Fat in Liver/Muscle Correlates More Strongly With Insulin Sensitivity in Rats Than Abdominal Fat

Abstract

Intrahepatic or intramuscular lipid (IHL/IML) content has been reported to be correlated with insulin resistance. Visceral fat has also been shown to be associated with insulin resistance. Thus, we investigated whether IHL/IML or visceral fat content is more closely associated with insulin resistance. Twenty Sprague‐Dawley rats were divided into two groups based on regular chow diet (RCD) or high‐fat diet (HFD; 40% fat). The insulin‐sensitivity index (ISI) was determined by euglycemic glucose clamp study, the amount of visceral fat by computed tomography (CT), and the IHL/IML content by magnetic resonance spectroscopy (MRS). Weight, food, and water intake, physical activity, energy expenditure, lipid profile, adiponectin, and high‐sensitivity C‐reactive protein (hsCRP) levels were measured. At the study end point, visceral fat, and the IHL/IML content were higher in the HFD group than in the RCD group. The IHL/IML content was more highly correlated with ISI than was visceral fat amount. Stronger correlations were also found between adiponectin or hsCRP level and IML/IHL content than visceral fat, especially in the HFD group. Furthermore, the IHL/IML content was significantly associated with the ISI in the multiple regression models but visceral fat was not. There was clear discrimination between RCD and HFD groups in scatter plots of IML/IHL against the ISI, but substantial overlap in that of visceral fat against the ISI. This result suggests that IHL/IML contents are closely related with insulin resistance or atherosclerosis and is a better metabolic index of insulin sensitivity than the visceral fat.

Modulation of Diabetes and Dyslipidemia in Diabetic Insulin-Resistant Rats by Mangiferin: Role of Adiponectin and TNF-α

“…Fat accumulation in the liver was previously reported to be associated with impaired insulin clearance and hyperinsulinemia (Lim et al 2009). Long term HFD-Fr was reported to upregulate the expression of hepatic sterol regulatory element binding protein (SREBP-1) and decrease the expression of PPAR-α receptor (Aragno et al 2009).…”

“…On the other hand, the elevation of adiponectin activates GSK3β, a key molecule involved in regulating glycogen homeostasis (Zhou et al 2010). The mechanisms by which adiponectin ameliorates insulin sensitivity include increased peripheral glucose uptake and suppressed hepatic glucose production (Lim et al 2009).…”

Testosterone: a metabolic hormone in health and disease

“…2). Indeed, fat in liver and muscle correlates more strongly with insulin sensitivity than abdominal fat in rats (Lim et al 2008). A growing body of studies has pointed to the presence of heterogeneity regarding insulin resistance and insulin sensitivity among different tissues (Stumvoll et al 2000); therefore, the mechanisms by which testosterone may impart beneficial actions on the development of T2DM and MetS are likely to be tissue dependent and involve multiple targets of lipid and carbohydrate metabolism (Table 1).…”

Ageing, adipose tissue, fatty acids and inflammation

“…The normal role of insulin is to facilitate cellular glucose metabolism through promoting glucose uptake and storage (Figure 1). There is considerable data to suggest linkage of intramuscular adiposity to the development of insulin resistance in both rodents and humans (Cree et al 2004;Lim et al 2009;Perseghin et al 2008), which suggests that in ageing, an increase in skeletal muscle adiposity could contribute to insulin resistance. Precisely how the increase in the adiposity within this site induces insulin resistance is unclear, with many intermediates and complex lipid metabolites thought to be involved.…”