Initiating mechanisms that impair gluconeogenic enzymes and spare lipogenic enzymes in diet-induced obesity (DIO) are obscure. Here, we examined insulin signaling to Akt and atypical protein kinase C (aPKC) in liver and muscle and hepatic enzyme expression in mice consuming a moderate high-fat (HF) diet. In HF diet–fed mice, resting/basal and insulin-stimulated Akt and aPKC activities were diminished in muscle, but in liver, these activities were elevated basally and were increased by insulin to normal levels. Despite elevated hepatic Akt activity, FoxO1 phosphorylation, which diminishes gluconeogenesis, was impaired; in contrast, Akt-dependent phosphorylation of glycogenic GSK3β and lipogenic mTOR was elevated. Diminished Akt-dependent FoxO1 phosphorylation was associated with reduced Akt activity associated with scaffold protein WD40/Propeller/FYVE (WD40/ProF), which reportedly facilitates FoxO1 phosphorylation. In contrast, aPKC activity associated with WD40/ProF was increased. Moreover, inhibition of hepatic aPKC reduced its association with WD40/ProF, restored WD40/ProF-associated Akt activity, restored FoxO1 phosphorylation, and corrected excessive expression of hepatic gluconeogenic and lipogenic enzymes. Additionally, Akt and aPKC activities in muscle improved, as did glucose intolerance, weight gain, hepatosteatosis, and hyperlipidemia. We conclude that Akt-dependent FoxO1 phosphorylation occurs on the WD/Propeller/FYVE scaffold in liver and is selectively inhibited in early DIO by diet-induced increases in activity of cocompartmentalized aPKC.

Insulin resistance with resultant hyperinsulinemia refl ects an impairment in insulin-regulated glucose homeostasis, and is a key pathogenic element in obesity, metabolic syndrome features, and type 2 diabetes mellitus (T2DM). In this regard, primary impairments in insulin-stimulated glucose transport in muscle owing to muscle-specifi c knockout of the insulin receptor, the Glut4 glucose transporter, or atypical protein kinase C (aPKC), PKC-can induce insulin resistance and development of obesity, metabolic syndrome, and T2DM ( 1, 2 ). However, dietary excesses appear to be particularly important contributors to the high prevalence of insulin-resistant disorders in Western/Westernized populations. Unfortunately, defects in glucose metabolism and underlying mechanisms that underlie insulin resistance in diet-induced obesity, and are only partly understood. Indeed, both the causes and required forms of dietary indiscretion that lead to insulin resistance are uncertain. In this regard, however, excessive activity of hepatic aPKC seems to be a commonly observed and critically important contributor to insulin resistance in high-fat-fed (HFF) mice ( 3-5 ), muscle-specifi c PKC-knockout mice ( 6 ), obese overtly diabetic ob/ob mice ( 3, 7 ), and type 2 diabetic rats ( 3, 7 ) and humans ( 8 ). Abstract This work was supported by funds from the Department of Veterans Affairs Merit Review Program and the National Institutes of Health Grants (7RO1DK 065969-09) to R.V.F. The authors declare no fi nancial confl icts of interest.Manuscript received 17 July 2014 and in revised form 5 November 2014. Published, JLR Papers in Press, November 13, 2014 DOI 10.1194 Hepatic insulin resistance in ob/ob mice involves increases in ceramide, aPKC activity, and selective impairment of Akt-dependent FoxO1 phosphorylation Abbreviations: ACC, acetyl-coA carboxylase; ACPD, 2-acetyl-1,3-cyclopentanedione; Akt, protein kinase B; aPKC, atypical protein kinase C; FoxO1, forkhead box O1 protein; G6Pase, glucose-6-phosphatase; GSK3 ␤ , glycogen synthase-3 ␤ ; GTT, glucose tolerance test; HFF, high-fatfed; NF B, nuclear factor B; mTOR, mammalian target of rapamycin; PEPCK, phosphoenolpyruvate carboxykinase; PI3K, phosphatidylinositol 3-kinase; SREBP-1c, sterol receptor binding protein-1c; T2DM, type 2 diabetes mellitus; WD40/ProF, 40 kDa WD(tryp-x-x-asp)-repeat propeller/FYVE protein .