Martin Carlsson

Novel mutations and a mutational hotspot in the MODY3 gene

Maturity-onset diabetes of the young 3 (MODY3) is a type of NIDDM caused by mutations in the transcription factor hepatocyte nuclear factor-1a (HNF-1α) located on chromosome 12q. We have identified four novel HNF-1α missense mutations in M0DY3 families. In four additional and unrelated families, we observed an identical insertion mutation that had occurred in a polycytidine tract in exon 4. Among those families, one exhibited a de novo mutation at this location. We propose that instability of this sequence represents a general mutational mechanism in M0DY3. We observed no HNF-1α mutations among 86 unrelated late-onset diabetic patients with relative insulin deficiency. Hence mutations in this gene appear to be most strongly associated with early-onset diabetes.

High Levels of Nonesterified Fatty Acids Are Associated With Increased Familial Risk of Cardiovascular Disease

To address the question of whether elevated concentrations of nonesterified fatty acids (NEFAs) are associated with an increased risk of cardiovascular disease, we measured NEFA concentrations in 140 diabetic and 343 nondiabetic unrelated Swedish subjects with a family history of type 2 diabetes and related the findings to history of cardiovascular disease in their parents. Parents of nondiabetic offspring belonging to the quartile of highest NEFA concentrations had a higher risk of myocardial infarction (35% versus 16%, P<0.01) and stroke (45% versus 16%, P<0.0005) than did parents of offspring from the lowest NEFA quartile. In a multiple logistic regression analysis, a high NEFA concentration in offspring was significantly associated with myocardial infarction and stroke in their parents. No such relationship was observed between diabetic offspring and their parents. Assuming that the same relationship between NEFA concentrations and cardiovascular disease is seen in the offspring and their parents, the findings suggest that elevated NEFA concentration is a risk factor for cardiovascular disease and could be pathogenically involved in the atherosclerotic process.

Common variants in the beta2-(Gln27Glu) and beta3-(Trp64Arg)--adrenoceptor genes are associated with elevated serum NEFA concentrations and type II diabetes

Aims/hypothesis. Higher NEFA concentrations predict Type II (non-insulin-dependent) diabetes mellitus but it is not known whether higher NEFA concentrations are genetically determined or reflect coexisting obesity. To address this question we studied whether common variants in two genes encoding for key regulators of lipolysis, the β2- and β3- adrenoceptors (B2AR and B3AR) are associated with NEFA concentrations and Type II diabetes. Methods. A total of 1054 Swedish subjects with varying degrees of glucose tolerance were genotyped for the Gln27Glu variant in the B2AR and for the Trp64Arg variant in the B3AR genes using PCR-RFLP. Results. The B2AR Gln27 allele was more frequent in 219 Type II diabetic patients than in 237 non-diabetic subjects (59.8 % vs 52.3 %; OR = 1.72, p = 0.02) while there was no significant difference in the frequency of the B3AR Arg64 allele. Subjects homozygous for the protective alleles (Glu27 and Trp64) had, however, a lower prevalence of diabetes than subjects with other genotype combinations (OR = 0.58, p = 0.03). Among sibling pairs discordant for the B2AR Gln27Glu polymorphism, siblings with an excess of the Gln27 allele had higher fasting insulin (n = 217; p = 0.02) and NEFA concentrations (107 sex-matched pairs; p = 0.01) than siblings with an excess of the Glu27 allele. Among sibling pairs discordant for the B3AR Trp64Arg variant, siblings with the Arg64 allele had higher 2 h glucose (n = 48; p = 0.01) and NEFA concentrations (16 pairs matched for sex; p < 0.04) than siblings with the Trp64Trp64 genotype. Conclusions/interpretation. Common variants in the β2- and β3- adrenoceptor genes are associated with increased fasting insulin and NEFA concentrations and could increase susceptibility to Type II diabetes. [Diabetologia (2001) 44: 629–636]

Angiotensin converting enzyme (ACE) gene polymorphism in sarcoidosis in relation to associated autoimmune diseases

Abstract. Papadopoulos KI, Melander O, Orho‐Melander M, Groop LC, Carlsson M, Hallengren B (University of Lund, Malmö University Hospital, Malmö, Sweden). Angiotensin converting enzyme (ACE) gene polymorphism in sarcoidosis in relation to associated autoimmune diseases. J Intern Med 2000; 247: 71–77.

The antimicrobial peptide LL-37 alters human osteoblast Ca2+ handling and induces Ca2+-independent apoptosis

The human antimicrobial peptide cathelicidin LL-37 has, besides its antimicrobial properties, also been shown to regulate apoptosis in a cell type-specific manner. Mechanisms involved in LL-37-regulated apoptotic signaling are not identified. Here, we show that LL-37 reduces the human osteoblast-like MG63 cell number and cell viability in the micromolar concentration range with an IC₅₀ value of about 5 µ<smlcap>M</smlcap>. Treatment with 4 µ<smlcap>M</smlcap> LL-37 increased the number of annexin V-positive cells and stimulated activation of caspase 3 showing that LL-37 promotes apoptosis. Treatment with 4 µ<smlcap>M</smlcap> LL-37 caused an acute and sustained rise in intracellular Ca²⁺ concentration assessed by laser-scanning confocal microscopy of Fluo-4-AM-loaded MG63 cells. LL-37 increased Ca²⁺ also in the presence of the respective L- and T-type voltage-sensitive Ca²⁺ channel blockers nifedipine and NiCl₂. LL-37 had no effect on Ca²⁺ in cells incubated with Ca²⁺-free solution. LL-37 (4 and 8 µ<smlcap>M</smlcap>) reduced the MG63 cell number both in the presence and absence of Ca²⁺ in the medium. In conclusion, LL-37 reduces the osteoblast cell number by promoting apoptosis, and furthermore, LL-37 stimulates Ca²⁺ inflow via a mechanism independent of voltage-sensitive Ca²⁺ channels. Interestingly, LL-37-induced lowering of the cell number seems to be mediated via a mechanism independent of Ca²⁺.

Pro-opiomelanocortin gene is associated with serum leptin levels in lean but not in obese individuals.

OBJECTIVE: Mutations in the pro-opiomelanocortin and melanocortin 4 receptor genes (POMC and MC4R) cause monogenic obesity, and the POMC locus (2p21) has been linked to leptin levels and body mass index (BMI). We searched for monogenic obesity due to mutations in POMC and MC4R among morbidly obese Swedes and studied the association of POMC variants with BMI and serum leptin levels.DESIGN: MC4R and POMC were screened for mutations in 102 obese Swedish subjects (40±11 y, 41.3±5.0 kg/m2) using the single-strand conformation polymorphism technique. The detected polymorphisms were genotyped in 118 lean control subjects (56±11 y, 22.6±1.3 kg/m2) and studied for association with BMI and serum leptin levels.RESULTS: No cases of monogenic obesity due to mutations in POMC or MC4R were identified and none of the four common POMC polymorphisms (RsaI, ins56, Glu188Gly and C8246T) were associated with obesity. Lean carriers of the C8246T CC-genotype had higher serum leptin levels compared to CT or TT carriers (9.7±6.6 vs 6.7±4.4 μg/l, P=0.003 for leptin levels adjusted for age, sex and BMI in regression analysis), especially lean females (P=0.004) and lean female carriers with the C8246T(CC)/RsaI(−−or +−) genotype combinations (P<0.0005). Neither the C8246T CC-genotype nor the C8246T(CC)/RsaI(−−or +−) were associated with serum leptin levels in obese subjects.CONCLUSIONS: Monogenic forms of obesity due to mutations in POMC and MC4R are rare in Swedish obese patients. Polymorphisms in POMC are associated with variation in serum leptin levels within the normal range in healthy lean but not in obese individuals.

Polymorphism at the rad Gene Is Not Associated With NIDDM in Finns

Recently, a trinucleotide repeat polymorphism at the rad (ras associated with diabetes) locus (RAD1) on chromosome 16q was described in association with NIDDM in white Americans. In an attempt to replicate this finding, we screened RAD1 and another microsatellite marker at the D16S265 loci, which is located near the rad locus, with a radioactive polymerase chain reaction method in 290 unrelated Finnish NIDDM patients and 270 control subjects and related the findings to measures of insulin sensitivity. Both groups were randomly selected from the western (189 NIDDM patients and 184 control subjects) and southern (101 NIDDM and 86 control subjects) parts of Finland. The allele frequency distributions of RAD1 and D16S265 did not differ between NIDDM patients and control subjects in the studied population groups. The genotype distribution was also analyzed by structural classes of the RAD1 polymorphism, and no difference was detected between the NIDDM and control groups. In addition, carriers of allele classes I, II, and IV (reported to be preferentially associated with NIDDM in white Americans) did not differ from the class III homozygotes with respect to age at onset of NIDDM, BMI, or rates of insulin-stimulated glucose disposal. In conclusion, we found no association between the rad locus and NIDDM or insulin resistance in Finnish NIDDM patients.