Serum Oxytocin Levels Decrease 12 Months Following Sleeve Gastrectomy and Are Associated with Decreases in Lean Mass

Increased copeptin may reflect vasopressin-related metabolic changes after bariatric surgery

OBJECTIVE

Mechanisms underlying metabolic improvement following metabolic and bariatric surgery (MBS) may provide insight into novel therapies. Vasopressin improves body composition and protects against hypoglycemia. Associations of copeptin, a stable cleavage product of vasopressin, with BMI and insulin resistance suggest an adaptive increase in vasopressin to counteract metabolic disruption. To our knowledge, no study has investigated copeptin before and after MBS in humans. This study's aim was to investigate copeptin changes following MBS and associations with metabolic parameters.

METHODS

This was a 12-month longitudinal study of 64 youth (78% female; mean age 18.7 [SD 2.8] y) with obesity (mean BMI 45.6 [SD 6.8] kg/m2) undergoing MBS (n = 34) or nonsurgical (NS) lifestyle management (n = 30). Fasting copeptin, hemoglobin A1c (HbA1c), homeostatic model assessment for insulin resistance (HOMA-IR), body composition, and resting energy expenditure (REE) were assessed.

RESULTS

Over 12 months, copeptin increased more (time-by-treatment p = 0.017) whereas HbA1c and adiposity decreased more after MBS than NS (ps ≤ 0.036). Copeptin changes correlated negatively with percentage fat mass and REE changes (rho ≤ -0.29; ps ≤ 0.025) in the whole group, and they correlated positively with HbA1c and HOMA-IR (rho ≥ 0.41; false discovery rate-adjusted p = 0.05) and negatively with REE changes (rho = -0.55; false discovery rate-adjusted p = 0.036) in the MBS group.

CONCLUSIONS

Increases in copeptin after weight loss in MBS compared with NS were associated with lower REE and higher HbA1c/HOMA-IR values. Vasopressin may contribute to MBS-related metabolic modifications.

Endocrine Dysfunction Following Bariatric Surgery: A Systematic Review of Postoperative Changes in Major Endocrine Hormones

Bariatric surgery (BS) is an effective intervention for obesity and related metabolic disorders, significantly improving metabolic health and alleviating hormonal imbalances. However, it induces complex endocrine changes that can lead to dysfunctions, impacting the somatotropic, gonadal, thyroid, pancreatic, and adrenal axes. This review highlights the dual effects of BS on the endocrine system. A comprehensive review of peer-reviewed studies using PRISMA guidelines was conducted, focusing on human research evaluating pre and postoperative endocrine parameters. Studies were selected for their relevance and quality in elucidating the endocrine consequences of BS. BS restores growth hormone secretion and improves fertility but may disrupt insulin-like growth factor-1 recovery and sex hormone balance, leading to bone loss and catabolic states. Postprandial insulin hypersecretion can result in hyperinsulinemic hypoglycemia, with impaired counter-regulatory hormone responses. Secondary hyperparathyroidism and reduced bone density highlight additional risks. Changes in thyroid hormone levels have implications for both hypothyroid and euthyroid patients. These findings underscore the interplay between improved metabolic control and potential endocrine dysfunctions. The current evidence predominantly comprises association studies that may not be of quality for safe clinical decision-making, highlighting the need for high-quality research to establish causality and refine therapeutic strategies. Bridging knowledge gaps in the mechanisms underlying these changes is crucial to optimizing BS outcomes. A holistic approach integrating preoperative screening, individualized postoperative care, and targeted therapies is essential to mitigate complications while maximizing benefits.

Impact of Sleeve Gastrectomy on Body Weight and Food Intake Regulation in Diet-Induced Obese Mice

The epidemic of obesity has increased worldwide and is associated with comorbidities such as diabetes and cardiovascular disease. In this context, strategies that modulate body weight and improve glycemic metabolism have increased, and bariatric surgeries such as Sleeve Gastrectomy (SG) have been highlighted in obesity treatment. However, the mechanism by which SG reduces body weight and improves glycemic control remains unknown. Thus, in this study, we aimed to evaluate food intake and the expression of hypothalamic genes involved with the regulation of this process in diet-induced obese mice submitted to SG. For this, we used C57BL/6 mice submitted to a 10-week high-fat diet protocol and submitted to SG. Food intake, fed and fasted glycemia, as well as hypothalamic anorexigenic and orexigenic gene expression were evaluated 4 weeks after the surgical procedure. First, we observed that SG reduces body weight (44.19 ± 0.47 HFD, 43.51 ± 0.71 HFD-SHAM, and 38.22 ± 1.31 HFD-SG), fasting glycemia (115.0 ± 4.60 HFD, 122.4 ± 3.48 HFD-SHAM, and 93.43 ± 4.67 HFD-SG), insulinemia (1.77 ± 0.15 HFD, 1.92 ± 0.27 HFD-SHAM, and 0.93 ± 0.05 HFD-SG), and leptinemia (5.86 ± 1.38 HFD, 6.44 ± 1.51 HFD-SHAM, and 1.43 ± 0.35 HFD-SG) in obese mice. Additionally, SG reduces food (5.15 ± 0.18 HFD, 5.49 ± 0.32, HFD-SHAM, and 3.28 ± 0.26 HFD-SG) and total (16.88 ± 0.88 HFD, 17.05 ± 0.42, HFD-SHAM, and 14.30 ± 0.73 HFD-SG) calorie intake without alterations in anorexigenic and orexigenic gene expression. In conclusion, these data indicate that SG improves obesity-associated alterations at least in part by a reduction in food intake. This effect is not associated with the canonical food intake pathway in the hypothalamus, indicating the involvement of non-canonical pathways in this process.

The Pivotal Role of Oxytocin's Mechanism of Thermoregulation in Prader-Willi Syndrome, Schaaf-Yang Syndrome, and Autism Spectrum Disorder

Oxytocin (Oxt) regulates thermogenesis, and altered thermoregulation results in Prader-Willi syndrome (PWS), Schaaf-Yang syndrome (SYS), and Autism spectrum disorder (ASD). PWS is a genetic disorder caused by the deletion of the paternal allele of 15q11-q13, the maternal uniparental disomy of chromosome 15, or defects in the imprinting center of chromosome 15. PWS is characterized by hyperphagia, obesity, low skeletal muscle tone, and autism spectrum disorder (ASD). Oxt also increases muscle tonicity and decreases proteolysis while PWS infants are hypotonic and require assisted feeding in early infancy. This evidence inspired us to merge the results of almost 20 years of studies and formulate a new hypothesis according to which the disruption of Oxt's mechanism of thermoregulation manifests in PWS, SYS, and ASD through thermosensory abnormalities and skeletal muscle tone. This review will integrate the current literature with new updates on PWS, SYS, and ASD and the recent discoveries on Oxt's regulation of thermogenesis to advance the knowledge on these diseases.

Non-canonical Ca2+- Akt signaling pathway mediates the antiproteolytic effects induced by oxytocin receptor stimulation in skeletal muscle

Although it has been previously demonstrated that oxytocin (OXT) receptor stimulation can control skeletal muscle mass in vivo, the intracellular mechanisms that mediate this effect are still poorly understood. Thus, rat oxidative skeletal muscles were isolated and incubated with OXT or WAY-267,464, a non-peptide selective OXT receptor (OXTR) agonist, in the presence or absence of atosiban (ATB), an OXTR antagonist, and overall proteolysis was evaluated. The results indicated that both OXT and WAY-267,464 suppressed muscle proteolysis, and this effect was blocked by the addition of ATB. Furthermore, the WAY-induced anti-catabolic action on protein metabolism did not involve the coupling between OXTR and Gαi since it was insensitive to pertussis toxin (PTX). The decrease in overall proteolysis induced by WAY was probably due to the inhibition of the autophagic/lysosomal system, as estimated by the decrease in LC3 (an autophagic/lysosomal marker), and was accompanied by an increase in the content of Ca2+-dependent protein kinase (PKC)-phosphorylated substrates, pSer473-Akt, and pSer256-FoxO1. Most of these effects were blocked by the inhibition of inositol triphosphate receptors (IP3R), which mediate Ca2+ release from the sarcoplasmic reticulum to the cytoplasm, and triciribine, an Akt inhibitor. Taken together, these findings indicate that the stimulation of OXTR directly induces skeletal muscle protein-sparing effects through a Gαq/IP3R/Ca2+-dependent pathway and crosstalk with Akt/FoxO1 signaling, which consequently decreases the expression of genes related to atrophy, such as LC3, as well as muscle proteolysis.