Limits...
Regulation of the fibrosis and angiogenesis promoter SPARC/osteonectin in human adipose tissue by weight change, leptin, insulin, and glucose.

Kos K, Wong S, Tan B, Gummesson A, Jernas M, Franck N, Kerrigan D, Nystrom FH, Carlsson LM, Randeva HS, Pinkney JH, Wilding JP - Diabetes (2009)

Bottom Line: Adipose tissue collagen has recently been found to be linked with metabolic dysregulation.In vitro experiments showed that leptin and insulin potently increased SPARC production dose dependently in visceral adipose tissue explants, while glucose decreased SPARC protein.Our data suggest that SPARC expression is predominant in subcutaneous fat and its expression and secretion in adipose tissue are influenced by fat mass, leptin, insulin, and glucose.

View Article: PubMed Central - PubMed

Affiliation: Diabetes and Endocrinology Research Unit, Clinical Sciences Centre, University Hospital Aintree, Liverpool, UK.

ABSTRACT

Objective: Matricellular Secreted Protein, Acidic and Rich in Cysteine (SPARC), originally discovered in bone as osteonectin, is a mediator of collagen deposition and promotes fibrosis. Adipose tissue collagen has recently been found to be linked with metabolic dysregulation. Therefore, we tested the hypothesis that SPARC in human adipose tissue is influenced by glucose metabolism and adipokines.

Research design and methods: Serum and adipose tissue biopsies were obtained from morbidly obese nondiabetic subjects undergoing bariatric surgery and lean control subjects for analysis of metabolic markers, SPARC, and various cytokines (RT-PCR). Additionally, 24 obese subjects underwent a very-low-calorie diet of 1,883 kJ (450 kcal)/day for 16 weeks and serial subcutaneous-abdominal-adipose tissue (SCAT) biopsies (weight loss: 28 +/- 3.7 kg). Another six lean subjects underwent fast-food-based hyperalimentation for 4 weeks (weight gain: 7.2 +/- 1.6 kg). Finally, visceral adipose tissue explants were cultured with recombinant leptin, insulin, and glucose, and SPARC mRNA and protein expression determined by Western blot analyses.

Results: SPARC expression in human adipose tissue correlated with fat mass and was higher in SCAT. Weight loss induced by very-low-calorie diet lowered SPARC expression by 33% and increased by 30% in adipose tissue of subjects gaining weight after a fast-food diet. SPARC expression was correlated with leptin independent of fat mass and correlated with homeostasis model assessment-insulin resistance. In vitro experiments showed that leptin and insulin potently increased SPARC production dose dependently in visceral adipose tissue explants, while glucose decreased SPARC protein.

Conclusions: Our data suggest that SPARC expression is predominant in subcutaneous fat and its expression and secretion in adipose tissue are influenced by fat mass, leptin, insulin, and glucose. The profibrotic effects of SPARC may contribute to metabolic dysregulation in obesity.

Show MeSH

Related in: MedlinePlus

A: Dose-dependent effects of d-glucose on SPARC protein production in VAT explants assessed by Western blotting. Densitometric analysis of SPARC immune complexes (35 kDA) were normalized to β-actin (40 kDa). Data are expressed as percentage difference of median of basal. B: Dose-dependent effects of insulin on SPARC protein production. C: Dose-dependent effects of leptin on SPARC production. *P < 0.05, **P < 0.01, ***P < 0.001, n = 6.
© Copyright Policy - creative-commons
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC2712789&req=5

Figure 4: A: Dose-dependent effects of d-glucose on SPARC protein production in VAT explants assessed by Western blotting. Densitometric analysis of SPARC immune complexes (35 kDA) were normalized to β-actin (40 kDa). Data are expressed as percentage difference of median of basal. B: Dose-dependent effects of insulin on SPARC protein production. C: Dose-dependent effects of leptin on SPARC production. *P < 0.05, **P < 0.01, ***P < 0.001, n = 6.

Mentions: Cell culture studies were performed to determine whether the observed correlations of SPARC with metabolic parameters are because of direct regulation by glucose, leptin, or insulin. Increasing doses of glucose (5, 10, 20, and 40 mmol/l) decreased SPARC protein expression (5 mmol/l: 100 ± 8 optical density units; 10 mmol/l: 93 ± 6 optical density units; 20 mmol/l: 24 ± 6 optical density units; 40 mmol/l: 19 ± 4 optical density units [SPARC/β-actin], respectively, n = 6; P < 0.01, Fig. 4A). In contrast, culture of VAT with insulin (0, 0.01, 1, and 100 nmol/l) increased SPARC expression (C: 100 ± 20 optical density units; 0.01 nmol/l: 105 ± 35 optical density units; 1 nmol/l: 156 ± 27 optical density units; 100 nmol/l: 292 ± 30 optical density units, n = 6; P < 0.001; Fig. 4B).


Regulation of the fibrosis and angiogenesis promoter SPARC/osteonectin in human adipose tissue by weight change, leptin, insulin, and glucose.

Kos K, Wong S, Tan B, Gummesson A, Jernas M, Franck N, Kerrigan D, Nystrom FH, Carlsson LM, Randeva HS, Pinkney JH, Wilding JP - Diabetes (2009)

A: Dose-dependent effects of d-glucose on SPARC protein production in VAT explants assessed by Western blotting. Densitometric analysis of SPARC immune complexes (35 kDA) were normalized to β-actin (40 kDa). Data are expressed as percentage difference of median of basal. B: Dose-dependent effects of insulin on SPARC protein production. C: Dose-dependent effects of leptin on SPARC production. *P < 0.05, **P < 0.01, ***P < 0.001, n = 6.
© Copyright Policy - creative-commons
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2712789&req=5

Figure 4: A: Dose-dependent effects of d-glucose on SPARC protein production in VAT explants assessed by Western blotting. Densitometric analysis of SPARC immune complexes (35 kDA) were normalized to β-actin (40 kDa). Data are expressed as percentage difference of median of basal. B: Dose-dependent effects of insulin on SPARC protein production. C: Dose-dependent effects of leptin on SPARC production. *P < 0.05, **P < 0.01, ***P < 0.001, n = 6.
Mentions: Cell culture studies were performed to determine whether the observed correlations of SPARC with metabolic parameters are because of direct regulation by glucose, leptin, or insulin. Increasing doses of glucose (5, 10, 20, and 40 mmol/l) decreased SPARC protein expression (5 mmol/l: 100 ± 8 optical density units; 10 mmol/l: 93 ± 6 optical density units; 20 mmol/l: 24 ± 6 optical density units; 40 mmol/l: 19 ± 4 optical density units [SPARC/β-actin], respectively, n = 6; P < 0.01, Fig. 4A). In contrast, culture of VAT with insulin (0, 0.01, 1, and 100 nmol/l) increased SPARC expression (C: 100 ± 20 optical density units; 0.01 nmol/l: 105 ± 35 optical density units; 1 nmol/l: 156 ± 27 optical density units; 100 nmol/l: 292 ± 30 optical density units, n = 6; P < 0.001; Fig. 4B).

Bottom Line: Adipose tissue collagen has recently been found to be linked with metabolic dysregulation.In vitro experiments showed that leptin and insulin potently increased SPARC production dose dependently in visceral adipose tissue explants, while glucose decreased SPARC protein.Our data suggest that SPARC expression is predominant in subcutaneous fat and its expression and secretion in adipose tissue are influenced by fat mass, leptin, insulin, and glucose.

View Article: PubMed Central - PubMed

Affiliation: Diabetes and Endocrinology Research Unit, Clinical Sciences Centre, University Hospital Aintree, Liverpool, UK.

ABSTRACT

Objective: Matricellular Secreted Protein, Acidic and Rich in Cysteine (SPARC), originally discovered in bone as osteonectin, is a mediator of collagen deposition and promotes fibrosis. Adipose tissue collagen has recently been found to be linked with metabolic dysregulation. Therefore, we tested the hypothesis that SPARC in human adipose tissue is influenced by glucose metabolism and adipokines.

Research design and methods: Serum and adipose tissue biopsies were obtained from morbidly obese nondiabetic subjects undergoing bariatric surgery and lean control subjects for analysis of metabolic markers, SPARC, and various cytokines (RT-PCR). Additionally, 24 obese subjects underwent a very-low-calorie diet of 1,883 kJ (450 kcal)/day for 16 weeks and serial subcutaneous-abdominal-adipose tissue (SCAT) biopsies (weight loss: 28 +/- 3.7 kg). Another six lean subjects underwent fast-food-based hyperalimentation for 4 weeks (weight gain: 7.2 +/- 1.6 kg). Finally, visceral adipose tissue explants were cultured with recombinant leptin, insulin, and glucose, and SPARC mRNA and protein expression determined by Western blot analyses.

Results: SPARC expression in human adipose tissue correlated with fat mass and was higher in SCAT. Weight loss induced by very-low-calorie diet lowered SPARC expression by 33% and increased by 30% in adipose tissue of subjects gaining weight after a fast-food diet. SPARC expression was correlated with leptin independent of fat mass and correlated with homeostasis model assessment-insulin resistance. In vitro experiments showed that leptin and insulin potently increased SPARC production dose dependently in visceral adipose tissue explants, while glucose decreased SPARC protein.

Conclusions: Our data suggest that SPARC expression is predominant in subcutaneous fat and its expression and secretion in adipose tissue are influenced by fat mass, leptin, insulin, and glucose. The profibrotic effects of SPARC may contribute to metabolic dysregulation in obesity.

Show MeSH
Related in: MedlinePlus