Human adipose tissue expresses intrinsic circadian rhythm in insulin sensitivity.

In humans, insulin sensitivity varies according to time of day, with decreased values in the evening and at night. Mechanisms responsible for the diurnal variation in insulin sensitivity are unclear. We investigated whether human adipose tissue (AT) expresses intrinsic circadian rhythms in insulin sensitivity that could contribute to this phenomenon. Subcutaneous and visceral AT biopsies were obtained from extremely obese participants (body mass index, 41.8 ± 6.3 kg/m(2); 46 ± 11 y) during gastric-bypass surgery. To assess the rhythm in insulin signaling, AKT phosphorylation was determined every 4 h over 24 h in vitro in response to different insulin concentrations (0, 1, 10, and 100 nM). Data revealed that subcutaneous AT exhibited robust circadian rhythms in insulin signaling (P < 0.00001). Insulin sensitivity reached its maximum (acrophase) around noon, being 54% higher than during midnight (P = 0.009). The amplitude of the rhythm was positively correlated with in vivo sleep duration (r = 0.53; P = 0.023) and negatively correlated with in vivo bedtime (r = -0.54; P = 0.020). No circadian rhythms were detected in visceral AT (P = 0.643). Here, we demonstrate the relevance of the time of the day for how sensitive AT is to the effects of insulin. Subcutaneous AT shows an endogenous circadian rhythm in insulin sensitivity that could provide an underlying mechanism for the daily rhythm in systemic insulin sensitivity.-Carrasco-Benso, M. P., Rivero-Gutierrez, B., Lopez-Minguez, J., Anzola, A., Diez-Noguera, A., Madrid, J. A., Lujan, J. A., Martínez-Augustin, O., Scheer, F. A. J. L., Garaulet, M. Human adipose tissue expresses intrinsic circadian rhythm in insulin sensitivity.

Glucocorticoids affect 24 h clock genes expression in human adipose tissue explant cultures.

AIMS: to examine firstly whether CLOCK exhibits a circadian expression in human visceral (V) and subcutaneous (S) adipose tissue (AT) in vitro as compared with BMAL1 and PER2, and secondly to investigate the possible effect of the glucocorticoid analogue dexamethasone (DEX) on positive and negative clock genes expression. SUBJECTS AND METHODS: VAT and SAT biopsies were obtained from morbid obese women (body mass index ≥ 40 kg/m(2)) (n = 6). In order to investigate rhythmic expression pattern of clock genes and the effect of DEX on CLOCK, PER2 and BMAL1 expression, control AT (without DEX) and AT explants treated with DEX (2 hours) were cultured during 24 h and gene expression was analyzed at the following times: 10:00 h, 14:00 h, 18:00 h, 22:00 h, 02:00 h and 06:00 h, using qRT-PCR. RESULTS: CLOCK, BMAL1 and PER2 expression exhibited circadian patterns in both VAT and SAT explants that were adjusted to a typical 24 h sinusoidal curve. PER2 expression (negative element) was in antiphase with respect to CLOCK and in phase with BMAL1 expression (both positive elements) in the SAT (situation not present in VAT). A marked effect of DEX exposure on both positive and negative clock genes expression patterns was observed. Indeed, DEX treatment modified the rhythmicity pattern towards altered patterns with a period lower than 24 hours in all genes and in both tissues. CONCLUSIONS: 24 h patterns in CLOCK and BMAL1 (positive clock elements) and PER2 (negative element) mRNA levels were observed in human adipose explants. These patterns were altered by dexamethasone exposure.

Circadian rhythm of clock genes in human adipose explants.

To analyze in severely obese women the circadian expression of the clock genes hPer2, hBmal1, and hCry1 in explants from subcutaneous (SAT) and visceral (VAT) adipose tissue (AT), in order to elucidate whether this circadian clockwork can oscillate accurately and independently of the suprachiasmatic nucleus (SCN) and if glucocorticoid metabolism-related genes such as glucocorticoid receptor (hGr) and 11beta-hydroxysteroid dehydrogenase 1 (h11 beta Hsd1) and the transcription factor peroxisome proliferator activated receptor gamma (hPPAR gamma) are part of the clock controlled genes. AT biopsies were obtained from morbid obese patients (BMI > or =40 kg/m(2)) (n = 7). Anthropometric variables were measured and fasting plasma lipids and lipoprotein concentrations were analyzed. In order to carry out rhythmic expression analysis, AT explants were cultured during 24 h and gene expression was performed at the following times (T): 0, 6, 12, and 18 h, with quantitative real-time PCR. Clock genes oscillated accurately and independently of the SCN in AT explants. Their intrinsic oscillatory mechanism regulated the timing of other genes such as hPPAR gamma and glucocorticoid-related genes. Circadian patterns differed between VAT and SAT. Correlation analyses between the genetic circadian oscillation and components of the metabolic syndrome (MetS) revealed that subjects with a higher sagittal diameter showed an increased circadian variability in hPer2 expression (r = 0.91; P = 0.031) and hBmal1 (r = 0.90; P = 0.040). Data demonstrate the presence of peripheral circadian oscillators in human AT independently of the central circadian control mechanism. This knowledge paves the way for a better understanding of the circadian contribution to medical conditions such as obesity and MetS.

N-6 from different sources protect from metabolic alterations to obese patients: a factor analysis.

First, to analyze the interactions among fatty acids (FAs) from diet, plasma and subcutaneous and visceral adipose tissue (AT), and second, the relationship among FAs from these different sources and obesity-related alterations in extreme obesity. We studied 20 extreme obese subjects. A food-frequency questionnaire was used to determine the FA intakes. Serum and AT (subcutaneous and visceral) FA concentrations were determined by gas chromatography. Cardiometabolic risk parameters were assessed. Principal factor analysis was performed to define specific FA factors in the metabolic alterations. We found important associations among diet, plasma, and AT FA and cardiometabolic parameters. In this regard, it is interesting to highlight the negative associations between plasma cholesterol and dietary n-3 FA. In the subcutaneous depot, as occurred in plasma, n-6 and polyunsaturated FAs (PUFA) were negatively associated with triacylglycerols (TGs). Factor analysis revealed TGs as the unique cardiovascular risk parameter appearing in the first factor (F1), together with n-6 (load factor = 0.94) and PUFA (0.91). Besides, n-3 from diet and plasma appeared in the third factor inversely related to cholesterol, low-density lipoprotein cholesterol (LDL-c), and insulin. In an opposite way, dietary and AT trans FAs and saturated FA (SFA) were associated to an increase of the metabolic risk. We have shown, for the first time, the importance of n-6 and PUFAs composition as protective factors against metabolic alterations in extreme obese subjects. These findings support current dietary recommendations to increase PUFA intakes and restrict saturated and trans FA intakes even in extreme obesity.

Role of DHEA-S on body fat distribution: gender- and depot-specific stimulation of adipose tissue lipolysis.

The objective of this work was to study the possible impact of DHEA-S on body fat distribution and the specific action of the hormone on lipolysis from visceral and subcutaneous human adipose tissue. First, a clinical evaluation was performed in 84 obese patients (29 men, 55 women), measuring serum DHEA-S, computed tomography (CT) anthropometric parameters of abdominal fat distribution. In a second experiment, subcutaneous and visceral adipose tissue samples were obtained from 20 obese patients (10 men, 10 women) and cultured in vitro under stimulation with DHEA-S to further assess a possible effect of this hormone on adipose tissue lipolysis. Serum DHEA-S was inversely and specifically associated with visceral fat area (VA) as assessed by CT in men and with waist-to-hip ratio in women. In vitro, DHEA-S increased lipolysis in women's subcutaneous adipose tissue at 2 h, while in men, the effect was evident in visceral tissue and after 24 h of treatment. In conclusion, DHEA-S contributes to gender-related differences in body fat distribution probably by a differential lipolytic action. We have demonstrated for the first time in vitro that DHEA-S stimulates lipolysis preferably in subcutaneous fat in women and in visceral fat in men.

Laparoscopic versus open gastric bypass in the treatment of morbid obesity: a randomized prospective study.

OBJECTIVE: The objective of the study was to compare the results of open versus laparoscopic gastric bypass in the treatment of morbid obesity. SUMMARY BACKGROUND DATA: Gastric bypass is one of the most commonly acknowledged surgical techniques for the management of morbid obesity. It is usually performed as an open surgery procedure, although now some groups perform it via the laparoscopic approach. PATIENTS AND METHODS: Between June 1999 and January 2002 we conducted a randomized prospective study in 104 patients diagnosed with morbid obesity. The patients were divided into 2 groups: 1 group with gastric bypass via the open approach (OGBP) comprising 51 patients, and 1 group with gastric bypass via the laparoscopic approach (LGBP) comprising 53 patients. The parameters compared were as follows: operating time, intraoperative complications, early (<30 days) and late (>30 days) postoperative complications, hospital stay, and short-term evolution of body mass index. RESULTS: Mean operating time was 186.4 minutes (125-290) in the LGBP group and 201.7 minutes (129-310) in the OGBP group (P < 0.05). Conversion to laparotomy was necessary in 8% of the LGBP patients. Early postoperative complications (<30 days) occurred in 22.6% of the LGBP group compared with 29.4% of the OGBP group, with no significant differences. Late complications (>30 days) occurred in 11% of the LGBP group compared with 24% of the OGBP group (P < 0.05). The differences observed between the 2 groups are the result of a high incidence of abdominal wall hernias in the OGBP group. Mean hospital stay was 5.2 days (1-13) in the LGBP group and 7.9 days (2-28) in the OGBP group (P < 0.05). Evolution of body mass index during a mean follow-up of 23 months was similar in both groups. CONCLUSIONS: LGBP is a good surgical technique for the management of morbid obesity and has clear advantages over OGBP, such as a reduction in abdominal wall complications and a shorter hospital stay. The midterm weight loss is similar with both techniques. One inconvenience is that LGBP has a more complex learning curve than other advanced laparoscopic techniques, which may be associated with an increase in postoperative complications.