Plasma cathepsin D activity is negatively associated with hepatic insulin sensitivity in overweight and obese humans

• Published in: Diabetologia Vol. 63; no. 2; pp. 374 - 384
• Main Authors: Ding, Lingling, Goossens, Gijs H., Oligschlaeger, Yvonne, Houben, Tom, Blaak, Ellen E., Shiri-Sverdlov, Ronit
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer Berlin Heidelberg 01.02.2020; Springer Nature B.V
• Subjects: Adipose Tissue - metabolism; Adipose Tissue - pathology; Antibiotics; Blood Glucose - metabolism; Body weight; Cathepsin D; Cathepsin D - blood; Clinical trials; Cytokines; Diabetes; Diabetes mellitus (non-insulin dependent); Diabetes Mellitus, Type 2 - blood; Diabetes Mellitus, Type 2 - pathology; Female; Glucose; Human Physiology; Humans; Inflammation; Insulin; Insulin - blood; Insulin resistance; Insulin Resistance - physiology; Interleukin 8; Internal Medicine; Liver; Liver - metabolism; Male; Medicine; Medicine & Public Health; Metabolic Diseases; Muscle, Skeletal - metabolism; Muscle, Skeletal - pathology; Obesity; Obesity - blood; Obesity - pathology; Overweight; Overweight - blood; Overweight - pathology; Plasma; Skeletal muscle; Supplements; Tumor Necrosis Factor-alpha - blood; Tumor necrosis factor-α; Type 2 diabetes; Lysosomal enzyme; Hepatic insulin sensitivity; Inflammatory cytokines
• ISSN: 0012-186X; 1432-0428
• DOI: 10.1007/s00125-019-05025-2

Aims/hypothesis Insulin resistance in skeletal muscle and liver plays a major role in the pathophysiology of type 2 diabetes. The hyperinsulinaemic–euglycaemic clamp is considered the gold standard for assessing peripheral and hepatic insulin sensitivity, yet it is a costly and labour-intensive procedure . Therefore, easy-to-measure, cost-effective approaches to determine insulin sensitivity are needed to enable organ-specific interventions. Recently, evidence emerged that plasma cathepsin D (CTSD) is associated with insulin sensitivity and hepatic inflammation. Here, we aimed to investigate whether plasma CTSD is associated with hepatic and/or peripheral insulin sensitivity in humans. Methods As part of two large clinical trials (one designed to investigate the effects of antibiotics, and the other to investigate polyphenol supplementation, on insulin sensitivity), 94 overweight and obese adults (BMI 25–35 kg/m 2 ) previously underwent a two-step hyperinsulinaemic–euglycaemic clamp (using [6,6- 2 H 2 ]glucose) to assess hepatic and peripheral insulin sensitivity (per cent suppression of endogenous glucose output during the low-insulin-infusion step, and the rate of glucose disappearance during high-insulin infusion [40 mU/(m 2 × min)], respectively). In this secondary analysis, plasma CTSD levels, CTSD activity and plasma inflammatory cytokines were measured. Results Plasma CTSD levels were positively associated with the proinflammatory cytokines IL-8 and TNF-α (IL-8: standardised β = 0.495, p < 0.001; TNF-α: standardised β = 0.264, p = 0.012). Plasma CTSD activity was negatively associated with hepatic insulin sensitivity (standardised β = −0.206, p = 0.043), independent of age, sex, BMI and waist circumference, but it was not associated with peripheral insulin sensitivity. However, plasma IL-8 and TNF-α were not significantly correlated with hepatic insulin sensitivity. Conclusions/interpretation We demonstrate that plasma CTSD activity, but not systemic inflammation, is inversely related to hepatic insulin sensitivity, suggesting that plasma CTSD activity may be used as a non-invasive marker for hepatic insulin sensitivity in humans.