Multiple antisense oligonucleotides targeted against monoacylglycerol acyltransferase 1 (Mogat1) improve glucose metabolism independently of Mogat1

Abstract

Objective Monoacylglycerol acyltransferase (MGAT) enzymes catalyze the synthesis of diacylglycerol from monoacylglycerol. Previous work has suggested the importance of MGAT activity in the development of obesity-related hepatic insulin resistance. Indeed, antisense oligonucleotide (ASO)-mediated knockdown of Mogat1 mRNA, which encodes MGAT1, reduced hepatic MGAT activity and improved glucose tolerance and insulin resistance in high-fat diet (HFD)-fed mice. However, recent work has suggested that some ASOs may have off-target effects on body weight and metabolic parameters via activation of the interferon alpha/beta receptor 1 (IFNAR-1) pathway. Methods Mice with whole-body Mogat1 knockout or a floxed allele for Mogat1 to allow for liver-specific Mogat1 -knockout (by either a liver-specific transgenic or adeno-associated virus-driven Cre recombinase) were generated. These mice were placed on an HFD, and glucose metabolism and insulin sensitivity were assessed after 16 weeks on diet. In some experiments, mice were treated with control scramble or Mogat1 ASOs in the presence or absence of IFNAR-1 neutralizing antibody. Results Genetic deletion of hepatic Mogat1 , either acutely or chronically, did not improve hepatic steatosis, glucose tolerance, or insulin sensitivity in HFD-fed mice. Furthermore, constitutive Mogat1 knockout in all tissues actually exacerbated HFD-induced obesity, insulin sensitivity, and glucose intolerance on an HFD. Despite markedly reduced Mogat1 expression, liver MGAT activity was unaffected in all knockout mouse models. Mogat1 overexpression in hepatocytes increased liver MGAT activity and TAG content in low-fat-fed mice but did not cause insulin resistance. Multiple Mogat1 ASO sequences improved glucose tolerance in both wild-type and Mogat1 null mice, suggesting an off-target effect. Hepatic IFNAR-1 signaling was activated by multiple Mogat1 ASOs, but its blockade did not prevent the effects of either Mogat1 ASO on glucose homeostasis. Conclusion These results indicate that genetic loss of Mogat1 does not affect hepatic MGAT activity or metabolic homeostasis on HFD and show that multiple Mogat1 ASOs improve glucose metabolism through effects independent of targeting Mogat1 or activation of IFNAR-1 signaling.

Antisense Oligonucleotide Technologies to Combat Obesity and Fatty Liver Disease

“…The authors demonstrated independently via RNAseq and quantitative PCR that the genes Ifit1 , Ifit3 , and Oasl1 were significantly elevated. In contrast to the Mogat1 -ASO studies by Lutkewitte et al (2021) , McCabe et al (2020) demonstrated that the effect on body weight gain was abolished in IFNAR1 knockout mice, indicating that this was an IFNAR1-dependent effect. However, when authors used liver-targeted GalNAc-ASOs, targeting hepatocytes, this response was not observed.…”

“…Epididymal WAT mass and hepatic triacylglycerol abundance were also significantly reduced in Mogat1 -ASO mice, although no improvements in liver inflammation or injury were observed, suggesting that targeting Mogat1 may provide metabolic benefit in early liver disease. Further studies by this group examined the effect of Mogat1 -ASOs in Mogat1 whole body knockout mice (MOKO) fed a high fat diet and demonstrated improved glucose tolerance in these mice ( Lutkewitte et al, 2021 ). These findings recapitulate their abovementioned findings with Mogat1 -ASO, however, they suggest that Mogat1 -ASOs may improve glucose homeostasis independent of Mogat1 knockdown.…”

“…Off-target effects present a substantial challenge to ASO based approaches, as highlighted by studies that administered Mogat1 -ASOs ( Lutkewitte et al, 2021 ). Induction of the type I interferon response observed in this study, was similarly reported in a recent publication by McCabe et al (2020) .…”

Monoacylglycerol O-acyltransferase 1 is required for adipocyte differentiation in vitro but does not affect adiposity in mice

“…Few studies have addressed the requirement for Mogat1 in adipose tissue expansion during the progression of obesity (10)(11)(12) and those that have, used global knockout of Mogat1 rather than deleting in an adipocyte-specific manner. We have recently shown global deletion of Mogat1 actually leads to unexpected increases in weight gain in mice fed a high-fat diet (7). Herein, we sought to determine the functional consequences of Mogat1 depletion during adipocyte differentiation in vitro and expansion in vivo by using mice harboring a floxed allele of Mogat1 and by generating adipocytes with conditional deletion of Mogat1.…”

“…While intestinal MGAT function has been studied for many years, less is known about the physiologic function of MGAT in other organs. We have recently shown that hepatic and constitutive Mogat1 deletion does not affect hepatic steatosis and insulin resistance in mice in the context of diet-induced obesity (7). However, it remains to be determined whether modulating MGAT activity in adipose tissue specifically might have efficacy for preventing or treating obesity-related metabolic disease.…”