Circulating adipocyte fatty acid binding protein is increased in chronic and acute renal dysfunction

BACKGROUND AND AIMS

The adipokine adipocyte fatty acid binding protein (AFABP) is positively associated with the development of the metabolic syndrome, diabetes mellitus, and cardiovascular disease. We hypothesized that AFABP also increases with deteriorating renal function.

METHODS AND RESULTS

Serum AFABP levels were quantified by enzyme linked immunosorbent assay in 532 patients with chronic kidney disease (CKD) covering the whole spectrum of estimated glomerular filtration rate (eGFR) categories from G1 to G5 (study population 1). Furthermore, AFABP was measured in 32 patients before and within 30 h after elective unilateral nephrectomy, a model of acute kidney dysfunction (AKD) (study population 2). Moreover, circulating AFABP was investigated in rats undergoing bilateral nephrectomy (BNE) as compared to sham-operated animals. Median serum AFABP levels adjusted for age, gender, and body mass index significantly increased with increasing eGFR category (G1: 22.0 μg/l; G2: 34.6 μg/l; G3: 56.7 μg/l; G4: 95.2 μg/l; and G5: 173.9 μg/l). Furthermore, renal dysfunction remained positively associated with AFABP in multivariate analysis in this cohort. In patients undergoing unilateral nephrectomy, AFABP increased significantly after surgery (42.1 μg/l) as compared to pre-surgical values (29.3 μg/l). Furthermore, relative changes of post-to-pre-surgical AFABP levels were independently associated with relative changes of post-to-pre-surgical creatinine concentrations. After BNE in rats, AFABP increased significantly as compared to sham-operated animals.

CONCLUSIONS

We show that AFABP is significantly elevated in CKD and AKD patients. Furthermore, measures of renal function are associated with circulating AFABP. Moreover, animal experiments indicate that AFABP levels strongly depend on renal function.

Time to do more: addressing clinical inertia in the management of type 2 diabetes mellitus

AIMS

Clinical inertia, the tendency to maintain current treatment strategies despite results demanding escalation, is thought to substantially contribute to the disconnect between clinical aspirations for patients with diabetes and targets achieved. We wished to explore potential causes of clinical inertia among physicians and people with diabetes.

METHODS

A 20-min online survey of 652 adults with diabetes and 337 treating physicians in six countries explored opinions relating to clinical inertia from both perspectives, in order to correlate perceptions and expectations relating to diagnosis, treatment, diabetes complications and therapeutic escalation.

RESULTS

Physicians had low expectations for their patients, despite the belief that the importance of good glycaemic control through lifestyle and pharmacological interventions had been adequately conveyed. Conversely, people with diabetes had, at best, a rudimentary understanding of the risks of complications and the importance of good control; indeed, only a small proportion believed lifestyle changes were important and the majority did not intend to comply.

CONCLUSIONS

The principal findings of this survey suggest that impairments in communication are at the heart of clinical inertia. This manuscript lays out four key principles that we believe are achievable in all environments and can improve the lives of people with diabetes.

Serum levels of fractalkine are associated with markers of insulin resistance in gestational diabetes

AIMS

Fractalkine has recently been introduced as an adipokine that improves glucose tolerance. Regulation of fractalkine in gestational diabetes, as well as its association with markers of obesity, glucose and lipid metabolism, inflammation and renal function, has not been elucidated.

METHODS

Circulating fractalkine was quantified by enzyme-linked immunosorbent assay in 74 women with gestational diabetes and 74 healthy, pregnant control subjects matched for age, BMI, and gestational age.

RESULTS

Median (interquartile range) levels of fractalkine were not significantly different between the two groups [gestational diabetes: 2.24 (2.16) μg/l; control: 2.45 (1.38) μg/l] (P = 0.461). In multivariate linear regression analysis, fractalkine remained independently associated with homeostasis model assessment of insulin resistance (β = -0.253, P = 0.002) and the proinflammatory adipokine progranulin (β = 0.218, P = 0.007).

CONCLUSIONS

Circulating fractalkine is not different between women with gestational diabetes and control subjects, but the adipokine is independently associated with markers of insulin resistance and proinflammatory progranulin in pregnancy.

Different associations of adipokines in lean and healthy adults

Regulation of adipokines in lean adults without metabolic disease and without eating disorders has not been comprehensively elucidated. We hypothesized that some of the established associations of these adipocyte-secreted proteins with anthropometric and biochemical measures of glucose homeostasis, lipid metabolism, renal function, as well as inflammation, differ in healthy and low weight adults as compared to overweight/obese patients. Eighty-one subjects with a body mass-index below 22.0 kg/m2 and without malnutrition or eating disorders, as well as fifty overweight/obese patients, were recruited for the study. Serum concentrations of seven adipokines (adiponectin, leptin, adipocyte fatty acid-binding protein [AFABP], chemerin, fibroblast growth factor [FGF]-21, resistin, retinol-binding protein [RBP]-4) were measured by enzyme-linked immunosorbent assays. Lean probands had significantly higher levels of adiponectin and resistin, as well as lower levels of leptin, AFABP, and RBP-4, as compared to overweight/obese subjects. Serum concentrations of adiponectin, leptin, AFABP, chemerin, and resistin were significantly higher in lean women as compared to men (p<0.05). In lean subjects, fasting insulin independently predicted leptin and resistin concentrations. Furthermore, C-reactive protein was independently associated with circulating AFABP and chemerin. Moreover, lean body mass was an independent predictor of leptin, fat mass predicted AFABP levels, whereas RBP-4 was independently correlated to age and triglycerides. In addition, high density lipoprotein cholesterol predicted AFABP. Our results support the notion that several of these adipokines are regulated in a different manner in lean adults as compared to overweight/obese subjects and patients with eating disorders.

Increased autophagy in peripheral nerves may protect Wistar Ottawa Karlsburg W rats against neuropathy

OBJECTIVE

Wistar Ottawa Karlsburg W (RT1(u)) rats (WOKW) develop obesity, dyslipidemia, moderate hypertension, hyperinsulinemia and impaired glucose tolerance prone to induce peripheral neuropathy (PN). Autophagy has been shown to prevent neurodegeneration in the central and peripheral nervous system. We analyzed the potential protective role of autophagy in an established rat model in preventing PN.

METHODS

We examined electrophysiology (motor-and sensory/mixed afferent conduction velocities and the minimal F-wave latency) and morphology, including ultrathin sections, myelin sheath thickness (g-ratio) and immunohistochemical markers of autophagy and inflammation in the sciatic nerve of five-month-old, male WOKW as compared to Wistar derived, congenic LEW.1W control rats, characterized by the same major histocompatibility complex as WOKW rats (RT1(u)). Moreover, the expression of axonal and synaptic proteins (NF68, GAP43, MP0), autophagy- (Atg5, Atg7, LC3), and apoptosis (cleaved caspase-3)-related markers was measured using Western blot.

RESULTS

No abnormalities in nerve electrophysiology and morphology were found in WOKW compared to LEW.1W rats. However, autophagosomes were more frequently apparent in sciatic nerves of WOKW rats. In Western blot analyses no significant differences in expression of neuronal structural proteins were found, but autophagy markers were up-regulated in WOKW compared to LEW.1W sciatic nerves. Immunostaining revealed a greater infiltration of Iba1/ED-1-positive macrophages, CD-3-positive T-cells and LC3-expression in sciatic nerves of WOKW rats.

CONCLUSIONS

Our results indicate that WOKW rats show an up-regulated autophagy and a mild inflammatory response but do not develop overt neuropathy. We suggest that autophagy and inflammatory cells may exert a protective role in preventing neuropathy in this rat model of the metabolic syndrome but the mechanism of action is still unclear.

Expression of anti-inflammatory macrophage genes within skeletal muscle correlates with insulin sensitivity in human obesity and type 2 diabetes

AIMS/HYPOTHESIS

Low-grade systemic inflammation and adipose tissue inflammatory macrophages are frequently detected in patients with obesity and type 2 diabetes. Whether inflammatory macrophages also increase in skeletal muscle of individuals with metabolic disorders remains controversial. Here, we assess whether macrophage polarisation markers in skeletal muscle of humans correlate with insulin sensitivity in obesity and type 2 diabetes.

METHODS

Skeletal muscle biopsies were obtained from individuals of normal weight and with normal glucose tolerance (NGT), and overweight/obese individuals with or without type 2 diabetes. Insulin sensitivity was determined by euglycaemic-hyperinsulinaemic clamps. Expression of macrophage genes was analysed by quantitative RT-PCR.

RESULTS

Gene expression of the inflammatory macrophage phenotype marker cluster of differentiation (CD)11c was higher in muscle of type 2 diabetes patients (p = 0.0069), and correlated with HbA1c (p = 0.0139, ρ = 0.48) and fasting plasma glucose (p = 0.0284, ρ = 0.43), but not after correction for age. Expression of TGFB1, encoding the anti-inflammatory marker TGF-β1, correlated inversely with HbA1c (p = 0.0095, ρ = -0.50; p = 0.0484, ρ = -0.50) and fasting plasma glucose (p = 0.0471, ρ = -0.39; p = 0.0374, ρ = -0.52) in two cohorts, as did HbA1c with gene expression of macrophage galactose-binding lectin (MGL) (p = 0.0425, ρ = -0.51). TGFB1 expression was higher in NGT individuals than in individuals with type 2 diabetes (p = 0.0303), and correlated with low fasting plasma insulin (p = 0.0310, ρ = -0.42). In exercised overweight/obese individuals, expression of genes for three anti-inflammatory macrophage markers, MGL (p = 0.0031, ρ = 0.71), CD163 (p = 0.0268, ρ = 0.57) and mannose receptor (p = 0.0125, ρ = 0.63), correlated with high glucose-disposal rate.

CONCLUSIONS/INTERPRETATION

Muscle expression of macrophage genes reveals a link between inflammatory macrophage markers, age and high glycaemia, whereas anti-inflammatory markers correlate with low glycaemia and high glucose-disposal rate.