@phdthesis{Bishop2022,
  author    = {Bishop, Christopher Allen},
  title     = {Influence of dairy intake on odd-chain fatty acids and energy metabolism},
  doi       = {10.25932/publishup-56154},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-561541},
  school      = {Universit{\"a}t Potsdam},
  pages     = {xii, 104, xv},
  year      = {2022},
  abstract  = {As of late, epidemiological studies have highlighted a strong association of dairy intake with lower disease risk, and similarly with an increased amount of odd-chain fatty acids (OCFA). While the OCFA also demonstrate inverse associations with disease incidence, the direct dietary sources and mode of action of the OCFA remain poorly understood. The overall aim of this thesis was to determine the impact of two main fractions of dairy, milk fat and milk protein, on OCFA levels and their influence on health outcomes under high-fat (HF) diet conditions. Both fractions represent viable sources of OCFA, as milk fats contain a significant amount of OCFA and milk proteins are high in branched chain amino acids (BCAA), namely valine (Val) and isoleucine (Ile), which can produce propionyl-CoA (Pr-CoA), a precursor for endogenous OCFA synthesis, while leucine (Leu) does not. Additionally, this project sought to clarify the specific metabolic effects of the OCFA heptadecanoic acid (C17:0). Both short-term and long-term feeding studies were performed using male C57BL/6JRj mice fed HF diets supplemented with milk fat or C17:0, as well as milk protein or individual BCAA (Val; Leu) to determine their influences on OCFA and metabolic health. Short-term feeding revealed that both milk fractions induce OCFA in vivo, and the increases elicited by milk protein could be, in part, explained by Val intake. In vitro studies using primary hepatocytes further showed an induction of OCFA after Val treatment via de novo lipogenesis and increased α-oxidation. In the long-term studies, both milk fat and milk protein increased hepatic and circulating OCFA levels; however, only milk protein elicited protective effects on adiposity and hepatic fat accumulation—likely mediated by the anti-obesogenic effects of an increased Leu intake. In contrast, Val feeding did not increase OCFA levels nor improve obesity, but rather resulted in glucotoxicity-induced insulin resistance in skeletal muscle mediated by its metabolite 3-hydroxyisobutyrate (3-HIB). Finally, while OCFA levels correlated with improved health outcomes, C17:0 produced negligible effects in preventing HF-diet induced health impairments. The results presented herein demonstrate that the beneficial health outcomes associated with dairy intake are likely mediated through the effects of milk protein, while OCFA levels are likely a mere association and do not play a significant causal role in metabolic health under HF conditions. Furthermore, the highly divergent metabolic effects of the two BCAA, Leu and Val, unraveled herein highlight the importance of protein quality.},
  language  = {en}
}
@article{BishopMachateHenningetal.2022,
  author    = {Bishop, Christopher Allen and Machate, Tina and Henning, Thorsten and Henkel-Oberl{\"a}nder, Janin and P{\"u}schel, Gerhard and Weber, Daniela and Grune, Tilman and Klaus, Susanne and Weitkunat, Karolin},
  title     = {Detrimental effects of branched-chain amino acids in glucose tolerance can be attributed to valine induced glucotoxicity in skeletal muscle},
  series = {Nutrition \& Diabetes},
  volume    = {12},
  journal   = {Nutrition \& Diabetes},
  number    = {1},
  publisher = {Nature Publishing Group},
  address   = {London},
  issn      = {2044-4052},
  doi       = {10.1038/s41387-022-00200-8},
  pages     = {9},
  year      = {2022},
  abstract  = {Objective: Current data regarding the roles of branched-chain amino acids (BCAA) in metabolic health are rather conflicting, as positive and negative effects have been attributed to their intake. Methods: To address this, individual effects of leucine and valine were elucidated in vivo (C57BL/6JRj mice) with a detailed phenotyping of these supplementations in high-fat (HF) diets and further characterization with in vitro approaches (C2C12 myocytes). Results: Here, we demonstrate that under HF conditions, leucine mediates beneficial effects on adiposity and insulin sensitivity, in part due to increasing energy expenditure-likely contributing partially to the beneficial effects of a higher milk protein intake. On the other hand, valine feeding leads to a worsening of HF-induced health impairments, specifically reducing glucose tolerance/ insulin sensitivity. These negative effects are driven by an accumulation of the valine-derived metabolite 3-hydroxyisobutyrate (3HIB). Higher plasma 3-HIB levels increase basal skeletal muscle glucose uptake which drives glucotoxicity and impairs myocyte insulin signaling. Conclusion: These data demonstrate the detrimental role of valine in an HF context and elucidate additional targetable pathways in the etiology of BCAA-induced obesity and insulin resistance.},
  language  = {en}
}
@article{BishopSchulzeKlausetal.2020,
  author    = {Bishop, Christopher Allen and Schulze, Matthias Bernd and Klaus, Susanne and Weitkunat, Karolin},
  title     = {The branched-chain amino acids valine and leucine have differential effects on hepatic lipid metabolism},
  series = {The FASEB journal : the official journal of the Federation of American Societies for Experimental Biology},
  volume    = {34},
  journal   = {The FASEB journal : the official journal of the Federation of American Societies for Experimental Biology},
  number    = {7},
  publisher = {Wiley},
  address   = {Hoboken},
  issn      = {0892-6638},
  doi       = {10.1096/fj.202000195R},
  pages     = {9727 -- 9739},
  year      = {2020},
  abstract  = {Dairy intake, as a source of branched-chain amino acids (BCAA), has been linked to a lower incidence of type-2-diabetes and increased circulating odd-chain fatty acids (OCFA). To understand this connection, we aimed to investigate differences in BCAA metabolism of leucine and valine, a possible source of OCFA, and their role in hepatic metabolism. Male mice were fed a high-fat diet supplemented with leucine and valine for 1 week and phenotypically characterized with a focus on lipid metabolism. Mouse primary hepatocytes were treated with the BCAA or a Ppar alpha activator WY-14643 to systematically examine direct hepatic effects and their mechanisms. Here, we show that only valine supplementation was able to increase hepatic and circulating OCFA levels via two pathways; a PPAR alpha-dependent induction of alpha-oxidation and an increased supply of propionyl-CoA for de novo lipogenesis. Meanwhile, we were able to confirm leucine-mediated effects on the inhibition of food intake and transport of fatty acids, as well as induction of S6 ribosomal protein phosphorylation. Taken together, these data illustrate differential roles of the BCAA in lipid metabolism and provide preliminary evidence that exclusively valine contributes to the endogenous formation of OCFA which is important for a better understanding of these metabolites in metabolic health.},
  language  = {en}
}
@article{WeitkunatBishopWittmuessetal.2021,
  author    = {Weitkunat, Karolin and Bishop, Christopher Allen and Wittm{\"u}ss, Maria and Machate, Tina and Schifelbein, Tina and Schulze, Matthias Bernd and Klaus, Susanne},
  title     = {Effect of microbial status on hepatic odd-chain fatty acids is diet-dependent},
  series = {Nutrients / Molecular Diversity Preservation International (MDPI)},
  volume    = {13},
  journal   = {Nutrients / Molecular Diversity Preservation International (MDPI)},
  number    = {5},
  publisher = {MDPI},
  address   = {Basel},
  issn      = {2072-6643},
  doi       = {10.3390/nu13051546},
  pages     = {15},
  year      = {2021},
  abstract  = {Odd-chain fatty acids (OCFA) are inversely associated with type-2-diabetes in epidemiological studies. They are considered as a biomarker for dairy intake because fermentation in ruminants yields high amounts of propionate, which is used as the primer for lipogenesis. Recently, we demonstrated endogenous OCFA synthesis from propionate in humans and mice, but how this is affected by microbial colonization is still unexplored. Here, we investigated the effect of increasing microbiota complexity on hepatic lipid metabolism and OCFA levels in different dietary settings. Germ-free (GF), gnotobiotic (SIH, simplified human microbiota) or conventional (CONV) C3H/HeOuJ-mice were fed a CHOW or high-fat diet with inulin (HFI) to induce microbial fermentation. We found that hepatic lipogenesis was increased with increasing microbiota complexity, independently of diet. In contrast, OCFA formation was affected by diet as well as microbiota. On CHOW, hepatic OCFA and intestinal gluconeogenesis decreased with increasing microbiota complexity (GF > SIH > CONV), while cecal propionate showed a negative correlation with hepatic OCFA. On HFI, OCFA levels were highest in SIH and positively correlated with cecal propionate. The propionate content in the CHOW diet was 10 times higher than that of HFI. We conclude that bacterial propionate production affects hepatic OCFA formation, unless this effect is masked by dietary propionate intake.},
  language  = {en}
}