glucose, and Free Fatty Acids: A Pilot Study

OBJECTIVE

Diet therapy in gestational diabetes mellitus (GDM) has focused on carbohydrate restriction but is poorly substantiated. In this pilot randomized clinical trial, we challenged the conventional low-carbohydrate/higher-fat (LC/CONV) diet, hypothesizing that a higher-complex carbohydrate/lower-fat (CHOICE) diet would improve maternal insulin resistance (IR), adipose tissue (AT) lipolysis, and infant adiposity.

RESEARCH DESIGN AND METHODS

At 31 weeks, 12 diet-controlled overweight/obese women with GDM were randomized to an isocaloric LC/CONV (40% carbohydrate/45% fat/15% protein; n = 6) or CHOICE (60%/25%/15%; n = 6) diet. All meals were provided. AT was biopsied at 37 weeks.

RESULTS

After ∼7 weeks, fasting glucose (P = 0.03) and free fatty acids (P = 0.06) decreased on CHOICE, whereas fasting glucose increased on LC/CONV (P = 0.03). Insulin suppression of AT lipolysis was improved on CHOICE versus LC/CONV (56 vs. 31%, P = 0.005), consistent with improved IR. AT expression of multiple proinflammatory genes was lower on CHOICE (P < 0.01). Infant adiposity trended lower with CHOICE (10.1 ± 1.4 vs. 12.6 ± 2%, respectively).

CONCLUSIONS

A CHOICE diet may improve maternal IR and infant adiposity, challenging recommendations for a LC/CONV diet.

Regulation of Body Composition and Bioenergetics by Estrogens

Evidence points to an important role of estradiol (E2) in the regulation of body composition and bioenergetics. Basic and preclinical research shows that the disruption of E2 signaling through either genetic manipulation or surgical intervention accelerates fat accumulation, with a disproportionate increase in abdominal fat. Clinical evidence for the regulation of body composition and bioenergetics by E2 is less consistent. Evidence exists both for and against menopause as the mediator of changes in body composition. Thus, a need remains to better understand the metabolic actions of estrogens in women and the potential impact on health after the menopause.

Femoral lipectomy increases postprandial lipemia in women

Femoral subcutaneous adipose tissue (SAT) appears to be cardioprotective compared with abdominal SAT, possibly through better triglyceride (TG) sequestration. We hypothesized that removal of femoral SAT would increase postprandial TG through a reduction in dietary fatty acid (FA) storage. Normal-weight (means ± SD; BMI 23.9 ± 2.6 kg/m(2)) women (n = 29; age 45 ± 6 yr) were randomized to femoral lipectomy (LIPO) or control (CON) and followed for 1 yr. Regional adiposity was measured by DEXA and CT. A liquid meal labeled with [(14)C]oleic acid was used to trace the appearance of dietary FA in plasma (6-h postprandial TG), breath (24-h oxidation), and SAT (24-h [(14)C]TG storage). Fasting LPL activity was measured in abdominal and femoral SAT. DEXA leg fat mass was reduced after LIPO vs. CON (Δ-1.4 ± 0.7 vs. 0.1 ± 0.5 kg, P < 0.001) and remained reduced at 1 yr (-1.1 ± 1.4 vs. -0.2 ± 0.5 kg, P < 0.05), as did CT thigh subcutaneous fat area (-39.6 ± 36.6 vs. 4.7 ± 14.6 cm(2), P < 0.05); DEXA trunk fat mass and CT visceral fat area were unchanged. Postprandial TG increased (5.9 ± 7.7 vs. -0.6 ± 5.3 × 10(3) mg/dl, P < 0.05) and femoral SAT LPL activity decreased (-21.9 ± 22.3 vs. 10.5 ± 26.5 nmol·min(-1)·g(-1), P < 0.05) 1 yr following LIPO vs. CON. There were no group differences in (14)C-labeled TG appearing in abdominal and femoral SAT or elsewhere. In conclusion, femoral fat remained reduced 1 yr following lipectomy and was accompanied by increased postprandial TG and reduced femoral SAT LPL activity. There were no changes in storage of meal-derived FA or visceral fat. Our data support a protective role for femoral adiposity on circulating TG independent of dietary FA storage and visceral adiposity.

Effects of pioglitazone or exercise in older adults with mild cognitive impairment and insulin resistance: a pilot study

AIMS

To examine the effects of pioglitazone or endurance exercise training on cognitive function in older adults with mild cognitive impairment (MCI) and insulin resistance.

METHODS

Seventy-eight adults (mean age ± SD: 65 ± 7 years) with central obesity and MCI were randomized to 6 months of endurance exercise, pioglitazone or control.

RESULTS

Sixty-six participants completed the study. Exercise training did not significantly increase peak oxygen uptake compared to control (p = 0.12). Compared to control, insulin resistance improved in the pioglitazone group (p = 0.002) but not in the exercise group (p = 0.25). There was no measureable effect of pioglitazone or exercise on cognitive performance compared to control.

CONCLUSION

In this pilot study, pioglitazone improved insulin resistance but not cognitive performance in older adults with MCI and insulin resistance.

Postprandial triglycerides and adipose tissue storage of dietary fatty acids: impact of menopause and estradiol

OBJECTIVES

Postprandial lipemia worsens after menopause, but the mechanism remains unknown. The hypothesized menopause-related postprandial lipemia would be (1) associated with reduced storage of dietary fatty acids (FA) as triglyceride (TG) in subcutaneous adipose tissue (SAT) and (2) improved by short-term estradiol (E2 ).

METHODS

Twenty-three pre- (mean ± SD: 42 ± 4 years) and 22 postmenopausal (55 ± 4 years) women with similar total adiposity were studied. A subset of postmenopausal women (n = 12) were studied following 2 weeks of E2 (0.15 mg) and matching placebo in a random, cross-over design. A liquid meal containing (14) C-oleic acid traced appearance of dietary FA in: serum (postprandial TG), breath (oxidation), and abdominal and femoral SAT (TG storage).

RESULTS

Compared to premenopausal women, healthy, lean, postmenopausal women had increased postprandial glucose and insulin and trend for higher TG but had similar dietary FA oxidation and storage. Adipocytes were larger in post- compared to premenopausal women, particularly in femoral SAT. Short-term E2 reduced postprandial TG and insulin but had no effect on oxidation or storage of dietary FA. E2 increased the proportion of small adipocytes in femoral (but not abdominal) SAT.

CONCLUSIONS

Short-term E2 attenuated menopause-related increases in postprandial TG and increased femoral adipocyte hyperplasia but not through increased net storage of dietary FA.

Adipose tissue insulin resistance in adolescents with and without type 2 diabetes

BACKGROUND

The incidence of type 2 diabetes mellitus (T2D) is increasing in youth, yet little is known about the underlying pathophysiology. Decreased insulin suppression of lipolysis and elevated non-esterified free fatty acid (NEFA) concentrations are known to be associated with insulin resistance and T2D in adults, but less is known about the relationship in adolescents.

OBJECTIVES

This study aimed to assess adipose tissue insulin resistance (IR; insulin suppression of lipolysis) and its metabolic correlates in lean, obese and T2D adolescents.

METHODS

Forty-seven lean, obese and T2D youth underwent hyperinsulinaemic (80 mU*m(-2) *min(-1)) euglycaemic clamps. NEFAs were measured at baseline and during steady state. Insulin-mediated suppression of lipolysis (%NEFA suppression from baseline) was calculated, and metabolic risk factors were assessed by %NEFA suppression tertile.

RESULTS

There was expected variability in %NEFA suppression within obese and T2D youth, but a subset had significantly reduced suppression of lipolysis. NEFA suppression tertile was significantly inversely associated with fasting triglycerides (P = 0.0001), log alanine aminotransferase (ALT; P = 0.02) and low-density lipoprotein cholesterol (P = 0.0002).

CONCLUSIONS

Marked adipose tissue IR occurs in some obese and T2D adolescents, which may result in release of triglycerides into the circulation and liver deposition of fatty acids, as evidenced by higher ALT in poor NEFA suppressors.

Subcutaneous adipose tissue insulin resistance is associated with visceral adiposity in postmenopausal women

OBJECTIVE

Whole body and subcutaneous adipose tissue (SAT) insulin resistance association with regional fat mass (FM) was determined.

METHODS

Postmenopausal women (mean ± SD; age 56 ± 4 years, n = 25) who were overweight or obese (BMI 29.9 ± 5.1 kg/m(2) ) were studied. Whole body and regional FM were measured by dual-energy X-ray absorptiometry (DXA) and computed tomography (CT). Women were studied during basal and insulin-stimulated (3-stage euglycemic clamp) conditions. Whole-body lipolysis was assessed by [(2) H5 ]-glycerol rate of appearance and abdominal and femoral SAT lipolysis by interstitial glycerol (microdialysis).

RESULTS

Whole body insulin resistance in skeletal muscle (insulin-stimulated glucose disposal) and adipose tissue (insulin-suppressed lipolysis) were independently related to trunk FM (r = -0.336 and 0.484, respectively), but not leg FM (r = -0.142 and -0.148, respectively). Local antilipolytic insulin resistance in abdominal, but not femoral, SAT was positively related to trunk FM (r = 0.552) and visceral FM (r = 0.511) but not related to leg FM (r = -0.289). Whole body and abdominal, but not femoral, adipose tissue insulin sensitivity were strongly related to skeletal muscle insulin sensitivity (r = -0.727 and -0.674, respectively).

CONCLUSIONS

The association of SAT insulin sensitivity (lipolysis) with adiposity and skeletal muscle insulin sensitivity was specific to the abdominal region.

A higher-complex carbohydrate diet in gestational diabetes mellitus achieves glucose targets and lowers postprandial lipids: a randomized crossover study

OBJECTIVE

The conventional diet approach to gestational diabetes mellitus (GDM) advocates carbohydrate restriction, resulting in higher fat (HF), also a substrate for fetal fat accretion and associated with maternal insulin resistance. Consequently, there is no consensus about the ideal GDM diet. We hypothesized that, compared with a conventional, lower-carbohydrate/HF diet (40% carbohydrate/45% fat/15% protein), consumption of a higher-complex carbohydrate (HCC)/lower-fat (LF) Choosing Healthy Options in Carbohydrate Energy (CHOICE) diet (60/25/15%) would result in 24-h glucose area under the curve (AUC) profiles within therapeutic targets and lower postprandial lipids.

RESEARCH DESIGN AND METHODS

Using a randomized, crossover design, we provided 16 GDM women (BMI 34 ± 1 kg/m2) with two 3-day isocaloric diets at 31 ± 0.5 weeks (washout between diets) and performed continuous glucose monitoring. On day 4 of each diet, we determined postprandial (5 h) glucose, insulin, triglycerides (TGs), and free fatty acids (FFAs) following a controlled breakfast meal.

RESULTS

There were no between-diet differences for fasting or mean nocturnal glucose, but 24-h AUC was slightly higher (∼6%) on the HCC/LF CHOICE diet (P = 0.02). The continuous glucose monitoring system (CGMS) revealed modestly higher 1- and 2-h postprandial glucose on CHOICE (1 h, 115 ± 2 vs. 107 ± 3 mg/dL, P ≤ 0.01; 2 h, 106 ± 3 vs. 97 ± 3 mg/dL, P = 0.001) but well below current targets. After breakfast, 5-h glucose and insulin AUCs were slightly higher (P < 0.05), TG AUC was no different, but the FFA AUC was significantly lower (∼19%; P ≤ 0.01) on the CHOICE diet.

CONCLUSIONS

This highly controlled study randomizing isocaloric diets and using a CGMS is the first to show that liberalizing complex carbohydrates and reducing fat still achieved glycemia below current treatment targets and lower postprandial FFAs. This diet strategy may have important implications for preventing macrosomia.

A novel index of whole body antilipolytic insulin action

OBJECTIVE

Assessment of antilipolytic insulin action is important in obesity research, but extensive isotopic tracer studies are not always feasible. We evaluated whether an index of antilipolytic insulin action could be derived from readily available insulin and glycerol concentrations obtained during clamps or oral glucose tolerance tests (OGTT).

DESIGN AND METHODS

We evaluated data collected from 29 subjects who had undergone a 3-stage hyperinsulinemic-euglycemic clamp (4, 8, and 40 mU/m(2)/min) with infusion of [(2) H5 ]glycerol to calculate the glycerol rate of appearance (GLYRA). Exponential decay curves for GLYRA across insulin concentrations were generated for each individual and suppression of lipolysis was calculated as the insulin concentration needed to half-maximally suppress GLYRA (GLYRA EC50). Areas under the curve for glycerol (GLYAUC) and insulin (INSAUC) were calculated and their products (INSAUC × GLYAUC) were calculated as an index of insulin suppression of lipolysis.

RESULTS

The clamp index was highly correlated with GLYRA EC50 (r = 0.862, P < 0.001), as was an OGTT-derived index (r = 0.720, P < 0.01).

CONCLUSIONS

These findings suggest that the products of the insulin and glycerol AUC from either a clamp or an OGTT are good biomarkers of the antilipolytic action of insulin and are comparable with direct measurement by isotopic tracer methods.

A losing battle: weight regain does not restore weight loss-induced bone loss in postmenopausal women

Previously, we reported significant bone mineral density (BMD) loss in postmenopausal women after modest weight loss. It remains unclear whether the magnitude of BMD change in response to weight loss is appropriate (i.e., proportional to weight loss) and whether BMD is recovered with weight regain. We now report changes in BMD after a 1-year follow-up. Subjects (n = 23) in this secondary analysis were postmenopausal women randomized to placebo as part of a larger trial. They completed a 6-month exercise-based weight loss program and returned for follow-up at 18 months. Dual-energy X-ray absorptiometry (DXA) was performed at baseline, 6, and 18 months. At baseline, subjects were aged 56.8 ± 5.4 years (mean ± s.d.), 10.0 ± 9.2 years postmenopausal, and BMI was 29.6 ± 4.0 kg/m(2). They lost 3.9 ± 3.5 kg during the weight loss intervention. During follow-up, they regained 2.9 ± 3.9 kg. Six months of weight loss resulted in a significant decrease in lumbar spine (LS) (-1.7 ± 3.5%; P = 0.002) and hip (-0.04 ± 3.5%; P = 0.03) BMD that was accompanied by an increase in a biomarker of bone resorption (serum C-terminal telopeptide of type I collagen, CTX: 34 ± 54%; P = 0.08). However, weight regain was not associated with LS (0.05 ± 3.8%; P = 0.15) or hip (-0.6 ± 3.0%; P = 0.81) bone regain or decreased bone resorption (CTX: -3 ± 37%; P = 0.73). The findings suggest that BMD lost during weight reduction may not be fully recovered with weight regain in hormone-deficient, postmenopausal women. Future studies are needed to identify effective strategies to prevent bone loss during periods of weight loss.

Oral dehydroepiandrosterone replacement in older adults: effects on central adiposity, glucose metabolism and blood lipids

OBJECTIVE

To determine the effects of dehydroepiandrosterone (DHEA) therapy on changes in central adiposity, insulin action and blood lipids. Many of the actions of DHEA in humans are thought to be mediated through its conversion to sex hormones, which are modulators of adiposity, muscularity and insulin sensitivity. The effects of DHEA replacement on regional tissue composition, glucose metabolism and blood lipid profile in older adults have been inconsistent.

DESIGN

A randomized, double-blinded, placebo-controlled trial. The intervention was oral DHEA 50 mg/day or placebo for 12 months.

PARTICIPANTS

Fifty-eighty women and 61 men, aged 60-88 years, with low serum DHEA sulphate (DHEAS) levels at study entry.

MEASUREMENTS

Computed tomography measures of abdominal fat areas, thigh muscle and fat areas, DXA-derived trunk fat mass, serum glucose and insulin responses to an oral glucose challenge, and fasted serum total cholesterol, HDL-cholesterol, LDL-cholesterol and triglycerides were assessed before and after the intervention.

RESULTS

There were no significant (P > 0·05) differences between the DHEA and placebo groups in the changes in regional tissue composition or glucose metabolism. HDL-cholesterol (P = 0·01) and fasted triglycerides (P = 0·02) decreased in women and men taking DHEA.

CONCLUSION

Restoring serum DHEAS levels in older adults to young adult levels for 1 year does not appear to reduce central adiposity or improve insulin action. The benefit of DHEA on decreasing serum triglycerides must be weighed against the HDL-lowering effect.

Sex differences in the association of thigh fat and metabolic risk in older adults

We have previously shown a favorable association of subcutaneous leg fat with markers of insulin resistance and dyslipidemia in postmenopausal women. It is not known whether there is a sex dimorphism in the association of lower-body adiposity with reduced metabolic risk. Thus, our primary aim was to determine whether the favorable association of thigh subcutaneous fat, independent of abdominal fat, is also observed in older men. Mid-thigh and abdominal fat areas were measured by computed tomography (CT) in 108 older men and postmenopausal women (mean ± s.d.; 69 ± 7 years). Additionally, trunk and leg fat mass (FM) were measured by dual-energy X-ray absorptiometry (DXA). Markers of insulin resistance and dyslipidemia were determined from oral glucose tolerance tests and lipid and lipoprotein measurements, respectively. Outcomes were fasted and postchallenge (area under the curve, AUC) insulin (INS(AUC)) and glucose (GLU(AUC)), product of the insulin and glucose AUC (INS(AUC) × GLU(AUC)), triglycerides (TG), and high-density lipoprotein (HDL)-cholesterol. Consistent with our previous findings in postmenopausal women, adjusting for DXA trunk FM revealed a favorable association of DXA leg FM with the metabolic risk outcomes in both older men and postmenopausal women. Likewise, adjusting for CT abdominal visceral fat generally revealed a favorable association of CT thigh fat with metabolic risk outcomes in women, but not men. The discordance between the DXA and CT results in men is unclear but may be due to sex differences in visceral fat accrual. The mechanisms underlying the protective effect of thigh fat on metabolic risk factors need to be elucidated.

Timing of ibuprofen use and bone mineral density adaptations to exercise training

Prostaglandins (PGs) are essential signaling factors in bone mechanotransduction. In animals, inhibition of the enzyme responsible for PG synthesis (cyclooxygenase) by nonsteroidal anti-inflammatory drugs (NSAIDs) blocks the bone-formation response to loading when administered before, but not immediately after, loading. The aim of this proof-of-concept study was to determine whether the timing of NSAID use influences bone mineral density (BMD) adaptations to exercise in humans. Healthy premenopausal women (n = 73) aged 21 to 40 years completed a supervised 9-month weight-bearing exercise training program. They were randomized to take (1) ibuprofen (400 mg) before exercise, placebo after (IBUP/PLAC), (2) placebo before, ibuprofen after (PLAC/IBUP), or (3) placebo before and after (PLAC/PLAC) exercise. Relative changes in hip and lumbar spine BMD from before to after exercise training were assessed using a Hologic Delphi-W dual-energy X-ray absorptiometry (DXA) instrument. Because this was the first study to evaluate whether ibuprofen use affects skeletal adaptations to exercise, only women who were compliant with exercise were included in the primary analyses (IBUP/PLAC, n = 17; PLAC/PLAC, n = 23; and PLAC/IBUP, n = 14). There was a significant effect of drug treatment, adjusted for baseline BMD, on the BMD response to exercise for regions of the hip (total, p < .001; neck, p = .026; trochanter, p = .040; shaft, p = .019) but not the spine (p = .242). The largest increases in BMD occurred in the group that took ibuprofen after exercise. Total-hip BMD changes averaged -0.2% +/- 1.3%, 0.4% +/- 1.8%, and 2.1% +/- 1.7% in the IBUP/PLAC, PLAC/PLAC, and PLAC/IBUP groups, respectively. This preliminary study suggests that taking NSAIDs after exercise enhances the adaptive response of BMD to exercise, whereas taking NSAIDs before may impair the adaptive response.

Increases in bone mineral density in response to oral dehydroepiandrosterone replacement in older adults appear to be mediated by serum estrogens

CONTEXT

The mechanisms by which dehydroepiandrosterone (DHEA) replacement increases bone mineral density (BMD) in older adults are not known.

OBJECTIVE

The aims were to determine the effects of DHEA therapy on changes in sex hormones and IGF-I and their associations with changes in BMD.

DESIGN, SETTING, AND PARTICIPANTS

A randomized, double-blinded, placebo-controlled trial was conducted at an academic research institution. Participants were 58 women and 61 men, aged 60-88 yr, with low serum DHEA sulfate (DHEAS) levels.

INTERVENTION

The intervention was oral DHEA 50 mg/d or placebo for 12 months.

MAIN OUTCOME MEASURES

BMD and serum DHEAS, testosterone, estradiol (E(2)), estrone (E(1)), SHBG, IGF-I, and IGF binding protein 3 were measured before and after intervention. Free testosterone and estrogen (FEI) indices were calculated.

RESULTS

The average changes in hip and spine BMD (DHEA vs. placebo) ranged from 1.1 to 1.6%. Compared with placebo, DHEA replacement increased serum DHEAS, testosterone, free testosterone index, E(1), E(2), FEI, and IGF-I (all P < 0.001) and decreased SHBG (P = 0.02) in women and, in men, increased DHEAS, E(1), FEI (all P < 0.001), and E(2) (P = 0.02) and decreased SHBG (P = 0.037). The changes in total and regional hip BMD were associated with 12-month E(2) (all P <or= 0.001) and FEI (all P <or= 0.013). The effects of DHEA treatment were eliminated by adjustment for 12-month E(2).

CONCLUSIONS

The significant increases in hip BMD in older adults undergoing DHEA replacement were mediated primarily by increases in serum E(2) rather than direct effects of DHEAS.

The metabolic syndrome

The "metabolic syndrome" (MetS) is a clustering of components that reflect overnutrition, sedentary lifestyles, and resultant excess adiposity. The MetS includes the clustering of abdominal obesity, insulin resistance, dyslipidemia, and elevated blood pressure and is associated with other comorbidities including the prothrombotic state, proinflammatory state, nonalcoholic fatty liver disease, and reproductive disorders. Because the MetS is a cluster of different conditions, and not a single disease, the development of multiple concurrent definitions has resulted. The prevalence of the MetS is increasing to epidemic proportions not only in the United States and the remainder of the urbanized world but also in developing nations. Most studies show that the MetS is associated with an approximate doubling of cardiovascular disease risk and a 5-fold increased risk for incident type 2 diabetes mellitus. Although it is unclear whether there is a unifying pathophysiological mechanism resulting in the MetS, abdominal adiposity and insulin resistance appear to be central to the MetS and its individual components. Lifestyle modification and weight loss should, therefore, be at the core of treating or preventing the MetS and its components. In addition, there is a general consensus that other cardiac risk factors should be aggressively managed in individuals with the MetS. Finally, in 2008 the MetS is an evolving concept that continues to be data driven and evidence based with revisions forthcoming.

Relative contributions of adiposity and muscularity to physical function in community-dwelling older adults

OBJECTIVE

To determine the relative contributions of adiposity and muscularity to multi-dimensional performance-based and perceived physical function in older adults living independently.

METHODS AND PROCEDURES

Data from 109 women and men, aged 60 or older, with low serum dehydroepiandrosterone (DHEA) sulfate levels were included in this cross-sectional analysis of baseline measures from a single-site, randomized, controlled trial of DHEA replacement therapy. Physical function was determined by means of performance on the 100-point Continuous Scale-Physical Functional Performance (CS-PFP) test and by self-reporting using the physical function subscale of the Medical Outcomes Short Form-36 (SF36PF). Body composition was measured by dual-energy X-ray absorptiometry (DXA). Linear regression analyses were used to determine the contributions of body mass index (BMI; kg body mass/m2), fat index (FI; kg fat/m2), and appendicular skeletal muscle index (ASMI; kg muscle/m2) to the CS-PFP and SF36PF scores, adjusted for age and sex.

RESULTS

Age-adjusted regression analyses indicated that FI, but not ASMI, was a significant (P<0.001) determinant of CS-PFP (R2=0.54) and SF36PF (R2=0.37). When adjusted for age and sex, BMI was nearly as good a predictor of CS-PFP (R2=0.50) and SF36PF (R2=0.34) as FI.

DISCUSSION

Adiposity was a stronger predictor of measured and self-reported physical function than was muscularity in older adults living independently. BMI, adjusted for sex, is a reasonable substitute for adiposity in the prediction of physical function.

Insulin secretion and clearance after subacute estradiol administration in postmenopausal women

CONTEXT

Data from large clinical trials of postmenopausal women suggest that the incidence of diabetes is reduced in women randomized to estrogen-based hormone therapy when compared with placebo. Whether this is due to an effect of estrogen on insulin or glucose metabolism remains unclear.

OBJECTIVE

Our objective was to test the hypothesis that estradiol (E(2)) increases insulin secretion and clearance.

DESIGN

Serum insulin and C-peptide (CPEP) responses to hyperglycemia (250 mg/dl) plus iv L-arginine were measured on 2 separate days, with (EST) and without [control (CON)] subacute (24 h) transdermal E(2) administration.

STUDY PARTICIPANTS

There were 11 postmenopausal women (mean +/- sd; 55 +/- 4 yr) included in this study.

MAIN OUTCOMES

Insulin secretion and clearance were estimated from the CPEP area under the curve and the molar ratio of CPEP to insulin area under the curve, respectively. Mean glucose disposal rate (GDR) was estimated from the rate of glucose infusion during the final 30 min of the hyperglycemic clamp.

RESULTS

There were no differences in insulin secretion or clearance between the EST and CON days. Fasting glucose was lower on the EST compared with the CON (93 +/- 6 vs. 98 +/- 8 mg/dl), but mean GDR was not different. However, when one outlier was excluded from analysis, GDR was increased after EST compared with CON. Furthermore, a strong inverse association was observed between years since menopause and E(2)-mediated changes in GDR (r = -0.794; P = 0.004).

CONCLUSIONS

Contrary to our hypothesis, 24-h transdermal E(2) administration did not alter insulin secretion or clearance in postmenopausal women. However, a longer time since menopause was associated with a reduced effect of E(2) to increase glucose uptake.

Effects of soy protein isolate and moderate exercise on bone turnover and bone mineral density in postmenopausal women

OBJECTIVE

The aim of this study was to assess the independent and additive effects of soy protein isolate (SPI) and moderate-intensity exercise (EX) on bone turnover and bone mineral density (BMD).

DESIGN

This study used a placebo-controlled, double-blind (soy), randomized 2 (SPI vs milk protein isolate [MPI]) x 2 (EX vs no EX) design. Sixty-one postmenopausal women were randomized, and 43 (62 +/- 5 y) completed the 9-month intervention (SPI, n = 10; MPI, n = 12; SPI + EX, n = 11; MPI + EX, n = 10). Serum C-terminal cross-linked telopeptides of type I collagen and serum bone-specific alkaline phosphatase were measured as markers of bone resorption and formation, respectively. BMD was measured by dual-energy x-ray absorptiometry.

RESULTS

At 9 months, SPI reduced serum C-terminal cross-linked telopeptides (-13.3% +/- 15.3% vs -1.5% +/- 21.0%; P = 0.02) and serum bone-specific alkaline phosphatase (-4.7% +/- 14.7% vs 6.5% +/- 17.7%; P = 0.02) compared to milk protein isolate. EX attenuated the reduction in serum C-terminal cross-linked telopeptides (-1.9% +/- 21.6% vs -12.4% +/- 15.3%; P = 0.04); however, no EX effects were apparent in serum bone-specific alkaline phosphatase at 9 months (2.8% +/- 16.1% vs -1.0% +/- 18.3%; P = 0.28). Neither SPI nor EX affected BMD at any site; however, change in BMD was related to change in fat mass (r = 0.40, P < 0.05).

CONCLUSIONS

In postmenopausal women (1) SPI reduces bone turnover with no impact on BMD over 9 months; (2) moderate-intensity endurance exercise training did not favorably alter bone turnover and had no impact on BMD; and (3) there were no additive effects of soy and exercise on bone turnover or BMD.

Acute modulation of adipose tissue lipolysis by intravenous estrogens

OBJECTIVE

The aim of this study was to determine whether intravenous (IV) conjugated estrogens (EST) acutely enhance the suppression of whole-body or regional subcutaneous adipose tissue (SAT) lipolysis by insulin in postmenopausal women.

RESEARCH METHODS AND PROCEDURES

We assessed whole-body lipolysis by [(2)H(5)]glycerol rate of appearance (Glyc(RA)) and abdominal and femoral SAT lipolysis (interstitial glycerol; Glyc(IS)) by subcutaneous microdialysis. Postmenopausal women (n = 12) were studied on two occasions, with IV EST or saline control (CON), under basal conditions and during a 3-stage (4, 8, and 40 mU/m(2)/min) hyperinsulinemic, euglycemic clamp. Ethanol outflow/inflow ratio and recovery of [(13)C]glycerol during microdialysis were used to assess blood flow changes and interstitial glycerol concentrations, respectively.

RESULTS

Compared with CON, EST did not affect systemic basal or insulin-mediated suppression of lipolysis (Glyc(RA)) or SAT nutritive blood flow. Basal Glyc(IS) in SAT was reduced on the EST day. However, insulin-mediated suppression of lipolysis in SAT was not significantly influenced by EST.

DISCUSSION

These findings suggest that estrogens acutely reduce basal lipolysis in SAT through an unknown mechanism but do not alter whole-body or SAT suppression of lipolysis by insulin.

Effects of dehydroepiandrosterone replacement therapy on bone mineral density in older adults: a randomized, controlled trial

CONTEXT

Dehydroepiandrosterone (DHEA) and its sulfate (DHEAS) decrease with aging and are important androgen and estrogen precursors in older adults. Declines in DHEAS with aging may contribute to physiological changes that are sex hormone dependent.

OBJECTIVE

The aim was to determine whether DHEA replacement increases bone mineral density (BMD) and fat-free mass.

DESIGN, SETTING, AND PARTICIPANTS

A randomized, double-blinded, controlled trial was conducted at an academic research institution. Participants were 70 women and 70 men, aged 60-88 yr, with low serum DHEAS levels.

INTERVENTION

The intervention was oral DHEA 50 mg/d or placebo for 12 months.

MEASUREMENTS

BMD, fat mass, and fat-free mass were measured before and after intervention.

RESULTS

Intent-to-treat analyses revealed trends for DHEA to increase BMD more than placebo at the total hip (1.0%, P = 0.05), trochanter (1.2%, P = 0.06), and shaft (1.2%, P = 0.05). In women only, DHEA increased lumbar spine BMD (2.2%, P = 0.04; sex-by-treatment interaction, P = 0.05). In secondary compliance analyses, BMD increases in hip regions were significant (1.2-1.6%; all P < 0.02) in the DHEA group. There were no significant effects of DHEA on fat or fat-free mass in intent-to-treat or compliance analyses.

CONCLUSIONS

DHEA replacement therapy for 1 yr improved hip BMD in older adults and spine BMD in older women. Because there have been few randomized, controlled trials of the effects of DHEA therapy, these findings support the need for further investigations of the benefits and risks of DHEA replacement and the mechanisms for its actions.

Sex hormone suppression reduces resting energy expenditure and {beta}-adrenergic support of resting energy expenditure

Resting energy expenditure (REE) decreases with aging and may decrease in women as a result of the menopause, potentially contributing to weight gain. REE has been observed to fluctuate during the menstrual cycle, suggesting regulation by sex hormones. The aim of the present study was to determine the effects of suppressing estrogen and progesterone on REE. Fourteen premenopausal women, 29 +/- 5 yr old (mean +/- sd), were studied in the midluteal menstrual phase (ML) and after 6 d of GnRH antagonist therapy (GnRHant) administered in the follicular menstrual phase. REE was measured by indirect calorimetry in the morning after a 12-h fast and again during beta-adrenergic blockade to determine sympathetic nervous system (SNS) support of REE. Treatment with GnRHant significantly decreased REE (1405 +/- 42 vs. 1334 +/- 36 kcal/d, mean +/- se, ML vs. GnRHant; P = 0.002). Additionally, SNS blockade tended to alter REE more during ML than during GnRHant (-19 +/- 10 vs. 5 +/- 11 kcal/d; P = 0.14). Suppression of sex hormones to postmenopausal levels by GnRHant reduced REE in young healthy women. These findings suggest that the withdrawal of estrogen and/or progesterone attenuates REE, possibly through a SNS-mediated mechanism.

Role of sympathetic neural activation in age- and habitual exercise-related differences in the thermic effect of food

The thermic effect of food (TEF) declines with advancing age in adult humans but is enhanced in the habitually exercising state. The responsiveness of the sympathetic nervous system (SNS) has been implicated in these differences in TEF. We tested the hypotheses that 1) the reduction in TEF with aging is associated with an attenuated SNS response to acute energy intake; and 2) the greater TEF observed in endurance exercise-trained adults is associated with an augmented SNS response. Four groups of healthy men were studied: 16 young and 11 older sedentary men and nine young and 10 older habitually exercising men. Metabolic rate (indirect calorimetry, ventilated hood), skeletal muscle sympathetic nerve activity (MSNA; peroneal microneurography), and plasma norepinephrine and plasma epinephrine concentrations were measured before and for up to 4 h after ingestion of a carbohydrate drink (2.5 g/kg fat-free mass). TEF was approximately 50% greater in young compared with older men (P < 0.05) and approximately 25% greater in exercising compared with sedentary men (P < 0.05). In contrast, the MSNA, plasma norepinephrine, and plasma epinephrine responses were not different among the four groups. Covarying for MSNA did not significantly alter the observed differences in TEF. Habitual exercise status did not affect the age-associated decline in TEF. These findings demonstrate that altered postprandial whole-body and skeletal muscle SNS activation is not an important mechanism mediating either the reduction in TEF with aging or the augmented TEF associated with the exercise-trained state in healthy men. Differences in beta-adrenergic responsiveness to postprandial sympathoadrenal stimulation and/or nonsympathetic adrenergic influences likely explain the age- and habitual exercise-related differences in TEF.