- Email: [email protected]
Chromium picolinate supplementation improves insulin sensitivity in Goto-Kakizaki diabetic rats
J. TraceE[em. Med. BioL.VoL.17 (4) 243-247 (2004) http://www.e[sevier-deutsch[and.de/jtemb
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Chromium picolinate supplementation improves insulin sensitivity in Goto-Kakizaki diabetic rats Dong-Sun Kim *,I, Tae-Wha Kim I and 3u-Seop Kang2 i Departmentof Internal Medicine, HanyangUniversityCollegeof Medicine, SeouL,Korea 2Department of Pharmacology, HanyangUniversityCollegeof Medicine, Seou[, Korea Received December 2002 • Accepted December 2003
Abstract Chromium pico[inate (CrP) supplementation has been studied as a potentiaL therapy of insulin resistance and Lipid abnormalities. There have been some reports invoLving chromium supplementation in patients with diabetes, but the results are varied. The present study was conducted to assessthe effects of CrP on insulin sensitivity and body weight in Goto-Kakizaki (GK) diabetic rats. We supplemented normal Sprague-DawLey (SD) rats and GK diabetic rats with suppLementaL CrP, 100 mg/kg/day once a day for 4 weeks. In the normal SD rats, the mean body weight of the control group increased by 50.5%, whereas that of the CrP-treated group increased by 65.9% (P < 0.05 vs controL). SimiLarLy, in the diabetic GK rats, CrP supplementation showed increased weight gain compared to the control group (133.4% vs 119.6% of the baseline weight, P < 0.01). GLucosetolerance tests (GTT) Lip injection of glucose; 2 g/kg] and insulin sensitivity tests [SQ injection of insulin (5 U/kg) plus ip injection of glucose (30 rain after insulin injection)] were conducted. During insulin sensitivity tests at the end of treatment, the glucose Levels were significantly Lower in CrP-treated rats compared with the control rats (AUCo_~2o; ]13.1 _+32.0 vs 170.5 _+49.0 mg-min/mL, P < 0.05). During GTTs,the glucose Levelsand insulin concentrations in the CrP-treated rats were not different from those in the control rats. The results of these studies suggest that CrP supplementation in GK diabetic rats Leadsto increase of weight gain and improvement of insulin sensitivity. This raises the possibility that CrP supplementation can be considered to improve carbohydrate metabolism in patients with type 2 diabetes me[titus. Key words: chromium, Goto-Kakizaki, insulin sensitivity, rats, diabetes
Introduction Chromium is an essential trace element for humans and animals. Since Schwartz and Mertz identified in 1959 chromium as the active component of the "g[ucose tolerance factor" (1), chromium supplementation has been studied as a potential therapy of insulin resistance and lipid abnormalities (2, 3). According to previous reports, severe chromium deficiency in patients receiving total
*Correspondence to: Dong-Sun Kim, Department of Internal Medicine, Hanyang University College of Medicine, 17 Haengdang-dong, Sungdong-gu, SeouL, 133-792, Korea, Phone: +82-2-2290-8328, Fax: +82-2-2298-9183, E-mail: [email protected]
parentera[ nutrition caused a peripheral neuropathy, brain dysfunction, and glucose intolerance requiring increasing amounts of insulin (4-6). Chromium is now routinely added to total parenteraL nutrition. There have been some reports about the effects of chromium in diabetic patients (7-10). It is not surprising that chromium supplementation in healthy human subjects on normal diet displayed no beneficial effects on carbohydrate metabolism or weight change (11). By contrast, decrease of glucose concentrations were reported in roughly half the diabetic patients supplemented with chromium. Chromium supplementation in chromium deficient diabetic rats that demonstrate symptoms of insulin resistance can lead to improvement of glucose intoter0946-672X/04/17/04-243 $ 30.00/0
244
D.-S. Kim, T.-W. Kim and 3.-S. Kang
ance, weight Loss, and lipid metabolism (:12). In the early years of onset of type 2 diabetes melLitus (DM), it was reported that plasma chromium concentrations were inversely correlated with plasma gLucose and that type 2 diabetic patients had high LeveLs of urinary chromium leading to increased Loss of chromium (:13). Moreover, dietary chromium intake in most countries tends to be suboptimal these days. According to StriffLer's study, chromium suppLementation in chromium deficient rats Leads to the improvement of insuLin response to glucose (:14). However, there are stiLl some controversies about the supplementation of chromium in patients with type 2 diabetes. This study was undertaken to elucidate the effect of chromium picolinate (CrP) on the insulin sensitivity and body weight in Goto-Kakizaki (GK) diabetic rats
(:15). Materials and methods
Results The changes of body weight during the study are shown in Fig. 1. In the normal SO rats, the mean body weight of the control group increased by 50.5%, whereas that of the CrP treated group increased by 65.9% (P < 0.05 vs control). Similarly, in the diabetic GK rats, the mean weight of the control group was 340.9 g (1:19.6% of the baseline weight) at the end of the experiment, and that of the CrP treated group was 373.5 g (133.4% of the initial weight, P < 0.01 vs control). The blood glucose Levels and AUCo_~12oafter the insulin and glucose Load (insulin sensitivity test) for both groups of rats are shown in Fig. 2A and Fig. 2B. CrP treatment induced the improvement of insulin sensitivity in GK rats. During insulin sensitivity tests, the glucose levels were significantly lower in GK-CrP rats compared with GK-contro[ rats. The AUCo_+t2oof the glucose concentrations in the GK-CrPgroup was 113.:1 + 32.0 mg-min/mL which was 66.3% of the GK-contro[ group (170.5 + 49.0 mg-min/mL, P < 0.05).
MaLe Sprague-DawLey (SD) rats (8 weeks, 242 g in average) were purchased from CharLes River Breeding Laboratories (Wilmington, MA, USA), and maLe Goto-Kakizaki (6K) diabetic rats (8 weeks, 270 g in average) having A 400 .-- ~>--- SD-Control more than :140 mg/dL of fasting bLood glucose were pur---~- SD-CrP chased from M & B Co. (Denmark). The rats were handLed GK-Control ............... and housed in a protected environment at a constant tem• GK-CrP . . " ~ perature of 20-23 °C in conventional plastic cages with ,-, 360 , .< free access to water and Purina Chow (Purina MiLts, Richmond, IN, USA) in Light-dark cycLes alternating every :12 "~ 320 hours beginning at 7 am. ExperimentaL animals were .~ divided into four groups: SD-Contro[, SD-CrP, GK-Contro[, and GK-CrP, with six rats respectiveLy. The rats of the CrP 280 groups were treated with CrP (100 m g / k g / d a y , po) for 4 weeks and those of the controL groups with an inert vehicle (normal saline, po). To see the effect of a chromium240 onLy treatment in diabetic rats, a high dosage (100 0 1 2 3 4 mg/kg/day) of chromium which had been proven to be non-toxic was chosen (16). Weeks When 4 weeks had elapsed, insulin sensitivity tests were carried out by intraperitoneal injection of glucose (2 B [ ~ Cr(-) g/kg) in conjunction with subcutaneous injection of Cr(+) 1 insulin (5 U/kg, Oaewoong-Lilly Co, Korea; administered 30 minutes before the glucose Load), and blood glucose 150 concentrations were measured at O, :10, 30, 60, 90, and ,-, :120 minutes after the glucose Load. The next day, glucose r tolerance tests (GTTs) were performed by intraperitoneaL "~ 1Do injection of glucose (2 g/kg) alone. BLood sampLes were drawn at O, 10, 30, 60, 90, and 120 minutes after the glu~tm cose Load from the tail vein, and plasma glucose and -~ insuLin Levels were measured. The area under the curve ~ 50 (AUC; minor-rain/L) of time-concentration during insulin sensitivity test or GTT was calculated for the glucose and insulin LeveLsaccording to the trapezoidal rule. The blood 0 SD Rat GK Rat glucose LeveLwas measured with an automated blood gLucose analyzer (GLUCOSEOT, Daiichi Co, 3apan). The plasma * significantly different from control, P < 0.05 insulin level was determined by a rat insuLin enzyme ** significantly different from control, P < 0.01 immunoassay kit (SPI-BIO Co., France). The data are expressed as means + SD. Significance was Fig. 1. A: Changes of body weight 4 weeks after treatment of assessed with a nonpaired t-test, and a value of P < 0.05 chromium. B: Comparison of body weight 4 weeks after treatment of chromium. was considered significant. J. Trace ELem. Med. BioL 17/4 (2004)
Improvement of insulin sensitivity in diabetes with chromium treatment 245 Fig. 3A, 3B and Table 1 show the glucose and insulin levels during the glucose tolerance tests (glucose only loaded) for the CrP-treated and control groups in GK rats. The glucose levels and insulin concentrations in the CrPtreated rats were not different from those in the control rats. The AUCo_~lzoof glucose in the CrP-treated group was not significantly different from the control group either (666.50 + 108.0 vs 632.9 + 80.3 mg-min/mL).
Discussion Since chromium has become known as "gtucose toterance factor" in the [ate 1950 (1), no unequivocal pharmacologic effects, to date, have been observed with chromium supptementation in healthy individuals or diabetic patients. A double-blind, p[acebo-contro[ted study in patients with type 2 diabetes performed by Uusitupa et a[.
A 650 600 E
550
V
500
O o 3
450
"O
400
O O ~
350
.... o... Control :
CrP Treated
300 0
10
3O
6O
90
120
Time (min) B
900
A J 300 "O O3 v
E ~) l/) 200 O O
(_9 "o 100 O O
m
....<> SD-Control • SD-CrP ....o GK-Control
........ ~
.!
A
.J
E
"~ 600
v
E
O 300
Control 0 10
30
60
Time
90
120
(min)
B
Cr-treated
Fig. 3. A: Blood glucose concentrations during glucose tolerance test. Glucose tolerance test was performed by intraperitonea[ injection of glucose (2 g/kg) alone. B: Area under curves of glucose concentrations during glucose tolerance test.
240 . - . 200
~....... ~ Control CrP Treated
Table 1. Insulin concentrations (ng/mL) during GTTsin GK rats.
J
E rE
v
-k 160
120
E
O
<
°i
80 40
SD Rat
GK Rat
* significantly different from control P < 0.05 Fig. 2. A: Blood glucose concentrations during insulin sensitivity test. Insulin sensitivity test was conducted by intraperitonea[ injection of glucose (2 g/kg) in conjunction with subcutaneous injection of insulin (5 U/kg, 30 min before the glucose load). B: Area under curves of glucose concentrations during insulin sensitivity test.
Time [min]
0
10
30
Control
0.95 _+0.16
0.66 0.60 0.54 0.48 0.39 _+0.26 _+0.15 _+0.29 _+0.29 _+0.09
CrP
0.88 _+0.24
0.68 0.54 0.64 0.59 0.91 _+0.29 _+0.11 _+0.17 _+0.06 _+0.15
Significance
ns
ns
ns
60
ns
90
ns
120
ns
ns: not significant
(7) showed no effects of chromium on glucose tolerance, lipid levels, and weight, and some other we[[ designed placebo-controlled studies of chromium supplementation in type 2 diabetes did not yield positive results either (8, 17). By contrast, the study performed by Anderson et aL (9) in Beijing in 1997 showed that supplementation of chromium had beneficial effects on glucose and insulin concentrations in patients with type 2 diabetes with no effects on body weight (9). The study design was double J. Trace Elem. Med. Biol. 17/4 (2004)
246
D.-S. Kim, T.-W. Kim and J.-S. Kang
blind and placebo controlled. The background of the supplementation of chromium in diabetic patients results from the findings that diabetic patients excrete more chromium than normal healthy people do and diabetic patients tend to lose the ability to convert chromium to an usable form that potentiates insulin action (:18, :19). Recently, Morris et al. (:13) reported that mean concentrations of plasma chromium were approximately 33% lower and urine concentrations almost :100% higher in patients with type 2 diabetes compared to a group of healthy individuals. Thus, the chromium requirement is postulated to increase in individuals with diabetes. In our experiment, though plasma insulin levels were not affected by chromium supplementation, the results of insulin sensitivity tests showed positive effects of chromium supplementation in GK diabetic rats. However, in normal healthy rats, chromium supplementation did not affect glucose levels during insulin sensitivity tests. The mechanism of chromium action on glucose metabolism is partly known. Recently, the molecular basis of the mechanism of the chromium action has been discovered by Vincent et al. (20). Chromium binds a unique chromium-binding oligopeptide named low-molecular weight chromium-binding substance (LMWCr) isolated and characterized by Wada and Yamamoto in the :1980s (2:1). LMWCr functions as a part of an insulin-signaling autoamplification mechanism by stimulating insulin receptor kinase activity (22). Regarding improvements of body composition with chromium supplementation, there have been several studies, but the results of these studies are varied. Anderson (23) reported that chromium increased lean body mass and decreased the percentage of body fat, which might lead to weight loss in humans, whereas Amato et al. (24) reported chromium supplementation alone did not appear to improve insulin sensitivity or body composition in non obese, healthy men and women of advanced age. Recently, Cefalu et al. reported the findings that in obese individuals given chromium picolinate, insulin sensitivity increased without any significant changes in body fat distribution (25). To date, there have been no data about weight change with chromium supplementation in individuals with diabetes. In the present study, the mean body weight in chromium treated Goto-Kakizaki diabetic rats was :1:1.2% heavier compared to the control group. This finding in diabetic rats is similar to the result that we reported previously in dexamethasone treated rats (26). In that study, chromium supplementation significantly recovered dexamethasone induced loss of body weight. This present experiment also demonstrates that in normal SD rats, chromium supplementation Leads to an increase of body weight (30.9% heavier than control group). It is possible that this anabolic effect of chromium can be attributed to a potentiation of insulin action. To elucidate which parts of the body are increased, further studies are needed. In summary, our data suggest that chromium supplementation improves insulin response to glucose and also increases body weight in Goto-Kakizaki diabetic rats. This raises the possibility that chromium can be considered as supplement in patients with diabetes. J. TraceElem. Med. Biol. 17/4 (2004)
References I. Schwarz K, and Mertz W (1959) Chromium(lll) and glucose tolerance factor. Arch. Biochem Biophys 85:292-295 2. Striffler iS, Polansky MM, and Anderson RA (1988) Dietary chromium decreasesinsulin resistance in rats fed a high-fat, mineral-imba[anced diet. Metabolism 47:396-400 3. Lee NA, and Reasner CA (1994) Beneficial effect of chromium supplementation on serum trig[yceride levels in NIDDM. Diabetes Care 17:1449-1452 4. Jeejeebhoy KN, Chu RC, Marliss EB, Greenberg GR, and Bruce-Robertson A (1977) Chromium deficiency, glucose intolerance, and neuropathy reversed by chromium supplementation in a patient receiving long-term total parentera[ nutrition. Am J C[in Nutr 30:5311-538 5. Brown RO, Forloines-Lynn S, Cross RE, and Heizer WD (1986) Chromium deficiency after long-term total parenteral nutrition. Dig Dis Sci 32:661-664 6. Striffler JS, Polansky MM, and Anderson RA (1999) Overproduction of insulin in the chromium-deficient rat. Metabolism 48:1063-1068 7. Uusitupa MI, Kumpulainen JT, Voutilainen E, Hersio K, Sar[und H, Pyorala KP, Koivistoinen PE, and Lehto JT (1983) Effect of inorganic chromium supplementation on glucose tolerance, insulin response, and serum [ipids in non-insulindependent diabetics. Am 3 Clin Nutr 38:404-4:10 8. Abraham AS, Brooks BA, and Eylath U (:1992) The effects of chromium supplementation on serum glucose and [ipids in patients with and without non-insulin-dependent diabetes. Metab C[in Exp 411:768-77:1 9. Anderson RA, Cheng N, Bryden NA, Poiansky MM, Cheng N, Chi J, and Feng J (:1997) Elevated intakes of supplemental chromium improve glucose and insulin variables in individuals with type 2 diabetes. Diabetes 46::1786-:179:1 :10. Elias AN, Grossman MK, and Va[enta LJ (:1984) Use of the artificial beta cell (ABC) in the assessment of peripheral insulin sensitivity: Effect of chromium supplementation in diabetic patients. Gen Pharmaco[ :15:535-539 :1:1. Lukaski HC (1999) Chromium as supplement. Ann Rev Nutr :19:279-301 :12. Anderson RA (:1995) Chromium and parentera[ nutrition. Nutrition :1:1:83-86 :13. Morris BW, MacNei[ S, Hardisty CA, He[[er S, Burgin C, and Gray TA (:1999) Chromium homeostasis in patients with type 11 (NIDDM) diabetes. J Trace Elem Med BioL :13:57-6:1 :14. Striffler iS, Law JS, Polansky MM, Bhathena SJ, and Anderson RA (:1995) Chromium improves insulin response to glucose in rats. Metabolism 44::1314-:1320 :15. Goto Y, Suzuki K, Ono T, and Toyota M (:1988) Development of diabetes in the non-obese NIDDM rat (GK rat). Adv Exp Med Bio[ 246:29-3:1 :16. Anderson RA, Bryden NA, and Polansky MM (:1997) Lack of toxicity of chromium chloride and chromium pico[inate in rat. 3 Am Coll Nutr :16:273-279 :17. Trow LG, Lewis J, Greenwood RH, Sampson MJ, Self KA, Crews HM, and Fairweather-Tait S3 (2000) Lack of effect of dietary chromium supplementation on glucose tolerance, plasma insulin, and [ipoprotein levels in patients with type 2 diabetes. Int J Vitam Nutr Res 70::14-:18 18. Doisy RJ, Streeten DHP, Freiberg JM, and Schneider AJ (:1976) Chromium metabolism in man and biochemical effects. In: Prasad AS, Ober[eas D (Eds) Trace Elements in Human Health and Disease: Essential and Toxic Elements. Marcel Dekker, New York :19. Tuman RW, Bilbo iT, and Doisy R3 (:1978) Comparison and effects of natural and synthetic glucose tolerance factor in normal and genetically diabetic mice. Diabetes 27:49-56
Improvement of insulin sensitivity in diabetes with chromium treatment 20. Vincent JB (2000) Quest for the molecular mechanism of chromium action and its relationship to diabetes. Nutr Reviews 58:67-72 21. Yamamoto A, Wada O, and Ono T (1987) Isolation of biologically active low-molecular-mass chromium compound from rabbit liver. Eur J Biochem 165:627-631 22. Davis CM, and Vincent JB (1997) Chromium oligopeptide activates insulin receptor tyrosine kinase activity. Biochemistry 15:4382-4385 23. Anderson RA (1998) Effects of chromium on body composition and weight loss. Nutr Rev 56:266-270
247
24. Amato P, Morales AJ, and Yen SS (2000) Effects of chromium pico[inate supplementation on insulin sensitivity, serum [ipids, and body composition in healthy, nonobese, older men and women. J Geronto[ A Bio[ Sci Med Sci 55:260-263 25. Cefalu WT, Bell-Farrow AD, Stegner J, Wang ZQ, King T, Morgan T, and Terry JG (1999) Effect of chromium pico[inate on insulin sensitivity in vivo. J Trace Elem Exp Med 12:71-83 26. Kim DS, Kim TW, Park IK, Kang JS, and Om AS (2002) Effects of chromium pico[inate supplementation on insulin sensitivity, serum [ipids, and body weight in dexamethasone treated rats. Metabolism 51:589-594
3. Trace Etem. Med. BioL 17/4 (2004)
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Chromium picolinate supplementation improves insulin sensitivity in Goto-Kakizaki diabetic rats Dong-Sun Kim *,I, Tae-Wha Kim I and 3u-Seop Kang2 i Departmentof Internal Medicine, HanyangUniversityCollegeof Medicine, SeouL,Korea 2Department of Pharmacology, HanyangUniversityCollegeof Medicine, Seou[, Korea Received December 2002 • Accepted December 2003
Abstract Chromium pico[inate (CrP) supplementation has been studied as a potentiaL therapy of insulin resistance and Lipid abnormalities. There have been some reports invoLving chromium supplementation in patients with diabetes, but the results are varied. The present study was conducted to assessthe effects of CrP on insulin sensitivity and body weight in Goto-Kakizaki (GK) diabetic rats. We supplemented normal Sprague-DawLey (SD) rats and GK diabetic rats with suppLementaL CrP, 100 mg/kg/day once a day for 4 weeks. In the normal SD rats, the mean body weight of the control group increased by 50.5%, whereas that of the CrP-treated group increased by 65.9% (P < 0.05 vs controL). SimiLarLy, in the diabetic GK rats, CrP supplementation showed increased weight gain compared to the control group (133.4% vs 119.6% of the baseline weight, P < 0.01). GLucosetolerance tests (GTT) Lip injection of glucose; 2 g/kg] and insulin sensitivity tests [SQ injection of insulin (5 U/kg) plus ip injection of glucose (30 rain after insulin injection)] were conducted. During insulin sensitivity tests at the end of treatment, the glucose Levels were significantly Lower in CrP-treated rats compared with the control rats (AUCo_~2o; ]13.1 _+32.0 vs 170.5 _+49.0 mg-min/mL, P < 0.05). During GTTs,the glucose Levelsand insulin concentrations in the CrP-treated rats were not different from those in the control rats. The results of these studies suggest that CrP supplementation in GK diabetic rats Leadsto increase of weight gain and improvement of insulin sensitivity. This raises the possibility that CrP supplementation can be considered to improve carbohydrate metabolism in patients with type 2 diabetes me[titus. Key words: chromium, Goto-Kakizaki, insulin sensitivity, rats, diabetes
Introduction Chromium is an essential trace element for humans and animals. Since Schwartz and Mertz identified in 1959 chromium as the active component of the "g[ucose tolerance factor" (1), chromium supplementation has been studied as a potential therapy of insulin resistance and lipid abnormalities (2, 3). According to previous reports, severe chromium deficiency in patients receiving total
*Correspondence to: Dong-Sun Kim, Department of Internal Medicine, Hanyang University College of Medicine, 17 Haengdang-dong, Sungdong-gu, SeouL, 133-792, Korea, Phone: +82-2-2290-8328, Fax: +82-2-2298-9183, E-mail: [email protected]
parentera[ nutrition caused a peripheral neuropathy, brain dysfunction, and glucose intolerance requiring increasing amounts of insulin (4-6). Chromium is now routinely added to total parenteraL nutrition. There have been some reports about the effects of chromium in diabetic patients (7-10). It is not surprising that chromium supplementation in healthy human subjects on normal diet displayed no beneficial effects on carbohydrate metabolism or weight change (11). By contrast, decrease of glucose concentrations were reported in roughly half the diabetic patients supplemented with chromium. Chromium supplementation in chromium deficient diabetic rats that demonstrate symptoms of insulin resistance can lead to improvement of glucose intoter0946-672X/04/17/04-243 $ 30.00/0
244
D.-S. Kim, T.-W. Kim and 3.-S. Kang
ance, weight Loss, and lipid metabolism (:12). In the early years of onset of type 2 diabetes melLitus (DM), it was reported that plasma chromium concentrations were inversely correlated with plasma gLucose and that type 2 diabetic patients had high LeveLs of urinary chromium leading to increased Loss of chromium (:13). Moreover, dietary chromium intake in most countries tends to be suboptimal these days. According to StriffLer's study, chromium suppLementation in chromium deficient rats Leads to the improvement of insuLin response to glucose (:14). However, there are stiLl some controversies about the supplementation of chromium in patients with type 2 diabetes. This study was undertaken to elucidate the effect of chromium picolinate (CrP) on the insulin sensitivity and body weight in Goto-Kakizaki (GK) diabetic rats
(:15). Materials and methods
Results The changes of body weight during the study are shown in Fig. 1. In the normal SO rats, the mean body weight of the control group increased by 50.5%, whereas that of the CrP treated group increased by 65.9% (P < 0.05 vs control). Similarly, in the diabetic GK rats, the mean weight of the control group was 340.9 g (1:19.6% of the baseline weight) at the end of the experiment, and that of the CrP treated group was 373.5 g (133.4% of the initial weight, P < 0.01 vs control). The blood glucose Levels and AUCo_~12oafter the insulin and glucose Load (insulin sensitivity test) for both groups of rats are shown in Fig. 2A and Fig. 2B. CrP treatment induced the improvement of insulin sensitivity in GK rats. During insulin sensitivity tests, the glucose levels were significantly lower in GK-CrP rats compared with GK-contro[ rats. The AUCo_+t2oof the glucose concentrations in the GK-CrPgroup was 113.:1 + 32.0 mg-min/mL which was 66.3% of the GK-contro[ group (170.5 + 49.0 mg-min/mL, P < 0.05).
MaLe Sprague-DawLey (SD) rats (8 weeks, 242 g in average) were purchased from CharLes River Breeding Laboratories (Wilmington, MA, USA), and maLe Goto-Kakizaki (6K) diabetic rats (8 weeks, 270 g in average) having A 400 .-- ~>--- SD-Control more than :140 mg/dL of fasting bLood glucose were pur---~- SD-CrP chased from M & B Co. (Denmark). The rats were handLed GK-Control ............... and housed in a protected environment at a constant tem• GK-CrP . . " ~ perature of 20-23 °C in conventional plastic cages with ,-, 360 , .< free access to water and Purina Chow (Purina MiLts, Richmond, IN, USA) in Light-dark cycLes alternating every :12 "~ 320 hours beginning at 7 am. ExperimentaL animals were .~ divided into four groups: SD-Contro[, SD-CrP, GK-Contro[, and GK-CrP, with six rats respectiveLy. The rats of the CrP 280 groups were treated with CrP (100 m g / k g / d a y , po) for 4 weeks and those of the controL groups with an inert vehicle (normal saline, po). To see the effect of a chromium240 onLy treatment in diabetic rats, a high dosage (100 0 1 2 3 4 mg/kg/day) of chromium which had been proven to be non-toxic was chosen (16). Weeks When 4 weeks had elapsed, insulin sensitivity tests were carried out by intraperitoneal injection of glucose (2 B [ ~ Cr(-) g/kg) in conjunction with subcutaneous injection of Cr(+) 1 insulin (5 U/kg, Oaewoong-Lilly Co, Korea; administered 30 minutes before the glucose Load), and blood glucose 150 concentrations were measured at O, :10, 30, 60, 90, and ,-, :120 minutes after the glucose Load. The next day, glucose r tolerance tests (GTTs) were performed by intraperitoneaL "~ 1Do injection of glucose (2 g/kg) alone. BLood sampLes were drawn at O, 10, 30, 60, 90, and 120 minutes after the glu~tm cose Load from the tail vein, and plasma glucose and -~ insuLin Levels were measured. The area under the curve ~ 50 (AUC; minor-rain/L) of time-concentration during insulin sensitivity test or GTT was calculated for the glucose and insulin LeveLsaccording to the trapezoidal rule. The blood 0 SD Rat GK Rat glucose LeveLwas measured with an automated blood gLucose analyzer (GLUCOSEOT, Daiichi Co, 3apan). The plasma * significantly different from control, P < 0.05 insulin level was determined by a rat insuLin enzyme ** significantly different from control, P < 0.01 immunoassay kit (SPI-BIO Co., France). The data are expressed as means + SD. Significance was Fig. 1. A: Changes of body weight 4 weeks after treatment of assessed with a nonpaired t-test, and a value of P < 0.05 chromium. B: Comparison of body weight 4 weeks after treatment of chromium. was considered significant. J. Trace ELem. Med. BioL 17/4 (2004)
Improvement of insulin sensitivity in diabetes with chromium treatment 245 Fig. 3A, 3B and Table 1 show the glucose and insulin levels during the glucose tolerance tests (glucose only loaded) for the CrP-treated and control groups in GK rats. The glucose levels and insulin concentrations in the CrPtreated rats were not different from those in the control rats. The AUCo_~lzoof glucose in the CrP-treated group was not significantly different from the control group either (666.50 + 108.0 vs 632.9 + 80.3 mg-min/mL).
Discussion Since chromium has become known as "gtucose toterance factor" in the [ate 1950 (1), no unequivocal pharmacologic effects, to date, have been observed with chromium supptementation in healthy individuals or diabetic patients. A double-blind, p[acebo-contro[ted study in patients with type 2 diabetes performed by Uusitupa et a[.
A 650 600 E
550
V
500
O o 3
450
"O
400
O O ~
350
.... o... Control :
CrP Treated
300 0
10
3O
6O
90
120
Time (min) B
900
A J 300 "O O3 v
E ~) l/) 200 O O
(_9 "o 100 O O
m
....<> SD-Control • SD-CrP ....o GK-Control
........ ~
.!
A
.J
E
"~ 600
v
E
O 300
Control 0 10
30
60
Time
90
120
(min)
B
Cr-treated
Fig. 3. A: Blood glucose concentrations during glucose tolerance test. Glucose tolerance test was performed by intraperitonea[ injection of glucose (2 g/kg) alone. B: Area under curves of glucose concentrations during glucose tolerance test.
240 . - . 200
~....... ~ Control CrP Treated
Table 1. Insulin concentrations (ng/mL) during GTTsin GK rats.
J
E rE
v
-k 160
120
E
O
<
°i
80 40
SD Rat
GK Rat
* significantly different from control P < 0.05 Fig. 2. A: Blood glucose concentrations during insulin sensitivity test. Insulin sensitivity test was conducted by intraperitonea[ injection of glucose (2 g/kg) in conjunction with subcutaneous injection of insulin (5 U/kg, 30 min before the glucose load). B: Area under curves of glucose concentrations during insulin sensitivity test.
Time [min]
0
10
30
Control
0.95 _+0.16
0.66 0.60 0.54 0.48 0.39 _+0.26 _+0.15 _+0.29 _+0.29 _+0.09
CrP
0.88 _+0.24
0.68 0.54 0.64 0.59 0.91 _+0.29 _+0.11 _+0.17 _+0.06 _+0.15
Significance
ns
ns
ns
60
ns
90
ns
120
ns
ns: not significant
(7) showed no effects of chromium on glucose tolerance, lipid levels, and weight, and some other we[[ designed placebo-controlled studies of chromium supplementation in type 2 diabetes did not yield positive results either (8, 17). By contrast, the study performed by Anderson et aL (9) in Beijing in 1997 showed that supplementation of chromium had beneficial effects on glucose and insulin concentrations in patients with type 2 diabetes with no effects on body weight (9). The study design was double J. Trace Elem. Med. Biol. 17/4 (2004)
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D.-S. Kim, T.-W. Kim and J.-S. Kang
blind and placebo controlled. The background of the supplementation of chromium in diabetic patients results from the findings that diabetic patients excrete more chromium than normal healthy people do and diabetic patients tend to lose the ability to convert chromium to an usable form that potentiates insulin action (:18, :19). Recently, Morris et al. (:13) reported that mean concentrations of plasma chromium were approximately 33% lower and urine concentrations almost :100% higher in patients with type 2 diabetes compared to a group of healthy individuals. Thus, the chromium requirement is postulated to increase in individuals with diabetes. In our experiment, though plasma insulin levels were not affected by chromium supplementation, the results of insulin sensitivity tests showed positive effects of chromium supplementation in GK diabetic rats. However, in normal healthy rats, chromium supplementation did not affect glucose levels during insulin sensitivity tests. The mechanism of chromium action on glucose metabolism is partly known. Recently, the molecular basis of the mechanism of the chromium action has been discovered by Vincent et al. (20). Chromium binds a unique chromium-binding oligopeptide named low-molecular weight chromium-binding substance (LMWCr) isolated and characterized by Wada and Yamamoto in the :1980s (2:1). LMWCr functions as a part of an insulin-signaling autoamplification mechanism by stimulating insulin receptor kinase activity (22). Regarding improvements of body composition with chromium supplementation, there have been several studies, but the results of these studies are varied. Anderson (23) reported that chromium increased lean body mass and decreased the percentage of body fat, which might lead to weight loss in humans, whereas Amato et al. (24) reported chromium supplementation alone did not appear to improve insulin sensitivity or body composition in non obese, healthy men and women of advanced age. Recently, Cefalu et al. reported the findings that in obese individuals given chromium picolinate, insulin sensitivity increased without any significant changes in body fat distribution (25). To date, there have been no data about weight change with chromium supplementation in individuals with diabetes. In the present study, the mean body weight in chromium treated Goto-Kakizaki diabetic rats was :1:1.2% heavier compared to the control group. This finding in diabetic rats is similar to the result that we reported previously in dexamethasone treated rats (26). In that study, chromium supplementation significantly recovered dexamethasone induced loss of body weight. This present experiment also demonstrates that in normal SD rats, chromium supplementation Leads to an increase of body weight (30.9% heavier than control group). It is possible that this anabolic effect of chromium can be attributed to a potentiation of insulin action. To elucidate which parts of the body are increased, further studies are needed. In summary, our data suggest that chromium supplementation improves insulin response to glucose and also increases body weight in Goto-Kakizaki diabetic rats. This raises the possibility that chromium can be considered as supplement in patients with diabetes. J. TraceElem. Med. Biol. 17/4 (2004)
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