Low-dose fish oil therapy
effective in IgA nephropathy
IgA
nephropathy is a fairly common
kidney disorder. It is caused by an
inflammation (glomerulonephritis) in
the network of small blood
vessels called capillaries
involved in the filtration of waste
products from the blood. Specifically, it manifests itself
through the deposit of the antibody
immunoglobulin A (IgA) in the mesangial cells, which support the
walls of the capillaries. The IgA
deposits cause swelling due to
inflammation due to lesions to
the capillaries interfere with
proper filtration of waste products
from the blood. IgA nephropathy is
more common in men than in women and
its incidence peaks between the ages
of 16 and 35 years. IgA nephropathy
is associated with a gradual decline
in kidney function leading to
end-stage renal disease within 5 to
25 years of diagnosis in 20-40% of
patients. The disease is usually
diagnosed after blood or excess
protein is observed in the urine.
Serum creatinine levels are
abnormally high in IgA nephropathy
because the kidneys are unable to
filter creatinine (a waste byproduct
of creatine, a protein that supplies
energy for muscle contraction) out
of the blood and excrete it in the
urine. A doubling in serum
creatinine level corresponds to a
50% decline in kidney function.
There are no pharmaceutical drugs
that will slow down or reverse the
progression of IgA nephropathy.
Researchers at the Mayo Clinic
previously reported that
supplementation with 1.9 grams/day
of EPA (eicosapentaenoic acid) plus
1.4 grams/day of DHA (docosahexaenoic
acid) is effective in retarding the
progression of IgA nephropathy. The
researchers have now carried out
another clinical trial to determine
whether doubling the daily dose of
fish oil supplement would be even
more effective. Their randomized
clinical trial involved 73 patients
with biopsy-diagnosed IgA
nephropathy. Ten of the patients had
quite severe disease as indicated by
a baseline serum creatinine level of
3.0-4.9 mg/dL while the remaining 63
patients had moderate disease (serum
creatinine between 1.5-2.9 mg/dL).
The fish oil supplement used in the
trial was supplied by Pronova in
Norway (trade name – Omacor)
in the form of highly purified ethyl
esters of EPA and DHA.
At the end of the 2-year study
period the serum creatinine level in
the low-dose group (1.9 g/day of EPA
plus 1.5 g/day of DHA) had increased
by 0.08 mg/dL per year while
patients in the high-dose group (3.8
g/day of EPA plus 3.0 g/day of DHA)
saw an average yearly increase of
0.10 mg/dL. Rapid deterioration in
kidney function (creatinine increase
of more than 0.5 mg/dL per year) was
observed in 70% of the patients with
severe disease as compared to only
23% in the group with moderate
disease. There was no significant
difference in the number of patients
in the low and high dose groups who
developed end-stage renal disease (ESRD).
At the end of 2 years 86% in the
low-dose group and 80% in the
high-dose group were still free of
ESRD. The corresponding numbers
after 3 years were 73% and 76%. The
2-year number of about 85% ESRD-free
compares to only 63% ESRD-free in a
previously investigated placebo
group.
The Omacor supplement was
generally well-tolerated, but two
patients (out of 73) did discontinue
their treatment as a result of
gastrointestinal intolerance. There
were no unfavourable effects on
serum lipid profiles (cholesterol
levels), hematocrits, peripheral
blood leucocytes or platelets. The
researchers conclude that low- dose
and high-dose fish oil
supplementation is equally effective
in slowing the progression of IgA
nephropathy.
Donadio, JV, et al. A randomized
trial of high-dose compared with
low-dose omega-3 fatty acids in
severe IgA nephropathy. Journal of
the American Society of Nephrology,
Vol. 12, 2001, pp. 791-99
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