Hyperlipidemia Flashcards
(19 cards)
Give a definition of cutaneous xanthoma
Cutaneous xanthomas are benign granulomatous skin or subcutis lesions
They are usually associated with fasting hyperlipidemia, and the elevation in triglycerides and/or cholesterol
What are the causes of hyperlipidemia
Hyperlipidemia results from abnormal lipid synthesis, metabolism or transportation
What is the pathomechanism leading to xanthomas formation
Xanthomas are formed when motion, friction, heat and inflammation cause extravasation of lipids from capillaries into tissue
- macrophages phagocytose lipids, resulting in aggregations of characteristic foam cells and extracellular cholesterol deposition
- foam cells may also arise from in situ lipid production by macrophages
What is the clinical presentation of xanthomas in cats
Cutaneous xanthomas may present as papules, plaques or nodules that are pale yellow to pink in color and can be intact or ulcerated
- they often appear in the periauricular and periorbital regions but can appear at sites of previous trauma
- a commonly reported site is where spinal nerves emerged through vertebral foramina, as vessels here are easily stretched or compressed by adjacent vertebrae during movement
What are clinical signs frequently observed in cats with xanthomas
Frequently observed clinical signs include:
- Horner’s syndrome
- sciatic, tibial and radial nerve paralysis
Are there any risk factors for xanthoma formation
Conditions causing secondary hyperlipidemia predispose to xanthoma formation and include:
- diabetes mellitus
- administration of exogenous progestins and glucocorticoids
Hypercholesterolemia can be caused by pancreatitis, hypoadrenocorticism, cholestasis and nephrotic syndrome
How is familial hypercholesterolemia defined
Familail hypercholesterolemia is a primary condition causing dyslipidemia
- it is characterised by elevated serum cholesterol with normal serum triglycerides concentrations
What is the role of cholesterol and triglycerides in lipoproteins
Of the four lipoproteins described:
- cholesterol makes up most of the lipids in low-density lipoproteins (LDL) and high-density lipoproteins (HDL) (the latter the most important)
- triglycerides make up most of the lipids in chylomicrons and very-low-density lipoproteins
Therefore:
- increased LDL and HDL leads to hypercholesterolemia
- increased chylomicrons and triglycerides leads to hypertriglyceridemia
How is it possible to differentiate lipoproteins
Lipoproteins can be differentiated using ultracentrifugation or agarose gel electrophoresis as they differ in densities and electrophoretic mobility
Which breed of cat has been described with a familiar form of lipoprotein metabolism disorder
Burmese cats
What is the role of pancreatic lipase in the metabolism of triglycerides
Pancreatic lipase is normally released into the duodenal lumen to degrade dietary triglycerides into free fatty acids and glycerol
- these fatty acid products are further emulsified with bile salts to form a mixed micelle, which is then taken up by enterocytes
What is the significance of increased serum lactescence
Triglyceride concentration greater than 300 mg/dL
Describe what is a refrigeration test
The serum sample is refrigerated and left undisturbed overnight
Chylomicrons, being the least dense lipoproteins, will float foarming a cream layer on the top of the serum sample
- if the serum below the chylomicron layer is clear, a non-fasted sample or primary hyperchilomicronemia should be suspected
- if the serum below the chylomicron layer is turbid, the other lipoproteins (i.e. VLDL) are present in excess in addition to hyperchylomicronemia
- if a cream layer doesn’t form after refrigeration then chylomicrons are not present and the lipidemia is due to an excess of other lipoproteins (i.e. VLDL)
What would be your therapeutic plan for excess chylomicrons
Chylomicrons result exclusively from dietary fat absorption, and if hyperchylomicronemia is present, dietary fat should be restricted below that being fed
Insoluble fibers decrease fat absorption , enhance bile acid loss and potentially reduced serum lipid concentrations
How are chilomicrons and other lipoproteins formed
Emulsified fatty acid products form mixed micelle which is then taken up by enterocytes
Within enterocytes, these mixed micelles are repackaged into chylomicrons, which are ultimately transported to the liver for further metabolism and assembly into protein and the fat-laden compounds called very low-density lipoproteins (VLDL)
- after conversion to VLDL, these newly formed lipoproteins are then released into the circulation to deliver cholesterol, fatty acids, and other compounds (e.g., fat soluble vitamins) throughout the body
How are fatty acids removed from VLDL
Fatty acids are removed from VLDL by lipoprotein lipase on the surface of endothelial cells, thereby converting VLDL into low-density lipoproteins (LDL), which continue through the peropheral circulation
- cholesterol bound within circulating LDL is then transferred to high-density lipoproteins (HDL) for transport back to the liver
Explain why moset serum cholesterol in healthy cats is in HDL form
Most serum cholesterol in healthy cats is in HDL form because, unlike humans, cats lack the enzyme necessary to transfer cholesterol back to LDL
What factors influence LPL production and activity
LPL production is increased by insulin
LPL activity is stimulated by thyroid hormone and inhibited by glucocorticoids
What is the cause of feline primary hyperchylomicronemia
Lack of LPL activity
- decreased LPL activity could be associated with idiopathic hypertriglyceridemia
