Circulating serum chemerin levels are elevated in lipodystrophy

The Role of Adipokines in the Pathologies of the Central Nervous System

Adipokines are protein hormones secreted by adipose tissue in response to disruptions in physiological homeostasis within the body's systems. The regulatory functions of adipokines within the central nervous system (CNS) are multifaceted and intricate, and they have been identified in a number of pathologies. Therefore, specific adipokines have the potential to be used as biomarkers for screening purposes in neurological dysfunctions. The systematic review presented herein focuses on the analysis of the functions of various adipokines in the pathogenesis of CNS diseases. Thirteen proteins were selected for analysis through scientific databases. It was found that these proteins can be identified within the cerebrospinal fluid either by their ability to modify their molecular complex and cross the blood-brain barrier or by being endogenously produced within the CNS itself. As a result, this can correlate with their measurability during pathological processes, including Alzheimer's disease, amyotrophic lateral sclerosis, multiple sclerosis, depression, or brain tumors.

Leptin Improves Parameters of Brown Adipose Tissue Thermogenesis in Lipodystrophic Mice

Lipodystrophy syndromes (LD) are a heterogeneous group of very rare congenital or acquired disorders characterized by a generalized or partial lack of adipose tissue. They are strongly associated with severe metabolic dysfunction due to ectopic fat accumulation in the liver and other organs and the dysregulation of several key adipokines, including leptin. Treatment with leptin or its analogues is therefore sufficient to reverse some of the metabolic symptoms of LD in patients and in mouse models through distinct mechanisms. Brown adipose tissue (BAT) thermogenesis has emerged as an important regulator of systemic metabolism in rodents and in humans, but it is poorly understood how leptin impacts BAT in LD. Here, we show in transgenic C57Bl/6 mice overexpressing sterol regulatory element-binding protein 1c in adipose tissue (Tg (aP2-nSREBP1c)), an established model of congenital LD, that daily subcutaneous administration of 3 mg/kg leptin for 6 to 8 weeks increases body temperature without affecting food intake or body weight. This is associated with increased protein expression of the thermogenic molecule uncoupling protein 1 (UCP1) and the sympathetic nerve marker tyrosine hydroxylase (TH) in BAT. These findings suggest that leptin treatment in LD stimulates BAT thermogenesis through sympathetic nerves, which might contribute to some of its metabolic benefits by providing a healthy reservoir for excess circulating nutrients.

Increased Growth Differentiation Factor 15 in Patients with Hypoleptinemia-Associated Lipodystrophy

Objective. Similar to obesity, lipodystrophy (LD) causes adipose tissue dysfunction and severe metabolic complications. Growth differentiation factor 15 (GDF15) belongs to the transforming growth factor β superfamily and is dysregulated in metabolic disease including obesity and diabetes mellitus. Circulating levels in LD and the impact of leptin treatment have not been investigated so far. Material and Methods. GDF15 serum levels were quantified in 60 LD patients without human immunodeficiency virus infection and 60 controls matched for age, gender, and body mass index. The impact of metreleptin treatment on circulating GDF15 was assessed in a subgroup of patients. GDF15 mRNA expression was determined in metabolic tissues of leptin-deficient lipodystrophic aP2-nSREBP1c-Tg mice, obese ob/ob mice, and control C57Bl6 mice. Results. Median GDF15 serum concentrations were significantly higher in LD patients (819 ng/L) as compared to the control group (415 ng/L) (p < 0.001). In multiple linear regression analysis, an independent and positive association remained between GDF15 on one hand and age, patient group, hemoglobin A1c, triglycerides, and C-reactive protein on the other hand. Moreover, there was an independent negative association between GFD15 and estimated glomerular filtration rate. Circulating GDF15 was not significantly affected by metreleptin treatment in LD patients. Gdf15 was upregulated in leptin-deficient lipodystrophic mice as compared to controls. Moreover, Gdf15 mRNA expression was downregulated by leptin treatment in lipodystrophic and obese animals. Conclusions. Serum concentrations of GDF15 are elevated in LD patients and independently associated with markers of metabolic dysfunction. Gdf15 expression is higher in lipodystrophic mice and downregulated by leptin treatment.

Serum concentrations of fetuin B in lipodystrophic patients

OBJECTIVE

Fetuin B is an adipokine/hepatokine which is significantly elevated in insulin resistance/type 2 diabetes mellitus and hepatic steatosis. Regulation of fetuin B in patients with lipodystrophy (LD) - a disease group which is characterized by subcutaneous adipose tissue loss, hypertriglyceridemia, hepatic steatosis, insulin resistance, and dysregulation of several adipokines - has not been elucidated so far.

MATERIAL AND METHODS

Serum fetuin B levels were determined in 37 patients with LD, as well as in a control cohort consisting of 37 non-LD participants matched for age, gender, and body mass index. Furthermore, fetuin B was correlated with parameters of lipid metabolism, glucose control, renal function, and inflammation.

RESULTS

Median fetuin B serum levels were not significantly different between patients with LD (2980.7 µg/l; interquartile range: 841.7 µg/l) and non-LD controls (2647.3 µg/l; interquartile range: 923.6 µg/l; p = .105). Fetuin B was associated with age, body mass index, markers of renal function, and C reactive protein (CRP) in univariate correlation analyses. The associations with age and creatinine remained significant in multiple linear regression analysis.

CONCLUSIONS

Fetuin B serum concentrations are not significantly different between patients with LD and non-LD controls. Fetuin B does not seem to be a major pathogenetic factor in LD.

Facial soft tissue volume decreases during metreleptin treatment in patients with partial and generalized lipodystrophy

PURPOSE

Lipodystrophy (LD) patients suffer from loss or maldistribution of subcutaneous adipose tissue accompanied by dysregulation of several adipocyte-secreted factors, e.g., leptin. The effect of recombinant leptin (metreleptin) therapy on facial soft tissue volume in patients with non-human immunodeficiency virus LD has not been quantified to date.

METHODS

Eight LD patients (six female, two male; six familial partial LD [FPLD], two generalized LD) were treated with metreleptin over 1 year. Anthropometric parameters and 3D stereophotogrammetric imaging of the patients´ faces were assessed at baseline and after 1 year of metreleptin treatment.

RESULTS

Median fat mass was significantly reduced during metreleptin treatment from 22.3 kg at baseline to 20.0 kg at 1 year (p = 0.031); however, body weight, body mass index, and waist-to-hip ratio were not significantly affected. Five of the six patients with FPLD lost between 4 and 114 cm³ of facial soft tissue volume in the pre-auricular, buccal, and submandibular area during metreleptin treatment whereas a slight volume gain was seen in one FPLD patient. The two patients with generalized LD developed a volume loss of 20 and 8 cm³ in the buccal region between baseline and 1 year of metreleptin therapy, respectively.

CONCLUSIONS

Metreleptin replacement leads to loss of facial soft tissue volume in FPLD and generalized LD. However, volume changes in most patients are not visible by the naked eye.

Adipocyte and epidermal fatty acid-binding protein serum concentrations in patients with lipodystrophy

OBJECTIVE

Lipodystrophy (LD) syndromes are associated with diabetes mellitus, hypertriglyceridemia, and coronary artery disease. One pathogenetic factor of LD is dysregulation of several adipokines. However, the insulin resistance- and dyslipidemia-promoting adipokines adipocyte (AFABP) and epidermal (EFABP) fatty acid-binding protein have not been investigated in non-HIV-associated LD so far.

MATERIAL AND METHODS

We performed a cross-sectional analysis of AFABP and EFABP serum concentrations in 37 LD patients and 37 age-, gender-, and body mass index-matched healthy controls. Moreover, AFABP and EFABP were correlated to clinical and biochemical parameters of inflammation, glucose control, and lipid metabolism.

RESULTS

There was no significant difference in median circulating AFABP and EFABP levels between LD patients (21.7μg/l and 7.5μg/l, respectively) and healthy controls (24.5μg/l and 8.6μg/l, respectively). Neither AFABP nor EFABP were related to markers of impaired glucose control or lipid metabolism. Multiple linear regression analysis showed a positive and independent association of AFABP with gender, serum leptin levels, and body mass index.

CONCLUSIONS

Circulating levels of AFABP and EFABP are not decreased in LD despite adipose tissue loss in contrast to other adipokines including leptin and adiponectin.

Progranulin is increased in human and murine lipodystrophy

AIMS

Lipodystrophies (LD) are genetic or acquired disorders sharing the symptom of partial or complete adipose tissue deficiency and a dysregulation of adipokines including leptin and adiponectin. Progranulin, an adipokine with proinflammatory and insulin resistance-inducing characteristics, has not been investigated in LD so far.

METHODS

Circulating progranulin was determined in LD patients (N=37) and in age-, gender-, and body mass index-matched healthy control subjects (N=37). Additionally, we investigated progranulin expression in an LD mouse model as compared to wild-type mice. Moreover, we elucidated circulating progranulin before and during metreleptin supplementation in 10 patients with LD.

RESULTS

Median [interquartile range] circulating progranulin was increased in patients with LD (82.9 [25.9] μg/l) as compared to controls (73.6 [22.8] μg/l) (p=0.005). C-reactive protein (CRP) remained an independent and positive predictor of progranulin in multivariate analysis. Progranulin mRNA was significantly upregulated in all adipose tissue depots, i.e. visceral, subcutaneous, and brown adipose tissue, and in muscle of LD animals versus wild-type mice. Progranulin levels did not significantly change during metreleptin supplementation.

CONCLUSIONS

Progranulin serum concentration is increased in patients with LD, and shows an independent and positive correlation with CRP. Different adipose tissue depots and muscle might be potential origins of elevated progranulin.

Inverse Relationship of the CMKLR1 Relative Expression and Chemerin Serum Levels in Obesity with Dysmetabolic Phenotype and Insulin Resistance

Background. In obesity there is a subclinical chronic low-grade inflammatory response where insulin resistance (IR) may develop. Chemerin is secreted in white adipose tissue and promotes low-grade inflammatory process, where it expressed CMKLR1 receptor. The role of chemerin and CMKLR1 in inflammatory process secondary to obesity is not defined yet. Methods. Cross-sectional study with 134 individuals classified as with and without obesity by body mass index (BMI) and IR. Body fat storage measurements and metabolic and inflammatory markers were measured by routine methods. Soluble chemerin and basal levels of insulin by ELISA and relative expression of CMKLR1 were evaluated with qPCR and 2^−ΔΔC_T method. Results. Differences (P < 0.05) were observed between obesity and lean individuals in body fat storage measurements and metabolic-inflammatory markers. Both CMKLR1 expression and chemerin levels were increased in obesity without IR. Soluble chemerin levels correlate with adiposity and metabolic markers (r = 8.8% to 38.5%), P < 0.05. Conclusion. The increment of CMKLR1 expression was associated with insulin production. Increased serum levels of chemerin in obesity were observed, favoring a dysmetabolic response. The results observed in this study suggest that both chemerin and CMKLR1 have opposite expression in the context of low-grade inflammatory response manifested in the development of IR.