Ketogenic propensity is differentially related to lipid-induced hepatic and peripheral insulin resistance

Netrin 4 is a novel cytokine associated with oxidative stress and insulin resistance in obese individuals

BACKGROUND

Netrin 4 (NTN4) has been reported to be involved in a variety of pathophysiological processes, such as the occurrence and development of tumors, viral replication and infection, and diabetic retinopathy. However, the relationships between NTN4 and metabolic diseases have not been reported.

METHODS

The PhenoScanner tool and R language were used for bioinformatics analysis. Serum NTN4 was measured by ELISA in 211 healthy women and 193 overweight/obesity (OW/OB) women. Alterations in the serum NTN4 level were examined during the cold-exposure tests, acute exercise, lipid infusion, OGTT and EHC.

RESULTS

GWAS and Bioinformatics analysis revealed that NTN4 was closely related to energy metabolism and OS. In a population-based cohort study, we observed that individuals with OW/OB and IR exhibited significantly elevated levels of circulating NTN4. In addition, the serum NTN4 concentration was found to be significantly correlated with indicators of obesity, IR, sex hormone and glucose/lipid metabolism.

CONCLUSIONS

NTN4 is associated with obesity-related IR.

TRIAL REGISTRATION

All research plans were approved by the Human Research Ethics Committee of Chongqing Medical University (No. (74)2012, No. (72)2014 and No. (74)2015).

Acetoacetate and d- and l-β-hydroxybutyrate have distinct effects on basal and insulin-stimulated glucose uptake in L6 skeletal muscle cells

Ketone bodies (acetoacetate and β-hydroxybutyrate) are oxidized in skeletal muscle mainly during fasting as an alternative source of energy to glucose. Previous studies suggest that there is a negative relationship between increased muscle ketolysis and muscle glucose metabolism in mice with obesity and/or type 2 diabetes. Therefore, we investigated the connection between increased ketone body exposure and muscle glucose metabolism by measuring the effect of a 3-h exposure to ketone bodies on glucose uptake in differentiated L6 myotubes. We showed that exposure to acetoacetate at a typical concentration (0.2 mM) resulted in increased basal glucose uptake in L6 myotubes, which was dependent on increased membrane glucose transporter type 4 (GLUT4) translocation. Basal and insulin-stimulated glucose uptake was also increased with a concentration of acetoacetate reflective of diabetic ketoacidosis or a ketogenic diet (1 mM). We found that β-hydroxybutyrate had a variable effect on basal glucose uptake: a racemic mixture of the two β-hydroxybutyrate enantiomers (d and l) appeared to decrease basal glucose uptake, while 3 mM d-β-hydroxybutyrate alone increased basal glucose uptake. However, the effects of the ketone bodies individually were not observed when acetoacetate was present in combination with β-hydroxybutyrate. These results provide insight that will help elucidate the effect of ketone bodies in the context of specific metabolic diseases and nutritional states (e.g., type 2 diabetes and ketogenic diets).NEW & NOTEWORTHY A limited number of studies investigate the effect of ketone bodies at concentrations reflective of both typical fasting and ketoacidosis. We tested a mix of physiologically relevant concentrations of ketone bodies, which allowed us to highlight the differential effects of d- and l-β-hydroxybutyrate and acetoacetate on skeletal muscle cell glucose uptake. Our findings will assist in better understanding the mechanisms that contribute to muscle insulin resistance and provide guidance on recommendations regarding ketogenic diets.