Abstract
South Asians (SA) are at higher risk of cardiometabolic disorders than Europeans (EU), yet the potential determinants of this risk are poorly understood. We tested the hypotheses that 1) South Asians (SA) have greater muscle inflammation compared to Europeans (EU) at similar fat mass 2) differential regional adiposity in SA compared to EU is associated with enhanced muscle inflammation in SA. This cross-sectional study was conducted at a tertiary academic center in Hamilton, Ontario, Canada. The study included 29 EU and 26 SA. Quantitative real-time PCR and western blot were used to measure muscle inflammation. Statistical analysis was done using a General Linear Model. Despite having similar macrophage content to EU, SA muscle had lower levels of chemokine CCL2 compared to EU at gene expression (β -1.099, SE β 0.521, p-value 0.04) and protein (0.84 ± 0.69 versus 1.10 ± 0.60, p-value 0.052) levels. SA had more pronounced abdominal and hepatic adiposity, with smaller Intramyocellular lipid particles compared to EU (0.26 ± 0.12 μm2 versus 0.15 ± 0.06 μm2, p-value 0.02). In conclusion, CCL2 downregulation in SA may be an attempt to protect muscle against macrophage infiltration, and defects in fatty acid partitioning to muscle may lead to the disproportionate adiposity and adverse cardiometabolic profile in SA.
Highlights
The expansion of different fat depots leads to distinctive consequences on metabolic profiles
While studies have focused on understanding inflammation in adipose tissue[10,11,12,13,14,15,16,17,18], and showed an excess of macrophages in obese adipose tissue in EU, there are no data regarding the effect of systemic and regional adiposity, including visceral adipose tissue (VAT), intrahepatocellular fat, and intramyocellular lipids (IMCL) on inflammation in skeletal muscle in SA compared to EU25–27
In the overall molSHARE study (n = 1 08), SA had greater fat mass, intrahepatic and VAT with higher rates of insulin resistance, lower HDL and higher triglycerides compared to EU8
Summary
The expansion of different fat depots leads to distinctive consequences on metabolic profiles. While studies have focused on understanding inflammation in adipose tissue[10,11,12,13,14,15,16,17,18], and showed an excess of macrophages in obese adipose tissue in EU, there are no data regarding the effect of systemic (total fat mass) and regional adiposity, including visceral adipose tissue (VAT), intrahepatocellular fat, and intramyocellular lipids (IMCL) on inflammation in skeletal muscle in SA compared to EU25–27. The secondary aims of this study are to determine if SA have differential adiposity patterns compared to EU, and if these depots are associated with a specific inflammatory profile in muscle that differs between SA and EU
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