Ethnic Differences in the Responsiveness of Adipocyte Lipolytic Activity to Insulin

Buthelezi, Ernest Philani; Merwe, M. van der; Lönnroth, Peter; Gray, I. P.; Crowther, Nigel J.

doi:10.1038/oby.2000.18

Cited by 29 publications

(20 citation statements)

References 43 publications

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“…43,44 This insulin effect was signi®cantly reduced in the OBW compared to OWW and a reduced sensitivity of isolated adipocytes to insulininhibition of lipolysis has been demonstrated previously in OBW. 45 During the late postprandial period of the extended OGTT, FFA concentrations were higher in the OWW than OBW and LWW. This may arise as a result of increased intravascular triglyceride hydrolysis by lipoprotein lipase activity (LPL) or net outward movement of FFA from adipose tissue due to increased hormone-sensitive lipase (HSL) activity or both.…”

Section: Discussionmentioning

confidence: 91%

Weight-related differences in glucose metabolism and free fatty acid production in two South African population groups

et al. 2001

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OBJECTIVE:The effects of free fatty acids (FFA), leptin, tumour necrosis factor (TNF) a and body fat distribution on in vivo oxidation of a glucose load were studied in two South African ethnic groups. DESIGN AND MEASUREMENTS: Anthropometric and various metabolic indices were measured at fasting and during a 7 h oral glucose tolerance test (OGTT). Body composition was measured using bioelectrical impedance analysis and subcutaneous and visceral fat mass was assessed using a ®ve-and two-level CT-scan respectively. Glucose oxidation was evaluated by measuring the ratio of 13 CO 2 to 12 CO 2 in breath following ingestion of 1-13 C-labelled glucose. SUBJECTS: Ten lean black women (LBW), ten obese black women (OBW), nine lean white women (LWW) and nine obese white women (OWW) were investigated after an overnight fast. RESULTS: Visceral fat levels were signi®cantly higher (P`0.01) in obese white than black women, despite similar body mass indexes (BMIs). There were no ethnic differences in glucose oxidation however; in the lean subjects of both ethnic groups the area under the curve (AUC) was higher than in obese subjects (P`0.05 for both) and was found to correlate negatively with weight (r 70.69, P`0.01) after correcting for age. Basal TNFa concentrations were similar in all groups. Percentage suppression of FFAs at 30 min of the OGTT was 24 AE 12% in OWW and 738 AE 23% (P`0.05) in OBW, ie the 30 min FFA level was higher than the fasting level in the latter group. AUC for FFAs during the late postprandial period (120 ± 420 min) was signi®cantly higher in OWW than OBW (P`0.01) and LWW (P`0.01) and correlated positively with visceral fat mass independent of age (r 0.78, P`0.05) in the OWW only. Leptin levels were higher (P`0.01) both at fasting and during the course of the OGTT in obese women from both ethnic groups compared to the lean women. CONCLUSIONS: Glucose oxidation is reduced in obese subjects of both ethnic groups; inter-and intra-ethnic differences were observed in visceral fat mass and FFA production and it is possible that such differences may play a role in the differing prevalences of obesity-related disorders that have been reported in these two populations.

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Section: Discussionmentioning

confidence: 91%

Weight-related differences in glucose metabolism and free fatty acid production in two South African population groups

et al. 2001

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“…Nevertheless, both techniques reveal similar responses to the antilipolytic effect of insulin in Abd sc and lower body adipose tissues. In vitro studies also show similar basal lipolytic rates in Abd and gluteal (Glt) or femoral adipocytes of premenopausal women, but Glt adipocytes are more sensitive to insulin ( 3,4 ). Whether this depot difference exists in postmenopausal women is not known, so this was one of the objectives of the current study.…”

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confidence: 80%

Resistance to the antilipolytic effect of insulin in adipocytes of African-American compared to Caucasian postmenopausal women

Fried

Tittelbach²,

Blumenthal³

et al. 2010

Journal of Lipid Research

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Increased availability of nonesterifi ed fatty acids (FA) contributes to the metabolic dysfunction associated with obesity, including systemic insulin resistance and hyperlipidemia ( 1 ). It is well established that central or upper body obesity, independent of total body fat, is associated with elevated systemic nonesterifi ed FA turnover in premenopausal women. In vivo studies of FA fl uxes show that on a per gram basis, abdominal (Abd) subcutaneous (sc) fat is the main source of the high systemic lipolysis in upper body compared with lower body obese premenopausal women and that leg fat is less lipolytically active ( 1 ). However, microdialysis studies detect no depot difference in lipolysis in nonobese, premenopausal Abd and femoral sc adipose tissue ( 2 ). Nevertheless, both techniques reveal similar responses to the antilipolytic effect of insulin in Abd sc and lower body adipose tissues. In vitro studies also show similar basal lipolytic rates in Abd and gluteal (Glt) or femoral adipocytes of premenopausal women, but Glt adipocytes are more sensitive to insulin ( 3, 4 ). Whether this depot difference exists in postmenopausal women is not known, so this was one of the objectives of the current study.Overweight African-American (AA) women are more hyperinsulinemic and resistant to insulin's glucoregulatory actions than body fat-matched Caucasian (C) women ( 5, 6 ). Thus, it is logical to postulate that AAs may also exhibit higher rates of lipolysis and resistance to the antilipolytic effect of insulin. However, results in the literature on this topic are inconsistent. In premenopausal women, Abstract High fatty acid (FA) fl ux is associated with systemic insulin resistance, and African-American (AA) women tend to be more insulin resistant. We assessed possible depot and race difference in the antilipolytic effect of insulin in adipocytes isolated from abdominal (Abd) and gluteal (Glt) subcutaneous (sc) adipose tissue of overweight, postmenopausal AA and Caucasian (C) women. Percent body fat, fasting insulin, visceral adiposity, and adipocyte size was higher in AA women. Disinhibited lipolysis (presence of adenosine deaminase) per unit adipocyte surface area was similar in Abd and Glt and in AA and C. However, rates of 'basal' [submaximal phenylisopropyl adenosine (PIA) -suppressed] and insulin-suppressed lipolysis were higher in Abd of AA compared with C women even after adjustment for percent fat and visceral fat area. The race difference in rates of PIA-and insulin-suppressed lipolysis in AA were correlated with their hyperinsulinemia, but AA race, independent of fasting insulin, was associated with lower responsiveness (percent suppression) to submaximal insulin concentrations, although sensitivity (ED50) was not affected. Overall, these data are consistent with the hypothesis that decreased responsiveness of Abd adipocytes to antilipolytic effectors may contribute to higher FA availability and thereby to racial differences in insulin resistance. -Fried,

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“…12 The women were in a fasted state. The scanning criteria were: (1) 10 mm slice thickness; (2) 120 kV; (3) 250 mA; (4) 2 s; and (5) 340 ± 480 mm ®eld of view (FOV), depending on the size of the subject.…”

Section: Ct Scan Measurementsmentioning

confidence: 99%

“…10,11 We have demonstrated a higher degree of in vitro adipose tissue insulin resistance in the BW compared with the WW (data in press). 12 In addition, the BW have a brisker in vivo adipose tissue lipolysis. 9,13 The resulting high postabsorptive free fatty acid (FFA) levels, 9,13 together with the relative insulinopenia of the black Southern African people, 9,14 ± 16 may therefore also have been instrumental in creating in vivo insulin resistance, 17,18 to glucose disposal in muscle tissue.…”

Section: Introductionmentioning

confidence: 99%

Evidence for insulin resistance in black women from South Africa

et al. 2000

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OBJECTIVE: The rate of glucose disposal was determined in 10 black and 10 white obese nondiabetic urban women from South Africa to assess insulin resistance. DESIGN AND METHODS: Euglycemic hyperinsulinemic clamp and body composition analysis. RESULTS: Age, body mass index (BMI), anthropometric measurements and body composition were similar in both groups of women. A ®ve-level computed tomography (CT) scan showed a similar mean subcutaneous fat mass in both groups of women (black obese women 555 AE 9.0 vs white obese women 532 AE 6.0 cm 2 ), but less visceral fat in black obese women (90 AE 3.0 vs 121 AE 3.1 cm 2 ; P`0.05). Black obese women had higher fasting free fatty acid (997 AE 69 vs 678 AE 93 m mmolal; P`0.05) and lactate concentrations (1462 AE 94 vs 1038 AE 39 m mmolal; P`0.05), but lower fasting insulin levels (87 AE 12 vs 155 AE 9 pmolal; P`0.001). Black obese women also had a more favorable HDL: total cholesterol ratio (30.5% vs 23.0%; P`0.04). The mean glucose disposal rate (M) and disposal expressed as glucose sensitivity index (MaI) were reduced in the black obese women vs white obese women (M: 7.1 AE 0.8 vs 13.7 AE 1.0 mmolakg Á min À1 Â100; P`0.01, and MaI: 0.12 AE 0.01 vs 0.24 AE 0.02 mmolakg Á min À1 apmolal Â1000; P`0.01). Only black obese women showed a signi®cant decrease in C-peptide levels during the clamp (2.9 AE 0.22 vs 1.2 AE 0.12 nmolal; P`0.001). During the euglycemic period, the black obese women had higher lactate levels at all time points, but only the white obese women had increased lactate levels (918 AE 66 to 1300 AE 53 m mmolal; P`0.05). CONCLUSION: Black obese women demonstrate a higher degree of insulin resistance, despite less visceral fat and a higher HDL: total-cholesterol ratio. In addition, endogenous b b-cell secretory function in black obese women appears to be more sensitive to the suppressive effect of exogenous insulin administration. The signi®cant increase in lactate levels in white obese women con®rms that they are more insulin sensitive.

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Ethnic Differences in the Responsiveness of Adipocyte Lipolytic Activity to Insulin

Cited by 29 publications

References 43 publications

Weight-related differences in glucose metabolism and free fatty acid production in two South African population groups

Weight-related differences in glucose metabolism and free fatty acid production in two South African population groups

Resistance to the antilipolytic effect of insulin in adipocytes of African-American compared to Caucasian postmenopausal women

Evidence for insulin resistance in black women from South Africa

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