Increased TLR2 expression in patients with type 1 diabetes: evidenced risk of microalbuminuria.

OBJECTIVE: To study the activation of an inflammatory cascade through leukocyte mRNA expression of TLR2, TLR4, MyD88, and pro-inflammatory cytokines in individuals with childhood onset type 1 diabetes. DESIGN AND METHODS: Seventy-six type 1 diabetic patients and 100 normoglycemic subjects (NG) 6 to 20 years old were recruited. Type 1 diabetic patients (DM1) were considered to have good (DM1G) or poor (DM1P) glycemic control according to the values of glycated hemoglobin. TLR2, TLR4, MyD88, interleukin -1ß (IL-1ß), IL-6, and tumor necrosis factor alpha (TNF-α) mRNA expressions were measured in peripheral blood leukocytes (PBL) by real-time polymerase chain reaction (PCR). Urea, creatinine, albumin, and total protein serum levels were determined. Urinary albumin-to-creatinine ratio (ACR) was calculated. RESULTS: DM1 and DM1P patients showed higher glycated hemoglobin (10 and 11%, respectively) and serum glucose concentrations (208 and 226 mg/dL, respectively) compared to NG (Glycated hemoglobin: 7% and glucose: 76 mg/dL) (p < 0.05). PBL mRNA expressions of TLR2, MyD88, IL-1ß, IL-6, and TNF-α were higher in DM1 and TLR2, IL-1ß, and IL-6 expressions were higher in DMP1 compared to NG (p < 0.05). In DM1, serum albumin and total protein were lower, while serum urea and ACR were higher in comparison to NG (p < 0.05). However, these differences compared to NG were more pronounced in DM1P, which included nine individuals with microalbuminuria. CONCLUSIONS: Increased mRNA expression of TLR2, MyD88, and pro-inflammatory cytokines in leukocytes of patients with childhood onset type 1 diabetes indicates the development of a TLR2-mediated pro-inflammatory process, which may also be associated with an early inflammatory process in the kidney and the occurrence of microalbuminuria.

Increased class A scavenger receptor and glomerular lipid precede mesangial matrix expansion in the bGH mouse model.

OBJECTIVE: Elevated neutral lipid content and mRNA expression of class A scavenger receptor (SRA) have been found in the renal cortex of the bovine growth hormone (bGH) mouse model of progressive glomerulosclerosis (GS). We hypothesize that the increased expression of SRA precedes glomerular scarring in this model. DESIGN: Real time RT-PCR and immunofluorescence were employed to measure SRA and collagen types I and IV in the bGH transgenic and control mice at 5 and 12 weeks (wk) of age to determine the chronology of change in SRA expression in relation to glomerular scarring. Alternative mechanisms for increasing glomerular lipid were assessed by measuring mRNA expression levels of low-density lipoprotein receptor (LDL-r), 3-hydroxy-3-methylglutaryl coenzyme A reductase (HMGR), and ATP-binding cassette transporter A1 (ABCA1). In addition, the involvement of macrophages in early GS was assessed by CD68 mRNA expression in kidney cortex. RESULTS: Both mRNA and protein levels of SRA were significantly increased in 5-wk bGH compared with control mice, whereas the expression of collagen I and IV was unaltered. Unchanged levels of LDL-r and HMGR mRNA indicate that neither regulated cholesterol uptake via LDL-r nor the cholesterol synthetic pathway played a role in the early lipid increase. The finding of increased ABCA1 expression was an indicator of excess intracellular lipid in the renal cortex of bGH mice at 5 wk. CD68 expression in bGH did not differ significantly from that of controls at 5 wk suggesting that cortical macrophage infiltration was not increased in bGH mice at this time point. CONCLUSION: An early increase in SRA mRNA and protein expression in the bGH kidney precedes glomerular scarring and is independent of macrophage influx.

Growth hormone promotes glomerular lipid accumulation in bGH mice.

BACKGROUND: Bovine growth hormone (bGH) transgenic mice develop progressive glomerulosclerosis and exhibit abnormalities in hepatic lipid metabolism. We have previously shown that growth hormone up-regulates the low-density lipoprotein (LDL) receptor and 3-hydroxy-3-methylglutaryl coenzyme A reductase (HMGR) in mouse mesangial cells. However, a role of lipid abnormalities in bGH kidney disease has not yet been demonstrated. METHODS: Groups of bGH mice (5 and 11 months old) presenting with, respectively, moderate and severe degrees of glomerulosclerosis were compared to age-matched controls. Neutral lipid content in kidney cortex was determined by oil red-O staining, serum cholesterol, and triglycerides by enzymatic assays, relative mRNA expression of LDL receptors, HMGR, and scavenger receptor by real-time reverse transcription-polymerase chain reaction (RT-PCR), and HMGR protein expression by immunoblotting. Two younger (5 and 12 weeks old) groups of mice were used to study scavenger receptor expression at earlier time points. RESULTS: Serum cholesterol was significantly increased in bGH mice at 5 months, but triglycerides were lower than control levels at both 5 and 11 months. Renal cortex HMGR expression was elevated at the mRNA but not at the protein level in the 11-month-old bGH group compared to controls. However, glomerular neutral lipid staining and scavenger receptor mRNA expression were markedly increased in all bGH mice, including those at 5 weeks of age compared to respective controls. CONCLUSION: The bGH mouse exhibits an increased mesangial lipid content and elevated scavenger receptor mRNA expression as early as at 5 weeks of age, suggesting that an increased kidney uptake of oxidized LDL could play a role in the development of glomerulosclerosis in this mouse model.