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Marta Borges-Canha,1,2 João Sérgio Neves,1,2 Fernando Mendonça,1 Maria Manuel Silva,1 Cláudia Costa,3 Pedro M Cabral,4 Vanessa Guerreiro,1 Rita Lourenço,5 Patrícia Meira,5 Daniela Salazar,1 Maria João Ferreira,1 Jorge Pedro,1 Ana Rita Leite,2 Madalena von-Hafe,2 Catarina Vale,2 Sara Viana,1 Ana Sande,1 Sandra Belo,1 Eva Lau,1 Paula Freitas,1,6 Davide Carvalho1,6 1Serviço de Endocrinologia, Diabetes e Metabolismo do Centro Hospitalar Universitário de São João, Porto, Portugal; 2Departamento de Cirurgia e Fisiologia, Faculdade de Medicina da Universidade do Porto, Porto, Portugal; 3Serviço de Endocrinologia do Instituto Português de Oncologia do Porto, Porto, Portugal; 4Serviço de Patologia Clínica do Centro Hospitalar Universitário Cova da Beira, Covilhã, Portugal; 5Faculdade de Ciências da Nutrição e Alimentação da Universidade do Porto, Porto, Portugal; 6Investigação e Inovação Em Saúde (I3s), Faculdade de Medicina da Universidade do Porto, Porto, PortugalCorrespondence: Marta Borges-CanhaServiço de Endocrinologia, Diabetes e Metabolismo do Centro Hospitalar Universitário de São João, Alameda Prof. Hernâni Monteiro, Porto, 4200-319, PortugalTel +351918935390Email marta.canha@gmail.comPurpose: We aimed to evaluate the association between vitamin D status and hepatic function parameters and scores: Fatty Liver Index (FLI, predictor of hepatic steatosis) and BARD (BMI, AST/ALT ratio and DM, predictor of hepatic fibrosis) in patients with morbid obesity.Patients and Methods: Cross-sectional study including patients with morbid obesity followed in our centre between January 2010 and July 2018. Patients with missing vitamin D levels or hepatic profile parameters were excluded. We divided the population according to two cut-offs of vitamin D levels (12ng/mL and 20ng/mL).Results: The included population (n=1124) had an average age of 43.3± 10.7 years and 84.3% were female. Seventy-point eight percent of the population had vitamin D levels lower than 20ng/mL and 34.8% lower than 12ng/dL. Patients with lower vitamin D levels (< 12ng/mL) had higher BMI, hip and waist circumferences and higher prevalence of hypertension. Higher FLI scores [OR= 0.77 (0.07), p< 0.01] and ALP levels [β= − 0.03 (− 0.06, − 0.01), p< 0.01] associated to lower vitamin D levels.Conclusion: Vitamin D deficiency is associated with a higher risk of hepatic steatosis in individuals with morbid obesity. Correction of vitamin D deficiency may have a beneficial role in the management of NAFLD in patients with morbid obesity.Keywords: vitamin D, fatty liver, NAFLD, obesity

Introduction: Non-alcoholic fatty liver disease (NAFLD) is strongly associated with obesity, and the prevalence of both diseases is increasing notably. The lack of effective treatment options for NAFLD is leading to a great consideration towards the identification of new approaches. Aim: We aimed to evaluate the change one year after bariatric surgery of parameters of hepatic function and in the hepatic scores, Fatty Liver Index (FLI, predictor of hepatic steatosis), and BARD, BMI, AST/ALT ratio and DM, (predictor of hepatic fibrosis). Methods: Observational retrospective cohort study in morbidly obese patients that underwent bariatric surgery between January 2010 and July 2018. We excluded patients missing hepatic function parameters before or one year after the surgical procedure. We used two linear regression models: 1) unadjusted; 2) adjusted for surgery type (gastric sleeve, gastric band and gastric bypass), sex, age, body mass index, diabetes and dyslipidaemia. Results: The included population (n=1955) had an average age of 43.1±10 years and 85.8% were female. We observed a relevant decrease in transaminases (pre-operative AST and ALT, 24.8±12.4 and 29.5±19.5U/L, vs 22.4 ± 11.1 and 22.2±14.7 post-operatively, respectively, p Conclusion: Bariatric surgery is associated with a reduction of the hepatic enzymes and an improvement of FLI and BARD. Bariatric surgery may represent an effective therapeutic approach to NAFLD.

Background: Obesity is a multifactorial disease that is strongly associated to other metabolic disorders, such as insulin resistance and type 2 diabetes. Bariatric surgery is nowadays considered the most effective treatment of morbid obesity. The role of insulin resistance (IR) in weight loss after bariatric surgery is highly unknown. Aim: To evaluate the association between Insulin Resistance (IR) and percentage of excess weight loss (EWL%) one, two, three and four years after bariatric surgery in patients with morbid obesity. Methods: Retrospective longitudinal study in patients with morbid obesity followed in our centre between January 2010 and July 2018 were included. Patients were excluded if they had diabetes. We evaluated baseline Homeostatic Model Assessment of IR (HOMA-IR), Homeostatic Model Assessment of β-cell function (HOMA-beta), Quantitative Insulin Sensitivity Check Index (QUICKI) and Matsuda and DeFronzo index, and performed a linear regression concerning each year’s EWL%. Results: After applying the exclusion criteria, 1723 patients were included in this analysis. The logarithm of HOMA-beta was negatively associated with EWL% at second-, third- and fourth-years post-surgery (β=-1.04 [-1.82 to -0.26], p Conclusion: IR at baseline seems to be associated to long term weight loss, explicitly after the first year post bariatric surgery.

Introduction: Bariatric surgery (BS) is an effective therapeutic approach for obese patients. It is associated with important gastrointestinal anatomic changes, predisposing these subjects to altered nutrient absorption that impact phosphocalcium metabolism. This study aims to clarify the prevalence of secondary hyperparathyroidism (SHPT) and its predictors in patients submitted to BS. Methods: Retrospective unicentric study of 1431 obese patients who underwent metabolic surgery between January/2010 and June/2017 and who were followed for, at least, a year. In this group, 185 subjects were submitted to laparoscopic adjustable gastric banding (LAGB), 830 underwent Roux-en-Y gastric bypass (RYGB) and 416 sleeve gastrectomy (SG). Data comprising 4 years of follow-up were available for 333 patients. We compared the clinical and analytical characteristics of patients with and without secondary hyperparathyroidism (considering SHPT a PTH˃69pg/mL), taking also into account the type of surgery. A multiple logistic regression was performed to study the predictors of SHPT after BS. Results: The overall prevalence of SHPT before surgery was 24.9%, 11.2% one year after surgery and 21.3% four years after surgery. At 12 months after surgery, LAGB had the highest prevalence of patients with SHPT (19.4%, N=36), RYGB had 12.8% (N=274) and SG 5.3% (N=131). At 48 months after surgery, RYGB had the highest prevalence of SHPT (27.0%, N=222), LAGB had 13.2% (N=53) and SG 6.9% (N=58). Multi-variate logistic analysis showed that increased body mass index and age, decreased levels of vitamin D and RYGB were independent predictors of SHPT one year after surgery. The only independent predictor of SHPT four years after surgery was RYGB. Conclusion: The prevalence of SHPT is considerably higher before and four years after BS than 1 year after surgery. This fact raises some questions about the efficacy of the implemented follow-up plans of vitamin D supplementation on the long term, mainly among patients submitted to RYGB.

This article attempts to improve the average efficiency and linearize the work-horse of RF power amplification- the class-B (or class AB) PA-relying, for example, on predistortion, dynamic load modulation or ET. Nevertheless, whenever higher efficiencies are desired, the current-mode class-B PA must be replaced by switchedmode PAs (for example, class-E or class-F), completely modifying the paradigm of RF amplification. In fact, as these are saturated circuits, they cannot respond to excitations of variable amplitude; and thus the original signal envelope must be restored by operating the PA as an AM modulator via dynamic supply adaptation. A good example of this is the EER arrangement.

In this paper, the main nonidealities appearing in polar transmitters will be addressed, together with several implementation considerations. Special attention will be paid to the role of AM modulation nonlinearity and parasitic AM-to-PM conversion, once architecture mechanisms such as time-delay mismatch between branches or limited bandwidth in the amplitude path are controlled. The device limiting factors for a highly efficient switched mode operation and a linear amplitude modulation will be identified. Some circuit design and implementation guidelines for the RF modulating stage and the envelope amplifier will be discussed, to finish with system-level analysis considerations under two-tone and real communication signal excitations.