Immune cell-mediated inflammation and the early improvements in glucose metabolism after gastric banding surgery

The Interplay between Obesity and Inflammation

Obesity is an important condition affecting the quality of life of numerous patients and increasing their associated risk for multiple diseases, including tumors and immune-mediated disorders. Inflammation appears to play a major role in the development of obesity and represents a central point for the activity of cellular and humoral components in the adipose tissue. Macrophages play a key role as the main cellular component of the adipose tissue regulating the chronic inflammation and modulating the secretion and differentiation of various pro- and anti-inflammatory cytokines. Inflammation also involves a series of signaling pathways that might represent the focus for new therapies and interventions. Weight loss is essential in decreasing cardiometabolic risks and the degree of associated inflammation; however, the latter can persist for long after the excess weight is lost, and can involve changes in macrophage phenotypes that can ensure the metabolic adjustment. A clear understanding of the pathophysiological processes in the adipose tissue and the interplay between obesity and chronic inflammation can lead to a better understanding of the development of comorbidities and may ensure future targets for the treatment of obesity.

T cells in obesity-associated inflammation: The devil is in the details

Obesity presents a significant health challenge, affecting 41% of adults and 19.7% of children in the United States. One of the associated health challenges of obesity is chronic low-grade inflammation. In both mice and humans, T cells in circulation and in the adipose tissue play a pivotal role in obesity-associated inflammation. Changes in the numbers and frequency of specific CD4+ Th subsets and their contribution to inflammation through cytokine production indicate declining metabolic health, that is, insulin resistance and T2D. While some Th subset alterations are consistent between mice and humans with obesity, some changes mainly characterize male mice, whereas female mice often resist obesity and inflammation. However, protection from obesity and inflammation is not observed in human females, who can develop obesity-related T-cell inflammation akin to males. The decline in female sex hormones after menopause is also implicated in promoting obesity and inflammation. Age is a second underappreciated factor for defining and regulating obesity-associated inflammation toward translating basic science findings to the clinic. Weight loss in mice and humans, in parallel with these other factors, does not resolve obesity-associated inflammation. Instead, inflammation persists amid modest changes in CD4+ T cell frequencies, highlighting the need for further research into resolving changes in T-cell function after weight loss. How lingering inflammation after weight loss affecting the common struggle to maintain lower weight is unknown. Semaglutide, a newly popular pharmaceutical used for treating T2D and reversing obesity, holds promise for alleviating obesity-associated health complications, yet its impact on T-cell-mediated inflammation remains unexplored. Further work in this area could significantly contribute to the scientific understanding of the impacts of weight loss and sex/hormones in obesity and obesity-associated metabolic decline.

Improved Insulin Secretion Response and Beta-cell Function Correlated with Increased Prolactin Levels After Laparoscopic Sleeve Gastrectomy in Morbidly Obese Patients with Acanthosis Nigricans

OBJECTIVE

To explore insulin secretion patterns, β-cell function, and serum prolactin (PRL) concentrations in Chinese morbidly obese patients with Acanthosis nigricans (AN) and their alterations after laparoscopic sleeve gastrectomy (LSG).

METHODS

A total of 138 morbidly obese subjects undergoing LSG were categorized as simple obesity without AN (OB group, n = 55) and obesity with AN (AN group, n = 83). Oral glucose tolerance test (OGTT), PRL, and related metabolic indices were performed pre- and 12 months post-LSG. Insulin secretion patterns were derived from insulin secretion peak time during OGTT: type I (peak at 30 or 60 min) and type II (peak at 120 or 180 min).

RESULTS

Preoperatively, AN group showed significantly higher proportions of type II insulin secretion pattern, fasting insulin (FINS), and homeostatic model assessment of insulin resistance (HOMA-IR) whereas lower oral glucose insulin sensitivity (OGIS), insulinogenic index (IGI), and disposition index (DI) than OB group, which were improved significantly at 12 months postoperatively in both groups, more pronounced in AN group. Intriguingly, serum PRL declined substantially in AN group than OB group at baseline whereas elevated only in the AN group post-LSG. After adjusting for confounding factors, elevated PRL correlated significantly with increased IGI and DI, and decreased HOMA-IR in both genders, as well as increased OGIS in females, which was detected only in the AN group CONCLUSION: Morbidly obese patients with AN presented delayed insulin secretion response, impaired insulin secretion, and β-cell dysfunction, which were significantly improved by LSG and might benefit from elevated PRL.

The serial changes of Neutrophile-Lymphocyte Ratio and correlation to weight loss after Laparoscopic Sleeve Gastrectomy

Purpose

This study aims to identify the pre- and postoperative changes in the neutrophil-lymphocyte ratio (NLR) and its correlations to clinical characteristics in obese patients who underwent laparoscopic sleeve gastrectomy (LSG).

Method

Retrospectively, we included patients who has undergone LSG in our institution between January 2019 and April 2021. A total of 100 patients whose body mass index over 32.5 and received primary laparoscopic sleeve gastrectomy without infectious condition were included.

Results

There was a significant decline in NLR (T0 vs. POM3 2.21 vs. 1.78, p = 0.005), neutrophil (T0 vs. POM3 5369 vs. 4050, p < 0.001) and lymphocyte count (T0 vs. POM3 2440: 2100, p < 0.001, respectively) at postoperative 3 months (POM3) compared to preoperative (T0) levels, but similar between POM3 and POM6. The declined counts (Neutrophile vs. Lymphocyte 1445.5/µl vs. 323.5/µl, p < 0.001) and percentage (Neutrophile vs. Lymphocyte 25.11% vs. 13.07%, p < 0.001) of neutrophile are higher than lymphocyte from T0 to POM3, but similar in POM3 and POM6. Preoperative NLR has a significant correlation with the preoperative body weight, preoperative insulin level, and excessive body weight loss (EBWL) at POM3. Preoperative NLR <2.36 had a sensitivity of 67.6% and a specificity of 62.5% in predicting successful weight loss (EBWL > 37.7%) at POM3 (AUC = 0.635, p = 0.032).

Conclusion

There was a significant decline in NLR, neutrophil, and lymphocyte count from T0 to POM3, but similar between POM3 and POM6. The declined counts and percentage of neutrophile are higher than lymphocyte. Preoperative NLR shows the potential to be used as a prognostic biomarker for predicting successful weight loss at POM3 after LSG. Further studies could be designed to evaluate the value of prediction in successful outcome after LSG and figure out the relationship between the changes of neutrophil function and oncogenesis.

Reduced Th1 response is associated with lower glycolytic activity in activated peripheral blood mononuclear cells after metabolic and bariatric surgery

BACKGROUND

Obesity promotes cellular immunometabolism changes that trigger the activation of macrophages and lymphocytes, leading to systemic inflammation. Activated leukocytes undergo metabolic reprogramming, increasing glycolytic activity.

OBJECTIVE

To examine whether the reduction in the inflammatory state associated with bariatric surgery is associated with decreased glycolytic activity in leukocytes. Setting Single-center, prospective observational study.

METHODS

This study involved 18 patients with obesity undergoing bariatric surgery. All measurements were performed preoperatively and six months postoperatively. Peripheral blood mononuclear cells and plasma were obtained to determine the glycolytic rate and mitochondrial membrane potential as surrogates of the metabolic switching and high-sensitivity C-reactive protein, adipokines, and CD69 expression as inflammatory and activation markers.

RESULTS

Glycolytic activity engaged by CD3/CD28 activation was reduced six months after bariatric surgery, associated with decreased levels of T helper (Th) 1 and Th17 signature cytokines. An overall reduction in inflammatory markers was observed, which correlated with a higher adiponectin/leptin ratio.

CONCLUSIONS

Metabolic and bariatric surgery-induced weight loss leads to reprogramming in T cells' metabolic machinery, resulting in reduced stimulation of glycolysis after activation, which may explain the decrease in systemic inflammation mediated by cytokines such as interferon-γ and interleukin-17A.

Determinants of type 2 diabetes remission after bariatric surgery in obese Japanese patients: a retrospective cohort study

Objective

Bariatric surgery (BS) improves glycemic control in type 2 diabetes; however, some patients show insufficient improvement. Understanding the pathophysiology of type 2 diabetes in obese patients can facilitate appropriate treatment for type 2 diabetes after BS. The homeostatic model assessment (HOMA) 2 enables the calculation of the values from C-peptide data and evaluation of insulin users. We aimed to evaluate the pathophysiology of type 2 diabetes using pre- and postoperative parameters and HOMA2 in obese patients who underwent BS.

Methods

We retrospectively reviewed data from 45 obese patients with type 2 diabetes who underwent BS. They were followed-up for 12 months. The relationship between the HOMA2 score and complete remission (CR) of type 2 diabetes after BS was analyzed. Patients with and without CR were assigned to the CR and non-CR groups, respectively. Multiple regression analysis was used to identify factors associated with improvement in type 2 diabetes after BS.

Results

BS significantly improved body weight and glucose metabolism. The preoperative glycosylated hemoglobin A1c level and insulin secretion (HOMA2-%B) significantly differed between the CR and non-CR groups. Postoperative weight reduction and improved insulin sensitivity correlated significantly with CR; multiple regression showed that the preoperative HOMA 2-%B independently predicted CR of type 2 diabetes after BS.

Conclusion

Preoperative insulin secretion, improvement in insulin sensitivity, and weight reduction after BS are related to CR of type 2 diabetes after BS. The results better reveal the pathophysiology of and treatment for type 2 diabetes in obese patients who undergo BS.

Intravital imaging of islet Ca2+ dynamics reveals enhanced β cell connectivity after bariatric surgery in mice

Bariatric surgery improves both insulin sensitivity and secretion and can induce diabetes remission. However, the mechanisms and time courses of these changes, particularly the impact on β cell function, are difficult to monitor directly. In this study, we investigated the effect of Vertical Sleeve Gastrectomy (VSG) on β cell function in vivo by imaging Ca²⁺ dynamics in islets engrafted into the anterior eye chamber. Mirroring its clinical utility, VSG in mice results in significantly improved glucose tolerance, and enhanced insulin secretion. We reveal that these benefits are underpinned by augmented β cell function and coordinated activity across the islet. These effects involve changes in circulating GLP-1 levels which may act both directly and indirectly on the β cell, in the latter case through changes in body weight. Thus, bariatric surgery leads to time-dependent increases in β cell function and intra-islet connectivity which are likely to contribute to diabetes remission.

Interplay between the Adaptive Immune System and Insulin Resistance in Weight Loss Induced by Bariatric Surgery

Low-grade chronic inflammation plays a pivotal role among other pathophysiological mechanisms involved in obesity. Innate and adaptive immune cells undergo systemic proinflammatory polarization that gives rise to an increased secretion of proinflammatory cytokines, which in turn leads to insulin resistance. Bariatric surgery is currently the most effective treatment for obesity, as it brings on significant weight loss, glucose metabolism improvement, and a decrease in systemic inflammation biomarkers. After bariatric surgery, several changes have been reported to occur in adaptive immunity, including reduction in CD4+ and CD8+ T cell counts, a decrease in the Th1/Th2 ratio, an increase in B regulatory cells, and reduction in proinflammatory cytokine secretion. Overall, there seems to be a major shift in several lymphocyte populations from a proinflammatory to an anti-inflammatory phenotype. Furthermore, increased antioxidant activity and reduced lipid and DNA oxidation products have been reported after bariatric surgery in circulating mononuclear cells. This paper highlights the shift in the adaptive immune system in response to weight loss and improved insulin sensitivity, as well as the interplay between immunological and metabolic adaptations as a result of bariatric surgery. Finally, based on data from research, we propose several mechanisms such as changes in adaptive immune cell phenotypes and their by-products, recruitment in adipose tissue, reduced oxidative stress, and modification in metabolic substrate availability as drivers to reduce low-grade chronic inflammation after bariatric surgery in severe obesity.

Obesity-related cognitive impairment: The role of endothelial dysfunction

Obesity is a global pandemic associated with macro- and microvascular endothelial dysfunction. Microvascular endothelial dysfunction has recently emerged as a significant risk factor for the development of cognitive impairment. In this review, we present evidence from clinical and preclinical studies supporting a role for obesity in cognitive impairment. Next, we discuss how obesity-related hyperinsulinemia/insulin resistance, systemic inflammation, and gut dysbiosis lead to cognitive impairment through induction of endothelial dysfunction and disruption of the blood brain barrier. Finally, we outline the potential clinical utility of dietary interventions, exercise, and bariatric surgery in circumventing the impacts of obesity on cognitive function.

Weight loss achieved by bariatric surgery modifies high-density lipoprotein subfractions and low-density lipoprotein oxidation towards atheroprotection

OBJECTIVES

Weight loss achieved by laparoscopic adjustable gastric banding (LAGB) induces an increase in high-density lipoprotein cholesterol (HDLc) but a small effect on low-density lipoprotein (LDL), although changes in their quality (size and composition) are uncertain. Our aim was to study the impact of weight loss, achieved 13-months after LAGB, on inflammation and dyslipidemia, focusing on HDL and LDL subfractions, and oxidized LDL (oxLDL).

DESIGN & METHODS

We evaluated standard lipid profile, HDL and LDL subfractions, oxLDL, interleukin (IL)-6 and C-reactive protein (CRP), in twenty obese patients, before (T0) and 13-months after LAGB (T1), and in seventeen healthy controls.

RESULTS

At T1, patients showed lower body weight (12% median weight loss) and anthropometric indices; reduction in TG, atherogenic indices, oxLDL, oxLDL/LDL ratio, CRP and IL-6, and enhancement in HDLc; an increase in large HDL and intermediate HDL subfractions, and a decrease in small HDL subfraction; LDL subfractions were not modified. Percentual change (%Δ) of oxLDL, from T0 to T1, correlated significantly and positively with %Δ of small HDL subfraction and with %Δ of body mass index.

CONCLUSIONS

Weight loss induced atheroprotective changes on inflammation, and lipid profile, enhancing larger HDL, the more atheroprotective subfraction, reducing the less protective subclass, small HDL, and reducing oxLDL and oxLDL/LDL ratio. Quality of lipoproteins appears useful cardiovascular risk biomarkers, deserving further studies.

Decreased Levels of Circulating Cancer-Associated Protein Biomarkers Following Bariatric Surgery

BACKGROUND

Epidemiological studies have identified obesity as a major risk factor for cancer in humans, and trials have demonstrated a significant reduction in the incidence of cancer after bariatric surgery. The rapidity of weight loss after bariatric surgery provides an opportunity to identify the molecular changes associated with effective obesity treatment. Indirectly, this may provide some insights into the mechanisms that drive the association between obesity and cancer. We sought to measure circulating cancer-associated proteins before and after laparoscopic sleeve gastrectomy (LSG).

METHODS

We prospectively enrolled 15 patients undergoing LSG. Thirty-four plasma protein biomarkers thought to be associated with cancer processes were analyzed at baseline and following successful weight loss at 12 weeks using a multiplex bead-based assay.

RESULTS

Mean excess body weight loss was 44 % at 12-week follow-up. After LSG, a significant reduction in circulating plasma levels was observed for half (17/34) of the proteins assessed: VEGF-A, VEGF-C, VEGF-D, endoglin, PLGF, sFASL, IGFBP-1, IL-18, prolactin, EGF, TGFα, sCD40L, IL-18, TNFα, IL-6, HB-EGF, and PAI-1. Nonsignificant decreases were found for the remaining proteins.

CONCLUSIONS

Circulating cancer-related biomarker levels were reduced by surgical weight loss, and this benefit was achieved as early as 3 months after operation. The observed reduction in cancer biomarkers may be related to the reported decrease in cancer incidence following bariatric surgery.

Role of innate and adaptive immunity in obesity-associated metabolic disease

Chronic inflammation in adipose tissue, possibly related to adipose cell hypertrophy, hypoxia, and/or intestinal leakage of bacteria and their metabolic products, likely plays a critical role in the development of obesity-associated insulin resistance (IR). Cells of both the innate and adaptive immune system residing in adipose tissues, as well as in the intestine, participate in this process. Thus, M1 macrophages, IFN-γ-secreting Th1 cells, CD8+ T cells, and B cells promote IR, in part through secretion of proinflammatory cytokines. Conversely, eosinophils, Th2 T cells, type 2 innate lymphoid cells, and possibly Foxp3+ Tregs protect against IR through local control of inflammation.

Glucose Metabolism After Gastric Banding and Gastric Bypass in Individuals With Type 2 Diabetes: Weight Loss Effect

OBJECTIVE

The superior effect of Roux-en-Y gastric bypass (RYGB) on glucose control compared with laparoscopic adjustable gastric banding (LAGB) is confounded by the greater weight loss after RYGB. We therefore examined the effect of these two surgeries on metabolic parameters matched on small and large amounts of weight loss.

RESEARCH DESIGN AND METHODS

Severely obese individuals with type 2 diabetes were tested for glucose metabolism, β-cell function, and insulin sensitivity after oral and intravenous glucose stimuli, before and 1 year after RYGB and LAGB, and at 10% and 20% weight loss after each surgery.

RESULTS

RYGB resulted in greater glucagon-like peptide 1 release and incretin effect, compared with LAGB, at any level of weight loss. RYGB decreased glucose levels (120 min and area under the curve for glucose) more than LAGB at 10% weight loss. However, the improvement in glucose metabolism, the rate of diabetes remission and use of diabetes medications, insulin sensitivity, and β-cell function were similar after the two types of surgery after 20% equivalent weight loss.

CONCLUSIONS

Although RYGB retained its unique effect on incretins, the superiority of the effect of RYGB over that of LAGB on glucose metabolism, which is apparent after 10% weight loss, was attenuated after larger weight loss.

The impact of bariatric surgery on inflammation: quenching the fire of obesity?

PURPOSE OF REVIEW

Numerous lines of evidence support the likelihood that inflammation drives the transition from obese/metabolically healthy to obese/type 2 diabetes (T2D). Given the temporal flexibility of inflammation in obesity-associated T2D, investigators have hypothesized that a precipitous drop in diabetogenic cytokines is critical for rapid 'T2D remission' following surgery but prior to significant weight loss. We review the evidence that changes in diabetogenic cytokines play a role in outcomes of bariatric surgery, including improved glycemic control.

RECENT FINDINGS

A 2016 indication for bariatric surgery to treat T2D integrates the large body of data showing rapid metabolic improvement. Parameters that account for improved glycemic control prior to significant weight loss, T2D recidivism over the long term, or failure of surgery to remit T2D in some patients are incompletely understood.

SUMMARY

We review the evidence that changes in diabetogenic cytokines play a role in outcomes of bariatric surgery, including improved glycemic control. We brainstorm future research directions that may improve surgical results.

From neutrophils to macrophages: differences in regional adipose tissue depots

Currently, we do not fully understand the underlying mechanisms of how regional adiposity promotes metabolic dysregulation. As adipose tissue expands, there is an increase in chronic systemic low-grade inflammation due to greater infiltration of immune cells and production of cytokines. This chronic inflammation is thought to play a major role in the development of metabolic complications and disease such as insulin resistance and diabetes. We know that different adipose tissue depots contribute differently to the risk of metabolic disease. People who have an upper body fat distribution around the abdomen are at greater risk of disease than those who tend to store fat in their lower body around the hips and thighs. Thus, it is conceivable that adipose tissue depots contribute differently to the inflammatory milieu as a result of varied infiltration of immune cell types. In this review, we describe the role and function of major resident immune cells in the development of adipose tissue inflammation and discuss their regional differences in the context of metabolic disease risk. We find that although initial studies have found regional differences, a more comprehensive understanding of how immune cells interrupt adipose tissue homeostasis is needed.

Associations of Circulating Lymphocyte Subpopulations with Type 2 Diabetes: Cross-Sectional Results from the Multi-Ethnic Study of Atherosclerosis (MESA)

OBJECTIVE

Distinct lymphocyte subpopulations have been implicated in the regulation of glucose homeostasis and obesity-associated inflammation in mouse models of insulin resistance. Information on the relationships of lymphocyte subpopulations with type 2 diabetes remain limited in human population-based cohort studies.

METHODS

Circulating levels of innate (γδ T, natural killer (NK)) and adaptive immune (CD4+ naive, CD4+ memory, Th1, and Th2) lymphocyte subpopulations were measured by flow cytometry in the peripheral blood of 929 free-living participants of the Multi-Ethnic Study of Atherosclerosis (MESA). Cross-sectional relationships of lymphocyte subpopulations with type 2 diabetes (n = 154) and fasting glucose and insulin concentrations were evaluated by generalized linear models.

RESULTS

Each standard deviation (SD) higher CD4+ memory cells was associated with a 21% higher odds of type 2 diabetes (95% CI: 1-47%) and each SD higher naive cells was associated with a 22% lower odds (95% CI: 4-36%) (adjusted for age, gender, race/ethnicity, and BMI). Among participants not using diabetes medication, higher memory and lower naive CD4+ cells were associated with higher fasting glucose concentrations (p<0.05, adjusted for age, sex, and race/ethnicity). There were no associations of γδ T, NK, Th1, or Th2 cells with type 2 diabetes, glucose, or insulin.

CONCLUSIONS

A higher degree of chronic adaptive immune activation, reflected by higher memory and lower naive CD4+ cells, was positively associated with type 2 diabetes. These results are consistent with a role of chronic immune activation and exhaustion augmenting chronic inflammatory diseases, and support the importance of prospective studies evaluating adaptive immune activation and type 2 diabetes.

Role of T cells in malnutrition and obesity

Nutritional status is critically important for immune cell function. While obesity is characterized by inflammation that promotes metabolic syndrome including cardiovascular disease and insulin resistance, malnutrition can result in immune cell defects and increased risk of mortality from infectious diseases. T cells play an important role in the immune adaptation to both obesity and malnutrition. T cells in obesity have been shown to have an early and critical role in inducing inflammation, accompanying the accumulation of inflammatory macrophages in obese adipose tissue, which are known to promote insulin resistance. How T cells are recruited to adipose tissue and activated in obesity is a topic of considerable interest. Conversely, T cell number is decreased in malnourished individuals, and T cells in the setting of malnutrition have decreased effector function and proliferative capacity. The adipokine leptin, which is secreted in proportion to adipocyte mass, may have a key role in mediating adipocyte-T cell interactions in both obesity and malnutrition, and has been shown to promote effector T cell function and metabolism while inhibiting regulatory T cell proliferation. Additionally, key molecular signals are involved in T cell metabolic adaptation during nutrient stress; among them, the metabolic regulator AMP kinase and the mammalian target of rapamycin have critical roles in regulating T cell number, function, and metabolism. In summary, understanding how T cell number and function are altered in obesity and malnutrition will lead to better understanding of and treatment for diseases where nutritional status determines clinical outcome.

Leukocyte profiles differ between type 1 and type 2 diabetes and are associated with metabolic phenotypes: results from the German Diabetes Study (GDS)

OBJECTIVE

Altered immune reactivity precedes and accompanies type 1 and type 2 diabetes. We hypothesized that the metabolic phenotype relates to the systemic cellular immune status.

RESEARCH DESIGN AND METHODS

A total of 194 metabolically well-controlled patients with type 1 diabetes (n = 62, mean diabetes duration 1.29 years) or type 2 diabetes (n = 132, 1.98 years) and 60 normoglycemic persons underwent blood sampling for automated white blood cell counting (WBC) and flow cytometry. Whole-body insulin sensitivity was measured with hyperinsulinemic-euglycemic clamp tests.

RESULTS

Patients with type 2 diabetes had higher WBC counts than control subjects along with a higher percentage of T cells and activated T helper (Th) and cytotoxic T (Tc) cells but lower proportions of natural killer (NK) cells. In type 1 diabetes, the percentage of activated Th and Tc cells was also higher compared with control subjects, whereas the ratio of regulatory T (Treg) cells to activated Th cells was lower, suggesting diminished regulatory capacity. Parameters of glycemic control related positively to Treg cells only in type 2 diabetes. Upon age, sex, and body mass adjustments, insulin sensitivity correlated positively with monocytes, while circulating lipids correlated positively with T cell subsets in type 1 diabetes.

CONCLUSIONS

Immune cell phenotypes showed distinct frequencies of occurrence in both diabetes types and associate with insulin sensitivity, glycemia, and lipidemia.