Adiponectin Downregulates Hyperglycemia and Reduces Pancreatic Islet Apoptosis After Roux-En-Y Gastric Bypass Surgery

Adipokines and Bacterial Metabolites: A Pivotal Molecular Bridge Linking Obesity and Gut Microbiota Dysbiosis to Target

Adipokines are essential mediators produced by adipose tissue and exert multiple biological functions. In particular, adiponectin, leptin, resistin, IL-6, MCP-1 and PAI-1 play specific roles in the crosstalk between adipose tissue and other organs involved in metabolic, immune and vascular health. During obesity, adipokine imbalance occurs and leads to a low-grade pro-inflammatory status, promoting insulin resistance-related diabetes and its vascular complications. A causal link between obesity and gut microbiota dysbiosis has been demonstrated. The deregulation of gut bacteria communities characterizing this dysbiosis influences the synthesis of bacterial substances including lipopolysaccharides and specific metabolites, generated via the degradation of dietary components, such as short-chain fatty acids, trimethylamine metabolized into trimethylamine-oxide in the liver and indole derivatives. Emerging evidence suggests that these bacterial metabolites modulate signaling pathways involved in adipokine production and action. This review summarizes the current knowledge about the molecular links between gut bacteria-derived metabolites and adipokine imbalance in obesity, and emphasizes their roles in key pathological mechanisms related to oxidative stress, inflammation, insulin resistance and vascular disorder. Given this interaction between adipokines and bacterial metabolites, the review highlights their relevance (i) as complementary clinical biomarkers to better explore the metabolic, inflammatory and vascular complications during obesity and gut microbiota dysbiosis, and (ii) as targets for new antioxidant, anti-inflammatory and prebiotic triple action strategies.

Bariatric Surgery: Targeting pancreatic β cells to treat type II diabetes

Pancreatic β-cell function impairment and insulin resistance are central to the development of obesity-related type 2 diabetes mellitus (T2DM). Bariatric surgery (BS) is a practical treatment approach to treat morbid obesity and achieve lasting T2DM remission. Traditionally, sustained postoperative glycemic control was considered a direct result of decreased nutrient intake and weight loss. However, mounting evidence in recent years implicated a weight-independent mechanism that involves pancreatic islet reconstruction and improved β-cell function. In this article, we summarize the role of β-cell in the pathogenesis of T2DM, review recent research progress focusing on the impact of Roux-en-Y gastric bypass (RYGB) and vertical sleeve gastrectomy (VSG) on pancreatic β-cell pathophysiology, and finally discuss therapeutics that have the potential to assist in the treatment effect of surgery and prevent T2D relapse.

Adiponectin/SIRT1 Axis Induces White Adipose Browning After Vertical Sleeve Gastrectomy of Obese Rats with Type 2 Diabetes

PURPOSE

White adipose tissue (WAT) browning plays a crucial role in energy metabolism. However, it remains unclear whether WAT browning is involved in the adipose reduction following sleeve gastrectomy (SG). Adiponectin is upregulated after Roux-en-Y gastric bypass surgery. The role of adiponectin in SG was further investigated in the current study.

MATERIALS AND METHODS

Diabetic Sprague Dawley rats were randomly divided into control, sham + libitum, sham + food restriction, and sleeve groups. Browning markers, including uncoupling protein 1 (UCP1), peroxisome proliferator-activated receptor (PPAR) γ, and PPARγ coactivator-1 alpha (PGC-1α), were examined 4 weeks after the operation.

RESULTS

UCP1, PPARγ, and PGC-1α expression were significantly higher in the sleeve group compared to the other study groups. The adipose tissue of the sleeve group exhibited tissue weight loss and additional morphological browning features. In addition, adiponectin expression in the sleeve group was significantly increased. Adiponectin upregulated the expression of the browning genes and sirtuin 1 (SIRT1) in 3T3-L1 adipocytes. SIRT1 could increase the WAT browning levels, revealing that adiponectin induced the browning process via the upregulation of SIRT1. Furthermore, SIRT1 represented a positive regulatory feedback loop for adiponectin. SIRT1 activated adenosine monophosphate-activated protein kinase (AMPK), which can mediate WAT browning. Inhibition of the AMPK signaling pathway by dorsomorphin decreased UCP1, PPARγ, and PGC-1α expression. However, additional studies are needed to understand the relationship between adiponectin and glucose homeostasis.

CONCLUSIONS

Sleeve gastrectomy increased adiponectin levels, which in turn upregulated SIRT1. Thus, SIRT1 may function as an endocrine signal to mediate WAT browning.

Effects of Hypnotherapy on Weight Loss and thus on Serum Leptin, Adiponectin, and Irisin Levels in Obese Patients

Objective: This study aimed to investigate effects of hypnotherapy on weight loss and thus on leptin, adiponectin (ADP), and irisin levels in obese patients who presented to the psychiatry outpatient clinic to participate in hypnotherapy sessions to develop a healthy and balanced diet. Methods: The study sample included 32 individuals with a body mass index (BMI) of ≥30 and who completed the 10-week hypnotherapy. First, the Personal Information Form was handed out to the participants and then each participant's weight (in the morning on an empty stomach) and height were measured and BMI was determined. Five-milliliter blood samples were drawn before the first session, and then irisin, leptin, and ADP levels were measured using the enzyme-linked immunosorbent assay method. Then, they participated in hypnotherapy sessions once a week for 10 weeks. At the end of the 10-week hypnotherapy, 5 mL of blood was taken again and the aforementioned biochemical analyses were performed. BMIs were measured again. Results: The mean BMI values of the patients were 33.43 ± 5.28 and 31.45 ± 4.98 at the beginning and end of the hypnotherapy sessions, respectively. Serum leptin, ADP, and irisin levels, which were 9.48 ± 5.48, 6.73 ± 3.27, and 1.43 ± 1.14, respectively, at the beginning of the hypnotherapy sessions, were 6.47 ± 2.69, 7.68 ± 3.34, and 1.53 ± 1.21, respectively, at the end of the hypnotherapy sessions. The results showed that BMI and serum leptin levels decreased significantly after the hypnotherapy sessions, whereas serum ADP and irisin levels increased significantly. Conclusions: This study indicates that hypnotherapy in obesity treatment leads to weight loss in obese patients and thus to considerable changes in leptin, ADP, and irisin levels. Hypnotherapy is easy to apply, cheap, and effective; has no potential for side effects; and can be applied both alone and in combination with other treatments. However, to confirm its effects, further studies should be conducted on this issue.

"Dysfunctions" induced by Roux-en-Y gastric bypass surgery are concomitant with metabolic improvement independent of weight loss

Metabolic surgery has been increasingly recommended for obese diabetic patients, but questions remain as to its molecular mechanism that leads to improved metabolic parameters independently of weight loss from a network viewpoint. We evaluated the role of the Roux limb (RL) in Roux-en-Y gastric bypass (RYGB) surgery in nonobese diabetic rat models. Improvements in metabolic parameters were greater in the long-RL RYGB group. Transcriptome profiles reveal that amelioration of diabetes state following RYGB differs remarkably from both normal and diabetic states. According to functional analysis, RYGB surgery significantly affected a major gene group, i.e., the newly changed group, which represented diabetes-irrelevant genes abnormally expressed after RYGB. We hypothesize that novel "dysfunctions" carried by this newly changed gene group induced by RYGB rebalance diabetic states and contribute to amelioration of metabolic parameters. An unusual increase in cholesterol (CHOL) biosynthesis in RL enriched by the newly changed group was concomitant with ameliorated metabolic parameters, as demonstrated by measurements of physiological parameters and biodistribution analysis using [14C]-labeled glucose. Our findings demonstrate RYGB-induced "dysfunctions" in the newly changed group as a compensatory role contributes to amelioration of diabetes. Rather than attempting to normalize "abnormal" molecules, we suggest a new disease treatment strategy of turning "normal" molecules "abnormal" in order to achieve a new "normal" physiological balance. It further implies a novel strategy for drug discovery, i.e. targeting also on "normal" molecules, which are traditionally ignored in pharmaceutical development.

Adipokines and Adipose Tissue-Related Metabolites, Nuts and Cardiovascular Disease

Adipose tissue is a complex structure responsible for fat storage and releasing polypeptides (adipokines) and metabolites, with systemic actions including body weight balance, appetite regulation, glucose homeostasis, and blood pressure control. Signals sent from different tissues are generated and integrated in adipose tissue; thus, there is a close connection between this endocrine organ and different organs and systems such as the gut and the cardiovascular system. It is known that functional foods, especially different nuts, may be related to a net of molecular mechanisms contributing to cardiometabolic health. Despite being energy-dense foods, nut consumption has been associated with no weight gain, weight loss, and lower risk of becoming overweight or obese. Several studies have reported beneficial effects after nut consumption on glucose control, appetite suppression, metabolites related to adipose tissue and gut microbiota, and on adipokines due to their fatty acid profile, vegetable proteins, l-arginine, dietary fibers, vitamins, minerals, and phytosterols. The aim of this review is to briefly describe possible mechanisms implicated in weight homeostasis related to different nuts, as well as studies that have evaluated the effects of nut consumption on adipokines and metabolites related to adipose tissue and gut microbiota in animal models, healthy individuals, and primary and secondary cardiovascular prevention.

Relevance of Leptin and Other Adipokines in Obesity-Associated Cardiovascular Risk

Obesity, which is a worldwide epidemic, confers increased risk for multiple serious conditions including type 2 diabetes, nonalcoholic fatty liver disease, and cardiovascular diseases. Adipose tissue is considered one of the largest endocrine organs in the body as well as an active tissue for cellular reactions and metabolic homeostasis rather than an inert tissue only for energy storage. The functional pleiotropism of adipose tissue relies on its ability to synthesize and release a large number of hormones, cytokines, extracellular matrix proteins, and growth and vasoactive factors, which are collectively called adipokines known to influence a variety of physiological and pathophysiological processes. In the obese state, excessive visceral fat accumulation causes adipose tissue dysfunctionality that strongly contributes to the onset of obesity-related comorbidities. The mechanisms underlying adipose tissue dysfunction include adipocyte hypertrophy and hyperplasia, increased inflammation, impaired extracellular matrix remodeling, and fibrosis together with an altered secretion of adipokines. This review describes the relevance of specific adipokines in the obesity-associated cardiovascular disease.

Pancreatic islet regeneration through PDX-1/Notch-1/Ngn3 signaling after gastric bypass surgery in db/db mice

In view of the compelling anti-diabetic effects of gastric bypass surgery (GBS) in the treatment of morbid obesity, it is important to clarify its enhancing effect on pancreatic islets, which is closely linked with diabetes remission in obese patients, as well as the underlying mechanisms. The present study evaluated the effects of GBS on glycemic control and other pancreatic changes in db/db mice. The db/db mice were divided into Control, Sham and GBS group. A significant improvement in fasting plasma glucose levels and glucose intolerance were observed post-surgery. At 4 weeks after surgery, further noteworthy changes were observed in the GBS group, including improved islet structure (revealed by immunohistochemical analysis), enhanced insulin secretion, pancreatic hyperplasia and a marked increase in the ratio of β-cells to non-β endocrine cells. Furthermore, notable changes in the levels of Notch-1, pancreatic and duodenal homeobox 1 (PDX-1) and neurogenin 3 (Ngn3) were observed in the GBS group, indicating a potential role of Notch signaling in pancreatic islet regeneration after surgery. In addition, results obtained in PDX-1 knockout (KO), Notch-1 KO and Ngn3 KO mouse models with GBS suggested that elevated PDX-1 resulted in the inhibition of Notch-1, further facilitated Ngn3 and thus promoted pancreatic β-cell regeneration after GBS. The present findings demonstrated that GBS in db/db mice resulted in pancreatic islet regeneration through the PDX-1/Notch-1/Ngn3 signaling pathway, which also reflected the important role of the gastrointestinal system in metabolism control.

Bariatric surgery: beta cells in type 2 diabetes remission

Bariatric surgery is a new emerging treatment that demonstrates a favourable effect on type 2 diabetes, although its underlying mechanisms still remain unknown. After receiving bariatric surgery, beta cells undergo the process of rebirth, which involves apoptosis evasion, regeneration and improved beta-cell function. Therefore, further studies are necessary to elucidate how bariatric surgery can resolve type 2 diabetes. Here, our review focuses mainly on beta cells, the insulin-generating cells, whose biological features change dramatically after bariatric surgery. Copyright © 2015 John Wiley & Sons, Ltd.

Bariatric surgery relieves type 2 diabetes and modulates inflammatory factors and coronary endothelium eNOS/iNOS expression in db/db mice

Overexpression of endothelial nitric oxide synthetase (eNOS)/inducible nitric oxide synthase (iNOS) and inhibition of inflammatory factors can improve vascular function. We hypothesized that bariatric (gastric bypass) surgery could inhibit inflammatory factors and improve the eNOS/iNOS expression of coronary arterioles in the db/db mice. The animals were randomly allocated to the following groups: sham-operated lean mice, lean mice that underwent surgery, sham-operated db/db mice, and db/db mice that underwent surgery (5, 10, 20, and 30 days post-operation). The plasma levels of adiponectin, ghrelin, and IL-6, as well as the protein expression of eNOS/iNOS in coronary arterioles were measured with Western blot. Bariatric surgery decreased body mass and blood glucose levels in db/db mice. Ghrelin receptor and GHS-R1a expression in the hypothalamus were increased in db/db mice, but surgery attenuated GHS-R1a expression. Bariatric surgery elevated plasma concentration and protein expression of adiponectin and ghrelin, and attenuated plasma concentration and protein expression of IL-6. Coronary protein expression of eNOS and SOD2 was lower in the sham-operated db/db mice, and bariatric surgery increased eNOS and SOD2 expression. Gastric bypass surgery upregulates ghrelin and adiponectin expression, and decreases IL-6 expression, which might induce up-regulation of eNOS and SOD2, and down-regulation of iNOS. These interactions could counteract the endothelium dysfunction in type 2 diabetes mellitus.

Islet inflammation: a unifying target for diabetes treatment?

In the past decade, islet inflammation has emerged as a contributor to the loss of functional β cell mass in both type 1 (T1D) and type 2 diabetes (T2D). Evidence supports the idea that overnutrition and insulin resistance result in the production of proinflammatory mediators by β cells. In addition to compromising β cell function and survival, cytokines may recruit macrophages into islets, thus augmenting inflammation. Limited but intriguing data imply a role of adaptive immune response in islet dysfunction in T2D. Clinical trials have validated anti-inflammatory therapies in T2D, whereas immune therapy for T1D remains challenging. Further research is required to improve our understanding of islet inflammatory pathways and to identify more effective therapeutic targets for T1D and T2D.

Postprandial adiponectin levels are associated with improvements in postprandial triglycerides after Roux-en-Y gastric bypass in type 2 diabetic patients

BACKGROUND

Postprandial hypertrygliceridemia is a known factor for cardiovascular disease and is often observed in patients with type 2 diabetes mellitus (T2DM) and visceral adiposity. Adiponectin is a hormone with antiatherogenic and anti-inflammatory effects, which decreases in obesity and T2DM subjects. The weight loss induced by diet or bariatric surgery could be restoring adiponectin levels.

OBJECTIVE

The aim of the study was to evaluate the impact of weight loss induced by bariatric surgery, which could restore adiponectin and triglycerides (TG) levels in obese and diabetic patients.

METHODS

Ten patients with T2DM (BMI 39.3+2.44) were evaluated before and at 7 and 90 days after Roux-en-Y gastric bypass (RYGB). A meal test was performed and plasma insulin, glucagon-like peptide-1 (GLP-1), glucose, TG, and adiponectin levels were measured at fasting and at 30, 60, 90, and 120 min postprandial.

RESULTS

Seven days after surgery, significant reductions in the insulin resistance were observed, while TG and adiponectin levels remained unchanged during the meal test. Ninety days after surgery, TG and glucose levels decreased significantly at fasting, and postprandial, adiponectin, GLP-1, and insulin curves increased significantly after meal ingestion. Both changes in the area under the curve (AUC) of adiponectin correlated with changes in the AUC of TG (R=-0.64, P=0.003) and changes in AUC of adiponectin correlated with changes in total fat mass. No correlation was found between changes in insulin, GLP-1, and TG levels.

CONCLUSIONS

The adiponectin levels may be involved in the mechanism responsible for high TG levels in obese and diabetic patients. These abnormalities can be reversed by RYGB.

The role of adipokines in β-cell failure of type 2 diabetes

β-Cell failure coupled with insulin resistance is a key factor in the development of type 2 diabetes. Changes in circulating levels of adipokines, factors released from adipose tissue, form a significant link between excessive adiposity in obesity and both aforementioned factors. In this review, we consider the published evidence for the role of individual adipokines on the function, proliferation, death and failure of β-cells, focusing on those reported to have the most significant effects (leptin, adiponectin, tumour necrosis factor α, resistin, visfatin, dipeptidyl peptidase IV and apelin). It is apparent that some adipokines have beneficial effects whereas others have detrimental properties; the overall contribution to β-cell failure of changed concentrations of adipokines in the blood of obese pre-diabetic subjects will be highly dependent on the balance between these effects and the interactions between the adipokines, which act on the β-cell via a number of intersecting intracellular signalling pathways. We emphasise the importance, and comparative dearth, of studies into the combined effects of adipokines on β-cells.