Fatty acid oxidation by skeletal muscle homogenates from morbidly obese black and white American women

doi:10.1016/S0026-0495(03)00034-9

Metabolism

Volume 52, Issue 6, June 2003, Pages 735-738

https://doi.org/10.1016/S0026-0495(03)00034-9 Get rights and content

Abstract

The purpose of this study was to determine if there were differences in the capacity of skeletal muscle from morbidly obese Black and White American women to oxidize fatty acids. The oxidation rates of ¹⁴C-palmitate, ¹⁴C-palmitoyl-CoA, and ¹⁴C-palmitoyl-carnitine were measured in whole homogenates of rectus abdominus from Black and White women who were similar in age and body mass index (BMI). The activities of muscle citrate synthase (CS), β-hydroxy acyl-CoA dehydrogenase (β-HAD), and mitochondrial and microsomal acyl-CoA synthetase (ACS) were measured in the 2 groups. The results showed that the rate of ¹⁴C-palmitate oxidation by muscle of Black women was 25% that of Whites (8.7 ± 1.5 v 34.4 ± 6.8 nmol ¹⁴CO₂ produced/gram tissue wet weight/ hour; P < .05), but the rates of ¹⁴C-palmitoyl-CoA and ¹⁴C-palmitoyl-carnitine oxidation were not different in the 2 groups. No differences were found in the activities of CS or β-HAD. However, the activities of both mitochondrial and microsomal ACS were lower in the Black women than the Whites (mitochondrial ACS 25.1 ± 3.9 v 36.4 ± 5.0 nmol/mg protein/min; P < .05; microsomal ACS 6.2 ± 0.5 v 8.5 ± 0.5; nmol/mg protein/min; P < .005). The lower rate of palmitate oxidation, and the lack of differences in the rates of palmitoyl-CoA and palmitoyl-carnitine oxidation indicate that there is a defect in the activation of the fatty acid in the muscle of the Black women. This was confirmed by the decrease in mitochondrial ACS activity in the Black women. The decreased fatty acid oxidation by skeletal muscle of obese Black women could result in shunting these fuels from muscle to adipose tissue for storage, which may contribute to the maintenance of obesity in the Black women.

Section snippets

Subjects

A total of 26 (12 White, 14 Black) morbidly obese (body mass index [BMI] >37) subjects, free of vascular disease, diabetes, or cancer, and currently not taking medications that affect carbohydrate and lipid metabolism participated in this study. Body mass and height were recorded to the nearest 0.1 kg and 0.1 cm, respectively, and BMI calculated. Rectus abdominus muscle biopsies were obtained from the participants undergoing gastric bypass surgery or total abdominal hysterectomy.21 We have

Results

Table 1 shows the physical and biochemical characteristics of the subjects who participated in this study. The 2 groups of women did not differ from each other with respect to age or BMI. No differences were found in plasma glucose or insulin levels between the 2 groups.

Table 2 shows the rates of CO₂ production from the oxidation of ¹⁴C-palmitate, ¹⁴C-palmitoyl-CoA, and ¹⁴C-palmitoyl-carnitine by whole homogenates of rectus abdominus from the 2 groups of women. The rate of palmitate oxidation

Discussion

The oxidation of fatty acids by mitochondria is a highly regulated process that involves the entry of fatty acids into the cell, their activation to acyl-CoA derivatives by ACS, and their entry into the mitochondrial matrix. Entry into the mitochondrial matrix is restricted by the impermeability of the inner mitochondrial membrane to long-chain acyl-CoAs, which is circumvented by the carnitine transport system. Fatty acyl-CoAs are converted to fatty acyl-carnitine by the enzyme CPT I and are

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African Americans have a higher prevalence of obesity [8] and type 2 diabetes mellitus [9] than Caucasians. The reasons for this disparity are not precisely known, but some possible explanations may be that African Americans have lower skeletal muscle fatty acid oxidation [10], resting metabolic rate [11], insulin sensitivity [12], and higher 24-hour RQ [13]. To our knowledge, only one study [14] has reported results on race and MF.
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^☆: Supported in part by grants from the North Carolina Institute of Nutrition, and the American Diabetes Association.

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Fatty acid oxidation by skeletal muscle homogenates from morbidly obese black and white American women☆

Abstract

Section snippets

Subjects

Results

Discussion

Am J Clin Nutr

Am J Clin Nutr

J Am Diet Assoc

Am J Clin Nutr

The National Health and Nutrition Examination Survey

JAMA

Obesity in minority populationsAn epidemiologic assessment

Obes Res

Trends in coronary heart disease mortality, morbidity, and risk factors from 1960 to 1986The Minnesota Heart Survey

Int J Epidmiol

Weight related attitudes and behavior of women who diet to lose weightA comparison of black dieters and white dieters

Obes Res

Weight loss methods used by African American and Euro-American women

Res Nurs Health

Differences in weight gain in relation to race, gender, age and education in young adultsThe CARDIA Study

Ethn Health

Black and white female’s perceptions of ideal body size and social norms

Obes Res

Differences in resting metabolic rates of inactive obese African American and Caucasian women

Int J Obes

Resting energy expenditure in obese African-American women and Caucasian women

Obes Res

Differences in resting energy expenditure in African American vs Caucasian overweight females

Int J Obes