The impact of cow’s milk-mediated mTORC1-signaling in the initiation and progression of prostate cancer

Nutrition & Metabolism (Impact Factor: 3.26). 08/2012; 9(1):74. DOI: 10.1186/1743-7075-9-74
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Prostate cancer (PCa) is dependent on androgen receptor signaling and aberrations of the PI3K-Akt-mTORC1 pathway mediating excessive and sustained growth signaling. The nutrient-sensive kinase mTORC1 is upregulated in nearly 100 % of advanced human PCas. Oncogenic mTORC1 signaling activates key subsets of mRNAs that cooperate in distinct steps of PCa initiation and progression. Epidemiological evidence points to increased dairy protein consumption as a major dietary risk factor for the development of PCa. mTORC1 is a master regulator of protein synthesis, lipid synthesis and autophagy pathways that couple nutrient sensing to cell growth and cancer. This review provides evidence that PCa initiation and progression are promoted by cow's milk, but not human milk, stimulation of mTORC1 signaling. Mammalian milk is presented as an endocrine signaling system, which activates mTORC1, promotes cell growth and proliferation and suppresses autophagy. Naturally, milkmediated mTORC1 signaling is restricted only to the postnatal growth phase of mammals. However, persistent consumption of cow's milk proteins in humans provide highly insulinotropic branched-chain amino acids (BCAAs) provided by milk's fast hydrolysable whey proteins, which elevate postprandial plasma insulin levels, and increase hepatic IGF-1 plasma concentrations by casein-derived amino acids. BCAAs, insulin and IGF-1 are pivotal activating signals of mTORC1. Increased cow's milk protein-mediated mTORC1 signaling along with constant exposure to commercial cow's milk estrogens derived from pregnant cows may explain the observed association between high dairy consumption and increased risk of PCa in Westernized societies. As well-balanced mTORC1-signaling plays an important role in appropriate prostate morphogenesis and differentiation, exaggerated mTORC1-signaling by high cow's milk consumption predominantly during critical growth phases of prostate development and differentiation may exert long-term adverse effects on prostate health. Attenuation of mTORC1 signaling by contemporary Paleolithic diets and restriction of dairy protein intake, especially during mTORC1-dependent phases of prostate development and differentiation, may offer protection from the most common dairypromoted cancer in men of Western societies.

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Available from: Bodo Melnik, Oct 07, 2015
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    • "mTORC1 steers prostate cancer (PCa) initiation and metastasis [69]. Accumulating evidence links PCa initiation and progression to increased milk protein consumption and milk-mediated activation of mTORC1 [70]. The European Prospective Investigation into Cancer and Nutrition confirmed that high intake of dairy protein is associated with an increased risk of PCa [71]. "
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    ABSTRACT: Milk protein intake has recently been suggested to improve metabolic health. This Perspective provides evidence that metabolic effects of milk protein intake have to be regarded in the context of the individual's pre-existing metabolic and exercise status. Milk proteins provide abundant branched-chain amino acids (BCAAs) and glutamine. Plasma BCAAs and glutamine are increased in obesity and insulin resistance, but decrease after gastric bypass surgery resulting in weight loss and improved insulin sensitivity. Milk protein consumption results in postprandial hyperinsulinemia in obese subjects, increases body weight of overweight adolescents and may thus deteriorate pre-existing metabolic disturbances of obese, insulin resistant individuals.
    Nutrition & Metabolism 10/2013; 10(1):60. DOI:10.1186/1743-7075-10-60 · 3.26 Impact Factor
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    • "Further research should investigate the precise trafficking of milk exosomes, which most likely reach the systemic circulation of the milk recipient. Continued mTORC1-activation by milk-derived exosomal transfer of miR-21 may represent a persistently adverse health effect of regular milk and dairy product intake, which may play an important role for the development and progression of mTORC1-driven diseases of civilization [77-88]. In analogy to the postulated Trojan exosome hypothesis explaining the role of exosomes for the spread of RNA viruses [90], the milk exosome system too appears to function as a Trojan horse “transfecting” the neonate´s metabolism to ensure species-specific mTORC1-driven growth and anabolism. "
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    ABSTRACT: Milk has been recognized to represent a functionally active nutrient system promoting neonatal growth of mammals. Cell growth is regulated by the nutrient-sensitive kinase mechanistic target of rapamycin complex 1 (mTORC1). There is still a lack of information on the mechanisms of mTORC1 up-regulation by milk consumption. This review presents milk as a materno-neonatal relay system functioning by transfer of preferential amino acids, which increase plasma levels of glucose-dependent insulinotropic polypeptide (GIP), glucagon-like peptide-1 (GLP-1), insulin, growth hormone (GH) and insulin-like growth factor-1 (IGF-1) for mTORC1 activation. Importantly, milk exosomes, which regularly contain microRNA-21, most likely represent a genetic transfection system enhancing mTORC1-driven metabolic processes. Whereas human breast milk is the ideal food for infants allowing appropriate postnatal growth and species-specific metabolic programming, persistent high milk signaling during adolescence and adulthood by continued cow s milk consumption may promote mTORC1-driven diseases of civilization.
    Nutrition Journal 07/2013; 12(1):103. DOI:10.1186/1475-2891-12-103 · 2.60 Impact Factor
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    • "Whey protein abuse by athletes and bodybuilders has recently been reported to induce acne flares 33,34. Milk is not a ‘simple food’ but has been identified as an endocrine growth–promoting signalling system of mammals, which activates mTORC1 signalling but inhibits FoxO1-dependent gene regulation 35 (Fig. 1). "
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    ABSTRACT: Acne in adolescents of developed countries is an epidemic skin disease and has currently been linked to the Western diet (WD). It is the intention of this viewpoint to discuss the possible impact of WD-mediated nutrient signalling in the pathogenesis of acne. High glycaemic load and dairy protein consumption both increase insulin/insulin-like growth factor-1 (IGF-1) signalling (IIS) that is superimposed on elevated IGF-1 signalling of puberty. The cell's nutritional status is primarily sensed by the forkhead box transcription factor O1 (FoxO1) and the serine/threonine kinase mammalian target of rapamycin complex 1 (mTORC1). Increased IIS extrudes FoxO1 into the cytoplasm, whereas nuclear FoxO1 suppresses hepatic IGF-1 synthesis and thus impairs somatic growth. FoxO1 attenuates androgen signalling, interacts with regulatory proteins important for sebaceous lipogenesis, regulates the activity of innate and adaptive immunity, antagonizes oxidative stress and most importantly functions as a rheostat of mTORC1, the master regulator of cell growth, proliferation and metabolic homoeostasis. Thus, FoxO1 links nutrient availability to mTORC1-driven processes: increased protein and lipid synthesis, cell proliferation, cell differentiation including hyperproliferation of acroinfundibular keratinocytes, sebaceous gland hyperplasia, increased sebaceous lipogenesis, insulin resistance and increased body mass index. Enhanced androgen, TNF-α and IGF-1 signalling due to genetic polymorphisms promoting the risk of acne all converge in mTORC1 activation, which is further enhanced by nutrient signalling of WD. Deeper insights into the molecular interplay of FoxO1/mTORC1-mediated nutrient signalling are thus of critical importance to understand the impact of WD on the promotion of epidemic acne and more serious mTORC1-driven diseases of civilization.
    Experimental Dermatology 05/2013; 22(5):311-5. DOI:10.1111/exd.12142 · 3.76 Impact Factor
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