Lower cardiorespiratory fitness contributes to increased insulin resistance and fasting glycaemia in middle-aged South Asian compared with European men living in the UK

• Published in: Diabetologia Vol. 56; no. 10; pp. 2238 - 2249
• Main Authors: Ghouri, N., Purves, D., McConnachie, A., Wilson, J., Gill, J. M. R., Sattar, N.
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer Berlin Heidelberg 01-10-2013; Springer; Springer Nature B.V
• Subjects: Adult; Aged; Angioplasty; Asian Continental Ancestry Group; Asian people; Biological and medical sciences; Blood Glucose - metabolism; Cardiovascular disease; Cultural differences; Diabetes; Diabetes. Impaired glucose tolerance; Endocrine pancreas. Apud cells (diseases); Endocrinopathies; Etiopathogenesis. Screening. Investigations. Target tissue resistance; European Continental Ancestry Group; Exercise; Fasting - blood; Glucose; Human Physiology; Humans; Insulin resistance; Insulin Resistance - physiology; Internal Medicine; Male; Medical sciences; Medicine; Medicine & Public Health; Metabolic Diseases; Middle age; Middle Aged; Motor Activity - physiology; Obesity; Oxygen Consumption - physiology; Physical fitness; Questionnaires; United Kingdom > UK; Maximal oxygen uptake; Obesity; Ethnicity; Glycaemia; Adiposity; Physical activity; Insulin resistance; South Asian; Sedentary; Fitness; Endocrinopathy; Physical exercise; Human; Oxygen; Fasting; Diabetes mellitus; Nutrition disorder; Metabolic diseases; Uptake; Target tissue resistance; Physical fitness; Nutritional status
• ISSN: 0012-186X; 1432-0428
• DOI: 10.1007/s00125-013-2969-y

Aims/hypothesis
This study aimed to determine the extent to which increased insulin resistance and fasting glycaemia in South Asian men, compared with white European men, living in the UK, was due to lower cardiorespiratory fitness (maximal oxygen uptake [
V
˙
O
2
max
]) and physical activity.
Methods
One hundred South Asian and 100 age- and BMI-matched European men without diagnosed diabetes, aged 40–70 years, had fasted blood taken for measurement of glucose concentration, HOMA-estimated insulin resistance (HOMA
IR
), plus other risk factors, and underwent assessment of physical activity (using accelerometry),
V
˙
O
2
max
, body size and composition, and demographic and other lifestyle factors. For 13 South Asian and one European man, HbA
1c
levels were >6.5% (>48 mmol/mol), indicating potential undiagnosed diabetes; these men were excluded from the analyses. Linear regression models were used to determine the extent to which body size and composition, fitness and physical activity variables explained differences in HOMA
IR
and fasting glucose between South Asian and European men.
Results
HOMA
IR
and fasting glucose were 67% (
p
 < 0.001) and 3% (
p
 < 0.018) higher, respectively, in South Asians than Europeans. Lower
V
˙
O
2
max
, lower physical activity and greater total adiposity in South Asians individually explained 68% (95% CI 45%, 91%), 29% (11%, 46%) and 52% (30%, 80%), respectively, and together explained 83% (50%, 119%) (all
p
 < 0.001) of the ethnic difference in HOMA
IR
. Lower
V
˙
O
2
max
and greater total adiposity, respectively, explained 61% (9%, 111%) and 39% (9%, 76%) (combined effect 63% [8%, 115%]; all
p
 < 0.05) of the ethnic difference in fasting glucose.
Conclusions/interpretation
Lower cardiorespiratory fitness is a key factor associated with the excess insulin resistance and fasting glycaemia in middle-aged South Asian, compared with European, men living in the UK.