Journal Club - Faculty of Public Health, KKU
A word from the Dean and Vice Dean for Research and Academic Service
Dear Students and Staff of the Faculty of Public Health,
A Faculty of a University is an academic institution. 'Academic work' involves to study and reasoning in the field of science. Science is defined as 'an intellectual and practical activity enclosing the structure and behaviour of the physical and natural world through observation and experiment'. Public Health is part of medical science and students and staff of a Faculty of Public Health are privileged to work for the health and wellbeing of the population on various 'specialties'. A student will be introduced to work within the field of science and the academic staff must introduce science and enhance the knowledge of the students. A 'Faculty' within a 'University' should have the ambition, that both groups, students and academic staff, understand that they can best serve the general public when embarking on a lifelong learning process to be up to date in research and service. This requires to see above narrow boundaries and to work against the trend 'to know more and more about less and less'. This first issue of a regular 'Online Journal Club' tries to work towards enhancing the view on scientific topics directly and indirectly related to Public Health.
With best regards
Prof. Dr. Wongsa Laohasiriwong Assoc. Prof. Dr. Pannee Banchonhattakit
Dean, Faculty of Public Health Vice Dean for Research and Academic Service
Journal Club – Faculty of Public Health, KKU
January 2020 (2563)
An easy model how the human metabolism works1
To control non-communicable diseases (NCDs) needs more than to encourage physical activity, refrain from unhealthy diets, sweetened beverages, too much alcohol and to fight against smoking. Not only in the field of nutrition but overall throughout ‘public health’ more attention should be given to human metabolism. However, it is demanding to find its way through the numerous difficult pathways which securing life and causing diseases. In the following a ‘birds view’ on the ‘road map of metabolism’ is provided, which helps to keep on orientation whenever one may be in danger to be lost in the labyrinth of the metabolism.
As a result of the ‘epidemiological transition’ non-communicable diseases (NCDs) emerged as a serious problem for the health delivery system of low- and middle-income countries2,3. To cope with cardiovascular diseases, diabetes, chronic obstructive pulmonary diseases, cancer and other chronic diseases turned out to be demanding for curative- but also public health medicine. While preparing a United Nation meeting in 2018 it was concluded, that no progress in working against NCDs was achieved and could also not expected up to 2030. The statement relates to the policy formulated as the ‘Sustainable Development Goals (SDG)’ aimed to decrease NCDs by one-third up to 2030, under the target 3.4. As the main risk factors smoking, unhealthy diets, physical inactivity and ‘harmful’ use of alcohol have been singled out and preventive measures, called the ‘16 best buy’ strategies are recommended. To strengthen the effort to work against NCDs somewhat rigorous measures by increasing taxes on very popular consumer products4, such as sugar and soft drinks, were not accepted by the UN member countries. To overcome the deadlock, it was recently suggested, those additional strategies of public health to work against NCDs, in supplementing already implemented strategies, might enhance the attempts to decrease premature death through NCDs5. It was argued that major risk factors for NCDs, especially ‘unhealthy nutrition interfere with human metabolism’. In this context advances in molecular biology, genetics, epigenetics and gerontology should be given more attention by academics and staff in the field of public health.
Metabolic pathways – a difficult field
Although ‘public health’ is part of medical sciences, academics within the field might struggle with the overwhelming numerous pathways within the human metabolism. A relatively easy model of how the metabolism works in principle has been suggested and was outlined in Science by Wang, Luan and Medzhitov in 20191. The model is of interest, since its focus on the metabolism about NCDs, but also on immunology and by this to infectious diseases as well. So, it hints towards the dual challenge the health delivery system of low- and middle-income countries face in the attempt to control NCDs and infectious diseases as major public health issues6.
Life history theory (LHT) – beneficial to shed light into the complexity of life
The model is based on the life history theory (LHT)7. The theory interprets strategies used by living organisms in responding to environmental challenges. In exploring the course of life of members of the animal kingdom, including humans, the theory is applied. Numerous disciplines find LHT beneficial when shedding light into the complex variation of life such as psychology8, anthropolgy9, and what matters here, biology7. Key concerns for life are birth, growth, reproductive maturity, fertility, life span and age. There are various lifestyles confronted by a favourable or hostile environment. For survival, the organism is equipped with the ability to grow, to reproduce and to support sustainability, or in terms of the authors ‘maintenance’. The latter means either to enable the organisms to defend itself against infection and injury or let the organism survive even in situations such as a shortage of nutrients. This state is called ‘dormancy’ by the authors. There are two distinctive metabolic processes, namely ‘energy-consuming’ anabolic and an ‘energy-generating’ catabolic processes which enables the metabolism to function.
Anabolic versus catabolic processes
Anabolic processes, permitted by ‘favourable’ environmental conditions, such as richness of nutrients, are supportive for growth and reproduction but are also required to react against infection and injury. Distinctive ‘biosynthetic’ processes are available for different anabolic tasks. Catabolism, on the other hand’, is an ‘energy-generating’ process falling back on the organism’s resources and is triggered by a ‘hostile’ environment such as nutrient deficiency. Energy is needed to shift available resources to ‘defence’ the organism in stress situations such as infections and injury or keep the organism in a state of ‘dormancy’. However, metabolism only can function properly when anabolic and catabolic processes interact with each other. Inflammation to a great extent stimulates anabolic processes to enable immune responses of various kinds of defence. In the state of dormancy, growth and reproduction are less favoured and programs are active to preserve energy.
Role of the hypothalamic-pituitary (HT) axes
Main coordinating programs for growth, reproduction and maintenance are linked to the ‘hypothalamic-pituitary (HP) axes’. Within the complex pathway to growth, the growth hormone-insulin-like growth factor (GH-IGF) plays an important role10. Reproduction is synchronized by the hypothalamic-pituitary-gonadal (HPG) axis11, and within a hostile environment such as infection, injury etc. the HP axes trigger the synthesis of glucocorticoids to ensure the defence of the organism to keep ‘maintenance’12. GH-IGF axis generates IGF-1 resulting in growth and storing of energy which is an anabolic process as well as the effect of sex hormones in increasing muscle- and adipose tissue13, while glucocorticoids support catabolic processes on the level of tissues14.
Homeostasis – a balance between catabolism and anabolism
The three principal life history programs, i.e. growth, reproduction and maintenance, the latter consisting out of defence and dormancy, depend on anabolic and catabolic processes, basically having opposite effects but are intermingled reacting to favourable or unfavourable environments. The important sensor in this complex condition is the HP axis. Inflammatory signals are mended to lead to immune responses and anabolic processes on the cellular level provide macrophages and T cells to fight infection. The sympathetic nervous system and glucocorticoids are more stimulated by anabolic processes. However, it must be kept in mind, that anabolic processes are also involved in energy reservation, which might be an oversupply and stored as fat within the fat tissue. Complex mechanisms within the anabolic metabolism support through anti-inflammatory signals the dysregulation of the metabolism finally resulting in NCDs such as diabetes and obesity. To avoid the dysregulation of the metabolism should be achieved by maintaining ‘homeostasis’ in balancing anabolic and catabolic processes15.
Responsible for the manuscript: F.P. Schelp, Faculty of Public Health, Khon Kaen University, Thailand
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