Jeroen Nijhuis

Neutrophil Activation in Morbid Obesity, Chronic Activation of Acute Inflammation

Recent studies show that morbid obesity is associated with activation of the innate immune response. Neutrophil activation is a fundamental process in the innate immune response. Therefore, the activation state of neutrophils in severely obese subjects and the effect of bariatric surgery on neutrophil activation was evaluated. Neutrophil activation was assessed by measuring circulating concentrations of myeloperoxidase (MPO) and calprotectin in 37 severely obese and 9 control subjects (enzyme‐linked immunosorbent assay). Moreover, membrane expression of CD66b on circulating neutrophils was measured using flow cytometry in a group of seven severely obese and six control subjects. Immunohistochemical detection of MPO was performed in adipose and muscle tissue. Plasma MPO and calprotectin levels were significantly increased in severely obese subjects as compared to healthy controls, 27.1 ± 10.8 vs. 17.3 ± 5.5 ng/ml (P < 0.001) and 115.5 ± 43.5 vs. 65.1 ± 23.1 ng/ml (P < 0.001) for MPO and calprotectin, respectively. In line, CD66b expression was significantly increased in severely obese individuals, 177.3 ± 43.7 vs. 129.7 ± 9.2 (mean fluorescence intensity) (P < 0.01). Bariatric surgery resulted in decreased calprotectin, but MPO plasma levels remained elevated. Adipose and muscle tissue did not contain increased numbers of MPO expressing cells in severely obese individuals. These results point out that circulating neutrophils are activated to a greater extent in severely obese subjects. Our data support the finding that the innate immune system is activated in severely obese individuals. Moreover, because neutrophils have a short life span, this indicates that the chronic inflammatory condition associated with morbid obesity is characterized by a continuous activation of the innate immune system.

Increased Hepatic Myeloperoxidase Activity in Obese Subjects with Nonalcoholic Steatohepatitis

Inflammation and oxidative stress are considered critical factors in the progression of nonalcoholic fatty liver disease. Myeloperoxidase (MPO) is an important neutrophil enzyme that can generate aggressive oxidants; therefore, we studied the association between MPO and nonalcoholic fatty liver disease. The distribution of inflammatory cells containing MPO in liver biopsies of 40 severely obese subjects with either nonalcoholic steatohepatitis (NASH) (n = 22) or simple steatosis (n = 18) was investigated by immunohistochemistry. MPO-derived oxidative protein modifications were identified by immunohistochemistry and correlated to hepatic gene expression of CXC chemokines and M1/M2 macrophage markers as determined by quantitative PCR. MPO plasma levels were determined by ELISA. The number of hepatic neutrophils and MPO-positive Kupffer cells was increased in NASH and was accompanied by accumulation of hypochlorite-modified and nitrated proteins, which can be generated by the MPO-H2O2 system. Liver CXC chemokine expression was higher in patients with accumulation of MPO-mediated oxidation products and correlated with hepatic neutrophil sequestration. Plasma MPO levels were elevated in NASH patients. Interestingly, neutrophils frequently surrounded steatotic hepatocytes, resembling the crown-like structures found in obese adipose tissue. Furthermore, hepatic M2 macrophage marker gene expression was increased in NASH. Our data indicate that accumulation of MPO-mediated oxidation products, partly derived from Kupffer cell MPO, is associated with induction of CXC chemokines and hepatic neutrophil infiltration and may contribute to the development of NASH.

Ghrelin, Leptin and Insulin Levels after Restrictive Surgery: a 2-Year Follow-up Study

Background: Ghrelin is a recently discovered orexigenic gastric hormone, whose production is induced by lack of food in the stomach. In morbidly obese individuals, ghrelin levels are low compared to lean persons. During dieting, plasma ghrelin levels increase, leading to an orexigenic signal, which could explain the lack of success of dieting in morbidly obese individuals. Morbid obesity is best treated with bariatric surgery, in which gastric bypass is reported to be more effective than restrictive surgery. A possible explanation could be the difference in plasma ghrelin levels after both operations for bariatric surgery. In this study, plasma ghrelin levels were investigated during a 2-year follow-up. Methods: 17 morbidly obese patients received gastric restrictive surgery. Plasma ghrelin, leptin and insulin levels were evaluated preoperatively and 1 year and 2 years postoperatively. Results: BMI decreased from 47.5 ± 6.2 kg/m2 to 33.2 ± 5.8 kg/m2 (P <0.001). Plasma ghrelin levels were significantly increased 1 year (P <0.05) and 2 years (P <0.02) postoperatively. Fasting plasma leptin and insulin levels were significantly lower at 2 years after surgery (P <0.001). Conclusion: After gastric restrictive surgery, ghrelin levels increased, in contrast to the reported fall in ghrelin levels after gastric bypass. This difference in ghrelin levels between these operations may be the k ey to understanding the superiority of gastric bypass in sustaining weight loss compared with restrictive surgery.

Activation of the complement system in human nonalcoholic fatty liver disease

Activation of the innate immune system plays a major role in nonalcoholic fatty liver disease (NAFLD). The complement system is an important component of innate immunity that recognizes danger signals such as tissue injury. We aimed to determine whether activation of the complement system occurs in NAFLD, to identify initiating pathways, and to assess the relation between complement activation, NAFLD severity, apoptosis, and inflammatory parameters. Liver biopsies of 43 obese subjects with various degrees of NAFLD and of 10 healthy controls were analyzed for deposition of complement factors C1q, mannose‐binding lectin (MBL), C4d, activated C3, and membrane attack complex (MAC)‐associated C9. Furthermore, hepatic neutrophil infiltration, apoptosis, and pro‐inflammatory cytokine expression were quantified. Whereas complement activation was undetectable in the liver of healthy subjects, 74% of the NAFLD patients showed hepatic deposition of activated C3 and C4d. C1q as well as MBL accumulation was found in most activated C3‐positive patients. Strikingly, 50% of activated C3‐positive patients also displayed MAC‐associated C9 deposition. Deposition of complement factors was predominantly seen around hepatocytes with macrovesicular steatosis. Subjects showing accumulation of activated C3 displayed increased numbers of apoptotic cells. Importantly, hepatic neutrophil infiltration as well as interleukin (IL)‐8 and IL‐6 expression was significantly higher in patients showing activated C3 deposition, whereas patients with C9 deposition additionally had increased IL‐1β expression. Moreover, nonalcoholic steatohepatitis (NASH) was more prevalent in patients showing hepatic C9 or activated C3 deposition. Conclusion: There is widespread activation of the complement system in NAFLD, which is associated with disease severity. This may have important implications for the pathogenesis and progression of NAFLD given the function of complement factors in clearance of apoptotic cells, hepatic fibrosis, and liver regeneration. (HEPATOLOGY 2009.)

Endothelial activation markers and their key regulators after restrictive bariatric surgery.

Objective: Increased plasma levels of endothelial activation markers in obese subjects reflect the positive association between cardiovascular diseases and obesity. The pro‐inflammatory state associated with obesity is thought to play a major role in endothelial cell activation in severely obese individuals. Previous studies demonstrated that long‐term weight loss after bariatric surgery is accompanied by a decreased proinflammatory state. However, little is known about the long‐term effects of bariatric surgery on endothelial cell activation.

Leptin in Morbidly Obese Patients: No Role for Treatment of Morbid Obesity but Important in the Postoperative Immune Response

Despite the current opinion that leptin can no longer be seen as a hormone which could be used therapeutically to prevent an energy surplus (it rather protects the organism for an energy deficit), leptin may still have an impact in clinical medicine. Leptin was shown to have several important functions. The pleiotropic properties of leptin include a regulatory function in the immune system. Reviewing the effects of leptin on different parts of the immune system reveals that the immune system is deregulated in an environment low in leptin. A strong reduction in leptin levels occurs in situations of starvation as seen after bariatric surgery. We postulate the hypothesis that the starvation-induced postoperative decrease of leptin is causative of the more serious course of complications observed after bariatric surgery.

Early insulin sensitivity after restrictive bariatric surgery, inconsistency between HOMA-IR and steady-state plasma glucose levels

BACKGROUND The low-grade inflammatory condition present in morbid obesity is thought to play a causative role in the pathophysiology of insulin resistance (IR). Bariatric surgery fails to improve this inflammatory condition during the first months after surgery. Considering the close relation between inflammation and IR, we conducted a study in which insulin sensitivity was measured during the first months after bariatric surgery. Different methods to measure IR shortly after bariatric surgery have given inconsistent data. For example, the Homeostatic Model Assessment of Insulin Resistance (HOMA-IR) levels have been reported to decrease rapidly after bariatric surgery, although clamp techniques have shown sustained insulin resistance. In the present study, we evaluated the use of steady-state plasma glucose (SSPG) levels to assess insulin sensitivity 2 months after bariatric surgery. METHODS Insulin sensitivity was measured using HOMA-IR and SSPG levels in 11 subjects before surgery and at 26% excess weight loss (approximately 2 months after restrictive bariatric surgery). RESULTS The SSPG levels after 26% excess weight loss did not differ from the SSPG levels before surgery (14.3 +/- 5.4 versus 14.4 +/- 2.7 mmol/L). In contrast, the HOMA-IR values had decreased significantly (3.59 +/- 1.99 versus 2.09 +/- 1.02). CONCLUSION During the first months after restrictive bariatric surgery, we observed a discrepancy between the HOMA-IR and SSPG levels. In contrast to the HOMA-IR values, the SSPG levels had not improved, which could be explained by the ongoing inflammatory state after bariatric surgery. These results suggest that during the first months after restrictive bariatric surgery, HOMA-IR might not be an adequate marker of insulin sensitivity.

Low number of omental preadipocytes with high leptin and low adiponectin secretion is associated with high fasting plasma glucose levels in obese subjects

Objective:  This study investigates whether fasting plasma glucose (FPG) levels in obese subjects are associated with the number of preadipocytes and their adipokine‐secretion capabilities.