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Transactions of the American Clinical and Climatological Association 02/1996; 107:175-85; discussion 185-6.
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ABSTRACT: Upper-body obesity (UBO) in white women is associated with increased fatty acid turnover and resistance to the effects of insulin on systemic glucose metabolism. The present study determined whether the abilities of insulin to stimulate glucose transport and suppress lipolysis are impaired in adipocytes from white UBO (W-UBO) women. Because the clinical risks associated with UBO are attenuated in black women, the effects of race on adipocyte insulin sensitivity were assessed. Forty-two healthy, equally obese women were selected for study on the basis of race (black or white) and body fat distribution (UBO or lower-body obesity [LBO]). In white women, both abdominal and gluteal fat cells from the UBO versus LBO group were less responsive to the stimulatory effects of insulin on glucose uptake and less sensitive to the antilipolytic effects of insulin and the adenosine analog, phenylisopropyladenosine (PIA). In contrast, in black women, fat cells from UBO and LBO groups were equally sensitive to the stimulatory effects of insulin on glucose transport and the suppressive effects of insulin and PIA on lipolysis. These in vitro data correlate well with previous clinical findings that UBO in white women but not in black women is associated with insulin resistance and dyslipidemia. Thus, resistance to the antilipolytic effects of insulin and adenosine at the level of adipose tissue may increase systemic lipolysis and play a role in the development or maintenance of peripheral insulin resistance associated with UBO in white women, but not in black women.
Metabolism 09/1995; 44(8):987-95. · 2.66 Impact Factor
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ABSTRACT: For Caucasian women, an excess of abdominal fat is a potent risk factor for the development of diabetes and cardiovascular disease. However, there is limited information regarding the health risks of upper body obesity for African-American women despite a higher prevalence of obesity and obesity-related diseases and a reportedly higher prevalence of abdominal fat accumulation. This study aimed to determine whether UBO, independent of total body fatness, is as potent a diabetic and CVD risk factor for black women as has been confirmed for white women. Diabetes and CVD risks and androgenic status were assessed in nondiabetic, premenopausal women of similar body fatness who differed by race (black or white) and body fat distribution (UBO or lower body obesity). In black women, high-density lipoprotein cholesterol was the only measurement adversely affected by abdominal fat; HDL cholesterol was significantly lower in the black UBO group (1.14 +/- 0.05 mM) compared with the black LBO group (1.37 +/- 0.08 mM). This contrasts markedly with our findings in white women. In confirmation of previous reports, white UBO women, compared with white LBO counterparts, had significantly higher glucose (967.6 vs. 709.2 mM/2 h) and insulin (120.5 vs. 52.1 pM/2 h) areas and significantly lower peripheral insulin sensitivities (0.99 vs. 2.95 x 10(-4) min-1/microU/ml). In addition, HDL cholesterol levels were significantly lower in the white UBO group (1.03 mM) compared with the white LBO group (1.49 mM), whereas plasma TG levels (white UBO, 1.72 vs. white LBO, 0.88 mM) and dBPs (white UBO, 84 vs. white LBO, 75 mmHg) were significantly higher.(ABSTRACT TRUNCATED AT 250 WORDS)
Diabetes 05/1993; 42(4):537-43. · 8.29 Impact Factor
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ABSTRACT: The absorption of inorganic, trivalent chromium (Cr) by the rat small intestine was investigated by quantifying three components of the absorptive process: 1) Cr uptake from a test meal, 2) Cr transport into the circulation and 3) Cr retention by the intestine. An in vitro, in situ double-perfusion technique was used in which the intestinal vasculature, from the superior mesenteric artery to the portal vein, and the intestinal lumen, from the duodenum to the ileum, were perfused simultaneously. The vasculature was perfused with a synthetic "plasma" (vascular perfusate) while the lumen was perfused with a nutrient-rich solution (intestinal perfusate) at concentrations of trivalent Cr of 0.2-20 mumol/l (10-1000 ppb). Dose-response curves, in which Cr transport, retention and uptake were plotted against the luminal Cr concentration, revealed that Cr absorption is a nonsaturable process. Regardless of the Cr concentration of the intestinal perfusate, 5.90 +/- 0.33% (mean +/- SEM) of the test dose was taken up from the meal, 5.52 +/- 0.33% was transported into the vascular perfusate and 0.38 +/- 0.03% was retained by the small intestine. Based on the criterion of saturability, it was concluded that inorganic, trivalent Cr is absorbed by the nonmediated process of passive diffusion in the small intestine of rats fed a Cr-adequate diet (1.44 micrograms Cr/g diet).
Journal of Nutrition 09/1989; 119(8):1138-45. · 3.92 Impact Factor
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ABSTRACT: A simplified method for preparing blood serum and plasma for Zeeman electrothermal atomic absorption spectrometry is described and applied to the measurement of chromium in human serum and plasma. This enzymatic degradation with bacterial protease (EC 3.4.21.3) requires little laboratory apparatus, decreases the work and time of sample preparation, and obviates some potential sources of contamination. We used bovine reference serum (USDA No. 7292) to validate Cr concentration. There was less Cr in serum than in plasma, whether sodium heparin or sodium citrate was used as anticoagulant. For six human subjects, Cr in serum averaged 0.15 (SD 0.02) micrograms/L, 0.26 (SD 0.03) micrograms/L in heparinized plasma, and 0.28 (SD 0.02) micrograms/L in citrated plasma. We postulate that the Cr concentration is lower in serum because some of the Cr binds to proteins complexed with the clot in the coagulation process.
Clinical Chemistry 08/1986; 32(7):1383-6. · 7.91 Impact Factor
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ABSTRACT: A chromium (Cr) balance study was conducted on a metabolic unit for 12 days in two normal males, ages 62 and 66, ingesting a nutritionally adequate, constant diet. Complete urine and stool collections were obtained daily. The diet, stool, and urine were analyzed for chromium by Zeeman atomic absorption spectrometry. On dietary Cr intakes of 36.9 and 36.7 micrograms/day, only a small fraction of the ingested Cr, 0.9 microgram and 0.5 microgram/day, was absorbed. Most of the dietary Cr, 36.0 micrograms and 36.2 micrograms/day, was excreted in the stool. Urinary Cr was constant from day to day with a mean of 0.30 microgram/day +/- 0.03 SD and 0.28 microgram/day +/- 0.05 SD. The Cr balances (apparent net retention) were positive, 0.6 and 0.2 microgram/day, indicating equilibrium. The average apparent net absorption of Cr for the two subjects was 1.8%.
American Journal of Clinical Nutrition 08/1986; 44(1):77-82. · 6.67 Impact Factor
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ABSTRACT: The mechanism of chromium (Cr) absorption by the rat small intestine was investigated using a double perfusion technique wherein the luman of the small intestine and the vasculature supplying it were separately perfused. The intestinal perfusate (IP) was a nutrient-rich tissue culture medium (TCM) with added inorganic Cr and /sup 51/Cr. The vascular perfusate (VP) was a Krebs-Ringer bicarbonate solution (KRB) containing 4.7% dextran, 0.1% glucose and 5% human serum. Cr absorption was calculated by the amount of /sup 51/Cr detected in the VP. To determine the transport mechanism for Cr, its absorption into the VP was measured at various Cr concentrations of the IP ranging from 10-400 ppb CrCl/sub 3/. The amount of Cr absorbed into the blood rose linearly with the intestinal Cr concentration suggesting a process of simple diffusion. Manipulations of the VP and IP constituents were made to investigate their effects on Cr absorption. When serum was omitted from the VP, Cr adsorption was suppressed, suggesting that serum component(s) are necessary for optimal Cr absorption. When either of 2 plasma transport proteins (apo-transferrin, albumin) were added to the serum-free VP at physiological levels, Cr absorption returned to, but did not exceed, control levels. When the TCM was replaced with a KRB solution; Cr absorption was suppressed indicating that there are nutrient(s) of the TCM which facilitate Cr absorption. Further suppression occurred when a Cr concentration gradient opposing Cr absorption was created (IP at 100 ppb Cr, VP at 400 ppb Cr).
02/1986
