Davison, Diane E.

Background Decreases in estrogen are shown to increase body fat in men. However, obese men have high levels of estrogen and the effects of weight gain on estrogen have not been previously investigated. The objective of this study was to investigate the relationship between regional fat depots and estrogen during modest weight in healthy men. Methods We investigated the effects of overfeeding in 25 healthy men (30 ± 7 years, 24.7 ± 3.1 kg/m 2 ). Changes in regional fat depot during weight gain were assessed using dual‐energy X‐ray absorptiometry and abdominal computed tomography scans. Participants gained approximately 5% body weight in 8 weeks. Estrone (E1), 17β‐estradiol (E2) and sex hormone binding globulin (SHBG) were measured at baseline and after weight gain. Results Overfeeding was accompanied by 3.9 ± 1.3 kg weight gain. These increases in weight resulted from increases in total body fat mass (18.3 ± 8.5 vs. 21.7 ± 8.8 kg, p<0.001) while the fat free mass did not change (58.4 ± 8.6 vs. 58.9 ± 8.7 kg, p=0.15). E1 (32.28 ± 14.25 vs. 33.44 ± 12.29 pg/mL, p=0.56) and E2 (25.04 ± 8.3 vs. 26.52 ± 7.8 pg/mL, p=0.28) did not change after weight gain. However, weight gain resulted in decreased SHBG (22.8 ± 10.5 vs. 20.8 ± 11.1 nmol/l, p=0.036) and increased E2/SHBG ratio (1.4 ± 1.0 vs 1.63 ± 1.0, p=0.027). The changes in E2/SHBG ratio, a surrogate marker of bioavailable E2, was positively associated with increases in abdominal fat mass (p=0.048, rho=0.39) and increases in visceral fat mass (p=0.049, rho=0.39). Conclusion Modest weight gain in healthy men does not alter circulating E1 and E2 levels. However weight gain results in decreased SHBG and increased free E2 (E2/SHBG ratio). The increased E2/SHBG ratio suggesting a pro‐estrogen effect is associated with increases in visceral fat mass during weight gain. Our study therefore suggests a complex relationship between abdominal fat gain and free E2 in men which may conceivably predispose to feminizing characteristics in obese men. Support or Funding Information PS is supported by AHA Grant 11SDG7260046 and NIH grant DK81014. NC is supported by AHA grant AHA 13POST16420009. MDJ is supported by NIH grants DK45343 and DK40484. VKS is supported by NIH Grants HL73211, and DK81014. This study was made possible by a grant from NCRR (1UL1 RR024150).

Background: Normal weight adults gain leg fat gain via adipocyte hyperplasia and upper body subcutaneous (UBSQ) fat gain via adipocyte hypertrophy. Objective: To understand whether regional fat loss mirrors fat gain and whether leg fat loss results in decreased adipocyte number vs. size. Design: We assessed UBSQ, leg and visceral fat gain and loss in response to over- and underfeeding in 23 young, healthy normal weight adults (15 men). Participants gained ∼5% weight over 8 weeks and lost ∼80% of gained fat over the following 8 weeks. We measured abdominal subcutaneous and femoral adipocyte size and number after weight gain and loss. Results: Volunteers gained 3.1 ± 2.1 kg of body fat with overfeeding and lost 2.4 ± 1.7 kg with calorie restriction. Although upper body subcutaneous (UBSQ) fat and visceral fat gains were completely reversed with weight loss, leg fat had not yet returned to baseline values by 8 weeks. Abdominal and femoral adipocyte size decreased significantly with weight loss, but the number of adipocytes did not decrease. Abdominal adipocyte size decreases correlated (rho= 0.76, p = 0.001) with UBSQ fat mass decreases and femoral adipocyte size decreases correlated (rho= 0.49, p=0.05) with leg fat mass decreases. Conclusion: UBSQ and visceral fat depots increase and decrease proportionately with short term weight gain and loss, whereas gain and loss of leg fat are less well linked. Loss of lower body fat is due to reduced fat cell size, not number, which may result in long-term increases in leg fat cell number. This may have implications for long-term weight control.

Introduction: Obesity is linked with heightened vulnerability to cardiovascular diseases including hypertension. Nonetheless, mechanistic studies addressing the effects of experimental weight gain on blood pressure are lacking. We sought to examine whether experimental weight gain raises ambulatory blood pressure in healthy individuals and identify any relationship between changes in blood pressure and changes in regional fat distribution. Methods: Twenty-six normal weight subjects were randomized to a 8-week period of weight gain through overfeeding (N=16; age 30.4±6.6 years, BMI 23.5±3.5 kg/m 2 ) or weight maintenance (N=10; age 27.1±7.7 years, BMI 23.6±2.7 kg/m 2 ). Measurements of body composition by dual-energy X-ray absorptiometry and abdominal computed tomographic scans and 24-h ambulatory blood pressure monitoring were obtained at baseline and at follow-up. Results: Overfeeding resulted in an increase in body weight of 3.7±1.5 kg ( p <0.001) in weight gainers, with increments seen in total (21994±8247.4 to 25180.7±8563.1 gr, p <0.001), visceral (61.6±32.7 to 75.5±30.9 cm 2 , p =0.002) and subcutaneous fat (135.5±77.4 to 167.9±82.9 cm 2 , p <0.001). No changes occurred in the maintenance group. Weight gainers exhibited an increase in 24-h systolic blood pressure at follow-up (113.7±8 to 117.7±7.9 mmHg, p =0.009) and mean blood pressure (MAP) (85.1±4.9 to 86.8±5.1 mmHg, p =0.02), while blood pressure was unchanged in controls. Changes in MAP were positively correlated only with changes in visceral fat (rho=0.452, p =0.02) but not with changes in weight or any other body composition measure. Conclusion: Modest weight gain leads to marked elevation in 24-h blood pressure in lean healthy subjects. The association between increased MAP and abdominal visceral fat accumulation suggests that visceral deposition of adipose tissue may contribute specifically and mechanistically to the enhanced risk of hypertension associated with weight gain.

Background: Endothelial dysfunction assessed by flow mediated dilation (FMD) of the brachial artery has been identified as an independent predictor of cardiovascular events. However, whether weight gain impairs endothelial function is unknown. Methods: A randomized blinded controlled-trial to assess the effects of weight gain on endothelial function. After a weight maintenance period supervised by an experience dietitian, volunteers were randomized to gain weight (4 kg) or maintain weight. We recruited lean (BMI 18.5–24.9 kg/m 2 ) healthy volunteers (no diseases, medications and non-smokers) from the community. Using ultrasound, endothelial function was measured by FMD and non-flow mediated dilation (NFMD) of the brachial artery in the early morning (6:30 a.m.). Endothelial function was measured at baseline, after fat gain at 8 weeks and after weight loss at 16 weeks for fat-gainers and at baseline and follow-up (8 weeks) for weight maintainers. Body composition techniques to measure body fat %, such as dual x-ray absorptiometry and abdominal CT scans were performed. Results: We recruited 35 fat-gainers and 8 weight maintainers. Mean age was 29 ± 6 years and 18 (42 %) were women. There were no differences in age, anthropometric and body composition measurements, blood pressure, heart rate or apnea hypopnea index at baseline between both groups. After an average gain of 4 kg, the fat-gainer group significantly increased their total, visceral and subcutaneous fat. Brachial artery FMD and NFMD remained unchanged in weight maintainers. However, it decreaed in fat-gainers (FMD=9.1 ± 3 vs. 7.6 ± 3.2, p=0.003 and NFMD=12.0 ± 4.9 vs. 10.1 ± 6.0, p=0.01), but recovered to baseline after subjects shed the gained weight (basleline vs. recovery: FMD=9.1 ± 3 vs. 9.0 ± 3, p=NS and NFMD =12.0 ± 4.9 vs.12.6 ± 5.0, p=NS). Visceral fat gain, but not subcutaneous fat gain was significantly correlated with the decrease in brachial artery FMD (rho =−0.42, p=0.004 and rho =−0.22, p=0.15, respectively). Conclusions: In lean healthy young subjects, modest weight gain results in impaired endothelial function, even in the absence of changes in blood pressure. Endothelial funcion recovers after weight loss. Viscerar rather than subcutaneous fat predicts endothelial dysfunction.

Background Expression of adiponectin, an anti‐atherogenic and insulin‐sensitizing adipokine, is decreased in obesity. Mechanisms underlying this reduction are not well understood. Increased adiponectin in obesity may protect against development of cardiac and metabolic disorders. Objective To investigate the role of leptin in regulating adiponectin expression in humans. Design 1) determining the relationship between leptin and adiponectin in healthy humans during modest weight gain; 2) in‐vitro validation of the role of leptin in adiponectin expression. Results Modest weight gain of 3.8 ± 1.2 kg over 8 weeks of overfeeding in normal weight healthy subjects (n=33, 22 men, 30±7 years) increased both leptin and adiponectin. Changes in leptin during weight gain correlated with changes in adiponectin (rho=0.35, p=0.045), suggesting that leptin may regulate adiponectin expression. In cultured differentiated human white preadipocytes, leptin increased adiponectin mRNA and protein expression. Conclusions Leptin induces adiponectin expression. In obesity, adipose tissue may be resistant to leptin signaling thus preventing increases in adiponectin. Therefore, impaired leptin signaling may contribute to low adiponectin in obesity. Targeting leptin resistance may be beneficial in preventing obesity‐associated cardiac and metabolic disorders. Support : AHA 11SDG7260046, R21 DK81014

Background: Decreased testosterone (TTST) and sex hormone binding globin (SHBG) contribute to development of cardiometabolic disorders in obese men. We aimed to determine the effect of weight gain and weight loss on TTST and SHBG in healthy men and to examine their relationship with endothelial function. Method: 25 normal weight healthy men underwent an overfeeding protocol to gain 5% body weight over 8 weeks. Following weight gain, they underwent 8 weeks of weight loss. TTST, SHBG and endothelial function (brachial artery flow‐mediated dilation, FMD) were measured at baseline (T1), after weight gain (T2) and after weight loss (T3). Results: Volunteers gained 4 ± 1.3 kg and subsequently lost 3.2 ± 1.5 kg of body weight. TTST levels did not change (T1: 18.85 ± 6.2 nmol/L, T2: 19.3 ± 6.9 nmol/L, T3: 20.3 ± 7.6 nmol/L). However, SHBG decreased during weight gain (p=0.04) and increased during weight loss (p=0.0005) (T1: 22.8 ± 10.5 nmol/L, T2: 20.8 ± 11.1 nmol/L, T3: 25.58 ± 11.5 nmol/L). Furthermore, SHBG reduction during weight gain tended to correlate with decreases in FMD (p=0.06; R 2 =0.15). During weight loss, increases in SHBG correlate negatively with changes in FMD (p=0.008; R 2 =0.32). Conclusion : In normal weight healthy men, SHBG decreases with modest weight gain and increases with weight loss. TTST does not change. Changes in SHBG partly predict improvements in endothelial function with weight loss. Grant Funding Source : Supported by AHA 11SDG7260046, R21 DK81014, AHA 13POST16420009

Abstract Introduction Voluntary sleep curtailment decreases insulin sensitivity. However, molecular mechanisms underlying impaired insulin signaling are not completely understood. To gain molecular insights, we examined the transcription of known cellular insulin-signaling regulators in adipose tissue obtained from subjects undergoing experimental sleep restriction. Methods Nineteen healthy subjects (males: 11; age: 19 - 36 years; BMI: 24.5 ± 3.6 kg/m2) underwent a normal (9 hours/night) and a restricted sleep (4 hours/night) sequence in a random order. Each inpatient stay included a screen visit followed by 4 days of acclimation and 9 days of experimental phase consisting of a controlled sleep opportunity. Eucaloric diet was provided to ensure weight maintenance. Abdominal fat sample was obtained at the screen and end of the experimental phase. mRNA was quantified by RT-PCR. Fasting morning blood draws were obtained at the end of acclimation and experimental phases. Mixed models were used for analysis. Results mRNA expression did not differ in normal and restricted sleep condition for SOCS3 [changes in normal Vs. restricted sleep, 0.02 (0.11, -0.01) Vs. 0.01 (0.12, -0.07), p=0.33], PTEN [-0.22 (0.18, -0.39) Vs. -0.10 (0.21, -0.20), p=0.22], PTB1B [-0.003 (0.04, -0.07) Vs. -0.01 (0.06, -0.06), p=0.74] and Cav-1 [-2.45 (0.78, -8.39) Vs. -6.31 (1.68, -8.29), p=0.34]. Further, transcription of insulin-receptor also did not change [0.01 (0.07, -0.06) Vs. -0.03 (0.09, -0.07), p=0.92]. However, within group analysis show significant decreases in Cav-1 mRNA only during sleep restriction (normal: p=0.09; restricted: p=0.003). Importantly, restricting sleep duration was associated with lowering of insulin (0.6 ± 1.9 Vs. -1.6 ± 1.7 uIU/ml; p=0.003), no change in glucose (-1.5 ± 3.8 Vs. -3.7 ± 4.12 mg/dl, p=0.06) and improvement in HOMA-IR index (0.12 ± 0.44 Vs -0.42 ± 0.43, p=0.002). Conclusion Chronic sleep restriction does not alter the transcription of cell-signaling regulators in abdominal adipose tissue. Moreover, restricting sleep duration without increasing calorie intake did not seem to decrease insulin sensitivity as determined by HOMA-IR. Support NIH grants HL114676, Mayo Clinic CCaTS UL1 TR002377; AHA grant 13POST16420009 to NC

Background Epidemiologic evidence suggests a link between short sleep duration and cardiovascular risk, although the nature of any relationship and mechanisms remain unclear. Short sleep duration has also been linked to an increase in cardiovascular events. Endothelial dysfunction has itself been implicated as a mediator of heightened cardiovascular risk. We sought to determine the effect of 8 days/8 nights of partial sleep restriction on endothelial function in healthy humans. Methods and Results Sixteen healthy volunteers underwent a randomized study of usual sleep versus sleep restriction of two‐thirds normal sleep time for 8 days/8 nights in a hospital‐based clinical research unit. The main outcome was endothelial function measured by flow‐mediated brachial artery vasodilatation ( FMD ). Those randomized to sleep restriction slept 5.1 hours/night during the experimental period compared with 6.9 hours/night in the control group. Sleep restriction was associated with significant impairment in FMD (8.6±4.6% during the initial pre‐randomization acclimation phase versus 5.2±3.4% during the randomized experimental phase, P =0.01) whereas no change was seen in the control group (5.0±3.0 during the acclimation phase versus 6.73±2.9% during the experimental phase, P =0.10) for a between‐groups difference of −4.40% (95% CI −7.00 to −1.81%, P =0.003). No change was seen in non‐flow mediated vasodilatation ( NFMD ) in either group. Conclusion In healthy individuals, moderate sleep restriction causes endothelial dysfunction. Clinical Trial Registration URL : ClinicalTrials.gov. Unique identifier: NCT 01334788.