Review Article Evidence for the Adverse Effect of Starvation on Bone Quality: a Review of the Literature
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Hindawi Publishing Corporation International Journal of Endocrinology Volume 2015, Article ID 628740, 7 pages http://dx.doi.org/10.1155/2015/628740 Review Article Evidence for the Adverse Effect of Starvation on Bone Quality: A Review of the Literature Janina Kueper,1 Shaul Beyth,2 Meir Liebergall,2 Leon Kaplan,2 and Josh E. Schroeder2 1 Charite´ University of Medicine, Chariteplatz´ 1, 10117 Berlin, Germany 2Department of Orthopedic Surgery, Spine Surgery, Hadassah Medical Center, Kiryat Hadassah, P.O. Box 12000, 91120 Jerusalem, Israel Correspondence should be addressed to Josh E Schroeder; [email protected] Received 9 December 2014; Revised 27 January 2015; Accepted 31 January 2015 Academic Editor: Kristin Eckardt Copyright © 2015 Janina Kueper et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Malnutrition and starvation’s possible adverse impacts on bone health and bone quality first came into the spotlight after the horrors of the Holocaust and the ghettos of World War II. Famine and food restrictions led to a mean caloric intake of 200–800 calories a day in the ghettos and concentration camps, resulting in catabolysis and starvation of the inhabitants and prisoners. Severely increased risks of fracture, poor bone mineral density, and decreased cortical strength were noted in several case series and descriptive reports addressing the medical issues of these individuals. A severe effect of severely diminished food intake and frequently concomitant calcium- and Vitamin D deficiencies was subsequently proven in both animal models and the most common cause of starvation in developed countries is anorexia nervosa. This review attempts to summarize the literature available on the impact of the metabolic response to Starvation on overall bone health and bone quality. 1. Introduction lack of food intake are not uncommon causes of starvation if the diseases are not diagnosed and treated correctly. Starvation describes the most severe form of malnutrition, where a severe deficiency in energy intake evokes a metabolic 1.2. Metabolic Response to Starvation. The initial metabolic response focused on the subsistence of the vital organs to response to starvation does not differ physiologically from the allow for the survival of the affected individual. Nearly 805 postabsorptive phase in between meals which may usually be million people are estimated to suffer from malnutrition. 25% observed in a well-nourished human being [3, 4]. The body of children experience stunted growth due to malnutrition, relies on the dietary glucose supplied by food intake initially, whilst approximately 45% of deaths in children under five can switching to fatty acids once all dietary glucose has been be correlated with starvation [1, 2]. absorbed and utilized. Although most of the body can subsist on the breakdown of fatty acids, the skin, kidney medulla, 1.1. Causes of Starvation. Starvationmaybecausedeitherby erythrocytes, and the brain amongst others require glucose an insufficient caloric intake or an inability to properly digest for their metabolism [5]. To maintain a steady concentration food. Environmental circumstances such as draughts or other of glucose in the blood stream, excess dietary glucose previ- natural catastrophes affecting the agriculture, poverty, or ouslystoredintheliverasglycogenisreducedbacktoglucose forceful withholding in certain geopolitical circumstances [6]. Once this glycogen storage of approximately 120 grams such as war or political prison camps may contribute to is used up, the body must revert to gluconeogenesis. This the unavailability of food. This occurs most commonly in process utilizes mostly glutamine and alanine with glycerol less developed countries. In more developed countries, the to produce glucose in the liver, kidney, and intestine [7, 8]. In primary causes of starvation are medical. Diseases such as parallel, the production of ketones such as 3-hydroxybutyrate anorexia nervosa or depression which lead to a self-induced and acetoacetate, substrates which are able to supply the brain 2 International Journal of Endocrinology as they are able to cross the blood-brain barrier, is initiated havethelowestcarcassweightsoftheirpopulationmostlikely in the liver [9, 10]. With no additional food intake, the body associated with starvation caused through overcrowding and slowly adapts, relying primarily on triglycerides deposited in an increased competition for feed [25, 26]. As opposed to adipose tissue and amino acids stored in smooth-, cardiac-, bears,Mooseshownoadaptationofbonemetabolismto and skeletal muscle as sources for its metabolism. Starvation starvation and exhibit bone opacity reduced almost in half in ensues when protein remains the only source of energy for animals subject to food deprivation. the body. The amount of glucose usually utilized by the body Prospective animal studies most commonly performed is reduced to a minimum, with the metabolic rate of the cells inaratmodelhaveshedgreatlightontheeffectofenergy being decreased significantly to allow for the subsistence of restriction and starvation on fetal bone development in utero, the organism as a whole [11–13]. Individuals who suffer from associated hormones and consequences for the adult animal. chronic starvation adapt, displaying similar basal metabolic Hermanussen et al. [27] demonstrated that stunted growth rates as healthy individuals when adjusted for fat free mass of long bones in both intact and GH-deficient rats induced since the visceral organs with the highest metabolic rates by starvation was not repairable through a reinitiating of such as the brain and the kidneys remain relatively unaffected feeding as the growth spurts responsible for growth simply [14, 15]. Both the reduction of the basal metabolic rate as well ceased during starvation and did not increase once feeding as the commonly present vitamin and nutrient deficiencies was commenced. Banu et al. [28, 29] were able to demonstrate have been hypothesized to contribute to stunted growth, bad a significant loss of endocortical bone as well as cancellous bonequality,andanearlieronsetofosteoporosisinlaterlife. bone area and cancellous bone mineral content in rats with food restrictions in addition to concomitant decreases in tibial muscle mass. Swift et al. [30] reported that food 2. Evidence for the Adverse Effect of restrictions in their rat model led to the greatest decrease Starvation on Bone Quality in bone mineral density in the cancellous bone of the tibia in comparison to restrictions of energy or calcium intake. Starvationmayoccurforeitherlimitedperiodsoftime The total body mineral content was found to be reduced followed by a return to a regular food intake or subsist by 13% whilst the total volumetric bone mineral density at over extended periods of time, thereby leading to a chronic the proximal tibia metaphysic were found to be reduced adaptation to the low caloric intake or absorption. by 8% compared with rats who received ad libitum access to their food and exercise. Talbott et al. [31] examined the 2.1. Animal Studies. Starvation induced changes of the bone effect of food and calcium intake on younger (3 months) have been described and experimented with in various and older (10 months) rats and found that both restrictions animal models. generally led to a higher rate of bone turnover measured The most naturally occurring physiologic cause of star- by urinary [3H]TC excretion. Solely older animals however vation which can be observed in nature occurs during the were found to have decreased bone mineral density resulting hibernation of black, brown, and polar bears. Osteoblastic from the food restriction. Overall, animals with a calcium and activity levels have been reported to decrease tremendously energy controlled diet lost approximately 0.5% bone mineral during hibernation, caused most likely by both immobility density whilst control animals experienced an increased bone and starvation [16]. Nonetheless, the bone area, bone mineral mineral density by more than three percent. Engelbregt et density, and cortical strength have been shown to show al. examined the effect of pre- and postnatal malnutrition on little change when compared to the period of time the bone composition [32]. They found that both pre- and post- bear does not spend in hibernation, returning to baseline natally deprived rats demonstrated a decreased total body after a short period of remobilization [17–20]. Various addi- mineralcontentbyamean0.4and0.9grams,respectively, tional mechanisms including maintenance of osteoblastic when compared to the mean total body mineral content of bone formation, increased parathyroid hormone levels and control animals-2.4 grams. Romano et al. [33]reportedon differential expression of genes responsible for osteoclast adult bone quality of rats exposed to malnutrition in utero formation and differentiation such as Ostf1, Rab9a, and c- through the creation of an artificial uteroplacental insuffi- Fos have been discussed as causes of this phenomenon [21– ciency after calcium supplementation treatment. They found 23]. A reduction of the baseline metabolic rate by 25% that, regardless of the supplementation, rats that experienced and the upregulation of the expression of anabolic genes the consequences of the insufficiency in utero demonstrated of the skeletal muscle- and cartilage metabolism