Ketone Testing and Diabetes Mellitus

• Investigation of glucose metabolism includes the fasting glycemia test and the oral glucose tolerance test
• When glucose concentration decreases, the body uses liver glycogen to release glucose to sustain glucose supply for about 16 hours
• During prolonged fasting or extreme exercise, gluconeogenesis (synthesis of glucose from noncarbohydrate compounds) occurs

Gluconeogenesis Substrates

• Lactate (from muscle activity)

• Alanine (from muscle protein breakdown)

• Glycerol (from fat breakdown)

• Glucose homeostasis is controlled by insulin (anabolic hormone) and catabolic hormones such as glucagon, catecholamines, cortisol, and growth hormone (counterregulatory hormones)

• Insulin and glucagon are secreted from the pancreatic islets of Langerhans

• Insulin is secreted by β cells, and glucagon by α cells

• The molar ratio of insulin to glucagon determines the pattern of fuel metabolism

• The endocrine system functions to maintain normal blood glucose levels

• Blood glucose levels reflect the balance between insulin and hormones that raise glycaemia

• A fasting blood glucose level is done if an imbalance of glucose homeostasis is suspected

• Venous, capillary, or arterial blood can be used

Factors Influencing Blood Glucose Interpretation

• Measurement method: Older chemical methods give higher readings than modern enzymatic methods
• Blood sample source: Arterial and capillary blood glucose levels are 5-15 mg% higher than venous blood
• Age: Fasting blood glucose increases with age, rising about 10 mg% every 10 years in older adults

Recommendations for Glucose Testing for Diabetes

• Anyone with a BMI over 25 (23 for Asian-Americans) with risk factors like high BP, abnormal cholesterol, or heart disease
• Individuals over 45 years old should be screened every 3 years
• Women who had gestational diabetes should be screened
• People with prediabetes should be screened every year

Self-Monitoring Glucose Device

• A glycemic reader, or glucose meter, is used by diabetic people to adjust and check their treatment through diet, insulin, and exercise

Steps for Using a Glucose Meter

• Wash hands
• Insert the test strip into the glucose meter
• Insert the lancet into the lancing device
• Prick the end of a finger
• If necessary, squeeze the end of your finger
• Apply blood to the test strip
• Wait a few seconds
• Read and record or store the result in the glucose meter
• A normal fasting blood sugar level is between 80-100 mg/dL (5.6 mmol/L)
• A fasting blood sugar level from 100 to 125 mg/dL (5.6 to 6.9 mmol/L) indicates impaired fasting glucose or prediabetes
• A diagnosis of diabetes is established if it's 126 mg/dL (7 mmol/L) or higher on two separate tests on two separate days

Oral Glucose Tolerance Test (OGTT)

• OGTT is used if a normal fasting blood glucose level doesn't exclude latent diabetes
• Assesses blood glucose response to a carbohydrate load
• Can unmask asymptomatic pre-existing diabetes in predisposed individuals

OGTT Indications

• Family history of diabetes mellitus
• Sudden unexplained weight loss
• Repeated infections, especially in the genitals or urinary tract
• Mothers with overweight newborn babies (above 4 kg)
• Premature cataract (below 50 years)
• Delayed wound healing

Conditions for Performing OGTT

• Patient fasts for 10 hours and test to be done in the morning
• Patient should sit to avoid stress or exercise-related plasma glucose changes
• Avoid drugs/medications when possible
• Avoid smoking, as nicotine stimulates catecholamine release, raising blood glucose
• Not performed on patients with recent illness, surgery, or major stress

Steps for OGTT

• Patient sits
• Fasting plasma glucose is measured from venous or capillary blood
• Patient drinks a standard glucose quantity (75 g in 300 mL of water), using anhydrous glucose
• Plasma glucose concentration is measured again after 120 minutes; sometimes at 20, 60, and 120 minutes
• Urine is examined for sugar and ketones
• Values are plotted on a graph for comparison with normals.

Interpreting Blood Glucose Levels

Normal Response

• Blood glucose peaks around 60 minutes after eating
• Returns to near-fasting levels within 120 minutes

Diabetes Diagnosis

• Diabetes is diagnosed if glucose stays above 11.1 mmol/L (200 mg/dL) at 120 minutes, even if fasting glucose was normal

Impaired Glucose Tolerance (IGT)

• IGT, a prediabetes condition, is indicated if fasting glucose is normal but post-load glucose is between 6.1-7.8 mmol/L (100-140 mg/dL)

• In a normal, fasting person, blood glucose rises from 90 to 120 to 140 mg/100 ml and returns to normal in about 2 hours after ingesting 1 gram of glucose per kilogram of body weight.

• In a diabetic person, fasting blood glucose is almost always above 115 mg/100 ml and often above 140 mg/100 ml

• After glucose, the concentration rises much greater than normal and decrease to normal in 4 to 6 hours, and it fails below the control level

• If blood glucose levels fall slowly and don't return to normal, it can suggest the normal increase in insulin secretion after glucose ingestion does not occur or the person has decreased sensitivity to insulin

• Diabetes mellitus can be established based on such a curve and type 1 & 2 can be distinguished by measurement of plasma insulin

  • Plasma insulin is low or undetectable in type 1 diabetes
  • Increased in type 2 diabetes

• If there is significance hyperglycemia, the blood glucose level should be rechecked 30-60 min later and the urine tested for ketones

• Insulin and C-peptide levels are determined with radioimmunological tests

• The normal blood level of insulin is above 10 pUI/ml

• Patients with marked decrease of insulin level are harder to balance metabolically

• The insulin levels are also useful in determining the cause of hypoglycaemia

• An acute first phase of insulin secretion occurs in response to an elevated blood glucose, followed by a sustained second phase

• The incretin effect means that the body releases more insulin when glucose is taken orally compared to when it's given intravenously, even if blood sugar levels rise the same amount

• This happens because the gut releases peptides that stimule insulin secretion, helping regulate blood sugar more efficiently

C-Peptide

• 31 amino acid polypeptide that connects insulin's A and B chains in the proinsulin molecule
• C-peptide and insulin are released from the pancreas at the same time and in about equal amounts
• Most insulin (~60%) secreted into portal blood is removed in first pass through liver, while C-peptide is not extracted by the liver
• C peptide levels can be measured by radioimmunoassay
  • Measure natural insulin in insulin-treated diabetic patients
  • In the levels of C peptide will usually be greatly decreased for individuals with Type 1 Diabetes

Glycated Hemoglobin (HbA1c)

• HbA1c measures average blood sugar levels over 2-3 months
• Forms when glucose attaches to hemoglobin in red blood cells
• Reflects average blood sugar over 2-3 months
• Normal range: 4.0%–5.9%
• HbA1c forms in blood erythrocytes at a rate proportional to the prevailing glucose concentration.
• Because the average lifespan of red blood cells is about 120 days, the HbA1c test is used mainly to assess average blood glucose concentrations for the previous three months
• HbA1c concentration may be affected by anemia and the presence of hemoglobin variants
• In United States HbA 1c measurements = percentage of total hemoglobin
• In Europe = mmol/mol
• HbA 1c used to diagnose diabetes and to monitor glycemic control
• Level of 48mmol/L (6.5%) or higher is for diabetes
• ADA recommends keeping HbA1c below 7% for most diabetic patients
• Stricter control may be risky due to hypoglycemia in young children and the elderly, so treatment goals should balance safety and effectiveness

Glucosuria

• In healthy people glucose does not appear in urine because the kidneys reabsorb it in the proximal tubule after filtration, but a small amount may be present
• Higher blood glucose = More glucose in urine, but urine glucose levels vary due to fluid intake.
• In diabetes, when blood glucose exceeds 180 mg/dL, the kidney can't reabsorb all of it, so glucose spills into the urine-this is called the renal reabsorption threshold.
• If blood glucose levels become elevated, as in persons with diabetes, the maximal tubular reabsorption rate (TM) is exceeded, and glucose appears in the urine.
• The detection of glucose using test strips relies on an enzymatic reaction involving glucose oxidase
• Clinical significance:
  • Diabetes Mellitus, gestational diabetes (placental hormones blocking insulin)
  • Hormonal disorders: Hypercortisolism
  • Renal tubular disorders prevent tubular reabsorption of glucose, renal diabetes

Ketonuria

• Ketone bodies are produced by the liver from fatty acids during periods of low food intake or glucose restriction; they serve as an energy source for the cells of the body.
• The level of ketone bodies rises if metabolic imbalance occurs in diabetes mellitus
• If their blood level rise they appear also in the urine (ketonuria)
• Normal level: 0,5 mg%
• Ketones or ketone bodies refers to three intermediate products in the metabolism of fatty acids:
  • Acetone
  • acetoacetic acid
  • beta-hydroxybutyric acid
• Elevated concentrations of ketones are not generally found in urine, as all these substances are completely metabolized, producing energy, carbon dioxide and water
• Increased concentration in blood, they turn positive in urine due to:
  • disruption of carbohydrate metabolism
  • inability to metabolize carbohydrates (in diabetes)
  • increase in fat metabolism (can be the result of starvation or malabsorption)
  • due to losses from frequent vomiting
• The test used in the urine test strips is based on the reaction of sodium nitroprusside (nitroferricyanide)
• Acetoacetic acid in an alkali medium reacts with the sodium nitroprusside producing a magenta coloured complex.
• The test does not measure beta-hydroxybutyric acid and it is only weakly sensitive to acetone when glycine is added to the reaction

Acetone Breath

• Occurs when the body produces high levels of ketones, especially in severe diabetes (Type 1).
• In diabetes, acetoacetic acid (a type of ketone) increases in the blood and gets converted to acetone.
• Acetone is volatile, so it enters the lungs and is exhaled, creating a fruity-smelling breath-a common sign of diabetic ketoacidosis (DKA).
• A ketone meter can measure acetone levels in the breath to help monitor ketosis or diabetes control.

Interpretation of Ketone Levels

• 0.0 = The person is not in ketosis state
• 0.1-0.5 = The person is in light state of ketosis
• 0.5-3.0 = The person is in full state of ketosis, which is optimal ketone
• 3.0 = The person is in starvation ketosis
• 5.0 = The person is in too much ketosis and need medical care
• 7.0 = The person is in ketoacidosis