Severe obesity is a chronic inflammatory disease where various cytokines/adipocytokines play a key role. Pro-inflammatory cytokines such as interleukin 6 (IL-6) and tumour necrosis factor-alpha (TNFalpha) are produced by human adipose tissue dependent on the degree of obesity. Mouse studies suggest a key role of adipose tissue-derived IL-6 in hepatic insulin resistance via modification of liver suppressor of cytokine signalling 3 (SOCS-3) expression.
We examined the effect of excessive weight loss on systemic levels, subcutaneous and visceral adipose tissue and liver expression of IL-6 and TNFalpha in 20 severely obese patients undergoing laparoscopic adjustable gastric banding (LAGB). Furthermore, we studied liver expression of SOCS3, an important regulator of insulin resistance, and fat tissue expression of the anti-inflammatory adipocytokine adiponectin and its receptors. Serum and tissue samples were collected before and 6 months after LAGB surgery.
IL-6/TNFalpha mRNA expression before weight loss were similar in subcutaneous and visceral adipose tissue and much higher compared to hepatic expression. Subcutaneous adipose tissue mRNA expression of both pro-inflammatory cytokines, but especially of IL-6 decreased dramatically after extensive weight loss whereas expression of adiponectin and its receptors increased. Weight loss also led to a significant reduction in liver IL-6 expression, whereas liver TNFalpha mRNA expression did not change. IL-6 and C-reactive protein serum levels decreased after weight loss whereas TNFalpha serum levels were below the detection limit before and after surgery. These effects were paralleled by reduced hepatic SOCS3 expression and improved insulin resistance 6 months after LAGB surgery.
Expression of IL-6 and TNFalpha mRNA is more pronounced in adipose compared to liver tissue in patients with severe obesity. Our results highlight excessive weight loss as a successful anti-inflammatory strategy.
"Interestingly, bariatric surgery might also correct the pro-inflammatory state associated with obesity . Indeed massive weight loss reduces adipose tissue pro-inflammatory mediators such as TNFa and IL6, which results in reduced expression of hepatic SOCS3, thus improving hepatic insulin resistance and inhibiting hepatic inflammation . The only other RCT of dietary intervention and exercise in NAFLD was conducted in type 2 diabetics and did not have histological endpoints . "
"TNFα and IL6 are two important proinflammatory adipocytokines and the expression of both is hugely increased in the fat cells of obese human subjects and patients with IR.178,179 In patients with severe obesity, the mRNA expression of IL6 and TNFα is clearer in adipose compared to liver tissue.180 "
[Show abstract][Hide abstract] ABSTRACT: Non-alcoholic fatty liver disease (NAFLD) is a clinicopathological change characterized by the accumulation of triglycerides in hepatocytes and has frequently been associated with obesity, type 2 diabetes mellitus, hyperlipidemia, and insulin resistance. It is an increasingly recognized condition that has become the most common liver disorder in developed countries, affecting over one-third of the population and is associated with increased cardiovascular- and liver-related mortality. NAFLD is a spectrum of disorders, beginning as simple steatosis. In about 15% of all NAFLD cases, simple steatosis can evolve into non-alcoholic steatohepatitis, a medley of inflammation, hepatocellular injury, and fibrosis, often resulting in cirrhosis and even hepatocellular cancer. However, the molecular mechanism underlying NAFLD progression is not completely understood. Its pathogenesis has often been interpreted by the "double-hit" hypothesis. The primary insult or the "first hit" includes lipid accumulation in the liver, followed by a "second hit" in which proinflammatory mediators induce inflammation, hepatocellular injury, and fibrosis. Nowadays, a more complex model suggests that fatty acids (FAs) and their metabolites may be the true lipotoxic agents that contribute to NAFLD progression; a multiple parallel hits hypothesis has also been suggested. In NAFLD patients, insulin resistance leads to hepatic steatosis via multiple mechanisms. Despite the excess hepatic accumulation of FAs in NAFLD, it has been described that not only de novo FA synthesis is increased, but FAs are also taken up from the serum. Furthermore, a decrease in mitochondrial FA oxidation and secretion of very-low-density lipoproteins has been reported. This review discusses the molecular mechanisms that underlie the pathophysiological changes of hepatic lipid metabolism that contribute to NAFLD.
Clinical and Experimental Gastroenterology 07/2014; 7(1):221-39. DOI:10.2147/CEG.S62831
"There are conflicting reports about the effect(s) of IL-6 on lipid and glucose metabolism and insulin sensitivity. The release of the adipokine IL-6 is related to BMI [127–129]. Fernandez-Real et al. demonstrated a positive association between IL-6 concentrations and the fasting insulin resistance index in 228 healthy volunteers . Subcutaneous injections of recombinant human IL-6 also increase blood glucose and glucagon levels without changes in C-peptide levels, supporting the idea that IL-6 alters insulin sensitivity . "
[Show abstract][Hide abstract] ABSTRACT: The lack of adequate physical activity and obesity created a worldwide pandemic. Obesity is characterized by the deposition of adipose tissue in various parts of the body; it is now evident that adipose tissue also acts as an endocrine organ capable of secreting many cytokines that are though to be involved in the pathophysiology of obesity, insulin resistance, and metabolic syndrome. Adipokines, or adipose tissue-derived proteins, play a pivotal role in this scenario. Increased secretion of proinflammatory adipokines leads to a chronic inflammatory state that is accompanied by insulin resistance and glucose intolerance. Lifestyle change in terms of increased physical activity and exercise is the best nonpharmacological treatment for obesity since these can reduce insulin resistance, counteract the inflammatory state, and improve the lipid profile. There is growing evidence that exercise exerts its beneficial effects partly through alterations in the adipokine profile; that is, exercise increases secretion of anti-inflammatory adipokines and reduces proinflammatory cytokines. In this paper we briefly describe the pathophysiologic role of four important adipokines (adiponectin, leptin, TNF- α , and IL-6) in the metabolic syndrome and review some of the clinical trials that monitored these adipokines as a clinical outcome before and after exercise.
Journal of Diabetes Research 01/2014; 2014(18):726861. DOI:10.1155/2014/726861 · 2.16 Impact Factor
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