Nuts are a good source of Monounsaturated Fatty Acids

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Nuts are a good source of Monounsaturated Fatty
Acids

• Diets containing nuts reduce coronary heart
  disease risk predominantly through their
  lipid-lowering effect.
• Yet, nuts are often avoided due to their high fat
  and energy content.
• Good News- Nuts can actually help reduce or
  control body weight
• Walnuts are unique because they are rich in n-6
  (linoleate) and n-3 (linolenate) polyunsaturated
  fatty acids.

Pictures from thenutfactory.com Fraser et al Arch
Intern Med 1992 152 1416 1424 Hu et al Br
Med J 1998 3171341 1345
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Lecture 11

• Dietary fat lifestyle I
• Transport and storage

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Role of Fatty Acids
Membrane structure and function
Energy production
Tissue lipids containing SFA MUFA PUFA
Cell division processes
Eicosanoid formation
Inflammation processes
Smooth muscle contraction Blood platelet clotting
n3 fatty acids are less active
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Summary of Fat Digestion

• Eat fat in the diet
• triglycerides --gt 2-monoglycerides glycerol
  fatty acids
• Pancreatic and intestinal lipase
• absorbed in the ileum
• reform the triglyceride molecule
• WHAT HAPPENS NEXT?

• Secreted into the lymphatic drainage for
  transport into bloodstream
• Transported to various cells in the body
• Used for structural processes and energy

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Lipid transport in the bloodstream

• Lipoproteins
• cluster of lipids with protein that transport
  lipids in the lymph and blood

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Lipoproteins

• transport vehicles for Fat in the bloodstream

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Lipoproteins

• There are 4 main classes of lipoproteins
• Chylomicrons
• VLDL (very low density lipoprotein)
• LDL (low density lipoprotein)
• HDL (high density lipoprotein)

size
Most lipoproteins synthesised by the liver
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Lipoproteins

• Each lipoprotein contain lipids
• Cholesterol, Phospholipid (PL), Triglyceride
• bound with protein

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LIPOPROTEINS

• icture of lipoprotein from Whitney Rolfes

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Lipoproteins

• Chylomicrons
• largest and least dense
• carry triglyceride from intestine to body via
  lymph system
• cells strip them of TAG as they move through the
  lymph
• become smaller and after 14hrs most of TAG
  depleted
• remaining remnants (PL, protein) which are
  collected by liver cells in blood and re-used or
  recycled

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Lipoproteins

• VLDL
• Liver is major site of fatty acid synthesis
• Liver packages synthesised lipids and those
  collected from chylomicrons together with
  proteins as VLDL
• carries mainly TAG from liver to periphery via
  bloodstream
• cells strip VLDL of TAG as they move through the
  blood
• become smaller and proportion of lipids shift
  becoming smaller an more dense (LDL)

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Lipoproteins

• LDL
• are rich in cholesterol
• travel throughout the body offering their lipids
  to cells of tissues including heart, muscle,
  adipose.
• cells take TAG, cholesterol and PL to build new
  membranes and hormones or store for later use.
• LDL receptors control blood levels of LDL by
  removing them from the circulation and depositing
  in the cells/tissues.
• LDL is considered the bad cholesterol
• Transports cholesterol to tissues

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Summary VLDL ? LDL

• cholesterol first built into VLDL with
  Triglycerides
• once VLDL discharges its Triglyceride
• becomes LDL cholesterol rich

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Lipoproteins

• HDL
• fat cells release glycerol, fatty acids and
  cholesterol, PL to the blood
• HDL carries cholesterol from cells to liver for
  recycling
• known as Reverse Cholesterol Transport
• HDL is considered as the good cholesterol
• Transports cholesterol away from tissues

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Video

• Summary of lipoprotein synthesis and transport
  and relevance to formation of atherosclerosis
• From Northern Arizona University
• Click Here
• (http//jan.ucc.nau.edu/d-ctel/bio/bio320/bioPlay
  er/bioPlayer_content.html)

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Lipid Storage

• FAT stored as Triglyceride in Adipose tissue
• dietary fat delivered to adipose tissue
• from liver in VLDL
• from intestines in Chylomicrons

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Lipid Storage

• Once transported to site of storage (adipose
  tissue), lipoproteins need to be broken down
  again (hydrolysed) to get fat into the cell.
• Lipoprotein lipase enzyme involved in this
  process
• Triglyceride ? Glycerol Fatty acids
  Monoglycerides
• Once inside the cell parts are reassembled into
  triglycerides

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Lipid Release

• stored triglyceride hydrolysed to free fatty
  acids released into blood when needed for
  ENERGY
• Hormone- sensitive lipase dismantles stored
  triglycerides

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Mobilisation of fat

Adipose cell
Triglycerides
FFA Glycerol
Hormone sensitive lipase
Liver
via bloodstream
This yields energy
Muscle
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Learning Outcomes

• How fat is digested
• How fat is transported
• How fat is stored
• How fat is released

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Recommended reading

• Whitney Rolfes (2005)
• Understanding Nutrition 10th Ed.
• Chapter 5. The Lipids Triglycerides,
  Phospholipids Sterols
• Note Highlight Five High fat foods..
• Chapter 18. Diet and Health