X-Message-Number: 30842
Date: Tue, 1 Jul 2008 22:18:02 -0700 (PDT)
From:
Subject: rat life span increase with chromium picolinate
The late Thomas Donaldson PhD devoted a chapter to the following chromium
paper in his book "A Guide to Antiaging Drugs". This paper is not available
anywhere on the net, partly because the journal it was published in, no
longer exists. Thomas obtained his copy of the paper directly from the
author, while I later obtained my own copy from Thomas. This is an important
paper because of the significant increase in longevity it documents when
plasma insulin is chronically lowered. So, for the first time, here is the
complete text of Gary Evans' paper detailing the effect of chromium
picolinate on Long-Evans rats.
(Note: Due to character set limitations, mcg is substituted for
micrograms, and mcl is substituted for microliters. There are some minor
grammar errors in the original paper, but I made no attempt to remove
these, while typing in the text.)
____________________________________________
Advances in Scientific Research Volume 1 Number 1 April 1994 page 19 - 23
LIFE SPAN IS INCREASED IN RATS SUPPLEMENTED WITH A CHROMIUM-PYRIDINE 2
CARBOXYLATE COMPLEX
Gary W. Evans and Lynn K. Meyer
Department of Chemistry, Bemidji State University, Bemidji, MN 56601-2699
(received 16 March 1994)
c1994 Institute for Advances in Scientific Research
Abstract
Chromium picolinate, a pyridine-2 coordination complex, known to be
efficacious in maximizing insulin function, was tested to determine its
effect on longevity in rats. Rats were fed ad libitum, from weaning, a
purified diet supplemented with various forms of chromium. At 200 and 1000
days, both plasma glucose and glycated hemoglobin were significantly lower
in rats fed chromium picolinate. At 1100 days, plasma insulin of rats fed
chromium picolinate was 50% less than that of rats in the other groups.
Median survival time of rats fed chromium picolinate was 25% greater than
that of rats in the other groups. The results demonstrate that chromium in a
utilizable form, like dietary restriction, prevents hyperglycemia,
hyperinsulinemia, protein glycation and extends life span.
INTRODUCTION
Cerani(1985) first suggested that elevated blood glucose levels may
decrease survival by accelerating the process known as protein glycation.
Later, Masoro et el. (1989) demonstrated that food restriction in rats
resulted in decreased serum glucose concentrations with a concomitant
decrease in glycation of hemoglobin.
The observations of Masoro et el. (1989) piqued our interest because
investigators in the area of trace element function have known for several
years that chromium is somehow involved in the regulation of blood glucose
levels (Schwarz 1959, Mertz 1969). Prior to the publication of Masoro et el.
(1989), we had completed a study with non-insulin-dependant diabetes
mellitus patients in which we noted a significant decrease in serum glucose
and glycated hemoglobin after six weeks of daily supplementation with
chromium in the form of the coordination complex chromium picolinate (Evans
1989). Because chromium-deficient diets had previously been linked to
increased mortality in rats (Mertz 1969, Schroeder 1968), we extended what
had begun as a toxicity study and compared the effects of various forms of
chromium on plasma glucose, glycated hemoglobin and longevity.
METHODS
Weanling, male Long-Evans rats were housed individually in plastic cages
and kept on a 12-hour light (0400 to 1600), 12-hour dark cycle (1600 to
0400). All animals were fed ad libitum a purified diet (Evans 1981) the
caloric content of which was 64.5% sucrose, 14.5% fat from corn oil and 21%
protein from egg white. Vitamins were provided by the addition of a rat
vitamin mix (Teklad Test Diets, Madison WI). Minerals were provided by the
addition of a chromium free AIN-76 Mineral mix (Teklad Test Diets, Madison
WI). To evaluate the efficiency of various chromium compounds, 1.0 mcg Cr/g
diet in the form of either chromium chloride, chromium dinicotinate
(Cr(nic)2(H2O)3(OH).H2O) or chromium tripicolinate (Cr(pic)3.H2O) was mixed
thoroughly with cellulose powder and added to the basal diet. The homogenous
chromium complexes were prepared as described by Evans and Pouchnick (1993).
The study described here consisted of three groups of ten rats each.
Since we were merely attempting to compare the effect of adding different
chemical forms of chromium to a basal diet, we did not prepare chromium
deficient diets for these experiments nor did we feed any rats the basal
diet without added chromium.
After 200 days and again at 1000 days, 50 mcl blood was drawn into
heparinized capillary tubes from the tail of each rat between the hours of
1400 and 1500. The tubes were centrifuged immediately and two 5 mcl aliquots
of plasma were frozen for glucose assay. Plasma glucose was assayed with the
glucose oxidase kit No. 315 obtained from Sigma Chemical. Ten days after
collecting blood for glucose analysis, a 20 mcl sample was drawn for
determination of glycated hemoglobin. Glycated hemoglobin was measured with
the Glycotest Kit from Pierce Chemical Company (Rockford, IL) which utiliaes
the affinity chromatography procedure described by Klenk et al. (1982).
At 1100 days between 1400-1500 hours 800 mcl blood was drawn into
heparinized tubes from the tail of the surviving rats for measurement of
plasma insulin concentration with the Incstar 125 I-Insulin Radioimmunoassay
Kit #20008 (Incstar Corp., Stillwater, MN). The tubes were immediately
centrifuged, 300 mcl of plasma was removed and mixed with 300 mcl of
polyethylene glycol solution supplied in the kit and mixture was centrifuged
at 1000 X G for 20 minutes at room temp. The supernatant was removed and
stored at -40C until 200 mcl of the supernatant was used to determine plasma
insulin concentration.
At death, the carcass was weighed after which all fat was removed and
weighed. The body organs were examined microscopically to determine cause of
death.
Statistically analyses were conducted using analysis of variance
(ANOVA). Significance was determined by Duncan's multiple range test.
RESULTS
At 200 and 1000 days, plasma glucose was significantly less (p<0.05) in
rats fed chromium picolinate than plasma glucose in rats fed either chromium
nicotinate or chromium chloride (Table 1). At 210 and 1010 days, glycated
hemoglobin was significantly less (p<0.05) in rats fed chromium picolinate
than that in rats fed chromium nicotinate or chromium chloride.
Plasma insulin concentration appeared to be inversely related to
survival. Insulin concentration in rats fed chromium picolinate was
approximately 50% less than insulin concentration in rats fed either
chromium nicotinate or chromium chloride (Table 2). Unfortunately we did not
become aware of the existence of a radioimmunoassay kit for rat insulin
until after some of the rats had died. Despite the fact that the number of
assays was small, the differences were statisically significant (p<0.05).
Both the median survival time and maximum length of life of rats fed
chromium picolinate were significantly greater (p<0.05) than that of rats
fed either chromium nicotinate or chromium chloride (Table 2).
At death, mean weight of the rats fed chromium picolinate was less than
that of the other rats but the differences were not significant (p<0.05).
However, body fat was significantly less (p<0.05) in the rats fed chromium
picolinate (Table 2). Autopsy indicated that the rats fed chromium
picolinate died primarily from leukemia, lymphoma and pituitary adenoma
while the rats in the other two groups died from cardiomyopathy,
nephropathy, leukemia, lymphoma and pituitary adenoma.
Table 1.
Plasma glucose and glycated hemoglobin in rats fed various forms of chromium
Supplement Glucose Glycated Hb Glucose Glycated Hb
mM % mM %
200 days 210 days 1000 days 1010 days
CrCl3 7.8+-0.11a,l 5.39+-0.08a,l 8.2+-0.18b,l 8.43+-0.28b,l
CrNic 7.7+-0.12a,l 5.19+-0.09a,l 8.3+-0.17b,l 8.29+-0.19b,l
CrPic 6.6+-0.12a,2 3.31+-0.08a,2 6.5+-0.14a,2 3.41+-0.09a,2
a mean+-S.E. Of 10 rats.
B mean+-S.E. Of 5 rats
l means in the same column with different superscripts are significantly
different (P<0.05)
Table 2
Insulin, body weight at death, body fat at death and survival rate in rats
fed various forms of chromium
Supplement Insulin Body weight Body fat Median age at
nM grams % death (days)
1100 days
Crcl3 1.3+-0.07a,l 501+-29,l 18.1+-2.7,l 1041 (950-1132)
CrNic 1.2+-0.05b,l 496+-35,l 17.5+-1.9,l 1059 (964-1154)
CrPic 0.5+-0.03c,2 486+-27,l 13.3+-1.2,2 1316 (1221-1441)
a mean+-S.E. Of 4 rats
b mean+-S.E. Of 5 rats
c mean+-S.E. Of 10 rats
l means in the same column with different numerical supperscripts are
significantly different (p<0.05)
DISCUSSION
The results of our experiments demonstrate that longevity of laboratory
rats can be extended by dietary supplementation of chromium coordinated with
picolinate. The increased survival rate in rats fed chromium picolinate is
apparently related to an increased efficiency of glucose and lipid
utilization. Throughtout life, plasma glucose in rats supplemented with
chromium picolinate was 15-20% lower than that in rats in the other two
groups and chromium picolinate inhibited the increase in hemoglobin
glycation that occurred in the animals not given that form of chromium.
Plasma insulin in aged rats that had been fed chromium picolinate from
weaning was 50% less than plasma insulin in rats fed other forms of chromium
which suggests that chromium in the form of chromium picolinate markedly
increased insulin sensitivity.
An increase in life span of rodents resulting from chromium
supplementation has been noted previously (Mertz 1969, Schroeder 1968).
Additions of CrO3 to the drinking water increased the survival of rats
compared to unsupplemented controls. A significant increase in the mean age
of the tenth-percentile survivors was observed when male rats fed a chromium
deficient diet were supplemented with chromium acetate in the drinking water
(5 mcg Cr+3/ml). In addition, the survival of male mice fed a chromium
deficient diet was significantly increased when the mice were supplemented
with chromium acetate in the drinking water (5 mcg Cr+3/ml).
The antiaging effect of chromium is undoubtedly related to the effect of
chromium on insulin action, since several investigations with cell cultures,
animals and human, provide evidence that chromium increases insulin
sensitivity. Over thirty years ago, Schwarz and Mertz (1959) first detected
impaired glucose utilization in rats fed diets deficient in chromium. Later,
investigators discovered that the symptoms of diabetes which developed
during long-term parenteral nutrition could be prevented by the addition of
chromium to the intravenous solution (Jeejeebhoy 1977; Freund 1979). When
either swine (Evock-Clover 1993) or heifer calves (Fernadez 1993) were fed
chromium picolinate in the diet, increased plasma glucose clearance rates
were accompanied by decreased plasma insulin levels.
Evans and Bowman (1992) and Evans and Pouchnik (1993) discovered that
insulin internalization was markedly increased in rat muscle cells cultured
in a medium that contained chromium picolinate and the increased
internalization rate was accompanied by a marked increase in the uptake of
both glucose and leucine. The effect was specific for chromium picolinate
since neither zinc picolinate nor any other form of chromium tested was
effective.
The observations described in this paper demonstrate that the element
chromium is involved in the aging process. Schroeder and his associates
(Schroeder 1968) established the fact that chromium deficiency leads to
increased mortality while our results prove that the form in which chromium
is ingested also influences the aging process. Chromium picolinate is a
neutral, lipophilic complex while chromium nicotinate is a charged complex
(Evans 1993). Chromium chloride of course dissociates into the ionic
components. Absorption experiments demonstrate that the charged forms of
chromium are not readily absorbed when mixed with the diet (Anderson 1993)
and tests of biological function indicate that chromium nicotinate and
chromium chloride are either unstable in physiological media or are simply
not utilized by cells (Mertz 1969; Evans 1992; Evans 1993). Thus, when
adequate quantities of chromium are ingested in a form that can be absorbed
and utilized inside the body, insulin resistance and the subsequent
hyperinsulinemia which occurs can be prevented. Because hyperinsulinemia has
been associated with long term deleterious effects (Reaven 1988), we suggest
that chromium, like dietary restriction, increases longevity by preventing
development of symptoms associated with insulin resistance.
REFERENCES
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