The anatomy and physiology of type 2 diabetes, its growing prevalence, how it affects wellbeing and the impact on the health service are explored in this first article in a new series

ABSTRACT Many people in the UK are living with diabetes, and most have type 2 diabetes. The prevalence of type 2 diabetes is rising nationally and globally in line with growing obesity

levels. It is important that nurses are aware of why type 2 diabetes develops and how it can be prevented, put into remission and treated. This article, the first in a series of three on

type 2 diabetes, considers the prevalence of diabetes and how the condition affects health and wellbeing. CITATION: NAZARKO L (2023) Type 2 diabetes: causes, diagnosis and impact on health

this series INTRODUCTION In the UK >5 million people are estimated to have diabetes; most have type 2 diabetes mellitus (T2DM), which is generally preventable (Diabetes UK, nd). Diabetes

increases the risk of developing long-term conditions, some of which – such as blindness and amputation – are life changing. This article will consider the prevalence of T2DM and how it

affects a person’s health and wellbeing. WHAT IS T2DM? Diabetes has been defined as “a chronic, metabolic disease characterised by elevated levels of blood glucose (or blood sugar), which

leads over time to serious damage to the heart, blood vessels, eyes, kidneys and nerves” (World Health Organization (WHO), nd). T2DM is the most common type and occurs when the body becomes

resistant to, or does not produce enough, insulin. T2DM mainly occurs in adults and over the past 30 years global prevalence has risen dramatically (WHO, nd). By contrast, type 1 diabetes,

once known as juvenile diabetes or insulin-dependent diabetes, is a chronic condition in which the pancreas produces little or no insulin by itself (WHO, nd). WHY DOES T2DM OCCUR? Blood

glucose is regulated by the pancreas, which has digestive and glucose regulation functions. Located in the curve of the duodenum (Fig 1), which is the first section of the small intestine,

the pancreas measures 12.5-15cm (Tortora and Derrickson, 2017). It consists of a head, a body and a tail. The pancreas is made up of two types of cells: * Those with an exocrine function

related to digestion; * Those with an endocrine function related to glucose regulation. Most of the pancreas comprises clusters, which are called acinar cells or acini. The acini produce

digestive enzymes. Scattered throughout the pancreas are endocrine cells, known as pancreatic islets; these are also called islets of Langerhans. There are thought to be around 1-2 million

islets of Langerhans in the pancreas (Tortora and Derrickson, 2017). Each islet is composed of five different endocrine cell types: * Alpha; * Beta; * Delta; * Epsilon; * Gamma. These

secrete at least five hormones respectively, including: * Glucagon; * Insulin; * Amylin; * Somatostatin; * Ghrelin; * Pancreatic polypeptide (PP) (El Sayed and Mukherjee, 2023; Tortora and

Derrickson, 2017). The interactions of pancreatic hormones are complex and not yet fully understood (El Sayed and Mukherjee, 2023; Tortora and Derrickson, 2017). Table 1 explains their

function. The main hormones responsible for regulating blood glucose are insulin and glucagon. Insulin is secreted from the beta cells in the pancreas. It maintains glucose homeostasis so

blood glucose remains within a narrow healthy range. Insulin lowers blood sugar. Normally, when we eat, levels of glucose in the blood rise and insulin is produced and released directly into

the bloodstream. Insulin binds to insulin receptors and this triggers the movement of glucose transporter type 4 – often abbreviated to GLUT4 – inside the cells. This enables cells in the

body to use glucose and convert it to energy (Taylor and Knight, 2021). When the body has enough energy, the liver takes glucose and stores it as glycogen. The liver can store up to 5% of

its mass as glycogen. When the liver has reached its storage capacity, insulin signals fat cells to take up glucose to be stored as triglycerides (El Sayed and Mukherjee, 2023; Tortora and

Derrickson, 2017). Glucagon is secreted from the alpha cells of the pancreas and stimulates the release of glycogen stored in the liver. This raises blood glucose (Tortora and Derrickson,

2017). T2DM is a progressive disease characterised by elevated blood glucose levels. Blood glucose levels are elevated because of a decline in beta-cell function. This may be accompanied by

reduced insulin sensitivity – this is known as insulin resistance (Heo and Choi, 2019). HOW COMMON IS DIABETES? Over the past 80 years, the number of people in the UK with diabetes has risen

from 200,000 to an estimated 5 million (Diabetes UK, nd). Globally, 537 million people have diabetes (International Diabetes Federation (IDF), 2021). In 2021, 6.7 million people died of

diabetes globally, which equates to one person every five seconds; the condition is one of the top causes of premature death (IDF, 2021). In the UK in 2021, 13.6 million people were at

increased risk of T2DM, and the number of people with a diabetes diagnosis is expected to rise to 5.5 million by 2030 (Diabetes UK, nd). DIAGNOSING DIABETES National Institute for Health and

Care Excellence (NICE) (2023) guidance recommends testing for diabetes if a person presents with persistent hyperglycaemia and has clinical features of diabetes. Table 2 provides a full

overview of these features, which include: * Polydipsia (excessive thirst); * Polyuria (increased urine output); * Polyphagia (increased appetite accompanied by weight loss); * Tiredness and

irritability; * Poor wound healing (NICE, 2023). An HbA1c blood test is commonly used to diagnose or monitor diabetes (London Diabetes Clinical Network, 2018). HbA1c measures glycated

haemoglobin. When haemoglobin – the protein in red blood cells that transports oxygen – attaches to glucose in the blood, the process is known as glycation. An HbA1c test measures the amount

of glucose attached to the haemoglobin over a two-to-three-month period, as this is how long the blood cells typically last in the body (MedlinePlus, 2022). An HbA1c test is not recommended

for: * People with a disease affecting haemoglobin, such as sickle cell disease; * People with chronic kidney disease; * People on haemodialysis; * Pregnant women. In such cases a different

test, glycated albumin, may be used (Zendjabil, 2020). WHO (2020) states that diabetes is defined as an HbA1c of >48mmol/mol. HbA1c levels indicate average blood glucose levels over time

and, the higher the HbA1c, the greater the risk of developing diabetes-related complications. Table 3 illustrates how HbA1c correlates with average blood glucose levels (Diabetes.co.uk,

2023a). HOW DIABETES AFFECTS HEALTH AND WELLBEING People with undiagnosed, or poorly managed, diabetes can feel very unwell. High blood glucose levels cause a lack of energy and increased

risk of tissue damage. Diabetes can affect a person’s life and that of their family. A person with poorly managed diabetes may not appreciate how unwell they are until diabetes control

improves: symptoms can develop slowly and they may think it is normal to lack stamina and tire easily. T2DM was once a disease that affected middle-aged and older people, but it is now

affecting many younger adults and children (Romieu et al, 2017; Kao and Sabin, 2016). People who develop T2DM aged <40 years are more likely to experience rapid deterioration in

pancreatic function and have a greater incidence of adverse outcomes (Magliano et al, 2020). Undiagnosed diabetes, or that which is poorly managed, is associated with premature death

(Harding et al, 2016). Diabetes can also lead to problems with vision and circulation, and increases the risk of: * Heart disease; * Stroke; * Dementia; * Nerve damage; * Sexual difficulties

(Diabetes.co.uk, 2023b). The main complications of diabetes are: * Microvascular disease affecting the eyes, nerves and kidneys; * Macrovascular disease, leading to cardiovascular disease,

cerebrovascular disease and lower-extremity artery disease (Chawla et al, 2016). Every week, diabetes leads to 184 amputations, >770 strokes, 590 heart attacks and 2,300 cases of heart

failure in the UK (Diabetes UK, nd) (Fig 2). HOW DIABETES AFFECTS THE HEALTH SERVICE People with diabetes are admitted to hospital more often than the general population, especially as

emergencies, and stay, on average, longer as inpatients (Dhatariya et al, 2020). Diabetes is thought to cost the NHS £10bn per year – around 10% of the NHS budget (NHS England, 2022); the

money is often spent treating the complications of an avoidable disease. T2DM can have a profound effect on a person’s health and increases the risk of renal failure, heart attack, stroke,

dementia, loss of vision and limb amputation. This topic will be covered in detail in the next article in this series. The increase in T2DM is a tragedy that is unfolding before our eyes. It

is a preventable global pandemic that unnecessarily claims the lives of many people: to put it into context, in 2021, 6.7 million people died of diabetes (IDF, 2021), while Covid-19, over

several years, has claimed more than 6.95 million lives so far (as of 6 September 2023) (WHO, 2023). We must begin to apply the same level of effort to reducing the number of lives lost and

marred by T2DM as we do to preventing Covid-19. CONCLUSION Most people in the UK who have diabetes have T2DM, and the number with this type of diabetes is rising year on year. People with

T2DM may experience a life marred by ill health. The NHS is struggling to provide care to ever-increasing numbers of people with T2DM but it does not have to be this way. We can work with

people to reduce the risks of T2DM and induce remission if diabetes occurs. KEY POINTS * Globally, diabetes claimed the lives of 6.7 million people in 2021 * In the UK, 1 in 16 adults has

diabetes and most of these have type 2 diabetes * The incidence of diabetes has reached epidemic proportions globally and nationally * It is predicted that there will be 5.5 million people

in the UK with diabetes by 2030 if action is not taken * Type 2 diabetes shortens lives and impairs health, but is often preventable ALSO IN THIS SERIES RESOURCES Go here to access a

calculator that can be used to: * Convert HbA1c levels to blood–glucose levels * Provide an average blood glucose level * The next article in this series will discuss how we can work with

people to reduce the risk of T2DM and how it is possible to induce remission through diet and exercise REFERENCES CHAWLA A ET AL (2016) Microvasular and macrovascular complications in

diabetes mellitus: distinct or continuum? _Indian Journal of Endocrinology and Metabolism_; 20: 4, 546-551. DHATARIYA K ET AL (2020) Safe care for people with diabetes in hospital. _Clinical

Medicine_; 20: 1, 21–27. DIABETES UK (nd) How many people in the UK have diabetes?_ diabetes.org.uk_ (accessed 12 September 2023). DIABETES.CO.UK (2023a) Convert HbA1c to average blood

sugar level. _diabetes.co.uk_, 25 January (accessed 12 September 2023). DIABETES.CO.UK (2023b) Diabetes and erectile dysfunction. _diabetes.co.uk_, 25 January (accessed 13 September 2023).

EL SAYED SA, MUKHERJEE S (2023) _Physiology, Pancreas_. StatsPearls Publishing. HARDING JL ET AL (2016) Age-specific trends from 2000-2011 in all-cause and cause-specific mortality in type 1

and type 2 diabetes: a cohort study of more than one million people. _Diabetes Care_; 39: 6, 1018-1026. HEO CU, CHOI C-I (2019) Current progress in pharmacogenetics of second-line

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K-T, SABIN MA (2016) Type 2 diabetes mellitus in children and adolescents. _Australian Family Physician_; 45: 6, 401-406. LONDON DIABETES CLINICAL NETWORK (2018) _Consensus Approach to the

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Endocrinology_; 16: 6, 321-331. MEDLINEPLUS (2022) Hemoglobin A1C (Hba1c) test. _medlineplus.gov_, 6 September (accessed 12 September 2023). NATIONAL INSTITUTE FOR HEALTH AND CARE EXCELLENCE

(2023) Diabetes – type 2: when should I suspect type 2 diabetes in an adult? _cks.nice.org.uk_, July (accessed 7 August 2023). NAZARKO L (2016) Diabetes care: prevalence and types. _British

Journal of Healthcare Assistants_; 10: 7, 323-329. NHS ENGLAND (2022) NHS prevention programme cuts chances of type 2 diabetes for thousands. _england.nhs.uk_, 28 March (accessed 12

September 2023). ROMIEU I ET AL (2017) Energy balance and obesity: what are the main drivers? _Cancer Causes and Control_; 28: 3, 247-258. TAYLOR J, KNIGHT J (2021) Endocrine system 6:

pancreas, stomach, small intestine and liver. _Nursing Times_ [online]; 117: 10, 46-50. TORTORA GJ, DERRICKSON BH (2017) _Tortora’s Principles of Anatomy and Physiology_. Wiley. WORLD HEALTH

ORGANIZATION (nd) Diabetes. _who.int_ (accessed 12 September 2023). WORLD HEALTH ORGANIZATION (2023) WHO coronavirus (Covid-19) dashboard. _covid19.who.in_t (accessed 12 September 2023).

WORLD HEALTH ORGANIZATION (2020) _HEARTS-D: Diagnosis and Management of Type 2 Diabetes_. WHO. ZENDJABIL M (2020) Glycated albumin. _Clinica Chimica Acta_; 502: 240-244.   HELP NURSING TIMES

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