Dectin-1 Activation Exacerbates Obesity and Insulin Resistance in the Absence of MyD88.

The underlying mechanism by which MyD88 regulates the development of obesity, metainflammation, and insulin resistance (IR) remains unknown. Global deletion of MyD88 in high-fat diet (HFD)-fed mice resulted in increased weight gain, impaired glucose homeostasis, elevated Dectin-1 expression in adipose tissue (AT), and proinflammatory CD11c+ AT macrophages (ATMs). Dectin-1 KO mice were protected from diet-induced obesity (DIO) and IR and had reduced CD11c+ AT macrophages. Dectin-1 antagonist improved glucose homeostasis and decreased CD11c+ AT macrophages in chow- and HFD-fed MyD88 KO mice. Dectin-1 agonist worsened glucose homeostasis in MyD88 KO mice. Dectin-1 expression is increased in AT from obese individuals. Together, our data indicate that Dectin-1 regulates AT inflammation by promoting CD11c+ AT macrophages in the absence of MyD88 and identify a role for Dectin-1 in chronic inflammatory states, such as obesity. This suggests that Dectin-1 may have therapeutic implications as a biomarker for metabolic dysregulation in humans.

Dectin-1 activation exacerbates obesity and insulin resistance in the absence of myD88

The underlying mechanism by which MyD88 regulates the development of obesity, metainflammation, and insulin resistance (IR) remains unknown. Global deletion of MyD88 in high-fat diet (HFD)fed mice resulted in increased weight gain, impaired glucose homeostasis, elevated Dectin-1 expression in adipose tissue (AT), and proinflammatory CD11c+ AT macrophages (ATMs). Dectin-1 KO mice were protected from diet-induced obesity (DIO) and IR and had reduced CD11c+ AT macrophages. Dectin-1 antagonist improved glucose homeostasis and decreased CD11c+ AT macrophages in chow-and HFD-fed MyD88 KO mice. Dectin-1 agonist worsened glucose homeostasis in MyD88 KO mice. Dectin-1 expression is increased in AT from obese individuals. Together, our data indicate that Dectin-1 regulates AT inflammation by promoting CD11c+ AT macrophages in the absence of MyD88 and identify a role for Dectin-1 in chronic inflammatory states, such as obesity. This suggests that Dectin-1 may have ther-apeutic implications as a biomarker for metabolic dysregulation in humans.

Chemical chaperones curcumin and 4-phenylbutyric acid improve secretion of mutant factor H R127H by fibroblasts from a factor H-deficient patient.

Factor H (FH) is one of the most important regulatory proteins of the alternative pathway of the complement system. Patients with FH deficiency have a higher risk for development of infections and kidney diseases because of the uncontrolled activation and subsequent depletion of the central regulatory component C3 of the complement system. In this study, we investigated the consequences of the Arg(127)His mutation in FH (FH(R127H)) previously described in an FH-deficient patient, on the secretion of this protein by skin fibroblasts in vitro. We observed that, although the patient cells stimulated with IFN-γ were able to synthesize FH(R127H), the mutant protein was largely retained within the endoplasmic reticulum (ER), whereas normal human fibroblasts stimulated with IFN-γ secrete FH without retention in the ER. Moreover, the retention of FH(R127H) provoked enlargement of ER cisterns after treatment with IFN-γ. A similar ER retention was observed in Cos-7 cells expressing the mutant FH(R127H) protein. Despite this deficiency in secretion, we show that the FH(R127H) mutant is capable of functioning as a cofactor in the Factor I-mediated cleavage of C3. We then evaluated whether a treatment could increase the secretion of FH, and observed that the patient's fibroblasts treated with the chemical chaperones 4-phenylbutiric acid or curcumin increased the secretion rate of FH. We propose that these chemical chaperones could be used as alternative therapeutic agents to increase FH plasma levels in FH-deficient patients caused by secretion delay of this regulatory protein.