Dissociation of body mass index, excess weight loss and body fat percentage trajectories after 3 years of gastric bypass: relationship with metabolic outcomes.

BACKGROUND/OBJECTIVES: Body weight, body mass index (BMI) and excess weight loss (EWL) are the most frequently used measures to analyse bariatric surgery outcomes. However, these measurements do not provide accurate information on body composition (BC) with body fat (BF), importantly determining the levels of cardiometabolic risk factors. Our aim was to analyse the evolution of BC after Roux-en-Y Gastric Bypass (RYGB) and its influence on the changes of cardiometabolic risk factors in comparison to BMI and EWL. SUBJECTS/METHODS: A group of 81 obese Caucasian patients (19 males/62 females) aged 44.9±1.3 years undergoing RYGB between January 2006 and December 2011 was prospectively followed up for a period of 3 years. BC was determined by air-displacement plethysmography. Visceral adiposity, physical activity and cardiometabolic risk factors were measured. RESULTS: BF was markedly (P<0.001) reduced after the first year, increasing progressively during the second and third years after RYGB, following a different trajectory than body weight, BMI and EWL that decreased up to the second year post surgery. Markers of glucose homeostasis decreased during the first month and continued to decrease during the first year (P<0.05), remaining stabilised or slightly increased between the second and third years following RYGB. However, markers of lipid metabolism decreased (P<0.05) markedly during the first 12 months, increasing thereafter in parallel to the changes observed in BC, with the exception of high-density lipoprotein-cholesterol, which increased progressively throughout the whole period analysed. CONCLUSIONS: The adverse switch in the changes in BC between the first and the second years after RYGB may underlie the changes observed in cardiometabolic risk factors. Tracking of adiposity during the follow-up of bariatric/metabolic surgery yields clinically relevant information to better identify patients in need of increased lifestyle advice or treatment intensification.

[Body weight- independent variations in HDL-cholesterol following gastric bypass]. / Las variaciones en cholesterol-HDL tras bypass gástrico proximal son independientes de la evolución ponderal.

BACKGROUND: Bariatric surgery has multiple beneficial effects on lipid profile in patients with morbid obesity. However, these changes can be attenuated by weight regain. This retrospective study was designed to assess the effects of gastric bypass(GBP) on different lipid fractions over a 6 year follow-up. PATIENTS AND METHODS: We studied 177 patients (135 women)with morbid obesity (BMI 44.2+0.4 kg/m2) aged 42.4+0.9 years before and 3, 6, 9, 12, 24, 36, 48, 60 and 72 months after laparoscopic proximal GBP. Anthropometry, body composition measurement (Bod-Pod) and fasting blood samples were taken in all evaluations to measure total cholesterol (TC),LDL-cholesterol (LDL-C), HDL-cholesterol (HDL-C), triglycerides(TG), glucose and insulin. RESULTS: GPB was followed by a significant BMI reduction (nadir BMI at 18 m 28.3+0.4 kg/m2 p<0,001) and fat mass decrease(p<0,001). Maximal percentage of excess BMI lost was 84.1%and that of body fat was 87% 18 months after GBP. These numbers decreased to 65.6% and 38.3% (p<0,005 vs nadir) respectively 72 months after the operation, indicating both weight and fat mass regain. TG and LDL-C values decreased 30% with respect to preoperative levels, while HDL-C increased 97%over initial values. This HDL-C increase was progressive even over the weight regain phase. Both TC/HDL-C and TG/HDL-Cratios normalized after GBP and values were sustained over the weight regain period until the end of the study. CONCLUSIONS: These results confirm the beneficial effects of GBP on all lipid fractions, which are maintained over 6 years of follow-up. Globally, the rise in HDL-C seems to be independent of weight or fat mass changes, since it increases even over the weight regain phase, so contributing to a reduction in the prevalence of dyslipidaemia and to cardiovascular risk reduction.

Las variaciones en colesterol-HDL tras bypass gástrico proximal son independientes de la evolución ponderal / Body weight- independent variations in HDL-cholesterol following gastric bypass

Fundamento: La cirugía bariátrica posee efectos beneficiosos sobre el perfil lipídico en pacientes con obesidad mórbida que pueden atenuarse con la recuperación ponderal. El presente estudio se ha llevado a cabo para evaluar el perfil lipídico antes y a lo largo de los seis años consiguientes a la realización de bypass gástrico proximal (BPG). Material y métodos: Se han estudiado 177 pacientes (135 mujeres) con obesidad mórbida (IMC 44,2+0,4 kg/m2) de 42,4+0,9 años de edad antes, 3,6,9, 12,24,36,48,60 y 72 meses después de realizar BPG. En todas las revisiones se evaluó el tratamiento hipolipemiante, antropometría (IMC, cintura), composición corporal (Bod-Pod) y determinaciones de colesterol total (CT), colesterol-LDL (LDL-C), colesterol-HDL (HDL-C), triglicéridos (TG), glucosa e insulina. Resultados: El BPG indujo marcada reducción de IMC (nadir IMC a 18 meses 28,3+0,4 kg/m2 p<0,001) y grasa corporal consiguiendo una pérdida de exceso IMC del 84,1% y del exceso de porcentaje de grasa del 87% que disminuyó al 65,6 y 38,3% (ambos p<0,005 respecto a nadir) respectivamente a los 6 años del BPG, indicando recuperación de peso y grasa corporal. Los valores de TG alcanzaron el 70% a los 60 meses, los de LDL-C el 70,6% a los 18 meses y los de HDL-C el 197% del valor pre-intervención a los 48 meses. La elevación de HDL-C aumentó durante la fase de recuperación ponderal de forma continuada (p<0,001). Tanto los cocientes CT/HDL-C como TG/HDL-C se normalizaron de forma mantenida durante los 6 años de seguimiento. Conclusiones: Estos resultados confirman la mejoría de todas las fracciones lipídicas 6 años después del BPG, con especial mención a HDL-C, que mantuvo progresión creciente incluso durante la recuperación ponderal, reduciendo la tasa de dislipemia a los 6 años del BPG (AU)

Background: Bariatric surgery has multiple beneficial effects on lipid profile in patients with morbid obesity. However, these changes can be attenuated by weight regain. This retrospective study was designed to assess the effects of gastric bypass (GBP) on different lipid fractions over a 6 year follow-up. Patients and Methods: We studied 177 patients (135 women) with morbid obesity (BMI 44.2+0.4 kg/m2) aged 42.4+0.9 years before and 3, 6, 9, 12, 24, 36, 48, 60 and 72 months after laparoscopic proximal GBP. Anthropometry, body composition measurement (Bod-Pod) and fasting blood samples were taken in all evaluations to measure total cholesterol (TC), LDL-cholesterol (LDL-C), HDL-cholesterol (HDL-C), triglycerides (TG), glucose and insulin. Results: GPB was followed by a significant BMI reduction (nadir BMI at 18 m 28.3+0.4 kg/m2 p<0,001) and fat mass decrease (p<0,001). Maximal percentage of excess BMI lost was 84.1% and that of body fat was 87% 18 months after GBP. These numbers decreased to 65.6% and 38.3% (p<0,005 vs nadir) respectively 72 months after the operation, indicating both weight and fat mass regain. TG and LDL-C values decreased 30% with respect to preoperative levels, while HDL-C increased 97% over initial values. This HDL-C increase was progressive even over the weight regain phase. Both TC/HDL-C and TG/HDL-C ratios normalized after GBP and values were sustained over the weight regain period until the end of the study. Conclusions: These results confirm the beneficial effects of GBP on all lipid fractions, which are maintained over 6 years of follow-up. Globally, the rise in HDL-C seems to be independent of weight or fat mass changes, since it increases even over the weight regain phase, so contributing to a reduction in the prevalence of dyslipidaemia and to cardiovascular risk reduction (AU)

Conversion of N-acyl-4-acyloxy-beta-lactams into 1,3-oxazin-6-ones: two consecutive pseudopericyclic processes

N-Acyl-4-acyloxy-beta-lactams are converted into 1,3-oxazin-6-ones under basic conditions. This transformation is believed to proceed via N-acylazetones, which rearrange to the final products by a sequence of two electrocyclic processes. The calculated (RHF and B3LYP) transition structures of both concerted reactions are shown to present characteristic pseudopericyclic orbital topologies.

On the mechanism of conversion of N-acyl-4-acyloxy-beta-lactams into 2-substituted 1,3-oxazin-6-ones. Can a low-barrier transition state be antiaromatic?

The mechanism of the conversion of N-acyl-4-acyloxy-beta-lactams into 1,3-oxazin-6-ones has been investigated using ab initio and density functional theories. It has been found that two pseudopericyclic reactions are involved in the whole process. The first key reaction is a retro-[4-exo-dig] cyclization instead of a thermal conrotatory electrocyclic ring opening. Magnetic characterization of the corresponding transition structure shows antiaromatic character, despite the low activation energy associated with this process. The second step is very exothermic and has no activation barrier. It corresponds to another pseudopericyclic reaction instead of a six-electron disrotatory electrocyclization. These results confirm that there is no correlation between aromaticity and pseudopericyclic reactions. In contrast, thermal-symmetry-allowed pericyclic reactions are always aromatic. Therefore, magnetic analysis of the corresponding transition structures constitutes a useful tool to distinguish between both kinds of processes.