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Abstract

Obesity is an epidemic, calling for innovative and reliable pharmacological strategies. Here, we show that ShK-186, a selective and potent blocker of the voltage-gated Kv1.3 channel, counteracts the negative effects of increased caloric intake in mice fed a diet rich in fat and fructose. ShK-186 reduced weight gain, adiposity, and fatty liver; decreased blood levels of cholesterol, sugar, HbA1c, insulin, and leptin; and enhanced peripheral insulin sensitivity. These changes mimic the effects of Kv1.3 gene deletion. ShK-186 did not alter weight gain in mice on a chow diet, suggesting that the obesity-inducing diet enhances sensitivity to Kv1.3 blockade. Several mechanisms may contribute to the therapeutic benefits of ShK-186. ShK-186 therapy activated brown adipose tissue as evidenced by a doubling of glucose uptake, and increased β-oxidation of fatty acids, glycolysis, fatty acid synthesis, and uncoupling protein 1 expression. Activation of brown adipose tissue manifested as augmented oxygen consumption and energy expenditure, with no change in caloric intake, locomotor activity, or thyroid hormone levels. The obesity diet induced Kv1.3 expression in the liver, and ShK-186 caused profound alterations in energy and lipid metabolism in the liver. This action on the liver may underlie the differential effectiveness of ShK-186 in mice fed a chow vs. an obesity diet. Our results highlight the potential use of Kv1.3 blockers for the treatment of obesity and insulin resistance.

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Inflammasome is a central player in the induction of obesity and insulin resistance.

Rinke Stienstra, Janna van Diepen, Cees J. Tack … (2011)

Inflammation plays a key role in the pathogenesis of obesity. Chronic overfeeding leads to macrophage infiltration in the adipose tissue, resulting in proinflammatory cytokine production. Both microbial and endogenous danger signals trigger assembly of the intracellular innate immune sensor Nlrp3, resulting in caspase-1 activation and production of proinflammatory cytokines IL-1β and IL-18. Here, we showed that mice deficient in Nlrp3, apoptosis-associated speck-like protein, and caspase-1 were resistant to the development of high-fat diet-induced obesity, which correlated with protection from obesity-induced insulin resistance. Furthermore, hepatic triglyceride content, adipocyte size, and macrophage infiltration in adipose tissue were all reduced in mice deficient in inflammasome components. Monocyte chemoattractant protein (MCP)-1 is a key molecule that mediates macrophage infiltration. Indeed, defective inflammasome activation was associated with reduced MCP-1 production in adipose tissue. Furthermore, plasma leptin and resistin that affect energy use and insulin sensitivity were also changed by inflammasome-deficiency. Detailed metabolic and molecular phenotyping demonstrated that the inflammasome controls energy expenditure and adipogenic gene expression during chronic overfeeding. These findings reveal a critical function of the inflammasome in obesity and insulin resistance, and suggest inhibition of the inflammasome as a potential therapeutic strategy.

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A role for the NLRP3 inflammasome in metabolic diseases--did Warburg miss inflammation?

Haitao Wen, Jenny P.-Y. Ting, Tyler J O’Neill (2012)

The inflammasome is a protein complex that comprises an intracellular sensor (typically a Nod-like receptor), the precursor procaspase-1 and the adaptor ASC. Inflammasome activation leads to the maturation of caspase-1 and the processing of its substrates, interleukin 1β (IL-1β) and IL-18. Although initially the inflammasome was described as a complex that affects infection and inflammation, subsequent evidence has suggested that inflammasome activation influences many metabolic disorders, including atherosclerosis, type 2 diabetes, gout and obesity. Another feature of inflammation in general and the inflammasome specifically is that the activation process has a profound effect on aerobic glycolysis (the 'Warburg effect'). Here we explore how the Warburg effect might be linked to inflammation and inflammasome activation.

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Obesity increases the production of proinflammatory mediators from adipose tissue T cells and compromises TCR repertoire diversity: implications for systemic inflammation and insulin resistance.

Hyunwon Yang, Yun-Hee Youm, Bolormaa Vandanmagsar … (2010)

Emerging evidence suggests that increases in activated T cell populations in adipose tissue may contribute toward obesity-associated metabolic syndrome. The present study investigates three unanswered questions: 1) Do adipose-resident T cells (ARTs) from lean and obese mice have altered cytokine production in response to TCR ligation?; 2) Do the extralymphoid ARTs possess a unique TCR repertoire compared with lymphoid-resident T cells and whether obesity alters the TCR diversity in specific adipose depots?; and 3) Does short-term elimination of T cells in epididymal fat pad without disturbing the systemic T cell homeostasis regulate inflammation and insulin-action during obesity? We found that obesity reduced the frequency of naive ART cells in s.c. fat and increased the effector-memory populations in visceral fat. The ARTs from diet-induced obese (DIO) mice had a higher frequency of IFN-gamma(+), granzyme B(+) cells, and upon TCR ligation, the ARTs from DIO mice produced increased levels of proinflammatory mediators. Importantly, compared with splenic T cells, ARTs exhibited markedly restricted TCR diversity, which was further compromised by obesity. Acute depletion of T cells from epididymal fat pads improved insulin action in young DIO mice but did not reverse obesity-associated feed forward cascade of chronic systemic inflammation and insulin resistance in middle-aged DIO mice. Collectively, these data establish that ARTs have a restricted TCR-Vbeta repertoire, and T cells contribute toward the complex proinflammatory microenvironment of adipose tissue in obesity. Development of future long-term T cell depletion protocols specific to visceral fat may represent an additional strategy to manage obesity-associated comorbidities.

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PubMed ID:: 23729813

PMC ID:: 3683782

DOI:: 10.1073/pnas.1221206110

ScienceOpen disciplines: Chemistry

Keywords: Adipose Tissue, Brown,drug effects,metabolism,Adiposity,Animals,Blood Glucose,Diet,Energy Intake,Energy Metabolism,Fatty Liver,physiopathology,prevention & control,Insulin Resistance,Kv1.3 Potassium Channel,antagonists & inhibitors,genetics,physiology,Leptin,blood,Lipids,Liver,pathology,Male,Mice,Mice, Inbred C57BL,Motor Activity,Obesity,Oxygen Consumption,Proteins,pharmacology,Weight Gain

Selective Kv1.3 channel blocker as therapeutic for obesity and insulin resistance.

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Most cited references 49

Inflammasome is a central player in the induction of obesity and insulin resistance.

A role for the NLRP3 inflammasome in metabolic diseases--did Warburg miss inflammation?

Obesity increases the production of proinflammatory mediators from adipose tissue T cells and compromises TCR repertoire diversity: implications for systemic inflammation and insulin resistance.

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