Type 1 Diabetes – Etiology and treatment (2)

Here’s my first post about the book. I’ve now read roughly two-thirds of it (400 pages) and I like this book.

Not all chapters give me a lot of new insights – for example I know a lot more about the topic covered in the chapter about the Relationship Between Metabolic Control and Complications in Diabetes than what is covered in the book, and the ten-page chapter on The Diabetic Foot which I’ll soon read will not match the detailed coverage in Edmonds et al. – but anything else would be very surprising, and most chapters contain some stuff which I did not know. I understand the mechanisms driving microvascular complications better now than I did, but I’m still fuzzy on some of the details; like some of the genetics stuff in the first chapters that part of the book is very technical, and so I decided against covering that stuff in detail here. If you’re curious about that stuff, here’s a relevant link covering some of what the book has on that topic, in what seems from a brief skim to be a roughly similar amount of detail. To people who know nothing about this stuff (i.e., people who haven’t read my posts on related topics in the past…), diabetes in the long term causes damage to small and large blood vessels and may cause various forms of nerve damage (neuropathies) – here’s a brief and non-technical overview article. The connection between hyperglycemia – too high blood glucose – and small vessel disease is better established (and very well established at this point) than is the connection between hyperglycemia and large vessel disease, and although it may not sound too bad that small blood vessels are damaged, the consequences can be dire; long-term diabetes may among other things cause blindness and kidney failure. How precisely the blood vessels are damaged in diabetics was not very well understood for a very long time, but significant progress seems to have been made over the last couple of decades, and a ‘unifying theory’ of sorts – which brings together four separate mechanisms – seems to have been developed at this point. As mentioned you can have a look at ‘the relevant link’ above if you want to know more about the details.

Age is an important factor in treatment, as different age groups will respond in dissimilar manners to treatment and will face different problems (biological factors, behavioural factors), so the book has separate chapters on diabetes management in very young children, adolescents, etc. Though the level remains high throughout the book, I’d incidentally note that I don’t believe these chapters on special management issues in specific patient subgroups are that technical, and I think many diabetics would be able to benefit from reading those chapters. To a diabetic, much of the stuff covered in the treatment part will be well known although there’ll also be some new stuff. I was continually bothered throughout some of those chapters by the fact that when comparing treatment outcomes of patients on intensive treatment regimes with subcutaneous insulin injections and patients on insulin pumps, the obvious problems with selection into treatment in the latter group were not commented upon when comparing outcomes (though it must be said that one of the authors do comment on this aspect in a later chapter).

Below I’ve selected out some stuff from the middle 200 pages or so of the book. I’ve not completely ignored passages which may be a bit hard to understand for people without any knowledge of this disease – this is also a post written in order to make it easier for myself to remember what was covered in some of those chapters – however as mentioned above I’ve left out the really technical stuff. I have also bolded some key concepts and a few observations for the ‘lazy’ readers who can’t be bothered to read all of it, in order to make the post easier to navigate.

“Since its introduction, insulin has been life sustaining for patients with type 1 diabetes […] Although it is relativly inexpensive in the developed world, in many developing countries with limited health care resources, it is not routinely available (9). Indeed, children with type 1 diabetes in sub-Saharan Africa often do not live longer than 1 yr (10).” (I was wondering if this was an observation based on very old data (data access is a notorious problem when dealing with developing countries), but that seems not to be the case: “A child diagnosed with type 1 diabetes in sub-Saharan Africa has a life expectancy that varies between 7 months and 7 years, depending on the country” – link, original source is this article which I haven’t found an ungated copy of).

[A] major risk of insulin therapy is weight gain. Insulin promotes fat storage in adipocytes and protein synthesis in muscles. […] [In the Diabetes Control and Complications Trial (DCCT)] the body mass index (BMI) increased approx 2 more units with intensive than with conventional treatment in both genders. In the whole DCCT cohort, the risk of becoming overweight was almost twofold greater with IT [intensive treatment – US] […] on average, adult subjects achieving a mean HbA1c of 7.2% gained 4.8 kg more during a 6-yr follow-up than their conventionally controlled counterparts” [my HbA1c is below 7.2%US.]

“Exposure to a mean HbA1c of 11% for less than 3 yr yields the same rate of retinopathy as exposure to a HbA1c of 8% for 9 yr. The message is clear: The less time we allow a patient to be exposed to high levels of blood glucose, the better […] The adverse hyperglycemic effects on the eyes and kidneys exhibit a carryover effect manifested by a kind of “metabolic memory” displayed by these target organs. […] there is a momentum factor in retinopathy and nephropathy contributed to by the combination of glycemic level and time. The process of tissue damage builds up slowly, but in an accelerated fashion at higher HbA1c levels […], it decelerates slowly at lower HbA1c levels […], but also resumes its progression slowly after a period of time at lower HbA1c levels”

“It has long been recognized that treating and controlling diabetes is difficult. Diabetes is not an illness where a pill, an injection, or a particular diet is a cure. At best, there is hope to control it well. Optimal treatment demands dedication, motivation, energy, and knowledge. […] Dealing with these issues on a daily basis can be a psychological burden […] Thus, it is common for those with diabetes and/or close members of their families to have guilt, sorrow, and depression […] Although depression is not a complication of diabetes, it frequently is a consequence of the illness. The prevalence of depression in adults varies. Levels of diagnosable depression among those with diabetes are approximately three times the estimated prevalence in the population at large (8). Depression also might be more severe in people with diabetes and has especially adverse effects. Difficulty evolves in treatment when clinical depression contributes to poor self-care, worsened glycemia, and deepened depression (9).”

“Hyperglycemia before eating slows gastric emptying and results in a more prolonged glycemic response (8), whereas hypoglycemia speeds emptying and results in a faster, higher, and earlier peak response (9).” [I was not aware of this!]

“Persons with type 1 diabetes may attempt to substitute protein for carbohydrates to attenuate postprandial glucose response. A large cross-sectional study in type 1 diabetes found that protein intakes greater than 20% of total energy intake were associated with higher albumin excretions than <20% dietary protein (43). Concern over the role protein intake plays in renal function suggests that consuming more than 20% protein in the diet is unwise.” [As I’ve pointed out before (the second paper in the post), salt intake seems like a more obvious place to intervene – but protein intake is not irrelevant].

“Diabetes is less frequent in preschool children than in older ages. In a large survey in Europe, age-specific incidence was compared among 3 age groups in more than 3000 cases during 1989–1990 (1). Eighteen percent of the cases were observed in children younger than 4 yr, 34% between 5 and 9 yr, and 48% in children aged 10–14 yr. Similar results have been obtained in North America (2). [I got diagnosed at the age of 2US] […] A major characteristic of metabolic control in type 1 preschool children is the unstable glycemic control with its accompanying risk of severe hypoglycemia […] In young children, severe and recurrent hypoglycemias are of major concern because they may impair normal brain development. When tested during adolescence, patients who presented with early-onset diabetes and/or a history of severe hypoglycemia showed global or selective neuropsychological dysfunction such as impairment of visual–spatial skills, psychomotor efficiency, attention, or memory (28–32). As early as 2 yr after disease onset, evidence exists for mild neuropsychological dysfunction (33). Onset of diabetes early in life (before 5 yr of age) predicted negative changes in neuropsychological performances over the first 2 yr of the disease (34).” [I’ve talked about this aspect of the disease before. Below’s a bit more on this stuff:]

“The long-term risk of recurrent severe episodes of hypoglycemia, involving coma or convulsions, on the development of permanent cognitive impairment remains controversial. […] There continue to be concerns about young children with type 1 diabetes, particularly those diagnosed less than 5 yr of age in whom defects in tests of cognitive function have consistently been found (126–131). […] It is likely that the developing brain is more susceptible to damage during episodes of metabolic derangement. Deficiencies have been found in a number of cognitive domains but especially those that are more likely to be those originating in the frontal lobe. Not all of these studies have found a link with prior episodes of severe hypoglycemia, although more recent investigations have shown links between hypoglycemia and cognitive impairment.”

“The pubertal growth spurt is induced by sex hormones in both boys and girls, leading to increased amplitude of growth hormone (GH) pulses, and a rise in circulating insulinlike growth factor-1 (IGF-1) (26). Both the sex hormones and GH contribute to insulin resistance (27) and worsening glycemic control (28) […] Insulin also plays an important anabolic role during puberty. Failure to adequately increase insulin doses during this period has adverse effects on diabetic control, leading to the impairment of growth and pubertal development […] The GH/IGF axis, which plays a central role in the growth acceleration of puberty, can be significantly disordered in the diabetic adolescent with poor diabetic control, contributing to both growth impairment and greater insulin resistance (30).” [Incidentally both my brothers are higher than I am, though I can’t be absolutely certain this has anything to do with my diabetes… – US] […]

“In a retrospective, longitudinal study of 118 adolescent 18-yr-olds with type 1 diabetes, studied at three-monthly intervals between 8 and 18 yr, we found a significant deterioration in metabolic control throughout the period of adolescence (52). […] Quality of life may also deteriorate during this time (53) […] Adolescents with diabetes, unlike younger children, were reported by their parents as having poorer emotional and behavioral outcomes and poorer self-esteem outcomes than the nondiabetic adolescents.”

“Few diabetic women lived to childbearing age before the advent of insulin in 1922. Until then, less than 100 pregnancies were reported in diabetic women and most likely these women had type 2 and not type 1 diabetes. Even with this assumption, these cases of diabetes and pregnancy were associated with a greater than 90% infant mortality rate and a 30% maternal mortality rate (1,2). As late as 1980, physicians were still counseling diabetic women to avoid pregnancy (3). […] There is an increased prevalence of congenital anomalies and spontaneous abortions in diabetic women who are in poor glycemic control during the period of fetal organogenesis, which is nearly complete by 7 wk postconception. A woman may not even know she is pregnant at this time. It is for this reason that prepregnancy counseling and planning is essential in diabetic women of childbearing age. Because organogenesis is complete so early on, if a woman presents to her health care team and announces that she has missed her period by only a few days, there is still a chance to prevent cardiac anomalies by swiftly normalizing the glucose levels. However, potential neural tube defects are probably already established by the time the menstrual period is missed. […] HbA1c values early in pregnancy are correlated with the rates of spontaneous abortion and major congenital malformations […] normalizing blood glucose concentrations before and early in pregnancy can reduce the risks of spontaneous abortion and congenital malformations nearly to that of the general population (6–12).”

The life expectancy for patients with diabetic end-stage renal failure is only 3 or 4 yr.” [I was wondering if perhaps this statement was based on old data (you never know), so I had a look around. It doesn’t seem to be – this is really how ‘well’ people do today. See e.g. the figure on page 6 of this study published earlier this year – half of the diabetics with end-stage renal failure were dead after 3 years, and only about a third survived 5 years. Yes, sometimes people get lucky – they ‘get a transplant and live for decades’. But most diabetics don’t; they just die, quite fast.]

“Although all cells in a person with diabetes are exposed to elevated levels of plasma glucose, hyperglycemic damage is limited to those cell types, such as endothelial cells, that develop intracellular hyperglycemia. Endothelial cells develop intracellular hyperglycemia because, unlike most other cells, they are unable to downregulate glucose transport when exposed to extracellular hyperglycemia […] vascular smooth muscle cells, which are not damaged by hyperglycemia, show an inverse relationship between extracellular glucose concentration and subsequent rate of glucose transport […] In contrast, vascular endothelial cells show no significant change in subsequent rate of glucose transport after exposure to elevated glucose concentrations”

Diabetic ketoacidosis (DKA) is a potentially life-threatening medical emergency that reflects a state of metabolic decompensation in patients with insulin-dependent diabetes mellitus (IDDM) […] At least 25% of patients with new-onset diabetes mellitus type 1, especially children, will present in ketoacidosis (1–6). […] The cardinal hormonal alteration that triggers the metabolic decompensation of DKA is insulin deficiency accompanied by an excess of glucagon and the stress hormones epinephrine, norepinephrine, cortisol, and growth hormone (2,3,6). Insulin stimulates anabolic processes in liver, muscle, and adipose tissues and thereby permits glucose utilization and storage of the energy as glycogen, protein, and fat […] Concurrent with these anabolic actions, insulin inhibits catabolic processes such as glycogenolysis, gluconeogenesis, proteolysis, lipolysis, and ketogenesis. Insulin deficiency curtails glucose utilization by insulin-sensitive tissues, disinhibits lipolysis in adipose tissue, and enhances protein breakdown in muscle. Glucagon acting unopposed by insulin causes increased glycogenolysis, gluconeogenesis, and ketogenesis. Although insulin and glucagon may be considered as the primary hormones responsible for the development of DKA, increased levels of the stress hormones epinephrine, norepinephrine, cortisol, and growth hormone play critical auxiliary roles. Epinephrine and norepinephrine activate glycogenolysis, gluconeogenesis, and lipolysis and inhibit insulin release by the pancreas. Cortisol elevates blood glucose concentration by decreasing glucose utilization in muscle and by stimulating gluconeogenesis. Growth hormone increases lipolysis and impairs insulin’s action on muscle. The catabolic and metabolic effects of each of these counterregulatory hormones are accentuated during insulin deficiency […] the effects are synergistic and not merely additive. Even in normal persons, high concentrations of these counterregulatory hormones can induce hyperglycemia and ketonemia” (see also this and this – US)

“The classical patient with DKA is characterized by dehydration, acidosis with hyperventilation, with varying degrees of cerebral obtundation, and peripheral circulatory compromise […] the most common precipitating factors following initial presentation are omission of insulin, infection, and, in adults, typical or atypical myocardial infarction (1,7). […] In children, the major complication of concern during treatment for DKA is cerebral edema and related intracerebral complications […] [children are] at a disproportionately higher risk for developing clinical cerebral edema as compared to adults with DKA. Clinically relevant cerebral edema is estimated to occur in 0.7–1.0% of episodes of diabetic ketoacidosis in children (26–28). […] Once clinically obvious, cerebral edema is associated with a mortality of about 70% and only 7–14% of these patients escape permanent impairment of neurological function (31).”

December 12, 2013 - Posted by | books, diabetes, medicine

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