practise questions
how do adipocytokines contribute to the pathogenesis of type 2 diabetes and cardiovascular disease?
Adipokines are a group of over 600 bioactive molecules produced by the adipose tissue that acts as a paracrine and endocrine hormones that are produced in adipose tissue. These molecules are important in the regulation of diverse processes including appetite and satiety, fat distribution, inflammation and and blood pressure. They act in different organs including adipose tissue, brain, and muscles. Examples of adipokines include, leptin, IL-6, TNF-a and IL-1. The pattern of secretion of these adipokines can can affect adipose tissue function, which can result in both type 2 diabetes and CVD. Both diseases usually start by obesity from either over nutrition, metabolic syndrome and/or genetic predisposition. The development of obesity is what modulates the adipokine profile resulting in a low grade inflammatory state which is associated with the increased risk of insulin resistance and CVD. DIAGRAM of normal adipocytes to obesity (across is over nutrition, genetic disposition and metabolic syndrome.) down from obesity is IL-6, TNF-a, leptin and low adiponectin. to form inflammation-insulin res- atherosclerosis An increase in adipose tissue creates an increase in the adipokine MCP-1 which increases the levels of IL-6 and TNF-a which causes a decrease in insulin signalling and an increase of lipolysis. This causes a decrease in the glucose uptake of muscles and an increase in glycogenolysis and gluconeogenesis in the liver which contributes to insulin resistance and diabetes. The imbalanced production of adipokines in obesity contributes to the pathogenesis of cardiovascular disease. When fat is dysfunctional because of an obesity state, it produces adipokines in an imbalanced inflammatory pattern. There is an increase in the production of resistin, leptin and IL-6 which is associated with CAD (coronary, artery diseases), increased vascular inflammation, increased circulating CRP levels (increased inflammation of the heart) and increased IL-6 and TNFa. These allure linked to an increased risk of atherosclerosis and CVD.
Proteins are an essential macro nutrient:. Discuss the quality of different food sources in terms of protein (50%) Review some current theories about why protein rich foods are thought to increase satiety. (50%)
Proteins are structural and functional elements within every cell of the body and are involved in a wide range of metabolic interactions. All cells and tissues contain protein; therefore, protein is essential for growth and repair. Protein provides the body with approximately 15% of its dietary energy. Proteins are large molecules made up of long chains of amino acids. Amino acids are the building blocks of proteins, the sequence of amino acids in a protein determines the proteins structure, size and shape. Amino acids are needed for immunity, hormone, cellular function, structural tissue and many other functions in the body. Different proteins contain different amounts and different combinations of amino acids. There are 20 amino acids, but 9 of them are essential, meaning we have to ingest them, our body cannot synthesise them. Typically meat sources are high quality in terms of essential aa compared to plant based proteins. For example a T-bone steak grilled contains around 9g of essential aa per 100g whereas boiled kidney beans contain nearly half of that 4g per 100g. this difference in quality of the protein means that vegetarian have to eat a range of protein to get a full profile as they may hit their protein target for the day but not receive all the essential aas. The average adult male needs around 56g of protein per day. The amount varies depending on age, weight, activity and gender as there are times when people will need more e.g breastfeeding. Any excess protein can be used as energy. Foods vary in the amount of protein they provide but the main sources are meat, fish, eggs and milk. The biological value of protein can decrease with cooking techniques, length of time before consumption and the processing of the food. (BV means the amount of protein the body can actually absorb) For example, grilled chicken breast has 32g of protein per 100g compared to red lentils has 7.6g per 100g. Thus, the complimentary combination of plant proteins can be substantial however it does require a much higher intake of the foods to reach the desired amount of protein. Protein and satiety Protein has been linked to increased satiety over other macronutrients like carbohydrates in many short-term studies. However, the mechanism for it is still unknown. There are four current theories around satiety and protein, the first is the thermic effect. The thermic effect of food is the increase in metabolic rate due to the processing of the food, protein is thought to have a higher thermic effect than carbs or fats. This increase in temperature has been linked to satiety and lower food intake, however, not enough to be used as a diet technique. The insulinotropic effect of protein theory suggests that protein induces an insulin response and that this quick release of insulin means that we have an increase in energy quickly, reducing the hunger feeling for food. The gluconeogenesis theory suggests that gluconeogenesis occurs in the intestine in response to amino acids which sends a signal to the brain to increase satiety. This was supported by a study on C-6-P knock out mice having no change in diet compared to the wild type mice eating less on the protein rich diet. The final theory is the serotonin theory of satiety, it suggests that whey peptides activate a serotonin receptor that this increase in 'happiness' reduces any hedonic need for food, increases satiety and decreasing food intake.
discusas good carbs vs bad carbs and the evidence for the health benefits and risks of these carbs and the WHO and UK guidelines
carbohydrates are our bodies essential energy source. when we eat carbs our body converts them into glycogen for energy, if they cannot be turned into glycogen then they are stored as fats. Total carbohydrate intake varies with countries, in the uk and western diets it makes up around 405 of the diet compared to African diets it takes up 80%. complex carbohydrates are usually explained as good carbs, they are foods high in fibre and starch taking a long time to be digested. They contain vitamins, minerals and antioxidants. Slow release energy is provided by these sorts of foods ; whole grains, beans and quinoa. simple carbohydrates are usually described as the bad carbs. They are foods containing natural sugars that are easily broken down by the body and provide quick energy. Fruits, some vegetables and milk. simple carbs are also found in highly processed foods like white sugar and pastries. Although natural foods like vegetables and fruits are simple carbs, they contain essential nutrients and fibre. Dietary fibre comes from both complex and simple carbs, the UK guidelines suggest 45 percent of our diet comes from carbs to meet our fibre requirements, about 25grams of fibre a day. Fiber reduces the risk of many diseases. High intake of fibre has been linked to decreased risk of heart disease, obesity, lowered blood cholesterol and cancer. However high sugar carbs has been shown to increase the likelihood of obesity, cavities in the teeth and metabolic diseases like type 2 diabetes. WHO advises less than 10% of our daily calories should be from sugar because of these negative effects.
is dietary fat good or bad? discuss the role of fat in the body and how different fats may contribute to health diseases?
dietary fats are important for several health related aspects and for optimal functioning of the body. Essential fatty acids (meaning they are fatty acids the body cannot produce, they have to be eaten) are not just a source of energy, they act as a structural component, carry vitamins and many other biological functions. provision of energy: fats are a source of energy in the human diet, together with carbohydrates and proteins. Fat is the most concentrated source of energy, 9kcal oer gram, double that of carbs. Fat is stored in adipose cells all around the body which release fatty acids when energy is required. structural component: the membranes around our cells in our body separate the inside from the outside of the cell and control what molecules enter and leave the cell. these are mainly made of phospholipids, triglycerides and cholesterol. The length and saturation of fatty acids affects the arrangement of the membranes and its fluidity. this influences the biological functions of the cell such as endocytosis. fta is also vital in the structure of the brain, as it is very rich in DHA fats and has a unique fatty acid composition. carrier of vitamins: fat is a carrier for fat-soluble vitamins A,D<E and K and supports their absoprtion in the intestine. Consuming sufficient vitamins and essential fatty acids is essential for adequate intake of these micronutrients. however, too much fat in the diet , especiallly saturated fat, can raise LDL (low-density lipoprotein) cholesterol, which increases the risk of heart disease. Cholesterol can also be carried in the blood by HDL (high density lipoprotein) cholesterol which has a positive effect by taking cholesteroo away from the places in the body where there is too much of it and taking it to th eliver to be disposed of. therefore satruated and trans fats may be considered 'bad' fats as they increase LDL cholesterol levels which increases the risk of diseases like CVD whereas, unsaturated and monounsaturated fats could be seen as 'good' dfats as they help protect the heart by maintaing levels of HDL cholesterol while reducing LDL. example of saturated fats are processed food and cheese , whilst avocados and nuts contain mono and unsatruated fats.
discuss critically the methods used to measure eating behaviours
hunger and appetite are different reactions, hunger is the physical reaction due to low glucose in the blood, it is an instinctive and protective mechanism that ensures the body receives enough fuel to function. Whereas appetite is a sensory or psychological response to food, influenced by emotions and sensory information. Appetite involves hedonistic aspects like the pleasure of eating. It is the integration of these two reactions in eating behaviour that makes it difficult to study and measure. There are several methods that are currently used, including appetite rating scales, lab studies, visual analogue scales, food cravings and three factor eating questionnaires (TFEQs), and food frequency response questionnaires. They each have strengths and weaknesses to their use and measurement of eating behaviour. appetite rating scales measure satiety (fullness) through subjective appetite ratings, bio molecules and measures of energy intake. the questions are given to participants to fill out at specific times like just after eating. sometimes these can be used in lab studies when the food intake can be controlled to compare the hedonistic aspect to see high/low satiety phenotype s. this technique is limited by bias from the participant as they may lie on the questions for many reasons, i.e embarrassment of being hungry still just after eating. another technique is food cravings inventory's, this is used to measure how many times a participant craves food over a period of time. these can be used along with three factor eating questionnaires to get a range of results. a strength of this techniques that it looks at both the hedonistic and physical aspect of eating behaviours. it asks questions on hunger, cognitive restraint, uncontrolled eating, emotional eating and external eating. another strength of this technique is that it can provide possible links to help look for solutions for issues with eating behaviour. food frequency questionnaires are also used to measure eating behaviour, they ask people to keep a food diary. however, a large issues with this is that participants may lie, forget to record food and simple the act of recording food intake can affect the participants eating behaviour subconsciously. These free-living studies therefore lack control of the variables compared to lab-studies where there is high control of food intake and variables. a strength of the free-living studies is however, that it is more similar to real life than lab studies. usually, a combination of all of these measurement techniques are used to get a holistic view of eating behaviours.
discuss the role of leptin and ghrelin in the regulation of appetite and body weight use diagrams to illustrate your answer
hunger is a biological mechanism in place to protect the body from having enough energy/fuel. Hunger is different to appetite, which is related to the psychological want for food because of hedonistic aspects. There are two main hormones involved in the homeostasis of hunger and satiety. Ghrelin and leptin, involved in the feeling of hunger and the feeling of satiety (fullness) respectively. It is the balance of these hormones that affects weight gain or loss. Ghrelin acts through a pathway, it is released in the GI cells, travels through the blood to activate GHSR receptors on the AgR/NPY neurons in the ARC of the hypothalamus in the brain. This activation causes a hunger feeling. Ghrelin also binds and inhibits GHSR receptors on the POMC neurons in the ARC of the hypothalamus which inhibits the production of alpha MSH. This hunger feeling encourages us to eat, we know this hormone is involved in this reaction as mice who had Ghrelin GHSR receptor mutations weighed less compared to wild type and when given a dose of ghrelin they did not increase their food intake whereas wild type mice did. Leptin is the hormone involved in satiety. It is produced by adipose cells (fat cells) all over the body, it binds to and activates receptors on the POMC neuron in the ARC of the hypothalamus, causing the release of alpha-MSH which is then converted to MC4R which causes the fullness feeling. Ghrelin also binds to and inhibits receptors on the AgR/NPY neurons in the ARC of the Hypothalamus which stops the hunger feeling. We know that leptin is involved of the fullness feeling as those with leptin resistance gene have increased weight i.e obesity. DIAGRAM left- adipose cells- leptin-leptin and insulin receptors (brain)- activate POMC- inhib AgRP-NPY-alpha MSH-MC4R-decreased hunger right- GI cells- ghrelin-GHSR- activate AgRP/NPY- inhib POMC-inc hunger
describe the factors that affect the development of the gut microbiota and explain the role of the gut microbiota in metabolic disorders such as obesity and diabetes
the gut microbiota (GM) is the collection of microorganisms that live in the gut,the GM has various important functions within the body and imblanaces in the comp-osition and diversity of those bacteria can cause several diseases. Diet, antibiotics, birthing method and environment can all influence the GM. The GM starts when a baby picks up microbes from the type of birth they go through (vaginal vs c-section, less in the latter) and their first contact with people, usually family, mkaing the baby have a similar GM to parents when young. The majority of the adult microbiome lives in the gut, a common bacteria is lactobilli. One major way the adult GM is affected is antibiotics, it has been found that 30% of the species in the GM are affected by antibiotics as they are non-selective. They also found that it took an average of 4 weeks for the GM to recover from the medication, in some cases the administration of antibiotics permanently changed the GM of the individual. Bifidobacteria is a group of bacteria called probiotics that live in the intensitne and stomach. They help the body perform essential functions like digestion, as 50% of ingested cellulose is broken down by gut bacteria, and help stave off harmful bacteria. The levels of bifidobacteria varies with age, factors that decrease the amount of BB are C-sections, allergies, medication and diet. The less BB you have in your GM, the lower your gut health. If the balance of the community of the GM is disrupted it can lead to gut dysbiosis which may have a role in causing obesity and diabetes. In a healthy gut the microbiome creates short chain fatty acids (SCFA) from digestion, including butyrate and acetate. Butyrate is an anti-obesogenic and acetate is an obesogenic, therefore a good balance of those SCFA is healthy but if there is an imblanace; too much acetate or too little butyrate, it could lead to a leaky gut and increased lipogenesis=increased LPS in the blood stream, making obesity and diabetes more likely to occur. the balance of SCFA can be affected by the diet of a person, for example plant protein ingestion increases BB in the gut and thus increases SCFA balance which strengthens the gut barrier and decreases inflammation= decreased likelihood of diabetes and obesity. Whereas animal protein decreases BB which results in lower levels of SCFA= leaky gut so an increased likelihood of CVD and obesity and diabetes.
describe two examples of vitamins or minerals and our current knowledge about their function, food sources and deficiency.
vitamin C, also known as ascorbit acid is necessary for growth, repair and development of all body tissues. Vitamin C acts as an enzyme co factor in collagen formation and metabolism, and the synthesis of amino acids. Vitamin c also functions as a powerful antioxidant by neutralising free radicals. It also aids in iron absorption by keeping it as Fe2+ in the intestine for absorption. It is absorbed as ascorbate in the intestine by active transport, it does not have a storage organ but is mostly found in the blood. The average middle aged man need 90mg a day of vitamin C. vitamin c is found in lots of natural foods, but like most vitamins, the actual value of vitamin C that the body gets from the food is affected by how long before consumption and the cooking technique. Guava contains 126mg of vitamin C, but the biological of guava may change. we have to get vitamin C from our diet as we have a mutated enzyme due to a diet high in vitamin C, we used to be able to synthesise vita,min C from glucose. vitamin C deficiency results in scurvy, characterised by haemorrhage of the gums and collagenous tissues. vitamin c deficiency can also lead to fatigue, impaired wound healing and bruising of the skin. It is difficult to have too much vitamin C as it is non toxic but it can increase iron absorption too much and cause hemochromatosis. iron is a mineral that is needed in the body for transport and storage of oxygen and electron transport in energy metabolism. the average middle aged man needs 8mg a day. Iron is stored in the liver, bone marrow and spleen. it is absorbed in the duodenum through food. Foods with high levels of iron are red meats, be and and nuts. the absorption of iron can be increased by the ingestion of vitamin C, but can be decreased by ingestion of phytic acid and tannins in tea and cereal, by binding with free iron, reducing the bioavalabiility of iron. A deficiency of iron is called iron deficiency anaemia, common symptoms include fatigue and becoming easily cold. It can be treated by an increase in iron rich foods, so avoiding becoming vegetarian and taking iron supplements.
