The existence of two yet unknown mutations within the apM-1 gene was demonstrated and RFLP analysis was established for rapid screening. Well defined cohorts of patients are necessary to determine the putative role of apM-1 gene mutations in the pathogenesis of metabolic disorders.

436 (77.9%) subjects were homozygous for the wildtype allele (Pro/Pro), 118 (21.1%) were heterozygous (Pro/Ala) and 6 (1.1%) were homozygous for the mutated allele (Ala/Ala). Genotype frequency was calculated to be 0.81 for the wildtype and 0.19 for the mutated allele. These frequencies did not differ from non-diabetic cohorts examined earlier. In contrast to females, total cholesterol and LDL-cholesterol were significantly higher in males (Total cholesterol: 281.8 +/- 51.3 vs 253.1 +/- 49.8 mg/dl, p < 0.0001; LDL-cholesterol: 182.0 +/- 49.2 vs 155.6 +/- 42.0 mg/d, p < 0.0001) in the presence of the mutated allele as compared to the wildtype subgroup. No differences were found with respect to BMI, HbA1c, blood pressure and serum levels of leptin nor to prevalence of retinopathy. Pro12Ala polymorphism of PPAR(gamma2) gene is not associated with diabetic retinopathy but is associated with dyslipidemia in male type 2 diabetic patients.

Aims/hypothesis. The human adipocyte-specific apM-1 (adipose most abundant gene transcript-1) gene encodes for a secretory protein of the adipose tissue that seems to play a role in the pathogenesis of obesityrelated insulin resistance and its expression is inhibited by TNF-α. Our aim was to characterize the tissuespecific regulation of the recently cloned apM-1 promoter and the mechanisms of TNF-α-induced downregulation of the apM-1 gene. Methods. We characterised the apM-1 gene by electrophoretic mobility shift assays (EMSA) and luciferase reporter gene assays (LRA). Results. Although several putative binding sites for transcription factors known to be involved in adipogenesis such as C/EBP and PPARγ are present in the promoter, we could not detect any binding of these nuclear proteins from differentiated adipocytes. However, a proximal SP1 binding site specifically binds both, recombinant SP1 protein and SP1 derived from adipocyte nuclear extracts. Since the expression of SP1 during adipocyte differentiation has not yet been analysed, we could show by using EMSA, that binding activity of SP1 is increased during adipocyte differentiation. The stimulatory activity of SP1 was confirmed in LRA by cotransfection experiments in S2 Schneider cells lacking endogenous SP factors. An inhibitory activity of SP3 on the stimulatory effect of SP1 could be confirmed in LRA by contransfection experiments in adipocytes. Nuclear extracts from adipocytes incubated with TNF-α showed a reduced binding activity of SP1. Conclusion/interpretation. SP1 is expressed and its binding activity is enhanced during adipocyte differentiation. SP1 has stimulatory effects, SP3 has inhibitory effects on apM-1 promoter activity, mediated by a proximal SP1 binding site. The mechanism of TNF-α-induced inhibition of apM-1 gene expression is, at least in part, due to a decrease of transcriptional SP1 binding activity caused by TNF-α and thus provides a new mechanism of TNF-α-dependent signalling. [Diabetologia (2002[Diabetologia ( ) 45:1425[Diabetologia ( -1433 Keywords apM-1, adipocyte, promoter, SP1, SP3, TNF-α, transcription, differentiation, diabetes, obesity. The adipose tissue has been considered as a special type of connective tissue, that stores energy in the form of triglycerides and releases energy in the form of non-esterified fatty acids whenever needed. However, increasing evidence suggests that the adipose tissue produces and secretes several highly active molecules. During the last 5 years it has become widely accepted that adipocytes do function as endocrine cells by secreting a variety of highly active molecules. These so-called adipocytokines [1] are secreted from the adipose tissue into the blood stream.

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Frequency of apM-1 gene polymorphisms and their association with metabolic parameters was evaluated in a population-based sample of 556 type 2 (316 males / 240 females) diabetic patients. PCR-based RFLP analysis was performed in blood samples. The T --> G transition at nucleotide +45 within exon-2 [Gly15Gly] was detected with an allelic frequency of 0.91 for the wildtype allele and 0.09 for the mutated allele. The missense point mutation (TAC --> CAC) at nucleotide +331 within exon 3 [Tyr111His] was detected with an allelic frequency of 0.97 and 0.03, respectively. These frequencies did not differ from a non-diabetic cohort examined earlier. Concerning the Gly15Gly polymorphism, the TT-genotype was found in 457 (82.2%) and the TG-genotype in 99 (17.8%), concerning the Tyr111His polymorphism, TT-genotype was found in 525 (94.4) and TC-genotype in 31 (5.6%) of type 2 diabetic patients. In TG-genotype as compared to TT-genotype significantly more patients had LDL-serum levels in high LDL-classes (<150 mg/dl: 24.4% (TG) vs. 41.4% (TT), 150mg/dl to 190mg/dl: 40.0% (TG) vs. 33.9% (TT), >190 mg/l: 35.6% (TG) vs. 25.0% (TT); p = 0.010). No differences in serum levels of lipids were found in genotype-subgroups of the Tyr111His polymorphism. Thus, Gly15Gly polymorphism of apM-1 gene might play a role in dyslipidaemia in type 2 diabetic patients.