@article{MayerLoefflerLozaValdesetal.2019,
  author    = {Mayer, Alexander E. and L{\"o}ffler, Mona C. and Loza Vald{\´e}s, Angel E. and Schmitz, Werner and El-Merahbi, Rabih and Trujillo-Viera, Jonathan and Erk, Manuela and Zhang, Thianzhou and Braun, Ursula and Heikenwalder, Mathias and Leitges, Michael and Schulze, Almut and Sumara, Grzegorz},
  title     = {The kinase PKD3 provides negative feedback on cholesterol and triglyceride synthesis by suppressing insulin signaling},
  series = {Science Signaling},
  journal   = {Science Signaling},
  edition   = {accepted manuscript},
  doi       = {10.1126/scisignal.aav9150},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-250025},
  year      = {2019},
  abstract  = {Hepatic activation of protein kinase C (PKC) isoforms by diacylglycerol (DAG) promotes insulin resistance and contributes to the development of type 2 diabetes (T2D). The closely related protein kinase D (PKD) isoforms act as effectors for DAG and PKC. Here, we showed that PKD3 was the predominant PKD isoform expressed in hepatocytes and was activated by lipid overload. PKD3 suppressed the activity of downstream insulin effectors including the kinase AKT and mechanistic target of rapamycin complex 1 and 2 (mTORC1 and mTORC2). Hepatic deletion of PKD3 in mice improved insulin-induced glucose tolerance. However, increased insulin signaling in the absence of PKD3 promoted lipogenesis mediated by SREBP (sterol regulatory element-binding protein) and consequently increased triglyceride and cholesterol content in the livers of PKD3-deficient mice fed a high-fat diet. Conversely, hepatic-specific overexpression of a constitutively active PKD3 mutant suppressed insulin-induced signaling and caused insulin resistance. Our results indicate that PKD3 provides feedback on hepatic lipid production and suppresses insulin signaling. Therefore, manipulation of PKD3 activity could be used to decrease hepatic lipid content or improve hepatic insulin sensitivity.},
  language  = {en}
}
@article{CaiElMerahbiLoeffleretal.2017,
  author    = {Cai, Kai and El-Merahbi, Rabih and Loeffler, Mona and Mayer, Alexander E. and Sumara, Grzegorz},
  title     = {Ndrg1 promotes adipocyte differentiation and sustains their function},
  series = {Scientific Reports},
  volume    = {7},
  journal   = {Scientific Reports},
  number    = {7191},
  doi       = {10.1038/s41598-017-07497-x},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-170565},
  year      = {2017},
  abstract  = {Adipocytes play a central role in maintaining metabolic homeostasis in the body. Differentiation of adipocyte precursor cells requires the transcriptional activity of peroxisome proliferator-activated receptor-γ (Pparγ) and CCAAT/enhancer binding proteins (C/Ebps). Transcriptional activity is regulated by signaling modules activated by a plethora of hormones and nutrients. Mechanistic target of rapamacin complexes (mTORC) 1 and 2 are central for the coordination of hormonal and nutritional inputs in cells and are essential for adipogenesis. Serum glucocorticoid kinase 1 (Sgk1)-dependent phosphorylation of N-Myc downstream-regulated gene 1 (Ndrg1) is a hallmark of mTORC2 activation in cells. Moreover, Pparγ activation promotes Ndrg1 expression. However, the impact of Ndrg1 on adipocyte differentiation and function has not yet been defined. Here, we show that Ndrg1 expression and its Sgk1-dependent phosphorylation are induced during adipogenesis. Consistently, we demonstrate that Ndrg1 promotes adipocyte differentiation and function by inducing Pparγ expression. Additionally, our results indicate that Ndrg1 is required for C/Ebpα phosphorylation. Moreover, we found that Ndrg1 phosphorylation by Sgk1 promotes adipocyte formation. Taken together, we show that induction of Ndrg1 expression by Pparγ and its phosphorylation by Sgk1 kinase are required for the acquisition of adipocyte characteristics by precursor cells.},
  language  = {en}
}
@article{VieraElMerahbiNieswandtetal.2016,
  author    = {Viera, Jonathan Trujillo and El-Merahbi, Rabih and Nieswandt, Bernhard and Stegner, David and Sumara, Grzegorz},
  title     = {Phospholipases D1 and D2 Suppress Appetite and Protect against Overweight},
  series = {PLoS ONE},
  volume    = {11},
  journal   = {PLoS ONE},
  number    = {6},
  doi       = {10.1371/journal.pone.0157607},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-179729},
  year      = {2016},
  abstract  = {Obesity is a major risk factor predisposing to the development of peripheral insulin resistance and type 2 diabetes (T2D). Elevated food intake and/or decreased energy expenditure promotes body weight gain and acquisition of adipose tissue. Number of studies implicated phospholipase D (PLD) enzymes and their product, phosphatidic acid (PA), in regulation of signaling cascades controlling energy intake, energy dissipation and metabolic homeostasis. However, the impact of PLD enzymes on regulation of metabolism has not been directly determined so far. In this study we utilized mice deficient for two major PLD isoforms, PLD1 and PLD2, to assess the impact of these enzymes on regulation of metabolic homeostasis. We showed that mice lacking PLD1 or PLD2 consume more food than corresponding control animals. Moreover, mice deficient for PLD2, but not PLD1, present reduced energy expenditure. In addition, deletion of either of the PLD enzymes resulted in development of elevated body weight and increased adipose tissue content in aged animals. Consistent with the fact that elevated content of adipose tissue predisposes to the development of hyperlipidemia and insulin resistance, characteristic for the pre-diabetic state, we observed that Pld1\(^{-/-}\) and Pld2\(^{-/-}\) mice present elevated free fatty acids (FFA) levels and are insulin as well as glucose intolerant. In conclusion, our data suggest that deficiency of PLD1 or PLD2 activity promotes development of overweight and diabetes.},
  language  = {en}
}